U.S. patent application number 10/663834 was filed with the patent office on 2004-04-01 for paper detecting apparatus for duplex image forming machine.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Hyun, Jae-Hwan.
Application Number | 20040061283 10/663834 |
Document ID | / |
Family ID | 32026072 |
Filed Date | 2004-04-01 |
United States Patent
Application |
20040061283 |
Kind Code |
A1 |
Hyun, Jae-Hwan |
April 1, 2004 |
Paper detecting apparatus for duplex image forming machine
Abstract
A paper detecting apparatus capable of detecting the presence of
the paper in the paper feed cassette and paper being fed along a
duplex printing paper path by using a single sensor in an image
forming machine having a duplex image forming function and feeding
paper using a paper feed cassette. A paper detecting apparatus of
an image forming machine according to the present invention
includes an actuator pivotably disposed above a paper feed cassette
in which paper is stacked and below a duplex printing paper path
along which a first side copy moves and moved by the paper, and a
paper sensor disposed next to the actuator that senses movement of
the actuator and generates a signal, wherein the actuator pivots in
a predetermined angle when no paper is stacked in the paper feed
cassette or paper is being fed along the duplex printing paper
path, and the paper sensor generates a signal upon sensing the
pivoting actuator.
Inventors: |
Hyun, Jae-Hwan; (Gumi-City,
KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-City
KR
|
Family ID: |
32026072 |
Appl. No.: |
10/663834 |
Filed: |
September 17, 2003 |
Current U.S.
Class: |
271/265.01 |
Current CPC
Class: |
B65H 2511/51 20130101;
B65H 2511/212 20130101; B65H 2553/612 20130101; B65H 7/02 20130101;
B65H 2511/212 20130101; B65H 2220/01 20130101; B65H 2220/11
20130101; B65H 2511/51 20130101; B65H 2220/03 20130101 |
Class at
Publication: |
271/265.01 |
International
Class: |
B65H 007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2002 |
KR |
2002-57014 |
Claims
What is claimed is:
1. A paper detecting apparatus of an image forming machine having a
duplex printing function comprising: an actuator pivotably disposed
above a paper feed cassette and below a duplex printing paper path,
that is moved by the paper; and a paper sensor disposed next to the
actuator that senses movement of the actuator and generates a
signal, wherein the actuator pivots in a predetermined angle when
no paper is stacked in the paper feed cassette or when paper is
being fed along the duplex printing paper path, and the paper
sensor generates a signal upon sensing the actuator pivot.
2. The paper detecting apparatus of an image forming machine
according to claim 1, wherein the actuator comprises: a hinge
shaft; a center pivotably assembled around the hinge shaft; a first
lever extending from the center that operates the paper sensor when
no paper is stacked in the paper feed cassette; a second lever at a
predetermined angle from the first lever, that operates the paper
sensor when paper is fed along the duplex printing paper path; and
a third lever, extending from the center and away from the first
and second levers, weighing more than the combined weight of the
first and second lever to have a tendency to pivot downward.
3. The paper detecting apparatus of an image forming machine
according to claim 2, wherein the predetermined angle is determined
so the second lever does not operate the paper sensor when the
third lever is in contact with paper on the paper feed
cassette.
4. The paper detecting apparatus of an image forming machine
according to claim 2, wherein the paper feed cassette has a slot
that allows the third lever to pass through.
5. The paper detecting apparatus of an image forming machine
according to claim 1, further comprising a stopper limiting
pivoting space of the actuator.
6. The paper detecting apparatus of an image forming machine
according to claim 1, wherein the paper sensor is a photo
sensor.
7. The paper detecting apparatus of an image forming machine,
including a hinge shaft under a duplex printing paper path,
comprising: an actuator, having a center, pivotably assembled on
the hinge shaft; a paper sensor, having a sensing area; a second
lever extending from the center and interfered by the paper when
the paper moves along the duplex printing paper path; a first lever
extending from the center at a predetermined angle from the second
lever; and a third lever extending from the center and away from
the first and second levers and heavier than the combined weight of
the first and second levers, wherein the third lever pivots
downward so the first lever is normally located inside the sensing
area of the paper sensor when no paper is stacked in the paper feed
cassette, and the second lever pivots into the sensing area of the
paper sensor, and then escapes from the sensing area of the paper
sensor due to the weight of the third lever when paper moves along
the duplex printing paper path.
