Stacker for flat material

A stacker for flat material sheets, said stacker having a rotatable stacker drum for tangentially receiving sheets of material from a sheet transport system at a first tangential position and arcuately moving the sheets to a stop at a second tangential position against which a stack is formed, said stacker drum having suction opening means at a predetermined location on the periphery thereof for gripping the leading edges of the sheets at said first tangential position and releasing said sheets at said second tangential position, said stacker drum having air opening means on the periphery thereof positioned behind said suction openings in the direction of rotation by an amount such that compressed air may be supplied to said air openings and to the sheets only after the leading edges thereof have been run up against the stop, said stacker having a weighting roller located ahead of the arcuate position at which compressed air is supplied in the direction of rotation, said weighting roller being biased toward said stacker drum for further moving the back half of the sheet material after the leading edge has been stopped at said stop.

A stacker for flat material sheets, said stacker having a rotatable stacker drum for tangentially receiving sheets of material from a sheet transport system at a first tangential position and arcuately moving the sheets to a stop at a second tangential position against which a stack is formed, said stacker drum having suction opening means at a predetermined location on the periphery thereof for gripping the leading edges of the sheets at said first tangential position and releasing said sheets at said second tangential position, said stacker drum having air opening means on the periphery thereof positioned behind said suction opening means in the direction of rotation by an amount such that compressed air may be supplied to said air openings and to the sheets only after the leading edges thereof have been run up against the stop, said stacker drum extending above a base plate and wherein at the position in which the sheet material is bent away from the stacker drum by said air opening means, said base plate is lowered by an amount such that the lower edge of the material sheet does not contact the base plate, said stacker including a guide rail for receiving the trailing edge of the sheet material blown from the drum, said guide rails sloping from the base plate to the level of the lower edges of the sheet material.