U.S. patent application number 10/856491 was filed with the patent office on 2004-12-23 for sheet transporting device.
This patent application is currently assigned to Kyocera Mita Corporation. Invention is credited to Eto, Takuya, Harada, Hiroyuki, Ota, Atsushi, Wada, Hiroshi.
Application Number | 20040256787 10/856491 |
Document ID | / |
Family ID | 33516087 |
Filed Date | 2004-12-23 |
United States Patent
Application |
20040256787 |
Kind Code |
A1 |
Wada, Hiroshi ; et
al. |
December 23, 2004 |
Sheet transporting device
Abstract
A roller shaft extends between a pair of frame walls. A feed
roller is mounted on the roller shaft for feeding a stack of sheets
placed on a feeding tray one by one from an uppermost sheet. A
transmission gear is concentrically coupled to one end portion of
the roller shaft to be rotated by driving of a driving motor. A
boss extends axially inwardly from a center position of the
transmission gear. The roller shaft has a flat key portion at the
one end portion thereof. The flat key portion has a substantially
D-shape in cross section. The flat key portion is coupled to the
boss by being received in a non-circular hole of the boss. With
this arrangement, an eccentric displacement of the roller shaft
relative to the transmission gear is suppressed, and the feed
roller is easily detachable from the roller shaft with a simplified
operation.
Inventors: |
Wada, Hiroshi; (Osaka-shi,
JP) ; Harada, Hiroyuki; (Osaka-shi, JP) ; Eto,
Takuya; (Osaka-shi, JP) ; Ota, Atsushi;
(Osaka-shi, JP) |
Correspondence
Address: |
CASELLA & HESPOS
274 MADISON AVENUE
NEW YORK
NY
10016
|
Assignee: |
Kyocera Mita Corporation
Osaka-shi
JP
|
Family ID: |
33516087 |
Appl. No.: |
10/856491 |
Filed: |
May 28, 2004 |
Current U.S.
Class: |
271/109 |
Current CPC
Class: |
B65H 2601/324 20130101;
B65H 2404/17 20130101; B65H 2403/42 20130101; B65H 2404/1317
20130101; B65H 3/0669 20130101; B65H 2404/134 20130101 |
Class at
Publication: |
271/109 |
International
Class: |
B65H 003/44 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2003 |
JP |
2003-153643 |
Claims
What is claimed is:
1. A sheet transporting device for use in an image forming
apparatus comprising: a pair of frame walls opposed to each other;
a roller shaft extending between the frame walls, opposite end
portions of the roller shaft being received in insertion holes
formed in the frame walls, respectively; a feed roller which is
mounted on the roller shaft and is rotatable about an axis of the
roller shaft, the feed roller for feeding sheets stacked on a sheet
stacking portion of the image forming apparatus one by one from an
uppermost sheet; a transmission gear which is provided at an outer
side of one of the frame walls, the transmission gear having a
center position opposed to the insertion hole of the frame wall;
and an attachment structure which is so configured as to mount the
roller shaft between the frame walls so as to transmit a driving
force of the transmission gear to the roller shaft, the attachment
structure including: a boss which is formed co-axially with the
transmission gear and projects in the axial direction of the roller
shaft to be received in the insertion hole of the frame wall, the
boss being formed with a non-circular hole extending in the axial
direction of the roller shaft; and an engaging end portion which is
formed in an end portion of the roller shaft and has such a
configuration as to be received in the non-circular hole of the
boss in a non-rotatable state relative to the transmission
gear.
2. The sheet transporting device according to claim 1, wherein the
other end portion of the roller shaft has a stopper structure which
is so configured as to keep the roller shaft from coming off the
frame wall through the insertion hole formed in the frame wall
unless an external force is applied, the stopper structure being
detachably attachable to the sheet transporting device.
3. The sheet transporting device according to claim 2, wherein the
stopper structure includes a cutaway groove which is formed in a
surface of the other end portion of the roller shaft, and a stopper
ring which is detachably mounted in the cutaway groove.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sheet transporting device
incorporated with a roller shaft mounting structure, which is
applicable to a sheet feeding device for feeding sheets one by one
into a main body of an image forming apparatus. The sheet
transporting device is applicable to image forming apparatuses such
as copiers, facsimile machines, and printers.
[0003] 2. Description of the Related Art
[0004] Heretofore, there has been known a sheet feeding device 90
as shown in FIGS. 8A, 8B, and 8C, as disclosed in Japanese Examined
Utility Model Publication No. 6-43071. FIG. 8A is a side view, and
FIG. 8B is a front view, respectively showing essential parts of
the sheet feeding device 90. FIG. 8C is an enlarged perspective
view showing an attachment structure 96 which makes it possible for
an operator to detachably attach a roller shaft 921.
[0005] The sheet feeding device 90 is adapted to feed sheets P one
by one from a sheet cassette 91 provided in an image forming
apparatus such as a copier into the image forming apparatus. As
shown in FIG. 8A, the sheet feeding device 90 includes feed rollers
92 which are rotated about an axis of the roller shaft 921 together
with the roller shaft 921, a guide plate 93 for guiding the
document sheet P dispensed from the sheet cassette 91 by the feed
rollers 92, and a pair of upper and lower registration rollers 94
which are disposed at a downstream end of the guide plate 93 in the
sheet feeding direction. The feed rollers 92 are arranged at such a
position as to come into contact with the uppermost document sheet
P in the sheet cassette 91. The document sheet P dispensed from the
sheet cassette 91 as timed with a rotation of the feed rollers 92
is fed between the registration roller pair 94 while being
supported on the guide plate 93, and is transported into the image
forming apparatus by rotation of the registration roller pair
94.
