US3917397A

US3917397A - Mechanism for removing residual toner from electrostatic copier drum

Info

Publication number: US3917397A
Application number: US456992A
Authority: US
Inventors: Susumu Tanaka; Yuji Enoguchi; Hidetoshi Kawabata
Original assignee: Minolta Co Ltd
Current assignee: Minolta Co Ltd
Priority date: 1973-04-02
Filing date: 1974-04-01
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04
Also published as: JPS5346096B2; DE2415470A1; JPS49125039A

Abstract

A mechanism for removing residual toner from a photosensitive drum in an electrostatic copier of the toner image transfer type includes a high speed rotary brush engaging the drum surface and being triboelectrically charged to the polarity of the toner by frictionally traversing a curved peripherally extending panel. An opposite panel is spaced from the brush periphery to form a passageway. The rotating brush removes the residual toner from the drum and electrostatically and centrifugally discharges it into the passageway through which an induced air stream carries the toner to an oppositely charged rotating drum having a coaxial high voltage wire, so as to electrically capture the toner which is then separated into an underlying receiver by a wiper member.

Description

' United States Patent [191 Tanaka et al.

Nov. 4, 1975 Inventors: Susumu Tanalra, Sakai; Yuji Enoguchi, Higashi; Hidetoshi Kawabata, Tondabayashi, all of Japan Minolta Camera Kabushiki Kaisha, Osaka, Japan Filed: Apr. 1, 1974 Appl. No.: 456,992

US. Cl. 355/15; 117/175; 118/104 Int. Cl. G03G 21/00 Field of Search 355/15; 118/637, 104;

References Cited .UNITED STATES PATENTS 5/1971 Yang 355/15 4/1972 3,655,373 Fisher et al. l5/l.5 X

OTHER PUBLICATIONS IBM Technical Disclosure Bulletin, Vol. 15, No. 12, May 1973, p. 3643; Brush Cleaner with Electrostatic Precipitator.

Primary Examiner-Richard M. Sheer Attorney, Agent, or FirmWolder & Gross [57] ABSTRACT A mechanism for removing residual toner from a photosensitive drum in an electrostatic copier of the toner image transfer type includes a high speed rotary brush engaging the drum surface and being triboelectrically charged to the polarity of the toner by frictionally traversing a curved peripherally extending panel. An opposite panel is spaced from the brush periphery to form a passageway. The rotating brush removes the residual toner from the drum and electrostatically and centrifugally discharges it into the passageway through which an induced air stream carries the toner to an oppositely charged rotating drum having a coaxial high voltage wire, so as to electrically capture the toner which is then separated into an underlying receiver by a wiper member.

15 Claims, 3 Drawing Figures U.S. Patent Nov. 4, 1975 3,917,397

.1. Hi- M T MECHANISM FOR REMOVING RESIDUAL TONER FROM ELECTROSTATIC COPIER DRUM The present invention relates to a residual toner removing apparatus for use in removing the residual toner left on the surface of an electrophotographic sensitive surface in an image transfer type electrostatic copier.

In general, with the electrophotographic process according to Carlson method, electrostatic charges having a specific polarity are uniformly applied to the surface of an electrophotographic sensitive plate, and then a light image corresponding to an original to be recorded is projected thereon, thus obtaining an electrostatic latent image. This latent image may be developed with a powdered developing material having an opposite polarity which is generally referred to as a toner, followed by the transfer and fixing to a copy paper of the powder image, thereby terminating the copying operation of an original to be recorded. However, upon transfer of the powder image to the copy paper, a certain amount of toner, the majority of which has been transferred to the copy paper, is left on the surface of the sensitive plate. For removing such residual toner, it has been a practice to use an A.C. erasing voltage for neutralizing the sensitive plate, followed by the cleaning thereof by means of a brush. This operation permits the removal of a majority of the residual toner, although the toner adhering to the cleaning brush may not be removed merely by resorting to suction means such as a fan, and thus the amount of adhering toner will be progressively increased, thereby not only lowering the cleaning efficiency, but also adversely effecting the service life of the brush itself. Moreover, by directly recovering the toner in a filter bag, without using an intermediate recovering means, necessitates the frequent replacement of the filter bag, with the attendant clogging of the filter which in turn lowers the efficiency of suction, thus raising difficulties in the achievement of high speed reproduction.