8. The paper detecting apparatus of an image forming machine
according to claim 7, wherein a rear end of a slot formed in the
duplex printing paper path interferes with the second lever when
the first lever is located inside the sensing area of the paper
sensor.
9. The paper detecting apparatus of an image forming machine
according to claim 7, wherein the second lever is not located
inside the sensing area of the paper sensor when the third lever is
in contact with paper stacked in the paper feed cassette.
10. The paper detecting apparatus of an image forming machine
according to claim 7, wherein the paper sensor is a photo
sensor.
11. A paper detecting apparatus of an image forming machine,
including a hinge shaft under a duplex printing paper path, having
a slot, a paper feed cassette in which paper is normally stacked,
and a sensor having a sensing area, comprising: an actuator, having
a center, on the hinge shaft; a first lever extending in a first
direction from the center of the actuator; a second lever extending
in a second direction from the center of the actuator such that a
free end of the second lever extends into the first slot of the
duplex printing path; a third lever extending in a third direction
from the center of the actuator, wherein the third lever causes the
actuator to pivot such that the first lever enters the sensing area
of the sensor when the paper is not stacked in the paper feed
cassette, and allows the actuator to pivot such that the second
lever enters the sensing area of the sensor when the paper moves
along the duplex printing path.
12. The paper detecting apparatus according to claim 11, wherein
the actuator is shaped like a letter "Y".
13. The paper detecting apparatus according to claim 11, wherein
the slot in the duplex printing path comprises a rear end.
14. The paper detecting apparatus according to claim 13, wherein
the slot in the duplex printing path has a length so the rear end
of the slot acts as a stopper for the second lever to limit a
pivoting space of the actuator when no paper is stacked in the
paper feed cassette.
15. The paper detecting apparatus according to claim 11, wherein
the third lever maintains contact with an upper surface of paper
stacked in the paper feed cassette.
16. The paper detecting apparatus according to claim 11, wherein
the paper sensor is normally between the first and second levers
when the paper is stacked in the paper feed cassette.
17. The paper detecting apparatus according to claim 11, wherein
the paper sensor includes a limited switch.
18. The paper detecting apparatus according to claim 11, wherein
the sensor comprises a photo-sensor.
19. The paper detecting apparatus according to claim 11, further
comprising a paper pressing plate having a slot into which the
third lever freely pivots when no paper is stacked in the paper
feed cassette.
20. The paper detecting apparatus according to claim 11, wherein
when the paper is stacked in the paper feed cassette, the first and
second levers are normally forced out of the sensing area of the
sensor.
21. The paper detecting apparatus according to claim 20, further
comprising a paper pressing plate in the paper feed cassette to
maintain the paper in the paper feed cassette at a predetermined
height as paper is fed from the paper feed cassette into the image
forming machine.
22. The paper detecting apparatus according to claim 21, further
comprising a slot in the paper pressing plate, wherein when the
last paper is fed from the paper feed cassette, the third lever
pivots into the slot, thereby causing the first lever to enter the
sensing area of the sensor.
23. The paper detecting apparatus according to claim 22, further
comprising a rear end of the slot in the duplex printing path to
stop the second lever from pivoting.
24. The paper detecting apparatus according to claim 23, wherein
when the first lever enters the paper sensing area of the sensor,
the sensor generates a signal that no paper remains in the paper
feed cassette.
25. The paper detecting apparatus according to claim 24, wherein
the image forming machine receives the signal from the sensor, and
compares a length of the signal with a standard length.
26. The paper detecting apparatus according to claim 25, wherein if
the length of the signal is shorter than the standard length, the
image forming machine judges that the paper is being fed along the
duplex printing path.
27. The paper detecting apparatus according to claim 25, wherein if
the length of the signal is longer than the standard length, the
image forming machine judges that no paper remains in the paper
feed cassette.
28. The paper detecting apparatus according to claim 21, wherein
when the paper moves along the duplex printing paper path after
being fed into the image forming machine, the paper impacts the
second lever, thereby causing the second lever to pivot into the
sensing area of the sensor.
29. The paper detecting apparatus according to claim 28, wherein
when the impact between the paper and the second lever dissipates,
the third lever causes the second lever to pivot out of the sensing
area of the sensor.
30. The paper detecting apparatus according to claim 29, wherein
during the period when the second lever is inside the sensing area
of the sensor, the sensor generates a signal that the paper is
being fed along the duplex printing path.
