U.S. patent application number 13/711353 was filed with the patent office on 2013-06-20 for image forming apparatus.
The applicant listed for this patent is Naoichi ASAKURA, Kouki MURAMOTO. Invention is credited to Naoichi ASAKURA, Kouki MURAMOTO.
Application Number | 20130154180 13/711353 |
Document ID | / |
Family ID | 48582649 |
Filed Date | 2013-06-20 |
United States Patent
Application |
20130154180 |
Kind Code |
A1 |
ASAKURA; Naoichi ; et
al. |
June 20, 2013 |
IMAGE FORMING APPARATUS
Abstract
An image forming apparatus includes a sheet cassette, a sheet
feed roller, and a separating blade. An image forming section and a
sheet conveying path for conveying a sheet to the image forming
section are placed in a position within the width of a cassette
body defined in a sheet feeding direction and above the cassette.
The tip of the separating blade is placed in a portion of stacked
sheets accommodated in the cassette between a front end portion and
a rear end portion of the cassette. The sheet feed roller is placed
in a position between the front end portion and the rear end
portion of the cassette and apart from the tip of the separating
blade toward the rear end portion.
Inventors: |
ASAKURA; Naoichi;
(Shinshiro-shi, JP) ; MURAMOTO; Kouki;
(Toyohashi-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASAKURA; Naoichi
MURAMOTO; Kouki |
Shinshiro-shi
Toyohashi-shi |
|
JP
JP |
|
|
Family ID: |
48582649 |
Appl. No.: |
13/711353 |
Filed: |
December 11, 2012 |
Current U.S.
Class: |
271/10.11 ;
271/109; 271/126 |
Current CPC
Class: |
G03G 15/6511 20130101;
B65H 3/66 20130101; B65H 2601/523 20130101; B65H 2801/09 20130101;
B65H 2405/3322 20130101; B65H 5/062 20130101; B65H 3/50 20130101;
B65H 5/00 20130101; B65H 3/0623 20130101; B65H 3/54 20130101 |
Class at
Publication: |
271/10.11 ;
271/109; 271/126 |
International
Class: |
B65H 5/00 20060101
B65H005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2011 |
JP |
2011-274864 |
Claims
1. An image forming apparatus comprising: a sheet cassette
configured to accommodate stacked sheets; a separating member
configured to separate an uppermost sheet from the stacked sheets
accommodated in the sheet cassette; a sheet feed roller configured
to feed the uppermost sheet from the stacked sheets accommodated in
the sheet cassette; an image forming section configured to form an
image on the sheet fed from the sheet cassette; and a sheet
conveying path placed between the sheet cassette and the image
forming section, wherein the image forming section and the sheet
conveying path are placed in a position within a width of the sheet
cassette defined between a front end and a rear end of the cassette
in a sheet feeding direction and above the sheet cassette, the
separating member has a tip to be placed to contact with a portion
of the stacked sheets accommodated in the sheet cassette between
the front end and the rear end of the cassette, and the sheet feed
roller is placed in a position between the front end and the rear
end of the sheet cassette and apart from the tip of the separating
member toward the rear end of the sheet cassette.
2. The image forming apparatus according to claim 1, further
including a sheet feed roller controller configured to control the
sheet feed roller to rotate reversely to feed the uppermost sheet
of the stacked sheets in a direction opposite to the sheet
conveying path and thereafter rotate forwardly to feed the sheet in
a direction toward the sheet conveying path.
3. The image forming apparatus according to claim 2, wherein an
amount of reverse rotation of the sheet feed roller to be
controlled by the sheet feed roller controller is determined to an
amount of rotation at which a leading end of a sheet is moved to a
position between the tip of the separating member and the sheet
feed roller.
4. The image forming apparatus according to claim 1, further
including a press-contact member configured to bring the tip of the
separating member into press-contact with the uppermost sheet of
the stacked sheets accommodated in the sheet cassette.
5. The image forming apparatus according to claim 1, further
including a conveying roller configured to convey the sheet toward
the sheet conveying path, the sheet having been fed by the sheet
feed roller from the stacked sheets accommodated in the sheet
cassette and separated by the separating member.
