RAIL PADS AND METHODS OF UPGRADING RAILWAY TRACK USING SUCH PADS

Abstract: A pad which is suitable to be placed on a foundation for a railway rail and to have the rail standing on it, the pad being generally rectangular and comprising a web (1) from which, when the web (1) is lying horizontally, protuberances (2, 3) project upwardly but no protuberances project downwardly, is characterised in that there are tens of the protuberances (2, 3) in the form of studs, each of which, except possibly at the edges of the pad, is completely surrounded by a portion of the web (1) which is free from protuberances (2, 3), the studs having convexly rounded tips and all the studs, except possibly at the edges of the pad, being substantially identical and of circular cross-section. The pad is further characterised in that it has two ears (8) projecting laterally from each of two opposite edges of the pad to receive between them a part projecting upwardly from the rail foundation whereby the pad is prevented from moving along the rail. The pad is still further characterised in that it is no more than 6.5mm. thick. Preferably, the pad is no more than 6mm. thick, and is desirably about 5.5mm. thick. A method of upgrading a section of railway track using such a pad is also disclosed.

Description: This invention relates to rail pads and methods of upgrading a section of railway track using sud pads. DE-A-1014139 discloses a pad which is suitable to be placed on a foundation for a railway rail and to have the rail standing on it, the pad being generally rectangular and comprising a web from which, when the web is lying in a particular orientation, protuberances project upwardly but no protuberances project downwardly. However, the protuberances on the pad disclosed in DE-A-1014139 are very few and they are large and widely spaced apart and are joined together by cross-pieces which undesirably limit the flexibility of the pad. According to a first aspect of the present invention, there is provided a pad which is suitable to be placed on a foundation for a railway rail and to have the rail standing on it, the pad being generally rectangular and comprising a web from which, when the web is lying horizontally, protuberances project upwardly but no protuberances project downwardly, characterised in that there are tens of the protuberances in the form of studs, each of which, except possibly at the edges of the pad, is completely surrounded by a portion of the web which is free from protuberances, the studs having convexly rounded tips and all the studs, except possibly at the edges of the pad, being substantially identical and of circular cross-section and further characterised in that the pad has two ears projecting laterally from each of two opposite edges of the pad to receive between them a part projecting upwardly from the rail foundation whereby the pad is prevented from moving along the rail and still further characterised in that the pad is no more than 6.5mm thick when the rail, secured to the foundation, is standing on it. Preferably, a pad embodying the first aspect of the present invention is no more that 6mm thick, and is desirably about 5.5mm thick. It is also preferable that in a pad embodying the first aspect of the present invention the studs are in parallel rows and in parallel columns inclined by an acute angle to the rows. In a pad embodying the first aspect of the present invention it is desirable that, except at the edges of the pad, each stud is surrounded by six other studs none of which is at a distance from it greater than the thickness of the stud. Preferably, in a pad embodying the first aspect of of the present invention the studs at each of two opposite edges of the pad are wider, in a direction from one of said edges to the other, than the studs nearer the centre of the pad. According to a second aspect of the present invention, there is provided a method of upgrading a section of railway track in which a rail stands on a first pad which lies on a foundation, in which method the first pad is replaced by a second pad embodying the first aspect of the present invention and of substantially the same thickness, when compressed, as is the first pad, when compressed, or no more than about 1mm. thicker. Reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a plan view of a rail pad embodying the first aspect of the present invention; Figure 2 shows a side view of the rail pad when viewed as indicated by the arrow II in Figure 1; and Figure 3 shows a sectional view on a larger scale of part of the rail pad when viewed as indicated by the arrow II in Figure 1. The pad illustrated in the drawings consists of a single moulding of polyurethane and is generally rectangular as seen in plan view. It consists of a generally rectangular web 1 2.5mm thick having many protuberances in the form of studs 2 of circular cross-section and studs 3 of elongate cross-section on one face 4 of the web. On the opposite face 5 of the web there are no protuberances and no recesses. The distance from the face 5 to the tips of the studs 2 and 3 is 5.5mm. The studs 2 have a diameter of 9.75mm at their tips and a slightly larger diameter at their roots because their flanks are inclined by an angle X of about 5° to the normal 6 to the web. The tips of the studs 2 are convex with a radius of 24mm. The studs 3 have a flat area 3A at their tips and a convexly curved area 3B at the sides of their tips nearer the centre of the pad. The studs 2 are arranged in columns which are vertical in Figure 1 and in rows which are inclined by an acute angle Y to the columns. There are eight columns each with eleven studs 2 and one stud 3 at each end of the column and, between those columns, seven columns each consisting of twelve studs 2. The pitches of the studs 2 in the columns are 11mm and the columns themselves have a pitch of 12.7mm, measured perpendicularly to the columns. Where two studs 2 or one stud 2 and one stud 3 in any one column have their roots adjoining one another there is a radius R of 0.55mm. At each of two opposite edges of the web there is a region 7 where the web thickness is 4mm and from each region 7 there project two ears 8 of the same thickness as the region 7, the intention being that a clip-retaining member for a so-called P-R clip or an e-clip is to lie partly between each two adjacent ears 8 whereby any tendency for the pad to move along the rail is opposed. A pad embodying the first aspect of the present invention can isolate the rail foundation from approximately 40% of a 40kHz vibratory force applied to the overlying rail. It should be noted that, although the pad described with reference to the Figures is made of polyurethane, a pad embodying the first aspect of the present invention could be made of any other suitably robust or hardened material, such as polyester, polyethylene or rubber. In some circumstances it may be desirable to secure the face 5 of the web, by a suitable adhesive, to a rail seat on a concrete rail foundation, for example a sleeper consisting of a concrete beam upon which two rails rest, or a block upon which only one rail rests and forming part of a sleeper comprising two blocks joined together by a steel tie-bar, or a long slab of concrete extending along the railway track. One of the reasons why it may be desirable to secure the pad by an adhesive is that this prevents sand, which is applied to the running surfaces of the rail, from penetrating between the pad and the concrete sleeper, where it can cause abrasion of both the pad and the sleeper. It is also possible to secure the illustrated pad by an adhesive to a steel railway sleeper. Furthermore an entirely different pad, but having protuberances and/or recesses on its upper face, but not on its lower face, may also have its lower face secured by an adhesive to a concrete or steel rail foundation. Pads according to the first aspect of the present invention are preferably employed in methods embodying the second aspect of the present invention, as will now be described. In some circumstances, it is desirable to upgrade a section of railway track, so as to allow that section to withstand heavier loads, for example because of the wish to use heavier railway vehicles and/or vehicles travelling at faster speeds. According to the second aspect of the present invention, firstly the means fastening the rail to the foundation are released. Typically, the rail fastening means comprise rail clips, such as a P-R clip or an e-clip, and to release the rail from retention by such clips the clips are extracted from respective clip-retaining members embedded in, or otherwise attached to, the rail foundation. When the rail has been released, the rail pad that had been lying between it and the rail foundation is removed and is replaced by a pad, embodying the first aspect of the present invention, which is of substantially the same thickness, when compressed, as the pad that it is replacing, when that pad is compressed, or no more than about 1mm. thicker. Since pads embodying the first aspect of the present invention have protuberances on only one face, it is possible to manufacture a pad which better isolates the foundation from dynamic forces than the pad which it is to replace, but is at the same time not substantially thicker than that pad. By replacing the first pad by such a pad, it is possible to re-use the rail clips, which were previously extracted so as to release the rail, to secure the rail once again to the rail foundation, without the distortion of the clips on driving them into position being so great that they exert too high a force on the rail. Since pads used in railway track to which methods embodying the second aspect of the present invention may be applied are generally 4.5mm to 6.5mm thick, and are typically 5.5mm in overall thickness, when compressed, pads embodying the first aspect of the present invention are, when compressed, no more than 6.5mm thick, are preferably no more than 6mm thick, and are desirably about 5.5mm thick.

