U.S. patent application number 11/646110 was filed with the patent office on 2007-11-08 for sheet feeding device and image forming apparatus.
Invention is credited to Shigeru Okazaki.
Application Number | 20070257424 11/646110 |
Document ID | / |
Family ID | 38590898 |
Filed Date | 2007-11-08 |
United States Patent
Application |
20070257424 |
Kind Code |
A1 |
Okazaki; Shigeru |
November 8, 2007 |
Sheet feeding device and image forming apparatus
Abstract
A sheet feeding device having a conveyance roller to convey a
sheet and a cleaning member in slide contact with the outer
circumferential surface of the conveyance roller for removing
foreign matter adhering to the conveyance roller, wherein the
cleaning member is formed by a conductive brush, and an image
forming apparatus having the sheet feeding device thereof.
Inventors: |
Okazaki; Shigeru; (Tokyo,
JP) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
US
|
Family ID: |
38590898 |
Appl. No.: |
11/646110 |
Filed: |
December 27, 2006 |
Current U.S.
Class: |
271/264 |
Current CPC
Class: |
B65H 2401/211 20130101;
B65H 2301/531 20130101; B65H 3/0684 20130101; B65H 5/06
20130101 |
Class at
Publication: |
271/264 |
International
Class: |
B65H 5/06 20060101
B65H005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2006 |
JP |
JP2006-070406 |
Claims
1. A sheet feeding device, comprising: a conveyance roller to
convey a sheet; and a cleaning member in slide contact with an
outer circumferential surface of the conveyance roller to remove
foreign matter adhering to the conveyance roller; wherein the
cleaning member is formed with a conductive brush.
2. The sheet feeding device of claim 1, wherein the outer
circumferential surface of the conveyance roller is formed with
urethane rubber.
3. The sheet feeding device of claim 1, wherein the outer
circumferential surface of the conveyance roller is formed with
urethane rubber having a hardness of 40.degree. to 60.degree..
4. The sheet feeding device of claim 1, wherein the outer
circumferential surface of the conveyance roller has a plurality of
projections forming asperity.
5. The sheet feeding device of claim 1, wherein a thickness of
bristles of the conductive brush is from 5 to 10 denier.
6. The sheet feeding device of claim 1, wherein an amount of
overlapping between an end of a bristle of the conductive brush and
the outer circumferential surface of the conveyance roller at a
position in which the conductive brush and the conveyance roller
press each other is from 0.5 mm to 1.5 mm.
7. The sheet feeding device of claim 1, wherein the cleaning member
is a rotation brush, which is rotated by a driving source.
8. An image forming apparatus, comprising: the sheet feeding device
of claim 1; and an image forming section to form an image on a
sheet conveyed from the sheet feeding device.
Description
[0001] This application is based on Japanese Patent Application No.
2006-070406 filed on Mar. 15, 2006, in Japanese Patent Office, the
entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a sheet feeding device used
for an image forming apparatus such as a copying machine, a
printer, a facsimile machine and a multi function machine having
the functions thereof, and in particular, to a sheet feeding device
provided with a cleaning member to remove foreign matter such as
paper dust adhering to an outer circumferential surface of a sheet
feeding roller.
[0003] There has been a fixed type foreign matter removing device
to remove the foreign matter like paper dust adhering to a surface
of a roller member by slidingly contacting a fixed type cleaning
member (flexible member such as brush, felt, PET sheet) onto the
roller member such as a sheet feeding roller and a conveyance
roller to convey a recording sheet.
[0004] An image forming apparatus of Patent document 1 has a
foreign matter removing device in which a fixed type cleaning
member like a felt is caused to be in contact with the conveyance
roller so as to clean a surface of the recording sheet through the
conveyance roller.
[0005] Also, there has been a rotation type foreign matter removing
device to remove the foreign matter such as the paper dust adhering
to the surface of the roller member such as the feeding roller and
the conveyance roller by contacting a cleaning roller (brush and
felt) with the roller member to convey the recording sheet.
[0006] An image forming apparatus in Patent document 2, wherein a
cleaning roller to clean the recording sheet to be conveyed is
cleaned by contacting a brush.
[0007] An image forming apparatus in Patent Document 3 uses a
method, wherein the cleaning roller is in contact with the
recording sheet to be conveyed.
[0008] A foreign matter removing device in Patent Document 4,
wherein a rotating brush roller is in contact with the conveyance
roller to clean the conveyance roller and a rotation roller is in
contact with this brush roller to clean the brush roller and then a
flexible sheet is in contact with the rotation roller to clean the
rotation roller.
[0009] [Patent document 1] Non-examined publication No.
