Abstract:
An apparatus for removing charged particles from a surface, the surface being capable of movement, including: a conductive brush in contact with the surface, the conductive brush having a first region thereof having a first polarity and a second region having a second polarity; the conductive brush includes a core and conductive fibers attached thereto, the core being electrically segmented into the first region and the second region.

Description:
This invention relates to an electrostatographic printer or copier, and more particularly concerns a cleaning apparatus for removing toner from an imaging surface. 
     Electrostatic brush (ESB) cleaners are designed to satisfy a requirement of cleaning a maximum toner mass entering the cleaner in a given number of passes through the cleaner. Generally these requirements are a maximum single pass cleaning requirement and a maximum two pass cleaning requirement. The single pass cleaning requirement is typically the residual toner mass on the photoreceptor belt following transfer under conditions of the highest developed mass (DMA) with the lowest transfer efficiency (TE). In some machines a mark-to-edge, or bleed edge, requirement raises the single pass cleaning requirement to the highest DMA level. The two pass cleaning requirement is typically cleaning of untransferred control patches and/or untransferred images in jam recovery. These input densities are equal to the highest DMA. It has been demonstrated that a two pass cleaning requirement is equivalent to cleaning half of the required toner mass in a single pass. 
     The two pass cleaning requirement, except in the case of mark-to-edge machines, is much more stressful than the single pass cleaning requirement. Therefore, the cleaning brushes are designed to clean the two pass requirement. Half of the toner is cleaned in each pass through the cleaner. In designing the cleaner the speed of the brushes, the number of fibers on the brushes, the interference of the brushes to the photoreceptor, the electrical bias on the brushes and the number of brushes are chosen to clean the equivalent single pass toner input. 
     Conventional multiple electrostatic brush cleaners consist of two or more brushes electrically biased to remove toner and other debris from the photoreceptor surface. Prior to the brushes a preclean charge device adjusts the toner charge of the incoming toner to the natural tribo charging polarity of the toner. This is known as right sign toner. Toner that does not charge to the polarity of the majority of the toner in the preclean charging step is known as wrong sign toner. The first brushes are biased opposite to the polarity of the right sign toner so that this toner can be removed. The last cleaning brush is biased opposite to the first brushes so that the wrong sign toner can be removed. Since there is only a small percentage of the toner that is wrong sign only a single brush is ever needed to clean the wrong sign toner mass. 
     Conventional multiple electrostatic brush cleaners have their single pass toner cleaning capacity limited by the amount of right sign toner that can be cleaned by the first brushes and the amount of wrong sign toner that can be cleaned by the last brush. As more cleaning capacity is required, such as for an increase in machine process speed, additional right sign cleaning brushes or additional cleaning passes must be added. These additions to the cleaning system are undesirable. Additional cleaning brushes increase the size and cost of the cleaner and may not fit in the available machine space. Additional cleaning passes decrease the productivity of the machine by requiring a longer recovery from paper jams. Additional cleaning passes impact the xerographic control of the machine by requiring a longer time to clean process control patches. 
     Briefly stated, and in accordance with one aspect of the present invention, there is provided An apparatus for removing charged particles from a surface, the surface being capable of movement, comprising: a conductive brush in contact with said surface, said conductive brush having a first region thereof having a first polarity and a second region having a second polarity; and mean for biasing said conductive brush. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features of the present invention will become apparent as the following description proceeds and upon reference to the drawings. 
         FIG. 1  is a schematic illustration of a printing apparatus incorporating the inventive features of the present invention. 
         FIG. 2  shows the cleaning device of the present invention. 
         FIG. 3  is a sideview of the cleaning device of the present invention. 
     
    
    
