Electrophotography – Image formation – Development
Reexamination Certificate
2001-04-26
2002-06-04
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Development
C399S296000
Reexamination Certificate
active
06400921
ABSTRACT:
BACKGROUND AND SUMMARY
Cross reference is made to the following applications filed concurrently herewith: entitled “TC Runtime Control Using Underdeveloped Solid, and Edge Enhancement” and entitled “Dynamic Duty Cycle For Increased Latitude”.
This invention relates generally to a hybrid jumping developer system, and more particularly concerns a scavenging device for such a system for improving edge enhancement of the develop image.
In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charges thereon in the irradiated areas. 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. 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 photoconductive member. The toner powder image is then transferred from the photoconductive member 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.
In a machine of the foregoing type, utilizing a hybrid jumping development (HJD) system, the development roll, better known as the donor roll, is powered by two development fields (potentials across an air gap). The first field is the ac jumping field which is used for toner cloud generation and has a typical potential of 2.25 k volts peak to peak at 3.25 kHz frequency. The second field is the dc development field which is used to control the amount of developed toner mass on the photoreceptor.
SUMMARY OF THE INVENTION
There is provided an apparatus for developing a latent electrostatic image on a charge retentive surface moving in a process direction with toner, said apparatus comprising: a supply of toner; a donor structure spaced from said charge retentive surface for conveying toner from said supply of toner to an area adjacent said charge retentive surface, a device for applying an alternating current directly to said donor structure to create an alternating electrostatic field between said donor structure and said charge retentive surface to produce a toner cloud adjacent said charge retentive surface for developing the latent electrostatic image thereon; and an edge enhancement device, adjacent to said donor structure, for redistributing toner on the developed latent electrostatic image.
REFERENCES:
patent: 4701042 (1987-10-01), Mimura et al.
Leclerc Gerald Scott
Maier Richard M.
Bean II Lloyd F.
Grainger Quana M.
Xerox Corporation
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