BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a mechanism for feeding sheets and a sheet guiding
equipment for conveying sheets in ,for example , an image forming apparatus.
2. Related Art of the Invention
[0002] Heretofore, as shown in Fig. 1, an image forming apparatus is provided with a sheet
feeding cassette 500 for storing sheets, a pick up roller 220 for feeding the sheet
from the sheet feeding cassette 500, and a guide plate 230 for guiding the sheet having
been fed by the pick up roller 220. On the upper central side of the guide plate 230
is provided a sheet feeding roller 100; on the lower central side of the guide plate
230 is provided a pad mounting plate 130; and a friction pad roller 800 mounted to
the pad mounting plate 130 is urged by a spring 200 being urging means so as to abut
on the sheet feeding roller 100.
[0003] Further downstream from the guide plate 230 are provided a pair of conveying rollers
240 and a pair of resist rollers 250 to feed the sheet to a photo-sensitive drum 210.
[0004] When the pick up roller 220 feeds a sheet from the sheet feeding cassette 500 toward
the sheet feeding roller 100, the friction pad roller 800 abutting on the sheet feeding
roller 100 moves downward by a thickness of the sheet against an urging force of the
spring 200, the sheet is held between the sheet feeding roller 100 and the friction
pad roller 800, and the sheet feeding roller 100 rotates in the arrow direction, thereby
conveying the sheet to the downstream side. At this point, when the pick up roller
220 feeds a plurality of sheets toward the sheet feeding roller 100, though those
sheets are held between the sheet feeding roller 100 and the friction pad roller 800,
only the upper-most sheet is conveyed to the downstream side, so that the friction
pad roller 800 prevents the multiple-feeding of the lower sheets by the friction force
thereof.
[0005] However, in such sheet feeding mechanism, when a plurality of sheets are fed as described
above, the remaining sheets without being conveyed is left held between the sheet
feeding roller 100 and the friction pad roller 800. At this point, when there is no
sheets in the sheet feeding cassette 500, the trying to draw the sheets in order to
supply sheets causes one end of the sheets to become in a fixed condition, thereby
developing a first problem that the sheets are wrinkled or torn.
[0006] Further the friction pad roller 800 in such sheet feeding mechanism cannot prevent
the multiple feeding if the part thereof abutting on the sheet feeding roller 100
moves in the sheet feeding direction, so that the friction pad roller 800 must be
fixed to a bracket 130 so as not to be rotated, or should have a special mechanism
for preventing the multiple feeding where it con be rotated, or operated in a manner
to be rotated and fixed each time it feeds the sheet.
[0007] Thus, a second problem develops that where the friction pad roller 800 is fixed to
the bracket 130, the part abutting on the sheet feeding roller 100 wears rapidly and
the friction pad roller 800 becomes short in life, while where it can be rotated,
the equipment becomes complex or its operation becomes complicated.
[0008] Further in the method of mounting the friction pad roller 800 in the sheet feeding
mechanism as arranged above, when the friction pad roller 800 wears at the surface
thereof and is replaced, it is necessary to remove the spring 200, replace the friction
pad roller 800, and then remount the spring 200.
[0009] Accordingly, before and after the replacement of the friction pad roller 800, a difference
is likely to occur in the urging force of the spring 200, thereby developing a third
problem that a change in the urging force causes a sheet feeding trouble such as non-sheet
feeding or multiple feeding.
[0010] On the other hand, a copying machine of prior art having a sheet feeding mechanism
by which a plurality of sheet feeding cassettes are generally provided with a first
conveying passage for feeding a sheet from one sheet feeding cassette thereof and
a second conveying passage for feeding a sheet from the other sheet feeding cassettes,
and further a third conveying passage which extends from the point where the first
and the second conveying passages join toward a pair of conveying rollers to convey
the sheet conveyed from the the first conveying passage and that from the second conveying
passage to the pair of conveying rollers provided upstream.
[0011] Now, where a sheet of the sheet feeding cassette on the first conveying passage side
is selected, the sheet is conveyed by a sheet feeding roller for that sheet feeding
cassette through the first conveying passage to the third conveying passage and fed
to the pair of conveying rollers, while where a sheet of the sheet feeding cassette
on the second conveying passage side is selected, the sheet is conveyed by a sheet
feeding roller for that sheet feeding cassette through the second conveying passage
to the third conveying passage and fed to the pair of conveying rollers.
[0012] However, in such sheet guiding equipment, depending on the conveying directions and
the joining condition of the first, the second and the third conveying passages, when
the sheet is conveyed by a first sheet feeding roller through the first conveying
passage to a third conveying passages , the sheet
feeding direction may change at a sharp angle, or the leading edge of the sheet conveyed
through the second conveying passage may hit an inner wall of the third conveying
passage to force its direction to be changed, in which case a forth problem develops
that the sheet bends and jams in the third conveying passage without being fed smoothly
to the pair of conveying rollers.
[0013] On the other hand, in a sheet feeding mechanism of prior art, as shown in Figs. 2
(a) and 2 (b), where the sheet feeding roller 100 of the copying machine is replaced
due to wear and the like, in order to perform efficiently the replacement, a sheet
feeding shaft 300 being a rotating shaft of the sheet feeding roller 100 is pivotably
supported at the central part thereof by a vertically folded end 350 of a supporting
member 340, and at the right end thereof on the drawing by a body frame 390. The left
end of the sheet feeding shaft 300 is free, from which the sheet feeding roller 100
is easily detachable. In order that the sheet feeding roller 100 is smoothly rotated
to allow sheet feeding to be certainly performed, the supporting member 340 is joined
at the end 360 vertically folded on the body frame side 390 side to the body frame
side 390, and at a central plate 330 to a guide plate 320. The guide plate 320 is
omitted in Fig. 2 (b).
