| 摘要 |
A combined registration, image transfer and pickoff assembly for an electrophotographic copier in which a transfer pressure roller having an elastomeric outer layer with a hardness approximating that of the copy paper is disposed across the imaging drum at a spacing from the drum greater than the thickness of the image toner layer but less than that of the copy sheet. A registration roller is urged into line engagement with the transfer roller to form a registration nip for receiving the leading edge of a copy sheet prior to its movement through the transfer nip. A selectively actuable gripper carried by the transfer roller is opened to receive the leading edge of the copy sheet when it enters the registration nip, then retracted to clamp the leading edge and carry it around with the transfer roller through the transfer nip, and reopened on the other side of the transfer nip to allow the leading edge to be peeled from the transfer roller and directed along an exit path. The transfer roller is driven independently of the imaging surface through a spring clutch which is overdriven by the imaging surface when the copy sheet is moving through the transfer nip and which finally disengages when the gripper is aligned with the registration roller. To prevent contamination by non-image toner deposits during start-up, the transfer roller is retracted from the imaging surface until the image-bearing portion of the imaging surface reaches the transfer station.
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