Abstract:
An image transfer system for use in an indirect printer includes a support roller for a transfix roller. The support roller is configured to apply pressure to a center portion of a nip formed between a transfix roller and an imaging drum while the transfix roller applies pressure to the ends of the nip. This configuration is particularly advantageous for use with imaging drums and transfix rollers having thin walls.

Description:
TECHNICAL FIELD 
       [0001]    The system described below relates to printers in which an ink image is transferred from a surface of an image receiving member to a recording medium, and, more particularly, to printers in which the image is transferred to the recording medium as the medium passes through a nip formed between a transfix roller and an image receiving member. 
       BACKGROUND 
       [0002]    The word “printer” as used herein encompasses any apparatus, such as a digital copier, book marking machine, facsimile machine, multi-function machine, etc., that produces an image with a colorant on recording media for any purpose. Printers that form an image on an image receiving member and then transfer the image to recording media are referenced in this document as indirect printers. Indirect printers typically use intermediate transfer, transfix, or transfuse members to facilitate the transfer and fusing of the image from the image receiving member to the recording media. In general, such printing systems typically include a colorant applicator, such as a printhead, that forms an image with colorant on the image receiving member. Recording medium is fed into a nip formed between the surface of the image receiving member and a transfix roller to enable the image to be transferred and fixed to the print medium so the image receiving member can be used for formation of another image. 
         [0003]    A schematic diagram for a typical indirect printer that includes a printhead that ejects phase change ink on the image receiving member to form an image on the member is illustrated in  FIG. 8 . The solid ink imaging device, hereafter simply referred to as a printer  110 , has an ink loader  112  that receives and stages solid ink sticks. The ink sticks progress through a feed channel of the loader  112  until they reach an ink melt unit  114 . The ink melt unit  114  heats the portion of an ink stick impinging on the ink melt unit  114  to a temperature at which the ink stick melts. The liquefied ink is supplied to one or more printheads  116  by gravity, pump action, or both. Printer controller  122  uses image data to be reproduced on media to control the printheads  116  and eject ink onto a rotating print drum or image receiving member  140  as image pixels to form an ink image. Recording media  120 , such as paper or other recording substrates, are fed from a sheet feeder  118  to a position where the ink image on the image receiving member  140  can be transferred to the media. To facilitate the image transfer process, the media  120  are fed into a nip between the transfer, sometimes called transfix roller  150 , and the rotating image receiving member  140 . In the nip, the transfix roller  150  presses the media  120  against the image receiving member  140 . An assembly  124  of lever arms, camshafts, cams, and gears urged into motion by an electrical motor responds to signals from the controller  122  to move the transfix roller into and out of engagement with the image receiving member  140 . Indirect or offset printing refers to a process, such as the one just described, of generating an ink or toner image on an intermediate member and then transferring the image onto some recording media or another member. 
         [0004]    To optimize image resolution in an indirect printer, the conditions within the nip are carefully controlled. The transferred ink drops should spread out to cover a specific area to preserve image resolution. Too little spreading leaves gaps between the ink drops while too much spreading results in intermingling of the ink drops. Additionally, the nip conditions are controlled to maximize the transfer of ink drops from the image member to the print medium without compromising the spread of the ink drops on the print medium. Moreover, the ink drops should be pressed into the paper with sufficient pressure to prevent their inadvertent removal by abrasion thereby optimizing printed image durability. Thus, the temperature and pressure conditions are important parameters for image quality and need to be carefully controlled throughout the nip. 
         [0005]    The image receiving member  140  is a hollow cylinder mounted about a shaft that is supported on its ends by stiff endbells incorporated into the shaft. The shaft of the image receiving member  140  deflects under the pressure of the transfix roller  150  at the nip  144 . Some deflection of the image receiving member  140  is inherent. Because the shaft of the image receiving member  140  is supported only at the endbells, it deflects more in the middle than at the ends and, thus, applies more pressure to the nip  144  at the ends than at the middle. However, too much deflection by the image receiving member  140  diminishes the quality of the print because of inconsistencies in the pressure at the nip  144 . The thickness of the image receiving member  140  is selected to require as little material as possible to keep manufacturing costs down. However, the thickness of the image receiving member  140  is also selected so that, under pressure from the transfix roller  150  at the nip  144 , it does not deflect so much that it diminishes the quality of the print. 
