Abstract:
One aspect of the invention is directed to a vehicle drive/suspension system including a chassis having a front portion, a rear portion and a pair of sides; a drive axle having opposed end portions extending between said sides; an elongated rocker arm, having opposed end portions, connected to each of said opposed end portions of said drive axle and pivotally mounted to each of said sides substantially at said opposed end portions of said drive axle; a sprocket rotatably fixed to each of said opposed end portions of said rocker arms; a rotatable drive sprocket connected to each of said opposed end portions of said drive axle; and a drive link for each rocker arm connected to rotate said sprockets in conjunction with said drive sprockets.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a vehicle drive/suspension system, particularly to a drive/suspension system for four-wheel drive all-terrain/utility type vehicles.  
         BACKGROUND OF THE INVENTION  
         [0002]    All-terrain/utility type vehicles are known in the art and have been utilized for many years. Typical of these types of vehicles are Gator® utility vehicles manufactured by John Deere Company and “Groundforce 100” manufactured by CheTech Company. Such vehicles have a wide variety of applications including industrial, governmental and private uses. Such vehicles have historically required heavy duty construction, the ability to negotiate rough terrain, ability to haul heavy loads, provide high ground clearance and provide a safe, reliable vehicle for the operator and, typically, at least one passenger.  
           [0003]    Recently, there has been a trend toward more frequent use of such vehicles under circumstances wherein they traverse ground or terrain that should not be disturbed or broken. Typical uses include landscaping and/or maintaining lawns or the grounds of office parks, etc. and golf courses, for example. Such uses oftentimes require that the turf underfoot not be disturbed or “scuffed.” Also, such uses often require operation in tight spaces that require comparatively tight turns, which exacerbates turf “scuffing.”  
           [0004]    Prior vehicles have tended to disturb the grounds such as by turf “scuffing” or destruction of the ground underfoot. This phenomenon has especially been a problem with respect to scuffing during turning of such all-terrain/utility type vehicles, especially four-wheel drive vehicles since they tend to disturb the turf much in the same way as treads on a military tank. This is especially important in relation to six-wheeled vehicles because the front wheels are not powered (as in a 4×4 vehicle), the front wheels do not contribute to turf “scuffing.” However, the effect of the four rear drive wheels is exacerbated.  
           [0005]    Safety is also an important issue in six- or eight-wheeled vehicles with axles mounted rigidly to the frame. This is clearly illustrated when such a vehicle climbs the crest of a hill or gully. The front wheels continue to climb, loosing contact with the ground until the vehicle progresses far enough that the center of gravity shifts and the vehicle “teeters”, slamming down on the front wheels (the rear wheels coming off the ground in the process), much like a tracked vehicle would be expected to perform. Accordingly, it has been a longstanding desire to manufacture an all-terrain/utility type vehicle that is capable of meeting the traditional requirements of such vehicles but also provide operator safety, high ground clearance, facilitate ease of turning and reduce and/or eliminate turf “scuffing.”  
         SUMMARY OF THE INVENTION  
         [0006]    One aspect of the invention is directed to a vehicle drive/suspension system including a chassis having a front portion, a rear portion and a pair of sides; a drive axle having opposed end portions extending between said sides; an elongated rocker arm, having opposed end portions, connected to each of said opposed end portions of said drive axle and pivotally mounted to each of said sides substantially at said opposed end portions of said drive axle; a sprocket rotatably fixed to each of said opposed end portions of said rocker arms; a rotatable drive sprocket connected to each of said opposed end portions of said drive axle; and a drive link for each rocker arm connected to rotate said sprockets in conjunction with said drive sprockets.  
           [0007]    Another aspect of the invention is directed to a vehicle drive/suspension system including a chassis having a front portion, a rear portion and a pair of sides; a drive axle having opposed end portions extending between said sides; an elongated rocker arm having opposed end portions and a pivot point pivotally mounted to each of said sides at said pivot points and connected to said opposed end portions of said drive axle, said pivot points being located at positions other than middle points along the length of said rocker arms; a sprocket rotatably fixed to each of said opposed end portions of said rocker arms; a rotatable drive sprocket connected to each of said opposed end portions of said drive axle; and a drive link for each rocker arm connected to rotate said sprockets in conjunction with said drive sprocket.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a bottom plan view of portions of a drive/suspension system in accordance with aspects of the invention.  
