Note: Descriptions are shown in the official language in which they were submitted.
'- 21 82845
-- 1 --
TITLE OF THE INVENTION
Snowmobile drive track.
FIELD OF THE INVENTION
The present invention pertains to a snowmobile drive track
5 and, more particularly, to a track for snowmobiles having an improved tread
configuration on its outer side.
BACKGROUND OF THE INVENTION
Snowmobile tracks are formed of an assembly of a molded
rubber base having, embedded therein, one or more layers or reinrorcing
10 fabric and a series of bars that extend crosswise of the track in central andlateral portions thereof. These crossbar portions display a series of raised
profiles, each defining a ground engaging projection which provides traction
and control to the track. These projections are a source of noise at certain
rotational speeds of the endless track. Indeed, at speeds of between 40 and
15 70 mph, noise produced by the track is heard; above 70 mph, the motor
noise usually overtakes the track noise.
OBJECT AND STATEMENT OF THE INVENTION
It has been found that this track noise can be greatly reduced
if the noise frequency generated by the track profiles is decreased thus
20 providing comfort to the driver and to the environment.
21 82845
-- 2
It is therefore an object of the present invention to provide the
outer side of a snowmobile drive track with a tread configuration that
includes profile-free regions to reduce this frequency and effect noise
reduction.
The present invention therefore relates to a snowmobile drive
track which consists of an endless body having a ground engaging outer
side and a suspension supporting inner side; the body defines a central
portion and opposite lateral portions interconnected by a plurality of
longitudinally spaced suspension bearing portions; the body also displays
0 a plurality of longitudinally spaced crossbar receiving areas extending
crosswise of the body in its central, lateral and suspension bearing portions,
each crossbar receiving area displaying, on the outer side of the body,
integrally formed pr~,e~ting profiles; the profiles of three successive crossbarreceiving areas define a tread pattern which is identically repeated on all
sllccessive threesome of crossbar receiving areas. The profiles of at least
one of the three successive crossbar receiving areas differ in configuration
from the profiles of the other while each crossbar receiving area includes a
profile-free region thereon.
Most snowmobile tracks are presently configured with a 48 or
a 54-pitch design; hence, the tread pattern of the present invention is
adaptable to such tracks.
Other objects and further scope of applicability of the present
invention will become apparent from the detailed description given
hereinafter. It should be unde,~lood, however, that this detailed description,
while indicating preferred embodiments of the invention, is given by way of
illustration only, since various changes and modifications within the spirit
and scope of the invention will become apparent to those skilled in the art.
21 û2~45
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a portion of a snowmobile
track bearing a tread design made in accordance with the present invention;
Figure 2 is a top plan view showing part of the ground
5 engaging outer side of the track; and
Figure 3 is a cross sectional view taken along lines 3-3 of
figure 2.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to figure 1, there is shown, in part, an endless
10 snowmobile track, generally denoted 10, for propelling a snowmobile over
snow, ice, or other similar ground structure. The mounting of this track to a
snowmobile is well known and needs not be detailed. The track has a
ground engaging outer side 12 and an inner side 14 that receives and
supports, on the lower run thereof, a suspension which may consist of a
15 wheel assembly or a slide rail assembly, both of which are also well known
in the art.
Conventionally, the track rotates by means of a motor driven
sprocket unit at the forward end of the vehicle and idle drive wheels are
mounted at the aft end of the vehicle to support the rear end of the track.
2 o Sprockets engage a series of lugs 15 integrally formed with the inner surface
of the track.
As illustrated in figure 2, the track defines a pair of opposite
lateral portions 16 and 18 and a central portion 20. These portions are
" 21 82845
interconnected by a plurality of longitudinally spaced suspension bearing
po, lions 22 and 24 which are each partially covered by metallic clips 26, 28.
These clips may have various forms; however, they are structured so that,
in the case of a slide rail suspension system, the rails that support the
5 chassis of the snowmobile slide on the rear faces 26', 28' of the clips. Such
clips may be found described in U.S. patent No. 4,474,414 issued October
2,1984 to Tokue.
The snowmobile track 10 also defines a plurality of crossbar
receiving areas 30 that extend through the central, lateral and suspension
10 bearing portions of the track. Referring to figure 3, these areas incorporate a crossbar 32 which preferably consists of a rod, made of composite
material, having a shape as illustrated with rounded corners. In the track
illustrated in figure 2, six crossbar receiving areas have been identified as
30a, 30b, 30c, 30d, 30e and 30f.
As can be seen in figure 3, the track is formed of an assembly
of a molded rubber base 34 and two layers of reinforcing fabric 36 and 38.
Some tracks may also include a plurality of longitudinally extending cords.
The reil,rorc;ng fabric is a woven fabric of synthetic fibers while cords,when
present, may be plastic or metal.
Referring to figure 2, the crossbar receiving areas 30a-30f
each display an arrangement of a trapezoidal-shaped profile region and a
profile-free region. For example, the crossbar receiving area 30a displays
two profiles 42 and 44; the crossbar receiving area 30b also displays two
crossbars 46 and 48 while the crossbar receiving area 30c displays three
profiles 50, 52 and 54. A profile-free region 56 is present between the
profiles 42 and 44 while a second profile-free region 58 is provided between
the two profiles 46 and 48. On the other hand, there are two profile-free
- 2 1 82845
-- 5
regions 60 and 62 between the profiles 50 and 52 and the profiles 52 and
54.
This arrangement of profiles and profile-free regions defines
a tread pattern which is repeated identically on the three successive
s crossbar receiving areas 30d, 30e and 30f as well as on the remaining
crossbar receiving areas.
In the embodiment illustrated, profiles 42 and 44 have the
same width but their width is different from that of profiles 46 and 48 so that
the profile-free region 56 is less wide than the profile-free region 58 of the
crossbar receiving area 30b. The profiles 50 and 54 of the crossbar
receiving area 30c extend only in the lateral portions 16 and 18 of the track
while the profile 52 extends in the central region of the track where are also
provided the two profile-free regions 60 and 62.
With this particular tread configuration, there is no profile-free
region which is present at the same location when viewed in the longitudinal
direction of the track. In both opposite lateral portions of the track 16 and
18, there is a profile for each crossbar receiving area while, in the central
portion 20 of the track, the profile-free regions are located at different places
so that the side edge 52a of trapezoidal profile 52 is closer to the sprocket
receiving portion 24 than the side edges 46b and 42b of profiles 46 and 42.
On the other hand, the side edges 42a, 46a and 50a are ~ cent the side
edge 10a of the track while the side edges 44b, 48b and 54b are ~rlj~cent
the side edge 10b of the track. Referring to figure 3, each profile includes
a leading wall and a trailing wall; for example, profile 42 has a leading wall
70 and a trailing wall 72. These walls include a series of vertical reinforcing
ribs 74 and 76 respectively, the function of which is described and claimed
in a copending application of applicant filed concurrently herewith.
Pleferably, the profiles include a V-shaped outline 78 with the apex being on
21 82845
-- 6
the leading wall of the profile. Similarly, the top edge of the profiles in the
area of the slide bearing portions 22 and 24 are preferably corrl~g~ted
Although the invention has been described above with respect
with one specific form, it will be evident to a person skilled in the art that it
5 may be modified and refined in various ways. For example, it is possible to
have a tread pattern where two of the three successive crossbar receiving
areas have the same profile configuration, but which is different from that of
the third crossbar receiving area. It is tt ,erefore wished to have it u nderslood
that the present invention should not be limited in scope, except by the terms
10 of the following claims.