[0006] It is necessary to detach the feed rollers 92 from a pair of
support frames 95 which support the roller shaft 921 extending in a
widthwise direction of the image forming apparatus, as shown by the
two-dotted-chain line shown in FIG. 8B, in order to carry out
maintenance service such as replacement and cleaning of parts of
the sheet feeding device 90. For this purpose, the attachment
structure 96 as shown in FIG. 8C is provided at an end portion of
the roller shaft 921.
[0007] The attachment structure 96 includes a coupling cylinder
961, a roller shaft end portion 962, and a compression coil spring
963. The coupling cylinder 961 is mounted on a driving shaft 97 to
be axially movable but non-rotatable together with the driving
shaft 97. The driving shaft 97 is passed through the support frames
95 concentrically with the roller shaft 921. The roller shaft end
portion 962 is detachably mounted in the coupling cylinder 961, and
is non-rotatable together with the coupling cylinder 961. The
compression coil spring 963 is wound around the driving shaft 97
between the coupling cylinder 961 and the support frame 95. A drive
gear 98 is fixedly mounted at a base end portion of the driving
shaft 97 to transmit a driving force of a drive source (not shown)
to the driving shaft 97.
[0008] An engaging pin 971 radially outwardly extends from a lead
end of the driving shaft 97. A cutaway groove 964 is formed in
parallel to an axial direction of the coupling cylinder 961 from an
opening end thereof toward a base end thereof. Engagement of the
engaging pin 971 in the cutaway groove 964 makes it possible to
reciprocate the coupling cylinder 961 in the axial direction
thereof while keeping the coupling cylinder 961 non-rotatable
together with the driving shaft 97.
[0009] An engaging pin 965 extends radially between the opposing
inner circumferential surfaces of the coupling cylinder 961 near
the opening end thereof. A cutaway groove 966 is formed in the
roller shaft end portion 962 to be engageable with the engaging pin
965. Engagement of the engaging pin 965 in the cutaway groove 966
with the roller shaft end portion 962 being received in the
coupling cylinder 961 makes it possible to couple the roller shaft
921 to the driving shaft 97, so that the roller shaft 921 is
rotatable together with the driving shaft 97 via the coupling
cylinder 961.
[0010] In the attachment structure 96 having the above
construction, when an operator wishes to detach the feed rollers 92
from the support frames 95, the operator can detach the roller
shaft end portion 962 from the coupling cylinder 961 by sliding the
coupling cylinder 961 toward the base end of the driving shaft 97
(leftward in FIG. 8B) against a resilient force of the compression
coil spring 963, as shown by the arrow in FIG. 8B. This arrangement
enables the operator to easily detach the roller shaft 921 without
disassembling the sheet feeding device 90 such as loosening a screw
which fastens the support frame 95 to the apparatus main body.
[0011] The attachment structure 96 as disclosed in Japanese
Examined Utility Model Publication No. 6-43071 has suffered from a
drawback that the number of parts is increased due to necessity of
providing additional parts such as the engaging pin 971 for the
driving shaft 97, and the engaging pin 965, as well as the driving
shaft 97, the coupling cylinder 961, and the compression coil
spring 963. As a result, the costs relating to the parts and
assembling of the parts are raised.
[0012] Further, the driving shaft 97 and the roller shaft 921 are
coupled to each other by way of the coupling cylinder 961 which is
axially movable, in other words, which may not provide sufficient
force to securely couple the driving shaft 97 and the roller shaft
961 concentrically with each other. Accordingly, the driving shaft
97 and the roller shaft 921 are likely to be eccentrically
displaced from each other. In order to solve this problem, it is
necessary to improve precision in processing, which raises another
problem that the processing cost may be raised.
SUMMARY OF THE INVENTION
[0013] In view of the above, it is an object of the present
invention to overcome the problems residing in the prior art. It is
another object of the present invention to provide a
simple-structured sheet transporting device incorporated with a
roller shaft mounting structure that enables to suppress eccentric
displacement of the roller shaft and to facilitate
attaching/detaching operation of a feed roller.
[0014] According to an aspect of the present invention, a sheet
transporting device is used in an image forming apparatus. The
sheet transporting device includes a pair of frame walls, a roller
shaft extending between the frame walls, a feed roller mounted on
the roller shaft for feeding sheets stacked on a sheet stacking
portion of the image forming apparatus one by one from an uppermost
sheet, and a transmission gear provided at an outer side of one of
the frame walls for transmitting a driving force to the roller
shaft.
[0015] The sheet transporting device is provided with an attachment
structure mounted on the roller shaft. The attachment structure
includes a boss to be received in a hole of the frame wall. The
boss is formed with a non-circular hole. An engaging end portion is
formed in an end portion of the roller shaft, and has such a
configuration as to be received in the non-circular hole of the
boss in a non-rotatable state relative to the transmission
gear.
[0016] These and other objects, features and advantages of the
present invention will become more apparent upon reading of the
following detailed description along with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view showing an example of a copier
to which a sheet transporting device in accordance with an
embodiment of the present invention is applied.
[0018] FIG. 2 is a perspective view seen from a left side of the
sheet transporting device, showing a document sheet feeding section
of the copier with a top wall and a rear wall not being illustrated
to explain a mounted state of the sheet transporting device.
[0019] FIG. 3 is a perspective view seen from a right side of the
sheet transporting device, showing the document sheet feeding
section of the copier with the top wall and the rear wall not being
illustrated to explain the mounted state of the sheet transporting
device.
[0020] FIGS. 4A and 4B are perspective views showing the sheet
transporting device which is mounted on the document sheet feeding
section of the copier, wherein FIG. 4A shows a state that a
document sheet feeding unit is detached from a driving unit, and
FIG. 4B shows a state that the document sheet feeding unit has been
attached to the driving unit.
