Original Publication Date: 1990-Jun-30
Included in the Prior Art Database: 2004-Apr-05
Xerox Disclosure Journal
A magnetic brush type development apparatus for developing electrostatic latent images, as disclosed for example in U.S. Patent 4,771,311 and references therein, may be modified to have operative and inoperative modes of development. The developer material is transported by a magnetic roller into the development zone. Developer material is attracted to the surface of the magnetic roller by a stationary magnet. A movable magnet translates from an operative position, where the magnet generates a weak magnetic field in the development zone, and a non-operative position, where the magnet generates a strong magnetic field in the development zone. In the operative position, Fig. 1, the weak magnetic field shown in Fig. 2 allows release of the developer material from the magnetic roller to allow for proper development operation. In this mode the development cannot be quickly disengaged by separating the photoreceptor and the roller because the developer would fly off the roller due to centrifugal forces. First, it has to be switched into the non-operative position. In this position, Fig. 3, the strong magnetic field shown in Fig. 4, attracts the developer material to the surface of the magnetic roller. Now the photorceptor and the roller can be separated to prevent development. Because of the strong magnetic field, the developer can not fly off the roller.