GB2343471A - Electrically insulating railway end post - Google Patents

Abstract

The end post, for placement between the ends of a pair of railway rails 2, has a relatively narrow waist region between first and second outwardly flared end portions and comprises first and second mutually interlocking elements 12, 14, the element 12 including at least the first outwardly flared end portion and the second element 14 including at least part of the waist region. The interlocking is provided by a disc-like end 20 of the element 14 and a re-entrant aperture 18 in the element 12, or the elements have arrays of teeth. A tool with a hooked end and a protrusion for abutting underneath the element 12 is used in the installation of the end post. Two hooked members coupled by an adjustable strap provide support to the end post to counter parting of the elements 12,14 upon track expansion/contraction.

Description

RAILWAY END POST The present invention relates in one aspect to an end post for electrically insulating ends of adjacent rails of a railway from each other.

In a railway network it is usual to provide an insulating member known as an end post between adjacent ends of consecutive rails. The end post has substantially the same I-shape as the cross section of the rails. If an electric current is passed into the rails on one side of a track, and current sensors are attached to the rails on the opposite side of the track, a current will be detected when the two sides of the track are electrically connected, for example when a train is on the track. By dividing the track into discrete electrically conducting sections, it is possible to accurately determine the position of the train along the track. Determination of train positions is of great importance with regard to signalling and safety on the rail network.

Unfortunately, the end post is prone to breaking, particularly in its thin section corresponding to the web of the rail. The upper part of the post can be knocked out by a passing train and the lower part drops below the rails.

The two rails can now come into contact or can be electrically interconnected by dirt and moisture resulting in an electrical short. Replacement of the end post requires the relevant section of track to be closed to traffic while the joint is dismantled, the end post replaced and the joint re-assembled. The replacement procedure is time consuming and inevitably causes delays and routing problems on the rail network.

It is an object of the present invention to provide an improved end post which obviates or mitigates at least some of the problems associated with prior art end posts.

According to a first aspect of the present invention, there is provided a platelike electrically-insulating end post for placement between ends of a pair of railway rails, said end post having a relatively narrow waist region between first and second outwardly flared end portions, characterised in that said end post comprises first and second mutually interlocking elements, said first element comprising at least the first end portion, said second element comprising at least part of said waist region.

Preferably, the post is of two-part construction.

Preferably, the first element is a snap fit with the second element.

In a preferred embodiment, the first and second elements each have correspondingly toothed regions which are capable of interlocking to form a ratchet-type connection.

According to a second aspect of the present invention, there is provided a method of inserting an end post in accordance with the first aspect of the present invention between adjacent ends of two railway rails at a joint without dismantling said joint, said method comprising the steps of: (i) inserting the first element of the end post between the rails from below the rails; (ii) inserting the second element of the end post between the rails from above the rails; and (iii) mutually interlocking the second element with the first element.

Preferably step (iii) is performed while maintaining the first element in a desired position relative to the rails.

According to a third aspect of the present invention, there is provided a tool for assisting in the method of said second aspect of the present invention, said tool comprising a substantially rigid strip having a hooked end adapted to receive at least one lower flanges of the pair of rails at a joint and a projection upstanding from the strip in the same direction as the hooked end.

Preferably, the distance between the hooked end and the projection corresponds to half the length of the first element of the end post.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is an exploded perspective view of part of a railway joint; Figure 2 is a front view of an end post in accordance with the first aspect of the present invention; Figure 3 shows the separate elements of Figure 2; Figures 4 and 5 are front view of modified end posts; Figure 6 shows another modified end post and a fitting tool in accordance with the third aspect of the present invention; Figure 7 is a view sitnilar to Figures 4 and 5 of a further alternative end post; and Figures 8 and 9 are side and plan views respectively of a safety device for use with any of the end post constructions disclosed herein.

Referring to Figure 1, a standard railway rail 2 has a generally I-shaped cross section with a web 2a connecting upper and lower flanges 2b, 2c. A channel 2d is formed on each side of the rail 2 between the flanges 2b, 2c and the web 2a. An electrically insulating end post 4 of substantially the same shape as the cross section of the rail 2 is sandwiched between adjacent ends 2e of two such rails 2 which are typically spaced 6 mm apart. The end post 4 is held in place between the rail ends 2e by a pair of electrically insulated fish plates 6 each of which locates in a respective channel 2d and extends either side of the end post 4. The rails 2 and end post 4 are clamped between the fish plates 6 by means of bolts (not shown) which pass through bores 8a, 8b provided in the rails 2 and the fish plates 6 respectively, so as to form a joint.

