Information
-
Patent Grant
-
6354584
-
Patent Number
6,354,584
-
Date Filed
Tuesday, October 12, 199924 years ago
-
Date Issued
Tuesday, March 12, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Ellis; Christopher P.
- Bower; Kenneth W
Agents
- Fitzpatrick, Cella, Harper & Scinto
-
CPC
-
US Classifications
Field of Search
US
- 271 1012
- 271 22
- 271 127
- 271 162
-
International Classifications
-
Abstract
A sheet feeding apparatus comprising a movable sheet supporting device for supporting a sheet, a sheet feeding roller urged against the sheet supported by the sheet supporting device and adapted to rotate in a sheet feeding direction to feed the sheet, a separating roller opposed to the sheet feeding roller and adapted to rotate in a direction along which the sheet is restored to separate the sheet fed from the sheet feeding roller, a feeding device disposed at a downstream side of the sheet feeding roller in the sheet feeding direction and adapted to feed the sheet fed from the sheet feeding roller, and a pressing and retracting device for moving the sheet supporting device to bring the sheet supported by the sheet supporting device into presser contact with the sheet feeding roller and release the pressure contact, and wherein the sheet supporting device which places the sheet into pressure contact with the sheet feeding roller is moved by the pressing and retracting device to release the pressure contact between the sheet feeding roller and the sheet before a leading end of the sheet fed from the sheet supporting device reaches the feeding device.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet feeding apparatus used in an image forming apparatus such as a copying machine, a printer and the like or in an image reading apparatus such as a facsimile, a scanner and the like.
2. Related Background Art
In the past, for example, in a sheet feeding portion of a copying machine or the like, a sheet separation using a retard roller rotated in a direction opposite to a sheet feeding direction has mainly been used as sheet conveying means for preventing more than one sheet from being fed simultaneously (referred to as “double-feed” hereinafter).
Now, a conventional sheet feeding apparatus using a retard separation system will be briefly described.
FIG. 17
is a schematic side view of a sheet feeding apparatus of retard separation type comprising a sheet feeding roller (sheet pick-up roller) and a separating roller (refer to Japanese Patent Application Laid-open No. 3-18532, U.S. Pat. No. 5,016,866). This is referred to as a first earlier technology hereinafter.
As shown in
FIG. 17
, sheets S stacked on an intermediate plate
506
in a cassette
507
are lifted together with the intermediate plate
506
by a pressing arm
508
and a sheet pressing spring
505
to be always urged against a sheet feeding roller
501
, thereby providing sheet feeding pressure.
Further, the sheet feeding roller
501
receives retard pressure from a separating roller
502
. In this state, when the sheet feeding roller
501
is rotated in a sheet feeding direction, the sheet S urged against the sheet feeding roller
501
is picked up to reach a nip between the sheet feeding roller
501
and the separating roller
502
. At this time, if a single sheet is pinched by the nip, the separating roller
502
is rotatingly driven in the sheet feeding direction by rotation of the sheet feeding roller
501
due to the presence of a torque limiter
503
formed integrally with a shaft of the separating roller, thereby feeding the sheet S.
However, if a plurality of sheets are pinched by the nip, the separating roller
502
is rotated with predetermined torque in a direction along which the double-fed sheets are returned, with the aid of the torque limiter
503
, thereby preventing the sheet from being double-fed.
FIGS. 18 and 19
are schematic side views of a sheet feeding apparatus using a retard separation system constituted by a planetary gear mechanism (refer to Japanese Patent Publication No. 1-32134). This is referred to as a second earlier technology hereinafter.
As shown in
FIG. 18
, the sheet feeding apparatus utilizes a planetary gear mechanism comprising a sun gear
601
, an intermediate gear
602
, a planetary gear
603
and a connecting arm
604
, and a sheet feeding roller
607
is connected to the planetary gear
603
. Further, a separating roller
609
is connected to a drive shaft
606
through a torque limiter, and a pair of draw rollers
610
for feeding a sheet S at a speed higher than a speed at which the sheet feeding roller
607
feeds the sheets S is disposed at a downstream side of the sheet feeding roller
607
in a sheet feeding direction.
Now, an operation of the sheet feeding apparatus will be briefly described with reference to FIG.
19
.
First of all, by rotating the drive shaft
606
, the planetary gear
603
and the sheet feeding roller
607
are revolved in a direction indicated by the arrow A, with the result that the sheet feeding roller
607
abuts against an uppermost sheet S of a sheet stack contained within a sheet cassette. Further, in synchronism with such revolution, a lever
618
lifts an intermediate plate
623
on which the sheets are stacked toward the sheet feeding roller (in a direction indicated by the arrow G).
By this operation, the sheet S urged against the sheet feeding roller
607
is sent to a nip between the sheet feeding roller
607
and the separating roller
609
, thereby effecting separation and feeding of the sheet. Further, the sheet S left the nip enters into the pair of draw rollers
610
, and the planetary gear mechanism and the sheet feeding roller
607
are returned to their original positions by transmitting a driving force of the pair of draw rollers
610
to the planetary gear mechanism through the sheet S. And, such operation is repeated.
Although two earlier technologies in the sheet feeding mechanism are shown, it is considered that such technologies can be improved in several points.
First, in the mechanism according to the first earlier technology, the sheets S stacked on the intermediate plate
506
within the cassette
507
are lifted together with the intermediate plate
506
by the sheet pressing spring
505
to be always urged against the sheet feeding roller
501
. Thus, a sheet feed/separation condition greatly depends upon the pressure of the intermediate plate, with the result that an optimum sheet feeding area is limited in consideration of the pressure of the intermediate plate as a function.
In particular, since the pressures of the intermediate plate generated by the sheet pressing spring
505
vary with the number of sheets stacked within the cassette
507
, the sheet feed/separation condition differs between a case where the cassette
507
is loaded up with the sheets and a case where a several number of sheets are stacked. Further, since the sheet S is always urged against the sheet feeding roller
501
, the pressure of the intermediate plate always acts on the stacked sheets S. Thus, while the uppermost sheet S is being fed, a next or succeeding sheet S′ is subjected to a feeding force due to friction between the sheets, with result that double-feeding of sheet S′ will easily occur.
In addition, even if the double-fed sheets are separated and tried to be restored, the sheets are pinched between the sheet feeding roller
501
and the intermediate plate
506
so that the double-fed sheets may not be restored smoothly.
Further, an allowable range of the appropriate sheet feed area is further limited in dependence upon the kind of sheet (for example, a sheet having a great coefficient of friction) and reduction of coefficients of friction of the sheet feeding roller and the separating roller due to wear of the sheet feeding roller and the separating roller, thereby worsening the stability.
Therefore, it is hard to say that this mechanism is a sheet feeding mechanism having high stability and high reliability.
Incidentally, in this mechanism, if it is tried that the double-feeding is unlikely to occur and the double-fed sheets can easily be restored, the restoring force provided by the torque limiter
503
must be set to a greater value or the retard force of the retard spring must be decreased considerably or the feeding pressure provided by the sheet pressing spring
505
must be decreased considerably.
However, in many cases, slippage between the sheet feeding roller
501
and the sheet and/or between the separating roller
502
and the sheet may easily be generated, with the result that the wear of the sheet feeding roller
501
and the separating roller
502
is accelerated, thereby reducing the service life of the sheet feeding roller
501
and the separating roller
502
greatly. As a result, the number of periodical replacing operations for worn parts is increased to increase the maintenance cost of the apparatus. Further, a torque of a driving force applying means (motor) must be increased, thereby making the apparatus expensive and increasing power consumption.
Further, when the restoring force of the torque limiter
503
is set to a greater value, in a space Z formed between a nip X (between the sheet feeding roller
501
and the separating roller
502
) and an abutment area between the sheet feeding roller
501
and the intermediate plate
506
, it is considered that the double-fed sheet (particularly, thin sheet having poor rigidity) may be buckled, thereby causing sheet jamming.
In addition, when a pair of feeding rollers are provided at a downstream side of the sheet feeding roller
501
and the separating roller
502
in the sheet feeding direction, the pair of feeding rollers must draw the sheet S (always pressurized) from the intermediate plate
506
and the nip between the sheet feeding roller
501
and the separating roller
502
, with the result that greater load will act on the pair of feeding rollers, thereby shortening the service life of the pair of feeding rollers.
Furthermore, since the intermediate plate
506
is always urged against the sheet feeding roller
501
by the sheet pressing spring
505
, if this conventional technology is applied to a manual sheet feeding portion, when the operator sets the sheets, he must press the intermediate plate
506
down against the sheet pressing spring
505
to create a gap between the intermediate plate
506
and the sheet feeding roller
501
and insert the sheets into the gap.
This results in poor operability, so that operator's sheet setting failure may easily occur, which would lead to sheet jamming and skewed feeding.
Next, in the mechanism according to the second earlier technology, the sheet feeding roller
607
is urged against and separated (retracted) from the stacked sheets S so that the intermediate plate
623
is pivotally moved by the lever
618
in upward and downward directions accordingly, thereby effecting pressurizing and releasing operations with respect to the sheet feeding roller
607
. Namely, when the sheets S stacked on the intermediate plate
623
are fed, the sheets S are pinched by the sheet feeding roller
607
and the intermediate plate
623
from above and below.
Further, the retracting operation of the sheet feeding roller
607
and the lowering operation of the lower
618
are effected by utilizing the feeding force obtained when the fed sheet S are pinched between the pair of draw rollers
610
. Accordingly, the stacked sheets S are pinched between the sheet feeding roller
607
and the intermediate plate
623
until a leading end of the fed sheet S reaches the nip of the pair of draw rollers
610
.
