Tensioned cushioning lug for track-type vehicles
BACKGROUND OF THE INVENTION 
     This invention relates to an endless track assembly for a track-type vehicle having a cushioning lug secured to each track shoe thereof to attenuate the noise level of the track assembly during operation. 
     A conventional track assembly comprises a plurality of track shoes secured to an articulated chain with the chain adapted to engage a drive sprocket. Engagement of the chain with the drive sprocket gives rise to high noise levels. In addition, engagement of drive bushings of the chain with the sprocket tends to unduly wear the bushings whereby they require periodic repair or replacement. 
     One solution to this problem may be found in U.S. Pat. No. 3,887,244, assigned to the assignee of this application, wherein a combined cushioning and impact lug is secured to each track shoe of the track assembly to reduce noise levels thereof. 
     As further disclosed in such patent, it has proven desirable to fully protect an elastomeric block of the cushioning lug to extend the service life thereof by covering it with a wear-resistant metallic cap. The cap is normally bonded to the block or is bolted to a track shoe, the latter arrangement being disclosed in U.S. Pat. No. 3,897,980, also assigned to the assignee of this application. Such prior art arrangements may tend to limit the desired multi-directional movement of the cap, which would otherwise insure substantial and continuous bearing contact as between the cap and the teeth of the drive spocket. 
     SUMMARY OF THIS INVENTION 
     The present invention is directed to overcoming one or more of the problems as set forth above. 
     The improved cushioning lug means of this invention comprises a resilient spring means having a cap means mounted thereon adapted to engage the teeth of a drive sprocket. A connecting means, comprising a non-rigid and flexible member exhibiting multi-directional flexiblity, is adapted to be secured and tensioned between a track shoe of an endless track assembly and the cap means for preloading the spring means and for permitting multi-directional movement of the cap means. As described hereinafter, the cushioning lug means of this invention insures optimum bearing contact with the teeth of the drive sprocket to substantially attenuate noise levels, provides for the &#34;self-cleaning&#34; of the sprocket teeth, exhibits a substantial fatigue or service life and may be pre-adjusted to compensate for any mismatch relative to the sprocket teeth. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects of this invention will become apparent from the following description and accompanying drawings wherein: 
     FIG. 1 is a partially sectioned side elevational view of an endless track assembly for a track-type vehicle, shown engaging a drive sprocket and having a plurality of cushioning lugs embodying this invention employed therein; 
     FIG. 2 is an enlarged end elevational and partially sectioned view of one of the cushioning lugs, taken in the direction of arrows II--II in FIG. 1; 
     FIG. 3 is a top plan view of the cushioning lug, taken in the direction of arrows III--III in FIG. 2; 
     FIG. 4 is a cross sectional view of the cushioning lug, taken in the direction of arrows IV--IV in FIG. 2; 
     FIG. 5 is a view similar to FIG. 4, but illustrating a first modification of the cushioning lug; 
     FIG. 6 is a view similar to FIG. 4, but illustrating a second modification of the cushioning lug; 
     FIG. 7 is a view similar to FIG. 4, but illustrating a third modification of the cushioning lug; 
     FIG. 8 is an end elevational and partially sectioned view of the FIG. 7 cushioning lug, taken in the direction of arrows VIII--VIII in FIG. 7; 
     FIG. 9 is a sectional view, taken in the direction of arrows IX--IX in FIG. 7; and 
     FIG. 10 is a view partially similar to FIG. 4, but illustrating a fourth modification of the cushioning lug. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, an endless track assembly 10 comprises a plurality of track shoes 11 secured to an articulated chain 12 in a conventional manner. Laterally spaced pairs of links 13 of the chain are pivotally interconnected by a pin and bushing assembly 14. Each pin and bushing assembly is adapted to engage within a notch or root defined between each circumferentially adjacent pair of teeth 15 of a sprocket 16 for driving the track assembly in a conventional manner. 
     This invention relates to a cushioning lug means 17 secured to each track shoe 11 and disposed intermediate (midpitch) adjacent pairs of pin and bushing assemblies 14 for attenuating the noise level of the track assembly and to insure continuous cleaning of the sprocket teeth. Referring to FIGS. 2-4, each cushioning lug means comprises a resilient spring means or cushioning block 18 suitably composed of an elastomeric material, such as rubber. A hardened metallic cap means 19 is mounted on the cushioning block and is adapted to engage the root defined between each pair of circumferentially adjacent teeth 15 of sprocket 16, as shown in FIG. 1. The cap means comprises a transversely extending cleaning and reinforcing flange 20 and a pair of offset drive or bearing flanges 21 and 22, secured on either side of the reinforcing flange. 