31. The paper detecting apparatus according to claim 30, wherein
the image forming machine receives the signal from the sensor, and
compares a length of the signal with a standard length.
32. The paper detecting apparatus according to claim 31, wherein if
the length of the signal is longer than the standard length, the
image forming machine judges that no paper remains in the paper
feed cassette.
33. The paper detecting apparatus according to claim 31, wherein if
the length of the signal is shorter than the standard length, the
image forming machine judges that the paper is being fed along a
duplex printing apparatus.
34. The paper detecting apparatus according to claim 31, wherein
when a rear end of the paper being fed along the duplex printing
path leaves the slot of the duplex printing paper shaft, the second
lever enters the slot in the duplex printing path.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Application
No. 2002-57014, filed Sep. 18, 2002, in the Korean Intellectual
Property Office, the disclosure of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a paper detecting apparatus
for an image forming machine, and more particularly, to a paper
detecting apparatus capable of detecting whether duplex paper is
fed and the presence of paper stacked on a paper feed cassette in
an image forming machine having a duplex image forming
function.
[0004] 2. Description of the Related Art
[0005] An image forming machine includes a printer, a copier and a
multifunction machine supplying paper to a paper feed cassette and
having a duplex printing function.
[0006] Generally, an image forming machine feeding paper using a
paper feed cassette and having a duplex printing function that
forms images on two sides of the supplied paper comprises a sensor
that detects whether paper is stacked in the paper feed cassette,
and another sensor that detects paper being conveyed in a duplex
printing operation.
[0007] FIG. 1 shows an embodiment of an image forming machine
having a conventional paper detecting apparatus that detects
whether paper passes a duplex printing paper path and whether paper
is stacked in the paper feed cassette.
[0008] Referring to FIG. 1, the conventional paper detecting
apparatus comprises a first detector 10 that detects the presence
of paper in the paper feed cassette 30, and a second detector 20
that detects the paper passing the duplex printing paper path
40.
[0009] The first detector 10 comprises a first actuator 13, a first
sensor 15, and an operating slot 34.
[0010] The first actuator 13 comprises a paper touching portion 11
being in contact with the stacked paper, and a sensor operator 12
that operates the first sensor 15, and is formed to have the sensor
operator 12 located outside the sensing area of the first sensor 15
when paper is stacked in the paper feed cassette 30. The first
actuator 13 is pivotably hinged on a first hinge shaft 14 with one
end disposed above the duplex printing paper path 40, and formed to
have the paper touching portion 11 weighing more than the sensor
operator 12. Accordingly, the first actuator 13 always has a
tendency to pivot downward around the first hinge shaft 14. The
duplex paper printing path 40 has a slot 41 of a predetermined size
formed to allow the paper touching portion 11 of the first actuator
13 to operate.
[0011] The first sensor 15 is disposed above the duplex paper
printing path 40 and senses the movement of the sensor operator 12
when there is no paper on the paper feed cassette 30. The first
sensor 15 uses a photo sensor.
[0012] The operating slot 34 is formed on a paper pressing plate 32
of the paper feed cassette 30. When no paper is stacked in the
paper feed cassette 30, the first actuator 13 pivots downward and
the paper touching portion 11 is inserted into the operating slot
34. The operating slot 34 is formed to have the paper touching
portion 11 stopped at the rear end of the operating slot 34 thereby
stopping the first actuator 13 when the sensor operator 12 of the
first actuator 13 is in the sensing area.
[0013] The second detector 20 includes a second actuator 23, a
second sensor 25, and a swing slot 42.
[0014] The second actuator 23 comprises a paper interfering portion
21 interfering with paper being fed to the duplex printing paper
path 40, and a sensor operating portion 22 that operates the second
sensor 25. The second actuator 23 is rotatably assembled around the
second hinge shaft 24 disposed above the duplex printing paper path
40. The paper interfering portion 21 is formed to weigh more than
the sensor operating portion 22, thereby always being located below
the sensor operating portion 22. Therefore, when paper is not fed
to the duplex printing paper path 40, the sensor operating portion
22 is located inside the sensing area of the second sensor 25.
[0015] The second sensor 25 is disposed above the duplex printing
paper path 40 and senses the operation of the sensor operating
portion 22 of the second actuator 23. The second sensor 25
generally uses a photo sensor.
