Electrophotography – Diagnostics – Image forming component
Reexamination Certificate
2000-09-25
2001-09-04
Pendegrass, Joan (Department: 2852)
Electrophotography
Diagnostics
Image forming component
C399S053000
Reexamination Certificate
active
06285837
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a development system as used in xerography, and more particularly concerns a “jumping” development system in which toner is conveyed to an electrostatic latent image by an AC field.
BACKGROUND OF THE INVENTION
In a typical electrostatographic printing process, such as xerography, a photoreceptor is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoreceptor is exposed to a light image of an original document being reproduced. Exposure of the charged photoreceptor selectively dissipates the charges thereon in the irradiated areas. This records an electrostatic latent image on the photoreceptor corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoreceptor, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoreceptor. The toner powder image is then transferred from the photoreceptor to a copy sheet. The toner particles are heated to permanently affix the powder image to the copy sheet. After each transfer process, the toner remaining on the photoconductor is cleaned by a cleaning device.
One specific type of development apparatus currently used in high-quality xerography is known as a hybrid jumping development (HJD) system. In the HJD system, a layer of toner is laid down evenly on the surface of a “donor roll” which is disposed near the surface of the photoreceptor. Biases placed on the donor roll create two development fields, or potentials, across the gap between the donor roll and the photoreceptor. The action of these fields causes toner particles on the donor roll surface to form a “toner cloud” in the gap, and the toner in this cloud thus becomes available to attach to appropriately-charged image areas on the photoreceptor.
In a practical application of hybrid jumping development, a crucial parameter for the quality of the resulting images is the width of the gap between of the donor roll and the photoreceptor. If the width of the gap is too large, noticeable defects in image quality will result. If the gap is too small, there is likely to be arcing between the donor roll and the photoreceptor, which is of course unacceptable. Unfortunately, with the desirable modular design of office equipment, this crucial gap width is hard to control if the module including the donor roll is separate from another module including the photoreceptor. Whenever one or the other module is replaced, the gap width is likely to change. It is therefore desirable to have a testing method, which can be automated by software within the printer, which can ascertain that the gap width is within an acceptable range.
DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 4,610,531 discloses the basic concept of jumping development with an AC field set up between a donor member and a photoreceptor.
U.S. Pat. No. 5,402,214 discloses a control system for a xerographic printing system in which the reflectivity of a test patch is measured, and the DC bias of a field associated with the development unit is adjusted accordingly.
U.S. Pat. No. 5,890,042 discloses a hybrid jumping development system, in which a donor roll is loaded with a layer of toner particles by a magnetic roll which conveys toner which adheres to carrier granules.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided, in an electrostatographic development system wherein toner is conveyed from a donor member over a development gap to a charge receptor by an AC development field in the development gap, a method comprising the following steps. An image of a predetermined type is developed with the AC field being set to default parameters, and reading a reflectivity of the developed image. In a first test, an image of the predetermined type is developed with the AC field being set a different amplitude relative to the default parameters, and a reflectivity of the developed image is read to yield a first test result. Based on at least the first test result, it is determined whether a width of the development gap is within a predetermined range.
REFERENCES:
patent: 4610531 (1986-09-01), Hayashi et al.
patent: 5402214 (1995-03-01), Henderson
patent: 5890042 (1999-03-01), Wong et al.
patent: 4-350864 (1992-12-01), None
patent: 8-286509 (1996-11-01), None
patent: 2001-27838 (2001-01-01), None
Budnik Roger W.
Kauffman Scott L.
Maier Richard M.
Pacer James M.
Swales Michael G.
Hutter R.
Pendegrass Joan
Xerox Corporation
LandOfFree
System for determining development gap width in a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System for determining development gap width in a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System for determining development gap width in a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2534912