GROUND ENGAGING SURFACE FOR ENDLESS TRACKS, WHEELS AND TYRES

Abstract: An endless track (27) for tracked vehicles comprising an endless flexible band (33) and a plurality of spaced elongated tread elements (41) provided on the outer surface of the band. Each tread element (41) is formed of resilient material and extends transversely of the direction of travel of the track. The tread elements (41) are each in the form of a loop having a ground engaging portion and a pair of side wall portions which are load supporting when the loop is in contact with the ground. The tread elements (41) may be formed integral with, or formed separately of and secured to, the endless flexible band (33). A track assembly is also described and claimed.

Description: "GROUND ENGAGING SURFACE FOR ENDLESS TRACKS, WHEELS AND TYRES" THIS [NV NTION relates to an endless track for a tracked vehicle, and to a track asscπibLy for a tracked vehicle. As traction means for vehicles, the benefits of endless tracks as opposed to ground wheels provided with pneumatic tyres, are well known. These benefits include better traction in soil and less ground compaction. However, endless tracks do have several deficiencies. The endless track comprise track sections joined to one another by pivotted connections which are prone to unacceptabiy high rates of wear, thereby limiting the service life of the tracks. A further deficiency is that endless tracks cause damage to finished road sur aces, especially when the vehicle is turning. A still further deficiency is that endless tracks are incapable of cushioning or absorbing shocks resulting from surface irreguLarities and so vehicle springing is required for satisfactory ride characteristics. The endless tracks also have higher noise levels and lower maximum travel speeds than wheels equiped with pneumatic tyres. With a view to overcoming some of the above-mentioned deficiencies, there have been various proposals to provide the endLess tracks with ground contacting elements formed of elasto eric material rather than metal. While elastomeric ground contacting elements do allow tracked vehicLes to travel on finished roads, they do not extend the service life of the tracks as the tracks are still formed of track sections joined to one another by pivotted connections which are susceptable to high rates of wear. Moreover, so as to have a useful 9. service life, the elastomeric elements are solid and not sufficiently resilient to provide effective cushioning of shocks resulting from bumps and surface irregulari ies encountered bv the tracks. I t is an object ot the present invention to provide a useful and novel track which is of relatively simple construction, which may travel on finished road surfaces and which can at least par Ly absorb shocks resulting from encountering bumps and surface irregulari ies. According to a first aspect of the invention there is provide an endless track for tracked vehicles comprising an endless flexible band having an inner surface and an outer surface, and a plurality of spaced elongated tread elements provided on the outer surface of the band, each tread element being formed of resilient material and extending transversely of the direction of travel of the track. The use of the endless flexible band obviaCes Che need for Crack, sections joined to one anocher by pivoCCed connections and so provides for an endless crack of rela iveiy simple consCruc ion. Furchermore, the resilient nature of the tread elements permics Che crack to travel on finished road surfaces and provides at least some cushioning of shocks encountered during travel. Preferably, each tread element is holLow so as to define a cavity which preferably is unpressurised. The tread elements may be formed integral with, or formed separately of and secured to, the endLess flexible band. Preferably, each tread element is in Che form of a loop having a ground engaging porcion and a pair of side wall pore ions which are load supporting when the loop is in contact with the ground. PreLerably, the loops are open at their ends. In this wav, the cavities defined within the loops open onto the exterior of the endless track. Preferaby, the loops are formed of reinforced elastomeric m teri I . Preferably, the endless band is formed of reinforced elastomeric material so as to be substantially longitudinally inextensible yet flexible. Each loop may be provided with a sacrificial wear pad attached to the ground engaging portion thereof. in one arrangement, the loops are provided by a length of resilient material arranged in a sinuous formation having alternating crests and troughs, the length of resilient material being anchored to the flexible band at locaCions corresponding Co aC lease some of the troughs. According to a second aspect of the invention there is provided a track assembly for a tracked vehicle, the track assembly comprising a plurality of track wheels at least one of which constitutes a drive wheel, and an endless track entrained around the track wheels, the endless track being in accordance with the first aspect of the invention as defined hereinbefore. Although a positive drive may be provided between the or each drive