GB2400879A

GB2400879A - Railway track maintenance

Info

Publication number: GB2400879A
Application number: GB0309164A
Authority: GB
Inventors: James Cooper
Original assignee: Wickham Land Ltd
Current assignee: Wickham Land Ltd
Priority date: 2003-04-23
Filing date: 2003-04-23
Publication date: 2004-10-27
Also published as: WO2004094727A1; GB0309164D0

Abstract

To maintain at its optimum position a railway track (2) having rails (4), <SL> <LI>i) the position of a rail (4) relative to its pre-determined optimum position is measured, <LI>ii) a shim (14) based on the measurement of the relative position of the rail (4) is selected, <LI>iii) the rail (4) is lifted <LI>iv) the shim (10) is placed beneath the rail (4), <LI>v) the rail (4) is lowered, whereby the rail (4) is located substantially at the optimum position. Preferably, the shim comprises steel. The optimum position of the rail (4) may correspond to a substantially horizontal track, or to a cambered track. </SL> The shim (14) is inserted between the rail (4) and its cross-tie (6), and a different-sized clip may be required between them.

Description

RAILWAY TRACK MAINTENANCE

This invention relates to the maintenance of railway tracks.

A railway track comprising rails secured by fasteners to sleepers or cross-ties is conventionally supported by ballast, resting on a substrate. The ballast invariably settles under the loads imposed by trains running on the track, and because of such factors as the non-uniform consistency of the ballast, variations in the substrate, and centrifugal forces generated at curved track positions, this settlement is uneven, so that the rails lose alignment. Alignment can be restored by tamping the ballast between the ties to consolidate it.

However, the slip planes in the ballast which have allowed re positioning by the tamper also allow a return to the position of lost alignment, which can be regarded as a "natural" position or profile from which the tamping has effected a distortion, necessarily for only a limited time, after which the tamping operation has to be repeated.

In order to increase the time between necessary re alignment operations, the ties can be lifted and stones (pea gravel) thus placed beneath them either manually with a shovel or by blowing stones carried in an air stream. The desired rail alignment can be obtained in this way with the ballast in its "natural" profile but the stones used to pack the crossties are inconvenient to handle and are moreover themselves subject to settlement. The adjustment of the track in this way can be relatively inaccurate and subjective, resulting in an uneven track level which may again settle and so lose alignment relatively quickly.

There exists a need for an improved method of maintaining a railway track.

According to the present invention there is provided a method of maintaining a railway track having rails, the method comprising: i) measuring the position of a rail relative to a pre determined optimum position; ii) selecting a shim based on the measurement of the relative position of the rail; iii) lifting the rail; iv) placing the shim beneath the rail; v) lowering the rail whereby the rail is located substantially at the optimum position.

Preferably, the shim comprises metal.

Conveniently, the shim comprises steel.

The optimum position of the rail may correspond to a substantially horizontal track or, if desired, to a cambered track.

Conveniently, the method is performed automatically.

Advantageously, the method is performed by an apparatus carried on the track.

Preferably, the rail is supported by a cross-tie and the shim is placed between the cross-tie and the rail.

Conveniently, the rail is secured to the cross-tie by a first clip which is replaced by a second clip of a different size to the first clip.

According to another aspect of the present invention, there is provided an apparatus for maintaining a railway track, the track having rails carried by cross-ties supported on ballast, the apparatus comprising: i) means for measuring the position of a rail relative to a pre-determined optimum position; ii) means for selecting a shim based on the measurement of the relative position of the rail; iii) means for lifting the rail; iv) means for placing the shim under the raised rail; v) means for lowering the rail.

Advantageously, a rail is secured to a cross-tie by a first clip and the apparatus further comprises: vi) means for replacing the first clip with a second clip of a different size to the first clip.

Preferably, the apparatus may travel on a track.

Conveniently, the means defined in sub-paragraphs (i) to (v) can operate automatically.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic cross-section through a rail supported on a sleeper, Figure 2 is a schematic cross-section of the track shown in figure 1 including a shim, and; Figure 3 is a schematic illustration of a railway train for maintaining a railway track in accordance with the method of the invention.

Figure 1 shows a railway track generally at 2 comprising a rail 4 supported on a sleeper 6. The sleeper 6 is supported by a layer of ballast shown at 8. The rail 4 is secured to the sleeper 6 by a spring clip (not shown) which is attached to a base 10 located between the sleeper 6 and the rail 4.

Due to the substantial forces exerted on railway tracks by passing trains and the fact that the ballast is liable to settle, the position of the rail 4 may change over a period of time. The optimum position of the track is shown in phantom at 12, corresponding to an aligned level track (on straight sections) or an aligned cambered track (on curved sections). On a straight section of track, the positions of the rails on each side of the track are substantially horizontal. In contrast, on a curve of a railway track, the relative vertical positions of the rails are such as to give the track a camber. The method of the present invention may be used to determine the optimum position of the relevant section of each of the tracks, taking into account the curve, and therefore the required camber, of the track. It can be seen that the actual position of the track 4 is lower than the optimum position 12 by a distance X. Modern measuring equipment is sufficiently sensitive to be able to detect the exact location and configuration of parts of railway tracks to a high degree of accuracy. For example, the position of the section of the rail 4 above the sleeper 6 may be accurately determined by such measuring equipment. The measured, actual position of track 4 may be compared with the pre-determined optimum position 12. The relative position of the track 4 away from the optimum position, i.e. the direction and distance X, may thus be obtained.