For avoiding the aforesaid drawbacks, U.S. Pat. No. 3,572,923 and US. Pat. No. 3,722,018 describe residual toner removing apparatus. According to the thus proposed apparatus, the cleaning brush is connected to a high voltage electric power source which applies a DC. bias of a polarity opposed to that of the toner or has an electrostatic charge applied from a corona discharging means and there is provided a toner collecting means which is connected to a high voltage electric power source having a polarity opposed to that of the toner, such collecting means being maintained in sliding contacting engagement with the cleaning brush. With such an arrangement, the toner remaining on the surface of the photosensitive plate is removed by means of a cleaning brush which is rotated at a relatively low speed of one-half to three times the surface speed of the photosensitive plate, while the toner adhering to the brush is caused to be electrically repelled therefrom by virtue of the aforesaid biasing or corona discharge for the subsequent collection in the aforesaid toner collecting means. It appears that this arrangement has solved some of the problems encountered with the prior art apparatuses. However, the toner is a minute particle, such that the polarity thereof is quite unstable, whereby toner particles having positive, negative or neutral polarity remain on the photosensitive plate, particularly after the transferring step. Thus, the

method of simply repelling toner adhered to the cleaning brush electrically is not sufficient, and it is thus desirable to remove the toner forcibly.

SUMMARY OF THE INVENTION It is accordingly a principal object of the present invention to provide an improved mechanism for removing residual toner from the photosensitive surface of an image transfer type electrostatic copier, after the transfer of powder image.

It is another object of the present invention to provide a residual toner removing mechanism which is of excellent reliability and durability, possessing a long lasting service life.

It is a further object of the present invention to provide a residual toner removing mechanism which is highly useful in high speed reproduction machines.

It is still a further object of the invention to provide a residual toner removing apparatus which is of highly compact size.

It has been found that the aforesaid and other related objects of the invention may be attained in a residual toner removing mechanism, in which an air flow is created due to the centrifugal force effected by a cleaning brush rotating at a high speed, whereby the toner adhering to the cleaning brush is positively removed therefrom, followed by the recovery of the toner by means of a toner collecting means which is charged to a high potential. More specifically, there is provided a residual toner removing apparatus having at least a cleaner section and a toner collecting section, whereby a cleaning brush housed within a split casing provided in the body of the apparatus is disposed in a sliding contact with one face of the split casing and rotated at a high speed for triboelectrically charging the brush itself to the polarity of the toner, while the cleaning brush rotating at a high speed is used to wipe the surface of the copier electrophotosensitive member, thereby removing the residual toner therefrom. Moreover, the toner adhering to the cleaning brush is caused to be electrically repelled therefrom, whereupon the toner is tranferred to the downstream side by the air flow created by the high speed rotation of the cleaning brush positioned in the gap defined between the brush and the opposite face of the split casing, whereby the toner thus freed may be collected on the surface of a toner collecting sleeve which has been charged to a high voltage.

For a fuller understanding of the nature and objects of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal cross-sectional view of a residual toner removing mechanism embodying the present invention;

FIG. 2 is a sectional view taken along line HH' of FIG. 1; and

FIG. 3 is a longitudinal cross-sectional view showing the essential part of the second embodiment of the residual toner removing apparatus of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, particularly FIGS. 1 and 2 thereof, which illustrate a preferred embodiment of the present invention, the improved toner removing mechanism is employed in cleaning a relatively slowly rotating photosensitive drum 1 of an image transfer type electrostatic machine, and has associated therewith in the known manner, a charging device B1, a light image projector CI for focussing in the known manner, onto drum 1 a light image of an original A1 and a toner applicator D1 for forming a toner powder image-of the latent electrostatic image, the powder image being transferred to copy paper by a conventional image transfer mechanism E1. The improved mechanism follows the transfer station and includes a cleaner section A, a toner collecting section B, a filter section C and a suction section D.

The cleaner section A comprises a high speed rotating brush 2, which is parallel to drum 1 and is in frictional brushing engagement with the periphery of the drum 1 and includes a cylindrical brush support or cone in which are anchored brush bristles 3 which are formed of artificial or natural filaments, such as acrylonitrile furs of such animals as rabbit or the like. The brush 2 is housed in a casing including upper casing section 4 and lower casing section 5, which are electrically insulated from each other, the casing having front and rear openings, the brush 2 engaging drum 1 through the front opening. The periphery of brush 2 frictionally engages a medial portion 4a of upper casing section 4 which is of lesser curvature than the brush periphery, and is spaced from the curved lower section 5 by a peripherally extending passageway defining gap 6. The brush 2 is rotated by a drive shaft 2 connected to a drive motor ml. The rotational speed of brush 2 depends on the circumferential length of the electrophotosensitive drum 1 and the rotational speed thereof. However, highly advantageously the brush 2 isrotated at 500 to 1,000 (revolutions per minute). For example,

