U.S. patent application number 10/944850 was filed with the patent office on 2005-06-30 for paper supply device of image forming apparatus and method.
Invention is credited to Jung-Yun, Won.
Application Number | 20050140082 10/944850 |
Document ID | / |
Family ID | 34698762 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050140082 |
Kind Code |
A1 |
Jung-Yun, Won |
June 30, 2005 |
Paper supply device of image forming apparatus and method
Abstract
A paper supply device and method for an image forming apparatus.
The paper supply device comprises a driving unit, a first idle gear
rotated by the driving unit, a first idle gear rotational shaft
which is installed to pass through the first idle gear and rotates
with the first idle gear, a paper conveying unit which is installed
to be rotated by the first idle gear and conveying paper inward
along the paper conveying path, and a multiple-feed preventing unit
which is installed to be rotated by the first idle gear and
preventing multiple-feed of the paper.
Inventors: |
Jung-Yun, Won; (Seoul,
KR) |
Correspondence
Address: |
ROYLANCE, ABRAMS, BERDO & GOODMAN, L.L.P.
1300 19TH STREET, N.W.
SUITE 600
WASHINGTON,
DC
20036
US
|
Family ID: |
34698762 |
Appl. No.: |
10/944850 |
Filed: |
September 21, 2004 |
Current U.S.
Class: |
271/121 |
Current CPC
Class: |
B65H 2403/732 20130101;
B65H 2301/4234 20130101; B65H 5/062 20130101; B65H 2301/44514
20130101; B65H 2403/42 20130101 |
Class at
Publication: |
271/121 |
International
Class: |
B65H 003/52; B65H
003/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 30, 2003 |
KR |
2003-100468 |
Claims
What is claimed is:
1. A paper supply device of an image forming apparatus, comprising:
a driving motor; a driving gear coupled to the driving motor for
rotating at a predetermined speed; a paper conveying unit for
rotating by the driving gear, and conveying paper inward along a
paper conveying path; and a multiple-feed preventing unit for
rotating by the driving gear, and preventing multiple-feeding of
the paper.
2. The paper supply device according to claim 1, wherein the
driving gear is connected to a first idle gear rotated by the
driving gear, and the paper conveying unit and the multiple-feed
preventing unit are rotated by the first idle gear.
3. The paper supply device according to claim 2, wherein the paper
conveying unit includes a forward gear which is installed to engage
with the first idle gear, a forward gear rotational shaft which is
installed to pass through the forward gear and rotates with the
forward gear, and a forward roller which is installed on the
forward gear rotational shaft and rotates with the forward gear
rotational shaft to convey the paper.
4. The paper supply device according to claim 3, wherein the
multiple-feed preventing unit includes a retard gear which is
installed to engage with the first idle gear, a retard gear
rotational shaft which is installed to pass through the retard gear
and rotates with the retard gear, a torque limiter which is
installed on the retard gear rotational shaft and rotates with the
retard gear rotational shaft and performs a forward or reverse
rotation according to paper feed friction force of the paper, and a
retard roller which is connected to the torque limiter and rotates
with the torque limiter and prevents the multiple-feeding of
paper.
5. The paper supply device according to claim 4, wherein the first
idle gear is a multi-stage gear and includes a first-stage idle
gear provided for engagement with the forward gear and a
second-stage idle gear provided for engagement with the retard
gear.
6. The paper supply device according to claim 5, wherein the
second-stage idle gear has a number of gear teeth smaller than that
of the first-stage idle gear so that the retard gear has a
rotational speed slower than that of the forward gear.
7. The paper supply device according to claim 4, wherein: the first
idle gear comprises a first idle gear rotational shaft which allows
the first idle gear to be rotated and rotates with the first idle
gear; and the first idle gear rotational shaft is provided with a
shaft distance maintaining unit for maintaining at least one of a
shaft distance between the first idle gear rotational shaft and the
retard gear rotational shaft and a shaft distance between the first
idle gear rotational shaft and the forward gear rotational shaft
within a predetermined range.
