Abstract: A radiating cable communication system for a transportation undertaking is given useful fire-survival characteristics by incorporating on the surface of the cable dielectric, inside the outer conductor and so in the electric field, of the mica paper tape. This is much more effective than, for instance, using flame-retardant grades of polyethylene for the dielectric and flame-retardant grades of PVC for the sheath and, surprisingly, it has less effect on the electrical transmission characteristics of the cable.

Abstract: An optical cable comprises a plurality of separately formed flexible tubes in at least one of which is loosely housed at least one flexible tape which, viewed in transverse cross-section, is corrugated so that it has a plurality of troughs extending along its length, at least two optical bundles and/or separate optical fibres being secured in some of the troughs. An outer protective sheath surrounds the plurality of tubes and at least one elongate reinforcing member is embedded in or surrounded by the sheath.

Abstract: A method and apparatus are provided for continuously extruding rod feedstock through a die orifice while gripping two opposed sides of the feedstock to a pressure greater than the yield strength of the material with means for applying lubricant to the ungripped surfaces, constraining walls between which the feedstock is fed in the gripped condition, a stop at one end of the constraining walls, and a die orifice near the stop through which the feedstock is extruded, said lubricant applying means including at least two cylinders each having an open end facing a respective one of the ungripped surface when the apparatus is in use and means for introducing compressed gas into each of the cylinders.

Abstract: A clamp includes a flexible member that can be wrapped round a cable and secured by means of end-fittings, integral with the flexible member or permanently attached to it. A pair of faying surfaces (one on each end-fitting) engage one another when the clamp is wrapped round a cable with any circumference in a working range in relative positions that vary (by displacement in the plane normal to the cable axis) with the circumference within that range.

Abstract: Voids in at least a part of an artificial or natural structures overlying a highly porous layer (e.g.

Abstract: An oil-filled electric cable installation, in which oil when flowing outwardly from the cable to a pressure-maintaining oil tank it passes through a percolating filter, preferably of an active material, to remove particulate and/or dissolved impurities. A one-way return passage bypasses the filter so that maintenance of pressure is not impaired, and if required a high-pressure bypass may be used to protect the filter from unusually high pressures.

Abstract: An optical cable comprises a plurality of separately formed flexible tubes in each of some or all of which is or are loosely housed at least one optical bundle and/or at least one seprate optical fibre. The plurality of tubes is surrounded by an outer protective sheath in which preferably they are so loosely housed as to permit limited relative movement between the tubes when the optical cable is flexed. Where the optical cable is likely to be subjected to a tensile force, preferably at least one elongate reinforcing member is embedded in or surrounded by the outer protective sheath.

Abstract: Apparatus is provided for use in combination with an electric power distribution cable and the normal source of voltage supply to said cable, the cable being connected between said normal source of voltage supply and at least one load normally applied to said cable, said apparatus detecting faults in said power cable and comprising a solid state switch unit comprising two thyristors arranged in an inverse-parallel configuration and continuously conducting current up to a pre-set maximum and becoming non-conductive after conducting a current in excess of the pre-set maximum for a pre-set period, a metering unit connected to said solid state switch unit for indicating the size of a current flowing through said cable, said metering unit including means for measuring the current in the solid state switch unit, and a trigger circuit connected to said solid state switch unit and metering unit which includes a manually operated trigger switch so connected to said solid state switch unit that when the trigger switch

Abstract: An electric cable support system is provided having means for supporting electric cables and an elongate metal duct housing said support means and divided transversely into separately formed parts that are detachably secured together, the internal surface of at least a part of the length of the elongate duct is lined with a continuous wall of thermal insulating material and/or absorbing material comprising a closed envelope, or at least two closed envelopes arranged adjacent one another, containing non-flammable evaporative cooling fluid. Preferably, the or each envelope is made of a flexible material which will melt at a temperature at or near the boiling point of the cooling fluid. In the event of an external fire, when the temperature of the duct wall is sufficient to melt the flexible material of an envelope, the cooling fluid will start to evaporate and cool the duct interior.

Abstract: In a method of continuously heating wire by induction, a short circuit electrical connection between wire entering a loop or loops, constituting the secondary winding of a transformer, and wire leaving the loop or loops is effcted by guiding a portion of advancing wire on to one of two pulleys, arranged on opposite sides of the transformer core, and guiding a portion of the advancing wire off this pulley in such a way that the portions of wire cross, but are not intertwined with, one another to form the loop or loops. The advancing wire entering and leaving the loop or loops is maintained under such tension that the position in space of the crossover is substantially constant and that the cross portions of the advancing wire are in continuous physical contact, the contact pressure at the position of crossover being sufficient to disturb any electrically non-conductive layers on the wire to provide clean portions for electrical contact.

Abstract: An optical cable comprises an extruded elongate body of rubber or plastics material having at least one bore extending lengthwise in the body, and, embedded in the extruded elongate body and arranged side-by-side with the bore or bores, at least one separate elongate reinforcing member, at least one substantially flat flexible support member, e.g. a flexible tape or a pair of overlying flexible tapes, is housed loosely in the bore or in at least one of the bores and, viewed in transverse cross section, the tape or at least one of the tapes is corrugated so that it has a plurality of troughs extending along its length, at least two optical bundles or optical fibers are secured in at least two of the troughs.

Abstract: An optical cable comprises at least one optical cable element and, surrounding the optical cable element or elements, a flexible tube of rubber or plastics material, the bore of the tube being of such a transverse cross-section having regard to the transverse cross-section of the optical cable element or to the transverse cross-sections of the optical cable elements that there is at least one elongate space formed between the element or elements and the internal surface of the tube.