[0014] Then where a sheet 310 is fed from a sheet feeding cassette 370 having a separating
jaw 380 as shown in Fig. 2 (a), a load applied to the sheet feeding roller 100 is
small at the time of sheet feeding, whereby an effect on the guide plate 320 and the
like is almost out of the question even with the
supporting method as described above.
[0015] However, with the method of feeding sheets utilizing a friction pad, the load at
the time of sheet feeding becomes large, whereby an abnormal sound becomes liable
to occur by the sheet feeding roller 100 and the friction pad, or by the vibration
of the guide plate 320 in itself. And although the abnormal sound occuring between
the sheet feeding roller 100 and the friction pad can be eliminated by considering
the material and shape thereof, a fifth problem develops that the abnormal sound due
to the vibration of the guide plate 320 in itself cannot be eliminated.
SUMMARY OF THE INVENTION
[0016] The present invention is made to solve the above first problem of the sheet feeding
mechanism of prior art and it is an object of the present invention to provide a sheet
feeding mechanism with which sheets are not wrinkled or torn when a sheet feeding
cassette thereof is pulled out.
[0017] That is, a sheet feeding mechanism is described which comprises;
a sheet feeding roller for feeding sheets,
an advance preventive member which is abuttable on the sheet feeding roller by
a use of urging means and is for preventing multiple feeding of sheets, and
the advance preventive member having a first acted part, and
while a sheet feeding cassette is on operation of being pulled out, a first acting
part provided to the sheet feeding cassette acting on the first acted part of the
advance preventive member,
thereby the advance preventive
member being separated from the sheet feeding roller against an urging force of the
urging means.
[0018] In the example, where a plurality of sheets are fed to a sheet feeding roller and
prevented from being multiply fed by an advance preventive member, and the sheet feeding
cassette thereof is pulled out with the remaining sheets prevented from being multiply
fed remaining held between the sheet feeding roller and the advance preventive member,
a rail provided to the sheet feeding cassette abuts on a protrusion of the advance
preventive member to allow the protrusion to be moved against the urging force of
urging means, whereby an arm formed integrally with the protrusion is pivoted to allow
a pad to be separated from the sheet feeding roller, and the sheets held between the
sheet feeding roller and the pad to be released.
[0019] The present invention is also made to solve the above second problem of the sheet
feeding mechanism of prior art and it is an object of the present invention to provide
a sheet feeding mechanism with which the life of the friction pad becomes longer,
and the equipment is simple and requires no special operation.
[0020] That is ,a sheet feeding mechanism is described which comprises;
a sheet feeding roller for feeding sheets ,
an advance preventive member which is abuttable on the sheet feeding roller by
use of urging means and for preventing multiple feeding of sheets,
a multiple feeding preventive roller of the advance preventive member being rotatable
only in a direction reverse to sheet feeding direction,
the advance preventive member having an acted part, and
where a sheet feeding cassette is pulled out/set, an acting part provided to the
sheet feeding cassette acts directly or indirectly on the acted part of the advance
preventive member, thereby the multiple feeding preventive roller being separated
from the sheet feeding roller against an urging force of the urging means.
[0021] In the present invention , when a sheet feeding cassette is pushed in/pulled out,
an acting part provided to the sheet feeding cassette acts on an acted part of an
advance preventive member to cause a multiple feeding preventive roller of the advance
preventive member to be separated from a sheet feeding roller, and a vibration at
the time of setting/pulling out of the sheet feeding cassette is transmitted to the
multiple feeding preventive roller to allow the multiple feeding preventive roller
becoming free from the sheet feeding roller to be rotated random in the direction
reverse to the sheet feeding direction, thereby changing the abutting part of the
multiple feeding preventive roller.
[0022] The present invention is also made to solve the above third problem of the multiple
feeding preventive equipment of prior art and it is an object of the present invention
to provide a multiple feeding preventive equipment with which before and after the
replacement of a friction pad roller, the urging force of a spring does not change
not to allow a poor sheet feeding to occur.
[0023] That is , a sheet feeding mechanism of the present invention comprises;
a guide plate for guiding sheets,
a side plate which has an opening and is connected downward to an end on a downstream
side of the guide plate,
a supporting member mounted to an underside of the guide plate,
a pad supporting plate connected pivotably under the guide plate to the supporting
member,
pad means mounted removably to the guide plate side of the pad supporting plate
for preventing multiple feeding, and
urging means provided between the other part of the pad supporting plate and a
part lower than the opening of the side plate in order to allow a pad of the pad means
to abut on the sheet feeding roller by it's urging force.
[0024] In the present invention , when pad means is replaced, utilizing an opening provided
to a side plate, the pad means is removed from a pad supporting plate and new pad
means is mounted to the pad supporting plate, and at this point, before and after
the replacement of the pad means, urging means is not removed, so that the urging
force thereof does not change.
[0025] The present invention is also made to solve the above forth problem of the sheet
guide equipment of prior art and it is an object of the present invention to provide
a sheet guide equipment which is simple in composition and inexpensive, and can convey
smoothly sheets.
[0026] That is ,a sheet guide equipment of the present invention comprises;
a first conveying passage,
a second conveying passage,
a third conveying passage formed as one passage by joining of the first conveying
passage with the second conveying passage, and
thin plate-like guide means which extends from a joining point of the first conveying
passage with the second conveying passage in a conveying direction and which abuts
on an inner wall of the third conveying passage, or a part of which is positioned
near the inner wall, and
the guide means being such that a part A having a specified length from a head
is more bendable than the remaining part B.
[0027] In the present invention , with a sheet of a sheet feeding cassette fed to a first
conveying passage, the sheet passing through the first conveying passage hits a hardly
bendable part B of guide means, changes certainly in the conveying direction, and
is guided by the surface of the guide means and fed through a third conveying passage
to a pair of conveying rollers ; while with a sheet of another sheet feeding cassette
fed to a second conveying passage, the sheet passing through the second conveying
passage is guided in a gap between the inner wall of the third conveying passage on
which the head of the guide means abuts or near which part of the guide means is positioned
and an easily bendable part A of the guide means, and pushes down smoothly the head
of the guide means, thereby being fed downstream.
