US Patent 8201823 Sheet feeding apparatus

A rotatable pick roller and a rotatable separating roller are formed integrally with a roller case. A retard roller opposes the separating roller and rotates in a direction opposite to that of the separating roller. A lift detecting sensor is mounted on the roller case. When a first sheet and second sheet that are stapled together are accidentally placed on a sheet table, the pick roller picks-up the first sheet and feed it in the gap between the retard roller and the separating roller, the second sheet abuts with the retard roller so that a portion of the first sheet and the second sheet gets lifted. The lift detecting sensor detects the lifted portion and stops rotations of the rollers.