wheel and the track, it is preferred that friction drive be employed. With friction drive, there is fricCionai engagemenC between the inner surface of the endless band and the outer peripliery of the or each drive wheel so that the drive wheel frictionally transmits - - power to the endless track. To facilitate frictionaL engagement between the drive wheel and the endless band, the outer periphery of the drive wheel may be coated with elastomeric material. Preferably, the track wheels are each provided with a circumferen ial recess which receives the endless band and serves to guide the band in its circuitous path around the track wheels. Preferably, a tensioning means is provided for tensioning the endless band about the track wheels. The tensioning means may comprise means for urging one of Che endmosC Crack wheels in a direccion away from Che oCher endmosC Crack wheei . The invencion will be beCCer undersCood by reference Co Che following descripcion of one specific embodimenc Chereof as shown in Che accompanying drawings in which: Figure 1 is a perspeccive view of a work vehicLe provided wich cracCion means incorporacing an endless Crack assembly according Co Che embodimenc; Figure 2 is a schemacic side view of Che work vehicle of figure 1 wich Che lower run of Che endless Crack assembly shown in Che condicion ic assumes under driving load; Figure 3 is a view of Che Crack assembly in par section ; Figure 4 is a deCail view of par of Che upper run of an endless Crack of Che Crack assembly; and Figure 5 is a decail view of pare of Che lower run of Che endless crack, deformed under driving load. - - Referring Co figure 1 of Che drawings, Chere is shown an amphibious work vehicle 11 having a traction means which includes a pair of Crack assemblies 13 according Co Che embodimenc arranged on opposiCe sides of Che vehicle. The vehicle is provided with a frame structure 15 and a body 17 which is carried on the frame structure and which provides an operator's cab 19, an engine compartment 21, and a load carrying compartment 23. Each crack assembly 13 comprises a pluraliCy of Crack wheels 25 and an endless Crack 27 ficced onCo Che Crack wheels. The Crack wheels 25 are supported on axLes which are direccly connecCed Co Che frame structure of the vehicle; that is, there is no spring system between the frame structure and the axles. One of the endmost track wheels constitutes a drive wheel to which power is selectively transmitted from an engine mounted in Che engine comparCmenC . A censioning means (noc shown) is provided for Censioning Che endless belc abouC Che Crack wheels. The censioning means is Che form of a means supporting the particular endmost track wheel which is not the drive wheel on the frame structure for movement aLong Che fore-and-afc direcCion of Che vehicle, and a power device (such as a hydraulic ram) for conCrolling such movement. Wich Chis arrangement, the movable endmost wheel can be moved in the direction away from the drive wheel thereby to tension the endless track, as will become more apparent later. The track wheels 25 (including the drive wheel) are each provided with a circumferential recess 29 to guidingly - 6 - receive the endless track for retaining the track in alignment with the track wheels. The recesses 29 are formed by circum erential flanges 31 provided on the ends of the track wheels, as best seen in figure 3 of the drawings . The endless track 27 comprises an endless flexible band 33 having an outer face 35, an inner face 37 and two longiCudinal edges. The endless band 33 is received in Che circumferencial recesses 29 of Che Crack wheels 25 wich Che longiCudinal edges of Che band closely adjacenc Che circumferencial flanges 31 of Che Crack wheels. While being flexible, Che endless band 33 is also longicudinally inexCensibie in characcer so as Co resisc undue screeching. To this* end, Che endless band may be in Che form of an eiasComeric rnaCerial reinforced wich sCeel cables or oCher reinforcing elements. The endless track 27 further comprises a plurality of spaced, elongated tread elements 41 provided on the outer face of the endLess band. The tread elements 41 are formed of resilient material and extend transversely of the direction of travel of the vehicle. Each tread element 41 is in Che form of a loop having a ground conCacCing porcion 43 and a pair of side wall porCions 45 which are load supporeing when Che Cread elemenC is in contact with the ground. While the tread elements 41 may be formed integrally with the endless band 33, in this embodiment the tread elements are formed separately of and secured to the - 7 - band. More particul rly, the tread elements are provided by a length 47 of resilient material which is arranged in a sinuous formation having alternate crests and troughs. Fastening means 49 secure the length of material 47 to the endless band 33 at locations corresoonding to each of the troughs. The resiLient material is required to have sufficient compressive strength to support the loads imposed on it when the loops are under load and to this end may be in the form of reinforced elastomeric maCeriai. The outer periphery of the drive wheel is provided with a