U.S. patent application number 12/844902 was filed with the patent office on 2011-02-03 for sheet feeding apparatus and image forming apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Hirofumi Hori, Akira Matsushima, Hitomi Suzuki, Yasuhiro Uchida.
Application Number | 20110024970 12/844902 |
Document ID | / |
Family ID | 43526243 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110024970 |
Kind Code |
A1 |
Uchida; Yasuhiro ; et
al. |
February 3, 2011 |
SHEET FEEDING APPARATUS AND IMAGE FORMING APPARATUS
Abstract
A sheet feeding apparatus including: a separation claw for
restraining both end portions of leading edges of sheets in a width
direction orthogonal to a sheet feeding direction, the sheets
having reached a sheet feeding position, and separating, one by
one, the sheets fed by a pickup roller; and a photosensor detecting
that the separation claw has reached a separation position for
separating the sheets when a sheet stacking board is raised to
detect that the sheets have reached the sheet feeding position, in
which the separation claw, which is movable in an up-and-down
direction, is moved to the separation position, the photosensor
detects that the sheets supported by the sheet stacking board have
reached the sheet feeding position of being feedable by the pickup
roller, by rise of the sheet stacking board.
Inventors: |
Uchida; Yasuhiro;
(Yokohama-shi, JP) ; Hori; Hirofumi; (Numazu-shi,
JP) ; Matsushima; Akira; (Susono-shi, JP) ;
Suzuki; Hitomi; (Yokohama-shi, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
1290 Avenue of the Americas
NEW YORK
NY
10104-3800
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
43526243 |
Appl. No.: |
12/844902 |
Filed: |
July 28, 2010 |
Current U.S.
Class: |
271/10.16 |
Current CPC
Class: |
B65H 1/14 20130101; B65H
3/06 20130101; B65H 2511/222 20130101; B65H 2511/20 20130101; B65H
2801/06 20130101; B65H 2511/20 20130101; B65H 2220/01 20130101;
B65H 2220/11 20130101; B65H 2220/02 20130101; B65H 2511/222
20130101; B65H 3/50 20130101; B65H 2220/11 20130101 |
Class at
Publication: |
271/10.16 |
International
Class: |
B65H 5/06 20060101
B65H005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2009 |
JP |
2009-181086 |
Claims
1. A sheet feeding apparatus configured to feed sheets, comprising:
a rising and lowering sheet supporting portion configured to
support the sheets; a raising and lowering mechanism configured to
raise and lower the sheet supporting portion; a feed roller
configured to feed out an uppermost sheet of the sheets supported
by the sheet supporting portion; a detecting portion configured to
detect the uppermost sheet of the sheets supported by the sheet
supporting portion; a separation claw, which is movable up and down
and configured to separate, one by one, the sheets fed by the feed
roller, by restraining a side end of leading edges of the sheets in
a width direction orthogonal to a sheet feeding direction; and a
control portion configured to control the raising and lowering
mechanism based on a detection by the detecting portion, wherein
the detecting portion is arranged to detect a position of the
separation claw, and the control portion controls the raising and
lowering mechanism based on the detection by the detecting portion
so that the uppermost sheet of the sheets supported by the sheet
supporting portion is located at a position of being feedable by
the feed roller.
2. A sheet feeding apparatus according to claim 1, further
comprising an air blowing portion configured to blow air to
trailing edges of the sheets supported by the sheet supporting
portion, wherein leading edge portions of the sheets in which the
air is blown to the trailing edges by the air blowing portion are
held down by the separation claw.
3. A sheet feeding apparatus according to claim 1, further
comprising a pair of regulating members configured to regulate
positions of the sheets in the width direction, the sheets being
supported by the sheet supporting portion, wherein the separation
claw is provided on each of the pair of regulating members so as to
move in an up-and-down direction.
4. A sheet feeding apparatus according to claim 3, wherein the
detecting portion is provided on each of the pair of regulating
members, the raising and lowering mechanism comprises two raising
and lowering mechanisms, which support, raise and lower both ends
of the sheet supporting portion in the width direction,
respectively, and when raising the sheet supporting portion, the
control portion stops drive of each of the two raising and lowering
mechanisms in response to detection of the separation claw by the
detecting portion provided on each of the pair of regulating
members.