8. The paper supply device according to claim 7, wherein the shaft
distance maintaining unit includes at least one coupling plate
having two coupling holes spaced apart from each other by a
predetermined distance, the two coupling holes being inserted by
the first idle gear rotational shaft and a shaft shifting up and
down while maintaining a predetermined distance from the first idle
gear rotational shaft, respectively.
9. The paper supply device according to claim 8, wherein the
coupling plate is further provided with a pressing means for
shifting and pressing one of the retard and forward rollers toward
the other so that the retard and forward rollers are brought into
contact with each other at a predetermined pressure.
10. The paper supply device according to claim 9, wherein the
pressing means includes an extension spring installed to pull one
end of the coupling plate toward the shifted roller, the one end of
the coupling plate being more adjacent to the first idle gear
rotational shaft.
11. The paper supply device according to claim 7, wherein the first
idle gear rotational shaft is further provided with a plurality of
feed rollers which are installed to rotate with the first idle gear
rotational shaft and conveys the paper inward along the paper
conveying path.
12. The paper supply device according to claim 2, further
comprising a second idle gear between the driving gear and the
first idle gear, the second idle gear being engaged with both the
driving gear and the first idle gear so as to transmit a rotational
force of the driving gear to the first idle gear.
13. The paper supply device according to claim 1, wherein the paper
conveying unit is installed on any one of upper and lower sides of
a paper conveying path.
14. The paper supply device according to claim 1, wherein the
multiple-feed preventing unit is installed on the other side of the
paper conveying path which corresponds to the paper conveying
unit.
15. A method for supplying paper for an image forming apparatus,
comprising: providing a driving motor; coupling a driving gear to
the driving motor for rotating at a predetermined speed; rotating a
paper conveying unit via the driving gear, and conveying paper
inward along a paper conveying path; and rotating a multiple-feed
preventing unit via the driving gear, and preventing
multiple-feeding of the paper.
16. The method according to claim 15, further comprising:
connecting the driving gear to a first idle gear rotated by the
driving gear; and rotating the paper conveying unit and the
multiple-feed preventing unit via the first idle gear.
17. The method according to claim 16, wherein the paper conveying
unit comprises a forward gear.
18. The method according to claim 17, further comprising: engaging
the forward gear with the first idle gear.
19. The method according to claim 18, further comprising: providing
a forward gear rotational shaft.
20. The method according to claim 19, wherein the forward gear
rotational shaft passes through the forward gear.
21. The method according to claim 20, further comprising: rotating
the forward gear rotational shaft with the forward gear.
22. The method according to claim 19, wherein the paper conveying
unit comprises a forward roller which is installed on the forward
gear rotational shaft.
23. The method according to claim 22, further comprising: rotating
the forward roller via the forward gear rotational shaft in order
to convey the paper.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119(a) of Korean Patent Application No. 2003-100468, filed on Dec.
30, 2003, the entire contents of which is 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 method. More particularly, the present invention relates to a
paper supply device of an image forming apparatus designed to
convey a printing medium or paper inward along a paper conveying
path and a method thereof.
[0004] 2. Description of the Related Art
[0005] An electrophotographic image forming apparatus such as a
laser printer, a facsimile or a copier typically performs an image
forming operation by developing an electrostatic latent image
formed on a photosensitive member into a visible image by means of
a toner, transferring the visible image by the toner to paper
conveyed from a paper cassette, and fixing the transferred image
onto the paper.
[0006] For the purpose of this operation, the image forming
apparatus is provided with a paper pick-up unit for sequentially
picking up sheets of paper loaded in the paper cassette, and a
paper supply device for conveying the picked-up paper one sheet at
a time toward a paper conveying path formed inside the image
forming apparatus.
[0007] Therefore, the paper supply device conveys the picked-up
sheet of paper inward along the paper conveying path, when the
paper pick-up unit picks up a sheet of paper placed on the top of
the paper loaded on the paper cassette using a pick-up roller and
so on.
