Abstract:
A track roller assembly may have a track roller, a roller shaft and collars press fit onto either end of the roller shaft to retain the track roller on the roller shaft with an axial clearance between the collars and the track roller. During assembly, the collars may be press fit onto the shaft ends and forced axially inwardly until further axial movement of the collars is prevented by engagement shoulders of the track roller. A compressive axial load may be applied to the roller shaft to reduce a shaft length of the roller shaft and to cause the roller shaft to slide inwardly relative to the collars. The compressive axial load is removed from the roller shaft so that the roller shaft extends back to the normal shaft length and the collars move axially farther apart as the roller shaft extends back to the normal shaft length.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates generally to track-type machines and, more particularly, to track roller assemblies for track-type machines and methods for fabricating track roller assemblies. 
       BACKGROUND 
       [0002]    Track-type machines, such as excavators, bulldozers, track-loaders and skid-steer loaders, are used in a variety of applications. Generally speaking, these machines have an operator station, a power source, an undercarriage and a pair of track systems laterally flanking the machine. Each track system may include a roller frame positioned along a lengthwise-extending direction of the track-type machine, a drive sprocket mounted on the roller frame and rotatably driven by the power source, and one or more idler wheels also mounted for rotation on the roller frame. An endless track that circumscribes the drive sprocket and the one or more idler wheels. The endless track is engaged by the drive sprocket so the power source can drive the endless track over the drive sprocket and the idler wheels and propel the track type-machine over a work surface. To further separate the endless track from the roller frame and cause the endless track to have a desired shape for driving the track-type machine, known track systems typically include one or more upper and/or lower track roller assemblies. These track roller assemblies are located along the lengthwise-extending axis of the roller frame between the drive sprocket and the one or more idler wheels to force the endless track along the desired path. 
         [0003]    The track roller assemblies may include a roller shaft mounted to the roller frame or to a support member to the track roller assembly, and a track roller having a through-bore may be rotatably mounted on the roller shaft. The roller shaft may be fixed in place and the track roller may rotate about the roller shaft when the track-type machine is in motion and the endless track passes over the track roller assembly. The track-type machine may operate in adverse environments wherein the track roller assemblies may be exposed to abrasive mixtures of water, dirt, sand, rock or other materials, and even chemical elements. These contaminants may enter a space between the roller shaft and the through-bore of the track roller and lead to wear of the surfaces of the roller shaft and the through-bore. Accordingly, track roller seals may be utilized to prevent the afore-mentioned contaminants from entering the space between the roller shaft and the through-bore, and to retain lubricant within the space between the roller shaft and the through-bore to minimize friction and wear in the track roller assembly. 
         [0004]    Track roller seals of the type generally described above are known in the art. For example, U.S. Pat. No. 6,568,684 issued to Bedford et al. on May 27, 2003, and entitled “Method of Forming a Seal Assembly Around a Shaft,” discloses a method for forming a seal assembly around a shaft. More specifically, a track roller seal utilizing two seal members engaging at a seal face limits ingress of contaminants into the track roller and mitigates leakage of lubricant from the track roller. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    In one aspect of the present disclosure, a method for assembling a track roller is disclosed. The method may include inserting a roller shaft having a shaft outer surface with a shaft outer diameter into a roller inner surface of the track roller having a varying roller inner diameter, wherein the shaft outer surface and the roller inner surface are configured so that the track roller can rotate about the roller shaft, and press fitting a first collar onto a first shaft end of the roller shaft and a second collar onto a second shaft end of the roller shaft, and forcing the first collar and the second collar axially inwardly until axially inward movement of the first collar is prevented by a first engagement shoulder of the track roller and axially inward movement of the second collar is prevented by a second engagement shoulder of the track roller. The method may further include applying a compressive axial load to the roller shaft to reduce a shaft length of the roller shaft from a normal shaft length to a compressed shaft length, wherein the roller shaft moves relatively inwardly relative to the first collar and the second collar, and removing the compressive axial load from the roller shaft so that the roller shaft extends back to the normal shaft length and the first collar and the second collar move axially farther apart as the roller shaft extends back to the normal shaft length. 