[0021] FIGS. 5A and 5B are perspective views showing an embodiment
of a transmission gear, wherein FIG. 5A shows a state immediately
before a flat key portion of a roller shaft is being received in a
non-circular hole of a boss of the transmission gear, and FIG. 5B
shows a state that the flat key portion has been received in the
non-circular hole.
[0022] FIGS. 6A, 6B, 6C, and 6D are illustrations for explaining
operations of the sheet transporting device, wherein FIG. 6A shows
a state that a hemispherical portion of the roller shaft is about
to be received in an insertion hole of a left-side frame wall, FIG.
6B shows a state that the hemispherical portion of the roller shaft
has been received in the insertion hole, followed by mounting of a
second bearing in the insertion hole, and also shows a state that
the flat key portion opposes a circular hole of a first bearing
which is mounted in an insertion hole of a right-side frame wall
while being mounted on the boss of the transmission gear, FIG. 6C
shows a state that the flat key portion is received in the circular
hole of the first bearing, and FIG. 6D shows a state that a stopper
ring is mounted in a cutaway groove of the roller shaft.
[0023] FIGS. 7A, 7B, and 7C are cross-sectional views showing a
modification as to how a roller shaft is coupled to a transmission
gear, wherein FIG. 7A shows a state that a coil spring is
dismounted from the transmission gear, FIG. 7B shows a state that a
bearing is mounted in an insertion hole after a hemispherical
portion of a roller shaft is received in the insertion hole, with a
flat key portion opposing a non-circular hole of the transmission
gear, and FIG. 7C shows a state that the roller shaft is coupled to
the transmission gear via the coil spring.
[0024] FIGS. 8A, 8B, and 8C are illustrations showing a
conventional sheet feeding device, wherein FIGS. 8A and 8B are side
view and a front view respectively showing essential parts of the
sheet feeding device, and FIG. 8C is an exploded perspective view
showing an attachment structure of detachably attaching a roller
shaft.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] FIG. 1 is a perspective view showing an example of a copier
to which a sheet transporting device in accordance with an
embodiment of the present invention is applied. As shown in FIG. 1,
the copier (image forming apparatus) 10 is constructed in such a
manner that a cover member 12 provided with a document sheet
feeding mechanism is mounted on a top of a box-like apparatus main
body 11.
[0026] The apparatus main body 11 is internally provided with an
optical system (not shown) for reading an image of a document sheet
fed by the document sheet feeding mechanism, a developing section
(not shown) provided with a photosensitive drum, a developing
device, and the like to transfer the document image read by the
optical system onto a copy sheet as a toner image, a fixing section
(not shown) provided with a pair of fixing rollers, and the like to
fix the transferred toner image on the sheet, and a sheet feeding
section (not shown) provided with a sheet cassette and the like to
store a stack of copy sheets therein.
[0027] A sheet fed by the sheet feeding section is fed to the
developing section via a predetermined transport path. Then, an
electrostatic latent image is formed on a circumferential surface
of the photosensitive drum based on the image data read by the
optical system, and the latent image is developed to a toner image
by supply of toner from the developing device, whereby the toner
image is transferred onto the sheet. After the image development,
the transferred toner image is fixed on the sheet by thermal
fixation by the fixing roller pair, and the sheet carrying the
fixed toner image is discharged onto a sheet discharging section
(not shown) provided at a side portion of the apparatus main body
11.
[0028] The cover member 12 is provided with a document sheet
feeding section 13 at a side portion thereof for feeding a document
sheet. The cover member 12 is further provided with a document
sheet feeding tray (sheet stacking portion) 14 extending obliquely
upwardly from the document sheet feeding section 13 toward the
other end of the cover member 12 opposite to the document sheet
feeding section 13, and a document sheet discharging tray 15 which
is disposed below the document sheet feeding tray 14 and
substantially extends over the entire surface of the cover member
12. A pair of document sheet alignment members 141 are provided at
a base portion (left side in FIG. 1) of the document sheet feeding
tray 14 to align the document sheets placed on the document sheet
feeding tray 14 in a widthwise direction of the apparatus main body
11. The document sheets on the document sheet feeding tray 14 are
aligned in the widthwise direction of the apparatus main body 11 by
regulating the inner distance between the pair of document sheet
alignment members 141.
[0029] The document sheet feeding section 13 is constructed in such
a manner that the sheet transporting device 20 (see FIG. 2)
according to the embodiment of the present invention is housed in a
space defined by a pair of frame walls 131 opposed to each other in
the widthwise direction of the apparatus main body 11, a top wall
132 which is pivotally opened and closed while being supported on
upper ends of the frame walls 131, and a rear wall 133 which
extends between the frame walls 131 and covers a space opposite to
the document sheet feeding tray 14. A document sheet feeding port
135 is defined by the pair of frame walls 131, and the top wall
132, and is formed opposite to the rear wall 133. Document sheets
placed on the document sheet feeding tray 14 are successively fed
into the document sheet feeding section 13, which will be described
later.
[0030] A stack of document sheets placed on the document sheet
feeding tray 14 with their respective lateral ends thereof aligned
by the document sheet alignment members 141 are fed into the
document sheet feeding section 13 one by one by driving the sheet
transporting device 20, whereby the image of each document sheet is
read by the optical system (not shown).
[0031] FIGS. 2 and 3 are perspective views showing the document
sheet feeding section 13 with the top wall 132 and the rear wall
133 not being illustrated to explain the mounted state of the sheet
transporting device 20. FIG. 2 is a diagram viewed from a left side
of the apparatus main body 11, and FIG. 3 is a diagram viewed from
a right side of the apparatus main body 11. FIGS. 4A and 4B are
perspective views of the sheet transporting device 20 which is to
be installed in the document sheet feeding section 13. FIG. 4A
shows a state that a document sheet feeding unit is detached from a
driving unit, and FIG. 4b shows a state that the document sheet
feeding unit has been attached to the driving unit.
