Abstract:
A guard for the axle seal of a wheeled tractor being an annular steel structure that bridges the plane of the seal between a spindle and final drive including a pair of axially spaced flanges having circular outer peripheries, at least one of the outer peripheries of the flanges being sized to produce a narrow gap seal with a circular interior surface of a wheel rim, a hub extending axially between the flanges and spaced radially inward of said flange outer peripheries, the flanges, hub and interior wheel surface defining an annular space adapted to trap debris.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to improvements in protective devices for drive lines of heavy equipment operating in adverse environments such as landfills. 
   PRIOR ART 
   Compactors in the form of heavy wheeled tractors are used in the landfill industry to compact refuse for full utilization of the landfill space. U.S. Pat. Nos. 5,330,260, 5,451,100, 5,553,932, and 5,820,230 disclose a type of cutting device associated with the wheels of a compactor. The cutter devices operate to sever strands of material that would otherwise wrap around the axle, accumulate and develop excessive friction and/or find their way into a seal area between the rotating and non-rotating parts and destroy the seal. Seal destruction results in expensive drive line repairs and loss of machine time when the compactor is being repaired. The patented cutters have proven to be effective for some machines, but have not been widely adopted on certain large machines that have proven to suffer drive line failures. There has remained a need for a device to effectively protect the wheel seals on large landfill compactors not fitted with cutters of the type disclosed in the aforementioned patents. 
   SUMMARY OF THE INVENTION 
   The invention is directed to a novel guard for use at each wheel of a compactor used in a landfill or similar operation. The guard design is inspired, in part, by the realization that a primary source of axle seal failure in such environments is the forced entry of a strand of wire, cable or like high-tensile strength material into the plane of contact of the sealing elements. The guard of the present invention is arranged, as a first measure of wheel seal protection, with mechanical narrow gap seal elements intended to exclude debris, especially stranded material, from entering the zone of the respective wheel seal. As a second measure of defense, the guard is provided with an essentially closed annular space surrounding the seal that is intended to trap any debris that might get past the first mechanical seal. The trap can be especially effective when stranded debris enters the annular zone. This type of debris, to the extent that it is being forcibly wrapped around the axle by motion of the wheel is harmlessly wrapped onto and thereby trapped by a spool-like hub flanged at both its ends. Debris getting past the narrow gap seal is thereby trapped by this wrapping action. 
   In the disclosed embodiment, the guard is formed as semi-circular segments to enable its installation on an axle without disassembly of the final drive. Additionally, in the preferred embodiment, the guard is provided with two supplemental interior mechanical seals. The seals are in series with each other and with the primary exterior narrow gap seal with reference to the path that any debris must follow to reach the wheel seal. The structures that form the end boundary of the annular debris trapping zone serve to form the interior mechanical guard seals. Additionally, an outboard, cantilever supported, one of the end boundary structures seals with the axle assembly itself. This structure, ideally, is a sufficiently close clearance fit with the axle so that this cantilevered end can be directly supported by the axle when foreign objects are jammed against its exposed surfaces thereby resisting permanent distortion and consequent loss of performance. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective somewhat schematic view of a wheeled tractor used for compacting refuse material in a landfill; 
       FIG. 2  is a perspective view of an axle seal guard of the invention used at each of the four wheels of the compactor of  FIG. 1 ; 
       FIG. 3  is an exploded perspective view of the axle seal guard, an axle housing, final drive, and a wheel; and 
       FIG. 4  is a cross-sectional view of the guard shown in its relation to the associated axle housing, final drive, and wheel. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The invention has utility with wheeled tractors, known in the industry as compactors. Compactors are relatively heavy machines, fitted with steel wheels, that are driven back and forth over refuse dumped in a landfill. Compaction of the debris allows more refuse to be received in a given volume of landfill space. A conventional wheeled tractor or compactor  10  is schematically shown in  FIG. 1 . The compactor  10 , as is common, has a pair of axles with each axle carrying a wheel  11  on each side of the machine so that the compactor has four wheels. On large equipment such as manufactured by Caterpillar® under Model Nos. D6 through D12, each side of an axle  12  has a final drive  13  on its outboard end to which a respective wheel  11  is bolted. Rotation of a wheel  11  requires relative rotation between the final drive  13  and a spindle  14  bolted in fixed relation to a housing  16  of the axle. In the case of a Caterpillar compactor, this relative rotation is accommodated by a so-called duo-cone seal  17  that excludes dirt from entering the axle housing  16  and retains lubricant within the axle housing and final drive  13 . The duo-cone seal  17  has its sealing surfaces contacting at a plane  18  perpendicular to the axis of rotation of an axle  12 , final drive  13 , and wheel  11 , all of which are common or coaxial. 
     FIGS. 2-4  illustrate details of a guard  20  embodying the invention and arranged to protect the duo-cone seal  17  associated with the final drive  13  of each of the four wheels  11  on a compactor  10 . As is conventional, a wheel  11  is removably assembled on a final drive assembly  13  by a plurality of bolts. The guard  20  is preferably made from steel plate or steel castings and is an annular structure comprising two generally circular half sections  21 . In the illustrated embodiment, each half section  21  includes semi-circular walls  22 ,  23  between which is a semi-cylindrical shell  24 . The walls  22 ,  23 , and shell  24  can be integrated as a steel weldment or can be cast to shape. The guard half-sections  21  are assembled around an axle housing  16  and mate at a diametral plane so as to make a fully circular structure. 
