Sheet handling apparatus and method of sheet handling for selective removal of sheets from a vacuum drum

Claim 1

A sheet handling apparatus, comprising: a rotatable drum defining an interal cavity, a cylindrical sheet transport surface, and a plurality of opening extending through said sheet transport surface and communicating with said cavity, means for supplying a partial vacuum to said cavity of said drum, such that said partial vacuum may be applied through said openings to a sheet on said sheet transport surface, said means for supplying a partial vacuum comprising a motor, having a shaft, said motor being mounted in one end of said drum, and an exhaust fan mounted on said shaft and driven by said motor such that the direction of air flow caused by said fan is outwards from said cavity of said drum, means for rotating said drum, a stationary deflection plate disposed adjacent said sheet transport surface, a vacuum shield means mounted in said cavity and movable from a first position remote from the wall of said cavity to a second position adjacent said wall of said cavity whereby said partial vacuum may be applied through said openings to a sheet supported on said sheet transport surface when said shield means is in said first position, and said partial vacuum is prevented from being applied through a number of said openings adjacent said deflector plate when said shield means is in said second position, and means for selectively moving said vacuum shield means between said first and second positions, whereby a sheet on said cylindrical sheet transport surface is retained thereon when said shield means is in said first position and a sheet on said cylindrical sheet transport surface deflects outward therefrom to contact said stationary deflection plate when said shield means is in said second position.