5. An image forming apparatus comprising a sheet feeding apparatus
configured to feed sheets and an image forming portion configured
to form an image on each of the sheets fed by the sheet feeding
apparatus, the image forming apparatus comprising: a rising and
lowering sheet supporting portion configured to support the sheets;
a raising and lowering mechanism configured to raise and lower the
sheet supporting portion; a feed roller configured to feed out an
uppermost sheet of the sheets supported by the sheet supporting
portion; a detecting portion configured to detect the uppermost
sheet of the sheets supported by the sheet supporting portion; a
separation claw, which is movable up and down and configured to
separate, one by one, the sheets fed by the feed roller, by
restraining a side end portion of leading edges of the sheets in a
width direction orthogonal to a sheet feeding direction; and a
control portion configured to control the raising and lowering
mechanism based on a detection by the detecting portion, wherein
the detecting portion is arranged to detect a position of the
separation claw, and the control portion controls the raising and
lowering mechanism based on the detection by the detecting portion
so that the uppermost sheet of the sheets supported by the sheet
supporting portion is located at a position of being feedable by
the feed roller.
6. An image forming apparatus according to claim 5, further
comprising an air blowing portion configured to blow air to
trailing edges of the sheets supported by the sheet supporting
portion, wherein leading edge portions of the sheets in which the
air is blown to the trailing edges by the air blowing portion are
held down by the separation claw.
7. An image forming apparatus according to claim 5, further
comprising a pair of regulating members configured to regulate
positions of the sheets in the width direction, the sheets being
supported by the sheet supporting portion, wherein the separation
claw is provided on each of the pair of regulating members so as to
move in an up-and-down direction.
8. An image forming apparatus according to claim 7, wherein the
detecting portion is provided on each of the pair of regulating
members, the raising and lowering mechanism comprises two raising
and lowering mechanisms, which support, raise and lower both ends
of the sheet supporting portion in the width direction,
respectively, and when raising the sheet supporting portion, the
control portion stops drive of each of the two raising and lowering
mechanisms in response to detection of the separation claw by the
detecting portion provided on each of the pair of regulating
members.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sheet feeding apparatus
and an image forming apparatus, in particular, a sheet feeding
apparatus and an image forming apparatus, which separate sheets one
by one by using a separation claw and feed the separated
sheets.
[0003] 2. Description of the Related Art
[0004] In recent years, an image forming apparatus such as a
printer, a copying machine, or a facsimile machine includes a sheet
feeding apparatus for separating sheets one by one and feeding the
separated sheets to an image forming portion. As the
above-mentioned sheet feeding apparatus, for example, there is
known an apparatus configured to raise and lower a sheet supporting
portion, which has the sheets stacked thereon, by drive from a
driving source such as a motor. In the sheet feeding apparatus, the
sheet supporting portion is raised so that an uppermost sheet of
the stacked sheets can be located at a position in a height
direction (that is, sheet feeding position), where it becomes
possible to feed the sheets by a feed roller.
[0005] Then, in order to continuously feed the sheets, it is
necessary to keep the height of the uppermost sheet on the sheet
supporting portion, at such a height (sheet feeding position) at
which the uppermost sheet can be fed by the feed roller. Therefore,
heretofore, the sheet feeding apparatus is provided with an optical
sensor and a sensor flag. The sensor flag pushed up by the
uppermost sheet shields the optical sensor from sensor light, to
thereby detect that the uppermost sheet has reached the sheet
feeding position. Then, the optical sensor detects that the height
of the uppermost sheet is lowered from the sheet feeding position
as a result that the sheets are fed, and based on such detection,
the rise of the sheet supporting portion is controlled so that the
height of the uppermost sheet can be maintained at the sheet
feeding position. This technology is disclosed in Japanese Patent
Application Laid-Open No. 2003-165633.
[0006] Further, heretofore, as a sheet feeding apparatus configured
to feed sheets prone to be adhered to one another, there has been
an apparatus including a mechanism for loosening a sheet bundle,
which is stacked in order to be fed, by blowing air thereto. In
this case, in order to enable surely a feed of the sheets prone to
be adhered to one another, for example, air is blown by air blowing
means to a side end of an upper portion of the sheet bundle stacked
on the sheet supporting portion, and air is allowed to pass through
among the sheets, so that the sheets are released from being
adhered to one another. Note that, in the sheet feeding apparatus
as described above, a sheet holding-down member for suppressing
flotation of the sheets to which air is blown is provided. This
technology is disclosed in Japanese Patent Application Laid-Open
No. 2008-87906.
[0007] However, in the conventional sheet feeding apparatus, when
the sheets are sequentially fed, a height of the sheet bundle is
thereby lowered, and following this, the sensor light of the
optical sensor becomes unshielded, then the sheet supporting
portion rises. At this time, when air is blown to trailing edges of
the sheets, a sheet surface against which the sensor flag abuts
floats up because the sheet holding-down member is arranged at a
position apart from the sheet surface. Then, in a case where the
sheet surface against which the sensor flag abuts floats up as
described above, then the sensor flag is pushed up, the sensor
light becomes shielded before the uppermost sheet reaches the sheet
feeding position, and the uppermost sheet cannot be held at the
sheet feeding position.
