GB2237833A

GB2237833A - Rail pad

Info

Publication number: GB2237833A
Application number: GB9022220A
Authority: GB
Inventors: Trevor Paul Brown
Original assignee: Pandrol Ltd
Current assignee: Pandrol Ltd
Priority date: 1989-11-08
Filing date: 1990-10-12
Publication date: 1991-05-15
Anticipated expiration: 2010-10-12
Also published as: CA2029276C; GB2237833B; GB9022220D0; GB8925238D0; CA2029276A1

Abstract

A pad, suitable for spacing the bottom of a railway rail from a rail foundation on which the rail stands, comprises a plate-like rail-supporting portion (1) and softer, resiliently-deformable, sealing means (3), which sealing means (3) are bonded to the rail-supporting portion (1) at a peripheral region thereof and are such that, when the pad is placed on a rail foundation and a rail is placed on the rail-supporting portion (1) of the pad, those means (3) deform under the weight of the rail so as to form a substantially watertight seal around the said peripheral region of the rail-supporting portion (1). <IMAGE>

Description

RAIL PADS The present invention relates to a pad suitable for spacing the bottom of a railway rail from a rail foundation on which the rail stands.

It has been found that, owing to the seepage of water, bearing particles of grit, sand, etc., between the pad and the rail foundation (commonly a concrete sleeper), erosion of the rail foundation and/or the pad can occur as the pad moves with respect to the surface of the rail foundation, owing to the passage of railway vehicles along the rail above it. Such erosion can be a particular problem where sand is applied to the rail to improve the grip of the wheels of a railway vehicle upon the rail.

According to the present invention, there is provided a pad suitable for spacing the bottom of a railway rail from a rail foundation on which the rail stands, the pad comprising a plate-like rail-supporting portion and softer, resiliently-deformable, sealing means, which sealing means are bonded to the rail-supporting portion at a peripheral region thereof and are such that, when the pad is placed on a rail foundation and a rail is placed on the rail-supporting portion of the pad, those means deform under the weight of the rail so as to form a substantially watertight seal around the said peripheral region of the rail-supporting portion.

In some circumstances it may be preferable that the sealing means, when deformed, do not extend beyond the periphery of the said rail-supporting portion, so that wearing of the sealing means by rail shoulders, rail clips, etc., can be avoided.

The sealing means advantageously comprise a layer of resilient material extending (when not deformed), at least substantially, over the entire lower surface of the said rail-supporting portion and preferably extending right up to (but desirably not beyond, except when deformed) the edges of the pad, but can also comprise a strip of resilient material extending around the peripheral region of the lower surface of the railsupporting portion. Advantageously, the sealing means may be partially located within a recess provided in the lower surface of the rail-supporting portion.

Preferably, the rail supporting portion is composed of hard polyurethane and the sealing means are composed of soft polyurethane. In a preferred embodiment, the polyurethane of the rail supporting portion has a Shore 'A' hardness value of 90 and that of the sealing means a Shore 'A' hardness value of 60.

Examples in accordance with the invention are described below with reference to the accompanying drawings, in which: Figure 1 shows a plan view from above of a pad embodying the present invention, when the pad is not under load; Figure 2 shows a cross-sectional side view taken along the line II-II in Figure 1; Figure 3 shows a plan view from above of another pad embodying the present invention, when the pad is not under load; Figure 4 shows a front elevational view looking in the direction of the arrow IV in Figure 3; Figure 5 shows a side view looking in the direction of the arrow V in Figure 3; Figure 6 shows a plan view from above of yet another pad embodying the present invention, when the pad is not under load; Figure 7 shows a cross-sectional side view taken along the line VII-VII in Figure 6; and Figures 8 and 9 show respective cross-sectional side views of two further pads embodying the present invention, when the pads are not under load.

A pad embodying the present invention includes a plate-like rail supporting portion 1, which may for example be composed of rubber or, for heavier duty conditions, hard polyurethane. In some circumstances, it may be desirable to provide some form of surface configuration (not shown) on the upper face of the rail-supporting portion 1.

In plan, the rail-supporting portion 1 of the pad of Figures 1 and 6 is in the form of a rectangle having additional ear portions 2 projecting from each corner thereof, so as to provide, on two opposing sides of the pad, respective recesses 2a for locating the pad when it is in use. In the pad of Figure 3, the ear portions 2 taper back from the recesses 2a to reduce the material content. In particular, the pad shown in Figures 3 to 5, which is suitable for a rail of base width 5.5 inches (14.97 cm), is of width 6.125 inches (15.56 cm) between the recesses 2a, and is 5.75 inches (14.61 cm) in width at the opposing ends of the pad not having the recesses 2a, the pad being of length 7 inches (17.78 cm). That is, the part of the rail-supporting portion 1 where the rail will sit is substantially in the form of a rectangle from which the corners have been cut away.The recesses 2a are of depth 0.625 inches (1.59 cm), so the width of the pad at its widest parts, that is between the most distant extremities of opposing ear portions, is also 7 inches (17.78 cm). The recesses 2a are of length 3.189 inches (8.1 cm). Please note, however, that the precise shape of the rail-supporting portion 1 is not essential to the present invention, and may take other forms.

A pad embodying the present invention also includes softer, resiliently-deformable, sealing means which are bonded to the lower surface of the rail-supporting portion 1 at least at a peripheral region thereof. The sealing means are preferably composed of soft polyurethane, but may be made of any other suitable resiliently-deformable material, such as rubber for example.