         [0006]    The transfix roller  150  includes a cylinder mounted about a shaft and is formed of steel, or another material with similar properties. As described above with reference to the image receiving member  140 , the transfix roller  150  deflects more in the middle than at the ends because it is supported only at the ends. The variation in deflection along the length of the transfix roller  150  results in variation of the pressure along the length of the nip  144 . The thickness of the transfix roller  150 , like that of the image receiving member  140 , is selected to balance material costs with the amount of deflection along the transfix roller  150 . 
         [0007]    When an indirect printer, such as the one shown in  FIG. 8 , is powered on, the image receiving member needs to be heated to a predetermined temperature that enables the melted phase change ink to remain on the surface of the image receiving member, yet be malleable enough for transfer and fixing to the recording media when the ink image enters the nip. An image receiving member with a larger thermal mass requires more thermal energy and more time to reach the predetermined temperature than an image receiving member that has a smaller thermal mass. One way to reduce the time required for an image receiving member to reach the predetermined temperature is to reduce the thickness of the wall of the image receiving member. While this reduction in wall thickness does decrease the time required for the image receiving member to reach the predetermined temperature, it also affects the pressure conditions in the nip formed with the transfix roller. Without a change in the transfix roller, the pressure in the nip becomes less uniform and weaker in the center of the nip between the ends of the transfix roller and the image receiving member, especially as the walls of the image receiving member are thinned. 
         [0008]    As shown in  FIG. 9 , a nip formed with an image receiving member having a thick wall (for example, 9 mm) has one pressure profile from one end to the other end of the nip across the width of the transfix roller and image receiving member, while a nip formed with an image receiving member having a thin wall (for example, 4.5 mm) has another profile. As used in this document, a “thin wall” refers to a wall of a roller having a thickness that is 7 mm or less, while a “thick wall” refers to a wall of a roller having a thickness that is 8.5 mm or more. The ends of the nip  144  correspond to the ends of the image receiving members  140  and the transfix rollers  150 . The pressure profile for the thin wall image receiving member has a pressure at each end of the profile that is greater than the pressure at each end of the profile for the thick wall image receiving member. The pressure is highest at the ends of the nips  144  because the image receiving members  140  and the transfix rollers  150  are supported at the ends and are the most rigid at those areas. Additionally, the pressure in the center of the thin wall image receiving member profile is substantially below the pressure in the center of the thick wall image receiving member profile. The pressure is lowest at the middle of the nips  144  because the image receiving members  140  and the transfix rollers  150  deflect the most at the middle, the area that is the farthest from the supported ends. These pressure differences across the length of the nip may cause wrinkles in the recording media and corresponding print quality defects. 
         [0009]    One way to modify the nip conditions to help ensure the print quality is adequate and the media is not distorted with thinner wall image receiving members is to add a crown to the transfix roller. As shown in  FIG. 10 , a crown  160  is a convex profile formed in the elastomer coat  153  of the transfix roller  150 . Accordingly, the diameter  190  of the transfix roller  150  is largest at the middle of the crown  160 . The crown  160  provides additional support to the center of the transfix roller  150 , increasing pressure at the center of the nip and compensating for the decreased pressure in the center of the nip generated by the thinner wall of the image receiving member. As the wall of the image receiving member is made thinner, the crown of the transfix roller needs to be larger to compensate for the additional image receiving member deflection. The height of a crown, however, is limited by practical constraints in manufacturing and usage. 
         [0010]    Additionally, the height of a crown can generate wrinkles and/or image quality defects when print conditions are particularly likely to form either transverse or longitudinal wrinkles. Longitudinal wrinkles are formed in the print media in a direction parallel to the direction that print media is fed through the nip (also known as the process direction). One print condition that is likely to generate longitudinal wrinkles is the center of the print media moving through the nip at a faster rate than the edges of the print media. This condition can result from a crown that is not high enough to compensate for the greater deflection, and resulting lower pressure, in the center of the nip. This condition can also result from high density, process direction images along the edges of the print. Another condition that is likely to generate longitudinal wrinkles is print media being A3 or a similar size. Another condition that is likely to generate longitudinal wrinkles is the orientation of the paper grain in a direction perpendicular to the direction that the print media is fed through the nip (also known as the cross-process direction). Increasing the pressure applied at the center of the nip reduces the occurrence of longitudinal wrinkles. 
