CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation-in-part of U.S. patent application Ser. No. 14/490,992 filed on Sep. 19, 2014, which claims priority to U.S. patent application Ser. No. 13/815,638, filed on Mar. 13, 2013, the entire contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to a shipping container. More specifically the present invention relates to improvements in locking mechanisms for a collapsible shipping container. 
       BACKGROUND OF THE INVENTION 
       [0003]    The shipping industry uses large cargo containers to ship cargo from one location to another in domestic and global commerce. Such containers are designed to be conveniently moved from one mode of transport to another across the land by road or on rail or over the sea. Such containers are sometimes referred to as “intermodal shipping containers”. The use of such containers has essentially eliminated the need for manually transferring cargo from one vessel to another, or from one vehicle or railcar to another in the effort to deliver the cargo to its final destination. 
         [0004]    Today, cargo containers are generally standardized by internationally recognized standards, and by national domestic standards with respect to dimensions and structure. Thus, the standard containers can be securely arranged in vertical stacks in side-by-side and end-to-end relationship with each other, and can be handled most effectively when transferring from one mode of transport to another. 
         [0005]    Often, these containers must be transported empty from one delivery point to the next location where cargo is available for shipment. Transport of empty containers costs the shipper money and erodes profits since transport of each such container incurs handling cost and occupies valuable space which could otherwise be used to ship a revenue producing container loaded with cargo. Additionally, the shipping of both loaded and empty containers creates problems such as how to arrange the lighter, empty containers and the heavier, loaded containers aboard ships in such a manner that the safety of the ships is not compromised. Beyond safety issues, the shipment of empty containers causes monetary losses for shippers, losses which result in either substantial financial impact on the shipper, or increased charges to customers for the handling and transport of loaded containers. Similar cost disadvantages apply when shipping empty containers over road or by rail. 
         [0006]    Long ago shippers recognized that significant economic savings in shipping could be realized if empty containers could be “folded” so as to occupy a substantially smaller space, so that less space need be sacrificed in the transporting of empty containers. Such an effort presently exists only for the “open frame” or flat rack type containers. To that end, the prior art proposed many foldable or nesting cargo containers of the enclosed types intended to reduce the space required for their shipment when empty. While such prior art foldable containers have been proposed, the market has not embraced the prior art containers as a substitute for the standard, non-foldable cargo containers. 
         [0007]    One common shortcoming in most foldable container designs is that structural features are incorporated in them which render the designs nearly incompatible for use in combination with existing, standard cargo containers. Accordingly, if these cargo containers were to become a part of the norm, they could not be used with existing standard containers, making the cost of implementation of these designs impractical, if not prohibitive. 
         [0008]    Another shortcoming of foldable containers of the prior art is the use of external locking mechanisms for securing the container in an erect position and the potential safety and security measures such a design leaves vulnerable. 
       SUMMARY 
       [0009]    The present invention discloses a system for collapsible shipping containers. More specifically, in an embodiment of the present invention an internal locking system for a collapsible container is provided. The internal locking system comprises a plurality of locking plate assemblies for securing the container front panel and door panel to corner posts and a plurality of lever latch assemblies positioned along an internal face of one or more side panels for coupling the one or more side panels to a skirt of the roof panel. 
         [0010]    In an alternate embodiment of the present invention, a slidable locking mechanism for a collapsible shipping container is provided. The slidable locking mechanism comprises a plate, a linkage bar coupled to the plate, a lever arm coupled to the linkage bar and having a hinge point at one end and a removable pin. The linkage bar and plate move in a lateral direction upon rotation of the lever arm about the hinge point. 
         [0011]    In an alternate embodiment of the present invention, a lever latch assembly is provided for a collapsible shipping container. The lever latch assembly comprises a lever arm, a lever latch having a locking tab and also coupled to the lever arm. The lever latch assembly further comprises a base hinge coupled to the lever arm and one or more capture plates having a recessed opening sized to receive the locking tab. 
         [0012]    In yet another embodiment of the present invention, a locking system for a collapsible shipping container is provided. The locking system comprises a plurality of locking plate assemblies for securing the front panel and door panel to corner posts and a plurality of lever latch assemblies positioned along an internal face of one or more side panels for securing the one or more side panels to a skirt of the roof panel. The locking system also comprises a plurality of locking levers having spring loaded locking tabs for securing the container in a collapsed condition. 
         [0013]    In yet another embodiment of the present invention, an external locking mechanism for securing a collapsible shipping container in a collapsed condition is provided. The external locking mechanism comprises one or more locking levers and one or more corner posts having an opening sized to receive a locking tab of the locking lever. 
         [0014]    Additional advantages and features of the present invention will be set forth in part in a description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned from practice of the invention. The instant invention will now be described with particular reference to the accompanying drawings. 
       OBJECTS OF THE PRESENT INVENTION 
       [0015]    An object of this invention is to provide a novel, foldable, enclosed shipping container which is compatible with existing standard non-foldable containers. 
         [0016]    It is another object of this invention to provide a container which does not require assembly and disassembly of loose parts of the container in its normal use. 
         [0017]    Another object and feature of the present invention is to provide a foldable shipping container which includes flat, horizontal, rigid unitary roof and base panels and vertical side panels hingedly connected to adjacent edges of the base panel whereby the side panels can pivot laterally inwardly relative to the roof and base panels during the process of folding the container from an unfolded condition to a folded condition in which the roof panel and base panel end up in close parallel relationship with each other. 
         [0018]    Yet another object of this invention is to provide a container structure of the general character referred to above which includes normally vertical end walls to maintain the roof, base and side panels in their normal positions. 
         [0019]    Still another object of this invention is to provide a container which includes vertical posts at the four corners of the container but which allow for free movement of the panels and their related parts while folding or unfolding the container. 
         [0020]    The foregoing and other objects and features of this invention will be fully understood from the following detailed description of one typical preferred embodiment of the invention throughout which description reference is made to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0021]    The present invention is described in detail below with reference to the attached drawing figures, wherein: 
           [0022]      FIG. 1  is a view of the present invention viewing the door panel and the right side panel. 
           [0023]      FIG. 2  is a view of the present invention viewing the door panel and the left side panel. 
           [0024]      FIG. 3  a view of the present invention viewing the front panel and the left side panel. 
           [0025]      FIG. 4  is a plan view of the top of the roof panel. 
           [0026]      FIG. 5  is a perspective view of the underside of the roof panel. 
           [0027]      FIG. 6  is a view of the inside of the front panel taken along line A-A of  FIG. 1 . 
           [0028]      FIG. 7  is an enlarged view of section B-B of  FIG. 6 . 
           [0029]      FIG. 8  is an enlarged view of section C-C of  FIG. 6 . 
           [0030]      FIG. 9  is a cross sectional view of the front panel taken along line D-D of  FIG. 3 . 
           [0031]      FIG. 10  is a partial view of the underside of the front end of the roof panel. 
           [0032]      FIGS. 11A and 11B  are plan views of the front first hinge members. 
           [0033]      FIG. 12  is a plan view of the front end of the roof panel. 
           [0034]      FIG. 13  is a plan view of the door end of the roof panel. 
           [0035]      FIG. 14  is a partial view of the underside of the door end of the roof panel. 
           [0036]      FIG. 15  is a plan view of the door first hinge members. 
           [0037]      FIG. 16  is a perspective view of the upper side of the left side of the base panel. 
           [0038]      FIG. 17  is a perspective view of the upper side of the right side of the base panel. 
           [0039]      FIG. 18  is a plan view of the front end of the base panel. 
           [0040]      FIGS. 19 ,  20  and  21  are views of base front tangs. 
           [0041]      FIG. 22  is a plan view of the door end of the base panel. 
           [0042]      FIG. 23  is a plan view of the right side door interlock. 
           [0043]      FIG. 24  is a plan view of the left side door interlock. 
           [0044]      FIG. 25  is a view of the base panel hammer locking mechanism and right door interlock. 
           [0045]      FIG. 26  is a view of the base panel hammer locking mechanism and left door interlock. 
           [0046]      FIG. 27  is a plan view of the underside of the base panel. 
           [0047]      FIG. 28  is a plan view of the upper side of the base panel. 
           [0048]      FIG. 29  is a plan view of the external surface of the right side panel. 
           [0049]      FIG. 30  is a cross sectional view of the flanges at the front edge of the right side panel. 
           [0050]      FIG. 31  is a cross sectional view of the flanges at the door edge of the right side panel. 
           [0051]      FIG. 32  is a plan view of the internal surface of the right side panel. 
           [0052]      FIG. 33  is a cross sectional view of a linear spring assembly. 
           [0053]      FIG. 34  is a cross sectional view of the upper end of a linear spring assembly. 
           [0054]      FIG. 35  is a cross sectional view of the lower end of a linear spring assembly. 
           [0055]      FIG. 36  is a plan view of a locking rod assembly in isolation. 
           [0056]      FIG. 37  is a plan view of the external surface of the left side panel. 
           [0057]      FIG. 38  is a cross sectional view of the flanges at the door edge of the left side panel. 
           [0058]      FIG. 39  is a cross sectional view of the flanges at the front. 
           [0059]      FIG. 40  is a plan view of the internal surface of the left side panel. 
           [0060]      FIGS. 41A and 41B  are plan views of the side hinge members. 
           [0061]      FIG. 42  is a plan view of the external surface of the front panel. 
           [0062]      FIGS. 43A and 43B  are plan views of the right and left front access panels. 
           [0063]      FIG. 44  is a plan view of the internal surface of the front panel. 
           [0064]      FIGS. 45A ,  45 B,  45 C and  45 D are views of the front pivot hinge. 
           [0065]      FIG. 46  is an internal view of the front end panel and right access panel. 
           [0066]      FIG. 47  is an enlarged view of section E-E of  FIG. 46 . 
           [0067]      FIG. 48  is an internal view of the front end panel and left access panel. 
           [0068]      FIG. 49  is an enlarged view of section F-F of  FIG. 48 . 
           [0069]      FIGS. 50 ,  51  and  52  are horizontal cross sectional views of the front panel interlocks. 
           [0070]      FIG. 53  is a cross sectional view taken along line H-H of  FIG. 50 . 
           [0071]      FIG. 54  is a cross sectional view of the right side interlock of the front panel. 
           [0072]      FIG. 55  is a cross sectional view taken along line I-I of  FIG. 50 . 
           [0073]      FIG. 56  is a cross sectional view of the left side interlock of the front panel. 
           [0074]      FIG. 57  is a perspective view of the right interlock of the front panel. 
           [0075]      FIG. 58  is an inside view of the right interlock of the front panel. 
           [0076]      FIG. 59  is an external view of the roller arm cover plate of the front right post. 
           [0077]      FIG. 60  is a perspective view of the roller arm cover plate of the front right post. 
           [0078]      FIG. 61  is an end view of the roller arm cover plate of the front right post. 
           [0079]      FIG. 62  is a perspective view of the left interlock of the front panel. 
           [0080]      FIG. 63  is an inside view of the left interlock of the front panel. 
           [0081]      FIG. 64  is an external view of the roller arm cover plate of the front left post. 
           [0082]      FIG. 65  is a perspective view of the roller arm cover plate of the front left post. 
           [0083]      FIG. 66  is an end view of the roller arm cover plate of the front left post. 
           [0084]      FIG. 67  is a perspective view of the front panel and right and left access panels. 
           [0085]      FIG. 68  is a view of a front right access panel hinge. 
           [0086]      FIG. 69  is a plan view of the inner surface of the front right access panel. 
           [0087]      FIG. 70  is a cross sectional view of the front right access panel. 
           [0088]      FIG. 71  is an enlarged view of section K-K of  FIG. 70 . 
           [0089]      FIG. 72  is a view of the slide locking mechanism of the front right access panel. 
           [0090]      FIG. 73  is a perspective view of the upper cap plate of the front right access panel. 
           [0091]      FIG. 74  is a perspective view of the front panel and right and left access panels. 
           [0092]      FIG. 75  is a view of a front left access panel hinge. 
           [0093]      FIG. 76  is a plan view of the inner surface of the front left access panel. 
           [0094]      FIG. 77  is a cross sectional view of the front left access panel. 
           [0095]      FIG. 78  is an enlarged view of section M-M of  FIG. 77 . 
           [0096]      FIG. 79  is a view of the slide locking mechanism of the front left access panel. 
           [0097]      FIG. 80  is a perspective view of the upper cap plate of the front left access panel. 
           [0098]      FIG. 81  is a plan view of the external surface of the door panel. 
           [0099]      FIG. 82  is a top view of the locking bar on the door panel. 
           [0100]      FIG. 83  is a plan view of the locking bar on the door panel. 
           [0101]      FIG. 84  is an internal view of the door end panel and right access panel. 
           [0102]      FIG. 85  is an enlarged view of section P-P of  FIG. 84 . 
           [0103]      FIG. 86  is an internal view of the door end panel and left access panel. 
           [0104]      FIG. 87  is an enlarged view of section Q-Q of  FIG. 86 . 
           [0105]      FIGS. 88A ,  88 B and  88 C are views of the door pivot hinge. 
           [0106]      FIG. 89  is a perspective view of the door panel and right and left access panels. 
           [0107]      FIG. 90  is a perspective view of the door panel and right and left access panels. 
           [0108]      FIG. 91  is a plan view of the external surface of the door right access panel. 
           [0109]      FIG. 92  is a plan view of the external surface of the door left access panel. 
           [0110]      FIG. 93  is a view of the front face of the door right post locking tang. 
           [0111]      FIG. 94  is a view of the door face of the door right post locking tang. 
           [0112]      FIG. 95  is a view of the front face of the door left post locking tang. 
           [0113]      FIG. 96  is a view of the door face of the door left post locking tang. 
           [0114]      FIG. 97  is a view of the door right post roller arm. 
           [0115]      FIG. 98  is a view of the door left post roller arm. 
           [0116]      FIG. 99  is a plan view of the inner surface of the door right access panel. 
           [0117]      FIG. 100  is a cross sectional view of the door right access panel. 
           [0118]      FIG. 101  is an enlarged view of section T-T of  FIG. 100 . 
           [0119]      FIG. 102  is a view of a door right access panel hinge. 
           [0120]      FIG. 103  is a view of the slide locking mechanism of the door right access panel. 
           [0121]      FIG. 104  is a perspective view of the upper cap plate of the door right access panel. 
           [0122]      FIG. 105  is a plan view of the inner surface of the door left access panel. 
           [0123]      FIG. 106  is a cross sectional view of the door left access panel. 
           [0124]      FIG. 107  is an enlarged view of section V-V of  FIG. 106 . 
           [0125]      FIG. 108  is a view of a door left access panel hinge. 
           [0126]      FIG. 109  is a view of the slide locking mechanism of the door left access panel. 
           [0127]      FIG. 110  is a perspective view of the upper cap plate of the door left access panel. 
           [0128]      FIG. 111  is a perspective view of the front end of the folded container. 
           [0129]      FIG. 112  is a perspective view of the door end of the folded container. 
           [0130]      FIG. 113  is a schematic plan view showing the base panel with the side panels folded down and laying on top of it. 
           [0131]      FIG. 114  is schematic cross sectional view taken along line  114 - 114  of  FIG. 113 . 
           [0132]      FIG. 115  shows a schematic side view of the base panel with the side panels in an unfolded position. 
           [0133]      FIG. 116  is a schematic transverse cross-sectional view through the base panel and the side panels adjacent one of the side hinge members and linear spring assemblies. 
           [0134]      FIG. 117  is a view of one of the hinge pin torsion spring assemblies secured to the base panel and a side panel. 