6. The image forming apparatus according to claim 5, further
including a guide member holding the separating member at one end,
the guide member being configured to be rotatable about a position
opposite to the separating member and to guide the sheet separated
by the separating member toward the sheet conveying path, wherein
the conveying roller is provided at the other end of the guide
member opposite to the separating member.
7. The image forming apparatus according to claim 5, further
including a conveying roller controller configured to control the
conveying roller to start rotation to convey the sheet toward the
sheet conveying path before the leading end of the uppermost sheet
of the stacked sheets accommodated in the sheet cassette reaches
the conveying roller.
8. The image forming apparatus according to claim 2, further
including: a conveying roller configured to convey the sheet toward
the sheet conveying path, the sheet having been fed by the sheet
feed roller from the stacked sheets accommodated in the sheet
cassette and separated by the separating member; a guide member
holding the separating member at one end, the guide member being
configured to be rotatable about a position opposite to the
separating member and to guide the sheet separated by the
separating member toward the sheet conveying path, wherein the
conveying roller is provided at the other end of the guide member
opposite to the separating member, and a conveying roller
controller configured to control the conveying roller to start
rotation to feed the sheet toward the sheet conveying path after
the sheet feed roller is started to rotate forwardly but before the
leading end of the uppermost sheet of the stacked sheets
accommodated in the sheet cassette reaches the conveying
roller.
9. The image forming apparatus according to claim 1, wherein the
sheet cassette includes a lifting plate having an angularly bent or
round curved shape to load the stacked sheets in the form of an
upward convex curve.
10. The image forming apparatus according to claim 1, wherein the
sheet cassette includes a slanted surface at the rear end, the
slanted surface being so slanted as to be more apart from the front
end of the sheet cassette with distance from a bottom plate of the
sheet cassette.
11. The image forming apparatus according to claim 10, wherein the
slanted surface is made of a high friction member having a larger
friction coefficient than a material forming other portions of the
sheet cassette than the slanted surface.
12. The image forming apparatus according to claim 11, wherein the
high friction member is made of cork.
13. The image forming apparatus according to claim 11, wherein the
high friction member is made of rubber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 2011-274864
filed on Dec. 15, 2011, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an image forming apparatus
and more particularly to an image forming apparatus provided with a
sheet feeding device configured to separate sheets one by one from
stacked sheets and convey each sheet to an image forming
section.
[0004] 2. Description of Related Art
[0005] Some image forming apparatus each include an image forming
section to form an image on a sheet and a sheet feeding device
(feeder) to feed the sheet to the image forming section. Many of
sheet feeding devices are each provided with a separating mechanism
for separating sheets one by one from stacked sheets to feed one
sheet each.
[0006] For example, JP-A-3(1991)-51230 discloses a sheet feeding
device configured to rotate a separating roller in a reverse
direction (see an arrow Tb in FIG. 1 of JP-A-3(1991)-51230) and
thereafter rotate the separating roller in a forward (normal)
direction (see an arrow Ta in FIG. 1 of JP-A-3(1991)-51230) to
convey a sheet. This is to separate an uppermost sheet from stacked
sheets and convey the sheet along a sheet conveying path.
JP-A-2002-87606 discloses a sheet feeding device including an
auxiliary roller which rotates in a reverse direction and
thereafter rotates in a forward direction (see FIG. 2 and others in
JP-A-2002-87606). This is to prevent double sheet feeding.
[0007] In recent years, meanwhile, there has been an increasing
demand for downsizing of an image forming apparatus to address
environmental issues or save office space. However, the width of a
conventional image forming apparatus is, as shown in FIG. 1, equal
to or larger than the sum ("A+B" in FIG. 1) of the width (see a
dimension line A in FIG. 1) of a sheet cassette and the width (see
a dimension line B in FIG. 1) of a section wherein a sheet
conveying path is contained. Accordingly, the size of the image
forming apparatus in a width direction has a lower limit at this
width (A+B). The same applies to sheet feeding devices disclosed in
JP-A-3(1991)-51230 and JP-A-2002-87606.
[0008] The present invention has been made to solve the above
conventional problems and has a purpose to provide an image forming
apparatus including a sheet feeding device configured to
sequentially feed sheets one by one from stacked sheets and ensure
a reduced width of the image forming apparatus.
