GB2288195A

GB2288195A - Supporting a cable passing through a lattice tower

Info

Publication number: GB2288195A
Application number: GB9406474A
Authority: GB
Inventors: Ralph Sutehall; Sam Armitage
Original assignee: Prysmian Cables and Systems Ltd
Current assignee: Prysmian Cables and Systems Ltd
Priority date: 1994-03-31
Filing date: 1994-03-31
Publication date: 1995-10-11
Anticipated expiration: 2014-03-31
Also published as: GB9406474D0; GB2288195B

Abstract

A lattice tower 10 for carrying overhead electric power transmission lines is provided with a support 30 for supporting an aerial cable 32 passing through the tower. The support comprises a single bar secured to the tower using respective mounting devices formed by the end portions of the bar and extends within the tower to provide a mounting point substantially centrally thereof from which the cable may be suspended. The support may be a single bar 34 with a hook 36 at each end and a central loop 44 which receives the shackle of a cable clamp. <IMAGE>

Description

Supporting Aerial Cables This invention relates to supporting an aerial cable, for example an optical fibre cable, from lattice towers for carrying overhead electric power transmission lines.

GB-A-2251132 discloses the use of a support comprising two angled bars suspended from mounting eyes on a lattice tower with their central portions brought together within the tower to define a mounting point substantially centrally thereof from which an aerial cable may be suspended.

An object of the present invention is to provide a simpler arrangement.

The invention provides a lattice tower for carrying overhead electric power transmission lines having a support for supporting an aerial cable passing through the tower, said support comprising a single bar secured to the tower using respective mounting devices formed by the end portions of the bar and extending within the tower to provide a mounting point substantially centrally thereof in the direction of passage of the cable through the tower from which the cable may be suspended.

Preferably each end portion is bent to form a said mounting device. Each of the bent end portions of the bar may be secured to the tower with a hook and eye connection. Thus one or both bent end portions may be formed as a hook for engagement with an eye secured to the tower or one or both bent end portions may be formed as an eye for engagement with a hook secured to the tower.

In a preferred embodiment, each of the bent end portions comprises a hook portion which is secured to an eyebolt of the tower by a shackle.

Whilst the bar may be secured to any members of the tower, the construction of the support by a single bar advantageously enables the end portions to be secured to respective diagonal cross members of the tower.

The bar is preferably provided with a central portion which is configured to locate a shackle. For example the central portion may be configured into a loop through which a said shackle may pass.

The tower may include a said shackle located at said central portion of the bar and having a cable clamp suspended therefrom.

The invention includes an installation comprising a plurality of towers as defined above and an aerial cable passing through said towers and being supported by the cable clamps thereof.

The invention also includes a method of modifying a lattice tower for carrying overhead electric power transmission lines so that it is also able to support an aerial cable passing through the tower, said method comprising securing a support comprising a single bar to the tower using respective mounting devices formed by the end portions of the bar such that said bar extends within the tower to provide a mounting point substantially centrally thereof from which the cable may be supported.

The invention further includes a support for a tower as defined above or for use in the method defined above, for supporting a cable passing through the tower, said support comprising a single bar provided with a central portion which is configured to locate a shackle and end portions which form mounting devices for enabling the bar to be secured to the tower.

In order that the invention may be well understood, an embodiment thereof, which is given by way of example only, will now be described with reference to the accompanying drawings, in which: Figures 1 and 2 are respectively face and side views of the bottom part of a lattice tower from which an aerial cable and overhead electric power cable lines are supported; Figure 3 shows a support bar of the tower for supporting the aerial cable therefrom; Figure 4 shows a connection between one end of the support bar and a tower member; Figure 5 shows an alternative connection between one end of the support bar and a tower member; and Figure 6 shows the support bar supporting an aerial cable.

Referring first to Figures 1 and 2, there is shown the bottom part of a lattice tower 10. The tower is of conventional construction, being formed from galvanised steel members. The tower comprises four legs of which only three referenced 12, 14 and 16 are visible in the Figures. Horizontal cross members 20 and diagonal cross members 22 interconnecting adjacent pairs of legs define four sides of the tower.

The tower is also provided with a cross-arm frame indicated generally at 24 which supports overhead electric power transmission lines 26 via insulator strings 28. For clarity, the transmission line 26 and insulator string 28 which would be visible in Figure 2 has been omitted therein.

The tower is also provided with a support, generally indicated at 30 for supporting an aerial cable 32 passing through the tower.

As best shown in Figure 3, the support comprises a single bar 34, the end portions 36 of which form respective mounting devices for use in securing the bar to the tower. The device is secured to opposite sides of the tower so as to extend within the tower and provide a mounting point substantially centrally of the tower in the direction of passage of the cable 32 through the tower from which the cable may be suspended.

As illustrated in Figure 3, each end portion 36 is bent to form the above-mentioned mounting device.

