Patent ID: 7048271

Claim:
A sheet separator for an automatic document feeder for separating and feeding a first sheet and a second sheet adjacent to the first sheet sequentially, the sheet separator comprising: a separating roller driven to rotate by a driving device; a friction roller having a first rotating state, in which the friction roller is driven to rotate by the separating roller, a second rotating state, in which the friction roller is driven to rotate by the second sheet, and a stationary state, in which the friction roller is stationary, wherein in the stationary state of the friction roller, the separating roller directly feeds the first sheet, and the friction roller pushes the second sheet toward the first sheet so as to make the first sheet slide on the second sheet; a first shaft inserting into the friction roller and providing a damping torque for stopping the rotation of the friction roller, and a force-applying mechanism for pushing the separating roller against the friction roller, wherein: the friction roller is rotatably mounted to the first shaft, and the first shaft provides the damping torque for stopping the rotation of the friction roller according to a damping force between the first shaft and the friction roller; and the friction roller comprises: an outer column being in contact with the separating roller in the first rotating state; an inner column rotatably supported on the first shaft, the inner column being arranged within the outer column; and a resilient member wrapping around the inner column and applying pressure on the inner column, such that the inner column and the first shaft act on each other to produce the damping torque.