Electrophotography – Cleaning of imaging surface – Having handling of removed material
Reexamination Certificate
2002-06-07
2004-04-13
Brase, Sandra (Department: 2852)
Electrophotography
Cleaning of imaging surface
Having handling of removed material
C399S344000
Reexamination Certificate
active
06721534
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image formation method and an image formation apparatus such as a copier, a printer and a facsimile.
BACKGROUND OF THE INVENTION
Recently, mass colored documents are handled even in an office and accordingly smaller and faster image formation apparatus such as full-color printers and full-color copiers are desired increasingly more than before. A recent widespread color laser printer is generally provided with a plurality of developing devices arranged touchable with one photosensitive member. Each of different colored toner images is formed per revolution of the photosensitive member and the images are transferred in turn from the photosensitive member to a recording material such as a recording paper and an OHP sheet to form a colored toner image. This printer is the so-called one-drum type of mainstream.
The one-drum image formation apparatus are classified into an intermediate transfer type and a direct transfer type. The former is configured to primarily transfer toner images of different colors from a photosensitive member and superimpose them on an intermediate transfer member, then secondarily transfer the toner images together onto a recording material. The latter is configured to transfer toner images of different colors from a photosensitive member sequentially onto a recording paper held on a transfer drum and the like to form a colored toner image.
The image formation apparatus of the direct transfer type has an advantage because of a simple structure, low cost and ability of high-speed image formation. The direct transfer type, however, is difficult to achieve stable transfers because resistances and water contents of the recording paper vary during sequential transfers of different color toners to the recording paper. In contrast, the image formation apparatus of the intermediate transfer type can achieve stable transfers because the transfer of the toner image to the recording paper is required only once. If the image formation apparatus of the direct transfer type employs a transfer drum which wraps a recording material thereon, it has a limitation in a thickness and type of the recording material. To the contrary, the image formation apparatus of the intermediate transfer type has an advantage because it has no limitations in thickness and types of recording materials and is possible to increase their versatility.
In the case of formation of a full-color image from four toner images superimposed, for example, either type of the one-drum image formation apparatus is required to rotate the photosensitive member at least four turns to form different color toner images. This is disadvantageous because formation of a color image requires a long time, which lowers a yield.
In order to respond to high-speed color image formation, plural (three or four in general) photosensitive members are arranged along a path which conveys a recording material. Plural developing devices are respectively mounted on the plural photosensitive members to develop latent images of different colors formed individually on the photosensitive members into toner images, which are transferred sequentially to and successively superimposed on the recording material conveyed to form a color image. Such the configuration can be found in an image formation apparatus of the so-called tandem or inline type proposed in the art. For example, Japanese Patent Application Laid-Open No. 53-74037 (U.S. Pat. No. 4,162,843) proposes an image formation apparatus, which comprises plural photosensitive members mounted thereon for sequentially multiple-transferring toner images on a recording material that is conveyed using a belt-like conveyer unit.
The image formation apparatus of the tandem or inline type is possible to form an image at a higher speed four times or more than that of the image formation apparatus of the one-drum type if the photosensitive members have the same speed on the perimeter. The image formation apparatus of the tandem or inline type is generally configured to transfer the toner image from the photosensitive member directly onto a recording material. This configuration causes several problems because of unstable transferring of the toner image onto the recording material and difficult positioning of the recording material at the time of transferring the toner image, as described above. An image formation apparatus of the so-called tandem intermediate transfer type is proposed to solve such problems, which belongs to the tandem type and employs an intermediate transfer member (see Japanese Utility Model Application Laid-Open No. 59-192159, for example).
The image formation apparatus of such the type is configured to form toner images of different colors on photosensitive members or image carriers using plural developing devices that contain different color toners therein. The toner images are transferred to and superimposed on an intermediate transfer member or a recording material. Then, different color toners not transferred and resided on the surfaces of the photosensitive members are removed and collected by a cleaning device which prepares the next image to be formed on the surfaces of the photosensitive members. The cleaning device may have a configuration for removing and collecting the non-transferred different color toners from the photosensitive members without mixing them. In this case, the different color toners removed and collected by the cleaning device from the photosensitive members can be reused as recycled toners when the collected toner is returned to the corresponding developing device that contains the same color toner.
A color image formation apparatus of the tandem type comprises plural (three or four in general) image formation units each including photosensitive members, developing devices and cleaning devices by the number corresponding to the different color toners required for full-color image formation. Each image formation unit is configured to individually form a toner image of each color. Accordingly, in this color image formation apparatus of the tandem type, non-transferred toner resided on each photosensitive member can be collected by the cleaning device corresponding to each photosensitive member without causing color mixture. Therefore, each color toner collected by each cleaning device can be returned to each developing device and easily reused as a recycled toner.
Recycling of the collected toner is particularly important in the image formation apparatus which forms color images as described above. The image formation apparatus of this type is often employed to create an image with a larger image area rate and a larger number of colors compared to a monochromic image, such as a photographic draft, and accordingly consumes relatively larger amounts of color toners. It is difficult, however, to reserve a storage space for housing sufficient amounts of color toners as the apparatus is downsized and weight reduced. Therefore, it is an important point to recycle the collected toner from the viewpoint of reducing its resource, space and running cost.
The conventional image formation apparatus has the following problem, however, if the collected toners of plural colors are employed as recycled toners.
In such the image formation apparatus that employs plural color toners to form an image, a different color toner may be mixed in the collected toner of each color that is removed and collected by the cleaning device from the photosensitive member. In this case, when the collected toner is reused as a recycled toner, influence from the color mixture may reduce the image quality.
The color mixture of the collected toner occurs in any types of image formation apparatus. In particular, the one-drum image formation apparatus is generally configured to create toner images of different colors sequentially on one photosensitive member and collect residual toners of different colors resided on the photosensitive member using one cleaning device. Therefore, the color mixture of the collected toner can not b
Brase Sandra
Ricoh Company Limited
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