11-52641
[0010] [Patent document 2] Non-examined Publication No.
11-208918
[0011] [Patent document 3] Non-examined Publication No.
8-314344
[0012] [Patent document 4] Non-examined Publication No.
2004-224451
[0013] When a printed sheet, in particular, an offset sheet passes
through a sheet feeding device or a sheet conveyance device
provided in an image forming apparatus or a post-process apparatus,
sprinkled powder, ink residue sticking on the sheet and coating
agent on the sheet surface adhere to an outer circumferential
surface of the sheet feeding roller and the conveyance roller, and
deteriorate a transportability of the sheet feeding roller and the
conveyance roller with the result that sheet transportation becomes
unstable.
[0014] In the foreign matter removing devices where the fixed type
cleaning member in contact with the aforesaid sheet feeding roller
and the conveyance roller removes the foreign matter, the foreign
matter accumulate in the cleaning member such as brush, foaming
urethane, felt, moquette member and PET sheet, thus it becomes
impossible to maintain cleaning performance for a long period of
time and a failure of sheet conveyance will occur. Also,
maintenance becomes necessary to replace the cleaning member.
[0015] In a reverse roller type sheet feeding roller method, a
rising fabric member such as a moquette and a flexible member such
as an urethane foam or a PET sheet are imposed on the roller to
remove the foreign matter such as the paper dust adhering to
rotation roller member such as a pick roller and the feeding
roller. However, in the rising fabric member and the flexible
member, since scraped foreign matter cannot be separated from the
roller, cleaning effect cannot be sustained and cleaning members
and rollers need to be cleaned or replaced periodically.
[0016] In the image forming apparatus of Patent Document 1, there
was a problem in durability that the foreign matter such as the
paper dust is accumulated in the cleaning member in short time,
then the paper dust exceeding a cleaning capacity is conveyed to a
transferring area.
[0017] In the rotation type foreign matter removing device wherein
the cleaning roller like the rotation brush is in contact with the
roller member such as the feeding roller and the conveyance roller,
unless a rubber material of the roller member and a material of the
cleaning roller are appropriate, the foreign matter such as the
paper dust cannot be removed stably for a long period of time. Thus
entering of the foreign matter into the transferring area cannot be
reduced.
[0018] In the image forming apparatus of Patent Document 2, there
was a problem that conveyance of a transfer material has an
unstable factor because it is configured to have a speed difference
between the cleaning roller and the transfer material.
[0019] In the image forming apparatus of Patent Document 3, there
was a problem in durability that cleaning becomes not effective
when the foreign matter such as the paper dust accumulates on the
surface of the cleaning roller.
[0020] In the image forming apparatus of Patent Document 4, unless
the material of the conveyance roller rubber and the cleaning
member are selected appropriately, stable sheet conveyance
performance and a high efficiency of cleaning cannot be
obtained.
SUMMARY
[0021] The present invention is achieved by the followings.
[0022] 1. A sheet feeding device, having a sheet conveyance roller
to convey a sheet and a cleaning member in slide contact with an
outer circumferential surface of the conveyance roller to scrape
the surface thereof for removing foreign matter sticking on the
conveyance roller; wherein the cleaning member is formed with
conductive brush.
[0023] 2. An image forming apparatus having the sheet feeding
device of 1 and an image forming section to form an image on the
sheet conveyed from the sheet feeding device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a structural view of an image forming apparatus
composed of an image forming apparatus main body, a post-processing
apparatus, a large capacity sheet feeding apparatus and an
automatic document conveyance apparatus.
[0025] FIG. 2 is a structural view of an image forming apparatus
related to the present invention.
[0026] FIG. 3 is a cross-sectional view of a first sheet feeding
device of a sheet feeding cassette.
[0027] FIG. 4 is a cross-sectional view of a second sheet feeding
device of the image forming apparatus main body.
[0028] FIG. 5 is a front view showing other embodiment of a sheet
feeding apparatus.
[0029] FIG. 6 is a plane cross-sectional view of the sheet feeding
apparatus.
[0030] FIG. 7 is a characteristic diagram showing changes of a
friction coefficient of an outer circumferential surface of a
conveyance roller.
[0031] FIG. 8 is a partial cross-sectional view of the conveyance
roller.
[0032] FIG. 9 is a characteristic diagram indicating changes of a
friction coefficient of a conductive brush resulting from elapsed
number of sheets passing through.
[0033] FIG. 10 is a cross-sectional view indicating an amount of
overlap between the cleaning member and the conveyance roller.
[0034] FIG. 11 is a characteristic diagram indicating a relation
between the amount of overlap and a loading torque of the
conveyance roller.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] Next, an image forming apparatus of the present invention is
explained with reference to the drawings.