         [0006]    In another aspect of the present disclosure, a roller assembly is disclosed. The roller assembly may include a track roller having a roller inner surface with a varying roller inner diameter, a roller shaft having shaft outer surface with a shaft outer diameter, wherein the shaft outer surface and the roller inner surface are configured so that the track roller can rotate about the roller shaft, a first collar that is press fit onto a first shaft end, and a second collar that is press fit onto a second shaft end. A collar axial clearance of the first collar and the second collar from the roller inner surface is created by compressing the roller shaft with a compressive axial load when the track roller prevents axial inward movement of the first collar and the second collar, and then removing the compressive axial load from the roller shaft to allow the first collar and the second collar to move axially outwardly as the roller shaft extends from a shaft compressed length to a shaft normal length. 
         [0007]    In a further aspect of the present disclosure, a method for assembling a track roller is disclosed. The method may include press fitting a first flange bushing and a second flange bushing into a roller inner surface of the track roller having a varying roller inner diameter, wherein the first flange bushing has a first bushing body having a hollow cylindrical shape and a first bushing flange extending radially outwardly from a first bushing end, and the second flange bushing has a second bushing body having a hollow cylindrical shape and a second bushing flange extending radially outwardly from a second bushing end, wherein the first flange bushing and the second flange bushing are press fit axially inwardly until the first bushing flange engages a first engagement shoulder and the second bushing flange engages a second engagement shoulder. The method may further include inserting a roller shaft having a shaft outer surface with a shaft outer diameter into the roller inner surface of the track roller, wherein the shaft outer surface, the first bushing body and the second bushing body are configured to provide a shaft radial clearance so that the track roller can rotate about the roller shaft, press fitting a first collar onto a first shaft end of the roller shaft until a first collar inward end engages the first bushing flange and a second collar onto a second shaft end of the roller shaft until a second collar inward end engages the second bushing flange, applying a compressive axial load to the roller shaft to reduce a shaft length of the roller shaft from a normal shaft length to a compressed shaft length, wherein the roller shaft moves relatively inwardly relative to the first collar and the second collar, and removing the compressive axial load from the roller shaft so that the roller shaft extends back to the normal shaft length and the first collar and the second collar move axially farther apart as the roller shaft extends back to the normal shaft length. 
         [0008]    Additional aspects are defined by the claims of this patent. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1A  is a perspective view of a track-type machine having track carrier rollers in accordance with the present disclosure; 
           [0010]      FIG. 1B  is a side view of an undercarriage of the track-type machine of  FIG. 1A ; 
           [0011]      FIG. 2  is a cross-sectional view of a track roller assembly of the track-type machine of  FIG. 1 ; 
           [0012]      FIG. 3  is an enlarged portion of the cross-sectional view of  FIG. 2  showing an alternative sealing arrangement in the track roller assembly; 
           [0013]      FIG. 4  is the enlarged portion of the cross-sectional view of  FIG. 3  showing a further alternative sealing arrangement in the track roller assembly; 
           [0014]      FIG. 5  is the enlarged portion of the cross-sectional view of  FIG. 3  showing another alternative sealing arrangement in the track roller assembly; 
           [0015]      FIG. 6  is the enlarged portion of the cross-sectional view of  FIG. 3  showing an additional alternative sealing arrangement in the track roller assembly; 
           [0016]      FIG. 7  is the enlarged portion of the cross-sectional view of  FIG. 3  showing a still further alternative sealing arrangement in the track roller assembly; 
           [0017]      FIG. 8  is the enlarged portion of the cross-sectional view of  FIG. 3  showing another alternative sealing arrangement in the track roller assembly; 
           [0018]      FIG. 9  is a flow diagram of a track roller assembly routine in accordance with the present disclosure; 
           [0019]      FIG. 10  is an enlarged cross-sectional view of the left portion of the track roller assembly of  FIG. 2  during assembly prior to compressive of a roller shaft; 
           [0020]      FIG. 11  is the enlarged cross-sectional view of  FIG. 10  during application of a compressive axial load on the roller shaft; and 
           [0021]      FIG. 12  is the enlarged cross-sectional view of  FIG. 10  after the compressive axial load is removed from the roller shaft. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Referring to  FIGS. 1A and 1B , a track-type machine  10  may embody a mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, waste handling or any other industry known in the art. For example, the machine  10  may be an earth moving machine such as a hydraulic excavator or other suitable machine. The machine  10  may include an implement system  12  configured to adjust the position or orientation of an implement such as a bucket  14 , a drive system in the form of a track undercarriage  16  for propelling the machine  10 , a power source  18  that provides power to the implement system  12  and the undercarriage  16 , and an operator station  20  for operator control of the implement system  12  and the undercarriage  16 . Though a hydraulic excavator is illustrated, the rollers disclosed herein may be implemented in any other types of machines having an undercarriage, such as material loaders, tractors and the like. 