' if the diameter of the electrophotosensitive drum 1 is 14 cm and the peripheral speed thereof is cm per second, the peripheral speed of the cleaning brush 2 should fall in the range of about 70 to 140 times or more thereof, and preferably in the range from 100 to 120 times andmore (700 to 800 rpm) of the peripheral speed of the electrophotosensitive drum 1. The upper and lower casing sections 4 and 5 are shown as being so constructed as to be separate from the apparatus proper T, being interposed between .the attaching

outer covers

7 and 8, while there is defined aflow path or passageway 9 between the upper casing section 4 and the body proper T. The

covers

7 and 8 are both grounded and adapted to attract the toner having its polarity reversed in the course of reproduction.

Moreover, there is provided a gap, sufficiently large to introduce the air between the free front edges of attaching

covers

7 and 8 which confront the drum 1 and the electrophotosensitive drum 1.

The upper casing-section 4 is made of a metal such as brass, and, due to the frictional rubbing thereof by the rotation of the cleaner brush 2, it charges the brush bristles 3 to a polarity the same as that of the toner, i.e., to a positive polarity, if the toner used is of positive polarity, while charging the upper casing section 4 to a polarity opposite that of the toner, i.e., to a negative polarity. Shown at 10 is a known dusting bar which is located in abutting or interrupting relation to the brush bristles 3.

' The toner collecting section B as shown in detail in FIG. 2 consists of a toner collecting sleeve 11 to attract and collect the majority of separated. toner which has been wiped and removed from the surfaceof the electrophotosensitive drum, a' sleeve cleaner 12 adapted to scrape the toner which has been attracted and caught on the surface of the collecting sleeve therefrom, and a toner collecting cassette or-receptacle 13 which is manually detachable and adapted to collect the toner thus scraped off.

The toner collecting sleeve 11 is positioned in close proximity to the cleaning brush 2, so as to attract the majority of toner being transferred from the cleaner section. The sleeve 11 includes a insulating layer or coating 11a such as of tetrafluoride ethylene or a polyester or the like,.having excellent heat resistance and low viscosity over the surface of the sleeve whose body 1 1b is of electrically conductive material. The sleeve 11 is electrically insulated from the casing sections 4 and 5 as well as from the body of the apparatus, having an inner hollow portion along the longitudinal center axis of which there runs a high-voltage generating wire, i.e., a so called corona electrode wire 15 connected to the electric power source of a corona discharge device or a high voltage electric power source 14 provided in separate relation, thereby providing electric charges having a polarity opposed to that of the toner. A semicircular shield plate 16 is provided in the inner hollow portion of the sleeve 11 in a direction parallel to the corona electrode wire.15 and affixed to the opposite side walls of the apparatus proper. The shield plate 16 functions to scatter in a given direction the electric charge discharged from the corona electrode wire 15, thereby preventing uneveness in the charged condition of the toner collecting sleeve 11, while maintaining at a high electric potential the surface of the toner collecting sleeve which is adjacent to the discharge opening for I the toner which has been removed from the cleaning brush 2, said opening being delineated by therear edges of the split casing sections 4 and 5. On the other the electrically conductive material, as described.

eariler, the entiresurface of the sleeve 11 may be charged, without rotating the sleeve 11.

The toner collecting sleeve 11 is connected by way of a drive shaft 25 to a motor M2 and normally rotates in the present embodiment at about 10 rpm (revolutions per minute) during the operation of the apparatus. However, this should not be construed as a limitation, the toner collecting sleeve may be intermittently rotated for collecting according to a technique which will be described hereinafter, at every time when there is collected the toner of such an amount as not to lower the function of the apparatus itself.

Shown at 12 is a sleeve cleaner for scraping the toner attracted to the surface of the toner collecting sleeve 11, the sleeve cleaner 12 being made of polyurethane the sleeve cleaner 12 is positively collected. In addition, the cassette 13 is so designed as to be withdrawn forward, as viewed in the drawing, being supported by supporting member 17 which engages the upper portion of the side wall of the cassette 13.

The filter section C consists of a filterbag 18 positioned at the rear of the toner collecting portion 8 but adjacent to the suction portion D which will be deis of a highly dense structure so as to collect the toner not recovered by the toner collecting section B.