Extra structural rigidity to the joint may be imparted by the use of hardened steel washer plates (not shown) which are secured to an outer exposed surface 6a of the fish plates 6. Since the end post 4 and the rails 2 are of the same general I-shape, a replacement end post 4 cannot be inserted between the rails 2 without removing at least one fish plate 6. This requires removing all the bolts and washer plates (if fitted) and is a time consuming process, during which the section of track is out of service.

Referring to Figures 2 and 3, a nylon end post 10 is plate-like and has a relatively narrow waist portion lOa between first and second outwardly flared end portions lOb, lOc. The end post 10 is of two-part construction and comprises first and second interlocking elements 12,14. The first element 12 (Figure 3) defines the first end portion lOb of the post 10 and has a flat lower surface 12a and upper surfaces 12b which are inclined relative to the lower surface 12a and which terminate in a pair of spaced-apart flanges 16 (defining part of the waist region 10a of the post 10) towards a mid-section 12c of the first element 12. The flanges 16 are mutually diverging towards their free ends and define a neck of a part-circular re-entrant recess 18 in the mid-section 12c of the first element 12.

The second element 14 (Figure 3) has an elongate portion 14a (defining part of the waist region 10a of the post 10) with a pair of shoulders 19 towards a first end which slope inwardly from the elongate portion 14a and then outwardly to form a disc-like first end region 20. At an opposite end, the elongate portion 14a flares outwardly to form a substantially rectangular second end region 22 (defining the second end portion lOc of the post 10).

In use, the first element 12 is introduced between the rail ends 2e of the joint to be repaired from beneath the rail ends, it being recognised that if necessary any remaining pieces of the broken end post 4 are first removed from between the rails 2. The first element 12 is held in position between the lower flanges 2c of the rails 2 and the second element 14 is introduced downwardly between the rail ends so that thedisc-like end region 20 of the second element 14 is presented to the recess 18 of the first element 12. The flanges 16 of the first element 12 act as a guide and assist in the correct positioning of the second element 14. Downward pressure on the second element 14 causes the flanges 16 to deform outwardly, thereby allowing the disc-like end region 20 of the first element 12 to be received in the recess 18.

The flanges 16 then snap back into their original position and grip the shoulders 19 of the second element 14, thereby preventing unwanted separation of the two elements 12,14.

The end post 10 is brightly coloured to distinguish it from the standard end post 4 and to make is easily visible, particularly in tunnels. This colouring allows engineers to subsequently identify where the replacement end post 10 has been used so that the joint may be inspected and/or dismantled at a convenient time.

Figure 4 shows a modified end post 10 in relation to the rail 2. The flanges 16 are relieved in relation to the profile of web 2a of the rail 2. Such relief allows the flanges 16 to deform outwardly without restriction by the fish plates 6 (Figure 1).

Figure 5 shows an end post 10 which has modified connection parts. The recess 18 in the first element 12 has substantially parallel boundary walls 18a which are provided with teeth or barbs 22. The end region 20 of the second element 14 is substantially rectangular and is provided with corresponding teeth or barbs 24. In this embodiment, less outward deformation of the flanges 16 (and hence less force) is required to interlock the first and second elements 12,14. The teeth or barbs 22,24 prevent unwanted disconnection.

Interlocking of the first and second elements 12,14 may be assisted by the use of an appropriate tool shown for convenience in Figure 6 in conjunction the elements 12,14 of general type shown in Figure 5. The tool 30 is a flat strip 31 formed into a hook 32 at one end. A handle (not shown) is provided at an opposite end. A small projection 34 is upstanding from the strip 31 in the same direction as the hook 32. The projection 34 may extend across the full width of the strip 31 or may be shorter and centrally disposed. The distance between the hook 32 and the projection 34 is designed to correspond to half the length of the first element 12 of the end post 10. The end post 10 in Figure 6 is similar to that shown in Figure 5, except that the first element 12 of the end post 10 is provided with a small indentation 36 in its lower surface 12a direct} below the recess 18 and the flanges 16 are relieved in relation to the profile of the web 2a of the rail 2.

In use, the hook 32 is passed under the rails at a joint to be repaired and hooked onto at least one of the rails forming the joint, the hook engaging at least one, but preferably both, the lower flanges 2c of the rails 2 at the joint.

The projection 34 of the tool 30 is desirably, but not essentially, sufficiently narrow that it projects into the 6 mm gap between the rails. The projection 34 locates in the indentation 36 of the first element 12 when the latter is correctly positioned between the rail ends 2e with the tool 30 hooked around the lower flanges 2c of the rails 2. In this position, the projection 34 is directly below the recess 18. Slight upward pressure is applied at the handle end of the tool 30 (indicated by arrow A) as the second element 14 is pressed downwardly (indicated by arrow B). The projection 34 serves as a fulcrum about which the first element 12 may flex, thereby reducing the force necessary to outwardly flex the flanges 16 (indicated by arrows C) to interlock the first and second elements 12,14.

