U.S. patent number 3,859,691 [Application Number 05/361,164] was granted by the patent office on 1975-01-14 for cleaning apparatus for electrophotography.
This patent grant is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Hajime Katayama, Talayuki Kitajima, Tsukasa Kuge, Syusei Tsukada.
United States Patent |
3,859,691 |
Katayama , et al. |
January 14, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
CLEANING APPARATUS FOR ELECTROPHOTOGRAPHY
Abstract
A cleaning apparatus for an electrophotographic apparatus
comprising an elastic cleaning blade with a holder arranged along a
surface of a photosensitive member for cleaning the toners which
still remain on the surface of a photosensitive member even after
transferring of developed images to a copying paper is finished.
The elastic cleaning blade preferably contacts with the surface of
the photosensitive member in such a way that the axis of the blade
and a tangent to said surface at the pre-cleaning side subtends an
obtuse angle specified in relation with the axis line of the blade
in the holder. The holder disposes the elastic cleaning blade
relative to the photosensitive member to engage a substantially
upwardly moving surface portion of the photosensitive member.
Inventors: |
Katayama; Hajime (Tokyo,
JA), Tsukada; Syusei (Tokyo, JA), Kitajima;
Talayuki (Yokohama, JA), Kuge; Tsukasa (Kawasaki,
JA) |
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JA)
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Family
ID: |
27457356 |
Appl.
No.: |
05/361,164 |
Filed: |
May 17, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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120256 |
Mar 2, 1971 |
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Foreign Application Priority Data
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Mar 10, 1970 [JA] |
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45-20285 |
Mar 17, 1970 [JA] |
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45-25511 |
Mar 17, 1970 [JA] |
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45-25512 |
Nov 24, 1970 [JA] |
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45-103504 |
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Current U.S.
Class: |
15/256.51;
399/351 |
Current CPC
Class: |
G03G
21/0029 (20130101) |
Current International
Class: |
G03G
21/00 (20060101); G03g 013/16 () |
Field of
Search: |
;15/256.51,256.5,256.52,1.5,100,4 ;118/637 ;355/15 ;101/425,169
;117/17.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bleutge; Robert L.
Assistant Examiner: Moore; C. K.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Parent Case Text
This is a continuation, of application Ser. No. 120,256, filed Mar.
2, 1971 and now abandoned.
Claims
We claim:
1. A cleaning apparatus for an electrophotographic copying device
wherein an electrophotographic latent image formed on the surface
of a photosensitive member is moved past a series of processing
stations including a developing station at which said latent image
is developed with toner to form a toner image and a transfer
station at which said toner image is transferred to copying
material, comprising an elastic cleaning blade for removing
residual toner from said photosensitive member after transfer of
said toner image to said copying material, said residual toner
being scratched off in the direction opposite to that of the
movement of said photosensitive member, one end of said elastic
cleaning blade having a cleaning edge, and holder means for
supporting the opposite end of said elastic cleaning blade and
disposing said cleaning edge in contact against the surface of said
photosensitive member, said holder means disposing said elastic
cleaning blade relative to said photosensitive member to engage a
substantially upwardly moving surface portion of said
photosensitive member, said elastic cleaning blade being placed
above the horizontal axis of a rotary member carrying said surface,
said holder means disposing said elastic cleaning blade relative to
said photosensitive member at an angle .theta..sub.1, at the
pre-cleaning side, subtended by the axis of the end portion of the
blade contacting the photosensitive member with said cleaning edge
and a straight line touching the surface of the photosensitive
member at the contact point, and at an angle .theta..sub.1, at the
pre-cleaning side, subtending by the axis of a portion of the blade
near said opposide end which is supported by said holder means and
said line, said angles .theta..sub.1 and .theta..sub.1 satisfying
the following relation:
.theta..sub.1 > .phi. > .pi./2
2. A cleaning apparatus for an electrophotographic copying device
wherein an electrophotograhpic latent image formed on the surface
of a photosensitive member is moved past a series of processing
stations including a developing station at which said latent image
is developed with a toner to form a toner image and a transfer
station at which said toner image is transferred to copying
material, comprising, in combination, an elastic cleaning blade for
removing residual toner from said photosensitive member after
transfer of said toner image to said copying material, one end of
said elastic cleaning blade having a cleaning edge, and holding
means for supporting the opposite end of said elastic cleaning
blade and disposing said cleaning edge in contact against the
surface of said photosensitive member to scratch off said residual
toner in a direction opposite to that of the movement of said
photosensitive member, said holder means disposing said elastic
cleaning blade relative to said photosensitive member to engage a
substantially upwardly moving surface portion of said
photosensitive member.