Since the sheet feeding roller
607
is urged against the sheets S during the separating operation, the sheets are difficult to be separated, and, further, since the leading end of the sheet S reaches the nip of the pair of draw rollers
610
during such urging, there is no timing for restoring the double-fed sheets.
In consideration of the sheet feed/separation condition, the sheet feeding mechanism according to the second earlier technology is the same as the sheet feeding mechanism according to the first earlier technology. Thus, as is in the first earlier technology, in this mechanism, since the appropriate sheet feed area is narrow, it is hard to say that it has high stability and high reliability. Further, the construction is very complicated and the number of parts is great.
Further, since the releasing of the pressure of the sheet feeding roller
607
against the sheet S and the revolving operation of the planetary gear mechanism and the sheet feeding roller
607
are effected by the feeding force of the pair of draw rollers
610
, great feeding load acts on the pair of draw rollers, thereby reducing the service life of the draw rollers.
As a problem common to the above two earlier technologies, there is a problem that stability and reliability of sheet feeding and separating operations cannot be maintained adequately because the pressure of the intermediate plate affects an influence upon the sheet feeding/separation condition. Further, during the separating operation, since the sheets stacked on the intermediate plate are urged against the sheet feeding roller, double-feeding occurs easily and there is no timing for restoring the double-fed sheets, and, in dependence upon the kind of sheet, the sheet may be buckled to cause sheet jamming.
SUMMARY OF THE INVENTION
The present invention aims to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to ensure sheet feeding and separating operations, to improve stability and reliability of a sheet feeding apparatus, to reduce a maintenance cost of the apparatus and to make the apparatus simpler and inexpensive.
According to the present invention, there is provided a sheet feeding apparatus comprising movable sheet supporting means for supporting a sheet, a sheet feeding roller to be urged against the sheet supported by the sheet supporting means to rotate in a sheet feeding direction to feed the sheet, a separating roller opposed to the sheet feeding roller to rotate in a sheet restoring direction to separate the sheet fed from the sheet a roller, feeding means disposed at a downstream side of the sheet feeding roller in the sheet feeding direction to convey the sheet fed from the sheet feeding roller, and pressing and a retracting means for moving the sheet supporting means to bring the sheet supported by the sheet supporting means into pressure contact with the sheet feeding roller and release the pressure contact, and wherein the sheet supporting means which places the sheet into pressure contact with the sheet feeding roller is moved by the pressing and retracting means to release the pressure contact between the sheet feeding roller and the sheet before a leading end of the sheet fed from the sheet supporting means reaches the conveying means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic sectional view of a copying machine having a sheet feeding apparatus according to the present invention;
FIG. 2
is a sectional view of a sheet feeding apparatus according to an embodiment of the present invention;
FIG. 3
is a drive development view (plan view) of a sheet feeding apparatus;
FIGS. 4A
,
4
B,
4
C,
4
D and
4
E are views showing an operation of a control gear in an embodiment of the present invention;
FIGS. 5A
,
5
B,
5
C,
5
D,
5
E and
5
F are views showing operations of a roller and an intermediate plate in an embodiment of the present invention;
FIG. 6
is a flowchart showing a sheet feeding operation in an embodiment of the present invention;
FIG. 7
is a timing chart showing a sheet feeding operation in an embodiment of the present invention;
FIG. 8
is a drive development view (plan view) of a sheet feeding apparatus according to an alteration of the embodiment of the present invention;
FIGS. 9A
,
9
B,
9
C,
9
D,
9
E and
9
F are views showing an operation of a control gear in the alteration;
FIGS. 10A
,
10
B,
10
C,
10
D,
10
E,
10
F and
10
G are views showing operations of a roller and an intermediate plate in the alteration;
FIG. 11
is a flowchart showing a sheet feeding operation in the alteration;
FIG. 12
is a timing chart showing a sheet feeding operation in the alteration;
FIG. 13
is a graph showing an appropriate sheet feeding area in a first earlier technology (μp=0.52, μr=1.58);
FIG. 14
is a graph showing an appropriate sheet feeding area in a first earlier technology (μp=0.7, μr=1.0);
FIG. 15
is a graph showing an appropriate sheet feeding area in the present invention (μp=0.52, μr=1.58);
FIG. 16
is a graph showing an appropriate sheet feeding area in the present invention (μp=0.7, μr=1.0);
FIG. 17
is a schematic side view showing a first earlier technology;
FIG. 18
is a schematic side view showing a second earlier technology (initial state); and
FIG. 19
is a schematic side view showing the second earlier technology (sheet feeding state).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, a sheet feeding apparatus according to the present invention will be fully described.
First of all, an image forming apparatus having a sheet feeding apparatus according to the present invention will be briefly explained.
FIG. 1
is a schematic sectional view of a copying machine as an image forming apparatus. In
FIG. 1
, an original glass plate
2
formed from a transparent glass plate is secured to an upper part of a main body
1
of the copying machine. An original pressure cover
3
serves to press and fix an original
0
rested on the original glass plate
2
at a predetermined position thereof with an imaged surface facing downwardly.
Below the original glass plate
2
, there is provided an optical system comprising a lamp
4
for illuminating the original
0
, reflection mirrors
5
,
6
,
7
,
8
,
9
,
10
for directing a light image of the illuminated original
0
to a photosensitive drum
12
, and an imaging lens
11
for imaging the light image. Incidentally, the lamp
4
and the reflection mirrors
4
,
5
,
6
,
7
are moved at a predetermined speed in a direction indicated by the arrow a to scan the original
0
.
As sheet feeding portions, there are provided cassette sheet feeding portions
34
,
35
,
36
,
37
for feeding sheets stacked in sheet cassettes
30
,
31
,
32
,
33
contained within the main body
1
of the copying machine to an image forming portion, a sheet feeding portion
51
,
53
,
55
,
70
(referred to as “multisheet feeding portion” hereinafter) for continuously feeding sheets having various materials and sizes from a sheet feeding tray
74
to the image forming portion.
The image forming portion includes the photosensitive drum
12
, a charger
13
for uniformly charging a surface of the photosensitive drum
12
, a developing unit
14
for forming a toner image to be transferred to the sheet S, by developing an electrostatic latent image formed by the light image illuminated on the surface of the photosensitive drum
12
charged by the charger
13
from the optical system, a transfer charger
19
for transferring the toner image developed on the surface of the photosensitive drum
12
onto the sheet S, a separation charger
20
for separating the sheet S to which the toner image is transferred from the photosensitive drum
12
, and a cleaner
26
for removing residual toner from the photosensitive drum
12
after transferring the toner image.
At a downstream side of the image forming portion, there are provided a transporting portion
21
for transporting the sheet S to which the toner image is transferred, and a fixing unit
22
for fixing the image on the sheet S transported by the transporting portion
21
as a permanent image. Further, there are provided discharge rollers
24
for discharging the sheet S to which the image is fixed by the fixing unit
22
out of the main body
1
of the copying machine, and a discharge tray
25
for receiving the sheet S discharged by the discharge rollers
24
is also provided outside of the main body
1
of the copying machine.
Next, the multisheet feeding portion of the image forming apparatus according to an embodiment of the present invention will be fully explained.
FIG. 2
is a sectional view showing the multisheet feeding portion and a drum portion, and
FIG. 3
is a drive development view (plan view) of the multisheet feeding portion. The main body
1
of the copying machine is provided with a multisheet feeding tray
74
for stacking and supporting a sheet bundle S. The multisheet feeding tray
74
is provided with a sheet detecting sensor
82
comprising a photo-interrupter or the like for detecting pressure/absence of the sheet S on the tray
74
.
An intermediate plate (sheet supporting means)
70
is pivotally movable around fulcrums
70
a,
70
b
with respect to front and rear side plates
63
,
64
and is biased toward a clockwise direction (
FIG. 2
) (direction along which the intermediate plate is urged against a sheet feeding roller
51
) by compression springs (pressing and retracting means)
72
a,
72
b
so that the sheet supported by the intermediate plate can be brought into pressure contact with the sheet feeding roller
51
as sheet conveying means (as shown by the broken line in
FIG. 2
) and released from the pressure contact (as shown by the solid line in
FIG. 2
) by a pressing and retracting portion which will be described later.
Further, a felt
71
for preventing double-feed of sheets S and for relieving shock on pressing the intermediate plate
70
against the sheet feeding roller
51
is provided on an abutment portion (against the sheet feeding roller
51
) of a distal end of the intermediate plate
70
. The sheet feeding roller
51
is secured to a sheet feeding roller support shaft
52
, and the support shaft
52
is rotatably supported by the front and rear side plates
63
,
64
in such a manner that the sheet feeding roller
51
is not rotated reversely (in an counter-clockwise direction in
FIG. 2
) by the action of a one-way clutch
91
disposed between the front side plate
63
and the support shaft
52
.
Further, a sheet feeding drive gear (drive transmitting means)
65
is secured to a rear end of the support shaft
52
. A control gear (drive transmitting means)
80
engageable with the sheet feeding drive gear
65
and having a toothless portion
80
a opposed to the sheet feeding drive gear
65
.
Further, a cam (pressing and retracting means)
80
c
for bringing the sheets supported by the intermediate plate
70
into pressure contact with the sheet feeding roller
51
and releasing the pressure contact is integrally formed with the control gear
80
.