[0008] Further, for example, in a case where leading edge portions
of the sheets stacked on the sheet supporting portion are curled
upward, a height of the sheet surface against which the sensor flag
abuts and a surface height of the leading edges of the sheets
differ from each other. In this case, when a height of the sheet
supporting portion is controlled based on a signal from the optical
sensor, the leading edges of the sheets become located more upward
than the sheet feeding position in terms of height. Therefore, when
the sheets are fed in this state, there is apprehension that the
leading edges of the sheets cannot smoothly enter a nip between
conveyor rollers located downstream thereof resulting in sheet
jamming.
SUMMARY OF THE INVENTION
[0009] In view of the above-mentioned circumstances, the present
invention has been made, and therefore, it is an object of the
present invention to provide a sheet feeding apparatus and an image
forming apparatus, which are capable of surely detecting that the
sheets have reached the sheet feeding position.
[0010] According to the present invention, there is provided a
sheet feeding apparatus configured to feed sheets, including:
[0011] a rising and lowering sheet supporting portion configured to
support the sheets;
[0012] a raising and lowering mechanism configured to raise and
lower the sheet supporting portion;
[0013] a feed roller configured to feed out an uppermost sheet of
the sheets supported by the sheet supporting portion;
[0014] a detecting portion configured to detect the uppermost sheet
of the sheets supported by the sheet supporting portion;
[0015] a separation claw, which is movable up and down and
configured to separate, one by one, the sheets fed by the feed
roller, by restraining a side end of leading edges of the sheets in
a width direction orthogonal to a sheet feeding direction; and
[0016] a control portion configured to control the raising and
lowering mechanism based on a detection by the detecting
portion,
[0017] wherein the detecting portion is arranged to detect a
position of the separation claw, and the control portion controls
the raising and lowering mechanism based on the detection by the
detecting portion so that the uppermost sheet of the sheets
supported by the sheet supporting portion is located at a position
of being feedable by the feed roller.
[0018] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a view illustrating a schematic configuration of a
laser beam printer as an example of an image forming apparatus
including a sheet feeding apparatus according to a first embodiment
of the present invention.
[0020] FIG. 2 is a view illustrating a configuration of a sheet
feeding deck as the sheet feeding apparatus.
[0021] FIG. 3 is a block diagram for performing control of a sheet
stacking board provided in the sheet feeding apparatus.
[0022] FIG. 4 is a view illustrating a separation claw provided on
the sheet feeding deck.
[0023] FIG. 5 is a view illustrating a configuration of a sheet
feeding deck as a sheet feeding apparatus according to a second
embodiment of the present invention.
[0024] FIG. 6 is a view illustrating another configuration of the
sheet feeding deck.
DESCRIPTION OF THE EMBODIMENTS
[0025] A description will be provided below in detail of
embodiments for implementing the present invention with reference
to the accompanying drawings. FIG. 1 is a view illustrating a
schematic configuration of a laser beam printer as an example of an
image forming apparatus including a sheet feeding apparatus
according to a first embodiment of the present invention. In FIG.
1, the laser beam printer 1, a laser beam printer main body 1A
(hereinafter referred to as a printer main body), and a deck-type
sheet feeding apparatus 2 (hereinafter referred to as a sheet
feeding deck) mounted under the printer main body 1A are
illustrated. An image forming portion 1B is provided in the printer
main body 1A, and forms an image by an electrophotographic method.
The image forming portion 1B includes: a photosensitive drum 14 on
which a toner image is formed; a laser exposure device 17 as a
laser exposure optical system configured to irradiate the
photosensitive drum 14 with a laser beam according to an image
signal; and a transfer roller 15 configured to transfer, to a sheet
S, the toner image formed on the photosensitive drum 14. The
photosensitive drum 14 is incorporated in a process cartridge 13
detachably mounted to the printer main body 1A. In a lower portion
of the printer main body 1A, a cassette 20 configured to stack and
contain the sheets S therein is detachably mounted to the printer
main body 1A, and the sheets S contained in the cassette 20 are
appropriately fed out in order from an uppermost one by a pickup
roller 21 provided in the printer main body 1A.
[0026] In FIG. 1, a feed roller 23 is provided in the printer main
body 1A, and a retard roller 24 rotates at a predetermined torque
through a torque limiter (not shown) in a direction of returning
the sheets conveyed by the feed roller 23. By the feed roller 23
and the retard roller 24 provided in the printer main body 1A, the
sheets S fed out by the pickup roller 21 are separated and fed one
by one. Pairs of conveyor rollers 11 and 12 are provided in the
printer main body 1A, and the pairs of conveyor rollers 11 and 12
sequentially receive the sheets S fed by the feed roller 23, and
convey the received sheets S toward a registration roller pair 25.