     While the present invention will be described in connection with a preferred embodiment thereof, it will 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 by the appended claims. 
     DETAILED DESCRIPTION 
     While the present invention will be described in connection with a preferred embodiment thereof, it will 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 by the appended claims. 
     For a general understanding of the illustrative electrophotographic printing machine incorporating the features of the present invention therein, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate identical elements.  FIG. 1  schematically depicts the various components of an electrophotographic printing machine incorporating the dual polarity electrostatic brush cleaner of the present invention therein. Although the dual polarity electrostatic brush cleaner of the present invention is particularly well adapted for use in the illustrative printing machine, it will become evident that the dual polarity electrostatic brush cleaner is equally well suited for use in a wide variety of printing machines and are not necessarily limited in its application to the particular embodiment shown herein. 
     Referring now to  FIG. 1 , the electrophotographic printing machine shown employs a photoconductive drum, although photoreceptors in the form of a belt are also known, and may be substituted therefor. The drum has a photoconductive surface deposited on a conductive substrate  14 . The drum moves in the direction of arrow  16  to advance successive portions thereof sequentially through the various processing stations disposed about the path of movement thereof. Motor  24  rotates roll  22  to advance drum in the direction of arrow  16 . Drum is coupled to motor  24  by suitable means such as a drive. 
     Initially successive portions of drum pass through charging station A. At charging station A, a corona generating device, in the form of a bias charge roll which is indicated generally by the reference numeral  26 , charges the drum  10  to a selectively high uniform electrical potential, preferably negative. Any suitable control, well known in the art including for example HVPS  28 , may be employed for controlling the corona generating device  26 . 
     In a digital printing machine as shown in  FIG. 1 , the drum  10  passes through imaging station B where a ROS (Raster Optical Scanner)  36  may lay out the image in a series of horizontal scan lines with each line having a specific number of pixels per inch. The ROS  36  may include a laser (not shown) having a rotating polygon mirror block associated therewith. The ROS  36  exposes the photoconductive surface  12  of the drum. 
     It should be appreciated that the printing machine may alternatively be a light lens copier. In a light lens copier a document to be reproduced is placed on a platen, located at the imaging station, where it is illuminated in known manner by a light source such as a tungsten halogen lamp. The document thus exposed is imaged onto the drum by a system of mirrors. The optical image selectively discharges the surface of the drum in an image configuration whereby an electrostatic latent image of the original document is recorded on the drum at the imaging station. 
     At development station C, a development system or unit, indicated generally by the reference numeral  34  advances developer materials into contact with the electrostatic latent images. Preferably, the developer unit includes a developer roller mounted in a housing. Thus, developer unit  34  contains a developer roller  40 . The roller  40  advances toner particles  45  into contact with the latent image. Appropriate developer biasing may be accomplished via power supply  42 , electrically connected to developer unit  34 . 
     The developer unit  34  develops the discharged image areas of the photoconductive surface. This developer unit contains magnetic black toner particles  45 , for example, which are charged by the electrostatic field existing between the photoconductive surface and the electrically biased developer roll in the developer unit. Power supply  42  electrically biases the magnetic roll  40 . 
     It should be evident that the present invention may be employed in a color printing machines; and as well in one component and two component development systems. 
     A sheet of support material  54  is moved into contact with the toner image at transfer station D. The sheet of support material is advanced to transfer station D by a suitable sheet feeding apparatus, not shown. Preferably, the sheet feeding apparatus includes a feed roll contacting the uppermost sheet of a stack of copy sheets. Feed rolls rotate so as to advance the uppermost sheet from the stack into a chute which directs the advancing sheet of support material into contact with the photoconductive surface of drum  10  in a timed sequence so that the toner powder image developed thereon contacts the advancing sheet of support material at transfer station D. 
     Transfer station D includes a corona generating device  58  in the form of a bias charge roll, which applies ions of a suitable polarity onto the backside of sheet  54 . This attracts the toner powder image from the drum  10  to sheet  54 . After transfer, the sheet continues to move, in the direction of arrow  62 , onto a conveyor (not shown) which advances the sheet to fusing station. 
     Fusing station includes a fuser assembly, indicated generally by the reference numeral  64 , which permanently affixes the transferred powder image to sheet  54 . Preferably, fuser assembly  64  comprises a heated fuser roller  66  and a pressure roller  68 . Sheet  54  passes between fuser roller  66  and pressure roller  68  with the toner powder image contacting fuser roller  66 . In this manner, the toner powder image is permanently affixed to sheet  54 . After fusing, a chute  70  guides the advancing sheet  54  to a catch tray  72  for subsequent removal from the printing machine by the operator. It will also be understood that other post-fusing operations can be included, for example, stapling, binding, inverting and returning the sheet for duplexing and the like. 
     After the sheet of support material is separated from the photoconductive surface of drum  10 , the residual toner particles carried by image and the non-image areas on the photoconductive surface are removed at cleaning station F. The vacuum assisted, electrostatic, brush cleaner unit or cleaning blade is disposed at the cleaning station F to remove any residual toner remaining on the surface of the drum. 
     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 incorporating the cleaning apparatus of the present invention therein. 
     According to the present invention and referring now to  FIG. 1 , cleaning station F, invariably, after the toner powder image has been transferred to the sheet of paper, residual toner particles remain adhering to the exterior surface of photoconductive drum  10 . At cleaning station F, the residual toner particles are removed from photoconductive drum  10 . Cleaning station F includes cleaner brush  100 , the brush  100  rotates in the direction of the respective arrow  101 . Brush  100  has a detoning roll  110 , to remove residual particles from the cleaner brush. The detoning roll  110  rotates in a direction shown by the arrow  111 . Scraper blade  112  removes the particles from the detoning roll  110  and guides these removed particles into a waste receptacle (not shown). It should be evident the present invention is applicable to cleaning systems where vacuum detone is used instead of bias roll detone. 
     Cleaning brush  100  includes a conductive core which is segment into brush segments  120 ,  121 ,  122 , and  123  (four quadrants are shown for illustration purposes it should evident that more or less quadrants could be used), so that brush pile fibers  130  connected to the core in brush segments  120 ,  121 ,  122 , and  123  can be biased both positively and negatively. Brush segments are biased through commutated contacts  200  and isolated by insulator (not shown) from each other to prevent shorting when biased to opposite polarities. Detoning roll  110  can be segmented as well (as shown in  FIG. 2 ), or the brush pile segment polarities can be reversed between cleaning and detoning against a grounded conventional detoning roll. 
     The dual polarity single brush cleaner of the present invention can be used to clean both right and wrong sign toner. Use of a single brush cleaner avoids the additional costs and space needed for a conventional dual brush cleaner. 
     In operation, power supply  205  and power supply  206  applies a bias of opposite polarity to commutated contacts  200 , which allows brush segments  120 ,  121 ,  122 , and  123  to be biased both positively and negatively. As residual toner coming out of region D is negatively charged by the negative preclean  73 , the brush  100 , rotating against the direction of motion, shown by arrow  16 , of the photoreceptor drum  10 , brush segment  120  is positively biased to remove negatively charged toner particles in residual region E. No residual toner should get to region B—that is past the bias charging roll and any toner that got to B from the cleaner would contaminate the BCR from the photoreceptor drum  10 . Toner cleaned from toner region E is detoned from the brush segments by segments of detoning roll  110  having the opposite polarity. The toner particles not removed (ie. “wrong sign” toner) by the first positively biased brush segment, on the photoreceptor belt  10 , are removed by the first negatively biased brush segment. The toner in cleaning brush segment is then removed by oppositely charged segment  105  of detoning roll  110 . 
     It is, therefore, apparent that there has been provided in accordance with the present invention, that fully satisfies the aims and advantages hereinbefore set forth. While this invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.