A cam follower (pressing and retracting means)
70
c
is integrally formed on a rear end of the intermediate plate
70
. The cam follower
70
c
extends up to the cam
80
c
through a hole
64
a
formed in the rear side plate
64
to engage with the cam
80
c
so that the clockwise rotation (
FIG. 2
) of the intermediate plate
70
is regulated.
Further, the control gear
80
is secured to a drive shaft
90
having a spring clutch
68
. One revolution of the spring clutch
68
is controlled by turning ON a control solenoid
69
for the spring clutch
68
by a time of T1 (sec). The phase angles of the spring clutch
68
and the toothless portion
80
a
are selected so that the toothless portion
80
a
of the control gear
80
is normally opposed to the sheet feeding drive gear
65
.
With this arrangement, in an initial state, the sheet feeding drive gear
65
, the support shaft
52
and the sheet feeding roller
51
can be rotated in a sheet feeding direction with no load.
A pair of draw rollers (conveying means)
55
are disposed at a downstream side of the sheet feeding roller
51
in the sheet feeding direction. A drive shaft of the drive draw roller
55
a
is rotatably supported by the front and rear side plates
63
,
64
via bearings (not shown), and an electromagnetic clutch
60
is provided on an end of the drive shaft so that a driving force from a draw motor M
2
can be connected to and disconnected from the drive shaft via gears
59
,
60
a.
The driven draw roller
55
b
is urged against the drive draw roller
55
a
via bearings (not shown) by springs
56
a
,
56
b
. Further, a gear
57
is secured to the drive shaft of the drive draw roller
55
a
so that a driving force can be transmitted to a drive shaft
54
of a separating roller via a gear
56
.
Incidentally, since the gears
57
,
56
are secured to the drive shaft of the drive draw roller
55
a
and the drive shaft
54
of a separating roller
53
, respectively, the pair of draw rollers
55
are rotated in synchronism with the drive shaft
54
of the separating roller
53
. Further, the gears
57
,
56
are selected so that the drive draw roller
55
a
is rotated in the sheet feeding direction (clockwise direction in
FIG. 2
) and the drive shaft
54
of the separating roller
53
is rotated in a direction opposite to the sheet feeding direction (clokwise direction in FIG.
2
).
Namely, when the electromagnetic clutch
60
is turned ON, the driving force of the draw motor M
2
is transmitted, with the result that the drive draw roller
55
a
is rotated in the sheet feeding direction and at the same time the drive shaft
54
of the separating roller
53
is rotated in the direction opposite to the sheet feeding direction.
Further, the separating roller
53
is rotatably supported on the drive shaft
54
via a torque limiter
62
for generating predetermined torque. The separating roller
53
is opposed to the sheet feeding roller
51
and is urged against the sheet feeding roller
51
with predetermined retard pressure by springs
73
a
,
73
b
via bearings (not shown).
Incidentally, a torque value of the torque limiter
62
and retard pressure of the separating roller
53
provided by the springs
73
a
,
73
b
are selected so that, in a stage that only a single sheet exists in a nip between the sheet feeding roller
51
and the separating roller
53
or a state that there is no sheet, the separating roller
53
follows the sheet feeding roller
51
by a friction force (also, the separating roller is stopped when the sheet feeding roller
51
is stopped) and, only when two or more sheets exist in the nip, the separating roller
53
is rotated reversely to generate a restoring force.
Further, an abutment plate
78
against which the sheets abut when the operator sets the sheets on the sheet feeding tray is secured between the separating roller
53
and the intermediate plate
70
. A guide
75
formed from a thin plate made of polyethylene or SUS and adapted to guide a leading end of the sheet to the nip between the sheet feeding roller
51
and the separating roller
53
is provided on a distal end of the abutment plate
78
. With this arrangement, the leading end of the sheet is prevented from abutting against the separating roller
53
to prevent the leading end of the sheet from being wound or bent.
Next, the drive transmitting means and the pressing and retracting means for the sheet feeding roller
51
and the intermediate plate
70
will be fully explained.
As mentioned above, at the engagement position of the sheet feeding drive gear
65
, there is provided the control gear
80
formed integrally with a gear portion
80
d
engageable with the sheet feeding drive gear
65
, a toothless portion
80
a
, and a cam
80
c
through which the intermediate plate
70
is urged against and retracted from the sheet feeding roller
51
. As mentioned above, one revolution of the control gear
80
can be controlled by the spring clutch
68
and the solenoid
69
. Incidentally, since the construction of the spring clutch
68
does not relate to the present invention, a detailed explanation thereof will be omitted.
Since the phase angle of the spring clutch
68
and the configuration and position of the toothless portion
80
a
are selected so that the toothless portion
80
a
of the control gear
80
is opposed to the sheet feeding drive gear
65
in the initial state, although the sheet feeding roller support shaft
52
can be rotated, the rotation of the support shaft
52
in the direction opposite to the sheet feeding direction is regulated by the one-way clutch
91
.
Further, the cam
80
c
abuts against the cam follower
70
c
provided at the end of the intermediate plate
70
, and the configuration of the cam
80
c
and the phase angle of the toothless portion
80
a
with the cam
80
c
are selected so that the intermediate plate
70
is retracted from the sheet feeding roller
51
against the compression springs
72
a
,
72
b
in the initial state. Thus, when the operator sets the sheet bundle, since the intermediate plate
70
is retracted from the sheet feeding roller
51
so that the pressure between the intermediate plate
70
and the sheet feeding roller
51
is released, the sheet bundle can easily be inserted until it abuts against the abutment plate
78
.
Next, the sheet feeding operation and the separating operation effected by the drive transmitting means and the pressing and retracting means will be explained.
When the solenoid
69
is turned ON by the time of T1 (sec), under the action of the spring clutch
68
, the control gear
80
starts to rotate. The control gear
80
is rotated in an counter-clockwise direction in
FIG. 4A
to rotate the cam
80
c
from an intermediate plate retracting position to an intermediate plate pressing position β
1
. During this rotation, the cam
80
c
is separated from the cam follower
70
c
, with the result that the intermediate plate
70
is moved to be urged against the sheet feeding roller
51
. As a result, an uppermost sheet S in the sheet bundle rested on the sheet feeding tray
74
is brought into pressure contact with the sheet feeding roller
51
(FIGS.
4
B and
5
B).
When the control gear
80
is further rotated up to a position β
2
, the gear portion
80
d
of the control gear
80
is engaged by the sheet feeding drive gear
65
, thereby starting the sheet feeding drive gear
65
to rotate. In response to this rotation, the sheet feeding roller
51
is rotated to feed out the uppermost sheet S in the sheet bundle rested on the intermediate plate
70
(FIGS.
4
C and
5
C).
When the sheet feeding operation is continued and the control gear
80
is rotated up to a position β
3
, the leading end of the fed sheet S reaches a position spaced apart from the nip between the sheet feeding roller
51
and the separating roller
53
by a distance L
1
. This sheet feeding amount L
1
is selected to become greater than a distance La from the sheet abutment portion
78
to the nip between the sheet feeding roller
51
and the separating roller
53
and smaller than a distance Lb from the nip to the pair of draw rollers
55
.
Further, the rotating speed of the sheet feeding drive gear
65
at this time is selected by determining the rotating speed of the sheet feeding motor M
1
and the number of teeth of the gears and diameters of rollers so that the sheet feeding speed of the sheet feeding roller
51
becomes equal to the feeding speeds of the pair of draw rollers
55
and a pair of registration rollers
81
.
Further, the phase angles of the control gear
80
and the cam
80
c
are selected so that the cam
80
c
is restored to the intermediate plate retracting position when the control gear
80
is rotated up to the position β
3
. With this arrangement, by rotating the control gear
80
to the position β
3
, the sheet S fed from the intermediate plate
70
is fed by the predetermined amount L
1
, and, at the same time, the sheet bundle on the intermediate plate
70
placed into pressure contact with the sheet feeding roller
51
is spaced apart from the sheet feeding roller
51
by lowering the intermediate plate
70
by the engagement between the cam
80
c
and the cam follower
70
c
of the intermediate plate
70
(FIGS.
4
D and
5
D).
When the pressure of the intermediate plate
70
against the sheet feeding roller
51
is released, even if double-feeding occurred, the intermediate plate
70
is not urged against the sheet feeding roller
51
, thus, the double-fed sheet(s) can surely be restored onto the intermediate plate
70
by the separating roller
53
.
The control gear
80
is further rotated, so that the sheet is fed by the sheet feeding roller
51
.
Incidentally, a feeding amount L
2
of the sheet feeding roller
51
at this time is selected by setting the number of teeth of the control gear
80
so that the leading end of the sheet S fed in front of the pair of draw rollers
55
before the pressure release of the intermediate plate
70
is surely received by the pair of draw rollers
55
and does not reach the pair of registration rollers
81
.
Further, when the rotation of the control gear
80
is continued to bring the toothless portion
80
a
to the position opposite to the sheet feeding drive gear
65
, the driving force is not transmitted to the sheet feeding drive gear
65
, thereby stopping the sheet feeding roller
51
. The rotation of the control gear
80
is finished and the control gear
80
is stopped at the initial position (FIGS.
4
E and
5
E).
Next, the sheet feeding operation using the multisheet feeding portion will be explained with reference to a flowchart shown in
FIG. 6 and a
timing chart shown in FIG.
7
.
In a state in which the sheet bundle is rested on the sheet feeding tray
74
, when a start button (not shown) is depressed, the draw motor M
2
and the sheet feeding motor M
1
start to rotate (step
1
), and an ON signal of the draw clutch
60
is emitted from a CPU
40
(step
2
).
