GB1580089A - Cable - Google Patents

Description

(54) CABLE (71) We, TELEFONAKTIEBO LAGET L M ERICSSON, a company organised under the laws of Sweden, of S-126 25 Stockholm, Sweden, 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 cable for transferring electrical energy or electrical and/or optical signals, for example self-floating cable for marine operations.

When transferring electrical power or electrical signals between marine crafts above and below the water surface, it is desirable to use cable of the self-floating type. Such a cable is, however, subject to bending forces perpendicular to its longitudinal direction due to the influence of water waves and this can cause damage to the cable. Further complications when working with cable in a marine environment are the forces which the cable will be subject to due to the influence of water streams.

According to this invention there is provided cable comprising two separate systems not surrounding each other of which one system is suitable for transferring electrical energy or electrical and/or optical signals and the other system is for taking up mechanical loads, the two systems being surrounded by a common cable mantle, in which cable there are in the said one system an inner friction layer of plastics material having a low coefficient of friction when contacting its own surface and surrounding inner conductors of the said one system an inner friction layer of plastics material having a low coefficient of friction when contacting its own surface and surrounding inner conductors of the said one system, a metallic layer covering the inner friction layer, a number of hollow cords of soft plastics material situated in parallel and surrounding the said metallic layer, the cords extending with a certain pitch along the longitudinal direction of the cable, and an outer friction layer of plastics material, with a low coefficient of friction when contacting its own surface, covering the said cords and situated nearest to the cable mantle.

The invention will now be described by way of example with reference to the accompanying drawing, in which: Figure 1 is a cross-section of one example of cable according to the invention, and Figure 2 shows the cable with a cable mantle removed.

The cable of Figure 1 consists of two separate systems 1 and 9 which are movable in the longitudinal direction of the cable and relative to the cable mantle 7. The mantle 7 consists of a rubber-like gas-tight plastics material. One system 9 is for transferring electrical energy or electrical and/or optical signals, and the other system 1 is intended as mechanical reinforcement for the cable. As well as providing mechanical reinforcement, the other system could be utilized for transferring liquid or gas, but in the present example system 1 is intended only to take up mechanical forces on the cable.

The conductor arrangement in the system 9 comprises insulated plural wire or coaxial twisted inner conductors 5 which are tightly packed together. Around the conductors 5 an inner friction layer is wound in the form of a band 3 of plastics material, for example Mylar (Registered Trade Mark). Above the band 3 a force equalizing layer 4 is wound which consists of metallic material, for example surface treated aluminium (so called A1-PS foil). The two bands 3 and 4 are both wound with a certain overlap, the overlapping and the overlapped parts of the band 3 easily being able to slip relative to each other.

The force equalizing layer 4 has the purpose of taking up pointwise outer forces on the cable mantle and reducing the influence of the pressure caused which approaches the conductors 5 by distributing these outer forces across a larger area. The stiffness of the layer can be reduced by, as mentioned above, winding the layer with certain overlap, a low friction between overlapping and overlapped strip parts being obtained by the influence of the treated metal surface. By providing noninsulated plural-wire conductors 10 between the layers 3 and 4, the layer 4 can also be used as an efficient protective conductor and as electrical screen for the inner conductors 5.

Above the force equalizing layer 4 a force absorbing layer is provided which consists of a great number of hollow cords 6 of soft plastics material, for example foampolyethylene. As appears from Figure 2, the cords are disposed around the forceequalizing layer 4 with a certain pitch relative to the longitudinal direction of the cable. Above the cords 6 a further outer friction layer is disposed which consists of the same material as the inner friction layer 3. The further friction layer, like the layer 3, consists of thin strips 2 which have a low friction coefficient when contacting their own surfaces and, therefore, are wound with great overlap around the force equalizing layer. The purpose of these is primarily to enable a longitudinal movement of the system 9 relative to the cable mantle 7. The overlap of the layers is indicated by dotted lines in Figure 2.

The width b of the overlap of the outer friction layer is suitably chosen somewhat greater than half the width of a strip 2.

The system 1 is intended as an absorbing system for loading mechanical forces in the longitudinal and the transverse direction of the cable. The system contains a number of cords of mechanically stable plastics material, for example "phyllistran". The cords are preferably twisted around each other but not rigidly moulded to the mantle.

Thereby, the system 1 will slip as a result of pull stresses in relation to the cable mantle, whereby the system 9 will not be subject to large pull forces in the longitudinal direction of the cable. The system 1 could, as mentioned above, additionally be designed as a liquid or gas transferring channel, for example comprising fibre-reinforced plastics material with high mechanical strength.

