Abstract:
A guard for off road vehicles to protect the final drive area from debris which otherwise causes destructive abrasion and seal failure and particularly suited for the final drive of a track chain sprocket on a crawler. The guard encloses the space surrounding the final drive spindle housing and seal between the housing and a hub on which the sprocket is mounted. The guard can be safely installed on existing machines without disassembly of major parts of the final drive.

Description:
This application is a continuation-in-part of application Ser. No. 09/324,666, filed Jun. 3, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to improvements for land vehicles such as off road equipment and, in particular, to guards for the drive of wheels or sprockets for the same. 
     U.S. Pat. No. 5,713,644 illustrates a cutter device to reduce wear and tear on the final drive of a crawler such as manufactured Caterpillar, Inc. This cutter device is especially useful on machines operating on landfills that accept residential and commercial refuse, for example. Landfill environments present severe service conditions on machinery due to the mix of debris typically found at such sites. Material over which a machine runs tends to be drawn up and around rotary parts eventually leading to excessive wear through abrasion and oftentimes to catastrophic failure because of destruction of seals between parts rotating relative to one another. A need exists for a device that can protect drive areas of equipment of the type described in landfills, construction sites and other off road situations where the environment is adverse and that provides an alternative to the cutter device disclosed in the aforementioned patent for situations that are less than extreme. 
     More specifically, rotating drive wheels in the form of track chain sprockets, for instance, rotate relative to their support housings and normally have associated seals to protect bearings and gears within the housings that support the sprocket hubs for rotation. The housings are subject to high wear rates through abrasion by debris entwined on the rotating parts. This debris eventually can wear through the walls of the housing causing catastrophic failure of bearings and related parts. 
     Where a seal on a final drive of a crawler is damaged prematurely by intrusion of debris, the cost to repair the same may range, by way of example, between $3,000 to $4,000. Wear on a final drive housing or sprocket hub can cost as much as $7,000 to $8,000 in repair. A loss of oil from a damaged seal can result in repair work for internal damage of as much as $50,000. 
     It is desirable, especially for large machines where the major drive components are too heavy to be manipulated by hand, that any protective guard be capable of being installed without dismantling and reinstalling such major components of the machine. 
     SUMMARY OF THE INVENTION 
     The invention provides a guard for drive assemblies of commercial land vehicles such as track mounted machines sometimes referred to as crawlers. Chain sprockets for the track are rotatably supported on housings at opposite sides of a crawler. In the disclosed embodiment, the guard extends between a fixed housing on the main body or frame of the machine and the hub supporting a track chain sprocket. The guard preferably has a relatively large diameter so it occupies most of the space available adjacent the path of the track chain. This geometry advantageously limits the amount of debris that can accumulate on the sprocket adjacent the rotating areas. 
     An important aspect of the invention is the ability of the guard to be installed on a machine without requiring disassembly and reassembly of major parts of the final drive system. The disclosed guard shares the original mounting bolt locations of the drive system but is configured to allow at least some of the mounting bolts to remain in place at locations circumferentially spaced around the axis of rotation of the sprocket while the guard is being installed. This feature ensures that various drive line parts will be safely held in place without being stressed in a manner that could cause physical damage or even bodily injury. 
     Another important feature of the invention is the provision of telescoping parts that enable the entire gap between the housing and sprocket to be protected from entry of debris. The telescoping guard portions in the illustrated embodiment have a labyrinth-like configuration which reduces the risk that debris could work its way into the guard. 
     The disclosed guard has demonstrated remarkable effectiveness in protecting the seals of the sprocket drive while achieving excellent durability. All of the reasons for the performance of the guard are not yet fully understood, but it is believed that major factors are related to the relatively large diameter of the guard in comparison to the diameter of the sprocket. First, since the circumference of the guard is relatively long, the risk that a strand of cable, rope, wire, strapping, fabric or the like will be long enough to wrap numerous times around the guard is reduced. Second, the close proximity of the guard to the underside surfaces of the track apparently allows the system to be self-cleaning such that the track “scrubs”, in a non-contact manner, the external surface of the guard. The smooth character of the circular guard in the circumferential direction, additionally, appears to play a role in the anti-wrapping and durability performance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a somewhat schematic side elevational view of a track mounted machine or tractor embodying the invention; 
