U.S. patent application number 11/150262 was filed with the patent office on 2006-07-20 for knock-up plate lifting device and image forming apparatus having the same.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Hun-sup Kim, Ho-il Lee.
Application Number | 20060157917 11/150262 |
Document ID | / |
Family ID | 36683081 |
Filed Date | 2006-07-20 |
United States Patent
Application |
20060157917 |
Kind Code |
A1 |
Kim; Hun-sup ; et
al. |
July 20, 2006 |
Knock-up plate lifting device and image forming apparatus having
the same
Abstract
A knock-up plate lifting device for lowering a knock-up plate
while inserting and withdrawing a paper feeding cassette, and
lifting the knock-up plate when the paper feeding cassette is
completely mounted. The knock-up plate lifting device includes a
mounting board. A first link is pivotably mounted by a first hinge
to the mounting board and has arms extended away from the first
hinge. A resilient member is connected to one of the arms of the
first link. A second link is pivotably mounted by a second hinge to
the mounting board and extends away from the second hinge by a
predetermined angle. One arm of the second link is connected with
the resilient member and the other arm moves up and down in
accordance with the operation of the first hinge.
Inventors: |
Kim; Hun-sup; (Ansan-si,
KR) ; Lee; Ho-il; (Seoul, KR) |
Correspondence
Address: |
ROYLANCE, ABRAMS, BERDO & GOODMAN, L.L.P.
1300 19TH STREET, N.W.
SUITE 600
WASHINGTON,
DC
20036
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
|
Family ID: |
36683081 |
Appl. No.: |
11/150262 |
Filed: |
June 13, 2005 |
Current U.S.
Class: |
271/147 |
Current CPC
Class: |
B65H 2405/1117 20130101;
B65H 1/12 20130101; B65H 1/26 20130101 |
Class at
Publication: |
271/147 |
International
Class: |
B65H 1/08 20060101
B65H001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 11, 2004 |
KR |
2004-81005 |
Claims
1. A knock-up plate lifting device comprising: a mounting board; a
first link pivotably mounted by a first hinge to the mounting board
and having first and second arms extending away from the first
hinge; a resilient member connected to the first arm of the first
link; and a second link pivotably mounted by a second hinge to the
mounting board and having first and second arms extending away from
the second hinge, wherein the first arm of the second link is
connected with the resilient member and the second arm moves up and
down in accordance with the operation of the first hinge.
2. The knock-up plate lifting device of claim 1, wherein the second
arm of the second link is disposed at a lower position when the
first link is vertical to the ground.
3. The knock-up plate lifting device of claim 2, wherein the first
and second arms of the second link have different lengths.
4. The knock-up plate lifting device of claim 3, wherein the
knock-up plate lifting device further comprises: a guiding
projection formed at the second arm of the second link; and a
guiding groove formed at the mounting board to guide the motion of
the guiding projection.
5. The knock-up plate lifting device of claim 3, further
comprising: an extension member formed at the end of the first arm
of the first link and connected to an end of the resilient
member.
6. The knock-up plate lifting device of claim 1, wherein the first
and second arms of the second link are at a predetermined angle
with respect to each other.
7. An image forming apparatus comprising: a pickup roller mounted
to a main body; a paper feeding cassette removably mounted to the
main body under the pickup roller and having a knock-up plate for
pushing a printing medium toward the pickup roller; a first link
mounted to a sidewall of the paper feeding cassette by a first
hinge and having first and second arms extended in opposite
directions from the first hinge; a resilient member connected to
the first arm of the first link; a second link mounted to the
sidewall of the paper feeding cassette by a second hinge and having
a first arm connected with the resilient member and a second arm
lifting and lowering the knock-up plate in accordance with the
operation of the first hinge; and an operation projection formed on
the main body to rotate the first link when the paper feeding
cassette is mounted into the main body.
8. The image forming apparatus of claim 7, wherein both sidewalls
of the paper feeding cassette include a first link, a resilient
member, and a second link, and both sides of the main body includes
an operation projection corresponding with the first links.
9. The image forming apparatus of claim 7, wherein the second arm
of the second link is disposed at a lower position when the first
link is vertical to the bottom of the paper feeding cassette.
