Apparatus For Cleaning A Residual Image From A Photosensitive Member

Abstract

A residual toner image remaining after transfer of a developed image from a photoconductive surface is cleaned therefrom in one embodiment by a conductive cleaning brush mounted in a vacuum chamber and having a flicker bar which is used to apply a potential to the brush opposite that of the residual toner particles to be removed from the photoconductive surface. In another embodiment, the brush is divided into a number of electrically insulated segments so that the polarity of the potential applied to a portion of the brush coming in contact with the photosensitive surface is opposite to the charge on the residual toner particles and a potential applied to a segment spaced from the photoconductive surface is the same as the charge on the toner particles on the brush segment so that they are repelled therefrom to clean the toner particles from the brush.

Parent Case Text

This application is a continuation of application Ser. No. 88,628, filed Nov. 12, 1970, now abandoned.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to apparatus for removing electrostatically adhering particles from a photoconductive member, and more particularly to improved apparatus for cleaning residual toner particles from an electrophotoconductive surface.

2. Description of the Prior Art

In a conventional electrophotographic process, an electrostatic image is formed on a photoconductive surface as by placing a uniform electrostatic charge on the photoconductive surface which surface is subsequently exposed to a radiation pattern to dissipate the charge in the exposed areas. This image is then toned by a suitable developing material, such as dry toner powder. The developed image is then transferred to a receiver. However, a small amount of residual toner usually remains on the photoconductive surface which must be removed therefrom prior to the forming and transfer of subsequent images to prevent ghost images from being formed during subsequent transfers.

Various attempts have been made to clean photoconductive surfaces. One method of cleaning a photoconductive surface utilizes a rotating brush. One example of a rotating cleaning brush is disclosed in U.S. Pat. No. 2,751,616 to Turner et al wherein the brush is treated with an impregnating material to control its conductivity. The brush is mounted within a dust hood and provided with a grounded flicker bar that contacts the brush fibers just before the brush contacts the photoconductor. The electrical conductivity of the brush and flicker bar assist in the neutralization of the residual charge on the toner particles. U.S. Pat. No. 2,752,271 to Walkup et al discloses the placing of a negative electrostatic charge on the photoconductive surface carrying the residual image and then rapidly brushing the photoconductive surface in the presence of a vacuum. To counteract the electrostatic attraction between the brush and particles to facilitate the release of such particles to the vacuum, an electrostatic charge is applied to the brush following brushing of the photoconductive surface. U.S. Pat. No. 3,313,623 to Bixby discloses a rotatable cleaning brush to which a potential is applied to assist in removal of toner from a photoconductive surface. In some environments, such cleaning devices have not been found entirely satisfactory. Residual toner particles remaining on the photoconductive surface and/or cleaning element have resulted in scumming and scratching of the photoconductive surface.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved apparatus for cleaning toner particles from a photoconductive surface.

Another object of the invention is to provide an improved apparatus for cleaning residual toner particles remaining after transfer of a developed image from a photoconductive surface.

Yet another object of the invention is to provide improved apparatus for continuously removing toner particles from a cleaning brush.

Still another object of the invention is to remove residual toner particles from a photoconductive surface with reduced scumming and scratching of the surface.

These and other objects are accomplished in accordance with one disclosed embodiment of the invention, by providing an electrically conductive cleaning brush mounted in an air flow or vacuum chamber, to which brush an electrical potential is applied by means of a flicker bar that contacts the fibrous brush material as the brush rotates. Maintaining the brush at a potential relative to ground attracts the residual toner particles to the brush by overcoming the electrostatic forces which hold the particles to the photoconductive surface. The flicker bar loosens the toner particles from the brush so that they are carried away from the brush by the air flow. In some cases, some of the residual toner particles will have a potential of positive polarity and others a potential of negative polarity. In these cases the speed and efficiency of the cleaning operation can be improved by applying to the residual toned image a charge of a polarity opposite to that applied to the cleaning brush before contacting the brush with the photoconductive surface. A flooding light is then used to reduce any potential remaining on the untoned areas of the photoconductive surfaces.