[0036] <Image Forming Apparatus>
[0037] FIG. 1 is a structural view of an image forming apparatus
composed of image forming apparatus main body A, post-processing
apparatus FS, large capacity sheet feeding apparatus FT and
automatic document conveyance apparatus DF.
[0038] Image forming apparatus main body A is composed of image
forming section 1, fixing device 9 and sheet conveyance system.
Image forming section 1 is composed of charging device 3 provided
in a peripheral area of image carrier 2, image exposing device 4,
developing device 5, transferring device 6, discharging device 7A,
separating claw 7B and cleaning device 8.
[0039] The sheet conveyance system has sheet feeding cassette 10,
first sheet feeding device 11, second sheet feeding device
(register roller) 12, conveyance device 13, sheet ejecting device
14, a first conveyance section having manual sheet feeding device
15, and circulating re-feeding section to circulate and re-feed
sheet S.
[0040] Sheet feeding cassette 10 and first sheet feeding device 11
are formed with a plurality of sheet feeding devices (3 stories in
the figure) to store and send various sizes of sheets S and. Sheet
S sent out from sheet feeding device 20 of large capacity sheet
feeding apparatus LT is fed to second sheet feeding device 12.
[0041] Document d placed on a document table of automatic document
conveyance apparatus DF is conveyed through sheet feeding device 21
and an image in document d is read by an image scanning device.
[0042] In image forming section 1, processes such as charging,
exposing, developing, transferring, separating and cleaning are
conducted. On sheet S fed from sheet cassette 10, manual sheet
feeding device 15 and large capacity sheet feeding apparatus LT, an
image is transferred through transferring device 6. The image
carried by Sheet S is fixed onto the sheet S through fixing device
9 and is ejected from sheet ejection device 14 to be sent to
post-processing apparatus FS.
[0043] <Post-Processing Apparatus>
[0044] Post-processing apparatus FS is composed of entrance
conveyance section 30, shift unit 31, stacker unit 32, staple unit
33 coversheet feeding device 34 and a sheet ejection section.
[0045] Coversheet K fed from coversheet feeding device 34 is
conveyed through a conveyance roller group to be stored in stacker
unit 32. Coversheet K is lapped over a plurality of sheets S to
form front cover and rear cover. Meanwhile, coversheet K can be an
inserter sheet to be inserted between the plurality of sheets
S.
[0046] When a predetermined number of sheets S are loaded on
stacker unit 32 and aligned, staple unit 33 staples sheet S at two
positions or one position of a corner to bind sheets S and a
booklet is made.
[0047] Sheets S after binding are nipped and conveyed by sheet
ejection device 35 then ejected onto main tray 36 to be piled
up.
[0048] <Sheet Feeding Device>
[0049] A sheet feeding device is applicable to first sheet feeding
device 11 and second sheet feeding device 12 of sheet feeding
cassette 10 disposed in image forming apparatus main body A, manual
sheet feeding device 15, sheet feeding device 20 of large capacity
sheet feeding apparatus LT, sheet feeding device 21 of automatic
document conveyance apparatus DF and coversheet feeding device 34
of post-processing apparatus FS.
[0050] FIG. 2 is a structural view of other image forming apparatus
related to the present invention. Meanwhile, parts having the same
function as in FIG. 1 have the same symbols. Here, different points
from FIG. 1 are explained.
[0051] Image forming apparatus A is called a tandem type color
image forming apparatus having a plurality of sets of image forming
sections 1Y, 1M, 1C, 1K, belt-shaped intermediate transfer
substance 7, sheet feeding device and fixing device 9.
[0052] Image forming section 1Y to form yellow (Y) color image has
charging device 3Y, image exposing device 4Y, developing device 5Y
and cleaning device 8Y, which are arranged in a peripheral area of
image carrier 2Y. Image forming section 1M to form magenta (M)
color image has image carrier 2M, charging device 3M, image
exposing device 4M, developing device 5M and cleaning device 8M.
Image forming section 1C to form cyan (C) color image has image
carrier 2C, charging device 3C, image exposing device 4C,
developing device 5C and cleaning device 8C. Image forming section
1K to form black (K) color image has image carrier 2K, charging
device 3K, image exposing device 4K, developing device 5K and
cleaning device 8K.
[0053] Intermediate transfer substance 7 trains about a plurality
of rollers and is supported to be able to rotate.
[0054] Each color image formed through image forming sections 1Y,
1M, 1C and 1K is consecutively transferred onto rotating
intermediate transfer substance 7 through first transfer device 6Y,
6M, 6C and 6K to form a combined color image.
