Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
2001-06-14
2002-11-19
Pendegrass, Joan (Department: 2852)
Electrophotography
Having particular structure
Modular or displaceable
C399S112000, C399S121000
Reexamination Certificate
active
06484003
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus employing an electrophotographic system such as a copying machine, a printer and a facsimile machine, and in particular, to a color image forming apparatus wherein toner images formed on a plurality of image carriers by a plurality of image carriers, latent image forming means and developing means are primarily transferred onto an intermediate transfer object, and then, are secondarily transferred onto a recording sheet.
In the case of a conventional color image forming apparatus employing an electrophotographic system, there have been proposed various types of systems wherein a plurality of image forming sections are arranged in parallel in the conveyance direction, and toner images each being different from others in terms of color formed respectively on photoreceptor drums in image forming sections are successively transferred on a recording sheet held on a transfer belt.
There is also known a color image forming apparatus wherein a transfer drum around which a recording sheet fed from a sheet feeding section is wound is used in place of the transfer belt stated above. By transferring toner images visualized by developing means onto the recording sheet wound around the transfer drum successively, a full color image is formed on the recording sheet. After this, the recording sheet is separated from the transfer drum and is subjected to fixing of the toner image conducted by a fixing means to be ejected out.
Further, in another color image forming apparatus, there is also proposed a system wherein a plurality of image forming sections are arranged in parallel, toner images each being different from others in terms of color formed respectively on photoreceptor drums in image forming sections are successively transferred onto an intermediate transfer object for forming superposed primary transfer images, and the primary transfer images are transferred onto a recording sheet held on a conveyance belt.
A color image forming apparatus of a tandem type of this kind having a plurality of photoreceptors wherein a color image is formed through one turn of each of plural photoreceptors can output full color images at higher speed, compared with a color forming apparatus of a multi-rotation type wherein a color image is formed through plural turns of a single photoreceptor.
A plurality of photoreceptors and intermediate transfer objects need to be removed from an apparatus main body because of their maintenance and life-times. Therefore, the structure which makes it easy to remove a plurality of photoreceptors and intermediate transfer objects has been required by the color image forming apparatus of a tandem type.
Since a plurality of photoreceptors, intermediate transfer objects in particular, rotating means to rotate the intermediate transfer objects, and intermediate transfer units including primary transfer means have considerable mass, it has been difficult for a user to draw out plural photoreceptors from positions where the photoreceptors have been mounted in the apparatus main body, and to take out directly intermediate transfer units from positions where the intermediate transfer units have been mounted in the apparatus main body, because it has been difficult to apply the physical power. In particular, it is not easy to pull out the heavy unit horizontally toward the front side of the apparatus main body. Furthermore, a unit such as a photoreceptor and an intermediate transfer object is weak against an impact, and there is a risk that the unit becomes unusable if a part of the unit is touched while it is pulled out. A scratch caused by a shock not only affects images in image forming in a single color but also has possibility that a desired color cannot be reproduced in color image forming, and the scratch turns out to be a fatal defect for a color image forming apparatus.
On the other hand, when each member is provided with its own mechanism to take out each member without interference, a large number of taking-out mechanisms (for example, slide rail mechanisms) are needed. Each taking-out mechanism requires its strength that withstands the weight. This makes an entire apparatus to be large.
The more the mechanism to take out each member individually is increased, the more difficult the positional adjustment between members is. In an image forming apparatus having plural photoreceptors, in particular, it is necessary to conduct superposition of each color in extremely high accuracy. If mutual positional deviation is caused for each maintenance of a unit, it is not possible to reproduce the color desired by a user. Furthermore, an intermediate transfer object is a member on which color toner images each being of a different color are superposed, and relative positions of intermediate transfer objects for plural photoreceptor drums are required to be accurate.
Further, when a color image forming unit of this kind is provided on a copying machine, there are further caused problems. Since a document image reading apparatus is arranged on the upper portion of the copying machine, there is needed a complicated opening/closing mechanism which opens the document image reading apparatus from the upper portion of the apparatus main body. Each of the document image reading apparatus and the opening/closing mechanism has considerable mass, and how to handle them is a problem. If an impact is applied on the document image reading apparatus in the course of opening/closing operations, there are caused problems of difficulty in maintaining accuracy of optical members, parts damages and injures of an operators. Drawing out from the upper portion of the apparatus main body has the aforesaid problems, although it is easy for a user to apply the physical power.
In the image forming apparatus which forms images on both sides of a sheet, a sheet fed from the a sheet feeding means is subjected to transfer and fixing of toner images formed on an image carrier on the first surface of the sheet, and then is branched from the sheet ejection path to be conveyed to a reversing means provided on the lower or upper portion. The sheet thus conveyed is reversed up side down, and then, is made to join a sheet conveyance path again from a sheet feeding section. The sheet which has joined the sheet conveyance path is conveyed to the image carrier again so that a toner image may be transferred onto the second surface of the sheet.
As a method to form images on a sheet from inputted multi-color images, TOKKAIHEI No. 9-006083 discloses an image forming apparatus wherein a plurality of developing units are arranged in parallel on one side of an image carrier representing a belt arranged longitudinally, and a sheet ejection section is provided on the other side, and charging, writing of a latent image and developing are conducted in succession within one turn of one image carrier.
In an image forming apparatus for a color image, when an image carrier on which a toner image is formed and a developing unit are arranged in the longitudinal direction, if joining from the reversing means is conducted in the vicinity of the sheet feeding unit positioned at the lower portion, the image forming apparatus is made to be large in the longitudinal direction, which is a problem.
For example,
FIG. 9
is an illustrative diagram of an image forming apparatus showing image forming flows to both sides of a sheet.
In
FIG. 9
, image forming apparatus
101
is provided with scanner section R, image carrier
110
, scorotron charging unit
111
, image writing means
112
, developing unit
113
, transfer means
115
, fixing means H, sheet feeding section
117
, bypass sheet feeding section
109
, reversing means S and with sheet ejection tray T.
The scanner section R reads an image of a document set through an optical system. The image writing means
112
exposes image carrier
110
to light to form a latent image, based on the image read. The latent image formed on the image carrier
110
is developed by developing unit
113
to turn into toner.
O
Fukuchi Masakazu
Kawamoto Motozi
Kimura Kazuyoshi
Minoshima Kosuke
Okui Susumu
Frishauf Holtz Goodman & Chick P.C.
Pendegrass Joan
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