Note: Descriptions are shown in the official language in which they were submitted.
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NARROW PROFILE STRADDLE-TYPE MOTORIZED SNOW VEHICLE
FIELD OF THE INVENTION
The present invention relates to motorized snow vehicles, and more
particularly to
straddle-type motorized tracked snow vehicle.
BACKGROUND OF THE INVENTION AND DESCRIPTION OF PRIOR ART
This background information is provided for the purpose of making known
information
believed by the applicant to be of possible relevance to the present
invention. No admission is
necessarily intended, nor should be construed, that any of the preceding
information, or the
reference in the drawings to "prior art" constitutes prior art against the
present invention.
Straddle- type motorized vehicles having an endless track for travelling on
snow are
well known since at least the 1960's.
Early versions of such motorized tracked vehicles typically incorporated a
pair of
parallel spaced-apart skis mounted forwardly of the vehicle and connected to a
pair of
handlebars for steering the vehicle and supporting the front of the vehicle on
snow.
Such dual-ski snowmobiles were and remain particularly unsuited for traversing
inclined snow-covered slopes. Specifically, due to such dual ski design the
vehicle must
incline in accordance with the amount of of incline of the slope , thereby
producing a tendency
for the vehicle and operator to roll downhill making such vehicles especially
unsafe, as the
vehicle may when traversing an inclined slope roll, and more particularly roll
over the
operator, seriously injuring or killing him/her.
Although some dual- ski snowmobiles, such as that depicted in US 6,923,287,
had
motor speed reduction gearing mounted in front of the engine rather than
beside the engine, and
effectively thereby reduced the width of such vehicle, such was more due to
limited lateral
engine room on a dual ski platform rather than any desire to reduce engine
width. Due to the
dual ¨ski configuration such models of snow vehicle remained relatively wide
and thereby
suffered the problems discussed below when traversing inclined slopes.
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Single ski motorized tracked vehicles, obviously of lesser width due to the
single ski as
opposed to the dual ski design, were developed typically from a desire to
convert an existing
motorcycle to a tracked snow vehicle.
For example, US 8, 910,738 entitled "Snow bike Conversion System", US 3,822,
755
entitled "Kit for Converting Conventional Motorcycle into Snowmobile", and US
6,431,301
entitled "Snow Vehicle Conversion Kit" together typify prior art kits for
converting a
motorcycle to a motorized snow vehicle in which the resulting conversion is a
snow vehicle
having a single ski.
Such kits ( and other similar kits) typically provided a single ski which was
adapted to
be mounted on (or to replace) the front tire of the motorbike, and further
provided an endless-
track bogey suspension to replace the rear wheel, with motive force to such
track and
suspension system being supplied by the existing motorcycle motor.
Notably, the resulting snow vehicle s arising from such prior art kit
conversions were
generally extremely unsatisfactory for traversing inclined mountain slopes.
Specifically, motorcycles (and the types mentioned in the aforementioned
patents)
typically possess kick-activated transmissions mounted to a lateral side of
the motor, thus
increasing the width of the resulting snow vehicle in the region of the motor,
which is typically
the region where the operator's legs are positioned when straddling and
operating the vehicle.
With the added width of the operator's legs, the combined width of the vehicle
in the region
of the engine causes problems and danger when the operator of the resulting
snow vehicle
attempts to traverse a steep inclined snow-covered slope. Specifically, when
the operator leans
such snow vehicle into a steep inclined slope to otherwise prevent sliding
down the slope,
due to the substantial width the operator's legs will typically contact the up-
hill side of the
slope resulting in the operator being unable to sufficiently lean the vehicle
into the slope of the
hill to avoid sliding down the hill. Alternatively, if the operator
nevertheless leans into the hill,
contact with the operator's uphill leg and the slope causes a buildup of snow
on the uphill side
of the vehicle preventing further passage of the vehicle along the slope, or
alternatively due to
forward momentum of the vehicle causes the operator to be brushed off the
vehicle by the
buildup of snow thereby cause the operator to lose complete control of the
vehicle and/or suffer
injury.
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Various dedicated (i.e non-kit) single-ski
snow vehicles have recently been
developed and commercially offered for sale..
For example, US 7,475,751 entitled "Snow Vehicle"
assigned to Bombardier
Recreational Products Inc. teaches such a single-ski non-kit snowmobile,
having a forward
mounted transverse muffler mounted forward of the engine. Although the
possibility of
utilizing a continuously variable transmission (CVT) is offered as a
possibility (ref. col. 4.1ines
9-11), no further details are provided as to how such could be implemented .
