Abstract:
A method of attachment of a ski to a snowmobile, the snowmobile capable of displacement about a gliding surface. The method comprises the step of providing the snowmobile with at least one steering link defining a push axis. It also comprises the step of providing a snowmobile ski having a ski body defining an undersurface, a snowmobile mounting member connected to the ski body, and at least one blade member attached to the ski body and arranged about the ski body undersurface, the blade member defining a leading end portion and a trailing end portion. The method finally comprises the step of attaching the snowmobile mounting member to the steering link such that the push axis substantially registers with the leading end portion of the blade member when the snowmobile glides on the gliding surface, thus enhancing adherence of the ski to the gliding surface.

Description:
FIELD OF THE INVENTION 
   The present invention relates to snowmobiles, and more particularly to a method of attachment of a ski on a snowmobile and to the resulting snowmobile. 
   BACKGROUND OF THE INVENTION 
   The steering of snowmobiles is conventionally accomplished by a pair of ground engageable skis which are mounted on the front of the snowmobile and are turned in the direction in which the snowmobile is to be propelled. The turning radius of a snowmobile which is equipped with conventional skis, traversing very hard snow or ice is very large because the conventional ski runners merely slide along the gliding surface without “digging in”. To overcome this, snowmobile skis are provided with keels on the underside thereof, having sharpened carbide blade members which cut or bite into the gliding surface to positively control the turning of the snowmobile. 
   However, merely providing blade members on the underside of the ski does not automatically bring about adherence of the ski to the gliding surface. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a method of attachment of a ski to a snowmobile, the snowmobile capable of displacement about a gliding surface, comprising:
         providing said snowmobile with at least one steering link defining a push axis;   providing a snowmobile ski having a ski body defining an undersurface, a snowmobile mounting member connected to said ski body, and at least one blade member attached to said ski body and arranged about said ski body undersurface, said blade member defining a leading end portion and a trailing end portion;   attaching said snowmobile mounting member to said steering link such that said push axis substantially registers with said leading end portion of said blade member when said snowmobile glides on the gliding surface, thus enhancing adherence of said ski to the gliding surface.       

   In one embodiment, said steering link is an elongated kingpin defining a longitudinal axis, said push axis coincides with said longitudinal axis of said kingpin, and said mounting member is pivotally connected to said steering link. 
   In one embodiment, said ski body comprises a longitudinal runner extending on its said undersurface, said blade member carried by and extending longitudinally along said runner. 
   In one embodiment, said snowmobile ski comprises a wear bar affixed to said ski body undersurface and arranged substantially about said runner, said wear bar comprising said blade member. 
   In one embodiment, said wear bar further comprises a curved, plate-like smoothing member located forwardly of said blade member for flattening irregularities in the gliding surface. 
   In one embodiment, said wear bar comprises a trailing rod located rearwards of said smoothing member, said trailing rod carrying said blade member. 
   In one embodiment, said runner defines a groove therealong, said wear bar trailing portion registering below said runner groove. 
   The present invention also relates to a snowmobile for riding on a gliding surface, comprising
         a snowmobile body comprising propelling means and a steering mechanism having steering control means;   at least one steering link defining a push axis, said steering link being operatively connected to said steering mechanism and being controlled by said steering control means;   a snowmobile ski having a ski body defining an undersurface, a snowmobile mounting member connected to said ski body, and at least one elongated blade member attached to said ski body and arranged about said ski body undersurface, said blade member defining a leading end portion and a trailing end portion, said snowmobile mounting member being attached to said steering link such that said push axis substantially registers with said leading end portion of said blade member when said snowmobile glides on the gliding surface.       

   In one embodiment, said steering link is an elongated kingpin defining a longitudinal axis, said push axis coincides with said longitudinal axis of said kingpin, and said mounting member is pivotally connected to said steering link. 
   In one embodiment, said ski body comprises a longitudinal runner extending on its said undersurface, said blade member carried by and extending longitudinally along said runner. 
   In one embodiment, said snowmobile ski comprises a wear bar affixed to said ski body undersurface and arranged substantially about said runner, said wear bar comprising said blade member. 
   In one embodiment, said wear bar further comprises a curved, plate-like smoothing member located forwardly of said blade member for flattening irregularities in the gliding surface. 
   In one embodiment, said wear bar comprises a trailing rod located rearwards of said smoothing member, said trailing rod carrying said blade member. 
   In one embodiment, said runner defines a groove therealong, said wear bar trailing portion registering below said runner groove. 
   In one embodiment, said trailing rod is cross-sectionally polygonal. 
   In one embodiment, said trailing rod is cross-sectionally quadrangular. 
   In one embodiment, upon said snowmobile resting on the gliding surface, said push axis forms an angle of between 30 to 45° with said elongated blade member. 