The sheet S on which a toner image is transferred is subjected to
heating and pressing treatments at the time of passing through a
fixing device 16, so that the toner image is fixed to the sheet
S.
[0027] In the laser beam printer 1 configured as described above,
when an image forming operation is started, first, the
photosensitive drum 14 is irradiated with light according to the
image signal by the laser exposure device 17, and then a latent
image is formed on the photosensitive drum by such irradiation of
the light according to the image signal. Next, this latent image is
developed by toner contained in the process cartridge 13, to
thereby form the toner image (visible image) on the photosensitive
drum. In parallel with such a toner image forming operation, for
example, the sheets S stacked on the cassette 20 are fed out in
order from the uppermost one by the rotation of the pickup roller
21. After that, the sheets S are separated and conveyed one by one
by a separation portion including the feed roller 23 and the retard
roller 24.
[0028] After that, the sheet S fed by the feed roller 23 is
conveyed toward the standstill registration roller pair 25 by the
pairs of conveyor rollers 11 and 12 provided in the printer main
body 1A, and then leading edge of the sheet S is allowed to abut
against a nip portion of the registration roller pair 25 so that a
loop is formed in the sheet S, to thereby correct the skew feed of
the sheet S. After that, the registration roller pair 25 starts to
rotate in synchronization with the image formed on the
photosensitive drum 14, and conveys the sheet S to a nip portion
between the photosensitive drum 14 and the transfer roller 15
opposite thereto. Further, when the sheet S is fed from the sheet
feeding deck 2 configured as described later, the sheet S is also
conveyed to a transfer portion comprising the photosensitive drum
14 and the transfer roller 15, by the registration roller pair 25
in synchronization with the image formed on the photosensitive drum
14. In the transfer portion, a bias is applied to the transfer
roller 15, so that the toner image is transferred to the sheet S
which comes from the cassette 20 or to the sheet S which comes from
the sheet feeding deck 2. After that, the sheet S on which the
toner image is thus transferred is conveyed to the fixing device
16, and is pressed and heated in the fixing device 16, so that the
toner image is fixed thereto. After that, the sheet S is delivered
by a delivery roller 18 to a delivery tray 19 provided in an upper
portion of the printer main body.
[0029] The sheet feeding deck 2 includes a sheet stacking board 55
that is provided, as being capable of rising and lowering, in a
sheet storage 2a as a sheet containing portion configured to
contain the sheets S therein, and is a sheet supporting portion
configured to stack and support a bundle of the sheets S. Further,
the sheet feeding deck 2 includes a trailing edge regulating plate
56 configured to regulate a position of a trailing edge as an
upstream side edge of a sheet bundle Sa in a sheet feeding
direction. Here, the sheet bundle Sa is stacked on the sheet
stacking board 55. Further, the sheet feeding deck 2 includes a
door 2c to be opened at the time of stacking the sheet bundle Sa on
the sheet stacking board 55. The door 2c is arranged on a front
side of the printer main body 1A. When the door 2c is opened, the
sheets S can be loaded and unloaded from an operation side of the
printer main body 1A.
[0030] Further, as illustrated in FIG. 2, the sheet feeding deck 2
includes side regulating plates 57 and 58 as a pair of regulating
members configured to regulate a position of the sheet bundle Sa in
a width direction orthogonal to the sheet feeding direction. Here,
the sheet bundle Sa is stacked on the sheet stacking board 55. The
sheet stacking board 55 is suspended through wires 60a to 60d, each
having an end fixed to a wire winding shaft 59. By rotating the
wire winding shaft 59 forward and reverse by a raising and lowering
motor (not shown), the wires 60a to 60d are wound in and wound off,
to thereby move (raise and lower) the stacking board 55 in an
up-and-down direction. In this embodiment, a raising and lowering
mechanism 60 configured to raise and lower the sheet stacking board
55 includes: the raising and lowering motor (not shown); the wires
60a to 60d; and the wire winding shaft 59.
[0031] Further, the sheet feeding deck 2 includes a sheet feeding
portion 2b configured to feed out an uppermost sheet S1 of the
sheet bundle Sa stacked on the sheet stacking board 55. The sheet
feeding portion 2b includes a pickup roller 51 as a feed roller
configured to feed out the sheets S1, which are stacked on the
sheet feeding board 55, in order from the uppermost one. Further,
the sheet feeding portion 2b includes: a feed roller 52 and a
retard roller 53, which serve as a separation portion configured to
separate and feed one by one the sheets S1 fed out by the pickup
roller 51; and a conveyor roller 54 configured to convey the sheet
S1, which is separated one by one by the separation portion, to the
printer main body 1A. Still further, in the vicinity of the
trailing edge regulating plate 56, a fan 30 as an air blowing
portion configured to blow air toward a trailing edge of an upper
portion (in the vicinity of the uppermost sheet S1) of the sheet
bundle Sa is arranged.