3. A cleaning apparatus according to claim 2 in which there are a
plurality of cleaning blades and holder means.
4. A cleaning apparatus according to claim 3 wherein said plurality
of blades are placed above the horizontal axis of a rotary member
carrying said surface and there is provided a sheet for guiding the
toner scratched off said photosensitive member to a toner receiver,
said toner being collected by gravitationally falling.
5. A cleaning apparatus according to claim 2 in which said cleaning
blade has a toner scratching part and a toner receiving part.
6. A cleaning apparatus according to claim 2 further comprising an
elastic cleaning roller coated with a cleaning member arranged
after said cleaning blade and a toner collecting portion for
collecting toners scratched off said photosensitive member.
7. A cleaning apparatus according to claim 2 in which said cleaning
blade consists of a first layer and a second layer, the modulus of
elasticity of said first layer being substantially greater than the
modulus of elasticity of said second layer.
8. A cleaning apparatus according to claim 2 in which only the end
portion of said cleaning blade having said cleaning edge is
composed of an elastic member having high abrasion resistance and
high solvent resistance.
9. A cleaning apparatus according to claim 2 in which said holder
means is provided movably with respect to said photosensitive
member and said cleaning blade is removably fitted to said holder
means in a cartridge type fit.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a cleaning apparatus for
electrophotography and, more particularly, to a cleaning apparatus
for removing toners remaining on a photosensitive member after
transferring the images in an electrophotographic reproduction
device of image-transferring type.
2. Description of the Prior Art
Representative conventional cleaning apparatuses are a web cleaning
apparatus and a fur brush cleaning apparatus. With respect to the
web cleaning apparatus, the material of web is limited and the
running cost is expensive, and further, cleaning ability varies
depending upon the humid state of the web. In addition, the web
should be frequently exchanged, and when reproduction of high
density is continuously carried out for a long time, the cleaning
can not be satisfactorily effected. Referring to the fur brush
cleaning apparatus, the apparatus is usually of a large scale since
the fur brush should be rotated at high speed, and the life of fur
brush is disadvantageously short. In addition, an apparatus for
removing the scattered developer by suction is necessary. Further,
when reproduction of high density is continued for a long time, the
cleaning capacity is not sufficient.
SUMMARY OF THE INVENTION
According to the present invention, the cleaning apparatus for an
electrophotographic apparatus of a developed image transferring
type comprises an elastic cleaning blade arranged along a surface
of a photosensitive member after transferring images and the
elastic cleaning blade is supported by a holder. The holder
disposes the elastic cleaning blade relative to the photosensitive
member to engage a substantially upwardly moving surface portion of
the photosensitive member. The elastic cleaning blade preferably
contacts with the surface of the photosensitive member to be
cleaned in such a way that an angle .theta..sub.1, at the
pre-cleaning side, subtended by an axis of the portion of the blade
contacting the photosensitive member and a tangent line to the
surface of the photosensitive member at the contact point and an
angle .phi..sub.1, at the pre-cleaning side, subtended by an axis
of the portion of the blade supported by the holder and the
above-mentioned tangent line satisfy the following relation:
.theta..sub.1 > .phi..sub.1 > .pi./2
The relation will be more fully understood by referring to FIG.
10.