As a result, as mentioned above, the pair of draw rollers
55
start to rotate in the sheet feeding direction and the drive shaft
54
of the separating roller
53
is rotated in the direction opposite to the sheet feeding direction, and the predetermined restoring force is generated in the separating roller
53
by torque generated by the torque limiter
62
. However, the separation roller
53
is still maintained in the stopped state by the friction force between the separating roller
53
and the sheet feeding roller
51
rotation of which is regulated by the action of the one-way clutch
91
.
Then, after a predetermined time period is elapsed, the solenoid
69
is turned ON by a time period T1 (sec) on the basis of a signal from the CPU
40
(step
3
) to start control of one revolution of the control gear
80
. By this operation, as mentioned above, first of all, the sheet bundle on the intermediate plate
70
abuts against the sheet feeding roller
51
. Then, the sheet feeding roller
51
is rotated to feed out the uppermost sheet S in the sheet bundle rested on the tray
74
by the pressing force of the intermediate plate
70
and the friction force between the sheet and the sheet feeding roller
51
.
Incidentally, the separation roller
53
is driven in the sheet feeding direction by the rotation of the sheet feeding roller
51
. By the way, in the above-mentioned sheet feeding operation, if two or more sheets are fed in an overlapped state (i.e., if double-feed occurs), the separating roller
53
acts to restore the double-fed sheet(s). At this time, however, since the intermediate plate
70
urges the sheet feeding roller
51
via the intermediate plate spring
72
, the separating operation of the separating roller
53
may be obstructed not to restore the double-fed sheet(s).
However, when the control gear
80
is further rotated, the sheets on the intermediate plate
70
are released from the pressure of the sheet feeding roller
51
by the action of the cam
80
c
and the cam follower
70
c.
At this time, since the turned-ON state of the draw clutch
60
is maintained, the drive shaft
54
of the separating roller
53
continues to rotate in the direction opposite to the sheet feeding direction, and the restraint of the double-fed sheet(s) is released due to the pressure release.
At this point, the separating roller
53
starts to rotate in the restoring direction until the double-fed sheet(s) caused by the above sheet feeding operation do not exist in the nip between the sheet feeding roller
51
and the separating roller
53
, thereby certainly avoiding double-feeding. Incidentally, in the state in which only a single sheet is pinched by the nip between the sheet feeding roller
51
and the separating roller
53
, the sheet feeding roller
51
, the separating roller
53
and the sheet S can be maintained in the stationary state by the action of the one-way clutch
91
and the friction forces between the sheet S and the sheet feeding roller
51
and between the sheet S and the separating roller
53
.
When the control gear
80
is further rotated, the leading end of the sheet S is received by the pair of draw rollers
55
. After the sheet is fed by the sheet feeding roller
51
by the predetermined distance L
2
, one revolution of the control gear
80
is completed to stop the sheet feeding roller
51
. However, since the pair of draw rollers
55
continue to rotate, the sheet S is fed up to the pair of registration rollers
81
.
At this time, since the toothless portion
80
a
of the control gear
80
is opposed to the sheet feeding drive gear
65
, any load does not act on the sheet feeding roller
51
. Thus, the sheet feeding roller
51
is subjected to the rotational force from the sheet S fed by the pair of draw rollers
55
, with the result that the sheet feeding roller
51
is rotatingly driven (idle rotation) until a trailing end of the sheet S leaves the nip between the sheet feeding roller
51
and the separating roller
53
.
Incidentally, in this drawing operation, since the intermediate plate
70
is retracted from the sheet feeding roller
51
, a succeeding sheet is not subjected to a friction force from the sheet S being drawn. Thus, the succeeding sheet is unlikely to be double-fed. However, if the succeeding sheet S should be double-fed, during the operation of the pair of draw rollers
55
, since the drive shaft
54
of the separating roller
53
is rotated in the direction opposite to the sheet feeding direction and the intermediate plate
70
is retracted from the sheet feeding roller
51
to release the pressure contact at that point, the separating roller
53
starts to rotate reversely to restore the double-fed sheet, thereby certainly avoiding double-feeding certainly.
Due to the above operation, the leading end of the sheet S is fed toward the nip of the pair of registration rollers
81
. The sheet detecting sensor
82
comprising a photo-interrupter or the like is disposed at an upstream side of the pair of registration rollers
81
so that, when the leading end of the sheet S is detected by the sensor (step
4
), by a timer means (not shown) of the CPU
40
for counting a time corresponding to the distance between the sensor
82
and the pair of registration rollers
81
, a signal for controlling the stop timing of the draw clutch
60
to form a proper loop between the pair of draw rollers
55
and the pair of registration rollers
81
is generated (step
6
).
It is well known that such a loop is formed in the sheet S to correct skew-feeding of the sheet. Further, by rotating the pair of registration rollers
81
in response to an image leading end synchronous signal emitted from the photosensitive drum
12
or the optical system for exposing the image, the sheet S is fed again to be sent onto the photosensitive drum
12
, where a toner image is transferred onto the sheet.
When a predetermined time period T2 (sec) is elapsed after the trailing end of the sheet S leaves the sheet detecting sensor
82
to ascertain the fact that the trailing end of the sheet S surely leaves the nip of the pair of registration rollers
81
, a registration clutch
83
is turned OFF (steps
9
,
10
and
11
). Incidentally, the sheet S to which the toner image was transferred is sent to the fixing unit
22
, where the image is fixed to the sheet. Thereafter, the sheet is discharged onto the discharge tray
25
.
The above-mentioned operations are repeated by a number of times corresponding to the set number of sheets to be treated (step
12
). When the predetermined number is completed, the draw clutch
60
is turned OFF (step
13
), and then the sheet feeding motor M
1
and the draw motor M
2
are stopped (step
14
), and the program is ended.
As fully mentioned above, the sheet S fed from the intermediate plate
70
is fed, and the intermediate plate
70
(urged against the sheet feeding roller
51
) is retracted from the sheet feeding roller
51
. In this case, since the restoring force of the separating roller
53
can be utilized, the double-fed sheet(s) S can surely be restored, thereby achieving a highly reliable sheet feeding operation.
Further, when the sheet S is fed by the pair of draw rollers
55
, since the pressure contact between the sheets on the intermediate plate
70
and the sheet feeding roller
51
is released, the pair of draw rollers
55
are not subjected to the feeding load due to pinching pressure generated by the pressure between the intermediate plate
70
and the sheet feeding roller
51
. Thus, the service life of the draw rollers can be extended.
Further, in the initial state, since the intermediate plate
70
is retracted from the sheet feeding roller
51
, the setting of the sheets effected by the operator is not obstructed. When the operator sets the sheets, he may merely abut the leading end of the sheet bundle against the abutment plate
78
. Thus, since the setting operation is very easy, occurrence of a sheet jam and skew-feeding due to poor setting can be reduced.
In addition, the synchronous operation between the intermediate plate
70
and the sheet feeding roller
51
is effected by the control gear
80
formed integrally with the cam
80
c
for controlling the intermediate plate
70
and the toothless portion
80
a.
As a timing of feeding the sheet, a timing of applying a pressure between the intermediate plate
70
and the sheet feeding roller
51
, and a timing of releasing the pressure determined by the phase angles of the cam
80
c
and the toothless portion
80
a,
there are few factors for causing dispersion, with the result that the stable sheet feeding and separating operations can be effected with low cost.
Since the control for rotation of the sheet feeding roller
51
and the application and release of the pressure of the intermediate plate
70
can be effected by one ON signal and one OFF signal for the solenoid
69
, the control is very easy and the severe control accuracy is not requested.
Further, since the pair of draw rollers
55
are synchronous with the drive shaft
54
of the separating roller and the control thereof is effected by the single draw clutch
60
, not only can the apparatus can be simplified but also such control can be effected independently from the rotation of the sheet feeding roller
51
. Thus, even in the state that the sheet feeding roller
51
is stopped, the restoring force of the separating roller
53
can be utilized, thereby providing the sheet feeding apparatus having high double-feed preventing ability.
Next, a multisheet feeding portion of an image forming apparatus according to an alteration of the illustrated embodiment of the present invention will be explained.
FIG. 8
is a drive development view of a multisheet feeding portion according to such an alteration. Incidentally, the same elements as those in the above-mentioned illustrated embodiment are designated by the same reference numerals and an explanation thereof will be omitted. In this alteration, a sheet feeding drive stage gear
100
as a drive transmitting means comprising an integral forming of a large diameter gear
100
a
and a small diameter gear
100
b
is secured to the rear end of the support shaft
52
of the sheet feeding roller
51
.
Further, a control gear (stage gear of the drive transmitting means)
101
having first and second sector gear portions
101
d,
101
e
engageable with the large diameter gear
100
a
and the small diameter gear
100
b
of the sheet feeding drive stage gear
100
and nonengagement portions
101
a,
101
b
which are not engaged by the sheet feeding drive stage gear
100
is disposed in a confronting relationship to the large diameter gear
100
a
and the small diameter gear
100
b
of the sheet feeding drive stage gear
100
. A cam (pressing and retracting means)
101
c
for bringing the sheets on the intermediate plate
70
into pressure contact with the sheet feeding roller (sheet feeding means)
51
and releasing the pressure contact is integrally formed with the control gear
101
.
A cam follower
70
c
formed integrally with the rear end of the intermediate plate
70
and extending through a hole
64
a
of the rear side plate
64
up to an abutment position of the cam
101
c
can abut against the cam
101
c.