Figure 7 illustrates a further, and currently preferred, shaping of the interlocking regions of the elements 12,14. It will be recognised that any of the elements 12,14 disclosed above can be applied using a tool 30 as described above, the elements being modified to include the undertaking 36 if desired.

Figures 8 and 9 show a safety strap which can be used in conjunction with the end post constructions described above. The strap comprises first and second hooks 41,. 42 and a flexible, variable length fastener 43 interconnecting the hooks 41,42. Each hook is formed from a short length of relatively rigid plastics strip having a centrally disposed hole adjacent one end and bent back upon itself at the other end to define a hook. The width of the length of strip from which each of the hooks 41,42 is formed is significantly wider than the maximum gap which can occur between rail ends in normal conditions.

The fastener 43 which interconnects the hooks 41,42 is in the form of a plastics cable tie of the kind consisting of an elongate strap one end of which includes an integral buckle containing a ratchet mechanism which cooperates with teeth moulded along one face of the strap. When one end of the strap is passed through the buckle so that the strap forms a loop the teeth and ratchet cooperate to permit the strap to be pulled through, thus tightening the loop, and at the same time prevent return movement of the strap through the buckle thus holding the loop of the strap at its preset length.

In use the strap is threaded through the holes of both of the hooks, and with the fastener close to its fully extended condition the safety strap is applied to the rail by hooking the hooks 41,42 around opposite lower flanges 2c of the rails and then tightening the strap by pulling the free end of the belt portion of the fastener to tension the fastener between the two hooks.

The safety strap is used in conjunction with any of the end post constructions described above in those conditions where the gap between the rails, into which the end post fits, can exceed more than twice the thickness of the material of the end post. Consider, for example, the situation in which during the heat of a hot day in summer, the gap between adjacent long lengths of rail is 6 mm. An end post the material of which is of 6 mm thickness can be fitted to the rail gap at the hottest part of the day, and there will be little or no clearance between the walls of the gap and the end post.

However, at an opposite extreme of ambient temperature contraction of the lengths of rail may produce a gap between the rail ends exceeding 12 mm and thus as a result of vibration it is conceivable that the two elements of the end post could move laterally with respect to one another within the rail gap, sufficiently far for the end region of the element 14 to disengage from the recess of the element 12. Thus in such circumstances, and in the absence of something beneath the rail gap the lower element 12 could fall from the rail gap. The safety strap, fitted beneath the rail gap, ensures that the hooks 41, 42 will always bridge even the largest rail gap and thus prevent an inadvertently detached lower element 12 falling from the rail gap.

Claims (10)

1. CLAIMS 1. An electrically insulating end post for placement between ends of a pair of railway rails, said end post having a relatively narrow waist portion between first and second outwardly flared end portions, said end post comprising first and second mutually interlocking elements, said first element comprising at least said first outwardly flared end portion, and said second element comprising at least part of said waist region.
2. 2. An end post as claimed in Claim 1 of two-part construction.
3. 3. An end post as claimed in Claim 1 or Claim 2, wherein said first element is a snap-fit with said second element.
4. 4. An end post as claimed in any one of Claims 1 to 3, wherein said first and second elements each have correspondingly toothed regions which are capable of interlocking to form a ratchet-type connection.
5. 5. An electrically insulating end post for placement between ends of a pair of railway rails substantially as hereinbefore described with reference to any one of the accompanying drawings.
6. 6. A method of introducing an end post as claimed in any one of preceding Claims 1 to 5, between adjacent ends of two railway rails at a joint without dismantling said joint, said method comprising the steps of: (i) inserting the first element of the end post between the rails from below the rails; (ii) inserting the second element of the end post between the rails from above the rails; and (iii) mutually interlocking the first and second elements.
7. 7. A method as claimed in Claim 6, wherein the step of mutually interlocking the first and second elements is performed while maintaining the first element in a desired position relative to the rails.
8. 8. A tool for assisting in the method claimed in Claim 6 or Claim 7, said tool comprising a substantially rigid strip having a hooked end adapted to receive at least one lower flange of one or both of said pair of rails adjacent the joint and a projection upstanding from the strip in the same direction as the hooked end.
9. 9. A tool as claimed in Claim 8, wherein the distance between the hooked end and said projection corresponds to half the length of the first element of the end post.
10. 10. In combination with one another an end post as claimed in any one of Claims 1 to 5 and a retaining strap for engagement with the rails adjacent the joint, the retaining strap comprising first and second hooks for engagement respectively with the opposite lower flanges of the rails and a flexible, variable length retainer for securing the hooks together.