Electrophotography – Document handling – Copy
Reexamination Certificate
2003-01-02
2004-05-25
Grimley, Arthur T. (Department: 2852)
Electrophotography
Document handling
Copy
Reexamination Certificate
active
06741831
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Japanese application serial no.2002-000878, filed on Jan. 7, 2002; 2002-326379, filed on Nov. 11, 2002.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to an image forming device for forming images on a sheet, and a feed device.
2. Description of Related Art
In the application of image forming devices, such as a printer or a copier, improving the productivity of sequential image forming operations has been in demand. One method to meet the demand is to reduce the distance between respective sheets, which are transferred through an image forming section.
However, merely reducing the distance between sheets as they are separately fed from a sheet housing section, such as a sheet tray, is prone to pose a problem that a preceding sheet and a following sheet overlap each other in the image forming section. The problem occurs when a sheet slips upon its separate feeding, a sheet transfer speed changes as time passes or operational environment changes, or a stop time for registering is uneven.
To avoid such a problem, it has been practiced that at least the distance of several ten mm is provided between preceding and following sheets when images are formed sequentially on the sheets. As a result, however, a time span in which actually no image is formed becomes longer in the sequential image forming, deteriorating the productivity of image forming operation.
An image forming section employing an electrophotograhic method is constituted so as to operate without stopping even when the image forming section actually forming no image once it starts forming images. Therefore, a long distance between sequentially fed sheets results in a longer idling of the image forming section, reducing the life of the image forming section to produce less printed materials than the amount expected to be produced in the original lifetime.
It will be appreciated that the electrophotographic image forming section having a digital write-in means includes a polygon mirror constituting part of the write-in means, wherein the rotating speed of the polygon mirror is limited. It may be tried to increase the transfer speed of sheets in the image forming section, and addition to that, it is essential to correspondingly increase the rotating speed of the polygon mirror in order to improve the productivity of image forming operation. However, since the polygon mirror has a limit of its rotating speed, the above effort is limited.
Under these circumstances, the applicant of the present application disclosed in the Japanese Laid Open Publication No. He2001-130812 an image forming device, which can improve the productivity of image forming operation in the case of sequential image forming. In the image forming device, an inverting passage and a sheet inverting means are provided in the middle of a sheet transfer passage to make a sheet switch back, reducing the distance between the sheets sent to an image forming section.
According to the above image forming device having the inverting passage and the sheet inverting means, a sheet is transferred through the sheet transfer passage to be sent to the inverting passage, where the sheet is temporarily stopped and made to switch back, and is sent to the image forming section. Upon switching back, the speed of sending the sheet to the inverting passage, the speed of sending the sheet out of the inverting passage, and the timing of sending the sheet out of the inverting passage are controlled. As a result, the distance between the sheets, which are sent to the image forming section after having switched back, can be reduced, which improves the productivity of image forming operation.
In the operation of the image forming device described above, however, as a sheet is sent to the inverting passage at a high speed, the sheet may come to skew. Such a skewed sheet sent out of the inverting passage skews in the image forming section, rendering the corner of the sheet folded, thus causing a problem of what is called folded edge.
To handle such a problem, efforts have been made to correct the skew of a sheet just before it is sent out from the inverting passage. That is, it has been carried out a sidewise registration operation to set the sheet in a proper arrangement in the direction (horizontal direction) perpendicular to the sheet transfer direction so as to correct the skew of the sheet sent to the inverting passage.
According to conventional sidewise registration operations for sheet position adjustment, a pair of side fences or joggers are operated in a symmetrical manner so as to keep the center of a sheet in a constant position (what is called a center reference), or a sheet is set along a side guide so as to keep the edge of the sheet passing through the same position (what is called an edge reference). Therefore, when sheets having the same width are transferred, the passing position of the sheet edges are constantly the same, which makes it a common case without almost no exception that the sheet edges are adjusted by a sheet width commonly employed (for example, for adjusting the width of A4 size, or the length of A3 size within—mm) and are passed between rollers.
When the sheet edges keep passing through the same position, however, the contact frequency between the sheet edges and the rubber rollers in a position other than the above same position becomes low, resulting in concentration of the contact between the edges and the rollers on the same position, damaging the part of the rollers corresponding to the position. This causes such an inconvenience as a surface exfoliation of a fixing roller, which leads to an earlier replacement of the roller. It will be also recognized that a temperature increase of the ends of the fixing rollers in the image forming section becomes another problem when the passing position of the sheet edges is constantly the same.
Besides, in conventional image forming devices, when a sheet on which images are formed is “sorted” for every print job, it is common that an image-fixed sheet is sorted over by shifting the position of the sheet in the direction perpendicular to the transfer direction (doggy tail).
In such a case, however, a dedicated large finisher and the like is required, which makes impossible for a single image forming device to execute a sorting operation.
SUMMARY OF THE INVENTION
According to the foregoing description, it is an object of this invention to provide a image forming device and a feed device, with which concentrated contact of sheet edges with transfer means, such as rollers, in a prescribed position can be avoided, and earlier replacement of the rollers, such as fixing rollers in a image forming section, due to their surface exfoliation, can be prevented.
It is another object of this invention to provide an image forming device and a feed device, with which an operation of “sorting” sheets according to the number of printing can be executed with a simple constitution.
According to an aspect of the present invention, in the image forming device of the present invention, sheets piled up and held in a sheet housing section are separately fed one after another by a separate feed means and an image is formed on the sheet transferred by a transfer means in an image forming section, comprises a movable member provided on the sheet transfer passage leading from said separate feed means to said image forming section and regulating the positioning of the edges of the sheet parallel to the transfer direction, the sheet being transferred through said sheet transfer passage; a regulating position change means for randomly changing a regulating position for positioning the sheet by said movable means; and a write-in position change means for changing a write-in start position in said image forming device in conformity to the position of the sheet transferred to said image forming section.
Accordingly, the regulating position for positioning the sheet by the movable member is randomly changed, and the wr
Gleitz Ryan
Grimley Arthur T.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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