         [0011]    Transverse wrinkles are formed in the print media in the cross-process direction. One print condition that is likely to generate transverse wrinkles is the edges of the print media moving through the nip at a faster rate than the center of the print media. This condition can result from a crown that is too high and overcompensates for the deflection, resulting in high pressure, in the center of the nip. This condition can also result from high density, process direction images in the center of the print or over the entire print. Another condition that is likely to generate transverse wrinkles is the print media being A3 or a similar size. Another condition that is likely to generate transverse wrinkles is a process direction orientation of the paper grain. Decreasing the pressure applied at the center of the nip reduces the occurrence of transverse wrinkles. 
         [0012]    As described above, longitudinal wrinkles and transverse wrinkles can be generated by opposite conditions and, thus be reduced by opposite adjustments. Accordingly, enabling adjustment of the pressure along the nip when print conditions include stresses likely to generate longitudinal or transverse wrinkles is a desirable goal. 
       SUMMARY 
       [0013]    An image transfer system for use in an indirect printer has been developed. The image transfer system includes a first roller, a second roller, and another rotatable roller. The first roller has a cylindrical body with a first length and a first diameter. The second roller has a cylindrical body with a second length and a second diameter. The first length and the second length are substantially equal and the first diameter is greater than the second diameter. The second roller is configured to move into and out of engagement with the first roller to apply pressure to a first end and a second end of the first roller. The other rotatable roller is positioned to interpose at least a portion of the second roller between the first roller and the other rotatable roller. The other rotatable roller has a cylindrical body with a third length, which is substantially less than the first length and the second length. The other roller is configured to apply pressure through the second roller to a location between the first end and the second end of the first roller. 
         [0014]    A method of operating a printer to transfer an ink image from an image receiving member to media has been developed. The method includes moving a roller having a thin wall into engagement with the image receiving member to form a nip, applying pressure to a first end and a second end of the roller, and applying pressure to a portion of the roller between the first end and the second end of the roller while media moves through the nip and the pressure is being applied to the first end and the second end of the roller. 
         [0015]    A replaceable unit configured for mounting in an image transfer system has been developed. The replaceable unit includes a first roller and another rotatable roller. The first roller has a cylindrical body with a first length and a thin wall. The other rotatable roller has a cylindrical body with a second length, which is substantially less than the first length. The other roller is configured to apply pressure to a first position on the first roller to transfer the pressure to a portion of a nip formed with the first roller and another roller 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  depicts an image transfer system having an image receiving member, a transfix roller, and a support roller to be used in an indirect printer. 
           [0017]      FIG. 2  depicts the image receiving member of  FIG. 1 . 
           [0018]      FIG. 3  depicts the transfix roller of  FIG. 1 . 
           [0019]      FIG. 4  depicts the support roller of  FIG. 1 . 
           [0020]      FIG. 5  depicts a side view of the image transfer system of  FIG. 1  also including a controller and actuators. 
           [0021]      FIG. 6  depicts another image transfer system having an image receiving member, a transfix roller, two support roller, a controller, and actuators to be used in an indirect printer. 
           [0022]      FIG. 7  depicts another image transfer system having an image receiving member, a transfix roller, and a support roller located within the transfix roller to be used in an indirect printer. 
           [0023]      FIG. 8  depicts a typical indirect printer capable of utilizing one of the image transfer systems depicted in  FIG. 1 ,  6  or  7 . 
           [0024]      FIG. 9  depicts a graph of a pressure gradient along a nip in a typical indirect printer. 
           [0025]      FIG. 10  depicts a transfix roller having a crown. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The image transfer system  200  shown in  FIG. 1  includes an image receiving member  220 , a transfix roller  240  and a support roller  260  that compensates for the deflection at the center of the image receiving member  240  and the pressure variation along the nip  290 . The transfix roller  240  is configured in a known manner to be moved into and out of engagement with the image receiving member  220 . The transfix roller  240  is configured to apply pressure to the ends of the image receiving member  240  and form the nip  290  for the transfer of the ink images from the image receiving member  220  to media passing through the nip  290 . The support roller  260  is configured to be moved into and out of engagement with the transfix roller  240  to apply varying amounts of pressure to the central area of the transfix roller  240 . The pressure applied by the support roller  260  is transferred through the transfix roller  240  to the central area of the image receiving member  220  at the nip  290 . 
