GB2409489A

GB2409489A - Electrically insulating railway end post with abutments that prevent relative migration

Info

Publication number: GB2409489A
Application number: GB0426518A
Authority: GB
Inventors: Gary Michael Elliot
Original assignee: Coronet Rail Ltd
Current assignee: Coronet Rail Ltd
Priority date: 2003-12-06
Filing date: 2004-12-03
Publication date: 2005-06-29
Anticipated expiration: 2024-12-03
Also published as: GB2409489B; GB0426518D0; GB0328358D0

Abstract

An electrically insulating end post 10 is placed between ends (2e, fig 10) of a pair of railway lines and is formed from first and second elements 11, 12 which can be snap-fitted together via a region 14 on the first element 11 being received in a slot 13 in the second element 12. Abutments 15, (15a) on the first element 11 cooperate with abutments 13a, 13b on the second element 12 so that the elements 11, 12 cannot move or migrate, in use, relative to one another in a direction of a length of rail (see fig 10). In another embodiment in order to stop migration the region 14 cooperates with strengthening flanges (12a, 12b, figs 6-8) and it is provided with notches (15, 15a) which are spanned by integral webs (19) that are received within complimentary grooves 21 in protrusions (18, 18a). A further embodiment dispenses with the flanges (12a, 12b) and the webs (19) have continuations (19a) protruding from an inclined wall of the region 14 to engage in corresponding grooves (21a) in the walls of slot 13.

Description

ELECTRICALLY INSULATING RAILWAY END POST

This invention relates to electrically insulating end posts for use between adjacent rail sections of a railway line to electrically insulate said adjacent sections from one another.

It will be recognised that defined lengths of railway line form part of an electrical circuit of, inter alla, a signalling system of the railway network. In simple terms, a train or carriage may bridge, and so electrically interconnect, two otherwise electrically insulated rail sections thereby informing the signalling system of its presence within a particular sector of the rail network. In the absence of an electrically insulating end post separating sections of rail at desired locations then there is a risk of inadvertent electrical interconnection of two adjacent rails thereby providing false input to the signalling system.

Known electrically insulating end posts are of one-piece construction and are formed from sheet insulating material and have substantially the same I-shape as the rail cross-section. The one-piece end posts are inserted between adjacent rail sections before the adjacent rail sections are interconnected by means of electrically insulated fish-plates and electrically insulated bolts.

However, the passage of trains over rail joints subjects the rail joints to considerable mechanical stress and it is known for the one-piece end posts to wear and break usually in their narrow section corresponding to the web of the rail. Once broken, the upper part of the end posts can be knocked out by passing trains and the lower part drops below the rails leaving two closely adjacent rail ends with no electrical insulator between them. The two - 2- adjacent rail sections can then quickly become electrically interconnected by dirt, moisture, and rail distortion, and also through rail expansion.

Replacement of the one-piece end post requires the relevant section of track to be closed to traffic while the relevant rail joint is dismantled, the end post is replaced, and the joint re-assembled. Such a replacement procedure is time consuming and inevitably gives rise to delays and routing problems on the rail network.

Our co-pending British Patent 2343471 discloses a two-part end post which can be used to replace a broken end post without needing to dismantle and then re-assemble the relevant rail joint. The two-part end post of British Patent 2343471 is introduced into the gap between the rail ends, and the two parts are pressed together longitudinally of the web region of the end post (that is to say vertically in relation to the rail in use) so that the two parts become interengaged in a longitudinal direction and are retained in position as a unit within the rail joint by abutment of the end regions of the end post with the fish plates on opposite sides of the rail joint.

The end post of British Patent 2343471 is formed from planar material, and one end region of one of the two parts of the end post is received within a slot in the other part of the end post, the interengagement of the two parts being such that the two parts will not be accidentally disconnected in a longitudinal direction. However, it is found that in isolated instances, where the width of the gap between the rail ends exceeds twice the thickness of the planar material of the end post, then there is a risk that the two parts of the end post may become detached from one another by migration of one part of - 3- the end post relative to the other part in the direction of the length of the rail, that is to say in the direction of the width of the gap between the rail ends.

Provided that there is a clearance between the end post and the rail ends exceeding the thickness of the material of the end post then such migration can result in the two parts of the end post becoming detached from one another and it is an object of the present invention to provide a two part end post in which this problem is obviated.