SUMMARY OF THE INVENTION
[0009] To achieve the above purpose, one aspect of the invention
provides an image forming apparatus comprising: a sheet cassette
configured to accommodate stacked sheets; a separating member
configured to separate an uppermost sheet from the stacked sheets
accommodated in the sheet cassette; a sheet feed roller configured
to feed the uppermost sheet from the stacked sheets accommodated in
the sheet cassette; an image forming section configured to form an
image on the sheet fed from the sheet cassette; and a sheet
conveying path placed between the sheet cassette and the image
forming section, wherein the image forming section and the sheet
conveying path are placed in a position within a width of the sheet
cassette defined between a front end and a rear end of the cassette
in a sheet feeding direction and above the sheet cassette, the
separating member has a tip to be placed to contact with a portion
of the stacked sheets accommodated in the sheet cassette between
the front end and the rear end of the cassette, and the sheet feed
roller is placed in a position between the front end and the rear
end of the sheet cassette and apart from the tip of the separating
member toward the rear end of the sheet cassette. In this image
forming apparatus, the overall or full width of the image forming
apparatus does not greatly differ from the width of the sheet
cassette. That is, downsizing of the image forming apparatus is
achieved.
[0010] According to the present invention, there is provided an
image forming apparatus including a sheet feeding device configured
to sequentially feed sheets one by one from stacked sheets and
ensure a reduced width of an image forming apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic configuration view to explain a
conventional image forming apparatus;
[0012] FIG. 2 is a schematic configuration view to explain an image
forming apparatus in an embodiment of the present invention;
[0013] FIG. 3 is a schematic configuration view to explain a sheet
cassette in the embodiment;
[0014] FIG. 4 is a view to illustrate conveying rollers and a
separating blade in the embodiment;
[0015] FIG. 5 is a view (Part 1) to show a sheet feeding operation
of the image forming apparatus in the embodiment;
[0016] FIG. 6 is a view (Part 2) to show the sheet feeding
operation of the image forming apparatus in the embodiment;
[0017] FIG. 7 is a view (Part 3) to show the sheet feeding
operation of the image forming apparatus in the embodiment;
[0018] FIG. 8 is a view to show a case where a number of sheets are
loaded in a sheet cassette in the embodiment;
[0019] FIG. 9 is a view to show a case where only one sheet is
loaded in the sheet cassette in the embodiment;
[0020] FIG. 10 is a schematic configuration view (Part 1) to
explain a sheet cassette in a modified example;
[0021] FIG. 11 is a schematic configuration view (Part 2) to
explain a sheet cassette in a modified example; and
[0022] FIG. 12 is a schematic configuration view (Part 3) to
explain a sheet cassette in a modified example.
DESCRIPTION OF EMBODIMENTS
[0023] A detailed description of a preferred embodiment of the
present invention will now be given referring to the accompanying
drawings. In the present embodiment, the invention is applied to a
black and white printer.
1. Image Forming Apparatus
[0024] An image forming apparatus 100 is a black and white printer
having a schematic configuration shown in FIG. 2. This image
forming apparatus 100 includes a sheet cassette 10, a sheet feed
roller 14, a sheet conveying path 20, an image forming section 30,
a transfer roller 40, a fixing unit 50, a pair of sheet discharging
roller 61, a discharge tray 62, a motor M, and a controller 90.
[0025] The sheet cassette 10 is arranged to accommodate stacked
sheets and feed an uppermost sheet from the stacked sheets. A fed
sheet is conveyed along the sheet conveying path 20 to the image
forming section 30. The details of this configuration will be
explained later. The sheet cassette 10 can be pulled out to the
front side (near side) in FIG. 2 from the image forming apparatus
100. In the present embodiment, hereinafter, a right-to-left
direction to the image forming apparatus 100 in FIG. 2 is referred
to as a width direction. A maximum size of the image forming
apparatus 100 in the width direction is referred to as a "full
width W" and a length of the sheet cassette 10 from a front end to
a rear end in a sheet feeding direction is referred to as a "width
W1"
[0026] The sheet feed roller 14 is used to pick up and feed an
uppermost sheet from stacked sheets loaded in the sheet cassette 10
toward the sheet conveying path 20. This sheet conveying path 20 is
arranged to convey the sheet fed out from the cassette 10 toward
the image forming section 30. The sheet conveying path 20 is
provided with a timing sensor 21 to determine the timing at which a
sheet is fed to the transfer roller 40. The sheet conveying path 20
is located in a position within the width W1 of the cassette 10 and
above the cassette 10. Accordingly, the full width W of the image
forming apparatus 100 in the present embodiment is not so greatly
different from the width W1 of the cassette 10. In other words, the
image forming apparatus 100 in the present embodiment is smaller in
size than the conventional image forming apparatus.