[0055] Sheet S stored in feeding cassette 10 of the feeding device
is fed by first sheet feeding device 11 and passes through second
sheet feeding device 12 then is conveyed to second transfer device
6A and then a color image is transferred onto the sheet S.
[0056] Sheet S on which the color image is transferred is pinched
then heated and pressed by fixing device 9 to fix the color toner
image (or toner image) on sheet S and then pinched by ejection
device 14 to be ejected.
[0057] On the other hand, after the color image is transferred onto
sheet S by second transfer device 6A, cleaning device 8A removes
the remaining toner from intermediate transfer substance 7 from
which sheet S is separated by curvature.
[0058] FIG. 3 is a cross sectional view of first sheet feeding
device 11. Meanwhile, since manual feeding device 15, sheet feeding
device 20 of large capacity sheet feeding apparatus LT, sheet
feeding device 21 of automatic document feeding apparatus DF and
coversheet feeding device 34 of post-processing apparatus FS have
the almost the same structure as first sheet feeding device 11,
first sheet feeding device 11 will be explained as a representative
below.
[0059] Sheet S loaded on hoisting bottom plate 101 is elevated
through hoisting member 102 by an unillustrated motor. When sheet S
reaches at a position where the outer circumferential surface of
pickup roller (conveyance roller) 111 comes in slide contact with a
top surface of sheet S, the top surface of sheet S is detected by
an unillustrated sensor and hoisting bottom plate 101 stops to
lift.
[0060] At this sheet upper limit position, predetermined pressure
P1 is imposed by own weight of pickup roller 111 and holder
114.
[0061] Pickup roller 111 and sheet feeding roller (conveyance
roller) 112 start to rotate with a sheet feeding signal. Pickup
roller 111 imposing the top surface of sheet S at predetermined
pressure P1 is released from the sheet surface, after sheets S is
conveyed to a nip position between sheet feeding roller 112 and
double feeding prevention roller (reverse roller) 113.
[0062] Double feeding preventing roller 113 is driven in a reverse
direction of a conveyance direction of sheet S through an
unillustrated torque limiter and imposed on sheet feeding roller
112 by an unillustrated spring at predetermined pressure P2.
[0063] When double feeding preventing roller 113 comes in contact
directly with sheet feeding roller 112, because sheet S does not
exist in the nip position or when one piece of sheet S is fed into
the nip position, the torque limiter slips beyond its limiting
torque and double feeding preventing roller 113 rotates in
accordance with the rotation of sheet feeding roller 112 to convey
one piece of sheet S.
[0064] However, in case two pieces or more sheets S are conveyed
into the nip position, the limit torque overcomes a friction force
between the sheets, and double feeding prevention roller 113
rotates in the reverse direction to push back sheets S locating
beneath top sheet S to prevent double feeding, thus one piece of
sheet S can be conveyed.
[0065] At a down stream side of a separating roller pair composed
of feeding roller 112 and double feeding prevention roller 113 in
the sheet feeding direction, a pair of conveyance rollers 117
composed of drive roller 117A and driven roller 117B are arranged.
The pair of conveyance rollers 117 nip one sheet S conveyed from
the separating roller pair and conveys it to second sheet feeding
device 12 shown in FIG. 1.
[0066] Above pickup roller 111, a cleaning member (cleaning brush)
116A fixed at an end of supporting plate 115 is arranged. Above
feeding roller 112, a cleaning member (cleaning brush) 116B fixed
at the other end of supporting plate 115 is arranged.
[0067] Cleaning member 116A scrapes against the outer
circumferential surface of pickup roller 111 to scrape away the
foreign matter adhering to the outer circumferential surface of
pickup roller 111. Cleaning member 116B scrapes against the outer
circumferential of feeding roller 112 to scrape away the foreign
matter adhering to the outer circumferential surface of feeding
roller 112.
[0068] Above drive roller 117A, cleaning member (cleaning brush)
116C is arranged. Cleaning member 116C scrapes against outer
circumferential surface to remove the foreign matter adhering to
the outer circumferential surface of drive roller 117A.
[0069] Cleaning member 116A, 116B and 116C are formed with
conductive brushes. Characteristics and specifications of the
conductive brush will be described later. Characteristics and
specifications of pickup roller 111, sheet feeding roller 11,
double feeding prevention roller 113 and drive roller 117A will
also be described later.
[0070] FIG. 4 is a cross-sectional view of a conveyance device of
second sheet feeding device 12 of image forming apparatus main body
A shown in FIG. 1.
