GB2383068A

GB2383068A - Forked railway track system

Info

Publication number: GB2383068A
Application number: GB0129960A
Authority: GB
Inventors: Neil Andrew; Barnaby Temple
Original assignee: Balfour Beatty PLC
Current assignee: Balfour Beatty PLC
Priority date: 2001-12-14
Filing date: 2001-12-14
Publication date: 2003-06-18
Also published as: GB0129960D0

Abstract

The system has a primary track 28 and two branch tracks. The ends of the rails of the primary track 28 are moveable between two positions, a first position for directing traffic from the primary track onto the first branch track 16,18 and a second position for directing traffic from the primary track onto the second branch track 20,22. In this arrangement, the branch tracks are fixed. This avoids the need to move tapered rail sections, so that these can instead be solidly mounted. The ends of the primary rails are instead moveable, and this can be achieved with a less complicated mounting arrangement, as the rigidity of the (non-tapered) rails of the primary track can be relied upon.

Description

FORKED RAILWAY TRACK SYSTEM This invention relates to a forked railway track system, and in particular to turnouts.

Conventional railway turnouts, often called points or switches, generally comprise a primary track and two branch tracks. Each rail of the primary track is continuous with a respective rail of each of the branch tracks and is known as a stock rail. The stock rails are thus parallel where they form the primary track and diverge from each other as the branch tracks lead away from the primary track. The other rails of the branch tracks each comprise a switch blade which is laterally shiftable between a first position in which one end of the switch blade contacts the inside edge of one of the stock rails for directing the wheels of a train travelling in a facing direction (that is from the primary track towards the branch tracks) away from the stock rail and onto the switch blade, so leading the train onto the corresponding branch track, and a second position in which the switch blade is displaced from the stock rail to form a flangeway gap for allowing the wheels of a train travelling in a facing direction to remain on the stock rail and travel down the other branch track.

Conventionally, the two switch blades associated with each branch track move in unison such that only one switch blade may contact a stock rail at any one time to prevent simultaneous selection of both branch tracks. In this way a train travelling in a facing direction can follow only one branch track. The switch blade shifting mechanism may be spring-loaded such that a train travelling in a trailing direction (that is from one of the branch tracks towards the primary track) can automatically reset the switch blades to allow it through the turnout. As the train approaches the turnout on one of the branch tracks with the switch blades set to the other branch track, the gauge of the rails decreases due to the displacement of the switch blade on

which the train is rolling. The wheel flanges on one side therefore urge the switch blade away from its displaced position and into contact with the stock rail against the force of the spring-loaded mechanism to allow the train through the turnout.

Switch blades are made from rails which are cut to appropriate length and machined to a taper along a large proportion of length to form a very narrow blade at their end where they contacts the stock rail, otherwise known as their toe. In this way, when seated snugly against the stock rail, the switch blade does not bring the gauge of the track out of tolerance. For high speed railway applications, the radius of curvature of track at a turnout must be relatively large to keep lateral forces exerted by the track on the trains down to a level which is comfortable for passengers. A large radius of curvature requires a long switch blade to allow it to be displaced sufficiently clear of the stock rail to provide an adequate flangeway gap along its entire length.

Current standards in UK as issued by Railtrack pic stipulate a minimum flangeway gap of 41mm to allow wheel flanges of a maximum width of 32.5mm (as used on Eurostar trains) to pass safely through.

Although conventional turnouts work in a satisfactory manner, the machining operation described above makes them very expensive and time consuming to manufacture. One problem particularly associated with the long switch blades required for high speed applications is that the switch blades themselves, which are necessarily very narrow towards the toe as described above, are flexible and require additional supporting structures to prevent them from flexing wildly both horizontally and vertically when trains pass over, or require train speeds to be limited to ensure safety. They are also susceptible to debris, rubbish and stones getting lodged between the switch blade and stock rail, so preventing the switch blade from seating properly. As a result, if a wheel flange hits the toe of the switch blade, this can have

dangerous consequences for trains travelling over the turnout. For this reason Railtrack pic standards stipulate a maximum allowable gap due to intrusive matter between switch blade and stock rail of 3. 5mm in a facing direction. This is a tight tolerance which can be hard to ensure in view of the flexibility of long switch blades. It is therefore often necessary to employ several actuators and detectors at various positions along the length of the switch blade to shift it in the required manner without flexing and to signal oncoming trains to stop if the gap tolerance is exceeded.