In accordance with a first aspect of the present invention there is provided 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 elements interengagable as a snap-fit and including abutting surfaces preventing migration of said first and second elements relative to one another in the direction of the length of the rail in use.

Preferably said first and second elements are snap-fitted together in a direction which, in use, is transverse to the length of the rails.

Desirably said first and second elements are planar.

Preferably said first element includes a region received in a slot in said second element.

Desirably said slot is open at one edge and opposite faces of said second element, and is re-entrant to receive, as a snap-fit, a complementarily shaped region of the first element. - 4

Preferably a wall of said slot and the periphery of said complementarily shaped region of said first element include surfaces which can abut in directions transverse to the plane of the first and second elements to prevent migration of the interengaged first and second elements relative to one another in said direction transverse to the plane of the elements.

Conveniently said surfaces comprise a protrusion on the periphery of one of said region and said slot which is received within a groove in the periphery of the other of said region and said slot.

Alternatively said region and said slot include first protrusions which abut to prevent relative migration of said first and second elements in one direction transverse to the plane of the elements, and second protrusions which abut to prevent relative migration of said elements in the opposite direction transverse to the plane of the elements.

In accordance with a second aspect of the present invention there is provided 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, inter-engagable elements, said first element having therein a slot open at one edge and both opposite faces of the first element and said second element having a region received in said slot and retained therein against disengagement of the first and second elements in a direction transverse to the length of said rails in use, said first and second elements including abutment means resisting migration of the first and second elements relative to one another in the direction of the length of the rails in use. - 5-

Preferably said slot is re-entrant and said region of the second element is complementarily shaped so as to engage therein as a snap-fit.

In the accompanying drawings: Figure 1 is a diagrammatic perspective view of an end post in accordance with a first example of the present invention; Figure 2 and Figure 3 are views similar to Figure 1 of the first and second elements of the end post disengaged from one another; Figure 4 is a front elevational view illustrating the interconnection of the elements of the end post of Figure 1; Figure 5 is a side elevational view of a first element of the end post of Figure 1; Figure 6 is a view similar to Figure 1 of an end post in accordance with a second example of the present invention; Figure 7 is a plan view of the second element of the end post of Figure 6; Figure 8 is a view similar to Figure 5 of part of the first element of the end post of Figure 6; Figure 9 is a front elevational view, exploded, of an end post in accordance with a third example of the present invention; and, Figure 10 is an exploded perspective view of a conventional rail joint including a conventional end post.

Referring first to Figure 10, a standard railway line 2 has a generally Ishaped cross-section with a web 2_ connecting upper and louver flanges 2b, 2c. A channel 2_ thus exists on each side of the rail 2 between the flanges 2_, 2_ and the web 2a. An electrically insulating end post 4 of substantially - 6- the same shape as the cross-section of the rail 2 is sandwiched between adjacent ends 2e of adjacent lengths of rail 2, the end post being received within a gap between rails which is typically 6mm in width. 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 in known manner. The rails 2 are interconnected by the fish plates 6, by way of bolts (not shown) which pass through bores 8a, 8_ provided in the rails 2 and the fish plates 6 respectively so as to form a rail joint. Generally the bolts will be electrically insulated from the rails so that although the two rail sections are physically interconnected they remain electrically isolated from one another.

As the end post 4 is the same shape as the rail cross-section it will be recognised that the end post has enlarged end regions connected by a narrow waist region which passes in use between the fish plates. If an end post fractures across the waist region then the lower part of the end post can drop from the gap between the rails and the upper part of the end post may be displaced from the gap by the passage thereover of a train. However, a replacement end post 4 cannot be inserted between the rails without removing at least one of the fish plates 6. Disassembly of the rail joint, introduction of a replacement end post 4, and reassembly of the rail joint is a time consuming exercise, during which the part of the rail network concerned is out of service. End posts in accordance with the present invention overcome this difficulty.