   
     DESCRIPTION OF THE DRAWINGS 
     In the annexed drawings: 
       FIG. 1  is an exploded perspective view of a snowmobile ski; 
       FIG. 2  is a bottom and assembled perspective view of the ski of  FIG. 1 ; 
       FIG. 3  is a front elevation at an enlarged scale of the ski of  FIG. 2 ; 
       FIG. 4  is an enlarged cross-sectional view of the ski taken along lines IV-IV of  FIG. 2 ; 
       FIG. 5  is a side elevation showing the ski of  FIG. 2  attached to the front end portion of the kingpin of a snowmobile, with the ski pressed against a gliding surface; and 
       FIG. 6  is a schematic front perspective view of a snowmobile equipped with two snowmobile skis as shown in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
     FIGS. 1-2  show a snowmobile ski  10  according to the present invention. Ski  10  comprises a rigid main body  12 , made of plastic for example, having an upturned leading end portion  12   a  and a slightly upturned trailing end portion  12   b.  The upper surface of ski main body  12  comprises an A-shaped projection  14  extending on the ski lengthwisely from the front to the rear end portions  12   a  and  12   b  of the ski main body  12 . A conventional tension bar  16  is fixed to the leading end portion  12   a  of the ski body  12 . The front in-turned end portion of tension bar  16  is pierced at  16   a  and is secured to a front section of A-shaped projection  19  using bolt  17   a  and nut  17   b,  as shown in  FIG. 1 . The T-shaped rear end portion of tension bar  16  is bored at  16   b,  and is secured to an intermediate section of A-shaped projection using bolt  18   a  and nut  18   b.    
   Ski  10  also comprises a cross-sectionally U-shape snowmobile mounting plate  20  affixed to an intermediate section of the top face of ski body  12 . Mounting plate  20  comprises a bottom wall  20   a,  and two parallel, trapezoid side flanges  20   b,    20   b  each projecting perpendicularly from one of the longitudinal edges of mounting plate bottom wall  20   a.  Each one of side flanges  20   b,    20   b  comprises an eyelet  26  made centrally in the central and widest section thereof, for engagement by one of the two front kingpins  72  of the snowmobile, as described hereinafter. Two bolts  22   a,    22   a  penetrate through spaced apart holes  23 ,  23  made through ski body  12  from the bottom up, and then through registering holes  24 ,  24  made in the mounting plate  20 , and corresponding nuts  22   b,    22   b  are screwed to the top free end of the bolts  22   a,    22   a,  thereby securing the mounting plate  20  to the ski. 
   As shown in  FIG. 2 , the undersurface of ski main body  12  is integrally formed with a runner  30  extending substantially between the front and trailing end portions  12   a  and  12   b  of the ski main body  12 . Runner  30  tapers at both of its ends, as can be seen in  FIG. 4 . Keel  30  also comprises a longitudinal groove  32  made therealong, intermediate its tapered ends. 
   Ski  10  further comprises a wear bar  40 , in turn having a trailing rod  42 , cross-sectionally square in the drawings, but which could also have a polygonal or circular cross-section in alternate embodiments. On the undersurface of trailing rod  42  is made a longitudinal, cross-sectionally triangular groove  44 , as seen in  FIG. 2 . A blade member  46 , made of carbide for example, defines a leading end portion  46   a  and a trailing end portion  46   b,  is fixedly received in groove  44 , and defines an elongated trailing portion  47  towards the trailing end of the ski, and a much shorter leading portion  48  located towards the leading end of the ski and having a cross-sectional area much smaller than that of trailing portion  47 . Both trailing and leading portions  47  and  48  respectively of the carbide blade member  46  are cross-sectionally diamond-shaped, and snugly engage and are welded to the cross-sectionally triangular groove  44 . 
   The front end portion of the wear bar trailing portion  42  merges with a smoothing member  50 . Smoothing member  50  defines a couple of tabs  52 ,  52  extending longitudinally on each side of the front end portion of trailing rod  42 , and are affixed thereto for example by welding. Opposite the free end of tabs  52 ,  52 , tabs  52 ,  52  merge with a progressively widening transitional portion  54 , into which the front end portion of trailing rod  42  also extends. Transitional portion  54  integrally merges with a plate portion  56  having a curved rectangular shape. Plate portion  56  in turn merges with a gradually narrowing neck portion  58 . Wear bar  40 , at the front end of neck portion  58 , terminates with a bent, Z-shaped attachment finger  60 . 
