Electrophotography – Document handling – Copy
Reexamination Certificate
2000-07-28
2002-02-05
Brase, Sandra (Department: 2852)
Electrophotography
Document handling
Copy
C399S021000
Reexamination Certificate
active
06345170
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus including a temporary paper storage positioned on a transport path, which extends to an image forming section, and conveying a paper sheet into the paper storage with the leading edge of the paper sheet at the head and then switching it back toward the image forming section with the trailing edge at the head. The image forming apparatus may be implemented as a printer, a copier, a facsimile apparatus, or a combination thereof.
It is a common practice with an electrophotographic image forming apparatus to sequentially feed paper sheets from a paper stack to an electrophotographic image forming section along a preselected transport path. The conventional apparatus uses a registration roller pair for matching the paper sheet and the position of an image at a position just short of the image forming section. This, however, brings about a problem when a plurality of paper sheets are continuously fed to the image forming section. Specifically, the paper sheets must be fed at the intervals of 10 mm or so due to irregularity in the position of the leading edge of the paper sheet separated from the other paper sheets, variation in paper conveying speed ascribable to aging and environment, and a period of time necessary for registration to be effected.
In light of the above, Japanese Patent Laid-Open Publication No. 5-289453, for example, teaches an image forming apparatus constructed to accelerate a paper sheet being conveyed along a transport path only for a preselected period of time. The acceleration reduces the interval between successive paper sheets without increasing the speed of an electrophotographic process and thereby enhances productivity as to image formation, However, when the length of the transport path to an accelerating position is great, all the paper sheets existing on the transport path must be accelerated to the same speed. As a result, the apparatus needs large-scale speed variation control and a sophisticated construction while aggravating noise.
Japanese Patent Laid-Open Publication Nos. 8-259045, 8-20106 and 5-97305 each disclose an image forming apparatus of the type forming an image on one side of a paper sheet, then guiding the paper sheet to a switchback path, and then switching back the paper sheet toward an image forming section in order to form an image on the other side of the paper sheet. None of these documents, however, teaches an arrangement in which paper sheets stacked on a cassette, tray or similar stacking section are directly fed to an image forming section by being switched back.
Particularly the apparatus taught in the above Laid-Open Publication No. 8-259045 cannot reduce the interval between successive paper sheets to a noticeable degree because three rollers are sequentially arranged to drive a paper sheet into and out of a paper reversing device such that the conveying speed is identical around the paper reversing device. Further, the position for effecting registration is remote from image forming means and is apt to cause the position of an image to be noticeably shifted due to conveyance errors. The apparatuses taught in Laid-Open Publication Nos. 8-20106 and 5-97305 also use three rollers and cannot reduce the interval between successive paper sheets.
When a paper jam occurs on the transport path of an image forming apparatus, It has been customary to interrupt paper conveyance in the apparatus in order to prevent the paper jam from being aggravated. Assume that a paper cassette loaded with paper sheets allows paper sheets to be replenished with a front-loading configuration, and that a paper sheet extends over both of the cassette and the transport path at the time of a paper jam Then, when the cassette is inadvertently pulled out of the apparatus, the above paper sheet tears and damages the apparatus or brings about another paper jam later.
Technologies relating to the present invention are also disclosed in Japanese Patent Laid-Open Publication Nos. 1-321231, 4-116570, 6-236086, 7-120984, 7-129057, and 7-261608.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an image forming apparatus capable of reducing the interval between successive paper sheets to be fed to an image forming section and thereby enhancing productivity as to image formation.
It is another object of the present invention to provide an image forming apparatus capable of correcting irregularity in the above interval at the time of switchback by controlling a paper conveying speed, thereby further reducing the interval.
It is another object of the present invention to provide an image forming apparatus capable of continuously driving a roller pair, which is a substitute for a conventional registration roller pair, to thereby maintain the interval accurate without resorting to a registering operation.
It is another object of the present invention to provide an image forming apparatus capable of reducing the wear of an image forming section ascribable to a long interval between successive sheets. thereby enhancing productivity.
It is another object of the present invention to provide an image forming apparatus capable of conveying paper sheets in a stable manner.
It is another object of the present invention to provide an image forming apparatus capable of switching a paper conveying speed in a stable manner.
It is another object of the present invention to provide an image forming apparatus capable of obviating the deterioration of paper conveyance ascribable to, e.g., slip occurring when a paper sheet is brought to a stop.
It is still another object of the present invention to provide an image forming apparatus capable of preventing, when a paper sheet jams a transport path, the paper sheet from tearing and damaging the apparatus or bringing about another jam.
It is yet another object of the present invention to provide an image forming apparatus allowing the operator of the apparatus to easily deal with a jam.
It is further object of the present invention to provide an image forming apparatus capable of reducing production cost.
In accordance with the present invention, an image forming apparatus includes a printer engine for forming an image on a paper sheet, a paper cassette loaded with a stack of paper sheets, and a paper feeder for feeding one of the paper sheets toward the printer engine at a time while separating it from the other paper sheets. A temporary paper storage is positioned on a paper transport path for temporarily storing the paper sheet fed from the paper cassette. A paper reversing device positions the paper sheet fed from the paper cassette in the paper storage with its leading edge at the head and then switches back the paper sheet toward the printer engine with its trailing edge at the head. The paper feeder feeds the paper sheet at a particular speed on each of part of the transport path extending between the paper cassette and the paper storage and part of the transport path extending between the paper storage and the printer engine.
In accordance with the present invention, an image forming apparatus includes a printer engine for forming an image on a paper sheet, a paper cassette loaded with a stack of paper sheets, and a paper feeder for feeding one of the paper sheets toward the printer engine at a time while separating it from the other paper sheets. A temporary paper storage is positioned on a paper transport path for temporarily storing the paper sheet fed from the paper cassette. A paper reversing device positions the paper sheet fed from the paper cassette in the paper storage with its leading edge at the head and then switches back the paper sheet toward the printer engine with its trailing edge at the head. The paper feeder feeds the paper sheet from the paper storage toward the printer engine at a speed higher than a paper conveying speed for image formation assigned to the printer engine.
In accordance with the present invention, a printer includes an image forming apparatus, an input terminal for recei
Muranaka Masakazu
Nakazato Yasushi
Seto Takashi
Brase Sandra
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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