Abstract:
An apparatus for removing electrostatically charged particles from a surface such as the backside of an image bearing belt of the type found in an electrostatographic printing apparatus or a drive roller supporting an image bearing belt. The apparatus includes an electrically biased brush having a substrate and a multiplicity of conductive fibers extending outwardly to contact the surface to be cleaned, a supporting device, and a cleaning device for removing collected particles from the brush. The supporting device for the brush rotates, thereby moving the brush and causing clean fibers to contact the surface to be cleaned.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to an electrostatographic printer or copier, and more particularly concerns a device for cleaning the backside of a photoreceptor belt used therein. 
     In an electrophotographic application such as xerography, a charge retentive surface (ie., photoconductor, photoreceptor or imaging surface) is electrostatically charged and exposed to a light pattern of an original image to be reproduced to selectively discharge the surface in accordance therewith The resulting pattern of charged and discharged areas on that surface form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image. Contacting it with a finely divided, electrostatically attractable powder referred to as “toner” develops the latent image. Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. This process is well known, and useful for light lens copying from an original and printing applications from electronically generated or stored originals, where a charged surface may be image-wise discharged in a variety of ways. Ion projection devices where a charge is image-wise deposited on a charge retentive substrate operate similarly. 
     One type of charge retentive surface typically utilized in the electrostatographic reproduction device is a photoreceptor belt having a base of flexible material The photoreceptor belt is entrained about a plurality of support rollers so as to form a closed loop path. The photoreceptor belt is driven about the closed loop path to present particular areas of the photoreceptor belt sequentially into association with electrographic process stations to form desired reproductions. Adhered to the backside of the photoreceptor belt is a substrate polycarbonate known as anti-curl back coating. The purpose of this coating is to balance the stresses within the photoreceptor belt and control edge curling. Over time as a photoreceptor belt repeatedly travels around the sharp corners of rollers, backer bars, and other surfaces, the anti curl back coating begins to wear and flake off in the form of low charged negative particles. As a result, a build up of anti-curl back coating particles occurs on all parts of the module which come in contact with the anti-curl back layer. Additionally, toner particles from the development system, the imaging surface cleaner, and toner airborne in the xerographic module are deposited on the back of the belt. In particular, there is a buildup of anti-curl back coating particles and toner particles on the drive roller, the backer bars, and in the Acoustic Transfer Assist (ATA) device. Debris particles on the drive roll cause the coefficient of friction of the drive roller to drop appreciably. This buildup of particles on the backside of the photoreceptor belt and drive roller may adversely affect performance of the photoreceptor belt as it is driven about the closed loop path and, ultimately, overall performance of the reproduction apparatus. In a non-contact development system, such as Hybrid Scavengeless Development (HSD), the spacing between the developer and the imaging surface is important. When debris builds up on the developer backer bars, the photoreceptor is lifted off the backer bars, causing the spacing in the development nip to decrease. When this occurs in a particular location, or several different locations on the developer backer bars, the different development fields produce streaks on copy in the process direction. Excessive debris in the ATA reduces the suction pressure in the ATA and creates transfer defects. 
     Several mechanisms have been employed for cleaning the backside of the photoreceptor belt. One mechanism includes a stationary pad of a material such as cotton. This pad can easily become saturated with debris, with the period of time required for the pad to become saturated not readily predictable. Saturation of the pad can cause excessive abrasion and scratching of the photoreceptor belt, necessitating frequent inspection and cleaning. To meet high volume copier applications, a cleaner for the backside of a photoreceptor belt or the drive roller is needed that would preserve drive capacity and prevent anti curl back coating contamination to sensitive subsystems. 
     The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows: 
     U.S. Pat. No. 4,853,741 to Ku utilizes an indexing web of material, such as a fabric of a non-woven blend of polyester and rayon for example. The web is periodically indexed by a motor, which is coupled to the mechanism. While this mechanism reduces the necessity for frequent inspection, it may scratch the dielectric support web if it picks up any abrasive particles or debris. 
     U.S. Pat. No. 5,655,205 to Ziegelmuller et al. discloses a mechanism for cleaning the backside of an image bearing dielectric support web including a cleaning blade which engages the backside of the dielectric support web at a predetermined angle so as to wipe the backside of the web. A catch tray attached to the blade collects debris removed from the backside of the web. 
