Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
1999-11-02
2001-01-09
Lee, Susan S. Y. (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S313000, C399S318000, C399S343000
Reexamination Certificate
active
06173137
ABSTRACT:
The present invention relates generally to an apparatus for developing a latent image, and more particularly concerns cleaning particles from the photoconductive member in the region of contact with the developing device so as to maintain a substantially uniform gap between the developing device and the photoconductive member.
Generally, an electrophotographic printing machine includes a photoconductive member which is charged to a substantially uniform potential to sensitize its surface. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. This forms a visible image on the photoconductive member which is subsequently transferred to a print sheet. The latent image is developed with a developer material which may be a liquid or a powder. After development, the print sheet is heated to permanently affix the image transferred thereto to the print sheet.
Many factors influence the quality of the developed image with a powder developer material, the most significant factor being the uniformity with which the toner particles are deposited on the latent image recorded on the photoconductive surface. Magnetic brush systems are frequently used to achieve the requisite uniformity in toner disposition. The magnetic brush system achieves a high degree of uniform toner deposition, and, therefore, numerous electrophotographic printing machines utilize this type of development system. Magnetic brush systems usually include a developer roll having a directional flux field adapted to bring the developer material into contact with the charged photoconductive surface. Generally, the developer roll of the magnetic brush development system is fixed relative to the photoconductive surface. It has been found that the spacing between the photoconductive surface and the developer roll is extremely critical to the performance of the electrophotographic printing machine. This spacing has significant effects on the solid area density and background performance of the system. When the development system is part of a customer replaceable unit, the spacing is also critical and has a direct impact on the life of the customer replaceable unit. A large amount of work has been done to optimize the spacing to yield both the life requirements and the expected print quality performance. Most frequently, the spacing is controlled by a pair of tracking rollers that are mounted on each end of the developer roller. The tracking rollers contact the surface of the photoconductive member to maintain a uniform gap between the developer roller and the photoconductive surface. However, it has been found, that during operation, toner builds up on the surface of the photoconductive member in the area in which the tracking rolls contact the photoconductive member. This loosely adhered toner causes the spacing between the photoconductive member and the developer roller to increase, which reduces the solid area density and uniformity across the image.
Systems adapted to space the developer roller from the photoconductive drum are well known. The following disclosure describes a system of this type:
U.S. Pat. No. 3,940,272
Patentee: Davidson
Issued: Feb. 24, 1976
The pertinent portions of this patent may be briefly summarized as follows:
U.S. Pat. No. 3,940,272 discloses a developer unit having a housing with a developer roller. The developer roller transports a developer mix into a development zone located between the photoconductive drum and the develop roller. The electrostatic latent image recorded on the photoconductive drum is developed by contact with the moving developer mix. The charged areas of the photoconductive drum electrostatically attract the carrier granules from the developer mix. In operation, a tracking wheel mounted on the developer housing contacts, the photoconductive drum to space the developer roller therefrom.
In accordance with the present invention, there is provided an apparatus for developing a latent image recorded on an image bearing member to form a visible image thereon and transferring the visible image from the image bearing member to a support member. The apparatus includes a developing device, positioned closely adjacent to the imaging member, to develop the latent image recorded thereon forming the visible image. A spacer is operatively associated with the developing device. The spacer spaces the developing device a selected distance from the image bearing member. The spacer is in contact with the tracking region of the image bearing member. A cleaning member, positioned to contact the tracking region, removes particles adhering to the tracking region of the image bearing member.
Pursuant to another aspect of the present invention, there is provided a printing machine of the type having a latent image recorded on an image bearing member. The improvement includes a developing device, positioned closely adjacent the image bearing member to develop the latent image recorded thereon forming a visible image. A spacer is operatively associated with the developing device for spacing the developing device a selected distance from the image bearing member. The spacer is in contact with the tracking region of the image bearing member. A cleaning member, positioned to contact the tracking region, removes particles adhering to the tracking region of the image bearing member.
In still another aspect of the present invention, there is provided an apparatus for removing particles from a tracking region on an image bearing member, wherein a spacer contacts the tracking region to space a developing device a selected distance from the image bearing member. The apparatus includes a cleaning member, positioned in contact with the tracking region, for removing particles adhering to the tracking region of the image bearing member.
Another aspect of the present invention is a method of printing including recording a latent image on an image bearing member. A latent image is developed with a developing device to form a visible image on the image bearing member. The developing device is spaced from the image bearing member by a spacing device contacting a tracking region of the image bearing member. The tracking region of the image bearing member is cleaned to remove particles adhering to the tracking region of the image bearing member.
REFERENCES:
patent: 3940272 (1976-02-01), Davidson
patent: 6044235 (2000-03-01), Hashimoto
patent: 58-85447 (1983-05-01), None
patent: 63-183477 (1988-07-01), None
patent: 4-52668 (1992-02-01), None
Fleischer H.
Lee Susan S. Y.
Xerox Corporation
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