[0028] The present invention is also made to solve the above fifth problem of the sheet
feeding roller holding mechanism of prior art and it is an object of the present invention
to provide a sheet feeding mechanism which inhibits a vibration of a guide plate in
itself and eliminates an abnormal sound.
[0029] That is ,a sheet feeding mechanism of the present invention comprises:
a sheet feeding roller for feeding sheets,
a sheet feeding shaft at one end of which the sheet feeding roller is detachably
mounted,
a body frame for holding the other end of the sheet feeding shaft,
a supporting member for supporting the sheet feeding shaft at the other end of
the sheet feeding roller,
a plate part mounted to the body frame for supporting the supporting member, and
a vibration preventive member which is supported by the body frame and a part of
which abuts on a specified position of the plate part, the supporting member or the
sheet feeding shaft in a manner to prevent a deformation to which they are subjected.
[0030] In the present invention , a body frame supports a vibration preventive member, and
part of the vibration preventive member abuts on a specified position of a plate,
a supporting member, or a sheet feeding shaft in a manner to prevent a deformation
to which they are subjected, whereby the vibration of the plate, the supporting member,
or the sheet feeding shaft is prevented to cause the abnormal sound to be eliminated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Fig. 1 is a schematic side view showing enlarged principal parts of a sheet feeding
mechanism of prior art.
[0032] Fig. 2 is a view showing a holding mechanism of the sheet feeding roller of prior
art.
[0033] Fig. 3 is a side view showing an embodiment of a sheet feeding mechanism according
to the present invention.
[0034] Fig. 4 is a side view showing a state of an embodiment mainly indicating an advance
preventive member of the sheet feeding mechanism according to the present invention.
[0035] Fig. 5 is a side view showing another state of the embodiment mainly indicating the
advance preventive member of the sheet feeding mechanism according to the present
invention.
[0036] Fig. 6 is a front view to help explanation of the movement of the advance preventive
member associated with the movement of the sheet feeding mechanism according to the
present invention.
[0037] Fig. 7 is a front view to help explanation of the movement of the advance preventive
member associated with the movement of the sheet feeding mechanism according to the
present invention.
[0038] Fig. 8 is a member view showing the internal structure of a friction pad roller of
the advance preventive member of the sheet feeding mechanism according to the present
invention.
[0039] Fig. 9 is a front view to help explanation of the movement of the advance preventive
member associated with the movement of the sheet feeding mechanism according to the
present invention.
[0040] Fig. 10 is a front view to help explanation of the movement of the advance preventive
member associated with the movement of the sheet feeding mechanism according to the
present invention.
[0041] Fig. 11 is a side view showing a state of an embodiment mainly indicating an advance
preventive member of the sheet feeding mechanism according to the present invention.
[0042] Fig. 12 is a side view showing another state of the embodiment mainly indicating
the advance preventive member of the sheet feeding mechanism according to the present
invention.
[0043] Fig. 13 is a side view showing another state of the embodiment mainly indicating
the advance preventive member of the sheet feeding mechanism according to the present
invention.
[0044] Fig. 14 is a side view showing another state of the embodiment mainly indicating
the advance preventive member of the sheet feeding mechanism according to the present
invention.
[0045] Fig. 15 is a side view showing the embodiment mainly indicating a conveying passage
joining part of the sheet feeding mechanism according to the present invention.
[0046] Fig. 16 is a front view of guide means provided in conveying passages of the sheet
feeding mechanism according to the present invention.
[0047] Fig. 17 is a side view of various guide means provided in conveying passages of the
sheet feeding mechanism according to the present invention.
[0048] Fig. 18 is a partially sectional view showing the holding mechanism of a sheet feeding
roller of a sheet feeding mechanism according to the present invention.
PREFERRED EMBODIMENTS OF THE INVENTION
[0049] With reference to drawings, embodiments of the present invention will be described
hereinafter.
[0050] Fig. 3 is a side view of part of an image forming apparatus including a sheet feeding
mechanism of an embodiment according to the first present invention. That is, the
image forming apparatus is provide with a sheet feeding cassette 5 for storing a sheet,
a pick up roller 22 for feeding the sheet from the sheet feeding cassette 5, and a
guide plate 23 for guiding the sheet having been fed by the pick up roller 22. On
the upper central side of the guide plate 23 is provided a sheet feeding roller 1,
and on the lower central side of the guide plate 23 is mounted an advance preventive
member 3 for preventing multiple sheet feeding in a manner to be abuttable on the
sheet feeding roller 1 by a spring 2 being urging means.
[0051] On the side further downstream from the guide plate 23 are provided a pair of conveying
rollers 24 and a pair of resist rollers 25 in order to feed the sheet to a photo-sensitive
drum 21.
[0052] The above-described advance preventive member 3 is formed with a supporting member
9 fixed to the guide plate 23, an arm 7 supported pivotably by the supporting member
9, a friction pad roller 8 which is mounted at one end of the arm 7 and is a pad abuttable
on the the sheet feeding roller 1, and a protrusion 4 which is an acted part mounted
on the sheet feeding cassette 5 side of the arm 7. To the lower end of the arm 7 is
connected a spring 2 being urging means for allowing the friction pad roller 8 to
abut on the sheet feeding roller 1 by the urging force thereof, and to the lower end
of the guide plate 23 is connected the other end of the spring 2.