Referring now to Figures 1 to 5, there is shown an end post 10 formed in two separate parts from a resilient, electrically insulating plastics material - 7- conveniently nylon. The end post 10 is planar, and can be moulded, or, if desired, can be cut from a plain sheet of plastics material. The end post 10 has a relatively narrow waist portion 10a corresponding to the web of the rail section, the portion 10a being positioned between first and second outwardly flared end portions lob, 10c. The two parts of the end post 10 comprise a first element 11 defining the waist portion 10a and the flared end portion 10b and a second element 12 defining the flared end portion 10c. The second element 12 has therein a slot 13 receiving a correspondingly shaped end region 14 of the element 11 as a snap-fit so that when the two elements are inter-engaged they define a unitary end post 10.

The end post 10, being planar, has a front face and a parallel rear face. The end region 14 of the element 11 has parallel side surfaces and an end surface at the free end of the region 14, at right angles to the side surfaces.

Moreover, the front face of the region 14 is relieved to a depth of half the thickness of the material of the element 11 by a recess 15. The recess 15 extends partway across the front face of the region 14 from one side surface thereof and breaks the end surface of the region 14. The wall of the recess extends at right angles to the front face of the region 14 and is shaped to include an inclined wall 16 extending from the end surface of the region 14 and inclined towards the side surface. The inclined wall 16 terminates in a curved wall 17 defining a notch, and itself terminating at the side surface of the region 14. The rear face of the region 14is similarly relieved adjacent to the opposite side surface of the region 14. Thus, as indicated in Figure 4 the region 14 includes, along its opposite edges, recesses 15, 15a bounded by inclined walls 16, 16a and curved walls 17, 17a defining notches. However, - 8- the recesses 15, 15_ are staggered in relation to one another by half the thickness of the material of the element 11.

The shape of the slot 13 in the second element 12 is the complement of the shape of the region 14 of the element 11, so that the region 14 can be received in the slot 13 as a close fit. Furthermore, it will be recognised that the slot 13 has, on its opposite side walls, curved protrusions 18, 18_ which are complementary to the notches 17, 17a and are received as a snap-fit therein in use.

It will be recognised that as the end region 14 of the element 11 is inserted into the slot 13 of the second element 12 the side walls of the slot 13 are flexed apart, by flexure of the base region of the element 12, as the inclined walls 16, 16_ pass between the protrusions 18, 18_. Thereafter, as the protrusions 18, 18a align with the notches 17, 17_ the resilience of the element 12 restores the side walls of the slot to their original configuration so that the protrusions 18, 18a snap-ft into the notches 17, 17a. Although the elements 11, 12 can be pulled apart in the opposite direction to that in which they are inter-engaged, they will not become detached inadvertently, as a result, for example, of vibration in use. Significant force is needed to flex the second element 12 sufficiently to permit withdrawal of the region 14 from the slot 13.

Moreover, it will be recognised that when the region 14 is seated within the slot 13 a front face region 13a of the element 12 seats within the recess 15, overlying the base surface of the recess 15 of the region 14 and so prevents movement of the element 11 relative to the element 12 forwardly, at right - 9 - angles to the plane of the elements. Simultaneously, a rear face region 13_ of the element 12 seats within the recess 15_ of the region 14 to prevent movement of the element 11 rearwardly with respect to the element 12 at right angles to the plane of the elements.

It will be recognised therefore that when the end post 10 is assembled the elements 11 and 12 are interlocked against movement relative to one another forwardly, rearwardly, and in the plane of the elements.

Figures 6, 7 and 8 illustrate a second embodiment of the two part end post.

Where appropriate Figures 6, 7 and 8 include reference numerals common to Figures 1 to 5. It can be seen that the region 14 of the first element 11 and the slot 13 of the second element 12 differ from the end post of Figures 1 to in that rather than being recessed on their front and rear surfaces adjacent to opposite edges, the region 14 and the slot 13 are symmetrical about a median plane of the end post normal to the plane of the material of the end post. Thus the arrangement of snap-fitting the region 14 into the slot 13 is similar to that described above. However, the mechanism for ensuring that the elements 11, 12 cannot migrate relative to one another in a direction normal to the plane of the material of the end post differs in that the free end tip of the region 14 extends downwardly into a region of the slot 13 which lies between integral lateral strengthening flanges 12_, 12_ of the element 12 (the element 12 having an inverted T-shaped cross-section). Furthermore, the notches 15, 15a in the side surfaces of the region 14 of the element 11 are spanned by integral webs 19 of the material of the element 11 which are received within complementary grooves 21 in the protrusions 18, 18a of the element 12. - 10-

The third embodiment of the invention illustrated in Figure 9 is similar to the embodiment illustrated in Figures 6, 7 and 8 but the slot 13 of the element 12 terminates short of the lower edge of the element 12, and thus the strengthening flanges 12a, 12b of the embodiment of Figure 6 are not needed. In place of the free tip of the region 14 cooperating with the flanges 12_, 12_, the webs 19 of the element 11 have continuations 19a protruding from the inclined walls of the region 14 to engage in corresponding grooves 21a in the walls of the slot 13.

