Track belt guide wheels assembly

Abstract

A track assembly comprising guide wheels in a region of greatest impacts on the guide rails of the track, which are also the regions of greater wearout of the guide rails, the guide wheels being further arranged in a staggered position, thereby yielding a reduction in noise generation.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority on Canadian application no 2,457,999 filed on Feb. 17, 2004.

FIELD OF THE INVENTION

The present invention relates to endless track belts. More specifically, the present invention is concerned with a track belt guide wheels assembly.

BACKGROUND OF THE INVENTION

An endless track belt assembly for propelling a snowmobile over snow, ice, or other similar ground structure typically comprises an endless elongated body made of polymeric material going around a sprocket wheel and a front wheel, and having a ground-engaging outer surface and an inner surface. The body of the belt may be reinforced with rods. The inner surface receives and supports, on a lower run thereof, a suspension comprising a plurality of guide wheels, and guide rails. The ground-engaging surface typically bears a series of spaced traction lug members or profiles, for transversal rigidity. Clips may further be provided on the profiles to enhance traction.

As may be seen in FIG. 1(A), small guiding wheels 10 are standardly positioned transversally in aligned pairs along guide rails 12 of the track, shocks being provided between the guide rails 12.

It is known that the noise generated by tracked vehicle such as snowmobiles is essentially produced by the endless belt track thereof. An analysis of a frequency spectrum of the noise generated by a tracked vehicle shows a main peak at a frequency corresponding to a driving frequency of the track belt and to harmonics thereof.

The driving frequency F_e of the track belt may be calculated from a number n of tooth of the sprocket wheel and a speed of rotation rpm of the sprocket in turn per minute, using the following relation: $F_e=\frac{n·\mathrm{rpm}}{60}$

Since the track has a constant pitch, factors that may modify the driving frequency thereof may comprise the mounting of the track on the sprocket, an action of the guiding wheels on the reinforcing rods, an action of the small guiding wheels on the guide rails, an action of the traction clips on the guide rails and an impact of the profiles with the ground, for example.

One of several methods actually contemplated for reducing an occurrence of peaks in acoustic spectra of tracked vehicle associated with repetitive events consists of breaking such repetitive sequences by causing a random spreading of the different events submitted to the track. The result is a distribution of energy on different harmonics of the critical frequency Fe.

It has been suggested to create such a random spreading by providing non-regular profiles on the ground-engaging surface of the track for example.

It has also been suggested to provide clips on each profile of the track.

There is still a need in the art for endless track belts producing reduced noise.

SUMMARY OF THE INVENTION

More specifically, there is provided an endless track belt assembly comprising an endless elongated body going around a sprocket wheel and a front wheel and having a ground-engaging outer surface and an inner surface, the inner surface receiving, on a lower run thereof, a suspension comprising a plurality of guide wheels and guide rails, wherein the plurality of guide wheels comprises guide wheels positioned transversally in ones of aligned pairs and staggered pairs in a forward region of the assembly, one of the pairs being located close to a curved region of the forward region of the assembly.

Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the appended drawings:

FIG. 1(A), labelled “Prior Art”, is a schematic diagram of an assembly according to the prior art;

FIG. 1(B) is a is a schematic diagram of an assembly according to an embodiment of the present invention;

FIG. 1(C) is a is a schematic diagram of an assembly according to a further embodiment of the present invention

FIG. 2 shows a noise frequency spectrum of an assembly as known in the art (dotted lines) and a noise frequency spectrum a vehicle of an assembly according to an embodiment of the present invention (full lines); and

FIG. 3 shows a noise frequency spectrum of an assembly as known in the art (dotted lines) and noise frequency spectrum of an assembly according to a further embodiment of the present invention (full lines).

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

There is provided an assembly for a tracked vehicle, producing reduced noise.

Tests performed on a variety of such conventional assemblies as illustrated in FIG. 1(A) show that the noise generated at the level of the guide wheels 10 is highly dependent on a positioning thereof. It is found that guide wheels located in a rear region or in a centre region of the assembly are a main source of noise. A zone situated in a forward region of the assembly is found to be a silent region.

An assembly according to the present invention is provided with guide wheels located in the forward region of the assembly.