Moreover, little
importance was devoted in such design to reducing the width of the snow
vehicle, since such
design further provided a fan 69 disposed on the right side of the engine
(ref. col. 4, lines 32-
33) as shown in Fig.'s 2-3 and Fig. 6, as well as a centrifugal clutch 56
likewise mounted on
an opposite side of the engine (ref. Fig.1, 4 & 5). Both of such
aforementioned components
clearly served to increase the width of the engine , thereby providing
relatively large vehicle
width when combined with the operator's legs/boots when the operator straddled
the vehicle
while operating it. Such excess width results in reduced side hill clearance,
which in turn limits
the amount of incline of a slope that such vehicle would be capable of safely
traversing.
Similarly, US 7,789,183 entitled "Personal Snow Vehicle" assigned to Yamaha
Motor
Corp. likewise teaches a non-kit, single ski motorized snow vehicle. Although
such patent
extols the advantage (of a single ski) and handle bars as a manner of reduced
vehicle width in
providing "motorcycle-like" handling (ref. col 8, lines 9-19), such patent
nonetheless overlooks
engine and powertrain width as a factor in reducing side hill clearance of the
vehicle. To the
contrary, transmission 44 appears to be mounted on the side of engine 42, and
protruding
portions 160 on vehicle body frame 20 significantly increase engine width in
the region of the
operator's legs providing clear evidence that no consideration was given to
increasing side hill
clearance by eliminating or otherwise repositioning such outwardly extending
accoutrements.
Accordingly, a clear need exists for snow vehicle adapted to allow better and
more safe
traversing of inclined slopes.
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SUMMARY OF THE PRESENT INVENTION
It is thus an object of the present invention to provide a motorized tracked
snow vehicle
which is well suited for effectively and safely permitting traversal of steep
inclined slopes
without tipping or slipping down the slope.
It is a further object of the present invention to provide a motorized
straddle-type tracked
snow vehicle of reduced width in a region of the operator's legs and feet.
It is a still further object of the present invention to provide a snow
vehicle which
allows increased leaning of such vehicle into a slope of a hill being
traversed, to thereby allow
better gripping of the vehicle on the slope of hill and thereby reduce the
tendency of the vehicle
to slide down the hill, roll over, or alternatively due to impaction of snow
on the uphill side of
the vehicle with the operator's legs , which impaction otherwise prevents
continued
movement of the vehicle along the slope or potentially causes dislodgement of
the operator
from the operating position on the vehicle.
It is a still further object of the present invention to provide a single- ski
snow vehicle
with a continuously variable transmission ("CVT") , and in particular a CVT
entirely located
aft of the engine to not only reduce lateral width of the vehicle, but to
further avoid the need to
change gears using a "kick" type motorcycle transmission which is awkward and
difficult to
do for snowboot-clad operators of snowmobiles.
It is a still further object of the present invention to provide an power
transmission
system configured so as to allow space immediately rearwardly of the motor to
allow directing
exhaust pipes in such vacant space where the exhaust pipe(s) would otherwise
have to be
directed on a side of the vehicle thereby undesirably increase the width of
the vehicle.
Accordingly, in order to provide inter alia the above objects and to provide a
motorized
snow vehicle suited to traversing steeply inclined snow covered slopes, in a
first broad
embodiment the present invention provides a narrow-profile straddle-type
motorized snow
vehicle, comprising :
-a single ski mounted forwardly of the vehicle for steering said vehicle;
- a rotatable endless track for providing propulsion in snow;
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-a motor, mounted rearwardly of said single ski;
-a continuously variable transmission, located rearwardly of said motor,
having:
(i) a primary pulley
mounted rearwardly of the motor and located
along a vertical plane aligned with a central longitudinal axis of said
vehicle
and located proximate said longitudinal axis of said vehicle,
said primary
pulley mounted on a first transverse shaft which is operatively coupled
to
said motor, a rotational axis of said first transverse shaft being transverse
to
a direction of travel of said snow vehicle;
(ii) a secondary pulley mounted rearwardly of said primary pulley and
in said same vertical plane, said secondary pulley mounted on a second
transverse shaft, said second transverse shaft being positioned
parallel to but
spaced rearwardly from said first transverse shaft;
and
a driven pulley or toothed sprocket mounted rearwardly of where an operator's
leg would be positioned when operating the vehicle, mounted for rotation on a
third
transverse shaft which is parallel to said first and second transverse shafts,
said third
transverse shaft extending within said endless track at a proximal end of said
endless
track for rotating said endless track, said driven pulley or toothed sprocket
mounted on
an end of said third transverse shaft adjacent said proximal end of said
endless track
and operatively coupled to said second transverse shaft.
