Abstract:
A track assembly having a drive sprocket capable of concentrically supporting several detachable drive rings containing drive teeth shaped to rotate without interfering with track support idler wheels, to provide a reduced center of gravity and substantially provide the same vehicle operating characteristic with tracks as with wheels. A track retainer guide member mounts along a peripheral edge of the track and overlies the track to resist track dislodgement. Independent and/or resiliently biased, rocker arms support track idler wheels to induce track flexion and conformance to encountered obstructions.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to tracked vehicles and, in particular, to an improved track drive assembly for all terrain vehicles wherein the assembly height profile is varied with modular drive tooth sprocket rings having offset drive teeth, wherein a support frame guide prevents track dislodgement, and wherein independent, resiliently biased idler wheel rocker arms provide conformal track flexion to encountered obstacles. 
         [0002]    A wide variety of personal, passenger and commercial all terrain vehicles have been developed for travel over terrains of all types, including stream and river beds, sand, sodden soil and swamp, rocks, snow and ice. Track assemblies have also been developed for converting wheeled vehicles into track vehicles. For example, track assemblies have been developed by applicant to convert wheeled passenger trucks and wheeled recreational all terrain vehicles (ATV) over to tracked vehicles able to operate over a wider range of terrains and operating conditions. 
         [0003]    Conversion track assemblies have also been developed for commercial, industrial and military vehicles that include working attachments such as booms, blades, trenchers, cultivation equipment, mowers, and towed equipment used to perform specific tasks at remote locations. These work vehicles typically support at least two track assemblies from appropriate chassis mounted suspensions; more typically, four track assemblies are used to replace the wheels/tires at each axle. Representative assemblies of the foregoing type developed by applicant are shown at U.S. Pat. Nos. 7,131,508; 6,904,986 and 5,607,210. 
         [0004]    Although the foregoing assemblies have proven beneficial, problems are occasionally encountered due to relatively high operating centers of gravity and accommodating operating or transportation height restrictions between work sites. That is, overhanging structures at a work site may prevent vehicle movement beneath the structure. Clearance problems can also exist in relation to bridges, high tension lines etc. during transport, necessitating track removal and re-mounting upon reaching a destination. 
         [0005]    Occasionally too the drive tracks can dislodge where terrain conditions present unusual lateral forces that can force the track from the idler wheel and drive sprocket support assembly. Other track issues can also develop where the track is not able to flex and conform sufficiently on exceptionally rough terrain. 
         [0006]    The present invention was developed to overcome the foregoing problems. The several different improved track assemblies particularly provide an improved track support assembly wherein the assembly height profile is altered to maintain a height profile at the vehicle that is substantially the same as when using wheels/tires. The height profile is particularly changed via modularly sized, offset drive tooth rings that mount to a supporting drive sprocket hub. Cooperating independent, idler wheel rocker arm suspensions improve track flexion at the track assembly and an associated track guide/retainer plate at the track support frame prevents track dislodgement. 
       SUMMARY OF THE INVENTION 
       [0007]    It is a primary object of the invention to provide an all terrain vehicle with an improved drive sprocket capable of supporting multiple drive rings that contain offset drive teeth of differing tooth heights. 
         [0008]    It is a further object of the invention to provide a vehicle wherein the drive teeth are shaped and/or spaced to cooperate with associated idler wheels (e.g. pass over and around the idler wheels). 
         [0009]    It is a further object of the invention to provide a vehicle wherein the drive teeth are secured in lateral offset relation to a drive sprocket hub. 
         [0010]    It is a further object of the invention to provide a vehicle wherein C-shaped drive teeth span between displaced, parallel rings and one of which rings fastens to a center hub of a drive sprocket. 
         [0011]    It is a further object of the invention to provide a track support framework that includes a retainer guide member that mounts substantially adjacent the peripheral edge of the track and also overlies a portion of the track to prevent lateral dislodgement of the track. 
         [0012]    It is a further object of the invention to provide several resiliently biased, idler wheel rocker arm suspensions that support the track to provide independent and conformal track flexion upon encountering obstacles. 