[0032] As shown in FIGS. 2, 3, 4A, and 4B, the sheet transporting
device 20 includes the document sheet feeding unit 30 for
successively feeding document sheets P placed on the document
feeding tray 14 into the apparatus main body 11, and the driving
unit 60 for driving the document sheet feeding unit 30.
[0033] The document sheet feeding unit 30 includes a roller shaft
31 extending between the pair of frame walls 131, a casing 40
pivotally mounted on an intermediate portion of the roller shaft
31, a feed roller unit 50 supported on the casing 40, and a pair of
stopper members 39 attached to the feed roller unit 50. As shown in
FIGS. 2 and 3, the roller shaft 31 extends between the frame walls
131 at a position slightly downstream (left side in FIG. 2, right
side in FIG. 3) relative to the document sheet alignment members
141. As shown in FIGS. 4A and 4B, the roller shaft 31 includes a
shaft main body 32, a flat key portion 33 formed at a right-end
portion of the shaft main body 32 in FIG. 4A, and a cutaway groove
34 formed in a left-end portion thereof.
[0034] The flat key portion (engaging end portion) 33 is formed to
detachably mount a one end portion (right-end portion in FIG. 4A)
of the roller shaft 31 to the driving unit 60 by way of a bearing
unit 21. The cutaway groove 34 is formed to mount a stopper ring
(stopper piece) 22 in the other end portion (left-end portion in
FIG. 4A) of the roller shaft 31 by way of the bearing unit 21 to
keep the roller shaft 31 from coming off the frame walls 131.
[0035] The bearing unit 21 includes a first bearing 211 for
receiving the flat key portion 33 formed at the right-end portion
of the roller shaft 31 in FIG. 4A, and a second bearing 212 for
receiving the left-end portion of the roller shaft 31 in FIG. 4A.
The first bearing 211 (second bearing 212) has such an outer
dimension as to be slidably received in an insertion hole 134 of
the corresponding frame wall 131, which will be described later. A
circular hole 213 is formed in the center of the first bearing 211
to receive a boss 642 of a transmission gear 64.
[0036] A bearing hole 214 having a circular shape in cross section
is formed in the center of the second bearing 212 with such an
inner dimension as to slidably receive the roller shaft 31.
Specifically, the bearing hole 214 has a bell-like shape such that
the inner dimension thereof is axially outwardly decreased from the
opening of the second bearing 212. The bearing hole 214 has the
bell-like shape to easily receive the roller shaft 31 which is to
be tiltingly inserted through the second bearing 212 (see FIG. 6A).
The shape of the bearing hole 214 is not limited to the bell-like
shape. Alternatively, the bearing hole 214 may have a constant
inner dimension over the entirety of the axial direction of the
hole.
[0037] A hemispherical portion 35 is formed at an end portion of
the roller shaft 31 where the cutaway groove 34 is formed. The
hemispherical portion 35 also facilitates inserting the end portion
of the roller shaft 31 through the second bearing 212. The shape of
the end portion of the roller shaft 31 is not limited to the
hemispherical shape. Forming a radially cutaway portion in the end
portion of the roller shaft 31 enables to support the roller shaft
31 in the second bearing 212.
[0038] The insertion hole 134 is formed in each of the frame walls
131 to support the roller shaft 31 (see FIGS. 6A through 6D). Each
of the insertion holes 134 has such a size and a shape as to
receive the bearing unit 21 (namely, the first bearing 211 and the
second bearing 212) in a non-rotatable state.
[0039] The casing 40 is provided to support the feed roller unit
50, and includes a top wall 41, and a pair of side walls 42
opposing to each other in the widthwise direction of the apparatus
main body 11. The side walls 42 are formed by bending side portions
of the top wall 41 downward. The casing 40 is mounted on the roller
shaft 31 by passing the roller shaft main body 32 through the side
walls 42. A cross shaft 43 is formed on each of the side walls 42
at a forward side of the roller shaft main body 32, namely, on the
side of the document sheet alignment members 141, as shown in FIG.
2, to support the stopper members 39.
[0040] The casing 40 is pivotally rotatable between a sheet feeding
state where an upstream end thereof (right side in FIG. 2) relative
to the roller shaft 31 is lowered to such a position as to feed the
uppermost document sheet P, and a retracted state where the
upstream end is lifted upward and retracted. While the casing 40 is
set to the retracted state, the document sheet P is placed on the
document sheet feeding tray 14.
[0041] The stopper members 39 are pivotally rotatable about an axis
of the cross shaft 43 while the casing 40 is set to the sheet
feeding state. With this arrangement, the document sheet P placed
on the document sheet feeding tray 14 is allowed to pass under the
casing 40. On the other hand, when the casing 40 is set to the
retracted state, a projection 391 formed on an upper portion of
each stopper member 39 engages an engaging recess (not shown)
formed in the underside of the top wall 132 of the document sheet
feeding section 13, whereby the casing 40 is held in the retracted
state, and the feed roller unit 50 is securely supported on the
casing 40.
[0042] The feed roller unit 50 is adapted to feed the sheets P
placed on the document sheet feeding tray 14 one by one into the
apparatus main body 11, after confirming that each document sheet P
is securely placed on the document sheet feeding tray 14 with its
lateral ends thereof being aligned by the document sheet alignment
members 141, and with its lead end thereof being pressingly held by
the pair of downwardly-oriented stopper members 39 (see FIGS. 2 and
3). As shown in FIGS. 4A and 4B, the feed roller unit 50 includes a
feed roller 51 which is mounted concentrically with the roller
shaft main body 32 between the side walls 42 of the casing 40, and
a pickup roller 52 which is provided at an upstream side relative
to the feed roller 51 (forward side on the plane of FIGS. 4A and
4B) between the side walls 42. The pickup roller 52 is rotatably
supported about an axis of a pickup roller shaft 53 extending
between the side walls 42.
