Abstract:
A track roller assembly for a track-type machine such as an excavator or a tractor includes an outer surface with no fluid ports and an inner surface free from any fluids. The track roller includes self-lubricated bushings, which include a substrate that has lubricating properties, such as a substrate that carries a solid lubricant, which allows the track roller to require no liquid lubrication requiring regular maintenance. The bushing is sealed to prevent debris from entering a clearance between the bushing and the shaft as well as preventing any of the bushing&#39;s solid lubricant from escaping.

Description:
TECHNICAL FIELD  
       [0001]    The present disclosure relates to the field of track roller assemblies for track type machines, and more specifically, to self-lubricated track roller assemblies. 
       BACKGROUND  
       [0002]    Track rollers used on track-type machines such as excavators and tractors are subject to extremely high levels or stress and wear due to the conditions that track-type machines frequently operate under. While operating in extreme conditions, such as hilly and rocky terrains, track rollers are more prone to getting damaged. Consequently, such track rollers are plagued with relatively high service costs, short wear life and numerous other problems with their operation. One of such problems arises from the need to constantly keep the track rollers well-lubricated. Operating track-type machines under difficult terrains often causes the leakage of lubrication fluid from the bearing assembly of the track roller in to other areas of the track roller. This results in increased service costs for repairing the leak or replacing the entire track roller assembly. Other problems associated with track roller designs in the past include constructing assemblies with high part counts, complex manufacturing processes and handling liquid lubricants during construction. 
         [0003]    U.S. Pat. No. 3,773,393 discusses an example of a liquid lubricated track roller assembly design. A pair of laterally spaced end caps receive a shaft and serve to support the shaft within a dead-end bore which is defined by a cylindrical inner wall and an end wall. A bearing assembly is mounted in the bore and interposed between the end cap and the shaft and includes a sleeve-type cylindrical bushing fixedly supported by the inner wall and a disc-type thrust washer secured to the end wall. A vertically extending channel formed within the end wall receives a liquid lubricant, such as oil that may be introduced to the roller assembly through a port. Although this patent teaches the use of bushings and thrust washers, it fails to address the longstanding problem of preventing lubricating fluid leaks that are prone to occur, such as under extreme operating conditions. 
         [0004]    The present disclosure is directed to one or more of the problems set forth above. 
       SUMMARY  
       [0005]    In one aspect, a track roller assembly comprises a first collar which includes a first inner cylindrical bore defined by a first inner wall surface. A second collar includes a second inner cylindrical bore defined by a second inner wall surface. A first self-lubricated bushing has a first inner bearing surface and an outer surface in contact with the first inner wall surface of the first collar. A second self-lubricated bushing has a second inner bearing surface and an outer surface in contact with the second inner wall surface of the second collar. A shaft has a first end received by the first inner bearing surface and a second end received by the second inner bearing surface. The shaft rotates relative to the first and second collars. 
         [0006]    In another aspect, a track type machine comprises a track roller frame that has a first bar and a second bar that is separated from the first bar by a roller receiving gap and a plurality of track roller assemblies. Each of the plurality of track roller assemblies includes a first collar fixedly attached to the first bar of the track roller frame. The first collar includes a first inner cylindrical bore defined by a first inner wall surface. A second collar includes a second inner cylindrical bore defined by a second inner wall surface. The second collar is fixedly attached to the second bar of the track roller frame opposite the first collar. A first self-lubricated bushing has a first inner bearing surface and an outer surface in contact with the first inner wall surface of the first collar. A second self-lubricated bushing has a second inner bearing surface and an outer surface in contact with the second inner wall surface of the second collar. A shaft has a first end received by the first inner bearing surface and a second end received by the second inner bearing surface. The shaft rotates relative to the first and second collars between the first bar and the second bar. 
