Electrostatographic reproducing machine and process unit therefor

Abstract

A process unit which can be removably mounted in a main assembly of an electrostatographic copying machine. The unit comprises a housing enclosing an imaging member and, optionally, other processing means such as a development device, a cleaner, and a charge corotron. The transfer corotron for transferring a toner image from the imaging member to a copy sheet is incorporated in the cassette housing, thus avoiding the need to provide a separate movable cover to protect the imaging member from contamination, physical damage, and light exposure when the cassette is removed from the main assembly of the copier. An electrically conductive guide member for guiding a copy sheet into contact with the imaging member and an electrically conductive guide member for guiding the copy sheet away from the imaging member are both formed integrally with the shield of the transfer corotron as extensions thereof. In consequence of electrically biasing the shield when the process unit is inserted into its operative position in the main assembly, the guides are maintained at the same potential as the shield thereby reducing charge leakage through the copy sheet in the transfer zone, enabling effective image transfer even for moist and relatively highly conductive copy sheets. The exit guide is suitably contoured to ensure that the trailing edge of the copy sheet positively contacts the imaging member.