GB2158133A - Two-part railway sleeper - Google Patents

Abstract

A railway sleeper assembly comprises two parts, each including a pot sleeper member (22) of reinforced concrete and an extension (24) by which the two parts can be joined, when in situ. The extension (24) may comprise an embedded metal bar, or a tapered concrete protrusion. A method of replacing a defective sleeper can be carried out with minimum disturbance by withdrawing ballast locally while leaving rails and chairs in situ, removing the defective sleeper and replacing that sleeper with the two part sleeper referred to. Each pot sleeper may be accurately positioned by a jack and guide sleeve before the two extensions (24) are secured together. <IMAGE>

Description

SPECIFICATION Railway sleeper This invention relates to railway sleepers sometimes known as railroad ties in the United States and other English speaking countries.

In the past railway sleepers have been made of impregnated timber and the permanent way is completed by bull-head rails supported on the sleepers by chairs of cast metal and chocks which firmly retain the rails in the chairs. The latter are conventionally bolted to the sleepers. Timber sleepers can also be used with flat-bottomed rails in which case the conventional chairs are omitted and base plates used which can be bolted or otherwise secured to the timber sleepers.

Being a natural product the longevity of the sleepers varies and premature failure of a sleeper as a result of rot or splitting may dictate the replacement of at least that sleeper and possibly others of that section of track, while the permanent way gang are operating on that section.

The fact that the sleepers are embedded in ballast of stone chippings reduces accessibility when it is required to replace one of a number of sleepers in a section without removal of the rails, so that ballast must be removed not only immediately beneath the particular sleeper to be replaced, but also laterally thereof and in some instances the lateral displacement of the sleeper to be replaced and insertion of a corresponding new sleeper presents difficulty because the removal and replacement are hindered by lineside services of various kinds.

in broad terms it is clearly desirable to be able to replace a timber sleeper by a sleeper of concrete as experience has clearly demonstrated the substantially increased longevity of concrete railway sleepers. However, such replacement in the conditions outlined, namely only one or a small number in any given section gives rise to the problem of manhandling the relatively heavier concrete sleeper allied to the fact that concrete sleepers of the monobloc kind are not normally used in conjunction with chairs on economic grounds, such as used with timber sleepers, and hence there is a need for an economic replacement of timber sleepers which, at the same time, can be manhandled without undue difficulty.

According to the present invention there is provided a railway sleeper assembly including two pads of reinforced concrete intended to lie beneath respective rails of the railway track, each pad having an extension formed by an elongate metal member embedded at one end portion in the pad and arranged to cooperate wish and be secured, when in situ to a corresponding extension of another said pad supporting the opposite rail.

According to the present invention in another aspect there is provided a method of replacing a defective sleeper of a railway track, comprising the steps of removing ballast from beneath the defective sleeper, removing the defective sleeper, introducing a first concrete pad with a metal extension projecting therefrom into the space vacated by the ballast, inserting the pad under one rail, inserting a second pad with a metal extension under the opposite rail of that track, securing the extensions together when the pads are properly located beneath respective rails, and re-ballasting the section of track.

Further according to the present invention there is provided a railway sleeper assembly comprising two members of reinforced concrete, each being intended, when in situ, to lie beneath a respective rail of the track, and an extension or prolongation of each member having a length dimension such that when in situ the extensions overlap, whereby the two members can be interconnected.

The invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawing in which Figure 1 is a side elevation of a defective timber sleeper carrying chairs and conventional bull-head rails supported thereby; Figure 2 illustrates a first stage in carrying out the method in accordance with the present invention; Figure 3 illustrates a second stage in the method in accordance with the invention; Figure 4 illustrates a third stage in the replacement of a defective railway sleeper; Figure 5 illustrates the siting of a guide member which ensures that during the final positioning of the pads no skewing of the pads takes place; Figure 6 illustrates a further step in the method; Figure 7 illustrates securing of one chair to one pad;; Figure 8 is a view similar to Figure 7 but with the jack removed and the extensions of the concrete pads secured together; and Figure 9 is a plan view of the sleeper assembly, together with chairs and rails as viewed from above.

Figure 1 illustrates a conventional timber sleeper 10 to which are bolted two spaced chairs of cast steel 12, and two rails 1 4 held to correct gauge by spring chocks 16. A compressible pad will normally be interposed between the undersurface of each chair and the sleeper. In the event that the sleeper becomes defective the ballast 18 is partially removed, the chairs unbolted and the defective sleeper is withdrawn. If, for one reason or another, it is difficult to withdraw the sleeper, as a whole, laterally it can be sawn into two parts and removed through the space between the rails.

Assuming that the chairs are in good, serviceable, order, the next stage is to introduce one half of a sleeper assembly 20 in accordance with the invention, which half comprises a pad or other member of reinforced concrete 22 from which projects an elongate angle section steel member 24, one end portion of this member being securely embedded in the concrete pad and preferably firmly secured, for example by welding, to the reinforcement cage (not shown) within the concrete. As finally installed and secured together the extensions 24 act as a tie bar.

It will be readily apparent that this half sleeper can be introduced from the space between the rails, and similar remarks apply to the other half of the sleeper assembly, the pad of which is introduced below the left hand rail, as shown. Preferably the angle section members are slightly offset, so that, as installed, the pads are precisely transversely aligned. In the embodiment illustrated the angle members are disposed with the horizontal limbs facing away from one another.

