U.S. patent number 3,572,923 [Application Number 04/755,267] was granted by the patent office on 1971-03-30 for cleaning method and apparatus for electrostatic copying machines.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Donald J. Fisher, Gerard T. Severynse.
United States Patent |
3,572,923 |
Fisher , et al. |
March 30, 1971 |
CLEANING METHOD AND APPARATUS FOR ELECTROSTATIC COPYING
MACHINES
Abstract
Method and apparatus for removing residual images from a
recording surface for reuse in a copying system. This is effected
by wiping the electrostatic recording surface with an electrically
nonconductive element to mechanically remove the toner particles
from the surface. At the same time, an electrical bias of a
polarity opposite that of the toner particles of sufficient
magnitude is applied to the element so as to pull toner from the
surface onto the element thereby removing substantially all of the
toner from the surface. The element is advanced past an
electrically biased means to remove the toner from the element
thereby freeing it of the residual toner so that continuous
cleaning action is obtained. After this, the toner is removed from
the electrically biased means and collected for reuse in the
system.
Inventors: |
Fisher; Donald J. (Fairport,
NY), Severynse; Gerard T. (Fairport, NY) |
Assignee: |
Xerox Corporation (Rochester,
NY)
|
Family
ID: |
25038415 |
Appl.
No.: |
04/755,267 |
Filed: |
August 26, 1968 |
Current U.S.
Class: |
399/358 |
Current CPC
Class: |
G03G
21/0047 (20130101); G03G 21/10 (20130101); G03G
2221/0005 (20130101) |
Current International
Class: |
G03G
21/00 (20060101); G03G 21/10 (20060101); G03g
015/00 () |
Field of
Search: |
;355/15 ;15/1.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Matthews; Samuel S.
Assistant Examiner: Mauro; T. A.
Claims
We claim:
1. Cleaning apparatus for removing electrostatically adhering toner
particles from an electrostatic recording surface for reuse
comprising:
wiper means including a support layer having electrically
nonconductive fibers extending therefrom, said wiper means being
adapted for movement past an electrostatic recording surface on
which electrostatically adhering toner particles are contacted said
fibers;
circuit means coupled to said wiper means including a first voltage
of a polarity opposite that of said toner particles and of a
magnitude sufficient to attract said toner particles onto said
fibers as they pass into contact with said recording surface;
roll means positioned in the path of said wiper means, said roll
means being coupled to a second voltage of the same polarity as
said first voltage and sufficiently high to attract said toner
particles from said fibers for deposit onto the surface thereof;
and
means positioned in the path of said roll means for removing
electrostatically adhering toner particles from the surface of said
roll means into a collection source whereby said toner particles
continuously removed from said electrostatic recording surface can
be reused.
2. Apparatus according to claim 1 including means for applying a
charge of the same polarity as said toner particles to said
recording surface before said toner particles are contacted by said
fibers.
3. Apparatus according to claim 1 wherein said circuit means
includes a plurality of uniformly spaced conductive elements
secured to and in electrical contact with said support layer, a
third voltage of a polarity opposite to that of said first voltage
and of a magnitude lower than said first voltage, and distributor
means to apply electrical power of different polarities according
to said first and third voltages to successive ones on said
elements as each element is advanced to a predetermined position
adjacent to said recording surface and said roll means.
4. Apparatus according to claim 2 wherein said first voltage ranges
from about 500 volts to about 2,000 volts and said second voltage
ranges from about 1,500 volts to about 3,000 volts.
5. Apparatus according to claim 3 wherein the potential difference
between said second and third voltages ranges from about 800 volts
to about 2,700 volts.
6. Apparatus according to claim 1 including means for moving said
wiper means toward and away from said recording surface and toward
and away from said roll means.
7. Apparatus according to claim 1 wherein the height of said fibers
ranges from about one-eighth of an inch to about three-sixteenths
of an inch.
Description
This invention relates to electrostatic imaging systems and more
particularly, to an improved apparatus for cleaning electrostatic
recording surfaces.
