CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/940,227, filed on Nov. 13, 2015, which is a continuation of U.S. patent application Ser. No. 13/423,338, filed on Mar. 19, 2012 (now U.S. Pat. No. 9,188,949 issued Nov. 17, 2015), which claims priority from Japanese Patent Application No. 2011-167116 filed Jul. 29, 2011. The contents of the above noted applications are incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to an image-forming device employing an electrophotographic system and a developer cartridge. 
       BACKGROUND 
       [0003]    One electrophotographic color printer known in the art is a tandem-type color laser printer. This printer has four photosensitive members and four developing rollers for supplying toner to respective photosensitive members, the photosensitive members and developing rollers provided respectively for the toner colors yellow, magenta, cyan, and black. 
         [0004]    An example of this type of tandem color laser printer includes an image-forming unit having photosensitive members and developing rollers; and toner cartridges accommodating toner. 
         [0005]    The image-forming unit in this type of printer is centrally disposed inside the printer, while the toner cartridges are detachably provided in a lateral section of the printer. 
       SUMMARY 
       [0006]    However, the toner cartridges in the conventional printer described above are mounted in and removed from the lateral section of the printer (that is, a cartridge-accommodating section) in the axial direction of the photosensitive member. Consequently, the printer must be installed such that a large space is available on the side of the printer for mounting and removing the toner cartridges. Hence, this configuration can make it difficult to install the printer in a small space (i.e., the structure is not conducive to reducing the required installation space of the printer). 
         [0007]    This printer configuration is also not conducive to installation on shelves and in other locations with limited space above and to the side of the printer, thereby reducing the user&#39;s options for locations in which the printer can be installed. 
         [0008]    Therefore, it is an object of the present invention to provide an image-forming apparatus provided with developer cartridge that can reduce the required installation space and increase the user&#39;s freedom in choosing locations for installing the device. 
         [0009]    In order to attain the above and other objects, there is provided an image forming apparatus including: a main casing; a plurality of process units; a plurality of developer cartridges; a process unit supporting member; a cartridge supporting member; and a moving mechanism. Each of the plurality of process units includes a photosensitive drum; and a developer carrying member. The developer carrying member is disposed in confrontation with the photosensitive drum. Each of the plurality of developer cartridges is configured to be provided for each of the plurality of process units. Each of the plurality of developer cartridges includes a developer accommodating section: and a transporting member. The developer accommodating section is configured to accommodate developer. The transporting member is configured to transport developer in the developer accommodating section to a corresponding one of the plurality of process units and to be moved between a communicated position, in which developer is transported to the corresponding one of the plurality of process units, and an interrupted position, in which transporting of developer to the corresponding one of the plurality of process units is interrupted. The process unit supporting member is configured to hold the plurality of process units together therein and to be withdrawn in a predetermined direction. The cartridge supporting member is configured to hold the plurality of developer cartridges together therein and to move between an attached position, in which the cartridge supporting member is attached to the main casing, and to withdrawn position, in which the cartridge supporting member is withdrawn from the main casing. The moving mechanism is configured to move each of the plurality of transporting members between the communicated position and the interrupted position. The transporting member positioned in the interrupted position allows the cartridge supporting member to move from the attached position to the withdrawn position and allows the process unit supporting member to be withdrawn, and the transporting member positioned in the communicated position prevents the cartridge supporting member from moving from the attached position to the withdrawn position and prevents the process unit supporting member from being withdrawn. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In the drawings: 
           [0011]      FIG. 1  is a cross-sectional view of a color printer according to an embodiment of the present invention; 
           [0012]      FIG. 2  is a perspective view of the color printer in  FIG. 1 , wherein a front cover is opened; 
           [0013]      FIG. 3  is a cross-sectional view of the color printer taken along a line A-A of  FIG. 1 , wherein a supply cylinder is in an advanced position; 
           [0014]      FIG. 4  is a cross-sectional view of the color printer taken along the line A-A of  FIG. 1 , wherein the supply cylinder is in a retracted position; 
           [0015]      FIG. 5  is an explanatory diagram illustrating a toner-cartridge-accommodating section shown in  FIG. 2  and is a plan view showing a translation cam and guide grooves; 
           [0016]      FIG. 6  is an explanatory diagram illustrating a movement of the supply cylinder in the toner-cartridge-accommodating section shown in  FIG. 2 , wherein the front cover is closed and the supply cylinder is in the advanced position; 
           [0017]      FIG. 7  is an explanatory diagram illustrating the movement of the supply cylinder in the toner-cartridge-accommodating section shown in  FIG. 2 , wherein the front cover is opened and the supply cylinder is in the retracted position; 
           [0018]      FIG. 8  is an explanatory diagram illustrating the toner-cartridge-accommodating section shown in  FIG. 2 , wherein a toner cartridge drawer is in a pulled-out position; 
           [0019]      FIG. 9  is an explanatory diagram illustrating the removal and mounting process cartridges shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
     1. Overall Structure of a Printer 
       [0020]      FIGS. 1 and 2  show a printer  1  serving as an example of the image-forming apparatus of the present invention. The printer  1  is an intermediate transfer tandem-type color printer. 
         [0021]    The printer  1  includes a main casing  2  constituting the device body, a sheet-feeding unit  3  for feeding sheets of a paper P to be printed. An image-forming unit  4  for forming images on the paper P supplied by the sheet-feeding unit  3 , and a toner-cartridge-accommodating section  5  for accommodating toner cartridges  46  (described later). 
         [0022]    (1) Main Casing 
         [0023]    The main casing  2  has a substantially rectangular box shape in a side view. A process-side access opening  6  is formed in a side wall of the main casing  2 . A front cover  7  as an opening/closing member is pivotably (movably) disposed on the same side wall of the main casing  2 . The front cover  7  is capable of pivoting about its lower end between a closed position for closing the process-side access opening  6  and an open position for exposing the process-side access opening  6 . 
         [0024]    An opening  8  that exposes the front end portion of a paper tray  10  (described later) is formed in a lower portion of the front cover  7 . A manual-paper-feed guide  9  provided on the front cover  7  extends obliquely rearward and downward from the upper edge of the opening  8  toward a position between the bottom wall of a process frame  27  (described later) and the front end portion of a paper-feeding member  18  (described later). 
         [0025]    In the following description, the side of the main casing  2  on which the front cover  7  is provided (the left side in  FIG. 1 ) will be called the “front side,” and the opposite side (the right side in  FIG. 1 ) will be called the “rear side.” Further, the left and right sides of the main casing  2  will be based on the perspective of a user facing the front side of the printer  1 . In other words, the near side in  FIG. 1  will be the “right side,” while the far side will be the “left side.” 
         [0026]    (2) Sheet-Feeding Unit 
         [0027]    The sheet-feeding unit  3  includes a paper tray  10  for accommodating sheets of paper P. 
         [0028]    The paper tray  10  is removably mounted in the bottom section of the main casing  2 . A grip part  11  is provided on the front wall of the paper tray  10  near the top edge thereof. The grip part  11  has a general U-shape in cross section, with the opening of the U-shape facing downward. The top surface of the grip part  11  vertically opposes the manual-paper-feed guide  9 , with a gap formed therebetween. The gap formed between the top surface of the grip part  11  and the manual-paper-feed guide  9  defines a manual-paper-feed opening  12  through which sheets of paper P other than those accommodated in the paper tray  10  may be hand-fed. 
         [0029]    The sheet-feeding unit  3  also includes a pick-up roller  13  disposed above the rear end of the paper tray  10 , a feeding roller  14  disposed to the rear of the pick-up roller  13 , a feeding pad  15  disposed so as to confront the feeding roller  14  from the bottom side thereof, a pair of top and bottom pinch rollers  16  disposed in contact with the rear side of the feeding roller  14 , and a pair of registration rollers  17  disposed above the feeding roller  14  and opposing each other in the front-to-rear direction. 