At the next stage illustrated in Figure 5 a temporary guide 26 (broken lines) is placed over the angle section extensions 24 of the pads 22 to ensure correct alignment in the transverse sense, and moreover, to ensure that that alignment is maintained during the next stage as illustrated in Figure 6. The guide may take the form of a channel section member with the base uppermost.

This next stage involves the insertion of a jack 28, (hydraulic, pneumatic or mechanical) which serves to displace the two pads 22 until at least one is lined up wish the bolt receiving apertures in one of the chairs so that bolts can be passed through that concrete pad, continued extension of the jack resulting in subsequent displacement only of the other pad until that pad is correspondingly aligned.

When the condition illustrated in Figures 8 and 9 is achieved, bolts are inserted in the other chair and the vertical limbs of the angle section extensions 24 are secured together by four bolts 30 which pass through apertures in the vertical limbs.

Finally the ballast is tamped so as to provide adequate support for the concrete pads.

In an unillustrated modification, the angle section extension is replaced by a concrete extension which is reinforced by an extension of the reinforcement cage incorporated in each pad. Suitable apertures for securing bolts will be defined by short tubes extending transversely of the extension in a similar manner to the bolt holes of the illustrated embodiment. The tubes will also assist in final alignment of the associated pad. The concrete extensions avoid problems of rusting inherent with metal extensions, more especially at the point of entry to the concrete pad.

In a further development of the modification described in the immediately preceding paragraph, the extensions are made, once again, of reinforced concrete, but are effectively continuous with the pads so that there is no abrupt change of section. The portion corresponding to the pad 22 may be of similar shape but the portion equivalent to each extension tapers from tne pad portion so that where the extensions overlap a scarf joint is formed. As for the modification of the immediately preceding paragraph there will be tubes to accommodate the interconnecting bolts.

The reinforcing cage will be appropriately configured.

This modification again avoids the use of exposed metal but additionally avoids stress concentrations at the abrupt changes in section.

Neither modification affects the method of replacement of an existing sleeper, the rails remaining undisturbed.

It will be readily apparent from the description of the method hereinbefore described and the sleeper assembly that individual sleepers can be readily replaced without the need for any clearance transversely of the permanent way, and because of the comparatively lightweight of the concrete/metal sleeper assembly when compared with concrete prestressed, one piece, sleepers the modulus of the track is not materially affected. It is generally considered unwise to replace with prestressed concrete sleepers only selected wooden sleepers in a section of track which will otherwise continue to include timber sleepers.

While the method in accordance with the invention has been described in relation to replacement of a single timber sleeper, it will be readily apparent that larger numbers, not involving the replacement of the rails can be replaced in a similar manner, preferably one at a time, to avoid affecting track alignment.

The pads 22 of reinforced concrete can readily be made of the same depth as the timber to be replaced so that the tamping after the replacement is made easier.

It will also be apparent that the invention is applicable to permanent way in which the original sleepers are of prestressed concrete and do not incorporate any chairs.

The extensions 24 of the pads may be of other section than as shown, for example inverted channel, so that one extension nests within the other. In this construction the guide 26 becomes superfluous.

The resilient pads (not shown) which conventionally lie between the chair and the sleeper or between a flat bottomed rail and the sleeper, can readily be used with the sleeper assembly in accordance with the present invention.

Claims (14)

1. A railway sleeper assembly including two pads of reinforced concrete intended to lie beneath respective rails of a railway track, each pad having an extension formed by an elongate metal member embedded at one end portion in the pad and arranged to cooperate with and be secured, when in situ, to a corresponding extension of another said pad beneath the opposite rail.

2. An assembly according to claim 1 wherein each extension is an angle-section bar.

3. An assembly according to claim 1 or claim 2 wherein each pad is of trapezoidal form as viewed in plan.

4. An assembly according to any one of the preceding claims wherein the extensions are offset from the transverse centre line of the two pads so that, when in situ, the pads can lie precisely transversely opposite to one another.

5. An assembly according to any one of claims 2 to 4 wherein securing means are provided which cooperate with the vertical limbs of the angle section members when the pads are in situ.

6. A method of replacing a defective sleeper of a railway track, comprising the steps of removing ballast from beneath and around the defective sleeper, removing the defective sleeper, introducing a first concrete pad with a metal extension projecting therefrom into the space vacated by the ballast, inserting the pad substantially under one rail, inserting a second pad with a metal extension substantially under the opposite rail of the track, accurately locating the pads beneath the rails, securing the extensions together, and re-ballasting the section of track.

7. A method according to claim 6 further comprising the step of aligning the extensions when the pads are partially located beneath their respective rails by means of a temporary elongate member, such as a channel section member.

8. A method according to claim 6 or claim 7 comprising the further step of locating the pads accurately beneath the respective rails by means of a jack.

9. A railway sleeper assembly comprising two members of reinforced concrete, each being intended, when in situ, to lie beneath a respective rail of the track, and an extension or prolongation of each member having a length dimension such that when in situ the extensions overlap, whereby the two members can be interconnected.

10. An assembly according to claim 9 wherein a concrete extension of each pad joins the pad at a smooth junction, with no abrupt change in the crosssection, the interconnected extensions being joined at a scarf joint.

11. An assembly according to claim 9 or claim 10, wherein a reinforcement cage extends continuously through the pad and the extension.

1 2. An assembly according to claim 9, claim 10 or claim 11, wherein the extensions are wedge-shaped.

1 3. A sleeper assembly substantially as hereinbefore described with reference to the accompanying drawings.

14. A method of replacing a railway sleeper in a railway track substantially as hereinbefore described with reference to the accompanying drawings.