[0043] The pickup roller shaft 53 is arranged at such a position
that the surface of the pickup roller 52 comes into contact with
the uppermost document sheet P in a state that the stack of sheets
P placed on the document sheet feeding tray 14 are temporarily held
by the stopper members 39. With this arrangement, the uppermost
document sheet P is fed toward the feed roller 51 aided by the
rotation of the pickup roller 52. The document sheet P picked up by
the pickup roller 52 is fed into the document sheet feeding section
13 by rotation of the downstream-located feed roller 51.
[0044] As shown in FIGS. 4A and 4B, a feed roller gear 54
concentrically rotated with the roller shaft main body 32 is
provided at the right side of the feed roller 51 in the casing 40,
and a pickup roller gear 55 is provided at the right side of the
pickup roller 52 to be rotatable about an axis of the pickup roller
shaft 53. An intermediate gear 56 is provided between the pickup
roller gear 55 and the feed roller gear 54. With this arrangement,
the feed roller 51 and the pickup roller 52 are rotated together in
the same direction (clockwise direction in the example of FIGS. 2,
4A, and 4B) to feed the document sheet P inside the document sheet
feeding section 13.
[0045] A one-way clutch is provided each between the feed roller 51
and the feed roller gear 54, and between the pickup roller 52 and
the pickup roller gear 55. The one-way clutch is provided to rotate
the feed roller 51 and the pickup roller 52 together with the gears
54, 55, respectively, while the feed roller gear 54 and the pickup
roller gear 55 are rotated forward (clockwise) to feed the document
sheet P inside the document sheet feeding section 13, and to keep
the feed roller 51 and the pickup roller 52 from being rotated
together with the gears 54, 55, respectively, while the feed roller
gear 54 and the pickup roller gear 55 are rotated backward
(counterclockwise).
[0046] In the embodiment of the present invention, when a sensor
(not shown) detects the document sheet P when the document sheet P
fed by the feed roller 51 reaches a pair of registration rollers
(not shown) provided in a rear part of the document sheet feeding
section 13, the driving unit 60 is driven reversely, based on the
detection signal, to rotate the registration roller pair forward
and to rotate the roller shaft 31 backward. The one-way clutch is
provided to prevent the document sheet P which has been fed into
the document sheet feeding section 13 by the forward rotation of
the feed roller 51 from being exerted with a force acting backward
when the roller shaft 31 is rotated backward.
[0047] The driving unit 60 is adapted to supply a rotating force to
the roller shaft 31, and is fixedly mounted to an outer side of the
frame wall 131 (right side in FIG. 2, left side in FIG. 3). As
shown in FIGS. 4A and 4B, the driving unit 60 includes a driving
motor 62 which is fixedly attached to the outer side of the frame
wall 131 with a support plate 61 interposed therebetween, and a
gear group 63 provided on the inner side of the frame wall 131.
[0048] The gear group 63 includes: a driving gear 631
concentrically and integrally rotated with an output shaft 621 of
the driving motor 62; a first driven gear 632 meshed with the
driving gear 631; a second driven gear 633 meshed with the first
driven gear 632; a transmission gear 64 meshed with the second
driven gear 633 to transmit the rotating force of the driving motor
62 to the roller shaft 31; a third driven gear 634 which is
concentrically and integrally rotated with the first driven gear
632 and has a diameter larger than that of the first driven gear
632; and a registration gear 65 meshed with the third driven gear
634 via a small gear. The registration gear 65 is coupled to a
registration roller (not shown) via a one-way clutch (not shown),
and is so constructed as to transmit the rotation of the
registration gear 65 to the registration roller only while the
driving motor 62 is rotated backward.
[0049] FIGS. 5A and 5B are perspective views showing the
transmission gear 64. FIG. 5A shows a state immediately before the
flat key portion 33 of the roller shaft 31 is being received in a
non-circular hole 643 of the boss 642 of the transmission gear 64.
FIG. 5B shows a state that the flat key portion 33 is received in
the non-circular hole 643. As shown in FIGS. 5A and 5B, the
transmission gear 64 includes a gear body 641 meshed with the
second driven gear 633, and the boss 642 which is formed
concentrically with the gear body 641 and protrudes axially
inwardly in the document sheet feeding section 13. The non-circular
hole (non-deformable hole) 643 substantially having a D-shape in
cross section is formed in an end portion of a transmission shaft,
so that the flat key portion 33 of the roller shaft 31 is fittingly
received in the non-circular hole 643. The roller shaft 31 is
coupled to the transmission gear 64 to be rotatable with the boss
642 when the flat key portion 33 is received in the non-circular
hole 643.
[0050] In the sheet transporting device 20 having the above
construction, as shown in FIG. 4B, an operator can attach the
roller shaft 31 to the driving unit 60 by passing the hemispherical
portion 35 of the roller shaft 31 through the second bearing 212,
mounting the second bearing 212 in the insertion hole 134 of the
left-side frame wall 131, temporarily moving the roller shaft 31
leftward, followed by moving the roller shaft 31 rightward, and
then inserting the flat key portion 33 in the non-circular hole 643
of the boss 642 supported on the first bearing 211. Likewise, the
operator can detach the roller shaft 31 from the driving unit 60 by
implementing the above steps in the reverse order.