[0027] The image forming section 30 is arranged to form an image on
a sheet. This image forming section 30 includes a photoconductor
drum 31, a charging unit 32, an exposing unit 33, and a developing
unit 34, and a cleaner 35. The photoconductor drum 31 is an image
carrier to carry a toner image thereon. This drum 31 is therefore
rotated in a direction indicated by an arrow D2 in FIG. 2. The
charging unit 32 is arranged to uniformly charge the surface of the
drum 31. The exposing unit 33 is configured to form an
electrostatic latent image on the surface of the drum 31. The
developing unit 34 is arranged to impart toner to the electrostatic
latent image on the surface of the drum 31. The cleaner 35 is used
to remove untransferred residual toner from the drum 31.
[0028] The transfer roller 40 is a transfer member for transferring
a toner image formed on the photoconductor drum 31 to a sheet. The
sheet having the toner image transferred thereon is then
transported along the sheet conveying path 20 in a direction
indicated by an arrow D1 in FIG. 2.
[0029] The fixing unit 50 is arranged to fix the transferred toner
image on the sheet. The pair of discharging rollers 61 are arranged
to discharge the sheet having the toner image fixed thereon to the
discharge tray 62. This tray 62 is a tray for receiving the sheet
having the toner image fixed thereon.
[0030] The motor M is a drive source to drive the photoconductor
drum 31 and various rollers to rotate. The sheet feed roller 14 and
conveying rollers 17 mentioned later are to be driven by the motor
M. Each component such as the drum 31 is also to be driven by the
motor M. These components are rotated in sync with the rotation of
the motor M. However, the rotation speeds of the components are not
necessary equal to each other because of the use of a reduction
gear or the like. The controller 90 is configured to control the
operation of each component of the image forming section 30 and the
rotation of the motor M.
[0031] As shown in FIG. 2, the image forming section 30 and the
sheet conveying path 20 are located in a position within the width
W1 of the sheet cassette 10 in the image forming apparatus 100 and
above the cassette 10.
2. Sheet Feeding Device
[0032] 2-1. Configuration of Sheet Feed Cassette
[0033] The configuration of the sheet cassette 10 will be explained
below. FIG. 3 is a schematic configuration view to explain the
sheet cassette 10. Specifically, this cassette 10 is configured to
separate an uppermost sheet P1 from stacked sheets P and
sequentially feed one sheet each to the sheet conveying path 20.
Herein, an end portion of the sheet P1, which becomes the head
(leading edge) of the sheet P1 during conveyance to the image
forming section 30, is referred to as a leading end PT. The other
end portion of the sheet P1, which becomes the tail (bottom edge)
of the sheet P1 during conveyance to the image forming section 30,
is referred to as a rear end PE. As shown in FIG. 3, the sheet
cassette 10 includes a cassette body 11, a lifting spring 12, and a
lifting plate 13.
[0034] The cassette body 11 is a sheet feed case for accommodating
stacked sheets P. The cassette body 11 has a bottom plate 11a, a
front end portion 11T, and a rear end portion 11E. The front end
portion 11T is a side wall of the cassette body 11 on a side facing
the leading end PT of the sheet P1 before conveyance (in a loaded
state). The rear end portion 11E is a side wall of the cassette
body 11 on the other side facing the rear end PE of the sheet P1
before conveyance (in the loaded state).
[0035] The rear end portion 11E of the cassette body 11 includes a
slanted surface 11b. This slanted surface 11b is slanted from the
bottom plate 11a to an upper end of the rear end portion 11E so
that the rear end portion 11E is more apart from the front end
portion 11T of the cassette body 11 with distance from the bottom
plate 11a. The slanted surface 11b can function, as mentioned
later, to guide the sheet P1 moved back by the sheet feed roller 14
to be warped or curved upward from the sheet cassette 10. The
lifting spring 12 is arranged to lift up the portions of the
stacked sheets P near the leading end PT by way of the lifting
plate 13. This lifting plate 13 is a sheet loading section to
actually load thereon the stacked sheets P.
