Note: Descriptions are shown in the official language in which they were submitted.
CA 02566225 2006-10-30
File number: 04 104-1 1 1
Revision: As Filed
Date: 2006/10/30
Title of the Invention
[0001] Elastomeric Track.
Cross-Reference to Related Applications
[0002] There are no cross-related applications.
Field of the Invention
[0003] The present invention generally relates to tracked vehicles which use
elastomeric
tracks for propulsion. More particularly, the present invention relates to the
elastomeric
tracks used on such tracked vehicles. Without being limitative in nature, the
present
invention particularly relates to elastomeric tracks for use on heavy tracked
vehicles (i.e.
vehicles weighing 5000 kg or more) such as military vehicles (e.g. tanks and
transport
vehicles) and heavy machinery (e.g. excavators, bulldozers, forestry
equipments).
Background of the Invention
[0004] Conventionally, elastomeric tracks used on tracked vehicles are
composed of a
main elastomeric track body having reinforcing elements embedded therein. The
reinforcing elements now used come in a variety of forms such a reinforcing
web or
fabric, reinforcing cables or strips and stiffening rods just to name few.
[0005] Moreover, prior art tracks also generally define a ground engaging
outer surface
and a wheel engaging inner surface. As it is commonly known, the outer surface
is
generally provided with a pattern of ground engaging traction lugs. The
pattern and the
shape of the traction lugs are generally designed for particular uses and
therefore can vary
according to the terrain upon which the vehicle adapted to be ridden.
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[0006] As mentioned above, the inner surface of the track is generally adapted
to
cooperate with a sprocket wheel and also generally with road and/or idler
wheels.
Though different configurations of inner surfaces exist, in a large number of
tracks, the
inner surface is generally provided with outwardly projecting drive lugs
adapted to
drivingly mate with the sprocket wheel. The inner surface can also be provided
with
guide lugs (also referred to as guide horns) which are generally adapted to
guide the track
in order to prevent occurrences of detracking. Generally, the guide lugs are
not used to
drive to the track.
[0007] Elastomeric tracks of the aforementioned configuration are used on a
plurality of
vehicles. For example, it is not uncommon to find elastomeric tracks on
snowmobiles,
skid-steer and even tanks. However, in order to accommodate the increase in
size, weight
and power, tracks used on large and/or heavy vehicles are generally made with
a thicker
body which generally provides greater support for the vehicle and better
resistance to the
strain to which the track is subjected. Yet, having a thicker body brings
problems which
are generally non-existent in tracks used on smaller vehicles such as, but not
limited to,
snowmobiles.
[0008] For example, as the body of the track gets thicker, the distance
between the
neutral axis of the band, where the reinforcing elements are generally
located, and the
base of the drive lugs, correspondingly increases due to the additional
elastomeric
material.
[0009] However, as this distance increases, the drive lugs are subjected to
greater
momentum when longitudinal forces are applied thereto. As the momentum
increases,
the drive lugs are more prone to flexion and elastic deformation. This
increased
deformation generally reduces the efficiency of the power transmission between
the
sprocket wheel and the drive lugs since a portion of the energy is lost in the
elastic
deformation of the drive lugs.
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[0010] Moreover, due to the increased deformation, there is an increased
probability of
occurrences of drive lugs skipping (also referred to as "teeth skipping" or
"sprocket
skipping"). Understandably, drive lugs skipping must generally be avoided in
order to
prevent premature damages to the track and undesirable noise but, more
particularly,
because it is limiting the power that can be effectively transmitted to the
ground.
[0011 ] Yet, to date, no one has provided an elastomeric track for use
particularly but not
exclusively on large and/or heavy vehicles which reconciles the need for
thicker track and
at the same time the need for an efficient power transmission while keeping
drive lugs
skipping to a minimum. Therefore, there is still a need for an improved
elastomeric track
which generally reconciles the aforementioned characteristics.
Objects of the Invention
[0012] Accordingly, an aspect of the present invention is to provide an
elastomeric track
for use on tracked vehicles which generally increases the efficiency of the
transmission of
power between the sprocket wheel and the track.
[0013] Another aspect of the present invention is to provide an elastomeric
track for use
on tracked vehicles which generally decreases the occurrences of drive lugs
skipping
(also referred to as "teeth skipping" or "sprocket skipping").