Claims: A pad which is suitable to be placed on a foundation for a railway rail and to have the rail standing on it, the pad being generally rectangular and comprising a web (1) from which, when the web (1) is lying horizontally, protuberances (2, 3) project upwardly but no protuberances (2, 3) project downwardly, characterised in that there are tens of the protuberances (2, 3) in the form of studs, each of which, except possibly at the edges of the pad, is completely surrounded by a portion of the web (1) which is free from protuberances (2, 3), the studs having convexly rounded tips and all the studs, except possibly at the edges of the pad, being substantially identical and of circular cross-section and further characterised in that the pad has two ears (8) projecting laterally from each of two opposite edges of the pad to receive between them a part projecting upwardly from the rail foundation whereby the pad is prevented from moving along the rail and still further characterised in that the pad is no more than 6.5mm thick when the rail, secured to the foundation, is standing on it. A pad according to claim 1, wherein the pad is no more than 6mm thick. A pad according to claim 1 or 2, wherein the pad is about 5.5mm thick. A pad according to any preceding claim, in which the studs are in parallel rows and in parallel columns inclined by an acute angle to the rows. A pad according to any preceding claim, in which, except at the edges of the pad, each stud is surrounded by six other studs none of which is at a distance from it greater than the thickness of the stud. A pad according to any preceding claim in which the studs (3) at each of two opposite edges of the pad are wider, in a direction from one of said edges to the other, than the studs (2) nearer the centre of the pad. A method of upgrading a section of railway track in which a rail stands on a first pad which lies on a foundation, in which method the first pad is replaced by a second pad according to any preceding claim and of substantially the same thickness, when compressed, as is the first pad, when compressed, or no more than about 1mm thicker. A method of upgrading a section of railway track in which a rail stands on a first pad which lies on a foundation, in which method the first pad is replaced by a second pad according to anyone of claims 1 to 6, said pad having protuberances on only one face thereof.

Inventors: LEEVES, GEOFFREY GORDON
Applicants: PANDROL LIMITED
Application year: 1990
Main classification: E01B9
IPC codes: E01B9