An object of this invention is to provide a novel cleaning
apparatus solving the drawbacks of the above-mentioned prior
arts.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1, FIG. 2 and FIG. 3 show embodiments of cleaning apparatus
for electrophotography according to this invention where a
plurality of elastic blades are used as the cleaning member;
FIG. 4 and FIG. 5 show other embodiments of the blade according to
this invention;
FIG. 6 and FIG. 7 show embodiments of this invention where an
elastic cleaning blade and a cleaning roller are employed;
FIG. 8 is a conventional cleaning blade;
FIG. 9 and FIG. 10 show embodiments of this invention and are
diagrammatical cross sectional views for explaining conditions of
blade arrangement with respect to the photosensitive member;
FIG. 11 shows a cross sectional side view of an embodiment of this
invention;
FIG. 12 shows a state of exchanging the blade; and
FIG. 13 shows a diagrammatical cross sectional view of a modified
embodiment of a blade according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a drum photosensitive member 1 is cleaned by
blades 2.sub.1 -2.sub.n fixed to holders 3. Blades 2.sub.1 -2.sub.n
are made of elastic material such as elastic synthetic resins and
rubbers. Toners scratched off from the photosensitive member 1 by
blades are collected to a toner receiver 4. In FIG. 1, some of
plural blades 2.sub.1 -2.sub.n are arranged under the axis line
X--X of the photosensitive member 1 and the photosensitive member 1
is rotated counterclockwise and toner T remaining on the
photosensitive member is scratched off by the first blade 2.sub.1
and falls down to a toner receiver 4 over the surface of the blade
2.sub.1 through the other end of the blade 2.sub.1. On the other
hand, the remaining toner T not removed by the first blade 2.sub.1
is removed by the second blade 2.sub.2 and in a similar way the
cleaning is repeated subsequently.
Referring to FIG. 2, the photosensitive member 1 is rotated
clockwise and the remaining Toner 2 is scratched off by a blade
2.sub.n at the nth step and the toner thus scratched off falls down
directly to the toner receiver 4 and therefore, the toner receiver
4 should be placed nearer to the photosensitive member 1 than FIG.
1. In general, a remaining toner not removed by a blade 2.sub.n at
nth step is removed by a blade 2.sub.n.sub.-1 at (n-1)th step (in
FIG. 2, corresponding to the second step) and the toner thus
removed once falls down to blade 2.sub.n at the nth step and then
to the toner receiver 4. In a similar way, the cleaning is
repeated.
Referring to FIG. 3, all blades 2.sub.1 -2.sub.n are arranged above
the axis line X--X and in a way similar to FIG. 2 the cleaning of
the photosensitive member 1 is carried out, but a sheet 5 is
necessary for introducing toner scratched off by the nth blade
2.sub.n to a toner receiver 4. In this case, the sheet 5 contacts
lightly with the photosensitive member 1, but does not scratch off
the remaining toner on the photosensitive member. The sheet 5
prevents the toner scratched off by a blade 2.sub.n from falling
down outside of the cleaning box.
Referring to FIG. 4, there is shown an embodiment where another
shape of blade is employed, that is, plural blades 6.sub.1 -6.sub.n
have toner scratching portion 7 and toner receiving surface 8 and
are fixed to a holder 3. Some blades are placed under the axis line
X--X of the photosensitive member 1. When the photosensitive member
1 rotates clockwise, the remaining toner T is scratched off by a
blade 6, with its scratching portion 7 and the toner thus scratch
off directly falls down to a toner receiver 4. On the other hand,
the remaining toner which is not removed by the scratching portion
7 of blade 6.sub.1 is removed by a scratching portion 7 of a blade
6.sub.2 and the toner thus removed is introduced into a toner
receiver 4 by way of a toner receiving surface 8 of a blade
6.sub.1. The cleaning of the photosensitive member 1 is
subsequently repeated in a way as mentioned above.