The formation and development of images on the surface of recording
materials by electrostatic means is well known. One basic process,
as taught in U.S. Pat. No. 2,297,691, by C. F. Carlson involved
placing a uniform electrostatic charge on a photoconductive
insulating layer, exposing the layer to a light-and-shadow image to
dissipate the charge on the areas of the layer exposed to the light
and developing the resulting latent electrostatic image by
depositing on the image a finely-divided electroscopic material
referred to in the art as "toner." The toner is normally attracted
to those areas of the layer which retain a charge, thereby forming
a toner image corresponding to the latent electrostatic image. This
image may then be transferred to a support surface such as paper.
The transferred image may subsequently be permanently affixed to a
support surface. After cleaning, the layer is ready for another
imaging cycle.
As is well known in recent years, the steadily increasing size of
various industries has required an enormous increase in the amount
of paper work that must be accomplished, maintained, and made
available for wide interplant circulation. In the present day
commercial automatic copiers/reproduction machines, the
electrostatic recording surface is in the form of a drum or belt
which moves at high rates in timed unison relative to a plurality
of processing stations. This rapid movement of the electrostatic
recording surface has required vast amounts of toner particles to
be used during development.
Associated with the increased amounts of toner is the difficulty in
removing the residual toner image remaining on the recording
surface after transfer. In the reproduction process of Carlson as
described above, the residual image is tightly retained on the
photoconductive surface by a phenomenon that is not fully
understood but believed to be caused by an electrical charge that
prevents complete transfer of the toner to the support surface,
particularly in the image area. The residual toner image is
normally removed by cleaning devices such as a "brush" type
cleaning apparatus or "web" type cleaning apparatus. A typical
brush cleaning apparatus is disclosed in U.S. Pat. No. 2,832,977 to
L. E. Walkup et al. and in U.S. Pat. No. 2,911,330 to H. E. Clark.
The brush-type cleaning means usually comprises one or more
rotating brushes which brush toner from the photoconductive surface
into a stream of air which is exhausted through a filtering system.
A typical web cleaning device which retains toner is disclosed in
U.S. Pat. No. 3,186,838 to W. P. Graff, Jr. et al.
While ordinarily capable of cleaning electrostatic recording
surfaces, conventional cleaning devices have not been entirely
satisfactory. Most of the known cleaning devices usually become
less efficient as they become contaminated with toner which cannot
be removed necessitating frequent replacement of the cleaning
device. As a result, valuable time is lost during "down time" while
a change is being made. A further problem is that cleaning devices
employed in current commercial copier/duplicator machines
permanently remove residual toner particles from the system. Since
toner is an expensive consumable, permanent removal of the residual
toner particles from the system during cleaning is undesirable
because it adds to the cost of machine operation. Both the web-type
and brush cleaning units normally do not return residual toner
particles to the reusable developer mass after the cleaning
operation due to the collection of lint from the web or brush.
Furthermore, the brush is normally rotated at rates which cause
heat to be generated resulting in physical and chemical changes in
the toner. In addition, an elaborate and noisy vacuum and filtering
system is necessary to collect the residual toner particles removed
by the brush. Moreover, large amounts of toner particles thrown
into the air by the rapidly rotating brush cleaner often drift from
the brush cleaning housing and form unwanted deposits on critical
machine parts.
While the web type cleaner has some advantages it is difficult to
align with the surface of the electrostatic recording surface and
uneven contact between the web and the surface as well as uneven
takeup of the web on a takeup roll is often encountered even with
complex alignment apparatus. Another problem with the web type
cleaner is that pressure contact between cleaning webs and some
imaging surfaces must be kept to a minimum to prevent destruction
of the imaging surface. Thus, there is a continuing need for a
better system for cleaning electrostatic recording surfaces.
It is, therefore, an object of this invention to provide method and
apparatus for cleaning electrostatic imaging surfaces which
overcome the above-noted deficiencies.
It is another object of this invention to improve the quality of
prints produced by electrostatic reproduction machines.
It is a further object of this invention to reduce toner
consumption in automatic electrostatic imaging machines.
It is also an object of this invention to utilize cleaning
apparatus in reproduction equipment which does not require
extensive alignment or adjustment.
It is still another object of this invention to remove residual
toner which is immediately reusable in an electrostatic imaging
system.
It is a further object of this invention to provide simple,
inexpensive and reusable apparatus for cleaning electrostatic
recording surfaces.
