Abstract:
This invention relates to a rotatable wheel for use on a work machine. The wheel is designed with improved wheel bearing positioning, stud retention method and bearing seal protection.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates generally to wheels for use to move work machines about the ground and more particularly to a geometric design for a wheel.  
         BACKGROUND  
         [0002]    Work machines, such as off-highway trucks and wheel loaders, typically have at least a pair of wheels that are rotatably mounted on corresponding axles or spindles. The wheels, when assembled on the work machine, may additionally attach to wet (liquid cooled) brake assemblies and have a rim and tire mounted to the wheel. Such wheels have a hub that defines a cavity for reserving a quantity of bearing lubricant, and a first seal arrangement serves to contain the lubricating oil in the hub. A second sealing arrangement serves to contain the brake coolant in the brake at the position where the non-rotatable portion of the brake interfaces with the rotatable wheel. There are two basic types of forces or loads exerted on the structure of the wheel. The first is an axial force caused by the pre-loading of the wheel bearings. To maximize the life of the wheel bearings, axial should be maintained nearest to the specifications of the bearing manufacturer as possible. Second is a radial force caused by the weight of the machine on each wheel. The radial forces on the wheel tend to be more dynamic and fluctuate greatly due to machine traveling across rough or uneven terrain. Because the rim mounting flange extends from the hub, the radial forces are translated to the hub. Additionally, the positioning of the wheel bearings in relation to the centerline of the load, also referred to as a load line, has a large impact on bearing life. This is particularly true for steerable wheels. For example, if one of the bearings on a steerable wheel is axially positioned near the load line of the wheel, there are higher twisting forces on the bearing than if the same bearing is positioned farther away from the load line.  
           [0003]    The geometric design of the wheel may additionally impact the life and functionality of the seals. It is most desirable to have a geometric design including a hub that is substantially cylindrical cross section between the wheel bearings with the rim mounting flange extending outward perpendicular to the hub. The cylindrical hub design translates pre-load forces through the hub primarily through axial force vectors and the radial forces are translated perpendicular to the axial forces. A hub having an oval or angled cross section translates the pre-load and radial forces through a greater combination of axial and radial force vectors, this results in a coupling of the independent pre-load and radial forces. The coupling of the independent forces now causes the critical pre-load become dynamically impacted. As with the design of many structures, the typical design of a wheel permits a predetermined amount of elastic deformation or flexing. It is desirable to permit some flexing of the rim mounting flange in order to minimize flexing near critical elements, such as, sealing surfaces and bearing mounting surfaces.  
           [0004]    An additional problem with work machines of this nature is that road conditions at many mine sites throughout the world are extremely bad. Many of the roads are typically constructed of dirt and rocks. Small rocks and debris gets picked up by the tires and may be dropped into the wheels, the rocks and debris may accumulate near seal cavities. Additionally, water is often spayed on the roads to reduce dust. The dirt is therefor turned to mud, and the mud is thrown onto the wheel. A build of debris, mud and rocks near the wheel seals may open or cause damage to the seals. A damaged seal may in turn cause a loss/or contamination of brake coolant or bearing lubrication, resulting in premature mechanical failure of associated components.  
           [0005]    The present invention is directed to overcome one or more of the problems described above.  
         SUMMARY OF THE INVENTION  
         [0006]    In one aspect of the present invention, a rotatable wheel for a work machine has a central axis and a cylindrical hub defined about the axis. The hub has an inside surface and an outside surface outwardly spaced from the inside surface. Additionally, the hub has an inboard end and an outboard end opposite the inboard end. Bearing mounting surfaces are located on the inside surface of the hub near the inboard and outboard ends. A first sealing surface is located near the inboard end and adjacent the hub&#39;s inner surface. The rotatable wheel comprises a rim mounting flange extending radially outward from the outside surface interposed the inboard and outboard ends, a second sealing surface extends about the hubs outside surface and a recessed portion is located on the outside surface between the mounting flange and the second sealing surface. The recessed portion provides a barrier to keep debris away from the second sealing surface.  