The suction section D is provided with a suction fan 19 driven by a motor 20, thereby aiding in the creation of an efficient air flow effected by the high speed rotation of cleaning brush 2. The fan 19 is so designed as to rotate in a direction to cause the air flow to travel in a righthand direction as viewed in the drawing.

In operation, the electrophotosensitive drum 1 is rotated in a counter-clockwise direction as shown by the arrow, while an electrostatic powder image is formed thereon by means (not shown), and then the powder image is transferred to copy paper. With the rotation of the electrophotosensitive drum 1 the motor M1 connected to a drive shaft 2', a motor M2 for driving and rotating the toner collecting sleeve 11 and a motor 20 for the Sirocco fan 19 are simultaneously energized, thereby rotating the cleaning brush 2 likewise in a counter-clockwise direction opposed peripherally in the area of engagement to that of the rotation of the electrophotosensitive drum 1, as'shown in the drawing, at a high speed, such as 800 rpm, while the toner collecting sleeve 11 is rotated clockwise at about rpm. The rotation of the cleaning brush 2 causes the brush bristle 3 to wipe the toner remaining on the surface of the electrophotosensitive drum 1, while the cleaning brush 2 rotates in sliding frictional engagement with the midportion 4a of the upper casing section 4. The rotation in sliding contact relation, of the cleaning brush with the upper casing 4 charges the brush bristles 3 triboelectrically to the potential of about 4 kilovolts and to a polarity the same as that of the toner, whereby the toner adherinng to the brush bristles are electrically repelled from the brush bristles. The toner is also forcibly separated from the cleaning brush 2 due to a centrifugal force caused by the high speed rotation of the cleaning brush 2 as well as a strong air flow in a direction as shown from the path gap 6 delineated by the lower casing section 5, said air flow being created by the high speed rotation of the brush 2 with the introduction of air from the gap defined by one end of lower casing section 5 and the sensitive member 1 and aided by the suction of the aforesaid Sirocco fan 19, after which the toner thus separated is fed into the toner collecting portion B.

The toner adhering to the aforesaid brush bristle contains toner of other polarities such as negative or neutral. However, such toner is also substantially completely removed by the strong air flow and the toner still remaining on the brush bristles even after such operations is removed by the brush bristle 3 abutting on the dusting bar 10 to be fed to the toner collecting section B.

Moreover, the arrangement of the brush bristles intimately contacting the midportion 4a of the upper casing 4 prevents the toner, separated from the brush bristle from being forced out toward the side of electrophotosensitive drum 1 due to the rotation of the cleaning brush 2.

Even if the separated toner should be forced out to the drum side, the toner will be sucked back into the toner collecting section B by means of the air flow running in the direction shown by the arrow through the flow path 9 between the upper casing section 4 and the 'cover 7, thus presenting no possibility of the toner being blown outside from the side of the electrophotosensitive drum 1.

The toner thus separated is fed to the toner collecting section B. In this respect, however, the surface of the toner collecting sleeve 1 1 is charged to maintain a constant high voltage at an electric potential opposed to that of the toner, by means of the corona electrode wire 15 which extends axially through the center of the ho]- low sleeve 11 and is connected to a high voltage electric power source 14. Experiments reveal that, in the case of the toner developing material having a positive polarity, a voltage of 5 KV to 9 KV is advantageously applied to the corona wire. For instance, when the corona electrode wire is disposed 25 m/m from the inner surface of the sleeve, the sleeve surface was found to have been charged to about 4.5 KV. This results in the development of an electrostatic field on the surface and in the vicinity of the sleeve, whereby the separated toner having a positive charge is attracted to the surface of the toner collecting sleeve 11.

Meanwhile, a particular portion of the sleeve surface which is in the close vicinity of the toner discharge opening delineated by the rear edges of the split casing sections 4 and 5 is maintained at a high potential, as the shield plate 16 scatters most of charges in such direction, such that the separated toner having the positive charge is positively attracted to the aforesaid portion of the sleeve surface.

Thus, the toner which has been captured by and adheres to the surface of the rotating sleeve 11 is scraped off by means of the sleeve cleaner 12 and then collected in the toner cassette 13. The toner thus collected may be reused as developing material. Accordingly, when the cassette is full with the toner, it may be supplied back to a developing material container for reuse in developing an electrostatic latent image.

On the other hand, because of the use of indirect charging method using corona electrode wire 15 running through the toner collecting sleeve, the surface of the sleeve may be maintained at a high potential for a long period of time, even after the electric power source is cut off, such that the toner floating in the air during idle time of the apparatus is attracted to the sleeve surface.