         [0023]    Power source  18  may embody an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine or any other type of combustion engine known in the art. It is contemplated that power source  18  may alternatively embody a non-combustion source of power such as a fuel cell, a power storage device, or another source known in the art. Power source  18  may produce a mechanical or electrical power output that may then be converted to hydraulic or pneumatic power for moving the implement system  12 , and converted into drive torque by an appropriate power transmission assembly (not shown) to drive tracks  22  of the undercarriage  16 . 
         [0024]    The undercarriage  16  may be a standard track drive system known in the art and includes a roller frame  24  connected to a body  26  of the machine  10  and having a drive sprocket  28  and one or more idler pulleys  30  pivotally connected thereto. The track  22  is supported by the drive sprocket  28  and idler pulleys  30 , but may not be taught so that the track  22  may move to provide stability for the machine  10  as it traverses uneven terrain. Track rollers  32  pivotally connected to the roller frame  24  support the machine  10  on the work surface. Above the roller frame  24 , the portion of the track  22  between the drive sprocket  28  and front idler pulley  30  is supported by at least one carrier roller  36 . The carrier roller  36  is rotatably mounted to a carrier stand  38  extending upwardly from the roller frame  24  so that the carrier roller  36  rotates as the track  22  moves between the drive sprocket  28  and the idler pulley  30 . The undercarriage  16  illustrated herein is a low sprocket-type undercarriage, but those skilled in the art will understand that the concepts disclosed herein may be implemented in other types of undercarriage such as elevated sprocket undercarriages having a drive sprocket  28  mounted above the roller frame  24  and idler pulleys  30  at the front and rear of the roller frame  24 . 
         [0025]      FIG. 2  illustrates an example of the track roller  32  that may be assembled according to an assembly routine in accordance with the present disclosure. The discussion herein may equally apply to the carrier roller  36  that may also be assembled according to the assembly routine. This configuration of roller collars, roller shafts and roller seals in the track rollers  32  and the carrier rollers  36  is exemplary only. The assembly routine in accordance with the present disclosure may be implemented in other rotating components mounted on a shaft, such as idler pulleys, sprockets and the like, that collectively are encompassed by the term “roller.” 
         [0026]    The track roller  32  is rotatably mounted to the roller frame  24  (or to the carrier stand  38  in the case of the carrier roller  36 ) by an axial roller shaft  40  extending through the track roller  32  and collars  42  that are press fit onto ends of the roller shaft  40  on either side of the track roller  32 . In the illustrated embodiment, the roller shaft  40  does not extend beyond outward surfaces of the collars  42 , and the collars  42  are engaged and retained by the roller frame  24  to hold the roller shaft  40  and the collars  42  against rotation relative to the roller frame  24  as the track roller  32  rotates about the roller shaft  40 . In alternative embodiments, the roller shaft  40  may have an end extending beyond one of the collars  42  and attached to the roller frame  24  in a cantilevered arrangement, or the roller shaft  40  may extend out of both sides of the track roller  32  and collars  42  and be dually supported by the roller frame  24 . 
         [0027]    The track roller  32  has a roller inner surface  44  having a varying roller inner diameter, and the roller shaft  40  has a shaft outer surface  46  having a substantially uniform shaft outer diameter. Portions of the roller inner surface  44  and the shaft outer surface  46  define a lubricant reservoir  48  there between proximate a longitudinal center of the track roller  32  in which a lubricant such as oil or grease is disposed to lubricate the moving components of the track roller  32 . The track roller  32  is rotatably mounted to the roller shaft  40  by bearings, such as a pair of flange bushings  50 . 