10. The image forming apparatus of claim 9, wherein the first and
second arms of the second link have different lengths.
11. The image forming apparatus of claim 10, further comprising: a
guiding projection formed at the second arm of the second link to
lift and lower the knock-up plate; and a guiding groove formed at
the sidewall of the paper feeding cassette to guide motion of the
guiding projection.
12. The image forming apparatus of claim 7, further comprising: an
extension member formed on the end of the first arm of the first
link and connected to an end of the resilient member.
13. The image forming apparatus of claim 7, wherein the first and
second arms of the second link are at a predetermined angle with
respect to each other.
14. An image forming apparatus comprising: a pickup roller mounted
to a main body; a paper feeding cassette removably mounted to the
main body, a knock-up plate mounted to the paper feeding cassette
for pushing a printing medium toward the pickup roller; and a first
knock-up plate lifting device, comprising: a first link pivotably
mounted to a sidewall of the paper feeding cassette, the first link
having first and second arms extending away from the first hinge; a
resilient member connected to the first arm of the first link; a
second link pivotably mounted to the sidewall of the paper feeding
cassette, the second link having a first arm connected with the
resilient member and a second arm for supporting the knock-up
plate; and an operation projection formed on the main body to
rotate the first link when the paper feeding cassette is mounted
into the main body, wherein when the first link is rotated by the
operation projection, the second arm raises the knock-up plate.
15. An image forming apparatus according to claim 14, further
comprising: a second knock-up plate lifting device, comprising: a
third link pivotably mounted to a second sidewall of the paper
feeding cassette, the third link having first and second arms
extending away from the first hinge; a second resilient member
connected to the first arm of the third link; a fourth link
pivotably mounted to the second sidewall of the paper feeding
cassette, the fourth link having a first arm connected with the
second resilient member and a second arm for supporting the
knock-up plate; and a second operation projection formed on the
main body to rotate the third link when the paper feeding cassette
is inserted into the main body.
16. An image forming apparatus according to claim 14, further
comprising: a guiding projection formed at the second arm of the
second link to support the knock-up plate; and a guiding groove
formed on the sidewall of the paper feeding cassette to guide the
motion of the guiding projection.
16. An image forming apparatus according to claim 14, wherein the
first and second arms of the second link are at a predetermined
angle with respect to each other.
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. 2004-81005, filed Oct. 11,
2004, the entire contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a paper feeding cassette
for an image forming apparatus. More particularly, the present
invention relates to a knock-up plate lifting device for raising
and lowering a knock-up plate of a paper feeding cassette.
[0004] 2. Description of the Related Art
[0005] Generally, an image forming apparatus includes a paper
feeding cassette for receiving a stack of a printing medium to
automatically supply the printing medium, and a pickup roller for
separating and conveying the stacked printing medium sheet by
sheet. The paper feeding cassette includes a knock-up plate for
biasing the stacked printing medium toward the pickup roller. One
end of the knock-up plate is hinged to the paper feeding cassette
while the other end is resiliently supported by a resilient member
such as a spring to bias the stacked printing medium toward the
pickup roller. However, since the knock-up plate is resiliently
supported, it may collide with the pickup roller while inserting
and withdrawing the paper feeding cassette with respect to a main
body of the image forming apparatus and thereby disturb the
insertion and withdrawal of the paper feeding cassette. Therefore,
a knock-up plate lifting device is preferably configured to lower
the knock-up plate during the insertion and withdrawal of the paper
feeding cassette and lift the knock-up plate toward the pickup
roller after completing the insertion.
[0006] Referring to FIGS. 1 and 2, a conventional knock-up plate
lifting device 10 comprises a link 40, a resilient member 30, and a
rectilinear-moving member 20. The link 40 has a bent form and is
fixed by a hinge 43 within a main body 70 (FIG. 3) of the image
forming apparatus that the knock-up plate lifting device 10 is
mounted in. The hinge 43 is formed at a joint portion of the link
40. The link 40 comprises a short arm 41 and a long arm 42 with
respect to the hinge 43. An end of the short arm 41 is connected to
one end of the resilient member 30 whereas an end of the long arm
42 has a guiding projection 51 for guiding vertical motion of the
link 40. A guiding groove 52 is formed in front of the guiding
projection 51 to correspond to a moving path of the guiding
projection 51.
