GB2051187A

GB2051187A - Composite Rail Pad

Info

Publication number: GB2051187A
Application number: GB7920609A
Authority: GB
Original assignee: Sumitomo Riko Co Ltd
Current assignee: Sumitomo Riko Co Ltd
Priority date: 1979-06-13
Filing date: 1979-06-13
Publication date: 1981-01-14
Also published as: GB2051187B

Abstract

A composite resilient rail pad for disposition between a railway rail and a supporting sleeper has its longitudinal edges of harder rubber than its central portion to prevent rail tilt. The pad comprises a rectangular plate 10 made of relatively soft rubber with longitudinal grooves 11 in its upper and lower surfaces and a pair of cut-away portions 12 formed in the lower longitudinal edges. A pair of edge reinforcement members 13 made of relatively hard elastic rubber material and each having a projecting portion 14 are inserted into and vulcanized in said cut-away portions, each member 13 having a pressure receiving portion 15 having a height "h" less than the maximum thickness "h'" of said tie-pad plate. An air gap 16 is formed between each of the members 13 and the plate 10. <IMAGE>

Description

SPECIFICATION Tie-pad Assembly This invention relates to a novel tie-pad assembly for disposition between rail base surfaces and ties or sleepers made of concrete for absorbing vibration generated by trains running thereon.

A conventional rectangular tie-pad 1 made of elastic rubber is provided on both of its sides with a number of grooves 2 as shown in Figures 1 and 2, which are a plan view and a cross sectional view thereof, respectively.

With respect to the properties of a tie-pad, the spring constant thereof is lowered or the thickness thereof is increased in order to provide an enhanced shock absorbing effect. However, such methods have the following defects. Figure 3 shows a tie-pad disposed between a rail 3 and tie or sleeper 4, where numeral 6 designates a pair of rail clips. Side portions a of the tie-pad are considerably expanded by the weight of the rails and any train passing thereover. In a curved portion of the railway, an undesirable phenomenon, so-called "rail tilting", is liable to occur due to a lateral pressure applied to the rails by a train running thereover.

Accordingly, an object of the present invention is to provide a novel construction of a tie-pad assembly to overcome the above-noted defects.

This and other objects of the present invention will be accomplished by providing a tie-pad assembly comprising a rectangular tie-pad plate made of relatively soft elastic rubber material having a plurality of longitudinal grooves provided on upper and lower surfaces thereof, and a pair of cut-away portions formed in the lower edges thereof which, in use, will extend in the longitudinal direction of the rail, a pair of reinforcement members made of relatively hard elastic rubber material, said members each having a projection portion inserted into said cut-away portion and a pressure receiving portion having a height less than the maximum thickness of said tie-pad plate, said members being secured to said tie-pad plate by vulcanisation, and an air gap being formed between each of said members and said tie-pad plate.

The present invention will be hereinafter described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a plan view of a prior art tiepad; Figure 2 shows a cross sectional view along the line Il-Il of Figure 1; Figure 3 is an illustration in cross section of a mounting state of the tie-pad according to the prior art method; Figure 4 is a cross section of a rail for i!lustrating the so-called "rail tilting"; Figure 5 shows a plan view of a tie-pad according to this invention; Figure 6 shows a cross sectional view of tiepad taken along the line VI--VI of Figure 5; Figure 7 shows a modified form of the tie-pad of the invention; and Figure 8 shows a practical embodiment of the tie-pad assembly of the invention.

Referring to Figures 5 and 6, a rectangular rubber plate 10 is made of soft resilient material having a hardness of Hs 600, which is softer than a conventional rubber plate by about Hs 100. A number of thin grooves 11 described hereinafter are provided on both sides of the rubber plate.

Longitudinal cut-away portions 12 are formed along both lower side edges of the rubber plate 10 extending in the direction of the railroad in which the plate is used.

