GB2491141A

GB2491141A - Insulated rail joint protection device

Info

Publication number: GB2491141A
Application number: GB201108712A
Authority: GB
Inventors: Paul Baker
Original assignee: PAUL S BAKER Ltd
Current assignee: PAUL S BAKER Ltd
Priority date: 2011-05-24
Filing date: 2011-05-24
Publication date: 2012-11-28
Also published as: GB201108712D0

Abstract

The protection device, for protecting an insulation layer sandwiched between first and second sections of rail, comprises an electrically conductive element 26 adapted to be electrically connected to the first section of rail 20 in the direction of train running and to contact a train wheel 30 passing over the insulation layer from the first section to a second section 22 of rail. This prevents potential arcing at the rail joint causing damage to the insulation and rail section ends and conductive bridging of the insulation.

Description

Insulated Rail Joints

Field of Invention

The present invention relates to insulated rail joints and more particularly to a device for protecting insulated rail joints.

tackgrouid to the Invention Insulated rail joints (IRJs) (sometimes referred to as "Insulated Block Joints") may be used as part of railway signalling systems, particularly in which the io rails of the track are used as conductors for signalling purposes. Signalling operations are performed based on knowledge of the position of trains on the track, wherein successive blocks or sections of rail are electrically insulated from each other to enable independent detection of trains to take place in those blocks/sections.

Figure 1 shows a conventional insulated rail joint (IRJ) in which two sections of rail 8, 10 have end faces which are perpendicular to the rail length. An insulation plate 12 is sandwiched between these two end faces. A fish plate 14 is provided on each side of the rail and these are bolted together through the two rail sections 8, 10 to form the IRJ. A row of bolts 16 clamp the two rail sections between the two fish plates 14. The fish plate 14 and bolts 16 are formed from electrically insulating material or electrically insulated from the rail to ensure that the two sections of rail 8, 10 are electrically insulated from each other.

Although lRJs can be assembled as part of a rail line on site, it is known to provide pre-assembled lRJs and introduce them into a rail network by welding the remote ends of the two rail sections into place on site.

lRJs may be prone to heavy wear at the joint, so that they require more frequent replacement than other parts of the track. Wear in the joints can also give rise to track circuit failures if a short circuit results between the two rail sections 8, 10.

In use, a potential difference can exist across an IRJ and this can cause a passing train's wheel(s) to conduct current as each wheel passes over the IRJ, thus providing a shunt path for a traction return current. It has been noted that the shunt path created by whe&s of passing trains can cause considerable damage to both the insulation plate and the abutting rail ends due to arcing associated with the making and, in particular, breaking of the shunt path circuit as wheels traverse the IRJ. Such spark erosion of rail ends and the insulation plate increases the need for inspection and maintenance of IRJs and typically results in the need for premature replacement of an IRJ.

Summary of the invention

According to a first aspect of the invention, there is provided an IRJ protection device for protecting an insulation layer sandwiched between first and second sections of rail, the device comphsing an electrically conductive element is adapted to be electrically connected to the first section of rail and to contact a train wheel passing over the insulation layer from the first to second sections of rail.

Embodiments may therefore mitigate IRJ spark erosion by diverting an arc generated by passing train wheels away from the interface of the insulation plate and the abutting rail end! An insulation layer and/or rail ends abutting the insulation layer of an IRJ may be protected from spark erosion.

The electrically conductive element may divert an arc by being located in close proximity to (i.e. adjacent), but not touching, the running edge of the running rail at the location of an IRJ.

The electrically conductive element may be spring loaded and positioned so as to provide contact between the flange or rear face of a train wheel as it passes over the IRJ.

According to another aspect of the invention, there is provided a rail joint comprising: first and second rail sections; an insulation layer sandwiched between the first and second rail sections; and an IRJ protection device according to the invenfion. Thus, embodiments of the invention may be provided as part of a pre-assembled IRJ adapted for introduction into a rail network.

Further developments of the invention are the subject-matter of the dependent claims.

Brief desçjption of the drawIpq An example of the invention wifl now be described with reference to the io accompanying diagrams, in which: FIG 1 shows a known insulated rail joint for a flat bottom rail; FIG 2 shows an IRJ according to an embodiment of the invention, wherein a train wheel has passed over the IRJ; and FIG 3 shows an IRJ protection device according to another is embodiment of the invetn ion.

