Abstract:
A bearing is provided comprising an elongated body including an outer surface and an inner bore. The body includes a front face and a rear face. The front face has at least one circumferential groove and the rear face has at least one circumferential groove. The inner bore and the front face groove define a first wall having a thickness. The front face groove and the rear face groove define a second wall having a thickness. The rear face groove and the outer surface define a third wall having a thickness. The first wall, second wall, and third wall form a pair of crenulations therebetween wherein the first wall thickness is greater than the second wall thickness.

Description:
BACKGROUND 
       [0001]    The present disclosure relates to a bearing that fits and is removable and/or securable to a wall of a reproduction apparatus. The features of the present disclosure provide in embodiments a mounting system advantageously for use in most any apparatus which requires bearings, for example, electrophotographic printing machines. 
         [0002]    Electrophotographic marking is a well-known, commonly used method of copying or printing documents. Electrophotographic marking is performed by exposing a charged photoreceptor with a light image representation of a desired document. The photoreceptor is discharged in response to that light image, creating an electrostatic latent image of the desired document on the photoreceptor&#39;s surface. Toner particles are then deposited onto that latent image, forming a toner image, which is then transferred onto a substrate, such as a sheet of paper. The transferred toner image is then fused to the substrate, usually using heat and/or pressure, thereby creating a permanent record of the original representation. The surface of the photoreceptor is then cleaned of residual developing material and recharged in preparation for the production of other images. Other marking technologies, for example, electrostatographic marking and ionography are also well-known. 
         [0003]    An electrophotographic marking machine generally includes bearings for supporting and connecting parts, for example, auger shafts or developer paddles passing through the housing. The bearings should be able to avoid wear and to minimize resistance, while at the same time having the capacity to seal a hole in the housing which may have a large tolerance variation. As an example, an upper limit of the fit tolerance for a nominal diameter of 16 millimeters due to manufacturing conditions is 300 microns. 
         [0004]    The bearings should also provide sealing capacity to prevent contamination of the machine with toner. Average dimension of some toner particles is on the magnitude of 6 microns. Other particles, for example, ferric particulates can be on the magnitude of 60 microns which can result in higher wear of moving parts due to abrasion by the component to the toner carrier material and shortening the lifespan of the developer. 
         [0005]    To reduce failure rate and improve performance an extra operation of bonding bearings with adhesives was introduced. This increases the cost of manufacturing and also introduces risk factors associated with adhesives and the possibility of contamination of the inner surface of the bearing. 
         [0006]    Other solutions, such as beam support circumferentially distributed around the bearing, are inappropriate for environments involving contaminants, as these require a full through hole to allow for large tolerances, thus allowing transport of contaminant across the bearing. Sealing one face only reduces the capacity of the bearing to deal with the large variation between the shaft and support hole and also limits the degree of dimensional variability with which it can accommodate. 
         [0007]    It is therefore desirable to provide a bearing which can be utilized in a wall while still providing generally high durability, minimizing frictional resistance, and maximizing sealing capacity. 
         [0008]    Reference is made to the following United States patents relating to reproduction machines and components such as bearings briefly summarized as follows: 
         [0009]    U.S. Pat. No. 6,024,497 relates to a bushing mountable in a housing for supporting a rotating member and for providing a bias force to the rotating member. The bushing includes a body defining an aperture therein and a mounting member for mounting the bushing to the housing. The bushing also includes a biasing member operably associated with said body and said mounting member. 
         [0010]    U.S. Pat. No. 5,632,684 relates to a shaft assembly and method of forming a shaft assembly having an elongated hollow shaft with a stepped portion on the surface of the shaft. The stepped portion of the shaft surface is formed of two straight edge sections joined by an inclined section. A gear having a corresponding straight/inclined edge configuration engages the shaft and contacts the shaft only on the corresponding straight edge portions. 
