Browse Prior Art Database

Original Publication Date: 1982-Oct-31
Included in the Prior Art Database: 2004-Apr-04

Publishing Venue

Xerox Disclosure Journal


The xchitecture and operation of certain printing machines require a development system which can be enabled or disabled quickly during the machine cycle. For example, applications in magnetography require that the image receptor be accelerated to a high speed so that the latent image can be magnetically recorded then decelerated to a much slower speed for image printing. In order to maximize document throughput and avoid spurious developer interference with the recording process, it is desirable to provide a swift and efficient speed transition between enablement and disablement. One arrangement for providing a selectively enabled development is illustrated in Figure 1. A stationary magnetic member 10 is disposed interiorly of rotating cylinder 12. Rotating cylinder 12 is constructed (for example, from a porous material such as a sintered metal) so as to be permeable to air. A thin, conductive elastomer sheath 14 is disposed about the exterior surface of cylinder 12. Pressurized air introduced into air duct 16 passes through the porous wall of cylinder 12 and inflates elastomer sheath 14 in a narrow sector in the region of the development nip. The resulting inflated bubble remains fixed in space reducing the size of the development gap to the point where the blanket of developer 18 is brought into contact with the latent image bearing member 20 enabling development of the latent image. After passing out of the development zone, away from the pressurized air duct, the influence of the magnetic field on the developer blanket is re-established. The combined force of the external air pressure, magnetic force of the developer blanket, and the elastic restoring force of sheath 14, force air back through the porous wall into the interior of cylinder 12 thereby collapsing the sheath's bubble. This disabling collapsing action is enhanced by maintaining a negative air pressure within cylinder 12.