Abstract: An optical cable comprises at least one optical bundle and/or at least one separate optical fibre housed loosely in and throughout the length of at least one bore extending lengthwise in an extruded elongate body of rubber or plastics material so that at any transverse cross-section of the cable throughout the whole of its length liimited relative movement between the optical fibre and the extruded elongate body can take place when the cable is flexed and, embedded in the extruded elongate body throughout the whole of the length of the body and arranged side by side with the bore or bores, at least one separate elongate reinforcing member. Preferably the bore or bores and the reinforcing member or members extend substantially parallel to the axis of the extruded body and their axes lie in a substantially common plane.

Abstract: In an optical cable comprising at least one optical bundle, individual fibres of the or each optical bundle and/or at least two fibre-groups each comprising an assembly of some of the fibres of the or each optical bundle being wholly or partially embedded in and mutually separated by encapsulating material throughout substantially the whole length of the bundle; at least one separate elongate non-optical reinforcing member; and, surrounding the bundle or bundles and the reinforcing member or members, an outer protective sheath, the or each optical bundle is loosely housed in a bore in the protective sheath, the or each reinforcing member is embedded in the sheath alongside the bore, each optical fibre has a continuous abrasion-resistant coating of a hardened material and the encapsulating material is of such a nature that, when appropriately treated, it can be removed from between the embedded fibres and/or the embedded fibre-groups at an end part of the cable or it can be softened to such an extent as to per

Abstract: An optical cable comprises a longitudinally extending flexible central reinforcing member, e.g. a steel wire or wires; a layer of compressible material, such as cellular rubber or cellular plastics material, surrounding the reinforcing member; a plurality of separate optical fibres stranded side by side about the central reinforcing member in such a way that each optical fibre is in contact with the layer of compressible material; and, surrounding the optical fibres, an outer protective sheath. When the separate optical fibres are subjected to a tensile force, at least some of them can move transversely inwardly of the cable to compress the compressible material and thereby reduce the strain that would otherwise be imparted to the fibres.

Abstract: In the manufacture of a cross-linked extruded product, a polymer capable of being cross-linked by the use of hydrolyzable unsaturated silane is metered into a first screw extrusion machine together with compounding ingredients comprising a hydrolyzable unsaturated silane, a free-radical generator and a silanol condensation catalyst. The compounding ingredients are mixed with the polymer in the barrel of the first extruder. The mixture of ingredients is fed directly without exposure to the atmosphere to a second screw extrusion machine in which its temperature is raised sufficiently to effect grafting of silane groups to the polymer (the amount of free-radical generator being sufficiently low to limit direct free-radical cross-linking to a level that will not prevent extrusion of the material). The reaction mixture is extruded from the second extruder through an extrusion die to form an elongate shaped product, and the grafted polymer is cross-linked in the shaped product by the action of moisture.

Abstract: In a method of making a cross-linked extruded product from polyethylene or other suitable polymer, the polymer is metered into a screw extrusion machine together with compounding ingredients comprising a hydrolysable unsaturated silane, a free-radical generator and a silanol condensation catalyst. The compounding ingredients are blended with the polymer in the barrel of the extruder and the mixture is heated sufficiently to effect grafting of silane groups to the polymer, the amount of free-radical generator being sufficiently low to limit direct free-radical cross-linking to a level that will not prevent extrusion of the material. The reaction mixture is extruded directly from the same extruder through an extrusion die to form an elongate shaped product and cross-linking is effected by subjecting the shaped product to the action of moisture.

Abstract: A continuous coating of hardenable material, e.g. a thermosetting enamel, is applied to an advancing optical fibre by causing the fibre to pass between two continuously moving endless surfaces, e.g. two rollers, which are positioned on opposite sides of the advancing fibre and each of which carries a layer of liquefied hardenable material in such a way that the advancing fibre is at least partially immersed in each of said layers, the distance that each endless surface is spaced from the advancing optical fibre and the thickness of the layer of hardenable material on each endless surface being such that opposite parts of the advancing fibre pass through said layers of hardenable material with substantially no physical contact taking place between the fibre and the endless sufaces themselves.

Abstract: Elongate copper bodies, such as rods and wires, of electric conductor grade are made by electrodepositing copper as brittle cathodes which are then broken into fragments and fed as such to a continuously-acting friction-effected extrusion machine (such as Conform or Linex) which consolidates, bonds and extrudes them. The fragments have a specific surface area of about 25 - 1000 mm.sup.2 /g, and they are not subjected to any high-temperature purification or grain growth step prior to extrusion, though moderate pre-heating is allowed. Avoidance of high-temperature processing, such as conventional casting and hot-rolling, saves much energy and in addition copper of higher quality is produced.

Abstract: In effecting a joint between two optical fibres an elongate gauge having a cross-sectional shape and size corresponding to that of each of the optical fibres to be jointed is laid on a substantially flat surface of a soft, substantially non-resilient metallic body, e.g. annealed copper, and is pressed into the surface to form in, and between two edges of, the surface a groove of a substantially complementary cross-sectional size. The gauge is removed and the two optical fibres are aligned in the groove so formed in such a way that neighboring ends of the optical fibres substantially abut. A second body having a flat surface is applied to the grooved surface in such a way that its flat surface is in interfacial contact with the grooved surface, and the two bodies are secured together.