Note: Descriptions are shown in the official language in which they were submitted.
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ENDLESS TRACK FOR TRACTION OF AN OFF-ROAD VEHICLE SUCH AS
AN ALL-TERRAIN VEHICLE (AN) OR A SNOWMOBILE
FIELD OF THE INVENTION
The invention relates generally to off-road vehicles such as all-terrain
vehicles
(ATVs) and snowmobiles and, more particularly, to endless tracks for providing
traction to ATVs, snowmobiles and other off-road vehicles.
BACKGROUND
Certain off-road vehicles, such as snowmobiles and all-terrain vehicles
(ATVs),
may be equipped with elastomeric endless tracks which enhance their traction
and floatation on soft, slippery and/or irregular grounds (e.g., soil, mud,
sand, ice,
snow, etc.) on which they operate
Traction, floatation and other performance aspects of tracked vehicles depend
on
various factors, including their endless tracks.
For example, rigidity characteristics of an endless track can have a
significant
influence on traction, floatation and other performance aspects of a vehicle
propelled by the track. For instance, while the track needs to be
longitudinally
flexible to flex around a track-engaging assembly (e.g., comprising a drive
wheel
and roller wheels) of the vehicle, large deflections of a bottom run of the
track
(e.g., in gaps between adjacent rollers wheels) may occur if the track's
longitudinal flexibility is too great, thereby detrimentally affecting
traction and
pressure distribution on the ground. Also, the track may comprise transversal
stiffening rods such that it is very rigid transversally or may be free of
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stiffening rods such that it is very flexible transversally, but a very high
transversal rigidity or flexibility may present drawbacks (e.g., poor traction
on
uneven ground areas if too rigid transversally, poor floatation if too
flexible
transversally, etc.).
For these and other reasons, there is a need to improve endless tracks for
ATVs,
snowmobiles and other off-road vehicles.
SUMMARY OF THE INVENTION
According to an aspect of the invention, there is provided an endless track
for
traction of an off-road vehicle. The endless track is mountable around a
plurality
of track-contacting wheels which includes a drive wheel for driving the
endless
track. The endless track comprises elastomeric material allowing the endless
track to flex around the track-contacting wheels. The endless track comprises
an
inner side for facing the track-contacting wheels and a ground-engaging outer
side for engaging the ground. The ground-engaging outer side comprises a
plurality of traction projections distributed along a longitudinal direction
of the
endless track. Each traction projection of the plurality of traction
projections
comprises: a transversal protrusion extending transversally to the
longitudinal
direction of the endless track; and an enlarged protrusion larger in the
longitudinal direction of the endless track than the transversal protrusion of
the
traction projection. The enlarged protrusions of the traction projections are
dimensioned and disposed relative to one another to enhance a rigidity of a
bottom run of the endless track in the longitudinal direction of the endless
track.
According to another aspect of the invention, there is provided an endless
track
for traction of an off-road vehicle. The endless track is mountable around a
plurality of track-contacting wheels which includes (i) a drive wheel for
driving the
endless track and (ii) a plurality of roller wheels for rolling on a bottom
run of the
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endless track. The endless track comprises elastomeric material allowing the
endless track to flex around the track-contacting wheels. The endless track
comprises an inner side for facing the track-contacting wheels and a ground-
engaging outer side for engaging the ground. The ground-engaging outer side
comprises a plurality of traction projections distributed along a longitudinal
direction of the endless track. Each traction projection of the plurality of
traction
projections comprises: a transversal protrusion extending transversally to the
longitudinal direction of the endless track; and an enlarged protrusion larger
in
the longitudinal direction of the endless track than the transversal
protrusion of
.. the traction projection. The enlarged protrusions of the traction
projections are
dimensioned and disposed relative to one another to oppose a tendency of the
bottom run of the endless track to flex inwardly in a gap between adjacent
ones
of the roller wheels.
According to another aspect of the invention, there is provided an endless
track
for traction of an off-road vehicle. The endless track is mountable around a
plurality of track-contacting wheels which includes a drive wheel for driving
the
endless track. The endless track comprises elastonneric material allowing the
endless track to flex around the track-contacting wheels. The endless track
comprises an inner side for facing the track-contacting wheels and a ground-
engaging outer side for engaging the ground. The ground-engaging outer side
comprises a plurality of traction projections distributed along a longitudinal
direction of the endless track. Each traction projection of the plurality of
traction
projections comprises: a transversal protrusion extending transversally to the
longitudinal direction of the endless track; and an enlarged protrusion larger
in
the longitudinal direction of the endless track than the transversal
protrusion of
the traction projection. A ratio of (i) a width of the enlarged protrusion of
a first
one of the traction projections in the longitudinal direction of the endless
track
over (ii) a longitudinal spacing of the first one of the traction projections
and a
second one of the traction projections which succeeds the first one of the
traction
projections in the longitudinal direction of the endless track is at least
0.8.
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According to another aspect of the invention, there is provided an endless
track
for traction of an off-road vehicle. The endless track is mountable around a
plurality of track-contacting wheels which includes a drive wheel for driving
the
endless track. The endless track comprises elastomeric material allowing the
endless track to flex around the track-contacting wheels. The endless track
comprises an inner side for facing the track-contacting wheels and a ground-
engaging outer side for engaging the ground. The ground-engaging outer side
comprises a plurality of traction projections distributed along a longitudinal
direction of the endless track. Each traction projection of the plurality of
traction
projections comprises: a transversal protrusion extending transversally to the
longitudinal direction of the endless track; a first enlarged protrusion
larger in the
longitudinal direction of the endless track than the transversal protrusion of
the
traction projection; and a second enlarged protrusion larger in the
longitudinal
direction of the endless track than the transversal protrusion of the traction
projection. The first enlarged protrusion and the second enlarged protrusion
of
the traction projection are spaced apart in a widthwise direction of the
endless
track. The first enlarged protrusion of the traction projection is larger in
the
longitudinal direction of the endless track than the second enlarged
protrusion of
the traction projection.
According to another aspect of the invention, there is provided an endless
track
for traction of an off-road vehicle. The endless track is mountable around a
plurality of track-contacting wheels which includes a drive wheel for driving
the
endless track. The endless track comprises elastomeric material allowing the
endless track to flex around the track-contacting wheels. The endless track
comprises an inner side for facing the track-contacting wheels and a ground-
engaging outer side for engaging the ground. The ground-engaging outer side
comprises a plurality of traction projections distributed along a longitudinal
direction of the endless track. Each traction projection of the plurality of
traction
projections extends transversally to the longitudinal direction of the endless
track.
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A ratio of (i) a bending stiffness of the traction projection in a widthwise
direction
of the endless track over (ii) a cross-sectional weight per unit length of the
traction projection at a cross-section of the traction projection is at least
5000 in.3.
According to another aspect of the invention, there is provided an endless
track
for traction of an off-road vehicle. The endless track is mountable around a
plurality of track-contacting wheels which includes a drive wheel for driving
the
endless track. The endless track comprises elastomeric material allowing the
endless track to flex around the track-contacting wheels. The endless track
comprises an inner side for facing the track-contacting wheels and a ground-
engaging outer side for engaging the ground. The ground-engaging outer side
comprises a plurality of traction projections distributed along a longitudinal
direction of the endless track. Each traction projection of the plurality of
traction
projections extends transversally to the longitudinal direction of the endless
track.
.. A cross-section of the traction projection has: a width in the longitudinal
direction
of the endless track; a minimal dimension in the longitudinal direction of the
endless track that is less than the width of the cross-section of the traction
projection; and a height in a thickness direction of the endless track. A
ratio of the
width of the cross-section of the traction projection over the minimal
dimension of
.. the cross-section of the traction projection in the longitudinal direction
of the
endless track is at least 4. A ratio of the height of the cross-section of the
traction
projection over the minimal dimension of the cross-section of the traction
projection in the longitudinal direction of the endless track is at least 6.
