Abstract:
Herein disclosed, a pair of anti-sinkage devices having runners and being rotatably mountable to corresponding hubs of two transversally opposite wheels of a motorized vehicle in a manner that the runners can maintain their attitude and position although the wheel rotates. The anti-sinkage devices can thus limit sinkage of the wheels in sinking terrain, which can allow a broader use of ATV&#39;s during the winter season, for example.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Patent Application No. 61/059,357, filed Jun. 6, 2008, the contents of which are hereby incorporated. 
     
    
     BACKGROUND 
       [0002]    The specification relates to a device and method for preventing the sinkage, also known as bogging, of a motorized vehicle in sinking terrain such as snow, bog, and sand, for example. 
       SUMMARY 
       [0003]    In accordance with one aspect, there is provided a pair of anti-sinkage devices having runners and being mountable to corresponding hubs of two transversally opposite wheels of a motorized vehicle in a manner that the runners can maintain their attitude although the wheel rotates, and which can allow a broader use of ATV&#39;s during the winter season, for example. 
         [0004]    In accordance with one aspect, there is provided a pair of anti-sinkage devices for use with two transversally opposite wheels of a motorized vehicle, each anti-sinkage device of the pair comprising a frame having a front end opposite a rear end, a wheel mount externally mountable to a corresponding one of the two wheels, a rotary connection having a transversally-oriented rotation axis rotatably connecting the wheel mount to the frame between the front end and the rear end thereof, a front runner at the front end, a rear runner at the rear end, the front runner and rear runner being aligned on a common runner plane, the common runner plane being radially offset from the axis of the rotary connection by a radial distance which is operatively lesser than a radius of the corresponding wheel, and a spacing between the front runner and the rear runner receiving the corresponding wheel at least partially therein and the axis of the rotary connection coincides with an axis of the corresponding wheel when the anti-sinkage device is mounted to the corresponding wheel. 
         [0005]    In accordance with another aspect, there is provided an anti-sinkage device for a wheel of a motorized vehicle, the anti-sinkage device comprising a frame having a front end opposite a rear end, a wheel mount externally mountable to the wheel of the vehicle, a rotary connection having a transversally-oriented rotation axis rotatably connecting the wheel mount to the frame, a front runner at the front end, a rear runner at the rear end, the front runner and rear runner being aligned on a common runner plane, the common runner plane being radially offset from an axis of the rotary connection by a radial distance which is operatively lesser than a radius of the wheel, and a spacing between the front runner and the rear runner receiving the wheel therein when the anti-sinkage device is mounted to the wheel, whereby, during use with the anti-sinkage device mounted to the wheel, the wheel rotates about the rotary connection. 
         [0006]    In accordance with another aspect, there is provided an anti-sinkage device for a wheel of a motorized vehicle, the anti-sinkage device comprising a runner having a front end opposite a rear end, a wheel mount externally mountable to the wheel of the vehicle, a rotary connection having a transversally-oriented rotation axis rotatably connecting the wheel mount to the runner, the runner having a runner plane being radially offset from an axis of the rotary connection by a radial distance which is operatively lesser than a radius of the wheel, whereby, during use with the anti-sinkage device mounted to the wheel, the wheel rotates about the rotary connection thereby allowing the runner to maintain a given attitude.. 
         [0007]    In accordance with another aspect, there is provided an anti-sinkage device for a wheel of a vehicle, the anti-sinkage device comprising a frame having a front end opposite a rear end, a front runner at the front end, a rear runner at the rear end, the front runner and rear runner being aligned on a common runner plane, a rotary mount located between the front end and the rear end mountable to a hub of the vehicle to maintain the anti-sinkage device at a fixed given position relative to the wheel, in which given position the runner plane is radially offset from an axis of the wheel by a radial distance which is operatively lesser than a radius of the wheel, and a spacing between the front runner and the rear runner at least partially receiving the wheel when the anti-sinkage device is in the given position.. 
         [0008]    In accordance with another aspect, there is provided a pair of anti-sinkage devices as described above, the anti-sinkage devices being mirror images of one another and being for use, respectively, on transversally opposite wheels of a vehicle. 
         [0009]    In accordance with another aspect, there is provided the use of a pair of anti-sinkage devices on corresponding front wheels of a motorized vehicle. 
