Abstract:
A track assembly for moving a vehicle which includes a track having lugs including both drive and guide portions on its inner surface. The guide portions substantially abut against the track rollers of the assembly. Such abutment maintains alignment of the track between those rollers so as to prevent it from moving from side to side and interfering with feeding of the drive portions onto the assembly drive sprocket. Further, the guide portions grab against the drive sprocket to maintain contact of the drive portions therewith. Each of the above functions permits uninterrupted movement of the vehicle since the track is enabled to move in a continued path.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to a track and track assembly for a track laying vehicle, and more specifically, to a track assembly including a track having lugs which resist movement of the track from the vehicle drive sprocket and from the track rollers associated with the track. 
   BACKGROUND OF THE INVENTION 
   The tracks of track laying vehicles are often made of an elastomeric material and have similarly constructed raised projections or lugs on an inner surface. In positive drive tracked vehicles, these lugs fit into grooves created between the teeth of a drive wheel or drive sprocket which, together with a series of track rollers and an idler, define a path along which the track moves. As the track moves along this path, the lugs serve at least two purposes. First, they provide surfaces on the track which a drive sprocket can grab to move the track and thus, the vehicle. Second, the lugs maintain alignment of the track with the sprocket, idler and track rollers. 
   Typically, the lugs mentioned above are of the same size and shape. Particularly, the lugs are many times straight or flat-faced on their side surfaces so as to not include nubs or any other formation which can help to lock them into the sprocket grooves. The height of the lugs are generally limited because of potential interference between the lugs and the teeth of the drive sprocket as the lugs enter and leave the sprocket. Because there is no locking mechanism and the height of the lugs are limited, the belt can become misaligned. For instance, when the vehicle is turned the belt is forced to slide on the ground and the resistance to this sliding causes substantial belt misalignment forces to be produced which may force the track rollers to climb over the lugs. Also, when the vehicle is on a hillside, the weight of the vehicle tends to shift the vehicle downhill. But this movement is resisted by engagement of the track with the ground, again generating misalignment forces which may cause the rollers to climb over the adjacent lugs. As the rollers climb over the lugs, the track is detracked and the driving engagement between the lugs and drive sprocket is lost. Thus, it would be beneficial to provide a track with lugs configured to retain their engagement with the sprocket and their alignment between the rollers in order to maintain continuous movement of the vehicle. 
   SUMMARY OF THE INVENTION 
   According to the present invention, there is provided a track assembly including a belt or track having lugs which retain their engagement with the sprocket and which maintain alignment of the track with the rollers, idler and the sprocket, even when subjected to substantial misalignment forces. 
   The lugs mentioned above are provided in two parallel, spaced rows. Each individual lug includes an inboard drive portion which engages the teeth of the sprocket and an outboard guide portion which braces against the side of the drive sprocket. The guide portion of each individual lug is taller than and is joined to its associated drive portion to form a substantially L-shaped lug. 
   Because the guide portion of the lug does not engage with the teeth of the sprocket, the drive portion moves freely into and out of engagement with a tooth on the sprocket. Thus it can have a fairly substantial height and provide a good guiding surface that will maintain track alignment when the track is operating on an incline and/or the vehicle is being turned. 
   The above and additional features and advantages of the present invention will become apparent from a reading of the following detailed description of the invention when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a vehicle in the form of a skid steer loader having a track and track assembly constructed according to the present invention. 
       FIG. 2  is a side perspective view of the track assembly shown removed from the vehicle. 
       FIG. 3  is a side perspective and elevated view of the track constructed according to the present invention and used in conjunction with the assembly of FIG.  2 . 
       FIG. 4  is a side perspective view of the left frame subassembly on which the track shown in  FIG. 3  is supported. 
       FIG. 5  is an exploded view of portions of the right side of the assembly shown in FIG.  4 . 
       FIG. 6  is an exploded view of portions of the left side of the assembly shown in FIG.  4 . 
       FIG. 7  is a side perspective and elevated sectional view of the track mounted to the frame subassembly and which provides a view of the placement of the idler wheel relative to the track. 
       FIG. 8  is a side perspective and elevated view of the track having a top portion removed to show placement of a set of track rollers thereon. 
       FIG. 9  is a side perspective view of the drive sprocket of the track assembly of FIG.  2 . 
       FIG. 10  is a side perspective of a half section of the drive sprocket according to FIG.  9 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Looking first to  FIG. 1 , there is shown a vehicle in the form of a skid-steer loader  10 . At its mid-section, the vehicle includes an operator&#39;s station  12  supported upon the vehicle frame  14 . The frame is supported by a track assembly or undercarriage  16  on each side. Each track assembly includes a ground engaging track  18  powered by a hydraulic motor  19 . 