These and other aspects of the invention will now become apparent to those of
ordinary skill in the art upon review of the following description of
embodiments of
the invention in conjunction with the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of embodiments of the invention is provided below, by
way
of example only, with reference to the accompanying drawings, in which:
Figures 1A and 1B show an example of an all-terrain vehicle (ATV) comprising
track assemblies which comprise endless tracks in accordance with an
embodiment of the invention;
Figures 2A and 2B show the AN equipped with ground-engaging wheels instead
of the track assemblies;
Figures 3 and 4 show perspective views of a front one and a rear one of the
track
assemblies;
Figures 5 and 6 show perspective views of the front one and the rear one of
the
track assemblies without their endless track;
Figures 7 and 8 show perspective views of a segment of the endless track of
the
rear track assembly, which depict features of an inner side and a ground-
engaging outer side of the endless track that are not depicted in Figures 1A,
1B,
3 and 4, including traction projections of the endless track;
Figures 9 and 10 show views of the ground-engaging outer side and the inner
side of the endless track of the rear track assembly;
Figure 11 shows a side view of the endless track of the rear track assembly;
Figures 12 and 13 show other views of the endless track of the rear track
assembly;
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Figure 14 shows a cross-sectional view of the endless track taken as indicated
in
Figure 9;
Figure 15 shows a partial cross-sectional view of the endless track taken in a
widthwise direction of the track;
Figure 16 shows a variant in which the endless track comprises transversal
stiffening rods in other embodiments;
Figures 17 to 23 show views of a segment of the endless track of the front
track
assembly, which depict features of an inner side and a ground-engaging outer
side of the endless track that are not depicted in Figures 1A, 1B, 3 and 4;
Figure 24A represents a smooth shape of a bottom run of the endless track of
the rear track assembly in contrast to Figure 24B which represents an
excessive
flexion of the endless track in gaps between wheels of the rear track assembly
that could occur if the endless track lacked certain features;
Figure 25A shows a controlled flexion of the endless track in its widthwise
direction in contrast to Figure 25B which represents an excessive flexion of
the
endless track in its widthwise direction that could occur if the endless track
lacked certain features;
Figure 26 shows a close-up perspective view of the endless track of the rear
track assembly;
Figure 27 shows another view of the ground-engaging outer side of the endless
track;
Figure 28 shows a close-up of the cross-sectional view of the endless track
taken
as indicated in Figure 9;
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Figure 29A shows an example of flexion of a traction projection of the endless
track in the track's longitudinal direction;
Figure 296 shows a situation if the traction projection of the endless track
was
not flexing in the track's longitudinal direction;
Figure 30A shows an example of controlled flexion of the endless track in its
widthwise direction;
Figure 306 shows a situation if there was excessive flexion of the endless
track
in its widthwise direction;
Figure 30C shows a situation if there was substantially no flexion of the
endless
track in its widthwise direction;
Figures 31 and 32 show variants of the endless track in accordance with other
embodiments of the invention in which a traction projection of the track
comprises an internal cavity;
Figure 33 shows a variant of the endless track in accordance with another
embodiment of the invention in which a traction projection of the track
comprises
composite elastomeric material;
Figure 34 shows a variant of the endless track in accordance with another
embodiment of the invention in which a traction projection of the track
comprises
composite cellular elastomeric material;
Figures 35 and 36 show variants of the endless track in accordance with other
embodiments of the invention which depict examples of other shapes of a
traction projection of the track; and
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Figure 37 shows an example of a snowmobile comprising an elastomeric endless
track in accordance with another embodiment of the invention.
It is to be expressly understood that the description and drawings are only
for the
purpose of illustrating certain embodiments of the invention and are an aid
for
understanding. They are not intended to be a definition of the limits of the
invention.
DETAILED DESCRIPTION OF EMBODIMENTS
Figures 1A and 1B show an example of an all-terrain vehicle (ATV) 10 in
accordance with an embodiment of the invention. The ATV 10 is a small open
vehicle designed to travel off-road on a variety of terrains, including
roadless
rugged terrain, for recreational, utility and/or other purposes.
In this embodiment, the ATV 10 comprises a prime mover 12, a plurality of
track
assemblies 161-164, a seat 18, and a user interface 20, which enable a user of
the ATV to ride the ATV 10 on the ground.
The prime mover 12 is a source of motive power that comprises one or more
motors. For example, in this embodiment, the prime mover 12 comprises an
internal combustion engine. In other embodiments, the prime mover 12 may
comprise another type of motor (e.g., an electric motor) or a combination of
different types of motor (e.g., an internal combustion engine and an electric
motor).
The prime mover 12 is in a driving relationship with one or more of the track
assemblies 161-164. That is, motive power generated by the prime mover 12 is
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transmitted to one or more of the track assemblies 161-162 via a powertrain of
the
ATV 10 (e.g., via a transmission and a differential of the powertrain).
In this case, the seat 18 is a straddle seat and the ATV 10 is usable by a
single
person such that the seat 18 accommodates only that person driving the AN 10.
In other cases, the seat 18 may be another type of seat, and/or the AN 10 may
be usable by two individuals, namely one person driving the AN 10 and a
passenger, such that the seat 18 may accommodate both of these individuals
(e.g., behind one another or side-by-side) or the AN 10 may comprise an
additional seat for the passenger. For example, in other embodiments, the AN
10 may be a side-by-side AN, sometimes referred to as a "utility terrain
vehicle"
or "UTV".
The user interface 20 allows the user to interact with the AN 10. More
particularly, the user interface 20 comprises an accelerator, a brake control,
and
a steering device that are operated by the user to control motion of the AN 10
on the ground. In this case, the steering device comprises handlebars. In
other
cases, the steering device may comprise a steering wheel or other type of
steering element. The user interface 20 also comprises an instrument panel
(e.g.,
a dashboard) which provides indicators (e.g., a speedometer indicator, a
tachometer indicator, etc.) to convey information to the user.
The track assemblies 161-164 engage the ground to provide traction to the AN
10. More particularly, in this example, front ones of the track assemblies 161-
164
provide front traction to the AN 10 while rear ones of the track assemblies
161-
164 provide rear traction to the AN 10. Each of the front ones of the track
assemblies 161-164 is pivotable about a steering axis of the AN 10 in response
to input of the user at the handlebars in order to steer the AN 10 on the
ground.
In this embodiment, each track assembly 16; is mounted in place of a ground-
engaging wheel that may otherwise be mounted at a position of the track
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assembly 16; to propel the ATV 10 on the ground. For example, as shown in
Figures 2A and 2B, the AN 10 may be propelled on the ground by four ground-
engaging wheels 151-154 with tires instead of the track assemblies 161-164.
Basically, in this embodiment, the track assemblies 161-164 may be used to
convert the AN 10 from a wheeled vehicle into a tracked vehicle, thereby
enhancing its traction and floatation on the ground.
With additional reference to Figures 3 to 6, in this embodiment, each track
assembly 16; comprises a frame 44, a plurality of track-contacting wheels
which
includes a drive wheel 42 and a plurality of idler wheels 501-5010, and an
elastomeric endless track 41 disposed around the frame 44 and the wheels 42,
501-5010. The track assembly 16; has a front longitudinal end 57 and a rear
longitudinal end 59 that define a length of the track assembly 16. A width of
the
track assembly 16; is defined by a width of the endless track 41. An envelope
of
the track assembly 16; is defined by a length of the track 41. The track
assembly
16; has a longitudinal direction, a widthwise direction, and a height
direction.
The elastomeric endless track 41 engages the ground to provide traction to the
AN 10. Referring additionally to Figures 7 to 14, the track 41 comprises an
inner
side 45 facing the wheels 42, 501-50,0 and defining an inner area of the track
41
in which these wheels are located. The track 41 also comprises a ground-
engaging outer side 47 opposite the inner side 45 for engaging the ground on
which the AN 10 travels. Lateral edges 631, 632 of the track 41 define the
track's
width. The track 41 has a top run 65 which extends between the longitudinal
ends 57, 59 of the track assembly 16; and over the drive wheel 42, and a
bottom
run 66 which extends between the longitudinal ends 57, 59 of the track
assembly
16; and under the idler wheels 501-5010. The track 41 has a longitudinal
direction,
a widthwise direction, and a thickness direction.
The endless track 41 is elastomeric in that it comprises elastomeric material
allowing it to flex around the wheels 42, 501-5010. The elastomeric material
of the
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track 41 can include any polymeric material with suitable elasticity. In this
embodiment, the elastomeric material includes rubber. Various rubber
compounds may be used and, in some cases, different rubber compounds may
be present in different areas of the track 22. In other embodiments, the
elastomeric material of the track 41 may include another elastomer in addition
to
or instead of rubber (e.g., polyurethane elastomer).
While it is flexible, in this embodiment, the endless track 41 has certain
rigidity
characteristics which are useful for traction and other performance aspects of
the
track assembly 16, as discussed later.
The endless track 41 comprises an elastomeric belt-shaped body 36 underlying
its inner side 45 and its ground-engaging outer side 47. In view of its
underlying
nature, the body 36 can be referred to as a "carcass". The carcass 36
comprises
elastomeric material 37 which allows the track 41 to flex around the wheels
42,
501-5010.
