ROAD PADS FOR TRACKED VEHICLES

Abstract: A road pad (10) for a tracked vehicle such as a tank is disclosed. The pad consists of a plastics backing plate (12) and a rubber cushion (14) bonded to the backing plate (12). The plate (12) includes latching projections (26, 28) which engage with latching surfaces (30, 32) in a track link to retain the pad (10) in place. One or more pressed steel reinforcing elements (40) are encapsulated within the backing plate (12) or between the backing plate (12) and the rubber cushion (14) and extend into the latching projections (26, 28) to reinforce them. The reinforcing elements (40) are cheap to manufacture and, being encapsulated, are not prone to corrosion.

Description: ROAD PADS FOR TRACKED VEHICLES This invention relates to road pads for tracked vehicles such as tanks. Road pads are incorporated into the tracks to cushion the impact between the tracks and the surface upon which the vehicle is driven. Between adjacent plates of the track, track links are located, coupled to the plates via bushes, to allow articulation of the track. The road pads are usually fixed to the track links. An example of an arrangement as described above can be found in UK patents nos. 1077444 and 1405742. In each case, the pad consists of a metallic backing plate and a rubber cushion bonded to one side of the backing plate. The edges of the backing plate project beyond the cushion and acts as guides which enable the pad to be slid into cooperating grooves in the track link. Part of the backing plate is cut out and raised to form a latching projection which cooperates with a latch on the track link to retain the pad in place. These road pads have been found to suffer from a number of disadvantages. Firstly, the size of the backing plate and the cost of the material from which it is made contribute significantly to the cost of producing the pad. Many pads are used on each vehicle and the cost of kitting out the vehicle is increased accordingly. Secondly, the backing plate is prone to corrosion. Although the life of the backing plate exceeds that of the rubber cushion, the pad can be reconditioned by vulcanising a replacement cushion to the plate. Corrosion of the plate can reduce considerably the number of times the pad can be reconditioned. It has recently been proposed to manufacture road pads almost entirely from polymeric material. The backing plates are formed from hard plastics material, either plain or fibre reinforced, to which the rubber cushion is bonded. The strength of the backing plate is sufficient to form the guide projections on either side of the pad to enable it to slide in and out of the track link. However, to date, no plastics backing plate material has been able to deal with the stresses which must be withstood by the latching projection. Such plastics-backed pads are therefore provided with metallic reinforcements moulded into the backing plate and projecting from it to form the latching projection. Such reinforcements are machined and are therefore expensive to manufacture. They are also subject to corrosion. It is an object of the present invention to address these problems. Accordingly, the present invention provides a road pad adapted for sliding engagement within a track link, the pad comprising a body of polymeric material having a latching projection adapted to cooperate with an abutment of the link to prevent withdrawal of the pad and in which the latching projection includes a reinforcing element encapsulated within the polymeric material. Because the reinforcing element is encapsulated within the polymeric material, it is not exposed to corrosive elements. As will be explained, the bulk of the latching projection can be formed from the polymeric material, enabling the reinforcing element to be manufactured inexpensively and using cost-effective manufacturing processes. To give the pad structural rigidity, the body preferably comprises a backing plate and a cushion, the reinforcing element being encapsulated within the backing plate or between the backing plate and the cushion. The backing plate is preferably formed from plastics material and the cushion from a rubber material. To impart a degree of flexibility to the latching projection, the reinforcing element may be resilient. For example, it may be formed from steel plate. Preferably, the reinforcing element comprises a flat and a resilient tongue projecting from it into the latching projection. The flat serves to anchor the reinforcing element in the body or backing plate and the tongue reinforces the latching projection. The tongue need only extend into that part of the latching projection which acts as the abutment surface to retain the pad in place in the track link. The tongue may be