[0014] Still another aspect of the present invention is to provide an
elastomeric track for
use on tracked vehicles which generally reduces drive lugs elastic deformation
when the
drive lugs are subjected to longitudinal forces.
[0015] Other and further objects and advantages of the present invention will
be obvious
upon an understanding of the illustrative embodiments about to be described or
will be
indicated in the appended claims, and various advantages not referred to
herein will occur
to one skilled in the art upon employment of the invention in practice.
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File number: 041 04-1 1 1
Revision: As Filed
Date: 2006/10/30
Summary of the Invention
[0016] Accordingly, the present invention consists of an elastomeric track. As
used
hereinabove and hereinafter, the term "elastomeric" relates to any generally
elastic and
primarily non metallic materials such as natural and/or synthetic rubber,
elastomers, or
other polymers and/or combinations thereof used in the manufacture of tracks.
[0017] The elastomeric track of the present invention generally comprises a
main body
which defines a ground engaging outer surface and a wheel engaging inner
surface. The
track body also generally comprises reinforcing elements embedded therein.
Though
other configurations are also possible, the reinforcing elements are generally
located
along the neutral axis of the track.
[0018] As known in the art, the neutral axis is the zero strain zone of a
flexed or bent
element. Thus, in the context of the present invention, the neutral axis of
the track is the
zone, along its thickness, which is subjected neither to compression nor
tension when the
track bends, for example, around the sprocket wheel.
[0019] In order to provide traction to the vehicle onto which the track is
mounted, the
ground engaging outer surface is preferably provided with ground engaging
traction lugs.
The traction lugs are generally disposed on the outer surface of the track
according to a
pattern which is chosen depending on the terrain upon which the vehicle is
used.
Understandably, the traction lugs can come in a plurality of shapes according
to the
intended use of the track. The present invention is not limited to any
particular shape of
traction lugs.
[0020] The inner surface of the track is generally adapted to cooperate with
at least a
sprocket wheel and also preferably with road and/or idler wheels. The inner
surface of the
track generally comprises one or more rows of preferably longitudinally
aligned drive
lugs which are adapted to drivingly mate with the sprocket wheel in order to
effect the
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transmission of power between the sprocket wheel and the track. Preferably,
but not
exclusively, the drive lugs are disposed near the side edges of the track.
[0021] Furthermore, the inner surface of the track also preferably comprises
at least one
row of longitudinally aligned guide lugs or horns. The guide lugs are
preferably
generally centrally located with respect to the width of the track though
other
configurations are also possible. The guide lugs are generally used to guide
the track
over the sprocket, road and idler wheels and hence, to prevent detracking.
Accordingly,
the guide lugs are generally neither adapted nor used to drive the track.
[0022] According to an aspect of the present invention, the inner surface of
the track is
generally divided into three areas or portions. It is however to be understood
that even if
the track defines a plurality of areas, the track still forms a single unitary
body. Hence,
the inner surface comprises a generally longitudinally extending central area
and two
generally longitudinally extending lateral areas, each of which being
respectively located
on each side of the central area. Other division patterns are also possible
and within the
scope of the invention.
[0023] According to another aspect the present invention, the drive lugs are
generally
longitudinally disposed on the lateral areas of the inner surface. Also,
should the inner
surface be further equipped with guide lugs, they would preferably be
longitudinally
disposed along the central area. Still, other configurations are also
possible.
[0024] Yet, according to an important aspect of the present invention, the
thickness of the
track body and more particularly the thickness of the track body, or track
material,
between the neutral axis and the inner surface along the lateral areas is
thinner than the
thickness of the track body and more particularly the thickness of the track
body, or track
material, between the neutral axis and the inner surface along the central
area.
[0025] Consequently, the drive lugs and more particularly their bases are
located nearer
the neutral axis. By being so located, the momentum created by the
longitudinal forces
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Revision: As Filed
Date: 2006/10/30
applied to the drive lugs when they mate with the sprocket wheel is reduced.
This
reduction in momentum is translated in a reduction of the flexion and elastic
deformation
of the drives lugs. By reducing this flexion and elastic deformation of the
drives lugs,
less energy lost in the elastic deformation thereof, thereby generally
increasing the
efficiency of the power transmission between the sprocket wheel and the drive
lugs.
Moreover, since the drive lugs are less flexed and elastically deformed, the
track is less
prone to drive lugs skipping.