Pc1!!Qtc11t!on Figure 2 shows an IRJ according to an embodiment of the invention, wherein a train wheel has passed over the IRJ in the direction indicated by the arrow labelled "Dl". 6: The IRJ comprises first 20 and second 22 rail sections supported on sleepers 23 with respective rail end faces 20a, 22a. An insulation layer 24 is sandwiched between the end faces 20a, 22a of first 20 and second 22 rail sections.

An electrically conductive element 26 is located in close proximity to (i.e. adjacent), but not touching, the running edge of the rail at the location of the IRJ. The electrically conductive element 26 is arranged to span across the insulation layer 24 and the abutted ends of the first 20 and second 22 rail sections in the longitudinal running direction of the rail (i.e. parallel to the rail length).

The electrically conductive element 26 is electrically connected to the first rail section 20 via a cable 28. Thus, the electrically conductive element 26 is electrically connected to the traction current return rail in rear of the IRJ (with respect to the direction of travel indicated by the arrow labeHed "Dl"). In other words, the electrically conductive element 26 is electrically continuous with the running rail immediately prior to the IRJ (i.e. the first rail section 20) as the train approaches.

The running rail immediately after the IRJ (i.e. the second rail section 22) has no electrical connection to the &ectricalfly conductive element 26. Thus, the electrically conductive element 26 is electrically insulated from the second rail section 22.

The electrically conductive element 26 is adapted to contact a train wheel 30 passing over the insulation layer 24 from the first rail section 20 to the second rail section 22.

In more detail, as a train wheel 30 approaches the IRJ (from the first rail section 20) in the direction shown by the arrow labelled "Dl", but prior to reaching the IRJ, it makes contact with the electrically conductive element 28.

A mechanical and electrical contact then exists between the train wheel 30 and the electrically conductive element 26. However, no current flows since the train wheel 30, the first rail section 20 and the electrically conductive element 26 are all at the same potential.

As the train wheel 30 reaches and then passes over the insulation layer 24, the mechanical and electrical contact between the train wheel 30 and the electrically conductive element 26 is maintained, and any potential difference existing between the first 20 and second 22 rails sections abutting the insulation layer 24 is equalised by the shunt current path provided by the wheel. ln other words, the wheel, the first rail section 20 and the second rail section 22 all remain at the same potential since they are all electrically connected to one another through electrically conductive element 26. Thus, there is no current interruption at the interface between the insulation layer 24 and the first 20 and second 22 rail sections, and therefore no associated spark erosion of the insulation layer 24 or the end faces 20a, 22a of first 20 and second 22 rail sections.

As the train wheel 30 passes beyond the insulation layer 24 and leaves the IRJ (i.e. travels on the second rail section 22) in the direction shown by the arrow lab&ed "Dl" the mechanical and electrical contact between the train wheel 30 and the electrically conductive element 26 is broken. An arc "A" is then drawn between the train wheel 30 and the electricafly conductive element 26 as the train wheel's 30 forward motion interrupts the shunt current path. This is due to the fact that only when the train wheel 30 leaves contact with the electrically conductive element 26 does the shunt circuit become interrupted.

The electrically conductive element 26 may therefore act as a sacrificial Sement which redirects spark erosion away from the IRJ. In the example of Figure 2, spark erosion is focussed towards the end of the electrically conductive element 26 adjacent to the second rail section 22. However, unlike a rail section or insulation ayer of an IRJ, the electrically conductive element 26 may be cheap and/or easily replaced and so spark erosion of the electrically conductive element 26 may be acceptable, or the electrically conductive element 26 may be made to be more resilient to the affects of spark erosion (when compared to an IRJ), or to tolerate more erosion.

Referring to Figure 3, an IRJ protection device according to another embodiment is shown. The 1RJ protection device is for protecting an insulation layer 32 sandwiched between first 34 and second 36 rail sections, and comprises an elongate metal member 38 that is electrically connected to the first rail section 34 via an electrical wire 40.

