Electrophotography – Image formation – Transfer
Reexamination Certificate
2003-03-19
2004-07-20
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Transfer
C399S066000
Reexamination Certificate
active
06766137
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a color image formation apparatus, a tandem color image formation apparatus and an image formation apparatus, which use multiple latent image substrates. For example, the invention relates to image formation apparatuses such as copiers, printers, facsimile machines, and the like.
BACKGROUND OF THE INVENTION
Conventionally, a color image formation apparatus, wherein toner images formed on multiple photosensitive bodies are sequentially transferred onto a single sheet of transfer paper such that the images are superimposed to obtain a color image, is known as disclosed for example in Japanese Patent No. 2677566.
In the conventional color image formation apparatus, a so-called tandem image formation unit, wherein image formation sections, each comprising a photosensitive body for a color, are arranged in conveyance direction of the transfer paper, and a transfer unit comprising a transfer belt, are both placed horizontally. Further, a paper-feed tray is placed on a side of the image formation unit and the transfer unit.
According to such a conventional color image formation apparatus, color toner images formed on multiple photosensitive bodies are superimposed on the transfer paper to obtain the color image.
In the above conventional tandem color image formation apparatus, since the image formation unit is placed horizontally and the paper-feed tray is placed on the side of the image formation unit, lateral breadth of the apparatus becomes wide and it has been desired to reduce more space required for installation of the apparatus.
There is, for example, an image formation apparatus disclosed in Japanese Laid Open Patent No. 11-95520, which is downsized by reducing the breadth of the apparatus. In the apparatus, multiple laser scanning units are stacked partially overlapping each other, and multiple image formation devices plus a transfer unit arranged opposite to the devices are placed diagonally. This structure enables reduction in breadth of the image formation section and breadth of the whole apparatus.
Recently, needs for image formation on both sides of paper have increased, and more apparatuses are equipped with a mechanism for reversing the sides of the paper. The apparatus disclosed in Japanese Laid Open Patent No. 11-95520 is also provided with a switchback conveyance path for reversing the paper, and re-feeds the paper to the image formation section after leading the paper passed through a fixing device to this switchback conveyance path and reversing the sides of the paper.
There are also image formation apparatuses such as copiers, printers, facsimile machines, and the like, wherein: a recording material is held on a belt that is rotary-driven; and a transfer conveyance belt device for transferring the developed image, formed on an image substrate, onto the recording material while conveying the recording material in accordance with rotation of the image substrate. Generally, these apparatuses have a structure wherein the recording material is fed to the image substrate and a transfer section that is in the transfer conveyance belt device, with a timing adjusted with a resistant unit such as resistant rollers or the like.
An image formation apparatus is also disclosed, wherein a transfer conveyance belt device is placed diagonally (in such a way that heights of an inlet and an outlet for a recording material are different) and a paper conveyance path is shortened, to reduce time needed for printing.
In this image formation apparatus, there are several ways of paper-ejection such as a paper-ejection tray provided on top face of the apparatus or on a side of the apparatus. For printers, for example, paper-ejection trays are provided on top of the apparatus to enable page collation.
On the other hand, many copiers eject paper to a side of the copier main body since they are equipped with a scanner, and/or an ADF (automatic document feeder) on top of the copier. When a duplex mechanism is provided in printers or copiers, the fixed paper is conveyed downward in some cases. As explained above, ways of conveying the fixed paper vary with the structure of the image formation apparatus.
In the conventional tandem color image formation apparatuses, although it is attempted to reduce volume of the apparatus by placing the image formation unit diagonally, the breadth is still large as the paper-feed tray is placed on the side, and further reduction in space required for the installation has been demanded.
In the apparatus disclosed in Japanese Patent Application Laid Open No. 11-95520, since the switchback conveyance path has a structure wherein the paper is conveyed in two horizontal directions to reverse the sides of the paper, breadth of the paper reversal section is wide. In other words, in the apparatus, a section that practically reverses the paper is the switchback conveyance path, and the paper is reversed in the section that is less than half the breadth of the whole apparatus. Therefore, if faces, of a large paper such as an A3 paper in a lengthwise direction, are to be reversed, the breadth of the apparatus must be wide. If the breadth of the apparatus is reduced too much, reversal of large paper becomes impossible.
In such conventional image formation apparatuses downsized by reducing the breadth of the apparatus, the reduction in the breadth of the image formation section is not turned to advantage, as the breadth of the paper reversal mechanism section has to be widened, even if the image formation device and the transfer unit are placed diagonally to reduce the breadth of the image formation section.
In the conventional image formation apparatuses having a structure wherein the transfer conveyance belt device is placed diagonally, when the fixing device is placed diagonally in accordance with the paper conveyance direction directed by the transfer conveyance belt device, the paper ejection direction of the fixing device becomes diagonal, and creates a problem that it can be both advantageous and disadvantageous in terms of compatibility of the apparatus to the above-described different directions of paper conveyance.
For example, when the paper is to be conveyed to the paper-ejection tray on top of the apparatus, ejection of the paper diagonally upward from the fixing device that is placed diagonally is preferable, in terms of paper conveyance. However, if the paper is to be fed to the duplex mechanism that is placed below the fixing device, the conveyance direction of the paper ejected diagonally upward from the fixing device that is placed diagonally has to be altered greatly, and this will increase length of the conveyance path and thus the space required for the apparatus.
Thus, even when the transfer conveyance belt device is to be placed diagonally, the apparatus may be made to correspond to various conveyance directions by providing the fixing device horizontally. For example, in an apparatus disclosed in Japanese Laid Open Patent No. 8-87151, although the transfer conveyance belt device is placed diagonally (in an embodiment of the apparatus, diagonally from the top to the bottom), the fixing device is placed horizontally. However, in the embodiment, the conveyance direction of the paper fed out from the transfer conveyance belt device is to be changed with a guide plate at an entrance of the fixing device. According to such a structure, the paper is bent as the paper, holding a toner image to be fixed, is slidingly scraped on the guide plate when the conveyance direction of the paper is altered. As a result, the unfixed toner image on the paper may be damaged.
According to the structure wherein the recording material is fed out to the image substrate and the transfer section of the transfer conveyance belt device with the timing adjusted by the above-described conventional resistant unit such as resistant rollers, the conveyance of the recording material may be affected during a process of delivering the recording material to the transfer conveyance belt device from the resistant rollers. For exampl
Nakahara Tomotoshi
Sato Masumi
Shijo Hiroyasu
Yasui Motokazu
Chen Sophia S.
Ricoh & Company, Ltd.
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