Abstract:
A system and method to replace a transfer belt of a color laser printer transfer belt assembly without replacing the entire assembly, including one or more novel holding fixtures and a method for releasing the tension on the transfer belt prior to removal of the transfer belt from the assembly, then reapplying tension to a replacement transfer belt and, optionally, replacing the motor assembly and/or the microchip that controls operation of the transfer belt assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a utility patent application based on, incorporates by reference and claims the benefit of priority of U.S. provisional patent application 60/949,121, filed Jul. 11, 2007. 

   FIELD OF INVENTION 
   The invention relates generally to the field of laser toner printers, and more specifically to repair and remanufacture color laser toner printer transfer belt assemblies. 
   BACKGROUND OF INVENTION 
   In recent years a plural color or full color image forming apparatus of the electro-photographic type, for example, laser color printers, there has been put into practical use a so-called in-line type image forming apparatus in which a plurality of photo-sensitive drums are arranged in a plane in conformity with respective colors arranged sequentially. Toner images of the respective colors are formed on respective photosensitive drums are successively super-imposed on a media, typically paper that is positioned on a transfer belt to thereby form a color image as the transfer belt and the media are advanced in a forward direction in the plane. The transfer belt is positioned around a plurality of rollers, each roller having its axis of rotation perpendicular to the plane in which the transfer belt moves as the color image is formed on the media. 
   U.S. Pat. No. 6,600,893 (“the &#39;893 patent”) describes a full-color image forming apparatus, also referred to as a full-color printer, as an example of a conventional electrophotoprinting; color laser printer including a conventional in-line transfer belt assembly. 
   The image forming assembly is provided with four image forming portions or sub-assemblies, often referred to as cartridges, e.g., a yellow image forming portion or yellow cartridge, a magenta image forming portion or magenta cartridge, a cyan image forming portion or cyan cartridge and a black image forming portion or black cartridge. Each of the cartridges also includes drum-shaped electro-photographic photosensitive members, referred to as drums that function as image bearing members. 
   Each drum is negatively charged and driven or rotated at a pre-determined speed through use of a stepper motor assembly. Primary chargers function to uniformly charge the surfaces of the respective drums to a predetermined potential of negative polarity. Each cartridge contains the toner therein and, during operation causes the toner of each color to adhere to an electrostatic latent image formed on each drum to thereby develop the latent image as a toner image. 
   The transfer rollers as transferring means are disposed in respective transferring portions or zones so as to be capable of contacting with the respective drum with the intermediate transfer belt interposed there between. 
   The transfer belt is passed over two belt-conveying rollers. This transfer belt is formed of dielectric resin such as polycarbonate, polyethylene terephtalate, resin film or polyvinylidene fluoride resin film. 
   The toner image is transferred directly to the transfer belt through the transferring rollers with the media interposed there between the transfer belt and the drums, thus forming a color image with un-fixed, pre-melted toner powder. The media with the pre-melted toner powder then moves on to the fuser rollers, which in turn fuse the toner by means of heat onto the paper and thus fixing it. 
   The transfer belt apparatus is, usually, an easy to remove mechanism that has to be replaced once a certain amount of cartridges has been used or when it is damaged. Normally, if not damaged, the printer will notify the user when it is time to replace the transfer apparatus. On some printers, once the message appears, it is possible to reset the unit again. In some models, though there is no option to reset the printer and failing to replace the unit will end-up in inability to print. Prior experience shows that on the models that the transfer unit can be reset the printer can function with reasonable performance for a great deal of time without replacing the transfer unit. 
   Failure to replace the transfer unit for a long period of time might cause poor transfer efficiency thus poor print result. Moreover, excess use of the transfer unit might cause complete failure of the transfer belt, which might cause a permanent damage to the printer or the cartridges. 
   SUMMARY OF THE INVENTION 
   The presently disclosed system and methods overcome the drawbacks of conventional color laser printers, particularly in regard to transfer belt assembly repair and replacement by providing structures and methods for replacing a transfer belt without the need to replace the entire transfer belt assembly. 
   It is an object of the present invention to provide a method and process for repairing and remanufacturing a transfer belt apparatus for color laser toner printers in which the original, worn out or damaged transfer belt is replaced with a new transfer belt. 