[0032] Further, as illustrated in FIG. 2, a drive gear 103 is
driven by a drive motor Md illustrated in FIG. 3, and the drive
gear 103 is fixedly attached to a roller shaft 104. Then, at the
time of feeding the sheets, the drive gear 103 is driven, to
thereby rotate the roller shaft 104. Following the rotation of the
roller shaft 104, a moment in a direction of allowing the pickup
roller 51 to abut against the sheets S1 is generated in a pick arm
106 from the roller shaft 104 taken as a fulcrum. In this manner,
the pickup roller 51 rotatably held on a rotation end of the pick
arm 106 abuts against the sheets S1. By reverse rotation of the
roller shaft 104, a moment in a direction of moving the pickup
roller 51 to be spaced apart from the sheets S1 is generated in the
pick arm 106, and the pickup roller 51 is spaced apart from the
sheets S1.
[0033] Further, a sheet feeding pressure is changed depending on a
friction coefficient between the sheet S1 and the pickup roller 51,
and a reaction force acts on the pickup roller 51 in a direction
reverse to the sheet feeding direction, by reaction force from the
sheet S1 at the time of feeding the sheet. Then, the roller shaft
104 (rotation fulcrum) of the pick arm 106 is arranged upstream in
the sheet feeding direction, and hence a component force in a
direction of being brought into pressure contact with the sheet S1
is generated in the pickup roller 51 by the reaction force that
acts on the pickup roller 51. The sheet feeding pressure is set
based on the component force and the own weight of the pickup
roller 51. Therefore, a force by which the pickup roller 51 is
brought into pressure contact with the sheet at the time of feeding
the sheet S1 is changed depending on the friction coefficient
between the sheets S1 and the pickup roller 51. For example, for
the sheets S1 in which a friction coefficient thereamong is small
and feeding with small feeding force is necessary, the sheet
feeding pressure is also reduced, and double feeding becomes less
likely to occur. On the contrary, for the sheets S1 in which the
friction coefficient thereamong is large and a large feeding force
is necessary, the sheet feeding pressure is also increased, and an
occurrence of a feeding failure of the sheets can be prevented. As
described above, the sheet feeding pressure with which the pickup
roller 51 abuts against the sheets S1 is generated in such a manner
that the pickup roller 51 is brought into pressure contact with the
sheet S1 by the moment generated in the pick arm 106 when a driving
force is transmitted to the pick arm 106 and the reaction force
when the pickup roller 51 feeds the sheet S1.
[0034] Then, in the sheet feeding deck 2 configured as described
above, when the stacking of the sheet bundle Sa onto the sheet
stacking board 55 is ended, and the door 2c is closed, a detection
sensor (not shown) detects the close of the door 2c. Based on the
detection of the detection sensor, a control portion C illustrated
in FIG. 3 rotates a raising and lowering motor ML. In this manner,
the wire winding shaft 59 rotates so that the wires 60a to 60d are
wound in, and the sheet stacking board 55 is raised. After moving
to a position capable of feeding the uppermost sheet S1, the sheet
stacking board 55 is controlled to rise and lower, so as to
maintain the position, by the control portion C based on a signal
coming from a photosensor 61 to be described later. After that, the
feeding of the sheets S1 is started by the pickup roller 51 that
has abutted against the sheets S1 raised to the position
(hereinafter referred to as a sheet feeding position) capable of
feeding the sheets S1 by the pickup roller 51. Note that, the sheet
feeding position is located within a certain range in the height
direction capable of feeding the sheets, and if the uppermost sheet
is located within the range, it is possible to feed the uppermost
sheet because the sheet feeding pressure generated between the
pickup roller 51 and the uppermost sheet remains within the range
capable of feeding the sheets. Here, in a case of feeding the
sheets S1, first, air is blown to the trailing edge of the upper
portion of the sheet bundle Sa by the fan 30, so that end portions
of the sheets are floated up (lifted by the blown air). After that,
the uppermost sheet S1 of the sheet bundle Sa stacked on the sheet
stacking board 55 is fed out by the pickup roller 51, and after
that, the sheets in the sheet bundle Sa are separated one by one by
the separation portion, followed by feeding, and further, are
conveyed to the printer main body 1A by the conveyor roller 54.
