fig1 and 2 are schematic drawings in which , for convenience in illustration , their dimensions are distorted so that important relationships , functions , and movements can more readily be understood or seen . fig1 shows a device 11 of my invention having been placed on and supported by a stack 13 of insulated glass panels . the stack is shown as comprising only six panels , identified as 13a - 13f . typically , there would be many more . the lay up method is conventional , and comprises laying up sheets of glass , with alternate pairs being separated at their margins by separating material in the form of strips . fig1 identifies the sheets 13f &# 39 ; and 13f &# 34 ; of panel 13f , and the strips 14 of such panel . the laid up stack then has a plastic sealant applied to all four of its sides to completely cover them . when the sealant dries , it provides a plastic coat or film 17 , which not only properly seals the edges of the various panels , but also inadvertently secures or bonds the panels to one another at their parting planes . it is this bond that needs to be ruptured or broken . my separator device is to perform this function . it comprises a beam 20 having feet 21 and 23 resting on the stack , and specifically on the top panel 13a , whereby the device is supported by the stack . at its right end , as the parts are shown , the device has a pad or stop 27 . the beam plus the pad may be considered as a j - shaped member . the feet function as depth guides to automatically locate the pad opposite the associated edge of the top panel 13a , but above the edges of the lower panels . at its left end , the beam has a bracket 29 supporting an actuator , which is shown in the form of a pneumatic piston and cylinder unit 31 . the unit has a piston 33 whose piston rod 35 carries a pad 37 . the latter is vertically located by the feet 21 and 23 at a level below that of the top panel 13a , preferably horizontally opposite the associated edge of the next lower panel 13b . now , if the piston and cylinder unit is actuated , the pad 37 will apply a horizontal thrust against the side of the stack , which is resisted by the engagement of the pad 27 with the top panel . this creates a shearing action . the resistance to movement of the top panel is less than that of panel 13b engaged by the pad 37 . therefore , the pad 37 and the piston rod remain stationary , but the reactive force causes the entire separator device , except for the rod and the pad , to be shifted to the left as shown in fig2 carrying the top panel 13a with it . this ruptures the plastic film 17 at the parting plane between the top panel 13a and the next lowest panel 13b , without harming the edge bond at the edges of either panel . now the clamping pressure is relaxed , the device lifted , the top panel pulled off the stack , the device replaced , and the operation repeated on the remaining panels in turn . fig3 - 5 show a device embodying my invention , wherein the proportions are more realistic than in fig1 and 2 . the beam 20 is shown as comprising a spring steel bar on which the depth guide feet 21 and 23 are mounted , in a manner to be presently explained . at the left hand end of the bar , as the parts are shown in fig3 and 4 , the bracket 29 has a through bore , receiving the left hand end of the bar 20 , the bracket being secured to the bar by screws 41 . the pneumatic piston and cylinder unit 31 is hung by bolts 43 from the bracket 29 . the piston and cylinder unit has its piston rod 35 projecting therefrom and projecting into and secured to the pusher bar 37 . the pusher bar is provided with a plastic face pad 37a , which has fixed pins 51 fitting in holes provided in the pusher bar and held in place by set screws . the depth guide foot 21 has a bracket 21a formed with a through bore to receive the bar 20 , the foot being secured to the bar by a screw 71 ( fig4 ). from the lateral ends of the bracket 21a are secured a pair of depth guide plates 21b and 21c which are secured to the bracket 21a by bolts 21d . the two depth guide plates are notched at their lower ends to provide edges 21f for contact with the upper panel 13a , and edges 21g for disposition next to the left side of the stack , as the parts are shown in fig3 . the lower edges 21h of the plates slidably rest on the upper faces of the face pad and the pusher bar . the importance of this will be evident presently . the other depth guide foot 23 has a bracket 23a from the lateral end of which depend a pair of depth guide plates 23b and 23c secured to the bracket by bolts 23d . the depth guide plates have lower edges 23e for contact with the upper surface of the stack , and more specifically the top panel . the bar 20 slidably extends through the bracket 23a but is releasably held in a desired position of adjustment along the bar by an adjustable tail block 81 . there are plural stop plates 83 formed with rectangular holes to receive the bar with sufficient looseness that the stop plates can assume the positions in fig4 inclined to the vertical , with their interior edges biting into the bar 20 . the tail block has a spring tongue 87 secured at its left hand end to