It is a still further object of this invention to provide cleaning
apparatus for an electrostatic imaging system which is more
efficient than existing cleaning devices.
It is still a further object of this invention to prevent powder
cloud formation at the cleaning station of a copier/duplicator
machine.
It is still a further object of this invention to reduce the noise
level of copier/duplicator machines.
These and other objects of the invention are attained generally
speaking by wiping the electrostatic recording surface with an
electrically nonconductive element to mechanically remove the toner
particles from the surface. At the same time, an electrical bias of
a polarity opposite that of the toner particles of sufficient
magnitude is applied to the element substrate so as to pull toner
from the surface onto the element thereby removing substantially
all of the toner from the surface. The element is advanced past an
electrically biased means to remove the toner from the element
thereby freeing it of the residual toner so that continuous
cleaning action is obtained. After this the toner is removed from
the electrically biased means and collected for reuse in the
system.
For a better understanding of the invention as well as other
objects and further features thereof, reference is had to the
following detailed description of the invention to be read in
conjunction with the accompanying drawings wherein:
FIG. 1 is a schematic sectional view of a reproduction machine
incorporating cleaning apparatus according to the present invention
with the processing components in section to better illustrate the
environment for the present invention;
FIG. 2 is an isometric view partly broken away to better illustrate
details of the cleaning apparatus;
FIGS. 3 and 4 are end views of the cleaning apparatus;
FIG. 5 is a sectional view illustrating further details of the
cleaning apparatus; and
FIG. 6 is an isometric view of a second embodiment of the cleaning
apparatus.
In FIG. 1, there is shown schematically a high speed automatic
electrostatic or xerographic reproduction machine incorporating
cleaning apparatus generally designated 10 according to the present
invention.
The automatic reproducing machine comprises an electrostatic
recording element or xerographic plate 20 including a
photoconductive layer or light-receiving surface on a conductive
backing and formed in the shape of a drum, which is mounted on a
shaft journaled in a frame to rotate in the direction indicated by
the arrow to cause the drum surface sequentially to pass a
plurality of processing stations.
For the purpose of the present disclosure, the several xerographic
processing stations in the path of movement of the drum surface may
be described functionally as follows:
A charging station, at which a uniform electrostatic charge is
deposited on the photoconductive layer of the xerographic drum;
An exposure station, at which a light or radiation pattern of copy
to be reproduced is projected onto the drum surface to dissipate
the drum charge in the exposed areas thereof and thereby form a
latent electrostatic image of the copy to be reproduced;
A developing station, at which a xerographic developing material
including toner particles having an electrostatic charge opposite
to that of the electrostatic latent image are cascaded over the
drum surface, whereby the toner particles adhere to the
electrostatic latent image to form a xerographic powdered image in
the configuration of the copy being reproduced;
A transfer station, at which the xerographic powder image is
electrostatically transferred from the drum surface to a transfer
material or a support surface; and
A drum cleaning and discharge station, at which any residual toner
particles remaining on the drum surface after image transfer are
removed, and at which the drum surface is exposed to a relatively
bright light source to effect substantially complete discharge of
any residual electrostatic charge remaining thereon.
The charging station located as indicated by reference character A
includes a corona charging device 21 which comprises a corona
discharge array of one or more corona discharge electrodes that
extend transversely across the drum surface. The charging device is
energized from a high potential source and is substantially closed
within a shielding member.
Next subsequent thereto in the path of motion of the xerographic
drum is an exposure station B. An optical scanning or projection
system is provided to project a flowing image onto the surface of
the photoconductive drum from a stationary original.
The optical scanning or projection assembly comprises a stationary
copyboard which consists of a transparent curved platen member 22,
such as, for example, a glass plate or the like, positioned on the
exterior of the cabinet, which is adapted to support a document to
be reproduced, the document being uniformly illuminated and
arranged in light projecting relation to the moving light-receiving
surface of the xerographic drum. Uniform lighting is provided by
banks of lamps LMPS-1 arranged on opposite sides of the
copyboard.