The control gear
101
is secured to a drive shaft
90
on which the spring clutch
68
is provided. One revolution (at a predetermined rotating speed) of the spring clutch
68
is controlled by transmitting the driving force of the sheet feeding motor M
1
to the spring clutch
68
by turning ON the solenoid
69
for controlling the spring clutch
68
by a time of T1 (sec).
Further, a pulley (connecting means)
57
is secured to the rear end of the support shaft
52
. Since a recipient pulley
58
to which a driving force is transmitted from a pulley
57
on the support shaft
52
through a belt
61
passed over the pulleys
57
,
58
are secured to the shaft
54
of the separating roller
53
, the shaft
54
of the separating roller
53
is rotated in the same direction as the support shaft
52
in synchronous with the rotation of the support shaft
52
.
Phase angles of the spring clutch
68
and the nonengagement portion
101
a
are selected so that the nonengagement portion
101
a
of the control gear
101
is normally opposed to the sheet feeding drive stage gear
100
. Further, in this alteration, the one-way clutch
91
disposed between the front side plate
63
and the support shaft
52
and used in the above-mentioned illustrated embodiment is omitted.
Thus, in the initial stage, although a slight rotational load of the torque limiter
62
acts on the sheet feeding drive stage gear
100
, the support shaft
52
and the sheet feeding roller
51
, the sheet feeding drive stage gear
100
, the support shaft
52
and the sheet feeding roller
51
can be rotated both in the sheet feeding direction and in the opposite direction.
Since the pair of draw rollers
55
disposed at the downstream side of the sheet feeding roller
51
in the sheet feeding direction and the members for driving the pair of draw rollers are the same as those in the above-mentioned embodiment, an explanation thereof will be omitted. Further, since the setting of the torque value of the torque limiter
62
provided on the drive shaft
54
of the separating roller
53
is the same as the above-mentioned embodiment, an explanation thereof will also be omitted.
The rotating speed of the draw motor M
2
, the outer diameter of the sheet feeding roller
51
and the number of teeth of the gears are selected so that the feeding speed of the pair of draw rollers
55
becomes a second feeding speed V
2
substantially equal to the feeding speed of the pair of registration rollers
81
(disposed at the downstream side of the pair of draw rollers
55
in the sheet feeding direction) for correcting the skew-feeding of the sheet and for synchronizing the sheet with the toner image on the photosensitive drum.
Next, the drive transmitting means and the pressing and retracting means for the sheet feeding roller
51
and the intermediate plate
70
will be fully explained with reference to
FIGS. 9A
to
9
E and
FIGS. 10A
to
10
G. As mentioned above, the control gear
101
formed integrally with the first and second sector gear portions
101
d,
101
e
engageable with the large diameter gear
100
a
and the small diameter gear
100
b
of the sheet feeding drive stage gear
100
, the two nonengagement portions
101
a,
101
b
which are not engaged by the sheet feeding drive stage gear
100
, and the cam
101
c
for applying a pressure between the intermediate plate
70
and the sheet feeding roller
51
and releasing the pressure is disposed in a confronting relationship to the sheet feeding drive stage gear
100
.
As is in the aforementioned control gear
80
, one revolution of the control gear
101
can be controlled by the spring clutch
68
and the solenoid
69
. Incidentally, since the construction of the spring clutch
68
does not relate to the present invention, a detailed explanation thereof will be omitted.
Since the phase angle of the spring clutch
68
and the configuration and position of the first nonengagement portion
101
a
are selected so that the first nonengagement portion
101
a
of the control gear
101
is normally opposed to the sheet feeding drive stage gear
100
, the sheet feeding roller support shaft
52
can be rotated both in the sheet feeding direction and in the opposite direction.
Further, cam
101
c
abuts against the cam follower
70
c
provided at the end of the intermediate plate
70
, and the configuration of the cam
101
c
and the phase angle between the cam
101
c
and the nonengagement portion
101
a
are selected so that the cam
101
c
normally separates the intermediate plate
70
from the sheet feeding roller
51
against the force of the compression spring
72
. Thus, when the operator sets the sheet bundle, since the intermediate plate
70
is retracted from the sheet feeding roller
51
, the sheet bundle can easily be inserted until the sheet bundle abuts against the abutment plate
78
.
Next, the sheet feeding and separating operations by using the drive transmitting means and the pressing and retracting means will be explained.
When the solenoid
69
is turned ON by the time T1 (sec), the control gear
101
starts to rotate under the action of the spring clutch
68
. When the control gear
101
is rotated in an counter-clockwise direction in
FIG. 9A
, first of all, the cam
101
c
is rotated from the intermediate plate retracting position to the intermediate plate pressing position α
1
. During this rotation, the cam
101
c
is separated from the cam follower
70
c,
thereby moving the intermediate plate
70
to be urged against the sheet feeding roller
51
.
As a result, the uppermost sheet S in the sheet bundle rested on the sheet feeding tray
74
abuts against the sheet feeding roller
51
(FIGS.
9
B and
10
B).
When the control gear
101
is further rotated up to a position α
2
, the first sector gear portion
101
d
of the control gear
101
is engaged by the large diameter gear portion
100
a
of the sheet feeding drive stage gear
100
, thereby starting the sheet feeding drive stage gear
100
to rotate.
Incidentally, the rotating speed of the sheet feeding motor M
1
, the outer diameter of the sheet feeding roller
51
and the number of teeth of the gears are selected so that the feeding speed of the sheet feeding roller
51
at this time becomes a first feeding speed V
1
lower than the second feeding speed V
2
provided by the pair of registration rollers
81
and the pair of draw rollers
55
.
When the control gear
101
is further rotated up to a position α
3
the sheet feeding roller
51
is rotated by the rotation of the control gear
101
, thereby feeding out the uppermost sheet S in the sheet bundle (FIGS.
9
C and
10
C).
Since the phase angle is selected so that the cam
101
c
integrally formed with the control gear
101
is restored to the intermediate plate retracting position at the time when the control gear
101
is rotated up to the position α
3
the cam
101
c
abuts against the cam follower
70
c,
thereby moving the intermediate plate
70
away from the sheet feeding roller
51
, with the result that the sheets on the intermediate plate
70
is released from the pressure of the sheet feeding roller
51
(FIGS.
9
D and
10
D).
When the control gear
101
is rotated up to a position α
4
, the sheet S is fed out by a predetermined amount L
1
(the sheet feeding operation up to this step is referred to as “first sheet feeding operation” hereinafter). Incidentally, the number of teeth of the first sector gear portion
101
d
is selected so that the sheet feeding amount L
1
during the first sheet feeding operation becomes greater than a distance La from the sheet abutment portion
78
to the nip between the sheet feeding roller
51
and the separating roller
53
and smaller than a distance Lb from the nip to the pair of draw rollers
55
.
In the first sheet feeding operation, if the sheets should be double-fed into the nip between the sheet feeding roller
51
and the separating roller
53
, the sheet feeding roller
51
is rotated in the sheet feeding direction by the driving force from the drive motor M
1
and the driving force is transmitted to the drive shaft
54
of the separating roller
53
through the pulley
57
,
58
and the belt
61
. Thus, the drive shaft
54
of the separating roller
53
is rotated in the direction opposite to the sheet feeding direction, and restraint of the double-fed sheets is released by pressure release of the intermediate plate
70
. At this point, the separating roller
53
starts to rotate in the restoring direction under the action of the torque limiter
62
until the double-fed sheets caused by the sheet feeding operation leave the nip between the sheet feeding roller
51
and the separating roller
53
, thereby certainly avoiding double-feeding.
Then, the first sector gear portion
101
d
of the control gear
101
is disengaged from the large diameter gear portion
100
a
of the sheet feeding drive stage gear
100
, and the second sector gear portion
101
e
of the control gear
101
starts to engage with the small diameter gear portion
100
b
of the sheet feeding drive stage gear
100
(FIGS.
9
E and
10
E). From this point, the feeding speed of the sheet feeding roller
51
is switched from the first feeding speed V
1
to the second feeding speed V
2
, and the roller is rotated in the sheet feeding direction.
Incidentally, diameters and phase angles of the sheet feeding drive stage gear
100
and the control gear
101
are selected so that the drive transmission from the control gear
101
to the sheet feeding drive stage gear
100
is not interrupted when the gear change is effected between the sheet feeding drive stage gear
100
and the control gear
101
. Further, the second nonengagement portion
101
b
is provided between the first sector gear portion and the second sector gear portion of the control gear
101
. However, the second nonengagement portion
101
b
does not interrupt the drive transmission from the control gear
101
to the sheet feeding drive stage gear
100
and has a purpose for making the control gear
101
simpler and inexpensive.
When the control gear
101
is further rotated to bring the first nonengagement portion
101
a
to a position opposed to the small diameter gear portion
100
b
of the sheet feeding drive stage gear
100
, the sheet feeding drive stage gear
100
does not receive the driving force, thereby stopping the sheet feeding roller
51
.
One revolution of the control gear
101
is completed, and the control gear is stopped at the initial position (FIGS.