   It is also an object of the present invention that a method for resetting the counter on the transfer belt assembly can be reset or replaced in order to allow for operation of the transfer belt assembly in a way that will yield printing operation that meets OEM specifications. 
   These and other embodiments, features, aspects, and advantages of the invention will become better understood with regard to the following description, appended claims and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and the attendant advantages of the present invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is cross-sectional, schematic view of a color laser printer illustrating the major components of the multi-color cartridges and transfer belt assembly; 
       FIG. 2  is a perspective view of the transfer belt assembly of  FIG. 1 ; and, 
       FIG. 3  is a perspective view of the transfer belt assembly of the type shown in  FIG. 1  and positioned in a belt replacement jig. 
   

   Reference symbols or names are used in the Figures to indicate certain components, aspects or features shown therein. Reference symbols common to more than one Figure indicate like components, aspects or features shown therein. 
   DETAILED DESCRIPTION 
   Referring to  FIG. 1  a cross-sectional, schematic view of a color laser printer, image-forming apparatus  20  is shown. Also, for convenience the major components of the printer will be described with reference to an x-y-z axis Cartesian coordinate system. Details of the construction and operation of a printer of the type shown in  FIG. 1  may be found in the &#39;893 patent. The printer  20  includes a housing  22  and a media exit shelf  24 . Typically the media is paper and shelf or tray  24  is referred to as the paper exit shelf or tray  24 . The printer also includes an internal paper feed tray  26  that generally lie in an x-z plane, with the x directions going from left to right, and the z directions going into and out of the page as shown in  FIG. 1 . The y directions go from bottom to top in  FIG. 1 . Pick-up rollers  28 ,  28  are shown with the paper feed in the direction of arrow  30 . The axes of rotation of the rollers  28 ,  28  extend into the page of  FIG. 1  in the z direction. 
   The printer  20  is provided with four image forming portions or cartridges portions that extend along in distances or regions  31 ,  32 ,  33  and  34  in the x direction: the yellow portion or region  31  having a cartridge with yellow toner; the magenta portion or region  32  having a cartridge with magenta toner; the cyan portion or region  32  having a cartridge with cyan toner; and a black portion or region  34  having a cartridge with black toner. The order of the color can vary. Drum-shaped electro-photographic photosensitive members, referred to as drums, are shown at  36 ,  38 ,  40  and  42 , and each of the axes of rotation extends into the page in the z direction. These drums function as image bearing members. 
   Each of the drums  36 ,  38 ,  40  and  42  is negatively charged by a corresponding primary charge roller,  44 ,  46 ,  48  and  50 , respectively, and driven at a pre-determined speed. The axis of rotation of each primary charge roller also extends into the page in the z direction as shown in  FIG. 1 . The primary charge rollers, also known as primary chargers function to charge the surfaces of the corresponding, respective drums to a predetermined, uniform electrical charge of negative polarity. During operation each developing device, i.e., cartridge contains the respective colored toner and causes the toner of each color to adhere to an electrostatic, latent image formed on each drum. This latent image then becomes, or is developed into a toner image. 
   Transfer rollers  52 ,  54 ,  56  and  58  are positioned below transfer belt  60  and each of these rollers also has an axis of rotation that extends in the z direction, i.e., into the page as shown in  FIG. 1 . The transfer rollers disposed in the respective transferring portions or zones so as to be capable of cooperating with their respective drums on the opposite side of transfer belt  60 . As shown in  FIG. 1 , the transfer belt  60  moves in a direction left to right, and extends in an x-z plane. The cartridges are positioned above the transfer belt in the y direction and the transfer rollers are below the cartridges, with the transfer belt interposed in between. 
   As shown in  FIG. 2  stepper motor assembly  68  is attached to transfer belt apparatus housing  70 . The assembly  68  includes stepper motor  72  and a microchip  74  mounted on board  76 . Drive shaft  78  and gear  80  for the motor  72  are also shown in  FIG. 2 , with drive shaft  78  extending along in the z-direction. Transfer belt  60  is shown in an x-z plane, in  FIG. 1 . 
