Abstract:
A swing arm for a snowmobile has an upwardly curved, stepped, or angled intermediate portion that increases the swing arm&#39;s ground clearance relative to conventional, straight swing arms. The increased ground clearance permits more snow and other elements to pass underneath the swing without contacting the swing arm.

Description:
CROSS-REFERENCE  
       [0001]    This application is a continuation-in-part of U.S. Design application Ser. No. 29/164,431, entitled “SWING ARM,” filed on Jul. 25, 2002, the entirety of which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention concerns the construction of a swing arm to which a ski of a snowmobile is attached. In particular, this invention encompasses a swing arm construction for the front suspension of a snowmobile that facilitates the passage of snow and other elements underneath the swing arm.  
           [0004]    2. Description of Related Prior Art  
           [0005]    [0005]FIG. 6 illustrates a conventional snowmobile  10 , which is manufactured by Bombardier Inc. of Montreal, Quebec, Canada. While only the left side of the snowmobile  10  is illustrated, those skilled in the art would readily appreciate that the right side is essentially a mirror image thereof.  
           [0006]    The snowmobile  10  is constructed with a frame  12  powered by a motor  14 . The motor  14  is preferably an internal combustion engine, which may be one of either the two-stroke or four-stroke variety. Handlebars  16  are disposed above and to the rear of the motor  14 . The handlebars  16  operatively connect to two skis  18 ,  20  disposed at the front of the snowmobile  10 . When turned by the handlebars  16 , the skis  18 ,  20  turn the snowmobile  10  in the desired direction.  
           [0007]    The skis  18 ,  20  are suspended from a front suspension system  23 . The front suspension system  23  includes, among other components, two straight swing arms  24 , one disposed on either side of the snowmobile  10 . The swing arms  24  connect to shock absorbers  26 .  
           [0008]    The motor  14  operatively connects to an endless track  30  at the rear of the snowmobile  10  beneath a tunnel of the frame  12 . The endless track  30  propels the snowmobile  10  forward (or backward, as the case may be).  
           [0009]    As illustrated in FIG. 7, a spindle  34  connects to the left ski  18  through a bridge  36 . The bridge  36  typically is an elongated U-shaped structure with a bottom portion  38  connected to the ski  18 . The spindle  34  and ski  18  are attached to the snowmobile front suspension system  23  via a spindle holder  56 , which is attached to a forward portion of the swing arm  24 . A rear portion of the swing arm  24  connects to the frame  12  via a pivot collar  58  and pin  60 . Connecting the swing arm  24  to the frame  12  of the snowmobile  10  in this manner serves at least two functions. First, the pivot collar  58  permits the swing arm  24  to pivot upwardly and downwardly, which allows the ski  18  to move up and down as the snowmobile  10  traverses the ground. The pivot collar  58  also holds the ski  18  in a generally fixed longitudinal position relative to the frame  12  so that the ski  18  does not move rearwardly during operation of the snowmobile  10 .  
           [0010]    A bracket  62  attaches to the forward portion of the swing arm  24  at the location of the spindle holder  56 . The bracket  62  operatively connects to the frame  12  via upper and lower radius arm assemblies  64  and  66 . The upper and lower radius arm assemblies  64 ,  66  serve at least two functions. First, they permit the swing arm  24  to pivot about the pivot collar  58 . This, in turn, permits the spindle  34  and ski  18  to move up and down relative to the frame  12 . Second, they keep the spindle  34  and ski  18  in a generally fixed lateral position with respect to a centerline  68  of the snowmobile  10 . In other words, the radius arm assemblies  64 ,  66  prevent the ski  18  from collapsing laterally inwardly or outwardly during operation.  
           [0011]    To cushion the forces experienced by the ski  18  as it traverses the ground (so that the forces are not transmitted to the rider), the shock absorber  26  extends between the bracket  62  and the frame  12 . The shock absorber  26  ensures that the frame  12  remains disposed above the ground. It also dampens any shocks encountered when the snowmobile  10  encounters rough terrain.  