[0035] By the way, as illustrated in FIG. 2, the side regulating
plates 57 and 58 are provided with, a pair of separation claws 101
and 102, which are arranged so as to be engaged with both corner
portions as both end portions of the leading edges (downstream
edges in the sheet feeding direction) of the sheets in the width
direction. Those separation claws 101 and 102 separate the sheets
by using deflection of the sheets, which is caused by stiffness
thereof. Specifically, when the each of sheets is fed out by the
pickup roller 51, both corner portions of the leading edge of the
sheet are restrained by the separation claws 101 and 102, and the
sheet in which the leading edge is restrained is deflected at both
corner portions. When the deflection reaches a predetermined amount
or more, the leading edge flicks and climbs over the separation
claws 101 and 102. As a result, one sheet is separated from the
others. Note that, upward movements of the separation claws 101 and
102 are restricted by stoppers 57a and 58a so that the separation
claws 101 and 102 can flick out one sheet while deflecting the one
sheet at the time of the separation thereof. The stoppers 57a and
58a are formed on the side regulating plates 57 and 58 in this
embodiment. Further, after elastically flicking out of the
separation claws 101 and 102 as described above, the sheet S is fed
to the separation portion including the feed roller 52 and the
retard roller 53.
[0036] Here, in this embodiment, the separation claws 101 and 102
are provided to the side regulating plates 57 and 58 so as to be
swingable (movable) in the up-and-down direction through a swing
shaft (not shown). Further, on the side regulating plate 58 as one
of the pair, the photosensor 61 is provided, which is a detecting
portion configured to detect that the uppermost sheet S1 of the
sheet bundle Sa has reached the sheet feeding position. Note that,
in a case where the uppermost sheet S1 has reached the sheet
feeding position as described above, when the uppermost sheet S1 is
fed by the pickup roller 51, the uppermost sheet S1 can smoothly
enter a nip (hereinafter referred to as a separation nip) between
the feed roller 52 and the retard roller 53. Further, on one-side
swing ends of the separation claws 101 and 102, claw portions 101a
and 102a which are engaged with corner portions of the sheets are
provided. Further, in this embodiment, on the other-side swing end
of the separation claw 101 as one of the pair, a sensor light
shielding portion 101b configured to shield sensor light of the
photosensor 61 is provided.
[0037] Here, in this embodiment, in the separation claws 101 and
102, the claw portions 101a and 102a are located at lower positions
until the sheet stacking board 55 is raised. At this time, the
sensor light shielding portion 101b of the separation claw 101 as
one of the pair has moved to a position of not shielding the sensor
light of the photosensor 61, the position being located above the
photosensor 61. In this state, when the sheet stacking board 55 is
raised, the corner portions of the uppermost sheet S1 and the claw
portions 101a and 102a are shortly engaged with each other, and
after that, the separation claws 101 and 102 swing while the claw
portions 101a and 102a are raised together with the sheets on the
sheet stacking board.
[0038] When the separation claws 101 and 102 swing as described
above, the separation claws 101 and 102 move in time to separation
positions of separating the sheets fed by the pickup roller 51. At
the separation positions, the separation claws 101 and 102 abut
against the above-mentioned stoppers 57a and 58a which restrict the
upward movement thereof. Then, when the separation claws 101 and
102 move to the separation positions as described above, the sensor
light shielding portion 101b provided on the separation claw 101
shields the sensor light of the photosensor 61, and the photosensor
61 outputs a trigger signal. Based on this trigger signal, the
control portion C determines that the uppermost sheet S1 has moved
to the sheet feeding position, and stops the raising and lowering
motor ML, to thereby stop the rise of the sheet stacking board 55.
In this manner, the sheet feeding deck 2 completes feeding
preparation thereof, and turns to a standby state. When a feeding
start signal is sent from the printer main body 1A to the sheet
feeding deck 2 after the sheet feeding deck 2 turns to the standby
state, the control portion C controls the drive motor Md of the
feeding portion of the sheet feeding deck 2, and rotates the pickup
roller 51, to thereby start a feeding operation of the sheet. At
this time, the drive of the fan 30 is started, and air is blown to
the trailing edge of the upper portion of the sheet bundle Sa on
the sheet stacking board, so that adherence between the uppermost
sheet S1 and the sheet in the vicinity thereof is released.
[0039] By the way, the sheet feeding operation is repeated so that
the sheets are sequentially fed, with the result that a height of
the sheet bundle Sa is lowered, and following this, the separation
claws 101 and 102 gradually swing in a direction in which the claw
portions 101a and 102a lower. Then, when the separation claws 101
and 102 swing as described above, the sensor light shielding
portion 101b provided on the separation claw 101 is raised, and
then, becomes unshielding the sensor light of the photosensor 61.