9
F and
10
F). At this stage the sheet S is fed out by a predetermined amount L
2
(this sheet feeding operation after the first sheet feeding operation is referred to as “second sheet feeding operation” hereinafter). The number of teeth of the second sector gear portion
101
e
is selected so that the sheet feeding amount L
2
ensures that the leading end of the sheet S (at the second feeding speed V
2
) is surely received by at least the pair of draw rollers
55
after the sheet S fed out from the intermediate plate
70
at the first feeding speed V
1
is separated and that the sheet does not still reach the pair of registration rollers
81
. Further, the outer diameter of the sheet feeding roller
51
, the rotating speed of the sheet feeding motor M
1
and the number of teeth of the gears are selected so that the second feeding speed V
2
of the sheet feeding roller
51
at this time becomes equal to the feeding speeds of the pair of registration rollers
81
and the pair of draw rollers
55
.
Next, the sheet feeding operation of the multisheet feeding portion will be explained with reference to a flowchart shown in
FIG. 11 and a
timing chart shown in FIG.
12
.
In a state that the sheet bundle is rested on the sheet feeding tray
74
, when a start button (not shown) is depressed, the draw motor M
2
and the sheet feeding motor M
1
start to rotate (step
1
), and an ON signal of the draw clutch
60
is emitted from a CPU
40
(step
2
).
Then, after a predetermined time period is elapsed, the solenoid
69
is turned ON by a time period T1 (sec) on the basis of a signal from the CPU
40
(step
3
) to start control of one revolution of the control gear
101
. By this operation, as mentioned above, first of all, the intermediate plate
70
is moved to be urged against the sheet feeding roller
51
, with the result that the sheet bundle supported on the intermediate plate
70
abuts against the sheet feeding roller
51
. Then, the sheet feeding roller
51
is rotated to feed out the uppermost sheet S in the sheet bundle rested on the tray
74
by the predetermined amount L
1
at the first feeding speed V
1
by the pressing force of the intermediate plate
70
and the friction force between the sheet and the sheet feeding roller
51
(the first sheet feeding operation).
At this time, the separation roller
53
is driven in the sheet feeding direction by the rotation of the sheet feeding roller
51
. By the way, in the above-mentioned sheet feeding operation, if two or more sheets are fed in an overlapped state (i.e., if double-feed occurs), the separating roller
53
acts to restore the double-fed sheet(s). At this time, however, since the intermediate plate
70
urges the sheet feeding roller
51
via the intermediate plate spring
72
, the separating operation of the separating roller
53
may be obstructed so not to restore the double-fed sheet(s).
However, at this time, when the control gear
101
is further rotated, the intermediate plate
70
is released from the pressure and retracted from the sheet feeding roller
51
by the engagement between the cam
101
c
and the cam follower
70
c.
Incidentally, as mentioned above, since the first feeding speed V
1
during the first sheet feeding operation is lower than the second feeding speed V
2
provided by the pair of registration rollers
81
and the pair of draw rollers
55
, in the first sheet feeding operation, double-feeding is unlikely to occur and any slippage of the sheet feeding roller
51
is also unlikely to occur, thereby providing the stable sheet feeding operation.
Since slippage is unlikely to occur as mentioned above, the pressing force of the intermediate plate
70
against the sheet feeding roller
51
can be set to a smaller value. Thus, the double-feeding is even more unlikely to occur.
When the control gear
101
is further rotated, the sheet feeding roller
51
feeds the sheet S at the second feeding speed V
2
, and the leading end of the sheet S is received by the pair of draw rollers
55
which are rotated at the second feeding speed V
2
. After the sheet is fed by the sheet feeding roller
51
by the predetermined amount L
2
, the control of one revolution of the control gear
101
is completed and the sheet feeding roller
51
is stopped. However, since the pair of draw rollers
55
continue to rotate, the sheet S is fed up to the pair of registration rollers
81
.
At this time, since the first nonengagement portion
101
a
of the control gear
101
is opposed to the sheet feeding drive stage gear
100
, the sheet feeding roller
51
is not subjected any load. Thus, the sheet feeding roller
51
is rotatingly driven (idle rotation) by the sheet S being fed by the pair of draw rollers
55
until the trailing end of the sheet S leaves the nip between the sheet feeding roller
51
and the separating roller
53
.
In this drawing operation, since the intermediate plate
70
is retracted from the sheet feeding roller
51
, a succeeding sheet is not subjected to a friction force from the sheet S being drawn. Thus, the succeeding sheet is unlikely to be double-fed. However, if the succeeding sheet should be double-fed, during the operation of the pair of draw rollers
55
, since the support shaft
52
is similarly rotatingly driven by the rotation of the sheet feeding roller
51
and the drive shaft
54
of the separating roller
53
connected to the support shaft
52
is rotated in the direction opposite to the sheet feeding direction and the intermediate plate
70
is released from the pressure of the sheet feeding roller
51
to release the pressure on the sheets on the intermediate plate
70
, at that point, the separating roller
53
starts to rotate reversely by the action of the torque limiter
62
to restore the double-fed sheet, certainly avoiding double-feeding.
If the sheet is jammed in the nip between the sheet feeding roller
51
and the separating roller
53
or if the sheet is caught by the nip of the pair of draw rollers
55
for any reason, in this alteration, since the sheet feeding roller
51
can be rotated both in the sheet feeding direction and in the opposite direction, the jammed sheet can be pulled in the direction opposite to the sheet feeding direction, thereby facilitating the sheet jam treatment.
This can be achieved because the control gear
101
has the nonengagement portions not engaged by the sheet feeding drive stage gear
100
and because there is no need for providing means such as a one-way clutch for connecting the driving between the sheet feeding roller
51
and the separating roller
53
to regulate the rotation.
That is to say, when the control gear
101
is disengaged from the sheet feeding drive stage gear
100
, the sheet feeding roller support shaft
52
can freely be rotated both in the sheet feeding direction and in the opposite direction. Thus, the jammed sheet can be pulled in the direction opposite to the sheet feeding direction.
Further, when the sheet is draw by the pair of draw rollers
55
, the sheet feeding roller
51
is rotatingly driven, and the rotation of the sheet feeding roller
51
is transmitted to the shaft
54
of the separating roller
53
through the pulleys
57
,
58
and the belt
61
, with the result that the shaft
54
of the separating roller
53
can always be rotated in the sheet restoring direction. Namely, even if a plurality of sheets are fed into the nip between the sheet feeding roller
51
and the separating roller
53
, under the action of the torque limiter
62
, the separating roller
53
can be rotated to restore the sheet onto the intermediate plate
70
.
The leading end of the sheet S is fed at the second feeding speed V
2
toward the pair of registration rollers
81
which are stopped, by the above-mentioned operation. A sheet detecting sensor
82
comprising a photo-interrupter or the like is disposed at an upstream side of the pair of registration rollers
81
so that, when the leading end of the sheet S is detected by the sensor (step
4
), by a timer means (not shown) of the CPU
40
for counting a time corresponding to the distance between the sensor
82
and the pair of registration rollers
81
, a signal for controlling the stop timing of the draw clutch
60
to form a proper loop between the pair of draw rollers
55
and the pair of registration rollers
81
is generated (step
6
).
It is well known that such a loop is formed in the sheet S to correct skew-feeding of the sheet. Further, by rotating the pair of registration rollers
81
in response to an image leading end synchronous signal emitted from the photosensitive drum
12
or the optical system for exposing the image, the sheet S is fed again at the second feeding speed V
2
to be sent onto the photosensitive drum
12
rotated at the second feeding speed V
2
, where the toner image is transferred onto the sheet.
When a predetermined time period T2 (sec) is elapsed after the trailing end of the sheet S leaves the sheet detecting sensor
82
to ascertain the fact that the trailing end of the sheet surely leaves the nip of the pair of registration rollers
81
, a registration clutch
83
is turned OFF (steps
9
,
10
and
11
). Incidentally, the sheet S to which the toner image is transferred is sent to the fixing unit
22
, where the image is fixed to the sheet. Thereafter, the sheet is discharged onto the discharge tray
25
. The above-mentioned operations are repeated by a number of times corresponding to the set number of sheets to be treated (step
12
). When the predetermined number is completed, the draw clutch
60
is turned OFF (step
13
), and then the sheet feeding motor M
1
and the draw motor M
2
are stopped (step
14
), and the program is ended.
As fully mentioned above, in this alteration, since the first feeding speed V
1
in the first sheet feeding operation is lower than the second feeding speed V
2
provided by the pair of draw rollers
55
and the pair of registration rollers
81
, in the first sheet feeding operation, double-feeding is unlikely to occur and the slippage between the sheet feeding roller
51
and the sheet S is also unlikely to occur, thereby providing the stable sheet feeding operation.
Furthermore, since the double-feed preventing arrangement is used, the torque value (sheet restoring force of the sheet separating roller
53
) of the torque limiter
62
can be set to a smaller value. Further, since occurrence of the slippage during the first sheet feeding operation can be reduced, the pressing force of the intermediate plate
70
against the sheet feeding roller
51
can be set to a smaller value, thereby improving the service lives of the sheet feeding roller
51
and the separating roller
53
. Thus, a sheet feeding apparatus having low maintenance cost can be provided.
Further, when the sheet S is fed by the pair of draw rollers
55
, since the intermediate plate
70
is already retracted from the sheet feeding roller
51
, the pair of draw rollers
55
are not subjected to the feeding load due to the pressure of the intermediate plate. Thus, the service life of the draw rollers
55
can be extended.
Further, in the initial state, since the intermediate plate
70
is retracted from the sheet feeding roller
51
, the setting of the sheet bundle effected by the operator is not obstructed. When the operator sets the sheets, he may merely abut the leading end of the sheet bundle against the abutment plate
78
. Thus, since the setting operation is very easy, occurrence of sheet jamming due to poor setting can be reduced.
