GB2204079A

GB2204079A - Electrical insulation of railway rails

Info

Publication number: GB2204079A
Application number: GB08809590A
Authority: GB
Inventors: David Rhodes
Original assignee: Pandrol Ltd
Current assignee: Pandrol Ltd
Priority date: 1987-04-22
Filing date: 1988-04-22
Publication date: 1988-11-02
Anticipated expiration: 2008-04-22
Also published as: HK37692A; GB8709484D0; GB8809590D0; GB2204079B

Abstract

A device for electrically insulating a railway rail having a web 22 and a flange 23 has a portion 11 which lies under the flange 23, a portion 12 which extends upwardly beside one edge of the flange, a portion 13 which lies on the upper surface of one side of the flange and a portion 14 which lies in contact with one side of the web of the rail. It has no part which lies beside the opposite edge of the flange, no part which lies on the upper surface of the opposite side of the flange and no part which lies in contact with the other side of the web of the rail. These parts of the rail are covered by a second device identical with the first. Each device has the portion 11 of reducing thickness, proceeding away from the portion 12, and above or below the portion 11 of the other device so as to present a uniform thickness of insulating material under the rail flange. A ledge 15 increases the surface leakage path between the rail and a clip which is not shown but bears downwardly on a cover plate 16 placed on the portion 13. <IMAGE>

Description

Electrical insulation of railway rails This invention relates to electrical insulation of railway rails.

According to a first aspect of the invention, there is provided an insulating device which is suitable for use in electrically insulating a railway rail, the device being a shaped electrically insulating body having a first-portion which is intended to lie underneath the flange at the bottom of a flange-footed railway rail, a second portion which is intended to lie alongside one edge of .the flange, a third portion which is intended to lie on the upper surface of one side of the flange, in contact with it, and a fourth portion which is intended to lie in contact with one side of the upstanding web of the rail, the device having no part intended to lie alongside the opposite edge of the flange or above the opposite side of the flange and the device being such that when it is free from stress, before being applied to a rail, the first, second and third portions form a pocket for receiving part of the flange and when the device is free from stress and is in a particular orientation with the first portion horizontal, the second portion projects upwardly from the first portion and the fourth portion projects upwardly from the third portion.

According to a second aspect of the invention, there is provided an installation including a foundation.for a railway rail, a flange-footed railway rail standing on the foundation, first and second insulating devices according to the first aspect of the invention, with the first portions of the devices lying between the bottom of the flange and the foundation and with one side of the flange projecting into the pocket' of the first device and the opposite side of the flange projecting into the pocket of the second device, and means projecting above the third portions of the devices for holding the rail down.

Two examples in accordance with the first and second aspects of the invention are described below with reference to the accompanying drawings, in which: Figure 1- diagrammatically shows a perspective view of part of a first assembly on a railway track, the assembly including a first insulating device, Figure 2 shows a plan view of a second insulating device, Figure 3 shows an end view and Figure 4 a side view of the second insulating device, taken as indicated by the arrows III and IV, respectively, in Figure 2, Figure 5 shows a sectional view of the second insulating device, taken as indicated by the arrows V in Figure 2, and Figure 6 shows an end view of a second assembly on a railway track, this assembly including the second insulating device.

The first assembly includes a flange-footed rail, a reinforced concrete railway sleeper having four socalled "shoulders", made of cast malleable iron, incorporated in it and four so-called "P-R" clips or "e" clips having substantially straight legs driven into passages through the shoulders, for example as shown in U.K. Patent Specification No. 1,213,762 or 1,510,224. These parts of the assembly are not shown in the drawing. On the concrete sleeper is placed a substantially rectangular pad 1 of electrically insulating material, for example rubber, having two ears 2 on one side, between which lies part of one of the shoulders, and two ears (not shown) on the opposite side, between which lies part of another of the shoulders.

Two identical electrically insulating devices 3A and 3B, made by moulding acetal co-polymer (such as is sold under the name -Kematal) are provided for electrically insulating the rail from the clips and from the shoulders and for further electrically insulating the rail from the sleeper. Each of the devices 3A and 3B includes a first portion 11, a second portion 12, a third portion 13 and a fourth portion 1-4, which succeed one another, in that order, proceeding from one extremity A to the opposite extremity B of -the device. All these parts have a length L which is about 30mm. greater than the width, measured parallel to the dimension L, of the pad 1, the width of the pad being about equal to the width of the top of the sleeper.

When the devices 3A and 3B are free from stress, before being fitted to the rail, but have the orientations which they.have when they are in use, with the portions 11 horizontal or nearly so, the portions 11 are flat, the portions 12 project substantially vertically upwardly from the portions 11, the portions 14 project upwardly from the portions 13, being inclined to the vertical by about 25 to 300, and the portions 13 lie above the portions 11 and are inclined to them. When the devices 3A and 3B are fitted to the rail, the portions 12 and 14- are substantially vertical. The portion 11 is a rectangular sheet the thickness of which decreases steadily from the edge where it adjoins the portion 12 to the extremity A.

