Abstract:
A vehicle, such as a snowmobile, includes a handlebar assembly for steering the vehicle. The handlebar assembly includes a riser pivotally secured to a steering shaft and handlebars pivotally secured to the riser. A clamp selectively engages both handlebars and steering shaft to fix the position of the riser relative to the handlebars and steering shaft. The clamp includes upper and lower clamps selectively drawn toward one another by a locking member embodied as a cam-lock including a rod having a cam eccentrically and pivotally connected to one end and an enlargement secured to the opposite end. A lever pivots the cam to shorten or lengthen the distance between a lower surface of the cam and the enlargement.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to snowmobiles and more specifically to steering systems for snowmobiles. 
     BACKGROUND OF THE INVENTION 
     Snowmobiles are manufactured in only a limited range of sizes and configurations, in contrast with the sizes of riders who enjoy riding snowmobiles. Riders will often use a snowmobile differently at different times. However, typical snowmobiles are designed for riders having a limited range of sizes and for a designated purpose. Typical snowmobiles are dedicated to purposes such as racing, long distance touring, mountain riding, and the like. 
     Such snowmobiles do not accommodate a variety of users and riding styles. Some attempts have been made to provide adjustable handlebars to accommodate riders of different sizes. However, the range of motion of many of these systems is limited to adjusting the length of a tube or pivoting a steering tube to which the handlebars secure. Such systems do not permit the user to adjust the angle of the handlebars in order to compensate for the change in orientation of the handlebars caused by the adjustment. Some systems allow greater adjustability but such systems have multiple points of adjustment with multiple fastening means, requiring the user to adjust one portion of the steering system and secure it, then adjust and secure another portion, then asses the suitability of the orientation, and then repeat the process until a suitable configuration is found. 
     It would therefore be an advancement in the art to provide a system allowing a user to readily adjust the position and orientation of handlebars and conveniently secure the handlebars in a desired orientation and height. 
     SUMMARY OF THE INVENTION 
     A vehicle, such as a snowmobile, includes a handlebar assembly for steering the vehicle. The handlebar assembly includes a riser pivotally secured to a steering shaft and handlebars pivotally secured to the riser. A clamp selectively engages both handlebars and steering shaft to fix the position of the riser relative to the handlebars and steering shaft. 
     The clamp includes upper and lower clamps selectively drawn toward one another by a locking member. The upper and lower clamps are preferably pivotally secured to the riser. In one embodiment, the locking member is a cam-lock including a rod having a cam eccentrically and pivotally connected to one end and an enlargement secured to the opposite end. A lever secures to the cam. The cam engages one of the upper and lower clamps and the enlargement engages the other of the upper and lower clamps. Pivoting of the lever causes the cam to shorten or lengthen the distance between a lower surface of the cam and the enlargement, thereby locking or releasing the upper and lower clamps. To prevent accidental release, a releasable latch secures the lever to the rod when the clamps are in a locked position. A spring engaging the riser and the lower clamp, biases the lower clamp away from the riser. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings: 
         FIG. 1  is isometric view of a snowmobile; 
         FIG. 2  is a isometric view of a steering system having an adjustable riser assembly, in accordance with an embodiment of the present invention; 
         FIG. 3  is an exploded view of a steering system having an adjustable riser assembly, in accordance with an embodiment of the present invention; 
         FIG. 4  is a isometric view of a cam-lock suitable for use in the adjustable riser assembly, in accordance with an embodiment of the present invention; 
         FIGS. 5A and 5B  are a side views of an adjustable riser assembly in released and locked positions, in accordance with an embodiment of the present invention; and 
         FIG. 6  is a isometric view of handlebars suitable for use in the adjustable riser assembly, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , a snowmobile  10  typically includes handlebars  12  mounted at the forward end of a seat  14  mounted to a tunnel  16  housing an endless track drive system. A driver wishing to travel large distances comfortably will typically prefer to have the handlebars positioned such that the user may sit upright with the legs bent at a comfortable angle and the arms slightly bent. On the other hand, a driver wishing to drive aggressively may sit close to the handle bars in a crouched position with the body forward and the arms bent sharply in order to shift the center of gravity of the combined snowmobile and driver toward the dimensional center of the snowmobile to improve handling. The mountain rider may stand frequently with more upright hand forward handlebars. 
     In each of these riding styles, the wrist and hands of the user will be at a different angle relative to the handlebars. In a similar fashion, the hands and wrists of riders having different heights will also be at different angles relative to the handlebars. Accordingly, the controls should also be positioned to be comfortably actuated by users of different heights and having different riding positions. 
     Referring to  FIG. 2 , in one embodiment of the present invention, a riser assembly  18  secures the handlebars  12  to a steering post  20 . The riser assembly  18  includes a lever  22  operated by a user to release or secure both the handlebars  12  and the steering post  20 . When released and in a disengaged state, the handlebars  12  and riser assembly  18  are permitted to rotate in rotational direction  24  to permit a second rotational adjustment about a second axis. Accordingly, the handlebars  12  are pivotable up and down to accomplish and adjustment in the vertical direction  26 . As the riser  18  is pivoted to adjust the general height of the handlebars  12 , the handlebars  12  may be rotated in a rotational direction  25  to permit a first rotational adjustment about a first axis and to maintain the proper orientation of the handlebars and the various controls attached thereto and to accomplish further height adjustment at the ends  28  of the angled handlebars  12 . 
     Referring to  FIGS. 2 and 3 , in one embodiment, the riser assembly  18  includes a frame  30  having seats  32   a ,  32   b  formed therein, or secured thereto, at its upper and lower ends. The upper seat  32   a  receives a central portion of the handlebars  12  and the lower seat  32   b  receives a steering post tube  34  secured to the steering post  20 . Upper and lower clamps  38   a ,  38   b  are positionable over the seats  32   a ,  32   b  to capture the handlebars  12  and steering post tube  34 , respectively between the frame  30  and the clamps  38   a ,  38   b . In the illustrated embodiment, the clamps  38   a ,  38   b  are pivotally secured to the frame  30 . 