           [0012]    The swing arm  24  is normally constructed of sheet metal that is bent to form a straight hollow channel. Tubular swing arms constructed from metals and carbon fibers are also known. One common feature of all swing arms is their straight-line construction from the front of the swing arm to the rear of the swing arm. Because the front end of the straight swing arm  24  is disposed at the spindle  34  and is therefore close to the ground, an intermediate portion of the swing arm  24  has a low ground clearance that creates an obstruction for passing snow and other elements. When traveling in powder snow, the skis  18 ,  20  tend to sink down into the snow and further reduce or eliminate the ground clearance of the swing arm  24 .  
         SUMMARY OF THE INVENTION  
         [0013]    It is, therefore, an aspect of one or more embodiments of the present invention to provide an improved snowmobile swing arm construction.  
           [0014]    According to another aspect of one or more embodiments of the present invention, a swing arm includes upward curves, steps, or angles that improve the swing arm&#39;s ground clearance.  
           [0015]    According to another aspect of one or more embodiments of the present invention, a swing arm assembly is provided with a rear portion adapted to pivotally connect to a snowmobile about a swing arm pivot axis, a forward portion having a bottommost point, and an intermediate portion extending between the front and rear portions and defining a lower edge. A portion of the lower edge is disposed above a line extending between the bottommost point and the swing arm pivot axis.  
           [0016]    The portion of the lower edge is spaced from the line by a distance that is preferably at least 2 cm, is more preferably at least 4 cm, and is even more preferably at least 6 cm.  
           [0017]    The lower edge may be curved or angled. The lower edge may alternatively form a step.  
           [0018]    The swing arm assembly may also include a pivot collar attached to the rear portion such that the pivot collar defines the swing arm pivot axis.  
           [0019]    The swing arm assembly may also include a spindle holder attached to the forward portion. The spindle holder is constructed and arranged to pivotally receive a ski  
           [0020]    The swing arm assembly may also include a bracket attached to the spindle holder. The bracket is adapted to receive at least one radius rod to attach the swing arm to a snowmobile.  
           [0021]    The swing arm assembly may be combined with a snowmobile that includes a frame pivotally connected to the rear portion of the swing arm, a straddle-type seat supported by the frame, a steering ski supported by the front portion of the swing arm, and an endless track supported by the frame.  
           [0022]    According to another aspect of one or more embodiments of the present invention, a swing arm assembly is provided with a rear portion adapted to pivotally connect to a snowmobile about a swing arm pivot axis, a forward portion having an upper front tip, and an intermediate portion extending between the front and rear portions and defining a lower edge. A portion of the lower edge is disposed above a line extending between the upper front tip and the swing arm pivot axis.  
           [0023]    Additional and/or alternative aspects, features, and objects of the embodiments of the present invention will become apparent from the following drawings and detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    As would be recognized by one skilled in the art, a snowmobile has a front, a left side, a right side, and a rear when viewed by an individual sitting on the vehicle facing the direction of vehicle travel. Where reference is made to one side of the vehicle, it is to be assumed the opposite side is its mirror image unless otherwise specified.  
         [0025]    Reference will be made hereinafter to the accompanying drawings, which illustrate embodiments of the present invention discussed herein, wherein:  
         [0026]    [0026]FIG. 1 is a side view of a snowmobile according to one embodiment of the present invention;  
         [0027]    [0027]FIG. 2 is a perspective view of a swing arm assembly of the snowmobile of FIG. 1;  
         [0028]    [0028]FIG. 3 is a side view of the swing arm assembly of FIG. 2 in conjunction with other elements of a front suspension system;  
         [0029]    [0029]FIG. 4 is a front view of the front suspension system of FIG. 3;  
         [0030]    [0030]FIG. 5 is a perspective view of a swing arm assembly according to an alternative embodiment of the present invention;  
         [0031]    [0031]FIG. 6 is a left side view of a conventional snowmobile manufactured by Bombardier Inc., of Montreal, Quebec, Canada; and  
         [0032]    [0032]FIG. 7 is an exploded view of a front suspension system of the snowmobile illustrated in FIG. 6.  