           [0135]      FIG. 118  is a view of a hinge pin of one of the hinge pin torsion spring assemblies. 
           [0136]      FIG. 119  is a view of a Torsion spring of one of the hinge pin torsion spring assemblies. 
           [0137]      FIG. 120  is a view of a hinge pin torsion spring fully assembled. 
           [0138]      FIG. 121  is a view showing a hinge pin of a hinge pin torsion spring received within a hole in a base hinge member. 
           [0139]      FIG. 122  is a view showing a hinge pin of a hinge pin torsion spring received within a hole in another base hinge member. 
           [0140]      FIG. 123  is an elevation view of an internal locking mechanism for a collapsible container. 
           [0141]      FIG. 124  is a perspective view of the internal locking mechanism of  FIG. 123 . 
           [0142]      FIG. 125  is an alternate perspective view of the internal locking mechanism of  FIG. 123 . 
           [0143]      FIG. 126  is a partial perspective of an alternate internal locking mechanism. 
           [0144]      FIG. 127  is a partial perspective view of the alternate internal locking mechanism of  FIG. 126 . 
           [0145]      FIG. 128  is a perspective view of a capture plate portion of the alternate internal locking mechanism of  FIG. 126 . 
           [0146]      FIG. 129  is a perspective view of the alternate internal locking mechanism of  FIG. 126 . 
           [0147]      FIG. 130  is a partial perspective view of an external locking mechanism for a collapsed container. 
           [0148]      FIG. 131  is a detailed perspective view of the external locking mechanism of  FIG. 130 . 
           [0149]      FIG. 132  is a perspective view of the locking lever of the external locking mechanism. 
           [0150]      FIG. 133  is a perspective view of the lever latch assembly for the collapsible shipping container in accordance with an alternate embodiment of the present invention. 
           [0151]      FIG. 134  is an enlarged perspective view of the locking tab coupled to the lever latch assembly of  FIG. 133 . 
           [0152]      FIG. 135  is a perspective view of the lever latch assembly of  FIG. 133  positioned within the collapsible shipping container. 
           [0153]      FIG. 136  is a frontal view of the locking tab decoupled from the lever latch assembly of  FIG. 133 . 
       
    
    
     DETAILED DESCRIPTION 
       [0154]    As shown in  FIG. 1  the preferred embodiment of the foldable container  10  of the present invention includes a roof panel  11 , a door panel, and a right side panel  14 , and as shown in  FIG. 2  the foldable container  10  further includes a left side panel  16 . Collectively, the right side panel  14  and the left side panel  16  may be referred to herein as the “side panels”, or individually either may be referred to as a “side panel”. As shown in  FIG. 3 , the foldable container further includes a base panel  17 , and a front panel  12  opposite the door panel  18 . 
         [0155]    Referring back to  FIG. 1 , the roof panel  11  includes a roof right edge  19 , a roof left edge  20 , a roof door edge  21 , and a roof front edge  22 . As shown in  FIGS. 1 and 3 , the roof panel  11  includes four standard corner fittings  36   a ,  36   b ,  36   c ,  36   d  of the type known in the art for lifting the foldable container  10  (as with a spreader), or for securing the foldable container  10  to another container which may be stacked on top of it. One corner fitting  36   a ,  36   b ,  36   c ,  36   d  is located on the roof panel  11  adjacent each end  13   a ,  13   b  of the roof front edge  22 , and adjacent each end  15   a ,  15   b  of the roof door edge  21  thereof, in accordance with the international standards. 
         [0156]    As shown in  FIGS. 4 &amp; 5 , a hollow, rectangular roof right beam  600  extends along the right edge  19  of the roof panel  11  from the corner fitting  36   a  on the front edge  22  adjacent the roof right edge  19  of the roof panel  11  to the corner fitting  36   b  on the roof door edge  21  adjacent the roof right edge  19  of the roof panel  11 . The roof right beam  600  is continuous except for the interruptions where the roof lifting beams  606 ,  607  pass through the roof right beam  600 . The end  601  of the roof right beam  600  adjacent the roof front edge  22  is rigidly attached to the adjacent corner fitting  36   a , preferably by welding, and the end  602  of the roof right beam  600  adjacent the roof door edge  21  is rigidly attached to the adjacent corner fitting  36   b , preferably by welding. Likewise, the roof right beam  600  is preferably welded to the roof lifting beams  606 ,  607  where they pass through the roof right beam  600 . As shown in  FIGS. 6 &amp; 7 , the roof right beam  600  is hollow and extends downwardly from the roof right edge  19  a distance of about four inches. 
         [0157]    As shown in  FIGS. 4 &amp; 8 , a hollow, rectangular roof left beam  603  extends along the roof left edge  20  of the roof panel  11  from the corner fitting  36   c  on the front edge  22  adjacent the roof left edge  20  of the roof panel  11  to the corner fitting  36   d  on the roof door edge  21  adjacent the roof left edge  20  of the roof panel  11 . The roof left beam  603  is continuous except for the interruptions where the roof lifting beams  606 ,  607  pass through the roof left beam  603 . The end  604  of the roof left beam  603  adjacent the roof front edge  22  is rigidly attached to the adjacent corner fitting  36   c , preferably by welding, and the end  605  of the roof left beam  603  adjacent the roof door edge  21  is rigidly attached to the adjacent corner fitting  36   d , preferably by welding. Likewise, the roof left beam  603  is preferably welded to the roof lifting beams  606 ,  607  where they pass through the roof left beam  603 . The roof left beam  603  is hollow and extends downwardly from the roof left edge  20  a distance of about four inches. The lower face  608  of the roof right beam  600  and the lower face  609  of the roof left beam  603  each contain a plurality of locking bolt holes  610 , the purpose of which is described below. 
         [0158]    As shown in  FIG. 1 , along the roof right edge  19  of the roof panel  11 , a right skirt  23  extends downwardly therefrom a length of about twelve inches, and as shown in  FIG. 2 , along the roof left edge  20  of the roof panel  11 , a left skirt  24  also extends downwardly therefrom a length of about twelve inches. 
         [0159]    The upper exterior surface  25  of the roof panel  11  is made from corrugated metal, preferably CorTen® steel. As shown in  FIGS. 3 &amp; 9 , the roof panel  11  includes a hollow, rectangular roof front beam  1000  that has one end  611  adjacent the roof right edge  19  and another end  612  adjacent the roof left edge  20 . The roof front beam  1000  extends along the roof front edge  22  of the roof panel  11 , and extends downwardly therefrom a distance of about four inches. More specifically, the rectangular roof front beam  1000  extends from the corner fitting  36   a  on the roof front edge  22  to the other corner fitting  36   c  on the roof front edge  22 . The end  611  of the front beam  1000  adjacent the corner fitting  36   a  is rigidly attached thereto, preferably by welding, and the end  612  of the roof front beam  1000  adjacent the corner fitting  36   c  is rigidly attached thereto, also preferably by welding. As shown in  FIG. 10 , the roof panel  11  further includes two front first hinge sets  613 ,  614 . The front first hinge set  613  includes two front first hinge members  31   a ,  31   b , each rigidly connected to the lower surface  615  of the corner fitting  36   a  adjacent the roof front edge  22  and the roof right edge  19 , preferably by welding. The front first hinge set  614  likewise includes two front first hinge members  31   c ,  31   d , each rigidly connected to the lower surface  616  of the corner fitting  36   c  adjacent the roof front edge  22  and the roof left edge  20 , preferably by welding. The front first hinge members  31   a ,  31   b , of the front first hinge set  613  adjacent the roof right edge  19  are fixed in spaced relation to each other for receiving a front hinge pivot  617 , as described in greater detail below, and the front first hinge members  31   c ,  31   d , of the front first hinge set  614  adjacent the roof left edge  20  are fixed in spaced relation to each other for receiving another front hinge pivot  618 , as described in greater detail below. A representative front first hinge member  31  is shown in isolation in  FIGS. 11A and 11B . Each front first hinge member has a front hinge edge  622 , front pivot hole  619 , a front bolt hole  620 , and a lug receiving slot  621 . The purpose of each of these features is described in greater detail below. 
         [0160]    As shown in  FIG. 5 , a front hinge plate  623 ,  624 , having a length substantially equal to the length of the front hinge edge  622  of the first hinge members  31   a ,  31   b ,  31   c ,  31   d , is fixedly secured between immediately adjacent first hinge members  31   a ,  31   b , and  31   c ,  31   d , preferably by welding along the length of each front hinge edge  622 . The combination of front hinge plate  623  and the first front hinge members  31   a ,  31   b  secured to it, form a roof front interlock  625  adjacent the roof right edge  19  of the roof panel  11 , and the combination of front hinge plate  624  and the first front hinge members secured to it  31   c ,  31   d , form a roof front interlock  626  secured to the corner fitting  36   c  adjacent the roof left edge  20  of the roof panel  11 . Each front roof interlock  625 ,  626  has a lower slot  627 ,  628  for receiving a large tang extending from the base panel  17  when the folding container  10  is in its fully folded condition, as described below. 
         [0161]    Referring again to  FIG. 5 , a front shelf beam  629  extends between the front first hinge sets  613 ,  614 , and the end  630  of the front shelf beam  629  adjacent the roof right edge  19  is fixedly secured to the inward front first hinge member  31   b , preferably by welding, such that the lower edge  632  of the front shelf beam  629  is approximately aligned with the lower edge  633  of the front hinge plate  623 . Likewise, the end  631  of the front shelf beam  629  adjacent the roof left edge  20  is fixedly secured to the inward front first hinge member  31   d , preferably by welding, such that the lower edge  632  of the front shelf beam  629  is approximately aligned with the lower edge  634  of the front hinge plate  624 . As shown in  FIG. 12 , mounted to the front shelf beam  629  adjacent each roof front interlock  625 ,  626 , and aligned with the bolt holes  620  therein, are hammer lock retainers  76 ,  77 . A hammer locking mechanism  78 ,  79 , including a slide hammer  80 ,  81 , and a hammer locking bolt  82 ,  83  is slideably secured to each of the hammer lock retainers  76 ,  77 , such that each hammer locking mechanism  78 ,  79  is positionable by use of one of the slide hammers  80 ,  81 , slideably mounted on one of the hammer locking bolts  82 ,  83 , between an unlocked position in which the respective hammer locking bolt  82 ,  83 , is in a retracted position substantially outside of the roof front interlock  625 ,  626 , immediately adjacent thereto, and a locked position in which the respective hammer locking bolt  82 ,  83  extends through the bolt holes  620  of the roof front interlock  625 ,  626  immediately adjacent thereto. 
         [0162]    As shown in  FIG. 13 , the roof panel  11  includes a hollow, rectangular roof door beam  635  that extends along the roof door edge  21  of the roof panel  11 , and extends downwardly therefrom a distance of about four inches. The hollow, rectangular roof door beam  635  extends from the corner fitting  36   b  on the roof door edge  21  adjacent the roof right edge  19  to the corner fitting  36   d  on the roof door edge  21  adjacent the roof left edge  20 . The end  636  of the roof door beam  635  adjacent the roof right edge  19  is rigidly attached to the corner fitting  36   b  adjacent the roof right edge  19 , preferably by welding, and the end  637  of the roof door beam  635  adjacent the roof left edge  20  is rigidly attached to the corner fitting  36   d  adjacent the roof left edge  20 , preferably by welding. The exterior vertical face  638  of the rectangular roof door beam  635  includes a plurality of lock hasps  90 , preferably four, rigidly secured thereto for receiving the upper ends  91  of each of the locking rods  92  of the door latch assembly  639  as described below. The roof panel  11  further includes a pair of locking straps  640 , removably secured thereto adjacent the lock hasps  90 . Each locking strap  640  is preferably made of steel, and has a shape of similar to that of an “I”. Adjacent each end of each locking strap  640  is a bolt hole  645 ,  646 , for receiving one of the strap bolts  647  that are used to removably secure the locking strap  640  to the container  10  when the container  10  is in its folded, and unfolded, condition, as described below. When the container  10  is in its unfolded condition, the strap bolts  647  are received within stored strap bolt holes  648 , not shown, that secure the locking strap  640  to the roof panel  11 . The roof panel  11  also includes two upper active strap bolt holes  649 , not shown, for use when the container  10  is in its folded condition, as described below. A plurality, and preferably four (4), pairs of upper door stop receivers  650  are welded to the exterior vertical face  638  of the rectangular roof door beam  635  adjacent the lock hasps  90 , the upper door stop receivers  650  of each such pair being in spaced relation to each other. Each of the upper active strap bolt holes  649  is aligned with one pair of upper door stop receivers  650 . As those skilled in the art will readily appreciate, when a locking strap  640  is secured by a strap bolt  647  to one of the upper active strap bolt holes  649 , the “T” at one end  645  of the locking strap  640  rests on one pair of the door stop receivers when the locking strap  640  is supporting a load. Accordingly, the thickness of the each locking strap  640 , and the load carrying ability of the upper door stop receivers  650  on which the locking strap  640  rests, must be sufficient to support, at a minimum, a weight equal to that of the entire container  10  when the container  10  is empty, which, in turn, depends on the material from which the container  10 , the locking straps  640 , and the upper door stop receivers  650  are made, as well as the strength of the welds securing the upper door stop receivers  650  to the roof door beam  635 . 
         [0163]    As shown in  FIG. 14 , the roof panel  11  further includes two door first hinge sets  651 ,  652 . The door first hinge set  651  includes two door first hinge members  653   a ,  653   b , each rigidly connected to the lower surface  654  of the corner fitting  36   b  adjacent the roof door edge  21  and the roof right edge  19 , preferably by welding. The door first hinge set  652  likewise includes two door first hinge members  653   c ,  653   d , each rigidly connected to the lower surface  655  of the corner fitting  36   d  adjacent the roof door edge  21  and the roof left edge  20 , preferably by welding. The door first hinge members  653   a ,  653   b , of the door first hinge set  651  adjacent the roof right edge  19  are fixed in spaced relation to each other for receiving a door hinge pivot  656 , as described in greater detail below, and the door first hinge members  653   c ,  653   d , of the door first hinge set  652  adjacent the roof left edge  20  are fixed in spaced relation to each other for receiving a front hinge pivot  666 , as described in greater detail below. A representative door first hinge member  653  is shown in isolation in  FIG. 15 . Each door first hinge member  653  has a door hinge edge  667 , door pivot hole  668 , and a door lug receiving slot  669 . The purpose of each of these features is described in greater detail below. 
         [0164]    Referring again to  FIG. 13 , a door hinge plate  670 ,  671 , having a length substantially equal to the length of the door hinge edge  667  of the door first hinge members  653   a ,  653   b ,  653   c ,  653   d , is fixedly secured between immediately adjacent door first hinge members  653   a ,  653   b ,  653   c ,  653   d , preferably by welding along the length of each door hinge edge  667 . 
         [0165]    As shown in  FIGS. 16 &amp; 17 , the base panel  17  includes a base right edge  99 , a base left edge  100 , a base front edge  101 , and a base door edge  102 . The base panel  17  includes four standard corner fittings  36   e ,  36   f ,  36   g ,  36   h  of the type known in the art for securing the container  10  to another container on which it may be stacked. One corner fitting  36   e ,  36   f ,  36   g ,  36   h  is located on the base panel  17  adjacent each end of the base front edge  101 , and adjacent each end of the base door edge  102 , in accordance with the international standards. 