In another disclosed embodiment of the invention a cleaning brush is provided with a number of segments each electrically insulated from each other. A first flicker bar is utilized to apply a potential to a segment of the brush to attract the toner particles to this segment as this segment wipes or rubs against the photoconductive surface and a second flicker bar is utilized to apply an opposite potential to a brush segment when the segment is no longer in contact with the photoconductive surface to repel the toner particles from that segment of the brush for removal by the air flow.

Other objects and advantages of the invention will become apparent from the detailed description of the preferred embodiments which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings wherein corresponding parts are identified by like numerals and in which:

FIG. 1 is a diagrammatic side elevation, partly in section, showing one embodiment of the present invention for cleaning a photoconductive belt of a conventional electrophotographic mechanism.

FIG. 2 is a fragmentary side elevation, partly in section, similar to FIG. 1, showing additional apparatus for charging and illuminating the photoconductive belt.

FIG. 3 is a fragmentary side elevation, partly in section, similar to FIG. 2, but showing another embodiment of the invention utilizing a segmented brush.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and in particular to FIG. 1, there is shown an electrophotographic mechanism M, which includes an endless photoconductive belt 2 extending around spaced rollers 4 and 6 and is illustrated as being driven by motor 8 through a drive belt 10. The belt 2 is driven past a charging station 12 which places a uniform electrical charge (either positive or negative) over its photoconductive surface; an exposure station 14 whereat the belt is exposed to a radiation pattern, such as a light image from an original, to discharge the photoconductive surface in accordance with the radiation pattern to form an electrostatic latent image; a developing station 16 whereat the latent image is developed by depositing toner thereon; a transfer station 18 whereat the developed image is transferred to a receiver; and finally a novel cleaning apparatus C whereat the photoconductive surface of the belt 2 is cleaned of residual toner particles. The charging, exposure, developing and transfer stations can be of any form known in the prior art, and may be selected as required by one skilled in the art.

Cleaning apparatus C includes a rotatable brush 22 which may be made of a soft fibrous material such as natural or artificial fur or flannel that has been rendered electrically conductive, as for example, by impregnating the brush fibers with nickel. The brush 22 is rotatably mounted as shown so that a portion of the brush fibers contacts the area of the photoconductive belt 2 to be cleaned. A platen 24 on the side of the photoconductive belt 2 opposite that of the brush 22 is provided to support the belt in frictional contact with the brush. Alternatively, platen 24 can be replaced by a roller. Advantageously, the brush 22 is rotated by means (not shown) so that it moves in a direction opposite to the movement of the photoconductive belt 2 at the point of contact therewith. An electrical potential opposite in polarity to the charge on the residual toner particles is applied to the brush 22, which is electrically isolated from its mountings, from a source 28 by means of a metal contactor 26 which touches the brush fibers as the brush rotates. Conveniently, the contactor 26 is also used as a flicker bar to loosen the toner particles attracted to the brush 22.

A shroud or housing 30 extends around a substantial portion of the brush 22 as shown, and is illustrated as being provided with an air inlet 32 and an air outlet 34 to which a vacuum can be applied to provide air moving means to withdraw the toner particles removed from the belt 2 from the vicinity of the brush. The toner particles are carried by the air flow to a disposable filter bag (not shown) or other equivalent device which can be easily replaced when the electrophotographic mechanism is normally shut down.

It has been found that in certain instances that some of the residual toner particles have a potential of positive polarity while other particles have a potential of negative polarity. In such instances, the conductive brush 22 with fibers charged to one polarity are not as effective in removing toner particles of the same polarity as the fibers. In such cases the speed and efficiency of the cleaning apparatus C can be improved as shown in FIG. 2 by providing means, such as a corona discharge device 36 upstream of brush 22. The corona 36 applies a uniform charge to the photoconductive surface of the belt 2 and the residual toner image of a polarity opposite to the potential applied to the brush 22 by the source 28. The charging by the corona 36 increases the charge on the residual image and increases the attraction between the image and the brush fibers. To reduce the charge in the untoned areas of the photoconductive belt 2 and thereby decrease the attraction between the photoconductive belt and the residual toner image, the corona charging is either accompanied by or followed by a flooding light 38 which is directed onto the photoconductive surface of the belt. Flooding light 38 also prevents charge buildup on the photoconductive surface as a result of charging with corona 36.

