Abstract:
An indirect printer includes a system for alternating the pressure in a transfer nip by manipulating the transfer roller. The system includes a pair of pivotable collars mounted about the ends of the transfer roller. The collars are pivoted towards or away from one another to bend the transfer roller and to increase or decrease, respectively, the pressure in the longitudinal center of the nip.

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, in the case of transfix and transfuse members, 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 provide desirable thermal properties for the imaging surface, which are described below, and 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 to 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 relatively 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 relatively thin wall (for example, 4.5 mm) has another profile. Whether a wall is considered relatively thick or thin depends on the length of the image receiving member, the material with which the image receiving member is made, and the level of pressure required in the transfix nip. As used in this document, a “thin wall” refers to a wall of a roller having a thickness that is 5 mm or less, while a “thick wall” refers to a wall of a roller having a thickness that is 8.5 mm or more for an aluminum roller approximately 345 mm long and generating a minimum peak nip pressure of about 7 MPa. 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 can 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 interference 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 indirect printer has been developed that can selectively bend a transfer roller to regulate the pressure in a transfer nip more precisely. The indirect printer includes a first roller, a second roller, a first pivotable collar and a second pivotable collar. The second roller has a first end and a second end, and is configured to move into and out of engagement with the first roller to apply pressure to the first roller. The first pivotable collar supports the first end of the second roller and is configured to apply a first moment to the first end of the second roller. The second pivotable collar supports the second end of the second roller and is configured to apply a second moment to the second end of the second roller. 
         [0014]    A roller assembly has been developed for removable insertion in an indirect printer that enables pressure in a transfer nip to be regulated more precisely. The roller assembly includes a thin wall roller, a first pivotable collar, a second pivotable collar, and an actuator. The thin wall roller has a first end and a second end. The first pivotable collar supports the first end of the roller and is configured to apply a first moment to the first end of the roller. The second pivotable collar supports the second end of the roller and is configured to apply a second moment to the second end of the roller. The actuator is operatively connected to the first collar and the second collar and is configured to pivot the first collar and the second collar to apply the first and second moments to the first and second ends of the roller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  depicts an image transfer system having an image receiving member, a transfix roller, and a support assembly to be used in an indirect printer. 
           [0016]      FIG. 2  is a cross-sectional view of the image receiving member of  FIG. 1 . 
           [0017]      FIG. 3  is a cross-sectional view of the transfix roller of  FIG. 1 . 
           [0018]      FIG. 4A  depicts the support assembly of  FIG. 1  in a concave position. 
           [0019]      FIG. 4B  depicts the support assembly of  FIG. 1  in a convex position. 
           [0020]      FIG. 5  depicts an alternative embodiment of the image transfer system of  FIG. 1 . 
           [0021]      FIG. 6  depicts the support assembly configured to be used with the image transfer system of  FIG. 5  in a concave position. 
           [0022]      FIG. 7  depicts the support assembly configured to be used with the image transfer system of  FIG. 5  in a convex position. 
           [0023]      FIG. 8  depicts a typical indirect printer capable of utilizing one of the image transfer systems depicted in  FIG. 1  or  5 . 
           [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  204 , a transfix roller  208  and a support assembly  212  that adjusts the deflection at the center of the transfix roller  208  and the pressure variation along the nip  216 . The transfix roller  208  is configured in a known manner to be moved into and out of engagement with the image receiving member  204 . The transfix roller  208  is configured to apply pressure to the image receiving member  204  and form the nip  216  for the transfer of the ink images from the image receiving member  204  to media passing through the nip  216 . The support assembly  212  is configured to apply varying amounts of pressure to the central area and the end portions of the transfix roller  208 . The pressure applied to the transfix roller  208  by the support assembly  212  is transferred through the transfix roller  208  to the image receiving member  204  at the nip  216 . 
         [0027]      FIG. 2  depicts detailed features of the image receiving member  204  including an image receiving member wall  220  forming an image receiving member body  224 . The image receiving member body  224  is cylindrically shaped and has an image receiving member length  228  and an image receiving member diameter  232 . The image receiving member  204  also has a first image receiving member end  236  and an opposite second image receiving member end  240 . Between the first image receiving member end  236  and the second image receiving member end  240  is an image receiving member central portion  244  that is approximately equidistant between the first image receiving member end  236  and the second image receiving member end  240 . 