[0053] Fig. 6 is a view showing a relationship in position between the sheet feeding cassette
5 and the protrusion 4 of the advance preventive member 3 as viewed in the X direction
of Fig. 3. That is, on the side face on the advance preventive member 3 side of the
sheet feeding cassette 5 is provided a rail 6 which acts as an acting part that is
formed with downward inclined faces A, B on the both sides and with a face C horizontal
in the moving direction on the central part. In Fig. 6, the sheet feeding cassette
5 is allowed to move leftward when pulled out, and rightward when set.
[0054] The operation of the above embodiment will be described hereinafter.
[0055] As shown in Fig. 4, when the sheet feeding cassette 5 has been fully pushed-in to
a set position (the sheet feeding cassette pulling out direction is vertical to the
drawing sheet), or fully pulled out and removed (not shown), the arm 7 has been pivoted
counter-clockwise as viewed on the drawing by a pulling force of the spring 2 with
the supporting member 9 as an axis, and the friction pad roller 8 has been pivoted
in the direction in which it can abut on the sheet feeding roller 1, whereby when
the sheet has been fed, the sheet is held between the sheet feeding roller 1 and the
friction pad roller 8, and when the sheet has not been fed, the friction pad roller
8 abuts on the sheet feeding roller 1.
[0056] When the sheet feeding cassette 5 is used , as shown in Fig.4 , the sheet is fed
by the pick up roller 22 to the guide plate 23. The sheet feeding roller 1 rotates
in the arrow direction, whereby the sheet is held between the sheet feeding roller
1 and the friction pad roller 8, and conveyed toward the pair of conveying rollers
24. When the pick up roller 22 has fed a plurality of sheets, those sheets are held
between the sheet feeding roller 1 and the friction pad roller in a similar manner
to for one sheet. However, the friction pad roller 8 not rotating has a friction force
larger than that between sheets, which causes the lower side sheets to remain as they
are, whereby the sheet feeding roller 1 conveys only the uppermost sheet. When the
uppermost sheet has been conveyed, the rotation of the sheet feeding roller 1 stops,
and the remaining sheets not conveyed are left held between the sheet feeding roller
1 and the friction pad roller 8.
[0057] When sheets are continuously used, the sheets held between the sheet feeding roller
1 and the friction pad roller 8 are first conveyed, while where there is no sheets
and then sheets should be supplied to the sheet feeding cassette 5 , the sheet feeding
cassette 5 must be pulled out in a condition that the sheets remain.
[0058] Now, pulling out the sheet feeding cassette 5 in order to supply sheets to the sheet
feeding cassette 5 causes the inclined face A of the rail 6 provided on the side face
of the sheet feeding cassette 5 to abut on an inclined corner face D of the protrusion
4, whereby the the protrusion 4 is pushed upward in association with the movement
(leftward) of the sheet feeding cassette 5, as shown in Fig. 6. At this point, from
the time immediately after the abutting of the protrusion 4, the friction pad roller
8 moving concurrently with the protrusion 4 rotates clockwise with the supporting
member 9 as a rotating axis, and begins to be separated from the sheet feeding roller
1, thereby releasing the holding of the sheets remaining between the sheet feeding
roller 1 and the friction pad roller 8 (refer to Fig.5 ).
[0059] Then, when the abutting position shifts from the inclined face A to the horizontal
face C of the rail 6, the horizontal face C abuts on an under face F of the protrusion
4, and the remaining sheets are held at the rear end thereof by a sheet separating
jaw (not shown) of the sheet feeding cassette 5, whereby the sheets are pulled out
together with the sheet feeding cassette 5. During this operation, the protrusion
4 is pushed upward, and the friction pad roller 8 is separated from the sheet feeding
roller 1 (refer to Fig. 5).
[0060] When the sheet feeding cassette 5 is further pulled out, the abutting position of
the rail 6 on the protrusion 4 shifts from the horizontal face C to the inclined face
B, whereby the inclined face B abuts on an inclined face E of the the protrusion 4.
When the protrusion 4 is returned to the lower side in association with the movement
of the sheet feeding cassette 5 and thus the inclined face E of the protrusion 4 is
separated from the inclined face B, the protrusion 4 is also returned to the original
position by the spring 2 to cause the friction pad roller 8 to abut on the sheet feeding
roller 1 (refer to Fig. 4). Needless to say , the sheets remaining between the sheet
feeding roller 1 and the friction pad roller 8 have been drawn together with the sheet
feeding cassette 5 before the protrusion 4 is separated from the inclined face B of
the rail 6.
[0061] Fig. 7 shows a sheet feeding mechanism of another embodiment. In this embodiment,
the sheet feeding cassette 5 is pulled up or set leftward/rightward on the drawing.
[0062] On the underside of the sheet feeding cassette 5 moving in the arrow direction when
set/pulled out is provided a protrusion 12 having a horizontal part C long in the
moving direction and inclined faces A, B at the both end thereof. On the lower side
of the protrusion 12 is provided a lever 11.
[0063] On the central part of the lever 11 is provided a pivoting shaft 14, and at one end
on the left side on the drawing is provided an abutting protrusion 13 in a manner
to be close to the inclined face A of the protrusion 12. At the other end of the lever
11 is provided a guide groove 30, into which a movable shaft 31 is fitted, and the
shaft 31 is mounted at one end of an arm 10. The arm 10 is pivotably supported by
a supporting member 15. To the shaft 31 side of the arm 10 is connected the spring
2, and at the other end is mounted the friction pad roller 8 which abuts on the sheet
feeding roller 1 by the urging force of the spring 2. The other end of the spring
2 is connected to one end of the guide plate 23, to which the above-described supporting
member 15 is mounted.