[0007] The resilient member 30 connects the link 40 and the
rectilinear-moving member 20. The long arm 42 of the link 40 moves
up and down by a predetermined angle in accordance with the motion
of the rectilinear-moving member 20. A tension coil spring may be
used for the resilient member 30.
[0008] The rectilinear-moving member 20 comprises a moving part 21
and a guiding part 22 for guiding the linear motion of the moving
part 21. The guiding part 22 is disposed within the main body 70
and the moving part 21 is connected to the other end of the
resilient member 30. On both sidewalls 81 of the paper feeding
cassette 80, operation projections 85 are formed to push the moving
part 21 of the rectilinear-moving member 20 in a direction for
mounting the paper feeding cassette 80, as shown in FIG. 3.
[0009] As the paper feeding cassette 80 is inserted into the main
body 70 of the image forming apparatus, the operation projections
85 formed on the sidewalls 81 of the paper feeding cassette 80 push
the moving part 21 of the rectilinear-moving part 20 in the
mounting direction of the paper feeding cassette 80, that is, the
direction illustrated by the arrow A in FIG. 2. Accordingly,
tension is applied to the resilient member 30, thereby applying a
force onto the short arm 41 of the link 40. The link 40 is pivoted
with respect to the hinge 43 by a predetermined angle by the force,
such that the end of the long arm 42 is lifted, as illustrated by
the solid lines in FIG. 2. Therefore, if the end of the long arm is
connected to the knock-up plate 83 of the paper feeding cassette
80, the knock-up plate 83 of the paper feeding cassette 80 is also
lifted by the link 40. The motion of the long arm 42 is guided by
the guiding projection 51 and the guiding groove 52.
[0010] When the paper feeding cassette 80 is withdrawn from the
main body 70, the operation projections 85 are separated from the
moving part 21, and, accordingly, the force applied to the moving
part 21 of the rectilinear-moving member 20 is removed. The
recovery force of the resilient member and the weight of the link
40 apply a force in the opposite direction, and, as a result, the
moving part 21 is restored. After recovery, the long arm 42 of the
link 40 is parallel with the bottom of the paper feeding cassette
80 (as shown in dashed lines), and, therefore, the knock-up plate
83 supported by the link 40 also becomes parallel with the
bottom.
[0011] Therefore, when the paper feeding cassette 80 is withdrawn
with respect to the main body 70, the knock-up plate 83 is lowered
by the knock-up plate lifting device 10, and when the paper feeding
cassette 80 is completely inserted into the main body 70, the
knock-up plate 83 is lifted so as to bring the printing medium
stacked on the knock-up plate 83 into tight contact with the pickup
roller (not shown), thereby enabling the pickup of the printing
medium.
[0012] However, in the conventional knock-up plate lifting device
10 described above, the lifting and lowering of the knock-up plate
83 depends on the rectilinear motion of the rectilinear-moving part
20. Thus, if the guiding part 22 is jammed with foreign substances
or if the sliding surfaces of the guiding part 22 and the moving
part 21 become rough due to long-term use, the knock-up plate
lifting device 10 may not operate smoothly. This may cause
difficulty in inserting and withdrawing the paper feeding cassette
80 with respect to the main body 70, thereby deteriorating
reliability of the product.
[0013] In addition, since the knock-up plate lifting device 10 is
disposed at a lower corner portion of the main body 70, assembly is
complex. Therefore, productivity deteriorates and manufacturing
costs increase.
[0014] Furthermore, the knock-up plate lifting device 10 is not
easily seen from the outside of the main body 70. Therefore,
maintenance and repair of the knock-up plate lifting device 10 is
not easy, and this may increase maintenance costs.
[0015] Accordingly, there is a need for an improved knock-up plate
lifting device that is more reliable and easier to manufacture and
maintain.
SUMMARY OF THE INVENTION
[0016] An aspect of the present invention is to solve at least the
above problems and/or disadvantages and to provide at least the
advantages described below. Accordingly, an aspect of the present
invention is to provide an improved knock-up plate lifting device
which is not influenced much by foreign substances located in the
lifting device or by roughness of sliding surfaces in the lifting
device.