         [0030]    The pick-up roller  13  rotates to supply sheets of paper P accommodated in the paper tray  10  (indicated by a solid line in  FIG. 1 ) between the feeding roller  14  and feeding pad  15 , whereby the rotation of the feeding roller  14  separates and feeds the paper one sheet at a time. The rotating feeding roller  14  subsequently supplies each sheet of paper P so as to pass sequentially between the feeding roller  14  and pinch rollers  16  and enter between the registration rollers  17  disposed above the feeding roller  14 . The registration rollers  17  rotate in order to supply the sheets to the image-forming unit  4  (between an intermediate transfer belt  41  and a secondary transfer roller  38 , both described later) at a prescribed timing. This feed path extending from the paper tray  10  to the image forming unit  4  through the pick-up roller  13 , the feeding roller  14 , the feeding pad  15 , the pair of pinch rollers  16 , and the pair of registration rollers corresponds to a first feed path. 
         [0031]    A manual-paper-feed path corresponding to second feed path is formed in the sheet-feeding unit  3  between the paper tray  10  and the bottom wall of a process frame  27  (described later). 
         [0032]    A paper-feeding member  18  is provided in the paper tray  10 . The paper-feeding member  18  constitutes the bottom wall of the manual-paper-feed path and confronts the bottom wall of a process frame  27  (described later). 
         [0033]    The paper-feeding member  18  has a generally flat plate shape that is elongated in the front-to-rear direction. The paper-feeding member  18  is disposed on the upper edges of the paper tray  10  by means of a pair of left and right support plates  19  and various compression springs  20 . 
         [0034]    Five tray-side feeding members  21  are rotatably provided in the paper-feeding member  18  at intervals in the front-to-rear direction. While a process frame  27  will be described later, five process-side feeding members  22  are rotatably provided on the bottom wall of the process frame  27  at positions opposing the tray-side feeding members  21 . 
         [0035]    The paper P hand-fed through the manual-paper-feed opening  12  (indicated by a dashed line in  FIG. 1 ) is guided by the manual-paper-feed guide  9  on the front cover  7  and the top surface of the grip part  11  provided on the paper tray  10  to a nip part between the forwardmost process-side feeding members  22  and the forwardmost tray-side feeding members  21 . Each of the process-side feeding members  22  is driven to rotate while the corresponding tray-side feeding members  21  follow, conveying the hand-fed sheet in a rearward direction between the bottom surface of a process frame  27  (described later) and the top surface of the paper-feeding member  18 . 
         [0036]    The hand-fed sheets of paper P are guided to the pick-up roller  13  at the rear end of the paper-feeding member  18  and conveyed between the feeding roller  14  and feeding pad  15  by the rotation of the pick-up roller  13 , as described above. The rotating feeding roller  14  then supplies the sheets of paper P sequentially through the feeding roller  14  and pinch rollers  16  to the nip part between the registration rollers  17  disposed above the feeding roller  14 . The rotating registration rollers  17  supply the sheets between an intermediate transfer belt  41  and secondary transfer roller  38 , both described later, at a prescribed timing. The manual-paper-feed path corresponds to a feed path extending from the manual-paper-feed opening  12  to the pick-up roller  13  through the tray-side feeding members  21  and the process-side feeding members  22 . 
         [0037]    (3) Image-Forming Unit 
         [0038]    The image-forming unit  4  is disposed above the sheet-feeding unit  3  and includes a process unit  23 , a transfer unit  24 , and a fixing unit  25 . 
         [0039]    (3-1) Process Unit 
         [0040]    The process unit  23  is movably disposed above the paper tray  10  in front of the pick-up roller  13 . The process unit  23  is capable of moving in the front and rear directions between a mounted position in which the process unit  23  is mounted in the main casing  2  (see  FIG. 1 ), and a pulled-out position in which the process unit  23  is pulled out of the main casing  2  (see  FIG. 9 ). 
         [0041]    The process unit  23  includes four process cartridges  26  as an image forming unit corresponding to the four colors used in image formation, and a process frame  27  for retaining the process cartridges  26  in a detachably mounted state. 
         [0042]    The process cartridges  26  are juxtaposedly arranged parallel to one another and spaced at intervals in the front-to-rear direction (a predetermined direction). More specifically, the process cartridges  26  include, in order from front to rear, a black process cartridge  26 K, a yellow process cartridge  26 Y, a magenta process cartridge  26 M, and a cyan process cartridge  26 C. 
         [0043]    Each process cartridge  26  integrally holds a photosensitive drum  28 , a Scorotron charger  29 , and a developing device  30 . 
         [0044]    The photosensitive drum  28  has a generally cylindrical shape and is oriented with its axis aligned in the left-to-right direction. 
         [0045]    The Scorotron charger  29  is disposed below and rearward of the corresponding photosensitive drum  28 . The Scorotron charger  29  confronts but is separated from the photosensitive drum  28 . 
         [0046]    The developing device  30  is disposed below and forward of the corresponding photosensitive drum  28 . The developing device  30  is provided with a developing roller  31  as a developer carrying member. 
         [0047]    The developing roller  31  is rotatably supported in the top of the developing device  30  and is disposed in confrontation with the photosensitive drum  28 . A portion of the surface of the developing roller  31  is exposed when viewed from above the developing device  30  (obliquely above and rearward of the developing device  30 ) and contacts the photosensitive drum  28  on the lower front side. 
         [0048]    Each developing device  30  also includes a supply roller  32  for supplying toner to the developing roller  31 , and a thickness-regulating blade  33  for regulating the thickness of toner carried on the developing roller  31 . Each developing device  30  also includes a toner reservoir  34  disposed below and rearward of the supply roller  32  for storing toner supplied from a toner cartridge  46  (described later). 
         [0049]    The black process cartridge  26 K also includes a belt-cleaning roller  90 , a waste toner reservoir  87 , a relay roller  88 , and a scraping blade  89 . 
         [0050]    The belt-cleaning roller  90  is rotatably supported in the black process cartridge  26 K in front of the corresponding photosensitive drum  28  and is positioned for contacting the lower portion of an intermediate transfer belt  41  (described later) from below. 
         [0051]    The belt-cleaning roller  90  functions to clean off any toner remaining on the surface of the intermediate transfer belt  41  (described later). The relay roller  88  temporarily retains toner cleaned off by the belt-cleaning roller  90 . The toner is subsequently scraped off the relay roller  88  by the scraping blade  89  and is collected in the waste toner reservoir  87 . 
         [0052]    An auger screw  91  is rotatably provided in the waste toner reservoir  87  of the black process cartridge  26 K. The auger screw  91  conveys waste toner collected in the waste toner reservoir  87  to a waste-toner-collecting unit (not shown) provided in the black toner cartridge  46  (described later). 
         [0053]    The process frame  27  provided in the main casing  2  is capable of sliding in forward and rearward directions. The process frame  27  includes four LED units  35  corresponding to the four photosensitive drums  28 . 
         [0054]    Each LED unit  35  is disposed on the rear side of the corresponding developing device  30  so as to face the bottom of the corresponding photosensitive drum  28 . Each LED unit  35  also includes an LED array  36  having a plurality of LEDs arrayed in the left-to-right direction. The LED unit  35  functions to expose the surface of the corresponding photosensitive drum  28  based on prescribed image data. 
         [0055]    (3-2) Transfer Unit 
         [0056]    The transfer unit  24  includes a belt unit  37 , and a secondary transfer roller  38 . 
         [0057]    The belt unit  37  is positioned above the process unit  23  when the process unit  23  is in the mounted position. The belt unit  37  is oriented in the front-to-rear direction so as to confront each of the photosensitive drums  28  from above. 
