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TEPZZ 59_99ZB_T EP B1 (19) (11) EP B1 (12) EUROPEAN PATENT SPECIFICATION

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(19) TEPZZ 59_99ZB_T (11) EP B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention of the grant of the patent: Bulletin 2014/33 (51) Int Cl.: B62D 55/04 ( )
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(19) TEPZZ 59_99ZB_T (11) EP B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention of the grant of the patent: Bulletin 2014/33 (51) Int Cl.: B62D 55/04 ( ) B62D 55/065 ( ) B62D 55/084 ( ) B62D 55/14 ( ) (21) Application number: (22) Date of filing: (54) Track system with overlapping wheel tandem frames Raupenkettenanordnung mit überlappenden Tandemradrahmen Dispositif de chenilles avec cadres de roues en tandem chevauchants (84) Designated Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR (30) Priority: US P (43) Date of publication of application: Bulletin 2013/20 (73) Proprietor: Soucy International Inc. Drummondville QC J2E 8A8 (CA) (72) Inventors: Pare, Steeve ST-MAJORIQUE, Québec J2B 8A8 (CA) Gasse, William DRUMMONDVILLE, Québec J2B 5K1 (CA) Todd, André MONT SAINT-HILAIRE, Québec J3H 6J4 (CA) (74) Representative: Vuillermoz, Bruno et al Cabinet Laurent & Charras Le Contemporain 50, Chemin de la Bruyère Dardilly Cédex (FR) (56) References cited: US-A US-A US-A EP B1 Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). Printed by Jouve, PARIS (FR) 1 EP B1 2 Description Cross-Reference to Related Applications [0001] The present patent application claims the benefits of priority of U.S. Provisional Patent Application No. 61/559,290, entitled Track System with Overlapping Wheel Tandem Frames and filed at the United States Patent and Trademark Office on November 14, Field of the Invention [0002] The present invention generally relates to track systems and traction assemblies used as wheel replacement for typically wheeled vehicles. More particularly, the present invention relates to track systems and traction assemblies for use on heavy vehicles such as, but not limited to, farming and agricultural vehicles (e.g. tractors, harvesters, etc.) and construction and industrial vehicles (e.g. excavators, combines, forestry equipments, etc.). Background of the Invention [0003] Several normally wheeled vehicles and particularly heavy wheeled vehicles (e.g. farming tractors, front loaders, harvesters, etc.) often have their wheels replaced by track systems which use an endless traction band instead of a tire for propulsion. Vehicles equipped with track systems typically have improved floatation and traction, particularly when they are operated over soft terrains. [0004] However, during operation, some components of the track systems, and more particularly the idler wheels and road wheels, can experience uneven load distribution. This is particularly true when the idler wheels and the road wheels are mounted in tandem on tandem frames. [0005] Indeed, in such track systems, the resultant force from the traction band tension and the traction band friction can induce a torque around the tandem frame pivot, resulting in the rotation of the tandem frame thereabout. This rotation then generally causes the wheels located at one end of the tandem frame to move upwardly while causing the wheels located at the other end of the tandem frame to move downwardly, resulting in an increased load on the wheels which are urged downwardly. The rotation of the tandem frame can also cause the trailing portion of the track system to rise. This uneven load distribution can reduce the efficiency of the track system and even lead to premature failure thereof. [0006] Furthermore, when the vehicle equipped with such track systems needs to frequently switch from moving in a forward direction to moving in a rearward direction, and vice-versa, there is often an unpleasant lag time before the track systems properly respond to the change in moving direction. This lag time is at least partially caused by the time it takes for the tandem frames to pivot back to their normal position and then to their new pivoted position. This lag time causes, among other things, unwanted delays in the operation of the vehicle. [0007] U.S. Patent No. 5,842,757, describing the preamble of claim 1, discloses such a typical track system comprising tandem frames for supporting the idler wheels and road wheels. [0008] Hence, there is a need for an improved track system which mitigates at least some shortcomings of prior art track systems. Summary of the Invention [0009] A track system in accordance with the principles of the present invention as defined by independent claim 1 generally mitigates at least some of the shortcomings of prior track systems by having the idler wheels and the road wheels mounted on overlapping tandem frames. [00] Hence, a track system in accordance with the principles of the present