         [0166]    As shown in  FIG. 17 , a hollow, rectangular base right beam  672  extends along the base right edge  99  of the base panel  17  from the corner fitting  36   e  on the base front edge  101  adjacent the base right edge  99  of the base panel  17  to the corner fitting  36   f  on the door edge  102  adjacent the right edge  99  of the base panel  17 . Each end  673 ,  674  of the base right beam  672  is rigidly attached to the adjacent corner fitting  36   e ,  36   f , preferably by welding. The base right beam  672  comprises base right beam lower portions  675 ,  676  which extend upwardly from the base right edge  99  a distance of about eight inches, and a base right beam upper portion  677  that extends further up from the base right edge  99  to a height of about twelve inches. Referring again to  FIG. 16 , a plurality of cable anchors  679 , the purpose of which is described in greater detail below, are secured to base right beam  672  in spaced relation to each other adjacent the upper edge  680  of the base right beam upper portion  677 . Sloped right transition portions  103   a ,  103   b , extend between each end  681 ,  682  of the base right beam upper portion  677  to the base right beam lower portions  675 ,  676  adjacent thereto. The top edge  683 ,  684  of each of the base right beam lower portions  675 ,  676 , is capped with a guide rail  401 ,  402 , preferably made of stainless steel. The purpose of the guide rails  401 ,  402 , and the purpose of the base right beam lower portions  675 ,  676  of the base right beam  672 , are discussed below. 
         [0167]    As shown in  FIG. 16 , a hollow, rectangular base left beam  685  extends along the base left edge  100  of the base panel  17  from the corner fitting  36   g  on the base front edge  101  adjacent the base left edge  100  of the base panel  17  to the corner fitting  36   h  on the door edge  102  adjacent the left edge  100  of the base panel  17 . Each end  686 ,  687  of the base left beam  685  is rigidly attached to the adjacent corner fitting  36   g ,  36   h , preferably by welding. The base left beam  685  comprises base left beam lower portions  688 ,  689  which extend upwardly from the base left edge  100  a distance of about eight inches, and a base left beam upper portion  690  that extends further up from the base left edge  100  to a height of about twelve inches. Referring again to  FIG. 17 , a plurality of cable anchors  691 , the purpose of which is described in greater detail below, are secured to base left beam  685  in spaced relation to each other adjacent the upper edge  692  of the base right beam upper portion  690 . Sloped left transition portions  104   a ,  104   b , extend between each end  693 ,  694  of the base left beam upper portion  690  to the base left beam lower portions  688 ,  689  adjacent thereto. The top edge  695 ,  696  of each of the base left beam lower portions  688 ,  689 , is capped with a guide rail  403 ,  404 , preferably made of stainless steel. The purposes of the guide rails  403 ,  404 , and the purpose of the base left beam lower portions  688 ,  689  of the base left beam  685 , are discussed below. 
         [0168]    As shown in  FIG. 18 , extending upward from each corner fitting  36   e ,  36   g  on the base panel  17  adjacent the front edge  101  is a base front tang  108   a ,  108   b . A representative base front tang  108  is shown in  FIGS. 19-21 . Each of the base front tang  108  has a rectangular base portion  700 , and a locking portion  702  extending therefrom. The locking portion  702  of each base front tang  108  includes an upper tapered locking hole  110  and a lower tapered locking hole  704 , each of which is substantially parallel to the front edge  101  of the base panel  17 , and each of which is sized and located so as to be able to receive therein one of the hammer locking bolts of the front panel  12 , as discussed below. 
         [0169]    Referring back to  FIG. 18 , the base portion  700  of each base front tang  108   a ,  108   b  is fixedly secured to the corner fitting  36   e ,  36   g  it extends from, preferably by welding. The base panel  17  includes a hollow, rectangular base front beam  706  that extends between the base portions  700  of the base front tangs  108   a ,  108   b . Each end  707 ,  708  of the base front beam  706  is rigidly attached to the base portion  700  of the base front tang  108   a ,  108   b  immediately adjacent thereto, preferably by welding. 
         [0170]    As shown in  FIG. 22 , the base panel  17  includes a hollow, rectangular base door beam  709  that extends along the door edge  102  of the base panel  17 , and extends upwardly therefrom a distance of about four inches. The base door beam  109  extends from the corner fitting  36   f  on the door edge  102  adjacent the right edge  99  of the base panel  17  to the corner fitting  36   h  on the door edge  102  adjacent the left edge  100  of the base panel  17 . Each end  710 , 711  of the base door beam  709  is rigidly attached to the adjacent corner fitting  36   f ,  36   h , preferably by welding. The exterior vertical face  712  of the base door beam  709  includes a plurality of lock hasps  90   b , preferably four, rigidly secured thereto for receiving lower end  713  of each of the locking rods  92  of the door latch assembly as described below. The door end of the base panel  17  further includes at least two pairs of lower door stop receivers  714  that are welded to the exterior vertical face  712  of the rectangular base door beam  709  adjacent the lock hasps  90   b  closest to the corner fittings  36   f ,  36   h , the lower door stop receivers  714  of each such pair being in spaced relation to each other. A lower active strap bolt hole  715  is aligned with each pair of lower door stop receivers  714 . As those skilled in the art will readily appreciate, when a locking strap  640  is secured by a strap bolt  647  to one of the lower active strap bolt holes  715 , the inverted “T” at one end of the locking strap  640  supports the load placed on it by the pair of door stop receivers  714  within which the locking strap  640  is received. Accordingly, the load carrying ability of the lower door stop receivers  714  which rest on the locking strap  640  must be sufficient to support, at a minimum, a weight equal to that of the entire container  10  when the container  10  is empty, which, in addition to those factors previously stated, depends on the material from which the lower door stop receivers  714  are made, as well as the strength of the welds securing the lower door stop receivers  714  to the base door beam  709 . 
         [0171]    Extending upwardly from each of the corner fittings  36   f ,  36   h  on the door edge  102  of the base panel  17  is a door interlock  116 ,  117 . As shown in  FIGS. 23 &amp; 24 , each door interlock  116 ,  117  has four walls: a door wall  718 ,  719  which faces the door edge  102  of the base panel  17 , a front wall  720 ,  721  which faces the front edge  101  of the base panel  17  and is parallel to, and in spaced relation with, the door wall  718 ,  719 , an inner wall  722 ,  723  that is perpendicular to the door wall  718 ,  719  and the front wall  720 ,  721  and faces the inner wall  720 ,  721  of the other door interlock  116 ,  117 , and an outer wall  724 ,  725  which is parallel to, and in spaced relation with, the inner wall  720 ,  721 . The door interlock  116  extending from the corner fitting  36   f  on the door edge  102  adjacent the base right beam  672  is rigidly attached to that corner fitting  36   f  and the door end  674  of the base right beam  672 , preferably by welding. Likewise, the door interlock  117  extending from the corner fitting  36   h  on the door edge  102  adjacent the base left beam  685  is rigidly attached to that corner fitting  36   h  and the door end  687  of the base left beam  685 , also preferably by welding. 
         [0172]    Each door interlock  116 ,  117  has a first bolt hole  726 ,  727  in the door wall  718 ,  719  thereof, and a second bolt hole  728 ,  729  in the front wall  720 ,  721  thereof aligned with the first bolt hole  726 ,  727  of the same door interlock  116 ,  117 . The diameter of the second bolt holes  728 ,  729  is preferably slightly larger than the diameter of the first bolt holes  726 ,  727  for reasons discussed below. 
         [0173]    As shown in  FIGS. 16 &amp; 17 , the lower portion  676  of the base right beam  672  and the lower portion  689  of the base left beam  685  each include a recessed portion  730 ,  731  immediately adjacent the door edge  102  of the base panel  17 . As shown in greater detail in  FIG. 25 , hammer lock retainers  732  are mounted in the recessed portion  730  of the lower portion  676  of the base right beam  672  adjacent the door interlock  116  and aligned with the bolt holes  726 ,  728  therein. Likewise, as shown in greater detail in  FIG. 26 , hammer lock retainers  733  are mounted in the recessed portion  731  of the lower portion  689  of the base left beam  685  adjacent the door interlock  117  and aligned with the bolt holes  727 ,  729  therein. As shown in  FIG. 25 , a hammer locking mechanism  78  is slideably secured to the hammer lock retainers  732  in the recessed portion  730  of the lower portion of the base right beam  676 . The hammer locking mechanism  78  therein includes a slide hammer  79  slideably mounted on a hammer locking bolt  80 . As those skilled in the art will readily appreciate, by sliding the slide hammer  79  against one of the hammer stops  734 ,  735 , the hammer locking bolt  80  can be selectively positioned at an unlocked position in which the hammer locking bolt  80  is in a retracted position substantially outside of the interlock  116  immediately adjacent thereto, and a locked position in which the locking bolt  80  extends through the bolt holes  726 ,  728  of the interlock  116  immediately adjacent thereto. 
         [0174]    Likewise, as shown in  FIG. 26 , a hammer locking mechanism  736  is slideably secured to the hammer lock retainers  733  in the recessed portion  731  of the lower portion of the base left beam  689 . The hammer locking mechanism  736  therein includes a slide hammer  737  slideably mounted on a hammer locking bolt  738 . As those skilled in the art will readily appreciate, by sliding the slide hammer  737  against one of the hammer stops  739 ,  740 , the hammer locking bolt  738  can be selectively positioned at an unlocked position in which the hammer locking bolt  738  is in a retracted position substantially outside of the interlock  117  immediately adjacent thereto, and a locked position in which the locking bolt  738  extends through the bolt holes  727 ,  729  of the interlock  117  immediately adjacent thereto. 
         [0175]    Referring again to  FIG. 16 , the base right beam  672  includes a plurality of right hinge recesses  741 in spaced relation to each other along the length of the base right beam  672 , and a base right hinge member  106  is fixedly secured within each of the right hinge recesses  741 . A close-up view exemplary of a base right hinge member  106  is shown in  FIG. 41 . Additionally, the base right beam  672  preferably includes a plurality of small recesses  742  spaced along the length thereof, within which tie-down bars  743  are rigidly mounted for receiving tie-down straps of the type known in the art for securing the contents of the container  10  during shipping. 
         [0176]    As shown in  FIG. 17 , the base left beam  685  includes a plurality of left hinge recesses  744  in spaced relation to each other along the length of the base left beam  685 , and a base left hinge member  745  is fixedly secured within each of the left hinge recesses  744 . The base left hinge member  745  is similar in design and function to the base right hinge member  106  shown in  FIG. 41 . Additionally, the base left beam  685  preferably includes a plurality of small recesses  746  spaced along the length thereof, within which tie-down bars  747  are rigidly mounted for receiving tie-down straps of the type known in the art for securing the contents of the container  10  during shipping. 
         [0177]    As shown in  FIGS. 3 ,  27  &amp;  28 , a plurality of base support beams  748  are secured to the base right beam  672  and the base left beam  685  and span therebetween to add structural rigidity to the floor  749  of the base panel  17 . Adjacent the base front edge  101 , the base panel  17  includes a “gooseneck tunnel”  750  of the type known in the art. As shown in  FIG. 3 , a pair of hollow, base lifting beams  751 ,  752  are secured to the base right beam  672  and the base left beam  685 , preferably by welding, and span therebetween to add structural rigidity to the base panel  17  and to provide means for lifting the foldable container  10  by use of a fork lift if desired. The floor  749  of the base panel  17  is preferably made of a sheet of Cor-Ten steel extending from the base right beam  672  to the base left beam  685 , and from the base front beam  706  to the base door beam  709 . The floor  749  is welded about its entire periphery to the right beam  672 , the base left beam  685 , the base front beam  706  and the base door beam  709 , to make the base panel  17  watertight with respect to the floor  749 . The floor  749  is also welded to the base support beams  748  and the base lifting beams  751 ,  752  for structural purposes. Preferably, the floor  749  is covered with plywood, or a similarly suitable flooring material. 
         [0178]    As shown in  FIG. 29 , the right side panel  14  includes a top edge  118 , a bottom edge  119 , a front edge  120  and a door edge  121 . Extending along the top edge  118  of the right side panel  14  along the length thereof is a right upper cap plate  122  having a front end  754 , a door end  755 , and a right roof flange  756  extending from the front end  754  to the door end  755 . Extending along the bottom edge  119  of the right side panel  14  along the length thereof is a right compound beam  757  that has a front end  758  and a door end  759 . The right compound beam  757  comprises a right upper horizontal beam  123   c  rigidly connected to two right lower horizontal beams  123   a ,  123   b , preferably by welding. As shown in  FIGS. 16 &amp; 29 , the lower edge  760  of the right compound beam  757  has a profile that matches the profile formed by the upper edge  680  of the base right beam upper portion  677 , the top edges  683 ,  684  of the base right beam lower portions  675 ,  676 , and the sloped right transition portions  103   a ,  103   b  of the base panel  17 , to provide mating sealing surfaces when the container  10  is in its unfolded condition. 
         [0179]    As shown in  FIG. 29 , a right front member  761  extends from the front end  754  of the right upper cap plate  122  to the front end  758  of the right compound beam  757 , and is fixedly secured to the front ends  754 ,  758 , preferably by welding. As shown in  FIG. 30 , the right front member  761  includes a long flange  762  and a short flange  763 , each of which extends along the length of the right front member  761  and towards the front edge  101  of the base panel  17 . As shown in  FIG. 29 , a right door member  764  extends from the door end  755  of the right upper cap plate  122  to the door end  759  of the right compound beam  757 , and is fixedly secured to the door ends  755 ,  759 , preferably by welding. The right door member  764  includes a long flange  765  and a short flange  766 , each of which extends along the length of the right door member  764  and towards the door edge  102  of the base panel  17 , as shown in  FIG. 31 . The right front member  761  and the right door member  764  each have a plurality, and preferably three, right side bolt holes  767 ,  768  for receiving locking bolts as described in greater detail below. 
         [0180]    Referring again to  FIG. 29 , corrugated sheet metal  769  extends from the right upper cap plate  122  to the right compound beam  757  along the entire length thereof, and from the right front member  761  to the right door member  764  along the entire length thereof. The corrugated sheet metal  769  is welded along its entire perimeter to the immediately adjacent right upper cap plate  122 , right front member  761 , right compound beam  757 , and right door member  764 . As shown in  FIG. 1 , the corrugated sheet metal  769  is welded to the right front member  761  and the right door member  764  such that the long flanges  762 ,  765  are visible from the exterior of the container  10  in its unfolded condition. 
         [0181]    As shown in  FIG. 29 , extending downwardly from the bottom edge  119  of the right side panel  14  are a plurality of right side hinge members  125 , each of which is fixedly secured to the right compound beam  757 . Each right side hinge member  125  is rotatably connected to one of the base right hinge members  106  of the base panel  17  by one or more hinge pins  770 , so as to allow the right side panel  14  to rotate relative to the base panel  17 . As shown in  FIG. 32 , a plurality of linear spring assemblies  771  are mounted to the right side panel  14  within corrugations  772  of the corrugated sheet metal  769 , as are a plurality of locking bolt assemblies  773 . 
         [0182]    As shown in  FIGS. 33-35 , each right side linear spring assembly  771 , includes a tube  802  fixedly secured to a tube base  803  mounted within the right upper horizontal beam  123   c . A compression spring  804 , cable  805 , and plunger  806  are received within each tube  802 . The upper end of the cable  805  is secured to the plunger  806 . Each plunger  806  has a plunger foot  808  which is in contact with the upper end  807  of the compression spring  804 , and each plunger foot  808  has a diameter  809  that is at least as large as the inner diameter  810  of the compression spring  804  to prevent the plunger  806  from sliding through the compression spring  804 . Referring again to  FIG. 32 , a tube shield  811  secured to the corrugated sheet metal  769  retains and protects the upper end  811   a  of each tube  802 , as well as the plunger  806  attached thereto, during use of the container  10 . 