Rubber reinforcement members 13 are made of a hard elastic material, such as a rubber of hardness of Hs 900, and each member 13 has a projecting portion 14 and a pressure receiving portion 1 5 integral therewith. The projecting portion 14 has a cross sectional configuration such as to fill the cut-away portion 12. A height h of the receiving portion 1 5 is somewhat lower than a height h' of the thickness of the rubber plate 10. In general, when a soft rubber is fully compressed, the maximum compression length thereof is about 10% of the original length thereof. For this reason, the heights h and h' are suitably determined. Then, the above-described members 13 are partially inserted into the cutaway portions 1 2 on both sides of the rubber plate with the cut-away portions filled with the projecting portions 14.The rubber plate is coupled to the reinforcement members with vulcanisation connection. An air space or gap 16 is formed between the rubber plate and the reinforcement member in the upper portion in assembly.

In the thus constructed tie-pad according to this invention, the height h of the pressure receiving portion of the hard elastic rubber reinforcement member (Hs 900) is somewhat (10%) lower than the height h' of the soft elastic rubber plate (Hs 600), and the reinforcement members are provided on both lower sides of the rubber plate in the railway direction. Therefore, though the shock absorbing or damping effect is enhanced using a small spring constant, the abnormal expansions toward the rail side directions are prevented. The gap 1 6 serves to lower the spring constant allowing the rubber plate to be freely deformed. In addition, the socalled "rail tilting" phenomenon is prevented by the resistances of the pressure receiving portions and the projecting portions of the hard rubber reinforcement members.The projecting portions also serve to enhance adhesive force to the rubber plate.

Figure 7 shows a modification. Though the projecting portion 14 of the preceding embodiment is shaped in a rectangular form in cross section, the projecting portion 14 may be wedge-shaped as shown in Figure 7.

Figure 8 shows a practical embodiment of a tie-pad assembly of the present invention, in a form in which it will be used in practice.

Dimensions in mm used in Figure 8 are only for reference.

As mentioned above, the rubber reinforcement members are used only along both edges of the rubber plate in the rail direction. The rubber reinforcement members may also be provided along the edges of the rubber plate normal to the railway. In this case, cut-away portions are also formed along both edges of the rubber plate, normal to the railway, and the cut-away portions are filled with extending portions of hard rubber reinforcement members, gaps being formed between the reinforcement member and the rubber plate in the same manner as that of the preceding embodiment. Processing is then carried out through an integral vulcanisation coupling.

Accordingly, undesirable displacement of the rubber plate of both edge portions normal to the railway, due to a waving phenomenon which occurs when the train passes through the railway is prevented.

The grooves formed in upper and lower surfaces of the rubber plate serve not only to reduce the spring constant but to enhance frictional forces against the rail and the tie, preventing slippages therebetween.

Claims

1. A tie-pad assembly comprising a rectangular tie-pad plate made of relatively soft elastic rubber material having a plurality of longitudinal grooves provided on upper and lower surfaces thereof, and a first pair of cut-away portions formed in the lower edges thereof which, in use, will extend in the longitudinal direction of the rail, a first pair of reinforcement members made of relatively hard elastic rubber material, said members each having a projecting portion inserted into said first cutaway portion and a pressure receiving portion having a height less than the maximum thickness of said tie-pad plate, said members being secured to said tie-pad plate by vulcanisation, and an air gap being formed between each of said members and said tie-pad plate.

2. A tie-pad assembly as claimed in Claim 1, wherein said tie-pad plate has a second pair of cut-away portions formed in lower side edges thereof laterally of said rail direction, and said assembly further comprises a second pair of reinforcement members made of relatively hard elastic rubber material, said second pair of reinforcement members each having a projecting portion to be inserted into each of said second pair of cut-away portions and a pressure receiving portion integral therewith, said second pair of reinforcement members being secured to said tiepad plate by vulcanisation.

3. A tie-pad assembly as claimed in Claim 1 or 2, wherein said projecting portions have a rectangular shape in cross section.

4. A tie-pad assembly as claimed in Claim 1 or 2, wherein said projecting portions are wedgeshaped in cross-section.

5. A tie-pad assembly as claimed in Claim 1 or 2, wherein the height of each of said pressure receiving portions is less than the maximum thickness of said tie-pad plate by 10% of the maximum thickness.

6. A tie-pad assembly substantially as hereinbefore described with reference to Figures 5 and 6, Figure 7 or Figure 8 of the accompanying drawings

7. A rail assembly including a rail and a supporting tie therefor and incorporating a tie-pad assembly according to any one of Claims 1 to 6, the tie-pad assembly being disposed between the rail and tie.