Abstract:
A unitized seal assembly is provided for installation between linkages of a chain drive designed for tracked vehicles. The seal assembly facilitates field preventative maintenance on the drive chain by utilizing an integral spacer that holds the critical sealing surfaces together at all times, and has a seal head that can be easily removed from the outer link bore of a chain link. Removal of the seal head from the outer link bore causes as-installed clearance passageways between the seal head and seat portions and the spacer to forcefully close and prevent abrasive particles from getting inside the seal and reaching the interior interface junction of the dynamic sealing surfaces during seal maintenance. The seal assembly also includes additional sealing features that provide improved performance.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to seal assemblies and more particularly to a seal assembly for use with chains used to drive a tracked vehicle.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     Drive chains are commonly used on vehicles having a track drive and typically include a chain bushing, a pin extending through the chain bushing and having an end projecting beyond the bushing and two chain links which are linked together by the pin and bushing on each side thereof. The chain links disposed on opposite sides of the chain bushing are overlapped in order to provide an inner chain link which is pressed onto the bushing and an outer chain link which is pressed onto the axially extending end of the pin.  
         [0003]     Drive chains of this type are widely used in track vehicles such as construction vehicles, earth moving vehicles, and other special purpose vehicles. To reduce the friction, and thus reduce adhesive wear and minimize the overall wear, which can lead to chain lengthening and which can decrease the life of the chain or link assemblies, the hinge joints are lubricated with grease or oil containing additives which limit corrosion and increase the lubricant life. Track vehicles are typically operated and even have maintenance performed in very dirty environments in which there is a significant chance of contaminating dirt getting within the sealed environment. In particular, chain preventative maintenance typically consists of dismantling each and every link in the chain and rotating the bushings 180 degrees to distribute wear from the drive sprockets, which only wear against one half of the outer surface of the bushings at a time. With presently used seal designs, this assembly and re-assembly process inevitably contaminates the dynamic sealing surfaces of both the mechanical face seal head and the ends of the bushings that serve as the sealing counterface or seal seat for the seal. After field preventative maintenance is completed, the contamination trapped between the mechanical face seal head and the bushing seal seat surface can separate these sealing surfaces and/or cause their abrasive destruction. If the seals are destroyed, the seal&#39;s ability to retain lubricant internal of the seal and exclude external abrasives and liquids from entering the seal system and contaminating the lubricant is also destroyed. The loss or contamination of the oil that lubricates between the drive bushing and link pins, in turn causes wear and failure of these components, and the drive train.  
         [0004]     Accordingly, it is an object of the present invention to provide a seal assembly that is capable of increasing the life of the sealing system and also facilitates field preventative maintenance in which the bushings are rotated. The system of the present invention provide a spacer sleeve that is disposed on the pin and provides a sealed relationship between the inner and outer links of a drive chain. A seal seat member is disposed on a first end of the spacer sleeve and a grommet member is disposed on the seal seat for engagement with a bore in the end of the bushing. A seal washer is disposed on the spacer sleeve adjacent to the seal seat member and a second seal member in the form of an elastomeric boot is seated on the seal washer. A spring seat is disposed on a second end of the spacer sleeve and supports a portion of the second seal member. A spring is disposed between the spring seat and the seal washer for biasing the spring seat and the attached portion of the second seal member against the mating bore portion of the outer link. The removal of the seal head portion, which is comprised of the elastomeric boot, spring seat, spring and seal washer from the outer link bore causes the as installed clearance passageways between the seal head and seat portions and the spacer to forcefully close and prevent abrasive particles from getting inside the seal and reaching the interior interface junction of the dynamic sealing surfaces. A radial lip seal portion of the seal seat extends and seals around the seal washer outer diameter to prevent abrasive particles from reaching the exterior interface junction of the dynamic sealing surfaces.  