         [0058]    The belt unit  37  includes a drive roller  39 , a follow roller  40 , an intermediate transfer belt  41 , and four primary transfer rollers  42 . 
         [0059]    The drive roller  39  and follow roller  40  are separated in the front-to-rear direction. 
         [0060]    The intermediate transfer belt  41  is placed around the drive roller  39  and follow roller  40  such that its lower portion contacts each of the photosensitive drums  28 . When the drive roller  39  is driven to rotate, the intermediate transfer belt  41  circulates such that the lower portion of the intermediate transfer belt  41  that contacts each of the photosensitive drums  28  moves in a rearward direction. 
         [0061]    The primary transfer rollers  42  are disposed so as to confront the corresponding photosensitive drums  28  with the lower portion of the intermediate transfer belt  41  interposed therebetween. 
         [0062]    The secondary transfer roller  38  is provided on the rear side of the belt unit  37  and confronts the drive roller  39  of the belt unit  37  with the intermediate transfer belt  41  interposed therebetween. 
         [0063]    (3-3) Fixing Unit 
         [0064]    The fixing unit  25  is disposed above the secondary transfer roller  38 . The fixing unit  25  includes a heating roller  43 , and a pressure roller  44  that confronts the heating roller  43 . 
         [0065]    (4) Toner-Cartridge-Accommodating Section 
         [0066]    As shown in  FIGS. 2 and 3 , the toner-cartridge-accommodating section  5  is provided on the right side of the process unit  23 . A cartridge-side access opening  132  as an opening is formed in the front end of the toner-cartridge-accommodating section  5  adjacent to the process-side access opening  6  on the right thereof. The cartridge-side access opening  132  is exposed simultaneously with the process-side access opening  6  when the front cover  7  is opened. A toner cartridge drawer  45  as a support member is accommodated in the toner-cartridge-accommodating section  5 . 
         [0067]    The toner cartridge drawer  45  integrally supports four toner cartridges  46  as a developer cartridge that each accommodates toner (developer) of a discrete color. 
         [0068]    The toner cartridge drawer  45  is arranged in a front-to-rear orientation so as to confront all process cartridges  26 . The toner cartridge drawer  45  is capable of moving between a mounted position in which the process cartridge  26  is mounted inside the main casing  2  (see  FIG. 2 ), and a pulled-out position in which the process cartridge  26  is pulled outside the main casing  2  (see  FIG. 8 ). 
         [0069]    As will be described later in greater detail, when the toner cartridge drawer  45  is in the mounted position, each of the toner cartridges  46  is arranged in a position opposing the right side of the corresponding process cartridge  26 . Each of the toner cartridges  46  is coupled to the right side of the corresponding process cartridge  26  and can supply toner into the toner reservoir  34  of the process cartridge  26 . 
         [0070]    (5) Image-Forming Operation 
         [0071]    Toner supplied into the toner reservoir  34  of the process cartridge  26  from the corresponding toner cartridge  46  is supplied from the toner reservoir  34  onto the supply roller  32 , and in turn supplied onto the developing roller  31 . 
         [0072]    The thickness-regulating blade  33  regulates the thickness of toner supplied to the developing roller  31  as the developing roller  31  rotates, maintaining the toner carried on the surface of the developing roller  31  at a thin uniform thickness. Further, toner supplied to the developing roller  31  is positively tribocharged between the thickness-regulating blade  33  and developing roller  31 . 
         [0073]    In the meantime, the Scorotron charger  29  applies a uniform positive charge to the surface of the corresponding photosensitive drum  28  as the photosensitive drum  28  rotates. The LED unit  35  subsequently exposes the charged surface of the photosensitive drum  28 , forming an electrostatic latent image on the surface that corresponds to an image to be printed on paper P. 
         [0074]    As the photosensitive drum  28  continues to rotate, the positively charged toner carried on the surface of the developing roller  31  is supplied to the latent image formed on the surface of the photosensitive drum  28 . The toner develops the latent image on the photosensitive drum  28  into a visible toner image through reverse development. 
         [0075]    The toner images developed on the surfaces of all photosensitive drums  28  are sequentially transferred onto the lower portion of the intermediate transfer belt  41 , as the lower portion of the intermediate transfer belt  41  moves rearward, as a primary transfer. The sequentially transferred toner images form a color image on the intermediate transfer belt  41 . 
         [0076]    The color image carried on the intermediate transfer belt  41  is subsequently transferred onto a sheet of paper P supplied from the sheet-feeding unit  3 , as the sheet passes between the intermediate transfer belt  41  and secondary transfer roller  38 , as a secondary transfer. 
         [0077]    Next, the color image transferred onto the paper P is fixed to the paper P in the fixing unit  25  by heat and pressure as the sheet passes between the heating roller  43  and pressure roller  44 . 
         [0078]    (6) Paper Discharge 
         [0079]    A discharge tray  47  is formed on the top surface of the main casing  2  for receiving sheets of paper P discharged from the main casing  2 . A paper-discharge unit  48  is formed on the top portion of the main casing  2  at the rear side thereof and protrudes farther upward than the discharge tray  47 . 
         [0080]    A discharge outlet  49  is formed in the paper-discharge unit  48  at a position above the discharge tray  47 . Paper is discharged from the main casing  2  through the discharge outlet  49 . The paper-discharge unit  48  also includes three discharge rollers  50  disposed inside the discharge outlet  49  for conveying sheets of paper P toward the discharge tray  47 . 
         [0081]    Hence, after a toner image is fixed to the sheet of paper P in the fixing unit  25 , the discharge rollers  50  discharge the sheet onto the discharge tray  47 . 
       2. Process Unit 
       [0082]    (1) Process Frame 
         [0083]    As shown in  FIGS. 1, 3, and 4 , the process frame  27  has a generally rectangular frame-like structure with a closed bottom and open top. More specifically, the process frame  27  includes a pair of side walls  53  arranged parallel to each other and separated in the left-to-right direction, a front wall  51  bridging the front ends of the side walls  53 , and a rear wall  52  bridging the rear ends of the side walls  53 . 
         [0084]    The front wall  51  has a handle  54  protruding forward therefrom. 
         [0085]    Guide rollers  55  are rotatably provided in the upper rear end of each of the side walls  53 . Although not shown in the drawings, protrusions elongated in the front-to-rear direction and protruding outward in left and right directions from the left and right side walls  53  are provided on the top edges of the side walls  53 . 
         [0086]    An exposure groove  56  is formed in the right side wall  53  for exposing a toner-receiving unit  66  (described later) of the developing device  30 . The exposure groove  56  is formed as a cutout in the top edge of the right side wall  53 , producing a concave groove that is recessed toward the lower side of the right side wall  53  and that is open on the top. 
         [0087]    (2) Process Cartridge 
         [0088]    Each process cartridge  26  is provided with a pair of left and right side plates  60 , the photosensitive drum  28 , the Scorotron charger  29 , and the developing device  30 . 
         [0089]    The side plates  60  are generally plate-shaped and elongated vertically. The side plates  60  are disposed parallel to each other and separated in the left-to-right direction. An exposure hole  59  is formed in the right side plate  60  to expose a toner-receiving unit  66  (described later). 
         [0090]    The photosensitive drum  28  is rotatably supported between the side plates  60 . The Scorotron charger  29  spans between the side plates  60 . 
         [0091]    The developing device  30  is provided between the side plates  60 . The developing device  30  also has a developer case  61 . 
         [0092]    The developer case  61  is integrally provided with a first frame  62  that supports both the developing roller  31  and supply roller  32 , and a second frame  63  that defines the toner reservoir  34 . 
