Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2000-12-27
2003-04-01
Walsh, Donald P. (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C271S010110, C271S121000, C271S125000, C271S262000, C271S263000
Reexamination Certificate
active
06540222
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a sheet material feeding mechanism of an image processing apparatus such as an image forming apparatus, e.g. a copying machine, or an image reading apparatus, e.g. an image scanner, and more particularly to a sheet material feeding mechanism of a hopper type or a tray type, which prevents overlap feeding of the sheet materials.
DESCRIPTION OF THE PRIOR ART
Hitherto, in an image processing apparatuses such as a printer or a facsimile machine, there has been widely adopted a method in which sheets of paper are mounted on a tray built in or detachably attached to a main body and automatically fed therefrom. There have been also known an image processing apparatus provided with a hopper type of paper feeding mechanism instead of a tray type of paper feeding mechanism, and a printer provided with both the tray and the hopper as standard equipment.
A tray is formed into a flat container shape, and then the tray suitable to the paper size is installed on an apparatus. The front edge and the back edge of the sheets accommodated in the tray are loosely restrained by a member such as a clamper. On the contrary, the hopper is usually attached to the external of the apparatus, and have a basic construction in which sheets are simply placed on the hopper equipped with a pair of guides by which the position of the sheets can be adjusted in accordance with the width of the sheets. Such a hopper type paper feeding mechanism is widely used for an image scanner which reads a large volume of documents different in size, paper quality, and thickness.
It is very important for an image processing apparatus to prevent the sheets of paper fed from a tray or a hopper from overlapping each other, namely to prevent overlap feeding. The overlap feeding frequently causes a paper jam, and markedly deteriorates the workability.
Accordingly, there has been generally adopted a paper feeding mechanism comprising a parting roller and a retarding roller disposed immediately downstream from a tray or a hopper equipped with a feeding roller for picking up and feeding the top one of stacked sheets so as to prevent the overlap feeding.
FIG.
11
A and
FIG. 11B
schematically show the essential section of a conventional paper feeding mechanism employing a parting roller and a retarding roller.
Referring to
FIG. 11A
, a feeding roller
52
is disposed on a stack of sheets P mounted on a hopper
51
, and a parting roller
53
and a retarding roller
54
are provided on the downstream side of the feeding roller
52
. The parting roller
53
comes in contact with the top surface of the sheet P fed by the feeding roller
52
, and the retarding roller
54
comes in contact with the bottom surface of the sheet P so that the sheet P is nipped therebetween. When the paper feeding mechanism is operated, the feeding roller
52
and the parting roller
53
are respectively driven to rotate in the same direction, as indicated by the arrows in the drawings. The retarding roller
54
is mounted on a main shaft (not shown) driven to rotate in the direction as indicated by the arrow in the drawings via a torque limiter (not shown), and usually driven to rotate in the direction as indicated by the arrow in the drawing, namely, in the direction to push the sheet P back to the hopper
51
. The retarding roller
54
is elastically urged against the parting roller
53
and can be adjusted by adapting the urging force to the quality or thickness of the sheet P.
In the feeding mechanism, when only one sheet P is fed from the hopper
51
and nipped between the parting roller
53
and the retarding roller
54
, the retarding roller
54
receives the rotational torque of the parting roller
53
, and thereby is driven to rotate in the direction in which the sheet P is fed. On the contrary, when two or more sheets P are fed and nipped, the retarding roller
54
puts back the lower sheet P toward the hopper
51
since the rotation is maintained in the direction as indicated by the arrow in the drawing based on the mutual relationship between the built-in torque limiter and the urging force applied to the parting roller
53
, so that the overlap feeding is prevented.
The hopper
51
is urged toward the feeding roller
52
by a spring (not shown) or the like, and set so that the contact pressure between the peripheral surface of the feeding roller-
52
and the top one of the stacked sheets P is maintained to be substantially constant. When the feeding roller
52
is driven to rotate and the top one P-
1
of sheets is picked up, the sheet P-
1
is nipped between the parting roller
53
and the retarding roller
54
as shown in
FIG. 11A
, and quickly fed.
Recently, an ultrasonic overlap feeding detection mechanism has been disseminated for prevent the overlap feeding of the sheets. As one example of using the ultrasonic wave, there is a mechanism disclosed in JP-A-4-129952, of which the schematic diagrams are presented in FIG.
12
A and FIG.
12
B.
As shown in
FIG. 12A
, the overlap feeding detection mechanism is provided with an ultrasonic transmitter
153
and an ultrasonic receiver
154
disposed across a feeding line of bank notes
151
and
152
, and further provided with a waveform analyzer
155
to which the output signals of the ultrasonic receiver
54
are inputted.
An ultrasonic wave transmitted from the ultrasonic transmitter
153
passes through the bank note
151
and is received by the ultrasonic receiver
154
as an ultrasonic signal. The received ultrasonic signal is then supplied in the form of an output voltage to the waveform analyzer
155
and analyzed as an output signal as shown in FIG.
12
B. The ultrasonic wave from the ultrasonic transmitter
153
attenuates when passing through the bank note
151
, and the attenuated signal is received by the ultrasonic receiver
154
. When a portion of an area A corresponding to one bank note
151
passes, an output voltage within the area A shown in
FIG. 12B
is analyzed, so that the voltage is set as a reference output signal. On the contrary, when a portion of an area B in which the bank note
152
overlaps on the bank note
151
passes, the volume of the attenuation of the ultrasonic wave increases, so that the output signal in the area B shown in
FIG. 12B
is analyzed. Accordingly, the overlap feeding of the bank notes
151
and
152
is detected by detecting the difference between the reference output signal and the attenuated output signal.
That is, in the overlap feeding detection of the sheets using the ultrasonic wave, a receiving intensity level obtained when one sheet passes is beforehand set as a reference level, and if the receiving intensity level of an actually detected signal is lower than the reference value, the overlap feeding is also detected.
Such overlap feeding detection of the sheets using the ultrasonic waves is adopted, in the same manner, in the fields of preventing the overlap feeding of the sheets in a printer, a copying machine and a printing machine, as shown in JP-A-1-115647, for example.
SUMMARY OF THE INVENTION
The sheets of paper mounted on the hopper or the tray are generally used as it is after drawn out from a package, so that the sheets of paper remain highly adhering to each other. In addition, since the sheets of paper are subjected to the urging force of the hopper against the feeding roller, when the sheet P is picked up by the feeding roller
52
, it sometimes happens that three sheets of paper P-
1
, P-
2
and P-
3
for example, or more sheets of paper are simultaneously fed to the nipping portion between the parting roller
53
and the retarding roller
54
due to the mutual contact friction therebetween, as shown in FIG.
11
B.
In such a case, according to the conventional paper feeding mechanism, the parting roller
53
and the retarding roller
54
part the sheets of paper P-
1
, p-
2
and P-
3
to allow only the uppermost sheet of paper P-
1
to pass, thereby the overlap feeding is prevented. However, if the adhesion among the three sheets of paper P-
1
, p-
2
and P-
3
is stron
Araki Takao
Toyomura Yushi
Tsuda Terumi
Matsushita Electric - Industrial Co., Ltd.
Miller Jonathan R
Stevens Davis Miller & Mosher LLP
Walsh Donald P.
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