GB2116922A

GB2116922A - Endless track sets for vehicles

Info

Publication number: GB2116922A
Application number: GB08307302A
Authority: GB
Inventors: Reinio Merilaien
Original assignee: Suokone Oy
Current assignee: Suokone Oy
Priority date: 1982-03-19
Filing date: 1983-03-16
Publication date: 1983-10-05
Also published as: FI76970B; SE8301402D0; FI76970C; GB8307302D0; SE8301402L; IE54201B1; FI820954L; IE830592L; GB2116922B

Abstract

A track set for connection to an axle assembly (12) of the traction wheels of a vehicle or a trailer consists of a track set frame (6), a drive wheel (4), two track wheels (8,19), a track mat (3) and a track mat tensioning mechanism (9). The track wheels (8,19) are located at the forward and rearward ends of the track set respectively. The drive wheel (4) is adapted to be connected to the traction axle (12) and is located between and above the track wheels (8,19). The tensioning mechanism (9) comprises two rollers (5,20), one located forward of and the other to the rear of the drive wheel (4). The rollers (5,20) are spring-loaded to urge the track mat (3) mainly downwards so that the contact angle between the track mat (3) and the drive wheel (4) is maximised. The interval between the teeth of the drive wheel (4) is substantially larger than the meshing element of the track mat (3) entering this interval, and the pitch of the track mat (3) is larger than the pitch of the drive wheel (4). The track set enables various kinds of standard type land vehicles, such as agricultural, forest and bog tractors and their trailers to be converted into track- borne vehicles, and operates reliably even in difficult conditions. <IMAGE>

Description

SPECIFICATION Track sets for vehicles This invention relates to a track set for a vehicle, consisting of a track set frame, at least two track wheels, a track mat and a track tensioning mechanism and attachable to the axle assembly of the traction wheel of a vehicle and/or trailer.

When aiming to increase the transporting capacity of transport equipment travelling over soft ground areas, such as woodland or bogs, one is compelled to replace conventional designs based on the use of wheels with track sets. In the track set designs of track -borne vehicles known in the art, the traction or drive wheel is usually placed at one end or the other of the track assembly. However, providing for mechanical power transmission in this design calls for an expensive and complicated chassis construction of the vehicle.

Another track set design known in the art is that in which the drive wheel has been disposed centrally in the track assembly. It is then easier to provide for proper power transmission, but the length of the track assembly is limited. This is because a large enough contact angle is required between the drive wheel and the track mat.

When a track set is desired which enables various kinds of standard type land vehicles such as agricul tural, forest and bog tractors and their trailers to be converted into track-borne vehicles, the track set must be directly connectable to the axle assembly of the traction wheel of the vehicle or trailer. This precludes the disposing of the drive wheel to be located at either end of the track set. An efficient enough track set cannot be achieved by those drive wheel designs either in which the drive wheel is placed in the central region of the track set, to serve this purpose, because a centrally placed drive wheel can only be used in the case of short track sets.

The present invention aims to eliminate the abovementioned drawbacks and to provide a track set which is substantially superior in efficiency to any design of the prior art, and which is connectable to the axle assembly of the traction wheel of a vehicle or trailer.

According to one aspect of the invention, there is provided a track set for a vehicle, consisting of a track set frame, a drive wheel, two track wheels, a track mat and a track mat tensioning mechanism, said track set being connectable to the axle assembly of the traction wheels of a vehicle and/or trailer, wherein one track wheel is located at the forward end of the track set and the other track wheel is located at the rear end of the track set, wherein the drive wheel is adapted to be connected to the traction axle of the vehicle and is located substantially in the central part of the track set between and above the track wheels, wherein the tensioning mechanism comprises two rollers, one being located forward of the drive wheel and the other rearward of the drive wheel, and wherein the rollers of the tensioning mechanism are spring-loaded to urge the track mat mainly downwards so that the contact angle between the track mat and the drive wheel is maximised.

It is a further aim of the invention to provide a track set design with higher reliability under difficult conditions. In designs of the prior art, the construction of the track set is based on the so-called fundamental chain, where the pitch circle of the gear wheel constituting the drive wheel coincides with the centre-line of the chain. In the fundamental chain structure, the meshing element of the chain substantially fills the tooth gap of the drive wheel entirely.

This is detrimental when operating in difficult conditions because in that case foreign objects entering the tooth gap, such as stones, sand, snow and ice cannot escape from between the track mat and the drive wheel. The consequence is damage to the structure and rapid wear.

