Abstract:
An endless track chain assembly for an endless track vehicle having drive teeth received in tapered slots in a drive wheel. The drive teeth are replaceable in situ by a movement in a direction parallel to the rotational axis of the drive wheel. The drive teeth inter-fit with tapered inserts on the endless chain assembly so that all the driving forces are transmitted between the two replaceable wear elements. The inserts are inter-connected with pairs of links in a three point mounting as a structural unit to increase torsional rigidity and enable bushings that inter-connect adjacent links to be smaller that conventional bushings. The inserts on the endless chain assembly are readily replaceable by fasteners accessed from the exterior of the endless chain assembly.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to endless track vehicles and more specifically to endless track chain assemblies used with such vehicles. 
       BACKGROUND OF THE INVENTION 
       [0002]    Endless track vehicles have been used since the beginning of the 1900&#39;s, both for military and for construction activities. Endless track vehicles may have a belt in the case of light duty, but for heavy duty applications the endless tracks are made of a number of rigid units that are pivotally joined to each other in a pair of endless tracks. Drive wheels at one end of the vehicle apply force to the tracks to move the endless track vehicle over the ground. Differential speeds on the tracks provide a directional capability. 
         [0003]    Such heavy duty endless track assemblies are subjected to substantial wear and tear going to the nature of the environment in which they operate. As a result, wear on the endless track eventually requires that the track be rebuilt and refurbished. Conventional endless track assemblies have individual track units pivoted to one another by what are known as bushings. These bushings also take the torque forces from the drive wheel and transfer them to the endless track. Such action causes a wear in the outer housing for the bushing, necessitating a rather substantial and skilled repair and, in many cases, transport of the endless track to a repair shop for replacement of worn components. A further complication of such an arrangement is that bushings which, are normally lubricated and sealed, have the seals broken when the repair and refurbishing operation occurs, thereby raising the possibility of contamination of the lubricant. 
         [0004]    Therefore, a need exists in the art for an easily repairable endless track assembly that avoids the above problems. 
       SUMMARY OF THE INVENTION 
       [0005]    In one form, the invention is an endless track chain assembly having at least one drive wheel and an endless track chain inter-engaging with the drive wheel to be guided and driven by the drive wheel. The components on the drive wheel and the endless track chain that engage one another are replaceable in situ. 
         [0006]    In another form the invention is an endless track vehicle having a frame, a prime mover mounted in the frame and a power transmission assembly receiving the output of the prime mover. At least a pair of drive wheels are connected to the power transmission for providing a torque output, the drive wheels being positioned on the opposite sides of the vehicle. Endless track chain assemblies each having an endless track chain inter-engage with the drive wheels to be guided and driven by the drive wheels. The components on the drive wheels and the endless track chain that engage one another are replaceable in situ. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a simplified drawing of an endless track vehicle with which the present invention may be used; 
           [0008]      FIG. 2  is an enlarged side view of an endless track chain assembly used in  FIG. 1 ; 
           [0009]      FIG. 3  is a bottom perspective view of the chain assembly of  FIG. 2 ; and 
           [0010]      FIG. 4  is an elevational perspective view of the chain assembly of  FIG. 4  with some of the components removed. 
           [0011]      FIG. 5  is a perspective view of a link incorporated in the endless track chain assembly of  FIGS. 2 ,  3 , and  4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]      FIG. 1  shows an endless track vehicle  10  having a prime mover generally indicated by reference character  12 . Prime mover  12  is usually a compression ignition, or diesel, engine because of its inherent fuel efficiency and long term durability. The output of prime mover  12  is connected to a power transmission generally indicated by reference character  14 . Power transmission  14  has rotary outputs on opposite sides of the vehicle to provide bi-directional controlled torque output. A frame  16  provides the structural foundation for the prime mover  12 , power transmission  14  and provides an operator station  18  wherein an operator can operate the endless track vehicle  10 , including accessories such as a scraper assembly  15 . The frame  16  also supports an endless track chain assembly  20  that has drive wheels, generally indicated by reference character  22 , connected to the output of power transmission  14  through a hub  19  and idler wheels  24  at the opposite end of the endless track assembly  20 . It should be noted that a variety of guide wheels and other components enabling accurate tracking of the endless chain assembly  20  may be provided. These are not shown in an effort to simplify the understanding of the invention. 
         [0013]    The endless track assembly  20  is shown in an enlarged view shown in  FIG. 2  and the views of  FIGS. 3 ,  4  and  5 . The drive wheel  22  includes a central hub  19  (not shown in  FIG. 2 ) which is attached to the power transmission  14  by appropriate removable fasteners. A circular rim  24  is attached to the hub  19  by various means including heat shrinking onto an outer circumference of hub  19 . Rim  24  has an inner diameter  26  and an outer diameter  28 . A plurality of drive teeth  30  are received in slots  32  formed in the periphery of rim  24 . Slots  32  have a base  34  and corresponding recesses  36  on opposite sides of base  32 . The recesses  36  receive corresponding extensions  37  of a base  38  for each tooth  30 . The drive portion  40  of tooth  30  extends radially outward from base  38  and its flank may be formed as an involute to provide a quieter running drive with fewer pulsations inherent with present drive tooth chain geometry. The slot  32  enables removal and insertion of tooth  30  in a direction parallel to the central axis of drive wheel  22 . A stop is provided for fixing the axial position of tooth  30  and, as illustrated, this involves a slight taper to slot  32  in a direction parallel to the rotational axis of drive wheel  22 . A taper of three degrees may be employed, but other taper angles may be selected for particular applications. As illustrated in  FIG. 2 , the small end of slot  32  is illustrated with the larger end of the slot  32  at the opposite side of the hub or the rim  24 . In order to pull tooth  30  into place, a tab  42  is received in a recess  44  in rim  24 . Tab  42  has a central threaded hole  46  that receives a screw  48 , the head of which extends towards the plane of  FIG. 2  from the opposite side. As will be illustrated below, screw  48  is tightened to pull the opposite face of tooth  30  towards the plane of the  FIG. 2  to position it axially relative to rim  24 . It should be apparent to those skilled in the art that other arrangements may be employed to set the axial position of drive teeth  30 . As is illustrated in  FIG. 2 , a plurality of drive teeth  30  are positioned around the periphery of rim  24  to provide a guiding and driving function to the endless chain  20 . 