         [0007]    In another aspect, a method of assembling a track roller assembly comprises the steps of press fitting a first self-lubricated bushing to a first inner cylindrical bore of a first collar, and press fitting a second self-lubricated bushing to a second inner cylindrical bore of a second collar. A first end of a shaft is inserted in to the first inner cylindrical bore of the first collar to contact a first inner bearing surface of the first self-lubricated bushing. A second end of the shaft is inserted in to the second inner cylindrical bore of the second collar to contact a second inner bearing surface of the second self-lubricated bushing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]      FIG. 1  is a side view of a track-type machine according to the present disclosure; 
           [0009]      FIG. 2  is a perspective inverted view of the track frame assembly of the track-type machine shown in  FIG. 1 ; 
           [0010]      FIG. 3  is a sectioned front view of a track roller from the machine shown in  FIG. 1 ; 
           [0011]      FIG. 4  is an exploded partially sectioned view of the track roller shown in  FIG. 3 ; and 
           [0012]      FIG. 5  is a sectioned front view of a track roller according to another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION  
       [0013]    Referring to  FIGS. 1 and 2 , a track-type machine  500  includes a track  520  that includes a track roller frame assembly  550  and a plurality of track roller assemblies  10  spaced apart along the length of the track  520 . The track roller frame assembly  550  includes a first bar  81  and a second bar  82  separated from the first bar  81 , by a roller receiving gap  83  that may be determined by the size of each track roller assembly  10 . 
         [0014]    Referring also to  FIGS. 3 and 4 , the track roller assembly  10  includes a first collar  20   a  and a second collar  20   b.  The first collar  20   a  has a first external surface  21   a  and a first inner wall surface  23   a  that defines a first inner cylindrical bore  25   a.  Similarly, the second collar  20   b  has a second external surface  21   b  and a second inner wall surface  23   b  that defines a second inner cylindrical bore  25   b.  Both the first and second collars  20   a  and  20   b  may also have at least one bolt hole  22  defined in their respective external surfaces  21   a  and  22   b.  The first collar  20   a  may be attached to the first bar  81  of the track roller frame assembly  550  using common attachment means, such as bolts that pass through the bolt holes  22  defined in the first collar  20   a.  Similarly, the second collar  20   b  may be attached to the second bar  82  of the track roller frame assembly  550  via similar attachment means as the attachment means used for attaching the first collar  20   a  to the first bar  81 . 
         [0015]    The track roller assembly  10  includes a first self-lubricated bushing  30   a,  which is received by the first inner cylindrical bore  25   a  of the first collar  20   a.  The track roller assembly  10  also includes a second self-lubricated bushing  30   b,  which is received by the second inner cylindrical bore  25   b  of the second collar  20   b.  The first and second self-lubricated bushings  30   a  and  30   b  may be tightly fit into the first and second inner cylindrical bores  25   a  and  25   b,  respectively and may be inserted into the bores  25   a  and  25   b  by press fitting or employing other similar methods that may provide a tight fit. The first self-lubricated bushing  30   a  has a first inner bearing surface  32   a  and a first outer surface  34   a  that may contact the first inner wall surface  23   a  of the first collar  20   a.    
         [0016]    Similarly, the second self-lubricated bushing  30   b  has a second inner bearing surface  32   b  and a second outer surface  34   b  that may contact the second inner wall surface  23   b  of the second collar  20   b.  The first and second inner wall surfaces  23   a  and  23   b  may be scored to inhibit rotational movement of the first and second self-lubricated bushings  30   a  and  30   b  relative to the first and second collars  20   a  and  20   b,  respectively. In the illustrated embodiment, the self-lubricated bushings  30   a  and  30   b  are press fitted in to their respective inner cylindrical bores  25   a  and  25   b  after the inner wall surfaces  23   a  and  23   b  of the first and second collars  20   a  and  20   b  have been scored. 
         [0017]    In the present disclosure, a self-lubricated bushing means any rotational load supporting member which does not require an external liquid lubricant. A few examples of self-lubricated bushings include Polymeric based lubricated bushings, Epoxy based lubricated bushings, Pellet lubricated bushings, Solid (low friction) lubricated bushings and Graphite based lubricated bushings which may be available at bearing suppliers such as GGB Bearing Technology, RCB Bearing and Lubron Bearing Systems. The first and second self-lubricated bushings  30   a  and  30   b  may include a substrate carrying a solid lubricant to provide lubrication on their respective inner bearing surfaces  32   a  and  32   b.    