         [0027]      FIG. 2  depicts detailed features of the image receiving member  220  including an image receiving member wall  222  forming an image receiving member body  224 . The image receiving member body  224  is cylindrically shaped and has an image receiving member length  226  and an image receiving member diameter  228 . The image receiving member  220  also has a first image receiving member end  230  and an opposite second image receiving member end  232 . Between the first image receiving member end  230  and the second image receiving member end  232  is an image receiving member central portion  234  having a middle area  236  that is approximately equidistant between the first image receiving member end  230  and the second image receiving member end  232 . 
         [0028]    The image receiving member  220  is made of aluminum or of some other material having similar thermal, mechanical and hardness properties. The surface of the image receiving member  220  is one to which ink temporarily adheres upon ejection from a printhead and also one from which ink can be transferred to print media upon application of pressure and heat at the nip  290  (shown in  FIG. 1 ). The image receiving member wall  222  is symmetrical because it rotates to receive ink from the ink applying device, which is configured to form ink images on the image receiving member wall  222 , and then deposit the ink on recording media passing through the nip  290  (shown in  FIG. 1 ). The image receiving member length  226  is approximately 13.6 inches to accommodate standard sheets of printing paper as the print media. The image receiving member diameter  228  should be large enough to enable efficient transfer of ink from the image receiving member  220  to the print media as the print media passes through the nip  290  (shown in  FIG. 1 ). For example, if the image receiving member diameter  228  is about 6.33 inches, the image receiving member  220  has a circumference of 19.9 inches and can make one full rotation per printed page for an 11″ by 17″ sheet of printing paper or two 8.5″ by 11″ sheets of paper. The image receiving member  220  in  FIG. 1  and  FIG. 2  has a diameter of about 6.33 inches and has a circumference of 19.9 inches. In other embodiments of the image receiving member described herein, the member has other commonly known diameters and circumferences. 
         [0029]      FIG. 3  depicts detailed features of the transfix roller  240  including a transfix roller wall  241  defining a transfix roller body  242  having a transfix roller length  244  and a transfix roller diameter  246 . The transfix roller wall  241  has a thickness  245 . The transfix roller body  242  is cylindrically shaped and defines a longitudinal opening  248  therethrough. The transfix roller  240  further includes a first transfix roller end  250  and an opposite second transfix roller end  252 . Between the first transfix roller end  250  and the second transfix roller end  252  is a transfix roller central portion  254  including a supported portion  256  which contacts the support roller  260 . 
         [0030]    The transfix roller length  244  is approximately 13.6 inches long to apply pressure evenly along the width of standard sheets of printing paper as the print media. In other words, the transfix roller length  244  is substantially equal to the image receiving member length  226  (shown in  FIG. 2 ). The transfix roller diameter  246  does not need to be as large as the image receiving member diameter  228  (shown in  FIG. 2 ) because the transfix roller  240  is used to apply pressure to transfer ink from only a portion of the image receiving member  220  to the print media. Thus, the transfix roller  240  can have a circumference of less than 19.9 inches and rotate at a higher frequency than the image receiving member  220 . 
         [0031]    The transfix roller  240  is slightly more flexible than the transfix roller  150  (shown in  FIG. 8 ). The transfix roller  240  can be made more flexible than the transfix roller  150  by thinning the walls of the roller  150  to the thickness  245  of the walls  241  of the transfix roller body  242 . For example, the thickness  245  of the walls  241  can be reduced from approximately 11.6 mm to approximately 2.6 mm. Alternatively, the transfix roller  240  can be made more flexible than the transfix roller  150  by making the transfix roller body  242  out of a material having a lower elastic modulus than steel. Alternatively, the transfix roller  240  can be made more flexible than the transfix roller  150  by thinning the walls  241  and making the transfix roller body  242  out of a material having a lower elastic modulus than steel. The flexibility of the transfix roller  240  enables it to receive and distribute loads applied at various points along the transfix roller length  244  to generate a more uniform pressure at the nip  290  (shown in  FIG. 1 ). 