The separated toner having negative and neutral polarities is transferred to the air flow running in downstream in the direction of the arrow, such air flow being the combination of the two air flows which are united in the toner collecting portion B, i.e., one air flow traversing the gap 6 and the other traversing the flow path The major part of such toner is attracted to and collected on the inner surface of the cover 7, because the cover 7 is grounded.

Most of the toner thus separated may be removed in the toner collecting portion B. However, the toner still contained in a small amount in the air flow is transferred to the filter portion C where it is recovered in the filter bag 18. Experiments demonstrate that over percent of the residual toner is collected in the toner collecting portion B.

FIG. 3 shows a second embodiment of the present invention which is the modification of compact size of the first described embodiment, wherein parts similar to those shown in FIG. 1 are designated by similar reference numerals, thus omitting the duplicate description.

The air circulating system shown consists of a cleaner section A and a toner collecting section B.

In the cleaner section A, there is provided an outer attaching cover 7 which is made of brass and formed with a bent portion 7a which contacts the bristles of a cleaning brush 2, thereby triboelectrically charging the rapidly rotating brush bristle 3 to the same polarity as that of the toner due to friction.

On the other hand, in the toner collecting section B, there is provided a sleeve cleaner 12 in sliding contact with the surface of the toner collecting sleeve 11, and the cleaner 12 is supported by the supporting member 17 secured to one end of the lower casing 5. Provided in the lower portion of the apparatus proper is a flow path 21 which is delineated by the lower attaching cover 8 and a supporting plate 20 extending in parallel therewith.

With this arrangement, the air flow caused by the high speed rotation of the cleaning brush 2 is directed, as shown by the arrows, through gap 6, via toner collecting portion B into the flow path 21, then back to the gap 6, thereby forming a circulating flow, while being united for circulation with the air flow, shown by an arrow, from an opening defined by the front edges of the upper and

lower covers

7, 8 and the surface of the electrophotosensitive drum 1. In this respect, it is preferred that the rotational speed of the cleaning brush be increased to insure the positive circulation of air flow, as compared with the first embodiment of the invention.

While there have been described and illustrated preferred embodiments of the present invention, it is apparent that numerous alterations, omissions and additions may be made without departing from the spirit thereof.

We claim:

1. A residual toner removing apparatus for use in removing toner from an electrophotosensitive member comprising:

a rotatably mounted cleaning brush (2) with the bristles (3) thereon moving in frictional contact with the surface of the electrophotosensitive member first (4, 7d) and second (5) casing members overlying a portion of said cleaning brush with said first casing member (4, 7a) in frictional rubbing contact with the bristles moving along a portion of the path of the periphery thereof so as to triboelectrically charge the bristles (3) to the same polarity as that of the toner, said second casing member (5) being spaced apart from the bristles so as to define an air flow path (6),

a rotatable sleeve member (11) mounted adjacent but spaced apart from said cleaning brush (2) for collecting toner recovered by said cleaning brush, said sleeve member having a corona electrode wire (15) running therethrough for being charged to potential opposite to that of toner polarity, and a grounded housing (7) for collecting toner with polarity reversed in course of copying processes.

2. The residual toner removing apparatus as set forth in claim 1 wherein said cleaning brush is rotated in the range of about 500 to 1000 rpm.

3. The residual toner removing apparatus as set forth in claim 1 wherein said sleeve member (11) includes two layers in which an electrically conductive layer (11b) is covered by an insulative layer (11a).

4. The residual toner removing apparatus as set forth in claim 1 wherein said sleeve member (11) further comprises a shield plate means (16) located between the electrode wire (15) and the sleeve member (11) for scattering electric charges generated from the corona electrode wire (15) in a predetermined direction for maintaining a portion of said sleeve at a relatively higher potential.

5. The residual toner removing apparatus as set forth in claim 1 further comprising a blade member (12) in contact with the surface of said sleeve means for scraping off the toner adhered to said sleeve member.

6. The residual toner removing apparatus as set forth in claim 5 further comprising a toner cassette (13) for collecting toner scraped off by said blade member.

