Abstract:
A load member is provided for a face seal that reduces the potential for elastomeric set to occur after a period of use. The load member includes a biasing member positioned in a flexible coating.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to face seal arrangements, and more particularly to a load member of a face seal arrangement.  
         BACKGROUND  
         [0002]    The present invention has particular application to track rollers, final drives, and other components of work machines. The problem of short bearing life in track rollers and final drive assemblies of work machines is one that has continuously plagued the industry. Such work machines typically operate in environments that are highly destructive to seals and consequently to the underlying bearings.  
           [0003]    One approach to this problem is the type seal disclosed in U.S. Pat. No. 5,527,046, which issued Jun. 18, 1996 to Bedford and is assigned to the assignee of the present application. This type of face seal has greatly improved component wear life. However, the load members of such seals are generally made from a resilient material such as an elastomer or rubber and can be damaged during assembly or fail during application. For example, one such problem with prior face seal assemblies involves the deterioration or damage to the load members. The load member can harden or become inflexible due to the repeated cycles of compression (compression set) or simply due to exposure from the corrosive environment in which the work machine operates. When this occurs, the load member may render the force applied to the seal ring ineffective or allow material to pass directly by the load member. Thus, contaminating the sealed and lubricated bearing areas.  
           [0004]    The present invention is directed to overcoming one or more of the problems as set forth above.  
         SUMMARY OF THE INVENTION  
         [0005]    In one aspect of the present invention a load member is provided that is used to apply a force to a seal ring of a face seal assembly. The load member includes a biasing member formed in an annulus. A flexible coating encases the exterior of the biasing member. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is an elevational view, partially in cross-section, of a track roller assembly utilizing a seal arrangement embodying the present invention;  
         [0007]    [0007]FIG. 2 is an enlarged view of the seal arrangement taken about detail  2  of FIG. 1;  
         [0008]    [0008]FIG. 3 is an enlarged cross section, taken along line  3 - 3 , of a load member shown in FIG. 2;  
         [0009]    [0009]FIG. 4 is an alternate embodiment of load member shown in FIG. 2;  
         [0010]    and  
         [0011]    [0011]FIG. 5 is another alternate embodiment of the load member shown in FIG. 2; and  
         [0012]    [0012]FIG. 6 is yet another alternate embodiment of the load member shown in FIG. 2. 
     
    
     DETAILED DESCRIPTION  
       [0013]    Referring to the drawings and particularly to FIG. 1, illustrates an exemplary environment of use for a seal arrangement shown generally at  10 . The environment in this example is a track roller assembly  12  used in a track-type work machine, such as a track-type tractor, excavator, or the like. It should be recognized that other uses of the seal arrangement  10  may be final drives, track chain assemblies, and the like. As well known, the roller assembly  12  is mounted by conventional means between the track roller frame (not shown) and the track (not shown) of the track-type work machine. The roller assembly  12  comprises a conventional roller element  14  rotatably mounted on a shaft  16 . A pair of bearing sleeves  18  lines the inner wall of the roller element  12  to provide a durable wear surface. The roller element  12  is confined between a pair of end caps  19  fixed at opposed ends of the shaft  14 . Each of the end caps  19  is secured to the shaft  14  by way of a pin  20  extending through apertures  22  in the end caps  19  aligned with a bore  24  through the shaft  14 . As a result, the end caps  19  are fixed axially relative to the shaft  14 , but a small amount of axial movement or play of the roller element  12  between the end caps  19  is permitted.  
         [0014]    With reference to FIGS. 1 and 2, seal arrangement  10 , is provided between the roller element  14  and each of the end caps  19 . As well known, the seal assemblies  10  are provided to retain lubricant, such as oil, in the vicinity of the bearing surfaces between the roller element  14  and the shaft  16  and also prevent foreign matter from reaching such bearing surfaces. Because each of the seal assemblies  10  may be substantially identical, only one of the seal assemblies  10  is described in further detail herein.  
         [0015]    Referring particularly to FIG. 2, the seal assembly  10  comprises a first and second annular seal rings  30 , 32  each made from metal or other suitable durable, hard material. In the embodiment disclosed herein the first seal ring  30  is positioned juxtaposed the second seal ring  32 . However, it should be understood that the first seal ring  30  may be positioned to contact a bushing end face or other abutting member (not shown) so as to perform a similar sealing function. A first load member or toric  34  is positioned between the first seal ring  30  and a bore  36  in the roller element  14  to provide a fluid-tight seal therebetween. A second load member or toric  38  is positioned between the second seal ring  34  and a recess  40  in the end cap  19  and provides a fluid-tight seal therebetween.  