         [0032]      FIG. 4  depicts detailed features of the support roller  260  including a support roller shaft  262  and a support roller body  268 . The support roller shaft  262  has a first support roller shaft end  264  and an opposite second support roller shaft end  266 . The support roller body  268  has a support roller length  270 . The support roller body  268  is cylindrically shaped and is positioned on the support roller shaft  262  to contact the supported portion  256  of the transfix roller  240  (shown in  FIG. 3 ). In other words, the support roller body  268  is positioned at a location approximately equidistant between the first image receiving member end  230  and the second image receiving member end  232  (shown in  FIG. 2 ) when the support roller  260  is arranged in the image transfer system shown in  FIG. 1 . The support roller length  270  is substantially less than the transfix roller length  244  (shown in  FIG. 3 ) and the image receiving member length  226  (shown in  FIG. 2 ) because the support roller  260  applies pressure to only a small area in the central portion  254  of the transfix roller  240  (shown in  FIG. 3 ). 
         [0033]    Returning to  FIG. 1 , the image transfer system  200  is arranged such that the transfix roller  240  is positioned between the support roller  260  and the image receiving member  220 . This arrangement enables the support roller  260  to apply pressure through the transfix roller  240  to the image receiving member  220 . The location of the support roller body  268  at the supported portion  256  of the transfix roller  240  enables the support roller  260  to apply pressure to the middle area  236  of the image receiving member  220 . 
         [0034]      FIG. 5  is a schematic diagram depicting an end view of the image transfer system  200 . As is illustrated more clearly from an end view, the image transfer system  200  includes a system of rotatable cylindrical rollers. In particular, the image receiving member  220  acts as a first roller, the transfix roller  240  acts as a second roller, cooperating with the first roller to form the nip  290 , and the support roller  260  acts as a third roller (also referred to as another rotatable roller or a single rotatable roller or a rotatable roller), interposing at least a portion of the second roller between the first roller and the third roller. Thus, the third roller (or the support roller  260 ) is configured to influence the nip  290  formed between the first roller (the image receiving member  220 ) and the second roller (the transfix roller  240 ) by acting on the second roller (the transfix roller  240 ). 
         [0035]    As shown in  FIG. 5 , the image transfer system  200  further includes a controller  280 , a transfix roller actuator  282 , and a support roller actuator  284 . The transfix roller actuator  282  is operatively connected to the transfix roller  240  and to the controller  280 . The support roller actuator  284  is operatively connected to the support roller  260  and to the controller  280 . The controller  280  is configured to operate the transfix roller actuator  282  to move the first transfix roller end  250  and the second transfix roller end  252  (shown in  FIG. 3 ) toward the first image receiving member end  230  and the second image receiving member end  232  (shown in  FIG. 2 ), respectively. The controller  280  is also configured to operate the support roller actuator  284  to move the first support roller shaft end  264  and the second support roller shaft end  266  (shown in  FIG. 4 ) toward the first transfix roller end  250  and the second transfix roller end  252  (shown in  FIG. 3 ), respectively. Thus, the controller  280  is configured to move the transfix roller  240  toward the image receiving member  220  to generate pressure at the ends of the nip  290  and to move the support roller  260  toward the transfix roller  240  to generate pressure at the center of the nip  290 . 
         [0036]    The controller  280  is further configured to receive data pertaining to print conditions that are likely to generate longitudinal wrinkles or are likely to generate transverse wrinkles. The data can include a longitudinal stress parameter or a transverse stress parameter such as, for example, a paper type or an amount and distribution of ink to be used to print an image. In particular, data pertaining to the paper type can include paper size, stiffness, and grain direction. Data pertaining to the amount and distribution of ink to be used can include the location of ink on the page, ink density at the center of the page, ink density at the edges of the page, and ink density across the whole page. The controller  280  is configured to use these data to identify a wrinkle parameter for an ink image to be printed. 