[0051] In the following, the operation of the sheet transporting
device is described referring to FIGS. 6A through 6D. FIG. 6A shows
a state that the hemispherical portion 35 of the roller shaft 31 is
about to be received in the insertion hole 134 of the left-side
frame wall 131. FIG. 6B shows a state that the second bearing 212
is mounted in the insertion hole 134 after the hemispherical
portion 35 of the roller shaft 31 is received in the insertion hole
134, and that the flat key portion 33 is opposed to the boss 642 of
the transmission gear 64. FIG. 6C shows a state that the flat key
portion 33 is received in the circular hole 213 of the boss 642.
FIG. 6D shows a state that the stopper ring 22 is mounted in the
cutaway grove 34 of the roller shaft 31.
[0052] In mounting the document sheet feeding unit 30 between the
pair of frame walls 131 of the document sheet feeding section 13,
as shown in FIG. 6A, first, an operator attaches the second bearing
212 to the end portion of the roller shaft 31 where the cutaway
groove 34 is formed. Then, the operator inserts the end portion of
the roller shaft 31 into the insertion hole 134 while holding the
roller shaft 31 tiltingly. After confirming that the flat key
portion 33 of the roller shaft 31 does not interfere with the
right-side frame wall 131, the operator holds the roller shaft 31
horizontally, and mounts the second bearing 212, as shown in the
two-dotted-chain line in FIG. 6B, in the insertion hole 134 of the
left-side frame wall 131 by sliding the second bearing 212 toward
the left-side frame wall 131, as shown by the leftward arrow in
FIG. 6B, while keeping the horizontal state of the roller shaft
31.
[0053] Next, the operator holds the roller shaft 31 in such a
manner that the flat key portion 33 opposes the non-circular hole
643 of the boss 642, and then moves the roller shaft 31 toward the
circular hole 213, as shown by the rightward arrow in FIG. 6B.
Thereby, as shown in FIG. 6C, the flat key portion 33 of the roller
shaft 31 is received in the non-circular hole 643 of the boss
642.
[0054] Then, when the operator mounts the stopper ring 22 in the
cutaway groove 34 of the roller shaft 31, as shown by the arrow in
FIG. 6C, the roller shaft 31 is kept from moving leftward in FIGS.
6A through 6D. Thus, as shown in FIG. 6D, the document sheet
feeding unit 30 is mounted between the pair of frame walls 131
while being kept from coming off the frame walls 131.
[0055] The sheet transporting device 20 can be detached from the
document sheet feeding section 13 of the copier 10 by implementing
the above steps in the reverse order.
[0056] As mentioned above in detail, the sheet transporting device
20 according to the embodiment of the present invention is
applicable to the copier 10, for instance. The sheet transporting
device 20 is constructed in such a manner that the roller shaft 31
is mounted between the pair of frame walls 131 with the feed roller
51 mounted thereon for successively feeding the document sheets
placed on the document sheet feeding tray 14 from the uppermost
one, the transmission gear 64 is concentrically coupled to the
roller shaft 31 at the one end of the roller shaft 31, so that the
roller shaft 31 is rotatable by driving of the driving motor 62,
the boss 642 projects from the center position of the transmission
gear 64, the roller shaft 31 is formed with the flat key portion 33
which is to be concentrically and detachably inserted in the
non-circular hole 643 of the boss 642, and the cutaway groove 34 is
formed in the end portion of the hemispherical portion 35 for
detachably receiving the stopper ring 22. This arrangement enables
the operator to implement the steps of: mounting the hemispherical
portion 35 of the roller shaft 31 in the insertion hole 134 of the
frame wall 131 before mounting the stopper ring 22; mounting the
second bearing 212 in the insertion hole 134 after confirming that
the flat key portion 33 does not interfere with the transmission
gear 64; inserting the flat key portion 33 in the non-circular hole
643 of the boss 642 of the transmission gear 64; and mounting the
stopper ring 22 in the cutaway groove 34 of the roller shaft 31.
When these steps are conducted, the roller shaft 31 is mounted
between the pair of frame walls 131 without likelihood that the
roller shaft 31 comes off the frame walls 131.
[0057] In detaching the roller shaft 31 from the pair of frame
walls 131, after detaching the stopper ring 22 from the roller
shaft 31, the operator moves the roller shaft 31 axially outwardly
from the frame wall 131 where the hemispherical portion 35 of the
roller shaft 31 is mounted, and tiltingly holds the roller shaft 31
to avoid interference of the flat key portion 33 with the frame
wall 131 after confirming that the flat key portion 33 of the
roller shaft 31 has left from the non-circular hole 643 of the boss
642 of the transmission gear 64. Thus, the operator is prepared to
detach the roller shaft 31 from the pair of frame walls 131.
[0058] While the roller shaft 31 is mounted between the pair of
frame walls 131, the roller shaft 31 is integrally rotated with the
transmission gear 64 with the flat key portion 33 being received in
the insertion hole 134. With this arrangement, the driving force of
the drive source is securely transmitted to rotate the feed roller
51 about an axis of the roller shaft 31 via the transmission gear
64 and the roller shaft 31. Thereby, the sheets P placed on the
sheet stacking portion 14 are fed one by one into the document
sheet feeding section 13.
[0059] In this way, the rotation of the transmission gear 64 is
directly conveyed to the roller shaft 31 without providing a
coupling cylinder between the transmission gear 64 and the roller
shaft 31, which has been required in the conventional arrangement.
This arrangement enables to securely convey the rotation of the
transmission gear 64 to the roller shaft 31 without eccentric
displacement of the roller shaft 31 relative to the transmission
gear 64 and to effectively prevent occurrence of a feeding-related
trouble due to eccentric rotation of the feed roller 51.