[0017] Another aspect of the present invention is to provide a
knock-up plate lifting device which can be mounted on the sidewalls
of the paper feeding cassette to save assembly time and reduce
manufacturing and maintenance costs.
[0018] Yet another aspect of the present invention is to provide an
image forming apparatus with a knock-up plate that is not
influenced much by foreign substances or by roughness of sliding
surfaces and that reduces manufacturing and maintenance costs.
[0019] In order to achieve the above-described aspects of the
present invention, a knock-up plate lifting device is provided. The
knock-up plate lifting device includes a mounting board. A first
link is pivotably mounted by a first hinge to the mounting board.
The first link has first and second arms extending in opposite
directions away from the first hinge. A resilient member is
connected to the first arm of the first link. A second link is
pivotably mounted by a second hinge to the mounting board. The
second link has first and second arms extending away from the
second hinge. The first arm of the second link is connected with
the resilient member so that the second arm moves up and down when
the first link is pivoted.
[0020] The second arm of the second link is disposed at a lower
position when the first link is vertical to the ground.
[0021] The arms of the second link have different lengths.
[0022] The knock-up plate lifting device further comprises a
guiding projection formed at the second arm of the second link, and
a guiding groove formed at the mounting board to guide the vertical
motion of the guiding projection.
[0023] The knock-up plate lifting device further comprises an
extension member formed at an end of the first arm of the first
link which is connected to an end of the resilient member.
[0024] According to another aspect of the present invention, an
image forming apparatus comprises a pickup roller mounted to a main
body and a paper feeding cassette removably mounted to the main
body under the pickup roller. The cassette includes a knock-up
plate for pushing a printing medium toward the pickup roller. A
first link is mounted to a sidewall of the paper feeding cassette
by a first hinge and has first and second arms extending in
opposite directions from the first hinge. A resilient member is
connected to the first arm of the first link. A second link is
mounted to the sidewall of the paper feeding cassette by a second
hinge and has first and second arms. The first arm of the second
link is connected with the resilient member and the second arm of
the second link lifts and lowers the knock-up plate in accordance
with the operation of the first link. An operation projection is
formed on the main body to rotate the first link when the paper
feeding cassette is mounted into the main body.
[0025] First links, resilient members, and second links are formed
on both sidewalls of the paper feeding cassette, and operation
projections are formed on both sides of the main body to correspond
to the first links.
[0026] The second arm of the second link is disposed at a lower
position when the first link is vertical to the bottom of the paper
feeding cassette.
[0027] The arms of the second link are different lengths.
[0028] The image forming apparatus further comprises a guiding
projection formed at the second arm of the second link to lift and
lower the knock-up plate, and a guiding groove formed at the
sidewall of the paper feeding cassette to guide the vertical motion
of the guiding projection.
[0029] The image forming apparatus further comprises an extension
member formed at an end of the first arm of the first link which is
connected to an end of the resilient member.
[0030] According to the embodiments of the present invention
described above, the knock-up plate is operated by rotation of the
first link, without using a sliding device. Thus, the operation of
the knock-up plate is not influenced much by foreign substances or
by roughness of sliding surfaces.
[0031] Also, since the knock-up plate lifting device can be mounted
on the sidewalls of the paper feeding cassette, assembly time for
the knock-up plate lifting device can be reduced as compared with
the assembly time when the knock-up plate is mounted within the
main body of the image forming apparatus. Therefore, maintenance
and manufacturing costs can be saved.
