| 摘要 |
PURPOSE:To prevent stains in a device and the damage of a fixing roller, etc., even in case of misoperation by conducting a bias voltage from a developing bias power source in series and prohibiting a copying action if any one of developing devices, at least, is not mounted in the device. CONSTITUTION:The wiring circuit of a bias power source device is constituted in order that the DC bias voltage is conducted and impressed in series on both of two developing sleeves 111A and 111B of the developing units 11A and 11B in need. Moreover, a controller for controlling the function of a main switch which switches ON-OFF entire copying functions is provided and it is constituted in order that the main switch can be switched ON with the action of the controller only when both developing units 11A and 11B are mounted on a copying device. Namely, the developing units 11A and 11B provide projecting cam members C1 and C2 on the sides of the containers in order that detection switches S1 and S2 are switched ON and the main switch is switched ON if the developing units 11A and 11B are respectively mounted in specified positions accurately. Thus, the damage of the fixing roller, etc., and the stains of the inside can be prevented even in case of misoperation.
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