[0060] Further, the above arrangement eliminates necessity of using
a coupling member such as the conventional coupling cylinder, and
urging means such as a coil spring for exerting an urging force to
the coupling member. Thereby, the number of the parts can be
reduced, and the roller shaft 31 can be detachably attached to the
frame members with a simplified operation.
[0061] The coupling mechanism in accordance with the embodiment of
the present invention has a simplified construction, namely,
comprises the boss 642 which projects from the end surface of the
transmission gear 64, the non-circular hole 643 formed in the boss
642, and the flat key portion 33 formed on the end portion of the
roller shaft 31. This arrangement contributes to reduction in costs
relating to the parts and the processing, and makes it possible for
an operator to detachably attach the roller shaft 31 to the
transmission gear 64 by merely inserting the flat key portion 33 in
the non-circular hole 643, thereby providing improved operability
to the operator.
[0062] Furthermore, the cutaway groove 34 is formed in the end
portion of the roller shaft 31, and the stopper ring 22 is mounted
in the cutaway groove 34. This arrangement keeps the roller shaft
31 from coming off the frame walls 131, namely, keeps the stopper
ring 22 from moving beyond the adjoining frame wall 131 because the
stopper ring 22 is mounted in the cutaway groove 34 of the roller
shaft 31 after the second bearing 212 is mounted on the roller
shaft 31. This arrangement securely prevents the roller shaft 31
from coming off the frame walls 131.
[0063] The roller shaft 31 can be detached from the pair of frame
walls 131 by detaching the stopper ring 22 from the roller shaft
31. Namely, the operator is allowed to axially move the roller
shaft 31 by detaching the stopper ring 22 from the roller shaft 31,
and thus is allowed to detach the roller shaft 31 from the frame
walls 131.
[0064] The present invention is not limited to the foregoing
embodiment, and the following modifications and alterations are
applicable.
[0065] In the foregoing embodiment, the stopper ring 22 is mounted
in the cutaway groove 34 formed in the roller shaft 31 to keep the
roller shaft 31 from coming off the frame walls 131. Alternatively,
the roller shaft 31 may be formed with a through hole, and a
stopper pin may be inserted in the through hole.
[0066] In the foregoing embodiment, the flat key portion 33 having
a substantially D-shape in cross section is formed on the one end
portion of the roller shaft 31, the boss 642 projecting from the
center position of the transmission gear 64 is formed, and the
non-circular hole 643 having such a shape as to fittingly receive
the flat key portion 33 is formed in the boss 642 so as to
integrally rotate the roller shaft 31 with the transmission gear
64. The cross-sectional shape of the flat key portion 33 and the
non-circular hole 643 is not limited to the substantially D-shape.
As far as the roller shaft 31 and the transmission gear 64 are
integrally rotatable about the axis of the roller shaft 31, any
shape including a polygonal shape may be applicable to the flat key
portion 33 and the non-circular hole 643.
[0067] In the foregoing embodiment, the copier 10 is shown as an
example of the apparatus to which the inventive sheet transporting
device 20 is applied. Alternatively, the present invention is
applicable to image forming apparatuses such as facsimile machines
and printers.
[0068] As shown in cross-sectional views of FIGS. 7A through 7C,
there is proposed a modified coupling mechanism of a roller shaft
and a transmission gear. FIG. 7A shows a state that a coil spring
is detached from the transmission gear, FIG. 7B shows a state that
the coil spring is mounted on the transmission gear, and FIG. 7C
shows a state that the roller shaft is coupled to the transmission
gear via the coil spring.
[0069] In the modification, a flat key portion is not formed at an
end portion of the roller shaft 31. Specifically, the roller shaft
31 has a circular cylinder 36 which is concentric with a roller
shaft main body 32 and has substantially the same diameter as the
roller shaft main body 32. The circular cylinder 36 corresponds to
the end portion (flat key portion) of the roller shaft 31 in the
foregoing embodiment. The circular cylinder 36 does not necessarily
have the same diameter as the roller shaft main body 32, but may
have a smaller diameter than the roller shaft main body 32.
[0070] A circular recess 644 is formed in an end surface of a boss
642 of the transmission gear 64. The circular recess 644 has an
inner diameter larger than an outer diameter of the circular
cylinder 36. With this arrangement, there is defined an annular
clearance between the circular cylinder 36 and the circular recess
644 when the circular cylinder 36 is received in the circular
recess 644. The coil spring 66 having such a dimension as to fit in
the annular clearance is mounted in the circular recess 644, as
shown in FIG. 7B. In this modification, the coil spring 66 is
formed by processing a drawn wire having a polygonal shape in cross
section into a helical spring.
[0071] In the coupling mechanism having the above construction, the
coil spring 66 is tightly wound around the circular cylinder 36, as
the transmission gear 64 is driven in such a direction as to wind
up the coil spring 66. Thereby, the rotation of the transmission
gear 64 is conveyed to the roller shaft 31. On the other hand, as
the transmission gear 64 is driven in such a direction as to loosen
the coil spring 66, transmission of the rotation of the
transmission gear 64 to the circular cylinder 36 is stopped.
Thereby, the rotation of the roller shaft 31 is suspended despite
the rotation of the transmission gear 64.
[0072] In this way, the coil spring 66 provided between the
circular recess 644 and the circular cylinder 36 serves as a
one-way clutch. Winding the coil spring 66 in such a direction as
to rotate the roller shaft 31 exclusively in the direction to feed
the document sheet P into the document sheet feeding section 13
eliminates a drawback that the roller shaft 31 is rotated backward
accompanied by backward rotation of the transmission gear 64. With
this arrangement, there is avoided a possibility that the document
sheet P may be fed backward accompanied by backward rotation of the
feed roller via the roller shaft 31.
