Patent Publication Number: US-7583911-B2

Title: Corona charging device cleaning apparatus and method of cleaning a corona charging device

Description:
BACKGROUND 
   The present disclosure relates to corona charging device cleaning apparatus and methods of cleaning corona charging devices. 
   Cross-referenced is a co-pending commonly assigned U.S. patent application Ser. No. 11/327,585 filed Jan. 6, 2006 by Michael F. Zona et al. entitled PIN ARRAY SCOROTRON CHARGING SYSTEM FOR SMALL DIAMETER PRINTER PHOTORECEPTORS, the disclosure of which is incorporated herein by reference in its entirety. That application discloses a compact corona charging system for uniformly charging a small radius moving surface. The charging system includes integral independently controllable leading and trailing corona charging sections for sequentially charging a small radius moving surface. The leading corona charging section includes a first elongated corona discharge member transverse to the moving surface and connectable to a first high voltage current supply and a first corona screen grid member connectable to a first screen grid control voltage supply. The trailing corona charging section includes a second elongated corona discharge member transverse to the moving surface and connectable to a second high voltage current supply and a second corona screen grid member connectable to a second screen grid control voltage supply and electrically independent of the first corona screen grid member and the first screen grid control voltage supply. The first corona screen grid member is interposed between the first elongated corona discharge member and the small radius moving surface. The second corona screen grid member is interposed between the second elongated corona discharge member and the small radius moving surface. 
   Charging photoreceptor drums has been accomplished using contact charging methods. Some methods use bias charging rolls due to their small size and ease of manufacture. Charge roll technology uses high AC voltages for uniform charging that generate reactants on the photoreceptor transport layer which can degrade the transport layer causing physical wearing of the surface. This wearing limits the useable life of the photoreceptor device, which in turn drives up system costs. These costs can be especially high in color systems that may have multiple photoreceptor devices. 
   Other charging methods implement corona charging systems that include electric corona discharge wires or pin arrays. These systems are known as corotrons or scorotrons (the latter having discharge screen control grids). The systems use corona discharge to generate ions that are directed to the surface of the drums or onto belts that are wrapped around drums. 
   A corotron usually consists of a thin wire(s) that is stirring within a metal enclosure which is open on one face. The wire is subjected to several thousand volts. The intense electric fields around the wires cause the air molecules to ionize, and thus charged ions, whose polarity depends on that of the high voltage, are driven onto the photoconductor surface. A typical corotron may have multiple individual corona wires placed at a relatively small distance from the photoconductor surface. 
   A scorotron usually consists of a series of corona wires with a screen or grid composed of larger diameter wires placed between the corona wires and the photoconductor surface. The screen wires are biased to a potential close to that desired at the photoconductor. The photoreceptor charging process ceases when the surface potential reaches the potential of the screen grid bias. 
   SUMMARY 
   The demand for more compact corona charging systems has increased as the technology relating to such devices as printers, copiers and fax machines has become more advanced and the devices more sophisticated. A smaller, compact footprint scorotron has been developed, for example, as described in the above-incorporated U.S. patent application Ser. No. 11/327,585. Due to the miniature nature of the developed scorotron, less airflow travels through the charging device as compared to a larger, conventional corotron or scorotron. As a result, toner and/or silica contamination collects on the inner surface of the side shield of the compact scorotron. The build up of contamination causes an insulating layer to be formed on each side shield, which adversely effects the field formation between the pin tip (or wires) and the side shield. That is, the resulting insulating layer reduces the electric field between the pin tip (or wires) and the side shield. The reduction of the electric field reduces the amount of ion generation at the pin tips and causes the photoreceptor voltage to become non-uniform. The non-uniformity yields poor halftone uniformity on document prints. 
   The present disclosure describes corona charging device cleaning apparatus and methods of cleaning corona charging devices that clean an inner surface of a side shield of a corona charging device to maintain superior electric field formation and maintain good uniformity over the life of the charging device. Exemplary cleaning apparatus and methods clean the side shields to prevent the contaminating insulating layer of toner particles and silica growth from being formed. 
   In exemplary embodiments, there is provided a corona charging device cleaning apparatus including a support member including two side surfaces that face in opposite directions; and a side shield cleaning member attached to each side surface to clean an inner surface of a side shield of a corona charging device. 