[0064] Now, pulling out the sheet feeding cassette 5 (moving leftward on the drawing) in
a condition that a sheet is held between the sheet feeding roller 1 and the friction
pad roller 8 causes the inclined face A of the protrusion 12 on the underside to abut
on the abutting protrusion 13 of the lever 11, whereby the abutting protrusion 13
is pushed downward and the lever 11 begins to pivot. Then, the guide groove 30 side
of the lever 11 moves upward to cause the shaft 31 to move leftward in the guide groove
30, and the arm 10 to be pivoted clockwise against the force of the spring 2. When
the arm 10 is pivoted, the friction pad roller 8 is separated from the sheet feeding
roller 1 to release the sheet. When the sheet feeding cassette 5 moves further, the
abutting protrusion 13 abuts on the horizontal part C of the protrusion 12 to keep
a condition that the friction pad roller 8 is separated from the sheet feeding roller
1, whereby the sheet is pulled out together with the sheet feeding cassette 5. Then,
when the sheet has been pulled out and the sheet feeding cassette 5 is further pulled
out, the abutting protrusion 13 is returned to the original position while abutting
on the inclined face B of the protrusion 12, and the lever 11 is also returned to
the original position, whereby the friction pad roller 8 abuts again on the sheet
feeding roller 1.
[0065] Although in the above-described embodiment, the pad roller is allowed to be separated
from the sheet feeding roller by pivoting the arm, in addition to such method, the
pad roller may be moved upward/downward in the guide groove provided to the supporting
member as in prior art, and the rail may be allowed to move a protrusion provided
on the pad roller itself.
[0066] Although in the above-described embodiment, a mechanical method is utilized, in addition
to such method, an electrical method may be utilized in which, for example, a micro-switch
is mounted to an acted part of the advance preventive member and a protrusion is formed
at a position of the sheet feeding cassette close to the micro-switch in a condition
that the sheet feeding cassette is set to the sheet feeding cassette position, whereby
when the sheet feeding cassette is pulled out, the protrusion pushes the micro-switch
to cause a solenoid mounted to the guide plate to pull the acted part of the advance
preventive member for a specified time, and thus to allow the pad roller to pivot
in a manner to be separated from the sheet feeding roller.
[0067] As apparent by the above description, the present invention has an advantage that
when sheet feeding cassette is pulled out, the sheet remaining at the pick up roller
is not wrinkled and torn.
[0068] The sheet feeding mechanism of an embodiment according to the second present invention
will be explained hereinafter. The embodiment is almost similar to the embodiment
of the first invention but the friction pad roller 8, and the guide means 6 and so
on are different.
[0069] Fig. 8 is a sectional view of the friction pad roller 8 of the advance preventive
member 3 in Fig. 3. As shown in Fig. 8, the friction pad roller 8 is formed by mounting
a pad 82 allowed to abut on the sheet feeding roller 1 on the surface of a collar
81 provided with a one-way clutch 83 having a mechanism rotatable only in one direction,
and mounted at one end of the arm 7 in a manner to be rotatable reversely to the sheet
feeding direction (rotatable only in the dotted-line arrow direction of Fig. 3).
[0070] On a side face on the advance preventive member 3 side of the sheet feeding cassette
5 is provided guide means 6 having downward inclined faces A, B on the both ends and
a central part formed with triangle wave face C, as shown in Fig. 9. That is, Fig.
9 is a view showing a relationship in position between the sheet feeding cassette
5 and the protrusion 4 of the advance preventive member 3 as viewed in the X direction
of Fig. 3. In Fig. 9, the sheet feeding cassette 5 is allowed to move leftward when
pulled out, and rightward when set.
[0071] The operation of the above embodiment will be described hereinafter.
[0072] As described above and shown in Fig. 4, when the sheet feeding cassette 5 has been
fully pushed in to a set position (the sheet feeding cassette pulling out direction
is perpendicular to the drawing), or pulled out and removed (not shown), the arm 7
is pivoted counterclockwise as viewed on the drawing by the spring 2 with the supporting
member 9 as an axis, and the friction pad roller 8 abuts on the sheet feeding roller
1.
[0073] When the sheet feeding cassette 5 is used (Fig. 4), the sheet is fed by the pick
up roller 22 to the guide plate 23. The sheet feeding roller 1 rotates in the arrow
direction, whereby the sheet is held between the sheet feeding roller 1 and the friction
pad roller 8, and conveyed toward the pair of conveying rollers 24. where a plurality
of sheets are fed, the friction pad roller 8 is fixed without being rotated in the
sheet feeding direction because of the one-way clutch 83, so that the friction force
causes the lower side sheets to remain as they are, whereby the sheet feeding roller
1 conveys only the uppermost sheet, thus preventing the multiple sheet feeding. Then
the abutting part of the friction pad roller 8, on which the sheet feeding roller
1 abuts, wears at the same part at all times without moving.
[0074] Now, pulling out the sheet feeding cassette 5 in order to supply sheets to the sheet
feeding cassette 5 causes the inclined face A of the guide means 6 provided on the
side face of the sheet feeding cassette 5 to abut on an inclined corner face D of
the protrusion 4, whereby the the protrusion 4 is pushed upward in association with
the movement (leftward) of the sheet feeding cassette 5. At this point, from the time
immediately after the abutting of the protrusion 4, the friction pad roller 8 moving
concurrently with the protrusion 4 rotates clockwise with the supporting member 9
as a rotating axis, and begins to be separated from the sheet feeding roller 1, whereby
the friction pad roller 8 becomes free to rotate .
[0075] Then, when the abutting position shifts from the inclined face A to the triangle
wave face C of the guide means 6, the triangle wave face C abuts sequentially on the
under face F and the inclined corner faces E, D, and the shifting of the abutting
causes the protrusion 4 to move repeatedly upward/downward (from the H to L of Fig.
9). The shock of the upward/downward movement is transmitted through the arm 7 to
the friction pad roller 8, and the vibration of that shock causes the friction pad
roller 8 to rotate a little in the dotted-line arrow direction of Fig. 5 in which
the roller is rotatable at all times since the friction pad roller 8 cannot rotate
the reverse direction because of the one-way clutch 83.