[0026] Moreover, by having the bases of the drive lugs located nearer to the
neutral axis
of the track, there is more latitude in the design of the drive lugs, more
particularly with
respect to their size and shape. Accordingly, the present invention generally
allows the
design of elastomeric tracks wherein the drive lugs are particularly designed
to reduce
drive lugs skipping and also to reduce interference between the drive lugs and
the
sprocket wheel when they drivingly mate with each other. An example of such
drive lugs
is disclosed in U.S. Patent No. 4,605,389 (Westhoff).
[0027] Understandably, in order to take into account the specific
configuration of the
inner surface of the track, the outer perimeters of the sprocket wheel and
possibly of the
road and idler wheels, are configured to be substantially conformed with the
configuration of the inner surface of the track.
[0028] The features of the present invention which are believed to be novel
are set forth
with particularity in the appended claims.
Brief Description of the Drawings
[0029] The above and other objects, features and advantages of the invention
will
become more readily apparent from the following description, reference being
made to
the accompanying drawings in which:
[0030] Figure 1 is a perspective view of the inner surface of a portion of a
prior art track.
[0031] Figure 2 is a cross-sectional view of the prior art track of Fig. 1.
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Revision: As Filed
Date: 2006/10/30
[0032] Figure 3 is a perspective view of the inner surface of a portion of a
track
according to an embodiment of the present invention.
[0033] Figure 4 is a cross-sectional view of the portion of the track of Fig.
3.
[0034] Figure 5 is a fragmentary perspective view of a portion of the track of
Fig. 3 in
cooperation with a sprocket wheel.
[0035] Figure 6 is a side view of a portion of the track of Fig. 3 in
cooperation with a
sprocket wheel.
[0036] Figure 7 is a cross-sectional view of a portion of the track and
sprocket wheel
along line A-A of Fig. 6.
[0037] Figure 8 is perspective view of the track of Fig. 3 as installed on a
vehicle.
Detailed Description of the Preferred Embodiment
[0038] A novel elastomeric track will be described hereinafter. Although the
invention is
described in terms of a specific illustrative embodiment, it is to be
understood that the
embodiment described herein is by way of example only and that the scope of
the
invention is not intended to be limited thereby.
[0039] In order to best understand the novel track 200 of the present
invention, it is
necessary to understand how prior art track 100 are generally designed.
Therefore,
referring first to Fig. 1, a prior art track 100 is shown. As commonly known,
the track 100
comprises a main track body 105 defining an outer surface 102 and an inner
surface 104.
[0040] Located on the outer surface 102 and generally longitudinally disposed
is a
plurality of traction lugs 110.
[0041] For its part, the inner surface 104 generally comprises a row of
longitudinally
aligned guide lugs 130, generally centrally located with respect to the width
of the track
100, and generally two rows of longitudinally aligned drive lugs 120,
generally located
near or adjacent to each side edge of the track 100.
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[0042] The guide lugs 130 are generally adapted to guide the track 100 over
the sprocket,
road and idler wheels (not shown). Accordingly, they are generally neither
adapted nor
used to transmit power from the sprocket wheel to the track 100.
[0043] Contrary to the guide lugs 130, the drive lugs 120 are generally
specifically
designed to matingly cooperate with the sprocket wheel of the vehicle (not
shown) on
which the track 100 is mounted in order to effectively transmit the power from
the
sprocket wheel to the track 100.
[0044] Furthermore, to provide space for the wheels, the drive lugs 120 and
guide lugs
130 are preferably laterally spaced apart in order to define wheel paths 140
therebetween.
[0045] Now referring to Fig. 2, the body 105 of the track 100 generally
further comprises
reinforcing elements 180, generally in the form of longitudinally extending
cables. These
reinforcing elements 180 are generally located at the neutral axis 103 of the
body 105.
The neutral axis is the zone of the body 105 which is subjected neither to
traction nor to
compression when the track 100 is bent.
[0046] Still referring to Fig. 2, the thickness 107 of the body 105 between
the neutral axis
103 in the inner surface 104 along the central area 150 (see also Fig. 1) is
the same as the
thickness 109 of the body 105 between the neutral axis 103 in the inner
surface 104 along
the lateral areas 150.
[0047] Now referring to Fig. 3, an embodiment of the track 200 according to
the present
invention is shown. As for track 100, the track 200 similarly comprises a main
track body
205 also defining an outer surface 202 and an inner surface 204.
