| 摘要 |
There is disclosed herein an electrophotographic copying apparatus and its method of operation in which electrically charged toner of one polarity is transferred from an oppositely charged electrostatic image on the outer surface of its photoconductive drum to the front side of a blank sheet for transforming the latter into an intended copy as the back side of the blank sheet engages the outer surface of a transfer roll positioned adjacent the drum. In accordance with one feature of this apparatus, both the front side of the blank sheet, before it receives toner, and the outer surface of the transfer roll are biased such that each carries the same charge as the drum surface and such that the combined voltage level of both is greater than the voltage level of the electrostatic image. In accordance with another feature, the biasing means is designed for changing this combined voltage level in a way which improves the transferring capability of the apparatus, especially when more than one copy is made from a single electrostatic image.
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