Advantageously, by using a CVT, due to its linear configuration, the vehicle
transmission may be located behind and not beside the engine, and in such
configuration on a
straddle-type vehicle of the present invention, thereby reduces the width of
the vehicle while
being able to effectively drive the endless track of the vehicle with a
minimum number of idler
gears and/or belts. In preferred embodiments, the CVT further incorporates an
integral clutch,
thereby advantageously eliminating any further motor width increases due to
having to
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otherwise possibly incorporate a centrifugal clutch on a side of the motor, as
is typically done
in motorcycles.
In one embodiment, the driven pulley or toothed sprocket mounted on the third
transverse shaft which drives/powers the endless track is positioned on said
vehicle rearwardly
of said primary pulley so as to better ensure that such driven pulley or
toothed sprocket is not
only located remotely from the operators legs (a safety hazard), but moreover
does not
otherwise increase the width of the vehicle in the region of the operators
legs.
In another embodiment, or in combination with one or both of the above
embodiments,
the third transverse shaft is positioned on the vehicle below the second
transverse shaft . In
such manner the second transverse shaft and secondary pulley thereon will thus
be higher on the
vehicle allowing the proximal end of the endless track to be positioned more
forwardly on the
vehicle and below the second transverse shaft and secondary pulley thereon,
thus reducing the
length of the vehicle. As well, such allows the second transverse shaft to be
vertically more
remote from the ground and snow thereon, thereby reducing the tendency for
snow to become
clogged in the secondary pulley and thus render inoperative the continuously
variable
transmission mechanism.
In still another embodiment, the third transverse shaft may be positioned on
the vehicle
below the first transverse shaft. This configuration , particularly in
combination with the
embodiment where the third transverse shaft is positioned below the second
transverse shaft,
likewise serves to allow the proximal end of the endless track to be
positioned more forwardly
on the vehicle and below the second transverse shaft and secondary pulley
thereon, thus
reducing the length of the vehicle.
The driven pulley or toothed sprocket on the third transverse shaft will
typically be
operatively coupled to the second transverse shaft by an endless belt or
chain, to allow the
motor, via the CVT (ie the primary and secondary pulleys) to thereby power the
endless track of
the snow vehicle.
In a preferred embodiment, the CVT located rearwardly of the motor further
includes
an integral clutch adapted to decouple the motor from powering the endless
track when the
motor is at idle rpm.
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In a more particular embodiment, the first transverse shaft and/or said second
transverse shaft further comprise clutch means, configured to decouple the
motor from
powering the endless track when the motor is at idle rpm.
In a further embodiment, the centrifugal clutch may on said first transverse
shaft, and
when engaged operatively couples said primary pulley to said secondary pulley
upon high
(non-idle) revolutions of said motor.
In a preferred embodiment, an operator-controlled disk brake is further
located on said
second transverse shaft. The provision of a second transverse shaft indirectly
coupled to the
endless track of the snow vehicle advantageously provides a means to brake the
vehicle over the
ground, and when coupled with the feature of the centrifugal clutch being
located on the first
transverse shaft allows an operator to release the gas , thereby allowing the
centrifugal clutch to
disengage the primary, secondary , and driven pulleys as well as the endless
track from the
motor, and allowing the secondary shaft and pulley and driven pulley and
endless track to be
"braked" to arrest movement of the snow vehicle on the ground.
In a preferred embodiment, again consistent with the objective of minimizing
the width
of the snow vehicle in the region of the engine, the motor comprises two
cylinders, each of
the cylinders located in a vertical plane of the longitudinal axis, in a
canted "v" format, each
cylinder driving a commonly powered crankshaft. The crankshaft of the motor is
thus
positioned rearwardly of each of said two cylinders and transverse to the
longitudinal axis,
and is further operatively coupled to the first transverse shaft, wherein the
first transverse
shaft is located rearwardly of the crankshaft.
In a further refinement of the embodiment of the invention having such
positioned two
cylinders, again with the purpose and objective of minimizing the width of the
snow vehicle in
the region of the engine, an exhaust pipe which extends from each of said
cylinders is provided,
wherein each of said exhaust pipes extend rearwardly from said cylinders into
a single
combined pipe which extends rearwardly substantially along said longitudinal
axis, above said
continuously variable transmission and below a seat of said vehicle. In such
manner, the
exhaust pipes , due to vertical space being created in the frame by the
longitudinal spacing of
the primary pulley and the rearwardly positioned secondary pulley, the exhaust
pipes from the
motor can be directed in such vertical created space aft of the cylinders, and
need not be
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directed to the side of the engine which would otherwise negatively affect the
width of the
vehicle in the region of the engine and in the region of the operator's legs
when operating the
snow vehicle.
In a further preferred embodiment , the motor is a two stroke piston engine,
and may be
(and preferably is) a liquid-cooled two stroke engine, but may alternatively
be an air cooled
motor, and/or a four-stroke motor.