         [0028]    Each flange bushings  50  may have a cylindrical bushing body  52  and a bushing flange  54  extending radially outwardly from one end of the bushing body  52 . The bushing body  52  may be a hollow cylinder having a bushing outer diameter causing an interference fit with a corresponding portion of the roller inner surface  44  that is longitudinally outward from the reservoir  48 . The bushing body  52  is press fit into the corresponding portion of the roller inner surface  44  so that the flange bushing  50  will rotate with the track roller  32  about the roller shaft  40 . A bushing inner diameter of the bushing body  52  and the bushing flange  54  is slightly greater than the shaft outer diameter to allow the track roller  32  and the flange bushings  50  to rotate relative to the roller shaft  40  with minimal radial movement relative to the roller shaft  40 . The bushing inner diameter creates a radial clearance that may be on the order of approximately 0.25 mm (approximately 0.009843 inch) between a bushing inner surface and the shaft outer surface  46  allowing lubricant from the reservoir  48  to flow between the bushing body  52  and the roller shaft  40 . The bushing flanges  54  have a flange outer diameter that is greater than roller inner diameter at the portions of the roller inner surface  44  into which the bushing bodies  52  are press fit. The roller inner surface  44  extends radially outwardly to define bushing engagement shoulders  56  that engage the bushing flanges  54  to properly position the flange bushings  50  along the roller inner surface  44 . 
         [0029]    The flange bushings  50  as illustrated having the bushing bodies  52  and the bushing flanges  54  formed as single unitary components. However, those skilled in the art will understand that the flange bushing  50  may be formed from multiple separate components that combine to perform the functions of the flange bushings  50  as described herein. For example, a cylindrical radial bearing may function as the bushing body  52  and be press fit into the corresponding portion of the roller inner surface  44  and have the bushing inner diameter that creates the radial clearance between a bushing inner surface and the shaft outer surface  46 . A washer or other type of the thrust bearing may function as the bushing flange  54  and be disposed on the roller shaft  40  and between the bushing engagement shoulder  56  and the corresponding collars  42  to absorb thrust loads imparted on the track roller  32 . Other configurations of bearings will be apparent when the term “flange bushing” is used herein. 
         [0030]    The collars  42  and outward portions of the roller inner surface  44  combine to define seal cavities  58  at either end of the track roller  32  and the roller shaft  40 . Seal assemblies  60  are disposed within the seal cavities  58  to form a seal between the components that are rotating relative to each other that retains the lubricant from the reservoir  48  within the track roller  32 , and prevents dirt, sand and other debris from passing through the seal cavities  58  and wear on the parts moving relative to each other. In the illustrated embodiment, each seal assembly  60  has a collar side seal portion formed by a first seal ring  62  and a first toroidal seal member  64 , and a roller side seal portion formed by a second seal ring  66  and a second toroidal seal member  68 . The seal rings  62 ,  66  are positioned side-by-side and abutting with the first seal member  64  engaging a collar seal cavity surface  70  and the second seal member  66  engaging a roller seal cavity surface  72  of the roller inner surface  44 . The collars  42  are press fit onto the roller shaft  40  in a position to form seals preventing the lubricant from passing between the seal rings  62 ,  66  and between the seal members  64 ,  68  and the seal cavity surfaces  70 ,  72 , respectively. To provide lubricant from the reservoir  48  to the seal assemblies  60 , axial clearance is provided between collar inward ends  74  of the collars  42  and the bushing flanges  54 . The axial clearance between the collar inward ends  74  and the bushing flanges  54  may be approximately 0.25 mm (approximately 0.009843 inch) in one exemplary implementation, though the actual axial clearance may vary based on the particular implementation of the track rollers  32 . Due to the constraints of illustration, the relatively small radial and axial clearances between the bushing bodies  52  and the roller shaft  40 , and between the collar inward ends  74  and the bushing flanges  54  are not visually apparent in many of the drawings figures include herewith. However, those skilled in the art will understand that such radial and axial clearances are present between the parts. Where appropriate for the purpose of illustration, dimensions of the components are exaggerated for the benefit of the reader&#39;s understanding of the present disclosure. 