[0032] Additionally, the image forming apparatus applying the above
knock-up plate lifting device has reduced maintenance and
manufacturing costs.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0033] The above and other objects, features, and advantages of
certain embodiments of the present invention will be more apparent
from the following description taken in conjunction with the
accompanying drawings, in which:
[0034] FIG. 1 is a schematic view of a conventional knock-up plate
lifting device;
[0035] FIG. 2 is a schematic view illustrating the operation of the
knock-up plate lifting device of FIG. 1;
[0036] FIG. 3 is a perspective view of an image forming apparatus
including the knock-up plate lifting device of FIG. 1;
[0037] FIG. 4 is a schematic view of a knock-up plate according to
an embodiment of the present invention;
[0038] FIG. 5 is a schematic view illustrating the operation of the
knock-up plate of FIG. 4;
[0039] FIG. 6 is a perspective view showing an image forming
apparatus including the knock-up plate lifting device according to
an embodiment of the present invention, before the paper feeding
cassette has been inserted; and
[0040] FIG. 7 is a partial, sectional view illustrating the
knock-up plate lifting device when the paper feeding cassette is
mounted in the image forming apparatus of FIG. 6.
[0041] Throughout the drawings, the same drawing reference numerals
will be understood to refer to the same elements, features, and
structures.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0042] The matters defined in the description such as a detailed
construction and elements are provided to assist in a comprehensive
understanding of the embodiments of the invention. Accordingly,
those of ordinary skill in the art will recognize that various
changes and modifications of the embodiments described herein can
be made without departing from the scope and spirit of the
invention. Also, descriptions of well-known functions and
constructions are omitted for clarity and conciseness.
[0043] Referring to FIGS. 4 and 5, a knock-up plate lifting device
110 according to an embodiment of the present invention comprises a
mounting board 100, a first link 120, a second link 140, and a
resilient member 130.
[0044] The first and the second links 120 and 140 are mounted on
the mounting board 110 by first and second hinges 123 and 143,
respectively, so that the links may rotate. By using a mounting
board 110, the knock-up plate lifting device 100 can be attached as
a separate unit. The mounting board 110 is attached to a place
employing the knock-up plate lifting device 100, such as main body
of a paper feeding cassette or an image forming apparatus, by a
fastening means (not shown) such as a screw. When a knock-up plate
lifting device 100' (FIG. 6) does not utilize a dedicated mounting
board 110, the first and the second links 120 and 140 are directly
hinged to a sidewall 181 (FIG. 6) of a paper feeding cassette 180
(FIG. 6) by the hinges 123 and 143.
[0045] The first link 120 is mounted by the first hinge 123 so that
it can rotate with respect to the mounting board 110. An upper (or
first) arm 121 and a lower (or second) arm 122, extend in opposite
directions away from the first hinge 123. The first link 120 is
vertical to the ground when no force is applied, and rotated when
applied with force due to interference between the upper arm 121
and an operation projection 171 (FIG. 7). The lower arm 122 of the
first link 120 is connected to an end of the resilient member 130.
The lower arm 122 of the first link 120 may further comprise an
extension member 124 for connection with the end of the resilient
member 130. The connection part 125 of the resilient member 130,
for connection with the extension member 124, is preferably
disposed so that the distance between the first hinge 123 and the
connection part 125 is almost constant whether the first link 120
is in a vertical posture and in a horizontal posture.
[0046] At a predetermined distance from the first link 120, the
second link 140 is rotatably mounted on the mounting board 110 by
the second hinge 143. The second link 140 includes a right (or
first) arm 141 and a left (or second) arm 142 extending away from
the second hinge 143. The right arm 141 (refer to FIG. 4) is
connected to the other end of the resilient member 130. The left
arm 142 (refer to FIG. 4) is lifted and lowered by a predetermined
angle according to the motion of the right arm 141. As shown in
FIG. 4, when the first link 120 is vertical to the ground, the left
arm 142 of the second link 140 is at a lower position, that is,
horizontal with respect to the ground, and the left arm 142 is
longer than the right arm 141. The second link 140 is formed as a
bent member wherein the left arm 142 and the right arm 142 are bent
at a predetermined angle with respect to each other, preferably in
the range of approximately 90.about.180.degree.. A reinforcing
piece 145 may be provided between the left and right arms 142 and
141 of the second link 140 to strengthen the arms 141 and 142. As
long as the left arm 142 of the second link 140 is lifted and
lowered by the predetermined angle, the second link 140 may have
various configurations according to the length of the first link
120, the positional relationship with the first link 120, and the
lifted height of the knock-up plate 183 (FIG. 6).