         [0010]    In accordance with another aspect, there is provided a motorized vehicle having a pair of anti-sinkage devices on corresponding front wheels thereof. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0011]    In the appended figures, 
           [0012]      FIG. 1  is a side elevation view showing an example of an anti-sinkage device mounted on a vehicle; 
           [0013]      FIG. 2  is an exploded perspective view of the device of  FIG. 1 ; 
           [0014]      FIG. 3  is a cross-sectional view taken along lines  3 - 3  of  FIG. 2 , shown unexploded; and 
           [0015]      FIG. 4  is a perspective view showing a pair of anti-sinkage devices mounted on corresponding transversally-opposite wheels of a vehicle. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  shows an example of an anti-sinkage device  10 . The anti-sinkage device  10  is mounted on a wheel  12  of a vehicle  14 . The anti-sinkage device  10  can be seen to include a frame  16  having a front end  18  and a rear end  20 . A front runner  22  is mounted to the front end  18 , and a rear runner  24  is mounted to the rear end  20  of the frame  16 , with a spacing  26  between the front runner  22  and the rear runner  24 . Both of the front runner  22  and the rear runner  24  are aligned on a common runner plane  28 . 
         [0017]    In this example, the anti-sinkage device  10  is mounted and maintained in a given position relative to the wheel  12  by a wheel mount  30  which is connected to the wheel  12 , more precisely to the hub (not shown), in a manner to rotate with the wheel  12  and hub during use of the vehicle. The frame  16  is mounted to the wheel mount  30  via a rotary connection  32 , which allows relative rotation between the wheel  12  and the frame  16 , in a manner that the attitude of the runner plane  28  can remain substantially horizontal during rotation of the wheel  12 . 
         [0018]    When the anti-sinkage device  10  is mounted to the vehicle  14  in the given position, the wheel  12  is received in the spacing  26  between the front runner  22  and rear runner  24 , the front runner  22  and rear runner  24  can thus be at least partially aligned with the travelling path of the wheel  12 , and even centrally aligned relative to the path of the wheel  12 , if desired. The rotary connection  32  has a transversal rotation axis  34  which coincides with the rotation axis of the wheel  12  and hub. The runner plane  28  is spaced, or offset, from the axis  34  by a radial distance  36  which is lesser than the radius of the wheel by a wheel excess distance  38 , in a manner that during use on a given type of terrain  40 , the runners  22 ,  24  normally remain out from gliding contact with the terrain (except for the tip of the front runner), but if wheel sinkage exceeding a given sinkage threshold, corresponding to the wheel excess distance  38 , occurs, the runners  22 ,  24  can come into gliding contact with the terrain  40  and prevent further sinkage of the wheel  12 . 
         [0019]    In this example, during use, the attitude of the runner plane  28  remains in fact slightly off perfect horizontal, and the front end of the front runner  22  normally remains in contact with the terrain, due a slight but inevitable amount of friction occurring in the rotary connection  32  and to the weight balance of the front runner  22  and the rear runner  24  relative to the pivotal connection  32 . This type of contact which can be referred to as runner tip contact is normal and is not encompassed by the meaning of the expression gliding contact as defined herein, which refers to gliding contact of sliding surface along the length of the runner plane which occurs in the event of wheel sinkage exceeding the given sinkage threshold. 
         [0020]    In view of alternate embodiments, the greater the radial distance  36  is made, the smaller the sinkage threshold before the runners  22 ,  24  come into the gliding contact with the terrain  40 , which contributes to the efficiency, or operability of the device  10 . However, the radial distance  36  should not be made too close to the radius of the wheel because a lesser wheel excess distance  38  typically translates into a lesser traction of the wheel during a wheel sinkage event. The expression “operable” is used herein to qualify a choice of relative radial distance  36  vs. wheel radius which suitably compromises sinkage threshold and tire traction during sinkage. Typically, the sinkage threshold  38  is made greater than the sum of a predetermined normal roughness of the given type of terrain  40  and a sinkage depth which can be considered normal given the type of terrain  40 . Henceforth, the radial offset distance  36  can be made operatively smaller than the tire radius to provide an anti-sinkage device in which the runner normally remains out from the gliding contact with the terrain and which provides for sufficient wheel traction when the gliding contact occurs, while providing a sinkage threshold which is satisfactorily low so that the anti-sinkage device can come into operation before an excessive sinkage. Further, it has been found that increasing the radial distance  36  within a certain extent generally results in a smoother ride. However, increasing the radial distance  36  too much can result in an unpleasing driving sensation of continuous friction or gliding contact by the runners. For illustrative purposes, in the example described above and illustrated, a wheel excess distance  38  of about 3 inches was very satisfactory for the application of an ATV running on snow with a wheel having a wheel radius of 12.5 inches and given type of tire thread, whereas a wheel excess distance  38  of about ½ inch was judged unsatisfactory. 
         [0021]    In the exploded view of  FIG. 2 , and the cross-sectional view of  FIG. 3 , the various components of this example of an anti-sinkage device  10  are shown in greater detail. In this example, the wheel mount  30  is mounted directly to the hub bolts  42  of the hub  44 . The rotary connection  32  includes an outer portion  46  which is connected to the frame  16  and an inner portion  48  which is connected to the wheel mount  30 . In this example, two ball bearings  50 ,  52  are used within the outer portion, and a shaft  54  having a threaded end  56 , is inserted through the ball bearings  50 ,  52 , and threaded into a threaded bore  58  provided in the wheel mount  30 . 