         [0018]    In an exemplary embodiment of the track roller assembly as shown in  FIGS. 1 ,  2 ,  3  and  4 , a shaft  40  has a first end  42   a  and a second end  42   b  that are received by the first and second collars  20   a  and  20   b  respectively. The first and second ends  42   a  and  42   b  of the shaft  40  may contact the first and second inner bearing surfaces  32   a  and  32   b  of the self-lubricated bushings  30   a  and  30   b.  In one embodiment, there is a clearance gap  65   a  between the first end  42   a  of the shaft  40  and the first inner bearing surface  32   a  of the self-lubricated bushing  30   a  so that the shaft  40  may rotate relative to the self-lubricated bushing  30   a.  There is a clearance gap  65   b  between the second end  42   b  of the shaft  40  and the second inner bearing surface  32   b  of the self-lubricated bushing  30   b.  The clearance gaps  65   a  and  65   b  are so small that the gaps may not be visible in the figures shown. However, those skilled in the art will appreciate the gaps to be big enough to allow the shaft ends  42   a  and  42   b  to rotate relative to their respective self-lubricated bushings  30   a  and  30   b.    
         [0019]    In the illustrated embodiment, the shaft  40  includes a first rim portion  43   a  adjacent the first end  42   a  of the shaft  40  and a second rim portion  43   b  adjacent the second end  42   b  of the shaft  40 . The rims  43   a  and  43   b  are separated by a shaft portion  47  that may have a wide variety of contours, including one that has a reduced diameter compared to the diameter of the first and second rim portions  43   a  and  43   b  and another that has an protruding center flange, so long as the shaft  40  is able to rotate the track. 
         [0020]    In an exemplary embodiment of the disclosure, the shaft  40  is solid and includes a solid internal volume, and may be manufactured by forming or other similar methods such as casting or lathing. A solid shaft may be preferred in some applications because it may be stronger than a hollow shaft and may be easier and faster to manufacture. In another embodiment encompassed within the spirit of the present disclosure, the shaft may be hollow and may also include a cylindrical bore running along the axis  45  of the shaft  40 . In one exemplary embodiment of the disclosure, the hollow section of the shaft is reduced or eliminated so that the total mating surface between the shaft halves increases the strength of the assembly, making it more robust for impact loading in quarry, mining or forestry applications. Therefore, alternate designs of the shaft that are not discussed in this disclosure remain within the spirit of the disclosure. 
         [0021]    Seals may be used to inhibit any solid lubricant from the self-lubricated bushing from escaping out of the clearance gaps  65   a  and  65   b  between the self-lubricated bushings  30   a  and  30   b  and the first and second ends  42   a  and  42   b  of the shaft  40 , respectively, and also to inhibit debris from entering into the clearance gaps  65   a  and  65   b.  In one embodiment, a first seal  55   a  may be located between the first collar  20   a  and the first rim portion  42   a  of the shaft  40  along an axis of the shaft  45  to seal off the clearance gap  65   a.  A second seal  55   b  may be located between the second collar  20   b  and the second rim portion  42   b  of the shaft  40  along the axis of the shaft  45  to seal off the clearance gap  65   b.  The first and second seals  55   a  and  55   b  may be selected from a wide variety of seals, such as mechanical seals, duo cone seals or cassette seals. In one embodiment, the seals  55   a  and  55   b  may include a first member placed on each of the first shaft end  42   a  and second shaft end  42   b,  respectively, and a second member placed on each of the first collar  20   a  and the second collar  20   b,  respectively, with the two members rotating relative to each other by staying stationary on the first and second shaft ends  42   a  and  42   b  and the collars  20   a  and  20   b,  respectively. In addition, the seals  55   a  and  55   b  may use a liquid lubricant to remain lubricated or be made of a self-lubricated material. 