[0047] The left arm 142 of the second link 140 has a guiding
projection 151 while the mounting board 110 has a guiding groove
152 for guiding the vertical motion of the guiding projection 151.
The guiding groove 152 is shaped to correspond to the arc of the
movement of the end of the left arm 142 of the second link 140. The
lower end of the guiding groove 152 is located where the left arm
142 of the second link 140 becomes horizontal, and the upper end of
the guiding groove 152 is located where the knock-up plate 183 is
pressed to its maximum lift height. The guiding groove 152 and the
guiding projection 151 define the angle of lifting and lowering the
second link 140 and stably guide the vertical motion of the second
link 140.
[0048] The resilient member 130 is interposed between the first and
the second links 120 and 140 to allow the left arm 142 of the
second link 140 to move up and down in accordance with rotation of
the first link 120. One end of the resilient member 130 is
connected to the lower arm 122 of the first link 120 or the
extension member 124, while the other end of the resilient member
130 is connected to the right arm 141 of the second link 140. When
the first link 120 is vertical, the resilient member 130 applies no
force to the second link 140. On the other hand, when the second
link 140 is horizontal, the resilient member 130 lifts up the left
arm 142 of the second link 140 and applies a force for pushing a
printing medium stacked on the knock-up plate 183 into tight
contact with the pickup roller 175 (FIG. 7). Any resilient material
capable of transmitting a force, preferably a coil spring, can be
used for the resilient member 130.
[0049] The operation of the knock-up plate lifting device 100 will
now be described with reference to FIG. 5. When a member for
rotating the first link 120, such as the operation projection 171
(FIG. 6), interferes with the upper arm 121 of the first link 120,
the first link 120 rotates by approximately 90.degree. to be
horizontal.
[0050] When the first link 120 rotates by approximately 90.degree.,
the resilient member 130 in connection with the lower arm 122 of
the first link 120 pulls the right arm 141 of the second link 140
to the right with respect to FIG. 5. Therefore, the second link 140
rotates clockwise about the second hinge 143, thereby moving the
left arm 142 of the second link 140 upward with the assistance of
the guiding projection 151 and the guiding groove 152. If the guide
projection 151 formed at the end of the left arm 142 of the second
link 140 is connected with the knock-up plate 183, the knock-up
plate 183 is lifted up.
[0051] As the interference is removed from the first link 120, the
guiding projection 151 returns to the lower end of the guiding
groove 152 due to the weight of the second link 140. Accordingly,
the left arm 142 of the second link 140 becomes horizontal and the
first link 120 returns to vertical by its own weight and the
recovery force of the resilient member 130.
[0052] Thus, by the knock-up plate lifting device 100 according to
an embodiment of the present invention, the left arm 142 of the
second link 140 can be moved up and down in accordance with the
rotation of the first link 120.
[0053] FIG. 6 is a perspective view showing the image forming
apparatus comprising a knock-up plate lifting device 100' according
to another embodiment of the present invention. FIG. 7 is a
partial, sectional view for illustrating the operation of the
knock-up plate lifting device 100' shown in FIG. 6 when the paper
feeding cassette is mounted in the image forming apparatus.
[0054] The paper feeding cassette 180 comprises a knock-up plate
lifting device 100' formed on a sidewall 181 of the cassette 180,
and the knock-up plate 183.
[0055] In the previously discussed embodiment, a sub-assembly
comprising the mounting board 110 (FIG. 4), the first and the
second links 120 and 140, and the hinges 123 and 143 is formed and
the sub-assembly is fixed onto the sidewall 181 of the paper
feeding cassette 180 to thereby mount the knock-up plate lifting
device 100. In this embodiment, the knock-up plate lifting device
100' includes first and second links 120 and 140 that are mounted
directly on the sidewall 181 of the paper feeding cassette by
hinges 123 and 143. The resilient member 130 connects the first and
the second links 120 and 140. The first link 120 is mounted
directly to the paper feeding cassette 180, but the structure of
the first link 120 is the same as in the previous embodiment.