In a further refinement, the motor is not naturally aspirated but is further
provided with
forced air induction, which may be by way of a supercharger such as a roots
blower, or forced
induction provided by way of a turbocharger. Again, consistent with the
objective of
minimizing the width of the snow vehicle in the region of the engine where the
operators legs
are positioned, any supercharger or turbocharger is located above , behind, or
in front of the
engine, and not on the side of the engine to avoid increasing width in such
region.
The above summary of various aspects and embodiments of the invention does not
necessarily describe the entire scope of the present invention. Other aspects,
features and
advantages of the invention will be apparent to those of ordinary skill in the
art upon a proper
review of the entire description of the invention as a whole, including the
drawings and
consideration of the specific embodiments of the invention described in the
detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
For purposes of this application, terms of direction and location used in this
specification including the claims to specify location of components on the
snow vehicle of
the present invention, such as "front", "back", "rear", "rearwardly",
"forward", "forwardly",
"front", "left", "right", "up", "down", "above", and " below", are each with
respect to the
intended direction of the snow vehicle, as such terms/directions would be
understood by a an
operator of a snow vehicle straddling the snow vehicle in a forward-facing
driving position.
The following drawings figures depict preferred and non-limiting embodiments
of the
invention, in which:
Fig. 1 is a frontal view of a prior-art dual ski snowmobile traversing an
inclined slope;
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Fig. 2 is a similar frontal view of a prior art single ski snowmobile having a
side
mounted transmission traversing an inclined slope, showing resulting impaction
of snow on the
uphill side of the snow vehicle when traversing such inclined slope;
Fig. 3 is a left frontal perspective view of the narrow-profile straddle type
motorized
snow vehicle of the present invention, showing the location of manner of
configuring a
continuously variable transmission "(CVT") to thereby avoid increased engine
compartment
width;
Fig. 4 is a left rear perspective view of the narrow-profile straddle type
motorized snow
vehicle of Fig. 3;
Fig. 5 is a right frontal perspective view of the narrow-profile straddle type
motorized
snow vehicle of Fig. 3, with a front fender added;
Fig. 6 is a right frontal perspective view of the narrow-profile straddle type
motorized
snow vehicle of Fig. 5;
Fig. 7 is a front view of the narrow-profile straddle type motorized snow
vehicle of
Fig. 5, showing the resulting large side hill clearance now obtained;
Fig. 8 is a left side elevation view of the narrow-profile straddle type
motorized snow
vehicle of Fig. 5;
Fig. 9 is a right side elevation view of the narrow-profile straddle type
motorized
snow vehicle of Fig. 5;
Fig. 10 is a top view of the narrow-profile straddle type motorized snow
vehicle of Fig.
5, showing the narrow profile capable of being obtained as a result of the
positioning of a
primary and secondary pulley of a CVT aft of the engine;
Fig. 12A is a side elevation view of the engine and transmission components
only, in
one embodiment/configuration of the present invention;
Fig. 12B is a cross-sectional view along plane B-B of Fig. 12A;
Fig. 13A is a side elevation view of the engine and transmission components
only, in
another embodiment/configuration of the present invention; and
Fig. 13B is a is a cross-sectional view along plane A-A of Fig. 13A.
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DETAILED DESCRIPTION OF SOME OF THE PREFERRED EMBODIMENTS OF
THE PRESENT INVENTION
Fig. 1 shows a motorized straddle-type motorized snow vehicle 1 of the prior
art,
having two frontal skis 2 used for steering and a rear endless belt 3 rotated
by a motor (not
shown) for advancing the vehicle 1 over snow.
Disadvantageously, when a driver (not shown) of such prior art snow vehicle 1
attempts to traverse a snow-covered steep incline 4 as shown in Fig. 1,
vehicle 1 is prone to
tipping (rolling over) resulting in the possibility of injury to the driver
and any accompanying
passenger.
Alternatively, if snow vehicle 1 does not roll over, prior art snow vehicle 1
tends to
slide downhill thereby rendering it impossible for the operator to cause snow
vehicle 1 to travel
in an intended direction when traversing inclined slope 4.
Fig. 2 shows another motorized straddle-type snow vehicle 10 of the prior art
having a
motor 12 straddled by a vehicle operator/ driver 11. Prior art snow vehicle 10
is steered by a
single ski 13 and is typically powered by a rotatable endless belt (not shown)
which contacts the
ground/snow and allows propulsion of the vehicle 10. Use of a single ski 13
allows tilting of
the vehicle 10 about a longitudinal axis along the direction of travel of the
vehicle, which the
operator 11 typically takes advantage of when traversing such inclined slope 4
as shown in
Fig. 2 to "lean" into the direction of an inclined slope 4 to thereby avoid
sliding down incline 4
and thus maintain an intended course when traversing inclined slope 4.
