Toning system for electrostatic imaging apparatus

Abstract

A method and apparatus is provided for toning a latent electrostatic image on an exposed photoconductive surface of an electrophotographic member, using liquid toner comprising toner particles suspended in an electrically insulating liquid dispersant. Plural, generally identical, toner modules are arranged side by side at a first level, each module comprising a toner tray having a development electrode mounted on the upper surface thereof. The development electrode has a planar upper surface. A motor operates an articulated linkage which causes the tray to be elevated to a second level for toning, one of the modules being selected from the others. Antifriction bearing surfaces are mounted on the upper surface of the tray at opposite ends of the development electrode. The antifriction surfaces extend upwardly of the development electrode a short distance slightly above the upper surface thereof to define a gap between the development electrode and the surface to be toned. A toggle actuated control valve can be provided to direct the toner flow over the electrode in the direction of the movement of said surface, changing the direction of flow during the reciprocal movement of said surface. Alternatively, the flow of toner may be continuous over the planar electrode. During toning, a bias voltage is applied between the development electrode and the photoconductive surface to establish an electrical field within the gap for assisting toning. The charge level to which the toner responds is above the residual level thereby leaving the nonimaged or background area of the photoconductive surface free of toner particles.