Scanning of the document on the stationary copyboard is
accomplished by means of a mirror assembly which is oscillated
relative to the copyboard in timed relation to the movement of the
xerographic drum. The mirror assembly, which includes an object
mirror 23, is mounted below the copyholder to reflect an image of
the document through a lens 24 onto an image mirror 25, which, in
turn, reflects the image onto the xerographic drum through a slot
in a fixed light shield 26 positioned adjacent to the xerographic
drum surface.
Adjacent to the exposure station is a developing station C in which
there is positioned a developer apparatus 30 including a casing or
housing having a lower or sump portion for accumulating developer
material. A bucket type conveyor is used to carry the developing
material to the upper part of the developer housing where it is
cascaded over a hopper chute onto the xerographic drum to effect
development. A toner dispenser is used to accurately meter toner to
the developing material as toner particles are consumed during the
developing operation. Any suitable dispenser may be used as, for
example, the dispenser described in U.S. Pat. NO. 3,013,703 to
Hunt.
Positioned next and adjacent to the developing station is the image
transfer station D which includes a sheet feeding arrangement
adapted to feed sheets of support material, such as paper or the
like, successively to the xerographic drum in coordination with the
presentation of the developed image on the drum surface at the
transfer station.
The sheet feeding mechanism includes a sheet feed device 40 adapted
by means of vacuum feeders to feed the top sheets of a stack of
sheets on a tray to rollers 42 cooperating with the belts of paper
transport 44 for advancing the sheet sufficiently to be held by
paper transport 44 which in turn conveys the sheet to a sheet
registration device 45 positioned adjacent the xerographic drum.
The sheet registration device arrests and aligns each individual
sheet of material and then in timed relation to the movement of the
xerographic drum, advances the sheet material into contact with the
xerographic drum in registration with a previously formed
xerographic powder image on the drum.
The transfer of the xerographic powder image from the drum surface
to the sheets of support material is effected by means of a corona
transfer device 51 that is located at or immediately after the line
of contact between the support material and the rotating drum. In
operation, the electrostatic field created by the corona transfer
device is effective to tack the support material electrostatically
to the drum surface, whereby the support material moves
synchronously with the drum while in contact therewith.
Simultaneously with the tacking action, the electrostatic field is
effective to attract the toner particles comprising the xerographic
powder image from the drum surface and cause them to adhere
electrostatically to the surface of the support material.
Immediately subsequent to the image transfer station, there is
positioned a stripping apparatus to paper pickoff mechanism 52 for
removing the sheets of support material from the drum surface. This
device, which is of the type disclosed in U.S. Pat. No. 3,062,536
to Rutkus et al. includes a plurality of small diameter orifices
supplied with pressurized aeriform fluid by a suitable pulsator or
other device. The pulsator is adapted to force jets of pressurized
aeriform fluid through the outlet orifices into contact with the
surface of the xerographic drum slightly in advance of the sheet of
support material to strip the leading edge of the sheet from the
drum surface and to direct it into an endless conveyor 55 whereby
the sheet material is carried to a fixing device 60. At the fixing
device, the transferred xerographic powder image on the sheet of
support material is permanently fixed or fused thereto as by heat.
After fusing, the reproduction is discharged from the apparatus at
a suitable point for collection externally of the apparatus by
means of the conveyor 65. In the embodiment shown, the
reproductions are discharged from conveyor 65 into a receiving tray
67.
The next and final station in the device is a drum cleaning station
E, at which cleaning apparatus 10 constructed in accordance with
the invention removes substantially all residual toner particles
remaining on the xerographic drum surface after transfer for reuse
in the system in a manner to be described. A discharge lamp LMP-2
floods the xerographic drum with light to cause dissipation of any
residual electrical charge remaining on the xerographic drum
subsequent to cleaning.
It is believed that the foregoing description is sufficient for the
purposes of this application to show the general operation of a
copying machine incorporating cleaning apparatus constructed in
accordance with the invention. Suitable drive means are provided to
drive the drum, rotating mirror and sheet feed mechanism at
predetermined speeds relative to each other, and to effect
operation of the bucket-type conveyor and toner dispenser mechanism
and the other operation mechanisms. For further details concerning
the specific construction of a copying machine similar to that
shown reference is made to U.S. Pat. No. 3,301,126 issued on Jan.
