Device for controlling automatically the suction zones of vacuum back in photomechanical camera (2)

Claim 1

A vacuum back in a photomechanical camera comprising: a vacuum film holder installed in the rear case of the camera, said holder including a plurality of substantially U-shaped air passages on its front surface, the open ends of said air passages arranged against a common datum edge vacuum passage at one end of said holder perpendicular to the direction of movement of said holder and thereby forming a plurality of rectangular vacuum contact zones with a common datum edge for vacuum retention of film thereon; means for imparting unilateral movement to said vacuum film holder in said camera for aligning the center of film with the optical axis of the camera lens; a cylinder; a piston in said cylinder; the axis of said cylinder being aligned with the direction of the movement of said vacuum film holder, and said cylinder and piston mounted for relative movement therebetween in accordance with the movement of said vacuum film holder; and, a plurality of openings aLong said cylinder, connected with said air passages, the number of said openings being substantially equal to the number of said zones, thereby enabling movement of the film holder for aligning the center of the film with the optical axis of the camera lens to select simultaneously the size of the vacuum contact zones to be evacuated in accordance with the size of film being centered.