Abstract:
A track rod for laterally locating an axle assembly with respect to a vehicle frame. The disclosed track rod is especially useful for large off highway vehicles. The track rod includes a first end piece pivotally connected to a vehicle structure such as a frame and a second end piece pivotally connected to a vehicle axle, one of the end pieces includes a housing having a fixed, force-receiving member The housing is adapted to receive a first elastomenc member located in a juxtaposed position with respect to one side of the fixed member A floating plate slidably received in the housing is located in a juxtaposed position with respect to the first elastomenc member The other end piece includes a portion receivable by the housing. A second elastomenc member is positioned between the end piece portion and the fixed member.

Description:
TECHNICAL FIELD 
     The present invention relates generally to suspensions and, in particular, to a new and improved track rod. 
     BACKGROUND ART 
     Track rods, also termed torque arms and panhard rods, are used in vehicles to laterally locate an axle assembly. in general, a track rod includes one end pivotally connected to a frame or chassis. The track rod extends laterally for a predetermined length and has its other end pivotally connected to an axle housing. The track rod inhibits relative lateral movement between the axle and the frame or chassis of a vehicle. Other suspension components such as struts or radius arms, longitudinally locate the axle with respect to the vehicle frame. 
     When a vehicle such as a mining truck is operated on rough terrain, substantial road-induced shocks can be transmitted to the track rod by the axle housing. These shocks, in turn, are transmitted to the vehicle frame. it has been found that with existing track rods, these road-induced shocks can eventually cause failure in the track rod and/or the mounting points on the frame and axle housing to which the track rod is attached. 
     DISCLOSURE OF INVENTION 
     The present invention provides a new and improved track rod which is capable of buffering shocks imparted to the axle housing by rough terrain such as unpaved roads used in mines. The track rod includes elastomeric members which are arranged to receive and absorb/dampen compressive forces when the track rod is placed in either compression or tension due to a road shock. With the disclosed invention, the potential for damage to the track rod and/or its mounting points on the vehicle and axle due to road shocks, etc. are reduced. 
     According to the invention, a track rod and a method for locating a vehicle axle is provided that includes a first end piece operatively coupled to a vehicle frame and a second end piece operatively coupled to a vehicle axle. At least one of the end pieces includes a housing that has a fixed, force receiving member. The housing is adapted to receive a first elastomeric member that is located in a force applying position with respect to one side of the fixed member. The other end piece includes a force applying portion that is receivable by the housing. A second elastomeric member is positioned between this force applying portion and another side of the fixed member. A force transmitting member is arranged to apply forces to the first elastomeric member when the end pieces move away from each other, When the end pieces move toward each other, the portion of the first end piece applies forces to the second elastomeric member. 
     In a more preferred embodiment, a floating plate is slidably received in the housing and is located in a force applying position with respect to the first elastomeric member. In its more preferred embodiment, the force transmitting member comprises a clamping element preferably in the form of a bolt and nut that extends through the end piece portion, the first and second elastomeric members, the fixed force receiving member and the floating plate. 
     According to a feature of a preferred embodiment, the track rod also includes a bushing assembly which permits relative movement between the first and second end pieces but establishes a fixed stop to limit the extent to which the end pieces can move towards each other. In a more preferred embodiment, the bushing assembly comprises a pair of interfitting bushings, one of which has an end that is engageable with one side of the fixed force receiving member and the other of which has an end which is engageable with the other side of said fixed force receiving member. 
     The method disclosed for locating the vehicle axle with respect to a vehicle frame buffers the shock loads between the vehicle and axle in two directions. When the shock load is due to forces tending to move the axial away from the frame, (which places the track rod in tension), the shock related force is buffered by one of the elastomeric members. When the shock load is due to a force tending to move the axle towards the vehicle frame, this force is buffered by the other elastomeric member. This is achieved by providing a force transmitting/coupling member arranged to apply compression forces to one elastomeric member when the track rod is placed in tension and to apply compression forces to the other elastomeric member when the track rod is placed in compression. 