31, 1967.
Referring now to FIGS. 2--5, there is shown details of the cleaning
apparatus 10. The cleaning apparatus of this invention is adapted
to remove the residual toner material in such a manner that it can
be reused with the developer material and at the same time be
effective for continuous cleaning whereby replacement of the
cleaning apparatus is not a concern.
Cleaning apparatus 10 comprises a housing 103 secured to the
machine frame which housing partially encloses a fabric cleaner
assembly 107. Fabric cleaning assembly 107 includes a conductive
cylindrical member 111 which is supported on an insulating member
113 which in turn is secured for movement to a rotatable shaft 117.
Cylindrical member 111 is in direct contact with the underside of a
layer 118 which serves as a backing layer for nonconductive fabric
cleaning fibers 119, it being understood that layer 118 may be made
out of either conductive or nonconductive materials for a purpose
to be described.
Shaft 117 is journaled for rotation in housing 103 and is driven in
a direction indicated by the arrow by a pulley 121 connected at one
end thereof which in turn is driven by a timing belt 123 encircling
pulley 121 and a drive pulley 124 which is mounted for rotation on
a drive motor 125. In this manner the fabric cleaner assembly 107
provides good wiping action between the cleaning fibers 119 and the
surface of the drum. For very efficient wiping action it is
desirable that the fabric cleaner assembly 107 be driven in an
opposite direction at the nip to the drum at speeds ranging from
about half to about three times the speed of rotation of the drum,
and preferably at about 1 to 1.5 times the drum speed.
Alternatively, the fabric cleaner assembly can be driven in the
same direction at the nip as the drum, it being kept in mind that
the assembly must then be driven at a higher speed so that there
will be sufficient relative motion to obtain the desired wiping
action of the cleaning fibers on the surface of the drum.
In accordance with the invention, as the cleaning fibers 119 are
moved past the drum surface, an external potential of a polarity
opposite to that of the toner particles is applied to conductive
cylindrical member 111 causing an electrical field or lines of
force to emanate radially from the support layer beneath the
cleaning fibers to thereby attract the toner particles from the
drum surface onto the cleaning fibers. To accomplish this, a DC
voltage 133 is applied to conductive cylindrical member 111 by one
or more brush members 131 as the fabric cleaning assembly is
rotated on a shaft 117. DC voltage 133 is of an opposite polarity
from the toner particles and ranges in magnitude up to several
thousand volts to enable attraction of the electroscopic toner
particles onto the cleaning fibers 119. It has been found that
voltages ranging from about 500 volts to about 2000 volts perform
well for this purpose. It should be noted that the DC voltage 133
can be varied and hence this voltage can be selectively changed to
obtain an optimum operating condition.
Desirably cleaning fibers 119 are made from any suitable
nonconductive material to prevent shorting of the voltage applied
from DC voltage 133 and is substantially uneffected by changes in
humidity. Typical cleaning fiber materials are acrylic velvets,
orlon, polypropylene fabric, nylon, rayon, acetates, mohair, arnel,
glass, dynel, dacron, cotton, and other natural and synthetic
fibrous or filamentary materials and mixtures thereof. In addition
in order to enhance the attraction of the toner particles to the
cleaning fibers 119, the fibers may be made out of or coated with a
material having a triboelectric attraction for the toner particles.
Typical materials having this relationship are described in U.S.
Pat. No. 2,618,551 to Walkup, U.S. Pat. No. 2,618,552 to Wise, U.S.
Pat. No. 2,638,416 to Walkup and Wise, and U.S. Pat. No. Re 25,136
to Carlson. It should be noted that the feature of the
triboelectric attraction to the cleaning fibers normally enables a
decrease in the voltage being applied.
Cleaning fibers 119 desirably have good mechanical wiping action on
the drum surface to thereby loosen the toner particles which are
then attracted to them due to the attractive force from the
electrical potential being applied. The cleaning fibers extend to
any suitable length which may range from about one-sixteenth of an
inch to about five-sixteenths of an inch and preferably range from
about one-eighth of an inch to about three-sixteenths of an inch
for a fiber density ranging from about 10,000 to about 750,000
fibers per square inch.