More specifically, each end portion of the bar comprises a hook portion and as illustrated in Figure 4 this hook portion is secured by a shackle 38 to an eye bolt 40 which itself is secured to a portion 42 of the tower. Instead the hook portion 36 may be secured directly to the eye bolt 40 as shown in Figure 5. It will also be understood that by utilising shackles 38 of different lengths, the bar 34 may be secured across different spans.

Whilst the illustrated bar 34 has end portions 36 formed as hooks, it is to be understood that instead they may be formed as eyes, in which case a hook member would be secured to the tower for engagement with the eye. Of course, it will be appreciated that one end portion of the bar 34 could be provided with a hook and the other end portion with an eye.

Further, it is also envisaged that the mounting devices formed by the end portions of the bar may be other than bent end portions. For example, the end portions may be threaded in order to receive a threaded connector which itself may define a hook or an eye.

As illustrated, the end portions 36 of the bar are secured to respective diagonal cross members 22 of the tower on opposite sides thereof and in particular at the cross over point of two diagonal cross members on each side. However, it is to be understood that they may be secured to other members of the tower and in particular the horizontal cross members 20. Also, whilst in the illustrated embodiment the bar extends within the tower in alignment with the aerial cable 32, it is to be understood that it may extend within the tower transversely to the aerial cable.

Specifically, the bar may extend between the side of the tower defined between the legs 12 and 16 and the side of the tower opposite thereto.

Referring now to Figures 3 and 6 it will be seen that the central portion 44 of the bar is configured to locate a shackle 46. As shown, the central portion 44 of the bar is configured into a loop through which the shackle 46 passes. Such an arrangement provides for positive location of the shackle 46 along the length of the bar. Alternatively, however, the central portion of the bar may merely define a Vee for locating the shackle.

A cable clamp for clamping the aerial cable 32 is suspended from the shackle 46 via link plates 50.

Adjacent the clamp 48, the cable 32 is provided with external stiffening 52, which typically comprises one or more layers of metal rods or wires 52. Also, plastics inserts 54 may be provided between the rods or wires 52 to provide an enlarged diameter resilient region for engagement by the clamp 48.

The illustrated arrangement is particularly applicable where the aerial cable is an optical fibre cable but it is to be understood that it is equally applicable to aerial cables of other types of similar weight.

It will also be appreciated that modification of a lattice tower so that it is able to support the aerial cable passing through the tower is readily carried out using the support described above. In this connection, it will be noted that the eye bolts 40 may be secured to the tower using holes already drilled for bolts and that any tolerances relating to the span between the eye bolts may be accommodated using shackles of different sizes.

Claims

CLAIMS:

1. A lattice tower for carrying overhead electric power transmission lines having a support for supporting an aerial cable passing through the tower, said support comprising a single bar secured to the tower using respective mounting devices formed by the end portions of the bar and extending within the tower to provide a mounting point substantially centrally thereof in the direction of passage of the cable through the tower from which the cable may be suspended.

2. A tower as claimed in claim 1, wherein each end portion is bent to form a said mounting device.

3. A tower as claimed in claim 2, wherein each of said bent end portions of the bar are secured to the tower with a hook and eye connection.

4. A tower as claimed in claim 2, wherein each of said bent end portions of the bar comprises a hook portion and is secured to an eye bolt of the tower by a shackle.

5. A tower as claimed in claim 1, 2 or 3, wherein end portions of the bar are secured to respective diagonal cross members of the tower.

6. A tower as claimed in any one of claims 1 to 5, wherein the bar is provided with a central portion which is configured to locate a shackle.

7. A tower as claimed in claim 6, wherein said central portion of said bar is configured into a loop through which a said shackle may pass.

8. A tower as claimed in claim 6 or 7, and including a said shackle located at said central portion of the bar and having a cable clamp suspended therefrom.

9. An installation comprising a plurality of towers as claimed in claim 8 and an aerial cable passing through said towers and being supported by the cable clamps thereof.

10. A method of modifying a lattice tower for carrying overhead electric power transmission lines so that it is also able to support an aerial cable passing through the tower, said method comprising securing a support comprising a single bar to the tower using respective mounting devices formed by the end portions of the bar such that said bar extends within the tower to provide a mounting point substantially centrally thereof from which the cable may be supported.

11. A support for a tower as claimed in claim 1 or for use in a method as claimed in claim 9, for supporting a cable passing through the tower, said support comprising a single bar provided with a central portion which is configured to locate a shackle and end portions which form mounting devices for enabling the bar to be secured to the tower.

12. A lattice tower for carrying overhead electric power transmission lines and having a support for supporting an aerial cable passing through the tower, substantially as hereinbefore described with reference to the accompanying drawings.

13. A method of modifying a lattice tower for carrying overhead power lines so that it is also able to support an aerial cable passing through the tower, substantially as hereinbefore described with reference to the accompanying drawings.

14. A support for a tower as claimed in claim 1 or for use in a method as claimed in 9 and substantially as hereinbefore described with reference to Figures 36 of the accompanying drawings.