Constant current charging device
AssigneeXerox Corporation
InventorJohn F. O'Brien
Life of this patent
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Abstract
Application of a constant density of surface charge on a dielectric medium by non-contact charging is accomplished by a rotatable charging roll having a relaxable layer surrounding a conductive axle and a protective leaky insulator overcoat layer applied to the relaxable layer. The charging roll is spaced from the dielectric medium to define an air gap of about 0.010-0.060 inch and the surface velocity of the charging roll is adjustable relative to the velocity of the moving dielectric medium. A constant current power source is coupled to the conductive axle to generate a charge buildup on the surface of the relaxable layer; part of this charge is transferred across the air gap to the surface of the dielectric medium. A blade or brush is provided to clean the charging roller as it rotates.
Claims12
Apparatus for depositing a constant density surface charge on a moving dielectric medium, comprising:
- a charging roller mounted adjacent to and spaced from said dielectric medium to define an ionizable air gap between the surface of said charging roller and said dielectric medium, said charging roller comprising an electrically relaxable insulator having a thickness which is greater than the thickness of said dielectric medium;
- means for moving the surface of said charging roller in the same direction as, independently of, and relative to said dielectric medium;
- and
- variable electrical bias means coupled to said charging roller for generating an electric field in said air gap to charge said dielectric medium with a substantially constant density surface charge.
Dependencies are inferred from the claim text.