         [0093]    The first frame  62  has a cylindrical shape elongated in the left-to-right direction. In cross section the first frame  62  has a U-shape with the opening of the “U” facing obliquely upward and rearward. An auger screw  67  is rotatably provided in the first frame  62  to the rear of the supply roller  32 . A toner supply hole  64  and a toner recovery hole  65  are both formed in the bottom rear portion of the first frame  62  at positions confronting the rear side of the auger screw  67 . 
         [0094]    The toner supply hole  64  is a generally rectangular through-hole formed in the left end portion of the first frame  62 . The toner recovery hole  65  is a through-hole having substantially the same shape and dimensions as the toner supply hole  64  and is formed in the right end portion of the first frame  62 . The toner supply hole  64  and toner recovery hole  65  are aligned with each other in the left-to-right direction. 
         [0095]    The second frame  63  is provided below the rear end of the first frame  62 . The second frame  63  is formed in a partial cylindrical shape and is elongated in the left-to-right direction. A cross section of the second frame  63  is generally C-shaped, opening obliquely upward and forward. More specifically, the top of the second frame  63  is formed continuously with the lower rear portion of the first frame  62 , forming a continuous peripheral edge above the toner supply hole  64  and toner recovery hole  65 . The upper portion of the second frame  63  is also formed continuously with the lower rear portion of the first frame  62  in the region in front of and below the bottom edges of the toner supply hole  64  and toner recovery hole  65 . 
         [0096]    The developing device  30  is further provided with a toner-receiving unit  66  on the right side of the toner reservoir  34 . 
         [0097]    The toner-receiving unit  66  has a double-cylinder structure with two coupled cylinders arranged one above the other. The lower cylinder is a conveying cylinder  68 , and the upper cylinder is a receiving cylinder  69 . 
         [0098]    The conveying cylinder  68  is formed continuously with the right wall of the second frame  63  and extends rightward therefrom. The conveying cylinder  68  has a generally cylindrical shape with a smaller diameter than that of the second frame  63  and has a common central axis with the second frame  63 . The left end of the conveying cylinder  68  that is continuously formed with the right wall of the second frame  63  opens into the interior of the second frame  63 , while the right end of the conveying cylinder  68  is closed. 
         [0099]    A toner-conveying member  81  is provided inside the second frame  63  and conveying cylinder  68 . 
         [0100]    The toner-conveying member  81  is integrally provided with an agitator  82  disposed inside the second frame  63 , and an auger screw  83  disposed inside the conveying cylinder  68 . The agitator  82  and auger screw  83  are formed continuously in the left-to-right direction and share the same rotational shaft. The right end of the toner-conveying member  81  is rotatably supported in the right wall of the conveying cylinder  68 . The left end of the toner-conveying member  81  is rotatably supported in the left wall of the second frame  63  so as to be capable of rotating relative to the left wall, and protrudes leftward therefrom. A drive gear  84  is provided on the left end portion of the toner-conveying member  81  outside the left wall of the second frame  63  and is incapable of rotating relative to the toner-conveying member  81 . A drive force generated in the main casing  2  is inputted into the drive gear  84  via a gear train (not shown). 
         [0101]    The receiving cylinder  69  is formed in a generally cylindrical shape that is elongated in the left-to-right direction. The lower portion of the receiving cylinder  69  is connected to the top portion of the conveying cylinder  68 . The left end of the receiving cylinder  69  is closed and is disposed at a position confronting the right side of the first frame  62  at a distance. The right end of the receiving cylinder  69  is open. The inner diameter of the receiving cylinder  69  is slightly larger than the outer diameter of a supply cylinder  98  (described later) of the toner cartridge  46  and is capable of receiving this supply cylinder  98 . A first reception opening  70  as a reception opening is formed in the right end portion of the receiving cylinder  69 , vertically penetrating the bottom portion of the same, and provides communication between the conveying cylinder  68  and receiving cylinder  69 . 
         [0102]    The receiving cylinder  69  further includes a process-side shutter  71 , and a coupling  72  as a first coupling member. The process-side shutter  71  is generally cylindrical in shape with a closed right end and is elongated in the left-to-right direction. The process-side shutter  71  has an outer diameter substantially equal to the outer diameter of the supply cylinder  98  (described later) and a left-to-right length equivalent to about half that of the receiving cylinder  69 . A coupling exposure hole  76  is formed through the right wall of the process-side shutter  71  for exposing a fitting member  75  (described later) of the coupling  72 . The coupling exposure hole  76  has a larger diameter than that of the fitting member  75  (described later). 
         [0103]    The process-side shutter  71  is disposed inside the receiving cylinder  69  and is capable of sliding between an open position (see  FIG. 3 ) in the left end of the receiving cylinder  69  for opening the first reception opening  70 , and a closed position (see  FIG. 4 ) in the right end of the receiving cylinder  69  for closing the first reception opening  70 . A compression spring  73  is also interposed between the left wall of the receiving cylinder  69  and the right wall of the process-side shutter  71  for constantly urging the process-side shutter  71  rightward toward the closed position. 
         [0104]    The coupling  72  is rotatably supported in the left wall of the receiving cylinder  69 . The coupling  72  specifically includes a drive shaft  74 , the fitting member  75 , and a drive input gear  77 . 
         [0105]    The drive shaft  74  has a generally columnar shape and extends in the left-to-right direction. The drive shaft  74  is rotatably supported in the left wall of the receiving cylinder  69 . 
         [0106]    The fitting member  75  is provided on the right end of the drive shaft  74  and is incapable of rotating relative thereto. The fitting member  75  is generally disc-shaped and shares a central axis with the drive shaft  74 . 
         [0107]    The drive input gear  77  is provided on the left end of the drive shaft  74  and is incapable of rotating thereto. The drive input gear  77  is positioned between the receiving cylinder  69  and first frame  62  and shares a central axis with the drive shaft  74 . A drive force generated from the main casing  2  is inputted into the drive input gear  77  via a gear train (not shown). 
       3. Toner Cartridges and Toner-Cartridge-Accommodating Section 
       [0108]    (1) Toner Cartridges 
         [0109]    As shown in  FIGS. 3 and 4 , each of the toner cartridges  46  includes a cartridge case  94  accommodating toner, and a supply cylinder  98  as a supply member for supplying toner in the cartridge case  94  to the toner reservoir  34  of the process cartridge  26 . 
         [0110]    The cartridge case  94  has a box shape that is generally rectangular in a side view. Within the cartridge case  94  are formed a toner-accommodating section  95  as a developer accommodating section for accommodating toner, and a supply-cylinder support unit  96  for supporting the supply cylinder  98 . 
         [0111]    The toner-accommodating section  95  is provided in all but the lower portion of the cartridge case  94 . The lower end of the toner-accommodating section  95  is tapered so that its horizontal cross section grows smaller toward the bottom. A through-hole  97  as a developer discharge opening is formed in the bottom end of the toner-accommodating section  95 , opening downward. 
         [0112]    The supply-cylinder support unit  96  is formed in the lower end of the cartridge case  94  as a through-hole in communication with the through-hole  97 . The supply-cylinder support unit  96  has a generally circular cross section and extends left-to-right. The inner diameter of the supply-cylinder support unit  96  is larger than the outer diameter of the supply cylinder  98 . 
         [0113]    A spring-accommodating section  93  is formed in the supply-cylinder support unit  96 . The spring-accommodating section  93  is provided at a midpoint of the supply-cylinder support unit  96  with respect to the left-to-right direction (more specifically, left of the left-to-right center of the supply-cylinder support unit  96 ) on the left side of the through-hole  97 . The spring-accommodating section  93  is generally circular in cross section and elongated in the left-to-right direction and has a larger diameter that expands radially outward from the inner diameter of the supply-cylinder support unit  96 . 