           [0007]    In a second aspect of the present invention, is provided a work machine having a plurality of rotatable wheels. The rotatable wheels are adapted for moving the work machine along a surface. Additionally, the work machine has a engine and a drive train. At least one of the rotatable wheels is connected to the drive train. At least one of the rotatable wheels comprises a cylindrical hub with central axis and an inside surface defined about the central axis. An outside surface is spaced outward of the inside surface. An inboard end is defined on the hub and an outboard end is spaced axially away from the inboard end. A bearing mounting surface is located on the inside surface near each of the inboard and outboard ends. A mounting flange extends radially outward from the outside surface. A first sealing surface is positioned inboard and adjacent to the inboard bearing surface. A second sealing surface is positioned between the mounting flange and the inboard end. A recessed portion of the hub is positioned between the mounting flange and the second sealing surface. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a perspective sectional view of the wheel of the present invention.  
         [0009]    [0009]FIG. 2 is a perspective sectional view of a front spindle for an off highway truck having a wet brake and the wheel of the present invention assembled thereon.  
         [0010]    [0010]FIG. 3 is a perspective sectional view of a rim attached to the rim mounting flange of a wheel.  
         [0011]    [0011]FIG. 4 is a perspective view of a stud for attaching a rim to a wheel. 
     
    
     DETAILED DESCRIPTION  
       [0012]    While the invention is open to various modifications and alternatives, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. There is no intent to limit the invention to the particular form disclosed.  
         [0013]    In the following detailed description of the invention, “inboard” refers to the end or side that is to the left of a load line. The load line extends vertically through the center of a tire, as viewed from the front of a work machine. The term “inboard” additionally corresponds to the end of the wheel that is closest to a longitudinal vertical center plane of the work machine.  
         [0014]    “Outboard” refers to a side or end that is furthest from the vertical centerline.  
         [0015]    [0015]FIG. 1 illustrates a rotatable wheel  10  having a typical cylindrical rim  12  fastened thereon. The rim  12  is adapted for having a tire (not shown) mounted on an exterior surface  14  of the rim  12 . The rotatable wheel  10  is typically manufactured from a casting. The casting is machined to the manufacturers specified dimensions using conventional machining techniques.  
         [0016]    The wheel  10  is defined about a central axis  16  that extends horizontally through the wheel  10  and the load line  18  that extends vertically through the wheel  10 . The load line  18  is defined relative to the axial center of a tire (not shown) as the tire would be viewed mounted on the rim  12 . The wheel  10  has a cylindrical hub  20  disposed about the central axis  16 . The hub  20  has an inside surface  22  at a distance radially outward of the central axis  16 . An outside surface  24  is disposed on the hub  20  at a distance radially outward of the inside surface  24 . The hub  20  further defines an inboard end  26  and an outboard end  28  opposite of the inboard end  26 . A threaded hole  29  extends from the inside surface  22  to the outside surface  24  at a location near the outboard end  26  of the hub  20 . The threaded hole  29  is adapted to engage plug (not shown) is. The outboard end  26  of the hub  20  has a flat surface  30  with a pattern of threaded holes  32  radially spaced about the flat surface  30 . The flat surface  30  also includes a circular groove  34  that is adapted to receive an o-ring (not shown). An inboard bearing mounting surface  36  and an outboard bearing mounting surface  38  are defined on the inside surface  22  of the hub  20 . The outboard bearing surface  38  is located adjacent the outboard end  28  of the hub  20  and an inboard bearing surface  36  is located adjacent the inboard end  26  of the hub  20 . A first distance d1 is representative of the distance from the load line  18  to the outboard bearing mounting surface  38 . A second distance d 2  is representative of the distance from the load line  18  to the inboard mounting surface.  
         [0017]    The inboard end  26  of the wheel  10  includes a rotatable disk anchor portion  40 . The rotatable disk anchor portion  40  has an inner annular portion  42 . An outside surface  46  of the rotatable disk anchor portion  40  is defined opposite the inside surface  44 . The outside surface  46  includes a plurality of parallel splines  48  spaced radially about the outside surface  46 . The splines  48  are oriented in an axial direction about the inside surface. The splines  48  are adapted to engage a plurality of rotatable disks (not shown) for a wet brake assembly  52 .  