an angled cut-out from the flat or it may be an angled extension of the flat. For increased security, the body may have two latching projections. Each latching projection may be reinforced by a reinforcing element or alternatively the latching projections may be reinforced by a common reinforcing element. Such a common reinforcing element may comprise a flat and two tongues projecting from it into the latching projections. The reinforcing element may form a channel section with the tongues as the uprights of the channel. The present invention will now be described with reference to the accompanying drawings in which: figs. 1A and IB illustrate a road pad made from a plastics backing plate and a rubber cushion; fig. 2A is a lateral section through a track link for use with such a plastics-backed plate; fig. 2B shows in longitudinal section a pad installed in the link of fig. 2A; and figs. 3A, 3B to 16A, 16B show in plan and in section a variety of reinforced plastics backing plates for use in a pad according to the present invention. As can be seen from figs. 1A and IB, a typical plastics- backed pad 10 consists of a rubber cushion 14 vulcanised onto a plastics backing plate 12. At either side of the pad, the edges of the backing plate 12 extend beyond those of the cushion 14 to form guides 16, 18. These guides are tapered at their leading edges and cooperate with grooves 20, 22 in the track link 24 illustrated in fig. 2. The pad 10 is located in the link 24 and pushed into place such that the guides 16, 18 slide within the grooves 20, 22. When the pad is pushed fully home, latching projections 26, 28 cooperate latching surfaces 30, 32 in the track link to retain the pad in place. The pad can be removed by releasing the latching projections 26, 28 from the latching surfaces 30, 32 using a specially-designed tool. Fig. 3A shows in plan and fig. 3B in section a reinforced, moulded plastics backing plate 12 for use in a pad according to the present invention. The plate 12 is similar to the plate 12 illustrated in figs. 1A and IB, but one of the latching projections 26 is strengthened by a reinforcing element 40. The reinforcing element 40 is formed from pressed steel plate and consists of a flat 42, both ends of which are turned down to form legs 44, 46 and include a return bend which forms feet 48, 50. A substantially rectangular section is stamped out of the steel sheet on three sides to form a cut-out tongue 52 which is bent out of the plane of the flat 42 along its fourth side and projects into the latching projection 26. The tongue 52 lies close to the inclined outer surface 54 of the latching projection 26 and extends almost as far as its abutment surface 56, i.e. the surface which engages a latching surface 30 of the track link 24. The pad includes a second latching projection 28 which is not reinforced. The surface of the backing plate 12 opposite the latching projections includes a depression 60 and keys 62 which help the vulcanised rubber cushion to bond to it. The backing plate 12 is injection moulded with the reinforcing element 40 in situ. The correct positioning of the insert 40 to ensure in this case that it does not contact the surfaces of the mould is important. The insert 40 is positioned in the mould by means of stepped retaining pins together with magnets which ensure that the insert 40 is not dislodged from the pins during the injection moulding process. Subsequently a rubber cushion 14 (not shown) is vulcanised to the recessed and keyed surface of the backing plate 12. Fig. 4A shows in plan and fig. 4B in section a reinforced, moulded plastics backing plate 12 in which both latching projections 26, 28 are reinforced by a common reinforcing element 40. The reinforcing element is again formed from pressed steel and is similar to the reinforcing element 40 of figs. 3A and 3B, but includes two substantially rectangular cut-out tongues 52, 53, each of which reinforces a respective latching projection 26, 28. Figs. 5A and 5B show a plastics backing plate 12 including a single reinforcing element 40 similar to that illustrated in figs. 3A and 3B, but in which the flat 42 is not turned down at either edge. In all essential respects, the reinforcing element is identical to that shown in figs. 4A and 4B, save insofar as it only reinforces one latching projection 26. Figs. 6A and 6B, 7A and 7B and 8A and 8B show three different designs of plastics backing plate 12 in which just one latching projection 26; 28 is reinforced. Again the reinforcing elements 40 are formed from pressed or rolled steel, but the tongue 52 is merely an extension of one end of the flat 42 and extends at ninety degrees to it. The tongue extends adjacent the abutment surface 56; 57 of the latching projection 