tab 108c as shown in fig5 tab 108c is received by a mating cut out 112 provided in inner section 66 to locate lever 108 so that arm 108a faces arm 94a while arm 108b faces both arm 94b and tab 72 in the normal unactuated position of bar 96 shown in fig3 and 5 roller 104 bears upon the mid section of arm 108b so as to hold that arm down against medial section 64 while arm 108a projects angularly therefrom toward arm 94a it will be noted that in this position of bar 96 roller 104 keeps arms 108b and 94b substantially parallel with each other and arms 108a and 94a converging toward each other in this position the spring assemblies acting upon the pressure plate keep the film sheet pressed flat between screens 50 and 54 as bar 96 is pushed to its actuated position shown in fig4 and 6 roller 104 is moved both out from under arm 94b and out from over arm 108b and then into engagement with both arms 94a and 108a thereby camming arms 94a and 108a away from each other and arms 94b and 108b toward each other as explained above such motion of rocker arm 94 tends to unload the spring force upon the pressure plate the simultaneous motion of bellcrank lever 108 causes upward swinging arm 108b thereof to engage and lift tab 72 and thereby urge the pressure plate and screen 50 away from screen 54 in this position of bar 96 therefore.