   Looking next to  FIG. 2 , a track assembly  16  is shown in more detail. The assembly  16  includes a frame subassembly  20  having a top, center plate  22  and side plates  40 . An idler wheel  28  is held at a first or front end  24  of the subassembly. A drive sprocket  29  is provided at the rear or second end  26  of the subassembly for transferring power from the motor  19  to the track  18 . A tensioning device  30  is supported on the top plate  22  between the idler  28  and sprocket  29 . 
   Preferably, and as shown in  FIGS. 4-6 , the tensioning device  30  includes a plurality of wheels  32  mounted on an axle supported at the free ends of arms  34 . The arms  34  are secured to a pivot member  35  supported on the side plates  40 , 42 . A ratcheting member  36  has one end anchored to the top plate  22  and its opposite end connected to a crank arm  37  on the axle  35 . To tension the track  18 , the ratcheting device  36  may be actuated to move the arms  34  and cause the wheels  32  to bear against the inner surface of the track  18  to keep it taut or tightly held against the idler  28 , sprocket and track rollers described below. After the proper tension is obtained, the arms  34  may be locked to the side plates by bolts  33  which pass through mating openings provided in the arms  34  and side plates  40 , 42 . 
   The frame subassembly  20  is best shown in  FIGS. 4-6 . Looking specifically to  FIG. 5 , slots  56 ,  57  and  58  are formed in the top plate  22  at the edges thereof for accepting gusset members or brackets  59 ,  60  and  61  welded to and extending from the side plate  42 . The brackets  59 - 61  are inserted into the slots  56 - 58  and then, preferably, are welded to the beam  22 . An additional bracket  62  welded to the plate  42  extends along the forward edge of the top plate  22  and is welded thereto. Preferably, each of the mounting plates  40 , 42  is welded to the edge of the top plate  22 . Also, as will be understood by those skilled in the art, the outer ends of the gussets or brackets  59 ,  60 ,  61  and  62  as seen in the  FIG. 5  exploded view will also be welded to the opposite side plate  40  shown in FIG.  6 . 
   The brackets or gussets  59 ,  60 ,  61  and  62  also extend to the outer side of the side plate  42  where they serve to secure right angle mounting members  63 . Spacers  64  are positioned between the brackets  59  and  60  and between the brackets  61  and  62 . Bolts  66  extend through and clamp the brackets, right angle mounting members  63  and spacers  64  together. The right angle members  63  serve to secure the completely preassembled track assemblies  16  to the vehicle frame  14  and the spacers  64  add rigidity. 
   As best shown in each of  FIGS. 5 and 6 , a plurality of track roller sets  44  are supported upon axles  46  and are disposed beneath the subassembly  20 . The ends of the axles  46  are received in semi-circular notches  68  formed in the lower edges of the side plates  40 , 42 . Winged retainers  76  engage in grooves (not shown) formed in the axles  46  and are secured to the lower edges of the side plates  40  and  42  by fasteners  78  to retain the axles  46  in position in the notches  68 . 
   Reinforcing plates  71  and  72 , as shown in  FIGS. 5-6 , are welded to the lower edges of the side plates  40 , 42  and cover the notches  68 . Plates  71  and  72  are also provided with notches which receive the heads of fasteners  78  so they do not project beyond the surface of the plates  40 , 42  where they may be susceptible to damage. As also shown in  FIGS. 4-6 , the reinforcing plates  71  and  72  include cutout portions  80  adjacent their ends. The side plates  40 , 42  are provided with screw receiving openings  81  in the area of the cutout portions for the purpose of mounting the rearmost set of track rollers  44  and the idler  28 . The idler  28  is carried on an axle  82  which is of a length slightly less than the distance between the interior surfaces of the side plates  40  and  42 . A retaining plate  84  is placed on the end of the axle  82  and is secured to the respective side plate  40  or  42  by screws  87  which extend through the screw receiving openings  81 . One of the screw receiving openings in the forward end of the side plates is in the form of a fore and aft oriented slot  83 , and a cap screw  86  extends through this slot and into a threaded bore in the end of the shaft  82 . 
   Relocation of the idler  28  on the assembly  16  can be achieved through loosening of the cap screws  86  and removal of the screws  87 . The idler  28  can then be slid fore and aft within the limits of the slots  83 . If the cap screws  86  are removed, the idler can be removed from the assembly. When the idler  28  is properly positioned, the screws  87  are inserted through appropriate openings  81  and all the screws are tightened to secure the idler  28  in the new position. 
   The rearmost track roller set is mounted in a similar manner with retaining plates  84  and screws  86  and  87 . However, there is no elongated slot  83  provided at the rear of the side plates  40 ,  42  and thus the rearmost set of rollers  44  is not adjustable. 
   Looking again at to  FIGS. 5 &amp; 6 , right mounting plate  42  includes a semi-circular portion  106  that extends above the top plate  22 . A circular cutout in the portion  106  receives a portion of the associated hydraulic motor  19 . The portion  106  has spaced screw openings that mate with tapped holes in a shoulder  107  associated with each of the motors  19 . The motor  19  is secured to the portion  106  of the plate  42  with bolts or fasteners  109  which extend through the openings in portion  106  and are threaded into the tapped holes in the shoulder  107 . 