         [0183]    As shown in  FIG. 35 , each tube base  803  includes a cable channel  812  within which is rotatably mounted a cable pulley  813  adjacent the lower edge  814  thereof. The upper end  815  of each tube base  803  has a diameter  816  that is at least as large as the inner diameter  810  of the compression spring  804  to support the compression spring  804  against the force applied by the plunger foot  808  at the upper end  807  of the compression spring  804 . In addition, the upper end  815  of each tube base  803  has an opening  817  through which the cable  805  passes, and the opening  817  has a diameter  818  that is smaller than the inner diameter  810  of the compression spring  804  to prevent the compression spring  804  from sliding therethrough. The lower end  819  of each cable  805  is attached to one of the cable anchors  679  secured to the base right beam upper portion  677  adjacent the upper edge  680  thereof. It is to be understood that when the container  10  is in the unfolded condition, each cable anchor  679  is vertically aligned with the tube  802  that contains the cable  805  that is attached to such cable anchor  679 . 
         [0184]    As shown in  FIG. 32 , the plurality of locking bolt assemblies  773  are mounted to the right side panel  14  within the corrugations  772  of the corrugated sheet metal  769 . As shown in  FIGS. 32 &amp; 36 , each locking bolt assembly  773  includes a pivot anchor  820 , a positioning lever  821  with a handle  822  attached thereto, a locking bolt  823 , a locking bolt guide  824 , and a pair of links  825  pivotably connecting the lower end  826  of the locking bolt  823  to the positioning lever  821 . Each of the locking bolt guides  824  includes a guide tube  827  that extends through, and is fixedly secured to the right upper cap plate  122 , and one locking bolt  823  is slideably received within each of the guide tubes  827 . Each pivot anchor  820  is fixedly secured to the corrugated sheet metal  769 , and each positioning lever  821  is pivotably connected to one of the pivot anchors  820 . 
         [0185]    As those skilled in the art will readily appreciate, each of the locking bolt assemblies  773  so described is selectively positionable between a first position in which the locking bolt  823  is received within one of the locking bolt holes  610  in the lower face  608  of the roof right beam  600 , when the container  10  is in the unfolded condition, and a second position in which the locking bolt  823  is fully withdrawn from that locking bolt hole  610 . 
         [0186]    As shown in  FIG. 37 , the left side panel  16  includes a top edge  774 , a bottom edge  775 , a front edge  776  and a door edge  777 . Extending along the top edge  774  of the left side panel  16  along the length thereof is a left upper cap plate  778  having a front end  779 , a door end  780   a , and a left roof flange  780   b  extending from the front end  779  to the door end  780 . Extending along the bottom edge  775  of the left side panel  16  along the length thereof is a left compound beam  781  that has a front end  782  and a door end  783 . The left compound beam  781  comprises a left upper horizontal beam  784  rigidly connected to two left lower horizontal beams  785 ,  786 , preferably by welding. As shown in  FIGS. 17 &amp; 37 , the lower edge  787  of the left compound beam  781  has a profile that matches the profile formed by the upper edge  692  of the base left beam upper portion  677 , the top edges  695 ,  696  of the base left beam lower portions  688 ,  689 , and the sloped left transition portions  104   a ,  104   b  of the base panel  17 , to provide mating sealing surfaces when the container  10  is in its unfolded condition. 
         [0187]    As shown in  FIG. 37 , a left front member  788  extends from the front end  779  of the left upper cap plate  778  to the front end  782  of the left compound beam  781 , and is fixedly secured to the front ends  779 ,  782 , preferably by welding. As shown in  FIG. 38 , the left front member  788  includes a long flange  789  and a short flange  790 , each of which extends along the length of the left front member  788  and towards the front edge  101  of the base panel  17 . Referring again to  FIG. 37 , a left door member  791  extends from the door end  780   a  of the left upper cap plate  778  to the door end  783  of the left compound beam  781 , and is fixedly secured to the door ends  780 ,  783 , preferably by welding. As shown in  FIG. 39 , the left door member  791  includes a long flange  792  and a short flange  793 , each of which extends along the length of the left door member  791  and towards the door edge  102  of the base panel  17 . The left front member  788  and the left door member  791  each have a plurality, and preferably three, left side bolt holes  794 ,  795  for receiving locking bolts as described in greater detail below. 
         [0188]    As shown in  FIG. 40 , corrugated sheet metal  796  extends from the left upper cap plate  778  to the left compound beam  781  along the entire length thereof, and from the left front member  788  to the right door member  791  along the entire length thereof. The corrugated sheet metal  796  is welded along its entire perimeter to the immediately adjacent left upper cap plate  778 , left front member  788 , left compound beam  781 , and left door member  791 . As shown in  FIG. 2 , the corrugated sheet metal  796  is welded to the left front member  788  and the left door member  791  such that the long flanges  789 ,  792  are visible from the exterior of the container  10  in its unfolded condition. 
         [0189]    As shown in  FIG. 37 , extending downwardly from the bottom edge  775  of the left side panel  16  are a plurality of left side hinge members  797 , each of which is fixedly secured to the left compound beam  781 . Each left side hinge member  797  is rotatably connected to one of the base right hinge members  745  of the base panel  17  by one or more hinge pins  798 , so as to allow the left side panel  16  to rotate relative to the base panel  17 . The hinge member  797  is shown in isolation, and in greater detail, in  FIGS. 41A and 41B . The design and function of hinge member  797  is the same as that of hinge member  125  on right side panel  14 . 
         [0190]    As shown in  FIG. 40 , a plurality of linear spring assemblies  799  are mounted to the left side panel  16  within corrugations  800  of the corrugated sheet metal  796 , as are a plurality of locking bolt assemblies  801 . The construction of the linear spring assemblies  799  is the same as those described with respect to the right side panel  14 , except that each tube base  803  is mounted within the left upper horizontal beam  784 , each tube shield  811  is secured to the corrugated sheet metal  796  of the left side panel  16 , and the lower end  819  of each cable  805  is attached to one of the cable anchors  691  secured to the base left beam upper portion  690  adjacent the upper edge  692  thereof. It is to be understood that when the container  10  is in the unfolded condition, each cable anchor  691  is vertically aligned with the tube  802  that contains the cable  805  that is attached to such cable anchor  691 . 
         [0191]    Likewise, the construction of the locking bolt assemblies  801  is the same as those described with respect to the right side panel  14 , except that each pivot anchor  820  is fixedly secured to the corrugated sheet metal  796  of the left side panel  16 , and each guide tube  827  extends through, and is fixedly secured to, the left upper cap plate  778 . As those skilled in the art will readily appreciate, each of the locking bolt assemblies  801  so described is selectively positionable between a first position in which the locking bolt  823  is received within one of the locking bolt holes  610  in the lower face  609  of the roof left beam  603 , when the container  10  is in the unfolded condition, and a second position in which the locking bolt  823  is fully withdrawn from that locking bolt hole  610 . 
         [0192]    Referring now to  FIGS. 42 ,  43 A and  43 B, the front panel  12  includes a front main panel  828 , a front right access panel  829 , and a front left access panel  830 . The front main panel  828  includes a top edge  56 , a bottom edge  57 , a right edge  58 , and a left edge  59 . Extending along the top edge  56  of the front main panel  828  is a header  60  and along the bottom edge  57  is a sill panel  61 , in spaced relation to the header  60 . A right front post  62 , hollow and rectangular in cross section, extends along the right edge  58  of the front main panel  828 , and a left front post  63 , also hollow and rectangular in cross section, extends along the left edge  59  of the front main panel  828 . Lateral support for the front main panel  828  is provided by corrugated sheet metal which extends between the two front posts  62 ,  63  along the entire length thereof, and is welded around its periphery to the immediately adjacent sill panel  61 , header  60 , the right front post  62 , and the left front post  63 . 
         [0193]    As shown in  FIGS. 42 ,  43 A,  43 B and  44 , extending upwardly from each of the front posts  62 ,  63  adjacent the top edge  56  of the front panel  828  is a front hinge pivot  617 ,  618 . When assembled to the roof panel  11 , each front hinge pivot  617 ,  618  is rotatably connected to one of the sets  613 ,  614  of front first hinge members  31   a ,  31   b ,  31   c ,  31   d  located adjacent the front edge  22  of the roof panel  11  by means of a hinge pin  52 , so as to allow the front panel  12  to rotate relative to the roof panel  11 . 
         [0194]    The front hinge pivot  617  adjacent the right edge  58  of the front main panel  828 , and the front hinge pivot  618  adjacent the left edge  59  of the front main panel  828  are identical, and a representative front hinge pivot  617  is shown in isolation in  FIGS. 45A ,  45 B,  45 C, and  45 D. As shown in  FIGS. 45A ,  45 B,  45 C, and  45 D, each front hinge pivot  617  has a pivot hinge pin hole  831  extending therethrough, and a cylindrical lug hole  832  extending therethrough as well. As shown in  FIGS. 42 and 44 , a cylindrical lug  833  extends through each cylindrical lug hole  832  and protrudes from each side of the front hinge pivots  617 . Each cylindrical lug  833  has a diameter that is only slightly less than the height  834   b  of the front lug receiving slot  621  on each of the front first hinge members  31   a ,  31   b ,  31   c  and  31   d  of the roof panel  11 . When incorporated into the present invention, the hinge pin  52  extends through the front pivot hole  619  of one of the front first hinge members  31   a ,  31   c , through the pivot hinge pin hole  831  of one of the front hinge pivots  617 , and through the front pivot hole  619  of another one of the front first hinge members  31   b ,  31   d  adjacent to the other front first hinge member  31   a ,  31   c  to allow for rotation between the front panel  12  and the roof panel  11 . As those skilled in the art will readily appreciate, when the front hinge pivots  617  are rotatably secured between two of the front first hinge members  31   a ,  31   b ,  31   c  and  31   d  by a hinge pin  52 , rotation of the cylindrical lugs  833  into the lug receiving slots  621  of the immediately adjacent front first hinge members  31   a ,  31   b ,  31   c  and  31   d , shifts much of the load carried by the front hinge pivots  617  from the hinge pins  52  to the cylindrical lugs  833 , allowing each of the front hinge pivots  617  to support more weight than either could carry on the hinge pin  52  alone. The construction and function of the front hinge pivot  618  adjacent the left edge  59  of the front main panel  828  is the same as that described for the front hinge pivot  617  adjacent the right edge  58 , except that the front hinge pivot  618  is received between the front first hinge members  31   c ,  31   d  adjacent the left edge  19  of the roof panel  11 . Front hinge pivot  617  is shown assembled to the front first hinge members  31   a ,  31   b  of the roof panel  11  in perspective in  FIG. 46 , and in greater detail in  FIG. 47 . Likewise, front hinge pivot  618  is shown assembled to the front first hinge members  31   c ,  31   d  of the roof panel  11  in perspective in  FIG. 48 , and in greater detail in  FIG. 49 . 
         [0195]    As shown in  FIGS. 50-56 , incorporated into the lower end portion  834 ,  835  of each of the front posts  62 ,  63  on the front panel  12  is a front panel interlock  836 ,  837 . Each front panel interlock  836 ,  837  has a door wall  838 ,  839  which faces the door panel  18 , a front wall  840 ,  841  that is parallel to, and in spaced relation with, the door wall  838 ,  839 , an inner wall  842 ,  843  that is perpendicular to the front wall  840 ,  841 , and the door wall  838 ,  839  and faces the inner wall  842 ,  843  of the other front panel interlock, and an outer wall  844 ,  845  which is parallel to, and in spaced relation with, the inner wall  842 ,  843 . 
         [0196]    Each front panel interlock  836 ,  837  has a first bolt hole  846 ,  847  in the outer wall  844 ,  845 , and a second bolt hole  848 ,  849  in the inner wall  842 ,  843 . The diameters of the second bolt holes  848 ,  849  are slightly larger than the diameters of the first bolt holes  846 ,  847 , and the first bolt holes  846 ,  847  and the second bolt holes  848 ,  849  are located on the inner walls  842 ,  843  and the outer walls  844 ,  845  of the front panel interlocks  836 ,  837 , such that when one of the base front tangs  108   a ,  108   b  of the base panel  17  is received therein, the upper tapered locking hole  110   a ,  110   b  in the base front tang  108   a ,  108   b  is aligned with the first bolt hole  846 ,  847  and the second bolt hole  848 ,  849  of the respective front panel interlock  836 ,  837 , such that the first bolt hole  846 ,  847  is immediately adjacent the smaller diameter end of the upper tapered locking hole  110   a ,  110   b , and the second bolt hole  848 ,  849  is immediately adjacent the larger diameter end of the upper tapered locking hole  110   a ,  110   b.    
         [0197]    Referring now to  FIGS. 44 ,  50 ,  53  and  55 , the sill panel  61  includes a lower sill beam  850  and an upper sill beam  851 , each of which extends between the fronts posts  62 ,  63  adjacent the lower end portions  834 ,  835  thereof. Each end  853 ,  854  of the lower sill beam  850  is fixedly secured to the inner wall  842 ,  843  of the front panel interlock  836 ,  837  immediately adjacent thereto, preferably by welding, such that the lower edge  855  of the lower sill beam  850  is approximately aligned with the lower ends  856 ,  857  of the front posts  62 ,  63 . Each end  858 ,  859  of the upper sill beam  851  is likewise fixedly secured to the inner wall  842 ,  843  of the front panel interlock  836 ,  837  immediately adjacent thereto, preferably by welding, such that upper sill beam  851  is parallel, and in spaced relation, to the lower sill beam  850 . A sill plate  860 , which is substantially aligned with the front walls  840 ,  841  of the front panel interlocks, extends from the upper sill beam  851  to the lower sill beam  850 , and from front left post  63  to the front right post  62 , and is welded about its periphery to the upper sill beam  851 , the lower sill beam  850 , the front left post  63 , and the front right post  62 . 
         [0198]    Adjacent each front panel interlock  836 ,  837 , and aligned with the bolt holes  846 ,  848 ,  847 ,  849  therein, are hammer lock retainers  861 ,  862  mounted to the sill panel  61 . As shown in  FIGS. 46 ,  48 ,  53  and  55 , a hammer locking mechanism  863 ,  864 , including a slide hammer  865 ,  866 , and a hammer locking bolt  867 ,  868 , is slideably secured to each of the hammer lock retainers  861 ,  862 , within the sill panel  61  such that each hammer locking mechanism  863 ,  864  is positionable by use of one of the slide hammers  865 ,  866  slideably mounted on one of the hammer locking bolts  867 ,  868 , between an unlocked position in which the respective hammer locking bolt  867 ,  868 , is in a retracted position substantially outside of the front panel interlock  836 ,  837 , and a locked position in which the respective hammer locking bolt  867 ,  868  extends through the bolt holes  846 ,  848 ,  847 ,  849  of the front panel interlock  836 ,  837  immediately adjacent thereto. 