[0076] When the sheet feeding cassette 5 is further pulled out, the abutting position of
the guide means 6 on the protrusion 4 shifts from the triangle wave face C to the
inclined face B of the guide means 6, and thus the inclined face B abuts on the inclined
corner face E of the protrusion 4. In association with the movement of the sheet feeding
cassette 5, the protrusion 4 is returned to the lower side, the inclined corner face
E of the protrusion 4 is separated from the inclined face B, and thus the guide means
6 for pushing up the protrusion 4 is separated, whereby the protrusion 4 is returned
to the original position by the spring 2 to cause the friction pad roller 8 to abut
on the sheet feeding roller 1 (refer to Fig. 4). At this point, the friction pad roller
8 had already been rotated a little, so that the abutting part of the pad 82 has shifted
to another position.
[0077] Where sheets are supplied to the sheet feeding cassette 5 to set (the sheet feeding
cassette moves rightward in Fig. 9), the protrusion 4 moves upward/downward in a similar
manner to for the above-described pulling out, while the friction pad roller 8 is
separated from the sheet feeding roller 1, thereby giving a vibration to the friction
pad roller 8 to change the abutting position of the pad 82.
[0078] Such a little rotation of the friction pad roller 8 due to vibration occurs random,
so that with a long-term usage, the circumferential whole surface of the pad 82 is
substantially evenly abutted.
[0079] Although in the above-described embodiment, the protrusion provided to the arm is
allowed to be acted directly by the guide means, the protrusion may be allowed to
be acted in directly through an intermediate lever by providing the guide means in
another position of the sheet feeding cassette.
[0080] Although in the above-described embodiment, the guide means has a shape of triangle
wave face, in addition to such shape, a wave face as shown in Fig.10 (a), or a plurality
of protrusions on the upper side of the horizontal face as shown in Fig. 10 (b) may
be provided. Alternatively, a flat face may be provided, in which case a little vibration
due to the pulling out/setting of the sheet feeding cassette occurs and is transmitted
to the pad to allow a little rotation.
[0081] As apparent by the above description, the present invention has an advantage that
the life of the friction pad roller becomes longer, and the equipment is simple in
structure and requires no special operation.
[0082] With reference to drawings, embodiments of the third present invention will be described
hereinafter.
[0083] Fig. 3 is a member view of part of an image forming apparatus provided with a multiple
feeding preventive equipment of an embodiment according to the third present invention.
That is, the image forming apparatus is provide with a sheet feeding cassette 5 for
storing a sheet, a pick up roller 22 for feeding the sheet from the sheet feeding
cassette 5, and a guide plate 23 for guiding the sheet having been fed by the pick
up roller 22. On the upper central side of the guide plate 23 is provided a sheet
feeding roller 1, and on the lower central side of the guide plate 23 is mounted an
advance preventive member 3 for preventing multiple sheet feeding in a manner to be
abuttable on the sheet feeding roller 1 by a spring 2 being urging means. A side plate
111 provided with an opening 110 for maintenance and checking is connected downward
to the end on the downstream side of the guide plate 23. A cover plate 112 with a
jaw 113 (refer to Fig. 4) and machine screws 114 is mounted to the opening 110.
[0084] On the side further downstream from the guide plate 23 are provided a pair of conveying
rollers 24 and a pair of resist rollers 25 in order to feed the sheet to a photo sensitive
drum 21.
[0085] As shown in Fig.4 , the above-described friction pad roller 8 is mounted to an L-shaped
pad mounting plate 115 to constitute a pad means 12 of the advance preventive means
3. The pad mounting plate 115 is fixed with a machine screw 16 to a bottom plate of
a U sectional-shaped pad supporting plate 7, which is pivotably supported by the supporting
member 9 provided to the guide plate 23. To the lower end of the pad supporting plate
7 is connected one end of the spring 2 being urging means for allowing the friction
pad roller 8 to abut on the sheet feeding roller 1 by the urging force thereof, and
to the lower end of the side plate 111 is connected the other end of the spring 2.
[0086] The operation of the above embodiment will be described hereinafter.
[0087] When the friction pad roller 8 wears due to a long-term usage, the roller must be
replaced with a new one. At this point, the power source of the image forming apparatus
is first to be opened, and a side door 116 shown in Fig. 3 to be opened.
[0088] Opening the side door 116 allows the cover plate 112 blocking the opening 110 of
the side plate 111 to be found. Then, as shown in Fig.4 the both side machine screws
114 mounting the cover plate 112 is to be loosened and removed. After removing the
machine screws 114, the cover plate 112 is to be removed in such a manner that as
shown in Fig. 11, the cover plate 112 is to be raised a little so as to pull out a
jaw 113 hooking at the lower end edge of the opening 110. When the cover plate 112
is removed, the opening 110 is opened to allow the inner friction pad roller 8 and
the pad supporting plate 7 to be found.
[0089] Then, loosening a machine screw 16 while supporting the friction pad roller 8 with
hands through the opening 110 allows the pad mounting plate 115 and the friction pad
roller 8 to be separated from the pad supporting plate 7 as shown in Fig. 12, so that
they are to be pulled out of the opening 110.
[0090] Then, a new friction pad roller 8 mounted to the pad mounting plate 115 is to be
inserted from the opening 110 and fastened and fixed with the machine screw 16 to
the pad supporting plate 7 in a similar manner to the above. In order to return the
cover plate 112 to the original position, the jaw 113 on the lower side of the cover
plate 112 is hooked at the lower end edge of the opening 110, and the upper side of
the cover plate 112 is fastened and fixed with the machine screws 114.
[0091] Thus, when the friction pad roller 8 is replaced, it is not necessary to remove the
spring 2, so that the urging force of the spring 2 does not change.
[0092] Figs. 13 and 14 show another embodiment.