         [0028]    The image receiving member  204  is made of aluminum or of some other material having similar thermal, mechanical and hardness properties. The surface of the image receiving member  204  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  216  (shown in  FIG. 1 ). The image receiving member wall  220  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  220 , and then deposit the ink on recording media passing through the nip  216  (shown in  FIG. 1 ). The image receiving member length  228  is approximately 13.6 inches to accommodate standard sheets of printing paper as the print media. The image receiving member diameter  232  should be large enough to enable efficient transfer of ink from the image receiving member  204  to the print media as the print media passes through the nip  216  (shown in  FIG. 1 ). For example, if the image receiving member diameter  232  is about 6.33 inches, the image receiving member  204  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  204  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, circumferences, and lengths. 
         [0029]      FIG. 3  depicts detailed features of the transfix roller  208  including a transfix roller wall  248  having a transfix roller body  252  with a transfix roller length  256  and a transfix roller diameter  260 . The transfix roller wall  248  has a thickness  264 . The transfix roller body  252  is cylindrically shaped and defines a longitudinal opening  268  therethrough. The transfix roller  208  further includes a first transfix roller end  272  and an opposite second transfix roller end  276 . Between the first transfix roller end  272  and the second transfix roller end  276  is a transfix roller central portion  280 . 
         [0030]    The transfix roller length  256  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  256  is substantially equal to the image receiving member length  228  (shown in  FIG. 2 ). The transfix roller diameter  260  does not need to be as large as the image receiving member diameter  232  (shown in  FIG. 2 ) because the transfix roller  208  is used to apply pressure to transfer ink from only a portion of the image receiving member  204  to the print media. Thus, the transfix roller  208  can have a circumference of less than 19.9 inches and can rotate at a higher frequency than the image receiving member  204 . 
         [0031]    The transfix roller  208  is slightly more flexible than the transfix roller  150  (shown in  FIG. 8 ). The transfix roller  208  can be made more flexible than the transfix roller  150  by thinning the walls of the roller  150  to the thickness  264  of the walls  248  of the transfix roller body  252 . For example, the thickness  264  of the walls  248  can be reduced from approximately 11.6 mm to approximately 2.6 mm. Alternatively, the transfix roller  208  can be made more flexible than the transfix roller  150  by making the transfix roller body  252  out of a material having a lower elastic modulus than steel. Alternatively, the transfix roller  208  can be made more flexible than the transfix roller  150  by thinning the walls  248  and making the transfix roller body  252  out of a material having a lower elastic modulus than steel. The flexibility of the transfix roller  208  enables it to receive and distribute loads applied at various points along the transfix roller length  256  to generate a more uniform pressure at the nip  216  (shown in  FIG. 1 ). 
         [0032]      FIG. 4A  and  FIG. 4B  depict detailed features of the support assembly  212  including a first pivotable collar  284 , a second pivotable collar  288 , and a support member  292 . The first pivotable collar  284  pivotably supports the first transfix roller end  272  (shown in  FIG. 3 ) while still allowing the transfix roller  208  to rotate relative to the nip  216  (shown in  FIG. 1 ). Similarly, the second pivotable collar  288  pivotably supports the second transfix roller end  276  (shown in  FIG. 3 ) while still allowing the transfix roller  208  to rotate relative to the nip  216  (shown in  FIG. 1 ). The support member  292  has a first end  296  and an opposite second end  300  coupled together at a pivot connection  304 . The first end  296  is fixedly coupled to the first pivotable collar  284  and the second end  300  is fixedly coupled to the second pivotable collar  288 . The first end  296  and the second end  300  of the support member  292  define an angle  308  between them and are able to pivot at the pivot connection  304  to change the angle  308 . 
         [0033]    When the angle  308  between the first end  296  and the second end  300  is changed, the angles of the first pivotable collar  284  and the second pivotable collar  288  also change. As shown in  FIG. 4A , when the angle  308  is less than 180 degrees, the support member  292  is in a concave position relative to the transfix roller  208  (shown in  FIG. 3 ) and the first pivotable collar  284  and the second pivotable collar  288  are angled toward each other. Conversely, as shown in  FIG. 4B , when the angle  308  is greater than 180 degrees, the support member  292  is in a convex position relative to the transfix roller  208  (shown in  FIG. 3 ) and the first pivotable collar  284  and the second pivotable collar  288  are angled away from each other. In alternative embodiments, the first and second pivotable collars  284 ,  288  can be angled toward or away from each other using different mechanisms. For example, cams, gears, or hydraulic pistons directly applying force to the support ends can be used to angle the first and second pivotable collars  284 ,  288 . 
