Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2000-03-08
2002-03-26
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
Reexamination Certificate
active
06361038
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a sheet feeding apparatus adapted to send out sheets stacked in a sheet feeding tray, a sheet feeding method, and an image forming apparatus, such as a printer, a copier and a facsimile transfer unit which use the same method.
2. Description of the Related Art
In an image forming apparatus, such as a printer, a copier and a facsimile transfer unit, a sheet feeding apparatus is generally provided so as to output an image formed in an image forming section thereof using an electrophotographic system. In this sheet feeding apparatus, sheets (paper), materials on which information is to be recorded including paper and OHP sheets are stacked in a sheet feeding tray or a sheet feeding cassette, from which the sheets are fed one by one, and sent to the image forming section.
In recent years, the image processing techniques used in this image forming section have progressed, and the formation of a large quantity of images can be carried out practically in a short period of time. In the meantime, it has become necessary to stack sheets in large quantities in a paper feeding tray or a paper feeding cassette, and the increasing of a sheet loading capacity of a paper feeding tray and a paper feeding cassette has been increasingly demanded.
In such an image forming apparatus, a sheet feeding method including lifting sheets after they have been stacked in a paper feeding tray of an increased load capacity by a user (operator), to a position of a predetermined height, and feeding in the same position the sheets one by one from the upper side of the stacked sheets is generally used. To lift the sheets, an elevator tray system in which a sheet-loaded bottom plate is moved up as the bottom plate is kept horizontal, or a lever system in which one end portion of a bottom plate is raised around the other end portion thereof is employed. In these systems, it becomes necessary to set a position (height) of an upper side of stacked sheets to the height of a lower surface of a nudger roll which contacts the upper side of the sheets, and maintain a pressure of the nudger roll against the sheets at a substantially constant level. Namely, in these sheet feeding apparatuses, it becomes necessary that a mechanism for detecting the height of the upper side of the sheets be provided besides a mechanism for detecting the presence or absence of a sheet the provision of which constitutes a prerequisite for the sheet feeding apparatuses.
The sheet feeding apparatuses of the related art include sheet feeding apparatuses disclosed in, for example, Japanese Patent Laid-Open Nos. 213483/1993, 221553/1993 and 172624 and Japanese Utility Model Publication No. 30753/1994. Japanese Patent No. 213483/1993 mentioned above, in which a bottom plate is not lifted, discloses the techniques for detecting a residual quantity of sheets by turning a pickup roll in accordance with the lowering of a sheet takeoff position, and displaying the shortage of the sheets before the sheets have run out. Japanese Patent Laid-Open No. 221553/1993 discloses the techniques for detecting the presence or absence of sheets on the basis of the condition of displacement, which occurs when a pivotable cassette is once lifted by a lifting member, of a takeoff unit provided at an upper portion of the cassette. Japanese Utility Model Publication No. 30753/1994 discloses the techniques for using a single mechanism for detecting both the height of a sheet in the uppermost position of stacked sheets and the run-out of the sheets, and thereby simplifying the structure of the detecting mechanism. Japanese Patent Laid-Open No. 172624/1995 discloses the techniques for detecting the absence of sheets and the height of lifted sheets with reference to the position of a lever type arm provided at an upper portion of a paper feeding tray.
However, according to the techniques disclosed in Japanese Patent Laid-Open No. 213483/1993, it is possible to detect a residual quantity of sheets during the transfer of the sheets but difficult to apply the techniques to the detection of a residual quantity of sheets in a bottom plate lifting type sheet feeding apparatus, and, furthermore, impossible to detect the presence or absence of sheets during an initial operation carried out prior to the lifting of a bottom plate.
According to the techniques disclosed in Japanese Patent Laid-Open No. 221553/1993, the presence or absence of sheets can be detected by a bottom plate lifting mechanism during an initial operation and in the midst of the transfer of the sheets but this detecting operation cannot be carried out until a pivotably provided cassette has been lifted by a lifting member, so that it takes much time before the detection of the absence of the sheets is started. Especially, in the case of a sheet feeding apparatus loaded with a large quantity of sheets, it takes an extremely long period of time until an initial detection of the absence of sheets is carried out, and such a long period of wasteful time poses a problem which can constitute a defect of the commodity specifications.
The techniques disclosed in Japanese Utility Model Publication No. 30753/1994 enable a sheet detecting mechanism to be simplified, and are adapted to execute the detection of the height of sheets and the run-out thereof by a single sensor. Therefore, even in a so-called initial operation, in which, for example, a sheet which has got into a jam is removed with a cover then closed, it is necessary to lower a bottom plate by a predetermined height after it has once been lifted, so that the time carrying out the detection of the presence or absence of the sheets during an initial sheet feeding operation further increases. When a tray of a certain construction is used, it moves wildly while it is lifted during an initial operation, to cause the possibility of breakage of the apparatus to arise.
The techniques disclosed in Japanese Patent Laid-Open No. 172624/1995 are very advantageous in view of their capability of detecting the absence of sheets and the height thereof in a lifted state by a simple structure. However, according to these techniques, the absence of the sheets cannot be detected until a bottom plate has once been lifted. Therefore, just as in the techniques disclosed in each of the above-mentioned publications, a delay in the detection of the absence of sheets during an initial operation in, especially, a large capacity sheet feeding tray poses a problem, and, when a position in which the sheets are set is improper, there is the possibility that a sheet feeding mechanism be destroyed due to the lifting of the sheets.
SUMMARY OF THE INVENTION
The present invention has been made so as to solve these technical problems, and provides a sheet feeding apparatus and a sheet feeding method which are capable of detecting the presence or absence of sheets during a so-called initial operation in which a bottom plate has not yet moved up, and which enable a wild movement of a sheet feeding tray during, for example, an upward movement of the bottom plate to be prevented; and an image forming apparatus using the same apparatus and method.
As shown in
FIG. 1
, the sheet feeding apparatus according to the present invention is characterized by including a tray
1
loaded with sheets P, a sheet nudging member
2
adapted to send out a sheet P from an upper side of the sheets P stacked in the sheet loading tray
1
, a first sensor
3
adapted to detect the sheet from an upper side of the sheets P stacked in the sheet loading tray
1
, a second sensor
4
adapted to detect the sheets P from a lower side of the same P stacked in the sheet loading tray
1
, and a control unit
5
adapted to detect the presence or absence of the sheets P on the basis of an output from the second sensor
4
during an initial operation, and the presence or absence of the sheet P on the basis of an output from the first sensor
3
during and after a sheet feeding operation.
A structural part on which the second sensor
4
is provided is not limited
Imada Daisuke
Komatsu Yasutaka
Tada Michio
Bower Kenneth W
Ellis Christopher P.
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
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