Electrophotography – Document handling – Copy
Reexamination Certificate
2001-10-25
2004-01-20
Braun, Fred L. (Department: 2852)
Electrophotography
Document handling
Copy
C271S186000, C271S274000, C271S902000
Reexamination Certificate
active
06681096
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image formation apparatus, and printer, copying machine, and a facsimile device using the image formation apparatus.
BACKGROUND OF THE INVENTION
A sheet feeding structure of a conventional image forming device is generally formed with a sheet separation/feeding unit that separates and feeds sheets stacked and stored in a sheet storage section one by one, a sheet conveying path that conveys the separated and fed sheet toward an image forming section, and regist rollers disposed at a position immediately before the image forming section on the sheet conveying path.
The sheet separated and fed by the sheet separation/feeding unit is conveyed along the sheet conveying path, is stopped temporarily at the position where the sheet comes into contact with the regist rollers, and fed into the image forming section at a timing at which an image is formed on an appropriate position of the sheet.
If a sheet is fed out by the regist rollers and the rear edge of this sheet and the front edge of a subsequent sheet overlap each other, these two sheets are fed into the image forming section in their overlapping state. Accordingly, one image is disadvantageously formed over the two sheets, therefore, image formation cannot be successfully performed on the sheet. Further, when the overlapping two sheets are fed into the image forming section, a sensor for detecting a sheet size detects that the sheet size is irregular, and the image forming operation is interrupted.
Therefore, when image formation is continuously performed, it has been required to widen each space between fore-and-aft sheets, and to separate and feed the sheets so that the two sheets are prevented from overlapping each other even if the subsequent sheet is fed when the preceding sheet stops at the regist rollers.
Further, in the sheet feeding structure of the conventional image forming device, a space between fore-and-aft sheets is widened by tens of millimeters and the sheets are fed when image formation is continuously performed considering that a slip may occur at the time of sheet separation and feeding by the sheet separation/feeding unit, a sheet conveying speed may be changed over time or depending on environment, or there may be variations in suspended time for registration. Therefore, it is difficult to improve productivity of image formation.
An image forming section based on an electrophotographic system cannot stop the operation because of its structure even when the sheet is not conveyed to the image forming section, and the section performs no-load operation. Therefore, a large space between continuously fed sheets makes longer the time for no-load operation, thus the life of the device is decreased so that the printing number of sheets becomes less than a possible printing number of sheets that the device originally has.
For the above-mentioned reasons, the applicants of this application have proposed an image formation apparatus with a reversing path and a sheet reversing unit provided in some midpoint of a sheet conveying path in Japanese patent application No. 11-239672 and Japanese patent application No. 2000-230153, or the like. More specifically, this image formation apparatus is capable of improving operating efficiency in image formation by narrowing a space between sheets fed into an image forming section when the image formation is continuously performed.
In accordance with the image formation apparatus provided with these reversing path and sheet reversing unit, a sheet separated and fed from a sheet storage section and conveyed along the sheet conveying path is fed into the reversing path, and the sheet is stopped temporarily on the reversing path and then switched back to be fed into the image forming section. Further, a subsequent sheet is fed into the reversing path while the sheet fed into the reversing path is switched back and is forwarded toward the image forming section. The subsequent sheet is started to be fed out from the reversing path toward the image forming section at a timing at which the preceding sheet to be forwarded to the image forming section reaches a predetermined position. Accordingly, the space between the sheets continuously fed into the image forming section can be narrowed, which makes it possible to improve the operating efficiency in image formation. Furthermore, in the image forming section, since the time for no-load operation without image formation is reduced, reduction in the life of the device due to no-load operation can be prevented.
However, according to the image formation apparatus with the reversing path and the sheet reversing unit disposed on some midpoint of the sheet conveying path, it is necessary to reliably switch a sheet conveying direction from the sheet conveying path to the reversing path, and from the reversing path to the sheet conveying path leading to the image forming section. Unsuccessful performance of this switching causes a jam to occur.
With regard to a structure of the sheet reversing unit that feeds a subsequent sheet into the reversing path while a preceding sheet is fed out from the reversing path, there have been requests for a structure that does not produce noise, a simple structure, or a structure such that sheets are fed out reliably.
When the space between fore-and-aft sheets is to be narrowed by switching back the sheet to be forwarded to the image forming section on the reversing path, it is required to set sheet conveying force by conveying rollers to be high in order not to decrease a sheet conveying speed to a value lower than a set value due to conveying load that acts on the sheet during its conveyance. However, by setting the sheet conveying force to be high, there may be such inconvenience that noise may easily be produced or power consumption may easily be increased. Further, by setting the sheet conveying force to be high, there may occur a problem that the front edge of a sheet that is rigid is forcefully pushed into a nip part of the regist rollers when they are stopped rotating and a position for image formation on the sheet is displaced.
SUMMARY OF THE INVENTION
It is an object of this invention to reliably perform switching between conveying directions of each sheet coming into or going away from a reversing path by reducing a space between sheets continuously fed into an image forming section using a reversing path and a sheet reversing unit.
Another object of this invention is to make compact a structure to switch between conveying directions of each sheet coming into or going away from the reversing path by reducing a space between conveyed sheets using the reversing path and the sheet reversing unit.
A further object of this invention is to simplify a structure to switch between conveying directions of each sheet coming into or going away from the reversing path by reducing a space between conveyed sheets using the reversing path and the sheet reversing unit.
A still further object of this invention is to reduce noise due to feeding out of a sheet from the reversing path by reducing a space between sheets continuously fed into the image forming section using the reversing path and the sheet reversing unit.
A still further object of this invention is to allow sheets to smoothly come into and go away from the reversing path by reducing a space between the sheets continuously fed into the image forming section using the reversing path and the sheet reversing unit.
A still further object of this invention is to simplify a structure of the sheet reversing unit by reducing a space between sheets continuously fed into the image forming section using the reversing path and the sheet reversing unit.
A still further object of this invention is to reliably feed out a sheet from the reversing path by reducing a space between sheets continuously fed into the image forming section using the reversing path and the sheet reversing unit.
A still further object of this invention is to prevent occurrence of noise due to sheet conveyance by reducing sheet conveying force
Muranaka Masakazu
Nakazato Yasushi
Seto Takashi
Braun Fred L.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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