Abstract: A developing agent for electrophotographic copier contains SiO.sub.2 and/or magnetite in addition to a toner such that talc can be effectively removed from the photoreceptor surface.

Abstract: An electrophotographic copying machine includes a combined developing-cleaning magnetic brush element for selectively conducting the developing operation and the cleaning operation. During the first revolution of the drum, a bias voltage of -200 V is applied to the combined developing-cleaning magnetic brush element to conduct the developing operation. During the second revolution of the drum, a bias voltage of +30 V or zero (0) volts is applied to the combined developing-cleaning magnetic brush element to attract the inversely charged residual toner from the drum surface. During the third revolution of the drum, the bias voltage of -200 V is again applied to the combined developing-cleaning magnetic brush element to attract the positively charged residual toner from the drum surface.

Abstract: A cleaning device for a monochromatic copying machine for processing residue toner removed by a blade assembly from a photoreceptor, which machine is of a type capable of accommodating selectively a plurality of developer boxes containing respective masses of toner of different colors, which device comprises a toner recovery duct extending between a cleaning box, adapted to accommodate therein residue toner removed from the photoreceptor, and a developer box, for feeding the residue toner accommodated within the cleaning box towards the developer box. One of the developer boxes for use with the mass of black-colored toner has a single chamber defined therein and communicated with the toner recovery duct when such a developer box is set in position within the copying machine, whereas each of the remaining developer boxes for use with the masses of toner of respective colors other than black has working and collecting chambers defined therein, separated by a partition wall from each other.

Abstract: An electrophotographic copying machine is provided having a photoreceptor, a corona discharger, a lamp, and a compensation circuit. The corona discharger is activated to provide a corona discharge toward the photoreceptor to uniformly and initially charge the surface of the photoreceptor. The lamp is illuminated at the same time as the corona discharge of the corona discharger to improve the charging on the photoreceptor. The compensation circuit is activated to provide an exponential voltage to be applied to the lamp in proportion to the sensitivity degradation of the photoreceptor, to thereby compensate the sensitivity degradation of the photoreceptor.

Abstract: An electrophotographic copying machine is of the type which starts, in response to the actuation of a copy start switch, its copying operation after a pre-copy process is conducted to stabilize the property of a photoreceptor. The copying machine comprises a selection circuit and a timer. The selection circuit is operated to start the timer upon the termination of a previous copying operation. During a time as set for the timer, the pre-copy process is carried out following the termination of the previous copying operation. In response to the actuation of the copy start switch, the following copying operation is started just following the termination of the previous copying operation.

Abstract: A metal paper guide is disposed near the transcription section for leading a copy paper into the transcription section. The metal paper guide is grounded in the normal operational mode at the normal humidity condition. When the copying machine is placed in a high humidity condition, the metal paper guide is isolated from the grounded terminal for preventing the leakage of charges supplied on the copy paper through the metal paper guide.

Abstract: An electrophotographic copying machine includes a combined developing-cleaning magnetic brush element. When the copy sheet is smaller than half the size of a photosensitive drum surface, two sheets of copy are obtained by three revolutions of the photosensitive drum in a multi-copy mode. During the first revolution of the photosensitive drum, the combined developing-cleaning magnetic brush element conducts the developing operation onto a first half section of the photosensitive drum and conducts the cleaning operation onto a second half section of the photosensitive drum. During the second revolution of the photosensitive drum, the first half section is cleaned and the second half section is developed. During the third revolution of the photosensitive drum, the first and second half sections are cleaned by the combined developing-cleaning magnetic brush element.

Abstract: A cleaning device for a monochromatic copying machine for processing residue toner removed by a blade assembly from a photoreceptor, which machine is of a type capable of accommodating selectively a plurality of developer boxes containing respective masses of toner of different colors, which device comprises a toner recovery duct extending between a cleaning box, adapted to accommodate therein residue toner removed from the photoreceptor, and a developer box, for feeding the residue toner accommodated within the cleaning box towards the developer box. One of the developer boxes for use with the mass of black-colored toner has a single chamber defined therein and communicated with the toner recovery duct when such a developer box is set in position within the copying machine, whereas each of the remaining developer boxes for use with the masses of toner of respective colors other than black has working and collecting chambers defined therein, separated by a partition wall from each other.