[0036] 2-2. Sheet Feed Roller, Guide Member, and others
[0037] The sheet feeding device includes the sheet feed roller 14
and the guide member 15 in addition to the sheet cassette 10. The
sheet feed roller 14 and the guide member 15 are provided in a main
body of the image forming apparatus 100 and are not allowed to be
pulled out together with the sheet cassette 10. The sheet feed
roller 14 is placed in a position upstream from the guide member 15
and a separating blade 16 mentioned later in a sheet conveying
path. Further, the sheet feed roller 14 is located between the
front end portion 11T and the rear end portion 11E of the cassette
body 11 and somewhat apart from the tip of the separating blade 16
toward the rear end portion 11E. The sheet feed roller 14 is
configured to, under the control of the controller 90, rotate in a
forward (normal) direction (indicated by an arrow DN in FIG. 3) to
move forward the sheet P1 to the sheet conveying path 20 and rotate
in a reverse direction (indicated by an arrow DR in FIG. 3) to move
backward the sheet P1 from the sheet conveying path 20.
[0038] The guide member 15 is an element for guiding conveyance of
the sheet P1 toward the sheet conveying path 20. The guide member
15 includes the separating blade 16 and the conveying rollers 17a,
17b. The blade 16 is attached to the leading end of the guide
member 15 and serves as a separating element for picking up and
separating the sheet P1 from the stacked sheets P. The blade 16 is
placed in such a manner that the tip of the blade 16 is in contact
with an uppermost surface of the stacked sheets P between the front
end portion 11T and the rear end portion 11E of the cassette body
11. The conveying rollers 17a, 17b are arranged on the end portion
of the guide member 15 opposite to the separating blade 16. The
conveying rollers 17a, 17b serve to feed the sheet P1 fed by the
sheet feed roller 14 to the sheet conveying path 20.
[0039] The guide member 15 is provided with a press-contact spring
18 that pulls the guide member 15 to swing, thereby swinging the
separating blade 16 together, so that the tip of the blade 16 is
urged in press-contact with the stacked sheets P in a thickness
direction thereof. Unless the blade 16 presses against the stacked
sheets P, there is a risk that the leading end PT of the sheet P1
moved back by the sheet feed roller 14 as mentioned later may go
under the blade 16 when the sheet P1 is thereafter moved forward.
It is to be noted that the press-contact spring 18 is not
illustrated in FIG. 4 and subsequent.
[0040] 2-3. Configuration of Guide Member
[0041] FIG. 4 is a view to illustrate the configuration of the
guide member 15 in the present embodiment. As shown in FIG. 4, the
separating blade 16 and the conveying rollers 17b are configured
integrally with the guide member 15. The blade 16 is used to press
the stacked sheets P. In case the sheet feed roller 14 delivers two
or more sheets in overlapping manner at a time, the blade 16 also
serves as a member for preventing double-sheet feeding in order to
convey only one uppermost sheet Pl. In the present embodiment, as
shown in FIG. 4, the separating blade 16 and the conveying rollers
17b are configured to be integral with the guide member 15. The
guide member 15 is supported so as to swing about the rotation axis
of the conveying rollers 17b. However, the rotation center of the
guide member 15 does not necessarily coincide with the rotation
axis of the conveying rollers 17b, and has only to be located near
the end portion of the guide member 15 opposite the blade 16. Of
course, the blade 16 and the conveying rollers 17b may be
configured to be separate from the guide member 15.
[0042] The guide member 15 and the separating blade 16 are each
made of a resin film such as polyester film or polyethylene film.
Instead, they may be made of stainless sheet or steel sheet. The
blade 16 may also be made of a material with a high friction
coefficient or designed in a shape subjected to surface finishing
to provide a high friction coefficient. This is because such a
separating blade 16 can easily separate the sheet P1 from the
stacked sheets P.