         [0011]    U.S. Pat. No. 5,538,475 relates to a shaft assembly comprising an elongated member having at least a portion which is hollow, tubular, shell like having an inside surface defining a shaft core and an outside surface defining a shaft functional surface, the shaft core being filled with a hardened, moldable material, and the shaft functional surface having at least one functional feature thereon, which is of hardened, moldable material integrally molded with the hardened, moldable material in the shaft core. U.S. Pat. No. 5,511,885 relates to a plain flanged bearing or bushing for supporting a rotating shaft in a thin walled frame of an electrophotographic printing machine. The composite bearing has a flanged end and is adapted to be inserted in an opening in a thin walled support member until the flange abuts the surface of the wall. A protruding tab formed by displacing a small portion of the flange extends in an axial direction along the bearing and cooperates with a corresponding opening in the wall to prevent rotation of the bearing. A friction push nut or snap ring is attached to the bearing on the side of the wall opposite the flange. The protruding tab prevents the bearing from rotating about an axis which can cause the bearing to be worn on the exterior surface by rotational contact with the thin wall. A shaft to support idler rolls or other rotating elements is inserted in an inner bore of the bearing and is rotatably supported thereby. 
         [0012]    U.S. Pat. No. 5,457,520 relates to a bearing for supporting a moving member on a support structure. The bearing includes a substantially U-shaped member having an internal periphery and an external periphery. The bearing also includes a first securer, associated with the internal periphery of the U-shaped member, for securing the moving member to the U-shaped member and a second securer, associated with the external periphery of the U-shaped member, for securing the U-shaped member to the support structure. 
         [0013]    U.S. Pat. No. 4,804,277 relates to a bearing mounting system for mounting and retaining a rotatable shaft between first and second bearings mounted to first and second spaced frame members of a machine frame, utilizing commercially available bearings, with respective inner and outer races. Both bearings inner races are press fitted onto the shaft. 
         [0014]    U.S. Pat. No. 4,134,175 relates to a non-rotating sleeve type bushing in which an eccentric flange integral with the bushing and projecting radially outwardly therefrom is so formed as to be received in a complementarily contoured flange recess in a bearing housing whereby rotation of the bushing with respect to the bearing housing is precluded by a positive mechanical locking action provided by the shear resistance of the flange member. 
         [0015]    U.S. Pat. No. 6,467,965 relates to a bearing for use in reproduction machines that fits and is removable and/or securable to a wall of a reproduction apparatus. The bearing provides a snap-fit mounting feature. 
         [0016]    All documents cited herein, including the foregoing, are incorporated herein by reference in their entireties. 
       SUMMARY 
       [0017]    In accordance with one exemplary embodiment of the present disclosure, there is provided a bearing comprising an elongated body including an outer surface and an inner bore. The body includes a front face and a rear face. The front face has at least one circumferential groove and the rear face has at least one circumferential groove. The inner bore and the front face groove define a first wall having a thickness. The front face groove and the rear face groove define a second wall having a thickness. The rear face groove and the outer surface define a third wall having a thickness. The first wall, the second wall, and the third wall form a pair of crenulations therebetween. The first wall thickness is greater than the second wall thickness. 
         [0018]    In accordance with another exemplary embodiment of the present disclosure, there is provided a bearing comprising an elongated body including an outer surface and an inner bore. The body has a front face and a rear face wherein at least one of the front face and the rear face having at least two circumferential grooves and the other of the front face and the rear face having at least one circumferential groove. The inner bore and a first front face groove define a first wall having a thickness. The first front face groove and a rear face groove define a second wall having a thickness. The rear face groove and a second front face groove define a third wall having a thickness. The second front face groove and the outer surface define a fourth wall having a thickness. The first wall, the second wall, the third wall, and the fourth wall form a plurality of crenulations therebetween. The first wall thickness is greater than the second wall thickness. 