Referring to FIG. 5, all blades are arranged above the axis line
X--X of the photosensitive member 1 and the cleaning of the
photosensitive member 1 is effected in a way similar to FIG. 4, but
toner scratched off by the scratching portion 7 of a blade 6.sub.1
is introduced to a toner receiver 4 using a sheet 5. In this case,
the sheet 5 is arranged in a way similar to FIG. 3 and serves
similarly.
In the above embodiments a plurality of blades for scratching off
toner are arranged along the surface of the drum photosensitive
member 1 after the transferring, and therefore, the cleaning of the
photosensitive member 1 can be repeated at each blade to clean
completely the photosensitive member. Since each blade is not
necessary to have such a strong contacting pressure against the
photosensitive member 1 as compared with a case where only one
blade is used for cleaning and thereby the surface of
photosensitive member 1 is not damaged. Each blade is so arranged
that toner scratched off from the surface of photosensitive member
1 can be introduced into a toner receiver 4 by way of each blade
and therefore, any particular sheet for guiding the toner is not
necessary. Thus, the cleaning apparatus can be of a small type and
inexpensive.
When an electroconductive blades are used and a bias voltage is
applied thereto so as to absorbing and removing the remaining toner
T, the cleaning of photosensitive member 1 can be conducted more
completely.
Referring to FIG. 6 and FIG. 7, further embodiments according to
this invention are illustrated. Blades 7 having holders 3 similar
to FIG. 4 and FIG. 5 are fixed to a cleaning box 9 with holders.
The cleaning blade may be made of synthetic resin such as Teflon
(Trade name, supplied by E. I. duPont de Nemours & Co. Inc.),
silicon rubber, polyester, and polyethylene, or rubbers. The
surface of an elastic roller 10 is coated with a cleaning coating
11, e.g., cloth, suede, and jersey and the hardness of the coating
is preferably about 20.degree.. A thin synthetic resin (such as
polyester) sheet 5 is provided to guide the toner scratched off
from the surface of photosensitive member 1 to a toner receiver 4
provided removably at the bottom of the cleaning box 9.
When the photosensitive member 1 rotates to a direction as shown by
the arrow, most of toner T remaining on the surface of the
photosensitive member 1 are scratched off by a blade 7 and then
falls down to a toner receiver 4 by way of a sheet 5 and further
the toner T' not removed by blade 7 is removed by rubbing with an
elastic roller 10 and falls down to a toner receiver 4 by way of a
toner receiving surface 8 and thereby the photosensitive member 1
is completely cleaned.
In FIG. 6, a cleaning brush 12 rotating to a direction as shown by
the arrow removes the toner on the cleaning coating 11 and the
toner attached to the brush is removed by a bar 13. Scattered
toners are taken out through a duct 14. In FIG. 7, the toner on the
cleaning coating 11 is removed by a vacuum duct 15.
According to the above-mentioned embodiments, both a blade and an
elastic roller which are different from each other in point of
function are used and this combination can compensate each drawback
to result in a complete cleaning. When a blade alone is employed,
some portions of the photosensitive member are not completely
cleaned, but a part of toner still remains on the photosensitive
member in a form of streak since a completely uniform contact
between the blade and the longitudinal line on the surface of a
drum photosensitive member is not easily obtained. On the contrary,
when an elastic roller alone is used, the insufficient cleaning
appears as a whole surface smudge.
In the above embodiments, these two cleaning means are combined to
scratch off about 90 percent or more of the remaining toner by the
blade and clean the still remaining toner in a form of streak by
the elastic roller uniformly contacting with the photosensitive
member in a longitudinal direction. Since the toner in a form of
streak is so little that the load to the roller is not heavy and
neither the whole roller becomes dirty. Therefore, the cleaning
roller is used only for finishing and further the contacting force
to the photosensitive member may be weak. And, therefore, the
photosensitive member is not damaged.
In addition, blades and sheets are inexpensive and simple and the
exchange thereof is easy.
It is very convenient that a part of the cleaning cloth around the
roller is adhered by an adhesive for facilitating the exchange of
the cleaning cloth.