[0008] Occasionally, due to paper-to-paper friction forces and so
on, two or more sheets of paper may be picked up at once and
conveyed inward along the paper conveying path (hereinafter, a
phenomenon that two or more sheets of paper are conveyed is called
"multiple-feed"). Accordingly, this multiple-feed brings about
various problems, for example a jam, inside the image forming
apparatus.
[0009] Hence, in recent years, a variety of approaches for
preventing the multiple-feed have been proposed.
[0010] One example of the approaches is a retard roller method for
preventing the multiple-feed using a torque limiter having a
predetermined critical torque value, a retard roller connected to
the torque limiter and so forth. Here, the torque limiter performs
a forward rotation when the paper feed friction force is greater
than the predetermined critical torque value, while it performs a
reverse rotation when the paper feed friction force is smaller than
the predetermined critical torque value. Further, the retard roller
performs either the forward or reverse rotation depending on the
torque limiter.
[0011] To be more specific, the retard roller method prevents the
multiple-feed by installing the torque limiter and the retard
roller on a lower side of the paper conveying path along which the
paper is conveyed. With this configuration, when either no or one
sheet of paper is conveyed along the paper conveying path, the
paper feed friction force becomes greater than the critical torque
value of the torque limiter, so that the torque limiter and the
retard roller rotate in the paper feed direction, thus conveying
the paper.
[0012] In contrast, when two or more sheets of paper are conveyed
along the paper conveying path, the paper feed friction force
becomes smaller than the critical torque value of the torque
limiter, so that the torque limiter and the retard roller rotate
opposite to the paper conveying direction. Thereby, it is possible
to prevent a multiple-feed.
[0013] One example of the paper supply device for the image forming
apparatus to which such a retard roller method is employed is
disclosed in U.S. Pat. No. 5,571,265 (issued on Nov. 5, 1996)
titled "SHEET SUPPLYING APPARATUS".
[0014] The disclosed sheet supplying apparatus is provided with a
torque limiter and a retard roller to prevent multiple-feeds of the
sheets of paper, in which the torque limiter and the retard roller
are arranged on a lower side of a path along which the sheets of
paper are conveyed sequentially. A retard gear for driving the
retard roller is constructed to receive a driving force from a
gear, which, in turn, is installed to receive a driving force from
a motor, namely a drive gear coupled to a drive roller, and
simultaneously via a plurality of idle gears. Further, the torque
limiter, which performs a forward or reverse rotation according to
paper feed friction force of the paper, is disposed on an
intermediate path along which the driving force is transmitted.
Thus, for the conventional sheet feeding apparatus, when driving
the motor causes a supply roller and the driver roller to rotate to
convey the sheets of paper, the retard gear also receives the
driving force through the drive gear coupled to the drive roller
and the plurality of idle gears engaged with the drive gear, thus
rotating in the same direction as that of the drive roller to
convey the sheets of paper. However, when two or more sheets of
paper are conveyed, the rotational direction becomes different from
the previous direction. Specifically, when two or more sheets of
paper are conveyed, the paper feed friction force becomes smaller
than a critical torque value of the torque limiter, so that the
torque limiter rotates in a direction opposite to that in which the
sheets of paper are conveyed. Therefore, the retard roller also
rotates in a direction opposite to that in which the sheets of
paper are conveyed with the torque limiter, thereby preventing
multiple-feeding of the sheets of paper.
[0015] In this manner, the conventional paper feeding apparatus
prevents multiple-feeding of sheets of paper using the retard
roller, but it employs a very complicated gear train in order to
drive the retard roller. This causes a problem in that the driving
force suffers a considerable loss when in use. Moreover, this loss
of the driving force results in an increase in a load which is
applied to the motor.
[0016] Further, because the conventional paper feeding apparatus
prevents multiple-feeding of the sheets of paper using the
complicated gear train, it has low operational stability as well as
high production costs.