[0093] In Fig. 13, the opening 110 is provided to the side plate 111 similarly to the above-described
embodiment. In order that the friction pad roller 8 is removable, a shaft 810 is fitted
into a U-shaped dent 131 of the pad mounting plate 115, which is fixed to the pad
supporting plate 7.
[0094] A worn friction pad roller 8 is to be replaced in a similar manner to the above by
opening a side cover 116, removing the cover plate 112 from the side plate 111, opening
the opening 110, pushing the lower side of the pad supporting plate 7 to the inner
side to pivot the pad supporting plate 7 through the opening 110 by a hand , separating
the friction pad roller 8 from the sheet feeding roller 1, and pulling out a friction
pad roller shaft 810 to a near side while shifting out from the dent 113 (refer to
Fig. 14). Then, the shaft 810 of a new friction pad roller 8 is to be fitted into
the dent 131 while the lower side of the pad supporting plate 7 remains pushed to
the inner side, and stopping the pushing causes the pad supporting plate 7 to be returned
to the original position by the spring 2, whereby the friction pad roller 8 abuts
on the sheet feeding roller 1.
[0095] Although in the above-described embodiment, a machine screw is used for fixing the
pad mounting plate, a quick fitting construction such as a hooking jaw and a holding
fixture may be used if they provide a certainly positive fixing.
[0096] As apparent by the above description, the present invention has an advantage that
before and after the replacement of the friction pad roller, the urging force of the
spring does not change to cause a poor sheet feeding no to occur.
[0097] With reference to drawings, embodiments of the forth present invention will be described
hereinafter.
[0098] As shown in Fig. 3, on a part of an image forming apparatus is provided the sheet
feeding cassette 5 storing sheets for a first conveying passage 600. On the upper
side of the sheet feeding cassette 5 is provided the pick up roller 22, on the downstream
side of which is provided the guide plate 23 for guiding sheets, in the midway of
which is provided the sheet feeding roller 1 for conveying the sheets on the upper
side, and the friction pad roller 8 for preventing the multiple sheet feeding on the
lower side. On the guide plate 23 is provided an inclined face 601 for guiding the
sheets to the downstream side of the friction pad roller 8, and the passage from the
sheet feeding roller 1 to the inclined face 601 forms the first conveying passage
600. To a joining point close to a tip head of the inclined face 601 is mounted guide
means 603. The tip head 604 is provided in a manner to abut on the inner wall on the
upper side of a third conveying passage 605.
[0099] On the lower side of the sheet feeding cassette 5 are provided another sheet feeding
cassette, pick up roller(which are not shown), guide plate , sheet feeding roller
401, and friction pad roller 430 in a similar manner to the above, and on a downstream
side of the guide plate is provided a conveying roller 607 for conveying sheets to
a second conveying passage 606. The second conveying passage 606 joins with the above-described
first conveying passage 600 to form the third conveying passage 605.
[0100] On the downstream side of the third conveying passage 605 are formed two guide plates
608a, 608b for guiding the sheets, close to the downstream side of which are provided
the pair of conveying rollers 24.
[0101] Fig. 16 is a plan view of the guide means 603 of the above-
described embodiment.
[0102] As shown in Fig. 16, in order to make part A of the thin plate-like resilient guide
means 603 more flexible than part B thereof, on the part A are provided a plurality
of slits 610 having a specified length from the head 604 thereof, while the part B
is left as it is.
[0103] The operation of the above embodiment will be described hereinafter.
[0104] In Fig.3, when the upper sheet feeding cassette 5 is selected in order to transfer
a toner image formed on the photosensitive drum 21, the pick up roller 22 feeds the
sheet stored in the sheet feeding cassette 5 toward the sheet feeding roller 1. The
fed sheet is fed along the face of the guide plate 23 by the sheet feeding roller
1 rotating in the arrow direction to the first conveying passage 600. At this point,
if a plurality of overlapped sheets are fed to the sheet feeding roller 1, the sheets
on the lower side are not conveyed due to the friction force of the friction pad roller
8 on the lower side, and only the uppermost one sheet abutting on the sheet feeding
roller 1 is fed .
[0105] As shown in Fig. 4, when a sheet 611 is fed to the first conveying passage 600, the
sheet 611 is moved along the inclined face 601 in the diagonally upper right direction,
and the leading edge of the sheet 611 hits the part B of the guide means 603 to cause
the conveying direction thereof to be bent leftward. At this point, the sheet 611
is conveyed along the face of the guide means 603 toward the pair of the conveying
rollers 24 while absorbing a deflection (bent) usually occurring in the sheet 611
by the elastic force of the part B of the guide means 603.
[0106] When a sheet of another sheet feeding cassette (not shown in Fig.3 ) provided below
the sheet feeding cassette 5 is selected, the sheet having been fed by a sheet feeding
roller 401 in a similar manner to the above is fed to the conveying roller 607 in
Fig. 3 ,by which the sheet is fed to the second conveying passage 606. At this point,
as shown in Fig. 15, the leading edge of the sheet 611 having been fed to the second
conveying passage 606 hits an inner wall 607 formed on the curved face of the third
conveying passage 605, and is bent along the curved face . Then, the sheet is conveyed
along into a gap which becomes gradually narrow and is formed between the inner wall
607 and the guide means 603. When the leading edge of the sheet 611 goes near to the
head 604 of the guide means 603, the part A including the head 604 of the guide means
603 which is formed in a manner to be more flexible than the part B is pushed downward
by the conveying force of the sheet 611, whereby the sheet 611 passes along the inner
wall 607 and smoothly between the inner wall 607 and the head 604 of the guide means
603, and is conveyed toward the pair of conveying rollers 24.
[0107] Thus, even where the sheet 611 is fed from the first conveying passage 600, or even
where the sheet 611 is fed from the second conveying passage 606, the guide means
603 utilizes the easily deflectable(bendable) properties of the part A and the hardly
deflectable properties of the remaining part B (though having resilient properties)
to allow the sheet 611 to be fed smoothly to the third conveying passage 605.