Referring to FIG. 8, there have been used an elastic blade 16
contacting slantingly with the photosensitive member 1 in
conventional devices and the cleaning has been carried out at the
acute angle side of angles made between the photosensitive member 1
and the blades. This structure is far better than a cleaning device
utilizing a fur web, but the resultant force R of a vertical
reaction force N which the blade 16 receives from the
photosensitive member 1 and a friction force F between the
photosensitive member 1 and the blade 16 is in a direction for
leaving the blade 16 from the photosensitive member 1. Therefore, a
force obstructing the toner is so weak that toner particles often
enters under the blade 16 and further when one particle enters
under the blade, the entering of toner particles easily propagates
itself over the whole length of the blade. As the result, the blade
should be often dismantled to clean the top edge portion of the
blade.
Referring to FIG. 9, the disadvantage as mentioned above is
eliminated by effecting the cleaning at the obtuse angle side of
angles made between the blade 16 and the photosensitive member 1.
In this case, one part of the resultant force R is stored as an
elastic strain of blade and all the other part of the resultant
force works as a cleaning force. The blade 16 is pushed to the
wedge-like space between the holder 17 and the photosensitive
member 1, that is, a direction of the frictional force F, and
thereby the toner-obstructing force is far larger than that in FIG.
8 and the entering of toner particles under the blade is almost
completely obstructed.
Referring to FIG. 10, assuming a tangent line Z--Z passing the
intersecting point P of an extension line of the axis Y--Y of the
holder 17 and the photosensitive member 1, among the angles
subtended by line Z--Z and line Y--Y, the angle at the pre-cleaning
side and the angle at the post-cleaning side are designated as
.phi..sub.1 and .phi..sub.2, respectively. Among the angles
subtended by the tangent line Z--Z and the axis line of the bending
portion of the blade 16, the angle at the pre-cleaning side and the
angle at the post-cleaning side are designated as .theta..sub.1 and
.theta..sub.2, respectively. When these various angles are in the
following relations:
.theta..sub.1 > .phi..sub.1
.theta..sub.2 < .phi..sub.2
.pi./2 .ltoreq. .theta..sub.1 .ltoreq. .pi.,
a good result is obtained. The relation
.theta..sub.1 .congruent. 2/3 .pi.
is preferably used.
The optimum value of angle .theta..sub.1 of blade 16 varies
depending upon physical properties of material (e.g., hardness) and
effective length (length of the blade outside of holder 17) of
blade 16. In general, there are obtained good results at hardness
of 30.degree. - 90.degree., thickness of 2 - 10 mm. and effective
length of 10 - 40 mm. For example, .theta..sub.1 .congruent.
150.degree. is optimum for silicone rubber having hardness of
80.degree., thickness of 7 mm and effective length of 30 mm. Upon
selecting a blade with respect to the material, there are taken
into consideration surface properties of the photosensitive member
such as a coefficient of friction between the blade and the
insulating layer at the surface of the photosensitive member,
modulus of elasticity and the like, and peripheral velocity. In
general, there are preferably used synthetic rubbers such as
urethane rubber, nitrile rubber, neoprene rubber and silicone
rubber, and natural rubber. In case of liquid development, urethane
rubber, nitrile rubber and neoprene rubber are preferable. In the
drawing attached hereto, there are shown only drum type
photosensitive members 1, but it will be understood that the above
matters referring to a cleaning blade may be similarly applied to a
plate type photosensitive member.
Referring to FIG. 13, an arc-shaped supporting member 18 which is
harder than the blade 16 is provided along the flexible blade 16 to
strengthen the blade 16 simultaneously retaining a desirable
softness at the edge portion contacting with the photosensitive
member 1 and thereby the whole length of the photosensitive member
1 can contact uniformly with the photosensitive member 1. Further,
it is also effective to use at the edge portion of the blade 16 an
elastic material of high abrasion resistance, high solvent-proof
and low coefficient of friction such as silicone rubber and Teflon
and use at the other portions of the blade 16 an inexpensive
materials such as neoprene rubber and metallic elastic
material.