         [0037]    The controller  280  is configured to operate the transfix roller actuator  282  and the support roller actuator  284  with reference to the identified wrinkle parameter for an ink image. In particular, the controller  280  is configured to adjust the pressure applied to the image receiving member  220  at the ends of the nip  290  by the transfix roller  240  and at the center of the nip  290  by the support roller  260 . These adjustments can regulate the pressure applied along the length of the nip  290  to avoid generating wrinkles during printing. Additionally, these adjustments can be made while the printer is in operation, avoiding time-consuming reprinting or manual adjustment of the image transfer system  200 . 
         [0038]    The controller  280  can be configured with electronic components and programmed instructions stored in a memory operatively connected to or made part of the controller. In response to the controller  280  executing the programmed instructions and operating the electronic components, the controller receives data, such as the data described above, and identifies a wrinkle parameter for an image to be printed. In one embodiment, the controller  280  can be configured to receive data from a user interface operatively connected to the controller  280  and operated by a user. The user identifies printed pages that are wrinkled and then enters information about each wrinkled page into the user interface. The user can enter information about, for example, the paper type, the amount and distribution of the ink, the presence of longitudinal wrinkles, and the presence of transverse wrinkles. The controller  280  adjusts the pressure along the nip  290  with respect to the information entered into the user interface and reprints the pages. Alternatively, the printer can scan printed pages for wrinkles and the controller  280  can receive the above information via a feedback loop rather than from the user interface. 
         [0039]    In another embodiment, the controller  280  can be configured to receive data pertaining to images to be printed prior to printing. The controller  280  can then adjust the pressure at the nip  290  with respect to the data to avoid printing wrinkled pages. Before commencing printing, the paper size, stiffness, and grain direction for the pages to be printed can each be entered manually or the information can be stored within the controller  280  and identified according to the paper type entered by the user. Additionally, the printer can generate electronic image information for images to be printed, including, for example, the location of ink on the page or the ink density at the center and the edges of the page and over the whole page. The controller  280  can use the data pertaining to the paper type and to the amount and distribution of the ink to identify wrinkle parameters for the images to be printed and adjust the pressure applied along the nip  290  to compensate for the wrinkle parameters and prevent wrinkled prints. 
         [0040]    In another embodiment, the controller  280  can be configured to store data received from the user interface or from within the printer in a memory. The controller  280  can thus generate a catalog of data and wrinkle parameters and use the catalog to identify conditions of new print jobs that are likely to generate wrinkled prints and adjust the pressure along the nip  290  accordingly. The controller  280  can, thus, gradually eliminate the need to receive data pertaining to wrinkle parameters from a user. Additionally, the controller  280  can be configured to receive the data from a network connected to other printers. The catalogs of the printers in the network can be combined to identify a greater number of conditions likely to generate wrinkled prints and the controller  280  can receive data from the combined catalog. 
         [0041]    Referring now to  FIGS. 1-5 , in operation, the image transfer system  200  applies pressure to both the edges and the center of the nip  290  and varies the amount of pressure applied to the center of the nip  290  to prevent the formation of longitudinal and transverse wrinkles. The controller  280  operates the transfix member actuator  282  to move the first and second transfix roller ends  250 ,  252  toward the first and second image receiving member ends  230 ,  232 . The controller  280  thereby moves the transfix roller  240  into engagement with the image receiving member  220  to form the nip  290 . The controller  280  regulates the amount of pressure applied to the image receiving member  220  at the ends of the nip  290  by controlling the force generated by the transfix member actuator  282  upon the first and second transfix roller ends  250 ,  252 . 
         [0042]    The controller  280  also operates the support roller actuator  284  to move the first and second support roller shaft ends  264 ,  266  toward the first and second transfix roller ends  250 ,  252 . The controller  280  thereby moves the support roller body  268  into engagement with the transfix roller  240 . The pressure applied to the support roller  260  is transferred through the support roller body  268 , through the supported portion  256  of the transfix roller  240 , and to the image receiving member  220  at the center of the nip  290 . The pressure applied to the transfix roller  240  by the support roller  260  increases the amount of pressure applied to the nip  290  by moving the transfix roller  240  into engagement with the image receiving member  220 . Accordingly, a transfix roller  240  with thinner walls can be used with fewer concerns about the transfix roller  240  being too flexible and being unable to apply enough pressure to the image receiving member  220 . As mentioned above, the walls  241  can have a thickness of, for example, 2.6 mm. 
