Electrophotographic copying apparatus

Claim 1

In an improved electrographic apparatus comprising a charge holding means, means for producing, on said charge holding means, an electrostatic latent image having a negative polarity, a chargeable drum composed of an electrically conductive member and a dielectric layer coated thereon, means for uniformly charging said chargeable drum, and means for bringing the thus uniformly charged chargeable drum into contact with said charge holding means which has said electrostatic latent image produced thereon and for moving said charge holding means, wherein the improvement comprises: said means for uniformly charging said chargeable drum comprises a direct current corona discharge device for charging said chargeable drum with a positive polarity, an alternating current corona discharge device including a grip disposed between said alternating current corona discharge device and said chargeable drum being supplied with a bias voltage having a positive polarity and in which said charge holding means is brought into contact with the chargeable drum of a previously uniformly charged opposite polarity, to thereby eliminate the electrostatic latent image having a negative polarity and to cause the charge having the positive polarity to remain at that region of said charge holding means on which said electrostatic latent image having a negative polarity has been deleted by exposed light.