Abstract: Most fluorocarbon polymer surfaces (especially PTFE and FEP) have hitherto been considered unsuitable for marking by laser printing, which would have obvious attractions for marking such materials in high performance electric cables. It has now been found that such surfaces can be made receptive for laser printed markings. A reflective surface is first formed, preferably by incorporating white pigment into a fluorocarbon base, and a light-transmitting (preferably translucent) ETFE pr ECTFE layer is applied over it. When the reflective layer is based on PTFE or FEP, a primer layer formed from a mixed dispersion of PTFE or FEP and ETFE or ECTPE (as appropriate) is preferably applied before the underlying PTFE or FEP composition is sintered.

Abstract: Polymeric material is plastified in an extruder and is then divided into a major part and a minor part. Either the major part or (more often) the minor part is modified by a chemical reaction, such as grafting (any necessary ingredients being added, if not already present). The major and minor parts are then recombined in an extrusion head so that the modified and unmodified materials form distinct parts of the product. In this way, a single extruder can be used to make, for instance, a product with surface characteristics modified by grafting, wire-covering with only a surface layer crosslinked, or heat-sealable crosslinked packaging film.

Abstract: A handtool for detecting whether or not an optical fibre is carrying a light signal includes a motor-driven operating mechanism mounted in the tool housing for causing a pressure member to move towards or away from an anvil so that when the pressure member is caused to move towards the anvil an optical fibre positioned between the pressure member and the anvil will be subjected to microbending of a gradually increasing extent. The motor-driven operating mechanism preferably comprises a screw-threaded shaft supported in the housing and rotatably driven about its axis by the motor in either rotational direction.

Abstract: In an overhead optical transmission system in which an optical cable is freely supported between towers employed to support overhead electric power transmission lines and in which each end of the suspended length of optical cable is secured to a tower by means of a metal termination fitting which surrounds and is clamped on a part of a length of the optical cable at or near this end, each metal termination fitting of the cable over a part of the length of the fitting extending to the end of the fitting remote from the tower and an immediately adjacent part of the length of the optical cable are surrounded by a shield of an electrically conductive metal or of a semi-conductive plastics material sufficiently conductive to reduce arcing and/or joule heating.

Abstract: A silicone base oil for use as impregnant in an electric power cable for fire hazard conditions is rendered non-gassing by the addition of about 2-8% of an aryl alkane having at least two benzene rings spaced apart by not less than one nor more than two aliphatic carbon atoms. The total number of aliphatic carbon atoms in the molecule is limited to six, and the silicone oil should be chosen with a sufficiently high flashpoint for the whole oil to have flashpoint above 150.degree.C. The preferred additive is 1-phenyl 1-(3,4 dimethylphenyl) ethane, also known as PXE.

Abstract: An electric circuit breaker for protecting an electric circuit of an electrical installation of a building is of such a construction that a substantial proportion of its components are standard for the preferred current ratings of the breaker and that some components having a limited useful life can be readily replaced.

Abstract: A cooling system for use in an enclosure housing heat-emitting electrical and/or electronic apparatus comprises, in combination, a fan unit and, separately formed with respect to the fan unit, a cooling unit 12. The fan unit includes electrically driven fans mounted with their axes vertical and the cooling unit includes open ended tubes arranged side by side with their axes in a horizontal plane and transversely spaced apart to form passages therebetween. One open end of each tube is adjacent the front of the rack and is open to the atmosphere through a grill; the other open end of each tube is spaced inwardly from the rear of the rack and opens into an otherwise fluid-tight compartment in which are housed electrically driven fans and associated deflectors.