releasably fit onto an upwardly projecting pin 89 on the bracket 23a . a stop or pusher bar 91 is accommodated within notches 23f of the plates 23b and 23c and is pivotally connected to the tail block by a single bolt 93 . the bar carries the pad 27 which is secured to the backup bar by a pair of pins 97 ( compare fig3 and 4 ). the notches 23f provide downwardly facing edges slidably resting on the upper face of the plastic face pad 27 . it is important to note that the depth guide plates 23c and 23d will locate the lower face of the plastic face pad just above the plane separating the uppermost panel 13a from the next lower panel 13b , while the plates 21b and 21c dispose the pad 37a below the top panel 13a and opposite the associated edges of panels 13b - 13d . in operation , when the pneumatic piston and cylinder unit is actuated , a thrust force is applied by the piston and cylinder unit through the pad 37a to the stack 13 . this thrust force transmitted by the bar 20 to the face pad 27 , pulls the latter against the upper panel 13a . since the left hand face pad 37 meets more resistance to moving the panels it contacts than does face pad 27 to moving the uppermost panel , the entire separator device , except for the face pad 37a and pusher bar 37 and piston rod 35 , shift to the left , carrying panel 13a with it , to rupture the film bond between the uppermost panel and the next lower one . note that when the device moves to the left , the depth guide plates simply slide on the bar 37 and pad 37a . now the supply of air under pressure is terminated to release the grip of the device on the stack . the device can simply be lifted off , the panel 13a removed and the device replaced onto the next uppermost panel 13b and the operation repeated to separate it from the next lowermost panel . if it is desired to shift the foot 23 along the bar 20 to adjust the device to wider stacks , the workman manually moves the set of stop plates 83 to a more upright position , against the resistance of a conventional bent wire spring ( not shown ), to release the grip of the stop plates 83 on the bar 20 . with stacks of small sized panels , it is possible to locate the separator device 11 approximately centrally of the panels , whereby the uppermost panel to be separated will be shifted to the left breaking the film bonds at the four sides of the stack and maintaining the upper panel in essentially a rectilinear line of movement . however , with larger panels , particularly longer ones , i have discovered it is better to locate the separator device near one end of the stack of panels and run it through its sequence of operation . this time , however , when the piston and cylinder unit is actuated , the end of the uppermost panel at which the separator device is located will be shifted the extent of travel of the piston and cylinder unit 31 , whereas the opposite end is shifted oppositely , so that the uppermost panel is now askew with reference to the lowermost panels , to break the bond between the panels . in order to accommodate this movement , the bar 91 as previously mentioned is pivoted at 93 to enable the bar and the pad to turn to maintain flush contact with the uppermost panel even though the uppermost panel is askew to the lower panels in the stack . while my device may entirely separate an upper panel from the next lower one , with some panel sizes , the separation may be less than complete . however , the workman need only give the upper panel a final twist to complete the separation . or , two devices could be provided , and located adjacent the opposite ends of the stack , to effect a complete separation . as is evident from fig3 the bins which mount the face pads to their bars are offset from the horizontal midplanes of the pads . this means that the bolts can be removed , the face pads inverted and resecured , whereby to locate the pads lower faces at a lower level than was previously the case . this means that with a simple adjustment , the unit shown is adaptable to operate on panels of two thicknesses rather than just one . to adapt the device to other thicknesses of panels , the guide feet can be replaced by feet having different sized notches . lifting of the spring tongue 87 permits separation of the tail block 81 from the bracket 23a . this enables the pad 27 to be inverted without removing the pad 91 from the tail block . preferably the depth guide plates are formed of a plastic material for easier contact with the glass panels . instead of mounting the stop plates 83 so that they engage the upper and lower edges of the beam 20 , the plates may be arranged to project horizontally and thus engage the sides of the beam , so that the upper and lower edges are not roughened by the action of the stop plates . the beam may be of i - shape in cross section , with the stop plates engaging the recessed portions of the sides of the beam . the source of air under pressure has not been shown . it may be that source typically available in shop surroundings , which will be connected by a hose to a foot pedal control ( not shown ) for controlling the supply of air to the piston and cylinder unit .