     
    
     DETAILED DESCRIPTION  
       [0033]    Throughout the description of the embodiments of the present invention, reference will be made to various elements, the construction of which is readily known to those skilled in the art. Instead of providing an exhaustive description of each and every common component, only those elements required for an understanding of the present invention are described in detail.  
         [0034]    [0034]FIG. 1 illustrates a snowmobile  120  according to one embodiment of the present invention. The snowmobile  120  includes a frame  114 . The frame  114  preferably includes a tunnel  115 . The tunnel  115  preferably comprises a sheet of metal that is bent into an inverted, U-shape. The tunnel  115  supports an endless track  130  via a rear suspension system  131 . A straddle-type seat  116  is also supported by the frame  114  and is adapted to accommodate a rider.  
         [0035]    A front swing arm suspension system  121  extends between the frame  114  and two steering skis  118 . Unlike conventional front swing arm suspension systems, the front swing arm suspension system  121  of the snowmobile  120  includes a curved swing arm assembly  100 . The swing arm assembly  100  includes a swing arm  124 , a spindle holder  156 , and a pivot collar  158 .  
         [0036]    As shown in FIGS. 2 and 3, the swing arm  124  includes a front portion  102 , a rear portion  104 , and an intermediate portion  106 . The spindle holder  156  attaches to the front portion  102  of the swing arm  124  at a first attachment point  108 . The attachment point  108  is defined as a center of the attachment between the swing arm  124  and the spindle holder  156 . A bottom  109  of the attachment between the spindle holder  156  and the swing arm  100  is disposed at the lowermost point of contact between the spindle holder  156  and the swing arm  124 . The bottom  109  is also preferably disposed at the lowermost point of the front portion  102  of the swing arm  124 . A top  107  of the attachment between the swing arm  124  and the spindle holder  156  is disposed at the uppermost point of contact between the spindle holder and the swing arm  124 . The top  107  of the attachment is also disposed at the upper front tip of the front portion  102  of the swing arm  124 . If the attachment between the spindle holder  156  and the swing arm  124  comprises integral formation, the first attachment point  108 , bottom  109 , and top  107  are defined where they would have been had the spindle holder  156  and the swing arm  124  been attached to each other after formation. A bracket  162  attaches to the spindle holder  156  and the front portion  102  of the swing arm  124  to provide additional support to the attachment point  108  and attachment points for two radius rods  110 ,  112  (shown in FIGS. 3 and 4).  
         [0037]    As shown in FIGS. 1 and 2, the pivot collar  158  attaches to the rear portion  104  of the swing arm  124  to enable the swing arm assembly  100  to pivot relative to the snowmobile  120  about a swing arm pivot axis  160 . This enables the ski  118  to move relative to the snowmobile  120  as described above with respect to the conventional straight swing arm  24 .  
         [0038]    As shown in FIG. 2, the swing arm  124  has a thickness t and height h which is shown to be uniform throughout the swing arm  124 . As would be recognized by one skilled in the art, swing arm  124  need not be of uniform thickness or height and may instead be tapered or vary in an irregular manner. The swing arm  124  may comprise bent sheet metal, carbon fiber, or any other suitable material. The swing arm  124  is preferably tubular to increase its strength but may alternatively have a variety of other cross-sectional shapes (e.g., solid, hollow, U-shape, C-shape, oval, square, rectangle, irregular, taper (longitudinally, laterally, or vertically), etc.).  
         [0039]    As shown in FIGS. 2 and 3, the spindle holder  156  is preferably a hollow cylinder that is adapted to accept a spindle  172 . The spindle  172  rotates within the spindle holder  156  to enable a driver of the snowmobile  120  to turn the steering ski  118  mounted to the spindle  172  (shown in FIG. 1).  
         [0040]    As best illustrated in FIG. 3, a lower edge  173  of the swing arm  124  is curved or bowed upwardly to increase the ground clearance of the intermediate portion  106  of the swing arm  124 . The curvature of the lower edge  173  in the illustrated embodiment is neither continuous nor even. A front portion of the lower edge  173  is straight. A rearward curved portion of the lower edge has a radius of curvature that varies as the lower edge  173  progresses rearwardly. It is nonetheless contemplated that the curvature could be continuous and/or have a constant radius of curvature without departing from the scope of the present invention.  