     Referring to  FIG. 4 , while still referring to  FIG. 3 , a lock  40  pulls the clamps  38   a ,  38   b  toward the frame  30  to fix the position of the frame  30  relative to the handlebars  12  and steering post tube  34 . In the illustrated embodiment, the lock  40  is a cam-lock device having a lever  22  actuating an over-center cam  44 . The lever  22  and cam  44  are pivotally mounted to a rod  46  having an enlarged portion, such as a cross bar  48  secured to the end opposite the lever  22 . In some embodiments, a latch  50  is provided to maintain the lever in a locked position when the riser assembly  18  is not being adjusted. A button  52  secured to a rod  54  is pushed by a user to disengage the latch  50  from the rod  46  to allow the lever  22  to be actuated to release the clamps  38   a ,  38   b . A spring may engage the latch  50  and lever  22  to bias the latch  50  in direction  56  toward engagement with the rod  46 . The latch  50  has an angled or rounded surface  58  positioned such that the latch  50  will be deflected when pressed against the rod  46 , such that the latch  50  automatically latches to the rod  46  when pressed thereagainst. 
     Referring again to  FIG. 3 , the cam  44  engages a seat  60  positioned over an aperture  62  formed in the upper or lower clamp  38   a ,  38   b . The seat  60  typically includes a wear resistant or low friction material facilitating movement of the cam  44 . In the illustrated embodiment, the upper clamp  38   a  includes a recess  64  or inset portion  64  shaped to receive the cam  44  or seat  60 . 
     The other of the upper and lower clamps  38   a ,  38   b  includes a seat  66  shaped to receive the cross bar  48 , or other enlargement, secured to the rod  46 . In the illustrated embodiment, the lower clamp  38   b  includes two flanges  68  each having a concave lower surface sized to receive the cross bar  48 . The gap between the flanges  68  is typically sufficiently large to allow the rod  46  and a mount  70  of the steering post tube  34  to pass therethrough. 
     A biasing mechanism, such as one or more springs  72 , bias one or both of the top and bottom clamps  38   a ,  38   b  away from the frame  30 . In the illustrated embodiment, the springs  72  engage the lower clamp  38   b  and are positioned near the free end of the clamp  38   b  such that the steering post tube  34  is positioned between the springs  72  and the hinged end of the clamp  38   b.    
     In some embodiments, retainers  74  secure to the frame  30  and engage the steering post tube  34 . The retainers  74  restrain the steering post tube  34  against lateral movement when the lower clamp  38   b  is released. In some embodiments, the retainers  74  may include projections  76  positioned within the ends of the steering post tube  34  or surrounding the ends of the steering post tube  34 . The projections  76  provide an axis about which the steering post tube  34  may rotate, such that even when the clamp  38   b  is released, the tube  34  is constrained to rotation about the projections  76  rather than shifting position within the seat  32   b  and the clamp  38   b.    
     A preferable method of using the riser assembly  18  is illustrated in  FIGS. 5A and 5B . In the released position of  FIG. 5A , the lever  22  is pivoted away from frame  30 , rotating the cam  44  such that the smaller radius portion of the cam profile is positioned over the seat  60 . The springs  72  pivot the lower clamp  38   b  away from the frame  30 . The springs  72  serve to maintain some clamping force on the upper clamp  38   a  through force transmitted by the rod  46 . In this manner, the handlebars  12  will retain their original position unless the user applies sufficient force to overcome the force of the springs  72 . Thus, a user is not required to adjust both the handlebar angle and riser angle at the same time, but may readily do so if desired. With the clamps  38   a ,  38   b  released, the frame  30  and handlebars  12  may be rotated. 
     Referring to  FIG. 5B , in the locked position, the lever  22  is pivoted toward the frame  30 , rotating the cam  44  such that a larger radius portion of the cam profile is positioned over the seat  60 . The clamps  38   a ,  38   b  are pivoted toward the frame  30  because of the decreased distance between the cam  44  and the cross bar  48 . In the locked position, the latch  50  is brought into engagement with the rod  46  to prevent accidental lifting of the lever  22 . 
     In some embodiments, inner surfaces of the clamps  38   a ,  38   b  or the seats  32   a ,  32   b  include one or more projections or recesses engageable with a corresponding projection or recess on the handlebars  12  and steering shaft tube  34  to restrain the handlebars  12  and steering shaft tube  34  when the clamps  38   a ,  38   b  are drawn toward the frame  30 . In the illustrated embodiment, the clamps  38   a ,  38   b  include splined or knurled areas  78  engaging corresponding splined or knurled areas  80  formed on the handlebars  12  and steering shaft tube  34 . 
     Referring to  FIG. 6 , while referring generally to  FIG. 3 , in some embodiments a stop  82  secures to either the top clamp  38   a  or the handlebars  12  to limit the rotation of the handlebars  12 . Limiting the range of rotation of the handlebars  12  promotes safety in the event of accidental release of the lock  40 . Limiting the range of motion also promotes ease of use by ensuring that the handlebars  12  will generally be positioned close to a zone of usable orientations. The stop  82  may also function to keep the handlebar  12  generally laterally centered by being captured within the frame  30 , such as between the sides of the seat  32 . 
     In the illustrated embodiment, the stop  82  is embodied as a projection  84  welded or otherwise secured to the handlebars  12 . In use, the stop  82  is positioned within the frame  30 . The frame  30  in the illustrated embodiment, has a generally boxed shape such that the space within the frame  30  provides room for some movement of the projection. 
     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.