     As more clearly shown in FIG. 2, a mounting plate 23 is disposed on track shoe 11 and secured thereon by a pair of bolts 24 and nuts 25, the latter being embedded in cushioning block 18. Block 18 is preferably bonded or otherwise suitably secured between the plate and cap means 19. A flexible cable or connecting means 26 is secured in tension between the mounting plate and the cap means for permitting multidirectional movement of the cap means on cushioning block 18 which is preloaded or compressed therebetween. 
     Cable 26 preloads cushioning block 18 which helps in precluding bond failure between the block and cap means 19 and plate 23. The placement of the elastomeric block under compression increases fatigue life and controls the height of the lug which tends to minimize the sprocket to lug mismatch. 
     The cable may be composed of braided filament material, such as steel, and has a pair of lower and upper anchoring members or balls 27 and 28, respectively, secured on either end thereof. Alternatively, the cable could be replaced with a flexible steel spring having balls 27 and 28 secured to opposite ends thereof. Although it is preferable to allow flexing of connecting means 26, the cable could be replaced by a bolt having spherical ends for universally connecting the bolt between the track shoe and cap means. 
     Ball 27 is disposed in a semi-spherical first socket 29 defined in a crimped retainer 30 of mounting plate 23. Ball 28 is mounted in a semi-spherical second socket 31, defined in a swaged or otherwise suitably formed generally annular retainer 32, formed integrally with one-piece cap means 19 and having bent annular flange means 33 for retaining ball 28 therein. It should be noted that the cap means proper covers socket 31 to prevent upward movement of ball 28. Although cable 26 is preferably interconnected between cap means 19 and plate 23 by the above-described ball and socket connections, it should be understood that other well known universal connections could be utilized in lieu thereof. 
     FIGS. 5, 6, 7-9 and 10 illustrate modified cushioning lugs 17a, 17b, 17c and 17d, respectively. In each modification, identical numerals depict corresponding constructions. The FIGS. 5-10 embodiments essentially differ from the FIGS. 1-4 embodiment in the manner by which ball 28 is attached and anchored to each respective cap means. 
     In FIG. 5, a retainer 32a comprises a cup-shaped separate member having its upper end welded or otherwise suitably secured to cap means 19a proper. An annular flange means 33a is formed on a lower end of the retainer to retain ball 28 in the socket defined therein. 
     In FIG. 6, an annular retainer 32b is formed integrally with the main body portion of a cap means 17b. A dirt-preventing plug in the form of a set screw 34 is threadably mounted in a threaded counterbore, formed on an upper end of the cap means. Upper ball 28 is supported in the socket defined in retainer 32b by an annular flange means 33b formed on a lower end of the retainer. 
     Referring to FIGS. 7-9, a retainer 32c secured to a cap means 19c comprises a stamped cage-like and cup-shaped member having a plurality of upstanding and circumferentially spaced legs 32c having upper ball 28 mounted therein. An annular dirt-preventing plug 35 is welded or otherwise suitably secured in a counterbore formed in the cap means. Ball 28 is supported by an annular flange means 33c formed on the retainer. The cap means has an annular boss 36 formed integrally thereon and disposed in surrounding relationship relative to retainer 32c to retain it in position with the aid of flanges 37 formed on an upper end of the retainer. The FIG. 10 embodiment 17d essentially differs from the FIGS. 7-9 embodiment 17c in that boss 36 has been eliminated from a cap means 19d. 
     When placed in operation, each of the above-described cushioning lug means embodiments will function in substantially the same manner. Referring to FIGS. 1-4, for example, when sprocket 16 rotates to drive track assembly 10, each cushioning lug means 17 will engage a respective notch defined between each circumferentially adjacent pair of teeth 15. The universal flexibility of the system will insure optimum bearing contact as between cap means 19 and the sprocket teeth for substantially attenuating the noise level of the track assembly and for continuously maintaining the sprocket teeth in a clean condition of operation.