As shown in Figure 15, in this embodiment, the carcass 36 comprises a
plurality
of reinforcements embedded in its elastomeric material 37. One example of a
reinforcement is a layer of reinforcing cables 381-38c that are adjacent to
one
another and that extend in the longitudinal direction of the track 41 to
enhance
strength in tension of the track 41 along its longitudinal direction. In some
cases,
a reinforcing cable may be a cord or wire rope including a plurality of
strands or
wires. In other cases, a reinforcing cable may be another type of cable and
may
be made of any material suitably flexible longitudinally (e.g., fibers or
wires of
metal, plastic or composite material). Another example of a reinforcement is a
layer of reinforcing fabric 40. Reinforcing fabric comprises pliable material
made
usually by weaving, felting, or knitting natural or synthetic fibers. For
instance, a
layer of reinforcing fabric may comprise a ply of reinforcing woven fibers
(e.g.,
nylon fibers or other synthetic fibers). Various other types of reinforcements
may
be provided in the carcass 36 in other embodiments.
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In this embodiment, the inner side 45 of the endless track 41 comprises an
inner
surface 32 of the carcass 36 and a plurality of wheel-contacting projections
481-
48N that project from the inner surface 32 and contact at least some of the
wheels 42, 501-5010 and that are used to do at least one of driving (i.e.,
imparting
motion to) the track 41 and guiding the track 41. In that sense, the wheel-
contacting projections 481-48N can be referred to as "drive/guide
projections",
meaning that each drive/guide projection is used to do at least one of driving
the
track 41 and guiding the track 41. Also, such drive/guide projections are
sometimes referred to as "drive/guide lugs" and will thus be referred to as
such
herein. More particularly, in this embodiment, the drive/guide lugs 481-48N
interact with the drive wheel 42 in order to cause the track 41 to be driven,
and
also interact with the idler wheels 501-5010 in order to guide the track 41 as
it is
driven by the drive wheel 42. The drive/guide lugs 481-48N are thus used to
both
drive the track 41 and guide the track 41 in this embodiment.
The drive/guide lugs 481-48N are spaced apart along the longitudinal direction
of
the endless track 41. In this case, the drive/guide lugs 481-48N are arranged
in a
plurality of rows that are spaced apart along the widthwise direction of the
endless track 41. The drive/guide lugs 481-48N may be arranged in other
manners in other embodiments (e.g., a single row or more than two rows). Each
drive/guide lug 48; is an elastomeric drive/guide lug in that it comprises
elastomeric material 68.
The ground-engaging outer side 47 of the endless track 41 comprises a ground-
engaging outer surface 31 of the carcass 36 and a plurality of traction
projections
611-61m that project from the outer surface 31 and engage and may penetrate
into the ground to enhance traction. The traction projections 611-61m, which
can
sometimes be referred to as "traction lugs" or "traction profiles", are spaced
apart
.. in the longitudinal direction of the track assembly 16i. The ground-
engaging outer
side 47 comprises a plurality of traction-projection-free areas 711-71F (i.e.,
areas
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free of traction projections) between successive ones of the traction
projections
611-61m. In this example, each traction projection 61; is an elastomeric
traction
projection in that it comprises elastomeric material 69.
.. In this embodiment, respective ones of the traction projections 611-61m
comprise
one or more recesses 931-93F extending from their outer end 77 to enhance
traction on certain types of ground surfaces, such as compacted snow and other
snow surfaces. For instance, in a traction projection 61; including a recess
93x,
part of the traction projection's outer end 77 adjacent to the recess 93õ can
apply
more pressure on, and thus can have a greater tendency to penetrate, a
compacted snow surface than if the recess 93x was omitted. In this example,
the
recesses 931-93F of successive ones of the traction projections 611-61m are
nonaligned in the widthwise direction of the endless track 41. For instance,
snow
can be compacted as it passes under a recess 93x of a traction projection 611
and
a subsequent traction projection 61k passing over the resulting compacted
snow,
with no recess aligned with the recess 93x of the traction projection 61; in
the
widthwise direction of the track 41, can engage and have better traction on
the
compacted snow.
The recesses 931-93F of the traction projections 611-61m may have any suitable
shape. In this embodiment, the recesses 931-93F of the traction projections
611-
61m taper in the thickness direction of the endless track 41. Also, in this
embodiment, a recess 93õ of a traction projection 61; has a depth dr measured
from the outer end 77 of the traction projection 611 which corresponds to a
.. substantial fraction of an overall height Ht_a of the traction projection
611. For
example, in some embodiments, a ratio dr/Ht, of the depth dr of the recess 93x
of
the traction projection 61; over the overall height Ht, of the traction
projection 61;
may be at least 0.15, in some cases at least 0.25, in some cases at least
0.35, in
some cases at least 0.45, and in some cases even more (e.g., at least 0.50).
The
ratio d1/H0 may have any other suitable value in other embodiments.
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In this example, the carcass 36 has a thickness Tc which is relatively small.
The
thickness Tc of the carcass 36 is measured from the inner surface 32 to the
ground-engaging outer surface 31 of the carcass 35 between longitudinally-
adjacent ones of the traction projections 611-61m. For example, in some
embodiments, the thickness Tc of the carcass 36 may be no more than 0.250
inches, in some cases no more than 0.240 inches, in some cases no more than
0.230 inches, in some cases no more than 0.220 inches, in some cases no more
than 0.210 inches, in some cases no more than 0.200 inches, and in some cases
even less (e.g., 0.180 or 0.170 inches). The thickness Tc of the carcass 36
may
have any other suitable value in other embodiments.
In this embodiment, as shown in Figure 15, the endless track 41 is free of
transversal stiffening rods embedded in its elastomeric material. That is, the
track
41 does not comprise transversal stiffening rods embedded in its elastomeric
material and extending transversally to its longitudinal direction. Figure 16
shows
a variant in which the track 41 may comprise transversal stiffening rods 531-
53m
embedded in its elastomeric material and extending transversally to its
longitudinal direction in other embodiments. This absence of transversal
stiffening rods makes the track 41 more flexible in its widthwise direction
than if
the track 41 had the transversal stiffening rods 531-53m but was otherwise
identical.
The endless track 41 shown in Figures 7 to 14 is that of a given one of the
rear
track assemblies 163, 164. Figures 17 to 23 show the endless track 41 of a
given
one of the front track assemblies 161, 162, which is similar to the track 41
of the
given one of the rear track assemblies 163, 164, except that it comprises bent
lateral edge portions 641, 642 adjacent its lateral edges 631, 632 to
facilitate
steering of the given one of the front track assemblies 161, 162 on the
ground, by
creating a smaller ground-contacting area. More particularly, the carcass 36
of
the track 41 of the given one of the front track assemblies 161, 162 is bent
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inwardly proximate the lateral edges 631, 632 of the track 41 such that its
inner
surface 32 and ground-engaging outer surface 31 are bent inwardly.
The endless track 41 may be constructed in various other ways in other
embodiments. For example, in some embodiments, the track 41 may comprise a
plurality of parts (e.g., rubber sections) interconnected to one another in a
closed
configuration, the track 41 may have recesses or holes that interact with the
drive
wheel 42 in order to cause the track 41 to be driven (e.g., in which case the
drive/guide lugs 481-48N may be used only to guide the track 41 without being
.. used to drive the track 41), and/or the ground-engaging outer side 47 of
the track
41 may comprise various patterns of traction projections.
The drive wheel 42 is rotatable about an axis of rotation 49 for driving the
endless track 41. The axis of rotation 49 corresponds to an axle of the ATV
10.
More particularly, in this example, the drive wheel 42 has a hub which is
mounted
to the axle of the ATV 10 such that power generated by the prime mover 12 and
delivered over the powertrain of the AN 10 rotates the axle, which rotates the
drive wheel 42, which imparts motion of the track 41. In this embodiment in
which
the track assembly 16, is mounted where a ground-engaging wheel 15, could
otherwise be mounted, the axle of the AN 10 is capable of rotating the drive
wheel 42 of the track assembly 16, or the ground-engaging wheel 15,.
In this embodiment, the drive wheel 42 comprises a drive sprocket engaging the
drive/guide lugs 481-48N of the inner side 45 of the track 41 in order to
drive the
track 41. In this case, the drive sprocket 42 comprises a plurality of teeth
461-46T
distributed circumferentially along its rim to define a plurality of lug-
receiving
spaces therebetween that receive the drive/guide lugs 481-48N of the track 41.