         [0031]      FIGS. 3-8  illustrate various alternative configurations of seal assemblies  60  that may be implemented in the track rollers  32  assembled in accordance with the present disclosure. Referring to  FIG. 3 , the roller seal cavity surface  72  may be modified so that a seal may be formed using only the first seal ring  62  and the first seal member  64  of the collar side seal portion. The first seal ring  62  faces and abuts the roller seal cavity surface  72  and the first seal member  64  is pressed against the collar seal cavity surface  70  to form seals there between. In  FIG. 4 , the collar seal cavity surface  70  is modified in a similar manner so that only the roller side seal portion consisting of the second seal ring  66  and the second seal member  68  is used to seal the seal cavity  58 . 
         [0032]    The seal cavity surfaces  70 ,  72  are modified in a similar fashion in  FIGS. 5 and 6 , but an alternative side seal portion configuration may be installed within the seal cavity  58 . Referring to  FIG. 5 , a collar side seal portion may be formed by a first seal ring  76  modified to receive a first load ring  78  on an outward side and a first sealing lip  80  on an inward side. The collar side seal portion is installed within the seal cavity  58  with the first load ring  78  engaging the collar seal cavity surface  70  and the first sealing lip engaging the roller seal cavity surface  72 . In  FIG. 6 , a roller side seal portion may be formed by a second seal ring  82  modified to receive a second load ring  84  on an inward side and a second sealing lip  86  on an outward side, with the roller side seal portion is installed within the seal cavity  58  with the second load ring  84  engaging the roller seal cavity surface  72  and the second sealing lip engaging the collar seal cavity surface  70 .  FIGS. 7 and 8  illustrate further alternative embodiments where combinations of the side seal portion configurations are implemented together within the seal cavity  58 . 
         [0033]    In previously known track roller and carrier roller assemblies where collars are not press fit onto the roller shaft, the collars are instead secured to the roller shaft by dowel pins inserted through holes in the roller shaft and the collar. Because the collars are slidable on the roller shaft before the dowels are inserted, lubricant can leak between the roller shaft and the collar unless O-ring grooves are machined into the outer surface of the roller shaft or the inner surface of the collar and O-rings are installed to seal the interface. In such configurations and in the configurations described herein, it is desirable to maintain tight control over the axial clearance between the bushing flanges  54  and the collar inward ends  74  to minimize the axial motion of the track roller  32  along the roller shaft  40 . Excessive axial motion can result in leakage at the seal assemblies  60  if the seal members  64 ,  68  or load rings  78 ,  84  disengage from the seal cavity surfaces  70 ,  72 , the seal rings  62 ,  66  disengage from each other, or other separation occurs to comprise the seal assemblies  60 . In the dowel-secured track rollers, the typical tolerance stack up for fabricating the dowels, the collars, the inner surface of the track roller and the flange bushings, and in machining the holes in the roller shaft and the collar can make the required axial clearance for the seal assemblies  60  of  FIGS. 3-8  unachievable. 
         [0034]    Tolerance stack up in the components of the seal assemblies  60  further increases the likelihood that a reliable seal cannot be formed. For example, in the dowel arrangement discussed above, tolerance stack up may allow for a total axial clearance between the bushing flanges  54  and the collar inward ends  74  within a range from approximately 0.50 mm (approximately 0.01969 inch) to approximately 1.50 mm (approximately 0.05906 inch) using typical tolerances for the manufactured components. Tighter control over the tolerances in the fabrication of the components of the track rollers  32  is possible, but the use of such controls for these components is cost prohibitive. 
         [0035]      FIG. 9  illustrates an embodiment of a track roller assembly routine  100  that may more reliably position the collar inward ends  74  of the collars  42  relative to the bushing flanges  54  to achieve the desired axial clearance there between for flow of lubricant without excessive and undesired axial movement of the track roller  32  along the roller shaft  40 . The track roller assembly routine  100  may begin at a block  102  where the flange bushings  50  are press fit into the corresponding portions of the roller inner surface  44 . The bushing bodies  52  are pressed into the corresponding portions of the roller inner surface  44  until the bushing flanges  54  are engaged by the bushing engagement shoulders  56  of the roller inner surface  44 . 