In this manner, the control portion C detects that the uppermost
sheet S1 has lowered in position than the sheet feeding position,
and drives the raising and lowering motor ML of the raising and
lowering mechanism 60 to raise the sheet stacking board 55 so that
the uppermost sheet S1 can be maintained at the sheet feeding
position. Though the sheets in the vicinity of the uppermost sheet
turn to a state of floating upward due to an influence of air blown
thereto from the fan 30 at this time, the leading edge portions of
the sheets, on which the separation claws 101 and 102 are arranged,
and particularly, the corner portions of the sheets are held in a
state of being adhered to one another by weight of the separation
claws 101 and 102. Specifically, in this embodiment, the separation
claws 101 and 102 also have a function to hold down the sheets for
the purpose of suppressing the flotation of the leading edge
portions of the sheets by air blown thereto by the fan 30. In other
words, even in a case where air is blown to the separation claws
101 and 102, the positions of the separation claws 101 and 102 are
not changed. Accordingly, if the positions of the separation claws
101 and 102 are detected, then the uppermost sheet S1 can be
maintained at the sheet feeding position without being affected by
the air.
[0040] As described above, in this embodiment, when the sheet
stacking board 55 is raised, the separation claws 101 and 102 which
have moved to the separation positions are detected, so that it can
be surely detected that the uppermost sheet has reached the sheet
feeding position. In other words, when the sheet stacking board 55
is raised, it is detected that the separation claws 101 and 102
have moved to the separation positions, so that it can be surely
detected that the uppermost sheet has reached the sheet feeding
position. Further, the sensor light shielding portion 101b is
provided on any one of the separation claws 101 and 102 as in this
embodiment, to thereby increase an amount of the stacked sheets as
compared with the case of providing the sensor light shielding
portion above the sheets. Further, in this embodiment, the
photosensor is used for detecting the position of the uppermost
sheet, however, other detection units may also be applicable as
long as similar effects can be obtained.
[0041] Though the sheets are separated by the separation claws 101
and 102 in this embodiment, the sheets do not sometimes come out of
the separation claws 101 and 102 if engaging amounts of the
separation claws 101 and 102 with respect to the sheets are
increased. Therefore, in order that the sheets can surely come out
of the separation claws 101 and 102, it is preferred to reduce the
engaging amounts of the separation claws 101 and 102 with respect
to the sheets. However, preferred engaging amounts differ depending
on types of the sheets. For example, in a case of special sheets
such as label sheets, which are perforated, if the engaging amounts
of the separation claws are reduced, such sheets are prone to be
bent at perforated portions. Therefore, at the time of feeding the
special sheets, the sheets cannot push back reaction force coming
from the separation claws 101 and 102 to thereby cause buckling on
the perforated portions, leading to a feeding failure.
[0042] Accordingly, in this embodiment, the perforated portions of
the perforated special sheets are covered with the separation claws
101 and 102, so that the reaction force coming from the separation
claws 101 and 102 may be received by portions other than the
perforated portions. In this embodiment, for example, as
illustrated in FIG. 4, an engaging amount Wb of the separation claw
101 in the sheet feeding direction is set at 3.5 times or more an
engaging amount Wa thereof in the sheet width direction. The same
applies to the separation claw 102 as the other of the pair.
Further, as illustrated in FIG. 2, the pickup roller 51 is provided
in the vicinity of the center in the width direction between the
pair of separation claws 101 and 102, and distances for ensuring a
sufficient sheet deflection amount are set between the pickup
roller 51 and the separation claw 101 and between the pickup roller
51 and the separation claws 102. With such a configuration, even
the perforated special sheets are not buckled at the perforated
portions, and can be stably separated and fed.
[0043] By the way, in the description above, the positions of the
separation claws are detected, to thereby hold the uppermost sheet
at the sheet feeding position without being affected by air blown
from the fan 30. However, the present invention is not limited to
this. For example, in some cases, sheets of which leading edges are
curled are stacked on the sheet stacking board. At this time, the
height of the sheet surface against which the sensor flag abuts and
the height of the sheet surface at the leading edges of the sheets
differ from each other as already mentioned. In this case, if the
height of the sheet stacking board 55 is controlled based on the
signal coming from the photosensor, the height of the leading edges
is located more upward than a nip (hereinafter referred to as a
separation nip) between the feed roller 52 and the retard roller
53, for example, in a case where the leading edges of the sheets
are curled upward. When the sheets are fed in this state, the
leading edges of the sheets cannot smoothly enter the separation
nip. However, even in a case of feeding the sheets in which the
leading edges are curled, the leading edges of the sheets can be
allowed to smoothly enter the separation nip if the positions of
the separation claws are detected.
[0044] FIG. 5 is a view illustrating a configuration of a sheet
feeding deck as described above as a sheet feeding apparatus
according to a second embodiment of the present invention. In FIG.