SUMMARY OF THE INVENTION
[0017] Therefore, an objective of the present invention is to
provide a paper supply device for an image forming apparatus,
capable not only of minimizing loss of power, but also of driving a
retard roller.
[0018] Another objective of the present invention is to provide a
paper supply device of an image forming apparatus, capable of
maximizing operational stability through a simplified gear train
and a method thereof.
[0019] In order to accomplish these objectives, there is provided a
paper supply device of an image forming apparatus and a method
thereof. The apparatus and method comprise a driving motor, a
driving gear coupled to the driving motor rotating at a
predetermined speed; a paper conveying unit for rotating via the
driving gear, installed on any one of upper and lower sides of a
paper conveying path, and conveying paper disposed inward along the
paper conveying path, and a multiple-feed preventing unit for
rotating via the driving gear, installed on the other side of the
paper conveying path which corresponds to the paper conveying unit,
for preventing multiple-feeding of the paper.
[0020] Preferably, the driving gear is connected to a first idle
gear rotated by the driving gear, and the paper conveying unit and
the multiple-feed preventing unit are rotated by the first idle
gear.
[0021] Further, the paper conveying unit, preferably, includes a
forward gear which is installed to engage with the first idle gear,
a forward gear rotational shaft which is installed to pass through
the forward gear and rotates with the forward gear, and a forward
roller which is installed on the forward gear rotational shaft and
rotates with the forward gear rotational shaft to convey the
paper.
[0022] Preferably, the multiple-feed preventing unit includes a
retard gear which is installed to engage with the first idle gear,
a retard gear rotational shaft which is installed to pass through
the retard gear and rotates with the retard gear, a torque limiter
which is installed on the retard gear rotational shaft and rotates
with the retard gear rotational shaft and performs a forward or
reverse rotation according to paper feed friction force of the
paper, and a retard roller which is connected to the torque limiter
and rotates with the torque limiter and prevents the multiple-feed
of the paper.
[0023] Furthermore, it is preferred that the first idle gear is a
multi-stage gear and includes a first-stage idle gear provided for
engagement with the forward gear and a second-stage idle gear
provided for engagement with the retard gear, and that the
second-stage idle gear has a number of gear teeth smaller than that
of the first-stage idle gear so that the retard gear has a
rotational speed slower than that of the forward gear.
[0024] Meanwhile, the first idle gear is preferably provided with a
first idle gear rotational shaft which allows the first idle gear
to be rotated with the first idle gear. The first idle gear
rotational shaft is preferably provided with a shaft distance
maintaining unit for maintaining at least one of a shaft distance
between the first idle gear rotational shaft and the retard gear
rotational shaft and a shaft distance between the first idle gear
rotational shaft and the forward gear rotational shaft within a
predetermined range. It is preferred that the shaft distance
maintaining unit includes at least one coupling plate having two
coupling holes spaced apart from each other by a predetermined
distance, the two coupling holes being inserted by the first idle
gear rotational shaft and a shaft shifting up and down while
maintaining a predetermined distance from the first idle gear
rotational shaft, respectively.
[0025] Further, it is preferred that the coupling plate is further
provided with a pressing means for shifting and pressing one of the
retard and forward rollers toward each other so that the retard and
forward rollers are brought into contact with each other at a
predetermined pressure. The pressing means, preferably, includes an
extension spring installed to pull one end of the coupling plate
toward the shifted roller, the one end of the coupling plate being
more adjacent to the first idle gear rotational shaft.
[0026] Furthermore, it is preferred that the first idle gear
rotational shaft is further provided with a plurality of feed
rollers which are installed to rotate with the first idle gear
rotational shaft and conveys the paper inward along the paper
conveying path.
[0027] In addition, preferably, the paper supply device further
comprises a second idle gear between the driving gear and the first
idle gear, the second idle gear being engaged with both the driving
gear and the first idle gear so as to transmit a rotational force
of the driving gear to the first idle gear.
