Abstract:
In a xerographic printing apparatus, a charge device is used to apply a charge to a photoreceptor. The charge device includes a wire. A shuttle moves along the charge device, and includes a brush wherein the sides of the bristles contact the wire. When the brush moves along the wire, an accumulation of stray particles on the wire is made relatively smooth.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   Cross-reference is hereby made to the following patent application, being filed simultaneously herewith: CLEANING SYSTEM FOR A CHARGING DEVICE IN A XEROGRAPHIC PRINTER, U.S. Ser. No. 11/228,898, Publication No. 20070065173, published Sep. 16, 2005. 
   TECHNICAL FIELD 
   The present disclosure relates to a xerographic printing apparatus, and specifically to a mechanism for cleaning a charging device associated with the apparatus. 
   BACKGROUND 
   In the well-known process of electrostatographic or xerographic printing, an electrostatic latent image is formed on a charge-retentive imaging surface, and then developed with an application of toner particles. The toner particles adhere electrostatically to the suitably-charged portions of the imaging surface. The toner particles are then transferred, by the application of electric charge, to a print sheet, forming the desired image on the print sheet. An electric charge can also be used to separate or “detack” the print sheet from the imaging surface. 
   For the initial charging, transfer, or detack of an imaging surface, the most typical device for applying a predetermined charge to the imaging surface is a “corotron,” of which there are any number of variants, such as the scorotron or dicorotron. Common to most types of corotron is a bare conductor, in proximity to the imaging surface, which is electrically biased and thereby supplies ions for charging the imaging surface. The conductor typically comprises one or more wires (often called a “corona wire”) and/or a metal bar forming saw-teeth, the conductor extending parallel to the imaging surface and along a direction perpendicular to a direction of motion of the imaging surface. Other structures, such as a screen, conductive shield and/or nonconductive housing, are typically present in a charging device, and some of these may be electrically biased as well. The corotron will have different design parameters depending on whether it is being used for initial charging, transfer, or detack. 
   In a practical application of charging devices, dust and other debris may collect in or around the corotron. Clearly, the presence of such material will adversely affect the performance of the corotron, and may cause dangerous arcing conditions. Therefore periodic cleaning of the charging device is often desired, and many schemes exist in the prior art for cleaning the charging device, such as by wiping the corona wire. In high-end printing machines, this wiping may be performed by a motorized wiper that travels along the corotron wire. 
   U.S. Pat. No. 5,485,255 discloses a wiping mechanism for cleaning a corona wire as well as a scorotron screen, which employs a lead screw. 
   U.S. Pat. No. 6,449,447 discloses a control system for a wiping mechanism for cleaning a corona wire, in which the wiping process is initiated when arcing conditions are detected in the charge device. 
   SUMMARY 
   According to one aspect, there is provided an apparatus useful in electrostatographic printing. A charge device, including a wire extending along an extension direction, places a charge on an imaging surface. A shuttle, movable along the extension direction, includes at least one brush including a plurality of bristles, the bristles defining sides contacting the wire. When the shuttle is moved in the extension direction, the brushes promote a substantially uniform layer of accumulated material on the wire. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevational view of a charging device associated with an Imaging surface. 
       FIG. 2  is a perspective view showing, in isolation, essential parts of the wiping mechanism for a charging device. 
       FIG. 3  is a plan view, such as shown by arrow  3  in  FIG. 1 , of a shuttle movable within a housing of a charge device. 
       FIG. 4  is an elevational view through line  4 - 4  in  FIG. 3 . 
       FIG. 5  is a photomicrograph of a portion of corotron wire that has undergone a certain amount of use. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is an elevational view of a charging device associated with an imaging surface. The imaging surface is shown as formed by a drum photoreceptor  10 , although belt photoreceptors and other charge receptors (such as intermediate belts, as used in color printing) are common as well. Disposed near the photoreceptor  10  is a charge device generally indicated as  20 , which, depending on a larger context, may be for initial charging, transfer, or detack in a printing process. As mentioned above, charge devices, such as corotrons, scorotrons, dicorotrons, etc., have many design variants, but typically include one or more corona wires such as  22 , a conductive shield and/or nonconductive housing  24  including sidewalls such as  26 , as well as a screen  28 ; each of these elements may be biased as required for a particular purpose. As shown, wire  22  extends parallel to the imaging surface formed by photoreceptor  10 , and in an “extension direction” perpendicular to a direction of rotation or motion of photoreceptor  10 . 
