Electrophotography – Document handling – Copy
Reexamination Certificate
1999-10-22
2001-10-30
Beatty, Robert (Department: 2852)
Electrophotography
Document handling
Copy
C399S016000
Reexamination Certificate
active
06311039
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus such as an electrophotographic type analog copying machine, a digital copying machine, a color copying machine, a printer or a page printer.
2. Related Background Art
The speedup of the image forming speed in an electrophotographic type image forming apparatus has heretofore been carried out by effecting, in addition to the supply and conveyance of a transfer material, all of a series of operations such as image forming processes, i.e., latent image formation, development, the transfer of a toner image to the transfer material (e.g. a transfer sheet or the like) and further, fixing, at a high speed. For example, to realize an apparatus capable of forming 60 sheets of images per minute, relative to an apparatus capable of forming 30 sheets of images per minute, there has been adopted a construction in which in addition to the supply and conveyance of the transfer material, image forming processes are carried out with a driving speed necessary therefor set to double.
In the above-described example of the prior art, however, in order to realize high-speed image formation, with the speedup of the sheet supply speed of transfer material supplying means for successively drawing out transfer materials supported on transfer material supporting means (e.g. a sheet supply cassette or the like), it has been necessary to provide inter-sheet taking into account a reduction in the accuracy of the interval between transfer materials during the continuous supply of the transfer materials, i.e., the inter-sheet interval (hereinafter referred to as the inter-sheet). Also, in addition to the conveyance of the transfer materials, it has been required to speedup the image forming processes and a large-scaled investigation has been required.
Thus, for example, in the latent image formation in the image forming processes, in a digital image forming apparatus, it is necessary to operate the image processing and latent image forming means thereof such as a laser at a high speed, and for example, when development is to be made from an apparatus capable of forming 30 sheets of images per minute to an apparatus capable of forming 60 sheets of images per minute, an image processing portion or the like of which the image clock frequency is doubled has been required. Also, in an analog image forming apparatus, it has been necessary to double the driving speed of an original scanner for scanning (reading-scanning) an original to be copied.
Further, in both of the digital and analog image forming apparatuses, the image forming processes such as the development and transfer of a toner image are the most important techniques, as it were, in an electrophotographic type image forming apparatus, and a long investigation time has been required before the construction and control technique thereof are determined, and there has been a problem to be solved that considerable resources are required for the development of an image forming apparatus resulting from high-speed image formation.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus in which the accuracy of sheet conveyance is improved and which is capable of effecting small inter-sheet control and high in reliability to thereby easily realize the speedup of the image forming speed without changing the speed of the image forming processes.
It is a further object to provide a sheet conveying apparatus which, when the interval between sheets has become shorter, can make the interval into a normal interval, and an image forming apparatus which is provided with the same and which makes the interval between sheets sent to an image forming part substantially constant and which is high in image forming efficiency as well as in productivity.
The image forming apparatus of the present invention is characterized by sheet feeding means for successively feeding sheets supported on sheet supporting means, first registration correcting means for taking the registration of the sheets fed from the sheet supporting means, second registration correcting means for taking the registration of the sheets between the first registration correcting means and an image recording position, sheet interval detecting means for detecting the interval between the sheets provided between the first registration correcting means and the second registration correcting means, judging means for judging whether the interval between the sheets detected by the sheet interval detecting means is a predetermined interval, and control means for controlling the sheet feeding means and the first registration correcting means independently of each other in conformity with the result of the judgement of the judging means.
Preferably, the sheet interval detecting means has a judgement sensor provided between the first registration correcting means and the second registration correcting means for detecting the sheets, and a judgement timer starting time counting in conformity with the detection by the judgement sensor, and the judgement reference of the judging means is a plurality of predetermined values compared with the counted value of the judgement timer.
Also, preferably, the judging means judges delay for a sheet of arrival timing exceeding a first judgement reference, judges delayed jam for a sheet of arrival timing exceeding a second judgement reference, judges early arrival for a sheet of arrival timing not exceeding a third judgement reference, and judges early arrival jam for a sheet of arrival timing not exceeding a fourth judgement reference, and in conformity with the results of the respective judgements, the control means controls the sheet feeding means and the first registration correcting means independently of each other.
The sheet conveying apparatus of the present invention is provided with sheet feeding means for feeding sheets from sheet supporting means on which the sheets are supported, first sheet conveying means, second sheet conveying means and third sheet conveying means successively disposed downstream of the sheet supporting means with respect to the feeding direction of the sheets for conveying the sheets, sheet interval judging means for detecting the passage of the sheets between the second sheet conveying means and the third sheet conveying means, and judging whether the interval between the sheets is a predetermined interval, and control means for controlling at least the first sheet conveying means and the second sheet conveying means of the sheet feeding means, the first sheet conveying means and the second sheet conveying means so that the sheets can be conveyed at a predetermined interval on the basis of the judgement of the sheet interval judging means.
The above-described sheet conveying apparatus of the present invention is adapted to feed sheets from the sheet supporting means by the sheet feeding means, and convey the sheets by the first, second and third sheet conveying means.
At this time, the sheet interval judging means detects the interval between the sheets, and judges whether the interval is a predetermined interval, and on the basis of this judgement, the control means controls at least the first and second sheet conveying means so that the sheets can be conveyed at the predetermined interval when the interval between the sheets is shortened.
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Funamizu Yoshihiro
Hirooka Kazuhiko
Kataoka Tatsuhito
Takahashi Katsumi
Beatty Robert
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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