Additional actuators and detectors add to the expense of the system, and maintenance costs associated with keeping the turnout operational and free from debris are also very high.

According to the invention there is provided a forked railway track system comprising a primary track and first and second branch tracks which converge at one end adjacent an end of the primary track, each track comprising first and second parallel rails, wherein the ends of the rails of the primary track are moveable between two positions, a first position for directing traffic from the primary track onto the first branch track and a second position for directing traffic from the primary track onto the second branch track.

In this arrangement, the branch tracks are fixed. This avoids the need to move tapered rail sections, so that these can instead be solidly mounted. The ends of the primary rails are instead moveable, and this can be achieved with a less complicated mounting arrangement, as the rigidity of the (non-tapered) rails of the primary track can be relied upon.

This also avoids the need to bring pairs of rails laterally into contact w-ith each other, so that the problem of debris preventing close contact does not arise.

Each branch track preferably comprises one non-tapered rail and one tapered rail.

A fixed flangeway gap is provided between the ends of the first rails of the two branch tracks and between the ends

of the second rails of the two branch tracks. In each position of the primary rails, one wheel flange will pass through the flangeway gap, which therefore must be sufficient in dimension to allow the flange to pass with any required clearance.

A guide mechanism is provided for locating a wheel flange in close proximity to one or other of the rails of the primary track. In particular, the wheel flange which is to pass through a flangeway gap is located close to the rail to ensure accurate alignment with the flangeway gap.

The guide mechanism is for locating a wheel flange in close proximity to one of the rails of the primary track when the ends of the rails of the primary track are in the first position and is for locating a wheel flange in close proximity to the other of the rails of the primary track when the ends of the rails of the primary track are in the second position.

A support structure may be provided for supporting the ends of the rails of the primary track and for moving the ends of the rails of the primary track between the first and second positions. By providing a length over which the rails of the primary track are unsupported, moving the ends of the rails provides the required radius of curvature in the profile of the rails of the primary track.

The invention can be applied to a toy railway.

The invention will now be further described by way of example with reference to the accompanying figures in which: Figure 1 is a plan view of a forked railway track system according to the invention in a first position; and Figure 2 is a plan view of a forked railway track system according to the invention in a second position.

Figure 1 shows a forked railway track system according to the invention comprising a railway turnout for use on a line bearing traffic in a facing direction as shown by the

arrow 10.

The system comprises a primary track having first and second rails 12,14 and first and second branch tracks. The first branch track has first and second parallel rails 16, 18, the first rail 16 being non-tapered and the second rail 18 being tapered. Similarly, the second branch track has first and second parallel rails 20,22, the first rail 20 being tapered and the second rail 22 being non-tapered. The branch tracks converge at one end adjacent an end of the primary track (in region 24).

Within region 24, the ends of the rails 12,14 of the primary track are moveable between two positions, a first position for directing traffic from the primary track onto the first branch track 16,18 and a second position for directing traffic from the primary track onto the second branch track 20,22.

The branch tracks can thus be fixed, which avoids the need to move any tapered rail sections. The primary track rails are instead moveable and these are not tapered.

Figure 1 shows the system in the first position. In this position, the inner edge of the primary first rail 12 is aligned with the inner edge of the first rail 16 of the first branch track, and the inner edge of the primary second rail 14 is aligned with the inner edge of the second rail 18 of the first branch track. As will be seen, the flange of the wheel carried by the first rail 12 of the primary track needs to pass through a flangeway gap 26 between the first rails 16,20 of the branch tracks. This fixed flangeway gap 26 is sufficient to allow the flange to pass with any required clearance.