         [0019]    In accordance with another exemplary embodiment of the present disclosure, there is provided a bearing in an electrostatographic machine comprising an elongated body including an outer surface and an inner bore. The body has a front face and a rear face wherein the front face has at least one circumferential groove and the rear face has at least one circumferential groove. The front face groove having a width and the rear face groove having a width. The front face groove width tapers from the front face to the rear face. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  illustrates a perspective view of a mounting system for an embodiment of the present disclosure; 
           [0021]      FIG. 2  illustrates an enlarged perspective view of the bearing of  FIG. 1 ; 
           [0022]      FIG. 3  illustrates a cross-sectional view of a first embodiment of the bearing; 
           [0023]      FIG. 4  illustrates a cross-sectional view of a second embodiment of the bearing; 
           [0024]      FIG. 5  illustrates a cross-sectional view of the bearing of  FIG. 4  disposed in a wall along with a shaft disposed in the bearing; 
           [0025]      FIG. 6  illustrates a cross-sectional view of another variation of the second embodiment of the bearing; and, 
           [0026]      FIG. 7  is a schematic elevational view of an electrophotographic printing machine utilizing the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    While the principles of the present disclosure will be described in connection with an electrostatographic reproduction machine, it should be understood that the present disclosure is not limited to that embodiment or to that application. Therefore, it is should be understood that the principles of the present disclosure extend to all alternatives, modifications and equivalents as may be included within the spirit and scope of the appended claims. 
         [0028]    The present disclosure relates to embodiments of a bearing for use in walls of reproduction machines. Although the bearing of the present disclosure is particularly well adapted for use in the illustrative printing machine, it will become evident that the bearing is equally well suited for use in a wide variety of machines and are not necessarily limited in its application to the particular embodiment shown herein. 
         [0029]    Referring to  FIG. 7  of the drawings, an illustrative reproduction machine incorporating the bearing of the present disclosure is shown. The reproduction machine employs a photoconductive belt  11 . Belt  11  moves in the direction of arrow  13  to advance successive portions sequentially through the various processing stations disposed about the path of movement thereof. Belt  11  is entrained about stripping roller  15 , tensioning roller  17 , idler roll  19  and drive roller  21 . As roller  21  rotates, it advances belt  11  in the direction of arrow  13 . 
         [0030]    Initially, a portion of the photoconductive surface passes through charging station M. At charging station M, two corona generating devices indicated generally by the reference numerals  23  and  25  charge the photoconductive belt  11  to a relatively high, substantially uniform potential. 
         [0031]    Next, the charged portion of the photoconductive surface is advanced through imaging station N. At the imaging station, an imaging module indicated generally by the reference numeral  27 , records an electrostatic latent image on the photoconductive surface of the belt  11 . Imaging module  27  includes a raster output scanner (ROS). The ROS lays out the electrostatic latent image in a series of horizontal scan lines with each line having a specified number of pixels per inch. Other types of imaging systems may also be used employing, for example, a pivoting or shiftable LED write bar or projection LCD (liquid crystal display) or other electro-optic display as the “write” source. 
         [0032]    The imaging module  27  (ROS) includes a laser  110  for generating a collimated beam of monochromatic radiation  122 , an electronic subsystem (ESS) associated with the machine electronic printing controller  76  transmits a set of signals via  114  corresponding to a series of pixels to the laser  110  and/or modulator  112 , a modulator and beam shaping optics unit  112 , which modulates the beam  122  in accordance with the image information received from the ESS, and a rotatable polygon  118  having mirror facets for sweep deflecting the beam  122  into raster scan lines which sequentially expose the surface of the belt  11  at imaging station N. A user interface (UI)  150  is associated with the controller  76 . 
         [0033]    Thereafter, belt  11  advances the electrostatic latent image recorded thereon to development station O. Development station O has three magnetic brush developer rolls indicated generally by the reference numerals  35 ,  36  and  38 . A paddle wheel picks up developer material and delivers it to the developer rolls. When the developer material reaches rolls  35  and  36 , it is magnetically split between the rolls with half of the developer material being delivered to each roll. Photoconductive belt  11  is partially wrapped about rolls  35  and  36  to form extended development zones. Developer roll  38  is a clean-up roll. The latent image attracts toner particles from the carrier granules of the developer material to form a toner powder image on the photoconductive surface of belt  11 . Belt  11  then advances the toner powder image to transfer station P. 
