Note: Descriptions are shown in the official language in which they were submitted.
1095563
; BACKGROVND OF THE INVENTION
A power driven snow cycle which is propelled by a power driven ski is
a newcomer to the field of winter recreation.
Presently there is a polarization between outdoor winter sports
enthusiasts. The purist adhere to skis propelled by gravity or skier's muscles,
while the modernists enjoy mounting a snowmobile which employs brute force to
propel itself and its riders. Power driven skis (shown in V.S. Patents Nos .
3,853,192 and 3,966,010) and the present invention bridge this gap between the
purists and the modernists. They do so by combining the excitement of using
one's sense of balance to control and steer with the excitement of controlling
one's propelling power, and they remove or reduce the objectionable aspect of
snowmobiling. For example, the total weight of a current power driven snow cycleis around 30 pounds and it is propelled by a 3~ HP engine, versus several hundred
pounds that the average snowmobile weighs, which are pushed by approximately a
ten times larger engine. In contrast to sno~nobiles, snow cycles have a minimal
; effect on the trail they pass, they do not develop large kinetic energy that
may endanger their rider and others and they are not likely to get stuck in the
snow, since the average rider can lift the unit with one hand. The small eng:inegenerates less acoustical energy which can be readily muffled to non-obtrusive
levels. Further, power driven snow cyclesare characterizedby tileir long and narrow
footprints, and have no stability of their own. Thus, the rider has, as on a
bicycle, to continuously generate centrifugal balancing forces, which makes
riding a power driven snow cycle an involving and exciting experience. As will
be explained later Oll, this characteristic of power driven snow cycle is closely
related to the present invention.
As here described, a power driven snow cycle is produced by forming a
frame the front end of which is connected to a steerable ski and its rear end toa power driven ski. The rear end of the power driven ski is biased downwards
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by resilient means to improve traction and steerability. In view of the previous
discussion it can be understood that responsive steering inpower driven snow cycle
type of device, is essential, because the rider's ability to maintain his pre-
carious balance relies on an accurate and predictable steering response. Thus,
as will be explained later on, the resilient means simultaneously improve traction
and improve steerability while at the sarne time assist the rider in overcoming
the adverse effects of hitting a bump or taking a sharp turn.
More particularly in accordance with the invention there is provided a
power driven snow cycle having a frame supported by a front steerable ski and a
rear power driven ski sub-assembly, said sub-assembly having an anterior ski
portion and a posterior tread carrying portion and being pivoted to the frame,
the improvement wherein spring means, supported between said frame and said sub-
assembly are located and arranged so as to forcibly bias said posterior portion
downwards and said anterior portion upwards in order to improve traction and
bias load to the front steerable ski, thereby also improving steerability of said
snow cycle.
Specific embodiments of the invention will now be described having
reference to the accompanying drawings in which; Figs. 1, 2 and 3 show a side,
bottom and front view of a power driven snow cycle, respectively.
Figs. 1, 2 and 3 show a power driven snow cycle 10 having a frame 11
supported by a front steerable ski 12 and a rear power driven ski sub-assembly 13,
whose rear end 14 is forcibly biased downwards by resilien-t means in the forrn of
a bent leaf spring 15. This bias achieves three of the objects of the present
invention: it improves traction, since it energizes the -tread 16 and the poster-
ior portion 17 of the power driven ski against the snowr and it improves steer-
ability and controllability by shifting some of the skier's weight to the front
ski 12. The nature and effect of this weight shift will be further discussed in
the next paragraph, and at this point therest of the power driven snow cycle
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hardware will be briefly reviewed: the front ski 12 is pivotly connected through
a pin 18 to steering shaft 19 which carries a handlebar 20 and which is connected
tc the frame 11 through two hinges 21. The power driven ski 13 is slightly
modified to be pivotly connected to the frame through a pin and it is also
equipped with a rounded stud 23 protruding from an engine bracket 24 which forms
part of a body 25 of the power driven ski 13. The leaf spring 15 is bent and
squeezed between the stud 23 and a rounded screw 26 which is threaded through
frame 11 and serves to adjust the force biasing the rear end 14 downwards. A
sea~ 27, and a feet-bar 28 are affixed to the frame 11. The detailed structure
of the power driven ski 13 can be found in U.S. Patents Nos. 3,853,192 and 3,g66,
010, therefore only its major components are illustrated, and they are an engine
29 coupled to the tread 16 through pullies 31 and 32 and belt 33. A jacketed
cable 34 which is connected to a handle 35 regulates the engine's power output.
At this point I would like to go back and review the effec-ts of the
spring 15, and to start the discussion it will be assumed that: the weight of the
skier (who is shown in phantom lines on FIG 1) and the power driven snow cycle
10 is represented by a sign 36 and an arrow 46, an arrow 37 represents a portion
of the weight which is supported through the front ski 12, while an arrow 38
represents a weight portion which is supported through the anterior portion 39
of the power driven ski and an arrow 40 represents the weight portion supported
by its posterior portion 17. I-t can be seen that as screw 26 is screwed inwards
it forces both the rear end 14 and the front steering ski 12 downwards energizing -,
them against the snow. It does so by shifting part (or all) of the weight portion
38 which was supported by the anterior ski portion 39, since it is obvious that
statically the sum of weight portions 37, 38 and 40 has to equal the total weight
represented by the arrow 46. The increased weight on the front steering ski 12
improves the steerability of the power driven snow cycle while the additional
weight on the posterior power driven ski portion 17 improves the traction generated
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by the tread 16. Now it is possible to increase the weight portion 37 on the
front ski by movi.ng the seat forward on the frame 11. This, however, will
decrease the weight portion 40, reducing the traction obtained by the tread 16,
and in addition it wil.l have adverse effects when the power driven snow cycle
encounters a bump or when the rider takes a sharp turn. The reason for this
adverse effect is that when the skier's weight increases suddenly due to an
upwards or centrifugal acceleration, such increased weight should ideally be
absorbed through the power driven ski 13 which cannot rotate due to such jolts
under the skier, whereas the front steering ski 12 can, and this tends to cause
the rider a loss of balance. In contrast, when the bulk of the weight 46 is
over the power driven ski 13, divided into portions 38 and 40, and then part of
the weight portion 3B is shifted to rear end ].4 and to the front ski 12, any jolt
due to vertical and cen-trifugal accelerations is absorbed by the long non-
rotating power driven ski 13 with minimal adverse effect on the rider's balance
while at the same time steerability and traction are maximiz.ed simultaneously.
: The amount of weight shifted from the anterior portion 39 to the
posterior portion 17 and to the front ski 12 is regulated by the screw 26
according to the rider's (or riders') weight and according to the type and depth
of snow.
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