         [0043]    The pressure applied by the support roller  260  is applied to a location on the image receiving member  220  that is approximately equidistant between the first and second image receiving member ends  230 ,  232 . The controller  280  regulates the amount of pressure applied to the image receiving member  220  at the center of the nip  290  by controlling the force exerted by the support roller actuator  284  upon the first and second support roller shaft ends  264 ,  266 . 
         [0044]    Thus, the controller  280  simultaneously controls the amount of pressure applied to the image receiving member  220  at both the ends and the center of the nip  290  while media moves through the nip  290 . The amount of pressure applied by the transfix roller  240  to the ends of the nip  290  can be different than the amount of pressure applied by the support roller  260  to the center of the nip  290 . Additionally, the controller  280  can vary the amounts of pressure applied to the ends and/or to the center of the nip  290  as necessary during operation of the printer to achieve and maintain the desired load along the length of the nip  290 . 
         [0045]    The controller  280  receives data to identify the wrinkle parameter for an image to be printed. The controller  280  then operates the transfix roller actuator  282  and the support roller actuator  284  with reference to the identified wrinkle parameter. When the identified wrinkle parameter indicates that the image to be printed includes stresses likely to generate longitudinal wrinkles, the controller  280  operates the transfix roller actuator  282  and the support roller actuator  284  such that the amount of pressure applied to the image receiving member  220  at the center of the nip  290  by the support roller  260  is increased relative to the amount of pressure applied to the image receiving member  220  at the ends of the nip  290  by the transfix roller  240 . Conversely, when the identified wrinkle parameter indicates that the image to be printed includes stresses likely to generate transverse wrinkles, the controller  280  operates the transfix roller actuator  282  and the support roller actuator  284  such that the amount of pressure applied to the image receiving member  220  at the center of the nip  290  by the support roller  260  is decreased relative to the amount of pressure applied to the image receiving member  220  at the ends of the nip  290  by the transfix roller  240 . 
         [0046]    In an alternative embodiment, the image transfer system  200  can include more than one support roller  260 . For example, as illustrated in  FIG. 6 , the image transfer system  200 ′ includes two support rollers  260 ′. The image transfer system  200 ′ is configured and operates in substantially the same manner as image transfer system  200  described above, except that the controller  280 ′ operates the support roller actuator  284 ′ to move two support roller bodies  268 ′ into contact with the transfix roller  240 ′ to apply pressure to the image receiving member  220 ′ at the center of the nip  290 ′. As shown in  FIG. 6 , the two support rollers  260 ′ are positioned at a different location on the circumference of the transfix roller body  242 ′. A front view of the image transfer system  200 ′ is substantially identical to the front view of the image transfer system  200  shown in  FIG. 1  because both support roller bodies  268 ′ are aligned along the length of the image receiving member  220 ′ and are positioned approximately equidistantly between the first and second image receiving member ends. 
         [0047]    In another alternative embodiment, shown in  FIG. 7 , the image transfer system  200 ″ includes a support roller  260 ″ positioned within the longitudinal opening  248 ″ of the transfix roller body  242 ″. The image transfer system  200 ″ is configured and operates in substantially the same manner as image transfer system  200  described above, except that only a portion of the transfix roller  240 ″, rather than the entire transfix roller  240 , is interposed between the support roller  260 ″ and the image receiving member  220 ″. The support roller body  268 ″ moves into contact with an inside surface  243 ″ of the transfix roller body  242 ″ and the pressure applied to the support roller  260 ″ is transferred through the transfix roller body  242 ″ to the image receiving member  220 ″ at the center of the nip  290 ″. 
         [0048]    The image transfer system  200 ″ having a support roller  260 ″ internally located within the transfix roller  240 ″ is preferred because it avoids adding wear to the outer surface of the transfix roller  240 ″. Use of an internally located support roller  260 ″ is only possible in a printer that has a transfix roller large enough to contain the support roller  260 ″ and operate properly. In a printer that has a smaller transfix roller, an externally located support roller  260  or  260 ′ is required due to practical size limitations. 
         [0049]    Those skilled in the art will recognize that numerous modifications can be made to the specific implementations described above. Therefore, the following claims are not to be limited to the specific embodiments illustrated and described above. The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.