Sheet feeding or delivering – Delivering to stack and feeding therefrom
Reexamination Certificate
1999-12-13
2001-07-03
Bollinger, David H. (Department: 3651)
Sheet feeding or delivering
Delivering to stack and feeding therefrom
C271S003130, C271S004010, C271S265010
Reexamination Certificate
active
06254078
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ADF (Automatic Document Feeder) mounted on an image forming apparatus and more particularly to an ADF of the type sending out a document via an image reading position while warping it.
An ADF of the type described is conventional with a copier, facsimile apparatus or similar image forming apparatus. Japanese Patent Laid-Open Publication No. 10-72141, for example, discloses ADF applicable to an image forming apparatus of the type reading a document by receiving a reflection from the document while holding optics in a halt below a slit glass shorter than the document. The ADF taught in this document conveys a document via the slit glass in a so-called sheet-through fashion.
Another conventional ADF is applicable to an image forming apparatus of the type stopping a document on a contact glass having a greater area than the document, and then moving optics to scan the document. Such an ADF sends a document to the contact glass, stops the document at the contact glass, and then sends it out after the document has been read.
In any case, should a document be conveyed in a plane that is the extension of the image reading position, the overall area of the ADF would increase. To make the ADF compact, it has been customary to send in a document to the image reading position while warping and reversing it from above the reading position, send it out from the image reading position while also warping it, and again reversing, if necessary, the document before the document is driven out to a tray.
The prerequisite with the sheet-through type ADF is that it conveys a document being read at a constant speed because the document conveying speed has critical influence on reading accuracy. In practice, however, the leading edge of a document moved away from the glass platen advances along a guide surface, abuts against one of a pair of rollers located downstream of the guide surface, and then enters a nip between the rollers. Generally, each roller has a smooth surface implemented by resin so as not to contaminate a document. This, coupled with resistance ascribable to the curvature of the roller, causes the document to slip on the roller before entering the above nip. The slip effects the document conveying speed and causes the document to temporarily stay at the reading position, causing the resulting image to be elongated.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Publication No. 7-120094 and Japanese Utility Model Publication No. 2,515,306.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a sheet-through type ADF for an image forming apparatus capable of preventing a document from temporarily staying at an image reading position and elongating an image, and insuring reliable conveyance and accurate reading of the document with a miniature configuration.
An ADF of the present invention includes a document send-in device for sending a document to an image reading position, a document send-out device including a pair of rollers for sending out the document being sequentially read at the image reading position, and a document sensor for sensing the arrival of the leading edge of the document at the document send-out device. One of the pair of rollers is movable toward and away from the other roller. The one roller is spaced from the other roller when the document sensor does not sense the leading edge of the document or moved toward the other roller when the document sensor senses the leading edge.
REFERENCES:
patent: 5072923 (1991-12-01), Coy
patent: 5181705 (1993-01-01), Ueda et al.
patent: 5197724 (1993-03-01), Kitajima et al.
patent: 5211386 (1993-05-01), Baba
patent: 7-120094 (1995-12-01), None
patent: 2515306 (1996-08-01), None
Bollinger David H.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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