Abstract:
A novel solution for converting a snowmobile for use as a four-wheeled vehicle for transport or recreation when there is no snow cover on the ground. The present invention consists of an integrated chassis frame to which four wheels are attached. The front wheels are pivotally attached to the frame and interconnected by a steering linkage. The rear wheels are attached to an axle that is rotated by a chain drive linkage that is in turn driven by an arrangement of frictionally connected rubber wheels. The present invention is employed by first driving a snowmobile onto the top of the chassis. The skis at the front of the snowmobile engage into channels formed at the front of the chassis that are pivotally connected to the chassis and integrally connected to the steering linkage for translating the steering action of the snowmobile to the carts front tires. The drive action generated by the snowmobile track is frictionally transferred into the rubber tire arrangement and thereby into the rear axle to provide the power required to rotate the rear tires and drive the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to and claims priority from provisional application No. 60/269,319, filed Feb. 16, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a cart device designed to convert a track vehicle to wheeled operation. More specifically, this invention relates to a four-wheeled cart device onto which a snowmobile is driven and through which the rotation of the snowmobile tracks is translated to forward motion of the cart. The device is designed to accept a variety of makes and models of snowmobiles and provide for their operation when snow cover is insufficient. 
     With the unpredictability of winter weather and inconsistent snowfall in many areas of the country, many snowmobile owners have snowmobiles that sit idle in their sheds for a great many more months of the year than are used for traveling over snowy trails. Since the owners have made a sizeable investment in purchasing these machines, there is a need to find a way to expand the duration of time during the year in which these snowmobiles can be used. An option available to these owners is to bring the snowmobile further north where there is greater snowfall and a longer winter season. However, in this case as well, it is costly in terms of time and money to transport these snowmobiles further north and the time during which these expensive machines can be used is still extremely limited. Also, even in northern climates the snow disappears in the early spring not to reappear until the late fall. 
     The limitation inherent to the snowmobile is that while it is adept at traveling at high speeds over snow, when the snow melts it cannot travel over other terrain. This limitation arises from the use of skis as the front steering and stabilization component and rubber tracks as the rear drive component, both of which would be damaged from travel over pavement or dirt trails. 
     Many attempts have been made to provide for all terrain usage of snowmobiles in the form of conversion kits to replace the front skis and rear tracks with wheels. All of these prior art conversion kits are extremely difficult to employ and require a time consuming and mechanically challenging process to convert the snowmobile. For example, in the prior art, there are kits that allow conversion of a snowmobile for all terrain use that require complete disassembly of the front suspension of the snowmobile so that wheels with spring loaded spindles can be installed in their place. To install the rear wheels, the track belt must be removed, all of the spring-loaded track bogies must be taken off their spindles and then the rear wheels can be installed and connected to the drive train. Because these types of devices are time consuming to assemble and require a fair amount of mechanical ability, most snowmobile owners cannot, or will not, use them. 
     SUMMARY OF THE INVENTION 
     The present invention provides a novel solution to allow a snowmobile to be used as a four-wheeled vehicle for transport or recreation when there is no snow cover on the ground. The present invention consists of a chassis frame to which four wheels are attached. The front wheels are pivotally attached to the frame and interconnected by a steering linkage. The rear wheels are attached to an axle that is rotated by a chain drive linkage that is in turn driven by an arrangement of frictionally connected rubber wheels. A brake assembly may be provided at one or more of the wheels for stopping the vehicle. 
     The present invention as described above is employed by first driving a snowmobile onto the top of the chassis using a fold down ramp connected to the rear of the chassis. The skis at the front of the snowmobile engage into channels formed at the front of the chassis. The channels are pivotally connected to the chassis and integrally connected to the steering linkage. The snowmobile skis are clamped into the channels, whereby the steering action of the snowmobile is translated to a steering of the carts front tires. When the snowmobile rests on top of the chassis, the snowmobile track is aligned over, and engages with the rubber drive wheels. The drive action generated by the snowmobile track is frictionally transferred into the rubber tire arrangement and in turn, translated into the rear axle to provide the power required to rotate the rear tires and drive the vehicle. An idler wheel arrangement is provided adjacent to the transfer tire to further support the surface of the snowmobile track as it rotates. The snowmobile is generally attached to the cart device of the present invention both by the clamps and channels holding the front skis and by an attachment at the tow hitch on the rear of the snowmobile. The front and rear attachment points provide both axial and lateral stability during use. 
