GB1598540A

GB1598540A - Electro-optical cables

Info

Publication number: GB1598540A
Application number: GB2613278A
Authority: GB
Original assignee: Associated Electrical Industries Ltd
Current assignee: Associated Electrical Industries Ltd
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-09-23

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTRO-OPTICAL CABLES (71) We, ASSOCIATED ELECTRICAL INDUSTRIES LIMITED, of 1 Stanhope Gate, London Wi A 1 EH, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to cables of the tupe including a single stranded electrical conductor, that is to say a single conductor constituted by a plurality of conducting units helically wound around a core composed of stranded metal wires or rods. It is an object of the invention to provide a cable of this type incorporating one or more optical transmission lines, thus forming an electro-optical cable.

According to the invention, an electrooptical cable consists of a core composed of a plurality of helically stranded metal wires or rods, and an assembly of units helically wound around the said core, which assembly consists of a plurality of electrically conducting units constituting a single stranded conductor, arranged in one or more layers around the core, and, replacing one or more of the said conducting units in said layer or layers, one or more optical fibre waveguide units as hereinafter defined.

The term 'optical fibre waveguide unit', as used herein, is to be understood to mean a unit consisting of a sheath of synthetic plastic material having one or more tubular bores therethrough, with one or more optical fibre waveguides disposed loosely in said bore or in each of said bores and substantially parallel to the axis of said sheath: in this connection the term loosely' is to be understood to mean that the bore, or each bore, of said sheath is of sufficiently large cross-section to permit freedom of movement of the fibre, or of each individual fibre, within it in both radial and axial directions.

If desired, one or more reinforcing members consisting of compression resistant filaments, for example of metal, glass or silica, may be embedded in the sheath wall of the optical fibre unit, or of each such unit, surrounding the bore or bores and disposed substantially parallel to the optical fibre or fibres.

The stranded conducting units are suitably arranged in two or more layers helically laid around the cable core, the optical fibre unit or units which replace one or more of the conducting units preferably being located in an inner layer. The units are preferably closely packed, and preferably also the interstices between the units, and between the layers, are filled with a viscous greasy medium such as petroleum jelly or silicone grease, which acts as a water repellent.

If desired, the cable may be provided with a protective outer sheath consisting of one or more layers of plastic material and/or tape, covering the assembly of stranded units.

A specific form of cable in accordance with the invention will now be described by way of example, with reference to the accompanying drawing, which shows a cross-section of the cable.

The cable of the example constitutes an overhead earth conductor for the electricity supply grid. The cable core consists of seven helically stranded steel wires 1, and the conductor is composed of three closely packed stranded layers of aluminium wires 2, 3, 4, helically wound around the core with a pitch of 20 to 30 cm, the layers 2 and 4 being arranged in a direction of lay opposite to that of the middle layer 3. The middle layer o of strands includes an optical fibre unit consisting of a single polyurethane-coated silica fibre waveguide 5, loosely disposed in the bore of a tubular nylon sheath 6. The steel wires of the core and the surrounding aluminium wires are all 3 mm in diameter, and the sheath of the optical fibre unit is of substantially the same external diameter, or slightly smaller.

A suitable grease 7 fills all the interstices between the aluminium wires, and between the inner layer 2 of such wires and the core.

In a modification of the cable described in the example, the core wires 1 may be composed of an aluminium alloy having a higher tensile strength than aluminium, and if desired the conductor wires may also be composed of such an alloy.

The cable of the example may be further modified by the inclusion of any desired number of optical fibre units, preferably symmetrically spaced apart in the middle layer 3 of aluminium wires.

The cable of the invention can be manufactured by conventional techniques for forming a stranded wire core and helically winding layers of wires around the core, one or more of the wires in said layers being replaced by an optical fibre unit or units as required, and the grease being incorporated during the winding.

WHAT WE CLAIM IS: 1. An electro optical cable consisting of a core composed of a plurality of helically stranded metal wires or rods, and an assembly of units helically wound around the said core, which assembly consists of a plurality of electrically conducting units constituting a single stranded conductor, arranged in one or more layers around the core, and, replacing one or more of the said conducting units in said layer or layers, one or more optical fibre waveguide units as hereinbefore defined.

2. A cable according to Claim 1, wherein the said stranded conducting units are arranged in two or more layers helically laid around the said core, and the optical fibre waveguide unit or units replacing one or more of the conducting units is or are located in an inner layer of the conducting units.

3. A cable according to Claim 1 or 2, wherein all the said units are closely packed and the interstices between the units are filled with a viscous greasy medium.

4. A cable according to Claim l, 2 or 3, which is provided with a protective outer sheath.

5. A cable according to Claim 1, substantially as shown in, and as hereinbefore described with reference to, the accompanying drawing.

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Claims

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symmetrically spaced apart in the middle layer 3 of aluminium wires.

The cable of the invention can be manufactured by conventional techniques for forming a stranded wire core and helically winding layers of wires around the core, one or more of the wires in said layers being replaced by an optical fibre unit or units as required, and the grease being incorporated during the winding.

WHAT WE CLAIM IS: 1. An electro optical cable consisting of a core composed of a plurality of helically stranded metal wires or rods, and an assembly of units helically wound around the said core, which assembly consists of a plurality of electrically conducting units constituting a single stranded conductor, arranged in one or more layers around the core, and, replacing one or more of the said conducting units in said layer or layers, one or more optical fibre waveguide units as hereinbefore defined.
2. A cable according to Claim 1, wherein the said stranded conducting units are arranged in two or more layers helically laid around the said core, and the optical fibre waveguide unit or units replacing one or more of the conducting units is or are located in an inner layer of the conducting units.
3. A cable according to Claim 1 or 2, wherein all the said units are closely packed and the interstices between the units are filled with a viscous greasy medium.
4. A cable according to Claim l, 2 or 3, which is provided with a protective outer sheath.
5. A cable according to Claim 1, substantially as shown in, and as hereinbefore described with reference to, the accompanying drawing.