         [0034]    Returning now to  FIG. 1 , the image transfer system  200  further includes a controller  312  and a support member actuator  316 . The support member actuator  316  is operatively connected to the pivot connection  304  of the support member  292  and to the controller  312 . The controller  312  is configured to operate the support member actuator  316  to move the pivot connection  304  and change the angle  308  between the first end  296  and the second end  300  of the support member  292 . The controller  312  is also configured to operate the support member actuator  316  to apply downward pressure to the first pivotable collar  284  and the second pivotable collar  288 . 
         [0035]    Thus, the support member actuator  316  is configured to apply a moment M to each of the first and second pivotable collars  284 ,  288 . Each moment M consists of an amount of force, supplied in the form of pressure from the support member actuator  316 , and a tendency to rotate in one direction, determined by the angle  308 . Accordingly, the moments M of the first and second pivotable collars  284 ,  288  are equal in force and opposite in direction, one having a tendency to rotate in a counterclockwise direction and the other having a tendency to rotate in a clockwise direction. 
         [0036]    The moments M of the first and second pivotable collars  284 ,  288  are applied to the first and second transfix roller ends  272 ,  276  to bend the transfix roller  208 . When the angle  308  is less than 180 degrees, the transfix roller  208  is bent such that the first and second transfix roller ends  272 ,  276  are closer to the image receiving member  204  than the transfix roller central portion  280 . Accordingly, the pressure generated by the transfix roller  208  is greater at the ends of the nip  216  than in the middle. Conversely, when the angle  308  is greater than 180 degrees, the transfix roller  208  is bent such that the first and second transfix roller ends  272 ,  276  are farther from the image receiving member  204  than the transfix roller central portion  280 . Accordingly, the pressure generated by the transfix roller  208  is greater in the middle of the nip  216  than at the ends. 
         [0037]    The controller  312  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  312  is configured to use these data to identify a wrinkle parameter for an ink image to be printed. 
         [0038]    The controller  312  is configured to operate the support member actuator  316  with reference to the identified wrinkle parameter for an ink image. In particular, the controller  312  is configured to adjust the pressure applied to the image receiving member  204  along the nip  216  by the bending the transfix roller  208 . Bending the transfix roller  208  can regulate the pressure applied along the length of the nip  216  to avoid generating wrinkles during printing. For example, bending the transfix roller  208  so that the transfix roller central portion  280  is positioned approximately 50-100 micrometers closer to the image receiving member  204  than the ends of the roller can eliminate transverse wrinkles. Conversely, for example, bending the transfix roller  208  so that the transfix roller central portion  280  is positioned approximately 50-100 micrometers farther from the image receiving member  204  than the ends of the roller can eliminate longitudinal wrinkles. 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 . 
         [0039]    The controller  312  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  312  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  312  can be configured to receive data from a user interface operatively connected to the controller  312  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  312  adjusts the pressure along the nip  216  with respect to the information entered into the user interface and reprints the pages. Alternatively, the printer can scan printed pages with an optical sensor mounted within the printer (not shown) and a processor within the printer can execute programmed instructions to analyze the image data produced by the optical sensor to detect wrinkles. The controller  312  is operatively connected to this processor to receive the image data analysis for control of the transfer roller. 
         [0040]    In another embodiment, the controller  312  can be configured to receive data pertaining to images to be printed prior to printing. The controller  312  can then adjust the pressure at the nip  216  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  312  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  312  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  216  to compensate for the wrinkle parameters and prevent wrinkled prints. 
         [0041]    In another embodiment, the controller  312  can be configured to store data received from the user interface or from within the printer in a memory. The controller  312  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  216  accordingly. The controller  312  can, thus, gradually eliminate the need to receive data pertaining to wrinkle parameters from a user. Additionally, the controller  312  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  312  can receive data from the combined catalog. 