     In one disclosed embodiment, the end pieces and/or housing are a weldments and may be in a rectangular or square configuration. The invention also contemplates end pieces and/or housing that are castings. In addition, the elastomeric member and housing may be constructed in an annular configuration. 
     Additional features of the invention will become apparent and a fuller understanding obtained by reading the followed detailed description made in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic representation of a vehicle axle and a track rod extending from the axle to a frame member; 
         FIG. 2  is a perspective view of a track rod constructed in accordance with the present invention; 
         FIG. 3  is an exploded view of the track rod shown in  FIG. 2 ; 
         FIG. 4  is a sectional view of the track rod as seen from the plane indicated by the line 4-4 in  FIG. 2 ; 
         FIG. 5  is a sectional view of the track rod as seen from the plane indicated by the line 5-5 in  FIG. 2 ; 
         FIG. 6  is a fragmentary sectional view of the track rod shown in a preloaded conditon; and 
         FIG. 7  is a fragmentary sectional view of the track rod shown in a tension condition. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates an axle assembly  10  and a track rod  12  that laterally couples the axle assembly to a vehicle frame  14 . A track rod, which is also referred to as a torque arm or panhard rod in some applications, laterally locates the axle assembly  10  and inhibits side-to-side movement of the axle assembly with respect to the vehicle frame  14 . 
     The track rod  12  of the present invention is disclosed in connection with heavy duty, off highway equipment such as mining trucks. It should be understood, however, that the principles of the invention can be applied to track rods, torque rods and panhard rods used in other vehicle applications. 
     As seen in  FIG. 1 , the track rod  12  is pivotally pinned to the axle housing  10  and the frame member  14 . In particular, one end of the track rod is pinned or otherwise operatively coupled to a lug  14   a  forming part of the vehicle frame and the opposite end of the track rod is pinned or coupled to a lug  10   a  forming part of the axle assembly  10 . 
     As seen best in  FIG. 2 , one end of the track rod includes a pair of parallel, extending arms  20 , each having an associated mounting hole  22 . In the illustrated embodiment, a lug, for example the lug  14   a , is received between the arms  20  and includes a mounting hole (not shown), which is aligned with the holes  22 . A suitable pin member or bolt is passed through the aligned holes, thereby securing the arms  20  to the lug  14   a.    
     The opposite end of the track rod  12  also includes a pair of extending arms  26 , each including an associated hole  28 . According to the example, the lug  10   a  is received between the arms  26  and includes an associated hole (not shown). The mounting hole is aligned with the holes  28  and as explained above, a suitable pin member or bolt is received in the aligned holes and secures the end of the track rod  12  to the lug  10   a.    
     Turning now to  FIG. 3 , the arms  20  form part of a first end piece indicated generally by the reference character  12   a . The arms  26  form part of a second end piece/housing  12   b . During vehicle operation and as will be explained, the end pieces  12   a ,  12   b  can move relative to each other in response to road-induced shocks as the axle  12  traverses the terrain. 
     Referring also to  FIG. 4 , the track rod  12  includes at least two elastomeric members to be described, which permit controlled, relative movement between the end pieces  12   a ,  12   b . The end piece  12   a  includes a rigid plate member  30  to which the arms  20  are suitably attached, as by welding. A pair of gusset plates  32  is welded to the plate member  30  and arms  20  to rigidize the connection between the plate member  30  and the arms  20 . 
     The end piece  12   b  includes a housing indicated generally by the reference character  36  that is partially formed by plate extensions  26   a  of the arms  26 . Gusset plates  38 ,  39  reinforce and rigidize the arms  26 . Pairs of upper and lower cover plates  40 ,  42  extend between and are welded to the arm extensions  26   a  and also partially define the housing  36 . 
     Referring also to  FIG. 4 , an intermediate plate member  44  is rigidly fastened within the housing  36 . A gap  48  between the cover plate  40  and the gusset  38  provides access to the inside of the housing  36 . 
     A first elastomeric plate-like member  50  is received in the housing  36  and, after assembly, abuts the left side (as viewed in  FIG. 4 ) of the intermediate plate member  44  A second elastomeric plate member  52  is installed through the opening  48  and abuts the opposite side of the intermediate plate member  44 . A sliding or floating plate member  56 , also installed through the opening  48 , abuts the second elastomeric member  52 , as seen best in  FIG. 4 . 
