Note: Descriptions are shown in the official language in which they were submitted.
CA 02422483 2003-03-18
ANGLED CLIP HOLE
Field of invention
This invention relates to an endless traction band used to propel snowmobiles
or any
other tracked vehicle making use of an improved clip hole configuration which
is
designed to avoid the fraying and the dislodging of the reinforcement fibers.
Background of the invention
The present invention relates to an endless traction band for a snowmobile.
Such a
traction band is designed to travel on snow since the use of wheeled vehicle
is of little
help.
A traction band is usually made of a reinforced molded rubber material, having
longitudinally spaced and transversely disposed stiffeners embedded in the
rubber
material. The band body comprises main tensile cords, organized in a matrix,
which
have fibers extending in the longitudinal direction and are embedded in the
rubber
material to enhance the physical properties of the traction band.
The endless band is flexible around a lateral axis so that it can follow the
curvature
around the drive and idler sprocket wheels. It is designed to support a
significant
portion of the total weight of the vehicle and apply a traction force on the
ground.
The body of the traction band has a ground-engaging outer side or surface and
an
inner surface. The ground-engaging outer side usually has a sequence of
profiles that
is repeated uniformly over the total length of the traction band. Each
sequence of
profiles or tread pattern comprises laterally extending lug profiles that are
longitudinally spaced apart by flat areas. Each lug profile comprises a series
of
outwardly projecting traction lugs which influences the band behavior on the
snow,
the snowmobile performances and on the comfort of the driver
The inner surface cooperates with a suspension system and delimits the
required space
for the powering system, like for instance the sprocket wheel and the idler
wheel.
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Along the circumference of the inner surface, two rows of holes sometimes
cooperate
with the teeth of the corresponding sprocket wheels and idler wheels or
alternatively,
the sprocket wheel may mesh with driving lugs that are inwardly projecting
from the
inner side of the band.
In the case where rows of holes are required, the reinforced rubber traction
band
needs to be cut or punched by an apparatus after it has been molded. Such
holes need
to be produced with relatively clean and precise cuts and through the
reinforced
rubber body. For instance, Vargo (US3,818,789) teaches about an apparatus
which
accomplishes the hole cutting task by holding the rubber sheet under tension
during
the punch and producing the punch with a progressive shearing action as it
passes
through the rubber sheet to minimize bunching and rubber deformation.
In the past, many inventions have incorporated the metal clip technology,
which
consists in the assembly of a metal clip on an uncut area of the traction
band, defined
between two consecutive holes. For instance, Courtemanche (US6,431,666,
US6,422,665 and US5,415,470) teaches about the use of various metal clip
configurations for snowmobiles. Thompson et al. (US5,713,645) use a typical
metal
clip configuration, with each clip area separated by a hole in the track.
All the inventions cited hereinabove make or require the use of the traction
band
holes. However, none of these improvements provides a hole configuration with
an
optimized cutting configuration, in order to prevent the main tensile cords
from
having fraying fibers, as the traction band wears with time.
This invention ensures a complete and clear cut of the fibers, and therefore
avoid the
fibers to fray with time.
Summary of the invention
The object of the invention is to create an endless traction band for a
snowmobile with
an improved clip hole configuration in order to keep its inner fibers in an
organized
matrix as the traction band is used and wears out.
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The rubber body is usually reinforced by main tensile cords having fibers
running
along a longitudinal direction. Traditionally, each hole comes in a square or
rectangular shape which has sides parallel to the longitudinal direction of
the
reinforcing fibers. In these known traction bands, some fibers tend to fray or
dislodge
themselves from their rubber embedded location.
For users of snowmobiles equipped with such an endless rubber traction band,
esthetic considerations, especially related to the apparent wear of the
snowmobile or
of its component parts, including the traction band, represent a
characteristic that
helps differentiate one product from the other and this feature can turn out
to be the
choice making decision to buy a specific product.
With this invention, each hole comprises two lateral walls which provide the
proper
support for the insertion and positioning of each metal clip. The walls of the
holes
allow a clear and complete cut of the fibers. A tapered head is therefore
created at the
cut fiber's extremity, giving it less tendency to fray or dislodge itself from
its
embedded rubber position.
In a preferred embodiment, each hole preferably has an hexagonal shape having
two
sides destined to provide support for the metal clips, and having four of its
sides not
parallel with the reinforcing fibers. Other side wall configurations may be
used, like
for instance arched sides or indented sides.