WHAT WE CLAIM IS: 1. Cable comprising two separate systems not surrounding each other of which one system is suitable for transferring electrical energy or electrical and/or optical signals and the other system is for taking up mechanical loads, the two systems being surrounded by a common cable mantle, in which cable there are in the said one system an inner friction layer of plastics material having a low coefficient of friction when contacting its own surface and surrounding inner conductors of the said one system, a metallic layer covering the inner friction layer, a number of hollow coids of soft plastics material situated in parallel and surrounding the said metallic layer, the cords extending with a certain pitch along the longitudinal direction of the cable, and an outer friction layer of plastics material, with a low coefficient of friction when contacting its own surface, covering the said cords and situated nearest to the cable mantle.

2. Cable according to claim 1, wherein the said metallic layer comprises bands which, with a certain overlap, are wound around the said inner friction layer.

3. Cable according to claim 1 or 2, wherein the outer friction layer comprises bands of plastics material which, with a large overlap, are wound around the said cords and the inner friction layer comprises bands of plastics material which, with a certain overlap, are wound around the inner conductors of the said one system.

4. Cable according to claim 3, wherein the bands of the inner friction layer are wound with an overlap the width of which exceeds half the width of the bands.

5. Cable according to any preceding claim, which is self-floating cable for marine operations.

6. Cable substantially as herein described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. purpose of taking up pointwise outer forces on the cable mantle and reducing the influence of the pressure caused which approaches the conductors 5 by distributing these outer forces across a larger area. The stiffness of the layer can be reduced by, as mentioned above, winding the layer with certain overlap, a low friction between overlapping and overlapped strip parts being obtained by the influence of the treated metal surface. By providing noninsulated plural-wire conductors 10 between the layers 3 and 4, the layer 4 can also be used as an efficient protective conductor and as electrical screen for the inner conductors 5. Above the force equalizing layer 4 a force absorbing layer is provided which consists of a great number of hollow cords 6 of soft plastics material, for example foampolyethylene. As appears from Figure 2, the cords are disposed around the forceequalizing layer 4 with a certain pitch relative to the longitudinal direction of the cable. Above the cords 6 a further outer friction layer is disposed which consists of the same material as the inner friction layer 3. The further friction layer, like the layer 3, consists of thin strips 2 which have a low friction coefficient when contacting their own surfaces and, therefore, are wound with great overlap around the force equalizing layer. The purpose of these is primarily to enable a longitudinal movement of the system 9 relative to the cable mantle 7. The overlap of the layers is indicated by dotted lines in Figure 2. The width b of the overlap of the outer friction layer is suitably chosen somewhat greater than half the width of a strip 2. The system 1 is intended as an absorbing system for loading mechanical forces in the longitudinal and the transverse direction of the cable. The system contains a number of cords of mechanically stable plastics material, for example "phyllistran". The cords are preferably twisted around each other but not rigidly moulded to the mantle. Thereby, the system 1 will slip as a result of pull stresses in relation to the cable mantle, whereby the system 9 will not be subject to large pull forces in the longitudinal direction of the cable. The system 1 could, as mentioned above, additionally be designed as a liquid or gas transferring channel, for example comprising fibre-reinforced plastics material with high mechanical strength. WHAT WE CLAIM IS:

1. Cable comprising two separate systems not surrounding each other of which one system is suitable for transferring electrical energy or electrical and/or optical signals and the other system is for taking up mechanical loads, the two systems being surrounded by a common cable mantle, in which cable there are in the said one system an inner friction layer of plastics material having a low coefficient of friction when contacting its own surface and surrounding inner conductors of the said one system, a metallic layer covering the inner friction layer, a number of hollow coids of soft plastics material situated in parallel and surrounding the said metallic layer, the cords extending with a certain pitch along the longitudinal direction of the cable, and an outer friction layer of plastics material, with a low coefficient of friction when contacting its own surface, covering the said cords and situated nearest to the cable mantle.

2. Cable according to claim 1, wherein the said metallic layer comprises bands which, with a certain overlap, are wound around the said inner friction layer.

3. Cable according to claim 1 or 2, wherein the outer friction layer comprises bands of plastics material which, with a large overlap, are wound around the said cords and the inner friction layer comprises bands of plastics material which, with a certain overlap, are wound around the inner conductors of the said one system.

4. Cable according to claim 3, wherein the bands of the inner friction layer are wound with an overlap the width of which exceeds half the width of the bands.

5. Cable according to any preceding claim, which is self-floating cable for marine operations.

6. Cable substantially as herein described with reference to the accompanying drawing.