It has been found that for a cleaning fiber length of about
three-sixteenths of an inch, very good results are obtained with
1,500 volts applied by DC voltage 133. Desirably the interference
between the cleaning fibers and the drum surface range from about
one-fourth to half the length of the fibers. In order to adjust the
interference between the cleaning fibers and the drum surface,
shaft 117 can be moved relative to the machine frame and hence the
drum surface by moving support plates 137 and 138 of housing 103
which are movable along adjusting members 141, 142, respectively,
by turning the adjusting members whereby the shaft 117 is able to
be moved toward and away from the drum surface. Screws 143 received
in housing 103 when tightened insure that support plates 137, 138
and hence shaft 117 are held firmly in place during the operating
conditions.
To further enhance the electrostatic attraction of the toner
particles onto the cleaning fibers 119, a corona generating device
145 is positioned in the path of the drum just prior to the fabric
wiper assembly to place a charge on the toner particles of the same
polarity as the particles which in this case would be negative.
This charge desirably reduces the attraction of the toner particles
to the surface of the drum and insures that the toner particles are
properly negatively charged so that they will be attracted to the
positive potential applied by DC voltage 133. It has been found
that a current ranging from about 2 to about 10 microamps for the
corona generating device is sufficient for this purpose. Corona
generating device 145 is suitably powered as by a variable source
of DC voltage 146.
After the toner particles have been removed from the drum surface
onto the cleaning fibers 119, the toner particles are then removed
from the fibers to ensure that the particles are not redeposited
onto the drum surface. To accomplish this, there is an electrically
biased roll 150 positioned in the path of the cleaning fibers 119
which is connected to an external potential of a polarity opposite
to that of the toner particles and of a sufficient magnitude to
attract them from the cleaning fibers onto the surface of the roll.
Roll 150 is mounted for rotation on a shaft 152 to move in a
direction opposite to that of the fabric wiper assembly at the nip
to obtain good relative movement therebetween. It should be
understood, of course, that the roll may be rotated in a reverse
direction by making appropriate changes in the speed and associated
cleaning parts.
Roll 150 is made from any suitable conductive material and may be
in the form of a cylinder or as a solid member. The roll is
electrically biased via a brush member 153 connected to a DC
voltage 154 which is of the same polarity as DC voltage 133 but is
desirably of a higher magnitude whereby as the cleaning fiber tips
contact the roll surface the toner particles are attracted to it.
DC voltage 154 may range from about 1,000 volts to about 3,000
volts. It has been found that an interference between the cleaning
fibers 119 and the surface of roll 150 ranging from about
one-fourth to about half the length of the fibers performs well
with DC voltage 133 being at about 1,500 volts and a cleaning fiber
length of about three-sixteenths of an inch. To vary the
interference between the cleaning fibers 119 and the surface of
roll 150, adjusting members 160, 161 are provided in housing 103
which when turned enable support plate 137, 138 and hence shaft 117
to be moved toward and away from their roll surface. Screws 165
received in support plates 167, 168 of housing 103 when tightened
ensure that shaft 117 is held firmly in place during the operating
condition.
The drive for the bias roll 150 ranges from about the same speed as
the fabric wiper assembly to more than double the speed of the
fabric cleaning assembly as an upper limit. It has been found that
where the bias roll is moved opposite in direction to the cleaner
fabric assembly at the nip that the same speed produces very good
results but that at least twice this speed is necessary where the
direction of the bias roll is in the same direction as the fabric
wiper assembly at the nip. Driving force is provided in any
suitable manner as by a timing belt 170 wound around a pulley 171
connected at one end of the bias roll shaft 152 and also wound
around a pulley 173 mounted for rotation on drive motor 174.
To present continuous cleaning surfaces and also to recover the
toner particles so that they may be returned and reused in the
development system of the machine, a scraper assembly 177 is
positioned in the path of roll 150. Scraper assembly 177 comprises
a blade member 179 which is held firmly in place by blade holder
elements 181, 182 by any suitable retaining means such as screws.
Blade holder elements 181, 182 are connected to housing 103 by one
or more adjustable bolt members 183 each of which is received
through an insulating block member 185 secured to the housing as by
screws. A nut 186 constrains blade holder elements 181, 182 against
a compression spring 189 seated against insulating block member
185. Contact pressure of the blade member 179 with roll 150 is
adjustable by turning nut 191 received on bolt member 183.