[0048] Similarly to track 100, the outer surface 202 of the track 200
comprises a plurality
of traction lugs 210 preferably longitudinally disposed along the length of
the track 200.
Still, the exact pattern and shape of the traction lugs 210 are not the
subject of the present
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invention and accordingly, the invention shall not be limited to the pattern
and shape
shown herein.
[0049] Still referring to Fig. 3, according to the preferred embodiment of the
present
invention, the inner surface 204 is preferably divided into three areas: a
central area 250
and two lateral areas 260 located on each side of the central area 250.
[0050] Preferably centrally located on the central area 205 of the inner
surface 204 are a
plurality of longitudinally aligned guide lugs 230. As for guide lugs 130,
guide lugs 230
are preferably adapted to guide the track 100 over the sprocket, road and
idler wheels (not
shown) and to prevent detracking.
[0051] The inner surface 204 further comprises preferably two rows of
longitudinally
aligned drive lugs 220 which are, according to the present invention, located
along the
lateral areas 260 of the inner surface 204.
[0052] As for prior art track 100, the guide lugs 230 and drive lugs 220 are
preferably
laterally spaced apart in order to space wheel paths 240 therebetween.
[0053] Though the boundary between the central area 250 and the lateral areas
260 is
shown located adjacent the drives lugs 220, it is to be understood that the
boundary could
also be located along the wheel paths 240 between the guide lugs 230 and the
drive lugs
220.
[0054] Now referring to Fig. 4, track 200 further preferably comprises
reinforcing
elements 280, preferably located at the neutral axis 203 of the track body
205.
[0055] According to the present invention, the thickness 209 of the body 205
between the
neutral axis 203 and the inner surface 204 in the lateral areas 260 is thinner
than the
thickness 207 of the body 205 between the neutral axis 203 and the inner
surface 204 in
the central area 250.
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[0056] This particular arrangement provides several advantages. For instance,
by keeping
a thick body 205 along the central area 250, the track 200 remains resistant
enough to
sustain the strains to which it will be subjected. Yet, by having a thinner
body 205 along
the lateral areas 260, the drive lugs 220 and more particularly their bases
are located
nearer the neutral axis 203. Consequently, when the drive lugs 220 mate with
the
sprocket wheel and are hence subjected to strong longitudinally forces, the
momentum of
the drive lugs 220 with respect to the neutral axis 203 is lessened. By
reducing the
momentum, the flexion and elastic deformation of the drive lugs 220 are
reduced.
[0057] Since the drive lugs 220 are less flexed and elastically deformed,
there is less
energy lost in the elastic deformation of the drive lugs 220 and accordingly,
the
transmission of power between the sprocket wheel and the track 200 is more
efficient.
[0058] Moreover, since the drive lugs 220 are less prone to flexion and
deformation, the
likelihood of drive lugs 220 or teeth skipping is reduced.
[0059] Now referring to Figs. 5 to 7, in order to take into account the
difference between
the thickness 207 of the central area 250 and the thickness 209 of the lateral
areas 260,
the outer perimeter 310 of the sprocket wheel 300 is preferably designed to be
complementary with both the central area 250 and the lateral areas 260. As
shown in Fig.
7, a notch or step 312 can be provided for that matter. For the remaining, the
sprocket
whee1300 is generally of common construction.
[0060] Now referring to Fig. 8, the track 200 of the present invention is
shown as
installed in a exemplary manner on a military vehicle 600. As shown therein,
the track
200 is disposed around a sprocket whee1300, preferably located at the fore of
the vehicle
600, an idler wheel 500, preferably located at the aft of the vehicle 600, and
a plurality of
road wheels 400 located therebetween. Understandably, a similar arrangement is
provided on the opposite side of the vehicle 600.
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[0061] It is to be understood that the present invention is generally embodied
in endless
elastomeric tracks. Such endless elastomeric tracks generally encompass tracks
made of a
single unitary loop and also tracks made of one or a plurality of elastomeric
track
segments joined end to end.
[0062] While illustrative and presently preferred embodiment of the invention
has been
described in detail hereinabove, it is to be understood that the inventive
concepts may be
otherwise variously embodied and employed and that the appended claims are
intended to
be construed to include such variations except insofar as limited by the prior
art.
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