Fitzpatrick, Cella, Harper & Scinto
Developing apparatus
 A plurality of developing devices or units are supported on a supporting member or turret which is rotatable to revolve the developing devices to move a desired developing device to a developing station where the developing operation is effected with the desired one of the developing devices. The developing devices are each provided with detecting elements for detecting the remaining amount of the developer or the concentration of the developer. The detecting elements are located at such a position that during the rotation of the supporting member the developer particles move with the rotation of the supporting member so that the detecting element is constantly cleaned by the moving developer. 
Canon Kabushiki Kaisha
G G G G
G03G G03G G03G G03G
inventional inventional inventional inventional
Akio Kiyoharu Kenji Shinichi Kenji Yusaku
Ohno Tanaka Yoshinaga Oguri Takeda Takada