[0108] Although in the above-described embodiment, the guide means are provided with a plurality
of slits to change the deflectable properties thereof, in addition to such method,
as shown in Fig. 17, the following methods may be used: (a) the thickness of the part
A of the guide means 603 is made thinner than the part B; (b) the thickness of the
whole guide means 603 is made thin, and the part B made double to exhibit the hardly
deflectable properties; (c) the thickness of the guide means 603 is made inclined
so that the mounting part of the guide means 603 becomes thick and the head 604 thin;
or (d) the material of the part A of the guide means 603 is made more deflectable
than that of the part B.
[0109] Although in the above-described embodiment, the part A of the guide means 603 abuts
on the inner wall, the part A may be positioned near the inner wall without being
in contact with the wall.
[0110] As apparent by the above description, the present invention includes guide means
in which the part A having a specified length from the head is more deflectable than
the part B, and thus has an advantage that the equipment is simple in structure, inexpensive
and can convey smoothly sheets.
[0111] With reference to drawings, embodiments of the fifth present invention will be described
hereinafter.
[0112] Fig. 18 is a schematic sectional view taken in the direction A of Fig. 3. That is,
to a rear frame 431 and a front frame 432 of a body frame 420 are fixed with machine
screws the both ends of a slender plate-like stay 461 and those of a guide plate 405
being a plate part. Between the central part of the stay 461 and the guide plate 405
therebelow is held an elastic member 407 made of rubber. The stay 461 and the elastic
member 407 form a vibration preventive member 406. On the surface of the guide plate
405 opposite to the side on which the elastic member 407 abuts is mounted a supporting
member 404 with a machine screw and the like. The supporting member 404 is bent vertically
at the both ends thereof and thus has a fixed part 441 and a receiving part 440.
[0113] The fixed part 441 of the supporting member 404 is fixed to the rear frame 431 by
means of welding and the like, and the receiving part 440 is provided with a bearing
434. By the bearing 434 and a bearing 433 provided to the rear frame 431, a sheet
feeding shaft 402 is rotatably supported. The left end of the sheet feeding shaft
402 is extended from the bearing 434 toward the front frame 432, and a sheet feeding
roller 401 is installed to the extended end of the sheet feeding shaft 402, which
is fixed with a stop ring 411 so that the roller 401 does not slip out. Under the
sheet feeding roller 401 is arranged a friction pad roller 430 for preventing the
multiple feeding of copying sheets (refer to Fig.3).
[0114] The operation of the above embodiment will be described hereinafter.
[0115] When copying operation is started and a copying heet of the sheet feeding cassette
5 is fed by the sheet feeding roller 401, the copying sheet is conveyed upperstream
while being held between the sheet feeding roller 401 and the friction pad roller
430. Where two or more copying sheets are fed, the friction pad roller 430 prevents
multiple feeding, whereby only the uppermost copying sheet on the sheet feeding roller
401 side is conveyed.
[0116] As described above, the sheet feeding roller 401 is supported only at one side by
the bearings 433, 434, so that the sheet feeding mechanism constructed to use the
friction pad roller 430 is subjected to a large load when conveying copying sheets,
and liable to receive the vibration of upward/downward motion. The vibration of the
sheet feeding roller 401 is transmitted from the bearing 434 to the supporting member
404, and then to the guide plate 405 to vibrate. The vibration of the guide plate
405 is transmitted to the elastic member 407 abutting on the guide plate 405, while
the elastic member 407 supported by the stay 461 mounted to the body frame 403 absorbs
the vibration of guide plate 405 by the resiliency thereof and the supporting force
of the stay 461, whereby the guide plate 405 inhibits an abnormal sound occurring
due to vibration.
[0117] Although in the above-described embodiment, the elastic member 407 uses rubber, in
addition to such material, for example, an elastic material of synthetic resin, metal
or spring may be used.
[0118] Although in the above-described embodiment, the thickness of the elastic member 407
is made equal to the gap formed by the stay 461 and the guide plate 405, the thickness
may be made a little larger, for example, 0.2 to 1.0 mm than the gap with the guide
plate 405 made deflected a little downward so that vibration further hardly occur.
In this case, the shape of the elastic member may be made thick at the central part
thereof.
[0119] Although in the above-described embodiment, the vibration preventive member 406 is
allowed to abut on the plate 405, the member may be allowed to abut on the supporting
member to inhibit the vibration.
[0120] Although in the above-described embodiment, the vibration preventive member 406 is
allowed to abut on the plate 405 from the upper side of the sheet feeding roller 401,
the member may be allowed to abut on the part from the lower side of the sheet feeding
roller 401. In this case, the member may be allowed to abut on the supporting member
404 instead of the plate 405.
[0121] Although in the above-described embodiment, the elastic member 407 of the vibration
preventive member 406 is allowed to abut on the plate 405 , the elastic member 407
may be formed between the vibration preventive member 406 and the frame mounting part,
or by forming the abutting part with a non-elastic material , and by positioning the
elastic member held between the abutting part and the vibration preventive member
,the vibration can be inhibited.
[0122] As apparent by the above description, in the sheet feeding roller holding mechanism
provided with a sheet feeding roller for feeding sheets, a sheet feeding shaft to
one end of which the sheet feeding roller is detachably mounted, a body frame for
holding the other end of the sheet feeding shaft, a supporting member for supporting
the sheet feeding shaft by the other end side of the sheet feeding roller, and a plate
part mounted to the body frame for supporting the supporting member, the present invention
has an advantage that them mechanism is supported by the body frame, and the part
there of abuts on a specified position of the plate part, the supporting member or
the sheet feeding shaft in a manner to prevent a deformation they are subject to,
thereby inhibiting the vibration of the guide plate in itself to eliminate an abnormal
sound.