         [0016]    The first seal ring  30  has a smooth seal face  42 , which confronts and engages a smooth seal face  44  on the second seal ring  32 . The plane of engagement between the seal faces  42  and  44  is referred to herein as the “seal plane”. The seal faces  42 , 44  are maintained in constant sealing engagement by way of load members  34 , 38 . More particularly, first seal ring  30  has an annular ramped surface  46  formed thereon, which is spaced from and confronts an annular ramped surface  48  formed in the bore  36  of the roller element  14 . Similarly, the second seal ring  32  has an annular ramped surface  50  formed thereon, which is spaced from and confronts an annular ramped surface  52  formed in the recess  40  of the end cap  19 . The length of the ramps  46 , 48  and  50 , 52  are selected so that a predetermined compression of the load members  34 , 38  is maintained, thus providing the desired load on the seal faces  42  and  44 .  
         [0017]    Ramps  46 , 48  and ramps  50 , 52  are angled such that they converge, respectively, in a direction away from the seal plane. More particularly, ramps  46 , 50  preferably extend at an  8  degree angle relative to an axis of rotation  54  of the roller element  14 , and ramps  48 , 52  preferably extend at a 10 degree angle relative to the axis of rotation  54 . Of course, other angles that converge in a direction away from the seal plane could also be used. In this regard, it should be noted that the term “converge” is not used in the sense that ramps  46 , 48  and ramps  50 , 52 , respectively necessarily physically intersect, but that they would intersect if extended farther away from the seal plane.  
         [0018]    As explained above, the converging angle of the ramps  46 , 48  and ramps  50 , 52  provide good resistance to external force on the load members  34 , 38 , such as force from mud packing, for example. The disclosed converging angles also provide relatively flat load vs. deflection characteristics so that seal face loading does not change substantially as the seal rings  30 , 32  move axially relative to the end cap  19 .  
         [0019]    Referring now to FIGS.  3 - 6 , load members  34 , 38  include a biasing member  56  surrounded by a flexible coating  58 . As shown in FIG. 3., the biasing member  56  can be a coil spring  60  constructed of a single strand of a round material  62  wrapped in a generally tight coil. Alternatively, FIG. 4 shows the biasing member  56  as being a coil spring  64  constructed of a single strand of flat material  66  wrapped in a generally tight coil. In another alternative, FIG. 5 shows the biasing member  56  as being a canted coil spring  68 . The term canted coil spring  68  as used herein means a coil spring constructed of a single strand of round material  70  with coils that are separated by a predetermined distance. The canted coil spring  66  reacts to a radial force, designated by arrow “F” by bending in the direction of arrows “C” as opposed to compressing or collapsing radially as is the case with the coil springs  60 , 62  shown in FIGS. 3 and 4. The material  62 , 66 , 70 , discussed above, used to make coils springs  60 , 64 , 68  preferably is a metallic spring wire, however may be a plastic or composite material as well. The flexible coating  58  may be made from any of a number of known elastomeric compounds commonly used to manufacture seals such as rubber compounds. Additionally, FIG. 6 show yet another alternative for the load member  34 , 38 . In this example biasing member  56  shows coil spring  60  completely imbedded in a flexible body  72 . The flexible body  72  may be made from any of a number of known elastomeric compounds commonly used to manufacture seals such as rubber compounds.  
         [0020]    As shown in FIGS. 2 and 3 the load member  34 , 38  may also include a support member  74 . Support member  74  is positioned inside the biasing member  56  and used to support or limit the amount of compression or deflection of the biasing member  56 . Support member  74  may be a cord or rope constructed of fibrous material but could also be an elastomeric cord or even a second smaller coil spring as well.  
       Industrial Applicability  
       [0021]    In operation the seal arrangement  10  functions to apply a force against the ramps  46 , 50  of the seal rings  30 , 32  respectively. As the roller element  14  moves axially between the end caps  19  the load rings  34 , 38  force the smooth seal face  42  of the first seal ring  30  against the smooth seal face  44  of the second seal ring  32  and visa-verse to retain lubricant and keep contaminants from entering the bore  36  of the roller element  14 .  
         [0022]    The length of the ramps  46 , 48  and  50 , 52  are selected so that a predetermined compression of the load rings  34 , 38  is maintained, thus providing the desired face load on seal faces  42  and  44 . More particularly, the load members  34 , 38  are compressed upon assembly to a predetermined strain level, which can be substantially maintained throughout the range of movement of the first and second seal ring  30 , 32  by providing sufficient length to the ramps  46 , 48  and  50 , 52 . The load members  34 , 38  have a maximum principle strain level of approximately 31% compression. This compression level is designed to be maintained in the range of 20% to 35%, depending on the deflection of the first and second seal ring  30 , 32  relative to the end cap  19 .  
         [0023]    The load member  34 , 38  of the present design provides additional support in the form of the biasing member  56  so that compressive set of the elastomeric material does not occur. Additionally, the load member  34 , 38  does not require redesign of existing machine elements such as roller assemblies, final drives and the like.