   In this exemplary embodiment, the side shield cleaning member prevents a contamination layer of toner or silica from forming an insulating layer on the inner surface of the side shields of the corona charging device. As a result, the electric field formation between charging components and a screen grid of the corona charging device is maintained, and the uniformity of the photoreceptor voltage is not adversely effected. 
   In various exemplary embodiments, a screen grid cleaning member is attached to a surface of a concavity of the support member to additionally clean a screen grid of the corona charging device. 
   In various exemplary embodiments, a charging-component cleaning member is disposed inside a cavity portion of the support member to additionally clean a charging component of the corona charging device. 
   In various exemplary embodiments, the corona charging device cleaning apparatus includes a combination of the side shield cleaning member, the screen grid cleaning member, and/or the charging-component cleaning member. 
   In various exemplary embodiments, the side shield cleaning member includes an abrasive material. 
   In various exemplary embodiments, the side shield cleaning member includes an abrasive material that is more abrasive than the screen grid cleaning member and more abrasive than the charging-component cleaning member. 
   In various exemplary embodiments, the side shield cleaning member is at least one of foam, felt, sandpaper, nylon, metal fibers, stiff plastic fibers, a brush. 
   In various exemplary embodiments, the charging-component cleaning member is comprised of bristles. 
   In various exemplary embodiments, the side shield cleaning member is replaceably attachable to the support member. In these exemplary embodiments, the side shield cleaning member can be replaced without having to replace the support member. 
   In various exemplary embodiments, the corona charging device cleaning apparatus may be incorporated in a xerographic device. 
   In various exemplary embodiments, the xerographic device may include a corona charging device, and an actuator that is operatively connected to the corona charging device cleaning apparatus. The actuator moves the cleaning apparatus substantially along a length of the corona charging device during a cleaning operation. 
   In various exemplary embodiments, the xerographic device may further include guide means connected to an end portion of the support member to guide an advancement of the cleaning apparatus along the length of the corona charging device. 
   In various exemplary embodiments, the corona charging device cleaning apparatus is detachably connected to a rod that is manually movable substantially along a length of the corona charging device. 
   Exemplary embodiments may provide a method of cleaning a corona charging device, the method including providing a side shield cleaning member to clean an inner surface of a side shield of the corona charging device, and moving the side shield cleaning member substantially along a length of the corona charging device to remove particles from the inner surface of the side shield. 
   In various exemplary embodiments of the method, the side shield cleaning member is abrasive. 
   In various exemplary embodiments of the method, the side shield cleaning member is at least one of foam, felt, sandpaper, nylon, metal fibers, stiff plastic fibers, a brush. 
   In exemplary embodiments, there is provided a corolla charging device cleaning apparatus including a support member having two side surfaces that face in opposite directions away from each other, a concavity, and a cavity portion. A side shield cleaning member is attached to the side surfaces to clean an inner surface of a side shield of a corona charging device. A screen grid cleaning member is attached to the concavity of the support member to clean a screen grid of the corona charging device. A charging-component cleaning member is disposed inside the cavity portion of the support member to clean a charging component of the corona charging device. 
   In these exemplary embodiments, the side shield cleaning member includes an abrasive material. 
   In these exemplary embodiments, the side shield cleaning member is more abrasive than the screen grid cleaning member and more abrasive than the charging-component cleaning member. 
   In these exemplary embodiments, the side shield cleaning member is at least one of foam, felt, sandpaper, nylon, metal fibers, stiff plastic fibers, a brush. 
   The term “image forming device” or “printer” as used herein broadly encompasses various printers, copiers, fax machines, multifunction machines or systems, xerographic or otherwise, unless otherwise defined in a claim. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various exemplary embodiments are described in detail, with reference to the following figures, in which: 
       FIG. 1  is a schematic side view of an exemplary compact corona charging device with which the disclosed cleaning apparatus may be used. 
       FIG. 2  is an inverted perspective view of an exemplary cleaning apparatus. 
       FIG. 3  is an inverted perspective view of an exemplary alternative cleaning apparatus. 
       FIG. 4  schematically illustrates a configuration of a xerographic device including an exemplary cleaning apparatus. 