         [0042]    With continued reference to  FIG. 1 , in operation, the image transfer system  200  applies pressure to both the edges and the center of the nip  216  and varies the amount of pressure applied along the nip  216  to prevent the formation of longitudinal and transverse wrinkles. The controller  312  operates the support member actuator  316  to change the angle  308  between the first and second ends  296 ,  300  of the support member  292  and to apply downward pressure to the first and second pivotable collars  284 ,  288 . The angle  308  between the first and second ends  296 ,  300  of the support member  292  determines the directional tendency of each of the first and second pivotable collars  284 ,  288  and the first pivotable collar  284  applies the moment M to the first transfix roller end  272  and the second pivotable collar  288  applies the moment M to the second transfix roller end  276 . The moments M move the first and second transfix roller ends  272 ,  276  toward or away from the first and second image receiving member ends  236 ,  240  and move the transfix roller central portion  280  oppositely. The controller  312  thereby moves the transfix roller  208  into engagement with the image receiving member  204  to form the nip  216 . Accordingly, a transfix roller  208  with thinner walls can be used with fewer concerns about the transfix roller  208  being too flexible and being unable to apply an appropriate distribution of pressure to the image receiving member  204  at the nip  216 . As mentioned above, and shown in  FIG. 3 , the walls  248  can have a thickness  264  of, for example, 2.6 mm. 
         [0043]    The controller  312  regulates the amount of pressure applied to the image receiving member  204  along the nip  216  by controlling the force exerted by the support member actuator  316  upon the first and second pivotable collars  284 ,  288  and regulates the location of the pressure applied to the image receiving member  204  along the nip  216  by controlling the angle  308  between the first and second ends  296 ,  300  of the support member  292 . Thus, the controller  312  simultaneously controls the amount and location of pressure applied to the image receiving member  204  at both the ends and the center of the nip  216  while media moves through the nip  216 . The amount of pressure applied by the transfix roller  208  to the ends of the nip  216  can be different than the amount of pressure applied by the transfix roller  208  to the center of the nip  216 . Additionally, the controller  312  can vary the amounts of pressure applied to the ends and/or to the center of the nip  216  as necessary during operation of the printer to achieve and maintain the desired load along the length of the nip  216 . 
         [0044]    The controller  312  receives data to identify the wrinkle parameter for an image to be printed on the specified media. The controller  312  then operates the support member actuator  316  with reference to the identified wrinkle parameter. When the identified wrinkle parameter indicates that the image to be printed on the specified media includes stresses likely to generate longitudinal wrinkles, the controller  312  operates the support member actuator  316  such that the amount of pressure applied to the image receiving member  204  at the center of the nip  316  by the transfix roller  208  is increased relative to the amount of pressure applied to the image receiving member  204  at the ends of the nip  216  by the transfix roller  208 . Conversely, when the identified wrinkle parameter indicates that the image to be printed on the specified media includes stresses likely to generate transverse wrinkles, the controller  312  operates the support member actuator  316  such that the amount of pressure applied to the image receiving member  204  at the center of the nip  316  by the transfix roller  208  is decreased relative to the amount of pressure applied to the image receiving member  204  at the ends of the nip  216  by the transfix roller  208 . 
         [0045]    In an alternative embodiment, the image transfer system can include a support assembly that is not directly coupled to the transfix roller. For example, as illustrated in  FIG. 5 , the support assembly  212 ′ includes a support member  292 ′, a threaded beam  320 ′, a first arm  324 ′, a second arm  328 ′, a first pressure applicator  332 ′, and a second pressure applicator  336 ′. The image transfer system  200 ′ of  FIG. 5  is configured and operates in substantially the same manner as image transfer system  200  described above, except that the controller  312 ′ operates an actuator  340 ′ that is operatively connected to the threaded beam  320 ′ to rotate the threaded beam  320 ′ relative to the support member  292 ′ and move the first and second pressure applicators  332 ′,  336 ′ along the first and second arms  324 ′,  328 ′, respectively. The controller  312 ′ also operates a support member actuator  316 ′ to apply downward pressure to the support member  292 ′. 
         [0046]    The threaded beam  320 ′ includes right-handed threads on one side and left-handed threads on the other side. The first and second pressure applicators  332 ′ and  336 ′ are positioned on opposite sides of the threaded beam  320 ′ and configured to engage the threads to move when the threaded beam  320 ′ is rotated. Accordingly, when the threaded beam  320 ′ is rotated, the first and second pressure applicators  332 ′ and  336 ′ move in opposite directions along the threaded beam  320 ′. In this way, the threaded beam actuator  340 ′ positions the first and second pressure applicators  332 ′,  336 ′ along the first and second arms  324 ′,  328 ′. 
