Electrophotography – Image formation – Transfer
Reexamination Certificate
1997-03-31
2001-01-09
Pendegrass, Joan (Department: 2852)
Electrophotography
Image formation
Transfer
C399S101000
Reexamination Certificate
active
06173149
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an electrophotographic printing apparatus such as laser printers, photo copy machines, and regular paper facsimile machines. More particularly, it relates to a transfer roller of a printing apparatus which includes first rollers and second roller having different resistance properties in order to prevent a large amount of toner from adhering the ends of its charging roller and photoconductive drum.
2. Description of the Related Art
Varying the resistivity along the length of the transfer roller is not new in the art. U.S. Pat. No. 4,379,630 for a
Transfer Roller For Electrophotographic Apparatus
to Suzuki '630 discloses a transfer roller with a resistance value that varies in either a continuous or a stepwise manner toward the respective end faces at two end portions of the transfer roller. Suzuki uses as a varying resistance transfer roller to eliminate the problems called multiple copy fog phenomenon and multiple-copy edge line phenomenon. The multiple copy fog phenomenon and the multiple copy edge line phenomenon can be suppressed by using a transfer roller whose resistivity at the ends are different from the resistivity at the center. Unlike the arrangement in the present invention, Suzuki '630 uses a transfer roller and a photoconductive drum whose lengths are less than the width of a sheet of recording medium conveyed therebetween. As a result, Suzuki addresses and tries to correct different problems than that of the present invention. The present invention relies on the fact that the transfer roller and the photoconductive drum are longer than the width of recording medium.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide a transfer roller for an electrophotographic printing apparatus which prevents a photoconductive drum from being stained with toner in order to achieve the best possible print quality, and a method of manufacturing such a transfer roller where the length of the transfer roller is greater than the width of a sheet of recording medium.
It is another objective of the present invention to provide a transfer roller for an image forming apparatus which prevents a photoconductive drum from being stained with toner to enhance the photoconductive drum's durability, and a method of manufacturing such a transfer roller where the length of the transfer roller is greater than the width of a sheet of recording medium.
It is still another objective of the present invention to provide a transfer roller for an image forming apparatus which prevents a photoconductive drum from being stained with toner to thereby increase a charging roller's durability, and a method of manufacturing such a transfer roller where the length of the transfer roller is greater than the width of a sheet of recording medium.
It is a further objective of the present invention to provide a transfer roller for an electrophotographic printing apparatus which prevents the photoconductive drum from being stained with toner while uniformly charging an outer surface of the photoconductive drum, and a method of manufacturing such a transfer roller where the length of the transfer roller is greater than the width of a sheet of recording medium.
It is still further objective of the present invention to provide a transfer roller for an electrophotographic printing apparatus which prevents the photoconductive drum from being stained with toner and also prevents large amounts of toner from adhering to paper's tail end where the length of the transfer roller is greater than the width of a sheet of recording medium.
In order to realize the above objectives, the present invention provides a transfer roller for preventing the photoconductive drum from being stained with toner in an image forming apparatus using electrophotography having a photoconductive drum rotating in a clockwise direction and at a predetermined velocity, a charging roller for uniformly charging the photoconductive drum's outer surface, and a scanner unit for scanning the photoconductive drum's charged area to form a latent image thereon. The inventive transfer roller is manufactured to have different properties at its center than at its edges so as to prevent a large quantity of positive charges from being applied to the edges of the photoconductive drum and the edges of the charging roller which are not covered by the paper.
According to another aspect of the present invention, there is disclosed a method of manufacturing a transfer roller for electrophotographic printing apparatus for preventing a photoconductive drum from being stained with toner, including the steps of fabricating a center roller, above the center section, to have resistance adequate to transfer a toner image on the photoconductive drum's outer surface to paper; fabricating a pair of edge rollers, above the edges, to each have resistance higher than the center roller's so as to prevent a large quantity of positive charges from being applied to the edges of the photoconductive drum during toner image transfer; tightly attaching the center roller on the middle of a shaft about which the transfer roller rotates; and attaching the edge rollers on both ends of the shaft so that one side of each of the edge rollers comes in close contact with one side of the center roller and so that the entire length of the transfer roller is greater than the width of a sheet of recording medium.
REFERENCES:
patent: 4379630 (1983-04-01), Suzuki
patent: 5168313 (1992-12-01), Hosaka et al.
patent: 5287152 (1994-02-01), Oka et al.
patent: 5287163 (1994-02-01), Miyashiro et al.
patent: 5406360 (1995-04-01), Asai
patent: 5410393 (1995-04-01), Watanabe
patent: 5459560 (1995-10-01), Bartholmae et al.
patent: 5475473 (1995-12-01), Masuda et al.
patent: 5483330 (1996-01-01), Ogiyama et al.
patent: 5571457 (1996-11-01), Vreeland et al.
patent: 5600420 (1997-02-01), Saito et al.
patent: 4-215680 (1992-08-01), None
patent: 7-199689 (1995-08-01), None
Bushnell , Esq. Robert E.
Pendegrass Joan
Samsung Electronics Co,. Ltd.
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