[0071] Second sheet feeding device 12 has drive roller (conveyance
roller) 121 and driven roller 122 to pinch and convey sheet S,
first cleaning member 123 composed of a cleaning brush to rotates
and scrapes against drive roller 121, second cleaning member 124 to
rotate and scrape against first cleaning member 123, and flexible
third cleaning member 125 in slide contact with the outer
circumferential surface of second cleaning member 124.
[0072] Drive roller 121 rotates in a clockwise direction, first
cleaning member (hereinafter called cleaning brush) 123 is rotated
in an anticlockwise direction by an unillustrated driving device
and second cleaning member 124 is rotated by an unillustrated
driving device in a clockwise direction. Third cleaning member 125
is imposed on the outer circumferential surface of second cleaning
member 124 in a counter direction of rotation.
[0073] Cleaning brush 123 is formed with a conductive brush.
Characteristics and specifications of the conductive brush will be
described later. Characteristics and specification of drive roller
121 also described later.
[0074] FIG. 5 is a front cross-sectional view showing another
embodiment of the sheet feeding device. FIG. 5 (a) shows a status
before sheet feeding and FIG. 5(b) shows a condition during sheet
feeding.
[0075] Meanwhile, parts having the same function as in FIG. 3 are
represented by the same symbols and explanation of the parts
thereof is omitted.
[0076] When a feeding start signal is inputted, pickup roller 111
swings centering on a rotation axis of sheet feeding roller 112 to
come to contact with the upper surface of sheet S by its own
weight. At the same time, an electric clutch CL explained later
engages with rotate feeding roller 112, and pickup roller 111
starts to rotate through an unillustrated transmission device like
a belt.
[0077] Sheet S is fed by rotation of pickup roller 111 and conveyed
to the nip position where feeding roller 112 and double feeding
prevention roller 113 are imposed each other, then sheet S is
separated one by one and reaches to a pair of conveyance rollers
117 (see FIG. 3) in a downstream side of the conveyance
direction.
[0078] When an unillustrated sensor detects that sheet S reaches to
the pair of conveyance roller 117, electric clutch CL is disengaged
then sheets S is withdrawn from nip position where feeding roller
112 and double feeding roller 113 are imposed each other and
conveyed by pinching conveyance of the pair of conveyance
rollers.
[0079] In first sheet feeding device 11, there are provided first
cleaning member (hereinafter called cleaning brush) 118A, second
cleaning member 118B, third cleaning member 118C and shielding
member 118D above a space where pickup roller 111 and sheet feeding
roller 112 opposes each other.
[0080] Cleaning brush 118A is composed of a cleaning brush, which
rotates and scrapes against the outer circumferential surface of
feeding roller 111. Cleaning brush 118A rotates in the
anticlockwise direction by a drive device described later. Cleaning
brush 118A and pickup roller 111 rotates in the same direction at a
scraping position having a speed difference. Cleaning brush 118A
and sheet feeding roller 112 rotate in the same direction at the
scraping position having a speed difference.
[0081] Cleaning brush 118A removes paper dust and foreign matter by
scraping pickup roller 111 and sheet feeding roller 112.
[0082] Second cleaning member 118B is a rotation roller to be
rotated by a drive device and scrapes against cleaning brush 118A.
Second cleaning member 118B removes the paper dust and the foreign
matter adhering to cleaning brush 118A to refresh it.
[0083] Third cleaning member 118C is formed by a flexible thin
plate, for example, such as PET (polyethylene terephthalate) in
contact with an outer circumferential surface of second cleaning
member 118B. An edge section of third cleaning member 118C is
imposed on the outer circumferential surface of second cleaning
member 118B in a counter direction of a rotation direction of
second cleaning member 118B. Third cleaning member 118C removes the
paper dust and the foreign matter adhering to second cleaning
member 118B and shields a space above pickup roller 111.
[0084] Shielding member 118D, which is a thin flexible plate formed
by, for example, PET (polyethylene terephthalate) or urethane
sheet, is arranged in a symmetrical position to third cleaning
member 118C, being in contact with the circumferential surface of
second cleaning member 118B. The edge section of shield member 118D
lightly is imposed on the outer circumferential surface of second
cleaning member 118D in a trailing direction. Shield member 118D
removes the paper dust and the foreign matter adhering to second
cleaning member 118B and shields a space above sheet feeding roller
112.
[0085] In first sheet feeding device 11, when sheet S failed to be
conveyed is removed, pickup roller 111 is lifted and swings upward
centering on a sheet feeding roller axis. At this stage, since the
space above cleaning brush 118A is shielded by third cleaning
member 118C and shield member 118D, the paper dust and the foreign
matter around second cleaning member 118B are prevented from
exsorption.