         [0114]    The supply cylinder  98  has a generally cylindrical shape and is elongated in the left-to-right direction and closed on both left and right ends. The supply cylinder  98  has a left-to-right length substantially equal to the left-to-right length of the cartridge case  94 . A supply opening  99  is formed in the left end of the supply cylinder  98 , penetrating the lower portion of the supply cylinder  98  vertically. Similarly, a second reception opening  109  as a developer reception opening is formed in the right end of the supply cylinder  98 , penetrating the upper portion of the supply cylinder  98  vertically. A flange part  101  is provided around the supply cylinder  98  at approximately the left-to-right center thereof and protrudes radially outward from the outer peripheral surface of the supply cylinder  98 . 
         [0115]    The supply cylinder  98  is provided with an auger screw  100  as a conveying member. The auger screw  100  is disposed inside the supply cylinder  98  and oriented in the left-to-right direction (in a horizontal direction). The right end of the auger screw  100  is rotatably supported in the right wall of the supply cylinder  98 , and the left end of the auger screw  100  is rotatably supported in the left wall of the supply cylinder  98  and protrudes leftward out from the left wall. 
         [0116]    A fitting part  102  as a second coupling member and a drive input member is formed on the left end portion of the auger screw  100 . The fitting part  102  is generally disc-shaped and shares a rotational center with the auger screw  100 . The fitting part  102  is fitted with the fitting member  75  provided on the coupling  72  of the toner-receiving unit  66  so as to be incapable of rotating relative to the fitting member  75 . 
         [0117]    The supply cylinder  98  is supported inside the supply-cylinder support unit  96  of the cartridge case  94  so that the flange part  101  is positioned in the spring-accommodating section  93 . 
         [0118]    This configuration for supporting the supply cylinder  98  enables the supply cylinder  98  to move left and right between a retracted position as an interrupt position and a closed position (see  FIG. 4 ) retracted inside the supply-cylinder support unit  96 , and an advanced position as a communication position and an open position (see  FIG. 3 ) advanced until the left end of the supply cylinder  98  is farther leftward than the left end of the supply-cylinder support unit  96 . 
         [0119]    When the supply cylinder  98  is in the retracted position, the flange part  101  is disposed in the right end of the spring-accommodating section  93  and the second receiving port  109  is shifted to the right side of the through-hole  97 , interrupting communication between the second receiving port  109  and through-hole  97 . Here, the through-hole  97  is closed from below by the upper edge of the supply cylinder  98  (the portion of the supply cylinder  98  on the left side of the second receiving port  109 ). Further, when the supply cylinder  98  is in the retracted position, the left and right end faces of the supply cylinder  98  are substantially flush with the left and right end faces of the cartridge case  94 . 
         [0120]    When the supply cylinder  98  is in the advanced position, the flange part  101  is disposed in the left end portion of the spring-accommodating section  93 , and the second receiving port  109  and through-hole  97  are aligned vertically and in communication with each other. 
         [0121]    A compression spring  103  as an urging member is interposed between the right surface of the flange part  101  and the left surface of the spring-accommodating section  93  for constantly urging the supply cylinder  98  rightward toward the retracted position. To be disposed in the advanced position, the supply cylinder  98  is moved leftward against the urging force of the compression spring  103 . 
         [0122]    As illustrated in  FIG. 1 , the black toner cartridge  46  is formed wider in the front-to-rear direction than the other toner cartridges  46  (cyan, magenta, and yellow toner cartridges  46 ). A waste-toner-accommodation section (not shown) is provided in the front region of the black toner cartridge  46  separately from the toner-accommodating section  95  for accommodating waste toner conveyed from the waste toner reservoir  87 . 
         [0123]    As shown in  FIG. 6 , the black toner cartridge  46  includes a waste-toner-conveying cylinder  104  coupled to the waste toner reservoir  87  of the black process cartridge  26 K. 
         [0124]    The waste-toner-conveying cylinder  104  is shaped substantially the same as the supply cylinder  98 . However, instead of the supply opening  99  formed in the left end of the supply cylinder  98 , a waste-toner-receiving port (not shown) is provided in the waste-toner-conveying cylinder  104 , vertically penetrating the upper portion thereof, for receiving waste toner from the waste toner reservoir  87 . 
         [0125]    When in the advanced position shown in  FIG. 6 , the waste-toner-conveying cylinder  104  is coupled to the waste toner reservoir  87  of the black process cartridge  26 K. However, when the waste-toner-conveying cylinder  104  is in the retracted position shown in  FIG. 7 , the waste-toner-conveying cylinder  104  is disconnected from the waste toner reservoir  87 . 
         [0126]    (2) Toner-Cartridge-Accommodating Section 
         [0127]    As shown in  FIGS. 2, 3, and 4 , a partitioning wall  113  divides the toner-cartridge-accommodating section  5  into left and right sides. The toner cartridge drawer  45  is accommodated in the left side, while a moving mechanism  111  is accommodated in the right side. 
         [0128]    Five pressing-member insertion holes  118  (see  FIG. 5 ) are formed in the lower end of the partitioning wall  113  for receiving the insertion of pressing members  121  (described later). 
         [0129]    The pressing-member insertion holes  118  are juxtaposed at intervals in the front-to-rear direction and formed at positions corresponding to the supply cylinders  98  and the waste-toner-conveying cylinder  104 . 
         [0130]    (2-1) Toner Cartridge Drawer 
         [0131]    As shown in  FIG. 1 , the toner cartridge drawer  45  has a frame-like structure that is elongated in the front-to-rear direction. The toner cartridge drawer  45  has a closed bottom but is open on the left and right sides. More specifically, the toner cartridge drawer  45  is integrally configured of a bottom wall  112 , a front wall  114 , a rear wall  115 , and three partitioning walls  116 . 
         [0132]    The bottom wall  112  has a flat plate shape that is substantially rectangular in a plan view and elongated in the front-to-rear direction. Drawer-side rollers  117  are provided on the rear edge of the bottom wall  112  near both left and right sides thereof. The drawer-side rollers  117  are fitted with play in guide grooves  123  (described later) formed in the toner-cartridge-accommodating section  5 . 
         [0133]    The front wall  114  has a generally flat plate shape and extends upward from the front edge of the bottom wall  112 . The rear wall  115  has a generally flat plate shape and extends upward from the rear edge of the bottom wall  112 . 
         [0134]    The partitioning walls  116  are arranged parallel to each other and spaced at intervals in the front-to-rear direction between the front wall  114  and rear wall  115 . Each of the partitioning walls  116  has a generally flat plate shape and extends upward from the bottom wall  112 . With this configuration, the toner cartridge drawer  45  is partitioned into four regions each having a front-to-rear length equivalent to the front-to-rear length of the corresponding toner cartridge  46 . 
         [0135]    Each of the toner cartridges  46  is detachably supported in the toner cartridge drawer  45  in areas defined by the front wall  114 , rear wall  115 , and partitioning walls  116 . 
         [0136]    As shown in  FIG. 5 , guide grooves  123  are formed in the bottom portion of the toner-cartridge-accommodating section  5  for receiving the drawer-side rollers  117  of the toner cartridge drawer  45 . Rail-side rollers  127  are also provided in the bottom portion of the toner-cartridge-accommodating section  5 . 
         [0137]    Two of the guide grooves  123  are formed in the left half portion of the toner-cartridge-accommodating section  5  at positions separated in the left-to-right direction and corresponding to the drawer-side rollers  117  of the toner cartridge drawer  45 . The guide grooves  123  are grooves recessed downward into the bottom surface of the toner-cartridge-accommodating section  5  and are substantially linear, extending in the front-to-rear direction. 
         [0138]    The rail-side rollers  127  are rotatably provided in the front ends of the guide grooves  123  such that their top portions protrude upward from the guide grooves  123 . 