     FIG. 2 is a fragmentary elevational view, taken from the rear, of the final drive system of the right side of the tractor protected by the guard of the invention; 
     FIG. 3 is a cross sectional partial view of the guard of the invention taken in a vertical plane parallel to the rotational axis of the track chain sprocket; 
     FIG. 4 is an exploded perspective view of an inboard base portion of the guard associated with a non-rotating spindle housing part of the final drive system; 
     FIG. 5 is an exploded perspective view of an outboard base portion of the guard mounted with the rotating parts of the final drive system; 
     FIG. 6 is a perspective view of an inboard shield half section; 
     FIG. 7 is a perspective view of an outboard shield plate; 
     FIG. 8 is a fragmentary perspective view of a modified form of an inboard base portion associated with the non-rotating housing part of the final drive system; 
     FIG. 9 is a perspective view of specialized bolts used with still another form of an inboard base portion of the guard of the invention; 
     FIG. 10 is a view similar to FIG. 3 illustrating a modified outboard base portion of the guard and showing the relationship of the guard to the track; and 
     FIG. 11 is a representation of a generalized sprocket segment and guard mounting bolt of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and in particular to FIG. 1, there is shown a land vehicle  10  in the form of a track mounted machine or crawler. The illustrated machine can represent the type of crawler design manufactured by Caterpillar, Inc. and referred to as a High Drive model. The machine  10  is of a known construction and has a prime mover, typically a diesel engine, and a drive train which includes a pair of final drives  11  represented by a spindle housing  12  and a hub assembly  13  on each side of the machine  10 . The hub assembly  13  rotates about an axis  14 . The non-rotating spindle housing  12  is a circular bell-shaped structure that is fixed on the machine frame, designated  29 , by bolts  16 . The bolts  16  are generally evenly spaced in a circular pattern concentric with the axis  14  and extend through a flange  17  of the housing  12 . 
     The hub  13  carries a sprocket  18  that is in the form of a plurality of arcuate segments  19 . The sprocket segments  19  are fixed to a flange  21  of the hub  13  by a plurality of bolts  22 . The bolts  22  are assembled axially through holes in the segments  19  and the hub flange  21  generally evenly spaced about the circumference of the hub. The end of an extension  23  of the hub  13  lies adjacent the housing  12  and a seal assembly generally indicated at  24  and known in the art is disposed between these elements to accommodate rotation of the hub  13  with its extension  23  relative to the housing  12  while sealing lubricant in these parts and excluding environmental debris, dust, water and the like. 
     The invention provides a guard  26  which in a preferred embodiment is fabricated as a weldment of steel plate and bar. The guard  26  includes two generally circular base portions  27 ,  28 . An inboard base portion  27  is associated with the spindle housing  12  and frame  29  of the machine  10  while the outboard base portion  28  is associated with the rotating sprocket  18  and hub  13 . Both the inboard and outboard base portions  27 ,  28  are split approximately in halves for purposes of installation. 
     The inboard guard base portion  27  has mating semi-circular halves  31 ,  32 . The halves  31 ,  32 , have their main bodies  30  rolled from steel plate stock and have an internal semi-circular radial flange  33  spaced a predetermined distance away from an associated end  34 . Each flange  33  has holes  36  that align with mounting holes in the housing flange  17 . On the external face of the flange  33  are welded or otherwise fixed a plurality of apertured spacers  37  in registry with the holes  36 . The spacers  37  are at least as long in the axial direction as the heads of the bolts  16  mounting the spindle housing  12 . The holes in the flange  33  and spacers  37  are sized to receive bolts of the same diameter as the bolts  16  mounting the spindle housing  12 . 
     FIG. 5 illustrates details of the generally cylindrical outboard base portion  28  which is comprised of two similar mating half shells  51 ,  52  fabricated primarily of steel plate. At their outer ends, the shells  51 ,  52  have external radial flanges or brackets  53  that are located at pre-determined spaced locations about the periphery or circumference of the guard base portion  28 . The flanges  53  have bolts  54  that align with holes in the hub flange  21  used to mount the sprocket segments  19 . The bolts  54  have shallow heads for clearance of the track chain and are preferably welded to the flanges  53 . 
