U.S. patent number RE38,124 [Application Number 08/567,344] was granted by the patent office on 2003-05-27 for snowmobile suspension.
This patent grant is currently assigned to Bombardier Inc., Polaris Industries Partners L.P.. Invention is credited to Gerard J. Karpik, Bertrand Mallette.
United States Patent |
RE38,124 |
Mallette , et al. |
May 27, 2003 |
Snowmobile suspension
Abstract
In a snowmobile track suspension, the slide frame is supported
upon downwardly and rearwardly angled front and rear suspension arm
assemblies. The suspension arm assemblies are of similar
construction, length, and orientation, having upper ends connected
to fixed pivots in the snowmobile chassis and lower ends pivoted to
the slide frame. The lower end of the rear suspension arm assembly
has a pivot mount that is movable longitudinally of the slide
frame. Movement in the forwards direction being blocked by an
abutment which ensures that during suspension travel the front end
of the slide frame cannot move higher than the rear end
thereof.
Inventors: |
Mallette; Bertrand
(Rock-Forest, CA), Karpik; Gerard J. (Eveleth,
MN) |
Assignee: |
Bombardier Inc. (CA)
Polaris Industries Partners L.P. (Minneapolis, MN)
|
Family
ID: |
27074451 |
Appl.
No.: |
08/567,344 |
Filed: |
November 30, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
804385 |
Dec 10, 1991 |
05265692 |
Nov 30, 1993 |
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Current U.S.
Class: |
180/193;
180/9.25; 180/9.56 |
Current CPC
Class: |
B62D
55/116 (20130101); B60G 2200/17 (20130101); B60G
2204/128 (20130101); B60G 2204/129 (20130101); B60G
2204/421 (20130101); B60G 2204/422 (20130101); B60G
2300/322 (20130101) |
Current International
Class: |
B62D
55/104 (20060101); B62D 55/116 (20060101); B62D
055/116 () |
Field of
Search: |
;180/190,193,184,9.25,9.5,9.54,9.56,9.52 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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895747 |
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Mar 1972 |
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CA |
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942802 |
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Feb 1974 |
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CA |
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944001 |
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Mar 1974 |
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CA |
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956674 |
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Oct 1974 |
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CA |
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994395 |
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Aug 1976 |
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CA |
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1026807 |
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Feb 1978 |
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CA |
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1029425 |
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Apr 1978 |
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CA |
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Primary Examiner: Hurley; Kevin
Attorney, Agent or Firm: Larson & Taylor PLC
Claims
What I claim as my invention is:
1. A snowmobile suspension comprising: a slide frame carried on
downwardly and rearwardly angled front and rear suspension arm
assemblies that are supported in the snowmobile chassis, said
suspension incorporating spring means acting on said arm assemblies
to urge said slide frame downwardly into contact with the
ground-engaging run of the snowmobile track belt; said front and
rear arm assemblies being substantially equal in length and
generally parallelly arranged to position said slide frame
substantially horizontally with respect to the snowmobile chassis;
said front arm assembly having upper and lower ends connected to
fixed first and second pivots on the snowmobile chassis and on the
slide frame respectively; said rear arm assembly having an upper
end connected to a third fixed pivot on said snowmobile chassis,
and having a lower end connected to a displaceable pivot that is
movable longitudinally of said slide frame; said slide frame
defining an abutment that establishes a forwardmost position of
said displaceable pivot relative to said slide frame, said abutment
being located such that in said forwardmost position of the
displaceable pivot, the front and rear arm assemblies define with
said slide frame and said chassis a parallelogram linkage which
prevents said second pivot from moving to a higher position
.[.that.]. .Iadd.than .Iaddend.said displaceable pivot relative to
said chassis; guide means on said slide frame adapted to
accommodate movement of said displaceable pivot rearwardly away
from said abutment to permit movement of said displaceable pivot to
a higher position than said second fixed pivot relative to said
snowmobile chassis.
2. A snowmobile suspension as claimed in claim 1 wherein said slide
frame comprises two laterally spaced longitudinally extending rails
with upwardly curved front ends, each rail having an upwardly
projecting lug forward of the mid point in its length, said lugs
being horizontally aligned; said front arm assembly comprising
horizontal upper and lower tubes spaced apart and interconnected by
transversely spaced longitudinal members to form a rigid structure,
said upper tube forming said first fixed pivot with said chassis
and said lower tube forming said second fixed pivot with said lugs
of said slide frame; said spring means comprising a combined coil
spring and hydraulic damper unit centrally arranged longitudinally
of said front arm assembly, said upper tube rigidly supporting a
radially extending short lug arm that forms a pivotal connection
with the upper end of said damper unit, the lower end of said
damper unit being connected to a linkage system that is coupled to
said slide frame and to said front arm assembly, said linkage being
so configured as to apply to said damping unit a compressive
displacement as upwards displacement of the slide frame
increases.