In the embodiment of the invention shown in FIG. 3, electrophotographic mechanism M' includes cleaning apparatus C' having a conductive cleaning brush 39, which is illustrated as having an insulative core 40 with spaced radial fins 41 to divide the brush into a plurality of segments, such as segments 42, 44, 46 and 48 respectively, each electrically insulated from the others. The brush segments are made of fur or other soft fibrous material that have been treated with an electrically conductive impregnating material. An electrical potential which will attract the residual toner particles during the wiping of the photoconductive surface of the belt 2 is applied to the brush fibers of each brush segment from a source 50 through a metal contactor 52 as the brush segments 42, 44, 46 and 48 pass the contactor 52. In FIG. 3, contactor 52 is shown applying an electrical potential to the brush fibers of brush segment 48. After the brush fibers have wiped the photoconductive surface of the belt 2 and are no longer in engagement therewith, an opposite potential which will repel the toner particles from the brush fibers is applied to each brush segment from a source 54 through a metal contactor 56 as the brush segments pass the contactor 56. In FIG. 3, contactor 56 is shown applying such potential to the brush fibers of brush segment 44. The metal contactors 52 and 56, in similarity to contactor 26, also function as flicker bars. Contactor 52 compresses the brush fibers of the brush 39 as they pass thereby. After being compressed by the contactor 52, the brush fibers spring outward assisted by centrifugal force and contact the photoconductive surface of the belt 2 with more than normal wiping force. Contactor 56 functions to assist in loosening the toner particles from the brush fibers so that they may be removed by vacuum means which includes shroud 58.

Optionally, the corona discharge device 36 and source of illumination 38 may be included, as previously described with respect to FIG. 2, to assist in removing bi-polar toner particles. Removal of bi-polar toner particles from the brush may be further assisted by utilizing alternating current for the source of potential 54 so that toner of both polarities will be repelled from the brush.

From the foregoing, the advantages of the present invention are readily apparent. Novel cleaning apparatus and methods have been disclosed which continuously remove toner particles from the brush. This is accomplished by use of a conductive member which serves the dual function of a flicker bar and a device for applying a potential to a cleaning brush. Accumulation of toner particles on the brush is, therefore, held to minimum levels to reduce scumming and the possibility of damage to the photoconductive surface.

The invention has been described in detail with reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention .

Claims

I claim:

1. A cleaning device for cleaning residual toner particles, at least some of said residual toner particles having a charge of a first polarity thereon, from a photoconductive surface, said cleaning device comprising:

a. an electrically conductive, movable, fibrous cleaning element, said element being divided into at least first and second electrically insulated segments;

b. means for mounting said element so that a portion of the element fibers contacts said photoconductive surface;

c. means for moving said element relative to said photoconductive surface along an endless path;

d. first flicking means mounted in interference relation to the fibers of said element, said first flicking means being positioned to contact said segments of said element before said segments contact said photoconductive surface;

e. second flicking means mounted in interference relation to the fibers of said element, said second flicking means being positioned to contact said segments of said element after said segments contact said photoconductive surface to dislodge toner particles from said segments; and

f. potential applying means for applying an electrical potential to said first flicking means of a second and opposite polarity of that of the residual toner particles so that said toner particles are attracted to said segments of said element.

2. Apparatus for removing residual toner particles from a photoconductive surface, said apparatus comprising:

a. a movable element, said element including at least first and second electrically conductive segments, said segments being electrically insulated from each other;

b. means for mounting said element so that said segments are sequentially movable between a charging position whereat said segments are charged to a first potential, a contacting position whereat at least one of said segments contacts the photoconductive surface, and a removing position whereat said segments are charged to a second potential;

c. means for sequentially moving said segments between said charging, contacting and removing positions;

d. first potential applying means cooperatively associated with said segments at said charging position for applying a first potential to said segments prior to said segments contacting the photoconductive surface, said first potential being of a polarity and magnitude sufficient to attract the residual toner particles from the photoconductive surface to said segments charged to said first potential; and

e. second potential applying means cooperatively associated with said segments at said removing position for applying a second potential to said segments after completion of said segments contact with the photoconductive surface, said second potential being of a polarity and magnitude sufficient to repel the residual toner particles from said segments.