friction surface for frictionai engagement with the inner surface of the endless band. In this way, the drive wheel frictionalLy transmits power to the endless band. Tension in the endless band is regulated by the tensioning means so as to maintain the frictionaL driving relationship between the endless band and the drive wheel. A scraper ' not shown) or other means may be provided to displace sand and other debris gathering between the inner surface of the endless band and the outer peripheries of the track wheels. The ground contacting portion of each loop may be provided with a sacrificial wear pad (not shown) if desired so as to extend the service life of the endless track. In operation, the tread elements deform under load and assume a configuration illustrated in figure 5 when the vehicle is undergoing straight line motion. When the vehicle is turning on finished road surfaces, the tread elements twist and drag over the surface without inflicting damage thereto. - 8 - The ability of the tread elements to deform under load provides the vehicle with a degree of springing which at least partiaLly absorbs shock forces resulting from bumps and other surface irregulaties encountered in the path of the vehicle. The traction means also provides a propulsion system for the vehicle when operating in water. In such situations, the lower run of the endless track is submersed and the upper run is above the water line. In this way, the tread elements act as paddles as the endless track follows its circuitous path. From the foregoing, its is evident that the present invention provides both an endless track assembly and an endless track, each of which is of relatively simple construccion and which can be operated on finished road surfaces without infiicCing damage Co such surfaces. Although Che invencion has been described as applied Co an amphibious work vehicLe, ic will be recognised Chae ic may be applied Co any suiCable cracked vehicle including earCh-moving machines, agriculCural machines and snowmobiles .

Claims: IriE CEAl.MS defining the invention are as follows:- 1. An endless track for tracked vehicles comprising an endless flexible band having an inner surface and an outer surface, and a plurality of spaced elongated Cread elemencs provided on Che outer surface of Che band, each Cread eLemenC being formed of resilienC material and extending transverseLy of the direction of travel of the track. 2. An endless track according to claim 1 wherein each Cread eiemenc is hoiLow so as Co define a cavicy. 3. An endless Crack according Co claim 2 wherein Che cavicy is unpressurised . 4. An endless Crack according Co any one of Che preceding claims wherein Che endless band is formed of reinforced elasComeric macerial so as Co be subsCanCially longiCudinally inexCensible yeC flexible. 5. An endless Crack according Co any one of Che preceding claims wherein each cread eiemenc is in Che form of a loop having a ground engaging porCion and a pair of side wall porcions which are load supporcing when Che loop is in contact with the ground. 6. An endless track according to claim 5 wherein the loops are open at their ends. 7. An endless track according to claim 5 or 6 wherein the Loops are formed of reinforced elastomeric material. 8. An endless track according to any one of the preceding claims wherein the tread elements are formed integral with the endless band. - 10 - 9. An endless track according to any one of the claim 1 to 7 wherein the tread elements are formed separately of and secured to the endless band. 10. An endless track according Co claim 9 as dependenC on claim 5, 6 or 7 wherein Che loops are provided by a iengch of resilienc maCerial arranged in a sinuous formacion having alCernaCing crests and troughs, the length of maCerial being anchored to the flexible band at ' locations corresponding to at least some of the troughs. 11. A track assembly for a tracked vehicle, the track assembly comprising a plurality of track wheels at least one of which constitutes a drive wheel, and an endless track according to any one of Che Dreceding claims entrained around the track wheels. 12. A track assembly according to claim 11 wherein a friction drive is provided between the or each drive wheel and the endless band. 13. A track assembly according to claim 11 or 12 wherein the track wheels are each provided with a circumferential recess which receives the endless band and serves to guide the band in its circuitous path around the track wheels. 14. A track assembly according to claim 11, 12 or 13 wherein a tensioning means is provided for tensioning the endless band about the track wheels. 15. A track assembly according to claim 14 wherein the tensioning means comprises means for urging one of the endmost track wheels in a direction away from the other endmost track wheel. 16. An endLess track substantially as herein described with reference to the accompanying drawings. 17. An endless track assembly substantially as herein described with reference to the accompanying drawings.

Inventors: BURNS ALAN ROBERT, BURNS, ALAN, ROBERT
Applicants: ALTRACK LTD, ALTRACK LIMITED
Application year: 1986
Main classification: B62D55
IPC codes: B62D55