Disadvantageously, however, such prior art snow vehicles 10 typically has
power
transmission components 14 and/ or belt drive components 15 for the
motorized track
mounted on a side of motor 22 thereby increasing the total width of the motor
12 and thus
vehicle 10. Such width was further effectively increased due to the width of
the drivers' legs
18 when straddling the motor 12 and operating the vehicle 10 as shown in Fig.
2.
Accordingly, due to such large width, large build-up of snow 9 would as a rule
occur on the
uphill side of vehicle 10 when such vehicle was attempted to be traversed
along a length of
inclined slope 4, rendering further passage along sloped incline 4 impossible
at such angle of
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"lean" and causing the vehicle to slide downhill if such angle of "lean" was
necessarily relaxed,
or alternatively if such angle of "lean" was maintained then brushing the
operator 11 from the
seat on the vehicle 20 due to snow buildup 9 on the uphill side of vehicle 10.
The narrow-profile straddle type motorized snow vehicle 30 of the present
invention
is depicted in Fig.s 3-11, which show various views of the present invention.
As may be seen, due to its configuration of components and more specifically
its
transmission system as more fully described below, a snow vehicle having
narrow width and
profile is obtained, particularly in regions "A", AV (ref. Fig.'s 7, 8
respectively), the latter
being the regions where the operator's legs or boots 100 are approximately
positioned when
straddling vehicle 30 (ref. Fig.'s 12A, 13A).
With such configuration advantageously the operator is better able to take
advantage of
the single ski configuration of the vehicle, and the resulting increased side
hill clearance better
allows the vehicle and operator to traverse inclined slopes without sliding
downhill and without
the uphill leg or boot of the operator contacting the inclined slope and
causing a build-up of
snow on such uphill side.
With reference to Figures 3-11, 12A, 12B, 13A, & 13B, vehicle 30 of the
present
invention in one broad embodiment comprises a frame 31, having a single
steerable ski 13
mounted thereto and forwardly of motor 40 to allow steering and support of
vehicle 30 at a
frontal end thereof. A conventional rotatable endless track 50 is mounted
rearwardly on frame
31.
Track 50 of vehicle 30 is mounted within a suspension system 60, which in a
preferred
embodiment comprises a single shock absorber 46 intermediate two metal guide
rails 43, a
further shock absorber 47 affixed at one end to one of metal guide rails 43
and affixed at
another end thereof to a pair of rotating bogey wheels 44 which assist in
rotatably suspending
track 50 within suspension system 60. A further pair of bogey wheels 46,
pivotably or spring
mounted to a lower of said metal guide rails 43, may further be provided
within said track 50 at
a distal (most rearwardly) end thereof to assist in guiding the track 50 over
guide rails 43 and
reducing the rolling friction of said track when powered by a motor 40.
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Motor 40, as further described below, is mounted on frame 31, and is typically
a liquid
¨cooled two stroke internal combustion motor 40 , comprising a first liquid
cooled cylinder 42a
and a second liquid cooled cylinder 42b, inclined at an "v" shaped angle to
one another. Two
stroke engines are generally preferred for their relative light weight and
increased power to
weight ratio in comparison to four stroke engines. Preferably, motor 40 is
provided with forced
air induction such as by way of a supercharger or turbocharger (not shown)
mounted on motor
40 typically other than at a location of a lateral side thereof to avoid
increasing the lateral width
of the motor 40 , to further increase the power to weight ratio of the motor
40 which is
advantageous as the operator will lean the vehicle 30 when operating such
vehicle 30 due to the
single ski configuration, which leaning can be cumbersome and require
substantial effort when
a heavier, as opposed to a lighter, motor 40 is utilized. Motor 40 in all
embodiments is
mounted rearwardly of single ski 13 and forwardly of endless track 50. Also,
while a four
stroke due the resulting increased motor size and consequent increased lateral
width of the
engine in the location of the operator's legs 100 (ref. Fig. 12A, 12B), such
will generally will
have the above detrimental impact on the performance of the vehicle 30 when
traversing
inclined slopes 4 as discussed above, and thus the use of four stroke may only
be suitable in
reduced sizes and displacements of such engines.