The width of the sheet is such.that the portion 11 -lies under substantially the whole width the flange. The portion 12 lies alongside one edge of the rail flange, preferably in contact with it and preferably fitting snugly on the radius at the bottom of the edge of the flange and on the radius at the top of the edge of the flange. The third portion 13 lies on the upper surface of the rail flange, in close contact with it, and where the upper surface of the flange has two parts of differing gradient, the third portion 13 likewise consists of two parts 13A and 13B which are inclined at differing angles, the part 13B being inclined at the greater angle, to the portion 11. The portion 14 presses, over its entire area, against one side of the web of the rail, owing to the resilience of the material of which the devices are made.

As the drawing shows, the device 3A extends under the flange of the rail and around the right-hand edge of the flange but has no part which extends upwardly from the left-hand side of its portion 11 to lie alongside the left-hand edge of the rail flange or above the left-hand side of the rail flange. Likewise the device 3B extends under the flange of the rail and around the left-hand edge of the flange but has no part which extends upwardly from the right-hand side of its portion 11 to lie alongside the right-hand edge of the flange or above the right-hand side of the flange.In fact the first portion 1-1 of the device 3B lies on the first portion 11 of the device 3A, although it could just as well lie under it, and since they are each of steadily reducing thickness, proceeding from portion 12 to extremity A, they together provide substantially unvarying thickness, about 4mm., of insulating material under the entire width of the rail flange. The thickness, measured horizontally, of the portion 12 is also about 4mm., the thickness of the portion 13 is about 2mm. and the thickness of the portion 14 is about 1 mum..

A ledge 15 on the portion 14 of each of the devices 3A and 3B projects generally towards the portion 12, i.e. away from the rail, horizontally or inclined downwardly, in order to increase the length of the surface leakage path between the web of the rail and the clip. As seen from the side, the ledge is in the form of a very wide inverted V or chevron, the uppermost part 15A of the ledge being on a level with the uppermost part B of the portion 14, although it could be a few millimetreslower, and the ledge having two downwardly-turned portions 15B at its opposite ends. The underneath face of the ledge is likely to remain dry during wet weather, so that it has a good resistance to surface leakage.

A malleable iron cover plate 16, or one made of nylon reinforced by glass fibre, is laid on the portion 13 of each device 3A and 3B, between two ramps 17 up which the so-called "toe" of a P-R clip or e clip can ride when the'clip is driven, in a direction parallel to the rail, so that its substantially straight leg is driven home in the passage through the shoulder. The toe of the clip eventually comes to rest on the plate 16 and presses downwardly on the plate, which in turn presses downwardly on the portion 13 of the device 3A or 3B, which in turn presses downwardly on the flange of the rail, whereby the rail is held down. On the illustrated plate 16 there are two lugs 16A, the righthand ends of which are not shown. Part of one of the shoulders lies between the two lugs in order to prevent the plate, and the associated device 3A or 3B, moving along the rail.

In Figures 2 to 6 the pad 1 is not shown; it can be included in the assembly or omitted. Figures 2 to 5 show one insulating device 3C and Figure 6 shows two identical insulating devices 3C which are as shown in Figures 2 to 5. The reference numerals and letters which appear both in Figures 2 to 6 and in Figure 1 denote corresponding parts.

In the devices 3C the portions 14 extend upwardly from the portions 13 when the devices 3C are in the illustrated orientation and are free from stress, at an angle of about 500 to the vertical. This angle could be anywhere between 200 and 550 or even above or below that range.

It will be seen that between the two ramps 17 in each device 3C there is a recess 17A, to the right of which (considering Figure 5) the portion 13 is thickened at 17B. to form a boundary wall 17C of the recess 17A. This recess receives a limb 20 of a cover plate 16, made by casting metal or moulded from suitable material, the cover plate 16 being of substantially L-shaped cross-section and thus having a second limb 21. The lugs 16A project from the limb 21, which is vertical in the assembly. Figure 6 shows the lower part-of the rail, which has a web 22 and a flange 23, the upper surface of which consists, at each side of the flange, of portions 23A and 23B which are differently inclined to the horizontal.The portions 14 of the devices 3C press against opposite faces of the web 22 and again the portions 11 taper as previously described.

The ledge 15 shown in Figures 2 to 6 is chevronshaped as seen in the side view (Figure 4), as is the ledge 15 shown in Figure 1. However, at the two ends of the ledge, shown at the top and bottom of Figure 2, the ledge is closer to the portion 12 of the device than is the centre of the length of the ledge, on the section plane IV, so that the ledge is also chevronshaped as seen in plan view (Figure 2).

In principle one ramp 17 will suffice if the clips to be used on opposite sides of the rail are identical and are similarly orientated when being driven.