[0028] Hereinafter, a detailed description will be made of a paper
supply device of an image forming apparatus according to an
embodiment of the present invention as well as the image forming
apparatus to which the paper supply device is applied.
[0029] With regard to the image forming apparatus to which the
paper supply device of the embodiments of the present invention are
applied, it comprises a main body forming an external appearance
and provided with a paper conveying path inside, a paper cassette
detachably mounted to the main body and loads a plurality of sheets
of paper, a paper pick-up unit mounted to the main body and picking
up the sheets of paper loaded in the cassette one by one from the
top sheet of paper, a paper conveying unit conveying the picked-up
paper inward along the paper conveying path, an image transferring
apparatus transferring a predetermined image to the conveyed paper,
a fixing apparatus semi-permanently fixing the transferred image,
and a central control apparatus controlling the image forming
apparatus as a whole.
[0030] Here, two or more sheets of paper are often picked up and
conveyed by the paper pick-up unit. The paper supply device
functions not only to convey the picked-up paper inward along the
paper conveying path, but also to prevent multiple-feed of the
picked-up paper.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The above and other features and advantages of embodiments
of the present invention will become more apparent to those of
ordinary skill in the art by describing in detail embodiments
thereof with reference to the accompanying drawings in which:
[0032] FIG. 1 is a perspective view illustrating a paper supply
device of an image forming apparatus according to an embodiment of
the present invention;
[0033] FIG. 2 is a perspective view illustrating a state where the
paper supply device of the image forming apparatus shown in FIG. 1
is driven;
[0034] FIG. 3 is an enlarged perspective view illustrating a state
where a first idle gear, a forward gear and a retard gear of the
paper supply device of the image forming apparatus shown in FIG. 1
are assembled; and
[0035] FIG. 4 is a perspective view illustrating a paper supply
device of an image forming apparatus according to another
embodiment of the present invention.
[0036] Throughout the drawings, it should be noted that the same or
similar elements are denoted by like reference numerals.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] A description will now be made in detail with regard to a
paper supply device 100 of an image forming apparatus according to
embodiments of the present invention with reference to FIGS. 1 to
4.
[0038] As shown in the drawings, the paper supply device 100 of the
image forming apparatus according to embodiments of the present
invention comprise a driving unit 150 which generates a driving
force, a paper conveying unit 120 which is driven by the generated
driving force and conveys paper 80 picked-up by a paper pick-up
unit (not shown) toward a paper conveying path 70 (see FIG. 2), a
multiple-feed preventing unit 130 which is driven by the generated
driving force and prevents multiple feeding of the paper, and a
driving force transmitting unit which transmits the driving force
of the driving unit 150 to the paper conveying unit 120 and the
multiple feed preventing unit 130.
[0039] Specifically, the driving unit 150 includes a driving motor
152 for generating a predetermined rotational force, and a driving
gear 154 coupled to the driving motor 152 and rotating at a
predetermined Revolution per Minute (RPM).
[0040] The paper conveying unit 120 is installed on one of upper
and lower sides of the paper conveying path 70 and functions to
convey the paper 80. The paper conveying unit 120 includes a
forward gear 122 which is installed to engage a first idle gear 170
of the driving force transmitting unit to be mentioned below, a
forward gear rotational shaft 126 which is installed to pass
through the forward gear 122 and rotates with the forward gear 122,
and a forward roller 121 which is installed on the forward gear
rotational shaft 126 and rotates with the forward gear rotational
shaft 126 to convey the paper 80 inward along the paper conveying
path 70. Here, the paper conveying unit 120 is preferably installed
on the upper side of the paper conveying path 70.