         [0139]    The toner cartridge drawer  45  is accommodated in the toner-cartridge-accommodating section  5  with the drawer-side rollers  117  fitted into the corresponding guide grooves  123 . The rail-side rollers  127  contact the bottom of the bottom wall  112  constituting the toner cartridge drawer  45 . 
         [0140]    (2-2) Moving Mechanism 
         [0141]    As shown in  FIGS. 2, 6, and 7 , the moving mechanism  111  is provided with a translation cam  122  as a moving member, and five pressing members  121 . The moving member  111  is disposed on an opposite side of the supply cylinder  98  from the process cartridges  26 . 
         [0142]    The translation cam  122  is provided in the right half of the toner-cartridge-accommodating section  5  and is capable of sliding (reciprocating) in forward and rearward directions. The translation cam  122  has a square columnar shape extending in the front-to-rear direction and is substantially rectangular in a plan view. 
         [0143]    The translation cam  122  includes four recessed parts  119  corresponding to the supply cylinders  98  and the waste-toner-conveying cylinder  104 , and a rack part  120  as an operating portion. 
         [0144]    The recessed parts  119  are aligned with each other and spaced at intervals in the front-to-rear direction. Each recessed part  119  has a generally trapezoidal shape in a plan view and is recessed rightward in the left surface of the translation cam  122 . Each recessed part  119  has a front surface  141  sloping rightward toward the rear, and a right surface  142  aligned in the front-to-rear direction and formed continuously from the rear end of the front surface  141 . The forwardmost recessed part  119  corresponding to the waste-toner-conveying cylinder  104  has a front-to-rear length approximately half that of the other recessed parts  119 . 
         [0145]    The rack part  120  extends in the front-to-rear direction and is formed on the left side of the translation cam  122  along the bottom edge near the front end thereof. Gear teeth (not shown) are formed in the bottom edge of the rack part  120 . 
         [0146]    The translation cam  122  is provided in the toner-cartridge-accommodating section  5  and is capable of sliding (reciprocating) between a first position (see  FIG. 6 ) accommodated in the toner-cartridge-accommodating section  5 , and a second position (see  FIG. 7 ) in which the front end portion of the translation cam  122  protrudes forward from the cartridge-side access opening  132 . 
         [0147]    When the translation cam  122  is in the first position, each of the recessed parts  119  is offset rearward from the corresponding pressing-member insertion holes  118 . When the translation cam  122  is in the second position, the recessed parts  119  are disposed opposite the corresponding pressing-member insertion holes  118 . 
         [0148]    A coupling member  128  is provided on the front cover  7 . By engaging the coupling member  128  with the rack part  120 , the translation cam  122  is coupled to the front cover  7 . 
         [0149]    More specifically, the coupling member  128  has a generally curved rod shape. When the front cover  7  is in the closed position, the coupling member  128  extends from the rear surface of the front cover  7 , curving downward and rearward. Gear teeth (not shown) are formed on the top surface of the coupling member  128 . When the front cover  7  is in the closed position, the coupling member  128  engages with the rack part  120  from below. 
         [0150]    When the front cover  7  is moved from the closed position to the open position, a forward drive force is transmitted to the translation cam  122  via the coupling member  128  for moving the translation cam  122  from the first position to the second position. As the front cover  7  moves further toward the open position, the coupling member  128  separates from the rack part  120  of the translation cam  122 . 
         [0151]    Conversely, as the front cover  7  is moved from the open position toward the closed position, the rear end (free end) of the coupling member  128  engages with the rear end of the rack part  120  provided on the translation cam  122 . As the front cover  7  moves further toward the closed position, a rearward drive force is transmitted to the translation cam  122  via the coupling member  128  for moving the translation cam  122  from the second position to the first position. 
         [0152]    The pressing members  121  are arranged at intervals on the left side of the translation cam  122  in positions corresponding to the supply cylinders  98  and the waste-toner-conveying cylinder  104 . Each pressing member  121  has a generally columnar shape and extends in the left-to-right direction. The left-to-right length of the pressing members  121  is slightly longer than the gap between the right surface  142  of the recessed parts  119  formed in the translation cam  122  and the right surface of the partitioning wall  113 . A flange part  129  is provided on the right end of each pressing member  121 . The flange part  129  protrudes radially outward from the outer surface of the pressing member  121 . 
         [0153]    Each pressing member  121  can be moved between a pressing position (see  FIG. 6 ) in which the pressing member  121  is inserted into the corresponding pressing-member insertion hole  118  and presses the corresponding supply cylinder  98  or waste-toner-conveying cylinder  104  leftward, and a release position (see  FIG. 7 ) in which the pressing member  121  is retracted to the right side of the corresponding pressing-member insertion hole  118 , releasing pressure on the corresponding supply cylinder  98  or waste-toner-conveying cylinder  104 . 
         [0154]    A compression spring  108  is interposed between the left surface of each flange part  129  and the right surface of the partitioning wall  113 . The compression springs  108  constantly urge the corresponding pressing members  121  rightward toward the release position. 
         [0155]    When the translation cam  122  is in the first position, the right end of each pressing member  121  contacts the left surface of the translation cam  122  on the front side of the corresponding recessed part  119 . In this state, each pressing member  121  has been moved leftward against the urging force of the compression spring  108  and is in the pressing position shown in  FIG. 6 . 
         [0156]    When the translation cam  122  is disposed in the second position, the right end of each pressing member  121  opposes the right surface  142  of the corresponding recessed part  119 . In this state, the pressing member  121  has been moved rightward by the urging force of the compression spring  108  and is in the release position shown in  FIG. 7 . 
       4. Main Casing 
       [0157]    As shown in  FIGS. 3, 6, and 9 , a partitioning wall  131  is provided in the main casing  2  for separating the image-forming unit  4  and toner-cartridge-accommodating section  5 . Process-unit guide grooves  134  are formed in the main casing  2  for guiding the process unit  23  as the process unit  23  slides. 
         [0158]    The partitioning wall  131  has a general flat plate shape. The partitioning wall  131  is disposed between the image-forming unit  4  and toner-cartridge-accommodating section  5 . Five through-holes  135  are formed in the partitioning wall  131  to allow insertion of the four supply cylinders  98  of the toner cartridges  46  and the waste-toner-conveying cylinder  104 . 
         [0159]    The through-holes  135  are substantially circular in a side view and are arranged at positions spaced in the front-to-rear direction that correspond to the supply cylinders  98  of the toner cartridges  46  and the waste-toner-conveying cylinder  104 . 
         [0160]    One of the process-unit guide grooves  134  is formed in the right surface of the left wall of the main casing  2  while the other is formed in the left surface of the partitioning wall  131 . The process-unit guide grooves  134  extend in the front-to-rear direction and are substantially linear. The process-unit guide grooves  134  have a width (vertical dimension) sufficient to receive the guide rollers  55  of the process unit  23 . 
       5. Operations for Mounting and Removing the Toner Cartridges 
       [0161]    To remove the toner cartridges  46  mounted in the main casing  2 , first the operator places the front cover  7  in the open position, as shown in  FIG. 2 , to expose the cartridge-side access opening  132 . 
         [0162]    When the front cover  7  is moved from the closed position to the open position, the translation cam  122  is pulled forward through the coupling member  128 , moving the translation cam  122  from the first position shown in  FIG. 6  to the second position shown in  FIG. 7 . 
         [0163]    When the translation cam  122  is moved to the second position, the urging force of the compression springs  108  moves the corresponding pressing members  121  from their pressing position to their release position. 
         [0164]    At the same time, the urging force of the compression springs  103  moves the corresponding supply cylinders  98  and the waste-toner-conveying cylinder  104  from their advanced position to their retracted position so that the supply cylinders  98  and the waste-toner-conveying cylinder  104  are extracted from the through-holes  135  of the partitioning wall  131 , as shown in  FIGS. 4 and 7 . That is, the moving mechanism  111  moves the supply cylinders  98  of all toner cartridges  46  altogether between the advanced position to the retracted position at a time. 
