Patent ID: 8348257
Filing Date: 2013-01-08
Classification: B65H

Abstract:
1. A retard roller module of an automatic document feeder, said retard roller module having a retard roller for providing a frictional force to separate a first document and a second document from each other, said first document lying on said second document, said retard roller module comprising: a retard roller frame; said retard roller installed on said retard roller frame, said retard roller comprising: a sleeve having a sleeve inner wall; a separation pad sheathed around said sleeve, and contacted with said second document; a helical spring disposed within said sleeve, and comprising a first spring segment and a second spring segment, wherein said first spring segment has a first spring inner diameter, said second spring segment has a second spring inner diameter smaller than said first spring inner diameter, and said first spring segment is contacted with said sleeve inner wall; and a rotating shaft penetrated through said helical spring and contacted with said second spring segment, wherein when said second document is moved in a first direction, said sleeve is rotated in a first rotating direction, said first spring segment is twisted in said first rotating direction, and said first spring inner diameter of said first spring segment is widened, so that said first spring segment is fixed on said sleeve inner wall and said second spring segment is twisted with respect to said rotating shaft to generate a first damping torque, wherein said first spring inner diameter of said first spring segment is widened and said second document is moved in a second direction opposed to said first direction, thereafter said sleeve is rotated in a second rotating direction, so that said second spring segment is fixed on said rotating shaft and said first spring segment is twisted to generate a second damping torque, wherein said first damping torque is greater than said second damping torque; and an elastic element disposed on said retard roller frame and contacted with said retard roller for providing an elastic force on said retard roller, so that said retard roller is movable upwardly and downwardly with respect to said retard roller frame.