Abstract: A two-cycle xerographic device having a multiple-roller magnetic brush developer which sequentially develops and then cleans the device's reusable photoconductor. The photoconductor provides one or more image panels for each revolution of the photoconductor. The photoconductor's interimage area, which separates the trailing edge of one panel from the leading edge of the same panel, or the leading edge of the next panel, is smaller (as measured in the direction of photoconductor movement) than the similar dimension spanned by the developer's spaced multiple rollers. As the panel's trailing edge leaves the first to-be-encountered roller, that roller's development electrode bias voltage is switched from a development to a cleaning bias. This switching function occurs sequentially, from one roller to the next, thus facilitating a small interimage area, and maximum photoconductor usage.

Abstract: Developer mix is purged from a magnetic brush developer in a xerographic copier or printer by moving the pick-up zone of a magnetic brush roller out of the throw-off zone of a magnetic transport roller. A purge door is located adjacent the throw-off zone. In a purge operation, a catching container is attached to the developer at the purge door. The purge door is opened, and the magnets of the magnetic brush roller are rotated so that the pick-up zone of the brush moves out of the throw-off zone of the transport. The developer is then driven, and the developer mix moves through the developer, out the purge opening and into the catcher.

Abstract: A scanning continuously variable reduction electrophotographic copier includes a servo motor for driving the document scanning carriages. Servo motor, and therefore carriage motion parameters of velocity, duration of acceleration and deceleration, length or time duration of travel and time of start of scan are selectable to produce a selected reduction ratio within a continuous range of reduction ratios. In one embodiment, three partially overlapping hybrid servo loops are used, one for acceleration and deceleration, another for constant velocity motion and a third for precise stopping control. In another embodiment, a single loop controls the entire motion.

Abstract: A continuously variable magnification optical system for use in document copier machines wherein multiple cams are used to provide motion input to the continuously variable drive system. Multiple cams are used in order to provide capability to the machine of copying at 1:1 reduction on various size copy papers without causing the scanning mechanism to scan beyond the usable length of the document glass. A cam-select mechanism is disclosed.

Abstract: A magnetic brush developer wherein the bias voltage applied to the brush roll is altered, i.e., reduced, during the transit therepast of the photoconductor drum's seal, thereby reducing the number of magnetic carrier beads which are carried out of the developer on the surface and edges of the drum seal.

Abstract: An electrophotographic copier's magnetic brush roller applies developer material to the surface of a photoconductor drum. Two parallel centerlines define the photoconductor drum surface a fixed gap distance from the magnetic brush roller's mating surface. Moving the magnetic brush roller adjusts the gap distance between the mating surfaces. Two sandwiches of conventional, standard-thickness, flexible, plastic sheets form tools; one having a total thickness slighty larger than the desired gap between the mating surfaces of the drum and roller, and the other having a thickness slightly less than the desired gap. The desired gap is set by separating the drum and roller surfaces, inserting the tool that is slightly smaller than the gap and closing the gap sufficiently so that each of the mating surfaces on the drum and roller contacts one surface of the tool.