         [0018]    A rim mounting flange  54  extends radially outwardly from the outside surface  24  of the hub  20 . The rim mounting flange  54  is interposed the inboard end  26  and the outboard end  28  of the hub  20 . The rim mounting flange  54  defines an inboard surface  56  and an outboard surface  58 . The outboard surface is  58  spaced at an axial distance outboard of the inboard surface  56 . An outer edge  60  is defined about the rim mounting flange  54  adjoining the inboard surface  56  and the outboard surface  58 . A circular raised portion  62  of the rim mounting flange  54  extends inwardly from the inboard surface  56 . The raised portion  62  is coaxial with the central axis  16  of the hub  20 . The raised portion  62  is located near the outer edge  60  of the rim mounting flange  54 . The raised portion  62  has a first surface  64  that faces the hub  20 , a second surface  66  facing away from the hub  20  and a third surface  68  joining the first and second surfaces  64 , 66 . A ring groove  70  is defined about the second surface  66  and adapted to receive a snap ring  72 .  
         [0019]    A plurality of holes  74  are disposed on, and extend axially through the rim mounting flange  54 . The plurality of holes  74  are radially spaced a predetermined distance  76  about the central axis  16  of the hub  20 . The each one of the plurality of holes  74  is adapted to receive a stud  78 . The studs  78  are cylindrical fasteners having a first end  80 , a second end  82  and an outer surface  84  therebetween. The outer surface  84  of the studs  78  include a threaded portion  86  that extends from the first end  80  toward the second end  82 . The second end  82  of the studs  78  have a head  88  defined thereon. The heads  88  of the studs  78  are larger in diameter than the holes  74  in the rim mounting flange  54 . The heads  88  of the studs  78  include a top surface  90  and an edge surface  92  adjacent to the top surface  90 . A flat portion  94  is defined on the edge surface  92 . Each stud  78  is adapted to be inserted into one of the plurality of holes  74 . Each stud  78  is positioned into its respective hole with the flat portion  94  of the head  88  positioned adjacent to the second surface  66  of the raised portion  62 . The stud  78  is further inserted until the head  88  of the stud  78  contacts the inboard surface  56  of the rim mounting flange  54 . The threaded portion  86  of the stud  78  protrudes through the outer surface  56  of the rim mounting flange  54 . The snap ring  72  is positioned into the ring groove  70  to hold the stud.  
         [0020]    The wheel  10  of the present invention further includes a first and second brake sealing portion  96 , 97 . The first brake sealing portion  96  is defined by a raised portion  98  that extends radially outward from the outside surface  24  of the hub  20  at an axial location interposed the rotatable disk anchor  40  and the rim mounting flange  54 . The first brake sealing portion  96  includes an inboard facing surface  98  and an outboard facing surface  100  opposite the inboard facing surface  98 . An outer edge  102  of the brake sealing portion  96  joins the inboard facing surface  98  and the outboard facing surface  100 . A circular sealing surface  104  is defined about the inboard facing surface  98  of the brake sealing portion  96 . The circular sealing surface  104  is defined coaxial with the central axis  16  of the hub  20 . The circular sealing surface  104  is adapted to engage a rubber toric  106  of a duo-cone face seal  108 . The second brake sealing portion  97  is disposed on the inboard end  26  adjacent the inside surface of the hub  20 . Other types of commonly known face seals may be interchanged with a duo-cone seal.  
         [0021]    A recessed portion  110  extends about the outside surface  24  of the hub  20 . The recessed portion  110  is interposed the brake sealing portion  96  and the inboard surface  56  of the rim mounting flange  54 . The recessed portion  110  is coaxial with the central axis  16  of the hub  20  and has an inside diameter  112  that is less than the outside diameter of the first brake sealing portion  96 .  
         [0022]    [0022]FIG. 2 illustrates the rotatable wheel  10  of the present invention having a rim  12  attached thereon. Additionally, the rotatable wheel  10  is shown assembled on a steerable spindle  114  assembly as used on large off-highway trucks. The spindle and wheel  10  assembly further includes a wet brake assembly  52  non-rotatably engaging the spindle  114  and rotatably engaging the wheel  10 .  
