Single sheet feeder with selectively engageable prefeeding rolls

摘要

A sheet feeder assembly includes a self-actuating prefeed roll located upstream of a deskewing device, which can include a document sensor switch and a deskew nip roll. After a sheet has been detected at the input of the assembly, a limited slip clutch causes the prefeed nip to close. The prefeed device selectively engages the sheet based on detection of the sheet at the input and then disengages upon detection of the sheet at the deskewing device. Thus, there are no obstructions at the input that the sheet must pass before engagement by the prefeed assembly. By this, chances of misfeeding a sheet that has not been sufficiently pushed into the document feeder are greatly reduced. Moreover, the assembly has increased latitude in the positioning of the input sheet and is particularly desirable for light weight documents since no obstructions exist within the paper path. Such an assembly is very user friendly because the machine reacts to the presence of a sheet and does not rely on the operator to push the sheet completely into the feeding assembly.