     SUMMARY OF THE INVENTION 
     Briefly stated, and in accordance with one aspect of the present invention, there is provided an apparatus for removing electrostatically charged particles from a surface. The apparatus includes an endless electrically biased conductive flexible belt brush having a substrate from which conductive fibers extend outwardly, rollers about which the belt brush is entrained, and a cleaning device for cleaning collected particles from the brush belt. One of the rollers supporting the brush belt is a drive roller which rotates, thereby moving the brush belt and causing clean fibers to contact the surface to be cleaned. 
     In accordance with another aspect of the present invention, there is provided an electrically biased conductive cylindrical brush having a substrate from which conductive fibers extend outwardly, a cylindrical core about which the substrate is entrained, and a cleaning device for cleaning collected particles from the cylindrical brush. The cylindrical core supporting the cylindrical brush rotates, thereby causing clean fibers to contact the surface to be cleaned. 
     In accordance with yet another aspect of the present invention, there is provided a printing machine of the type having a photoconductive member in the form of an image bearing belt and an apparatus for removing particles which accumulate on the backside of the image bearing belt or the drive roller supporting the image bearing belt. The apparatus for removing accumulated particles includes an electrically biased brush belt, which contacts the surface to be cleaned, and which is supported by a plurality of rollers, one of which is a drive roller, and a cleaning device to remove particles collected by the brush belt. The drive roller for the brush belt rotates, thereby moving the brush belt to bring clean fibers into contact with the backside of the image bearing belt or the drive roller supporting the image bearing belt. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the instant invention will be apparent and easily understood from a further reading of the specification, claims and by reference to the accompanying drawings in which: 
     FIG. 1 is a schematic illustration of a printing apparatus incorporating the inventive features of the present invention 
     FIG. 2 is an elevational view of the present invention. 
     FIG. 3 is an elevational view of another embodiment of the present invention. 
     FIG. 4 is an elevational view of still another embodiment of the present invention 
    
    
     All references cited in this specification, and their references, are incorporated by reference herein where appropriate for teaching additional or alternative details, features, and/or technical background. 
     While the present invention will be described hereinafter in connection with a preferred embodiment thereof, it should be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
     For a general understanding of an electrophotographic printer or copier, in which the present invention may be incorporated, reference is made to FIG. 1, which depicts schematically the various components thereof. Hereinafter, like reference numerals have been used throughout to identify identical elements. Although the brush belt cleaner apparatus of the present invention is particularly well adapted for use in an electrophotographic printing machine, it should become evident from the following discussion that it is equally well suited for use in other applications and is not necessarily limited to the particular embodiment shown herein. 
     Referring now to the drawings, the various processing stations employed in the reproduction machine illustrated in FIG. 1 will be described briefly hereinafter. It will no doubt be appreciated that the various processing elements also find advantageous use in electrophotographic printing applications from an electronically stored original, and with appropriate modifications, to an ion projection device which deposits ions and image configuration on a charge retentive surface. 
     A reproduction machine, in which the present invention finds advantageous use, has a photoreceptor belt  10 , having a photoconductive (or imaging) surface  11 . The photoreceptor belt  10  moves in the direction of arrow  12  to advance portions of the belt  10  sequentially through the various processing stations disposed about the path of movement thereof. The belt  10  is entrained about a stripping roller  14 , a tension roller  16 , a drive roller  20 , and backer bars indicated generally as  15 . Drive roller  20  is coupled to a motor  21  by suitable means such as a belt drive. The belt  10  is maintained in tension by a pair of springs (not shown) resiliently urging tension roller  16  against the belt  10  with the desired spring force. Both stripping roller  14  and tension roller  16  are rotatably mounted. These rollers are idlers, which rotate freely as the belt  10  moves in the direction of arrow  12 . 
     With continued reference to FIG. 1, initially a portion of the belt  10  passes through charging station A. At charging station A, a corona device  22  charges a portion of the photoreceptor belt  10  to a relatively high, substantially uniform potential, either positive or negative. At exposure station B, a Raster Output Scanner (ROS)  33  exposes the charged portions of photoreceptor belt  10  to record an electrostatic latent image thereon. 