[0086] Cleaning brush 118A is formed with a conductive brush.
Characteristics and specifications of the brush will be explained
later. Characteristics and specifications of pickup roller 111,
sheet feeding roller 112 and double feeding prevention roller 113
are explained later.
Embodiment
[0087] Image forming apparatus main body A: Digital multi function
machine bizhub7085.TM. (registered trade name by Konicaminolta)
modified.
[0088] Pickup roller 111, sheet feeding roller 112 and double
feeding prevention roller 113: hardness of rubber 56.degree., ether
type urethane rubber, outer diameter 32 mm, rubber thickness 4 mm
having embossing formed by asperities of 30 to 50 .mu.m on a
surface. The rubber hardness is indicated by a durometer, type A
spring type hardness meter prescribed by ISO 7619 (JIS K6253).
[0089] Since silicone rubber has merits that rubber hardness can be
soft, the rubber material itself do not tend to accumulate the dust
and the roller surface can be roughen to increase a friction
coefficient, it is used widely for roller material. On the other
hand, since it has demerits that it is not durable against rubbing
and is easy to be worn out, and an initial friction coefficient is
low, an urethane rubber is more favorable than the silicone rubber
as a material for rollers.
[0090] AS a representative of the cleaning member, cleaning brush
118A is explained below.
[0091] The specifications of the brush are as follows
TABLE-US-00001 Dimensions Material of bristle Conductive acryl
Thickness of bristle 6.25 denier (1 denier means a thickness of
fiber where 450 m in length and 50 mg in weight) Density of bristle
100,000 pcs./25.4 mm.sup.2 Outer Diameter of brush 16 mm Length of
bristle 4 mm Overlap Between pickup roller 111 0.5 to 1.5 mm and
cleaning brush 116 Between feeding roller 112 0.5 to 1.5 mm and
cleaning brush 116
[0092] <Hardness of Rubber>
[0093] FIG. 7 is a characteristic diagram indicating results of
measurement of change in a friction coefficient of the outer
circumferential surface of pickup roller 111 and sheet feeding
roller 112 resulting from the number of sheets passed. Offset
printed sheets are used as the sheets.
[0094] As the rollers, (a) EPDM rubber (ethylene propylene rubber),
(rubber hardness 35.degree.) (b) urethane rubber (rubber hardness
75.degree.), (c) urethane rubber (rubber hardness 56.degree.), (d)
urethane rubber (rubber hardness 44.degree.) and (e) urethane
rubber (rubber hardness 35.degree.) are compared and studied. (f)
means a lower limit of conveyance performance. TABLE-US-00002 TABLE
1 Friction coefficient (.mu.) of conveyance roller (a) (b) (c) (d)
(e) (f) Start 1.68 1.28 1.52 1.62 1.37 1 After 1.49 1.20 1.40 1.55
1.27 1 200 pcs. After 1.09 1.24 1.32 1.53 1.22 1 300 pcs. After
1.06 1.24 1.33 1.52 1.15 1 900 pcs. After 0.96 1.26 1.38 1.50 0.94
1 1500 pcs. After -- 1.23 1.33 1.45 0.86 1 2000 pcs. After -- 1.08
1.34 1.48 0.90 1 3000 pcs. After -- 1.12 1.34 1.44 0.92 1 5000 pcs.
After -- 1.11 1.25 1.40 1.01 1 7000 pcs. After -- 1.11 1.29 1.43
1.00 1 9000 pcs. Note: (a): EPDM rubber (ethylene propylene rubber)
(rubber hardness 35.degree.) (b): Urethane rubber (rubber hardness
75.degree.) (c) : Urethane rubber (rubber hardness 56.degree.) (d):
Urethane rubber (rubber hardness 44.degree.) (e): Urethane rubber
(rubber hardness 35.degree.) (f): Lower limit of conveyance
performance
[0095] Table 1 is data of experiment showing changes of friction
coefficients of rollers in accordance with number of print sheets
which is pinched and conveyed by the rollers formed with various
kinds of rubbers.
[0096] According to the experience, both (c) urethane rubber
(rubber hardness 56.degree.) and (d) urethane rubber (rubber
hardness 44.degree.) have the friction coefficient .mu. of more
than 1.25 and the rollers obtained a stable conveyance
performance.
[0097] EPDM rubber roller (a) having low rubber hardness has high
performance of sheet conveyance at initial stage of printing,
however in case of an offset print sheet is conveyed, sprinkled
powder, paper dust and ink residue adhering to sheet S are
transferred onto the roller surface and they become difficult to be
removed then a durability of sheet conveyance performance is
decreased.
