Sheet stacking apparatus

Claim 1

Apparatus for stacking limp paper sheets with their end edges in generally upright approximate alignment, said apparatus comprising in combination: generally horizontal endless stacking conveyor means for effectively constantly and completely supporting and moving shingled sheets in a path; means for continuously forming limp paper sheets into a shingled stream on said stacking conveyor means with the leading edge of each sheet beneath the immediately preceding sheet and close behind the leading edge of said preceding sheet and the trailing edge portion of each sheet projecting a short distance behind the trailing edge of said preceding sheet, so that only a short leading end portion of a sheet, between the leading edge of said sheet and the leading edge of the next succeeding sheet, has its bottom face exposed to contact with said stacking conveyor means; a stop above the stacking conveyor means in the path of said shingled sheets for forming said sheets on said stacking conveyor means into a stack that is generally perpendicular to the plane of the conveyor means; and vacuum means beneath the stacking conveyor means which is positioned and arranged to draw said short leading end portions of said shingled sheets constantly and firmly downwardly against said stacking conveyor means to subject each leading end portion to a strong conveying force, said vacuum means having a downstream end effectively directly beneath the stop so as to hold each said leading end portion until the leading edge abuts the stop and then release it rapidly as the leading edge of the next succeeding sheet is advanced beneath the leading end portion of the sheet next above it and against said stop, whereby each limp paper sheet is advanced by a strong conveying force beneath said forming stack and against said stop and said conveying force on each sheet is then quickly reduced.