3. Sheet Feeding Operation in Sheet Feeding Device
[0043] A sheet feeding operation carried out in the sheet feeding
device will be explained below. As shown in FIG. 5, the sheet feed
roller 14 is first rotated in the direction indicated by the arrow
DR (reverse rotation) in FIG. 5. The amount of rotation with which
this roller 14 is to be rotated reversely may be determined in
advance. However, the amount of reverse rotation corresponds to the
amount of rotation to move the leading end PT of the sheet P1 in a
range between the tip of the separating blade 16 and the sheet feed
roller 14. Specifically, it is necessary to hold the sheet P1 free
from pressure contact with the blade 16 but in pressure contact
with the sheet feed roller 14. This reverse rotation of the sheet
feed roller 14 moves the uppermost sheet P1 from the stacked sheets
P in a direction away from the sheet conveying path 20. Thus, the
sheet P1 is substantially separated from the stacked sheets P.
Then, the rear end PE of the sheet P1 bumps against the slanted
surface 11b, thereby curling or curving upward. At that time, the
conveying rollers 17a, 17b are not rotated.
[0044] Subsequently, the sheet feed roller 14 is rotated in the
direction indicated with the arrow DN (forward rotation) in FIG. 6,
thus moving the uppermost sheet P1 toward the sheet conveying path
20. Therefore, the sheet P1 is separated from the stacked sheets P
by the separating blade 16 and conveyed toward the sheet conveying
path 20. At the timing when the leading end PT of the sheet P1 goes
up onto the separating blade 16, the conveying rollers 17a, 17b
start to rotate in the direction indicated by the arrow D3 in FIG.
6. Thus, the rotation of the rollers 17a, 17b has started before
the leading end PT of the sheet P1 reaches the conveying rollers
17a, 17b.
[0045] As shown in FIG. 7, after the leading end PT of the sheet P1
passes the conveying rollers 17a, 17b, the sheet P1 is conveyed by
the conveying rollers 17a, 17b and the sheet feed roller 14 into
the sheet conveying path 20. At that time, the sheet feed roller 14
is rotated in the direction indicated by the arrow DN (forward
rotation) in FIG. 7 and the conveying rollers 17a, 17b are rotated
in the direction indicated by the arrow D3 in FIG. 7, respectively.
When the leading end PT of the sheet P1 reaches the timing sensor
21, conveyance of the sheet P1 is temporarily stopped. In
accordance with the timing of forming an image on the
photoconductor drum 31, the conveying rollers 17a, 17b and the
sheet feed roller 14 are rotated to move forward the sheet P1 to
the location of the transfer roller 40. Thereafter, the sheet P1 is
subjected to transfer of a toner image by the transfer roller
40.
4. Sheet Loading Amount
[0046] The number of stacked sheets P loaded on the sheet cassette
10 decreases every time image formation. Thus, the following
explanation is given to changes in the angle of the separating
blade 16 according to the amount of sheets loaded in the sheet
cassette 10.
[0047] 4-1. Full Loaded Condition
[0048] FIG. 8 illustrates a case where the stacked sheets P are
loaded up to a maximum loading capacity. In this case, the lifting
spring 12 is sufficiently compressed by the weight of the stacked
sheets P. Accordingly, the angle OA of the lifting plate 13 to the
bottom plate 11a is not so large. At that time, the angle between
the upper surface of the stacked sheets P and the separating blade
16 is an angle .theta.1.
[0049] 4-2. Empty Condition
[0050] FIG. 9 illustrates a case where only one sheet P1 is
accommodated in the sheet cassette 10. In this case, the lifting
spring 12 is in almost fully elongated state. The angle .theta.B of
the lifting plate 13 to the bottom plate 11a of this state is
larger than the angle .theta.A of the lifting plate 13 to the
bottom plate 11a in the full loaded condition. Also in this case,
the separating blade 16 makes the pressing action. However, because
no stacked sheets P exist under the blade 16, the separating blade
16 presses the lifting plate 13 directly. The angle .theta.2
between the upper surface of the sheet P1 (the lifting plate 13)
and the separating blade 16 is smaller than the angle .theta.1 in
the full loaded condition.