         [0013]    The foregoing objects, advantages and distinctions of the invention are obtained in improved drive track assemblies shown at the attached figures. In one assembly, the track support framework provides a sprocket that concentrically supports several detachable drive tooth containing rings. Each drive ring comprises a pair of annular rings supported in displaced parallel relation. Spanning between the rings are C-shaped teeth that extend with differing radial offsets or heights from a center sprocket hub. The shape and offset of the teeth permits the teeth to contact drive lugs at the drive track yet pass over and clear idler wheels that support the track. The modular drive rings provide an ability to maintain a vehicle&#39;s height profile to be substantially the same as with wheels relative to attached tools. The track assemblies also maintain a low center of gravity at the vehicle and ensure substantially the same vehicle operating speeds as with wheels. 
         [0014]    The track support framework also includes a retainer or guide member mounted along a lateral side of the framework substantially adjacent the peripheral edge of the track. A portion of the guide member overlies the track to prevent lateral dislodgement of the track. The retainer is supported to a tubular cross member arm of the track framework and an idler wheel support axle. A second flanged portion of the guide member projects laterally outward at an angle to prevent wear on the track, if contacted, direct the track back onto the framework, and direct debris away from the track assembly. 
         [0015]    Also provided at the track assembly is a resiliently biased outer rocker arm assembly coupled to center sets of idler wheels. Inner and outer rocker arms independently pivot from the track framework. The outer rocker arm suspension is biased with flexibly compressible elastomer or bladder members and the inner suspension is either unbiased or spring biased. The independent, idler wheel rocker arm suspensions facilitate track flexion with encountered obstacles and a smoother vehicle riding characteristic. That is, the track is able to flex and conform to encountered obstacles, yet maintain a low center of gravity. 
         [0016]    Still other objects, advantages, distinctions, constructions and combinations of individual features of the invention will become more apparent from the following description with respect to the appended drawings. Similar components and assemblies are referred to in the various drawings with similar alphanumeric reference characters. The description to each combination should therefore not be literally construed in limitation of the invention. Rather, the invention should be interpreted within the broad scope of the further appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The following figures disclose presently preferred constructions of the invention. Similar components and assemblies are referred to in the various drawings with similar alphanumeric reference characters and callouts. 
           [0018]      FIG. 1  is a perspective drawing shown in partial cutaway to expose an improved, offset toothed track drive sprocket and an associated track retainer guide at the track assembly support frame. 
           [0019]      FIG. 2  is a front plan view to the track assembly depicting a reduced height profile and alternative movement conditions of rocker arm mounted track support idler wheels. 
           [0020]      FIG. 3  is a cross section side view of the track assemblies of  FIGS. 1 and 2 . 
           [0021]      FIG. 4  is a perspective drawing showing the drive sprocket removed from the track assembly. 
           [0022]      FIG. 5  is a perspective view showing front and right side views of the track guide/retainer removed from the track assembly. 
           [0023]      FIG. 6  is a perspective view showing rear and left side views of the track guide retainer removed from the track assembly. 
           [0024]      FIG. 7  depicts a perspective view to another track assembly having a bladder biased, outer rocker arm assembly that couples center sets of idler wheels to pivot from the track framework independent of inner sets of rocker arm mounted idler wheels. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    The present invention finds application with a variety of industrial and commercial all terrain vehicles (ATV) having a chassis that typically supports four improved track assemblies  10  of the invention. A suitable operator and/or passenger compartment or body is typically supported by the chassis. The track assemblies  10  allow the vehicle to traverse wide ranging types of terrain and ground conditions, including streams, mud, rocky terrain, timbered terrain, sand, and snow and ice covered terrain. 
         [0026]    Hydraulically controlled tool assemblies (e.g. blade assembly, bucket, boom, trencher etc.) are typically secured to the vehicle to accommodate defined work functions. A variety of alternative tool assemblies can be outfitted to the vehicle. A variety of tool assemblies can also be or towed by the vehicle and derive operating power through a hydraulic coupling with the engine. 
         [0027]    The track assemblies  10  couple to driven or passive axles  8  that laterally extend from the chassis. Typically, the axles  8  are independently driven and may include intervening power transfer assemblies such as planetary gearing, universal joints or the like. Most typically the axles  8  are powered but some can be passively coupled and merely follow vehicle motion. Wheels can also be fitted to some of the axles  8 . More typically, each axle  8  supports one of the present track assemblies  10  since they enhance the operational capabilities of the vehicle. 