3. A snowmobile suspension as claimed in claim 2 wherein the rear
suspension arm assembly likewise comprises horizontal upper and
lower tubes spaced apart and interconnected by transversely spaced
longitudinal members to form a rigid structure in which said upper
tube forms said third fixed pivot with said chassis and said lower
tube forms said displaceable pivot, each end of the rear suspension
arm assembly lower tube carrying a slide block, each slide block
being received in a respective longitudinally extending guideway
carried on an upwardly projecting lug plate on the respective slide
rail.
4. A snowmobile suspension as claimed in claim 3 wherein each end
of the lower tube of the rear suspension arm assembly defines a
cylindrical stub shaft that is pivotally received in a low-friction
slide block, said stub shaft projecting through an elongate slot in
said lug plate, and said guideway being defined between said lug
plate and a cover plate that is detachably secured
thereto..Iadd.
5. A snowmobile suspension comprising: a slide frame carried on
downwardly and rearwardly angled front and rear suspension arm
assemblies that are supported in the snowmobile chassis, said
suspension incorporating spring means acting to urge said slide
frame downwardly into contact with the ground-engaging run of the
snowmobile track belt; said front and rear arm assemblies being
substantially equal in length and generally parallelly arranged to
position said slide frame substantially horizontally with respect
to the snowmobile chassis; said front arm assembly having upper and
lower ends connected to fixed first and second pivots on the
snowmobile chassis and on the slide frame respectively; said rear
arm assembly having an upper end connected to a third fixed pivot
on said snowmobile chassis, and having a lower end connected by a
connection to a displaceable pivot that is connected to said slide
frame in such a manner as to be movable longitudinally of said
slide frame; said slide frame defining an abutment that establishes
a forwardmost position of said displaceable pivot relative to said
slide frame, said abutment being located such that in said
forwardmost position of the displaceable pivot, the front and rear
arm assemblies define with said slide frame and said chassis a
parallelogram linkage which limits the height to which the front
end of the slide frame can be moved relative to the height of the
rear end thereof during upward displacement of said slide frame
relative to said chassis; the connection between said displaceable
pivot and said slide frame being adapted to accommodate movement of
said displaceable pivot rearwardly away from said abutment to
permit movement of said displaceable pivot to a higher relative
position than said second fixed pivot during upwards displacement
of said slide frame relative to said snowmobile chassis..Iaddend.
Description
BACKGROUND OF THE INVENTION
a) Field of the Invention
This invention relates to a new or improved snowmobile track belt
suspension.
b) Description of the Prior Art
Snowmobile track belt suspensions often employ a slide frame
pressed into contact with the upper side of the ground engaging run
of the track belt loop by spring arrangements associated with
suspension arm assemblies by which the slide frame is connected to
the snowmobile chassis. Typically, two angulated arm assemblies are
employed to connect the slide frame to the snowmobile chassis, and
these arm assemblies are movable independently of one another to
permit the slide frame to accommodate itself to static and dynamic
forces arising in operation.
Irregularities in the terrain travelled by the snowmobile produce
displacements and deflections of the snowmobile front suspension
that supports the vehicle on the skis, and of the rear suspension.
Depending upon their magnitude, frequency, and strength, these
deflections cause more or less discomfort to the operator of the
snowmobile. The present inventor theorizes that suspension
displacements that produce angular acceleration of the snowmobile
and its operator about a transverse horizontal axis produce more
discomfort than displacements that merely produce vertical
acceleration of the vehicle and its operator.
Accordingly it is an object of the invention to provide a
snowmobile track belt suspension that will provide a reduced
angular acceleration as compared to prior art snowmobile track
suspensions.
SUMMARY OF THE INVENTION
The invention provides a snowmobile suspension comprising: a slide
frame carried on downwardly and rearwardly angled front and rear
suspension arm assemblies that are supported in the snowmobile
chassis, said suspension incorporating spring means acting on said
arm assemblies to urge said slide frame downwardly into contact
with the ground-engaging run of the snowmobile track belt; said
front and rear arm assemblies being substantially equal in length
and generally parallelly arranged to position said slide frame
substantially horizontally with respect to the snowmobile chassis;
said frame arm assembly having upper and lower ends connected to
fixed first and second pivots on the snowmobile chassis and on the
slide frame respectively; said rear arm assembly having an upper
end connected to a third fixed pivot on said snowmobile chassis,
and having a lower end connected to a displaceable pivot that is
movable longitudinally of said slide frame; movement of said
displaceable pivot forwardly of said slide frame being limited by
an abutment that is positioned so that the suspension arms form a
parallelogram linkage, and which thus prevents the front end of the
slide frame from moving to a higher position than the rear end
thereof relative to said chassis; guide means on said slide frame
adapted to accommodate movement of said displaceable pivot
rearwardly away from said abutment to permit movement of the rear
end of said slide frame to a higher position than the front end
thereof relative to said snowmobile chassis.