     The first and second elastomeric members  50 ,  52 , the plate members  30 , 56  and the intermediate plate member  44  include associated holes  50   a .  52   a ,  30   a ,  56   a ,  44   a , respectively. When assembled, the holes are aligned. As seen in  FIG. 4 , the first elastomeric member  50  receives a bushing  60  that includes a smaller diameter portion  60   a  that extends through the hole  44   a  in the intermediate plate  44 . A smaller bushing  62 , having an inside diameter that corresponds to the reduced diameter portion  60   a  of the first bushing  60 , is sized to be received by the hole  52   a  in the second elastomeric member  52  and has an inside bore  62   a  that receives the narrow diameter portion  60   a  of the first bushing  60 . The smaller bushing  62  also includes an inside shoulder  62   b  which, as will be explained, serves as a stop. 
     As seen best in  FIG. 6 , the components are held together by a through bolt  70  which extends through the hole  56   a  formed in the sliding plate member  56 , the bore defined by the first bushing  60  and the bore  30   a  in the rigid plate member  30 . The through bolt  70  extends through the rigid plate member  30  forming part of the first end piece  12   a  and is adapted to receive a securement fastener such as a nut  70   a  and washer (not shown) to maintain the assemblage. It should be apparent from  FIG. 4 , that once the bolt  70  is installed, the end pieces  12   a ,  12   b  are clamped together. 
     With the disclosed construction, the first elastomeric member  50  is clamped between the intermediate plate  44  (forming first part of the housing  36 ) and the rigid end plate  30  forming part of the first end piece  12   a . The second elastomeric plate member  52  is clamped between the intermediate plate  44  and the floating plate  56 . According to a preferred embodiment, the elastomeric members  50 ,  52  are preloaded during assembly. This is achieved by the configuration of the first and second bushings  60 ,  62 . In particular, the clamping bolt  70  is tightened until the shoulder  62   b  of the smaller or second bushing  62  abuts the end of the first bushing  60 . Once the bushings abut, no further movement is permitted between the end plate  30  and the intermediate plate  44  and between the floating plate  56  and the intermediate plate  44 . The bushings are sized so that the elastomeric members are compressed a predetermined amount when the bushing  60 ,  62  abut each other. 
       FIG. 6  illustrates a position of the track rod components after the track rod has been preloaded. As indicated above, after preloading, the bushing  60 ,  62  abut each other and relative axial movement, toward each other, is inhibited. In particular, the reduced diameter section  60   a  includes an external stop surface  61 , which, in the illustrated embodiment, is an angled or chamfered surface. The bushing  62 , which includes a bore segment  63  adapted to slidably receive the reduced diameter portion  60   a  of the bushing  60 , has an outside diameter that is the same or substantially similar to the outside diameter of the larger diameter portion of the bushing  60 . The bushing  62  includes the inside shoulder  62   b  that defines a stop surface  65  which is abutably engageable with the stop surface  61  defined by the bushing  60 , 
     The intermediate plate  44 , which is fixed in the housing  36 , includes counter bores  67   a ,  67   b  that define circular recesses on either side of the bore  44   a . The circular recesses  67   a ,  67   b  have a diameter that corresponds to the outer diameters of the bushing  60  and the bushing  62 . 
     According to a feature of the invention, the circular recesses allow the bushings  60 ,  62  to move relative to the fixed intermediate plate  44  when forces are applied to the track rod during vehicle operation. 
     As discussed above, the elastomeric members  50 ,  52  are preloaded during assembly, The extent of preload is determined by the stop surfaces  61 ,  65  defined by the bushing  60 ,  62 . As should be apparent from  FIG. 6 , the bolt  70  and associated nut  70   a  are tightened in order to move the plate  30  (which forms part of the end piece  12   a ) and the floating plate  56  towards each other. Once the stop surfaces  61 ,  65  engage, no further relative movement between the plates  30 ,  56  are permitted. The amount of preload for the elastomeric members  50 ,  52  is determined by the total axial length defined by the bushings  60 ,  62  when their associated stop surfaces  61 ,  65  abutably engage. 