   The drive sprocket  29  is best shown in  FIGS. 9 and 10 . The sprocket  29  includes an inner mounting ring  104  and an outer periphery with two annular rows  108 , 110  of alternating track engaging teeth  112  and associated grooves  114 . Each of the rows  108 , 110  is separated by a smooth ring portion  116 . The inner ring  104  is provided with spaced mounting holes which mate with like tapped bores in a shoulder ring  111  (see  FIG. 5 ) on the hydraulic motor  19 . Cap screws  105  extend through the openings in the mounting ring  104  and into the tapped bores  128  on the shoulder ring  111  to secure the sprocket  29  to the hydraulic motor  19 . The sprocket  29  is made of two equal halves  124  and  126 , and one of the halves  126  is shown in FIG.  9 . This construction makes it easier to mount the sprocket  29  on the hydraulic motor  19  and removal of half of the sprocket  29  facilitates the mounting and removal of the track on the subassembly. 
   The track  18  is shown most clearly in  FIGS. 3 and 8  and it includes an outer surface  48  and an inner surface  50 . The outer surface  48  will include a suitable tread (not shown) for engaging the ground. Extending from the inner surface  50  are two spaced rows of raised projections or lugs  51 . As shown, the two rows of lugs straddle the centerline of the track  18  between its lateral edges and the lugs are directly opposed to one another. Each of the lugs  51  includes a generally rectangular first or drive portion  52  joined with a substantially taller second or guide portion  54 . Together, the drive portion  52  and guide portion  54  form a right angle or L shaped lug. 
     FIG. 7  provides a sectional view of the placement of the drive and guide portions  52 ,  54  of the lugs  51  relative to the idler wheel  28  when the track  18  is installed on the subassembly  20 . As shown, the idler  28  consists of left, middle and right discs  88 , 90 , 92 , respectively, which are mounted on the idler axle  82 . The guide portions  54  can be seen to abut an inside surface of each of the left and right discs  92  and  88  to help maintain track alignment. The inner disk  90  runs on the inner surface  50  of the belt between the spaced rows of lugs while the outer disks  88  and  92  run on the inner surface  50  outside of the spaced rows. 
   In  FIG. 8 , an exemplary track roller set  44  is shown to have three rollers or discs  98 , 100 , 102 . Use of three rollers or discs further helps to keep the track  18  aligned between the rollers  44  and the idler  28  since each row of lugs will be restricted between the middle discs  90  and  100  and the respective outer discs  88 , 92  and  98 , 102 , as shown in  FIGS. 7 and 8 . As further shown in both  FIGS. 7 and 8 , the drive portions  52  of the lugs  51  fit in close proximity to the middle discs  90 , 100  without contacting it so as not to damage the lugs  51  and the ability of the sprocket  29  to engage them. 
   When track misalignment forces can be the greatest, in the area of the idler and track rollers, the outermost surfaces of the lug guide portions  54  cooperate with the idler  28  and track rollers  44  in retaining alignment of the track  18 . As shown in  FIG. 8 , a bottom outer surface portion  117  of each guide portion  54  substantially abuts against an inside surface  118 , 120  of a respective track roller  98 , 102  to resist lateral movement of the track  18 . 
   When coming into contact with the sprocket  29 , the inner surface of the guide portions  54  may bear against an outside surface  122  on each side of the drive sprocket  29  to align the track  18  and sprocket  29  as the drive portions  52  move into engagement with the sprocket teeth  112 . This is best shown in FIG.  2 . As contact occurs on each of the opposite sides  122  of the sprocket, the lug drive portions  52  become seated or retained within the grooves  114  of the sprocket  29  until they are rotated out of engagement therewith. 
   When removal of the track  18  is desired, an operator may begin by removing a first or second half  124  or  126  of the drive sprocket  18  that is not engaged with the track  18 . Thereafter, rotation of one the engaged sprocket halves  124  or  126  180 degrees is necessary. With this rotation, enough slack will be obtained to remove a rear portion of the track  18  from the subassembly  20 . Having this slack, an operator can now begin to remove the track  18  from engagement against the front idler  28 . 
   To disengage the track  18  from the idler wheel  28 , the retaining plates  84  at the idler wheel  28  need to be released from engagement with the plates  40 ,  42  by removal of the screws  87  shown in  FIGS. 5 and 6 . This permits the idler  28  to be moved to its rearmost position or towards the sprocket  29 . After this occurs, the track  18  may be subsequently removed from the subassembly  20  by sliding it to one side relative to the beam  22 . To install the track  18 , the process is reversed. 
   Thus, there is provided a track having lugs which resist its movement from the sprocket and from between the track rollers and a track subassembly containing such a track which can be completely preassembled before it is secured to a vehicle. 
   Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.