The elongate metal member 38 affixed to the side of the first 34 and second 36 rail sections (across the insulation layer 32) using an electrically insulating contact layer 42. In this way, the no surface of the elongate metal member 38 directly contacts either of the rail sections 34 or 36 and so is electrically insulated from the rail sections 34 and 36 (except for the deliberate electrical connection made between the elongate metal member 38 and the first rail section 34 using the wire 40).

The elongate metal member 38 is adapted to contact a train wheel passing over the insulation layer from the first 34 to second 36 sections of rail (in the direcflon indicated by the arrow Iab&ed "D2". Specifically, in the embodiment of Figure 3, the elongate metal member 38 is adapted to make contact with a train wheel on the first rail section 34, to maintain contact with the train wheel as it passes over the insulation layer 32, and to break contact with the train wheel on the second rail section 36. As has been explained above with reference to the embodiment of Figure 2, this arrangement prevents current io interruption at the interface between the insulation layer 32 and the first 34 and second 36 rail sections, and therefore prevents or reduces associated spark erosion of the 1RJ.

Here, the biasing means (not visible) are provided between the elongate metal member 38 and rail section 34 and 36. The biasing means (such as a tension or compression spring) are adapted to bias the elongate metal member 38 towards a train wheel as it passes over the insulation layer so as to help maintain physical and electrical contact between the elongate metal member 38 and the train wheel, Advantages associated with embodiments of the invention may be summarized as follows: -Damage to rail heads may be reduced/minimized; -A requirement for IRJ inspections may be reduced; -The electrically conductive element may be designed to be more resilient to the affects of spark erosion when compared to an IRJ interface; Embodiments may help to reduce the maintenance requirements of lRJs; -The time period between replacement of IRJs may be increased; renewal -The electrically conductive element may be easily replaced when -Resources required to replace the electrically conductive element may be reduced when compared to those required to replace an IRJ; and -Embodiments may require minimal maintenance and instaflation skills.

It is to be noted that the above embodiments have been described in relation s to a single rail of a one-way (i.e. uni-directional) rail line employing a single rail track circuit. Embodiments of the invention may be used with both rails of a bi-directional rail line that employ double rail track circuits. For example, first and second protection devices according to the invention can be employed on the first and second rails of a bi-directional train track, wherein the protection io devices are arranged in opposing directions. In such an exemplary arrangement, a first protection device may be electrically connected to the first rail section of the first rail (like the embodiments described in Figures 2 and 3), and a second protection device may be connected to the second rail section of the second rail. Thus, the first protection device would be adapted is to cater for a train wheel crossing over the IRJ of the first rail in one direction, and the second device would be adapted to cater for a train wheel crossing over the IRJ of the second rail in the opposite direction.

Embodiments can be used in any combination of single and double rail track circuits on both uni and bi-directional tracks.

Embodiments of the invention may therefore be used in combination to protect a plurality of different lRJs across different rail lines While specific embodiments have been described herein for purposes of illustration, various modifications will be apparent to a person skilled in the art and may be made without departing from the scope of the invention.

Claims

C'aims 1. An insulated rail joint, IRJ, protection device for protecting an insulation layer sandwiched between first and second sections of rail, the device comprising; an electrically conductive element adapted to be electrically connected to the first section of rail and to contact a train wheel passing over the insulation layer from the first to second sections of rail.
2. The IRJ protection device of claim 1, wherein the electrically conductive element is adapted to make contact with the train wheel on the first section of rail, to maintain contact with the train wheel as it passes over the insulation layer, and to break contact with the train wheel on the second rail section.
3. The IRJ protection device of claim 1 or 2, further comprising an insulating layer adapted to electrically insulate the electrically conductive element from the second section of rail.
4. The IRJ protection device of any preceding claim, further comprising biasing means adapted to bias the electrically conductive element towards the train wheel as it passes over the insulation layer.
5. The IRJ protection device of any preceding claim, wherein the electrically conductive element is adapted to span across the extent of the insulation layer in the longitudinal running direction of the first and second sections of rail.
6. The IRJ protection device of any preceding claim, wherein the electrically conductive element comprises an elongate metal member.
7. A rail joint comprising: first and second rail sections; an insulation hayer sandwiched between the first and second raU sections; and an DRJ protection device according to any preceding claim.
8. An insuGated raH joint protection device substantiafly as herein described above with reference to the accompanying figures.