Electrophotography – Image formation – Development
Reexamination Certificate
2002-01-31
2003-09-23
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Development
C399S298000, C399S302000, C399S358000, C399S359000
Reexamination Certificate
active
06625414
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus available as, for example, an electrophotographic copying machine.
Recently, opportunity of use of color images has been increased in offices, and electrophotographic color image forming apparatuses, particularly, color printers and color MFP, have been installed in offices. In many offices and the like that are large to some extent, a black-and-white copying machine is used together with a color printer. However, as color printers penetrate into smaller offices, the color MFP are required in place of the black-and-white copying machines.
In this case, it is desired that the color MFP should have the same performance of black-and-white copying as a black-and-white copying machine and should be capable of color printing. At present, a method of the most widespread method color image forming apparatuses is a method using an intermediate transfer member. In this method, an image of each color is developed on a photosensitive member, the developed images are sequentially transferred on the intermediate transfer member such that the images of four colors are superposed thereon, and the images are transferred together on paper.
One of the developing methods in the color image forming apparatuses is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 60-214377. According to this method, a plurality of development units for respective colors are collectively arranged in an approximately columnar shape on a rotation member, and the development units are sequentially made to be opposite to the photosensitive member for development by rotating the rotation member.
As for a monochrome printing apparatus, a cleaner-less system emitting no waste toner has been noticed from the viewpoint of environmental friendliness. In this cleaner-less system, when a photosensitive member turns at one time and returns to a development position, residual toner on the photosensitive member generated when a toner image is transferred from the photosensitive member to an image-transferred member, is recovered at a developer unit.
However, the following problem arises in a case where the cleaner-less technique for the monochrome printing apparatus is applied to the above-mentioned color image forming apparatus. For example, when an yellow toner image is transferred from the photosensitive member to the intermediate transfer member, yellow transfer residual toner is generated on the photosensitive member. In the color image forming apparatus, however, an yellow developer unit is changed to a magenta developer unit while the transfer residual toner is moved to the development position by the rotation of the photosensitive member. For this reason, the yellow transfer residual toner on the photosensitive member is recovered by the magenta developer unit and the magenta toner and the yellow toner are mixed.
To solve this problem, a measure of employing a recovery device wherein a plurality of recovery units for recovering the transfer residual toner are arranged around the photosensitive member or a plurality of recovery units are collectively arranged in an approximately columnar shape on a rotary member, and the recovery units are sequentially made to face the photosensitive member by the rotation of the rotary member to recover the residual toner, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-23696, is proposed.
In this case, however, the recovered toner cannot be reused, or the apparatus becomes large such that the manufacturing costs are increased.
BRIEF SUMMARY OF THE INVENTION
The present invention has been accomplished in consideration of the above-described circumstances, and the object of the present invention is to provide an image forming apparatus capable of recovering residual toner without upsizing and of reusing the recovered toner.
An image forming apparatus according to the present invention comprises an image forming device which separates image information into a plurality of color information items, which scans information light on a rotating image carrier for exposure in accordance with the separated color information items, and which sequentially forms electrostatic latent images of respective colors, developing units of a plurality of colors, which sequentially feed developers of the respective colors to the electrostatic latent images of the respective colors formed by the image forming device, at a developing position, to develop the electrostatic latent images, a rotation member which retains the developing units of the plurality of colors along a rotating direction, and which rotates to sequentially move the developing units to the developing position, an intermediate transfer member which sequentially superposes and transferring the developer images formed on the image carrier, and which transfers the superposed and transferred developer images together to an image-transferred member, and a plurality of recovery devices retained on the rotation member, between the developing units of the plurality of colors, for recovery of developers after the transfer of the developer images to the intermediate transfer member, and to make the recovered developers return to the developing units of the same colors as the colors of the developers.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 4707108 (1987-11-01), Ohno
patent: 5442430 (1995-08-01), Ishii et al.
patent: 5765087 (1998-06-01), Yano et al.
patent: 6337967 (2002-01-01), Izumi et al.
patent: 5-19662 (1993-01-01), None
patent: 9-23696 (1997-01-01), None
patent: 9-96939 (1997-04-01), None
Kabushiki Kaisha Toshiba
Royer William J.
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