         [0034]    At transfer station P, a copy sheet is moved into contact with the toner powder image. First, photoconductive belt  11  is exposed to a pretransfer light from a lamp (not shown) to reduce the attraction between photoconductive belt  11  and the toner powder image. Next, a corona, generating device  41  charges the copy sheet to the proper magnitude and polarity so that the copy sheet is tacked to photoconductive belt  11  and the toner powder image is attracted from the photoconductive belt to the copy sheet. After transfer, corona generator  42  charges the copy sheet to the opposite polarity to detack the copy sheet from belt  11 . Conveyor  44  then advances the copy sheet to fusing station Q. 
         [0035]    Fusing station Q includes a fuser assembly  46  which permanently affixes the transferred toner powder image to the copy sheet. Preferably, fuser assembly  46  includes a heated fuser roller  48  and a pressure roller  51  with the powder image on the copy sheet contacting fuser roller  48 . The pressure roller is cammed against the fuser roller to provide the necessary pressure to fix the toner powder image to the copy sheet. The fuser roll  48  is internally heated by a quartz lamp. Release agent, stored in a reservoir, is pumped to a metering roll. A trim blade trims off the excess release agent. The release agent transfers to a donor roll and then to the fuser roll. 
         [0036]    After fusing, the copy sheets are fed through a decurler  52 . Decurler  52  bends the copy sheet in one direction to put a known curl in the copy sheet and then bends it in the opposite direction to remove that curl. 
         [0037]    Forwarding rollers  54  then advance the sheet to duplex turn roll  56 . Duplex solenoid gate  58  guides the sheet to the finishing station R, or to duplex tray  61 . At finishing station R, copy sheets are stacked in a compiler tray and attached to one another to form sets. When duplex solenoid gate  58  diverts the sheet into duplex tray  61 . Duplex tray  61  provides an intermediate or buffer storage for those sheets that have been printed on one side and on which an image will be subsequently printed on the second, opposite side thereof, i.e., the sheets being duplexed. The sheets are stacked in duplex tray  61  facedown on top of one another in the order in which they are copied. 
         [0038]    To complete duplex copying, the simplex sheets in tray  61  are fed, in seriatim, by bottom feeder  62  from tray  61  back to transfer station P via conveyor  64  and rollers  66  for transfer of the toner powder image to the opposed sides of the copy sheets. Inasmuch as successive bottom sheets are fed from duplex tray  61 , the proper or clean side of the copy sheet is positioned in contact with belt  11  at transfer station P so that the toner powder image is transferred thereto. The duplex sheet is then fed through the same path as the simplex sheet to be advanced to finishing station R. 
         [0039]    The high capacity variable sheet size sheet feeder  100  is the primary source of copy sheets. Feed belt  81  feeds successive uppermost sheets from the stack to a take-away drive roll  82  and idler rolls  84 . The drive roll and idler rolls guide the sheet onto transport  86 . Transport  86  advances the sheet to rolls  66  which, in turn, move the sheet to transfer station P. 
         [0040]    Secondary tray  68  and auxiliary tray  72  are secondary sources of copy sheets. Copy sheets are fed to transfer station P from the secondary tray  68  or auxiliary tray  72 . Sheet feeders  70 ,  74  are friction retard feeders utilizing feed belts and take-away rolls to advance successive copy sheets to transport  64  which advances the sheets to rolls  66  and then to transfer station P. The copy sheet is registered just prior to entering transfer station P so that the sheet is aligned to receive the developed image thereon. 
         [0041]    Invariably, after the copy sheet is separated from the photoconductive belt  11 , some residual particles remain adhering thereto. After transfer, photoconductive belt  11  passes beneath corona generating device  94  which charges the residual toner particles to the proper polarity. Thereafter, the pre-charge erase lamp (not shown), located inside photoconductive belt  11 , discharges the photoconductive belt in preparation for the next charging cycle. Residual particles are removed from the photoconductive surface at cleaning station S. Cleaning station S includes an electrically biased cleaner brush  88  and two de-toning rolls  90 . 