   The end walls  22  are bolted to inboard sides of an end flange  26  on the axle housing  16  with bolts  27 . Where the tractor  10  is originally manufactured for use as a compactor for landfill operations, it is typically fitted with a flat plate on the end flanges  26 . This original plate is removed to allow the end walls  22  to be mounted as shown. Preferably, the inside periphery of each of the end walls  22  is scalloped so that radially outer parts of this inner periphery do not interfere with some of the original bolts used to bolt the spindle  14  to the axle housing  16 . This avoids the necessity of removing or at least largely unbolting the final drive  13  to install the guard  20 . Radially inward parts of the end walls  22  have holes located to align with some of the original holes in the axle housing end flanges  26  and spindle  14 . Bolts are assembled in these aligned holes to fix the guard sections  21  to the axle housing with the end walls  22  directly abutting the axle and flanges  26 . 
   In its assembled state, the guard  20 , at an inboard end wall  32 , formed by the semi-circular walls  22 , is thus fixed to the axle housing by the bolts  27 . Each section  21  of the guard  20  is held in place by a plurality of these bolts arranged along a corresponding part of the circular periphery of the axle housing flange  26 . The outboard end of the guard, represented by an end wall  33 , formed by the semi-circular walls  23 , is supported in cantilever fashion from the inboard end wall through the medium of the semi-cylindrical shells  24 . The half-sections  21  mate along respective edges in a diametral plane parallel to and extending through the axis of rotation of the wheel  11 . Adjacent the outboard end wall  33 , the guard half-sections  21  are fixed together by bolts  36  received in flanges  37  extending radially from the edges of the shells  24 . 
   The guard  20  is installed around the axle  12  while the wheel  11  is not mounted on the final drive  13 . The outboard end wall  33 , comprising the semi-circular walls  23 , has an inner circumference that is slightly larger than the local outside diameter of the housing of the final drive  13  that it surrounds, thereby forming a “narrow gap seal”  39  at this location. As used herein, a narrow gap seal is preferably less than ¼″, more preferably 3/16″ or less and, most preferably, less than ⅛″ in radial dimension. The outboard and inboard end walls  33 ,  32 , have outer circular peripheries sized relative to an inside diameter of an inner shell  38  of the wheel  11  to similarly produce a “narrow gap seal”  41 ,  42  at each of these locations. The guard  20  is constructed and arranged to protect the duo-cone seal  17  from entry therein of debris and, ultimately, destruction of this critical part. With particular reference to  FIG. 4 , it will be understood that the inboard end wall  32  is held tight against the axle flange  26  thereby preventing passage of solid debris through the interface between these bodies into the area of the seal  17 . The narrow gap seals  41 ,  42 , formed by the outer periphery of the inboard and outboard walls  32 ,  33  and the inside surface areas of the inner wheel shell  38 , serve to exclude debris from the seal  17 . As mentioned, an unprotected duo-cone seal  17  is particularly susceptible to destruction by cable, wire, or other high-tensile strength strand, because such a strand can be caught or entrained by the wheel  11  or material caught on the wheel and wound around the axle. Debris filling the space between the chassis of the compactor  10  and the wheel  11  can press material, including strands, into the interior of the wheel and ultimately into the sealing plane  18  of the duo-cone seal  17 . 
   In the unlikely event that debris or refuse material finds its way or is forced through the narrow gap seal  41 , such material is trapped in the annular zone, designated  43 , bounded by the end walls  32 ,  33 , semi-cylindrical shells  24  forming a hub  30 , and inner wheel shell  38 . It is desirable, though believed not as important as the inboard narrow gap seal  41 , that the second narrow gap seal  42  is formed by the outboard wall  33 . The presence of the outboard wall  33  will confine any strand material that enters the zone  43  and is wrapped onto the hub  30  formed by the semi-cylindrical shells  24  and positively prevent it from reaching the duo-cone seal  17 . While improbable, if material passes through the second narrow gap seal  42 , it will be obstructed from reaching the duo-cone seal  17  by the third narrow gap seal  39 . 
   The geometry and structure of the disclosed guard  20  has additional benefits. The outboard end wall  33  imparts a high rigidity to the guard  20 , making it easier to maintain the narrow gap seals  39 ,  41  and  42 . Radial deflection of the outboard end of the guard  20  caused by unusual force levels is limited by contact between the outboard end wall  33  and the final drive housing  13  thereby adding support to the guard  20 . The guard  20 , moreover, exhibits high rigidity because of its box-like structure. With the guard hub  30  spaced radially closely to the spindle  14 , the volume of the zone  43  is relatively large, giving it the capacity to trap a considerable volume of refuse material which, over time, might be able to accumulate after passing through the narrow gap seal  41 . 
   It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.