         [0199]    As shown in  FIGS. 57-66 , a front roller arm  869 ,  870  is fixedly secured to the door wall  838 ,  839  of each of the front interlocks  836 ,  837 , and extends downward therefrom, and the outer wall  844 ,  845  of each of the front interlocks  836 ,  837  includes a roller recess  871 ,  872 . A roller cover plate  873 ,  874  is removably secured to the outer wall  844 ,  845  of each of the front interlocks  836 ,  837 , preferably with bolts  875 ,  876 . The upper edge  877 ,  878  of each roller cover plate  873 ,  874  extends upward along the outer wall  844 ,  845  to which it is attached so as to cover the roller recess  871 ,  872  immediately adjacent thereto, and the lower edge  879 ,  880  of each roller cover plate  873 ,  874  extends downward along the outer wall  844 ,  845  to which it is attached about 2 inches below the lower end  881 ,  882  of the immediately adjacent front roller arm  869 ,  870 . A first front roller  883 ,  884  is rotatably attached to each of the front roller arms  869 ,  870  adjacent the lower end thereof, and is secured in place by an axle pin  885 ,  886  that extends between each roller arm  869 ,  870  and the roller cover plate  873 ,  874  immediately adjacent thereto. Likewise, a second front roller  887 ,  888  is rotatably attached to each of the outer walls  844 ,  845  of the front interlocks  836 ,  837  within the roller recess  871 ,  872  therein, and is secured in place by an axle pin  889 ,  890  that extends between the outer wall  844 ,  845  of the respective front interlock  836 ,  837  and the roller cover plate  873 ,  874  immediately adjacent thereto. Each of the first front rollers  883 ,  884  and the second front rollers  887 ,  888  is aligned with one of the rails  401 ,  403  of the base panel  17  and rides on such rails  401 ,  403  during the folding, and unfolding, of the container  10  as described in more detail below. 
         [0200]    Referring to  FIGS. 67 ,  68  and  74 , the front right post  62  includes a front right hinge plate  891  that extends towards the door edge  21  of the roof panel  11  when the container  10  is in the unfolded condition. Attached to the inward surface  892  of the front right hinge plate  891 , in spaced relation to each other, are a plurality of, and preferably four, first front right hinge members  893 . Each of the first front right hinge members  893  is fixedly secured to the inward surface  892  of the front right hinge plate  891 , preferably by welding. 
         [0201]    As shown in  FIG. 67 , a front right access panel  894  is pivotably attached to the front right post  62 , and as shown in  FIG. 69 , the front right access panel  894  includes a top edge  214 , a bottom edge  216 , a front edge  218 , and a door edge  220 . Extending along the top edge  214  of the front right access panel  894  along the length thereof is a front right upper cap plate  895  having a front end  896 , a door end  897 , and preferably, as shown in  FIGS. 67 and 74 , a front right roof flange  898  extends from the front end  896  to the door end  897 . Extending along the bottom edge  216  of the front right access panel  894  along the length thereof is a front right beam  900  that has a front end  901  and a door end  902 . 
         [0202]    As shown in  FIG. 69 , a first front right access member  903  extends from the front end  896  of the front right upper cap plate  895  to the front end  901  of the front right beam  900 , and is fixedly secured to the front ends  896 ,  901 , preferably by welding. As shown in  FIG. 69 , a second front right access member  906  extends from the door end  897  of the front right upper cap plate  895  to the door end  902  of the front right beam  900 , and is fixedly secured to the door ends  897 ,  902 , preferably by welding. As shown in  FIGS. 69 ,  70  and  71 , the second front right access member  906  includes a long flange  907  and a short flange  908 , each of which extends along the length of the second front right access member  906  and towards the door edge  21  of the roof panel  11  when the container  10  is in the unfolded condition. Located between the long flange  907  and the short flange  908  are a plurality of locking bolt holes  909 , preferably three, that extend through the second front right access member  906 . When the container  10  is in the unfolded condition, the locking bolt holes  909  are aligned with the right side bolt holes  767  of the right side panel  14   
         [0203]    Referring again to  FIG. 69 , corrugated sheet metal  910  extends from the front right upper cap plate  895  to the front right beam  900  along the entire length thereof, and from the first front right access member  903  to the second front right access member  906  along the entire length thereof. The corrugated sheet metal  910  is welded all along its entire perimeter to the immediately adjacent front right upper cap plate  895 , first front right access member  903 , front right beam  900 , and second front right access member  906 . As those skilled in the art will readily appreciate, the second front right access member  906  is welded to the corrugated sheet metal  910  such that the long flange  907  is visible from the interior of the container  10  when the container  10  is in its unfolded condition. As shown in  FIGS. 67-69 , attached to the inward surface  911  of the first front right access member  903  in spaced relation to each other, are a plurality of second front right hinge members  912 . As shown in  FIG. 68 , each of the second front right hinge members  912  is rotatably secured to one of the first front right hinge members  893  by a hinge pin  913  so as to allow the front right access panel  894  to swing relative to the front main panel  828 . 
         [0204]    Referring again to  FIG. 69 , immediately adjacent each of the locking bolt holes  909  in the second front right access member  906  is a recess  914  in the corrugated sheet metal  910 , and within each recess  914  and aligned with the locking bolt holes  909  in the second front right access member  906  are slide lock retainers  915 . As shown in  FIGS. 69 and 72 , a slide locking mechanism  916 , including a slide lock lever  917 , and a slide locking bolt  918 , is slideably secured to each of the slide lock retainers  915  within the recesses  914  such that each slide locking mechanism  916  is positionable by use of one of the slide lock levers  917  between an unlocked position in which the respective slide locking bolt  918  is in a retracted position outside of the right side bolt holes  767  of the right side panel  14 , and a locked position in which the respective slide locking bolt  918  extends through the immediately adjacent locking bolt hole  909  of the second front right access member  906  and one of the right side bolt holes  767  of the right side panel  14 . 
         [0205]    Referring again to  FIGS. 67 and 69 , at least one locking bolt assembly  919  is mounted to the front right access panel  894  within corrugations  920  of the corrugated sheet metal  910 . The construction of the locking bolt assembly  919  is the same as those described with respect to the right side panel  14 , except that each pivot anchor  820  is fixedly secured to the corrugated sheet metal  910  of the front right access panel  894 , and each guide tube  827  extends through, and is fixedly secured to, the front right upper cap plate  895 , as shown in  FIG. 73 . As those skilled in the art will readily appreciate, each of the locking bolt assemblies  919  so described is selectively positionable between a first position in which the locking bolt  823  is received within one of the locking bolt holes  610  in the lower face  608  of the roof right beam  600  when the container  10  is in the unfolded condition, and a second position in which the locking bolt  823  is fully withdrawn from that locking bolt hole  610 . 
         [0206]    As shown in  FIGS. 67 ,  74  and  75 , the front left post  63  includes a front left hinge plate  2891  that extends towards the door edge  21  of the roof panel  11  when the container  10  is in the unfolded condition. Attached to the inward surface  2892  of the front left hinge plate  2891 , in spaced relation to each other, are a plurality of, and preferably four, first front left hinge members  2893 . Each of the first front left hinge members  2893  is fixedly secured to the inward surface  2892  of the front left hinge plate  2891 , preferably by welding. 
         [0207]    As shown in  FIG. 74 , a front left access panel  2894  is pivotably attached to the front left post  63 , and as shown in  FIG. 76 , the front left access panel  2894  includes a top edge  2214 , a bottom edge  2216 , a front edge  2218 , and a door edge  2220 . Extending along the top edge  2214  of the front left access panel  2894  along the length thereof is a front left upper cap plate  2895  having a front end  2896 , a door end  2897 , and preferably as shown in  FIGS. 67 &amp; 74  a front left roof flange  2898  extends from the front end  2896  to the door end  2897 . Extending along the bottom edge  2216  of the front left access panel  2894  along the length thereof is a front left beam  2900  that has a front end  2901  and a door end  2902 . 
         [0208]    As shown in  FIG. 76 , a first front left access member  2903  extends from the front end  2896  of the front left upper cap plate  2895  to the front end  2901  of the front left beam  2900 , and is fixedly secured to the front ends  2896 ,  2901 , preferably by welding. As shown in  FIG. 76 , a second front left access member  2906  extends from the door end  2897  of the front left upper cap plate  2895  to the door end  2902  of the front left beam  2900 , and is fixedly secured to the door ends  2897 ,  2902 , preferably by welding. As shown in  FIGS. 76 ,  77  and  78 , the second front left access member  2906  includes a long flange  2907  and a short flange  2908 , each of which extends along the length of the second front left access member  2906  and towards the door edge  21  of the roof panel  11  when the container  10  is in the unfolded condition. Located between the long flange  2907  and the short flange  2908  are a plurality of locking bolt holes  2909 , preferably three, that extend through the second front left access member  2906 . When the container  10  is in the unfolded condition, the locking bolt holes  2909  are aligned with the left side bolt holes  794  of the left side panel  16 . 
         [0209]    Referring again to  FIG. 76 , corrugated sheet metal  2910  extends from the front left upper cap plate  2895  to the front left beam  2900  along the entire length thereof, and from the first front left access member  2903  to the second front left access member  2906  along the entire length thereof. The corrugated sheet metal  2910  is welded all along its entire perimeter to the immediately adjacent front left upper cap plate  2895 , first front left access member  2903 , front left beam  2900 , and second front left access member  2906 . As those skilled in the art will readily appreciate, the second front left access member  2906  is welded to the corrugated sheet metal  2910  such that the long flange  2907  is visible from the interior of the container  10  when the container  10  is in its unfolded condition. As shown in  FIGS. 74-76 , attached to the inward surface  2911  of the first front left access member  2903  in spaced relation to each other, are a plurality of second front left hinge members  2912 . Each of the second front left hinge members  2912  is rotatably secured to one of the first front left hinge members  2893  by a hinge pin  2913  so as to allow the front left access panel  2894  to swing relative to the front main panel  828 . 
         [0210]    Referring again to  FIGS. 74 &amp; 76 , immediately adjacent each of the locking bolt holes  2909  in the second front left access member  2906  is a recess  2914  in the corrugated sheet metal  2910 , and within each recess  2914  and aligned with the locking bolt holes  2909  in the second front left access member  2906  are slide lock retainers  2915 . As shown in  FIGS. 76 and 79 , a slide locking mechanism  2916 , including a lock lever  2917 , and a slide locking bolt  2918 , is slideably secured to each of the slide lock retainers  2915  within the recesses  2914  such that each slide locking mechanism  2916  is positionable by use of one of the slide lock levers  2917  between an unlocked position in which the respective slide locking bolt  2918  is in a retracted position outside of the left side bolt holes  794  of the left side panel  16 , and a locked position in which the respective slide locking bolt  2918  extends through the immediately adjacent locking bolt hole  2909  of the second front left access member  2906  and one of the left side bolt holes  794  of the left side panel  16 . 
         [0211]    Referring again to  FIG. 76 , at least one locking bolt assembly  2919  is mounted to the front left access panel  2894  within corrugations  2920  of the corrugated sheet metal  2910 . The construction of the locking bolt assembly  2919  is the same as those described with respect to the right side panel  14 , except that each pivot anchor  820  is fixedly secured to the corrugated sheet metal  2910  of the front left access panel  2894 , and each guide tube  827  extends through, and is fixedly secured to, the front left upper cap plate  2895 , as shown in  FIG. 80 . As those skilled in the art will readily appreciate, each of the locking bolt assemblies  2919  so described is selectively positionable between a first position in which the locking bolt  823  is received within one of the locking bolt holes  610  in the lower face  609  of the roof left beam  603  when the container  10  is in the unfolded condition, and a second position in which the locking bolt  823  is fully withdrawn from that locking bolt hole  610 . 
         [0212]    As shown in  FIGS. 81 ,  84  and  86 , the door panel  18  includes a door main panel  921 , a door right access panel  922 , and a door left access panel  923 . The door main panel  921  includes a top edge  928 , a bottom edge  929 , a right edge  930 , a left edge  931 , two door posts  924 ,  925 , and two doors  926 ,  927 . The right door post  924 , hollow and rectangular in cross section, extends along the right edge  930  of the door main panel  921 , and a left door post  925 , also hollow and rectangular in cross section, extends along the left edge  931  of the door main panel  921 . 
         [0213]    Referring again to  FIG. 81 , each door  926 ,  927  is of the type known in the shipping container art, and is hinged to one of the door posts  924 ,  925  by a plurality of door hinges  932  so as to be rotatable between a first position in which such door  926 ,  927  is closed, and a second position in which such door  926 ,  927  is open. Each door  926 ,  927  has a door latch assembly  639  attached thereto, and each door latch assembly preferably includes two locking rods  92  rotatably attached to the outer surface  934 ,  935  of such door  926 ,  927  by rod guides  933 . The locking rods  933  of the present invention are of the type known in the art and commonly used on shipping containers. Such locking rods  92  have knuckles  940  at the upper ends  91  thereof, and knuckles  941  at the lower ends  713  thereof, and each locking rod  92  has a handle  936  attached thereto to rotate such locking rod  92  approximately 180 degrees. As those skilled in the art will readily appreciate, when the container  10  is in the unfolded condition and the doors  926 ,  927  are closed, rotating each of the locking rods  92  by means of the handles  936  attached thereto causes the knuckles  940  at the upper ends  91  of such locking rods  92  to rotate into one of the lock hasps  90   a  on the roof panel  11  while simultaneously causing the knuckles  941  at the lower ends  713  of such locking rods  92  to rotate into one of the lock hasps  90   b  on the base panel  11 , thereby securing the doors  926 ,  927  in the closed position. 
         [0214]    As shown in  FIGS. 82 and 83 , a locking bar  943  is pivotably connected at one end  944  to one of the locking rods  92  of the right door  926 , and a locking block  945  is fixedly secured to the left door  927  at a location that is aligned with the locking bar  943  when both of the doors  926 ,  927  are closed. The locking bar  943  further includes a lock pin hole  946  that extends vertically through the locking bar  943 , and the locking bar  943  has a locking rod recess  947  adjacent the distal end  948  of the locking bar  943 . The locking block  945  has an upper flange  949  and a lower flange  950  in spaced relation to each other for receiving the locking bar  943 , and a pin receiving hole  951  that is the same diameter as the lock pin hole  946  extends vertically through the upper flange  949  and lower flange  950 . The lock pin hole  946  is located on the locking bar  943  such that, when the locking bar  943  is received within the flanges  949 ,  950  of the locking block  945  and a locking rod  92  on the left door  927  is received within the locking rod recess  947  (the “locked position”), the lock pin hole  946  of the locking bar  943  and pin receiving hole  951  of the locking block  945  are substantially coaxial, so as to allow a locking pin  952  to be inserted through the pin receiving hole  951  of the upper flange  949 , through the lock pin hole  946  of the locking bar  945 , and into the pin receiving hole  951  of the lower flange  950 . 
         [0215]    As shown in  FIG. 81 , extending upwardly from each of the door posts  924 ,  925  adjacent the top edge  928  of the door main panel  921  is a door hinge pivot  953 ,  954 , and as shown in  FIGS. 84-87 , each door hinge pivot  953 ,  954  is rotatably connected to one of the sets  651 ,  652  of door first hinge members  653   a ,  653   b ,  653   c ,  653   d  located adjacent the door edge  21  of the roof panel  11 . Each door hinge pivot  953 ,  954  has a hinge pin  955 , as shown in  FIG. 81 , that extends through one of the door hinge pivots  953 ,  954  and the door pivot holes  668  of the immediately adjacent door first hinge members  653   a ,  653   b ,  653   c  and  653   d  so as to allow the door panel  12  to rotate relative to the roof panel  11 . 