         [0022]    The track roller assembly  10  defines a first spacing  60   a  between the first rim portion  43   a  of the shaft  40  and the first collar  20   a  and a second spacing  60   b  between the second rim portion  43   b  of the shaft  40  and the second collar  20   b.  The spacings  60   a  and  60   b  prevent the shaft  40 , or rim portions  43   a  and  43   b  of the shaft  40 , from rubbing against the collars  20   a  and  20   b  when the machine on which the track roller assembly  10  is positioned, is operating in extreme conditions. 
         [0023]    The size of the spacings  60   a  and  60   b  may not be so large as to allow debris and other particles from entering into the track roller assembly  10 . Therefore, the spacings  60   a  and  60   b  may be of a size that will allow the shaft  40  to rotate freely relative to the collars  20   a  and  20   b  even under extreme conditions when the shaft  40  is bending, and also inhibit any, if not all, of the debris from entering into the track roller assembly  10 . In other embodiments of the disclosure, there may not be a need to maintain spacing because the shaft may be made without protruding rims or because there is minimal risk in the collars making any contact with the shaft. The first spacing  60   a  may be set by separating the first collar  20   a  from the first rim portion  43   a  of the shaft  40  by a first spacing distance. Similarly, the second spacing  60   b  may be set by separating the second collar  20   b  from the second rim portion  43   b  of the shaft  40  by a second spacing distance. 
         [0024]    Those skilled in the art may contemplate the use of a seal, such as a labyrinth seal or a v-ring seal that may be positioned at or around the spacing  60   a,  to stop any debris from entering the track roller assembly  10 . 
         [0025]    The track roller assembly  10  may also include a first and second thrust washer  36   a  and  36   b  to reduce the wear on the inner wall surfaces  23   a  and  23   b  of the collars  20   a  and  20   b  and the ends of the shaft  42   a  and  42   b,  as the worn material may hinder the rotational movement of the shaft  40  relative to the collars  20   a  and  20   b.  In a preferred embodiment of the present disclosure, the first thrust washer  36   a  is inserted between the first inner wall surface  23   a  of the first collar  20   a  and the first end  42   a  of the shaft  40 . The second thrust washer  36   b  is inserted between the second inner wall surface  23   b  of the second collar  20   b  and the second end  42   b  of the shaft  40 . The thrust washers  36   a  and  36   b  may or may not be attached to the collars  20   a  and  20   b.  Further, the thrust washers  36   a  and  26   b  may be made of the same or similar material used for the self-lubricating bushings. Those skilled in the art will recognize that the use of thrust washers  36   a  and  36   b  is optional and may be preferred to prevent damage to the surfaces of the shaft and the collars. 
         [0026]    The track roller assembly  10  may have a portless outer surface  15  and a fluidless inner volume  18 . An outer surface  15  of the track roller assembly  10  is defined by the entire outer surface of the track roller assembly including the outer surface of the shaft and the external surface of the collar. A portless outer surface means an outer surface of the track roller having no ports that may be used to add liquid lubricant to the track roller assembly. An inner volume  18  of the track roller assembly  10  is defined by the entire inner volume enclosed within the track roller assembly, including any volume inside the shaft, if any, and inside the self-lubricated bushings. A fluidless inner volume means an inner volume of the track roller assembly having no fluid lubricants at all. In the illustrated embodiment shown in  FIG. 3 , the shaft  40  is made from a solid piece and the inner volume  18  of the shaft  40  is not hollow. 
         [0027]    Referring now to  FIG. 5 , another exemplary embodiment of the present disclosure is shown. A track roller assembly  110  is similar to the track roller assembly  10  described in  FIGS. 1 ,  2 ,  3  and  4  but has a different shaft configuration. In the exemplary embodiment shown in  FIG. 4 , the shaft  140  includes two identical shaft halves  141   a  and  141   b  that are attached together at a shaft joint  144  by friction welding or other similar methods of attachment. It may be conceived by those skilled in the art that the shaft may come in different shapes, contours and may also be constructed in different manners. For instance, the shaft  140  may be made as a single piece, more than one piece in which the piece or pieces may even be solid or hollow. Those skilled in the art may appreciate that the shaft  140  may also be made from one solid piece sized to the right dimensions by lathing or other similar methods. The scope of the disclosure should not be limited to the embodiments described within the present disclosure, but should include other embodiments with alternate shaft designs that move a track that fall within the spirit of the disclosure. 