With such an arrangement it is ensured that the loading imposed
upon the track suspension by undulations in the terrain over which
the snowmobile travels acts more on the front part of the track
suspension than on its rear part, and thus effectively moves the
average point of application of the vertical forces forwardly
closer to the center of gravity of the vehicle, and accordingly
reduces the resulted couple that produces the undesired angular
acceleration.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will further be described, by way of example only,
with reference to the accompanying drawings wherein:
FIGS. 1A and 1B are generally schematic side elevations of a
snowmobile;
FIG. 2 is a somewhat schematic side elevation of a slide frame and
the suspension arm assemblies of a snowmobile track suspension;
FIGS. 3A and 3B are schematic views illustrating the action of the
components of FIG. 2;
FIG. 4 is a somewhat more detailed side elevational view of a
snowmobile slide frame and suspension arm assemblies;
FIG. 5 is a somewhat schematic view of the front portion of the
suspension of FIG. 4; and
FIG. 6 is a top rear and side perspective view of the snowmobile
slide suspension of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1A and 1B, a snowmobile chassis 10 is
schematically illustrated as being supported in the usual manner
upon a pair of steerable skis 11 at its forward end and upon the
ground engaging run of a driven track belt 12 at its rearward end.
FIG. 1A represents the situation that exists with a track
suspension of prior art construction wherein the loading point 13
where ground induced forces absorbed by the track suspension are
applied to the snowmobile chassis is positioned rearwardly of the
snowmobiles center of gravity 14 by a distance l.
It will be understood that the angular acceleration .alpha. applied
to the snowmobile when the track encounters an undulation that
generates a force F at the loading point 13 will be directly
proportional to the couple T and inversely proportional to the
moment of inertia I of the snowmobile about its center of
gravity.
In other words
The couple T is the product of the force F and the distance l, so
that accordingly the angular acceleration for a given force F is
directly proportional to the distance l.
FIG. 1B represents the dynamic condition in which the snowmobile
track suspension is re-configured so that under the same operating
conditions the force F is applied at a loading point 15 that is
spaced further forwardly than in FIG. 1A at a distance l' from the
center of gravity 14. It will be appreciated that with this
configuration the angular acceleration applied to the snowmobile is
greatly reduced. The snowmobile track suspension now to be
described in relation to FIGS. 2 through 6 has been designed to
achieve a reduction in this angular acceleration
Referring to FIG. 2, the track suspension includes an elongate
slide frame 21 with an upwardly curved forward end 22, and carrying
at its rear end in known manner, adjustable idler wheels 23 over
which the track belt is constrained to pass. The slide frame 21
contacts the upper side of the ground engaging run of the track
belt 12 and is in turn connected to the snowmobile chassis 10 by
front and rear suspension arm assemblies 24, 25. The suspension arm
assemblies 24, 25 are of substantially the same length, and are
arranged at a similar orientation, i.e. inclined downwardly from
front to rear, being connected at their upper ends to fixed pivots
26, 27 respectively on the snowmobile chassis 10. The suspension
arm assemblies 24, 25 extend at substantially the same angle
.theta. to the horizontal as indicated in FIG. 2, the front arm
assembly having its lower end attached to a fixed pivot 28 and the
rear arm assembly having its lower end attached to a movable pivot
29. The movable pivot 29 is received in a guide means 30, being
movable longitudinally thereof, and the guide means defining an
abutment 31 at its forward end positioned as shown in FIG. 2.
FIG. 2 shows the static position of the track suspension. The front
and rear arm assemblies 24, 25 are of the same length L and are
arranged at the same angle .theta. with respect to the horizontal,
the movable pivot 29 being in this condition at the forward end of
its range of movement and adjacent the abutment 31. In this
condition it will be seen that when the front suspension arm 24 is
pivoted upwardly about pivot 26, the rear suspension arm 25 is
constrained to follow the same movement since the arms are forced
to act as a parallelogram linkage. Accordingly the slide frame 21
will remain horizontal as it deflects upwardly. Specifically the
front end of the slide frame cannot move to a higher location than
the rear end during this displacement since the movable pivot 29 is
blocked by the abutment 31.
However the slide frame will be free to assume a position as shown
in broken lines in FIG. 3B as might occur as a result of tension in
the track 12 or otherwise. This movement is accommodated by
rearward displacement of the movable pivot 29 in the guide 30.