     The guard includes an inboard shield  56  conveniently formed as a mating pair of similar generally semi-circular parts  57 ,  58 . These parts  57 ,  58  have the same cross section when viewed in a plane parallel to the axis  14  as in FIG.  3 . One of the parts  57  is illustrated in FIG.  6  and includes an inner semi-cylindrical steel plate  59 , a spacer bar  60  rolled into a semi-circular shape and a semi-cylindrical outer steel plate  61 . These pieces  59 - 61  are welded together so that the outer plate  61  is radially outward of and concentric with the inner plate  59  and a cylindrical groove  62  is formed between these plates. An inboard side of the inner plate  59  extends axially away from the bar  60  and the outer plate  61  leaving its outer surface area  63  uncovered. A plurality of circumferentially spaced countersunk holes  64  are formed in the inboard side of the inner plate  59  through the surface  63 . The holes  64  are located so that they can be aligned with threaded holes  65  in the inboard base portion  27 . Flat head socket type bolts  74  are assembled flush in these holes  64 ,  65  to retain the shield parts  57 ,  58  on the inboard base portion  27 . The inner surface of the inner plate  59  has a radius substantially equal to the outer radius of the base portion  27 . 
     The guard  26  has an outboard cylindrical shield  67  made of a plurality of steel plates  68 . The plates  68  have plain cylindrical segment configurations and an inside radius substantially equal to the outside radius of the outer surface of the outboard base  28 . These shield plates  68  have countersunk holes  69  that align with threaded holes  72  in the outboard base portion  28  and receive bolts that retain the plates in place on the outboard base. The bolts  70  can be flat head socket type fasteners that fit with their heads flush in the countersunk holes  69 . 
     The guard  26  is provided over the final drive  11  on each side of the machine  10 . The disclosed guard  26  has the ability to be safely installed without disassembly of the track, designated  66 , sprocket  18  or hub  13 . The inboard guard base portion  27  is assembled by first removing a limited number of bolts  16  that mount the spindle housing  12  to the machine frame  29  leaving at least about half of these bolts in place generally evenly distributed about the circumference of the housing  12 . The particular bolts  12  that are removed are determined by the positions of the spacers  37 , the bolts being removed where the spacers exist. The base portion halves  31 ,  32 , are put in position and longer substitute bolts  71  are assembled through the flanges  33 , spacers  37  and spindle housing flange  17  and are suitably tightened. 
     The outboard guard base portion  28  is installed in place after the inboard base portion  27  is installed as just described. A limited number of sprocket segment mounting bolts  22  at locations around the sprocket  18  are removed. The bolts  22  are removed at locations corresponding to the flanges  53  and bolts  54  on the shell halves  51 ,  52 . Nuts on the outside of the sprocket segments  19  are suitably tightened onto the bolts  54 . It will be seen that the flanges  53  and bolts  54  are arranged to leave at least about half of the original bolts  22  in place distributed around the circumference of the sprocket so that the sprocket segments  19  are safely held in place during this installation process. 
     The inboard shield  56  is mounted on the inboard base  27  and retained, as indicated above, by the bolts  74 . The bolt holes  64 ,  65  are arranged to permit the joints between the shield halves  57 ,  58  to be angularly spaced from the joints between the base halves  31 ,  32  so as to rigidify this assembly. Thereafter the outboard shield plates  68  are mounted on the outboard base  28  with portions received in the annular groove  62 . The respective holes  69  in the plates  68  are arranged relative to the holes  72  in the outboard base such that the joints between them are angularly displaced from the joints between the base halves  51 ,  52  thereby rigidifying this assembly. 
     With particular reference to FIG. 3 it will be seen that the assembled guard  26  completely envelopes the annular space between the spindle housing  12  and the sprocket  18 . The guard  26  protects the final drive  11  in several ways. It substantially closes off this annular area making it impossible for any large quantity of debris to be entrained with the sprocket or wheel  18 . The housing  12  is shielded from abrasion which otherwise occurs when entrained debris rotates with the hub assembly  13  and sprocket  18 . Such abrasion can eventually result in destruction of the housing  12  and major repair costs. Importantly, the guard  26  prevents strand-like material such as cable, wire, rope, strapping or even vine-like vegetation from finding its way into the seal assembly  24  between the housing  12  and hub extension  23  where it can ruin the seal with catastrophic results to the internal parts of the drive. The telescoping relation of the inboard and outboard shields  56 ,  67  at the groove  62  presents a serpentine or labyrinth path to effectively block the passage of any foreign objects tending to be directed towards the annular area enclosed by the guard  26 . As shown, the radial clearances or gaps between the shields  56 ,  67  is small compared to the axial length of such clearances or gaps. Where the guard  26  is exposed to a particularly hostile environment the shields  56 ,  57  may be eventually consumed by abrasion but this is preferable to destruction of the housing  12  or seal assembly  24  since these elements can be easily removed and replaced with new units at significantly less cost. Steel bands, not shown, can be suitably fastened around the rows of bolts  70 ,  74 . 
