Document size detecting device.

摘要

A document size detecting device with the arm (3) which folds by interlocking with the reciprocating motion of the optical system of the image forming apparatus and extends and contracts by interlocking with the reciprocating motion of the optical system. The optical sensor (37) for detection of the document size is installed at a prescribed position of the arm(3) and the feeder line (11a) for the light source (11) is held. Therefore, the special mechanism for holding the feeder line (11a) is not necessary and it is possible to achieve simplified construction of the image forming apparatus. Also, because the feeder line (11a) is caused to curve along the outside of the arm (3) at the rotating section thereof, it is possible to provide a large radius of the bent portion of the feeder line (11a) there will be no considerably concentrated stress which is locally applied to the feeder line (11a), therefore the life of the feeder line (11a) can be extended.