     Thereafter, the belt  10  advances the electrostatic latent image to developing station C. At developing station C, developer housings  34 ,  36 ,  38 , or  40  are brought into contact with the belt  10  for the purpose of developing the electrostatic latent image. Each developer housing  34 ,  36 ,  38 , and  40  supports a developing system such as magnetic brush rolls  42 ,  43 ,  44 , and  45 , which provides a rotating magnetic member to advance developer mix (i.e. carrier beads and toner) into contact with the electrostatic latent image. The electrostatic latent image attracts toner particles from the carrier beads, thereby forming toner powder images on the photoreceptor belt  10 . 
     The photoreceptor belt  10  then advances the developed image to transfer station D. At transfer station D, a sheet of support material such as paper copy sheets is advanced into contact with the developed images on the belt  10 . A corona generating device  46  charges the copy sheet to the proper potential so that it becomes tacked to the photoreceptor belt  10  and the toner powder image is attracted from the photoreceptor belt  10  to the sheet Acoustic Transfer Assist device  47  provides vibrational energy to photoreceptor belt  10  at a frequency sufficient to assist in loosening the toner powder image and thereby facilitating transfer of the image to the sheet. After transfer, the corona generator  48  charges the copy sheet to an opposite polarity to de-tack the copy sheet from the belt  10 , whereupon the sheet is stripped from the belt  10  at stripping roller  14 . 
     Sheets of support material  49  are advanced to transfer station D from a supply tray  50 . Sheets are fed from tray  50 , with sheet feeder  52 , and advanced to transfer station D along conveyor  56 . 
     After transfer, the sheet continues to move in the direction of arrow  60 , to fusing station E. Fusing station E includes a fuser assembly indicated generally by the reference numeral  70 , which permanently affixes the transfer toner powder images to the sheets. Preferably, the fuser assembly  70  includes a heated fuser roller  72  adapted to be pressure engaged with a backup roller  74  with the toner powder images contacting the fuser roller  72 . In this manner, the toner powder image is permanently affixed to the sheet, and such sheets are directed via a chute  62  to an output  80  or finisher. 
     Residual particles, remaining on the image side of photoreceptor belt  10  after each copy is made, may be removed at cleaning station F, represented by the reference numeral  92 . At cleaning station  92  residual toner particles are removed and may also be stored for disposal. 
     Residual particles, collecting on the backside of photoreceptor belt  10 , may be removed at back of belt cleaning station G. The cleaning apparatus of the present invention is represented by the reference numeral  94 , which will be described in greater detail in FIGS. 2-4. Removed residual particles may also be stored for disposal 
     A machine controller  96  is preferably a known programmable controller or combination of controllers, which conventionally control all of the machine steps and functions described above. The controller  96  is responsive to a variety of sensing devices to enhance control of the machine, and also provides connection diagnostic operations to a user interface (not shown) where required. 
     As thus described, a reproduction machine in accordance with the present invention may be any of several well-known devices. Variations may be expected in specific electrophotographic processing, paper handling and control arrangements without effecting the present invention. However, it is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an electrophotographic printing machine, which exemplifies one type of apparatus employing the present invention therein. Reference is now made to FIGS. 2-4, where the showings are for the purpose of illustrating preferred embodiments of the present invention and not for limiting the same. 
     Wear debris accumulates on the back side of the photoreceptor belt and the drive roller as the result of movement of the photoreceptor belt over the backer bars and rollers supporting the photoreceptor bell Adhesion of the debris to the back of the belt is low because there is a low triboelectric relationship between the particles and the back of the photoreceptor belt. Therefore, a minimal charge is developed as the particles rub against the backer bars and rollers supporting the photoreceptor belt. Removal of such debris adhered to the back side of a dielectric surface can be accomplished by mechanical, electrical or electro-mechanical means. The belt brush cleaner of the present invention employs a combination of electrical and mechanical forces to detach and remove debris from the back side of the photoreceptor belt. 
     Reference is now made to FIG. 2, which shows an elevational view of one embodiment of the present invention. The flexible belt brush  110  is shown in operable condition in contact with the backside of photoreceptor belt  10  through cleaning nip  150 . Flexible belt brush  110  is electrically biased to suitable magnitude and polarity and is comprised of a continuous loop of conductive backing material (e.g. urethane, polycarbonate or polyester) to which conductive brush fibers are attached with conductive glue in segments, to form a segmented belt brush The flexible belt brush  110  is entrained about four rollers  102 ,  104 ,  106  and  108 , one of which is a drive roller, and moving in direction  130  opposed to the movement of photoreceptor belt  10 . The two rollers  102  and  104  support the belt  110  in brushing contact with photoreceptor belt  10 . The third and fourth rollers  106  and  108  support belt  110  as the conductive brush fibers are brought into contact with flicker bars  120 , which engage the fibers of the brush belt as the fibers move past the flicker bars. As the fibers rebound from contact with the flicker bars  120 , the fibers release debris particles, which fall into waste chamber  140 . Coupled to the drive roller is a drive means which indexes the belt brush segmentally in direction  180  as the fiber segment contacting the backside of the photoreceptor belt becomes saturated with debris particles. Although entraining the belt brush about four rollers is suitable for many applications, it is understood that some applications may require an alternate number of support rollers. Such alternate plurality of support rollers is included within the spirit and scope of the present invention as defined by the appended claims. 