         [0028]    In the illustrated embodiment shown in  FIG. 5 , the shaft  140  has a center guide flange  147  instead of rims. The center guide flange  147  may simplify the manufacturing process and may reduce the risk of shaft damage in extreme applications. The shaft  140  is hollow and contains an inner volume  118 . The outer surface  115  of the shaft  140  is portless because there are no ports from which fluids may enter the track roller assembly. Furthermore, the inner volume  118  is fluidless because there is no liquid lubricant inside the volume  118 . In the illustrated embodiment, the inner volume has internal support structures  52 , such as brackets to prevent the inner volume cavity from collapsing under the stress. A first seal  155   a  is placed between the first collar  20   a  and the first shaft half  141   a  and a second seal  155   b  is placed between the second collar  20   b  and the second shaft half  141   b,  wherein both the seals  155   a  and  155   b  are placed along an axis of the shaft  145 . The seals  155   a  and  155   b  may be mechanical seals, cassette seals or may include a combination of seals which inhibit debris from entering the clearance between the shaft and the self-lubricated bushings as well as inhibit solid lubricant from leaving the clearance gaps  65   a  and  65   b.  The illustrated embodiment may also include seals  170   a  and  170   b.  These seals may be labyrinth seals, such as v-ring seals to inhibit any debris from entering the track roller via the spacings  160   a  and  160   b  located between the collars  20   a  and  20   b  and the shaft  140 . A first spacing seal  170   a  is placed between the shaft  140  and the first collar  20   a  and a second spacing seal  170   b  is placed between the shaft and the second collar  20   b.  Labyrinth seals may be effective because of their ability to make the travel path through the seal difficult for debris, such as pebbles and mud. The labyrinth seals may be attached to the collar or the shaft and a variety of different seals may be used. Those skilled in the art understand that the use and assembling of seals in track roller assemblies is considered routine skill. It is intended that the scope of the present disclosure may not be limited to the embodiments described herein, but the scope includes other embodiments that include features that form the spirit of the present disclosure. For instance, a track roller assembly that has a hybrid liquid oil lubricant and self-lubricated bushings is one embodiment of a track roller assembly that also falls within the intended scope of the disclosure. 
       INDUSTRIAL APPLICABILITY  
       [0029]    The present disclosure finds potential application in any track-type machine that uses track roller assemblies. The present disclosure may also find application in most types of track rollers, carrier rollers, idlers, excavators, track loaders or any system with an undercarriage. The present disclosure aims to solve the longstanding problem of lubricant fluid leaks that were prone to occur in track roller assemblies when operating in extreme conditions. 
         [0030]    Referring to the Figures, the first and second collars  20   a  and  20   b  attach to the first and second bars  81  and  82 , respectively, via bolts that pass through the respective bolt holes  22  of the first and second collars  20   a  and  20   b.  While the track-type machine  500  is in motion, the shaft  40  of the track roller assembly  10  may rotate relative to the first and second collars  20   a  and  20   b.  The first and second ends  42   a  and  42   b  of the shaft  40  rotate inside the first and second self-lubricated bushings  30   a  and  30   b  while rubbing against their respective inner bearing surfaces  32   a  and  32   b.  There may be little or no rotation of the self-lubricated bushings  30   a  and  30   b  relative to the first and second collars  20   a  and  20   b  because the self-lubricated bushings  30   a  and  30   b  are tightly fit inside the inner cylindrical bores  25   a  and  25   b  of their respective collars  20   a  and  20   b.  In a preferred embodiment, the relative rotation between the self-lubricated bushings and the collars are further inhibited because the first and second inner wall surfaces  23   a  and  23   b  are scored. Nevertheless, versions that allow or even encourage relative rotation between the self-lubricated bushings and their respective collars are within the intended scope of the disclosure. 