         [0042]    The various machine functions are regulated by a controller  76 . The controller  76  can be preferably a programmable microprocessor which controls all of the machine functions hereinbefore described. The controller provides a comparison count of the copy sheets, the number of documents being recirculated, the number of copy sheets selected by the operator, time delays, jam corrections, etc. The control of all of the exemplary systems heretofore described may be accomplished by conventional control switch inputs from the printing machine consoles selected by the operator. Conventional sheet path sensors or switches may be utilized to keep track of the position of the document and the copy sheets. 
         [0043]    Turning now to  FIGS. 1 and 2 , illustrated are partial cut-away views from the  FIG. 7  reproduction machine illustrating one of the bearings  210  of the present disclosure as it is installed in a housing wall  250 . Also shown is a shaft  240  as it is installed into a shaft support portion  212  of the bearing  210 . The shaft support portion  212  can have an inner bore  214  that is formed in a generally cylindrical shape to allow rotation of the shaft  240  therein. 
         [0044]      FIG. 2  displays an enlarged view of the bearing  210  mounted in the housing  250 . The assembly includes a base molding  252  and bearing support housing  250  associated therewith. A front and rear auger  254 ,  256  can be positioned inside the base molding  252 . Shafts  244 ,  246 , respectively, of the augers  254 ,  256  can be positioned in a bearing. The outer surface of the bearing can be supported in molded embossment of housing. A gear  266  can be mounted at the end of shaft  246 . A similar gear can be located at the end of shaft  244  (not shown). The gear train inside the bearing housing transfers the motion from a magnet roll  258 , which can be driven by an electrical motor from the opposite end, to a paddle  260  and augers  256 ,  254 . The shafts can be restricted from axial movement with circlips  270 . It is to be appreciated that the entire assembly can be enclosed by a cover (not shown), thereby prohibiting contamination of the machine with toner. 
         [0045]    The bearing  210  can be inserted into a housing hole  262  and the shaft  244  then passes through the bearing  210 , as shown in  FIG. 2 . To be described in more detail hereinafter, upon insertion, radial interference compresses the outer walls of the bearing, with the degree of compression decreasing towards the inner bore  214 , which has minimal compression. The shaft  244 , inserted through the inner bore  214 , provides sliding fit with the bearing  210  and support of the shaft  244  through the housing wall  250 . As the bearing  210  allows for large tolerance variation between its outer surface  216  and the hole  252  in the housing  250  without having any through cuts, it is able to perform in environments where sealing capacity is desired, such as developers. 
         [0046]    Referring to  FIG. 3 , the bearing includes an outer surface  216 , an inner bore  214 , and front and rear faces  280 ,  282 . Circumferential grooves  272 ,  274 ,  276  can be provided on the front and rear faces. The number of grooves or cuts producing the crenulations can vary from a single cut upwards. The number of cuts can be generally dependent upon the dimensions of the bearing. Increasing the number of cuts increases the bearing radial flexibility. The cuts can be rounded in root areas  273 ,  275 ,  277  to reduce stresses and to prevent premature failure from crack propagation due to cyclic loading. The thickness of the outer shell wall  290  provides control over the flexibility of the bearing at its interface with the housing. The thickness of the inner bore wall maintains the rigid support of the shaft and including tighter tolerances of the interface between the shaft and the inner bore wall. The thickness of the intermediate wall, along with the number of cuts, controls the flexibility of the bearing and the degree of tolerance variation that can be accommodated. The bearing can be constructed from polyacetal filled with polytetrafluoroethylene, which allows dry bearing application. It is to be appreciated that other suitable materials for dry bearings can be used, such as Iglidur J. 