       FIG. 5  is a perspective view of an exemplary cleaning apparatus with a rod that is detachably connected to the cleaning apparatus. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
     FIG. 1  provides a schematic representation of one example of a corona charging device  10  for charging the surface of a small diameter photoreceptor  12  with a compact scorotron  20  which may be substantially conventional other than as described herein. This scorotron  20  has first and second separate pin charging members  21  and  22 . The pin charging members  21  and  22  may be differently angled (that is, they are not parallel to each other). The charging members may be comprised of wires instead of pins. Electrical connections to the pin charging members  21  and  22  for their corona generation may be separate, adjustable high voltage DC current supplies  21 A and  22 A. The generated electrical corona emissions from the tips of the charging members  21  and  22  are respectively controlled by a dual or split screen system of underlying separate screen grids  23  and  24  between the charging members  21  and  22  and the surface  12 . The screen grids  23  and  24  may be differently angled. The screen grids  23  and  24  may have separately adjustable control voltage supplies  23 A and  24 A. 
   The pin arrays  21  and  22  and two electrically independent grids  23  and  24  provide a suitable non-contact charging system for various small diameter photoreceptor surfaces. For example, in some embodiments, photoreceptor diameter is less than 60 mm. The charging device  20  also is relatively compact. For example, in some embodiments, the charging device  20  may be about 18 mm wide. In some embodiments, the pin arrays  21  and  22  may be spaced as close as 6 mm apart from each other from charging tip end to charging tip end. Each may be angled so that each is approximately perpendicular to a line drawn tangent the surface of the photoreceptor  12 . Each of the screen grids  23  and  24  may be positioned perpendicular to its respective pin array and may be spaced approximately 6 mm away from its pin array charging tip end, in some embodiments. The spacing between the screen grids  23  and  24  and the surface of the photoreceptor  12  may be approximately 1.5 to 2.0 mm, in some embodiments. Each of the grids  23  and  24  are electrically isolated from the other so that an independent DC voltage from  23 A and  24 A can be applied to each. The angle of the charging pin arrays  21  and  22  relative to the surface of the photoreceptor  12  and the angle of the two screen grids  23  and  24  relative to the surface of the photoreceptor  12  allows for an overall system width smaller than normal in the conventional two pin array charging devices. 
   Side shields  25  and  26  of the charging device  20  may be positioned on either side of the two pin arrays. In some embodiments, the side shields  25  and  26  may be spaced approximately 18 mm from each other with the two pin arrays  21  and  22  centered therebetween. Each of the side shields  25  and  26  may be electrically connected to its closest grid. 
   Owing to the compactness of the corona charging system, toner contamination collects on the inner surfaces  25 A,  26 A of the side shields  25  and  26 . The build up of toner contamination causes an insulating layer to be formed on the side shields  25  and  26  which adversely effects the field formation between the tips of the pin arrays  21  and  22  (or wires) and the side shields  25  and  26 . That is, the resulting insulating layer reduces the electric field between the tips of the pin arrays  21  and  22  (or wires) and the side shields  25  and  26 . The reduction of the electric field reduces the amount of ion generation at the tips the pin arrays  21  and  22  and causes the voltage of the photoreceptor  12  to become non-uniform. The non-uniformity yields poor halftone uniformity on document prints. 
     FIG. 2  is a perspective inverted representation of one corona charging device cleaning apparatus  30 . The apparatus  30  may be used to clean a corotron, scorotron or any other corona charging device that is used in printers, copiers, fax machines or other image forming devices. In this exemplary embodiment, the apparatus  30  is relatively compact so as to clean a compact corona charging device. A compact corona charging device may be one that charges a photoreceptor having a diameter, for example, of 60 mm or less. In this exemplary embodiment, the apparatus may have a width of about 18 mm or less in order to movably fit between the side shields  25  and  26  of the charging device  20 . However, in other embodiments, the dimensions of the apparatus  30  may be larger in order to clean a relatively larger corona charging device that charges a photoreceptor having a diameter greater than 60mm. That is, the cleaning apparatus  30  and method are not limited to use with compact charging devices that charge small diameter photoreceptors. 
   The corona charging device cleaning apparatus  30  includes a support member  32 . The support member  32  may be comprised of a metal, a plastic, or a composite material. The support member  32  is not limited to any particular shape, except that the shape preferably is compatible to fit within and clean components of the charging device  20 . The support member  32  includes two side surfaces  33  and  34 . The side surfaces  33  and  34  face in opposite directions from each other, such that each side surface  33  and  34  faces a corresponding inner surface  25 A,  26 A of the side shields  25  and  26  of the charging device  20 . The side surfaces  33  and  34  may be planar or non-planar. The configuration (orientation, shape, etc.) of the side surfaces  33  and  34  may match the inner surfaces  25 A,  26 A of the side shields  25  and  26 . 