     In operation, the track rod receives tension and compression forces as the vehicle traverses the terrain.  FIG. 7  illustrates positions of the components when the track rod  12  is under tension. When the track rod is placed in tension, the end pieces  12   a ,  12   b  are urged apart. As seen in  FIG. 7 , the plate  30  forming part of the end piece  12   a  tends to move away from the fixed intermediate plate  44 . Since the plate  30  is locked to the floating plate  56  via the bolt  70  and bushings  60 ,  62 , the floating plate  56  is moved towards the intermediate plate  44 , placing the elastomeric member  52  under further compression. The compression force exerted on the elastomeric member  50  is correspondingly reduced. The left end of the bushing  62  (as viewed in  FIG. 2 ) moves into the circular recess  67   b  defined by the fixed intermediate plate  44 . 
     When the track rod is placed in compression, the end piece  12   a  moves towards the end piece  12   b . In so doing, the plate  30  of the end piece  12   a  moves toward the intermediate plate  44 , whereas the floating plate  56  moves away from the plate  44  because it is locked to the plate  30  via the bushings  60 ,  62  and bolt  70 . This movement tends to further compress the elastomeric member  50  and the preload, compression force on the elastomeric member  52  is reduced. 
     According to a feature of the invention, the elastomeric members  50 ,  52  include peripheral flanges  51 ,  53 , respectively. When the track rod is placed in either tension or compression, the peripheral flange of the elastomeric member being compressed may move into contact with the associated confining plates  40 ,  42  which serve to reduce the amount of compression that is permitted in the elastomeric member. The peripheral flanges  51 ,  53  also aid in maintaining alignment of the elastomeric members  50 ,  52  during and after installation. In particular, the peripheral flanges tend to inhibit rotation of the elastomeric members  50 ,  52  within the housing  36 . 
     As should be apparent, the controlled relative movement that is permitted between the end pieces  12   a ,  12   b  reduces the shock loads applied to the rear axle and/or frame of the vehicle during vehicle operation, especially over rough terrain. 
     With the disclosed construction, shocks received by the track rod  12  apply only compressive forces to the elastomeric members  50 ,  52  even if the shock/impact places the track rod in tension. For example, if the road induced shock urges the end pieces  12   a ,  12   b  towards each other (i.e. places the track rod  12  into compression), the first elastomeric member  50  receives an increased compressive force due to the shock the first elastomeric plate member is further compressed. If the shock urges the end pieces  12   a ,  12   b  apart (i.e. places the track rod  12  into tension), the second elastomeric member  52  receives a compressive force and the second elastomeric plate member  52  is further compressed. The disclosed apparatus buffers these shocks, thereby reducing the shock loads applied to the frame  14  and the axle housing  10 , thus reducing the chances of damaging either the frame mount  14   a  or the axle mount  10   a.    
     According to a feature of the invention, the cover plates  40 ,  42  (seen best in  FIG. 4 ) tend to confine the elastomeric members  50 ,  52  and thus improve the performance and reliability of the elastomeric members  50 ,  52  and inhibit them from being over deformed. 
     According to the preferred embodiment, the elastomeric members  50 ,  52  are made from rubber or urethane having a durometer in the range of  50  to  90 . It should be understood that other types of elastomeric materials may be used and are contemplated by the present invention. Shook absorbing members  50 ,  52 , not made of elastomeric materials, are also contemplated. For example, metal springs or Belleville washers may be used in place of the illustrated members  50 ,  52 . 
     The illustrated track rod  12  is shown as a weldment. It should be understood that the first and second end pieces  12   a ,  12   b  may be formed from castings as well. In addition, the housing  36  and the associated plate and elastomeric members  30 ,  50 ,  52 ,  56 ,  44  are shown as rectangular in shape. It should be understood that circular or an annular shaped housing is also contemplated which would utilize annular plate members and elastomeric members. 
     Although the invention has been described with a certain degree of particularity, it should be understood that those skilled in the art can make various changes to it without departing from the spirit or scope of the invention as hereinafter claimed.