[0016] The swing slot 42 is formed on the duplex printing paper
path 40 and has a size allowing the paper interfering portion 21 to
move freely.
[0017] The conventional paper detecting apparatus having the above
described structure operates as described hereinafter.
[0018] Firstly, to describe the operation of the first detector 10,
when paper is stacked in the paper feed cassette 30, the paper
touching portion 11 is located above the paper as shown in FIG. 1
and the sensor operator 12 is located outside the sensing area of
the first sensor 15. (shown in broken lines in FIG. 1) Although
paper supply is continued, the paper touching portion 11 maintains
its location by the paper pressing plate 32 of the paper feed
cassette 30. When the rear end of the last paper stacked in the
paper feed cassette 30 passes the operating slot 34, the paper
touching portion 11 is inserted into the operating slot 34, and the
sensor operator 12 is located inside the sensing area of the first
sensor 15 as the first actuator 13 pivots. The first sensor 15 then
generates signals. When signals are generated from the first sensor
15, the image forming machine senses that no paper is stacked in
the paper feed cassette 30 and indicates the absence of the paper
in the paper feed cassette 30.
[0019] To describe the operation of the second detector 20, when
paper that has received first side imaging while passing an image
forming apparatus of an image forming machine, enters the duplex
printing paper path 40, the front end of the paper is interfered
with by the paper interfering portion 21 of the second actuator 23.
As the paper continues to move, the paper interfering portion 21
pivots upward, and the sensor operating portion 22 escapes from the
sensing area of the second sensor 25. Then the second sensor 25
generates signals. When the signals are generated from the second
sensor 25, the image forming machine senses that the paper is
moving along the duplex printing paper path 40 and performs
necessary operations.
[0020] When the paper is continually fed, the paper touching
portion 11 of the first actuator 13 is pushed upward thereby
operating the first sensor 15. However, when the image forming
machine receives signals from the second sensor 25, the signals
from the first sensor 15 are ignored during a predetermined period
until the paper escapes from the area in which it is interfered
with the first detector 10. Accordingly, the paper being fed along
the duplex printing paper path 40 can be detected regardless of the
operation of the first sensor 15.
[0021] By using the conventional paper detecting apparatus
described above, the image forming machine can detect the presence
of the paper in the paper feed cassette and paper being fed along
the duplex printing paper.
[0022] However, the conventional paper detecting apparatus uses two
identical sensors each requiring a separate actuator, and a slot on
the duplex printing paper path that allows the actuators to
operate, thereby increasing material costs. In addition, since such
a paper detecting apparatus employs a lot of parts, the number of
assembling processes increases and therefore productivity declines.
Moreover, since two sensors are used, it is highly likely to have
malfunction of the sensors and accordingly, the product can be
assessed as being unreliable.
SUMMARY OF THE INVENTION
[0023] An aspect of the invention is to solve at least the above
and/or other problems and disadvantages and to provide at least the
advantages described hereinafter.
[0024] Accordingly, aspect of the present invention is to solve the
foregoing and/or other problems by providing a paper detecting
apparatus of an image forming machine capable of sensing the
presence of the paper in the paper feed cassette and paper being
fed along a duplex printing paper path by using a single sensor
thereby reducing material costs and improving productivity and
reliability.
[0025] Additional and/or other aspects and advantages of the
invention will be set forth in part in the description which
follows and, in part, will be obvious from the description, or may
be learned by practice of the invention.
[0026] The foregoing and/or other aspects and advantages are
realized by providing a paper detecting apparatus of an image
forming machine having a duplex printing function comprising an
actuator, pivotably disposed above a paper feed cassette in which
paper is stacked and below a duplex printing paper path along which
the paper moves during printing of a side, the actuator being moved
by the paper, and a paper sensor, disposed next to the actuator
that senses movement of the actuator and generates a signal,
wherein the actuator pivots in a predetermined angle when no paper
is stacked in the paper feed cassette or paper is being fed along
the duplex printing paper path, and the paper sensor generates the
signal upon sensing the pivoting actuator.
[0027] The actuator comprises a hinge shaft, a center pivotably
assembled around the hinge shaft, a first lever extended from the
center that operates the paper sensor when no paper is stacked in
the paper feed cassette, a second lever extended from the center
having a predetermined angle from the first lever that operates the
paper sensor when paper is fed along the duplex printing paper
path; and a third lever extended from the center toward the
opposite direction of the first and second levers and weighing more
than the combined weight of the first and second lever, wherein the
first lever and the second lever have a tendency to rotate in one
direction by the third lever.