It will be understood that not all rail networks use the same rail crosssection, and so end posts will be provided in a number of shapes which correspond to the rail cross-sections with which the end posts are to be used. Furthermore, the rail-to-rail gap within a rail joint is not necessarily consistently 6mm when the rail joint is constructed. Thus it is possible to stock end posts of different thicknesses to suit different rail-to-rail gaps.

In order to assemble an end post of the kind illustrated above in place of a missing end post, the element 11 is inserted into the gap between the rail ends from above the rails, whilst simultaneously the element 12 is introduced into the gap from below the rails. The two elements 11, 12 are then brought together so that the region 14 of the element 11 enters the slot 13 of the element 12 and the elements are pressed towards one another (vertically and at right angles to the length of the rails in use) , to snap the region 14 of the element 11 into the slot 13 of the element 12 so interconnecting the two elements to constitute the end post 10). If desired a tool may be provided to - 11 provide leverage pressing the element 12 upwardly and/or the element 11 downwardly to snap engage the two.

It will be recognised that the shapes of the inter-engagable elements 11, 12 can be varied to suit the applications for which they are intended, and moreover, the shaping of the snap-fit components can be altered. - 12

Claims

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 elements interengagable as a snap-fit and including abutting surfaces preventing migration of said first and second elements relative to one another in the direction of the length of the rail in use.
2. An end post as claimed in Claim 1, wherein said first and second elements are snap-fitted together in a direction which, in use, is transverse to the length of the rails.
3. An end post as claimed in Claim 1 or Claim 2, wherein the first and second elements are planar.
4. An end post as claimed in any one of Claims 1 to 3, wherein said first element includes a region received in a slot in said second element.
5. An end post as claimed in Claim 4, wherein said slot is open at one end and opposite faces said second element, and is re-entrant to receive, as a snap-fit, a complementarily shaped region of the first element.
6. An end post as claimed in Claim 5, wherein a wall of said slot and the periphery of said complementarily shaped region of said first element include surfaces which can abut in directions transverse to the plane of the first and - 13 second elements to prevent migration of the interengaged first and second elements relative to one another in said direction transverse to the plane of the elements.
7. An end post as claimed in Claim 6, wherein said region and said slot include first protrusions which abut to prevent relative migration of said first and second elements in one direction transverse to the plane of the elements, and second protrusions which abut to prevent relative migration of said elements in the opposite direction transverse to the plane of the elements.
8. An end post as claimed in Claim 6, wherein said surfaces comprise a protrusion on the periphery of one of said region and said slot which is received within a groove in the periphery of the other of said region and said slot.
9. An end post as claimed in Claim 8, wherein said protrusion is a web spanning a notch in a side surface of said region.
10. An end post as claimed in Claim 9, wherein respective webs span notches in the respective side surface of said region, the webs being received within respective complementary grooves in respective protrusions of said slot.
11. An end post as claimed in any one of Claims 8 to to, wherein part of said slot lies between lateral flanges of the second element. - 14
12. 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, inter-engagable elements, said first element having therein a slot open at one edge and both opposite faces of the first element and said second element having a region received in said slot and retained therein against disengagement of the first and second elements in a direction transverse to the length of said rails in use, said first and second elements including abutment means resisting migration of the first and second elements relative to one another in the direction of the length of the rails in use.
13. An end post as claimed in Claim 12, wherein said slot is re-entrant and said region of the other element is complementarily shaped so as to engage therein as a snap-fit.
14. An electronically insulating end post substantially as hereinbefore described, with reference to, and as shown in Figures 1 to 5, or Figures 6 to 8, or Figure 9 of the accompanying drawings.