Electrophotographic printer with exchangeable image prodn. unit - has developer bunker for receiving developer material and image prodn. machine detecting light beams which cross developer bunker

摘要

The amount of light detected by a sensor unit is compared with a predetermined threshold value. so that it can be established whether the image prodn. unit is installed or not. The developer bunker has two detection windows of semi-transparent material. The predetermined threshold value reproduces the amount of light, detected by the unit if the developer bunker is empty. The image prodn. unit is not installed if the detection result is greater than the predetermined threshold value. ADVANTAGE - Quickly establishes if image prodn. unit is not installed without taking account of stirrer position. Image prodn. unit (10) can be in cassette form.