[0051] As explained in detail above, the sheet conveying path 20 is
placed within the range of the sheet cassette 10 in the width
direction and above the cassette 10. Thus, the full width of the
image forming apparatus 100 in the present embodiment is not so
greatly different from the width of the sheet cassette 10. That is,
the size of the image forming apparatus 100 in the present
embodiment is smaller than the size of the conventional image
forming apparatus.
5. Modified Examples
[0052] 5-1. Shape of Cassette Body
[0053] Modified examples of the present embodiment are explained
below.
[0054] Although the above embodiment provides the slanted surface
11b in the cassette body 11, the slanted surface 11b is not
necessarily provided. As shown in FIG. 10, a sheet cassette 210
with no slanted surface 11b may also be adopted. A cassette body
211 of this cassette 210 includes a rear end portion 211E not
slanted, located on a rear end side of the stacked sheets P, in
addition to a bottom plate 211a and a front end portion 211T.
[0055] As shown in FIG. 10, when the sheet feed roller 14 is
reversely rotated (in a direction indicated by an arrow DR in FIG.
10), an uppermost sheet P1 is moved to the opposite side to the
sheet conveying path 20. At that time, the sheet P1 bends in a
curve while the rear end PE is in contact with the rear end portion
211E of the cassette body 211. This bending allows the sheet P1 to
separate from the stacked sheets P. Since static electricity of the
sheet P1 is somewhat released into the atmosphere, the sheet P1 is
less likely to stick to the stacked sheets P again. The image
forming apparatus including this sheet cassette 210 does not need
the width for providing the slanted surface 11b, and is smaller in
full width than the image forming apparatus 100 of the above
embodiment.
[0056] 5-2. Shape of Lifting Plate
[0057] As shown in FIG. 11, as another example, a lifting plate 313
with an angular bent shape may be adopted for loading stacked
sheets P instead of the lifting plate 13 shown in FIG. 3. In a
sheet cassette 310, the stacked sheets P loaded on the lifting
plate 313 are also bent in the form of an upward convex curve.
Thus, when an uppermost sheet P1 is to be fed, this uppermost sheet
P1 is easily separated and moved from the stacked sheets P.
Furthermore, noise during sheet separation is low. The shape of the
lifting plate may also be designed to take a round bent shape of an
upward convex curve.
[0058] 5-3. High Friction Member
[0059] As shown in FIG. 12, a sheet cassette 410 including a high
friction member 412 may be used. This configuration is obtained by
making the slanted surface 11b of the cassette body 11 (see FIG. 3
and others) from the high friction member. Accordingly, the high
friction member 412 is placed on a rear end portion 411E of the
cassette body 411. Herein, the high friction member 412 is made of
a material having a larger friction coefficient than that of any
other portions (a bottom plate 411a and a front end portion 411T)
of the sheet cassette 410 than the slanted surface 11b. For
example, this material is selectable from cork, rubber, or the
like. Thus, the separating blade 16 can easily separate an
uppermost sheet P1 from the stacked sheets P.
6. Conclusion
[0060] As explained in detail above, the image forming apparatus
100 in the embodiment is configured such that the sheet feed roller
14 and the separating blade 16 to convey the sheet P1 to the
section above the cassette body 11 are provided within the width W1
of the sheet cassette 10. Accordingly, there is realized the image
forming apparatus 100 capable of feeding each sheet P1 sequentially
from the stacked sheets P and conveying the sheet P1 to the sheet
conveying path 20 located above the cassette 10.
[0061] In the image forming apparatus 100 in the embodiment, the
sheet conveying path 20 is also placed in the upper section within
the width W1 of the sheet cassette 10. Thus, the full width W of
the image forming apparatus 100 is not so greatly different from
the width W1 of the sheet cassette 10. That is, the image forming
apparatus 100 is smaller in size than the conventional image
forming apparatus. Such a size-reduced image forming apparatus can
be achieved.
[0062] The above embodiments are mere examples not limiting the
invention thereto. The present invention may be embodied in other
specific forms without departing from the essential characteristics
thereof. For instance, the invention is not limited to the black
and white printer, but alternatively may be a color printer.
Further, the invention is applicable to a copying machine as well
as the printer. The invention can be applied to an image reading
apparatus and an image forming apparatus configured to
transmit/receive print jobs through public lines, and a combination
machine. Moreover, the invention is applicable to any type of
apparatus regardless of the kinds of toner and also to an image
forming apparatus using a liquid color forming agent instead of
toner. The guide member 15 and the separating blade 16 may be
provided as an integral single piece.