The transmission of vehicle 30 for transmitting motor torque to endless track
50 is
provided via a continuously variable transmission ("CVT") 24, located
immediately
rearwardly of, and not beside, motor 40. Use of a CVT, in comparison to
motorcycle
transmissions having selectable gears of various speed reducing and speed
increasing ratios, is
particularly suited for the within application due to its relatively narrow
width. All components
of CVT 24, in the configuration herein stipulated, can be positioned
rearwardly of motor 40
and substantially along the vehicle 30 centerline, thereby eliminating any
excess width which
would otherwise be acquired by vehicle 30 if one or both of the primary 20 or
secondary pulley
22 were to be mounted on the crankshaft of motor 40 and thus on the side of
the motor 40.
In regard to the particular CVT contemplated for the arrangement of the
present
invention, CVT 24 comprises a primary pulley or sheave 20 mounted immediately
rearwardly of, and driven indirectly or directly by in one of the manners
hereinafter described,
motor 40. Primary pulley 20 is located along a vertical plane aligned with
a central
longitudinal axis of vehicle 30 and located proximate, and preferably on, said
central
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longitudinal axis. Primary pulley/sheave 20 which has an adjustable operating
diameter for use
with a mechanical belt endless belt 26. Specifically , primary pulley/sheave
20 in a preferred
embodiment is constructed of two grooved halves. The two main "halves" of the
pulley 20
can be moved closer together or farther apart, thus altering the operational
diameter of pulley
20. The usual construction utilizes one half with a threaded central shaft and
one half with a
threaded center. By rotating the components one can "screw" the parts closer
together or further
apart, thus changing the distance between the two halves and allowing the belt
26 to ride higher
or lower in the groove on pulley 20. Primary pulley 20 is mounted on a first
transverse shaft 70
which is journalled for rotation at opposite ends within bearings 95a, 95b
which are in turn
affixed and mounted to frame 31. First transverse shaft 70 is operatively
coupled, using one
of the mechanisms elaborated on below, to motor 40. The rotational axis of
first transverse
shaft 70 is perpendicular (i.e. transverse) to a direction of travel
and the central longitudinal
axis of snow vehicle 30.
CVT 24 further comprises a similar secondary pulley/sheave 22 mounted
rearwardly
of primary pulley 20 and in said same vertical plane, which is operatively
coupled via
endless belt 26 to primary pulley 20. Like the construction of primary pulley
20, secondary
pulley/sheave 22 is in a preferred embodiment constructed of two conically-
grooved halves.
The two main "halves" of the pulley 22 can be moved closer together or farther
apart, by
mechanism 22' in conjunction with the moving farther apart or closer together
of halves of
primary pulley 20 by mechanism 20'. Specifically, weights/cams (not shown) in
mechanism
20' which rotate with primary pulley 20 move due to centrifugal force and
thereby laterally
moves one half sheave of pulley 20 further or closer to the opposite half
sheave, in direct
proportion to the speed of rotation . Actual lateral movement of one half
sheave of primary
pulley 20 relative to the other half sheave is controlled by rollers on
helical ramps and a spring.
The spring (not shown) is biased in one position so as to cause the effective
diameter of the
primary pulley 20' to be as small as possible at low or no rpm, namely so as
to cause the two
conical half sheaves of pulley 20 to be separated so as to thereby reduce the
effective diameter
of pulley 20 to a maximum extent. A spring forming part of mechanism 22" may
further be
provided for biasing the secondary pulley 22 to provide an opposite effect,
namely to cause the
two half sheaves of pulley 22 to be moved closer together at low or no rpm to
thereby increase
the effective diameter of pulley 22 to the greatest extent possible. At high
motor rpm (and thus
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high rpm of primary pulley 20 and secondary pulley 22, each biasing of each of
the two springs
is overcome by the centrifugal force of the weights acting against the
respective springs, so that
the opposite result as to effective diameter of each pulley 20, 22 is
achieved.. In such manner
the operational diameter of primary pulley 20 (greater or smaller) can be
manipulated in a
manner opposite to that of the secondary pulley (ie. smaller or greater, as
the case may be), thus
altering the speed and torque applied by pulley 20 to pulley 22 via belt 26 .
A detailed
explanation as to the operation of a CVT 24 suitable for the purposes set out
herein can be
found at the internet URL location
https://www.youtube.com/watch?v=uCEvBGT8twM.
Secondary pulley 22 (and mechanism 22') is mounted on a second
transverse
shaft 72, which is likewise is journalled for rotation at opposite ends
thereof within bearings
73a, 73b which are in turn affixed and mounted to frame 31. Second transverse
shaft 72 is
positioned parallel to but spaced rearwardly from first transverse shaft 70,
as best shown in
Fig.s 12B and 13B, and has mounted thereon, typically at one or other end
thereof a driving
pulley or sprocket 34.