[0041] The multiple feed preventing unit 130 is installed on the
other side, corresponding to the paper conveying unit 120, of the
upper and lower sides of the paper conveying path 70 and functions
to prevent multiple-feeding of the paper 80. The multiple-feed
preventing unit 130 includes a retard gear 131 which is installed
to engage with the first idle gear 170, a retard gear rotational
shaft 135 which is installed to pass through the retard gear 131
and rotates with the retard gear 131, a torque limiter 137 which is
installed on the retard gear rotational shaft 135 so as to have a
predetermined critical torque value. The torque limiter 137
performs a forward rotation when a predetermined paper feed
friction force is greater than the critical torque value, and
performs a reverse rotation when the predetermined paper feed
friction force is smaller than the critical torque value, and a
retard roller 132 which is connected to the torque limiter 137,
performs a forward or reverse rotation with the torque limiter, and
prevents multiple-feeding of the paper 80. Preferably, the
multiple-feed preventing unit 130 is installed on the lower side of
the paper conveying path 70. Further, the retard roller 132 of the
multiple-feed preventing unit 130 is preferably installed on a
lower side of the forward roller 121 so as to come into rolling
contact with the forward roller 121. Preferably, the torque limiter
137 performs the forward or reverse rotation depending on the paper
feed friction force of the paper which is conveyed between the
forward roller 121 and the retard roller 132. Further, the
multiple-feed preventing unit 130 including the retard roller 132
and the retard gear rotational shaft 135 is preferably installed to
shift up and down at a predetermined distance so that the paper 80
can be introduced and conveyed between the retard roller 132 and
the forward roller 121 which are brought into rolling contact with
each other.
[0042] The driving force transmitting unit includes the first idle
gear 170 which is engaged with both the forward gear 122 of the
paper conveying unit 120 and the retard gear 131 of the
multiple-feed preventing unit 130, a second idle gear 160 which
transmits the rotational force of the driving gear 154 to the first
idle gear 170, and first and second idle gear rotational shafts 175
and 163 which are installed to pass through the first and second
idle gears 170 and 160 and rotate with the first and second idle
gears 170 and 160.
[0043] Here, the first idle gear 170 is formed of a multi-stage
gear, which is engaged with the forward gear 122 and the retard
gear 131. To this end, the first idle gear 170 is provided with a
first-stage idle gear 171 for engagement with the forward gear 122,
and a second-stage idle gear 173 for engagement with the retard
gear 131 (see FIG. 3). With this configuration, both the forward
gear 122 and the retard gear 131 are engaged with the first idle
gear 170. The second-stage idle gear 173 with which the retard gear
131 is meshed has a smaller number of teeth than that of the
first-stage idle gear 171 with which the forward gear 122 is
meshed. In this manner, the forward and retard gears 122 and 131
which are engaged with the first idle gear 170 rotate in proportion
to the number of teeth of the first- and second-stage idle gears
171 and 173, and the retard gear 131 meshing with the second-stage
idle gear 173 rotates at a relatively low speed compared with the
forward gear 122 meshing with the first-stage idle gear 171.
[0044] Further, the first and second idle gear rotational shafts
175 and 163 are installed to pass through the first and second idle
gears 170 and 160 so that the first and second idle gears 170 and
160 can rotate respectively, and are fixed to a main body 90 of the
image forming apparatus. Here, the first and second idle gear
rotational shafts 175 and 163 are preferably installed on an upper
side of the paper conveying path 70 similar to the foregoing paper
conveying unit 120. Hence, at least one of the first and second
idle gear rotational shafts 175 and 163, for example, the first
idle gear rotational shaft 175 is additionally provided with a
plurality of feed rollers 140 so as to more smoothly convey the
paper 80 conveyed by the forward roller 121. In this case, the
paper 80 conveyed by the forward roller 121 is more smoothly
conveyed inward along the paper conveying path 70 by the feed
rollers 140.
[0045] The retard gear 131 of the multiple-feed preventing unit 130
is installed to engage with the first idle gear 170. This
engagement of the retard gear 131 must continue to be maintained
even when the multiple-feed preventing unit 130 shifts up and down
at a predetermined distance, so that the paper 80 can be introduced
and conveyed between the retard roller 132 and the forward roller
121.