As mentioned above, there have been many previous attempts at methods of maintaining railway tracks, including placing materials beneath a rail or sleeper in order to adjust the position of the rail. However, these previous methods were relatively inaccurate and subjective and could lead to further problems with settling as discussed above.

Instead, the present invention relies upon the accurate determination of the relative position of the track 4 in relation to a pre-determined optimum position. Based upon this information, a shim or spacer may be specifically selected which may be used to accurately adjust the position of the rail 4 in order to locate it substantially at the optimum position. This method also has the advantage of providing a more permanent solution than previous methods, as the track is less liable to undergo settling or other movements away from alignment.

Turning to figure 2, the rail 4 is shown having been adjusted to the optimum position. In order to achieve this, the spring clip was removed and the rail 4 was raised above the sleeper 6 and spring clip base 10 and a specifically selected shim 14 was located therebetween. The rail 4 was then lowered onto the shim 14, thus bringing the rail 4 into the optimum position, and the spring clip was replaced.

Because the insertion of the shim has altered the distance between the cross-tie and the rail, a different sized clip may be required to replace the original clip.

In an alternative embodiment, there is provided means for securing the shim in place on the cross-tie.

It can be appreciated that the supporting ballast layer 8 beneath the track has not been disturbed by being rearranged or augmented with new material. Thus the existing, settled layer 8 will remain substantially stable in the same position without further settling occurring. The shim 14 is made of steel. In other embodiments the shim may be made of other materials including other metals.

Turning to figure 3, a train is shown generally at 16 comprising a front carriage 18 and a rear carriage 20. The train 16 runs on a railway track 22. Within the front carriage 18 there is located means 24 for measuring the position of the rails of the track 22 and comparing them with a predetermined optimum position. As the train 16 moves forward along the track 22, the rear carriage 20 becomes located above the section of the track 22 which was measured by the equipment 24 in the front carriage 18. The rear carriage 20 has means 26 for raising and lowering a section of the track 22. Within the rear carriage 20 there is also provided a stock 28 of differently-sized shims and spring clips.

There is an apparatus for retrieving specific shims from the range of shims in stock based upon the information from the front carriage 18 as to the relative position of a specific piece of rail.

There is also an apparatus for retrieving specific spring clips from the range of clips in stock based upon the size of the shim and the size of the original clip. If the distance between the track 22 and the cross-tie is within the correct range of the original clip, it would not need to be replaced.

The apparatus then places the shim beneath the raised section of rail which is then lowered onto the shim. The original spring clip, or a differently sized replacement clip, is used to secure the rail to the cross-tie. The section of rail is then located substantially at the optimum position.

The train 16 continues forwards on the track 22 measuring and adjusting sections of the track as it goes along. The action of the train 16 moving along the track 22 acts to tamp the track into place.

Claims

1. A method of maintaining a railway track having rails, the method comprising: 5i) measuring the position of a rail relative to a pre determined optimum position; ii) selecting a shim based on the measurement of the relative position of the rail; iii) lifting the rail; 10iv) placing the shim beneath the rail; v) lowering the rail whereby the rail is located substantially at the optimum position.

2. A method according to claim 1 wherein the shim comprises metal.

3. A method according to claim 1 or 2 wherein the shim comprises steel.

4. A method according to claim 1, 2 or 3 wherein the optimum position of the rail corresponds to a substantially horizontal track.

5. A method according to claim 1, 2 or 3 wherein the optimum position of the rail corresponds to a cambered track.

6. A method according to any of the preceding claims which is performed automatically.

7. A method according to any of the preceding claims which is performed by an apparatus carried on the track.

8. A method according to any of the preceding claims wherein the rail is supported by a cross-tie and the shim is placed between the cross-tie and the rail.

9. A method according to claim 8 wherein the rail is secured to the crosstie by a first clip which is replaced by a second clip of a different size to the first clip.

10. An apparatus for maintaining a railway track, the track having rails carried by cross-ties supported on ballast, the apparatus comprising: i) means for measuring the position of a rail relative to a pre-determined optimum position; ii) means for selecting a shim based on the measurement of the relative position of the rail; 5iii) means for lifting the rail; iv) means for placing the shim under the raised rail; v) means for lowering the rail.

11. An apparatus according to claim 10 wherein a rail is secured to a cross-tie by a first clip, further comprising 10vi) means for replacing the first clip with a second clip of a different size to the first clip. I

12. An apparatus according to claim 10 or 11 which may travel on a track.

13. An apparatus according to claim 10, 11 or 12 wherein the means defined in sub-paragraphs (i) to (v) can operate t automatically.

14. A method substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

15. An apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

16. A railway track substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

17. Any novel feature or combination of features disclosed herein.