In the preferred embodiments shown in Figures 1 and 2 and Figures 3 to 5, the sealing means comprise a plate-like sealing layer 3, which layer extends over the lower surface of the rail-supporting portion 1. When the pad is in use, between a rail and a rail foundation, the weight of the rail presses down upon the rail-supporting portion 1 of the pad, which in turn brings about deformation of the sealing layer 3, which thereby forms a substantially watertight seal around the peripheral region of the rail-supporting portion 1. The railsupporting portion may have a thickness of 4mm or above, preferably 5mm, and the sealing layer 3 is desirably, for practical reasons, no less than 1.5mm thick.

In Figures 1 and 2 the sealing layer 3 is of the same shape, in plan, as the rail-supporting portion 1, but is slightly smaller in size such that there is a small gap between the edge of the sealing layer 3 and the periphery of the rail-supporting portion 1. This gap is such that, when the sealing layer 3 is deformed under the weight of a rail, the sealing layer 3 does not extend beyond the periphery of the rail-supporting portion 1, thereby protecting the sealing layer 3, made of soft material, from erosion by external elements bearing upon the pad.

In Figures 3 to 5, however, the sealing layer 3 extends over the entire undersurface of the rail-supporting portion 1, i.e. it terminates in line with the edges of that portion when the pad is not under load. This arrangement has the advantage, over the arrangement of Figures 1 and 2, that it is better at preventing seepage of water between the pad and the rail foundation, and is also easier to manufacture.

Furthermore, the greater the area of the underside of the rail-supporting portion 1 that is covered by the sealing material, the less pressure there will be on that sealing material from the load applied to the pad by the rail clips and rail traffic. Thus, the life of the sealing material is likely to be longer if it extends over the entire under surface of the rail-supporting portion 1, even though, when deformed, the sealing material will extend beyond the periphery of the rail-supporting portion 1.

The pad illustrated in Figures 6 and 7 differs from the pad described with reference to Figures 1 and 2 only in regard to the sealing means. In the pad of Figures 6 and 7 the sealing means are constituted by a sealing strip 3a, of any suitable resiliently-deformable material which is softer than the material of the rail-supporting portion 1, bonded to the lower surface of the railsupporting portion 1. The sealing strip 3a extends along the edge of the rail-supporting portion 1, preferably at a short distance therefrom for the same reasons as discussed above with reference to Figures 1 and 2.

Modifications of the pad shown in Figures 6 and 7 are shown in Figures 8 and 9. In Figure 8 the sealing means comprise a sealing strip 3b which is located partially within a recess 4 formed in the lower surface of the rail-supporting portion 1, thus enabling the lower surface of the rail-supporting portion 1 to contact the rail foundation when the pad is in position beneath the rail. Figure 9 illustrates a pad in which the sealing means, comprising a sealing strip 3c partially located in a recess 4, are not spaced from the edge of the rail-supporting portion 1.

It may be desirable, in some circumstances, to seat the sealing layer 3 of Figures 1 and 2 in a recess formed in the underside of the rail-supporting portion 1.

In each of the pads shown in Figures 8 and 9, the sealing means are bonded to the rail-supporting portion 1.

In each of the pads described with reference to Figures 1 to 9, the sealing means may be bonded to the rail-supporting portion 1 at the time of manufacturing the rail-supporting portion 1 and sealing means, for example by injecting the hard and soft material simultaneously into a single mould, or may alternatively be bonded to the rail-supporting portion 1 at a later stage of manufacture of the pad, for example by means of an adhesive.

As pads embodying the present invention are provided with sealing means which deform, under the weight of a rail placed upon the pad, so as to form a substantially watertight seal around the peripheral region of the rail-supporting portion of the pad, water carrying sand, grit, or other particles, can be prevented from seeping between the base of the pad and the rail foundation, thereby substantially avoiding the problem of erosion of the rail foundation and/or the pad which might otherwise be caused through such water seepage.

Claims

1. A pad suitable for spacing the bottom of a railway rail from a rail foundation on which the rail stands, the pad comprising a plate-like rail-supporting portion and softer, resiliently-deformable, sealing means, which sealing means are bonded to the rail-supporting portion at a peripheral region thereof and are such that, when the pad is placed on a rail foundation and a rail is placed on the rail-supporting portion of the pad, those means deform under the weight of the rail so as to form a substantially watertight seal around the said peripheral region of the rail supporting portion.

2. A pad as claimed in claim 1, wherein the said sealing means comprise a layer of resilient material extending over the lower surface of the said rail-supporting portion.

3. A pad as claimed in claim 2, wherein the said layer extends to the edges of the lower surface of the said rail-supporting portion.

4. A pad as claimed in claim 1, wherein the said sealing means comprise a strip of resilient material extending around the peripheral region of the lower surface of the said rail-supporting portion.

5. A pad as claimed in claim 2 or 4, wherein the said sealing means are partially located within a recess provided in the lower surface of the said rail-supporting portion.

6. A pad as claimed in claim 2, 4 or 5, wherein the said sealing means, when deformed, do not extend beyond the periphery of the said rail-supporting portion.

7. A pad as claimed in any preceding claim, wherein the said rail-supporting portion is composed of hard polyurethane and the said sealing means are composed of soft polyurethane.

8. A pad as claimed in claim 7, wherein the hard polyurethane is of Shore 'A' hardness 90 and the soft polyurethane is of Shore 'A' hardness 60.

9. A pad as claimed in any preceding claim, in which the said rail-supporting portion is in the shape of a rectangle having additional ear portions projecting substantially from the corner regions thereof, the ear portions each being substantially triangular and arranged such that respective locating recesses are formed between adjacent ones of the ear portions.

10. A pad substantially as hereinbefore described with reference to Figures 1 and 2, or Figures 3 to 5, or Figures 6 and 7, or Figure 8, or Figure 9, of the accompanying drawings.