Therefore, a detailed description of the first link 120 is not
repeated. The guiding groove 152 is formed on the sidewall 181 of
the paper feeding cassette 180 to guide the guiding projection 151
of the left arm 142 of the second link 140, and the guiding
projection 151 of the second link 140 is mounted to support the
bottom of the knock-up plate 183. Since the second link 140 has the
same structure as in the previous embodiment, a detailed
description is not repeated. The knock-up plate lifting device 100'
may be formed on only one sidewall 181 of the paper feeding
cassette 180. Preferably, however, knock-up plate lifting devices
100' are provided on both sidewalls 181 to more stably support the
vertical motion of the knock-up plate 183.
[0056] The main body 170 of the image forming apparatus that mounts
the paper feeding cassette 180 has an operation projection 171 to
operate the knock-up plate lifting device 100'. As the paper
feeding cassette 180 is inserted in the main body 170, the
operation projection 171 rotates the first link 120. When the paper
feeding cassette 180 is completely inserted, the operation
projection 171 maintains the horizontal state of the first link
120, as shown in FIG. 7. When knock-up plate lifting devices 100'
are formed on both sidewalls 181 of the paper feeding cassette 180,
a second operation projection 171 is formed to corresponding to the
second knock-up plate lifting device.
[0057] With reference to FIGS. 6 and 7, the vertical motion of the
knock-up plate 183 of the paper feeding cassette 180 in the
above-structured image forming apparatus will now be described.
[0058] As shown in FIG. 6, when the paper feeding cassette 180 is
drawn from the main body 170, the knock-up plate 183 is placed on
the bottom of the paper feeding cassette 180. In this state, the
second link 140 of the knock-up plate lifting device 100' is
horizontal and the first link 120 is vertical to the bottom of the
paper feeding cassette 180.
[0059] When the paper feeding cassette 180 is inserted into the
main body 170 and advanced by a predetermined distance, the upper
arm 121 of the first link 120 of the knock-up plate lifting device
100' contacts the operation projection 171 formed on the main body
170. As the paper feeding cassette 180 is completely inserted, the
first link 120 of the knock-up plate lifting device 100' is kept
horizontal by the operation projection 171.
[0060] When the first link 120 rotates, tension is applied to the
resilient member 130. The resilient member is connected to the
lower arm 122 of the first link 120 and the right arm 141 of the
second link 140. Thus, the right arm 141 is pulled to the right
with respect to FIG. 7 by the resilient member 130. Accordingly,
the second link 140 rotates clockwise about the second hinge 143
and the guiding projection 151 formed at the end of the left arm
142 of the second link 140 moves upward along the guiding groove
152 of the paper feeding cassette 180. Consequently, the knock-up
plate 183, which is supported by the guiding projection 151, is
lifted. Since the knock-up plate 183 is supported by the guiding
projection 151, the pickup roller 175 disposed above the knock-up
plate 183 is pushed with a certain force by the knock-up plate 183,
as shown in FIG. 7.
[0061] When the paper feeding cassette 180 is withdrawn from the
main body 170, the upper arm 121 of the first link 120 escapes from
the interference with the operation projection 171, thereby
rotating the first link 120 clockwise. As the paper feeding
cassette 180 is further withdrawn, the first link 120 completely
escapes from the interference of the operation projection 171 and
becomes vertical to the bottom of the paper feeding cassette 180.
Also, the left arm 142 of the second link 140 is moved to the lower
end of the guiding groove 152 by the weight of the second link 140
and the knock-up plate 183 so that it is horizontal. The knock-up
plate 183 is located at the bottom of the paper feeding cassette
180 at this time and does not interfere with the pickup roller 175
mounted in the main body 170 above the paper feeding cassette 180.
Therefore, the paper feeding cassette 180 can be withdrawn smoothly
from the main body 170 of the image forming apparatus.
[0062] After the paper feeding cassette 180 has been refilled with
the printing medium P and is remounted to the main body 170, the
knock-up plate 183 is lifted by the knock-up plate lifting device
100' to bias the printing medium P toward the pickup roller 175,
thereby enabling the pickup roller 175 to pick up and convey the
printing medium P sheet by sheet.
[0063] While the invention has been shown and described with
reference to certain embodiments thereof, it will be understood by
those skilled in the art that various changes in form and details
may be made therein without departing from the spirit and scope of
the invention as defined by the appended claims.
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