     Accordingly the object of the present invention is to provide a device for converting a track powered vehicle for use on wheels. Additionally, it is an object of the present invention to provide a device for converting a snowmobile to wheeled use with out requiring disassembly of the snowmobile. It is also an object of the present invention to create a device that allows convenient off-season use of a snowmobile that is both easy to use and that can be used with a variety of manufactured snowmobiles. 
     Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings which illustrate the best mode presently contemplated for carrying out the present invention: 
     FIG. 1 is a perspective view of the snowmobile conversion device of the present invention; 
     FIG. 2 is a plan view thereof; 
     FIG. 3 is a detail plan view of the front portion of the device; 
     FIG. 3 a  is a detail view of the front wheel assembly of the device; 
     FIG. 4 is a detail plan view of the rear portion of the device; 
     FIG. 5 is a rear view thereof showing the loading ramp in the raised position; 
     FIG. 5 a  is a side view of the rear portion of the device showing the loading ramp in the lowered position; and 
     FIG. 6 is a side view thereof with a snowmobile mounted thereon. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, the snow mobile conversion device of the instant invention is illustrated and generally indicated at  10  in FIGS. 1-6. As will hereinafter be more fully described, the instant invention provides for a device that allows easy conversion of a snowmobile for wheeled use without disassembly of the snowmobile. The invention provides a novel solution that offers an improvement over the prior art devices that require extensive disassembly of the snowmobile before implementation. 
     FIG. 1 shows the present invention in a perspective view. As can be seen generally the device  10  has a structural frame  12  and four wheels  14 ,  16 ,  18  and  20  rotatably mounted to the frame. The front wheels  14 ,  16  are connected to the frame  12  using pivotable wheel mounts  22  that allow for the ability to steer the device  10 . As is best seen in FIGS. 2 and 6 the wheel mounts  22  include mounting channels  24  into which the front skis  28  of the snowmobile  26  rest and are fastened by clamps  25 . The mounting channels  24  are connected to the frame  12  using pivots  30  to allow the steering action of the front skis  28  of the snowmobile  26  to be transferred through a steering linkage  32  to the front wheels  14 ,  16  of the present invention  10 . The rear wheels  18 ,  20  of the device  10  are mounted to the device  10  using an axle  34  that is rotatably mounted at the rear of the frame  12 . Adjacent to the axle  34  is an arrangement of power transfer axles  36 ,  38  that allow for frictional transfer of the power generated by the snowmobile  26  from the track  40  of the snowmobile to the rear axle  34  subsequently driving the device  10  forward. Between the power transfer axles  36 ,  38  and the front mounting channels  24 , several idler wheels  42  are mounted to the frame  12  to provide support for the leading edge of the snowmobile track  40  and to assist in keeping the track  40  in level and firm contact with the power transfer axle  36 . 
     As is seen best in FIG. 2, the frame  12  of the device  10  is generally constructed having two parallel side rails  44 ,  46  and front and rear cross members  50 ,  48  connecting the side rails  44 ,  46 . The side rails  44 ,  46  are constructed so as to have an adjustable length to allow the frame to be extended or shortened as required to accommodate various lengths of existing snowmobiles. The frame  12  serves as the structure to which all of the other operable components of the device  10  mount in addition to providing a firm structure to which the snowmobile  26  can be attached without modification. On the top side of the frame  12 , along the length of both sides, are two longitudinal skid pads  52 ,  54 . The skid pads  52 ,  54  provide a path over which the front skis  28  of the snowmobile  26  can be directed as it is driven onto the device  10  from the rear. 
