RAPID CUT-OFF DEVELOPMENT FOR HIGHLIGHT COLOR
Original Publication Date: 1987-Apr-30
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
It is desirable to be able to rapidly switch between operative developer units of a copier. Specifically, to be able to switch rapidly between normal black development of the photoreceptor and "highlight" color development without losing copier pitches in the change-over delay. Physically moving entire developer units towards and away from the photoreceptor is slow and relatively mechanically complex due to the mass of the unit and its developer contents. The system here provides this desired switch-over feature by simple apparatus for rapidly collapsing or reestablishing one or more of the magnetic brushes in one or more developer units of a copier. Rotation of the developer magnets themselves to collapse the field and therefore the development brush is possible, but not desirable, because of the high moving mass required. A better solution is to provide a thin, low mass, rapidly moveable, "C" shaped magnetic shield of "Mu-metal" or other known suitable magnetic-field-blocking material, in the shape of a partial cylinder of roughly 45 degrees or less, rotatable inside the developer roller. During development, this shield may be "parked"an inoperative position in a non-development zone such as the toner return area, where it will not interfere with normal development. To stop development it is rapidly solenoid rotated into the development zone, interposed between the field magnets and the developer roller to block the magnetic field. I.e., this shield is intermittently partially rotated, concentrically inside the developer roller, when a non-development signal is provided by the copier controller for that unit, to provide rapid magnetic shut-off of development by that unit, as one way of achieving rapid switching between developers. The general magnetics principles per se are disclosed in Azoplate U. S. Patent No. 3,392,432.