[0028] The predetermined angle is determined so the second lever
does not operate the paper sensor when the third lever is in
contact with paper on the paper feed cassette. The paper feed
cassette has a slot that allows the third lever to pass
through.
[0029] The paper detecting apparatus of an image forming machine
according to the present invention further comprises a stopper
limiting pivoting space of the actuator.
[0030] The paper detecting apparatus of an image forming machine
according to the present invention comprises a first slot formed on
a duplex printing paper path a hinge shaft disposed under the
duplex printing paper path, a center pivotably assembled on the
hinge shaft, a second lever extended from the center toward inside
of the first slot and interfered by paper when the paper moves
along the duplex printing paper path, a first lever extended from
the center having a predetermined angle from the second lever and
located outside sensing area of the paper sensor when paper is
stacked in a paper feed cassette, a third lever extended from the
center toward the opposite direction of the first and second levers
and heavier than the combined weight of the first and second
levers, a paper sensor disposed between the first and second levers
for sensing movement of the first and second lever, and a second
slot formed on the paper feed cassette for allowing the third lever
to pass through, wherein the third lever pivots downward and the
first lever is located inside sensing area of the paper sensor when
no paper is stacked in the paper feed cassette, and the second
lever pivots and is located inside sensing area of the paper
sensor, and then escapes from sensing area of the paper sensor by
the third lever when paper moves along the duplex printing paper
path.
[0031] The second lever is interfered with by a rear end of the
first slot when the first lever is located inside sensing area of
the paper sensor and not located inside sensing area of the paper
sensor when the third lever is in contact with paper stacked in the
paper feed cassette.
[0032] The paper sensor is a photo sensor.
[0033] As described above, the paper detecting apparatus of an
image forming machine according to the present invention is able to
detect whether paper is stacked in the paper feed cassette and the
paper is conveyed to the duplex printing paper path using a single
sensor. Therefore, according to the present invention, a paper
detecting apparatus of an image forming machine with material costs
reduced and productivity and reliability improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] These and/or other aspects and advantages of the invention
will become apparent and more readily appreciated from the
following description of the preferred embodiments taken in
conjunction with the accompanying drawings in which:
[0035] FIG. 1 is a view showing an image forming machine having a
conventional paper detecting apparatus;
[0036] FIG. 2 is a view showing an image forming machine having a
paper detecting apparatus according to an embodiment of the present
invention;
[0037] FIG. 3 is a view showing an actuator of the paper detecting
apparatus of FIG. 2 when paper is stacked in a paper feed
cassette;
[0038] FIG. 4 is a view showing the actuator of FIG. 3 when no
paper is stacked in the paper feed cassette;
[0039] FIG. 5 is a view showing the actuator of FIG. 3 rotated by
paper being fed along a duplex printing paper path;
[0040] FIG. 6 is a view showing the actuator rotating in the
reverse direction after the operation of FIG. 5;
[0041] FIG. 7 is a flow chart showing a method for an image forming
machine to detect the absence of paper in a paper feed cassette and
paper being fed along the duplex printing paper path by the
operation of the paper sensor; and
[0042] FIG. 8 is a flow chart showing another method for an image
forming machine to detect the absence of paper in a paper feed
cassette and paper being fed along the duplex printing paper path
by the operation of the paper sensor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] Reference will now be made in detail to a paper detecting
apparatus of an image forming machine according to a preferred
embodiment of the present invention, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to the like elements throughout. The embodiments are
described below in order to explain the present invention by
referring to the figures.
[0044] Referring to FIG. 2, the paper detecting apparatus 100 of
the image forming machine 200 according to the present invention
comprises an actuator 110, a paper sensor 120, a first slot 142,
and a second slot 134.
[0045] The actuator 110 is pivotably disposed around a hinge shaft
105 disposed below a duplex printing paper path 140. The actuator
110 comprises a first lever 111, a second lever 112, and a third
lever 113 extended from the center 115 and therefore has a shape
similar to the letter Y.
[0046] The center 115 is rotatably hinged on the hinge shaft 105
disposed below the duplex printing paper path 140.
[0047] The first lever 111 located inside the sensing area of the
paper sensor 120 when no paper is stacked in a paper feed cassette
130, and outside the sensing area of the paper sensor 120 when
paper is stacked in the paper feed cassette 130.