   When it is desired to clean wire  22 , or screen  28 , there is provided what is here generally called a “shuttle”  30 . With further reference to  FIG. 2 , shuttle  30  is a piece which includes a tooth  32  which interacts with the windings of a lead screw  34 ; shuttle  30  further includes brushes  36 ,  37  for cleaning wire  22 , as will be described in detail below, and wiper  38  which cleans screen  28 . 
   As can be seen in  FIG. 2 , shuttle  30  interacts with lead screw  34  so that, when lead screw  34  is rotated in a particular direction, the shuttle  30  travels along the lead screw, whereby a wiper such as  36  or  38  can wipe or clean the wire  22  and screen  28 . The lead screw  34  is here rotated by a motor  40 , which can rotate the lead screw in either direction. (In a practical embodiment, there may also be any number of guide rails or other surfaces, not shown, to facilitate proper motion of the shuttle  30 .) Although the present embodiment includes a lead screw, other mechanisms for moving the shuttle  30  can be used, such as a linear motor, or other mechanisms for converting the rotational motion of a motor such as  40  to linear motion, such mechanisms including pulleys, belts, racks, etc. 
     FIG. 3  is a plan view, such as shown by arrow  3  in  FIG. 1 , of a shuttle  30  movable within housing  24  of charge device  20  (only a portion of the entire length of charge device  20  is shown). Disposed on the shuttle  30  and moveable therewith are two scrapers, each indicated as  50 . Each scraper  50  contacts a portion of the inner surface of an adjacent sidewall  26 . In one embodiment, each scraper  50  is largely made of a flexible material, such as Mylar® or of a thin strip of metal such as copper and is mounted on shuttle  30  to exhibit a natural resiliency, causing the scraper  50  to be urged against sidewall  26 . When shuttle  30  is moved along the length of charge device  20 , each scraper  50  scrapes residual toner and any other material from the inner surface of sidewall  26 . 
     FIG. 4  is an elevational view through line  4 - 4  in  FIG. 3 , showing how each brush  36 ,  37  contacts, on the sides (as opposed to the ends) of some of the bristles thereof, a portion of the surface of wire  22 . Although it is known in the prior art to use a brush to wipe a flat surface, such as the side of a member forming a pin array, in a charging device, the use of brushes to clean a wire presents unique advantages. 
     FIG. 5  is a photomicrograph of a portion of corotron wire such as  22 , which has undergone a certain amount of use. As can be seen, with use in a printer, the wire attracts stray materials such as airborne dirt and airborne droplets of oil. When these stray materials accumulate on the wire  22 , the materials, such as oxides, form a non-smooth surface coating on the wire  22 , in particular a surface characterized by “fuzz” and/or distinct “dendrites” which grow with further use of the wire in the relatively dirty airborne environment within a xerographic printer. 
   The use of the sides of bristles of brushes to clean or otherwise affect the surfaces of a corona wire  22  disturbs the growth of dendrites on the corona wire, which promotes a relatively uniform surface of accumulated material on the wire. In contrast, the use of a foam material on the shuttle, which is common in the prior art, has the object of actually removing accumulated material from the wire surface. In some practical situations, the maintenance of a fairly uniform layer of accumulated material on the wire results in a longer life (as opposed to periodically removing the layer) of the wire before replacement of the wire is mandated. 
   In one practical embodiment, the brushes  36 ,  37  are made of natural monofilament polypropylene having a fiber diameter of 0.007 inch (0.18 mm) and a fiber density of 125 ends per inch. Each brush is ultrasonically welded to its backing to withstand a pullout force of 22 newtons. 
   It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.