         [0165]    This retraction interrupts communication between the supply openings  99  of the supply cylinders  98  and the first reception openings  70  of the receiving cylinders  69  and also interrupts communication between the second receiving ports  109  of the supply cylinders  98  and the through-holes  97  of the toner-accommodating sections  95 . In addition, the fitting parts  102  of the supply cylinders  98  are moved rightward and separated from the fitting members  75  of the corresponding receiving cylinders  69 , and the waste-toner-conveying cylinder  104  is uncoupled from the waste toner reservoir  87 . 
         [0166]    At this time, the toner cartridge drawer  45  can be pulled forward. 
         [0167]    Further, the process-side shutters  71  are moved to the closed position by the urging force of the corresponding compression springs  73  at this time. 
         [0168]    To move the toner cartridges  46 , the operator pulls the toner cartridge drawer  45  forward through the cartridge-side access opening  132 . When the toner cartridge drawer  45  reaches the pulled-out position, the drawer-side rollers  117  contact the rear side of the rail-side rollers  127 , as shown in  FIG. 8 . This contact between the rail-side rollers  127  and the drawer-side rollers  117  restricts the toner cartridge drawer  45  from being pulled farther. 
         [0169]    To remove the toner cartridges  46 , the operator lifts the toner cartridges  46  up and out of the toner cartridge drawer  45 . This completes the operation to remove toner cartridges  46  from the main casing  2 . 
         [0170]    In order to mount toner cartridges  46  in the main casing  2 , the procedure described above for removing the toner cartridges  46  is performed in reverse. 
         [0171]    Specifically, while the toner cartridge drawer  45  is disposed in the pulled-out position, the operator inserts the toner cartridges  46  into the toner cartridge drawer  45  from above to a prescribed position within the toner cartridge drawer  45 . 
         [0172]    To mount the toner cartridges  46  in the main casing  2 , the operator then pushes the toner cartridge drawer  45  rearward through the cartridge-side access opening  132 . As the toner cartridge drawer  45  is pushed rearward, the rear end of the toner cartridge drawer  45  contacts the rear wall of the toner-cartridge-accommodating section  5 , as shown in  FIG. 7 . At this time, the toner cartridge drawer  45  is in the mounted position. 
         [0173]    In this position, the supply cylinders  98  of the toner cartridge  46  face the right sides of the receiving cylinders  69  in the corresponding process cartridges  26  through the through-holes  135  formed in the partitioning wall  131 . The waste-toner-conveying cylinder  104  of the toner cartridge  46  confronts the right side of the waste toner reservoir  87  in the black process cartridge  26 K through the through-hole  135  of the partitioning wall  131 . 
         [0174]    Next, the operator moves the front cover  7  to its closed position, thereby closing the cartridge-side access opening  132 . As the front cover  7  moves from the open position to the closed position, the translation cam  122  is pushed rearward through the coupling member  128 , moving the translation cam  122  from the second position shown in  FIG. 7  to the first position shown in  FIG. 6 . 
         [0175]    As the translation cam  122  moves toward the first position, each of the pressing members  121  is pushed leftward by the sloping front surfaces  141  of the recessed parts  119 . Hence, the pressing members  121  move from their release position to their pressing position against the urging force of the compression springs  108 . 
         [0176]    At the same time, the supply cylinders  98  and the waste-toner-conveying cylinder  104  are pressed leftward by the corresponding pressing members  121 . As shown in  FIG. 3 , the supply cylinders  98  and the waste-toner-conveying cylinder  104  move from their retracted position to their advanced position against the urging force of the compression springs  103  and are inserted through the through-holes  135  formed in the partitioning wall  131 . 
         [0177]    Consequently, each of the supply cylinders  98  contacts the right ends of the process-side shutters  71  in the corresponding process cartridges  26  from the right side. As the supply cylinders  98  are pressed further leftward, each of the supply cylinders  98  is inserted into the corresponding receiving cylinders  69  against the urging force of the compression springs  73  while pressing the process-side shutters  71  leftward. 
         [0178]    When the supply cylinders  98  reach the advanced position, the process-side shutters  71  are disposed in their open position. Similarly, the waste-toner-conveying cylinder  104  is coupled to the waste toner reservoir  87 . By inserting the supply cylinders  98  into the receiving cylinders  69  and coupling the waste-toner-conveying cylinder  104  with the waste toner reservoir  87 , the toner cartridge drawer  45  is no longer movable in forward and rearward directions. 
         [0179]    At this time, the supply openings  99  in the supply cylinders  98  and the first reception openings  70  of the receiving cylinders  69  oppose each other vertically and are in communication. Further, the second receiving ports  109  of the supply cylinders  98  vertically oppose the through-holes  97  of the toner-accommodating sections  95  and are in communication with the same. The fitting parts  102  of the supply cylinders  98  are fitted with the fitting members  75  of the corresponding receiving cylinders  69  through the coupling exposure holes  76  of the process-side shutters  71 . 
         [0180]    This completes the process for mounting the toner cartridges  46  in the main casing  2 . 
       6. Operations for Supplying Toner from the Toner Cartridges to the Process Cartridges 
       [0181]    At the beginning of an image-forming operation performed on the printer  1 , a drive source (not shown) in the main casing  2  inputs a drive force into the drive input gears  77  of the receiving cylinders  69 . As shown in  FIG. 3 , the drive force is transmitted to the auger screws  100  of the toner cartridges  46  via the couplings  72  of the receiving cylinders  69  for rotating the auger screws  100 . 
         [0182]    The drive source (not shown) provided in the main casing  2  also inputs a drive force into the drive gears  84  of the toner reservoirs  34 . The drive force is transmitted to the toner-conveying members  81  of the toner reservoirs  34  to rotate the same. 
         [0183]    As a result, the auger screws  100  convey toner, which has been supplied from the toner-accommodating sections  95  of the toner cartridges  46  into the supply cylinders  98  through the through-holes  97  and second receiving ports  109 , leftward through the supply cylinders  98 . The toner conveyed leftward in the supply cylinders  98  is supplied through the first reception openings  70  formed in the process cartridges  26  via the supply openings  99 . 
         [0184]    Toner supplied through the first reception openings  70  is conveyed leftward through the conveying cylinders  68  by the auger screws  83  of the toner-conveying members  81  and is supplied into the toner reservoirs  34  of the process cartridges  26 . 
         [0185]    Toner supplied to the toner reservoirs  34  is subsequently agitated by the agitators  82  of the toner-conveying members  81  while being conveyed leftward through the toner reservoirs  34 . The toner is supplied through the toner supply holes  64  into the first frames  62  of the developing devices  30 . 
         [0186]    The toner supplied into the first frames  62  is accumulated therein and subsequently supplied to the developing rollers  31  by the supply rollers  32 , as described above. 
         [0187]    The auger screws  67  in the first frames  62  (see  FIG. 1 ) convey toner in the first frames  62  from the left side toward the right side. Excess toner passes through the toner recovery holes  65  and is collected in the toner reservoirs  34  so that the level of toner in the first frames  62  does not exceed a prescribed level. 
       7. Mounting and Removing the Process Cartridges 
       [0188]    To remove the process cartridges  26  when the process cartridges  26  are mounted in the main casing  2 , the operator first places the front cover  7  in the open position, as shown in  FIG. 2 , thereby exposing the process-side access opening  6 . 
         [0189]    Next, the operator pulls the process unit  23  forward through the process-side access opening  6 . As the process unit  23  is pulled forward, the guide rollers  55  of the process frame  27  are guided in the process-unit guide grooves  134  formed in the main casing  2  until the process unit  23  reaches the pulled-out position. 