[0048] The second lever 112 extends from the center 115 having a
predetermined angle from the first lever 111, and has a free end
located in the first slot 142 formed on the duplex printing paper
path 140 and interfering with paper being fed along the duplex
printing paper path 140. The second lever 112 is to be stopped at
the rear end 142a of the first slot 142 when no paper is stacked in
the paper feed cassette 130 and accordingly the actuator 110
pivots. In addition, the second lever 112 is to be outside the
sensing area of the paper sensor 120 when the third lever 113 is in
contact with the upper surface of the paper stacked in the paper
feed cassette 130.
[0049] The third lever 113 extends from the center 115 away from
the first lever 111 and the second lever 112. The third lever 113
maintains contact with the upper surface of the paper stacked in
the paper feed cassette 130 when the first lever 11 is in the
sensing area of the paper sensor 120. The third lever 113 weighs
more than the combined weight of the first lever 111 and the second
lever 112 and, accordingly, the third lever 113 has a tendency to
pivot downward. In addition, the third lever 113 pivots upward by
the impact occurring when the paper being fed along the duplex
printing paper path 140 hits the second lever 112. Therefore, the
third lever 113 is heavier than the combined weight of the first
lever 111 and the second lever 112 and at the same time light
enough so as to be moved by the impact brought by the paper moving
along the duplex printing paper path 140. To satisfy such
conditions, the inside of the third lever 113 is cut out.
[0050] It would be appreciated by those skilled in the art that the
phenomenon of the third lever causing a tendency for the actuator
to pivot in a counter-clockwise direction and be movable when paper
moving along the duplex printing paper path 140 impacts the second
lever can be achieved in ways beside making the third lever heavier
than the combined weights of the first lever 111 and the second
lever 112.
[0051] The paper sensor 120 is disposed next to the first lever 111
and the second lever 112 of the actuator 110 below the duplex
printing paper path 140. When paper is stacked in the paper feed
cassette 130, the paper sensor 120 is located in the space between
the first lever 111 and the second lever 112. The paper sensor 120
can use any device such as a limited switch as long as it can sense
the operation of the first lever 111 and the second lever 112 but
preferably, it uses a photo sensor.
[0052] The first slot 142 is formed on the duplex printing paper
path 140 for the second lever 112 to freely pivot. The length of
the first slot 142 is formed so a rear end 142a of the first slot
142 acts as a stopper limiting the pivoting space of the actuator
110 when no paper is stacked in the paper feed cassette 130.
Therefore, the length of the first slot 142 is formed so the second
lever 112 is stopped by the rear end 142a of the first slot 142 and
the first lever 111 is located inside the sensing area of the paper
sensor 120 when the third lever 113 is inserted into the second
slot 134.
[0053] The second slot 134 is formed on the paper pressing plate
132 of the paper feed cassette 130 for the third lever 113 of the
actuator 110 to freely pivot. The length of the second slot 134 may
extend along the entire length of the paper pressing plate.
However, the front end 134a of the second slot 134 acts as a
stopper when the rear end 142a of the first slot 142 does not act
as a stopper. That is, the length of the second slot 134 is
determined for the actuator 110 to stop pivoting with the first
lever 111 located inside the sensing area of the paper sensor 120
when the actuator 110 pivots with the third lever 113 being
inserted into the second slot 134.
[0054] Hereinafter, the operation of the paper detecting apparatus
100 of an image forming apparatus 200 according to the present
invention having the above-described structure will be described in
detail referring to the accompanying FIGS. 2 through 6.
[0055] Beginning with the operation of detecting the presence of
paper in the paper feed cassette 130, when paper 101 is stacked in
the paper feed cassette 130, the actuator 110 pivots to appear as
in FIG. 3. Even while the paper 101 is continually being fed, the
actuator 110 maintains its position as the paper pressing plate 132
keeps the paper 101 in a predetermined height. When the last paper
is fed from the paper feed cassette 130, the third lever 113 of the
actuator 110 pivots downward, thereby being inserted into the
second slot 134 formed on the paper pressing plate 132. The
actuator 110 stops pivoting as the second lever 112 is stopped by
the rear end 142a of the first slot 142 and, accordingly, the first
lever 111 integrally formed with the third lever 113 pivots,
thereby being located inside the sensing area of the paper sensor
120. (see FIG. 4) When the first lever 111 is located inside the
sensing area of the paper sensor 120, the paper sensor 120
generates signals. The image forming machine receives signals from
the paper sensor 120, and then indicates that no paper remains in
the paper feed cassette 130.