It is preferred that the CVT 24 for the within application further
incorporates an
integral clutch arrangement, wherein the primary pulley 20 (which is
initially, at low rpm's, of
a small diameter, or applying high torque and low speed to secondary pulley
22) only becomes
of larger diameter to tighten belt 26 and effectively drive secondary pulley
22 upon increased
engine revolutions, namely upon pressure applied to a throttle to supply more
fuel to motor 40.
In such manner a separate centrifugal clutch (not shown) is not needed to
allow the endless
track 50 not to be directly coupled to motor 40 when motor 40 is merely idling
and/or disk
calipers are effectively braking rotation of said second and/or third
transverse shafts 73, 74.
Thus further motor width, due to not having to mount a centrifugal clutch (not
shown) on a side
of motor 40 such as at the location of idler gears 48, is not necessary and is
thereby avoided.
A driven pulley or toothed sprocket 36, depending on whether a smooth or
toothed belt
(not shown) or alternatively an endless chain 38, is mounted on a third
transverse shaft 74.
Driving pulley or sprocket 34 mounted on second transverse shaft 72 is used
via said belt or
endless chain 38 to couple the second transverse shaft 72 to a third
transverse shaft 74 and
thereby provide rotational energy from the second transverse shaft 72 to the
third transverse
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shaft 74 via driven pulley or toothed sprocket 36, and thus to endless track
50. Third
transverse shaft 74 is rotatably journalled on frame 31 via bearings 75a, 75b
at mutually
opposite ends thereof, each positioned adjacent a proximal end of said endless
track 50. Third
transverse shaft 74 extends within endless track 50 at a proximal end of said
endless track 50
as shown for example in Fig.s 12B, 13B, and has protruding sprockets 77
thereon for
engaging and rotating endless track 50.
CVT 24 comprising primary pulley 20 secondary pulley 22 and an endless belt
26,
operates in the manner of conventional CVT's in providing a selectable speed
and mechanical
advantage when providing motive force to endless belt 50. CVT 24's manner of
operation is
well within the knowledge of persons of skill in the art. One such CVT 24
particularly suited
for the present application is a CVT manufactured by Team Industries, Inc. of
105 Park Avenue
NW Bagley, Minnesota.
Specifically, CVT 24 operates to increase speed of endless belt 50 by pushing,
in
response to increased motor rpm and thus increased rotational speed of pulley
20, endless belt
26 towards the outer extremity of primary pulley 20 (namely moving the two
halves of pulley
closer together via mechanism 20' to force endless belt 26 higher within a
groove separating
the two halves of pulley 20 and effectively thereby increasing the diameter of
pulley 20), while
simultaneously pushing endless belt 26 to inner extremities of secondary
pulley 22 via
mechanism 22', namely moving the two halves of pulley 22 farther apart
together to allow
20 endless belt 26 to ride lower on a groove separating the two halves of
secondary pulley 22 and
effectively thereby decreasing the diameter of secondary pulley 22 in response
to increased rpm
of primary pulley 20. CVT 24 operates in an opposite manner in response to
lower motor rpm,
namely pushing endless belt 26 to inner diametric extremity of primary pulley
20 and
simultaneously pushing endless belt 26 to outer extremities of secondary
pulley 22 in response
to decreased rpm of primary pulley 26, to thereby increase torque applied to
endless track 50
via driven pulley/sprocket 36 and third transverse shaft 74.
In such manner, using a CVT in the aforementioned configuration the lateral
width
(profile) of vehicle 30 and the combined width of the operators legs when
straddling the vehicle
30, when the operator footrests 99a, 99b (ref. Fig. 10) are placed on opposite
side of motor 40,
is reduced.
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Preferably, to ensure the lateral width of motor 40 when mounted on frame 31
of
vehicle 30 is a minimum, in a preferred embodiment motor 40 comprises a pair
of cylinders
42a, 42b aligned in a plane of the longitudinal axis 58 of vehicle 30 and
arranged in a canted
"v" and coupled to a mutual crankshaft 51 , wherein crankshaft 51 is
positioned and aligned on
frame 31 rearwardly of the cylinders 42a, 42b and transverse to the
longitudinal axis 58 of
vehicle 30. In such configuration power transmission from motor 40 to first
transverse shaft 70
may be provided via one or more toothed gears 48 , which drive a corresponding
gear 48
mounted on first transverse shaft 70, as shown in Fig.s 3,4,8 & Figs. 12A,
12B, 13A, 13B.
Alternatively, a belt or chain (not shown) extending between crankshaft 51 and
first transverse
shaft 70, may be substituted in place of gears 48. It is noted that neither of
gears 48 nor a belt
(not shown) take up as much lateral width when mounted on a side of motor 40
as does one or
other of primary 20 or secondary pulley 22, which pulleys 20, 22 of CVT 24
typically possess
belt tensioning and repositioning mechanisms 20' and 22', as shown , which
take up
considerable more lateral width than do a simple belt or number of coplanar
gears 48, as shown
and as clearly evidenced in the cross-sectional views in Fig. 13A, 13B.