In addition, since the interlocking operation between the intermediate plate
70
and the sheet feeding roller
51
is effected by the control gear
101
formed integrally with the cam
101
c
for controlling the intermediate plate
70
and the two nonengagement portions
101
a,
101
b
and since the timings for feeding the sheet and for applying and releasing a pressure between the intermediate plate
70
and the sheet feeding roller
51
are determined by the phase angles of the nonengagement portions
101
a,
101
b
and the cam
101
c,
there are few factors for causing dispersion, with the result that the stable sheet feeding and separating operations can be effected with low cost.
Since the control for rotation and stoppage of the sheet feeding roller
51
and the complication and release of the pressure of the intermediate plate
70
can be effected by one ON signal and one OFF signal for the solenoid
69
, the control is very easy and the severe control accuracy is not requested.
Further, by connecting the shaft
54
of the separating roller
53
to the sheet feeding roller support shaft
52
, means such as a one-way clutch for regulating the rotational direction which was required in the conventional sheet feeding apparatuses can be omitted, thereby making the sheet feeding apparatus inexpensive. In addition, since the shaft
54
of the separating roller
53
can always be rotated in the sheet restoring direction by rotatingly driving the sheet feeding roller
51
by the sheet drawn by the pair of draw rollers
55
, the separating ability can be improved.
In this alteration, when the control gear
101
is in the initial state, since the nonengagement portion
101
a
of the control gear
101
is opposed to the sheet feeding drive stage gear
100
, although slight rotational resistance of the torque limiter
62
acts on the sheet feeding roller
51
and the separating roller
53
, these rollers can freely be rotated in both directions. Thus, if the sheet is jammed in the sheet feeding portion, the jammed sheet can be pulled both in the sheet feeding direction and in the opposite direction, thereby greatly improving the jam treating ability.
Incidentally, in the alteration, while an example that the pulley
57
,
58
are provided on the sheet feeding roller support shaft
52
and the separating roller shaft
54
, respectively and the pulleys
57
,
58
are interconnected through the belt
61
to transmit the driving force from the sheet feeding motor M
1
is explained, a connecting gear may be provided on the sheet feeding roller support shaft
52
and a separating roller gear may be provided on the shaft
54
of the separating roller
53
and a driving force may be transmitted through a gear train including idler gear(s) which engages with the connecting gear and the separating roller gear. This construction can also have the same technical advantage as the above alteration.
Now, a difference in appropriate sheet feeding area between the earlier technologies and the present invention will be explained with reference to the accompanying drawings.
The appropriate sheet feeding area of the sheet feeding apparatus according to the present invention is shown in FIG.
15
. Further, as mentioned above,
FIG. 13
shows the appropriate sheet feeding area of the sheet feeding apparatus according to the first earlier technology (values are calculated values). Incidentally, the numerical values and formulae (expressions) used in
FIG. 13
are quoted from those used in the first earlier technology. Such expressions are as follows:
Expression of sheet feed condition
Pb>Ta/μr
+((μ
p/μr
)−1)
Pa
Expression (1)
Expression of separation condition
Pb<Ta/μp−
2
Pa
Expression (2)
here, Pb is retard pressure, Ta is a sheet restoring (returning) force of the separating roller, Pa is intermediate plate pressure, μp is a coefficient of friction between the sheets, and μr is a coefficient of friction between the sheet and the sheet feeding roller or the separating roller.
Incidentally, Ta is a value obtained from the following equation:
Ta
=(torque of a torque limiter)/(radius of a separating roller)
In
FIGS. 13 and 15
, a relationship between the sheet restoring force Ta, the intermediate plate pressure Pa and the retard pressure Pb is formulated as mentioned above, and the sheet feed condition and the separation condition are sought regarding Pa=100 g, 200 g, 300 g, respectively. However, when the present invention is used, in the separating operation and in the second sheet feeding operation, since the intermediate plate is retracted from the sheet feeding roller, the intermediate plate pressure Pa is not generated. Thus, the sheet feed condition (in the second sheet feeding operation) and the separation condition are expressed as a function of only the restoring force Ta and the retard pressure Pb. The sheet feed condition and the separation condition in the present invention are as follows:
Expression of sheet feed condition
Pb>Ta/μr
Expression (3)
Expression of separation condition
Pb<Ta/μp
Expression (4).
Incidentally, assuming that the frictional coefficient μp between the sheets and the frictional coefficient μr between the sheet and the sheet feeding roller or the separating roller are 0.52 and 1.58, respectively in accordance with the first earlier technology, the calculation is performed.
In case of the first earlier technology in which the intermediate plate is urged against the sheet feeding roller in the separating operation, the relationship between the restoring force Ta of the separating roller and the retard pressure Pb is greatly influenced by the intermediate plate pressure Pa; and, when the restoring force Ta<400 g, there is no appropriate sheet feeding area. Since the intermediate plate pressures Pa vary with the number of sheets stacked on the intermediate plate, it is considered that it is very difficult to stabilize the appropriate sheet feeding area and to widen the range of the appropriate sheet feeding area in the first earlier technology.
To the contrary, the case of the present invention, since the intermediate plate is retracted from the sheet feeding roller in the separating operation, the relationship between the restoring force Ta of the separating roller and the retard pressure Pb is not influenced by the intermediate plate pressure Pa at all. Thus, the appropriate sheet feeding area can be maintained with a wide range.
FIGS. 14 and 16
show a relationship between the restoring force Ta of the separating roller and the retard pressure Pb when a sheet having great frictional coefficient between the sheet is fed and separated by a worn sheet feeding roller. As μp and μr, numerical values 0.7 and 1.0 are used, respectively. The other numerical values and expressions are the same as above-mentioned ones.
As shown in
FIG. 14
showing the relationship between Ta and Pb in the first earlier technology, in a range of the restoring force Ta<900 g, it can be seen that there is no appropriate sheet feeding area. In this condition, it is very difficult to effect the stable sheet feeding and separating operations. However, in
FIG. 16
showing the relationship between Ta and Pb in the present invention, there is the appropriate sheet feeding area. Thus, being greatly influenced by the material of the sheet and wear of the rollers, the stable sheet feeding and separating operations can be performed. The difference in appropriate sheet feeding area between FIG.
14
and
FIG. 16
depends upon the presence/absence of the intermediate plate pressure Pa.
Although not shown, a relationship between the restoring force and the retard pressure in the second earlier technology is substantially the same as that in the first earlier technology. The reason is that the sheet feeding pressure of the sheet feeding roller is released from the sheets stacked on the intermediate plate by entering the fed sheet into the nip of the pair of draw rollers in the second earlier technology. This means that the intermediate plate is still urged against the sheet feeding roller in the separating operation.
That is to say, there is the separating operation similar to that in the first earlier technology in which the intermediate plate pressure Pa affects an influence upon the relationship between the restoring force Ta of the separating roller and the retard pressure Pb during the separating operation. Thus, the relationship between the restoring force and the retard pressure in the second earlier technology becomes similar to that in the first earlier technology.
As mentioned above regarding the difference in appropriate sheet feeding area between the earlier technologies and the present invention, the present invention can widen the appropriate sheet feeding area in comparison with the earlier technologies. Thus, the reliable and stable sheet feeding and separating operations can be realized.
Further, since the intermediate plate
70
can be retracted from the sheet feeding roller
51
before the fed sheet S reaches the pair of draw rollers
55
and, in this case, since the restoring force of the separating roller
53
can be applied to the sheet, the sheet(s) double-fed in the sheet feeding operation can surely be restored, thereby achieving high reliable sheet feeding.
When the sheet S is fed by the pair of draw rollers
55
, since the intermediate plate
70
is already retracted from the sheet feeding roller
51
, the feeding load due to the intermediate plate pressure does not act on the pair of draw rollers
55
, thereby improving the service life of the draw rollers.
Further, in the normal state, since the intermediate plate
70
is retracted from the sheet feeding roller
51
, when the operator sets the sheet bundle, the setting is not obstructed. When the operator sets the sheets, since he may merely abut the leading end of the sheet bundle against the abutment plate
78
, the setting operation is very easy, thereby reducing sheet jamming and skew-feeding due to a poor setting.
Since the interlocking operation between the intermediate plate
70
and the sheet feeding means is controlled by the control gear
80
integrally formed with the cam
80
c
for controlling the intermediate plate
70
and the toothless portion
80
a
or the control gear
101
integrally formed with the cam
101
c
and the nonengagement portions
101
a,
101
b
and since the sheet feeding timing and the timing for applying and releasing the pressure of the intermediate plate
70
are determined by the phase angle between the toothless portion
80
a
and the cam
80
c
or the phase angle between the nonengagement portions
101
a,
101
b
and the cam
101
c,
there is few factors for dispersion, thereby achieving the stable sheet feeding and separating operation with low cost.
Further, since the control for rotation and stoppage of the sheet feeding roller
51
and the application and release of the pressure of the intermediate plate
70
can be effected by one ON signal and one OFF signal for the solenoid
69
, the control is very easy and the severe control accuracy is not requested.
Furthermore, when the pair of draw rollers
55
are synchronized with the drive shaft
54
of the separating roller
53
, since the control is effected by the single draw clutch
60
, the apparatus can be simplified, and, since the rollers
55
and the shaft
54
can be driven independently from the rotation of the sheet feeding means, a sheet feeding apparatus having high double-feed preventing ability can be provided.
