Automatic document feeder and registration system therefor

Abstract

Documents are advanced to a registered position along the trailing edge of the exposure platen of an electro-photographic copier by a flat belt supported adjacent to the registration edge by a pulley formed with axially spaced indentations to produce corresponding corrugations in the belt. A registration gate having a blocking position in which transversely spaced fingers extend into the belt corrugations arrests the documents at the registration edge while the normal-diameter portions of the belt pulley press the document downwardly to prevent it from riding over the registration gate. Position pulses from an encoding wheel are counted to determine the position of the document, and drive motor is slowed to one-fifth its normal speed when the document advances within a predetermined distance of the registration edge. After the platen belt is stopped for copying of a first original, a second original is advanced from a stack into a nip formed by the belt and a preregistration roller adjacent the entrance end of the platen. Upon actuation of the belt to feed the preregistered sheet to the platen, the feed elements for advancing the sheets from the stack are momentarily reactuated to ensure separation of the sheet supplied to the preregistration nip from the remaining sheets in the stack. A relatively long prefeed time is allowed for advancing the first original to the preregistration nip to prevent the erroneous declaration of a fault while an initially loaded stack is becoming entrained in the stack feeding elements.