Electrophotography – Image formation – Development
Reexamination Certificate
2001-08-17
2003-02-04
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Development
Reexamination Certificate
active
06516173
ABSTRACT:
BACKGROUND OF THE OF THE INVENTION
The present invention relates to development of latent electrostatic images, and more specifically, to electrode members for use in a developer unit in electrophotographic printing machines. Specifically, the present invention relates to electrode wires fabricated such that the phenomena known as wire history and wire contamination are minimized.
Generally, the process of electrophotographic printing includes charging a photoconductive member to a substantially uniform potential so as to sensitize the photoconductive member thereof. The uniformly charged portion of the photoconductive member is exposed to light corresponding to an original document being reproduced. The source of the light may be light reflected from an original document or light emanating from a laser. This records an electrostatic latent image on the photoconductive member.
After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed depositing developer material onto the latent electrostatic image. Two component and single component developer materials are commonly used for rendering the latent electrostatic images visible.
A typical two-component developer material comprises magnetic carrier granules having toner particles adhering triboelectrically thereto. A single component developer material typically comprises toner particles such as silica and titanium and also contain debris picked up from the environment. Toner particles are attracted to the latent image forming a toner powder image on the photoconductive member. The toner powder image is subsequently transferred to a copy sheet. Finally, the toner powder image is heated to permanently fuse it to the copy sheet in image configuration.
One type of development apparatus for developing latent images and comprising single component developer is known as a scavengless development system, one that uses a donor roll for transporting charged toner to a development zone. At least one, but preferably a plurality of electrode members is closely spaced to the donor roll in the development zone. An AC voltage is applied to the electrode members thereby forming a toner cloud in the development zone, area between the electrode members and the imaged surface. The electrostatic fields emanating from the latent images attract toner from the toner cloud thereby effecting development of the latent images.
Another type of development apparatus for developing latent images on a charge retentive surface such as a photoconductor comprises a two-component developer and is known as a Hybrid Scavengless Development (HSD) system that employs a magnetic brush developer roller for transporting carrier having toner adhering triboelectrically thereto. A donor roll is used in this configuration also to transport charged toner to the development zone. The donor roll and magnetic roller are electrically biased relative to one another. Toner is attracted to the donor roll from the magnetic roller. The electrically biased electrode members cause detachment of toner particles from the donor roll forming a toner powder cloud in the development zone, and the latent image attracts the toner particles thereto. In this way, the latent image recorded on the photoconductive member is rendered visible.
Various types of development systems have hereinbefore been used as illustrated by the following disclosures, which may be relevant to certain aspects of the present invention. In addition to possibly having some relevance to the question of patentability of the present invention, these references, together with the detailed description to follow, may provide a better understanding and appreciation of the present invention.
U.S. Pat. No. 4,868,600 granted to Hays et al describes an apparatus wherein a donor roll transports toner to a region opposed from a surface on which a latent image is recorded. A plurality of electrode members are positioned in the space between the latent image surface and the donor roll and electrically biased to detach toner from the donor roll to form a toner cloud. Detached toner from the cloud develops the latent image.
U.S. Pat. No. 4,984,019 granted to Folkins discloses a developer unit having a donor roll with electrode members disposed adjacent thereto in a development zone. A magnetic roller transports developer material to the donor roll. Toner particles are attracted from the magnetic roller to the donor roller. When the developer unit is inactivated, the electrode members are vibrated to remove contaminants therefrom.
U.S. Pat. No. 5,124,749 granted to Bares discloses an apparatus in which a donor roll advances toner to an electrostatic latent image recorded on a photoconductive member wherein a plurality of electrode wires are positioned in the space between the donor roll and the photoconductive member. The wires are electrically biased to detach the toner from the donor roll so as to form a toner cloud in the space between the electrode wires and the photoconductive member. The powder cloud develops the latent image. A damping material is coated on a portion of the electrode wires at the position of attachment to the electrode supporting members for the purpose of damping vibration of the electrode wires.
U.S. Pat. Nos. 5,300,339 and 5,448,342 both granted to Hays et al., the subject matter of each which is hereby incorporated by reference in their entirety, disclose a coated toner transport roll containing a core with a coating thereover.
U.S. Pat. No. 5,172,170 granted to Hays et al discloses an apparatus in which a donor roll advances toner to an electrostatic latent image recorded on a photoconductive member. The donor roll includes a dielectric layer disposed about the circumferential surface of the roll between adjacent grooves.
U.S. Pat. No. 5,422,709 teaches an apparatus in which a donor roll advances toner to an electrostatic latent image recorded on a photoconductive member. A plurality of electrode wires is positioned in the space between the donor roll and the photoconductive member. The electrode wires extend in a transverse direction relative to the longitudinal axis of the donor roll. The electrode wires are electrically biased to detach the toner from the donor roll so as to form a toner cloud in the space between the electrode wires and photoconductive members. Detached toner from the toner cloud develops the latent image. Electrode wires contact a portion of the surface of the donor roll. As the donor roll rotates, friction between the electrode wires and donor roll causes trapped debris to move away from the toner powder cloud region so as to minimize contamination-produced streaks on the developed image.
U.S. Pat. No. 5,734,954 granted to Eklund et al discloses an apparatus for developing latent electrostatic images wherein a power supply controller, in communication with the power supply, is adapted to adjust an electrode member electrical biasing to avoid air breakdown induced contamination of the electrode member with toner.
U.S. Pat. No. 5,778,290 granted to Badesha et al discloses an apparatus and process for reducing accumulation of toner from the surface of an electrode member in a development unit of an electrostatographic printing apparatus by providing a composite coating on at least a portion of the electrode member.
U.S. Pat. No. 5,787,329 granted to Laing et al discloses an electrode member positioned in the space between the surface and the donor member, the electrode member being closely spaced from the donor member and being electrically biased to detach toner from the donor member thereby enabling the formation of a toner cloud in the space between the electrode member and the surface with detached toner from the toner cloud developing the latent image, wherein opposed end regions of the electrode member are attached to wire supports adapted to support the opposed end regions of said electrode member; and an organic coating on at least a portion of nonattached regions of said electrode member.
U.S. Pat. No. 5,805,964 granted to Badesha e
Grainger Quana M.
Sklar Ben
Xerox Corporation
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