Automatically continuously variable fold position sheet folding system

Abstract

An improved sheet folder for flimsy printed sheets with an automatic fold position correction system. The folder may have an input sheet feeder, a fold chute with a chute entrance, reversible sheet feeding rollers in the fold chute adjacent to the chute entrance, fold rollers, a folded sheets output path, and a sensor system for sensing the length of folded sheets in the folded sheets output path. A sheet to be folded is may be partially fed into the fold chute, engaged by the reversible rollers, and fed thereby further into the chute by a selected distance corresponding to a desired folding position along the sheet. Then, the reversible rollers are stopped at a selected sheet stopping position and reversed to feed the sheet into the fold rollers, cooperatively with the input sheet feeder. The fold rollers feed the folded sheet into the folded sheets output path. The sensor system there provides a control signal modifying the selected stopping position of the reversible rollers, to provide a fold position correction system. For integral or separate fold skew correction, the reversible rollers are transversely spaced and separately servo driven, and the sensor system is a plural sensor array extending transversely across the folded sheets path to provide skew correction signals differently controlling the selected stopping positions of the separately driven reversible rollers. Additionally disclosed is a special fold position correction system for 1/2 or even-folded sheets.