     An alternative construction of the inboard guard base portion  27 A is illustrated in FIG.  8 . In this arrangement, the flange  33  is replaced by a plurality of relatively short arcuate brackets  76 . Original bolts holding the housing  12  to the machine frame  29  at the locations of the brackets  76  are removed. With the modified guard base portion  27 A in place substitute somewhat longer bolts are assembled through holes in the brackets  76  into the machine frame. 
     FIG. 9 illustrates still another variant of the invention where special bolts  81  are substituted for the original bolts  16  mounting the housing  12 . The bolts  81  are threaded on opposite sides of a central hex head  82 . The bolts  81  are tightened onto the housing and thereafter the inboard guard base portion  27 B is installed by assembling it so that the ends of the special bolts  81  extend through holes  83  in a flange  84  and nuts are thereafter tightened onto these ends. It will be understood that as many as all of the original housing mounting bolts  16  can be exchanged with the double ended bolts  81  where a suitable number of holes  83  are provided in the inboard guard portion flange  84 . The substitution of bolts can be done one or a few at a time so that the static forces on the housing  12  are safely held by the remaining bolts. 
     It will be understood that when either guard base portion  27  or  28  is being assembled, a large number of the original bolts  16 ,  22  are left in place at circumferentially spaced locations on the housing  12  or hub assembly  13 . In all cases, bolts holding the housing  12  or sprocket  18  in place will preferably exist at spaced locations in an arc greater than 180° on either of these circular elements. 
     FIG. 10 illustrates a modified form of an outboard base portion  86  of the guard  26 . Various parts of the guard shown in FIG. 10 that are the same as or similar to the parts illustrated in FIG.  3  and described hereinabove are given the same reference numerals. An outboard base portion  86  has semi-circular flanges  87  extending radially outwardly from the half shells  51 ,  52 . The flanges  87  have axially oriented holes  88  aligned with the bolt holes of the sprocket segments  19  and hub flange  21 . Special sprocket segment and guard mounting bolts  89 , described below, are assembled through the guard flange holes  88 , the hub flange  21  and sprocket segments  19  and are tightened with nuts  91  to secure the outboard base portion  86  in place. Hex head bolts  92 , serving the function of the flat head bolts  70  of FIG. 3 to hold the outboard shield  67  in place, can be protected from abrasion and other damage by semi-circular steel bands  95  welded to the exterior of the shield  67  and provided with clearance holes for the heads of these bolts. 
     FIG. 10 illustrates the general relationship of the track  66  to the final drive  11  and guard  26 . The corresponding arrangement on the other side of the vehicle  11  is symmetrical. As is common in the industry, the track  66  comprises an endless loop of links  93  interconnected by pins  94  assembled through bushings  96 . The track  66  also includes shoes or pads  97  bolted or otherwise fixed to the links  93 . The track shoes engage the ground on which the vehicle  10  operates. At each side of the vehicle  10 , the track  66  is trained around the drive sprocket wheel  18  and lower idler wheels  15  and  20 . As shown in FIG. 10, the track shoes  97  extend inboard and outboard of the sprocket  18  with the inboard portions covering, i.e. encircling, substantially all of the guard  26 . The radially innermost or smallest path of the track  66  around the sprocket  18  is taken by inward facing surfaces  98  of the links  93 . The guard  26  accommodates movement of the track  66  along this path by configuring the bolts  89  and flange members  87  (or the bolts  54  and flanges  53  of FIG. 3) to lie within the width of the teeth  90  of the sprocket  18  (i.e. within the planes of the radial faces of the teeth  90 ) and the outboard base portion  28  to lie radially within but relatively close to this path. Inboard of the track links  93 , the guard  26  increases in diameter so that it is near the underside of the track shoes  97 . 
     The ability of the guard  26  to avoid excessive build-up of material around it is not fully understood. It is believed that the track  66  by its close proximity to the guard is able to “scrub” or knock off material when it starts to build-up on the guard. Additionally, the relatively large diameter of the guard as compared, for example, to the diameter of the housing and hub at the seal assembly  24  reduces the tendency of strand-like material to wrap several times around the guard because its circumference is relatively large. Additionally, the relatively smooth circumferential outer surface of the guard, interrupted only negligibly by the flush or recessed bolts  74 ,  70  or  92 , and the joint lines between the sections of the inboard shield  56  and between the plates of the outboard shield  67 . 
     When the invention is applied to the High Drive models built by Caterpillar, Inc., the guard parts can be efficiently mounted on the sprocket wheel with bolts having the following approximate dimensions (inches): 
     
