Patent ID: 7841596
Filing Date: 2010-11-30
Classification: B65H

Abstract:
1. A sheet feeder comprising: a feed passage; a plurality of feed roller pairs arranged along the feed passage for feeding sheets of paper in a feed direction along the passage by nipping the sheets, rotational speeds of the feed roller pairs being adjustable according to a voltage applied thereto; sensors each fitted at or near one of the feed roller pairs and each adapted to sense a specified point on each of the sheets when the sheet is nipped by at least the associated roller pair; and a controller including a memory for storing reference feed timings as proper feed timings at each of which the specified points on the sheets should pass one of the sensors; the controller being adapted to find the real feed timing when each of the sensors senses the specified point on the sheet nipped by at least the associated roller pair, wherein, when each of the sensors senses the specified point on the sheet nipped by at least the associated roller pair, the controller finds the time difference between the associated reference feed timing and the associated real feed timing and controls, according to the found time difference, the feed speed at which the feed roller pair or pairs nipping the sheet feed the sheet by adjusting the rotational speeds of the feed roller pairs, the sheet feeder further comprising a registration roller disposed near and upstream of a processing unit in the feed direction, wherein