         [0023]    The spindle  114  is defined about the central axis  16  and has a outboard end  116  and an inboard end  118  disposed opposite the outboard end  116 . An outer surface  120  is defined about the inboard end  118  of the spindle  114  and spaced a distance outward from the central axis  16 . An outboard bearing surface  122  is defined on the outer surface  120  adjacent the outboard end  116 . An inboard bearing surface  124  is defined inboard of the load line  18  on the outer surface  120  of the spindle  114 . A large diameter portion  126  with an outside circumferential surface  128  is defined inboard of the inboard bearing surface  124 . The large diameter portion  126  of the wheel  10  spindle has a series of parallel splines  130  about the outside circumferential surface  128 . The inboard end  118  of the spindle  114  has a bore  131  disposed in a substantially vertical orientation. The bore  131  is adapted to receive one end of a strut (not show) of a suspension system of a work machine.  
         [0024]    The wet brake assembly  52  includes a non-rotatable member, or brake anchor  132 , and a plurality of brake disks (not shown). The brake anchor  132  defines a substantially cylindrical member having an inboard end  136 , an outboard end  138  and a cylindrical inner portion  140  that extends from the inboard end  136  to the outboard end. The outboard end  138  of the brake anchor  132  defines a sealing surface  142  for engaging a rubber toric  106  of a duo-cone seal  108 . The inner portion  140  of the brake anchor  132  defines a first inner surface  142  adjacent the inboard end  138  and a second inner surface  144  adjacent the outboard end  138 . A cavity  146  is defined between the first inner surface  142  and the second inner surface  144 . A plurality of radially inwardly face splines  150  are disposed about the first inner surface  142  of the brake anchor  132 . The splines  150  are adapted to mate with a plurality of radially outwardly face splines  152  disposed on the large diameter portion  126  of the spindle  114 . The second inner surface  144  of the brake anchor  132  is of a larger diameter that the first inner surface  142 . A plurality of radially inwardly facing splines  154  are disposed about the second inner surface  144  of the brake anchor  132 . The cavity  146  serves as a housing for typical working components of the wet brake assembly  52  and will not be discussed in detail.  
         [0025]    The brake disks of the brake assembly  52  include a plurality of non-rotatable disks (not shown) and a plurality of rotatable disks. The non-rotatable disks and the rotatable disks include a first side, a second side, an inner circumference and an outer circumference. The outer circumference of the non-rotatable disks includes a series of teeth spaced evenly thereabout. The plurality of teeth on the non-rotatable disks are adapted to engage the splines of the second inner surface  144  of the of the brake anchor  132 . A plurality of teeth are defined about the inner circumference of the rotatable disks. The plurality of teeth on the rotatable disks are adapted to engage the splines  48  on the wheel  10 . The rotatable disks and non-rotatable disks are assembled into the brake assembly  52  in alternating order.  
       INDUSTRIAL APPLICABILITY  
       [0026]    The construction and geometric design of the rotatable wheel  10  of the present invention provides several advantages over those previously know in the art. More particularly, the recessed portion  110  of the wheel  10  serves to mechanically de-couple the rim mounting flange  54  and the second brake sealing surface  97 . For example, during dynamic loading of the wheel  10  the rim mounting flange  54  is permitted to flex, without the second brake sealing surface  97 . Additionally, debris and dirt falling from the inboard surface  56  of the rim mounting flange  54  tends to drop into the recessed portion, thus reducing debris build up in the area of the duo-cone seal  108 . The substantially cylindrical hub  20  design isolates axial pre-load and dynamic radial loading, thus maintaining the predetermined pre-load and extending bearing  174  life.  
         [0027]    The use of the brake anchor  132  having a splined mating surface  150  to engage the spindle  114 , allows the spacing of the inboard bearing surface  124  to be moved farther inboard in relation to the load line  18 . The greater distance inboard of the load line  18 , reduces twisting forces on the inboard tapered roller bearing assembly  172 .  
         [0028]    Usage of studs  78  as described for fastening a rim  12  to the hub  20  simplifies replacement of studs  20 . To replace the stud  78  the snap ring  72  is removed from the ring groove  70 , the stud  78  can be easily pushed to the inboard end  26  of the hub  20 . New studs  78  are simply inserted into the holes  74  with the flat portion  94  aligning with the raised portion  62  of the rim mounting flange  54 , the snap ring  72  is positioned back into the ring groove  70  to hold the studs  78  in their respective holes  74 . During loosening or tightening of nuts from the studs  78 , the studs  78  are prevented from turning due to the engagement of the flat portion  94  with the second surface  66  of the raised portion  62  of the rim mounting flange  54 .