       
         
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 G 
                   
               
               
                   
                 A 
                 B 
                 C 
                 D 
                 E 
                 F 
                 THREAD 
               
               
                 OVERALL 
                 SHANK 
                 BEVEL 
                 THREAD 
                 HEAD 
                 SHANK 
                 DIAMETER/ 
                 NUMBER OF 
               
               
                 MODEL 
                 LENGTH 
                 LENGTH 
                 LENGTH 
                 LENGTH 
                 LENGTH 
                 DIAMETER 
                 PITCH 
                 BOLTS/SIDE 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 D4H, D5M 
                 2.272 
                 1.272 
                 .180 
                 .707 
                 .31 
                 .675 
                 5/8-18 
                 20 
               
               
                 D5H; D6M,H,R 
                 2.437 
                 1.437 
                 .180 
                 .812 
                 .31 
                 .675 
                 5/8-18 
                 23 
               
               
                 D7H,R; D8N,R 
                 2.875 
                 1.687 
                 .187 
                 1.00 
                 .31 
                 .801 
                 3/4-16 
                 25 
               
               
                 D8L 
                 3.062 
                 1.687 
                 .187 
                 1.187 
                 .31 
                 .801 
                 3/4-16 
                 27 
               
               
                 D9N,R 
                 3.312 
                 2.00 
                 .187 
                 1.120 
                 .31 
                 .937 
                 7/8-14 
                 30 
               
               
                 D9L 
                 3.50 
                 2.120 
                 .250 
                 1.120 
                 .437 
                 .930 
                 7/8-14 
                 27 
               
               
                 D10N 
                 3.875 
                 2.437 
                 .187 
                 1.250 
                 .375 
                 1.056 
                 1-14 
                 30 
               
               
                 D11 
                 4.28 
                 2.937 
                 .187 
                 1.45 
                 .410 
                 1.18 
                 1-1/4-14 
                 32 
               
               
                   
               
             
          
         
       
     
     The dimensions given above represent a shortening of the head length and a lengthening of the shank compared to factory-supplied bolts. Typically, the factory bolts have head lengths greater than 50% of their shank diameters while suitable geometry for the present invention involves bolt head lengths shorter than 50% of the shank diameter. The disclosed bolt geometry enables the bolts  89  to be not substantially greater in length than the width of the teeth  90  of the sprocket  18  but also to accommodate the thickness of the guard flange  87 . The dimensions given for the bolt head length (height) and the shank length are for a flange  87  with an axial thickness of ½″. Where other flange thicknesses are used, the dimensions can be suitably modified. Accordingly, length dimensions given above are approximate and can be modified to account for different thicknesses of the flange  87  which can be reduced to ¼″ for example in the smaller machines. Similarly, the diameter of the shanks can vary according to industry standards for like finish bolts. Additionally, if desired, the bolts can have a thread diameter increased from that shown up to the diameter of the respective shank. The heads of the bolts  89  have hexagonal cross-sections of standard size. 
     Various modifications of the guard of the invention are envisioned. Routine changes can involve welding various parts or their equivalents together rather than bolting or making such parts integral with others. It is desirable, as with the disclosed arrangement of the invention, that at least a portion of the guard can be disassembled to provide access to the bolts retaining the spindle housing in place on the frame. This permits the established practice of servicing the planetary drive of the sprocket hub by simultaneously removing both the spindle housing and the sprocket hub. The invention is useful with a variety of track-type vehicles including both loaders and bulldozers with conventional drive sprocket wheels near ground level. 
     While the invention has been shown and described with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein shown and described will be apparent to those skilled in the art all within the intended spirit and scope of the invention. Accordingly, the patent is not to be limited in scope and effect to the specific embodiments herein shown and described nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.