To ensure alignment of the wheel flange with the gap 26 as the train passes over the turnout, a guide mechanism 28 is provided for locating the wheel flange in close proximity the first rail 12 of the primary track. The guide mechanism has a steering bar 28a, which over its length ensures the wheel flange is smoothly brought closely adjacent (although not

necessarily in contact with) the inner edge of the rail 12.

This steering bar 28a may be laterally moveable, or it may be vertically or rotationally moveable.

In the position in Figure 1, the wheel on the second rail 14 of the primary track does not pass through a flangeway gap, and although the guide mechanism 28 includes a steering bar 28b for the rail 14, it is out of operation in this first position of the primary rails, and is used for the second position (in Figure 2).

Figure 2 shows the system in the second position. In this position, the inner edge of the primary first rail 12 is aligned with the inner edge of the first rail 20 of the second branch track, and the inner edge of the primary second rail 14 is aligned with the inner edge of the second rail 22 of the second branch track.

In this case, the flange of the wheel carried by the second rail 14 of the primary track needs to pass through a flangeway gap 27 and the steering bar 28b comes into operation for alignment of the wheel flange with the flangeway gap 27.

The rails of the primary track are carried by a support structure supporting the ends of the rails 12,14. The movement of the primary rails 12,14 is over a length 30 so that moving the ends of the rails provides the required radius of curvature in the profile of the rails of the primary track. However, the rigidity of the rails of the primary track means the rails do not need to be supported in as many locations as for moveable tapered rails.

To control the turnout, the rails of the primary track are moved between the two positions and the steering bars 28a, 28b are moved into or out of operation, to provide the two modes of operations shown in the Figures.

The invention is described herein with reference to Figures 1 and 2 by way of example only. It will be clear that the invention extends to further modifications not described.

For example, the specific example above shows lateral movement of a steering bar. In fact any mechanical arrangement may be used which acts to reduce locate the wheel flange in the desired position.

The minimum flangeway gap will be selected according the particular rail system. Gaps of 38mm or 41mm are possible examples. The minimum gap between the check rail and the stock rail may be less than the minimum gap between the convergent ends of the branch tracks.

The railway track system according to the invention can be used with any rail cross section.

The arrangement has been described in connection with facing direction traffic only. It is of course possible to use the arrangement in the trailing direction also (traffic from right to left in the figures), but the primary track needs to be correctly positioned, and the system described does not automatically reset to allow traffic to flow in the trailing direction.

Claims

Claims 1. A forked railway track system comprising a primary track and first and second branch tracks which converge at one end adjacent an end of the primary track, each track comprising first and second parallel rails, wherein the ends of the rails of the primary track are moveable between two positions, a first position for directing traffic from the primary track onto the first branch track and a second position for directing traffic from the primary track onto the second branch track.
2. A system as claimed in claim 1, wherein each branch track comprises one non-tapered rail and one tapered rail.
3. A system as claimed in claim 1 or 2, wherein a flangeway gap is provided between the ends of the first rails of the two branch tracks and between the ends of the second rails of the two branch tracks.
4. A system as claimed in any preceding claim, further comprising a guide mechanism for locating a wheel flange in close proximity to one or other of the rails of the primary track.
5. A system as claimed in claim 4, wherein the guide mechanism is for locating a wheel flange in close proximity to one of the rails of the primary track when the ends of the rails of the primary track are in the first position and is for locating a wheel flange in close proximity to the other of the rails of the primary track when the ends of the rails of the primary track are in the second position.
6. A system according to claim 4 or 5, wherein the guide mechanism is laterally movable.

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7. A system as claimed in any preceding claim, further comprising a support structure for supporting the ends of the rails of the primary track and for moving the ends of the rails of the primary track between the first and second positions.
8. A toy railway comprising a forked railway track system according to any preceding claim.