   Wear bar  40  is attached to ski body  12  first by inserting the attachment finger  12  in a hole  31  made centrally through ski body  12 , on runner  30  (see  FIGS. 2 ,  3  or  5 ). A number of threaded shanks  62  (three shanks  62  are provided in the illustrated embodiment), are welded to the trailing rod  42  of the wear bar  40 , on its upper surface, i.e. the surface opposite groove  44 . Shanks  62  are received in the groove  32  made along runner  30 , through the lumen of a T-shaped washer  66 —in turn received in holes  64  made across ski body  12 —and through holes  68  made across mounting plate bottom wall  20   b.  A nut  70  is screwed on the free end of each threaded shank  62 , thus securing the wear bar to the ski body  12 . As can be seen in  FIG. 4 , trailing rod  40  is located just below groove  32  in runner  30 , and will be able to recoil therein if the gliding ski encounters a rock or other rigid obstacle. 
   As shown in  FIG. 5 , ski  10  is destined to be connected to the kingpin 72 —also referred to generically as a steering link herein—of a snowmobile S. Kingpin  72  comprises a mounting block  74  comprising laterally projecting swivel pins (only one swivel pin  75  is shown in  FIG. 5 ), extending through the swivel holes  26 ,  26  made in ski mounting plate side walls  20   b,    20   b.  This pivotal connection allows ski  10  to swivel relative to kingpin  72  along a substantially horizontal axis extending between both swivel holes  26 ,  26 . Furthermore, mounting block  74  is fixedly connected to a steering rod  76 . Steering rod  76  is in turn operatively connected to the steering mechanism (not shown) of the snowmobile, allowing the kingpin  72  to move concomitantly with the handlebars (or other steering control means) of the snowmobile S. Snowmobile S is of conventional construction and is schematically shown in  FIG. 6 , and generally comprises a bodywork B, conventional snowmobile propulsion means P (for example a belt-type propulsion assembly driven by a combustion engine lodged in the bodywork of the snowmobile), and handlebars H connected to the steering mechanism of the snowmobile (not shown), used to steer the snowmobile S when in forward motion. 
   Kingpin  72  defines a push axis A, as illustrated in  FIG. 5 , coinciding substantially with the longitudinally axis of steering rod  76 . As illustrated in the figures, ski  10  is pivotally attached to kingpin  72  such that when the snowmobile S rests on the ground, the push axis A ( FIG. 5 ) coincides with the leading end portion  46   a  of blade member  46 , and the angle between push axis A and the longitudinal axis of elongated blade member  46  may be between 30° to 45°. 
   To drive the snowmobile having the ski/steering link arrangement described above, the user conventionally starts the snowmobile&#39;s engine, and actuates the propulsion means P of the snowmobile (for example by rotating the right handle). The snowmobile is consequently set in forwards motion about the snow- or ice-covered surface. Often, snowmobile are only allowed to ride on dedicated snowmobile trails, and these trails are marked with furrows already dug by the skis of previous snowmobiles. Such furrows can become a hazard as they have the tendency to destabilize the gliding motion of the skis of a snowmobile subsequently gliding thereon, and thus compromise the directional stability thereof. Therefore, as the snowmobile S glides forwardly on the snowy ground G ( FIG. 5 ), its smoothing member  50 , and more especially its curved plate member  56 , will flatten out and even out irregularities in the incoming snow path to avoid the destabilizing action of the previously dug furrows. It will also tend to hard-pack, thus enhancing the biting action of the blade member  46  trailing immediately behind the smoothing member  50 . 
   Moreover, and more importantly, since the push axis A registers substantially with the leading end portion  46   a  of the blade member  46 , the push force applied by the snowmobile S, and more especially by the kingpin  72 , on the snowmobile ski  10  (which is a compound force resulting from the weight of the snowmobile and the propulsion force), will be applied to a greater extent on the leading end portion  46   a  of the blade member  46 . This will ensure that as the snowmobile S glides on a snowy and/or icy surface G, the leading end portion  46   a  of the blade member  46  bites very efficiently in the gliding surface G, thus promoting better adherence of the ski  10  on the snowy and/or icy gliding surface. 
   Indeed, if the force is applied more towards the end of the blade member, it has been found that the ski will have a tendency to shake in a quivering motion, especially in “hard-to-bite” surfaces such as icy or very hard-pack snowy surfaces. On the other end, it has been found that concentrating the force applied by the snowmobile on the ski, as it glides, on the front end of the blade member will ensure adequate bite action and adherence of the ski to the underlying surface. 
   Various modifications could be made to the present invention without departing from the scope of the appended claims. 
   For example, in an alternate embodiment, the illustrated kingpin  72  could be replaced with a suitable alternate steering link having a resultant push axis registering with the leading end portion of the blade member. 
   In an alternate embodiment, the ski undersurface could be provided with additional blade members for increasing the bite of the ski on the gliding surface. 
   Moreover, although blade member  46  discussed above has a diamond-shaped cross-section, it is understood that the blade member could have any other shape suitable for biting into a snowy or icy gliding surface.