[0098] The roller formed by (b) urethane rubber (rubber hardness
75.degree.) having a low friction coefficient due to high hardness
of the rubber causes slip and sheet conveyance performance
decreases.
[0099] The roller formed with (e) urethane rubber (rubber hardness
35.degree.) has a preferable sheet conveyance performance at
initial stage of use due to the high friction coefficient, however
after 1000 pieces of sheet conveyance, the friction coefficient
decreases and slip is caused and then the sheet conveyance
performance decreases.
[0100] According to the above results, the rollers formed with poly
ether type urethane rubber (a), (b) and (c) have preferable sheet
conveyance performance.
[0101] Also in a condition where a roller surface is tainted by
sprinkled powder, paper dust, and ink residue, the more the surface
roughness Rz (an average roughness of 10 points) increases, the
higher friction coefficient can be obtained.
[0102] In order to make the roller surface rougher, there are two
methods, i.e. (1) a method to grind the roller surface and (2) a
method where a roller forming surface of a roller forming metal die
is roughen by embossing. In case of EDPM rubber rollers and
silicone rubber rollers, method (1) is still capable of forming
rough surface. In case of urethane rubber rollers, method (2) can
make a rougher surface than method (1).
[0103] FIG. 8 is a partial cross-sectional view of a conveyance
roller.
[0104] In case of pickup roller, it is effective that from 20 to 30
grooves having depth of 0.1 to 0.5 mm and width of 0.5 mm are
formed on a circumference of the roller. However, in case of
feeding rollers and double feeding prevention rollers, it will
cause a bias wear, and no groove is preferred.
[0105] <Cleaning Member>
[0106] If the brush of cleaning member to clean the conveyance
roller surface by scraping against sheet conveyance rubber rollers
is not conductive, the surface of the rubber roller is charged and
the paper dust and the foreign matter adhering to the surface of
sheet conveyance rubber roller becomes difficult to be removed, and
the surface of the sheet is also charged, and then a problem that a
failure of image transfer in a transferring section of image
forming apparatus A is caused occurs. Therefore the brush for
cleaning is given the conductivity.
[0107] Brush 118A to clean pickup roller 111 and sheet feeding
roller 112 is particularly needed to be small. However, there is a
limit in size. A metal core where raised brushes are winded has to
have an outer diameter of at least 6 mm for strength and the outer
diameter of 8 mm is preferred to exert a stable cleaning
function.
[0108] Regarding the bristle of cleaning brush 118A, a length of
not less that 3 mm is needed. Thus adding the diameter of the metal
core and the length of the bristle, the outer diameter of cleaning
brush 118A has to be not less than 14 mm.
[0109] FIG. 9 is a characteristic diagram indicating results of
measurement of change in a friction coefficient of the conductive
brush in respect to a conductive brush of cleaning brush 118A in
accordance with elapsed numbers of sheets passed.
[0110] Conductive brush (a) has the following dimensions:
Thickness of bristle: 6.25 denier
Density of bristle: 100,000 pieces per 25.4 mm.sup.2
Outer diameter: 16 mm
Length of bristle: 4 mm
[0111] Conductive brush (b) has the following dimensions:
Thickness of bristle: 15 denier
Density of bristle: 60,000 pieces per 25.4 mm.sup.2
Outer diameter: 16 mm
Length of bristle: 4 mm
[0112] (c) means a lower limit of conveyance performance.
[0113] In a conductive brush having a thickness of bristle 3 denier
and a density of bristle 200000 per square inch (one inch is 25.4
mm), a torque loaded onto the conveyance roller is large and the
conveyance rollers in the downstream side of first sheet feeding
device 11 causes failures. TABLE-US-00003 TABLE 2 Friction
coefficient (.mu.) of urethane rubber roller 56.degree. (a) (b)
Thickness of the Thickness of the bristle: 6.25 denier bristle: 15
denier Density of the Density of the Lower limit bristle: bristle:
of 100,000/25.4 mm.sup.2 60,000/25.4 mm.sup.2 performance Start
1.52 1.52 1 After 1.33 1.09 1 900 pcs. After 1.34 0.85 1 2000 pcs.
After 1.34 -- 1 3000 pcs. After 1.34 -- 1 5000 pcs. After 1.25 -- 1
7000 pcs. After 1.29 9000 pcs.
[0114] Table 2 is data of an experiment showing changes of friction
coefficients of rollers in accordance with number of print sheets
which is conveyed by the cleaning brush 118A formed with the
aforesaid various kinds of conductive brushes and the rollers
formed with urethane rubber (rubber hardness: 56.degree.).
