GB2311551A - Insulated rail joints - Google Patents

Description

Insulated Rail Joints The present invention is concerned with rail joints formed between aligned lengths of rail, whereby a strong connection is formed between the rail lengths while isolating them electrically from each other.

In laying a railway track, or in repairing damaged track, it is very important that the ends of adjacent lengths of rail be connected together in a manner which gives a very strong joint without any irregularities. For this purpose, fishplates or rail joints may be used, which are two metal plates, usually forged or rolled, which have bolt holes aligned with holes in the rail ends and which, when tightened together on the two sides of the track with bolts1 secure the rail ends together. It is an alternative current practice to weld together the adjacent rail ends, whereby long lengths of "continuously welded rail" are produced in situ. However it is also a usual requirement that the rail be electrically isolated into sectors at intervals, typically of the order of one mile, so that the location of a train along the track, or the status of a set of points, may be determined electrically and for that information to be conveyed to a control point such as a signal box.

Thus there is a need to provide, at intervals along the track, a rail joint which provides the necessary strong connection between adjacent rail lengths, while at the same time isolating the rail lengths electrically from each other. Various attempts have been made to provide such insulated rail joints but such jointing devices as are available suffer from various disadvantages.

By way of example, one prior device for this purpose takes the form of a preformed insulator which is designed to match closely the contour of one of the upright faces of the rail and to enclose on three sides a steel joint bar by which the adjacent rail ends are interconnected. The preformed insulator is intended to be adhered to the rails and to the steel joint bar by means of an adhesive resin applied in situ at the track side but before that can be done it is necessary to grit blast, de-grease and prime both the steel joint bars and the rail ends. Because of the difficulty of carrying out all these operations satisfactorily at the track side, it has become a practice to carry out this work in a workshop and then to take the resulting section of jointed rail and weld it at the required position into the track.

An alternative prior approach has been to rely upon a jointing bar which is itself made wholly of insulating material. Thus such a bar is available which is made of an epoxy/glass fibre resin in which the fibre is in the form of continuous nonwoven glass filaments. The bar is able to provide the desired strong link between the rails without itself providing an electrically conductive path from one rail end to the next. However, in view of the combined insulating and strength properties which the bar is required to have, it is an expensive product which adds significantly to the normal cost of providing an insulating rail joint.

Against the foregoing background, it is an object of the present invention to provide an improved rail jointing bar by which some at least of the disadvantages of such hitherto available insulating jointing systems are reduced or avoided.

The improved rail jointing bar according to the present invention comprises an elongate steel body carrying first and second contact bars secured respectively within the regions of the upper and lower edges of said body, the orientation of said contact bars upon said elongate steel body being such that, when said body is secured to a railway rail generally parallel to the length of the rail, the first contact bar abuts an under surface of the head of the rail and the second contact bar abuts an upper surface of the rail base, the railcontacting surface of each said contact bar being electrically insulated from the elongate body.

It will be readily understood that, by means of the rail jointing bar of the present invention, two adjacent rail ends may be held rigidly together by the elongate body but the latter body does not provide an electrical path from one rail to the other.

In its simplest form, the rail jointing bar according to the invention comprises just three parts, namely the elongate steel body and two contact bars each made of a rigid or compressible insulating material. These insulating contact bars may be mounted upon two inclined surfaces of the elongate steel body but more preferably are located within elongate channels within these respective surfaces. In either case, the contact bars are preferably secured to the steel body by an adhesive material, preferably an insulating adhesive, for example a rubber compound.

However it is much preferred to present a metal surface, especially a steel surface, to the rail and therefore, in a particularly preferred form of the jointing bar according to the present invention, the two contacting bars are of steel and are mounted upon the elongate body in a manner which insulates the contacting bars electrically from the body. Such steel contacting bars must not themselves provide an electrically conductive link between the rail ends and should therefore each be in the form of two or more aligned sections, each section being electrically insulated from the next one.

When the rail-contacting bars are of steel as described above, they may be insulated from the elongate body by means of strips of insulating material, each interposed between a contact bar and the body. Preferably these components, that is the contact bars, insulating strips and elongate body, are all held together by means of an insulating adhesive.

The invention will now be further described and illustrated with reference to the accompanying drawings, which illustrate, by way of example only, two preferred embodiments of the rail jointing bar according to the present invention and wherein: Fig. 1 is a vertical cross sectional view of a rail to which two of the first form of tinting bars are fitted; Fig. 2 is a corresponding perspective view, to a smaller scale, of the rail and jointing bars of Fig. 1; Fig. 3 is an elevation from the front of an alternative form of jointing bar; and Fig. 4 is a perspective view of a joint alignment tool to assist installation of a rail jointing bar according to the invention.

The rail 10 illustrated in the drawings is of a common railway type having a rail head 11 and a wide flat base 12. Two lengths of this rail, 13 and 14, of which only the adjacent ends are shown, are aligned but are insulated from each other by an end post 15 of insulating material, such as is conventionally used for this purpose.

The two jointing bars 16, 17, seen in section in Fig. 1, each comprises an elongate body 18 of steel, so shaped and dimensioned as to fit into the space on each side of the rail between the head and base of the rail. Into the upper and lower ends of each of the elongate bodies is machined a channel 19 extending uniformly throughout its length and each channel 19 is provided with an extruded, insulating strip 20 of generally squared U-shaped cross-section.