         [0031]    It is also within the intended scope of the disclosure to produce track roller assemblies that have identical shaft halves. Even though manufacturing procedures may produce slight tolerance variations between the two halves, it is within the spirit of the disclosure that the two shaft halves function identically. Therefore, when describing the interaction of one end of the shaft and one bushing in one half of the track roller assembly, those skilled in the art will appreciate that the description applies to the interaction of the other end of the shaft and the other bushing as well. 
         [0032]    As the shaft  40  rotates relative to the first inner bearing surface  32   a  of the first self-lubricated bushing  30   a,  the first inner bearing surface  32   a  wears the substrate carrying solid lubricant, exposing the lubricant to the first end  42   a  of the shaft  40  and thereby lubricating the area between the first end  42   a  of the shaft  40  and the first inner bearing surface  32   a  of the self-lubricated bushing  30   a.  The substrate that may wear off the inner bearing surface  32   a  of the bushing  30   a  remains within the clearance gap  65   a  between the first end  42   a  of the shaft  40  and the first self-lubricated bushing  30   a  because the seal  55   a  inhibits the lubricant from escaping to the other parts of the track roller assembly. Also, the seal  55   a  inhibits the entry of any debris from entering the clearance gap  65   a  between the shaft  40  and the self-lubricated bushing  30   a.  The seal  55   a  may be placed on the end of the shaft, or the self-lubricated bushing or the collar, or on any combination of the shaft, self-lubricated bushing and collar. 
         [0033]    The type of seal used and the method of assembling the seal in the track roller assembly may be appreciated by those skilled in the art to fall within the standard of routine skill and knowledge. In addition, the seal may require some external lubrication such as oil or grease, or may be made of a self-lubricated material such as the ones used for the self-lubricated bushings. The use of lubricants to lubricate the seal falls within the intended scope of the disclosure. In one embodiment, the shaft  140  may be separated from the first and second collars  20   a  and  20   b  by a first spacing  160   a  and a second spacing  160   b,  respectively. The first and second spacings  160   a  and  160   b  may be large enough to avoid the shaft  140  from contacting either of the collars  20   a  and  20   b  at any time during operation. This may reduce any damage due to wear to the outer surface  15  of the track roller assembly  110  and the collars  20   a  and  20   b.    
         [0034]    This disclosure encompasses an embodiment of a track roller assembly that contains no fluid lubricant and may solve the problem of fluid lubricants leaking from the track roller assembly while operating. In an exemplary embodiment, the track roller assembly  10  may contain no lubrication ports for lubricating the track roller assembly  10  and may have no fluid lubricants inside the track roller assembly  10 . The benefits that may be reaped from the present disclosure may not be limited to finding a solution to the issue of lubrication leaks. Rather, the disclosure provides a track roller assembly design that may have a reduced part count and a simpler manufacturing process. In one embodiment, the assembly requires only 5 different parts and 9 total parts (2 collars, 2 bushings, 2 bearings, 2 seals and a shaft). Further, because there may be no external lubrication required, the design may be more durable and reliable as it reduces the risk of any leakage of the fluid from either the lubrication port plug becoming loose or through damage to the track roller assembly in general. Additionally, the track roller design may eliminate the need of having a lubricant port, which may eliminate the cost associated with manufacturing a design incorporating the port and a lubricant volume chamber. In one embodiment of the disclosure, because the track roller assembly may be made of two identical halves, the manufacturing of such a track roller design may be less costly, less complicated and more robust than track roller assembly designs in the past. The maintenance of self-lubricated bushings in a track roller assembly may be done easier than maintaining a track roller assembly with liquid lubricants because the self-lubricated bushings may be easily removed and replaced from the track roller assembly without having to deal with the mess caused by the liquid lubricant. 
         [0035]    It should be understood that the above description is indeed for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.