26; 28 to provide the requisite reinforcement. It is clear from figs. 6B, 7B and 8B that the reinforcing element 40 is coterminous with the surface of the backing plate 12 to which the rubber cushion is to be bonded. There is no need when manufacturing this plate 12 to prevent the reinforcing element 40 from contacting the surface of the mould; indeed that possibility can be exploited to advantage by locating the reinforcing element 40 on the requisite surface and retaining it there by means of magnets during the injection moulding process. When the rubber cushion is vulcanised in place, the encapsulation of the reinforcing element within the polymeric material is complete. Figs. 9A and 9B illustrate a backing plate 12 including two reinforcing elements 40, 41 which are essentially identical to those shown in figs. 6A and 6B. Each reinforcing element reinforces a respective latching projection. Figs. 10A and 10B illustrate a backing plate 12 in which a common reinforcing element strengthens both latching projections. The reinforcing element 40 is again formed from rolled steel plate, but two tongues 52, 53 project upwards from the flat 42 to form a reinforcing element 40 in the from of a channel section. Both latching projections 26, 28 are reinforced by a respective tongue 52, 53. Figs. 11A and 11B, 12A and 12B and 13A and 13B show three different designs of plastics backing plate 12 in which one or two latching projections 26, 28 are reinforced by dowels 55 which are welded to and project from the flat 42 of a reinforcing element 40 at right angles. The dowels are located adjacent the latching surfaces 56, 57 of the latching projections 26, 28 in question. Figs. 14A and 14B, 15A and 15B and 16A and 16B show three different designs of plastics backing plate 12 in which one or two latching projections 26, 28 are reinforced by a continuous reinforcing element 40 which closely follows the contours of the latching projections 26, 28. In figs. 14A, 14B, 15A and 15B, the reinforcing element 40 consists of a flat 42, an upstand 60 and an angled continuation 62 lying below the tapered surface of the latching projection. In figs. 16A and 16B, a further upstand 64 and continuation 66 are provided.

Claims: Claims 1. A road pad adapted for sliding engagement within a track link, the pad comprising a body of polymeric material having a latching projection adapted to cooperate with an abutment of the link to prevent withdrawal of the pad and in which the latching projection includes a reinforcing element encapsulated within the polymeric material. 2. A pad according to claim 1 in which the body comprises a backing plate and a cushion, the reinforcing element being encapsulated within the backing plate or between the backing plate and the cushion. 3. A pad according to claim 2 in which the backing plate is formed from plastics material. 4. A pad according to claim 2 or claim 3 in which the cushion is formed from a rubber material 5. A pad according to any preceding claim in which the reinforcing element is resilient 6. A pad according to claim 5 in which the reinforcing element is formed from steel plate 7. A pad according to any preceding claim in which the reinforcing element comprises a flat and a limb projecting from it into the latching projection. 8. A pad according to claim 7 in which the limb is a resilient tongue. 9. A pad according to claim 8 in which the tongue is an angled cut-out from the flat 10. A pad according to claim 8 in which the tongue is an angled extension of the flat. 11. A pad according to claim 7 in which the limb is a dowel projecting from the flat. 12. A pad according to claim 7 in which the limb is an upstand projection from the flat and the reinforcing element further comprises a continuation of the upstand which lies adjacent the surface of the latching projection. 13. A pad according to any preceding claim in which the body has two such latching projections 14. A pad according to claim 13 in which each latching projection is reinforced by a reinforcing element 15. A pad according to claim 13 in which the latching projections are reinforced by a common reinforcing element 16. A pad according to claim 15 in which the reinforcing element comprises a flat and two limbs projecting from it into the latching projections. 17. A pad according to claim 16 in which the reinforcing element forms a channel section with the limbs as the uprights of the channel. 18. A pad substantially as described herein with reference to any one of figures 2A to 16B of the accompanying drawings.

Inventors: BAKER PETER EDWARD, BAKER, PETER, EDWARD
Applicants: BAKER PETER EDWARD, WILLIAM COOK CAST PRODUCTS PLC, BAKER, PETER, EDWARD
Application year: 1996
Main classification: B62D55
IPC codes: B62D55