invention generally comprises a drive wheel configured to be mounted to an axle of a vehicle, a support frame (or support frame assembly) configured to be mounted to the vehicle, front and rear idler wheels, typically respectively mounted at the front and at the rear of the track system, road wheels, typically mounted longitudinally between the idler wheels, and an endless traction band disposed about the drive wheel, the idler wheels and the road wheels. [0011] The idler wheels and the road wheels are pivotally mounted to tandem frames which are pivotally mounted to the support frame at longitudinally spaced apart pivoting points. The tandem frames allow the idler wheels and the road wheels to move or pivot with respect to the pivoting points, thereby allowing the traction band, and more particularly the lower run thereof, to generally follow the irregularities of the terrain over which the track system is operated. [0012] In accordance with the principles of the present invention, adjacent tandem frames are overlapping, i.e. the tandem frames extend into one another. Due to the overlapping configuration of the tandem frames, the movements of the idler wheels and/or of the road wheels with respect to the pivoting points are limited. [0013] In typical though non-limitative embodiments of a track system in accordance with the principles of the present invention, the diameter of the idler wheels is larger than the diameter of the road wheels. In such embodiments, when a tandem frame support both idler wheels and road wheels, the longitudinal distance between the rotation axis of the idler wheels and the rotation axis of the pivoting point of the tandem frame is typically smaller than the longitudinal distance between the rotation axis of the road wheels and the rotation axis of the pivoting point of the tandem frame. When a tandem frame supports only road wheels, the longitudinal distances between the rotation axes of the road wheels and the rotation axis of the pivoting point of the tandem frame is typically substantially equal. 2 3 EP B1 4 [0014] In typical though non-limitative embodiments of a track system in accordance with the principles of the present invention, the rotation axes of the pivoting points of the tandem frames which respectively support the front and rear idler wheels are respectively located longitudinally in front of and behind the rotation axis of the drive wheel. [0015] In some non-limitative embodiments of a track system in accordance with the principles of the present invention, at least some of the road wheels are pivotally mounted to at least one tandem sub-frame, the at least one tandem sub-frame being pivotally mounted to one of the tandem frames. [0016] A track system in accordance with the principles of the present invention generally improves the load distributions between the idler wheels and the road wheels, and/or generally decreases the tendency of the pivoting point located behind the rotation axis of the drive wheel to move upwardly when the vehicle moves forwardly, and vice-versa, and/or generally reduces the lag time when the vehicle moving in a forward direction switches to move in a rearward direction, and vice-versa. [0017] Other and further aspects and advantages of the present invention will be obvious upon an understanding of the illustrative embodiments about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice. 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 Drawings [0018] The above and other aspects, features and advantages of the invention will become more readily apparent from the following description, reference being made to the accompanying drawings in which: Figure 1 is a perspective view of a vehicle having mounted thereto four track systems in accordance with the principles to the present invention. Figure 2 is a perspective view of one of the track system of Fig. 1. Figure 3A is a side view of the track system of Fig. 2. Figure 3B is a side view of the track system of Fig. 2. Figure 4 is an exploded perspective view of the track system of Fig. 2, without the endless traction band. Figure 5 is a perspective view of another embodiment of a track system in accordance with the principles to the present invention, without the endless traction band. Figure 6 is a side view of the track system of Fig. 5. Figure 7 is a perspective view of a variant of the track system of Fig. 2, viewed from the inboard side. Figure 8 is a perspective view of another embodiment of a track system in accordance with the principles to the present invention, without the endless traction band. Figure 9 is a side view of the track system of Fig. 8. Detailed Description of the Preferred Embodiment [0019] A novel track system with overlapping wheel tandem frames will be described hereinafter. Although the invention is described in terms of specific illustrative embodiments, it is to be understood that the embodiments