[0063] The aforementioned image forming apparatus preferably
includes a sheet feed roller controller configured to control the
sheet feed roller to rotate reversely to feed the uppermost sheet
of the stacked sheets in a direction opposite to the sheet
conveying path and thereafter rotate forwardly to feed the sheet in
a direction toward the sheet conveying path. This makes it possible
to appropriately feed an uppermost sheet from stacked sheets.
[0064] In the aforementioned image forming apparatus, preferably,
an amount of reverse rotation of the sheet feed roller to be
controlled by the sheet feed roller controller is determined to an
amount of rotation at which a leading end of a sheet is moved to a
position between the tip of the separating member and the sheet
feed roller. Thus, each sheet can be temporarily moved back to be
appropriately separated from the stacked sheets, and fed forward
one by one.
[0065] The aforementioned image forming apparatus preferably
includes a press-contact member configured to bring the tip of the
separating member into press-contact with the uppermost sheet of
the stacked sheets accommodated in the sheet cassette. This
configuration can prevent the leading end of each sheet to be fed
from going under the separating member.
[0066] The aforementioned image forming apparatus preferably
includes a conveying roller configured to convey the sheet toward
the sheet conveying path, the sheet having been fed by the sheet
feed roller from the stacked sheets accommodated in the sheet
cassette and separated by the separating member. The separated
sheet is thus delivered into the sheet conveying path.
[0067] In the aforementioned image forming apparatus, preferably,
there is provided a guide member holding the separating member at
one end, the guide member being configured to be rotatable about a
position (axis) opposite to the separating member and to feed the
sheet separated by the separating member toward the sheet conveying
path, wherein the conveying roller is provided at the other end of
the guide member opposite to the separating member. Thus, the
separated sheet can be directed to the sheet conveying path
irrespective of the amount of sheets in the sheet cassette.
[0068] The aforementioned image forming apparatus preferably
includes a conveying roller controller configured to control the
conveying roller to start rotation to convey the sheet toward the
sheet conveying path before the leading end of the uppermost sheet
of the stacked sheets accommodated in the sheet cassette reaches
the conveying roller. Thus, the separated sheet can be reliably
delivered into the sheet conveying path. The rotation of the
conveying roller may also be started after the forward rotation of
the sheet feed roller is started.
[0069] In the image forming apparatus, preferably, the sheet
cassette includes a lifting plate having a bent or curved shape to
load the stacked sheets in the form of an upward convex curve. This
configuration makes it easy to separate an uppermost sheet from the
stacked sheets.
[0070] In the image forming apparatus, preferably, the sheet
cassette includes a slanted surface at the rear end, the slanted
surface being so slanted as to be more apart from the front end of
the sheet cassette with distance from a bottom plate of the sheet
cassette. Accordingly, it is possible to prevent a sheet
temporarily moved back from being folded.
[0071] In the image forming apparatus, preferably, the slanted
surface is made of a high friction member having a larger friction
coefficient than a material forming other portions of the sheet
cassette than the slanted surface, so that separation of each sheet
can be performed adequately.
[0072] The high friction member may include cork or rubber.
Reference Sings List
[0073] 10, 210, 310, 410 Sheet cassette [0074] 11, 211, 411
Cassette body [0075] 11a, 211a, 411a Bottom plate [0076] 11b
Slanted surface [0077] 11T, 211T, 411T Front end portion [0078]
11E, 211E, 411E Rear end portion [0079] 12 Lifting spring [0080]
13, 313 Lifting plate [0081] 14 Sheet feed roller [0082] 15 Guide
member [0083] 16 Separating blade [0084] 17a, 17b Conveying roller
[0085] 18 Press-contact spring [0086] 20 Sheet conveying path
[0087] 30 Image forming section [0088] 40 Transfer roller [0089] 50
Fixing unit [0090] 61 Pair of discharging rollers [0091] 62
Discharge tray [0092] 90 Controller [0093] 100 Image forming
apparatus [0094] 412 High friction member [0095] P Stacked sheets
[0096] P1 Sheet [0097] PT Leading end [0098] PE Rear end
* * * * *