         [0047]    Referring again to  FIG. 3  wherein a cross sectional view of the bearing  210  is therein shown. The bearing  210  can have a number of blind circular grooves sequenced from its outer side inward and from its inner side outwards. In one embodiment, the bearing  210  can be made of plastic by means of molding and can include a cylindrical body with a number of deep circular grooves positioned sequentially in a radial direction between its front and rear faces. The inner surface bears the shaft and the outer surface has an interference fit with the surface of the through hole in a molded housing. In the embodiment shown in  FIG. 3 , the bearing has three grooves  272 ,  274 ,  276  and four walls  290 ,  292 ,  294 ,  296 . The walls have corresponding thicknesses T 1 , T 2 , T 3 , T 4 . The wall thickness T impacts the radial stiffness of the bearing  210 . In one variation, the wall thicknesses of the bearing can follow the pattern wherein T 1 &gt;T 2 &gt;T 3 &gt;T 4 , i.e. the wall thickness decreases from T 1  to T 4 . The decrease can follow an arithmetic or geometric series as needed. In assemblies where there is a large variation between the housing  250  and the through shaft  244 , another variation of the bearing can be supplied which provides compression of the bearing  210  in the middle of the cross-section. In this arrangement, the bearing can follow another pattern, namely, T 1 &gt;T 2 , T 2 =T 3 , and T 3 &lt;T 4  (not illustrated). This pattern supplies the lowest wall thickness to the middle section thereby providing a parabolic distribution of wall thicknesses. 
         [0048]    Another feature impacting the radial stiffness of the bearing  210  includes the groove width G. The grooves  272 ,  274 ,  276  have corresponding widths G 1 , G 2 , G 3 . In one variation, the groove width of the bearing can follow the pattern wherein G 1 &lt;G 2 &lt;G 3 , i.e. the groove width increases from G 1  to G 3 . The increase can follow an arithmetic or geometric series. In assemblies where there is a large variation between the housing and the through shaft, another variation of the bearing can be supplied which provides compression of the bearing in the middle of the cross-section. In this arrangement, the bearing can follow another pattern, namely, G 1 &lt;G 2  and G 2 &gt;G 3  (not illustrated). This pattern supplies the greatest groove width to the middle section thereby providing a parabolic distribution of groove width. It is to be appreciated that the groove wall angle can be tapered to vary stiffness along the axis of the bearing  210 . The taper can be arranged such that the groove narrows towards the blindside of the cut. The number of grooves can vary which provides for variable bearing stiffness and tolerance of housing location. 
         [0049]    When bearing is fitted into housing, the outer cylindrical section, due to its reduced thickness, is easily compressed to accommodate higher dimensional variations. As the gradient of the groove width reduction decreases towards the inner bore, the latter is capable of accommodating an appropriate sliding fit with a shaft. As there are no extra axial holes to reduce radial stiffness, the sealing performance of the bearing is not compromised. When loads are applied to the shaft and transferred to the bearing due to the reduced stiffness of the outer circumference of the bearing contact pressure distribution between the bearing and the housing stays positive preventing particles to defeat the seal. 
         [0050]    In operation, the bearing  210  is inserted into the wall  250  until an inside surface of the bearing contacts an inside surface  251  of the wall  250 . A circlip  270  can be used to hold the bearing  210  substantially secured to the wall  250  thereby preventing axial movement. The spring action of the bearing  210  ensures high contact force between bearing  210  and housing  250  thereby reducing sliding and wear, while at the same time minimizing the increase in force between the bearing  210  and shaft  244 . 
         [0051]    The developer provides a mixture of toner and magnetic particles supplied from a supply bottle inside the cavity of the rear auger  256  through an opening in the top cover. The rear auger moves the mixture in axial direction and transfers it to the front auger. The front auger distributes the mixture alongside the paddle. The paddle supplies the mixture to the magnet roll. The latter then provides a photoreceptor with quantities of toner. During operation the bearings provide support to the augers and paddle shafts and can compensate for wide ranges of tolerances of the cylindrical holes in the molded embossments through deflections of the walls between the grooves. The bearings also serve as seals preventing contamination of the machine with toner. 