         [0005]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0007]      FIG. 1  is a cross-sectional view of the unitized seal with integral spacer according to the principles of the present invention;  
         [0008]      FIG. 2  is a cross-sectional view of the seal of  FIG. 1  shown in an assembled configuration on a drive chain;  
         [0009]      FIG. 3  is a top plan view of a drive chain section which incorporates the seal assembly according to the principles of the present invention;  
         [0010]      FIG. 4  is a plan view of a bushing and pin assembly of the chain drive according to the principles of the present invention;  
         [0011]      FIG. 5  is a perspective view of the spacer sleeve of the seal according to the principles of the present invention;  
         [0012]      FIG. 6  is a cross-sectional view of a boot used in the seal according to the principles of the present invention;  
         [0013]      FIG. 7  is a cross-sectional view of a spring seat used in the seal according to the principles of the present invention;  
         [0014]      FIG. 8  is a cross-sectional view of the seal washer used in the seal in accordance with the principles of the present invention;  
         [0015]      FIG. 9  is a cross-sectional view of a seal seat used in the seal in accordance with the principles of the present invention;  
         [0016]      FIG. 10  is a cross-sectional view of a grommet utilized in the seal in accordance with the principles of the present invention;  
         [0017]      FIG. 11  is a cross-sectional view of an end cap used in accordance with the principles of the present invention; and  
         [0018]      FIG. 12  is a cross-sectional view of a second embodiment of the seal assembly according to the principles of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0020]     With reference to  FIG. 3 , a drive chain  10  is shown including identical links  12 ,  14 ,  16 ,  18  each mounted to a pin  20  and bushing  22 . Each link  12 ,  14 ,  16 ,  18  includes an inner end  24  and an outer end  26 . The inner end  24  includes an aperture  28  extending therethrough and sized for receiving the end portion  22   a  of bushing  22 . The outer end  26  includes an aperture  30  extending therethrough and sized for receiving the pin  20  therein. The bushing  22  is provided with a recessed bore portion  32  and the outer end  26  of links  12 ,  14 ,  16 ,  18  include a recessed bore portion  34  which combine with bore portion  32  to define a chamber portion therebetween for receiving seal assembly  40 , according to the principles of the present invention.  
         [0021]     With reference to  FIGS. 1 and 2 , the seal assembly  40 , according to the principles of the present invention, will now be described. The seal assembly  40  includes a spacer sleeve  42  slidably received on the pin  20 . A seal seat  44  is slidably mounted on a first end of the spacer sleeve  42 . A seal washer  46  is disposed adjacent to the seal seat  44  and is also slidably mounted on the spacer sleeve  42 . A first seal member in the form of a boot  48  is seated on the seal washer  46  and includes a forward portion thereof  48   a  supported by a spring seat  50 . A wave spring  52  is disposed between the spring seat  50  and the seal washer  46 . A second seal portion in the form of an elastomeric grommet  54  is disposed on the seal seat  44  and includes a lip seal portion  54   a  engaging the seal washer  46 .  
         [0022]     In the assembled configuration, the seal head portion  60  of the seal assembly  40 , which is comprised of the boot  48 , spring seat  50 , wave spring  52  and seal washer  46  are received in the bore portion  36  of outer ends  26  of links  12 ,  14 ,  16 ,  18 . The seal seat portion  62  of seal assembly  40 , which is comprised of the seal seat member  44  and grommet  54  are received in the recessed bore portion  32  provided in the end of bushing  22 . In the assembled condition, as shown in  FIG. 2 , the spring seat  50  is pressed axially inward away from end cap  56  and the seal seat  44  is pressed axially inward away from end cap  58  with the spacer sleeve  42  providing proper spacing between the outer end  26  of links  12 ,  14 ,  16 ,  18  and the end portion of bushing  22 .  
         [0023]     With reference to  FIG. 5 , the spacer sleeve  42  is shown and includes a cylindrical body. The spacer sleeve has a length equal to a desired spacing between the shoulder  66  within the bore  32  of bushing  22  and the bore  36  of the links  12 ,  14 ,  16 ,  18 . The spacer sleeve  42  has an inner diameter sufficient to receive the pin  20  therein.  
         [0024]     With reference to  FIG. 6 , the boot  48  is shown including a radially inwardly extending flange portion  70  and axially extending flange portion  72  which are designed to seat against the seal washer  46 . The boot  48  includes an arcuate body portion  74  extending from the radially inwardly extending flange portion  70  and axially extending flange portion  72 . The arcuate-shaped body portion  74  terminates in a radially extending lip portion  76  which is engaged by the spring seat  50 . A seal lip  78  extends radially from the arcuate body portion  74  intermediate the forward inwardly extending lip portion  76  and flange portions  70 ,  72 .  
         [0025]     With reference to  FIG. 7 , the spring seat  50  is shown and includes an annular steel disk having an opening  80  provided in the center thereof, and including an outer arcuate ring portion  82  having a terminal end  84  which engages the radially inwardly extending lip  76  of boot  48 . The wave spring  52  engages the spring seat  50  radially inward of the arcuate shaped outer ring portion  82 .  
         [0026]     With reference to  FIG. 8 , the seal washer  46  is shown. The seal washer  46  includes an annular ring made of sintered bronze, although other materials may also be utilized. The seal washer  46  includes a recessed shoulder portion  90  adapted to receive the axially extending flange portion  72  of boot  48 .  
         [0027]     With reference to  FIG. 9 , the seal seat  44  is shown in the form of an annular ring preferably formed from hardened steel, although other materials may be utilized. The seal seat  44  is also preferably oil impregnated to provide enhanced lubrication properties. The seal seat  44  includes an inner recessed shoulder portion  92  which is adapted to receive the radially extending flange portion  58   a  of end cap  58 .  