3. A cleaning device as claimed in claim 1, further including:

means for moving air relative to said element to withdraw from the vicinity of said element toner particles dislodged from said segments.

4. A cleaning device as claimed in claim 1 wherein some of said residual toner particles are charged to said first polarity and other of said residual particles are charged to said second opposite polarity, said cleaning device further comprising:

potential applying means for applying an alternating potential to said second flicking means to repel toner particles from said segments of said element.

5. A cleaning device for cleaning electrically charged residual toner particles from a photoconductive surface, said device comprising:

a. an electrically conductive, rotatable cleaning brush mounted within a shroud, said brush being divided into at least first and second electrically insulated segments;

b. means for mounting said brush so that a portion of the brush fibers contacts the photoconductive surface;

c. means for rotating said brush;

d. means to cause relative motion between the axis of said brush and the photoconductive surface;

e. charging means for applying a uniform electrical charge of a first polarity to the photoconductive surface and the residual toner particles prior to the surface's contacting said brush;

f. a first electrically conductive contactor mounted in interference relation to the brush fibers, said first contactor being positioned so that it contacts said brush segment before said brush segments contact the photoconductive surface;

g. potential applying means connected to said first contactor for applying to the brush fibers an electrical potential of a second polarity opposite said first polarity to attract the residual toner particles from the photoconductive surface to said brush segments;

h. a second electrically conductive contactor mounted in intereference relation to the brush fibers, said second contactor being positioned so that it contacts said brush segments after said brush segments contact the photoconductive surface to dislodge toner particles from said brush segments; and

i. vacuum means connected to said shroud for withdrawing from the vicinity of said brush an airstream containing therein suspended toner particles dislodged from said brush.

6. A cleaning device as claimed in claim 5 further including:

second potential applying means for applying to said second contactor an electrical potential of said first polarity to repel toner particles from said brush segments.

7. A cleaning device as claimed in claim 5, further including:

means for illuminating said photoconductive surface to actinic radiation prior to said surface's contacting said brush.

8. A cleaning device as claimed in claim 7 wherein said illuminating means is activated subsequently to said charging means.

9. A cleaning device for cleaning residual toner particles from a photoconductive surface, some of the residual toner particles being charged to a first polarity and other of said residual toner particles being charged to a second polarity, said cleaning device comprising:

a. an electrically conductive, rotatable cleaning brush mounted within a shroud, said brush being divided into at least first and second electrically insulated segments;

b. means for mounting said brush so that a portion of the brush fibers contact said photoconductive surface;

c. means for rapidly rotating said brush;

d. means to cause relative motion between the axis of said brush and said photoconductive surface;

e. a first electrically conductive contactor mounted in interference relation to the brush fibers, said first contactor being positioned to contact said segments of said brush before said segments contact said photoconductive surface;

f. a second electrically conductive contactor mounted in interference relation to the brush fibers, said second contactor being positioned to contact said segments of said brush after said segments contact said photoconductive surface to dislodge toner particles from said brush;

g. a corona discharge electrode positioned and disposed to apply a uniform electrostatic charge of said first polarity to said photoconductive surface ahead of said brush in the direction of movement of said photoconductive surface;

h. a source of illumination positioned and disposed to illuminate said photoconductive surface to actinic radiation downstream of said corona discharge electrode and ahead of said brush in the direction of movement of said photoconductive surface;

i. a source of direct current potential connected to said first contactor for applying to said brush segments an electrical potential of said second polarity so that said residual toner particles are attracted to said brush segments;

j. a source of alternating current potential connected to said second contactor for applying to said brush segments electrical potentials of said first and second polarities to repel said toner particles from said brush segments; and

k. vacuum means connected to said shroud for withdrawing from the vicinity of said brush an airstream containing therein suspended toner particles dislodged from said segments of said brush.