[0115] According to the results of the experience, conductive brush
(a) with bristle thickness of 6.25 denier and bristle density of
100,000/25.4 mm.sup.2, has less decrease of the friction
coefficient .mu. due to the elapsed number of printing sheet
processed and a stable sheet conveyance force of roller.
[0116] Contrary to it, in conductive brush (b) with bristle
thickness of 15 denier and bristle density of 60,000/25.4 mm.sup.2,
the friction coefficient .mu. remarkably decreases due to the
elapsed number of printing sheet passed and the sheet conveyance
performance of roller decreases at about 2,000 pcs.
[0117] <An Overlapping Amount Between the Cleaning Member and
the Conveyance Roller>
[0118] FIG. 10 is a cross-sectional view showing an overlapping
amount between the cleaning member and the conveyance roller.
[0119] FIG. 11 is a characteristic diagram showing a relationship
between the loading torque and overlapping amount at a position
where the cleaning member and the conveyance roller are in contact
each other.
[0120] <Upper Limit of the Overlapping Amount>
[0121] The more overlapping amount increases, the more an
efficiency to scrape off the paper dust and the foreign matter
adhering to the conveyance roller is improved.
[0122] After leaving cleaning brush 118A for 100 hours, under the
condition where the overlapping amount is 2 mm, temperature is
30.degree. C. and humidity is 80%, a change of outer diameter of
cleaning brush 118A is measured. As the result, bristles of the
brush is deformed from an initial outer diameter of 16 mm to 15.5
mm, thus the overlapping amount is changed from 2 mm to 1.5 mm.
Consequently, an upper limit of the overlapping amount is 1.5 mm in
cleaning brush 118A with bristle length of 4 mm. Meanwhile, it is
obvious that the longer bristle, the more overlapping amount.
[0123] Though the overlapping amount is more than 1.5 mm, the
bristle of the brush lies down and the overlapping amount
decreases. If the overlapping amount changes from initial one,
stable cleaning performance cannot be obtained. Thus, the upper
limit of overlapping amount is preferred to be not more than 1.5
mm.
[0124] The change of length of the bristle is predicted as
follow:
[0125] When the length of bristle is 3 mm and a maximum overlapping
amount is 1.5 mm, since a limit of overlapping amount is
proportional to the length of the bristle, the limit of overlapping
amount is predicted as: 1.5 mm.times.(3 mm/4 mm)=1.1 mm. When the
length of bristle is 2 mm and a maximum overlapping amount is 1.5
mm, the limit of overlapping amount is predicted as: 1.5
mm.times.(2 mm/4 mm)=0.75 mm.
[0126] <Lower Limit of Overlapping Amount>
[0127] FIG. 11 shows a result of measurements of loading torque of
the conveyance roller which represents cleaning ability of cleaning
brush 118A to scrape away the paper dust and the foreign
matter.
[0128] At overlapping amount of 0.3 mm, the loading torque is 5
gfcm, which is almost 0. At overlapping amount of 0.5 mm, the
loading torque is 50 gfcm, which is the lowest value of a desired
loading torque. Thereby, the overlapping amount is needed to be set
in between the lowest value of 0.5 and the highest value of 1.5
mm.
[0129] Meanwhile, in the present embodiment, while conductive
acrylic material is used as the conductive brush, the present
invention is not limited to the acrylic material. For example,
conductive polyester material can be used. In case the conductive
polyester material is used, it is predicted that durability is
improved compared to the case of using conductive acrylic material.
In the embodiment of the present invention, while post-processing
apparatuses having a side stitch function has been explained as
post-processing apparatuses connected to the image forming
apparatus main body A, applications of the post-processing
apparatus of the present invention for the image forming system is
not limited to the applications, it is also applicable to
post-processing apparatus such as gumming bookbinding machines,
edge cutting machines, glued-on cover casing-in machines and cast
sealing machines and image forming systems to which a plurality of
these post-processing apparatuses are connected.
[0130] Also, in the embodiment of the present invention, while a
post-processing apparatus connected to a copying machine has been
explained, it is also applicable to image forming systems connected
to image forming apparatuses such as shortrun printers, printers,
facsimile machines and multi function machines.
[0131] According to the above embodiments, it is possible to
provide a foreign matter removing device in which the foreign
matter such as paper dust can be removed for a long period of time,
entering of the foreign matter into the transfer area is reduced
and a preferable image quality is obtained, and an image forming
apparatus using the foreign matter removing device thereof.
[0132] Further, there are obtained effects that cleaning effect and
durability of the feeding rollers and conveyance rollers are
improved, conveyance performance of a sheet with more paper powder
is improved and conveyance performance of an offset printed sheet,
in particular, for an offset printed coated sheet is improved.
* * * * *