Patent ID: 6918583

Claim:
A sheet feeder, comprising: a sheet mounting plate that mounts sheets thereon; a pick-up roller provided so as to face the sheet mounting plate, the pick-up roller picking up and feeding one sheet at a time from the sheets mounted on the sheet mounting plate by rotating the pick-up roller when the pick-up roller and the sheet contact each other; a drive motor that generates a drive force; and a transmission device that transmits the drive force from the drive motor to the pick-up roller, the transmission device including: a first drive force transmission device that constantly cooperates with a rotation shaft of the pick-up roller; a switching device that makes a switch between a first condition where a drive force from the drive motor is transmittable to the first drive force transmission device and a second condition where the drive force from the drive motor is not transmittable to the first drive force transmission device; a second drive force transmission device that transmits the drive force from the drive motor to the switching device; and an actuator that moves in accordance with a presence or an absence of the sheets on the sheet mounting plate, the actuator setting the switching device in the second condition when none of the sheets are mounted on the sheet mounting plate.