Electrophotography – Control of electrophotography process – Control of charging
Reexamination Certificate
2000-02-15
2003-01-07
Braun, Fred L. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of charging
C399S174000, C399S176000
Reexamination Certificate
active
06505013
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to xerographic printing apparatus, and in particular relates to a system and method for extending the useful life of a charge receptor, such as a photoreceptor used in such apparatus.
BACKGROUND OF THE INVENTION
Electrostatographic printing methods, such as xerography, involve creation of an electrostatic latent image on a charge receptor, such as a photoreceptor. As is well known, in such apparatus, the photoreceptor is imagewise discharged in a manner conforming to an image desired to be copied or printed, and then this latent image is developed with toner. The developed toner image is in turn transferred to a print sheet, which is then fused to fix the transferred toner image thereon.
The properties of the charge receptor, such as a photoreceptor, are clearly very important to the overall functioning of a printing apparatus, and to the ultimate quality of images created therewith. The electrical stresses placed on a photoreceptor, with the printing of thousands of images therewith contributes to the degradation of the photoreceptor. As the photoreceptor degrades the quality of images that can be created therewith degrades as well. Thus, in practical embodiments of xerographic printers and copiers, it is inevitable that the photoreceptor will have to be periodically replaced. Replacement of the photoreceptor represents a large expense. It is therefore desirable to provide a method and system by which the photoreceptor, even a pre-existing photoreceptor, can be extended significantly.
DESCRIPTION OF THE PRIOR ART
In the prior art, U.S. Pat. No. 5,613,173 discloses a novel type of charging apparatus for use in charging the photoreceptor in a xerographic printer. In combination with the bias roll which initially charges the photoreceptor is a special “clipping” circuit comprising a diode and resistor. The clipping circuit has the function of clipping an oscillating voltage applied to the bias roll, and in turn to the photoreceptor, as the bias roll charges the photoreceptor. The long-term effect of this clipping is that lesser electrical stresses are experienced by the photoreceptor with extended use, and in turn the degradation of the photoreceptor is slowed down.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a method of operating an electrostatographic printing apparatus, the apparatus including a charge-retentive member defining an imaging surface and a charging device for placing a charge on the imaging surface, comprising the steps of determining an age of the charge-retentive member, and providing a correction circuit of a predetermined design associated with the charging device, as a result of said determining step.
According to another aspect of the present invention, there is provided various apparatus useful in electrostatographic printing in which a charging device places a charge on an imaging surface. The apparatus, which may itself be an electrostatographic printing apparatus, or a portion thereof, includes a correction circuit of a predetermined design associated with the charging device. The correction circuit can include various arrangements of diodes, zener diodes, resistors, and capacitors.
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Bedford Keith L.
Less Krzysztof J.
Masham Roger D.
Braun Fred L.
Hutter R.
Xerox Corporation
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