         [0216]    The door hinge pivot  953  adjacent the right edge  930  of the door main panel  921  and the door hinge pivot  954  adjacent the left edge  931  of the door main panel  921  are identical, and a representative door hinge pivot is shown in isolation in  FIGS. 88A-88C . Each door hinge pivot  953 ,  954  has a pivot hinge pin hole  956  extending therethrough, and a cylindrical lug hole  957  extending therethrough as well. As shown in  FIG. 81 , a cylindrical lug  958  extends through each cylindrical lug hole  957  and protrudes from each side of the door hinge pivots  953 ,  954 . Each cylindrical lug  958  has a diameter that is only slightly less than the height  959  of the door lug receiving slot  669  on each of the door first hinge members  653   a ,  653   b ,  653   c ,  653   d  of the roof panel  11 . When incorporated into the present invention, the hinge pin  955  extends through the door pivot hole  668  of one of the door first hinge members  653   a ,  653   c  through the pivot hinge pin hole  956  of the door hinge pivot  953 , and through the door pivot hole  668  of another one of the door first hinge members  653   b ,  653   d  adjacent to the other door first hinge member  653   a ,  653   c  to allow for rotation between the door panel  18  and the roof panel  11 . As those skilled in the art will readily appreciate, when the door hinge pivots  953 ,  954  are rotatably secured between two of the door first hinge members  653   a ,  653   b ,  653   c ,  653   d  by a hinge pin  955 , rotation of the cylindrical lugs  958  into the lug receiving slots  669  of the immediately adjacent door first hinge members  653   a ,  653   b ,  653   c ,  653   d , shifts much of the load carried by the door hinge pivots  953 ,  954  from the hinge pins  955  to the cylindrical lugs  958 , allowing the door hinge pivots  953 ,  954  to support more weight than either could carry on the hinge pins  955  alone. The construction and function of the door hinge pivot  954  adjacent the left edge  931  of the door main panel  921  is the same as that described for the door hinge pivot  953  adjacent the right edge  930 , except that the door hinge pivot  954  is received between the door first hinge members  653   c ,  653   d  adjacent the left edge  20  of the roof panel  11 . 
         [0217]    As shown in  FIGS. 89-92 , at the lower end  960 ,  961  of each of the door posts  924 ,  925  of the door panel  18  is a tang  962 ,  963 . Each door tang  962 ,  963  has a front face  964 ,  965  which faces the front panel  12 , and a door face  966 ,  967  which faces away from the front panel  12 . As shown in greater detail in  FIGS. 93 and 94 , the door tang  962  attached to the door right post  924  includes a hole  968 , which extends from the front face  964  to the door face  966  of the door tang  962 , and the hole  968  tapers from a first diameter at the front face  964  to a slightly smaller diameter at the door face  966 . As shown in  FIGS. 95 and 96 , the construction of the door tang  963  attached to the door left post  925  is the same as that for the tang  962  attached to the door right post  924 , except that the hole  968  extends from the front face  965  of the door tang  963  attached to the door left post  925  to the door face  967  of the door tang  963  attached to the door left post  925 . 
         [0218]    As shown in  FIGS. 93-96 , each of the door posts  924 ,  925  has a door roller arm  969 ,  970  fixedly secured thereto adjacent the lower end thereof  960 ,  961 , and each door roller arm  969 ,  970  extends downward along the immediately adjacent tang  962 ,  963 , but in spaced relation thereto. The lower end  971 ,  972  of each door roller arm  969 ,  970  extends about two inches below the lower end  973 ,  974  of the immediately adjacent door tang. 
         [0219]    As shown in  FIGS. 93-98 , a spacer  975 ,  976  is secured to each door roller arm  969 ,  970  adjacent the lower end  971 ,  972  thereof, and each spacer  975 ,  976  has a roller cover plate  977 ,  978  removably secured thereto in spaced relation to the immediately adjacent door roller arm  969 ,  970 . The lower edge  979 ,  980  of each roller cover plate  977 ,  978  extends downward along the immediately adjacent door roller arm  969 ,  970  and then about half an inch to an inch below the lower end  973 ,  974  thereof. A door roller  981 ,  982  is rotatably attached to each of the roller arms  969 ,  970  adjacent the lower end  973 ,  974  thereof, and is secured in place by an axle pin  983 ,  984  that extends between the door roller arm  969 ,  970  and the roller cover plate  977 ,  978  immediately adjacent thereto. Each of the door rollers  981 ,  982  is aligned with one of the rails  402 ,  404  of the base panel  17  and rides on such rails  402 ,  404  during the folding, and unfolding, of the container  10  as described in more detail below. 
         [0220]    Referring back to  FIGS. 89 and 90 , the door right post  924  includes a door right hinge plate  3891  that extends towards the front edge  22  of the roof panel  11  when the container  10  is in the unfolded condition. Attached to the inward surface  3892  of the door right hinge plate  3891 , in spaced relation to each other, are a plurality of, and preferably four, first door right hinge members  3893 . Each of the first door right hinge members  3893  is fixedly secured to the inward surface  3892  of the door right hinge plate  3891 , preferably by welding. 
         [0221]    A door right access panel  3894  is pivotably attached to the door right post  924 , and as shown in  FIGS. 99 and 105 , the door right access panel  3894  includes a top edge  3214 , a bottom edge  3216 , a front edge  3218 , and a door edge  3220 . Extending along the top edge  3214  of the door right access panel  3894  along the length thereof is a door right upper cap plate  3895  having a front end  3896 , a door end  3897 , and preferably as shown in  FIG. 90 , a door right roof flange  3898  extends from the front end  3896  to the door end  3897 . Extending along the bottom edge  3216  of the door right access panel  3894  along the length thereof is a front right beam  3900  that has a front end  3901  and a door end  3902 . 
         [0222]    As shown in  FIG. 99 , a first door right access member  3903  extends from the door end  3897  of the door right upper cap plate  3895  to the door end  3902  of the door right beam  3900 , and is fixedly secured to the door ends  3897 ,  3902 , preferably by welding. As shown in  FIGS. 91 and 99 , a second door right access member  3906  extends from the front end  3896  of the door right upper cap plate  3895  to the front end  3901  of the door right beam  3900 , and is fixedly secured to the front ends  3896 ,  3901 , preferably by welding. As shown in  FIGS. 99-101 , the second door right access member  3906  includes a long flange  3907  and a short flange  3908 , each of which extends along the length of the second door right access member  3906  and towards the door edge  21  of the roof panel  11  when the container  10  is in the unfolded condition. Located between the long flange  3907  and the short flange  3908  are a plurality of locking bolt holes  3909 , preferably three, that extend through the second door right access member  3906 . When the container  10  is in the unfolded condition, the locking bolt holes  3909  are aligned with the right side bolt holes  768  of the right side panel  14   
         [0223]    Referring again to  FIG. 99 , corrugated sheet metal  3910  extends from the door right upper cap plate  3895  to the door right beam  3900  along the entire length thereof, and from the first door right access member  3903  to the second door right access member  3906  along the entire length thereof. The corrugated sheet metal  3910  is welded all along its entire perimeter to the immediately adjacent door right upper cap plate  3895 , first door right access member  3903 , door right beam  3900 , and second door right access member  3906 . As those skilled in the art will readily appreciate, the second door right access member  3906  is welded to the corrugated sheet metal  3910  such that the long flange  3907  is visible from the interior of the container  10  when the container  10  is in its unfolded condition. As shown in  FIGS. 89 ,  99  and  102 , attached to the inward surface  3911  of the door right access panel  3894  and the first door right access member  3903  in spaced relation to each other, are a plurality of second door right hinge members  3912 . Each of the second door right hinge members  3912  is rotatably secured to one of the first door right hinge members  3893  by a hinge pin  3913  so as to allow the door right access panel  3894  to swing relative to the door main panel  921 . 
         [0224]    Immediately adjacent each of the locking bolt holes  3909  in the second door right access member  3906  is a recess  3914  in the corrugated sheet metal  3910 , and within each recess  3914  and aligned with the locking bolt holes  3909  in the second door right access member  3906  are slide lock retainers  3915 . As shown in  FIGS. 99 and 103 , a slide locking mechanism  3916 , including a lock lever  3917 , and a slide locking bolt  3918 , is slideably secured to each of the slide lock retainers  3915  within the recesses  3914  such that each slide locking mechanism  3916  is positionable by use of one of the slide lock levers  3917  between an unlocked position in which the respective slide locking bolt  3918  is in a retracted position outside of the right side bolt holes  768  of the right side panel  14 , and a locked position in which the respective slide locking bolt  3918  extends through the immediately adjacent locking bolt hole  3909  of the second door right access member  3906  and one of the right side bolt holes  768  of the right side panel  14 . 
         [0225]    Referring again to  FIG. 99 , at least one locking bolt assembly  3919  is mounted to the door right access panel  3894  within corrugations  3920  of the corrugated sheet metal  3910 . The construction of the locking bolt assembly  3919  is the same as those described with respect to the right side panel  14 , except that each pivot anchor  820  is fixedly secured to the corrugated sheet metal  3910  of the door right access panel  3894 , and each guide tube  827  extends through, and is fixedly secured to, the front right upper cap plate  3895 , as shown in  FIG. 104 . As those skilled in the art will readily appreciate, each of the locking bolt assemblies  3919  so described is selectively positionable between a first position in which the locking bolt  823  is received within one of the locking bolt holes  610  in the lower face  608  of the roof right beam  600  when the container  10  is in the unfolded condition, and a second position in which the locking bolt  823  is fully withdrawn from that locking bolt hole  610 . 
         [0226]    Referring back to  FIGS. 89 and 90 , the door left post  925  includes a door left hinge plate  4891  that extends towards the front edge  22  of the roof panel  11  when the container  10  is in the unfolded condition. Attached to the inward surface  4892  of the door left hinge plate  4891 , in spaced relation to each other, are a plurality of, and preferably four, first door left hinge members  4893 . Each of the first door left hinge members  4893  is fixedly secured to the inward surface  4892  of the door left hinge plate  4891 , preferably by welding. 
         [0227]    A door left access panel  4894  is pivotably attached to the door left post  925 , and as shown in  FIG. 105 , the door left access panel  4894  includes a top edge  4214 , a bottom edge  4216 , a front edge  4218 , and a door edge  4220 . Extending along the top edge  4214  of the door left access panel  4894  along the length thereof is a door left upper cap plate  4895  having a front end  4896 , a door end  4897 , and preferably as shown in  FIG. 89 , a door left roof flange  4898  extends from the front end  4896  to the door end  4897 . Extending along the bottom edge  4216  of the front left access panel  4894  along the length thereof is a door left beam  4900  that has a front end  4901  and a door end  4902 . 
         [0228]    As shown in  FIG. 105 , a first door left access member  4903  extends from the door end  4897  of the door left upper cap plate  4895  to the door end  4902  of the door left beam  4900 , and is fixedly secured to the door ends  4897 ,  4902 , preferably by welding. As shown in  FIGS. 92 and 105 , a second door left access member  4906  extends from the front end  4896  of the door left upper cap plate  4895  to the front end  4901  of the door left beam  4900 , and is fixedly secured to the front ends  4896 ,  4901 , preferably by welding. As shown in  FIGS. 105-107 , the second door left access member  4906  includes a long flange  4907  and a short flange  4908 , each of which extends along the length of the second front left access member  4906  and towards the front edge  22  of the roof panel  11  when the container  10  is in the unfolded condition. Located between the long flange  4907  and the short flange  4908  are a plurality of locking bolt holes  4909 , preferably three, that extend through the second front left access member  4906 . When the container  10  is in the unfolded condition, the locking bolt holes  4909  are aligned with the left side bolt holes  795  of the left side panel  16   
         [0229]    Referring again to  FIG. 105 , corrugated sheet metal  4910  extends from the door left upper cap plate  4895  to the door left beam  4900  along the entire length thereof, and from the first door left access member  4903  to the second door left access member  4906  along the entire length thereof. The corrugated sheet metal  4910  is welded all along its entire perimeter to the immediately adjacent door left upper cap plate  4895 , first door left access member  4903 , door left beam  4900 , and second door left access member  4906 . As those skilled in the art will readily appreciate, the second door left access member  4906  is welded to the corrugated sheet metal  4910  such that the long flange  4907  is visible from the interior of the container  10  when the container  10  is in its unfolded condition. As shown in  FIGS. 90 ,  105  and  108 , attached to the inward surface  4911  of the door left access panel  4894  and the first door left access member  4903  in spaced relation to each other, are a plurality of second door left hinge members  4912 . Each of the second door left hinge members  4912  is rotatably secured to one of the first door left hinge members  4893  by a hinge pin  4913  so as to allow the door left access panel  4894  to swing relative to the door main panel  921 . 
         [0230]    Immediately adjacent each of the locking bolt holes  3909  in the second door left access member  4906  is a recess  4914  in the corrugated sheet metal  4910 , and within each recess  4914  and aligned with the locking bolt holes  4909  in the second front left access member  4906  are slide lock retainers  4915 . As shown in  FIGS. 105 and 109 , a slide locking mechanism  4916 , including a slide lock lever  4917 , and a slide locking bolt  4918 , is slideably secured to each of the slide lock retainers  4915  within the recesses  4914  such that each slide locking mechanism  4916  is positionable by use of one of the slide lock levers  4917  between an unlocked position in which the respective slide locking bolt  4918  is in a retracted position outside of the left side bolt holes  795  of the left side panel  16 , and a locked position in which the respective slide locking bolt  4918  extends through the immediately adjacent locking bolt hole  4909  of the second door left access member  4906  and one of the left side bolt holes  795  of the left side panel  16 . 
         [0231]    As shown in  FIG. 105 , at least one locking bolt assembly  4919  is mounted to the door left access panel  4894  within corrugations  4920  of the corrugated sheet metal  4910 . The construction of the locking bolt assembly  4919  is the same as those described with respect to the right side panel  14 , except that each pivot anchor  820  is fixedly secured to the corrugated sheet metal  4910  of the door left access panel  4894 , and each guide tube  827  extends through, and is fixedly secured to, the door left upper cap plate  4895 , as shown in  FIG. 110 . As those skilled in the art will readily appreciate, each of the locking bolt assemblies  4919  so described is selectively positionable between a first position in which the locking bolt  823  is received within one of the locking bolt holes  610  in the lower face  609  of the roof left beam  603  when the container  10  is in the unfolded condition, and a second position in which the locking bolt  823  is fully withdrawn from that locking bolt hole  610 . 
         [0232]    As those skilled in the art will readily appreciate, further embodiments can be incorporated to reduce cost and weight. One of these embodiments includes elimination of the access panels, replacing the side hinge members and linear spring assemblies with a torsion pin hinge, and increasing the height of the side panels to provide more strength to the base panel and reduction of weight from the top panel. 
         [0233]    The primary function of the access panels is to minimize the side panel section height near the door panel and the front panel to give access thereto.  FIG. 113  is a schematic view plan view looking down on the base  17 , showing the side panels folded down on the base  17 . The area marked by the “X”  5000 , shows the area occupied by the side panels when they are folded down. The two areas  5001 ,  5002 , immediately adjacent the side panels are areas that are not occupied by the side panels because in this view the access panels are folded into the front panel or the door panel. A side view of the base  17  shown in  FIG. 113  is shown in  FIG. 114 , which shows that since the side panels do not extend the entire length of the base, notched areas  5003 ,  5004  are formed at the ends of each side panel, because the stacked-up height  5005  of the base  17  and the side panels is substantially greater than the height  5006  of the base panel  17  at the two areas  5001 ,  5002 , immediately adjacent the side panels. As shown by the curved arrows  5007 ,  5008 , these notched areas  5003 ,  5004  allow the door panel and the front panel to clear the folded-down side panels as they swing along the paths shown by the curved arrows  5007 ,  5008  during the folding process. Unfortunately, inherent in this notched design are surfaces that may be difficult to seal effectively, and structural issues require additional weight in to achieve desirable rigidity of the container. This further embodiment eliminates the access panels all together by extending the side panels the entire length of the base. This eliminates the sealing requirements between the access panels and the side panels, reduces cost, and also significantly improves the structural aspects of the container. 