         [0014]    Endless chain  20  includes a series of ground engaging shoes  50  having a base plate  52  with leading and trailing sections  54  and  56  beveled to inter-fit with adjacent shoes  50 . A downward directed rib  57 , integral with base plate  52 , may be employed to enhance traction. Each shoe  50  has a link  58  on either side of the shoe  50 . In the view shown in  FIG. 2 , the near side link has been removed to enable a clearer understanding of the invention. The links  58  have a sidewall  60  having a first through hole  62  and second through hole  64  to receive bushing assemblies  66  that provide a means for pivotally interconnecting adjacent links  58 . Bushing assemblies  66  are in usual form with a central lubrication system so the details of such system are not shown to enable a better focus on the invention. However, because of the novel construction of the links  58 , the diameters of the bushing assemblies  66  are smaller than on prior art systems that use the bushing assemblies to transfer torque from a drive wheel to an endless track assembly. 
         [0015]    Links  58  have a center portion  68  in the form of a structural bridge extending at right angles to the plane of link  58 , as particularly shown in  FIG. 5 . As viewed in  FIG. 2 , the bridge  68  extends out of the plane of the figure. Pairs of links  58  have corresponding bridges  68  that form a structural support for an insert  70 . Insert  70  has an inner surface  72  and tapered end surfaces  74  that correspond to interfit with teeth  30 . Insert  70  is approximately the width of each tooth  30  so that driving engagement occurs between tooth  30  and insert  70 . Insert  70  is secured to adjacent bridges  68  by screws  76  extending through shoe  50  through a bore  78  in bridge  68  and threadedly engaging insert  70  at threaded section  79 . The insert  70  is secured to pairs of bridges  68  by pairs of screws  76 . The base of link  58  is secured to shoe  50  by screws  80  extending through shoe  50  and through bores  82  to be received in nuts  84  positioned within openings  86  in link  58 . The openings  86  not only provide access to nut  84  but provide sufficiently large evacuation openings for removal of debris that is trapped in the interstices of chain assembly  20 . As shown particularly in  FIGS. 3 ,  4  and  5 , the arrangement of the screws  76  and  80  through bores  78  and  82 , respectively provide a triangular structural support between the shoes  50 , the links  58  and inserts  70 . This triangular structural interconnection substantially increases the rigidity of the structure and enables a reduction in the diameter of bushings  66  since they only provide a pivotal interconnection between adjacent rings and do not contact the drive teeth  30 , particularly shown in  FIGS. 2 and 4 . 
         [0016]    The endless chain assembly described above has easily replaceable elements for the wear parts. These elements constitute the teeth  30  and the inserts  70 . They are easily replaceable in situ by a operator having normal technical skills, as described below and therefore can be formed from standard materials using ordinary heat treatments or material composition. When the wear elements need to be replaced in situ, or in the field, the drive wheel  22  is rotated so that the teeth  30  are free from the inter-engagement with the endless chain  20 . In that position, which is generally from 2 o&#39;clock to 4 o&#39;clock as shown in  FIG. 1 , the screws  48  are disengaged and the teeth axially displaced in the direction of the more open portion of slot  32 . A replacement tooth  30  is then inserted in the slot  32 , the screw  48  threaded into tab  42 , and tightened to pull the tooth against the stop provided by the taper within slot  32  and the extensions  37  of base  38 . When the necessary teeth  30  are replaced, the corresponding inserts  70  may be replaced by positioning them in the uppermost position between drive wheel  22  and idler wheel  24 . Because screws  76  are accessible from the exterior of shoes  50 , it is an easy and straightforward procedure to disconnect insert  70  and replace it with a new insert as needed. It should be apparent to those skilled in the art that this procedure may be performed without any special tools by a standard mechanic in the field. 
         [0017]    Thus it is seen that the drive wheel  22  and endless track assembly have wear parts that are totally replaceable in the field without any special equipment such as presses or other devices. The replacement of the wearable teeth  30  and inserts  70  is done without disturbing the bushings  66  and associated lubrication system. Accordingly, the life of the bushings  66  is extended significantly beyond the life of a standard bushing assembly that receives torsional driving forces between the drive wheel and the endless track assembly. It should also be noted that the inner surface  72  of the insert  70  would ride on the outer diameter of the idler wheel  24 , thus further reducing scalloping of the endless chain assembly. 
         [0018]    By providing a side insertion of the replaceable teeth  30 , the inner diameter  26  of rim  24  is maximized to provide a greater outer diameter for the hub  19 . 
         [0019]    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.