The drive wheel 42 may be configured in various other ways in other
embodiments. For example, in embodiments where the track 41 comprises
recesses or holes, the drive wheel 42 may have teeth that enter these recesses
or holes in order to drive the track 41. As yet another example, in some
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embodiments, the drive wheel 42 may frictionally engage the inner side 45 of
the
track 41 in order to frictionally drive the track 41.
The idler wheels 501-5010 are not driven by power supplied by the prime mover
12, but are rather used to do at least one of supporting part of the weight of
the
AN 10 on the ground via the track 41, guiding the track 41 as it is driven by
the
drive wheel 42, and tensioning the track 41. More particularly, in this
embodiment, the idler wheels 501, 502 and the idler wheels 509, 5010 are
respectively front idler wheels (leading idler wheels) and rear idler wheels
(trailing
.. idler wheels) that maintain the track 41 in tension, and can help to
support part of
the weight of the AN 10 on the ground via the track 41. The idler wheels 503-
508
are roller wheels that roll on the inner side 45 of the track 41 along the
bottom
run 66 of the track 41 to apply the bottom run 66 on the ground. The idler
wheels
501-5010 move on respective ones of a plurality of idler wheel paths 501, 502
of
the inner surface 32 of the carcass 35 of the endless track 41. Each of the
idler
wheel paths 501, 502 extends adjacent to respective ones of the drive/guide
lugs
481-48N to allow these lugs to guide motion of the track 41. As the roller
wheels
503-508 roll on respective ones of the idler wheel paths 501, 502, these paths
can
be referred to as "rolling paths".
The idler wheels 501-5010 may be arranged in other configurations and/or the
track assembly 16; may comprise more or less idler wheels in other
embodiments.
In this embodiment, the drive/guide lugs 481-48N and the idler wheel paths
501,
502 of the endless track 41 are laterally offset towards the lateral edge 631
of the
track 41. In this example, the lateral edge 631 of the track 41 is an inboard
lateral
edge of the track 41 that is closest to a centerline 81 of the AN 10, while
the
lateral edge 632 of the track 41 is an outboard lateral edge of the track 41
that is
farthest from the centerline 81 of the AN 10. This lateral offset may help for
traction, stability and steering of the AN 10 since it allows the track
assembly 16;
17
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to have a ground-contacting area (i.e., "contact patch") that emulates a
ground-
contacting area that a ground-engaging wheel 15; would have if mounted in
place
of the track assembly 16. Basically, the track assembly 16; applies more
pressure on the ground in a first half 831 of the width of the track 41 that
is
adjacent the inboard lateral edge 631 of the track 41 than in a second half
832 of
the width of the track 41 that is adjacent to the outboard lateral edge 632 of
the
track 41, instead of applying substantially equal pressure on both halves 831,
832
of the track 41.
More particularly, in this embodiment, as shown in Figure 10, the drive/guide
lugs
481-48N and the idler wheel paths 501, 502 are asymmetrically disposed
relative
to a centerline 79 bisecting the width of the track 41 into its halves 831,
832. Each
of a widthwise span 80 of the drive/guide lugs 481-48N and a widthwise span 84
the idler wheel paths 501, 502 is thus asymmetrically disposed relative to the
centerline 79 and located closer the inboard lateral edge 631 of the track 41
than
to the outboard lateral edge 632 of the track 41.
The frame 44 supports components of the track assembly 16, including the idler
wheels 501-5010. More particularly, in this embodiment, the front idler wheels
501,
502 are mounted to the frame 44 in a front longitudinal end region of the
frame 44
proximate the front longitudinal end 57 of the track assembly 16, while the
rear
idler wheels 509, 5019 are mounted to the frame 44 in a rear longitudinal end
region of the frame 44 proximate the rear longitudinal end 59 of the track
assembly 16i. The roller wheels 503-508 are mounted to the frame 44 in a
central
region of the frame 44 between the front idler wheels 501, 502 and the rear
idler
wheels 509, 501o. Each of the roller wheels 503-508 may be rotatably mounted
directly to the frame 44 or may be rotatably mounted to a link which is
pivotally
mounted to the frame 44 to which is rotatably mounted an adjacent one of the
roller wheels 503-508, thus forming a "tandem".
18
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The frame 44 is supported at a support area 39. More specifically, in this
case,
the frame 44 is supported by the axle of the ATV 10 to which is coupled the
drive
wheel 42, such that the support area 39 is intersected by the axis of rotation
49
of the drive wheel 42.
In this embodiment, the frame 44 is pivotable about a pivot axis 51 to
facilitate
motion of the track assembly 16; on uneven terrain and enhance its traction on
the ground. More particularly, in this embodiment, the pivot axis 51
corresponds
to the axis of rotation 49 of the drive wheel 42 and the frame 44 can pivot
about
the axle of the ATV 10 to which the drive wheel 42 is coupled. In other
embodiments, the pivot axis 51 of the frame 44 may be located elsewhere (e.g.,
lower) than the axis of rotation 49 of the drive wheel 42. In yet other
embodiments, the frame 44 may not be pivotable.
Also, in this embodiment, the track assembly 16; comprises an anti-rotation
connector 52 to limit a pivoting movement of the track assembly 16; relative
to a
chassis of the ATV 10. In this example, the anti-rotation connector 52
comprises
a spring and a damper and is connected between the frame 44 of the track
assembly 16; and the chassis of the ATV 10 (e.g., via one or more mounting
brackets and/or fasteners).
In this embodiment, the endless track 41 has rigidity characteristics which
are
useful for traction and other performance aspects of the track assembly 16.
For
example, in this embodiment, the track 41 has a longitudinal rigidity (i.e.,
rigidity
in its longitudinal direction) such that, although it can flex in its
longitudinal
direction to move around the wheels 42, 501-5010, it is sufficiently rigid in
its
longitudinal direction to help maintain a "smooth" shape of the bottom run 66
of
the track 41 for proper traction, as conceptually represented in dotted line
in
Figure 24A, by tending to prevent the bottom run 66 of the track 41 from
flexing
inwardly in gaps between adjacent ones of the idler wheels 501-5010 (e.g.,
when
bearing against a rock, a bump, or other ground unevenness), as conceptually
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represented in dotted line in Figure 24B. In addition, in this embodiment, the
track 41 has a widthwise rigidity (i.e., rigidity in its widthwise direction)
such that,
although it can flex in its widthwise direction (e.g., notably since it has no
transversal stiffening rods in this embodiment) to accommodate a ground
surface
which is uneven in its widthwise direction (e.g., a rut, bump, or side hill),
it is
sufficiently rigid in its widthwise direction to help maintain proper
floatation and
traction over the uneven ground surface, as conceptually represented in dotted
line in Figure 25A, by tending to prevent an excessive flexion of the track 41
in its
widthwise direction, as conceptually represented in dotted line in Figure 25B.
More particularly, in this embodiment, the traction projections 611-61m are
designed to control the rigidity characteristics of the endless track 41,
while
maintaining a weight of the track 41 relatively low. A shape and a material
composition of each of the traction projections 611-61m are selected to
achieve
the rigidity characteristics of the track 41. In this example, the traction
projections
611-61m have a dominant effect on the rigidity characteristics of the track 41
since the track 41 is free of transversal stiffening rods and its carcass 36
is thin.
Each traction projection 61, extends transversally to the longitudinal
direction of
the endless track 41. That is, the traction projection 61, has a longitudinal
axis 54
extending transversally to the longitudinal direction of the track 41. In this
example, the longitudinal axis 54 of the traction projection 61, is
substantially
parallel to the widthwise direction of the track 41. In other examples, the
longitudinal axis 54 of the traction projection 61, may be transversal to the
longitudinal direction of the track 41 without being parallel to the widthwise
direction of the track 41.
In this embodiment, the traction projection 61, extends across at least a
majority
of the width of the endless track 41. More particularly, in this example, the
traction projection 61õ extends across substantially an entirety of the width
of the
track 41. The traction projection 61, has longitudinal ends 601, 602 adjacent
to
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respective ones of the lateral edges 631, 632 of the track 41. The traction
projection 61x may extend across any suitable part of the width of the endless
track 41 in other embodiments.
The traction projection 61x varies in cross-sectional shape along its
longitudinal
axis 54. That is, cross-sections of the traction projection 61x at different
positions
along the longitudinal axis 54 of the traction projection 61x are different.
As
shown in Figure 14, a cross-section of the traction projection 61x at a given
position along the longitudinal axis 54 of the traction projection 61x is
taken
parallel to the longitudinal direction of the track 41 and a has width Wt
(i.e., a
maximal dimension in the longitudinal direction of the track 41) and a height
Ht
(i.e., a maximal dimension in the thickness direction of the track 41). More
particularly, in this embodiment, the traction projection 61x varies in width
and
height along its longitudinal axis 54. Also, in this embodiment, at a given
position
along its longitudinal axis 54, the traction projection 61x varies in
widthwise
dimension in the thickness direction of the track 41.