described herein are by way of example only and that the scope of the invention is not intended to be limited thereby. [0020] Referring first to Fig. 1, four track systems 20 made in accordance to the principles of the present invention are shown mounted to a vehicle. In Fig. 1, the vehicle is a front-loader typically used in construction. Notably, in Fig. 1, the track systems 20 are used to replace the wheels which are typically used on such vehicle. [0021] In Fig. 1, all four track systems 20 are identical though the left and right track systems 20 are mirror image of each other. Still, the front and rear track systems 20 could be different depending, among other things, on the configuration of the vehicle. For instance, some farming vehicles (e.g. tractors) sometimes use smaller front track systems and larger rear track systems. [0022] Referring now to Figs. 2 and 3A, one of the four track systems 20 is shown in greater details. [0023] In the present embodiment, the track system 20 comprises a drive wheel 22 configured to be mounted to the axle (not shown) of the vehicle. The drive wheel 22 defines a rotation axis 23 about which it rotates. The drive wheel 22 comprises, along its periphery 24, a plurality of evenly disposed sprocket teeth 26 configured to engage drive lugs (not shown) located on the inner surface 30 of the traction band 28. In the present embodiment, the drive wheel 22 is a sprocket wheel. [0024] The track system 20 also comprises a frame assembly 34 pivotally mounted to the drive wheel 22. Understandably, though the frame assembly 34 can pivot with respect to the drive wheel 22, the frame assembly 34 does not rotate with the drive wheel 22 as the frame assembly 34 is not drivingly engaged to the drive wheel 22. Though in the present embodiment, the frame assembly 34 is pivotally mounted to the drive wheel 22, in other embodiments, such as the one shown in Fig. 7, the frame assembly 34 could be configured to be mounted directly to the vehicle, typically to its frame. In such embodiments, the frame assembly 34 would typically comprise an attachment frame or assembly 90 configured to secure the frame assembly 34 to the vehicle. [0025] In the present embodiment, the frame assembly 34 pivotally supports two tandem frames 36 and 38. The front tandem frame 36 is pivotally mounted to the frame assembly 34 at front pivoting point 40 while the rear tandem frame 38 is pivotally mounted at rear pivoting point 42. [0026] The front pivoting point 40 defines a rotation 3 5 EP B axis 41 while the rear pivoting point 42 defines a rotation axis 43. As best shown in Fig. 3A, in the present embodiment, the rotation axis 41 is located longitudinally in front of the drive wheel rotation axis 23 while the rotation axis 43 is located longitudinally behind the drive wheel rotation axis 23. [0027] In the present embodiment, the longitudinal distance between the rotation axis 41 and the drive wheel rotation axis 23 is substantially equal to the longitudinal distance between the rotation axis 43 and the drive wheel rotation axis 23. In other embodiments, these two distances could be different. [0028] Referring back to Figs. 2 and 3A, in the present embodiment, the front tandem frame 36 pivotally supports front idler wheels 44 and rear road wheels 46. In a substantially symmetrical fashion, the rear tandem frame 38 pivotally supports rear idler wheels 48 and front road wheels 50. [0029] The track system 20 also comprises the traction band 28, already introduced above, which is disposed about the drive wheel 22, the idler wheels 44 and 48 and the road wheels 46 and 50. The traction band 28 is typically made from reinforced elastomeric material and comprises an inner wheel-engaging surface 30 and an outer ground-engaging surface 32. [0030] Though not shown in the figures, the inner surface 30 of the traction band 28 typically comprises one or more rows of longitudinally aligned drive lugs and/or one or more rows of longitudinally aligned guide lugs (collectively referred to as inner lugs ). The drive lugs are configured to be drivingly engaged by the sprocket teeth 26 of the drive wheel 22. [0031] In other embodiments, the inner surface 30 of the traction band 28 could only comprises guide lugs, and thus be devoid of drive lugs, such as to be frictionally engaged by the drive wheel 22 instead of being positively engaged thereby. [0032] Though not shown in the figures, the outer surface 32 of the traction band 28 typically comprises traction lugs configured to engage the terrain over which the track system 20 is operated. [0033] Referring now more particularly to Fig. 3A, the front pivoting point 40 allows the front tandem frame 36 to pivot thereabout, allowing the front idler wheels 44 and the rear road wheels 46 to move substantially vertically in opposite directions (e.g. upwardly and downwardly). Similarly, the rear pivoting point 42 allows the rear tandem