Importance

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Abstract

A rotatable drum is disclosed for securing thereto various sizes of sheets of film by a partial vacuum. The drum includes a cylindrical body and first and second circular end blocks connected for closing the body. The drum is mounted for rotation about its central axis. The first end block defines concentrically therethrough a central passageway, connected to a source of partial vacuum so that the drum may be partially evacuated. The cylindrical body defines on its outer surface a plurality of parallel, identical grooves extending circumferentially about the body. A plurality of holes also extend through the body, each of the holes opening on the outer surface into one of the grooves. Importantly, the cross-sectional area of each hole is approximately equal to the cross-sectional area of each of the grooves, and no porting or valving is provided for the drum interior to close unneeded holes. The first block further defines a plurality of auxiliary passageways, each of the auxiliary passageways opening at a first end through the inner face of the block and connecting at a second end with the central passageway. The auxiliary passageways are disposed within the first block symmetrically about the axis of the drum.

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First Claim