Electrophotography – Machine operation – Electrical connection
Reexamination Certificate
1999-02-04
2001-09-11
Braun, Fred L (Department: 2852)
Electrophotography
Machine operation
Electrical connection
C428S088000
Reexamination Certificate
active
06289187
ABSTRACT:
This invention relates generally to a development system adapted for use in an electrophotographic printing machine, and more particularly concerns an improved commutator brush for use therein.
Generally, the process of electrophotographic printing includes charging a photoconductive surface to a substantially uniform potential and selectively discharging areas by exposure to light, thereby forming an electrostatic latent image of an original document being created. The electrostatic latent image is developed by bringing a developer material into contact therewith. Two component and single component developer materials are frequently used. A typical two component developer material has magnetic carrier particles with toner particles adhering triboelectrically thereto. A single component developer material typically comprises toner particles. Toner particles are attracted to the latent image, forming a toner powder image on the photoconductive surface. The toner powder image is subsequently transferred to a sheet of support material. Finally, the toner powder image is heated to permanently fuse it to the sheet in image configuration.
One type of single component development system is a scavengeless, or non-interactive development system that uses a donor roll for transporting charged toner to the development zone. A plurality of electrode wires are closely spaced to the donor roll in the development zone. An AC voltage is applied to the wires forming a toner cloud in the development zone. The electrostatic fields generated by the latent image attract toner from the toner cloud to develop the latent image. A hybrid scavengeless development unit employs a magnetic brush developer roller for transporting carrier having toner particles adhering triboelectrically thereto. The donor roll and magnetic roll are electrically biased relative to one another. Toner is attracted to the donor roll from the magnetic roll. The electrically biased electrode wires detach the toner from the donor roll forming a toner powder image in the development zone. The latent image attracts toner particles thereto from the toner powder cloud. In this way, the latent image recorded on the photoconductive surface is developed with toner particles.
In order to alleviate the problems associated with the use of electrically activated wires in the development zone, an electroded or commutated donor roll is used. This eliminates the contamination and vibrational instabilities associated with the use of individual wires for detaching the toner from the surface of the donor roll. However, it has been found that when an electroded donor roll is employed, electrical discharges frequently occur at the points of high voltage electrical commutation.
In order to improve the performance of the development system, it has been found that the stationery commutator having a brush contacting the electrodes on the donor roll must reliably transmit complex high voltage wave forms to the narrow electrode pads of the rotating donor roll without distortion to, or deterioration of, the wave form.
The commutator brush is typically a conductive fiber brush made of conductive fibers protruding from a composite plastic or a solid graphite brush. Typically, only the electrode in the nip between the donor roll and the photoconductive surface is electrically biased. As the donor roll rotates, the electrodes in the nip contact the brush. The use of a stationery commutator brush in contact with the electrodes on the periphery of the donor roll has problems. Many materials for the contact brush have been considered, including metal and non-metal materials. A carbon fiber brush and a solid graphite brush have been found to be most successful. Inasmuch as the brush is in rubbing contact with the electrodes on the donor roll, the electrodes wear and reduce the life of the expensive donor roll. The abrupt connection and disconnection of the brush with the respective electrodes on the donor roll create electrical noise and arcing between the brush and the electrode. This may further reduce the life of the donor roll. In addition, brushes hereinbefore manufactured were excessively heated during the mechanical or laser cutting process. This resulted in a degradation of the mechanical and electrical properties of the brush.
Various types of brushes have hereinbefore been developed. The following disclosures may be relevant to certain aspects of the present invention:
U.S. Pat. No. 5,139,862
Patentee: Swift et al.
Issued: Aug. 18, 1992
U.S. Pat. No. 5,250,756
Patentee: Swift et al.
Issued: Oct. 5, 1993
U.S. Pat. No. 5,270,106
Patentee: Orlowski et al.
Issued: Dec. 14, 1993
U.S. Pat. No. 5,289,240
Patentee: Wayman
Issued: Feb. 22, 1994
U.S. Pat. No. 5,599,615
Patentee: Swift
Issued: Feb. 4, 1997
U.S. Pat. No. 5,794,100
Patentee: Bell et al.
Issued: Aug. 11, 1998
U.S. Pat. No. 5,812,908
Patentee: Larocca et al.
Issued: Sep. 22, 1998
The disclosures of the above-identified patents may be briefly summarized as follows:
U.S. Pat. Nos. 5,139,862; 5,270,106; 5,599,615; 5,794,100; and 5,812,908 all describe various types of carbon fiber brushes which may be used for electrically contacting a rotating member.
U.S. Pat. No. 5,250,756 discloses a carbon fiber brush encased in a resin binder. A laser is used to cut individual components for use as electrical contacts. The laser cuts the resin and carbon fibers to form a contact region of the desired length. The types of lasers that may be used include a carbon dioxide laser, a carbon monoxide laser, a YAG laser, or an argon ion laser.
U.S. Pat. No. 5,289,240 discloses a commutator brush which is adapted to contact electrodes on a donor roll in a development system. The commutator brush may include a central portion of filaments bounded on each side by boundary filaments. The filaments in the boundary portions are of a higher resistivity than the filaments in the central portion. The filaments may be made from carbon fibers.
Pursuant to the features of the present invention, there is provided an electrical component having at least one end for electrically contacting another component. The electrical component includes a support and a plurality of electrically conductive fibers having at least a portion thereof extending outwardly from the support to form a brush-like structure. The brush-like structure has a free end adapted to contact the other component with the free end being cold cut by a laser beam so as to minimize heating of the fibers being cut.
In accordance with another aspect of the present invention, there is provided a method of making an electrical component having at least one end for electrically contacting another component. The method includes feeding a plurality of carbon fiber layers into a mold and surrounding the carbon fiber layers in the mold with a resin material. The carbon fiber layers are then cut along opposed front and rear surfaces. A conductive adhesive is applied to the rear face to bond the carbon fibers to one another. The front face is cold cut to form a brush contact region.
In still another aspect of the present invention, there is provided an apparatus for depositing developer material on a surface to develop a latent image recorded thereon. The apparatus includes a donor roll spaced from the surface and adapted to advance developer material to the latent image recorded on the surface. A plurality of electrodes are disposed on the donor roll. A commutator contacts the electrodes along the exterior circumferential surface of the donor roll. The commutator comprises a plurality of electrically conductive fibers to form a brush-like structure having a free end adapted to contact the electrodes. The free end is cold cut by a laser beam so as to minimize heating of the fibers being cut.
REFERENCES:
patent: 5139862 (1992-08-01), Swift et al.
patent: 5177529 (1993-01-01), Schroll et al.
patent: 5250756 (1993-10-01), Swift et al.
patent: 5270106 (1993-12-01), Orlowski et al.
patent: 5289240 (1994-02-01), Wayman
patent: 5599615 (1997-02-01), Swift et al.
patent: 5794100 (1998-08-01
Andrews John R.
Swift Joseph A.
Braun Fred L
Fleischer H.
Xerox Corporation
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