[0046] Therefore, in order to maintain this engagement, the paper
supply device 100 of the embodiments of the present invention is
realized by maintaining a distance between the shafts of the gears
170 and 131 in a predetermined range. For this purpose, the first
idle gear rotational shaft 175 passing through the first idle gear
170 is provided with a shaft distance maintaining unit 180, which
functions to maintain a shaft distance between the first idle gear
rotational shaft 175 and the retard gear rotational shaft 135 in a
predetermined range.
[0047] The shaft distance maintaining unit 180 is implemented as a
coupling plate 185 having two coupling holes 183 spaced apart from
each other by a predetermined distance (i.e., a distance which must
be maintained between the first idle gear rotational shaft 175 and
the retard gear rotational shaft 135), in which one of the two
coupling holes is inserted by the first idle gear rotational shaft
175 and the other is inserted by the retard gear rotational shaft
135 as the shaft capable of shifting up and down while maintaining
a predetermined distance from the first idle gear rotational shaft
175. In this case, the coupling plate 185 is preferably provided
with at least two pairs of coupling holes 183. In addition, the
coupling plate 185 is formed in a ".PI." or "U" shape, where both
its ends are bent at a predetermined angle. These paired coupling
holes 183 are preferably formed on the both ends, which are bent
either downward or upward. Therefore, even when the multiple-feed
preventing unit 130 shifts up and down at a predetermined distance,
the shaft distance between the first idle gear rotational shaft 175
and the retard gear rotational shaft 135 continues to be maintained
by the shaft distance maintaining unit 180 at a predetermined
distance, so that the retard gear 131 and the first idle gear 170
continue to be engaged with each other. Meanwhile, the shaft
distance maintaining unit 180 may be equally applied between the
first idle gear rotational shaft 175 and the forward gear
rotational shaft 126 except between the first idle gear rotational
shaft 175 and the retard gear rotational shaft 135.
[0048] Further, after the paper 80 is introduced between the
forward roller 121 and the retard roller 132, the retard roller 132
installed to come into rolling contact with the forward roller 121
must contact the forward roller 121 with a predetermined pressure
in order to smoothly convey the paper 80. Therefore, the coupling
plate 185 of the shaft distance maintaining unit 180 is provided
with a pressing means, which shifts and presses one of the retard
and forward rollers 132 and 121 toward each other (herein, one
example will be taken from the case of shifting and pressing the
retard roller 132 toward the forward roller 121).
[0049] The pressing means is preferably implemented as an extension
spring 187, which is installed to pull one end of the coupling
plate 185 which is inserted by the first idle gear rotational shaft
175 and the retard gear rotational shaft 135 and is closer to the
first idle gear rotational shaft 175. Preferably, one end of the
extension spring 187 is hooked on the one end of the coupling plate
185 which is adjacent to the first idle gear rotational shaft 175,
and the other end of the extension spring 187 is hooked on the main
body 90 located at a lower portion of the retard roller 132. Hence,
elastic tension of the extension spring 187 is applied to the one
end of the coupling plate 185, as shown in FIG. 2. As a result, the
retard gear rotational shaft 135 inserted into the coupling plate
185 in parallel shifts upward by a predetermined distance by a
turning movement generated by the elastic tension of the extension
spring 187, thus pressing the retard roller 132 toward the forward
roller 121.
[0050] In the drawings, each of reference numerals 124, 133, 156,
165, 172 and 174 represents a gear tooth.
[0051] Hereinafter, a detailed description will be provided
regarding operation and effects of an image forming apparatus
according to an embodiment of the present invention as well as the
paper supply device 100 of the image forming apparatus.
[0052] When a plurality of sheets of paper 80 are loaded in a paper
cassette (not shown) and the paper cassette (not shown) is mounted
into the main body 90 of the image forming apparatus, the top sheet
of paper 80 in the paper cassette is picked up.
[0053] When the top sheet of paper 80 is picked up, the paper
supply device 100 drives the driving motor 152 so as to convey the
picked-up sheet of paper inward along the paper conveying path 70
provided in the main body 90.