Referring to FIG. 11 and FIG. 12, there is provided a cleaning
cover 9 for preventing toners from scattering, and packings 30 are
provided at both ends of the photosensitive drum corresponding to
the opening of the cover 9 so as to seal as far as possible. At the
upper part of the blade 16 there is provided a plate 19 and the
blade is removably fitted to the holder in a cartridge system.
Holder is composed of a main part 17.sub.1 and a movable part
17.sub.2 movably attached to the main part 17.sub.1, and the main
part 17.sub.1 is rotatably fitted to the both side plates of the
cover 9 with bracket 21 and shaft 22. Cam 23 is fitted to a cover 9
with a shaft 24, and a holder stopper is represented by 25.
When cam 23 is loosed by a knob outside of cover 9, holder
17.sub.1, 17.sub.2 hangs down around shaft 22 to a direction
leaving from photosensitive member 1 due to the own weight of
holder as illustrated in FIG. 12. Since the distance between the
main part 17.sub.1 and the movable part 17.sub.2 can open, to some
extent, against a plate spring 20, blade 16 can be inserted between
the main part 17.sub.1 and the movable part 17.sub.2. It is
preferable to form a bending part 19.sub.1 at the upper part of the
plate 19 and hang the bending part 19.sub.1 on the movable part
17.sub.2 so as to prevent the blade 16 from falling down and,
further, this serves to set the position in a vertical direction.
When cam 23 is fastened, holder 17.sub.1, 17.sub.2 is pushed by cam
23 and stopper 25 to hold tightly the blade 16. These various parts
should be so designed as to satisfy the angle relations among
blade, holder and photosensitive member as mentioned above. Cover 9
may be rotatably fitted to the housing of the copying machine with
the shaft 26 for the purpose of facilitating the removing of blade
16.
Toners scratched off by the blade 16 are introduced to the bottom
portion of the cover by way of a guide plate 27 and then
transferred to a recovery box by a screw conveyor 28 followed by an
appropriate treatment for reuse. It is not desirable that toners
deposit around the edge of blade 16 contacting the photosensitive
member 1 since such deposited toners cause reduction of cleaning
ability and lowering of blade life due to abrasion of the blade.
Therefore, air or a liquid may be ejected from a nozzle 29 to the
edge portion to prevent such deposit. In place of ejection, vacuum
suction also may be used. Such removing of deposited toner is far
more important for a liquid developing system than for a dry
developing system since a liquid developer usually contains a
fixing agent and removing of the dried or half-dried toner is
extremely difficult. Therefore, it is effective to weaken the
adhesiveness of toners to the photosensitive member by ejecting a
liquid such as Isopar (trade name, supplied by ESSO) and Freon
(trade name, supplied by E. I. du Pont de Nemours & Co. Inc.)
and to scratch off the deposited toners.
The cleaning apparatus according to this invention is very
effective for cleaning a photosensitive member of
electrophotographic apparatus. It is particularly useful for a
photosensitive member having a surface insulating layer which is
subjected to primary charging, imagewise exposure simultaneously
with secondary charging of polarity opposite to that of the primary
charging or AC corona discharging and, if desired, whole surface
exposure.
The above-mentioned electrophotographic methods can produce
electrostatic latent images having surface potential as high as
several V to 2000 V on the insulating layer and the resulting
latent image is developed with a toner to form a visual toner
image, which is then transferred to a copying paper or web.
Thereafter, toner remaining on the surface of the photosensitive
member is taken away by a cleaning means. The photosensitive member
having an insulating layer at the surface has an advantage that the
photoconductive layer present under the insulating layer is not
damaged by the cleaning member, but the very high surface potential
on the insulating layer disadvantageously renders a complete
cleaning of toner remaining surface very difficult. However,
according to the cleaning apparatus of this invention, the complete
cleaning is possible.
* * * * *