More particularly, in this embodiment, as shown in Figures 7, 9, 11 to 14, 26
and
27, the traction projection 61x comprises a transversal protrusion 55 and a
.. plurality of enlarged protrusions 561, 562 which comprise respective
portions of its
elastomeric material 69.
The transversal protrusion 55 of the traction projection 61x extends
transversally
to the longitudinal direction of the endless track 41. Specifically, the
transversal
protrusion 55 extends along the longitudinal axis 54 of the traction
projection 61x.
In this embodiment, the transversal protrusion 55 comprises a lateral portion
671
between the lateral edge 631 of the track 41 and the enlarged protrusion 561,
a
central portion 70 between the enlarged protrusions 561, 562, and a lateral
portion 672 between the lateral edge 632 of the track 41 and the enlarged
protrusion 562. In this example, the central portion 70 and the lateral
portions
671, 672 of the transversal protrusion 55 are generally straight such that the
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transversal protrusion 55 is generally straight. The transversal protrusion 55
may
have any other suitable shape in other embodiments.
Each of the enlarged protrusions 561, 562 of the traction projection 61x is
larger in
the longitudinal direction of the endless track 41 than the transversal
protrusion
55 of the traction projection 61x. That is, a width Wt_e of each of the
enlarged
protrusions 561, 562 is greater than a width Wt_t of the transversal
protrusion 55.
Thus, the transversal protrusion 55 is a relatively narrow protrusion and each
of
the enlarged protrusions 561, 562 is a relative wide protrusion that is wider
than
the transversal protrusion 55. For example, in some embodiments, a ratio Wt-e/
Wt-t of the width Wt_e of a given one of the enlarged protrusions 561, 562
over the
width Wt_t of the transversal protrusion 55 may be at least 2, in some cases
at
least 2.2, in some cases at least 2.4, in some cases at least 2.6, and in some
cases even more (e.g., 3 or more). The ratio Wt_e/Wt_t may have any other
suitable value in other embodiments.
The width Wt_e of each of the enlarged protrusions 561, 562 is therefore
greater
than a minimum width Wt-min of the traction projection 61. In this example in
which the transversal protrusion 55 of the traction projection 61x is
generally
straight, the minimum width Wt-min of the traction projection 61x corresponds
to
the width VVt_t of the transversal protrusion 55. For example, in some
embodiments, a ratio Wt-e/Wt-min of the width Wt-e of a given one of the
enlarged
protrusions 561, 562 over the minimum width Wt_t of the traction projection
61x
may be at least 2, in some cases at least 2.2, in some cases at least 2.4, in
some
cases at least 2.6, and in some cases even more (e.g., 3 or more). The ratio
Wt_
eANt-min may have any other suitable value in other embodiments.
The width Wt-e of a given one of the enlarged protrusions 561, 562 is a
maximum
width Wt_max of the traction projection 61x. In this embodiment, the widths
Wt_e of
the enlarged protrusions 561, 562 are different such that the width Wt_e of
one of
the enlarged protrusions 561, 562 is greater than width Wt_t of the other one
of the
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enlarged protrusions 561, 562 and is the maximum width Wt-max of the traction
projection 61,. For example, in some embodiments, a ratio Wt_max/ Wt_min of
the
maximum width Wt-max of the traction projection 61, over the minimum width Wt_
min of the traction projection 61, may be at least 2, in some cases at least
2.2, in
some cases at least 2.4, in some cases at least 2.6, and in some cases even
more (e.g., 3 or more). The ratio W
-t-max/Wt-min may have any other suitable value
in other embodiments.
The width Wt-e of a given one of the enlarged protrusions 561, 562 of the
traction
projection 61, corresponding to the maximum width Wt-max of the traction
projection 61, is significant in relation to a longitudinal spacing Dt of the
traction
projection 61, and a traction projection 61y which succeeds the traction
projection
61, in the longitudinal direction of the track 41. The longitudinal spacing
Dt, which
is a longitudinal distance between respective centers of the successive
traction
projections 61,, 61y, can be referred to as a "pitch" of the successive
traction
projections 61,, 61y. For example, in some embodiments, a ratio Wt-e/Dt of the
width Wt-e of a given one of the enlarged protrusions 561, 562 of the traction
projection 61, over the pitch Dt of the successive traction projections 61,,
61y may
be at least 0.8, in some cases at least 0.85, in some cases, at least 0.9, in
some
cases 0.95, in some cases at least 1.0, in some cases at least 1.05, and in
some
cases even more (e.g., 1.10 or more). In this example of implementation, the
ratio Wt-e/Dt is about 1.05. The ratio Wt-e/Dt may have any other suitable
value in
other embodiments.
In this embodiment, each of the enlarged protrusions 561, 562 of a traction
projection 61 is elongated such that it has a longitudinal axis 62 transversal
to
the longitudinal axis 54 of the traction projection 61,. More particularly, in
this
example, each of the enlarged protrusions 561, 562 is elongated in the
longitudinal direction of the track 41 such that its longitudinal axis 62 is
substantially parallel to the longitudinal direction of the track 41. In this
case,
each of the enlarged protrusions 561, 562 has a tapered configuration, here a
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triangle-like configuration, at the outer end 77 of the traction projection
61,. This
may be help for printing and traction of the traction projection 61x on the
ground
(e.g., on a side hill by providing sideways support). Each of the enlarged
protrusions 561, 562 may have any other suitable shape in other embodiments.
The enlarged protrusions 561, 562 of the traction projections 611-61m are
dimensioned and disposed relative to one another to enhance the longitudinal
rigidity of the endless track 41, notably the longitudinal rigidity of the
bottom run
66 of the track 41. In that sense, the enlarged protrusions 561, 562 of the
traction
projections 61 1-61m constitute "longitudinal rigidifiers" which
longitudinally rigidify
(i.e., enhance the longitudinal rigidity of) the track 41.
The longitudinal rigidifiers constituted by respective ones of the enlarged
protrusions 561, 562 of the traction projections 611-61m form a plurality of
elongated longitudinal rigidification structures 911, 912 which are spaced
apart in
the widthwise direction of the track 41. The enlarged protrusions 561 of the
traction projections 611-61m form the elongated longitudinal rigidification
structure
911 and the enlarged protrusions 562 of the traction projections 611-61m form
the
elongated longitudinal rigidification structure 912.
To that end, in this embodiment, the enlarged protrusion 561 of a traction
projection 61; and the enlarged protrusion 561 of a traction projection 61j
succeeding the traction projection 61; in the longitudinal direction of the
track 41
are aligned with one another in the widthwise direction of the track 41 (i.e.,
at
least part of the enlarged protrusion 561 of the traction projection 61; and
at least
part of the enlarged protrusion 561 of the traction projection 61j overlap in
the
widthwise direction of the track 41) and the enlarged protrusion 562 of the
traction
projection 61; and the enlarged protrusion 562 of the traction projection 61j
are
aligned with one another in the widthwise direction of the track 41 (i.e., at
least
part of the enlarged protrusion 562 of the traction projection 61; and at
least part
of the enlarged protrusion 562 of the traction projection 61j overlap in the
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widthwise direction of the track 41). This contributes to forming the
elongated
longitudinal rigidification structures 911, 912 which longitudinally rigidify
the track
41.
In this embodiment in which the widths Wt_e of the enlarged protrusions 561,
562
of each of the traction projections 611-61m are different, larger ones of the
enlarged protrusions 561, 562 of the traction projections 611-61m alternate
from
side to side of the track 41 over successive ones of the traction projections
611-
61m such that: the enlarged protrusion 561 of the traction projection 61,
which is
larger than the enlarged protrusion 562 of the traction projection 61; in the
longitudinal direction of the track 41, is aligned in the widthwise direction
of the
track 41 with the enlarged protrusion 561 of the traction projection 61j,
which is
smaller than the enlarged protrusion 562 of the traction projection 61j in the
longitudinal direction of the track 41; and the enlarged protrusion 562 of the
traction projection 61, which is smaller than the enlarged protrusion 561 of
the
traction projection 611 in the longitudinal direction of the track 41, is
aligned in the
widthwise direction of the track 41 with the enlarged protrusion 562 of the
traction
projection 61j, which is larger than the enlarged protrusion 561 of the
traction
projection 61j in the longitudinal direction of the track 41.