     The skid pads  52 ,  54  terminate near the front of the frame  12  at the trailing edge of the front mounting channels  24 . The front mounting channels  24  consist of a left and right platform mounted to the top side of the front of the frame  12  using bearings  30  to allow the mounting channels  24  to pivot. The mounting channels  24  have guides  56  fixed on their upper surface that are spaced apart so as to reside on either side of the front skis  28  of the snowmobile  26 . The guides  56  properly align the snowmobile skis  28  on the device  10 . Once the snowmobile  26  is mounted on the device  10 , clamps are added that connect to the underside of the channel guides  56  at their peripheral edges and span over the top of the channels  56  to firmly clamp down onto the snowmobile skis  28  further retaining the skis within the channels  56 . It is an important feature of the present device  10  that the snowmobile skis  28  remain retained within the channels  56  on the front mounting channels  24  as this provides stability for retaining the snowmobile  26  on the device  10  and allows translation of the steering action of the snowmobile  26  to the device. 
     Steering of a snowmobile  26  is accomplished by directing the front skis  28  of the snowmobile in the desired direction of travel using the snowmobile&#39;s normal handlebar  58 . The prior art required the user who desired wheeled conversion of a snowmobile  26  to remove the front snowmobile skis  28  and associated suspension components to replace them with an alternate suspension assembly and a set of front wheels, thereby directly transferring the steering action from the handlebar  58  to the front wheels  14 ,  16 . Since the present invention  10  does not require disassembly of the snowmobile  26 , an alternative method for transferring the steering action was developed. The translation of the steering force begins in the front mounting channels  24 . The clamps and channels  56  retaining the front skis  28  on the pivotally mounted front mounting channels  24  allow transfer of the pivotal steering motion directly into pivotal motion of the mounting channels  24 . The steering action is then further transferred to the front wheels  14 ,  16  of the device  10  using any manner of steering linkage  32  as is well known in the art. 
     Turning to FIGS. 4 and 4 a , the left and right front wheel assemblies  22  are pivotally mounted to the underside of the frame  12 . The wheel assemblies each consist of a spindle  58  with top and bottom mounting points  60 ,  62  to allow the spindle  58  to be firmly mounted to the frame  12  while still allowing it to pivot side to side. An axle  64  is connected to the spindle  58  to which the front wheels  14 ,  16  are attached. A control arm  66  is also rigidly connected to each spindle  58 . At the end of each control arm  66  is a ball joint  68  for mounting a linkage  32  between the left and right wheel assembly  22  to maintain the front wheels  14 ,  16  in a parallel tracking relationship as they are pivoted to turn the device  10 . The linkage  32  may be provided with a length adjustment to increase or decrease its length to allow adjustment of the alignment of the front wheels  14 ,  16  and maintain their parallel relationship. 
     As shown in FIG. 4, the rear wheels  18 ,  20  of the device  10  are connected to an axle  34  mounted to the underside of the rear of the frame assembly. In the present embodiment, the rear axle  34  is rigid but may also be constructed with a right and left axle section connected by a differential assembly as is well known in the art. The rear axle  34  provides the point of transfer allowing the snowmobile power  26  to propel the present device. In the present embodiment, a sprocket  70 , or pulley wheel, is rigidly mounted to the axle  34  at a location between the frame assembly  12  side rails. Power transfer is accomplished through a belt or chain drive  72  mounted to the sprocket  70  and running to the power transfer assembly. A braking assembly  74  may be provided at the rear axle  34  using a conventional disk or drum brake arrangement installed on the rear axle  34  of the device. A long handle  76  is provided extending from the braking assembly  74  to within reach of the user on the snowmobile  26  to allow the user to activate the braking action while still seated on the snowmobile  26 , thus slowing the rotation of the rear axle  34  and thereby stopping the device. 
