Land vehicles – Runner vehicle – Runner bases
Reexamination Certificate
1999-11-03
2002-08-13
Mai, Lanna (Department: 3619)
Land vehicles
Runner vehicle
Runner bases
C280S022000, C280S022100
Reexamination Certificate
active
06431561
ABSTRACT:
TECHNICAL FIELD
The invention relates to snowmobiles, and, in particular, to snowmobiles have asymmetrical skis.
BACKGROUND OF THE INVENTION
Snowmobiles are unique vehicles with respect to the way in which they engage the ground. Unlike cars, trucks, motorcycles, and just about every other type of land vehicle, they have no ground-engaging wheels. And, unlike other tracked vehicles such as military tanks or earth-moving caterpillars, the track of a snowmobile is not involved in steering—just propulsion.
The steering of a snowmobile is accomplished by its two front skis. The skis of a snowmobile actually perform two functions, however. Not only are they the only means for steering the vehicle, but they also must provide “floatation” for the front of the snowmobile—i.e., being the forward most ground-engaging structure on the snowmobile, they must cause the snowmobile to ride up on top of the snow. In hard-packed snow, groomed trails, or icy conditions, floatation is usually not an issue. In fresh snow or off-trail riding (common conditions, e.g., in mountain riding), however, the ability of the skis to keep the front end of the snowmobile from sinking too deeply in the snow is important for a pleasurable riding experience.
These two functions of the skis, steering and floatation, can be at odds with each other when it comes to designing the physical configuration of a ski. Better floatation is achieved by making the ski relatively flat on the bottom, and relatively wide. Such a ski profile, however, does not provide much “bite” for steering purposes. In groomed trail, hard packed snow, and ice conditions, a relatively shallow keel on the bottom of the ski, in combination with a conventional steering skag, typically provides sufficient bite for effective steering. In deep powder conditions, however, it is desirable to have a much deeper keel for more effective steering. A deeper keel typically also requires the keel to be wider at its base, but the wider and deeper the keel is, the less flat the skis profile becomes; consequently, the ski gives less floatation.
Simply making the ski wider usually is not practical. Most snowmobile manufacturers already make the ski stance (i.e., the front suspension system) the widest part of the snowmobile (providing good stability), and a very practical limit on a snowmobile's width is the desire of users to place two snowmobiles side by side—ski to ski—on a conventional width trailer. Thus, simply widening the ski may interfere with users'ability to utilize conventional trailers.
Thus, compromises must be made between the floatation and steering characteristics of skis in such powder conditions.
SUMMARY OF THE INVENTION
The invention provides a snowmobile having asymmetrical skis, which provide increased floatation without sacrificing keel depth and without increasing the overall width of the snowmobile.
A snowmobile of the invention includes a chassis, a straddle-type seat mounted to the chassis, a pair of handlebars carried by the chassis adjacent to the seat, and an endless track carried by a rear suspension system mounted to the chassis. The snowmobile includes left and right steerable skis carried by a front suspension system that in turn is mounted to the chassis, the skis being steerably connected to the handlebars. Each ski has a longitudinal length more than twice as long as its width, a downwardly extending longitudinal keel, and inner and outer floatation portions extending laterally from the keel. The inner floatation portion of each ski is wider than the outer floatation portion of such ski, making the ski asymmetrical with respect to the keel.
Preferably the front suspension system includes left and right generally downwardly and forwardly extending spindles. Each spindle has a lower end and is rotatable around a steering axis. The left and right skis are carried, respectively, at the lower ends of the left and right spindles. Each ski is aligned with its spindle such that the steering axis of the spindle passes through the keel.
This configuration provides an added benefit when the snowmobile turns a corner. The forward angle of the spindles causes the skis to tilt in the direction that they are being turned. Thus, in a left-hand turn, the skis tilt to the left. This tends to raise the inner floatation portion of the left ski, giving it less floatation, while lowering the inner floatation portion of the right ski, maintaining its floatation. The net effect is to cause the snowmobile to lean into the turn, an advantageous performance characteristic.
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Fredrikson & Byron , P.A.
Mai Lanna
Polaris Industries Inc.
Royal, Jr. Paul
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