         [0009]    [0009]FIG. 2 is a perspective view of the drive/suspension system shown in FIG. 1 taken from the rear and above.  
         [0010]    [0010]FIG. 3 is a perspective view of the drive/suspension system from FIG. 1 shown from the rear and below.  
         [0011]    [0011]FIG. 4 is a perspective view of the drive/suspension system shown in FIG. 1 from the rear and below and further showing a drive chain utilized in accordance with aspects of the invention.  
         [0012]    [0012]FIG. 5 is a side elevational view of the drive/suspension system from FIG. 1.  
         [0013]    [0013]FIG. 6 is a perspective view of a portion of a chassis taken from the drive/suspension system in accordance with the invention.  
         [0014]    [0014]FIG. 7 is a perspective view of a drive axle in accordance with aspects of the invention having several parts broken away for ease of understanding.  
         [0015]    [0015]FIG. 8 is a perspective view of a rocker arm in accordance with aspects of the invention.  
         [0016]    [0016]FIG. 9 is a perspective view of a pivot pin utilized in accordance with aspects of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    It will be appreciated that the following description is intended to refer to specific embodiments of the invention selected for illustration in the drawings and is not intended to define or limit the invention other than in the appended claims.  
         [0018]    Referring now to the drawings generally, a vehicle drive/suspension system  10  is shown. Chassis  12  includes sides  14  and  16 , rear-cross member  18  which generally defines a rear portion, and a middle-cross member  20 . No front cross portion is shown. However, a front-cross member is typically included at the front portion. For example, a steering axle is typically mounted to the front of the vehicle chassis. Such front wheels would not typically be drive wheels. A drive axle  22  connects between sides  14  and  16 . Drive axle  22  includes an axle housing  24  and an elongated axle shaft  26  having opposed portions  28  and  30 . Affixed to axle shaft  26  are a pair of drive sprockets  32  and  34 . A pair of brakes  36  and  38  are also mounted to axle shaft  26  inwardly of drive sprockets  32  and  34 . Preferably, brakes  36  and  38  are drum type brakes, although they can be other types of brakes such as disc brakes and the like.  
         [0019]    Axle housing  24  contains typical gear apparatus well known in the art and not described herein that connects to universal joint  40  which, in turn, connects to a drive shaft (not shown).  
         [0020]    It should be understood that the axle is not limited to being driven by a coupled drive shaft as shown. For example, it may also be driven by a belt-engaged torque converter clutch. The drawings show an axle with a universal joint  40  for simplicity of illustration. Different axles may be used such as an axle with a stub shaft that a driven torque-converter clutch is mounted to. There may also be an additional mounting point between the axle and the chassis to help stabilization.  
         [0021]    As best shown in FIGS. 5 and 6, a pair of mounting plates  42  and  44  are affixed to each of side rails  14  and  16  and extend downwardly toward elongated rocker arms  46  and  48 .  
         [0022]    The rocker arms  46  and  48  have opposed end portions  50  and  52  and a center point  54 , which is equidistant between the opposed end portions  50  and  52 . Each opposed end portion  50  and  52  connects to a sealed bearing housing  56 . The sealed bearing houses  56  have axles  58  onto which wheels (not shown) may be mounted.  
         [0023]    On each inboard end of axle  58  is mounted a sprocket  60  to which drive chains  62  as shown in FIG. 4 are connected. Each pair of sprockets  60  on rocker arms  46  and  48  is linked to corresponding drive sprockets  32  and  34 . Tension sprockets  62  and  64  are slidably mounted onto rocker arms  46  and  48 , respectively. Tension sprockets  62  and  64  may be utilized to facilitate changing of chains  62 .  
         [0024]    A dampener  66  in the form of a shock absorber connects between each of the rocker arms  46  and  48  and chassis  12  by a connection  68  mounted on cross member  20 . Connectors  68  are best shown in FIG. 6.  
         [0025]    Rubber stops  70  are mounted to the underside of side rails  14  and  16  at the rearward portion of chassis  12  and are positioned in alignment with rocker arms  46  and  48 . Rubber stop members  70  prevent rocker arms  46  and  48  from pivoting upwardly and into contact with side rails  14  and  16 , respectively.  