   The transfer belt  60  is an endless loop type belt that is passed over two belt conveying rollers  62  and  64  as shown in  FIGS. 1-2 . These rollers rotate in the direction shown with arrow  66  in roller  64  in  FIG. 1 . Their axes of rotation also extend in the z-direction in  FIG. 1 . The transfer belt is formed of a dielectric resin such as polycarbonate, polyethylene terephtalate, resin film or polyvinylidene fluoride resin film. 
   During operation the toner image on each of the drum  44 ,  46 ,  48  and  50  in  FIG. 1  is transferred directly to the media, typically paper, that is positioned on the transfer belt. This image transfer takes place through operation of the transfer rollers and together these components cooperate to form a color image with one or more layers of un-fixed, pre-melted toner powder forming an image on the paper as the transfer belt moves right to left through the various cartridge regions  31 - 34  as shown in  FIG. 1 . The paper with the pre-melted toner powder then moves on to fuser rollers  63  and  65  as shown in  FIG. 1 . The fuser rollers heat the toner in each of the various layers sufficient to cause the toner to fuse to the paper, and thus fix the color image to the paper. 
   The transfer belt assembly apparatus is removable from the printer housing for repair and/or replacement once a certain amount of cartridges has been used or when the belt on any other component in the assembly has been damaged. Typically, during normal operation the printer will notify the user when it is time to replace the transfer apparatus, with this notification based on the number of counts of rotation of the stepper motor. On some printers, once the message appears, it is possible to reset the counter so that the printer will operate again. In some models no reset option is provided to reset the printer. For those models, failing to replace the transfer belt assembly will means that the printer will not be operable to print. It is believed that for the models of printers in which the transfer belt assembly counter can be reset, those printers can function with reasonable performance for a significant time without a need to replace the transfer belt assembly. 
   Failure to replace the transfer unit for a long period of time might cause poor transfer efficiency and thus poor quality printing. Moreover, excessive use of the transfer belt assembly could cause complete failure of the transfer belt assembly, which in turn could cause permanent damage to the printer or to one or more of the cartridges. 
   With reference to  FIG. 3  a preferred embodiment of a holding fixture and method of transfer belt replacement will be described. First a spent or damaged transfer belt assembly is removed from the printer housing. Next the original transfer belt is removed through use of a novel holding fixture and process. Shown in  FIG. 3  is a novel first holding fixture  82  that holds the transfer belt assembly in a vertical position. During the repair operation and simultaneously with removal of the belt  60 , a bar  84  is slid into the transfer belt assembly in the z-direction and adjacent the spring-biased or loaded tensioning roller  86 . The spring tension release bar  84  is mounted on a second fixture, not shown. The second fixture is a structure that moveably holds or engages the bar  84  and permits movement of the bar  84  in the x-direction to move roller  86  to relieve or remove the spring tension that maintains tension on the transfer belt  60 . The spring-loaded roller  86  is also shown in  FIG. 1 . This operation releases tension on the belt and allows removal of the transfer belt  60  from the transfer belt housing  88  in a way that minimizes the potential for damaging the transfer belt and maximizing removal speed and efficiency. 
   Once the belt  60  has been removed from the assembly, a replacement belt is installed by reversing the order of actions described above. For convenience of disassembly and re-assembly, the holding fixture positions the transfer belt assembly vertically, as shown by arrow  90  pointing in the x-direction in  FIG. 3 . Bar  84  can also be integrated into the fixture  82  in order to permit pulling back the spring loaded rollers  86 , known also as tension rollers, that create the tension on the belt, in order to pull the old transfer belt out and to install the replacement transfer belt. The sides of the replacement belt are placed in the designated slots of two guide ribs, not shown, to prevent sideways slipping of the transfer belt during operation. Also, the motor assembly  68  and/or the microchip  74  can be removed and replaced with new or repaired components. 
   The bar  84  functions to permit replacement of the transfer belt  60  without disassembling the springs of the spring loaded roller  86 . In the absence of use of the bar  84 , replacement of the transfer belt would require bending of the transfer belt and that in turn has the potential of causing damage to the transfer belt, ultimately causes problems with printing quality. 
   Although specific embodiments of the invention have been described, various modifications, alterations, alternative constructions, and equivalents are also encompassed within the scope of the invention. 
   The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that additions, subtractions, deletions, and other modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims.