Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1998-08-04
2001-12-25
Lee, Cheukfan (Department: 2722)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C399S396000, C271S270000
Reexamination Certificate
active
06333797
ABSTRACT:
This application is based on application No. 9-215354 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a document feeder, and a method of document reading and more particularly to a document feeder which picks up stacked documents one by one and feeds each document on an image reading position over a stationary image reading device at a constant speed.
2. Description of Related Art
Recently, various types of document feeders adopting a method in which the image of a document separated from a stack and fed to a reading position is read by a scanner, namely, a document-feeding image reading method have been provided. In such a document feeder, generally, separating/feeding means (rollers) is so structured to rotate following a document which is transported by transport means which is located downstream. Accordingly, when the trailing edge of the document passes the separating/feeding means, the load on the transport means changes, which changes the transport speed, thereby resulting in noise in the read image.
In order to solve this problem, conventionally, either of the following measures have been taken: a document is fed over the reading position once so that the trailing edge of the document certainly passes the separating/feeding means, and thereafter, the document makes a switchback and while being fed on the reading position again, the image is read; and the pressure for separating documents in the separating/feeding means is set low so that a change in load which occurs when the trailing edge of a document passes the separating/feeding means will be small.
However, in the former, because image reading is carried out after a switchback of a document, the copying productivity is low. In the latter, because the separating pressure is low, it is likely that a plurality of documents are fed at a time.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a document feeder and a method of document reading which takes measures to prevent a change in load on a transport system from occurring during image reading without lowering the copying productivity nor degrading the separating efficiency.
In order to attain the object, a document feeder according to the present invention comprises: a stacking section on which a plurality of documents are stacked; separating/feeding means for separating a document from the documents stacked on the stacking section and feeding the documents one by one; reading means for reading an image of the fed document at a specified position; and transporting means for transporting the fed document to a reading position where image reading is carried out by the reading means; and the separating/feeding means feeds a document at a higher speed than the transporting means does.
Because of the speed difference, the document curves between the separating/feeding means and the transporting means. When the trailing edge of the document passes the separating/feeding means, a change in load which occurs at this time is absorbed in the curved portion of the document. This arrangement eliminates the necessity of circulating the document, thereby lowering the copying productivity, and the necessity of degrading the separating efficiency, which have been taken for the purpose of suppressing noise during image reading. Also, this is only speed control and never increases the size of the apparatus.
Another document feeder according to the present invention adopts an arrangement of setting the distance between the separating/feeding means and the reading position longer than the length of a document in the feeding direction instead of or in addition to adopting the speed control. In this structure, after the trailing edge of a document passes the separating/feeding means, the leading edge of the document reaches the reading position, and image reading is started. Therefore, even if the load on the transporting means changes when the trailing edge of the document passes the separating/feeding means, the change in load never influences the image reading. Needless to say, this arrangement does not lower the copying productivity and does not degrade the separating efficiency.
Preferably, only when large documents are to be fed, the distance between the separating/feeding means and the reading position is lengthened. For this purpose, detecting means for detecting the length of documents stacked on the stacking section is provided, and when the documents are judged to be long in the feeding direction, the stacking means and the separating/feeding means are moved backward together, or the route is changed so that each of the documents takes a bypass with a longer length.
Further, another document feeder according to the present invention comprises a document curving area where while the leading edge of a fed document is held at a position immediately before the reading position by the transporting means, the document curves until the trailing edge of the document passes the separating/feeding means. In this structure, after the trailing edge of a document passes the separating/feeding means, image reading is started. Therefore, a change in load which occurs when the trailing edge of a document passes the separating/feeding means never influences image reading. This arrangement does not lower the copying productivity and does not degrade the separating efficiency.
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patent: 5575466 (1996-11-01), Tranquilla
patent: 5666609 (1997-09-01), Aoki
patent: 5687010 (1997-11-01), Van Tilborg
patent: 5692742 (1997-12-01), Tranquilla
patent: 5755435 (1998-05-01), Fujiwara
patent: 5848784 (1998-12-01), Tranquilla
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Johdai Akiyoshi
Katsuta Hiroko
Katsuta Kunihiko
Murakami Tohru
Tanahashi Hirofumi
Burns Doane , Swecker, Mathis LLP
Katsuta Hiroko
Lee Cheukfan
Minolta Co. , Ltd.
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