[0054] As the driving motor 152 rotates, the driving gear 154
coupled to the driving motor 152 rotates.
[0055] As the driving gear 154 rotates, the second idle gear 160
engaged with the driving gear 154 rotates, and simultaneously the
first idle gear 170 engaged with the second idle gear 160
rotates.
[0056] Subsequently, the first idle gear 170 rotated by the second
idle gear 160 rotates the forward and retard gears 122 and 131 in a
direction in which the paper is conveyed, wherein the forward and
retard gears 122 and 131 are engaged with the first and
second-stage idle gears 171 and 173 of the first idle gear 170
respectively.
[0057] Thus, the forward roller 121 coupled to the forward gear
122, and the torque limiter 137 and the retard roller 132 which are
coupled to the retard gear 131 rotate to convey the picked-up sheet
of paper 80 inward along the paper conveying path 70. In this case,
the reason the torque limiter 137 rotates in the direction in which
the picked-up sheet of paper 80 is conveyed is that the paper 80
conveyed between the two rollers 121 and 131 is one sheet. In other
words, the paper feed friction force of the paper 80 is greater
than the critical torque value of the torque limiter 137.
[0058] However, when two or more sheets of the paper 80 are picked
up and conveyed in this manner, the paper feed friction force of
the conveyed paper 80 is smaller than the critical torque value of
the torque limiter 137, so that the torque limiter 137 rotates in a
direction opposite to that of the paper 80. Thus, the retard roller
132 rotates in the direction opposite to that in which the paper 80
is conveyed with the torque limiter 137, so that it is possible to
prevent multiple-feeding of the paper 80.
[0059] Meanwhile, when the paper 80 is conveyed inward along the
paper conveying path 70 by the paper supply device 100, an image
transferring apparatus (not shown) transfers a predetermined image
to the paper 80, and a fixing apparatus (not shown) fixes the
transferred image on the paper 80. Then, the paper 80 is
discharged. Thereby, the image forming operation of the image
forming apparatus is completed.
[0060] As can be seen from the foregoing, the paper supply device
of the image forming apparatus according to embodiments of the
present invention drive the retard roller and forward roller using
a relatively small number of gears, thus minimizing the energy lost
during power transmission of the gears. Thus, a load applied to the
motor is reduced, so that it is possible to considerably save
electric power consumed by the driving of the motor.
[0061] Further, the paper supply device of the image forming
apparatus according to embodiments of the present invention provide
numerical minimization and structural simplification of the idle
gears to convey the paper without the multiple-feed, so that it is
possible to provide improved operation stability and minimized
production costs.
[0062] Furthermore, the paper supply device of the image forming
apparatus according to embodiments of the present invention
maintain the shaft distance between the first idle gear rotation
shaft and the retard gear rotation shaft at a predetermined
distance by means of the shaft distance maintaining unit. Thus,
even when the multiple-feed preventing unit with the retard roller
shifts up and down at a predetermined distance, the retard gear can
continue to engage with the first idle gear.
[0063] In addition, the paper supply device of the image forming
apparatus according to embodiments of the present invention is
provided with the pressing means capable of pressing the retard
roller toward the forward roller, so that the retard roller can
continue to come into contact with the forward roller at a
predetermined pressure. Thus, the multiple-feed of the paper
conveyed between the retard roller and the forward roller can be
minimized.
[0064] Moreover, the paper supply device of the image forming
apparatus according to embodiments of the present invention is
additionally provided with the feed roller on the first idle gear
shaft, so that the paper conveyed inward along the paper conveying
path by the forward roller can be more smoothly conveyed by such a
feed roller.
[0065] It should be understood by those skilled in the art that
while the present invention has been described with reference to
certain embodiments, the described embodiments are simply
illustrative of the principle of the present invention, and that
various other modifications and changes may be devised. Thus, the
scope of protection of the present invention should be limited only
by the scope and equivalent of the following claims.
* * * * *