         [0028]    The track assemblies  10  are presently constructed to provide a relatively low or squat profile in contrast to predecessor track conversion assemblies  10  sold by applicant. The reduced height profile lowers the center of gravity of the vehicle which stabilizes the vehicle. The flexibility in varying the height profile of the assembly  6  allows the user to maintain a substantially identical relative ride height between a wheel supported and a track supported vehicle and any operating attachments. The relatively large drive sprocket also substantially maintains a top operating speed for the vehicle regardless of wheel or track configuration. The vehicle is also more readily transported and able to operate at sites with vehicle height requirements. 
         [0029]    The enhanced variable height profile characteristic of the track assembly  10  is achieved with an improved drum-shaped, drive sprocket assembly  20  that drives the track  22 . The configurations of the ground engaging lugs of the track  22  are not shown for convenience.  FIGS. 1 through 3  depict detailed views to the improved track assembly  10  removed from a support vehicle. The track  22  is trained about the drive sprocket assembly  20  and several sets of adjacent idler wheels  24  that are mounted to a support framework  26 . Forward and aft sets of the idler wheels  24  that span the track  22  are supported from unbiased or biased rocker arm assemblies  28  that induce the track  22  to flex and conform to the terrain as shown in dashed line to alternative idler wheel positions at  FIG. 2 . 
         [0030]    Each rocker arm assembly  28  includes a rocker arm  25  that pivots about a pivot axle  27  fitted to the framework  26 . Two sets of three laterally displaced idler wheels  24 , six wheels  24  in total, are supported from each axle  27  at the rocker arms  25 , reference  FIG. 4 . When a resilient biasing member is included, it typically comprises a coiled spring or a compressively resilient elastomer member that is positioned between each rocker arm  25  and the framework  26  to bias the rocker assemblies  28  to an equilibrium condition. Bi-directional bias mechanisms can be included. An alternative track assembly having inner and outer rocker arm assemblies  28  and  82  is shown and discussed below with respect to  FIG. 7 . The rocker arm assembly  82  can be used alone or combined with the assemblies  28 . 
         [0031]    Approximately centered at the framework  26  is the drive sprocket assembly  20 . The sprocket assembly  20  includes a center hub  30  that attaches to a planetary gear assembly and vehicle axle  8 . A track drive ring assembly  32  concentrically attaches to the hub  30 . A mounting ring  33  fastens the sprocket assembly  20  to the hub  30 . In lieu of a solid mounting ring  33 , several spokes  33  can radiate from the hub  30  to support the drive ring assembly  32 . 
         [0032]    The drive ring assembly  32  supports a number of drive teeth  38  that span the width of the sprocket  20  and interact with drive lugs  36  that project from the interior surface of the track  22  to propel the track  22 . Laterally displaced from the mounting ring  33  is a parallel, annular tooth support ring  35 . 
         [0033]    Plate-like drive teeth  38  span between the rings  33  and  35  and include shaped tooth protrusions  40  that engage the track drive lugs  36 . The tooth protrusions  40  project from ends of a connecting link  42  such that the teeth  38  collectively exhibit a “C-shape”. The teeth  38  can exhibit a variety of shapes so long as they can rotate around and between and/or generally not strike the idler wheels  24 , see  FIG. 3 . The teeth  38  are welded to the rings  33  and  35  at slots  44  formed into the links  42 . 
         [0034]    The width of the links  42  and radial projection of the tooth protrusions  40  are tailored to allow the teeth  38  to engage the drive lugs  36  yet pass over and between the lower lying track idler wheels  24  supported to the framework  26  as shown in the lower portion of the cross section view of  FIG. 3 . Drive ring assemblies  32  of differing diameters and/or having drive teeth  38  of differing widths and lengths of protrusions  40  can be fitted to the hub  30  to accommodate a preferred height profile at the track assembly  10  and center of gravity at the vehicle  2 . 