In this example of implementation, the larger ones of the enlarged protrusions
561, 562 of the traction projections 61, 61, i.e., the enlarged protrusion 561
of the
traction projection 611 and the enlarged protrusion 562 of the traction
projection
61j, overlap in the longitudinal direction of the track 41. There is a
longitudinal
overlap Vt_e between the enlarged protrusion 561 of the traction projection
611 and
the enlarged protrusion 562 of the traction projection 61j.
The traction-projection-free area 71x between the traction projections 61, 61j
comprises a flex zone 74 where the traction-projection-free area 71 bends most
in the longitudinal direction of the track 41 as the track 41 moves around the
wheels 42, 501-5010, and the enlarged protrusions 561, 562 of the traction
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projections 61, 61j are configured to limit a size of the flex zone 74 and
therefore
longitudinally rigidify the track 41.
More particularly, in this embodiment, each of a longitudinal gap 721 between
the
enlarged protrusion 561 of the traction projection 611 and the enlarged
protrusion
561 of the traction projection 61j and a longitudinal gap 722 between the
enlarged
protrusion 562 of the traction projection 611 and the enlarged protrusion 562
of the
traction projection 61j is significantly smaller than a largest longitudinal
gap 73
between the traction projection 61; and the traction projection 61j. Each of
the
longitudinal gaps 721, 722 thus forms a constriction of the flex zone 74 of
the
traction-projection-free area 71x that makes the flex zone 74 "narrow" and
helps
to longitudinally rigidify the track 41.
A dimension Gt_e of each of the longitudinal gaps 721, 722 between the
enlarged
.. protrusions 561, 562 of the traction projections 61, 61j is thus
significantly less
than a dimension Gt-max of the largest longitudinal gap 73 between the
traction
projections 61, 61j. For example, in some embodiments, a ratio Gt-e/Gt-max of
the
dimension Gt_e of each of the longitudinal gaps 721, 722 between the enlarged
protrusions 561, 562 of the traction projections 61õ 61j over the dimension
Gt_max
of the largest longitudinal gap 73 between the traction projections 61, 61j
may be
no more than 0.4, in some cases no more than 0.35, in some cases no more
than 0.3, in some cases no more than 0.25, in some cases no more than 0.2, and
in some cases even less (e.g., no more than 0.15 or less). The ratio Gt-e/Gt-
max
may have any other suitable value in other embodiments.
In this example, each of the longitudinal gaps 721, 722 between the enlarged
protrusions 561, 562 of the traction projections 61, 61j is a smallest
longitudinal
gap between the traction projection 61; and the traction projection 61j such
that
its dimension Gt_e is a dimension Gt-min of the smallest longitudinal gap
between
these traction projections. Thus, in this example, a ratio Gt-min/Gt-max of
the
dimension Gt-min of the smallest longitudinal gap 721 or 722 between the
traction
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projection 61; and the traction projection 61j over the dimension Gt-max of
the
largest longitudinal gap 73 between the traction projection 61; and the
traction
projection 61j may be no more than 0.4, in some cases no more than 0.35, in
some cases no more than 0.3, in some cases no more than 0.25, in some cases
no more than 0.2, and in some cases even less (e.g., no more than 0.15 or
less).
The ratio Gt-min/Gt-max may have any other suitable value in other
embodiments.
In addition to limiting the size of the flex zone 74 of the traction-
projection-free
area 71., in this embodiment, the enlarged protrusions 561, 562 of each of the
traction projections 61, 61j impart a deviation of the flex zone 74 such that
the
flex zone 74 is not straight. That is, a centerline 75 of the flex zone 74
passing
through the longitudinal gaps 721, 722 between the enlarged protrusions 561,
562
of the traction projections 61, 61j is not parallel to the widthwise direction
of the
track 41. This deviation of the flex zone 74 may further longitudinally
rigidify the
track 41 since it makes it harder for the track 41 to bend across its width.
To that end, in this embodiment, the longitudinal gaps 721, 722 between the
enlarged protrusions 561, 562 of the traction projections 61, 61j are
nonaligned
with one another in the longitudinal direction of the track 41. There is a
longitudinal offset Og between respective centers of the longitudinal gaps
721,
722 between the enlarged protrusions 561, 562 of the traction projections 61,
61j.
For example, in some embodiments, a ratio Og/Gt-max of the longitudinal offset
Og
of the longitudinal gaps 721, 722 between the enlarged protrusions 561, 562 of
the
traction projections 61, 61i over the dimension Gt-max of the largest
longitudinal
gap 73 between the traction projection 61; and the traction projection 61j may
be
at least 0.1, in some cases at least 0.2, in some cases at least 0.3, and in
some
cases even more (e.g., at least 0.4 or more). The ratio Og/Gt-max may have any
other suitable value in other embodiments. The longitudinal gaps 721, 722
between the enlarged protrusions 561, 562 of successive ones of the traction
projections 611-61m are thus staggered in the longitudinal direction of the
track
41.
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In this embodiment, the enlarged protrusions 561, 562 of each of the traction
projections 611-61m enhance the longitudinal rigidity of the rolling paths
501, 502
of the inner surface 32 of the carcass 35 of the track 41 over which move the
idler wheels 501-5010. In that sense, the enlarged protrusions 561, 562 of
each of
the traction projections 611-61m constitute "rolling path rigidifiers". This
may
promote a smooth shape of the bottom run 66 of the track 41 for proper
traction,
as shown in Figure 24A, by opposing a tendency of the bottom run 66 of the
track 41 to bend inwardly in gaps between adjacent ones of the idler wheels
501-
.. 5010 (e.g., when bearing against a rock, a bump, or other ground
unevenness),
as shown in Figure 24B.
More particularly, in this embodiment, the enlarged protrusions 561, 562 of
each
of the traction projections 611-61m are aligned in the widthwise direction of
the
.. endless track 41 with the rolling paths 501, 502 of the inner surface 32 of
the
carcass 35 of the track 41 over which move the idler wheels 501-5010 (i.e., at
least part of the enlarged protrusion 561 of a traction projection 61,
overlaps the
rolling path 501 in the widthwise direction of the track 41, and at least part
of the
enlarged protrusion 562 of the traction projection 61, overlaps the rolling
path 502
in the widthwise direction of the track 41). Respective ones of the idler
wheels
501-5010 rolling on the rolling paths 501, 502 thus bear against more rigid
regions
of the traction projections 611-61m which causes less bending of the bottom
run
66 of the track 41 where these wheels are located.
In this example of implementation, the relatively high ratio Wt_e/Dt of the
width Wt_
e of a given one of the enlarged protrusions 561, 562 of each of the traction
projections 611-61m over the pitch Dt of successive ones of the traction
projections 611-61m helps to keep respective ones of the idler wheels 501-5010
longer on more rigid regions of the track 41. This may help to reduce
vibrations in
the track 41.
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The width Wt, of an enlarged protrusion 56y of a traction projection 61; over
which passes a roller wheel 50y may be significant in relation to a diameter
Dw of
the roller wheel 50y. For example, in some embodiments, a ratio VVt_e/Dw of
the
width Wt_e of the enlarged protrusion 56y over the diameter Dw of the roller
wheel
50y may be at least 0.3, in some cases at least 0.4, in some cases at least
0.5,
and in some cases even more (e.g., 0.6 or more). The ratio Wt_e/Dw may have
any other suitable value in other embodiments.
Also, in this embodiment, the longitudinal gaps 721, 722 between the enlarged
protrusions 561, 562 of successive traction projections 61i, 61j are aligned
in the
widthwise direction of the track 41 with the rolling paths 501, 502 of the
inner
surface 32 of the carcass 35 of the track 41. Since these longitudinal gaps
721,
722 are relatively small, respective ones of the idler wheels 501-5010 on the
rolling
paths 501, 502 spend less time on the flex zone 74 of the traction-projection-
free
area 71x of the successive traction projections 61, 61j which causes less
bending
of the bottom run 66 of the track 41 where these wheels are located.
The dimension Gt_e of a longitudinal gap 72y between aligned ones of the
enlarged protrusions 561, 562 of the successive traction projections 61, 61j
over
which passes a roller wheel 50y may be relatively small in relation to the
diameter
Dw of the roller wheel 50y. For example, in some embodiments, a ratio Gt_e/D,
of
the dimension Gt, of the longitudinal gap 72, between aligned ones of the
enlarged protrusions 561, 562 of the successive traction projections 61, 61j
over
the diameter D,, of the roller wheel 50, may be no more than 0.15, in some
cases
no more than 0.10, in some cases no more than 0.08, and in some cases even
less (e.g., 0.05 or less). The ratio Gt..e/D,,, may have any other suitable
value in
other embodiments.