[0073] As described above, an inventive sheet transporting device
for use in an image forming apparatus comprises: a pair of frame
walls opposed to each other; a roller shaft extending between the
frame walls, opposite end portions of the roller shaft being
received in insertion holes formed in the frame walls,
respectively; a feed roller which is mounted on the roller shaft
and is rotatable about an axis of the roller shaft, the feed roller
for feeding sheets stacked on a sheet stacking portion of the image
forming apparatus one by one from an uppermost sheet; a
transmission gear which is provided at an outer side of one of the
frame walls, the transmission gear having a center position opposed
to the insertion hole of the frame wall; and an attachment
structure which is so configured as to mount the roller shaft
between the frame walls so as to transmit a driving force of the
transmission gear to the roller shaft.
[0074] The attachment structure includes a boss which is formed
co-axially with the transmission gear and projects in the axial
direction of the roller shaft to be received in the insertion hole
of the frame wall, the boss being formed with a non-circular hole
extending in the axial direction of the roller shaft; and an
engaging end portion which is formed in an end portion of the
roller shaft and has such a configuration as to be received in the
non-circular hole of the boss in a non-rotatable state relative to
the transmission gear.
[0075] In the above arrangement, the roller shaft is mounted
between the frame walls when an operator implements the steps of:
while tiltingly holding the roller shaft, inserting the other end
portion of the roller shaft, which is opposite to the one end
portion of the roller shaft where a flat key portion (engaging end
portion) is formed, in the corresponding insertion hole of the
frame wall after confirming that the engaging end portion of the
roller shaft does not interfere with the frame wall; and inserting
the engaging end portion of the roller shaft in the non-circular
hole of the boss of the transmission gear.
[0076] On the other hand, the roller shaft is detached from the
frame walls when the operator implements the steps of: moving the
roller shaft axially, so that the other end portion of the roller
shaft is away from the frame wall; holding the roller shaft
tiltingly to avoid interference with the frame wall in a state that
the engaging end portion of the roller shaft is away from the frame
wall; and withdrawing the roller shaft to disengage the engaging
end portion from the insertion hole of the frame wall.
[0077] Since the roller shaft is integrally rotated with the
transmission gear about the axis of the transmission gear by the
operation of the coupling mechanism in a state that the roller
shaft extends between the frame walls, the driving force of the
drive source is transmitted to the feed roller to rotate the feed
roller about the axis of the roller shaft via the transmission gear
and the roller shaft. With this arrangement, the sheets stacked on
the sheet stacking portion are fed successively.
[0078] The rotation of the transmission gear is directly
transmitted to the roller shaft without providing an additional
coupling member such as a coupling cylinder and a stopper pin
between the roller shaft and the transmission gear, which has been
required in the conventional arrangement. This arrangement is
advantageous in transmitting the rotation of the transmission gear
to the roller shaft without eccentric displacement of the roller
shaft relative to the transmission gear, and in effectively
preventing occurrence of a feeding-related trouble due to eccentric
rotation of the feed roller.
[0079] Further, since the coupling mechanism has a simplified
construction, as compared with the conventional arrangement, the
above arrangement contributes to reduction in the number of parts,
and secures improved operability in detachably attaching the roller
shaft.
[0080] The other end portion of the roller shaft may preferably
have a stopper structure which is so configured as to keep the
roller shaft from coming off the frame wall through the insertion
hole formed in the frame wall unless an external force is applied,
the stopper structure being detachably attachable to the sheet
transporting device.
[0081] In the above arrangement, since the stopper structure
enables to keep the roller shaft mounted between the frame walls
from coming off the frame walls, there is no likelihood that the
roller shaft may come off the frame walls during its rotation.
[0082] The stopper structure may preferably include a cutaway
groove which is formed in a surface of the other end portion of the
roller shaft, and a stopper ring which is detachably mounted in the
cutaway groove.
[0083] In the above arrangement, the stopper ring is mounted in the
cutaway groove of the roller shaft in a state that the roller shaft
extends between the frame walls. This arrangement makes it possible
to keep the roller shaft from axially displacing in such a
direction as to come off the frame walls, namely from axially
moving outwardly beyond the frame wall. Thus, there is no
likelihood that the roller shaft may come off the frame walls.
[0084] In the above arrangement, in detaching the roller shaft from
the frame walls, the operator is allowed to move the roller shaft
in the axial direction of the roller shaft by simply detaching the
stopper ring from the roller shaft, and thus, the roller shaft is
detachable from the frame walls.
[0085] In this way, constituting the stopper structure by the
cutaway groove formed in the roller shaft, and the stopper ring
detachably mounted in the cutaway groove enables to securely keep
the roller shaft from coming off the frame walls, while simplifying
the stopper structure.
[0086] In the inventive sheet transporting device, rotation of the
transmission gear is directly conveyed to the roller shaft without
providing various parts of a complicated structure between the
transmission gear and the roller shaft, which has been required in
the conventional arrangement. This arrangement is advantageous in
transmitting the rotation of the transmission gear without
eccentric displacement of the roller shaft relative to the
transmission gear, and in effectively preventing occurrence of a
feeding-related trouble due to eccentric rotation of the feed
roller.
[0087] Further, the number of parts can be remarkable reduced while
simplifying the construction of the sheet transporting device, and
to secure improved operability in detachably attaching the roller
shaft.
[0088] This application is based on Japanese Patent Application No.
2003-153643 filed on May 30, 2003, the contents of which are hereby
incorporated by reference.
[0089] Although the present invention has been fully described by
way of example with reference to the accompanying drawings, it is
to be understood that various changes and modifications will be
apparent to those skilled in the art. Therefore, unless otherwise
such changes and modifications depart from the scope of the present
invention hereinafter defined, they should be construed as being
included therein.
* * * * *