When the drive transmission between the sheet feeding roller
51
and the separating roller
53
is effected by using the connecting means, by drivingly connecting the shaft
54
of the separating roller
53
to the sheet feeding roller support shaft
52
, means such as a one-way clutch for regulating the rotational direction can be omitted, thereby making the sheet feeding apparatus inexpensive; and, by rotatingly driving the sheet feeding roller
51
by the sheet drawn by the pair of draw rollers
55
, since the shaft
54
of the separating roller
53
can always be rotated in the restoring direction, the separating ability can be improved.
Further, in the state that the nonengagement portion
101
a
of the control gear
101
is opposed to the sheet feeding drive stage gear
100
, although the slight rotational resistance of the torque limiter
62
acts on the sheet feeding roller
51
and the separating roller
53
, these rollers can freely be rotated in both directions. Thus, the jammed sheet can be pulled both in the sheet feeding direction and in the opposite direction, thereby improving the sheet jamming treating ability greatly.
Incidentally, in the above-mentioned embodiment and its alteration, while an example that one revolution of the control gear
80
is controlled by the spring clutch
68
is explained, the present invention is not limited to such an example, but, for example, a stepping motor may be used as the sheet feeding motor M
2
to control one revolution.
Further, in the above-mentioned embodiment and its alteration, while an example that the sheet feeding means and the intermediate plate
70
are driven by the sheet feeding motor M
1
and the pair of draw rollers
55
and the separating roller
53
are driven by the draw motor M
2
is explained, the present invention is not limited to such an example, but the driving force may be distributed from motors for driving the photosensitive drum
12
and the fixing unit
22
.
Further, in the above-mentioned embodiment and its alteration, while an example that the torque limiter
62
is provided on the separating roller
53
to apply to the separating roller
53
the predetermined torque directing toward the direction opposite to the sheet feeding direction is explained, the present invention is not limited to the torque limiter
62
so long as such torque can be applied to the separating roller
53
.
In the above-mentioned embodiment and its alteration, while an example that the present invention is applied to the multisheet feeding porion is explained, of course, the present invention can be applied to a cassette sheet feeding portion or a deck sheet feeding portion.
Lastly, in the above-mentioned embodiment and its alteration, while an example that the sheet feeding apparatus according to the present invention is applied to the copying machine as the image forming apparatus is explained, the present invention is not limited to such an example, but, for example, the present invention can be applied to an image reading apparatus by providing an image reading portion at a downstream side of the sheet feeding apparatus according to the present invention in the sheet feeding direction.
Claims
- 1. A sheet feeding apparatus comprising:movable sheet supporting means for supporting a sheet; a sheet feeding roller for urging against the sheet supported by said sheet supporting means and rotating in a sheet feeding direction to feed the sheet; a separating roller opposed to said sheet feeding roller and rotatable in a sheet restoring direction to separate the sheet fed from said sheet feeding roller, wherein said separating roller urges against said sheet feeding roller; conveying means disposed downstream of a separating portion, in which said sheet feeding roller is in pressure contact with said separating roller, in the sheet feeding direction for conveying the sheet fed from said sheet feeding roller; and pressing and retracting means for moving said sheet supporting means to place the sheet supported by said sheet supporting means into pressure contact with said sheet feeding roller and to release the pressure contact between said sheet feeding roller and the sheet, wherein said pressing and retracting means moves said sheet supporting means to separate the sheet, which has been in pressure contact with said sheet feeding roller, from said sheet feeding roller to release the pressure contact between said sheet feeding roller and the sheet after a leading end of the sheet reaches said separating portion and before the leading end of the sheet reaches said conveying means.
- 2. A sheet feeding apparatus according to claim 1, wherein said separating roller has torque limiter means for imparting a predetermined torque to said separating roller.
- 3. A sheet feeding apparatus according to claim 1, wherein said separating roller is driven by a drive source for said conveying means.
- 4. A sheet feeding apparatus according to claim 1, further comprising:drive transmitting means for transmitting a rotational driving force to said sheet feeding roller to rotate said sheet feeding roller, said drive transmitting means including a partially toothless gear to which the rotational driving force is imparted and a sheet feeding drive gear engageable with said partially toothless gear for rotating said sheet feeding roller.
- 5. A sheet feeding apparatus according to claim 4, further comprising:a sheet feeding roller shaft for supporting said sheet feeding roller; and connecting means for mechanically connecting said sheet feeding roller shaft to a separating roller shaft for rotatably supporting said separating roller to transmit a rotational force transmitted by said drive transmitting means to said separating roller to rotate said sheet feeding roller.
- 6. A sheet feeding apparatus according to claim 5, wherein said connecting means comprises pulley members attached to said sheet feeding roller shaft and said separating roller shaft.
- 7. A sheet feeding apparatus according to claim 5, wherein said connecting means comprises a gear train including a connecting gear provided on said sheet feeding roller shaft, a separating roller gear provided on said separating roller shaft, and an idler gear engaged by said connecting gear and said separating roller gear.
- 8. A sheet feeding apparatus according to claim 4, wherein said pressing and retracting means comprises a cam rotatably integral with said partially toothless gear and a cam follower provided on said sheet supporting means and engageable with and disengageable from said cam, and wherein said cam is rotated by a rotation of said partially toothless gear to be disengaged from and engaged with said cam follower to bring the sheet supported by said sheet supporting means into pressure contact with said sheet feeding roller and release the pressure contact.
- 9. A sheet feeding apparatus according to claim 8, wherein said pressing and retracting means comprises a rocking spring for imparting an urging force to said sheet supporting means in a direction urging said sheet supporting means against said sheet feeding roller, and wherein when said cam is engaged with said cam follower, the pressure contact between the sheet and said sheet feeding roller is released against the urging force of said rocking spring, and, when said cam is disengaged from said cam follower, the sheet is brought into pressure contact with said sheet feeding roller by the urging force of said rocking spring.
- 10. A sheet feeding apparatus according to claim 4, wherein said drive transmitting means comprises a stage gear, including first and second sector gears, and two sheet feeding drive gears rotatably integral with said sheet feeding roller, each engageable with a respective sector gear, and wherein rotation of said stage gear transmits a driving force to said two gears rotatable integrally with said sheet feeding roller to a rotating speed of said sheet feeding roller is changed by transmitting a rotation of said stage gear to said sheet feeding drive gears as said sheet feeding roller is rotated.
- 11. A sheet feeding apparatus according to claim 10, wherein said first sector gear has a small diameter and a small angle and said second sector gear has a large diameter and a large angle, and one of said two sheet feeding drive gears comprises a large diameter gear engaged with said first sector gear, and the other of said two sheet feeding drive gears comprises a small diameter gear engageable with said second sector gear, and wherein when said stage gear is rotated, said first sector gear is engaged with said large diameter gear to rotate said sheet feeding roller at a first feeding speed to thereby feed out the sheet on said sheet supporting means and subsequently said second sector gear is engaged with said small diameter gear to rotate said sheet feeding roller at a second feeding speed higher than the first feeding speed to thereby further feed the fed-out sheet.
- 12. A sheet feeding apparatus according to claim 11, wherein the second feeding speed is equal to a sheet conveying speed of said conveying means.
- 13. An image forming apparatus comprising:movable sheet supporting means for supporting a sheet; a sheet feeding roller for urging against the sheet supported by said sheet supporting means and rotating in a sheet feeding direction to feed the sheet; a separating roller opposed to said sheet feeding roller and rotatable in a sheet restoring direction to separate the sheet fed from said sheet feeding roller, wherein said separating roller urges against said sheet feeding roller; conveying means disposed downstream of a separating portion, in which said sheet feeding roller is in pressure contact with said separating roller, in the sheet feeding direction for conveying the sheet fed from said sheet feeding roller; image forming means for forming an image on the sheet conveyed by said conveying means; and pressing and retracting means for moving said sheet supporting means to place the sheet supported by said sheet supporting means into pressure contact with said sheet feeding roller and to release the pressure contact between said sheet feeding roller and the sheet, wherein said pressing and retracting means moves said sheet supporting means to separate the sheet, which has been in pressure contact with said sheet feeding roller, from said sheet feeding roller to release the pressure contact between said sheet feeding roller and the sheet after a leading end of the sheet reaches said separating portion and before the leading end of the sheet reaches said conveying means.
- 14. An image reading apparatus comprising:movable sheet supporting means for supporting a sheet; a sheet feeding roller for urging against the sheet supported by said sheet supporting means and rotating in a sheet feeding direction to feed the sheet; a separating roller opposed to said sheet feeding roller and rotatable in a sheet restoring direction to separate the sheet fed from said sheet feeding roller, wherein said separating roller urges against said sheet feeding roller; conveying means disposed downstream of a separating portion, in which said sheet feeding roller is in pressure contact with said separating roller, in the sheet feeding direction for conveying the sheet fed from said sheet feeding roller; image reading means for reading image information on the sheet conveyed by said conveying means; and pressing and retracting means for moving said sheet supporting means to place the sheet supported by said sheet supporting means into pressure contact with said sheet feeding roller and to release the pressure contact between said sheet feeding roller and the sheet, wherein said pressing and retracting means moves said sheet supporting means to separate the sheet, which has been in pressure contact with said sheet feeding roller, from said sheet feeding roller to release the pressure contact between said sheet feeding roller and the sheet after a leading end of the sheet reaches said separating portion and before the leading end of the sheet reaches said conveying means.
Priority Claims (2)
Number |
Date |
Country |
Kind |
10-291961 |
Oct 1998 |
JP |
|
11-132397 |
May 1999 |
JP |
|
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