     In order to exert an electrostatic force on the debris particles, which may develop a low triboelectric charge as the debris particles rub against the back side of the photoreceptor belt and the supporting rollers and backer bars, an electric potential is applied to the conductive fibers of the brush belt. This potential creates an electric field between the fibers and the ground plane of the photoreceptor belt. The force experienced by the debris particles must exceed the small adhesion force between the debris particles and the backside of the photoreceptor belt in order to detach the particles. The electrical force, when combined with the mechanical (deflection) forces of the fibers, detaches and removes slightly charged debris particles from the backside of the photoreceptor belt. 
     Reference is now made to FIG. 3, which shows an alternate embodiment of the present invention. As in the previous embodiment, the flexible belt brush  110  is shown in operable condition in contact with the backside of photoreceptor belt  10  through cleaning nip  150 . Flexible belt brush  110  is electrically biased to suitable magnitude and polarity and is comprised of a continuous loop of conductive backing material (e.g. urethane, polycarbonate or polyester) to which conductive brush fibers are attached with conductive glue to form an endless brush belt. The flexible belt brush  110  is entrained about four rollers  102 ,  104 ,  106  and  108 , one of which is a drive roller, and moving in direction  130  opposed to the movement of photoreceptor belt  10 . The two rollers  102  and  104  support the belt  110  in brushing contact with photoreceptor belt  10 . The third and fourth rollers  106  and  108  support belt  110  as the conductive brush fibers are brought into contact with flicker bar  120 , which engages the fibers of the brush belt as the fibers move past the flicker bar. As the fibers rebound from contact with the flicker bar  120 , the fibers release debris particles, which fall into waste chamber  140 . Coupled to the drive roller is a drive means, which continuously rotates the drive roller to move the belt brush in direction  130 . Although entraining the belt brush about four rollers is suitable for many applications, it is understood that some applications may require an alternate number of support rollers. Such alternate plurality of support rollers is included within the spirit and scope of the present invention as defined by the appended claims. 
     As may be appreciated by one skilled in the art, the embodiments illustrated in FIGS. 2 and 3 may also be configured to remove debris particles accumulating on drive roller  20 , which supports photoreceptor belt  10 , or on other surfaces which contact the backside of photoreceptor belt  10 . Reference is now made to FIG. 4, which illustrates the a third embodiment of the present invention configured to remove debris particles from drive roller  20 , as an example of one such configuration. As shown in FIG. 4, the cylindrical belt brush  110  is in operable contact with drive roller  20  through cleaning nip  160 . The cylindrical brush  110  is electrically biased to suitable magnitude and polarity and is comprised of a backing material to which conductive brush fibers are attached, and a cylindrical core, which may be solid or tubular. Coupled to the cylindrical core is a drive means, which continuously rotates the cylindrical brush  110 . The cylindrical brush  110  rotates in direction  130 , opposed to the movement of drive roller  20 , which rotates in direction  170 , and is in brushing contact with drive roller  20  through cleaning nip  160 . As cylindrical brush  110  rotates, the conductive brush fibers are brought into contact with flicker bar  120 , which engages the fibers of the cylindrical brush as the fibers move past flicker bar  120 . As the fibers rebound from contact with the flicker bar  120 , the fibers release debris particles, which fall into waste chamber  140 . 
     It is therefore apparent that there has been provided, in accordance with the present invention, a brush belt for removing electrostatically charged particles from a surface that fully satisfies the aims and advantages set forth hereinabove. While this invention has been described in conjunction with specific embodiments thereof, it will be evident to those skilled in the art that many alternatives, modifications, and variations are possible to achieve the desired results. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variations which may fall within the spirit and scope of the following claims.