[0056] When paper is stacked in the paper feed cassette 130, the
third lever 113 pivots clockwise and the first lever 111 moves
outside the sensing area of the paper sensor 120 as shown in FIG.
3.
[0057] The operation of detecting the paper being fed along the
duplex printing paper path during the duplex printing will be
described in the following.
[0058] The paper 102 with the front side printed with an image
passing an image forming unit (not shown) enters the duplex
printing paper path 140. The paper 102 with the front side printed
with an image entering the duplex printing paper path 140 continues
to move forward, hitting the second lever 112, and thereby allowing
the second lever 112 to pivot clock-wise. When the paper 102 hits
the second lever 112, the actuator 110 rotates clockwise by the
impact, and the second lever 112 is located inside the sensing area
of the paper sensor 120 as shown in FIG. 5. After the impact
created by the paper 102 dissipates, the actuator 110 rotates
counter-clockwise due to the weight of the third lever 113. When
the actuator 110 rotates counter-clockwise, the second lever 112
escapes from the sensing area of the paper sensor 120, thereby
pressing the paper 102 passing the first slot 142 upward. (see FIG.
6) That is, when paper 102 is fed along the duplex printing paper
path 140, the second lever 112 is temporarily located inside the
sensing area of the paper sensor 120 by the impact between the
paper 102 and the second lever 112 and escapes from the sensing
area of the paper sensor 120 by the weight of the third lever 113.
Accordingly, the paper sensor 120 generates signals for a short
period during which the second lever 112 is inside the sensing
area. When the rear end of the paper 102 completely passes the
first slot 142, the second lever 112 is inserted into the first
slot 142 and the actuator 110 returns to the position shown in FIG.
3.
[0059] As described above, the period signals generated when no
paper is stacked in the paper feed cassette and the period signals
generated by the paper being fed along the duplex printing paper
path are different. Therefore, the image forming machine can
identify whether the signals are due to a detected absence of paper
in the paper feed cassette or a detected paper being fed along the
duplex printing paper path in accordance to the length of the
signals.
[0060] As shown in FIG. 7, after receiving an "on" signal from the
paper sensor, (150) the image forming machine measures the length
of the signal and compares the length of the received signal with
the standard length. (160) If the length of the signal received
from the paper sensor is shorter than the standard length, it is
judged that the paper is being fed along the duplex printing paper
path. (170) On the other hand, if the length of the signal received
from the paper sensor is longer than the standard length, it is
judged that there is no paper in the paper feed cassette. (180) The
standard length here is determined by measuring how long it takes
for the second lever to escape from the sensing area of the paper
sensor by the weight of the third lever after the second lever of
the actuator enters inside the sensing area of the paper sensor by
the paper fed into the duplex printing paper path.
[0061] Another method by which an image forming machine detects the
paper being fed along the duplex printing paper path by the signal
of the paper sensor is now described.
[0062] Referring to FIG. 8, the image forming machine receives a
signal from the paper sensor (190) and then a controller (not
shown) in the image forming machine judges if the image forming
machine is in a duplex printing mode. (200) If the image forming
machine is in the duplex printing mode, it judges that paper is
being fed to the duplex printing paper path. (210) However, if the
image forming machine is not in the duplex printing mode, the
signal received by the controller will indicate that there is no
paper in the paper feed cassette, and the controller judges that
there is no paper in the paper feed cassette. (220) That is, if the
image forming machine receives a signal from the paper sensor in
the duplex printing mode, it judges that paper is being fed to the
duplex printing paper path.
[0063] As described above, the paper detecting apparatus of an
image forming machine according to the present invention can judge
the presence of paper in the paper feed cassette and paper being
fed to the duplex printing paper path by a single sensor.
Therefore, material costs and the number of assembling processes
can be reduced. Moreover, the product reliability can be improved
as the malfunction of sensors is decreased by reducing the number
of sensors.
[0064] Although a few embodiments of the present invention have
been shown and described, it would be appreciated by those skilled
in the art that changes may be made in this embodiment without
departing from the principles and sprit of the invention, the scope
of which is defined in the claims and their equivalents.
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