     The power transfer assembly is located adjacent to the rear axle  34  and is mounted to the upper side of the frame assembly  12 . The power transfer assembly consists of two power transfer axles  36 ,  38  mounted adjacent to one another. Both power transfer axles  36 ,  38  are mounted to the left and right frame rails of the frame assembly  12  using bearings to allow them to freely rotate. The first power transfer axle  36  has transfer wheels  78  mounted along its center section. The transfer wheels  78  are generally constructed with a rubber outer surface to allow good frictional contact and power transfer in the balance of the power transfer arrangement. When the snowmobile  26  is mounted on the device  10 , the rear track  40  of the snowmobile  26  rests on and is in frictional contact with the transfer wheels  78 . The driving motion of the snowmobile  26 , which is traditionally accomplished through the rotation of the drive track  40  against a snow covered surface, causes the transfer wheels  78  and first power transfer axle  36  to rotate in a reverse direction with respect to the device. The rubber surface of the transfer wheels  78  increases the friction between the transfer wheels  78  and snowmobile track  40  providing effective and positive power transfer. 
     A second transfer axle  38  is mounted adjacent to and slightly lower than the first transfer axle  36 . The second transfer axle  38  also has transfer wheels  80  with a rubber surface that is in frictional contact with the transfer wheels  78  on the first transfer axle  36 . This frictional contact provides for transferring the rotational energy from the first transfer axle  36  to the second transfer axle  38  and creates a rotation that is in a forward direction relative to the device  10 . The second transfer axle  38  also has a sprocket  83  or pulley wheel mounted thereon corresponding to the sprocket  70  on the rear axle  34 . A belt or chain drive  72  is connected between the second transfer axle  38  and the rear axle  34  to transfer the power to the rear axle  34  and drive the vehicle  10 . 
     As can be understood, a great number of variations of the power transfer assembly can be created that allow frictional transfer of the rotational energy from the track  40  of the snowmobile  26  to the present invention  10  without modification of the snowmobile  26 . The present disclosure is one example of the preferred embodiment of such a transfer but is intended to also cover any variation is transfer wheels and rotational transfer assemblies. It is also anticipated that a variety of different sizes of wheels and sprockets can be used to allow a stepping up or down of the rotational speed of the snowmobile track relative to the final rotational speed of the rear axle using adjustable gear ratios as is well know in the art. A device for articulating the first transfer axle  36  into and out of contact with the snowmobile track  40  or a similar arrangement between the first transfer axle  36  and second transfer axle  38  or in the linkage between the second transfer axle  38  and the rear axle  34  to provide for selective engagement and disengagement of the driving power of the device  10  is also provided for in the present invention. 
     A set of idler wheels  42  can be mounted between the side members of the frame  12  ahead of the power transfer assembly. The idler wheels  42  provide support for the leading portion of the snowmobile track  40  and allow the track suspension and subsequently the snowmobile  26  to be fully supported along the entire contact surface of the track drive  40 . 
     Turning to FIGS. 5 and 5 a , a ramp  84  is provided and pivotally connected to the rear cross member  48  of the frame assembly  12 . The ramp  84  is extended down to the ground to allow the user to drive the snowmobile  26  directly onto the device  10 . Once the snowmobile  26  is positioned on the device  10 , the ramp  84  is raised to a vertical position and is locked into place. Once in this position, the ramp  84  also provides to stabilize the rear of the snowmobile  26  and prevent lateral movement of the rear of the snowmobile  26  relative to the device  10 . This is accomplished by inserting a pin  86  through two rings  88  provided on the rear surface of the ramp  84  and the standard tow hitch  92  that is provided on all manufactured snowmobiles  26 . This pin  86  engages the back of the snowmobile  26  with the back of the device  10  keeping them in firm contact. The clamps discussed earlier are then installed on the front skis  28  of the snowmobile  26  thereby firmly maintaining the front connection. The snowmobile  26  is dismounted from the present invention either by removing the pin  86  and clamps that retain the snowmobile  26  on the device  10  and backing the snowmobile  26  down the ramp  84  or by driving the snowmobile  26  forward over the front of the device, which is designed to allow the snowmobile  26  to pass over the front mounting and steering assemblies without contacting them or damaging them. 
     While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.