Fitted into each of the insulating strips 20 is a contact bar or bearing bar 21, made of steel and of rectangular cross-section. Each bearing bar 21 is interrupted by a short break filled with an adhesive insulating rubber compound 22 in the region of the middle of the length of the bar, in order to prevent the bar forming an electric conducting bridge between the rails 13 and 14. The bearing bars and insulating strips are retained in position in the channels of the body 18 by means of the same insulating rubber compound.

Each of the jointing bars 16, 17 is penetrated by a number of bolt holes 23, designed to receive bolts or multigroove locking pins by which the jointing bars are secured to the rails. Each bolt is insulated from the bars by either surrounding ferrules (not shown) or an insulating layer of material attached to the bolt. As the bolts are thightened, the jointing bars are drawn towards the rail into the tapering gap between the rail head and base, where the bearing bars 21 abut the rail and form a tight joint.

The jointing bars 16, 17 hold the adjacent rails 13, 14 firmly together but, by virtue of the insulating strips 20 and the end part 15 and insulant 22, the two rails are electrically isolated from each other.

The spaces on each side of the rails between the rail and the bars 23 is filled with a rust inhibitor and/or insulating sealant 24 to ensure that the electrical resistance of joint bar to rail cannot be bridged by any contaminant conductive material.

The jointing bar of the present invention may readily be adapted to rails of a range of different cross-sections by modifying the shape of the bar, in particular by changing the overall height of the bar and the relative positions of the channels 19 and bearing bars 21. The rail jointing bar can further be used for connecting together two rails of differing cross-section and/or of differing wear characteristics, for example as illustrated in Fig. 3.

The two rails 30 and 31 shown in Fig. 3 are of different vertical dimensions, so that when the respective rail heads 32, 33 are aligned (as of course they must be, in use) the bases 34, 35 are at different heights. The jointing bars 36 (only one of which is seen) are therefore of a modified elongate shape, such that one section of their length fits into the space between the head 32 and base 34 of the rail 30 while the other section of their length fits into the corresponding space of the rail 31.

In general, the jointing bars 36 of Fig.

3 resemble the jointing bars 16, 17 of Figs.

1 and 2. Each of the contact bars 38 is interrupted in the region of the middle of its length at a position adjacent to an end post 37 of insulating material located between the adjacent ends of the rails 30, 31.

The joint alignment tool illustrated in Fig. 4 comprises a set of three components, namely a double-pronged first component 40 and two identical single-pronged components 41, only one of which is shown. Each of the components takes the form of a flat base with either two or one tapered prongs 42 extending perpendicularly from the base and with two or one rounded handles 43 on the other face of the base, by means of which handles the component is manipulated.

When a pair of jointing bars such as the bars 16, 17 of Figs. 1 and 2 (or similar bars having only four bolt holes 23) are to be installed to connect two aligned rails, the bars are placed over the prongs 42 of the joint alignment tool components; the component 40 projects through the middle two holes of one of the jointing bars and the two components 41 project through the outer holes of the other bar. The jointing bars are thus offered to the rails and the prongs assist the alignment of the respective bolt holes.

One of the outer components 41 is now withdrawn and an insulating ferrule and bolt are inserted through the jointing bars. The exercise is repeated at the other end of the jointing bars and then in the middle holes.

In the case where the jointing bars each have six holes 23, two holes in each bar remain free when the alignment tool components are first inserted. Ferrules and bolts may thus be inserted in these holes before any of the tool components are removed.

Claims (11)

1. A rail jointing bar for connecting together aligned lengths of rail, which comprises an elongate steel body carrying first and second contact bars secured respectively within the regions of the upper and lower edges of said body, the orientation of said contact bars upon said elongate steel body being such that, when said body is secured to a railway rail generally parallel to the length of the rail, the first contact bar abuts an under surface of the head of the rail and the second contact bar abuts an upper surface of the rail base, the railcontacting surface of each said contact bar being electrically insulated from the elongate body.

2. A rail jointing bar as claimed in Claim 1, wherein said contact bars are located within elongate channels within said elongate body.

3. A rail jointing bar as claimed in Claim 1 or Claim 2, wherein said contact bars are made of an insulating material.

4. A rail jointing bar as claimed in Claim 3, wherein said contact bars are secured to said elongate body by an adhesive material.

5. A rail jointing bar as claimed in Claim 1 or Claim 2, wherein said contact bars are of steel and are mounted upon said elongate body in a manner which insulates the contact bars electrically from the body.

6. A rail jointing bar as claimed in Claim 5, wherein a strip of insulating material is interposed between each contact bar and said elongate body.

7. A rail jointing bar as claimed in Claim 6, wherein each said strip of insulating material is of generally squared U-shaped cross-section.

8. A rail jointing bar as claimed in either of Claims 6 and 7, wherein said contact bars, insulating strips and elongate body are held together by means of an insulating adhesive.

9. A rail jointing bar as claimed in any of Claims 5 to 8, wherein each said contact bar is in the form of two or more aligned sections, each said section being electrically insulated from the next one.

10. A rail jointing bar substantially as hereinbefore described with reference to, and as illustrated in, Figs. 1 and 2 of the accompanying drawings.

11. A rail jointing bar substantially as hereinbefore described with reference to, and as illustrated in, Fig. 3 of the accompanying drawings.