There is therefore provided an improved traction band for use with a
snowmobile,
comprising:
a) a central band portion, which extends longitudinally along the
circumference of said traction band,
b) a pair of lateral band portions which extend longitudinally along the
circumference of said traction band and are located on each side of said
central band portion,
c) reinforcing fibers having a fiber direction and which are embedded in said
traction band in an organized matrix;
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d) holes through said traction band, each of which defines a hole shape
having lateral walls and side walls, said side walls having a side wall
direction;
wherein said side wall direction, is not parallel to said fiber direction.
Other aspects and many of the attendant advantages will be more readily
appreciated
as the same becomes better understood by reference to the following detailed
description and considered in connection with the accompanying drawings in
which
like reference symbols designated like elements throughout the figures.
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 figures
Figure 1 is a top view showing angled clip holes on an endless traction band
in
accordance with the invention.
Figure 2 is a section view taken from line 2-2 of figure 1.
Figure 3 is a detail view taken from enclosure 3 of figure 1.
Figure 4 is a top view showing one of the prior art traction band having
rectangular
clip holes.
Figure 5 is a detail view taken from enclosure 5 of figure 1.
Figure 6 is a detail view showing another embodiment of the invention taken
from
the enclosure 5 of figure 1.
Figure 7 is a detail view showing another embodiment of the invention taken
from
the enclosure 5 of figure 1.
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Figure 8 is a detail view showing another embodiment of the invention taken
from
the enclosure 5 of figure 1.
Figure 9 is a detail view showing a first angle configuration of the preferred
embodiment taken from the enclosure 9 of figure 3.
Figure 10 is a partial view of the view shown in figure 9.
Figure 11 is a detail view showing a second angle configuration of the
preferred
embodiment taken from the enclosure 9 of figure 3.
Figure 12 is a partial view of the view shown in figure 11.
Detailed description of a preferred embodiment
A traction band equipped with angled clip holes is described hereinafter
according to
a preferred embodiment of the present invention and illustrated in the
appended
figures.
As shown in figures 1 and 2, the band 100 is made of an endless body 102 of
reinforced rubber material, with longitudinally spaced and transversely
disposed
stiffeners 104 that may or may not be completely embedded in the rubber
material of
the endless body 102. The body 102 comprises a central portion 150 and two
lateral
band portions (160 and 170) which are located on each side of the central
portion 150.
The central portion 150 and the lateral band portions (160 and 170)
longitudinally
extend along the circumference of the endless body 102.
The body 102 of the band 100 has a ground-engaging outer side 108 comprising a
selection of different lug profiles 110 which are separated from each other by
a flat
area 130. The lug profiles 110 and their relative arrangement with respect to
one
another, on the traction band 100, affect the band 100 behavior on the ground
and the
general snowmobile driving comfort which help differentiate one product from
the
other for the customer.
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The inner side 106 offers an inner surface 116 and a plurality of guide lugs
126. which
cooperate with the sprocket/wheel system (not shown) to provide a sliding
surface and
ensure power transmission to the traction band 100. The guide lugs 126 are
preferably
disposed in rows and at a pre-determined interval (not shown) from one another
along
the circumference of the traction band 100.
The central portion 150 and each lateral . portion (160 and 170) are separated
by a
circumferentially extending clip-hole portion 180. Each clip hole portion 180
is made
from a succession of holes 185 through the body 102 and are separated from
each
other by clip areas 195. A clip area 195 is an area of the rubber body 102,
located in
the clip hole portion 180, which has not been cut or molded to form a hole 185
and
onto which a metal clip 198 is mounted. The holes 185 have certain size and
configuration requirements to allow the insertion of the metal clips 198 and
sometimes, to avoid the interference of the rotating toothed wheels (not
shown) as
they mesh with the endless traction band 100.
The rubber body 102 is usually reinforced by fabric and cords (some shown in
figure
2) organized in a matrix of reinforcing fibers 112, many of which usually run
along a
longitudinal direction. The longitudinally extending reinforcing fibers 112
will have a
tendency to fray or partially dislodge themselves from their rubber embedded
location.
Figure 4 illustrates a typical case from the prior art, showing how a traction
band 40
equipped with metal clips 46 reacts to use and wear with regards to the holes
48 made
through the rubber body 41. Traditionally, each hole 48 comes in a square or
rectangular shape. The side walls 44 of the holes 48 are in a generally
parallel
direction to the longitudinal direction of the reinforcing fibers (not shown).
In such
prior art bands, loose fibers 42 will detach themselves from their rubber
containment
through the side walls 44. In another case, if a fiber (not shown) as been
incompletely
cut or at an uncontrolled angle, the wrongly cut extremity (not shown) will
have a
tendency to fray.