Furthermore, in this embodiment, since the longitudinal gaps 721, 722 between
the enlarged protrusions 561, 562 of successive traction projections 61i, 61j
are
nonaligned with one another in the longitudinal direction of the track 41,
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respective ones of the idler wheels 501-5010 on the rolling paths 501, 502 may
not
pass over these longitudinal gaps 721, 722 simultaneously, and this may cause
less bending of the bottom run 66 of the track 41 where these wheels are
located. This may also reduce vibrations and noise since the idler wheels 501-
5010 transition between rigid and flexible regions at different times.
The longitudinal offset Og of the longitudinal gaps 721, 722 between the
enlarged
protrusions 561, 562 of successive traction projections 61, 61i over which
pass
roller wheels 50y, 50, may be related to the diameter D of each of the roller
wheels 50y, 50,. For example, in some embodiments, a ratio Og/D, of the
longitudinal offset Og of the longitudinal gaps 721, 722 between the enlarged
protrusions 561, 562 of the traction projections 61, 61i over the diameter Dw
of
each of the roller wheels 50y, 50, may be at least 0.05, in some cases at
least
0.1, in some cases at least 0.15, and in some cases even more (e.g., at least
0.2
or more). The ratio Og/D may have any other suitable value in other
embodiments.
Since in this embodiment the rolling paths 501, 502 of the inner side 45 of
the
track 41 are laterally offset towards the inboard lateral edge 631 of the
track 41
and the enlarged protrusions 561, 562 of each of the traction projections 611-
61m
are aligned in the widthwise direction of the track 41 with the rolling paths
501,
502, the enlarged protrusions 561, 562 of each of the traction projections 611-
61m
are thus also laterally offset towards the inboard lateral edge 631 of the
track 41.
More particularly, in this embodiment, the enlarged protrusions 561, 562 of
each
of the traction projections 611-61m are asymmetrically disposed relative to
the
centerline 79 bisecting the width of the track 41 into its halves 831, 832. A
widthwise span 88 of the enlarged protrusions 561, 562 of each of the traction
projections 611-61m is thus asymmetrically disposed relative to the centerline
79
and located closer the inboard lateral edge 631 of the track 41 than to the
outboard lateral edge 632 of the track 41.
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With respect to the widthwise rigidity of the endless track 41, in this
embodiment,
each traction projection 61, is designed such that a cross-section of the
traction
projection 61x has an area moment of inertia (i.e., a second moment of area)
It
which is relatively high and/or its elastomeric material 69 has a modulus of
elasticity Et which is relatively high. As a result, a bending stiffness Bt =
EtIt of the
traction projection 61x in the widthwise direction of the track 41 is
relatively high,
while a weight of the traction projection 61, may be kept relatively low.
Referring additionally to Figure 28, in this example, the cross-section of the
traction projection 61x is taken in the transversal protrusion 55 of the
traction
projection 61x. The area moment of inertia It is calculated with respect to an
axis
parallel to the longitudinal direction of the track 41 at a base 76 of the
cross-
section of the traction projection 61,. In cases where the modulus of
elasticity Et
of the elastomeric material 69 of the traction projection 61x varies along the
traction projection 61x, the modulus of elasticity Et at the cross-section of
the
traction projection 61), is considered. A cross-sectional weight per unit
length Mt
of the traction projection 61x at the cross-section of the traction projection
61, is
calculated by multiplying a density pt of the elastomeric material 69 of the
traction
projection 61), at the cross-section by a cross-sectional area At of the
traction
projection 61x at the cross-section (Mt = ptAt).
For example, in some embodiments, a ratio Bt/Mt of the bending stiffness Bt of
the traction projection 61x in the widthwise direction of the endless track 41
(in
lb.in.2) over the cross-sectional weight per unit length Mt of the traction
projection
61x at the cross-section of the traction projection 61, (in lb/in.) may be at
least
5000 in.3, in some cases at least 5200 in.3, in some cases at least 5400 in.3,
and
in some cases even more (e.g., 5500 in.3 or more). The ratio Bt/Mt may have
any
other suitable value in other embodiments.
In some embodiments, a hardness St of the elastomeric material 69 of the
traction projection 61x may be used to characterize this elastomeric material,
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instead of its modulus of elasticity Et. In cases where the hardness St of the
elastomeric material 69 of the traction projection 61x varies along the
traction
projection 61x, the hardness St at the cross-section of the traction
projection 61x
is considered. For instance, in some embodiments, the hardness St of the
elastomeric material 69 of the traction projection 61x may be at least 75
durometers Shore A, in some cases at least 80 durometers Shore A, and in
some cases even more (e.g., 85 durometers Shore A).
The cross-section of the transversal protrusion 55 of the traction projection
61x
may have any suitable shape.
In this embodiment, the cross-section of the transversal protrusion 55 of the
traction projection 61x tapers in the thickness direction of the endless track
41. A
minimal dimension wt-t-min of the cross-section of the transversal protrusion
55 in
the longitudinal direction of the track 41 is less than the width Wt_t of the
cross-
section of the transversal protrusion 55. For example, in some embodiments, a
ratio Wt/wt-t-min of the width Wt_t of the cross-section of the transversal
protrusion
55 over the minimal dimension wt-t-min of the cross-section of the transversal
protrusion 55 in the longitudinal direction of the track 41 may be at least 4,
in
some cases at least 4.5, in some cases at least 5, in some cases at least 5.5,
and in some cases even more (e.g., 6 or more). The ratio Wawtmin may have
any other suitable value in other embodiments.
More particularly, in this embodiment, the cross-section of the transversal
protrusion 55 of the traction projection 61 tapers in such a way that the
minimal
dimension wt-t-min of the cross-section of the transversal protrusion 55 in
the
longitudinal direction of the track 41 is at the outer end 77 of the traction
projection 61x. In this example, the cross-section of the transversal
protrusion 55
tapers continuously outwardly from the base 76 to the outer end 77 of the
traction
projection 61x. The transversal protrusion 55 thus comprises a "thin" or
"sharp"
outer edge 78 in this case. The minimal dimension wt-t-min of the cross-
section of
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the transversal protrusion 55 in the longitudinal direction of the track 41
may be
located between the base 76 and the outer end 77 of the traction projection
61,
in other embodiments.
Also, in this embodiment, a height Elm of the cross-section of the transversal
protrusion 55 of the traction projection 61, is significantly larger than the
minimal
dimension wt-t-min of the cross-section of the transversal protrusion 55 in
the
longitudinal direction of the track 41. For example, in some embodiments, a
ratio
Ht..t/wt-t-min of the height Flt_t of the cross-section of the transversal
protrusion 55
over the minimal dimension wt-t-min of the cross-section of the transversal
protrusion 55 in the longitudinal direction of the track 41 may be at least 6,
in
some cases at least 7, in some cases at least 8, and in some cases even more
(e.g., 9 or more). The ratio Ht_tiwt-t-min may have any other suitable value
in other
embodiments.
In this example, the cross-section and the material properties of the
elastomeric
material 69 of the transversal protrusion 55 of the traction projection 61,
are such
that the transversal protrusion 55 is relatively stiff in the widthwise
direction of the
endless track 41, which may help to prevent excessive bending of the track 21
in
its widthwise direction and therefore help for proper traction and floatation.
At the
same time, the cross-section and the material properties of the elastomeric
material 69 of the transversal protrusion 55 of the traction projection 61,
are such
that the transversal protrusion 55 extends relatively high and is flexible at
its thin
or sharp outer edge 78 in the track's longitudinal direction, which may help
for
proper traction, vibration absorption, and durability.
For instance, in this embodiment, as shown in Figure 29A, the flexibility of
the
transversal protrusion 55 of the traction projection 61, in the longitudinal
direction
of the track 41 may allow an outer end portion 90 of the traction projection
61,
adjacent to its outer end 77 to flex relative to a base portion 87 of the
traction
projection 61, adjacent to its base 76 for proper traction on certain ground
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surfaces. For example, on compacted snow, flexion of the outer end portion 90
of
the traction projection 61, relative to the base portion 87 of the traction
projection
61, may cause a gradual pressure variation on the snow engaged by the traction
projection 61, which may avoid a stress concentration in the snow that could
" break" the snow and result in traction loss. Basically, as shown in Figure
29B, if
the outer end portion 90 of the traction projection 61, did not flex relative
to the
base portion 87 of the traction projection 61,, an abrupt pressure variation
on the
snow engaged by the traction projection 61, would induce a stress
concentration
in the snow that could break the snow and result in traction loss. While the
transversal protrusion 55 of the traction projection 61, bends as shown in
Figure
29A, the enlarged protrusions 561, 562 of the traction projection 61, may not
bend
or bend less than the transversal protrusion 55 in the track's longitudinal
direction
due to their size. The flexibility of the transversal protrusion 55 of the
traction
projection 61, in the longitudinal direction of the track 41 may be useful on
other
types of snow (e.g., medium-density snow if the track 41 undergoes high-speed
spinning) or other types of grounds (e.g., hard terrain where this flexibility
may
give more traction into terrain details).