   A side shield cleaning member  35  is attached to each side surface  33  and  34 . The side shield cleaning member  35  cleans an inner surface  25 A,  26 A of the side shields  25  and  26  of the charging device  20  when the cleaning apparatus  30  is moved relative to the charging device  20 . Each side shield cleaning member  35  may be disposed within the boundary of its side surface  33  or  34 , or may extend beyond the side surfaces  33  and  34 . The side shield cleaning member  35  may include an abrasive material that scrubs the inner surfaces  25 A,  26 A of the side shields  25  and  26  (when the cleaning apparatus is moved relative to the charging device  20 ) to remove toner or silica contamination that collects on the inner surface of the side shields  25  and  26  as a result of the charging operation of the charging device  20 . The build up of toner contamination causes an insulating layer to be formed on the side shields  25  and  26 , which reduces the electric field between the charging-components of the charging device  20  and the side shields  25  and  26 . When used regularly to clean the charging device  20 , the side shield cleaning member  35  prevents the contaminating insulating layer from being formed, and thus maintains superior electric field formation and good uniformity over the life of the charging device  20 . 
   Each side shield cleaning member  35  may be comprised of one or a combination of foam, felt, sandpaper, nylon, metal fibers, stiff plastic fibers, and a brush. Additionally, each side shield cleaning member  35  may be replaceable. That is, if the side shield cleaning member  35  becomes worn, or otherwise is in need of repair, it may be detached from the support member  32  and replaced with a new or refurbished side shield cleaning member  35 . Thus, if the support member  32  has a longer usable life than the side shield cleaning member  35 , the support member  32  would not need to be replaced when the side shield cleaning member  35  is no longer effective due to regular use over the period of its normal life. This embodiment saves costs associated with providing a new support member  32  when the side shield cleaning member  35  is in need of repair or replacement. 
   The corona charging device cleaning apparatus  30  may include a guide  40  connected to an end portion  31  of the support member  32  to guide movement of the apparatus  30  along the length of the charging device  20 . The guide  40  may include an aperture through the end portion  31  of the support member  32 . The aperture may slidably accommodate therein a dowel, track or rail along which the apparatus  30  moves during a cleaning operation. In another embodiment, the guide  40  may include a slot or groove. Further, the guide  40  may be connected to a portion of the support member  32  other than the end portion  31 . 
     FIG. 3  is an inverted schematic view of an alternative cleaning apparatus  30 ′. The apparatus  30 ′ may include all of the features and alternatives of the cleaning apparatus  30  illustrated and discussed with respect to  FIG. 2 . In the alternative embodiment, the support member  32 ′ further includes a concavity  37  extending between the side surfaces  33  and  34 . A screen grid cleaning member  36  is attached to the concavity  37  so as to clean a screen grid  23 ,  24  of the charging device  20 . Thus, the cleaning apparatus  30 ′ of this embodiment additionally cleans the screen grids  23 ,  24  during the cleaning operation of the side shields  25  and  26 . 
   The support member  32 ′ also includes a cavity portion  39  between the side surfaces  33  and  34 . Charging-component cleaning members  38  are disposed inside the cavity portion  39  so as to clean the charging components (such as wires or the pin arrays  21  and  22 ) of the charging device  20 . The charging-component cleaning member  38  includes a plurality of bristles. Thus, the cleaning apparatus  30 ′ of this preferred embodiment cleans all at once the inner surface of each side shield  25  and  26 , the screen grids  23  and  24 , and the charging component ( 21  and  22 ) of the charging device  20  during the cleaning operation of the side shields  25  and  26 , during one cleaning operation. 
   As an alternative, the charging component cleaning members  38  can be provided in combination with the side shield cleaning members  35 , but without providing the grid cleaning members  36  on the support  32 ′. 
   In preferred embodiments, the side shield cleaning member  35  is more abrasive (that is, it is rougher and/or harder) than the screen grid cleaning member  36  and/or the charging-component cleaning member  38 . 
   In each of the alternative embodiments, the side shield cleaning member  35  may be made of one or a combination of foam, felt, sandpaper, nylon, metal fibers, stiff plastic fibers, and a brush. Additionally, the side shield cleaning member  35  may be replaceable. Further, the corona charging device cleaning apparatus  30 ′ in each of the alternative embodiments may include the guide  40  described with respect to the embodiment of  FIG. 2 . 