         [0036]    With the flange bushings installed  50  at the block  102 , control of the routine  100  may pass to a block  104  where the side seal portions of the seal assemblies  60  are installed within the collar seal cavity surface  70  and/or the roller seal cavity surface  72  depending on the particular configuration of the seal assemblies  60 , such as those shown in  FIGS. 2-8  or other seal assembly arrangements that may be used in a particular implementation. When inserted, the engagement between the seal members  64 ,  68  or the load rings  78 ,  84  and the seal cavity surfaces  70 ,  72  will align the seal rings  62 ,  66 ,  76 ,  82  approximately concentrically with the track roller  32  and the collar  42  to facilitate insertion of the roller shaft  40  and the collars  42 . 
         [0037]    After the side seal portions are installed in the track roller  32  and/or the collars  42 , control may pass to a block  106  where the roller shaft  40  is inserted into the roller inner surface  44  of the track roller  32 . The radial clearance between the shaft outer surface  46  and the bushing body  52  allows the roller shaft  40  to slide into the track roller  32 . The roller shaft  40  is positioned relative to the track roller  32  so that shaft ends  108  of the roller shaft  40  extend beyond corresponding roller ends  110  of the track roller  32 . This positioning will allow for the collars  42  to be installed on the roller shaft  40 . 
         [0038]    At a block  112 , the collars  42  are installed on the corresponding shaft ends  108  of the roller shaft  40 . A collar inner diameter of collar inner surfaces  114  is dimensioned to create an interference fit with the shaft outer surface  46  so that the collars  42  must be press fit onto the roller shaft  40 . At this point of the assembly process, the collars  42  are pressed axially inwardly until the collar inward ends  74  abut the corresponding bushing flanges  54 , thereby leaving no axial clearance between the collars  42  and the flange bushings  50  as shown in  FIG. 10 . With the collars  42  abutting the flange bushings  50 , the collars  42  are positioned axially inwardly on the roller shaft  40  relative to their final assembled position that will provide axial clearance from the bushing flanges  54 . Consequently, for purposes of illustration, the shaft ends  108  may extend beyond collar outward ends  116  of the collars  42  in preparation for adjusting the positions of the collars  42  on the roller shaft  40 . 
         [0039]    With the collars  42  installed on the roller shaft  40 , control may pass to a block  118  where a compressive axial load  120  is applied to the shaft ends  108  of the roller shaft  40  as shown in  FIG. 11 . The compressive axial load  120  has a sufficient magnitude to compress and shorten the length of the roller shaft  40 . Because the collars  42  are engaged with the flange bushings  50  to prevent inward axial movement of the collars  42 , the shaft outer surface  46  will slide relative to the collar inner surfaces  114  as the roller shaft  40  shortens. The compressive axial load  120  has a desired shaft compressive load value that will compress the roller shaft  40  by an amount approximately equal to two times the specified axial clearance distance between the collar inward ends  74  and the bushing flanges  54 . For example, if the specified axial clearance distance between one of the collar inward ends  74  and the corresponding bushing flange  54  is 0.25 mm (0.009843 inch), the shaft compressive load value may be the compressive load necessary to compress the roller shaft  40  by 0.50 mm (0.01969 inch) to account for two collar-to-bushing axial clearances. In the illustrated embodiment, the compressive axial load  120  may be sufficient to compress the roller shaft  40  until the roller ends  110  are flush with the corresponding collar outward ends  116 . In alternate embodiments, one or both of the roller ends  110  may extend beyond the collar outward ends  116  before and after the roller shaft  40  is compressed. The magnitude of the compressive load will vary based on factors such as the length and outer diameter of the roller shaft  40  and the material from which the roller shaft  40  is fabricated, the inner diameter of the collar inner surfaces  114  and corresponding frictional force between the surfaces  46 ,  114  resisting relative axial movement between the roller shaft  40  and the collars  42 , and the like. 
         [0040]    After the roller shaft  40  is compressed and displaced relative to the collars  42  at the block  118 , control of the assembly routine  100  may pass to a block  122  where the compressive axial load  120  is removed from the roller shaft  40 . When the compressive load is removed from the roller shaft  40 , the roller shaft  40  extends in the axial direction and returns to its normal length that it had before the compressive axial load  120  was applied. Due to the interference fit between the roller shaft  40  and the collars  42  and the absence of any constraint on the collars  42  from move axially outwardly relative to the track roller  32 , the collars  42  will move with the roller shaft  40  as it extends so that a distance between the collars  42  increases by the amount that the roller shaft  40  was shortened in the axial direction. Consequently, in the above example, the collars  42  will be separated by an additional approximately 0.50 mm (approximately 0.01969 inch) after the roller shaft  40  returns to its normal length while the collar outward ends  116  remain flush with the shaft ends  108 . 
