Apparatus for singularizing stacked sheets

Abstract

A cylindrical drum of a rotary transfer conveyor rotates below an opening at the bottom of a magazine for a stack of superimposed sheets. The drum carries a first pivotable gripping lever and one or more second pivotable gripping levers. The common pivot axis of the levers is parallel to the axis of the drum, and the levers are pivotable by cams so that their speed relative to the magazine is less than the peripheral speed of the drum during travel immediately below the opening in the bottom of the magazine. At such time, a set of suction cups flexes a portion of the lowermost sheet of the stack through the opening and between the first and second gripping levers so that the speed of the engaged sheet need not be immediately accelerated to the peripheral speed of the drum but merely to the relatively low absolute speed of the levers. The levers extract the lowermost sheet from the magazine and simultaneously accelerate the extracted sheet to the peripheral speed of the drum prior to moving apart so that the sheet can descend by gravity. The levers subsequently return to positions below the opening in the bottom of the magazine to proceed with extraction of the next lowermost sheet.