5, the same reference symbols as those already mentioned in FIG. 2
denote the same or equivalent portions. Further, a description of
the same operations as those in the first embodiment is omitted.
Here, until the sheet stacking board 55 is raised, the separation
claws 101 and 102 swing so that the claw portions 101a and 102a can
be located at lower positions. At this time, the sensor light
shielding portion 101b of the separation claw 101 as one of the
pair has moved to the position of not shielding the sensor light of
the photosensor 61, the position being located above the
photosensor 61. In this state, when the sheet stacking board 55 is
raised, for example, the corner portions of the uppermost sheet S1
in which the leading edge portion is curled upward and the claw
portions 101a and 102a are engaged with each other, so that the
separation claws 101 and 102 swing in the direction in which the
claw portions 101a and 102a is raised. When the separation claws
101 and 102 swing as described above, the sensor light shielding
portion 101b provided on the separation claw 101 shields the sensor
light of the photosensor 61, and the photosensor 61 outputs the
trigger signal.
[0045] Then, based on this trigger signal, a control portion (not
shown) detects that the uppermost sheet S1 of the stacked sheet
bundle Sa is moved to the sheet feeding position in which the
uppermost sheet S1 can be fed by the pickup roller 51 to smoothly
enter the separation nip. Then, the control portion stops the rise
of the sheet stacking board 55 based on the detection, to thereby
complete the feeding preparation. Then, the sheet feeding deck 2
turns to the standby state. Here, in this embodiment, the
separation claws 101 and 102 is raised in accordance with the rise
of the uppermost sheet S1 curled upward, and thus, the position
where the sheet stacking board 55 stops is a position where the
leading edge of the sheet can smoothly enter the separation nip.
Specifically, in a case of detecting the positions of the
separation claws 101 and 102 as in this embodiment, the sheet
stacking board 55 can be stopped at the position where the leading
edge of the sheet can smoothly enter the separation nip even if the
sheet is curled.
[0046] In the description above, the position control for the sheet
stacking board 55 is performed based on the position of the
separation claw 101 as one of the pair. However, the present
invention is not limited to this. For example, as illustrated in
FIG. 6, photosensors 61 and 62 may be provided on the two side
regulation plates 57 and 58, respectively, and the sensor light
shielding portions 101b and 102b may be provided on the other-side
swing ends of the two separation claws 101 and 102. Note that, in
this case, the wires 60a and 60b which support one of side end
portions of the sheet stacking board 55 are wound in or wound off
by a wire winding shaft 65. Further, the wires 60c and 60d which
support the other side end portion of the sheet stacking board 55
are wound in or wound off by a wire winding shaft 64. Specifically,
in a case where the photosensors 61 and 62 are provided to the side
regulating plates 57 and 58, respectively, two raising and lowering
mechanisms 60A and 60B are provided in order to raise and lower the
sheet stacking board 55.
[0047] With the configuration as described above, when the sheet
stacking board 55 is raised, the claw portions 101a and 102a are
engaged with the corner portions of the uppermost sheet S1 in which
the leading edge portion is curled upward, so that the separation
claws 101 and 102 swing in the direction in which the claw portions
101a and 102a is raised together with the uppermost sheet. When the
separation claws 101 and 102 swing as descried above, the sensor
light shielding portions 101b and 102b provided on the separation
claws 101 and 102 shield the sensor light of the photosensors 61
and 62, and the photosensors 61 and 62 output the trigger signals.
Based on the trigger signals, the control portion stops the raising
and lowering mechanisms 60A and 60B, so that the sheet stacking
board 55 can be stopped at the position where the uppermost sheet
S1 reaches the sheet feeding position.
[0048] Here, a curl amount sometimes differs between both corners
of the leading edge of the sheet. When the sheet is fed in this
state, then in some cases, the leading edge of the sheet does not
smoothly enter the separation nip, and the sheet is skew-fed.
However, even in a case where there is a difference in the curl
amount as described above, the drive of the two raising and
lowering mechanisms 60A and 60B is individually stopped in response
to the detection of the separation claws 101 and 102 by the
photosensors 61 and 62, to thereby control a rising and lowering
amount of the sheet stacking board 55 in the width direction. With
such a configuration, even in a case where the curl amount differs
between both corners of the leading edge of the sheet, both corners
of the leading edge of the sheet can be maintained at the sheet
feeding position, and as a result, the leading edge of the sheet
can be allowed to smoothly enter the separation nip without
skew-feeding the sheet.
[0049] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0050] This application claims the benefit of Japanese Patent
Application No. 2009-181086, filed Aug. 3, 2009, which is hereby
incorporated by reference herein in its entirety.
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