Abstract: An automatic document feeder includes a paper transmitting path for guiding documents, a driving motor for providing driving torque, a pickup device disposed at the upstream of the paper transmitting path, an output device disposed at the downstream of the paper transmitting path and transmitting rollers disposed along the paper transmitting path for transmitting the documents, a first driving gear disposed between the pickup device and the output device, a transmitting gear swing arm equipped with a transmitting gear set and axially hinged with the first driving gear to swing according to the driving torque between a first position meshing the transmitting gear set with the pickup device and a second position idling the transmitting gear set, an actuator connected with the output device and a braking device disposed on the output device for locking the transmitting gear swing arm according to the position of the output device.

Abstract: A transmission device for an automatic document feeder includes a driving gear set driven by a driving motor, a first swing arm equipped with a first driving roller set, a second swing arm equipped with a second driving roller set, and a one-way gear set driven by the driving gear set to keep transmitting rollers rotating in the same direction. The first swing arm is driven by the driving gear set and swingable between a first position and a second position to mesh the first driving roller set with a pickup device or an output device. The second swing arm is driven by the driving gear set and swingable between a third position and a fourth position to mesh the second driving roller set with the pickup device or the output device. When the first swing arm swings toward the first/second position, the second arm swings toward the fourth/third position.