         [0234]      FIG. 115  shows a schematic side view of the base  17  with the side panels erect. As previously described, the side panels are structurally tied to the base panel  17  by side hinge members that provide both a hinge function for the side panels, and shear load capability for the container in its unfolded condition. While this design may perform satisfactorily, it incorporates structural features that may not be desirable in certain applications. Unfortunately, the side panels, which provide 80% of the load carrying capability of the base panel  17  (by effectively increasing the beam-height from a structural point of view), do not extend all the way to the ends of the base panel  17  where the right and left side door interlocks, and the right and left side front interlocks take all of the vertical loading. Consequently, stress is concentrated at the points  5009 ,  5010 , where the ends of the side panels meet the base panel  17 . By extending the side panels the full length of the base panel  17 , to the end of the beam, this stress concentration can be eliminated. 
         [0235]      FIG. 116  shows schematically a transverse cross-sectional view through the base panel  17  and the side panels adjacent one of the side hinge members and linear spring assemblies. As the left side panel is rotated down from its vertical position (as shown by the dashed lines) the spring mechanism in the linear spring assembly (not shown) is compressed, developing a tensile force in the cable  5045  which is preferably adjusted to provide the appropriate force to counter-balance the weight of the left side panel as it is folded down. Unfortunately, this design requires that the right side panel be shortened by a distance “D”  5011 . As a result, the right side skirt, which extends down from the top panel, must be longer to compensate for the shortened height of the right side panel, as compared to if the right side panel height did not have to be shortened by a distance “D”  5011  to accommodate the cable  5045 . As those skilled in the art will readily appreciate, since the right and left side skirts are less rigid than the rest of the top panel from which they extend, the distance which the side skirts extend down from the top panel should preferably be as short as possible, and the side panels should be as tall as possible, to maximize the structural rigidity of the container. 
         [0236]    A further embodiment significant improvement to this arrangement is the use of hinge pin torsion spring assemblies, an example of which is shown in  FIG. 117 , instead of the linear spring assemblies and side hinge members attached to the right and left side panels described in the preferred embodiment. The hinge pin torsion spring replaces the “pin” in  FIG. 116  torsion feature interior to the bottom beam. Preferably, each hinge pin torsion spring assembly  5000  includes a side panel hinge member  5020 , base hinge members  5021 ,  5022 , and a hinge pin torsion spring  5023 . Although the hinge pin torsion spring assembly shown in  FIG. 117  is shown and described attached to the to the left side panel, it is to be understood that the hinge pin torsion spring assemblies used on the right side panel are similar. 
         [0237]    The hinge pin torsion spring  5023 , as shown in  FIG. 118 , includes a hinge pin  5024  having a cylindrical main section  5025 , a non-cylindrical section  5026 , preferably hexagonal in cross-section, at one end of the hinge pin, and a pin ratcheting feature  5027  at the end opposite the non-cylindrical section  5026 . The pin ratcheting feature  5027 , which is preferably a cylindrical disk, includes a plurality of gear teeth  5028  which face the non-cylindrical section  5026  and which are all canted in the same circumferential direction. The non-cylindrical section  5026  and the pin ratcheting feature  5027  are integral with the cylindrical main section  5025 , so that rotation of the non-cylindrical section  5026  necessarily causes the pin ratcheting feature  5027  to rotate in the same direction. 
         [0238]    As shown in  FIG. 119 , the torsion spring  5029  of the hinge pin torsion spring  5023  includes a coil spring  5030 , an attachment ring  5031 , a spring ratcheting feature  5032 , and a spring shield  5033 . The attachment ring  5031  and the spring ratcheting feature  5032  each have an inner bore having a diameter that is greater than the outer diameter of the cylindrical main section  5025  of the hinge pin  5024  to allow the cylindrical main section  5025  of the hinge pin  5024  to slide therethrough without binding. Likewise, the inner diameter of the coil spring  5030  is greater than the outer diameter of the cylindrical main section  5025  of the hinge pin  5024  to avoid binding between the cylindrical main section  5025  of the hinge pin  5024  and the coil spring  5030  at all operating positions of the hinge pin torsion spring  5023 . The attachment ring  5031  is fixedly attached, preferably by welding, to one end of the coil spring  5030 , and the spring ratcheting feature  5032  is fixedly attached, preferably by welding, to the opposite end of the of the coil spring  5030 . The spring ratcheting feature  5030 , which is preferably generally cylindrical, includes a plurality of gear teeth  5034  which face away from the attachment ring  5031  and which are all canted in the same circumferential direction, which is opposite the direction in which the gear teeth  5028  of the pin ratcheting feature are canted. The spring ratcheting feature  5032  includes a non-cylindrical portion  5035 , which is preferably hexagonal in cross section, the purpose of which is described below. The spring shield  5033  which is tubular and may be cylindrical or non-cylindrical, fits loosely around, and protects, the coil spring  5030 . 
         [0239]    The hinge pin torsion spring  5023  is shown in  FIG. 120  fully assembled, with the hinge pin  5024  inserted into the torsion spring  5029 . As those skilled in the art will readily appreciate, in this assembled condition, the gear teeth  5028  of the pin ratcheting feature  5027  are interlocked with the gear teeth  5034  of the spring ratcheting feature  5032 , and due to the canted nature of the gear teeth  5028 ,  5034 , can only be rotated in one direction, and the gear teeth  5028 ,  5034  will lock together if rotation in the opposite direction is attempted. 
         [0240]    As shown in  FIG. 121  the hinge pin  5024  of the hinge pin torsion spring  5023  is received within a hole  5036  in base hinge member  5022 . The hole  5036  is slightly larger than the outer diameter of the cylindrical main portion  5025  of the hinge pin  5024  so as to allow the hinge pin to rotate freely therein. In addition, the attachment ring  5031 , is fixedly attached to the base hinge member  5022 , either by welding or by some other attachment method that prevents rotation between the attachment ring  5031  and base hinge member  5022 . Base hinge member  5022  is welded to the base left beam  685  along the vertical edge  5037  immediately adjacent thereto, and to the base left beam  685  along the horizontal edge  5038  immediately adjacent thereto. 
         [0241]    As shown in  FIG. 122  the hinge pin  5024  of the hinge pin torsion spring  5023  is received within a hole  5039  in base hinge member  5021 . The hole  5039  is slightly larger than the outer diameter of the cylindrical main portion  5025  of the hinge pin  5024  so as to allow the hinge pin to rotate freely therein. Base hinge member  5021  is welded to the base left beam  685  along the vertical edge  5040  immediately adjacent thereto, and to the base left beam  685  along the horizontal edge  5041  immediately adjacent thereto. 
         [0242]    Referring again to  FIG. 117 , the hexagonal portion  5026  of the hinge pin  5024  is received within a hexagonal hole  5042  in side panel hinge member  5020 . The hexagonal portion  5026  of the hinge pin  5024  welded, or otherwise fixedly secured to side panel hinge member  5020  to prevent the hinge pin  5024  from inadvertently sliding out of the torsion spring  5029 . Side panel hinge member  5020  is welded to the left side panel  16  along the vertical edge  5043  immediately adjacent thereto, and if desired, may include a stop  5044  to insure that the side panel  16  stops rotating once the side panel  16  is vertical to prevent it from rotating past the vertical position. 
         [0243]    As those skilled in the art will readily appreciate, in the fully assembled condition shown in  FIG. 117 , an open-end wrench can be used on the hexagonal portion  5035  of the spring ratcheting feature  5032  to rotate the spring ratcheting feature  5032 , thereby increasing the torque on the hinge pin  5024  and increasing the counterbalancing effect of the coil spring  5030  on the side panel  16 . Once the torque has been so set, the hinge pin torsion springs provide torque to the side panels as they are rotated down, thereby counterbalancing the weight of the side panels. 
         [0244]    The hinge pin torsion spring assembly  5000  eliminates the need for the step up in height from height  5006  to height  5005  in  FIG. 114 , eliminates the requirement that either side panel  14 ,  16  be shortened to provide clearance for the cable  5045  from the linear spring assembly. Each hinge pin torsion spring assembly  5000  replaces a pin, cable and linear spring, among others. With no need to shorten the side panels to accommodate the cables, the height of the side panels can be increased to minimize the distance that the right and left skirts  23 ,  24  extend down from the roof panel, simplifying sealing in this area. With the elimination of the cable  5045 , the risk that this cable, which is exposed and always under tension, may get caught on something and break, or injure someone, is eliminated as well. Likewise, elimination of the access panels allows each side panel to span the full length of the container, and the use of the hinge pin torsion springs allows height of each side panel to be maximized, resulting in a container that is lighter in weight and more rigid than a container incorporating access panels and linear spring assemblies with cables. 
         [0245]    To fold the container of the present invention, the locking bolts on the access panels are retracted from their respective bolt holes in the roof panel, and the slide locking mechanisms in each of the access panels are used to retract the slide locking bolts from the bolt holes in the right and left side panels. One of the access panels on the front panel and one of the access panels on the at the door panel is then swung toward the interior of the folding container until they lie substantially flat against the respective front, or door, main panel. The remaining access panels are then swung toward the interior of the folding container until they lie substantially flat against the other access panel. (Of course, if the embodiment of the present invention is the one which eliminates the access panels by extending the length of each side panel to the full length of the container, the foregoing folding steps related to the access panels do not occur in the folding process.) 
         [0246]    The doors are then swung closed, but the locking rods are left in the unlocked position. The locking bar is swung into the locking block so that it is received between the flanges of the locking block, and a locking rod on the adjacent door is received within the locking rod recess of the locking bar. Then a locking pin is inserted through the pin receiving hole of the upper flange of the locking block and into the lock pin hole of the locking bar, thus securing the doors together to prevent the doors from opening during the folding process. 
         [0247]    Next, the locking bolts on the left and right side panels are retracted from their respective bolt holes in the roof panel, thereby freeing the side panels to be rotated inwardly. One of the side panels is then swung from its vertical position to a position in which the side panel is resting on the floor of the base panel, after which the other side panel is then swung from its vertical position to a position in which it is resting on the other side. As each of the right and left side panels is rotated inward, the weight of that side panel is substantially counter balanced by the spring force provided by the springs in the linear spring assemblies, or the hinge pin torsion spring assemblies, depending on which is used, thereby allowing one or two people to safely fold the left and right side panels from a vertical position to a horizontal position without additional equipment. At this point, a spreader attaches to the roof panel at each of the four corner fittings in the manner similar to lifting typical shipping containers, so that the roof panel of the container is thus supported by both the spreader and the posts of the front panel and the door panel. 
         [0248]    Then the hammer locking mechanisms in the recessed portions of the base right beam and base left beams adjacent the door main panel are used to retract the hammer locking bolts from the base door interlocks, and in doing so the holes in the door tangs at the lower ends of the right and left door posts, thus freeing the door panel from the base panel. Then and the hammer locking mechanisms in the recessed portions of the base right beam and base left beams adjacent the door main panel are used to retract the hammer locking bolts from the base door interlocks, and in doing so the holes in the door tangs at the lower ends of the right and left door posts, thus unlocking the door panel from the base panel. Likewise, the hammer locking mechanisms in the sill panel of the front panel are used to retract the hammer locking bolts from the base front interlocks, and in doing so the hammer locking bolts retract from the holes in the base front tangs in the lower ends of the right and left door posts, thus unlocking the front panel from the base panel. 
         [0249]    The spreader then lifts the roof panel along with the attached front panel and door panel until the rollers at the lower ends of the door posts and front posts are just a little higher than the guide rails on the base panel immediately adjacent thereto, at which point the door tangs and base front tangs are in a position such that they are fully withdrawn from the interlocks of the door panel and front panel. At this point, the roof panel has been lifted to the highest point necessary in the folding process. Then workers push inwardly on the door panel to swing the bottom edge thereof to be positioned above the base panel well inward of the door edge of the base panel, while workers simultaneously push inwardly on the front panel to force the bottom edge thereof to be positioned above the base panel well inward of the front edge of the base panel. As the workers are so positioning the door panel and front panel, the spreader begins to slowly lower the roof panel until each of the rollers mounted on the lower ends of the door posts and front posts are resting on the immediately adjacent guide rails of the base panel. 
         [0250]    Lowering of the roof panel then continues, causing the rollers of the door panel to roll along the guide rails of the base panel towards the front panel, guided by the cover plates which slide along, but outward of, the guide rails to keep the rollers from sliding off such guide rails. At the same time, lowering of the roof panel causes the rollers of the front panel to roll along the guide rails of the base panel towards the door panel, guided by the cover plates which slide along, but outward of, the guide rails to keep the rollers from sliding off such guide rails. Further lowering of the roof panel continues until the front panel and door panel are substantially parallel to the base panel, the roof panel is resting on the base panel, and each of the base tangs extending from the base panel is received within one of the interlocks of the roof panel. The container is then ready to be locked in its folded position. 
         [0251]    The hammer locks located on the roof panel adjacent the front edge thereof are engaged by hammering the locking bolts into the holes of the interlocks and the holes of the base tangs received therein, as shown in  FIG. 111 . This locks the roof panel to the base panel at the front edges thereof. Then, the pair of locking straps are removed from their stored position, and then re-attached to the folded container such that each locking strap is located between a pair of upper door stop receivers in the roof panel, and a pair of lower door stop receivers in the base panel. Each locking strap is secured to the folded container by bolting the upper end of each locking strap to the roof panel with a bolt that is threaded into one of the upper active strap bolt holes and tightened, and by bolting the lower end of each locking strap to the roof panel with a bolt that is threaded into one of the lower active strap bolt holes and tightened. In this position, as shown in  FIG. 112 , each “T” end of each locking strap is resting against the upper or lower door stop receivers immediately adjacent thereto, so that the load carried by the locking straps during lifting of the folded container is carried by such door stop receivers rather than the bolts that secure the locking straps to the roof panel and base panel. At this point, locking of the roof panel to the base panel has been completed, and the folded container is ready to be moved, stacked, shipped or stored. At this point the spreader can lift the folded container to be stacked onto other folded containers for shipment to the intended destination. 
         [0252]    Unfolding of the preferred embodiment of the present invention is essentially the reverse of the folding process, however when the roof panel has been raised to what was the highest point in the folding process, workers pull the door panel and front panel outwardly to properly position the tangs on the door panel above the interlocks in the base at the door end of the base panel, while workers position the interlocks at the bottom of the front posts over the base front tangs. The workers then hold these positions until the roof panel is lowered and the door tangs and base front tangs are received within the adjacent interlocks. The hammer locks located on the base panel adjacent the door end are then secured by driving each locking bolt through the hole in the adjacent interlock and into the hole in the door tang received therein, and the hammer locks located in the sill panel of the front panel are secured by driving each locking bolt through the hole in the adjacent interlock and into the hole in the base front tang received therein. Then the left and right side panels are lifted to their vertical, unfolded positions (assisted by the counterbalance provided by the springs in the spring tubes), and the locking bolts on the side panels are extended into the bolt holes on the roof panel to lock the left and right side panels to the roof panel. Then, the access panels are unfolded from the door panel and front panel so as to be parallel with the side panels, the slide locking mechanisms in the access panels are used to drive the slide locking bolts into the bolt holes in the right and left side panels, and the locking bolts on the access panels are extended into the bolt holes on the roof panel to lock the access panels to the roof panel. At this point the container is ready for use in shipping cargo. 