The illustrated devices 3A, 3B and 3C are made by moulding but if the ramps 17 were omitted and the ledge 15 omitted or made straight, it would be possible to make it by extruding a long length of 'the insulating material and then cutting it into portions.

The invention can also'be employed in the case where one rail is laid, or both rails are laid, on a single slab of reinforced concrete extending along the track and incorporating shoulders as described above.

Then there are preferably employed a series of discrete pads ', one to each pair of shoulders, instead of a continuous pad extending along the track. If the pads are 6 to 8 mm. thick and the combined thickness of the portions 11 of the devices 3A and 3B is 4mm., there will,then be an air gap of 10 to 12 mm. width between the top of the slab and the bottom of the rail flange at locations between the pads. Again the devices 3A-, 3B and 3C will project at both ends beyond the sides of the pad in order to increase the lengths of the relevant surface leakage paths between the rail and the metal parts of the assembly, i.e. the shoulders, the clips and the plate-s 16.

The parts 11, 12 and 13 of each of the devices 3A, 3B and 3C forms a pocket to receive one edge of the rail flange. The fact that each device has to be fitted around only one edge of the rail flange, in contrast to known devices which fit around both edges, makes installation easier.

If desired, the portions 11 of the devices 3A, 3B and 3C could each extend, from the portions 12, only to a location at about the middle of the width of the flange, our even to a location well short of the middle, in which case they will have a constant thickness.

Claims

1. An insulating device which is suitable for use in electrically insulating a railway rail, the device being a shaped electrically insulating body having a first portion which is intended to lie underneath the flange at the bottom of a flange-footed railway rail, a second portion which is intended to lie alongside one edge of the flange, a third portion which is intended to lie on the upper surface of one side of the flange, in contact with it, and a fourth portion which is intended to lie in contact with one side of the upstanding web of the rail, the device having no part intended to lie alongside the opposite edge of the flange or above the opposite side of the flange and the device being such that when it is free from stress, before being applied to a rail, the first, second and third portions form a pocket for receiving part of the flange and when the device is free from stress and is in a particular orientation with the first portion horizontal, the second portion projects upwardly from the first portion and the fourth portion projects upwardly from the third portion.

2. A device according to claim 1 which is such that when it is free from stress and in said orientation the second portion projects substantially vertically upwardly from the first portion.

3. A device according to claim 1 or 2 which is such that when it is free from stress and in said orientation the fourth portion projects upwardly from the third portion at an angle to the vertical within the range 200 to 55 .

4. A device according to any preceding claim which is such that when it is free from stress and in said orientation the third portion is inclined to the first portion.

5. A device according to claim 4 which is such that when it is free from stress and in said orientation, the part of it nearer to the second portion is inclined at one angle to thefirst portion and the part of it further from the second portion is inclined at a greater angle to the first portion.

6. A device according to any preceding claim in which the first portion is of steadily reducing thickness, proceeding from its extremity nearer the second portion to its extremity further from the second portion.

7. A device according to any preceding claim in which a ledge projects from the fourth portion, generally towards the second portion.

8. A device according to claim 7 in which the ledge is chevron-shaped as seen in a side view.

9. A device according to claim 8 in which at the two ends of the ledge the- ledge is closer to the second portion than it is at the centre of the length of the ledge, so that the ledge is also chevron-shaped as seen in a plan view.

10. A device according to any preceding claim having a ramp on the third portion up which a toe of a rail clip may run when the clips being driven into a position to hold down the rail.

11. A devlce according to claim 10 having a second ramp on the third portion, there being a recess between the two ramps to receive a -cover plate on which the toe of a clip presses when the clip has been fully driven.

12. A device according to any one of claims 1 to 5 in which the first portion is of constant thickness and its width is no more than half the width of the flange of the rail for which the device is intended.

13. An insulating device which is suitable for use in electrically insulating a railway rail, substantially as hereinbefore described with reference to Figure 1 or Figures 2- to 6 of the accompanying drawings.

14. An installation including a foundation for a railway rail, a flange-footed railway rail standing on the foundation, first and second insulating devices according to any preceding claim, with the first portions of the devices lying between the bottom of the flange and the foundation and with one side of the flange projecting into the pocket of the first device and the opposite side of the flange projecting into the pocket of the second device, and means projecting above the third portions of the devices for holding the rail down.

15. An installation according to claim 14 in which the insulating devices are in accordance with claim 6 and each of the first portions lies under substantially the whole width of the flange, one of the first portions lying on the other so that together they provide a substantially unvarying thickness of insulating material over the entire width of the rail flange.

16. An installation according to claim 14 or 15 in which a respective cover plate projects over the third portion of each insulating device and a clip bears downwardly on the cover plate.

17. An installation according to any one of claims 14 to 16 in which there is an electrically insulating pad under the two first portions of the two insulating devices.

18. An installation on a railway track substantially as hereinbefore described with reference to Figure 1 or Figures 2 to 6 of the accompanying drawings.