For users of snowmobiles equipped with such an endless rubber traction band
100,
any esthetic consideration, especially related to the wear of apparent
features of the
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snowmobile, represents a characteristic that helps differentiate one product
from the
other and can turn out to be the choice making decision to buy a specific
product.
Figure 3 and 5 describe into details the preferred embodiment, which comprises
a hole
185 configuration with side walls 186 oriented at an angle with respect to the
reinforcement fibers 112. It has been found that the use of clip holes 185
having an
hexagonal shape is particularly useful. The two lateral walls 188 provide the
proper
lateral length 180 of the clip area 195, which then offers the same typical
lateral
support for the assembly of any metal clips 198.
Other side wall shapes may offer an acceptable hole configuration to prevent
the
fibers from fraying. In the embodiments shown in figure 6, the holes 285 are
defined
with lateral walls 288 and side walls 286 having an arched configuration to
provide a
complete tapering of the reinforcing fibers 212.
Figure 7 illustrates another embodiments where the side walls 386 are indented
in a
zigzag shape to ensure complete tapering of the fibers 312. The lateral walls
388 keep
the same configuration to allow insertion of metal clips (not shown).
In still another embodiment shown in figure 8, the fabric and cords are
positioned in
such a way that the reinforcing fibers 412 extend at an angle with respect to
the side
walls 486 of the holes 485. In this configuration, the hole 485 shape can
still adopt
any combination of side walls 486 and lateral walls 488, even the traditional
square or
rectangular shape, and generally prevent the occurrences of loose and fraying
fibers in
the holes 485
In the embodiments shown in Figure 5, 6, 7 and 8, the side walls (186, 286,
386, 486)
are not parallel to the reinforcing fibers (112, 212, 312, 412). The process
to produce
the holes (185, 285, 385, 485) generates fiber extremities (114, 214, 314,
414) which
are tapered at an angle with respect to the side walls (186, 286, 386, 486).
The relative
angle a between the side walls (186, 286, 386, 486) and the fibers (112, 212,
312,
412) is preferably selected between 5 to 90 degrees. However, one of the main
criteria
to evaluate the minimal angle a is to ensure that the tapered fiber extremity
(114, 214,
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314, 414) will have a length no more than the quarter of the distance between
two
lateral walls (188, 288, 388, 488).
For instance, in the preferred embodiment of Figure 5, the distance between
the two
lateral walls 188 is 1.5 inches and a fiber 112 has a diameter of 1/16 inches.
An angle
a of approximately 9.5 degrees or more will ensure a completely tapered fiber
extremity 114 along a side wall 186, before a quarter of the distance between
the two
lateral walls 188 has been covered.
The general criteria to establish the value of the angle a is that the side
walls 186
should not be parallel to the fibers 112 to help reduce the fraying of the
fibers 112. A
smaller angle a has the advantage of clear-cutting the reinforcing fibers 112
to prevent
them from fraying and without removing too much rubber material to the
traction
body 102 when compared to the traditional square or rectangular hole 48 from
the
prior art, as seen in figure 4. However, a larger angle a may result in a cost
reduction
for the customer since larger holes necessitate less material to mold a
traction band
100 with the advantage of still having completely tapered fibers extremities
114. A
larger hole 185 also provides more space for the metal clip (not shown)
insertion and
in the case where the rows of holes cooperate with the teeth of the
corresponding
sprocket wheels and idler wheels (not shown), a traction band 100 with larger
holes
offers less friction than the traditional traction band of the prior art with
rectangular
holes.
As the traction band operates with time, the tapered fiber extremities 114
generated
when producing each hole 185 can be affected by wear, dirt, and environmental
conditions. Figures 9, 10, 11 and 12 illustrates how each tapered fiber
extremity 114 is
subjected to external forces 133 which normally induce the fraying of the
fibers 112 in
a traction band from the prior art. These forces 133 comprise a compression
component (133b,133d) and a shear component (133a,133c) which affect the
tapered
fiber extremity 114 and the walls (186,188) of each hole 185. The angle al of
Figures
9 and 10 is smaller than the angle a2 of Figure 11 and 12. It is believed that
the shear
component wears the rubber material of the side walls 186 more than the
compression
component. For a2 the shear component 133c is larger than the shear component
133a
of a,. It has therefore been found that it is preferable to select a smaller
angle, like al,
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in the range of 5 to 45 degrees, even if a larger angle, like a2 still
achieves the object
of the invention.
Although a preferred embodiment of the invention has been described in detail
herein
and illustrated in the accompanying figures, it is to be understood that the
invention is
not limited to this precise embodiment and that various changes and
modifications
may be effected therein without departing from the scope or spirit of the
present
invention.
