Sheet feeding and aligning apparatus for rotary printing machine

Claim 1

Sheet feeding and aligning apparatus to pick up a sheet (20) of a printing substrate, particularly paper, for transfer to a moving sheet transport mechanism and having a make-ready table (20); a vacuum suction pick-up and sheet transport element (3) including a tubular housing (11); a suction tube (4) movably guided in said housing for telescopic movement with respect thereto; bias means (16) for biassing the suction tube (4) towards a sheet (20) to be gripped; and pull-in means (6) for pulling the suction tube inwardly within the tubular housing upon adhesion of a sheet thereto under vacuum applied to the interior of said tubular housing (11), so that the pick-up element (3) will be of variable length, the pick-up element being positioned for engagement with the leading edge of the sheet (20) located on the make-ready table in aligned position and supported for pivoting movement for transporting a sheet after being picked up; and comprising a locking element (23) selectively positionable in said housing (11) to contain telescoping pull-in motion of the suction tube within the tubular housing to a limited distance, and permit, after repositioning, continued telescoping movement of the suction tube within the tubular housing; and means for controlling the pick-up motion of the pick-up element (3) in steps (a) for pick-up of the leading edge of the sheet and lifting the sheet off the make-ready table (2) by the limited distance (R-1 mm) defined by the locking means by foreshortening said length by pulling in said suction tube for said limited distance; and then (b) for lifting the leading edge of the sheet for the remaining distance (R-r) and further foreshortening the pick-up element by further pulling in said suction tube upon repositioning of said locking means and pivotally moving said pick-up element to a position required for engagement with the transport mechanism and accelerating the sheet by moving the leading edge of the sheet in a rotary path as the element foreshortens to feed the sheet to said moving transport mechanism.