         [0035]    Collectively, the improved sprocket assemblies  20  fitted with an appropriate drive ring  32  reduces the center of gravity and improves the stability of the vehicle. The selection of the proper diameter drive ring  32  particularly ensures the ride height of the vehicle and general vehicle operating characteristics will be substantially the same whether supported from wheels and tires or the track assemblies  10 . The mounting and support heights of any attached tools and equipment are also thereby made substantially universal. The use of a large diameter sprocket assembly  20  also substantially maintains the operating top speed of the vehicle. 
         [0036]      FIGS. 1 ,  5  and  6  depict another improvement to the track assembly  10  which is a track retainer guide  50  that is fitted to the support framework  26 . The retainer guide  50  mounts to lie substantially adjacent and parallel to a lateral peripheral edge of the track  22  and over a portion of the track  22 . A flat plate portion  58  of the retainer  50  is secured with fasteners  54  to the framework  26  at a tubular arm  56  that laterally extends from the framework  26 . The plate member  58  radially projects from the arm  56  and is separately secured with other fasteners  54  to the framework  26  aft of idler wheel  60 . 
         [0037]    A nose piece  62  of the guide  50  separately extends laterally over the aft end of the track  22  and an underlying idler wheel  60 . The idler wheel  60  is mounted to a supporting axle and the framework  26 . The plate  58  and nose piece  62  capture and engage the track  22  to prevent track dislodgement or runoff during normal track rotation. 
         [0038]    A diverter flange  64  projects transversely at an angle in the range of 20° to 50° from the bottom edge of the plate  58 . If the track  22  does start to dislodge, the diverter flange  64  provides a smooth, rounded surface that resists the track movement and runoff without damaging or fraying the edge of the track  22 . Sufficient resistance from the flange  64  can induce the track to re-center on the framework  26 . The diverter flange  64  also disperses debris, dirt, snow etc. away from the track assembly  10 . 
         [0039]    Although a single retainer guide  50  is shown, guides  50  can be mounted to both sides of the track assembly  10 . The guides  50  are typically provided only at the aft idler wheels  60 , but can also be mounted to lay adjacent nose idler wheels  66 . 
         [0040]    Threaded tensioner assemblies  68  also project from the framework  26  and engage each axle that supports a nose idler wheel  66 . The track tension is varied by extending and retracting the threaded tensioners  68 . 
         [0041]      FIG. 7  depicts an alternative track assembly  80  that includes the foregoing improvements and several independent rocker arm suspensions that support the track idler wheels. The track assembly  80  particularly includes two rocker arm assemblies  28  similar to those at the track assembly  10  that support four sets of 3-wide idler wheels  24  from the rocker arms  25 . A separate rocker arm, idler wheel suspension  82  independently and resiliently supports and biases a set of interior, center idler wheels  84  mounted below the improved sprocket assembly  20  and forward of the aft rocker arm assembly  28 . 
         [0042]    The sets of interior idler wheels  84  are affixed to a rocker arm  86  that pivots at the same axle  27  as the aft rocker arm assembly  28 . The arm  86  however pivots from the framework  26  independent of the rocker arm assembly  28 . A resilient, compressible member  90  (e.g. compressively-resilient elastomer member, coiled spring or air bladder) secured to between the framework  26  and rocker arm  86  engages and biases the rocker arm  86  and the idler wheels  84  to an equilibrium condition (e.g. flat, level center as shown at  FIG. 7 ). The idler wheels  84  rotate about axles  92  secured to the rocker arm  86 . The independent pivoting of the rocker arm suspensions  28  and  82  also enhance the terrain conforming movements of the track  22 . 
         [0043]    While the invention is shown and described with respect to presently preferred track assemblies and several considered improvements, modifications and/or alternatives thereto, still other track assemblies and arrangements may be suggested to those skilled in the art. It is to be appreciated therefore that the foregoing track assembly improvements can be arranged in different combinations. For example, either or both of the idler wheel rocker arm suspensions can be provided at a track assembly outfitted with either or both of the improved drive sprocket assembly and/or track guide retainer. The track guide retainer can be used alone with any track assembly or multiple guides can be fitted to a track assembly. The sprocket drive rings can be configured differently and/or be outfitted with different drive teeth. The improved track assemblies can also be mounted to a variety of different vehicles whose operation will essentially remain the same, yet with all the advantages offered by tracks. The foregoing description should therefore be construed to include all those embodiments within the spirit and scope of the following claims.