         [0052]    The dimensions of the bearing are well suited for applications inside a reproduction machine although additional sizes and uses are envisioned. In one exemplary embodiment, an 8 mm shaft can be supported via the bearing in an 18 mm through hole, with one groove in both the front and the rear faces of the bearing, giving the first wall against which the shaft is held a thickness of 1.3 mm, a 0.8 mm groove, a second wall of 0.8 mm, a second groove of 0.8 mm and a third wall of 1.3 mm. 
         [0053]      FIGS. 4 and 5  illustrate cross-sectional views of a second embodiment of a bearing  310  disposed in wall  250 . The bearing  310  is intended to support rotatable shaft  244  which may be used for idler rollers, drive rollers, belt rollers or any other shaft use within a reproduction machine. In  FIG. 5 , illustrated is a cross-sectional view of the bearing  310  of  FIG. 4  disposed in wall  250 . The bearing  310  can be removably securable to wall  250 . Shaft  244  is installed into an end of bearing  310  and extends partially out the other end. 
         [0054]    The bearing  310  can have a number of blind circular grooves sequenced from its outer side inward and from its inner side outwards. In the embodiment shown in  FIGS. 4 and 5 , bearing  310  has two grooves  372 ,  374 , and three walls  390 ,  392 ,  394 . The walls have corresponding thicknesses T 11 , T 21 , T 31 . The wall thickness T impacts the radial stiffness of the bearing  310 . In one variation, the wall thicknesses of the bearing can follow the pattern wherein T 11 &gt;T 21 &gt;T 31 , i.e. the wall thickness decreases from T 11  to T 31 . The decrease can follow an arithmetic or geometric series. In assemblies where there is a large variation between the housing  250  and the through shaft  244 , another variation of the bearing can be supplied which provides compression of bearing  310  in the middle of the cross-section. In this arrangement, the bearing can follow another pattern, namely, T 11 &gt;T 21  and T 21 &lt;T 31  (not illustrated). This pattern supplies the lowest wall thickness to the middle section thereby providing a parabolic distribution of wall thicknesses. 
         [0055]    Another feature impacting the radial stiffness of the bearing  310  includes the groove width G. The grooves  372 ,  374  have corresponding widths G 11 , G 21 . In one variation, the groove width of the bearing can follow the pattern wherein G 11 &lt;G 21 , i.e. the groove width increases from G 11  to G 21 . It is to be appreciated that the groove wall angle can be tapered to vary stiffness along the axis of the bearing  310 . The taper can be arranged such that the groove narrows towards the blindside of the cut. Edge fillets (not illustrated) on the edges of the outer surface and inner bore can allow ease of fit of the bearing into the support wall and the shaft into the bearing. 
         [0056]      FIG. 6  illustrates another variation of the second embodiment of the bearing. Similar elements are referenced with like numbers including a suffix (′) and new elements are referenced with new numbers. Bearing  310 ′ can include chamfers, or angled walls, along the front and/or rear faces to provide greater flexibility as needed. Chamfering walls in roots of the grooves provide more even distribution of the radial stiffness alongside of the latter when the wall is going to be bent and twisted rather than simply compressed. 
         [0057]    Other embodiments and features of the bearing are also envisioned. The bearing may be constructed of plastic including Delrin™. 500CL which is commercially available from Dupont™. The bearing may include a plastic resin such as an Acetal resin. Other materials such as nylon may also be used so as to provide a generally low friction bearing surface for the rotation shaft. The inside surface of the bearing may have a coefficient of friction ranging from about 0.2 to about 0.3. The plastic may have hardness of about 1.3 ft-lb/in. The bearing can be made of one material using a generally simple molding process. 
         [0058]    The bearings described herein can generally be easily mounted in a reproduction machine, can generally allow easier assembly, and can generally be replaced without the necessity of complex disassembly of many components. 
         [0059]    While this disclosure has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.