7. In combination with a photosensitive member in an electrostatic copier of the image transfer type including means for forming a latent electrostatic image of an original on said photosensitive member means for applying a finely divided toner having charge properties of a predetermined polarity to said latent image to form a powder image and means for transferring said powder image to a substrate, a mechanism for removing residual toner from said photosensitive member, comprising a cylindrical brush having chargeable bristles and rotatable across the surface of said photosensitive member, means for electrically charging said bristles to said predetermined polarity of said toner, a collector member spaced from said brush member, means for charging said collectormember to a polarity opposite to said predetermined polarity and means for guiding a flow of air from the periphery of said brush to said collector member.

8. The combination of claim 7 wherein said means for charging said brush includes triboelectric charging means.

9. The combination of claim 8 wherein said triboelectric charging means comprises a first section having a face extending along the length of and frictionally engaged by the relatively moving bristles of said rotating brush member.

10. The combination of claim 9 including a second section extending longitudinally peripherally about said brush opposite to said first section and delineating with said brush a first air passageway extending in a direction from the proximity of the front of said brush and spaced from said photosensitive member toward said collector member, the periphery of said brush delineating said passageway advancing rearwardly with the rotation of said brush.

11. The combination of claim 10 including means for rapidly rotating said brush member.

12. The combination of claim 11 wherein said collector comprises a hollow sleeve including a conducting substrate and an insulating outer face, a discharge electrode disposed within said sleeve and spaced from the surface thereof and means for charging said electrode to a high voltage potential opposite to that of said toner.

13. The combination of claim 12 wherein said electrode comprises a wire extending coaxially in 'said sleeve and comprising means for rotating said sleeve, a wiper member engaging the face of said sleeve and a toner receiver receptacle underlying said sleeve.

14. The combination of claim 13 wherein said first section comprises a curved first panel coaxial with and of lesser curvature than said brush, a second panel spaced from the periphery of said brush and comprising a fourth panel extending along the front portion of and spaced from said front portion to delineate an air passageway extending rearwardly from a point spaced from said photosensitive member and communicating with the space ambient to said collector member.

Page 1 of 2 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION- Patent 2 917 397 movpmb r 4 1975 Inventor(s) Susumu Tanaka, et a1.

It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Figure one should appear as shown on the attached sheet.

Signed and Scaled-this [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oj'latenls and Trademarks second D a Of March 1 9 76 Pat No. $917,397 Page 2 f2

Claims

1. A residual toner removing apparatus for use in removing toner from an electrophotosensitive member comprising: a rotatably mounted cleaning brush (2) with the bristles (3) thereon moving in frictional contact with the surface of the electrophotosensitive member (1), first (4, 7a) and second (5) casing members overlying a portion of said cleaning brush with said first casing member (4, 7a) in frictional rubbing contact with the bristles moving along a portion of the path of the periphery thereof so as to triboelectrically charge the bristles (3) to the same polarity as that of the toner, said second casing member (5) being spaced apart from the bristles so as to define an air flow path (6), a rotatable sleeve member (11) mounted adjacent but spaced apart from said cleaning brush (2) for collecting toner recovered by said cleaning brush, said sleeve member having a corona electrode wire (15) running therethrough for being charged to potential opposite to that of toner polarity, and a grounded housing (7) for collecting toner with polarity reversed in course of copying processes.

7. In combination with a photosensitive member in an electrostatic copier of the image transfer type including means for forming a latent electrostatic image of an original on said photosensitive member means for applying a finely divided toner having charge properties of a predetermined polarity to said latent image to form a powder image and means for transferring said powder image to a substrate, a mechanism for removing residual toner from said photosensitive member, comprising a cylindrical brush having chargeable bristles and rotatable across the surface of said photosensitive member, means for electrically charging said bristles to said predetermined polarity of said toner, a collector member spaced from said brush member, means for charging said collector member to a polarity opposite to said predetermined polarity and means for guiding a flow of air from the periphery of said brush to said collector member.

13. The combination of claim 12 wherein said electrode comprises a wire extending coaxially in said sleeve and comprising means for rotating said sleeve, a wiper member engaging the face of said sleeve and a toner receiver receptacle underlying said sleeve.

14. The combination of claim 13 wherein said first section comprises a curved first panel coaxial with and of lesser curvature than said brush, a second panel spaced from and extending along said first panel and delineating a second air passageway extending rearwardly of said brush member, a filter member having a front face communicating with the space ambient to said collector member and suction means communicating with the rear face of said filter member.

15. The combination of claim 13 wherein said second section includes a third panel extending along and spaced from the periphery of said brush and comprising a fourth panel extending along the front portion of and spaced from said front portion to delineate an air passageway extending rearwardly from a point spaced from said photosensitive member and communicating with the space ambient to said collector member.