As illustrated in FIG. 1(B), guide wheels 14 may be located in aligned pairs in the forward region of the assembly in such a way that a first group of guide wheels 14 is located close to a curved region 20 of the forward region of the assembly.

As illustrated in FIG. 1(C), the guide wheels 16 may be located in non-aligned pairs in the forward region of the assembly such a way that a first group of guide wheels 16 is located close to a curved region 20 of the forward region of the assembly. Therefore, each guide wheel of a given pair is now in a staggered position with respect to its counterpart, which contributes to cancel simultaneous occurrences of impacts.

It is found that the noise-reduction effect of such a positing of the guide wheels depends on a distance separating the two guide wheels of a pair. Along the guide rails 12, the guide wheels are laterally separated by a distance less than a distance separating two successive profiles of the track so as to avoid producing a simultaneity of impacts, and less than the pitch of the track so as to allow a sufficient time of impact between the guide wheels and the reinforcing rods.

It is found that the staggered position of the guide wheels is all the more efficient in the noise-reduction as it is applied to the pair close to a point of attachment of the assembly (see pair 22 in FIG. 1C).

Moreover, the guide wheels may be mounted inside or outside the guide rails 12. It is found that such a position relative to the guide rails, when the guide wheels are located in the forward region of the assembly, does not affect the noise generated. However, when the guide wheels are located further away from the forward region in the forward region of the assembly, either in the center region or in the rear region thereof, a mounting of the guide wheels in between the guide rails 12 results in an increased noise of production.

As may be seen in FIG. 2, such an assembly as illustrated in FIG. 1(C) allows an overall noise reduction of up to 5 dB (A), and a reduction of up to 9 dB (A) of the main peak of the frequency spectrum (compare the spectrum measured with the present assembly comprising guide wheels in a forward position in full line, with a spectrum measured with a conventional assembly as used in the art, in dotted line).

The assembly may further be improved by mounting clips in each profile of the ground-engaging surface of the track (not shown). As may be seen in FIG. 3, such an assembly is characterised by an overall noise attenuation of up to 7 dB (A), as well as by a decreasing effect on harmonics of the drive frequency of the track (compare the spectrum measured with the present improved assembly comprising clips in each profile in dotted line, with a spectrum measured with a conventional assembly comprising clips in each three profile as used in the art, in full line).

It is further shown that providing the belt with apertures such as punch holes in between the profiles also reduces the sound level.

Interestingly, people in the art will appreciate that with such a forward position of the guide wheels further contributes to reducing and preventing wearout of the guide rails, which is known to occur especially in a front region.

Therefore, there is provided a track assembly comprising guide wheels in a region of greatest impacts on the guide rails of the track, which are also the regions of greater wearout of the guide rails, the guide wheels being further arranged in a staggered position.

The track assembly may further comprise clips mounted in each profile of the ground-engaging surface of the track, which results in a larger distance between the track and the guide wheels, thereby reducing a force of impact during contacts between rods and wheels.

Although the present invention has been described hereinabove by way of embodiments thereof, it may be modified, without departing from the nature and teachings of the subject invention as described herein.

Claims

1. An endless track belt assembly comprising an endless elongated body going around a sprocket wheel and a front wheel, and having a ground-engaging outer surface and an inner surface, the inner surface receiving, on a lower run thereof, a suspension comprising a plurality of guide wheels and guide rails, wherein said plurality of guide wheels comprises guide wheels positioned transversally in ones of aligned pairs and staggered pairs in a forward region of the assembly, one of said pairs being located close to a curved region of the forward region of the assembly.

2. The endless track belt assembly as recited in claim 1, wherein the guide wheels are positioned transversally in staggered pairs in the forward region of the assembly, each guide wheel of a given pair being in a staggered position with respect to a counterpart thereof.

3. The endless track belt assembly as recited in claim 2, wherein a pair of guide wheels close to a point of attachment of the assembly is in a staggered position.

4. The endless track belt assembly as recited in claim 1, wherein the ground-engaging surface bears a series of spaced profiles.

5. The endless track belt assembly as recited in claim 4, wherein clips are provided on the profiles.

6. The endless track belt assembly as recited in claim 4, wherein the endless belt is provided with aperture in between the profiles.