         [0041]    The additional separation of the collars  42  will provide axial clearance between the bushing flanges  54  and the collar inward ends  74  so that gaps  124  (shown with the distance exaggerated for the purpose of illustration in  FIG. 12 ) will exist between the collars  42  and the flange bushings  50 . The radial clearance between the shaft outer surface  46  and the bushing body  52  will allow for relative axial movement between the track roller  32  and the roller shaft  40  by an amount equal to the increased separation between the collars  42 , so the width of the gaps  124  will vary between no separation when one collar inward end  74  contacts the corresponding bushing flange  54  to a maximum of the increased separation distance. Of course, the distance of the gap  124  will vary between the extremes as the track roller  32  operates to guide the endless track  22  around the roller frame  24 . 
         [0042]    With the compressive axial load  120  removed, and the roller shaft  40  returned to its normal length and the collars  42  positioned, control may pass to a block  126  where the collars  42  are secured to their respective shaft ends  108 . The roller shaft  40  and the collars  42  may be secured using any appropriate attachment method or mechanism for preventing relative movement between the roller shaft  40  and the collars  42 . For example, cold metal transfer (CMT), controlled short circuit (CSC), laser or other type of welding may be used. Alternatively, an additional connection component such as a swage ring can be included in the assembly. Other mechanisms capable of maintaining the collars  42  in the positions established when the compressive axial load  120  is removed will be apparent to those skilled in the art and are contemplated by the inventor. 
         [0043]    Once the track roller  32 , the roller shaft  40  and the collars  42  are assembled, control may pass to a block  128  where the roller assembly is filled with lubricant. The track roller  32  may include a lubricant opening (not shown) extending through the track roller  32  to fluidly connect the lubricant reservoir  48  to the ambient atmosphere surrounding the track roller  32 . Lubricant may be added to the lubricant reservoir  48  through the lubricant opening, which is then sealed by a threaded plug (not shown) or other appropriate closing mechanism. The lubricant in the lubricant reservoir  48  may then flow past the flange bushings  50  to the seal cavities  58 . At this point, the roller assembly is ready for installation and control may pass to a block  160  where the roller shaft  40  and/or the collars  42  are mounted to the roller frame  24 , bogie  34  or other support structure. Regardless of the support structure, the roller shaft  40  or the collars  42  are secured to prevent movement relative to the support structure. At the same time, the track roller  32  is free to rotate about the roller shaft  40  to guide the endless track  22 . 
       INDUSTRIAL APPLICABILITY 
       [0044]    The configuration of the track roller  32 , the roller shaft  40  and the collars  42  and the accompanying assembly routine  100  provide tighter tolerance matching for the axial clearance between the collars  42  and the flange bushings  50 . Tolerance stack in the radial clearance is substantially eliminated as the compression and length reduction of the roller shaft  40  is the only parameter affecting the additional spacing distance between the collars  42  after press fitting and being placed into engagement with the bushing flanges  54 . As a result, the machining processes for the other components of the assembly, and in particular the components of the seal assemblies  60 , do not require as precise control of tolerances in order to maintain the seals in the seal cavities  58 . Consequently, the machine costs for the assembly may be significantly reduces. 
         [0045]    The configuration also eliminates some components and corresponding machining processes in their entirety. Dowels are no longer necessary for retaining the collars  42  in position relative to the roller shaft  40 . Without dowels, machining processes for forming dowel holes in the roller shaft  40  and the collars  42  are eliminated from the fabrication process. Additionally, the interference fits between the shaft outer surface  46  and the collar inner surfaces  114  may be sufficient to prevent leakage of lubricant. Consequently, O-ring seals and machining processes for the corresponding O-ring grooves are eliminated from the design. These reductions can result in further reducing the cost of the roller assemblies. 
         [0046]    While the preceding text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of protection is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the scope of protection. 
         [0047]    It should also be understood that, unless a term was expressly defined herein, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to herein in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning.