Abstract: A toner supply control system of the electrophotographic apparatus which includes a developing unit 3 for developing with a developer composed of toner and carrier; a toner hopper 4 for storing the toner; a toner empty sensor 7 for detecting the remainder of toner in the toner hopper 4; and a toner supply drive unit 5 for conveying toner from the outside of the apparatus into the toner hopper 4. Toner is conveyed from the outside into the toner hopper 4 by driving the toner supply drive unit 5 over a predetermined period of time without stopping the operation of the electrophotographic apparatus when the toner empty sensor 7 detects over a predetermined period of time that the remainder of toner in the toner hopper 4 is small.

Abstract: An image forming apparatus includes a main assembly and a process cartridge. The main assembly contains and retains an electrophotographic photosensitive member, and therefore, the photosensitive member is not contained in the process cartridge. The process cartridge contains an electric charger, a developing device and/or cleaning device. The process cartridge is detachably mountable into the main assembly.

Abstract: An image forming apparatus provided with a mechanism for discharging the sheet which has been image-processed. The sheet supplying station accommodating a cassette or the like and the image forming station containing a photosensitive member or the like are substantially vertically aligned. The apparatus comprises a sheet reversing and discharging mechanism for inverting the face orientation of the sheet and then discharging it. The sheet reversing and discharging mechanism has a sheet switch-back passage which is disposed between the sheet supplying station and the image forming station, the sheet switch-back passage extending substantially horizontally. Additionally, the apparatus includes a device for selectively shifting the discharged sheets so as to form groups of sheets, without disturbing already-formed groups.