Patent ID: 7866653
Filing Date: 2011-01-11
Classification: H04N

Abstract:
1. A duplex document feeder for cooperating with a scanning device and transporting a sheet to a scanning module, said duplex document feeder comprising: a pick-up module for guiding a first face of said sheet into a first feed channel and passing through said scanning module; a sheet-controlling roller module comprising a first sheet-controlling roller, a second sheet-controlling roller, and a third sheet-controlling roller, wherein said first sheet-controlling roller and said second sheet-controlling roller are in contact with each other for generating a first nip force to feed said sheet outside of said duplex document feeder, and said second sheet-controlling roller and said third sheet-controlling roller are in contact with each other for generating a second nip force to feed said sheet into the interior of said duplex document feeder; and an ejection module comprising an active roller and a pressing element, said active roller and said pressing element are in contact with each other for generating a third nip force to feed said sheet outside of said duplex document feeder or to refeed said sheet into a second feed channel to make a second face of said sheet be scanned, wherein said first nip force generated by said first sheet-controlling roller and said second sheet-controlling roller and said second nip force generated by said second sheet-controlling roller and said third sheet-controlling roller are both at least five times larger than said third nip force generated by said active roller and said pressing element and the motion accuracy of said sheet is thereby controlled by said first and second nip forces such that said sheet is successfully fed into the nip of said active roller and said pressing element without jamming as a result of an overlap of a leading edge and a trailing edge of said sheet.