Advantageously, the second transverse shaft 72 in the arrangement of power
transmission components, due to its position centrally of vehicle 30
between the first
transverse shaft 70 and the third transverse shaft 74 and being usually in a
raised position
vertically above first transverse shaft 70 and third transverse shaft 74 and
thus more clear of
snow, is well suited to having an additional disk thereon, namely a disk 80
fixedly coupled
thereto which brake calipers (not shown) can be applied to function as a disk
brake to prevent
further rotation of the endless track 50 and thus forward or rearward motion
of vehicle 30.
Accordingly, in a preferred embodiment the second transverse shaft possesses a
disk brake 80
(calipers not shown). Similar disk(s) (not shown), along with associated brake
calipers, may
alternatively or in addition be provided on the third transverse shaft 74 to
likewise provide disk
braking.
To prevent stalling of motor 40 when disk brake 80 is applied or when the
motor 40 is
idling and the vehicle is stationary, a speed-activated integral clutch within
CVT 24 ,
comprising mechanisms 20', 22', operates in the manner described above to
reduce the
effective diameter of pulley 22 and increase in the effective diameter of
pulley 22, along with
simultaneously loosening tension applied to belt 26, thus disengaging of the
driving of
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secondary pulley 22 by primary pulley 20.
Should it be desired, although not necessary when CVT's 24 of the type
manufactured
by TEAM Industries, Inc. are utilized which advantageously utilize by their
manner of operation
an integral clutch, a centrifugal clutch (not shown) may further be provided
elsewhere on
vehicle 30 and other than integral with CVT 24. In such an embodiment, a
centrifugal clutch
(not shown) may be located on and operatively coupled to first transverse
shaft 70 . Such
positioning of a centrifugal clutch on vehicle 30 is advantageous in that
disengagement of the
motor 40 with first transverse shaft 70 results in disengagement (and thus
unnecessary rotation
of) all "downstream" transmission components. Examples of two currently
available
centrifugal clutches are Arctic Cat Z120/ZR120 snowmobile centrifugal clutch,
Polaris
XCR120 / 120 XC SP snowmobile centrifugal clutch.
Advantageously, in keeping with the design objective of minimizing vehicle 30
width,
particularly where a two cylinder motor 40 is employed having each of such two
cylinders 42a,
42b located in a vertical plane of the longitudinal axis 58 (see Fig. 10) of
vehicle 30, each of
cylinders 42a, 42b have an exhaust pipe 65, 66, respectively (see Fig. 6)
extending rearwardly
from such cylinders. Advantageously, due to the positioning of the primary and
secondary
pulleys 20, 22, particularly where primary pulley 20 is located vertically
below, but forward of
secondary pulley 22, such positioning allows exhaust pipes 65, 66 to then
extend immediately
above both primary and secondary pulleys 20, 22 and beneath the operator's
seat 104,
substantially along longitudinal axis 58, to thereby duct motor exhaust gases
rearwardly of the
operator, thereby keeping such (hot) exhaust pipes remote from an operator's
legs, while
nevertheless not increasing and thereby maintaining the width of vehicle 30 to
a minimum.
Exhaust pipes 65,66 may further, but need not necessarily, combine rearwardly
of the
operator's seat 104, into a single common muffler 67, as shown in Fig. 11,
before motor
exhaust therein is then expelled to atmosphere.
In the embodiment shown, respective cylinders 42a, 42b are separately provided
with
respective air inlets 43a, 43b, mounted on a side of motor 40,and preferably
forwardly of the
operator's legs 100 so as to not increase the motor width in the region of the
operators legs 100.
Of course, such motor air inlets 43a, 43b (see Fig. 6) , may be located in
other locations on the
engine, remote from an engine side, particularly if forced induction, such as
a turbocharger is
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utilized and such additional turbine components necessitate the positioning of
the air 43a, 43b
away from a side of motor 40 to thereby maintain a narrow profile motor 40 and
vehicle 30.
Use of examples in the specification, including examples of terms, is for
illustrative
purposes only and is not intended to limit the scope and meaning of the
embodiments of the
invention set out and described in the disclosure. In the specification, the
word "comprising" is
used as an open-ended term, substantially equivalent to the phrase "including,
but not limited
to," and the word "comprises" has a corresponding meaning.
The scope of the claims should not be limited by the preferred embodiments set
forth in
the foregoing examples, but should be given the broadest interpretation
consistent with the
description as a whole, and the claims are not to be limited to the preferred
or exemplified
embodiments of the invention.
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