frame 38 to pivot thereabout, allowing the rear idler wheels 48 and the front road wheels 50 to move substantially vertically in opposite directions (e.g. upwardly and downwardly). The ability of the idler wheels 44 and 48 and of the road wheels 46 and 50 to move substantially vertically as the tandem frames 36 and 38 pivot allows the lower run of the traction band 28, i.e. the portion of the traction band 28 which generally engages the ground, to substantially follow the irregularities of the terrain over which the track system 20 is operated. [0034] Still referring to Fig. 3A, in the present embodiment, the diameter of the idler wheels 44 and 48 is larger than the diameter of the road wheels 46 and 50. Having larger idler wheels 44 and 48 generally allows the track system 20 to more easily overcome obstacles and also to overcome larger obstacles. Larger idler wheels also generally reduce rolling resistance as it is easier to bend an elastomeric traction band around larger idler wheels than around smaller idler wheels. [0035] In addition, in the present embodiment, the longitudinal distance between the rotation axis 45 of the front idler wheels 44 and the rotation axis 41 of the front pivoting point 40 is smaller than the longitudinal distance between the rotation axis 47 of the rear road wheels 46 and the rotation axis 41 of the front pivoting point 40. Similarly, the longitudinal distance between the rotation axis 49 of the rear idler wheels 48 and the rotation axis 43 of the rear pivoting point 42 is smaller than the longitudinal distance between the rotation axis 51 of the front road wheels 50 and the rotation axis 43 of the rear pivoting point 42. [0036] As already mentioned above, the diameter of the idler wheels 44 and 48 is larger than the diameter of the road wheels 46 and 50. The present combination of the different longitudinal distances between the rotation axes and of the different wheel diameters generally allows a more balance load distribution between the larger idler wheels 44 and 48 and the smaller road wheels 46 and 50. Indeed, due to their smaller diameter, the smaller road wheels 46 and 50 have a load bearing capacity which is generally inferior to the load bearing capacity of the larger diameter idler wheels 44 and 48. Hence, to prevent the road wheels 46 and 50 from sinking excessively into the inner surface 30 of the elastomeric traction band 28, it is preferable to more evenly balance the load transmitted to and/or supported by the idler wheels 44 and 48 and by the road wheels 46 and 50 during operation of the track system 20. [0037] Typically, the load bearing capacity of a wheel will be generally proportional to its diameter. Hence, a wheel with a diameter twice as large as the diameter of another wheel would be able to support approximately twice the load. [0038] Thus, to generally evenly balance the load distribution between the idler wheels 44 and 48 and the road wheels 46 and 50, the ratio of the longitudinal distance between the rotation axis of the road wheels and the rotation axis of the tandem frame, to the longitudinal distance between the rotation axis of the idler wheels and the rotation axis of the tandem frame should be approximately equal to the ratio of the diameter of the idler wheels to the diameter of the road wheels. [0039] Understandably, other parameters (e.g. wheel width) could affect the relation between the longitudinal distances and the wheel diameters. In addition, one could choose particular distances and/or wheel diameters such as to change the load distribution. [0040] Referring now to Fig. 3B, when the track system 20 is operated such as to move in a forward direction, 4 7 EP B1 8 indicated by arrow F, the drive wheel 22 will rotate in a counterclockwise direction as indicated by arrow S. The rotation of the drive wheel 22 will pull on the portion of the traction band 28 located behind the drive wheel 22. This pulling, indicated by arrow T, will impart an upward motion to the rear idler wheels 48 as indicated by arrow RI. Because of the pivotal connection of the rear tandem frame 38 to the frame assembly 34, the upward motion of the rear idler wheels 48 will cause an opposite downward motion of the front road wheels 50 as indicated by arrow FR. [0041] However, as the longitudinal distance between the rotation axis 51 of the front road wheels 50 and the rotation axis 43 of the rear pivoting point 42 is larger than the longitudinal distance between the rotation axis 49 of the rear idler wheels 48 and the rotation axis 43 of the rear pivoting point 42, the downward motion of the front road wheels 50 will be countered, thereby limiting the upward motion of the rear idler wheels 48 and thus limiting the overall pivotal movement of the rear tandem frame 38. Indeed, the longer longitudinal distance between the rotation axis 51 of the front road wh
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