         [0047]    In alternative embodiments, the first and second pressure applicators  332 ′,  336 ′ can be positioned along the first and second arms  324 ′,  328 ′ using alternative methods. For example, the first and second pressure applicators  332 ′,  336 ′ can be positioned along the first and second arms  324 ′,  328 ′ using solenoids or mechanical linkages, such as gear trains or the like. 
         [0048]    The first arm  324 ′ is fixedly coupled to the first pivotable collar  284 ′ and the second arm  328 ′ is fixedly coupled to the second pivotable collar  288 ′. Accordingly, the downward pressure applied to the support member  292 ′ by the support member actuator  316 ′ is applied to the first and second arms  324 ′,  328 ′ via the first and second pressure applicators  332 ′,  336 ′. The downward pressure applied to the first and second arms  324 ′,  328 ′ is transferred to the first and second transfix roller ends  272 ′,  276 ′ by the first and second pivotable collars  284 ′,  288 ′. The controller  312 ′ applies moments M to the first and second transfix roller ends  272 ′,  276 ′ by operating the threaded beam actuator  340 ′ to position the first and second pressure applicators  332 ′,  336 ′ along the first and second arms  324 ′,  328 ′ and then, once the first and second pressure applicators  332 ′,  336  are positioned, operating the support member actuator  316 ′ to apply downward pressure that is transferred to the first and second pivotable collars  284 ′,  288 ′. 
         [0049]    As shown in  FIG. 6 , rotating the threaded beam  320 ′ to move the first and second pressure applicators  332 ′,  336 ′ toward the outward ends  344 ′ of the first and second arms  324 ′,  328 ′ and then applying a downward pressure applies a moment to the first and second pivotable collars  284 ′,  288 ′ to bend the transfix roller  208 ′ (shown in  FIG. 5 ) into a concave position such that the first and second transfix roller ends  272 ′,  276 ′ (shown in  FIG. 5 ) are closer to the image receiving member  204 ′ (shown in  FIG. 5 ) than the transfix roller central portion  280 ′ (shown in  FIG. 5 ). Accordingly, the pressure generated by the transfix roller  208 ′ is greater at the ends of the nip  216 ′ than in the middle. 
         [0050]    Conversely, as shown in  FIG. 7 , rotating the threaded beam  320 ′ to move the first and second pressure applicators  332 ′,  336 ′ toward the inward ends  348 ′ of the first and second arms  324 ′,  328 ′ and then applying a downward pressure applies a moment to the first and second pivotable collars  284 ′,  288 ′ to bend the transfix roller  208 ′ (shown in  FIG. 5 ) into a convex position such that the first and second transfix roller ends  272 ′,  276 ′ (shown in  FIG. 5 ) are farther from the image receiving member  204 ′ (shown in  FIG. 5 ) than the transfix roller central portion  280 ′ (shown in  FIG. 5 ). Accordingly, the pressure generated by the transfix roller  208 ′ is greater in the middle of the nip  216 ′ than at the ends. 
         [0051]    In an alternative embodiment, the transfix roller  208 ′ can include a crown in the elastomer coat, like that shown in  FIG. 10 . To compensate for the increased pressure at the middle of the nip  216 ′ due to the inherent crown in the transfix roller  208 ′, the support assembly  212 ′ is configured to bend the transfix roller  208 ′ only in the concave direction, as shown in  FIG. 6 . 
         [0052]    In another alternative embodiment, the transfix roller  208 ′ can include a flare in the elastomer coat. A flare is the inverse of a crown and forms a greater diameter on the ends of the transfix roller  208 ′ than in the middle. To compensate for the increased pressure at the ends of the nip  216 ′ due to the inherent flare in the transfix roller  208 ′, the support assembly  212 ′ is configured to bend the transfix roller  208 ′ only in the convex direction, as shown in  FIG. 7 . Because the first and second pressure applicators  332 ′,  336 ′ are positioned toward the inward ends  348 ′ to bend the transfix roller  208 ′ in the convex direction, this configuration is advantageous for cases where there is little space for the image transfer system  200 ′ within the printer beyond the ends of the transfix roller  208 ′ because the threaded beam  320 ′ need not extend beyond the first and second pivotable collars  284 ′,  288 ′. 
         [0053]    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.