         [0026]    As best shown in FIGS. 3 and 8, rocker arms  46  and  48  have pivot mounts  72  and  74 . Each pivot mount is comprised of a pair of upwardly extending plates  76  and  78  extending upwardly therefrom and include a sealed bearing housing  80 . Sealed bearing housing  80  is aligned with the central axis of axle shaft  26  and openings  82  and  84  in mounting plates  42  and  44  such that rocker pin  86  extends through mounting plate  44 , mounting plate  76 , sealed bearing housing  80 , mounting plate  78  and through the opening in axle shaft  26 . The threads  88  of rocker pin  86  engage nut  90  that is welded to mounting plate  42  to secure the rocker arms  46  and  48  to chassis  12  and drive axle  22 .  
         [0027]    Although pivot member  72  may be mounted at substantially any position along elongated rocker arms  46  and  48 , it is highly advantageous and especially preferred that mounting member  72  be mounted at a position removed or away from center point  54 . Mounting the pivot mount away from center point  54  causes a “preloading” of either the front portion or rear portion of the vehicle in which the system is installed, thereby reducing the load distribution on either the front or rear wheels associated with the system (not necessarily the vehicle, depending on the number of wheels). This, in turn, assists in reducing turf “scuffing”, especially during turning. Also, such preloading eases the act of turning the vehicle from the operator&#39;s standpoint. It is especially preferred to have preloading in the range of about 55-65% of the load distribution to the rear of the system/vehicle, especially about a 60% preloading.  
         [0028]    In operation, a vehicle utilizing the drive/suspension system of the invention can provide all of the additional requirements of all-terrain/utility type vehicles and also achieves a surprising degree of ability to reduce turf scuffing, ease turning of the vehicle and provide improved ground clearance for enhanced operation of the vehicle. Application of power from any type of drive device such as gasoline engine, diesel engine, electric motor or the like is transferred through the drive shaft (not shown) to universal joint  40  and into the gear system in axle housing  24 . Driving motion is transmitted through axle shaft  26  toward drive sprockets  32  and  34 . Further drive action is transmitted through chain  62  to sprockets  60 , through axles  58  and to the wheels (not shown). Reduction between the engine shaft and the wheels is preferably achieved within the gear reduction of axle housing  24 . Additional reduction can be achieved by utilizing different-sized sprockets  60  in comparison to other drive sprockets  32  and  34 . Preferably, there is about a 5% reduction between the sets of sprockets.  
         [0029]    The unique drive/suspension system of the invention allows all-terrain/utility type vehicles to avoid traditional suspension systems based on leaf springs, coil springs, shock absorbers or the like as typically configured. The resulting structure is far stronger and less subject to inordinate wear, yet provides a comparatively soft ride for the cargo and/or passengers by virtue of the utilization of the dampers  66 .  
         [0030]    Use of the drive/suspension system of the invention in a six-wheeled vehicle is especially advantageous. Its advantages are in direct relation to other six-wheeled vehicles, wherein either one or both of the rear drive axles are rigid to the frame. The advantage to the invention system is that all four drive wheels have an independent action to the chassis, thereby providing 1) consistent traction in uneven terrain by allowing all four wheels to engage the ground at all times, and 2) a smoother ride to the passengers since the floating axles average out a lot of the bumps in the terrain (for example, driving over a 6″ diameter log only raises the chassis about 3″, due to the ratio of the pivot arms.  
         [0031]    Although this invention has been described in connection with specific forms thereof, it will be appreciated that a wide variety of equivalents may be substituted for the specific elements described herein without departing from the spirit and scope of the invention as described in the appended claims. For example, although a drive chain  62  having openings sized and shaped to receive teeth has been shown in conjunction with sprockets  32 ,  34 ,  60 ,  62  and  64 , all having teeth, other components may be used. As an example, a pulley and belt system can be used as well as any number of other drive/linking systems known in the art. Thus, although the term “sprocket” is used herein to refer to use of such sprockets with teeth, its definition is sufficiently broad to cover other configurations, constructions and components such as the aforementioned pulleys and the like so long as the component is rotatable and capable of engaging a drive belt, chain or link of some type.  
         [0032]    Also, although gas/piston type shock absorbers utilized as dampeners  66  are shown as the preferred embodiment, other types of dampeners may be used. For example, coil springs or similar devices may be used.