The structure of the slide frame 21 and the suspension arm
assemblies 24, 25 and their associated components is more clearly
illustrated in relation to FIGS. 4, 5 and 6. Referring to FIG. 6 it
will be seen that the slide frame 21 comprises two transversely
spaced elongate runners 35 interconnected by suitable transverse
struts 36. In conventional manner, the runners 35 are upwardly
curved towards their forward ends and also include on their
undersides friction reducing coatings or the like (not shown) for
engagement with the snowmobile track belt 12. The friction
generated in this engagement can be further reduced by idler wheels
37, 38 arranged in pairs at intermediate locations on the slide
frame and having lower peripheries projecting slightly below the
underside of the slide frame runners 35.
The rear suspension arm assembly 25 as best seen in FIG. 6
comprises a horizontal upper tube 39 interconnected to a horizontal
lower tube 40 by laterally spaced upwardly divergent longitudinal
members 41. The outboard ends of the upper tube 39 carry idler
wheels 42 to support the return run (not shown) of the track belt
12, and also support stub shafts 43 which provide the pivot
attachment 27 to the snowmobile chassis.
The lower tube 40 carries on its outboard ends the movable pivots
29 in the form of slide blocks 29a of suitable lower friction
material, which are longitudinally movable in the guide means 30.
As shown, each runner 35 has an upwardly extending lug plate 44
having an elongate slot through which the associated end of the
lower tube 40 passes. The guide means 30 is defined by a cover
plate 45 that is releasably secured to the lug plate 44 by suitable
fastener means.
An intermediate cross piece 46 is mounted on the longitudinal
members 41 and supports the forward ends of a pair of spaced
parallel gusset plates 47 the rear ends of which are supported on
the lower tube 40. Intermediate their ends the gusset plates 47
provide a pivotal mounting 48 for a bell crank plate 50 which has
an intermediate pivotal connection 51 to a diagonally arranged
strut 52 that is pivotally supported on the slide frame, and a
further pivotal connection 53 to the lower end of a combined coiled
spring/hydraulic damper unit 54. The upper end of the damper unit
forms a pivotal connection 55 to a radially projecting lug arm 56
that is rigidly attached to the upper tube 39.
From this it will be seen that the damper unit 54 extends below and
generally longitudinally of the rear suspension arm assembly 25.
The configuration of the linkage provided by the bell crank 50, the
strut 52 and the lug arm 56 is such that the resistance of the
damper unit to upwards deflection of the rear suspension arm
assembly 25 is applied at a desired rate.
The front suspension arm assembly 24 is similarly configured to the
rear suspension arm assembly including upper and lower tubes 39a
and 40a interconnected by longitudinal members 41a, the upper tube
having stub shafts 43a at its ends, but not supporting any idler
wheels. The lower tube 41 is connected to the pivot axis 28
provided in upwardly projecting lug plates 44a on the runners 35.
Gusset plates 47a are supported between a cross piece 46a and the
lower tube 40a and provide a pivot 48a for a bell crank plate 50a
which is likewise pivoted at 51a to a strut 52a and at 53a to the
lower end of a damper unit 54a. The upper end of the damper unit
has a pivotal connection 55a to a lug arm 56a on the upper tube
39a.
For convenience in illustration, the elements are shown in somewhat
simplified form in FIGS. 4 and 6, and in particular the damper
units 54, 54a are shown without their coil springs. These
components are of well known design and need not be illustrated in
detail.
From the foregoing description and a consideration of the drawings,
and in particular FIGS. 2, 3a and 3b, it will be evident that under
uniform loading applied to the suspension from the slide frame 21,
the arm assemblies 24 and 25 will occupy the relative positions
shown in FIG. 2, i.e. will be parallel, so that the slide frame 21
will lie essentially parallel to the line between the upper pivots
26 and 27, and, as shown in broken lines in FIG. 3a, will maintain
this parallel relationship during variations in the magnitude of
the uniform loading. As will be apparent, this parallelogram
linkage will be maintained even in the event that the slide frame
22 is subjected to non-uniform loading where the load point is
offset towards the front end. This is because, by virtue of the
parallelogram arrangement of the suspension and the fact that the
movable pivot 29 at the lower end of the rear suspension arm
assembly 25 is in engagement with the abutment 31, the forward
lower pivot 28 is prevented from moving to a higher level relative
to the chassis than the level of the movable pivot 29. However in
the event that a non-uniform loading is applied to the chassis 21
offset towards the rear end thereof, it will be evident that the
rear suspension arm assembly 25 can deflect upwardly to a greater
extent than the front suspension arm assembly 24, as illustrated
schematically in FIG. 3b, this increased deflection being
accommodated by the fact that the movable pivot 29 can in this made
move rearwardly in the guide 30.
* * * * *