Corona charging device
AssigneeXerox Corporation
InventorsThomas G. Davis, George J. Safford
Life of this patent
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Abstract
A corona discharge device including a corona discharge electrode and a conductive shield located adjacent the electrode, the electrode being coated with relatively thick dielectric material so as to substantially prevent the flow of conduction current therethrough. The delivery of charge to the photoconductive surface is accomplished by means of a displacement current or capacitative coupling through the dielectric material. The flow of charge to the surface to be charged is regulated by means of a d.c. bias applied to the corona shield.
Claims28
In combination, a charge collecting surface, said surface carried on with a conductive substrate held at a reference potential, a corona discharge member positioned above said surface, said member comprising a thin wire, coated at least in the discharge area with a dielectric material, means for coupling a corona generating a.c. voltage intermediate said substrate and said wire, a conductive shield adjacent said wire and first biasing means for holding said shield at a potential different than said reference potential, said dielectric material having a thickness sufficient to prevent the flow of a net d.c. current though said wire.
A method for depositing a charge on an adjacent surface comprising the steps of
- locating a corona discharge electrode adjacent said surface, the electrode including a coating of dielectric material to prevent the passage of a d.c. current therethrough,
- coupling an a.c. corona generating potential to said electrode,
- positioning a conductive shield adjacent said electrode,
- positioning a field defining member on the side of said surface opposite said electrode, and
- establishing a d.c. electric field between said shield and said member.
A corona generating device for depositing a negative charge on an imaging surface carried on a conductive substrate held at a reference potential comprising:
- a corona discharge electrode including an elongated conductive member coated with a thick dielectric coating, the thickness of the coating adapted to prevent a net d.c. current from said source through said electrode,
- conductive shield located adjacent said electrode, and
- power supply means for applying an a.c. corona generating potential to said member and a negative d.c. potential to said shield relative to said reference potential.
A corona generating discharge device for altering the charge on an imaging surface carried on a conductive substrate comprising a corona discharge member including an inner conductive electrode with an outer dielectric coating, the thickness of said coating being selected to prevent a net d.c. current from being drawn from said source through said electrode, a conductive shield located adjacent said member, power supply means for applying an a.c. corona generating voltage to said electrode and providing a d.c. potential between said substrate and said shield, and means for varying said power supply means to change the charge delivered by said device to an imaging surface at a given potential.
An improved method for changing the characteristic output of a corona generating device in an electrostatographic reproduction machine including an imaging surface carried on a conductive substrate comprising the steps of:
- locating a corona generating member adjacent an imaging surface, said member including a conductive electrode coated with a dielectric material,
- positioning a conductive shield adjacent said member
- connecting an a.c. corona generating potential to said electrode,
- applying an electrical potential between said substrate and shield, and
- varying either of said potentials to change the characteristic charge output of said corona device.
In combination, a corona discharge member, a charge collecting surface, a conductor positioned on the side of said surface remote from said member and held a reference potential, said corona discharge member comprising a wire coated at least in the discharge area with a dielectric material, means for generating an a.c. corona discharge adjacent said member, a conductive shield adjacent said wire and biasing means for holding said shield at a potential different than said reference potential, said dielectric material preventing a net d.c. current through said wire.
In combination, a corona discharge member including an electrode having a dielectric coating to substantially prevent the flow of conduction current therethrough, a surface to be charged, first and second conductors, said surface to be charged positioned intermediate said first conductor and said member, biasing means for holding said second conductor at a constant potential relative to said first conductor in order to define a field therebetween, and means for creating an a.c. corona discharge adjacent said member.
Dependencies are inferred from the claim text.