| abstract |
A printer comprises a process unit which includes a photoconductive drum, a developing device having a toner storage section, a replaceable toner cartridge for supplying toner to the toner storage section, a cleaner for clearing the photoconductive drum of the toner remaining thereon after transfer, and a waste toner storage section for receiving the toner removed by means of the cleaner. The developing device is provided with a locking member for locking the mounted toner cartridge lest it be replaceable, a sensor for detecting a reduction of the amount of the toner in the toner storage section in the developing device below a predetermined value, and an unlocking member for unlocking the toner cartridge locked by the locking member when the reduction of the toner amount below the predetermined value is detected by the sensor. |