Also, in this embodiment, as shown in Figure 30A, the traction projection 61,
allows the track 41 to be relatively stiff without being rigid in its
widthwise
direction to provide proper traction as well as moderate side support on
certain
ground surfaces. For instance, on compacted snow, this results in a gradual
pressure variation which may avoid a stress concentration in the snow that
could
break the snow and cause a loss of traction. In contrast, as shown in Figure
30B,
if the traction projection 61õ was too flexible in the widthwise direction of
the track
41, although it would have high side support, the track 41 could bend too much
in
its widthwise direction and cause an abrupt pressure variation resulting in a
stress concentration that could lead to traction loss. Conversely, as shown in
Figure 30C, if the track 41 was rigid in its widthwise direction, floatation
could be
maximized but there would be little or no side support.
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The traction projections 611-61m may be configured in various other ways in
other
embodiments.
For example, in other embodiments, the enlarged protrusions 561, 562 of each
of
the traction projections 611-61m may have any other suitable shape. In other
embodiments, a traction projection 61, may comprise any other number of
enlarged protrusions such as the enlarged protrusions 561, 562 (e.g., only one
or
three or more). In yet other embodiments, a traction projection 61, may not
comprise any enlarged protrusion such as the enlarged protrusions 561, 562.
As another example, in other embodiments, the enlarged protrusions 561, 562 of
a traction projection 61; and the enlarged protrusion 561, 562 of a traction
projection 61j succeeding the traction projection 61; in the longitudinal
direction of
the track 41 may be aligned with one another in the widthwise direction of the
track 41 and arranged such that, when the traction projections 61, 61j are on
the
ground, the enlarged protrusions 561 of the traction projections 61, 61j touch
one
another and/or the enlarged protrusions 562 of the traction projections 61,
61j
touch one another (i.e., the longitudinal gaps 721, 722 discussed above become
closed such that the enlarged protrusions 561 of the traction projections 61,
61j
become contiguous and/or the enlarged protrusions 562 of the traction
projections 61, 61j become contiguous when the traction projections 61, 61j
are
on the ground).
As another example, in other embodiments, the cross-section and the material
properties of the elastomeric material 69 of the transversal protrusion 55 of
a
traction projection 61, may respectively have any other suitable shape and/or
any
other suitable values. For instance, in other embodiments, the height Ht_t of
the
cross-section of the transversal protrusion 55 of a traction projection 61,
may be
lower and the modulus of elasticity Et and/or the hardness St of the
elastomeric
.. material 69 of the transversal protrusion 55 may be higher.
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As another example, in other embodiments, as shown in Figure 31, a traction
projection 61, may have an internal cavity 82 to increase the area moment of
inertia It of the cross-section of the traction projection 61, while keeping
the
weight of the traction projection 61, relatively low. Basically, the internal
cavity 82
allows more area of the cross-section of the traction projection 61, to be
spread
outwardly, thus increasing its area moment of inertia It (e.g., the cross-
section of
the traction projection 61, may be wider and/or higher). In some cases, as
shown
in Figure 31, the internal cavity 82 may be left empty after manufacturing of
the
track 41 such that it constitutes a hollow cavity. The internal cavity 82 may
be
formed, for instance, by placing an insert (e.g., a rod) where the internal
cavity 82
is to be created during molding of the track 41 and by removing the insert
after
molding of the track 41 to reveal the hollow cavity. In other cases, as shown
in
Figure 32, the internal cavity 82 may contain a filler 84 having a density
lower
than that of the elastomeric material 69 of the cross-section of the traction
projection 61, such that the weight of the traction projection 61, is less
than if the
cavity 82 was omitted and replaced by more of the elastomeric material 69. For
instance, in some examples of implementation, the filler 84 may be a foam
material. In other examples of implementation, the filler 84 may comprise a
rod, a
roll of fabric, cord or fiber glass, or any other suitable material.
As another example, in other embodiments, as shown in Figure 33, the
elastomeric material 69 of a traction projection 61, may be a composite
elastomeric material to control its modulus of elasticity E. The composite
elastomeric material 69 is constituted of an elastomer matrix (e.g., a rubber
matrix) 86 in which reinforcements 891-89R are disposed. For instance, in some
embodiments, the reinforcements 891-89R may be arranged such that the
modulus of elasticity Et is greater in one part of the traction projection 61,
than in
another part of the traction projection 61,. For example, in this embodiment,
the
modulus of elasticity Et is greater in the base portion 87 of the traction
projection
61, adjacent to its base 76 than in the outer end portion 90 of the traction
projection 61, adjacent to its outer end 77 such that the base portion 87 is
more
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rigid than the outer end portion 90, which is more flexible. This is achieved
by
providing a greater concentration of the reinforcements 891-89R in the base
portion 87 than in the outer end portion 90 (which may have none of the
reinforcements 891-89R).
In this embodiment, the composite elastomeric material 69 is a fiber-
reinforced
elastomeric material 69 such that the reinforcements 891-89R are fibers. For
instance, in some cases, each of the fibers 891-89R may extend along at least
a
majority of the length of the traction projection 61.. In other cases, the
fibers 891-
89R may be shorter (e.g., the fibers 891-89R may be "chopped" or otherwise cut
fibers which are few millimeters or centimeters long and are distributed
throughout the traction projection 61,). The fibers 891-89R may be implemented
in
various manners. For example, in some embodiments, the fibers 891-89R may be
polymeric fibers (e.g., aramid fibers, polyvinyl alcohol (PVA) fibers, etc.),
bamboo
fibers, metallic fibers, carbon fibers, glass fibers, etc.
As another example, in other embodiments, as shown in Figure 34, the
elastomeric material 69 of a traction projection 61, may be cellular
elastomeric
material (e.g., cellular rubber) which contains cells (e.g., bubbles) 961-98c
created by introducing a gas (e.g., air) or a gas-producing agent (e.g.,
sodium
bicarbonate) during manufacturing of the cellular elastomeric material 69 to
reduce weight of the material. The cells 961-96c of the cellular elastomeric
material 69 may include closed cells and/or open cells.
As another example, in other embodiments, the traction projections 611-61m may
have any other suitable shape. For example, in some embodiments, as shown in
Figure 35, the cross-section (e.g., of the transversal protrusion 55) of a
traction
projection 61õ may be a flanged cross-section, which includes one or more
flanges and one or more webs, to increase its area moment of inertia It. For
instance, in this embodiment, the cross-section of the traction projection 61,
is an
I-shaped cross-section with top and bottom flanges 941, 942 and a web 95. As
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another example, in some embodiments, as shown in Figure 36, the cross-
section (e.g., of the transversal protrusion 55) of a traction projection 61x
may
have a generally convex outer surface 92 which may help to promote gradual
pressure variation and thus reduce stress concentration when the track 41 is
on
certain types of ground surfaces, such as compacted snow, similar to what was
discussed above.
While in this embodiment the track assembly 16; is part of an AN, in other
embodiments, a track assembly, including an endless track, constructed
according to principles discussed herein may be used as part of track
assemblies
of other types of off-road vehicles. For example, in some embodiments, as
shown in Figure 37, an endless track 141 constructed according to principles
discussed herein may be used as part of a track assembly 116 of a snowmobile
110.
The AN 10 and the snowmobile 110 considered above are examples of
recreational vehicles. While they can be used for recreational purposes, such
recreational vehicles may also be used for utility purposes in some cases.
Also,
while these examples pertain to recreational vehicles, a track assembly,
including
an endless track, constructed according to principles discussed herein may be
used as part of track assemblies of off-road vehicles other than recreational
ones.
Any feature of any embodiment discussed herein may be combined with any
feature of any other embodiment discussed herein in some examples of
implementation.
Although various embodiments and examples have been presented, this was for
the purpose of describing, but not limiting, the invention. Various
modifications
and enhancements will become apparent to those of ordinary skill in the art
and
are within the scope of the invention, which is defined by the appended
claims.
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