         [0253]    As those skilled in the art will readily appreciate, the access panels allow workers to easily enter and exit the container to assist with the folding and unfolding of the side panels. If this flexibility is not desired, the side panels could be extended to span the entire length between the front panel and the door panel, and locking features could be added to the side panels to lock the side panels to the front panel and the door panel, thus eliminating the access panels altogether. 
         [0254]    An alternate series of locking mechanisms for a collapsible container is provided in  FIGS. 123-132 . Referring now to  FIGS. 123-129 , elements forming an internal locking mechanism are depicted. More specifically, with respect to  FIGS. 123-125 , a locking plate assembly  6000  is depicted at the region between a side panel  14  and a corner post  6002 . The locking plate assembly  6000  secures the front panel  12  and door panel  18  to the corner post  6002 . More specifically, the locking plate assembly  6000  comprises a plate  6004  and a linkage bar  6006  with the linkage bar  6006  coupled to the plate  6004 . Referring to  FIG. 125 , the plate  6004  has a generally rectangular shape. However, the specific size and shape of the plate  6004  can vary depending on the container geometry. 
         [0255]    The locking plate assembly  6000  also comprises a lever arm  6008  that is coupled to the linkage bar  6006  and generally parallel to the linkage bar  6006 . The lever arm  6008  has a hinge point  6010  at one end and is pivotable about the hinge point  6010 . The locking plate assembly  6000  also includes a removable pin  6012  which, when installed between the linkage bar  6006  and the lever arm  6008 , secures the locking plate assembly  6000  in its engaged position (with the plate  6004  positioned within corner post  6002 ). 
         [0256]    The locking plate assembly  6000  is movable between an engaged position (where the plate  6004  engages the corner post  6002 ) and a disengaged position (where the plate  6004  has been slidably removed from the corner post  6002 ). More specifically, the plate  6004  engages and passes through a first opening  6014  in the corner post  6002 . In order to engage the plate  6004  in the corner post  6002  a force is applied to the lever arm  6008  in a direction towards the side panel  14  such that the lever arm  6008  pivots about the hinge point  6010 . Movement of the lever arm  6008  causes the linkage bar  6006  (and hence the plate  6004 ) to move laterally due to the connection point between the linkage bar  6006  and the lever arm  6008 . A removable pin  6012  can then be placed through the linkage bar  6006  and the lever arm  6008  to lock the plate  6004  in place. 
         [0257]    In an embodiment of the present invention, a collapsible shipping container utilizes four locking plate assemblies, one between each of four corner posts  6002  and an adjacent front panel  12  and door panel  18 . Therefore, in order to collapse the container and permit the front panel  12  and door panel  18  to collapse, each of the four locking plate assemblies  6000  must be moved from an engaged (i.e. locked) position to a disengaged position, where the plate  6004  is removed from the corner post  6002 . 
         [0258]    The locking plate assembly  6000  is preferably fabricated from A514 or a similar high strength steel having an ultimate yield strength of 80 ksi or greater. Such a material is preferred for purposes of strength and corrosion resistance. 
         [0259]    Referring now to  FIGS. 126-129 , an additional component of the internal locking system is depicted. Referring to  FIG. 126 , a partial perspective view of a plurality of lever latch assemblies  6100  is shown. The lever latch assemblies  6100  are positioned along an inner face or surface  14   a  of the of one or more side panels  14  and/or  16 . As a result, the lever latch assemblies  6100  serve to removably engage the one or more side panels  14  and/or  16  to a skirt portion  23  and/or  24  of the roof panel  11 . 
         [0260]    More specifically, the lever latch assembly  6100  is shown in more detail in  FIGS. 127-129 . The lever latch assembly  6100  comprises a lever arm  6102  having a first end  6104  and an opposing second end  6106 . A lever latch  6108  is coupled to the lever arm  6102  and has a first end  6110  and an opposing second end  6112 . The first end  6110  is coupled to the lever arm  6102  and the second end  6112  has a locking tab  6114 . The lever latch assembly  6100  also comprises a base hinge  6116  that is coupled to the second end  6106  of the lever arm  6102 . 
         [0261]    Referring to  FIGS. 127 and 128 , the lever latch assembly  6100  also includes one or more capture plates  6118 , with the plates  6118  having a recessed opening  6120  sized to receive the locking tab  6114 . The recessed opening  6120  can take on a variety of shapes and configurations. For example, the capture plate  6118  shown in  FIG. 128  has a generally U-shaped slot. The one or more capture plates  6118  are secured to the skirt  23  and  24  of the container  10  by a means such as welding. The one or more plates  6118  provide the region in which the locking tab  6114  engages. The lever latch assembly  6100  also comprises a removable pin (not shown) used to lock the lever latch assembly  6100  in an engaged or locked position. The removable pin can be placed on the lever arm  6102 . A tab (not shown) can be placed long a corrugation  14   b  to which the removable pin would lock, thereby locking the lever latch assembly  6000 . The lever latch assembly  6100  is preferably fabricated from A514 or a similar high strength steel having an ultimate yield strength of 80 ksi or greater. 
         [0262]    Another feature of the lever latch assembly  6100  is the ability for the lever latch  6108  to rotate approximately 180 degrees such that it can be positioned generally parallel and adjacent to the lever arm  6102  or extending away from the lever arm  6102 , as shown in FIG.  127 . The side panel  14  has a series of corrugations  14   b  formed in the sheet metal wall making up the side panel  14 . That is, according to an embodiment of the present invention, when the lever latch assembly  6100  is in a disengaged position, the lever latch  6108  can rotate to be positioned generally parallel and adjacent to the lever arm  6102  and thereby generally contained in the corrugations  14   b  of the side panel. 
         [0263]    As discussed above, the lever latch assembly  6100  provides a system for locking the side panels  14  and  16  in place and for sealing the region between the side panels and the skirt portion  23  and/or  24  of the roof panel  11 . In operation, to secure a side panel in place, the side panel is raised and the lever latch  6108  is rotated upwards towards the one or more capture plates  6118 . Once the locking tab  6114  is positioned within the recessed opening  6120  of the capture plate  6118 , a force is applied to the lever arm  6102 , thereby causing the lever latch  6108  to pull downwards and securing the locking tab  6114  in the recessed opening  6120  of the one or more capture plates  6118 . This process is repeated for each of the multiple lever latch assemblies  6100  located along the interior of the container  10 . 
         [0264]    As discussed above, when the side panels  14  and  16  are unlocked, these side panels can rotate to a collapsed condition where the side panels  14  and  16  are generally parallel to the roof panel  11  and base panel  18 . In order to lower the side panels  14  and  16 , with respect to the lever latch assembly  6100 , it is necessary to disengage the lever latch assembly  6100  from the skirt  23  and/or  24 . 
         [0265]    In order to disengage the lever lock assemblies  6100  in preparation for folding the side panels, the above-described process is reversed. More specifically, a securing pin is removed and a force is applied to the lever arm  6102  in a direction away from the side panel. As a result of the force applied to the lever arm  6102 , the lever arm  6102  pivots about the base hinge  6116 , causing the lever latch  6108  to move in an upwards direction and releasing the locking tab  6114  from the recessed opening  6120  of the one or more capture plates  6118 . Accordingly, the lever latch  6108  can then be pulled out of the one or more capture plates and rotated back to its disengaged position. 
         [0266]    As it can be seen from  FIG. 126 , the lever latch assemblies  6100  can vary in geometry depending on the geometry of the skirts  23  and  24  and side panels  14  and  16 . Specifically, the location of the one or more latch plates  6118  can vary as well as the respective lengths of the lever latch  6108  and lever arm  6102 . 
         [0267]    As discussed above, in one embodiment of the present invention, the locking plate assembly  6000  and the lever latch assembly  6100  are positioned generally along internal surfaces of the collapsible shipping container. However, in an alternate embodiment of the present invention, the locking plate assembly  6000  and the lever latch assembly  6100  can be positioned along exterior walls of the collapsible shipping container so as to be accessible from outside the container. Depending on the certification standards, such an arrangement for the locking plate assembly and lever latch assembly may be required. Given the relative uniform construction of the collapsible shipping container, it is understood that each of the locking mechanisms could be placed on the exterior of the collapsible container with relatively minor modifications to the design discussed above. 
         [0268]    Referring now to  FIGS. 130-132 , an external locking mechanism  6200  for securing a shipping container in a collapsed condition is disclosed. More specifically, the external locking mechanism  6200  comprises one or more locking levers  6202  with each locking lever  6202  comprising a pair of mounting plates  6204  and an arm  6206 . For the embodiment of the present invention shown, the mounting plates  6204  are secured adjacent a top skirt portion  23  and near a roof panel  11 . The locking lever  6202  also comprises an arm  6206  that is pivotally mounted to the pair of mounting plates  6204 . The arm  6206  has a locking tab  6208  at one end of the arm. 
         [0269]    The external locking mechanism  6200  also comprises one or more corner posts  6002 , which are adjacent to the base panel  17 . The one or more corner posts  6002  contain a second opening  6015  sized to receive the locking tab  6208 . The second opening  6015  is positioned opposite of the first opening  6014  discussed above and depicted in  FIGS. 123 and 124 . 
         [0270]    The locking levers  6202  are biased so as to remain in an “engaged” or locked state by a bushing or other mechanism, such as a spring-loaded mechanism. Maintaining the locking levers  6202  in an engaged or use condition provides a fail-safe measure to ensure the locking levers  6202  are actively locking the container in a collapsed position, once the container has been folded. In order to disengage the locking lever  6202  and overcome its biased positioning, a force is applied to the arm  6206  at an end opposite of the locking tab  6208 . The locking lever  6202  can further include a pin lock (not shown) for maintaining the locking lever in a locked position when in use. 
         [0271]    For the embodiment of the present invention disclosed herein, two locking levers  6202  and corresponding corner posts  6002  are positioned adjacent a front panel  12  and an additional two locking levers  6202  and corresponding corner posts  6002  are positioned adjacent a door panel  18  of the container. Use of four locking levers  6202  provides sufficient locking redundancy and security for a collapsed storage container. 
         [0272]    In an alternate embodiment of the present invention, a locking system for a collapsible shipping container is provided comprising a combination of the locking systems outlined in detail above. For example, the locking system comprises a plurality of locking plates for securing the front panel and door panel, a plurality of lever latch assemblies for securing the side panels, and a plurality of locking levers for securing the container when in a collapsed condition. 
         [0273]    As discussed above, roof panels of collapsible shipping containers are secured to the side panels of the shipping container through use of locking assemblies. When collapsible shipping containers are in their expanded state, the locking assemblies of the shipping containers provide a clamping force between the roof panel and the side panels of the container. However, the current locking assemblies have a fixed length. Throughout prolonged use of the shipping container, the roof panel and adjacent side panels become deformed. In turn, the fixed length of the locking assemblies may no longer provide an appropriate clamping force between the roof and adjacent side panels, thereby not providing adequate sealing. 
         [0274]    Referring now to  FIG. 133 , an improved embodiment of the lever latch assembly is depicted. In this improved embodiment, the lever latch assembly  6300  is comprised of the same general components of the lever latch assembly initially depicted in  FIG. 129 , but contains adjustability enhancements. More specifically, the lever latch assembly  6300  is comprised of a lever latch  6308 , which is coupled to the lever arm  6302 . The lever arm  6302  comprises both a first end  6304  and an opposing second end  6306 . Additionally, lever latch  6308  has a first end  6310  and an opposing second end  6312 . 
         [0275]    The improvement to the lever latch assembly  6300  can be seen proximate the opposing second end  6312  of the lever latch  6308 . The opposing second end  6312  of the lever latch  6308  further comprises a locking tab  6314  having an arm coupling portion  6316  and a plate coupling portion  6318 . 
         [0276]    Referring now to  FIG. 134 , the lever latch assembly  6300  is shown in greater detail. In  FIG. 134 , the locking tab  6314  is located proximate an end of the second arm  6312 . The locking tab  6314  is comprised of an arm coupling portion  6316  and a plate coupling portion  6318 . In addition, coupling cylinder  6320  is located coaxial to lever latch  6308  for the purposes of coupling lever latch  6308  to locking tab  6314 . The arm coupling portion  6316  is provided with a male threading, while coupling cylinder  6320  is provided with counterpart female threading. The male threading of arm coupling portion  6316  may be actuated into the counterpart female threading of coupling cylinder  6320  through simple rotational motion. Providing rotational motion to plate coupling portion  6318  will shorten or lengthen the lever latch assembly  6300 . A shorter or longer lever latch assembly  6300  will change the amount of downward force applied to each corresponding capture plate  6118 , as shown in  FIG. 128 . That is, by shortening the length of the lever latch assembly  6300 , a greater downward force can be applied to improve sealing between a roof panel and a sidewall. 
         [0277]      FIG. 135  shows the improved lever latch assembly  6300  located within the foldable shipping container  10 . In this alternate embodiment of the present invention, a plurality of lever latch assemblies  6300  are provided for improved sealing of the roof panel  11  to a side panel  14 . Shown in  FIG. 135  is a lever latch  6308 , having a first end  6310  and an opposing second end  6312 . The opposing second end  6312  further comprises a locking tab  6314  having an arm coupling portion  6316  and a plate coupling portion  6318 . Additionally, the lever latch  6308  further comprises a coupling cylinder  6320  for the purposes of receiving threaded arm coupling portion  6316 . Also depicted in  FIG. 135  is a plurality of capture plates  6118  having recesses  6120  for receiving plate coupling portion  6318 . As it can be seen from  FIGS. 134 and 135 , the plate coupling portion  6318  is generally perpendicular to arm coupling portion to  6316 . 
         [0278]    Referring now to  FIG. 136 , locking tab  6314  is decoupled from the improved lever latch assembly  6300 . The locking tab  6314  is shown to have an arm coupling portion  6316  positioned perpendicular to the receiving plate coupling portion  6318 . It is to be understood that locking tab  6314  and its subcomponents are manufactured from a material capable of handling the load requirements provided to the lever latch assemblies through deformation of the roof and side panels without yielding. It is known that high strength alloy steels, such as ASTM 514, are adept at performing this task, although the scope of this invention is not limited to this type of material. 
         [0279]    As shown in  FIG. 136 , the arm coupling portion  6316  is threaded to allow for length adjustment of the lever latch assembly  6300 . The thread pitch and diameter will determine the rate at which the length of the lever latch assembly  6300  is adjusted. The arm coupling portion  6316  is received within coupling cylinder  6320 , located proximate opposing second end  6312 . In order for a user to provide length adjustment to the lever latch assembly  6300 , the shortening or lengthening can be actuated through rotating plate coupling portion  6318  when the locking tab  6114  is not located within recess  6120 . It is to be understood that each of the plurality of the lever latch assemblies  6300  can be adjusted independently of one another, as deformation of roof panel  11  may vary along the length of the roof panel. 
         [0280]    The above description clearly establishes the advantages provided by the present invention which need not be explained in greater detail to those skilled in the art, who will also recognize that various design modifications and differing components can be introduced within the scope of the present invention as set forth below. 
         [0281]    While the invention has been described in what is known as presently the preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment but, on the contrary, is intended to cover various modifications and equivalent arrangements within the scope of the following claims. The present invention has been described in relation to particular embodiments, which are intended in all respects to be illustrative rather than restrictive. 
         [0282]    From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects set forth above, together with other advantages which are obvious and inherent to the system and method. It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and within the scope of the claims.
The present invention discloses a novel apparatus and way for folding a shipping container in order to improve safety and security of the shipping container. A foldable shipping container is provided having improved locking mechanisms to improve sealing of the container given deformations in container geometry.