         [0041]    The curved swing arm  124  has a greater ground clearance than conventional straight swing arms and therefore provides an increased area for snow or other elements to pass between the ski spindle  172  and the track  130  without contacting the swing arm  124 .  
         [0042]    The degree of elevation of the intermediate portion  106  of the swing arm  124 , which is proportional to the increase in ground clearance, can be measured with respect to a line  174  that extends between the bottommost point  109  (or the bottommost point on the front portion  102  of the swing arm  124 ) and the spindle holder  156  and the swing arm pivot axis  160 . A point on the lower edge  173  is spaced from the line  174  by a distance x, which is preferably between 0 and 20 cm, is more preferably between 2 and 15 cm, is even more preferably greater than 4 cm, and is even more preferably greater than 6 cm.  
         [0043]    The degree of elevation of the intermediate portion  106  of the swing arm  124  can alternatively be measured with respect to a line  175  that extends between the top  107  of the attachment (or the upper front tip of the front portion  102  of the swing arm) and the swing arm pivot axis  160 . A point on the lower edge  173  is spaced from the line  175  by a distance z, which is preferably between 0 and 20 cm, is more preferably between 2 and 12 cm, and is even more preferably greater than 4 cm.  
         [0044]    [0044]FIGS. 3 and 4 show the swing arm assembly  100  connected to upper and lower radius rods  110  and  112  as well as the spindle  172 . While the combination swing arm assembly, radius rods, and spindle shown in FIGS. 3 and 4 are viewed from the left-hand side of the snowmobile, identical numbers have been used to that of the swing arm shown in FIG. 2 because both swing arms are mirror images of each other.  
         [0045]    [0045]FIG. 4 shows a front view of the swing arm assembly  100 , spindle  172  and radius rods  110 ,  112  combination. Like the swing arm  124 , the radius rod  112  preferably curves upwardly to increase the ground clearance of the radius rod  112 . The radius rod  112  has a first end  126  adapted to be pivotally connected to the snowmobile  120  and a second end  128  adapted to be pivotally connected to the bracket  162 . The radius rod  110  also has a first end  132  adapted to be pivotally connected to the snowmobile  120  and a second end  134  adapted to be pivotally connected to the bracket  162 . Radius rods  110  and  120  help maintain the ski spindle  172  and the swing arm  124  in the correct orientation as described above.  
         [0046]    [0046]FIG. 5 shows a second embodiment of a swing arm assembly  200 , which may replace the swing arm assembly  100  on the snowmobile  120 . The swing arm assembly  200  includes a swing arm  224 , a spindle holder  256 , and a pivot collar  258 .  
         [0047]    The swing arm  224  has a front portion  202 , a rear portion  204 , and an intermediate portion  206 . The intermediate portion  206  includes a step that increases the ground clearance of the swing arm  224 . It is contemplated that the step might include one or more angles and/or curves so that the swing arm  224  includes multiple steps. Alternatively, the step may be formed by a single angle formed between the front and rear portions  202 ,  204  of the swing arm  224 .  
         [0048]    The spindle holder  256  attaches to the front portion  202  of the swing arm  224 . A bottom  257  of the attachment is defined at the bottommost point of this attachment. The rear portion  204  of the swing arm  224  attaches to the swing arm pivot collar  258 , which pivotally connects to the snowmobile  120  for relative pivotal movement about a swing arm pivot axis  260 . A line  262  extends between the bottom  257  and the swing arm pivot axis  260 . As with the swing arm  124 , the step is constructed such that a portion of a lower edge  264  of the swing arm  224  is spaced from the line  262  by a distance y, which is preferably between 0 and 20 cm, is more preferably greater than 2 cm, is even more preferably greater than 4 cm, and is even more preferably greater than 6 cm.  
         [0049]    While the invention has been described with reference to several preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention. In addition, many modifications may be made to adapt a particular situation, component, or material to the teachings of the present invention without departing from its teachings as claimed.