         [0190]    In this state, the operator can lift the process cartridges  26  up and out of the process frame  27 , thereby completing the removal of the process cartridges  26  from the main casing  2 . 
         [0191]    When mounting the process cartridges  26  in the main casing  2 , the procedure for removing the process cartridges  26  described above is performed in reverse. That is, while the process frame  27  is disposed in the pulled-out position, the operator inserts the process cartridges  26  into the process frame  27  from above until the process cartridges  26  are in a prescribed position. 
         [0192]    Next, the operator pushes the process unit  23  rearward through the process-side access opening  6 . As the process unit  23  moves rearward, the guide rollers  55  of the process frame  27  are guided in the process-unit guide grooves  134  formed in the main casing  2  until the process unit  23  reaches the mounted position. 
         [0193]    Next, the operator moves the front cover  7  into its closed position to cover the process-side access opening  6 , thereby completing the operation for mounting the process cartridges  26  in the main casing  2 . 
       8. Operational Advantages 
       [0194]    (1) As illustrated in  FIGS. 6, 7, and 8 , after the supply cylinders  98  are moved from the advanced position to the retracted position in the printer  1  of the embodiment, the toner cartridge drawer  45  can be pulled in a forward direction from the mounted position out of the main casing  2 . 
         [0195]    Hence, the toner cartridge drawer  45  having a structure for providing communication between the toner cartridges  46  and process cartridges  26  in the left-to-right direction can be moved forward and rearward by retracting the supply cylinders  98  of the toner cartridges  46  rightward from the process cartridges  26 . 
         [0196]    With this configuration, the space on the right side of the printer  1  required for mounting and removing the toner cartridges  46  can be greatly reduced, thereby minimizing the space required for installing the printer  1 . 
         [0197]    Further, even when the printer  1  is installed on a shelf or other location with limited space on left and right sides of the printer  1 , the toner cartridge drawer  45  can be pulled forward for replacing the toner cartridges  46 . As a result, this configuration enhances the user&#39;s options for locations in which the printer  1  can be installed. 
         [0198]    (2) As shown in  FIGS. 6 and 7 , the moving mechanism  111  of the printer  1  can move the supply cylinders  98  of all toner cartridges  46  altogether between the advanced position and retracted position at a time. Therefore, the moving mechanism  111  can move all supply cylinders  98  from the advanced position to the retracted position or from the retracted position to the advanced position in one operation. 
         [0199]    (3) As shown in  FIG. 2 , the translation cam  122  in the printer  1  of the embodiment includes the rack part  120  on the front end thereof. With this construction, an operator can easily access the rack part  120  of the translation cam  122  from the same side (front side) as the toner cartridge drawer  45 . 
         [0200]    (4) As shown in  FIGS. 6 and 7 , the supply cylinders  98  can be maintained constantly in the retracted position by the urging force of the compression springs  103 , interrupting communication between the supply openings  99  and corresponding first reception openings  70 . 
         [0201]    Further, through a simple structure for reciprocating the translation cam  122  in forward and rearward directions, the supply cylinders  98  can be moved between the advanced position and retracted position. 
         [0202]    (5) As shown in  FIGS. 6 and 7 , the supply cylinders  98  can be moved to the retracted position in association with the opening operation of the front cover  7  and can be moved to the advanced position in association with the closing operation of the front cover  7 . 
         [0203]    (6) As shown in  FIG. 3 , each supply cylinder  98  in the printer  1  has the auger screw  100  for conveying toner toward the supply opening  99 . Hence, the printer  1  can reliably convey toner toward the supply opening  99  to maintain a stable supply of toner in the process cartridge  26 . 
         [0204]    Further, since the auger screw  100  and supply cylinder  98  move together between the retracted position and the advanced position, the auger screw  100  does not interfere with movement of the toner cartridge drawer  45  in the forward and rearward directions. Therefore, the toner cartridge drawer  45  can be moved smoothly in the forward and rearward directions. 
         [0205]    (7) With the printer  1  described above, by moving the supply cylinder  98  from the retracted position to the advanced position and coupling the coupling  72  of the receiving cylinder  69  with the fitting part  102  of the supply cylinder  98 , as shown in  FIG. 3 , a drive force generated in the main casing  2  can be transmitted to the supply cylinder  98 . 
         [0206]    Further, by moving the supply cylinder  98  from the advanced position to the retracted position and decoupling the coupling  72  of the receiving cylinder  69  from the fitting part  102  of the supply cylinder  98 , as shown in  FIG. 4 , transmission of the drive force to the supply cylinder  98  can be cancelled. 
         [0207]    (8) As shown in  FIG. 9 , the process cartridges  26  can be mounted in the main casing  2  or pulled out of the main casing  2  in the front-to-rear direction. Therefore, maintenance can be performed on the process cartridges  26  from the front side of the printer  1 . 
         [0208]    (9) As shown in  FIGS. 3 and 4 , direct communication can be established between the toner-accommodating section  95  of the toner cartridge  46  and the toner reservoir  34  of the developing device  30  in the corresponding process cartridge  26 , without any separate member interposed therebetween, simply by moving the supply cylinder  98 . 
         [0209]    (10) As shown in  FIGS. 8 and 9 , the toner cartridges  46  and process cartridges  26  can be replaced independently of each other by retracting the supply cylinders  98 . 
         [0210]    (11) As shown in  FIG. 3 , the supply cylinder  98  of the toner cartridge  46  can open and close the through-hole  97  formed in the toner-accommodating section  95  and can supply toner from the toner-accommodating section  95  leftward. 
         [0211]    Hence, operations for opening and closing the through-hole  97  and for supplying toner can be achieved simultaneously through a simple structure that does not require separate members for opening and closing the through-hole  97  and for supplying the toner leftward. 
         [0212]    (12) As shown in  FIG. 7 , the supply cylinder  98  can be maintained constantly in the retracted position by the urging force of the compression spring  103 , thereby closing the through-hole  97 . 
         [0213]    (13) As shown in  FIG. 3 , the supply cylinder  98  of the toner cartridge  46  includes the auger screw  100  for conveying toner leftward. Hence, through a simple yet reliable construction, a stable supply of toner can be conveyed leftward to the process cartridge  26 . 
         [0214]    (14) As shown in  FIG. 3 , a drive force is easily inputted into the fitting part  102  when the supply cylinder  98  is moved to the left side. 
       9. Variations of the Embodiment 
       [0215]    In the embodiment described above, the supply cylinders  98  are moved to the retracted position in association with the opening operation of the front cover  7  and are moved to the advanced position in association with the closed operation of the front cover  7 . However, instead of associating the operations of the front cover  7  and translation cam  122 , the printer  1  may be configured such that the user directly operates the front end of the translation cam  122  after opening the front cover  7 . 
         [0216]    In this case, the front cover  7  is not provided with the coupling member  128 , and the rack part  120  is not provided on the translation cam  122 . 
         [0217]    The user first opens the front cover  7  and subsequently pulls the translation cam  122  forward to move the supply cylinders  98  into the retracted position. The user pushes the translation cam  122  rearward to move the supply cylinders  98  into the advanced position.
An image forming apparatus includes process units and developer cartridges; a process unit supporting member; a cartridge supporting member; and a moving mechanism. Each developer cartridge includes a transporting member configured to transport developer to a corresponding process unit. The moving mechanism is configured to move each transporting member between a communicated position, in which developer is transported to the corresponding process unit, and an interrupted position, in which transporting of developer to the corresponding process unit is interrupted. The transporting member positioned in the interrupted position allows the cartridge supporting member to move from an attached position to a withdrawn position and allows the process unit supporting member to be withdrawn, and the transporting member positioned in the communicated position prevents the cartridge supporting member from moving from the attached position to the withdrawn position and prevents the process unit supporting member from being withdrawn.