Browse Prior Art Database

Original Publication Date: 1990-Jun-30
Included in the Prior Art Database: 2004-Apr-05

Publishing Venue

Xerox Disclosure Journal


In corona generating devices used in electrostatographic printing machines th corona generates a variety of undesirable contaminating species in addition to those desired for charging the imaging surface. The presence of these species can result in a reduction in image contrast. The Figure illustrates an electrostatic precipitator filter for reducing contamination of an and improving xerographic stability. It can be part of the machine or alternatively be incorporated in a process cartridge which is removable from the main frame of the machine. The charging assembly 10 which is adjacent the photoreceptor belt 12 moving in the direction indicated by the arrow includes two corona wires 14 at 5-6 kilovolts above a control grid 16 at 750-950 volts. Two conductive electrostatic filtering elements 18 are positioned on each side of the corona device and are at a potential greater than about 3 kilovolts from the corona wires. The filtering elements are an open cell polyurethane foam having about 30 pores per linear inch coated with about an equal amount by weight of a conductive activated carbon doped with 2% silver by weight of the carbon. A channel 20 provides for the flow of clean air through the charging assembly at about 1-2 cubic feet per minute through the filter medium to the output vent. With such an air flow and charged filter collecting various particles and other charged species xerographic stability can be maintained. In addition the filter provides chemical reaction sites that can remove silicone oil vapor that otherwise would be growing on the corona wires and grid as silicon diode dendrites.