         [0022]    As it will be understood by those skilled in the art, because a user may need to remove the anti-sinkage device  10  from the wheel regularly, it is preferable that the anti-sinkage device  10  be configured to allow easy removal of the runners  22 ,  24  and frame  16  from the wheel  12 , without having to dismount the wheel  12  from the hub  44 . In this example, this is provided with the single central shaft  54  of the rotary connection  32  which is also a fastener having a threaded end  56  which is detachable from the wheel mount  30 , while the wheel mount  30  can remain permanently fastened to the wheel  12  and the hub  44 . In this example, the removal of the frame and runners from the wheel mount  30  is thus achieved by disassembling the rotary connection  32 . 
         [0023]    It was found experimentally that to obtain a smooth ride with the anti-sinkage device  10 , the components which rotate with the wheel should be well balanced. This includes having a relatively precise alignment, or coincidence, between the axis  34  of the rotary connection and the axis of the wheel hub, and an evenly distributed weight of the wheel mount about these coinciding axes. 
         [0024]    In this example, it will be understood that the motorized vehicle  14  is of a type having four hub bolts  42  extending from the hub  44  across the wheel  12  and by which the wheel  12  is normally fastened to the hub  44 . In alternate embodiments, alternate vehicles can have more than four hub bolts as known to those skilled in the art, and the wheel mount can be adapted accordingly. In this example therefore, the wheel mount thus includes four extension nuts  60 , each extension nut  60  being securably threaded onto a corresponding hub bolt  42 , similarly to how a hub bolt nut is normally used. However, each extension nut  60  has two opposite threaded ends  62 ,  64 . The wheel mount  30  also includes a central disk  66  having the central threaded bore  58  and four secondary bores  68 . Four extension bolts  70  are provided to secure the disk  66  to the extension nuts  60  by insertion through the corresponding secondary bore  68  and threading into the exposed threaded end  64  of the corresponding extension nut  60 , opposite the hub bolt  42 . The disk  66  can thus remain permanently attached to the wheel  12  and hub  44 , whereas the rotary connection  32 , the frame  16  and the runners  22 ,  24  can be removed from the disk  66  by removing the central shaft  54 . Alternate configurations are possible as well. 
         [0025]    Because the disc  66  has secondary bores  68  at given positions, the disc  66  is adapted to a specific wheel hub type. It is possible in alternate embodiments to make the disc  66  adaptable to different hub sizes by substituting radial slots to the secondary bores. However, this can pose a further challenge with respect to the balancing of the rotating components. 
         [0026]    In  FIG. 4 , a pair of anti-sinkage devices are shown mounted in corresponding given positions on corresponding, laterally opposite wheels of a vehicle. In this example, the wheels on which the anti-sinkage devices are used, are the front, traction wheels, of the motorized vehicle. 
         [0027]    It will be understood that the exemplary embodiment described above and illustrated, is provided for illustrative purposes only. Various alternate embodiments and variants to this exemplary embodiment can be provided in view of specific alternate embodiments. For example, the rotary connection of the anti-sinkage device can be omitted in some alternate embodiments where the anti-sinkage device is mounted to non-rotary components of the vehicle but nevertheless maintained in the given position relative to the wheel during use. For example, a pair of anti-sinkage devices can be mounted to non-rotary components of a trailer, each anti-sinkage device of the pair being associated with a corresponding wheel. This can help make the trailer more versatile and prevent sinkage thereof when pulling the loaded trailer out from snowy terrain. 
         [0028]    Also, in alternate embodiments, the front runner and the rear runner can be provided as a front and rear portion of a single runner, without a spacing therebetween, the runner being provided adjacent the wheel instead of in the path of the wheel. The configuration of the runners themselves can vary, any suitable shape allowing to glide over the sinkable terrain can be used. In the example given above, the front runner and rear runner are provided in the form of skis, but other shapes such as sliding disks can be used as well. In the example given above, a front ski having about twice the length of the rear ski was used, though the length of the rear ski can vary between about 0.4 and 0.6 time the length of the front ski in alternate embodiments. The anti-sinkage device can be used on any desired type of vehicle which is suitable for its use. The sinkage threshold or the wheel excess distance, can vary in alternate embodiments and be adapted to specific types of terrain or to different tire thread depths. For illustrative purposes, a wheel excess distance of about 0.2 to 0.3 time the radius of the wheel was used in view of use of the anti-sinkage device with an ATV on snowy terrain. Various other variants and adaptations in view of specific applications are possible as well. 
         [0029]    The scope is indicated by the appended claims.