The invention aims to improve the reliability of the track set construction under difficult conditions by providing a track set for a vehicle, consisting of a track set frame, a drive wheel, at least one track wheel, a track mat and a track mat tensioning mechanism, said track set being connectable to the axle assembly of the traction wheels of a vehicle or trailer, wherein the drive wheel is provided with teeth, wherein the track mat is provided with meshing elements, wherein the interval between the teeth of the drive wheel is substantially wider than the meshing elements of the track mat entering this interval, and wherein the pitch of the track mat is greater than the pitch of the drive wheel.

In such a design as taught by the invention, there will be sliding between the tooth of the drive wheel and the meshing element of the track mat when the vehicle is in motion. This implies that the meshing element of the track mat will at the same time scrape clear every tooth interval of the drive wheel. In a standard construction, large play causes, particularly when reversing direction, impact-like peak loads which shorten the life span of the track set. As taught by the invention, this problem has been solved in that the pitch of the track mat, when the track mat is upon the drive wheel, is suitably wider than the tooth pitch of the drive wheel. This ratio is so selected that operation free of play or dead motion, is obtained within the region determined by the contact angle between the track mat and the drive wheel.As a result of the minimal play, the peak loads remain small in connection with reversal of direction and of unexpected loads, for instance. When the vehicle is in motion, again, the sliding between the meshing element of the track mat and the drive wheel takes place in such manner that on the distance determined by the contact angle between them the meshing element of the track mat moves, in contact with the drive wheel, from one boundary to the other of the drive wheel's tooth interval.

A still further aim of the invention is to improve the connection of a track set to the traction wheel of a vehicle.

Accordingly, another aspect of the invention provides a track set for a vehicle, consisting of a track set frame, a drive wheel, at least one track wheel, a track mat and a track mat tensioning mechanism, said track set being connectable to the axle assembly of the traction wheels of a vehicle or trailer, wherein the frame of the track set is adapted to be suspended from the axle assembly of the traction wheels of the vehicle by a pivot, and wherein an additional fixing point is provided on the frame which is adapted to be suspended by a linkage rod from the chassis of the vehicle or from another axle assembly thereof.

It is possible with a track set like this, according to the invention, to make the track set even as long as the vehicle and still to suspend it firmly from the frame of the vehicle. The additional fixing point may be, for instance, the fixing member of the front wheel in a vehicle with rear-wheel drive.

The invention will now be further described, by way of example, with reference to the drawings, in which Figure 1 is a side elevation of a tractor and trailer on which have been mounted track sets according to one embodiment of the invention; Figure 2 is a side elevation of a second embodiment of a full track set according to the invention for mounting on a tractor; Figure 3 is a part-sectioned plan view of the track set shown in Figure 2; and Figure 4 shows a detail of a track set according to the invention, with the drive wheel and the track mat tensioning mechanism schematically indicated.

Referring now to Figure 1, in the agricultural tractor 1 therein depicted, track sets according to the invention have been mounted to replace its rear wheels, and on the axle of the trailer 2. It is seen in Figure 1 that in order to maintain the track mat 3 in engagement with the drive wheel 4, tensioning wheels 5 and 20 have to be used. In this embodiment, the track set is symmetrical with reference to the vertical plane passing through the axle.

In Figures 2 and 3 is depicted a track set according to the invention intended to constitute the full track set of an agricultural tractor. In this embodiment, the track set has greater length forward of the drive axle 12, extending up to the front axle 14, to which it has also been connected by a suspension. In other respects the construction is equivalent to that shown in Figure 1. The track set consists of a frame 6, the drive wheel 4, track wheels 8 and 19, carrying wheels 7, the track mat 3 and a track mat tensioning mechanism 9. The tensioning mechanism 9 comprises levers 21 and 26 loaded by springs 17 and 23, the tensioning rollers 5 and 20 being mounted on the ends of these levers. The frame 6 of the track set is connected to the rear axle 12 of the tractor by means of a pivot element 10 and to the front axle 14 by means of a linkage rod 11.The carrying wheels 7 are mounted on arm members 27, pivotally carried on the frame 6 of the track set by means of respective pivots 15. The drive wheel 4 is affixed to a drive wheel fixing element 13 which replaces the tractor's rear wheel. The tensioning mechanism 9 is rotatably carried in the drive wheel fixing element 13.