         [0028]     With reference to  FIG. 10 , the grommet  54  is shown in the form of an annular ring made of an elastomeric material such as polyurethane, or other known seal materials. The grommet  54  includes a radially inwardly extending flange portion  98  which is adapted to engage an axial face of the seal seat  44 . Grommet  54  includes sealing ribs  100  on an outer face thereof. Three sealing ribs  100  are shown, although more or fewer ribs can be utilized in accordance with the principles of the present invention. The grommet  54  includes a radially inwardly extending lip seal  54   a  which is adapted to engage seal washer  46 .  
         [0029]     With reference to  FIG. 11 , a cross-sectional view of the end caps  56 ,  58  is provided. The end caps  56 ,  58  each include an axially extending flange portion  56   b ,  58   b  and a radially extending flange portion  56   a ,  58   a . The end caps  56 ,  58  are preferably made from steel and are press fit onto the spacer sleeve  42 .  
         [0030]     The unitized seal assemblies  40 , according to the principles of the present invention, are installed seal seat portion ( 62 ) first into bores and counter-bores  32  of bushings  22 , and are held firmly from rotating in the bore by the grommet&#39;s  54  triple sealing beads  100 . The seal head portion  60  of unitized seal assembly  40  virtually install themselves into the outer link bores  36  when the links  12 ,  14 ,  16 ,  18  are pressed onto the pins  20 .  
         [0031]     The integral spacer sleeve  42  of unitized seal assembly  40  establishes the proper installed length of the seal  40  and opens internal running clearance inside the seal  40 . Deflection of the boot  48  in the seal head portion  60  at installation, plus further deflection of the already pre-compressed wave spring  52  inside the assembly  40 , provide long life axial seal preload. Inward compression of the boot&#39;s retaining lip  48   a , axial boot portion  74 , and spring forces clamping the boot tail against the bore bottom  36 , plus biased expansion of the boot body section  74  into the bore diameter prevent the seal head portion  60  of the seal assembly  40  from rotating in the outer link bore  36 . The stretch of the boot  48  around the seal washer  46 , the biased compression of the boot around the seal washer  46  during installation, and the axial clamping of the boot inward radiating flange  70  against the rear of the seal washer  46  all prevent the seal washer  46  from rotating relative to the boot  48 .  
         [0032]     The seal seat portion  62  of the unitized seal assembly  40  features the grommet  54  having an integral extending lip seal  54   a  which stretches and seals around the outer diameter of the seal washer  46 . This auxiliary lip seal  54   a  helps prevent abrasives exterior to the seal from reaching the exterior junction of the dynamic sealing surfaces of the seal.  
         [0033]     During field preventative maintenance, when the link pin  20  is driven out of an outer link  12 ,  14 ,  16 ,  18 , the boot  48  of the seal head portion  60  decompresses with the aid of the spring  52  easing removal of the seal head portion  60  from the outer link bore  36 . At this time, the seal head portion  60  is held in the bore solely by the compression of the boot retaining lip  78 . As soon as the link pin  20  is driven out of the outer link  12 ,  14 ,  16 ,  18 , the unitized seal assembly  40  expands axially with the aid of the spring  52  until the spring seat  44  seats against the flanged end cap  58  on one end of the integral spacer sleeve  42 , and the spring seat  50  abuts against the flanged end cap  56  on the other end of the spacer sleeve  42 , thus, closing running clearance passageways and preventing abrasives exterior to the seal  40  from entering the assembly and reaching the interior junction of the dynamic sealing surfaces of the seal. By virtue of the unitized construction of the spacer sleeve  42  holding the dynamic sealing surfaces together at all times, plus an auxiliary lip  54   a  preventing abrasives from reaching the exterior junction of the sealing surfaces, plus the closing of running clearances the moment the seal is decompressed preventing abrasives from reaching the interior junction of the sealing surfaces, the seal assembly  40  of the present invention is uniquely capable of surviving field disassembly and reassembly of the drive chain linkage of tracked vehicles without abrasives finding their way into the critical dynamic sealing interface of the seal.  
         [0034]     With reference to  FIG. 12 , a cross-sectional view of an alternative seal assembly, according to the principles of the present invention, are shown. In the alternative seal assembly  200 , as shown in  FIG. 12 , the seal washer has been eliminated and the boot  248  is provided with an integrally formed annular base portion  248   a . In this construction, the auxiliary sealing lip  54   a  of grommet  54  engages the base portion  248   a  of modified boot  248 . The lip seal  78  of the boot  48  shown in  FIG. 6  is also removed to assure easier removal of the sealing boot  248  from the outer link bore  36 . Accordingly, with the embodiment of  FIG. 12 , the seal washer is formed integrally with the boot  48  and provides an exterior surface against which the auxiliary sealing lip  54   a  of grommet  54  is disposed.  
         [0035]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.