Patent ID: 7860445

Claim:
A document feeder, comprising: an input tray configured to receive a document; an output tray positioned one of above and below the input tray; a document transfer path extending between an input tray and the output tray; transfer elements for transferring the document from the input tray to the output tray; a bidirectional feed path having two ends which are connected to predetermined positions of the document feeding path, respectively; a bidirectional feed system provided to the bidirectional feed path to feed the document from a downstream side of an image reading position to an upstream side of the image reading position with a leading end and a trailing end of the document being reversed; a driving system configured to apply a driving force to the bidirectional feed system; a first transmitting mechanism configured to transmit the driving force for feeding the document in a first direction to the bidirectional feed system in accordance with one of the forward and backward rotations of the driving system, and to transmit the driving force for feeding the document in a second direction to the bidirectional feed system in accordance with the other one of the forward and backward rotations of the driving system; a second transmitting mechanism configured to cut off or transmit the driving force of the driving system to the bidirectional feed system; an actuator configured to selectively drive the second transmitting mechanism based on whether or not the driving force is desired to be transmitted to the bidirectional feed system, the second transmitting mechanism cutting off the driving force to the bidirectional feed system when the rotation of the driving system is switched from one of forward and backward rotation directions to the other rotation direction, and transmitting the driving force to the bidirectional feed system when the driving system rotates in the other rotation direction and when the actuator is operated; and a controller configured to actuate the actuator for a predetermined period, and to detect a rotating amount of the driving system in the other rotation direction during the predetermined period, wherein the controller determines whether or not to actuate the actuator again in accordance with the rotating amount of the driving system in the other rotation direction, wherein, if the rotating amount of the driving system within a period in which the actuator is actuated is less than the predetermined amount, the controller actuates the actuator after the driving system starts rotating in the other rotation direction, and the controller is further configured to actuate the actuator again when the driving system is stopped due to lack of memory for storing image data read from the document within a period in which the actuator is actuated.