The track mat 3 consists of a track belt 18 and of meshing elements 16. The track mat is maintained in engagement with the drive wheel 4 by means of the tensioning rollers 5 and 20 of the tensioning mechanism 9. The tensioning force is adjustable by means of the springs 17 and 23. It is advantageous to set the rigidity of the springs such that the mechanism allows the track mat on the traction side to straighten and to yield in response to roughness of the ground, to stones, stumps or the like, and at the same time prevents oscillation of the track mat due to sudden impact loads. The interrupted lines in Figure 2 indicate the movements of the track mat 3 and of the tensioning mechanism in different loading cases.

Figure 4 illustrates the cooperation between the track set drive wheel 4 and track mat 3 of the track set according to the invention. With a view to obtaining play-free operation, the dimensioning of the track mat 3 and of the drive wheel 4 has to be adjusted so that the pitch Ptkj of the track mat 3 when the track mat is on the drive wheel 4 is wider by a suitable amount than the tooth pitch Pvpj of the drive wheel.

When this condition is met, sliding will occur between the tooth 24 of the drive wheel 4 and the meshing element, or track pad, 16 of the track mat 3 which is in engagement, for which reason the bottom of the tooth interval 25 will be scraped clean.

By proper selection of the dimensioning of the drive wheel 4 and track mat 3, a desired magnitude of the contact angle ss between them is obtained for accomplishing play-free operation e.g. in connection with reversal of direction and of unexpected loads. It is seen in Figure 4 that as the drive wheel 4 rotates through the contact angle p, the track pad 16 of the track mat 3 slides in the tooth interval 25 of the drive wheel 4 so that the track pad 16 moves from one boundary to the other of the tooth interval 25.

It will be evident to a person skilled in the art that different embodiments of the invention may vary within the scope of the following claims.

Claims

1. A track set for a vehicle, consisting of a track set frame, a drive wheel, two track wheels, a track mat and a track mat tensioning mechanism said track set being connectable to the axis assembly of the traction wheels of a vehicle and/or trailer, wherein one track wheel is located at the forward end of the track set and the other track wheel is located at the rear end of the track set, wherein the drive wheel is adapted to be connected to the traction axle of the vechicle and is located substantially in the central part of the track set between and above the track wheels, wherein the tensioning mechanisms comprises two rollers, one being located forward of the drive wheel and the other rearward of the drive wheel, and wherein the rollers of the tensioning mechanism are spring-loaded to urge the track mat mainly downwards so that the contact angle between the track mat and the drive wheel is maximised.

2. A track set for a vehicle, consisting of a track set frame, a drive wheel, at least one track wheel, a track mat and a track mat tensioning mechanism, said track set being connectable to the axle assembly of the traction wheels of a vehicle or trailer, wherein the drive wheel is provided with teeth, wherein the track mat is provided with meshing elements, wherein the interval between the teeth of the drive wheel is substantially wider than the meshing elements of the track mat entering this interval, and wherein the pitch of the track mat is greater than the pitch of the drive wheel.

3. A track set for a vehicle, consisting of a track set frame, a drive wheel, at least one track wheel, a track mat and a track mat tensioning mechanism, said track set being connectable to the axle assembly of the traction wheels of a vehicle or trailer, wherein the frame of the track set is adapted to be suspended from the axle assembly of the traction wheels of the vehicle by a pivot, and wherein an additional fixing point is provided on the frame which is adapted to be suspended by a linkage rod from the chassis of the vehicle or from another axle assembly thereof.

4. A track set according to any one of claims 1 to 3, wherein the rollers of the track mat tensioning mechanism are disposed on the ends of levers rotatably carried on the axle assembly of the drive wheel.

5. A track set according to claim 4, wherein the levers ofthetensioning mechanism are loaded with at least one spring to be turnable with respect to each other, the rollers being disposed to urge the track mat against the drive wheel so that the contact angle between the track mat and the drive wheel is maximised.

6. A track set according to any one of claims 1 to 5, wherein the tensioning mechanism is turnably carried on the axle assembly of the drive wheel in such a manner that it is freely turnable with varying tension of the track mat on different sides of the drive wheel depending on the direction of rotation of the drive wheel and on the operating conditions.

7. A track set according to any one of claims 1 to 6, wherein the material of the track mat consists of fabricreinforced rubber belt.

8. A track set according to any one of claims 1 to 7, wherein the material of the drive wheel is polyamide.

9. A track set according to any one of claims 1 to 8, wherein the material of the track wheels is polyamide.

10. A track set according to any one of claims 1 to 9, wherein the track set comprises, in addition to the track wheels, one or more carrying wheels located between the track wheels.

11. Atracksetaccording toclaim 10, wherein the or each carrying wheel is made of polyamide.

12. Atracksetfora vehicle substantially as described herein with reference to the drawings.