     FIG. 4  illustrates a configuration of xerographic device  42  having an exemplary corona charging device cleaning apparatus  30 , the charging device  20 , the photoreceptor  1 - 2 , and an actuator  46 . In the xerographic device  42  of this embodiment, the charging device  20  is disposed above the photoreceptor  12  at a predetermined distance, for example at a distance of approximately 1.5 to 2.0 mm. The cleaning apparatus  30  is disposed within the xerographic device  42  so that it can be moved into and then within the charging device  20  so as to be movable substantially along the length of the charging device  20  during a cleaning operation. The apparatus  30  is operatively connected to the actuator  46 . The actuator  46  moves the apparatus  30  along substantially an entire length of the charging device  20  during a cleaning operation. The actuator  46  can be, for example, a motor and lead screw configuration. The operation, connection and control of the actuator  46  with the apparatus  30  may be accomplished by appropriate operation and connection of conventional control systems. In an exemplary system, a lead screw is placed through a threaded hole in support member  32  of the cleaning apparatus  30 . A motor, mounted inside the xerographic machine is mechanically coupled to one end of the lead screw. The motor is actuated in one direction to rotate the lead screw to traverse the cleaning apparatus  30  along the length of the charging device  20 . A sensing mechanism is used to sense when the cleaning apparatus  30  has reached the end of the charging device  20 , after which the motor is reversed to return the cleaning apparatus  30  to its original, pre-cleaning position. The apparatus  30  may be removable from within the charging device  20  for maintenance or replacement of a cleaning member of the apparatus  30 . After cleaning, the cleaning apparatus  30  preferably is moved to a position where it is outside of the imageable area of the photoreceptor  12  so that the cleaning apparatus  30  does not interrupt the imaging process. As an alternative to movably mounting the cleaning apparatus  30  within the xerographice device  42 , the cleaning apparatus  30  can be a stand-alone device used, for example by a technician to manually clean the charging device  20 . 
     FIG. 5  illustrates an exemplary cleaning apparatus  30 ″ with a rod  50  that is detachably connected to the cleaning apparatus  30 ″. In this embodiment, the support member  32 ″ of the apparatus  30 ″ includes a connection portion  52  on a surface substantially perpendicular to the direction of movement of the apparatus during a cleaning operation. The connection portion  52  includes insertion openings  56  disposed along a hollow perimeter thereof. The rod  50  may have a plurality of protruding teeth  54  at a first end thereof. To detachably connect the rod  50  to the apparatus  30 ″, the teeth  54  of the rod  50  are inserted into the insertion openings  56  and the rod  50  is rotated along its longitudinal axis to rotate the teeth  54  to a locking position within the hollow perimeter of the connection portion  52 . To disconnect the rod  50  from the apparatus  30 ″, the rod is rotated along its longitudinal axis in a direction opposite the direction for insertion, until the teeth  54  are able to be withdrawn from the insertion openings  56 . Alternatively, the connection of the rod  50  and the apparatus  30 ″ may be accomplished by other conventional connection systems (for example, threads). 
   When attached to the support member  32 ″ of the apparatus  30 ″, the rod  50  may be used to manually move the cleaning apparatus  30 ″ substantially along a length of the charging device  20 . The rod  50  may be comprised of a metal, a plastic, or a composite material. The rod  50  may be attached to an embodiment of the apparatus  30 ″ in which the apparatus  30 ″ has already been installed in the xerographic device  42 . 
   In practice, the charging device  20  is cleaned by providing the side shield cleaning member  35  that cleans an inner surface  25 A,  26 A of the side shields  25  and  26  of the charging device  20 , and moving the side shield cleaning member  35  substantially along a length of the charging device  20  to remove particles from the inner surface  25 A,  26 A of each side shield  25  and  26 . Optionally, at least one of the screen grid cleaning member  36  and the charging-component cleaning member  38  may be provided to additionally clean the screen grids  23  and  24  and the charging component (such as  21  and  22 ) of the charging device  20 . In each of the above options, the alternative embodiments of the apparatus  30 , the actuator  46  and/or the rod  50 , as discussed above, may be incorporated. 
   While the invention has been described in conjunction with exemplary embodiments, these embodiments should be viewed as illustrative, and not limiting. 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, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art and are also intended to be encompassed.