As the toner particles are removed from the surface of roll 150 by
the blade element they are collected in a tray 193 from which they
are removed by an auger 195 mounted for rotation on a shaft 196
driven by the roll shaft 152 through gears 197, 198 which are
connected to the shaft 152 and shaft 196, respectively. Auger 195
rotates through the toner material collected in the tray in a
direction shown by the arrow to move the toner toward one or more
conduits 200 from which the toner particles are discharged either
by gravity or any suitable means for reuse at the development
station.
A second embodiment of the present invention in which the fabric
cleaner assembly is in the form of a segmented roll is shown in
FIG. 6 where like numerals identify like elements. The segment roll
enables different potentials to be applied to obtain greater
selectivity and control in the removal of the toner particles from
the drum surface for collection and reuse. With this embodiment a
fabric cleaner assembly 207 comprises a plurality of conductive
commutator segments 211 which are embedded in a suitable insulating
member 213, which, in turn, is secured for movement to a rotatable
shaft 217. Commutator segments 211 are in direct contact with the
underside of a layer 218 which is the backing layer for
nonconducting cleaning fibers 219. Layer 218 may be a continuous
piece as shown or instead may be formed as a plurality of separate
elements which correspond to each of the conducting segments 211.
As in the embodiment of FIGS. 1--5 above, an external potential of
a polarity opposite that of the toner particles is applied to the
commutator segments 211 causing an electrical field or lines of
force to emanate from the support below the cleaning fibers to
thereby attract the toner particles from the drum surface onto the
fibers. To this end, one or more brush elements 231 are connected
to DC voltage 133 to contact each commutator segment as the shaft
rotates thereby enabling the toner particles to be attracted to
cleaning fibers from the drum surface. As in the other embodiment
above, the cleaning fibers 219 are moved past a bias roll 150
connected to a DC voltage 154. At the vicinity of interference
intermediate the cleaning fibers 219 and the surface of bias roll
150, commutator segments 211 are contacted by one or more brush
elements 269 which are connected to a DC voltage 275. DC voltage
275 is of the same polarity as the toner particles so that the
toner particles are thereby repelled in the direction of the bias
roll 150. DC voltage 275 may range from ground to about 2,000 volts
depending upon the voltage applied by the DC voltage 154, the
height of the cleaning fibers and the extent of the interference
between the cleaning fibers and the surface of bias roll 150.
Generally speaking, the higher the voltage applied to the bias roll
surface, the lower the DC voltage 275 is and vice versa. It has
been found that the potential difference between the voltage on the
bias roll surface and the DC voltage 275 on the commutator segments
ranging from about 800 to about 2,700 performs very well.
Above is described a new and novel cleaning apparatus capable of
removing substantially all of the residual toner particles on the
surface of an electrostatic recording member and for collecting the
toner for reuse in the copier/duplicating machine. Heretofore,
cleaning of the recording surface was accomplished by a rotating
brush or web which had to be discarded and replaced after periodic
use and which prevented the toner from being reused in the
development system again. With the present invention, the toner
particles are removed from the recording surface in such a manner
that objectionable filming of the toner does not occur and hence
the toner is adapted for reuse in the system repeatedly.
Furthermore, no powder cloud is formed at the cleaning station
which undesirably can cause a malfunction of the machine. Also, the
cleaning apparatus of the present invention does not require
extensive repair or adjustment as in the case of the prior art
cleaning devices. In short, the apparatus of the invention not only
provides cleaning greatly efficient but is also inexpensive and
reusable while permitting toner collected to be used
repeatedly.
While the invention has been described with reference to the
structure disclosed herein, it should not be confined to the
details set forth since it is apparent that various modifications
can be made. Thus a plurality of units can be used instead of one
and the cleaning fibers may be in the form of an endless belt with
an appropriate biasing potential applied through an electroded
substrate opposite the photoconductor drum. Other modifications
will occur to those skilled in the art and it is intended to cover
such modifications or changes as may come within the purposes and
improvements of the scope of the following claims.
* * * * *