Abstract: A helically grooved flexible optical cable core comprising a plurality of helically laid flexible bodies 1 of sector-shaped cross-section is manufactured by drawing a multiplicity of flexible non-metallic reinforcing elements 2 under tension through electrically insulating plastics material 3 in a semi-liquid state; causing the plastics encapsulated reinforcing elements to pass through an elongate die 23 having an outlet orifice 25 of sector-shape, which die, between its ends, is of such a shape that reinforcing elements adjacent the arcuate surface 4 of the body are travelling at a greater linear speed than reinforcing elements remote therefrom, and which has a blade 26 protruding inwardly of the die and forming in the arcuate surface of the body a longitudinally extending groove 5; causing the body as it emerges from the die to follow a helical path with its grooved arcuate surface outermost and so cooling the helically advancing body that the plastics material sets; partially filling the groove in the arcu

Abstract: An optical cable, especially suitable for use as an aerial cable, comprises a circumferentially rigid flexible tube which is of composite form and comprises a plurality of elongate flexible bodies helically laid up together, each of which bodies is of a cross-section approximating to a sector of an annulus and comprises extruded electrically insulating plastics material and a mulitiplicity of longitudinally stressed elongate flexible non-metallic reinforcing elements encapsulated in said plastics material, e.g. polypropylene or nylon, the multiplicity of non-metallic reinforcing elements being substantially evenly distributed throughout the cross-sectional area of the body. An outer protective non-metallic sheath surrounds the tube and at least one flexible optical guide, e.g. a separate optical fibre, optical bundle or optical fibre ribbon structure, is housed in the bore of and is movable relative to the tube.

Abstract: A PTC adaptor for a pluggable data connector socket comprises an insulating housing (1) including a plug region (6) for insertion into the pluggable data connector socket, a socket region (16) including a plug receiving cavity (21) in which a pluggable data connector may be received, and a cord receiving region including a cavity (9) in which a plurality of insulated conductors may be received. The housing further includes a plurality of electrical contacts (24), each contact comprising a plug portion (26) extending into the plug region (6) for making an electrical connection with the pluggable data connector socket, a socket portion (28) extending into the plug receiving cavity (21), and a terminating portion (27) extending into the cord receiving cavity (9) for penetrating the insulating covering of the insulated conductors to make an electrical connection with the conductors therein.

Abstract: An optical fibre element for use in an optical cable comprises a flexbile elongate member having within and partially bounded by the elongate member throughout its length an elongate compartment; at least one optical fibre loosely housed in the elongate compartment; and means for retaining the optical fibre within the elongate compartment. The elongate member is resiliently set in such a form that the central longitudinal axis of the member follows a longitudinally extending path which, between any two longitudinally spaced positions, is greater in length than the rectilinear distance between the two positions. When the resiliently set elongate member is subjected to a longitudinally applied tensile force, the elongate member will tend to straighten in a lengthwise direction against the action of its resilient set, thereby to reduce the tensile force applied to the optical fibre. When the tensile force is removed, the elongate member will return under the action of its resilient set towards its original form.

Abstract: A coil of cable is formed by winding a predetermined length of cable (1) on to a spool (2) and fastening to the cable a clip (7), the clip including first and second recesses (8,9). Each recess receives a portion of the cable (1) to secure the free end (6) of the cable to the coil (3).The recesses (8,9) receive a portion of the penultimate turn (10) and final turn (11) respectively. The clip may be applied to the cable as the penultimate or final turns are being wound.

Abstract: An optical cable suitable for suspension beside an electrical railway or other location where an electric communication cable would be subjected to electrical interference comprises an optical cable element which is loosely housed in and extends helically throughout the length of an outer protective sleeve which has embedded in and at spaced positions around the sleeve a plurality of elongate non-metallic reinforcing members which extend lengthwise of the sleeve. Each reinforcing member has, in the member, undulations that serve to improve the mechanical bonding of the member within the sleeve and the flexibility of the cable. The optical cable element comprises a plurality of plastic tubes helically laid around a central non-metallic reinforcing member and surrounded by an outer sheath. In each of some of the tube is loosely housed a separate optical fibre.

Abstract: An optical cable having a bore in which is loosely housed two helically extending optical fibre ribbons and which is filled with a greasy water-impermeable medium is manufactured by feeding four flexible cords of electrically insulating material into circumferentially spaced, longitudinally extending grooves in the outer surface of a stationary rigid tubular elongate guide of circular cross-section, helically lapping two optical fibre ribbons around the guide and the flexible cords so that the cords support the helically lapped ribbons, applying longitudinally to and transversely folding around the guide and the optical fibre ribbon a flexible strip of electrically insulating material to form a tube, introducing water-impermeable medium in a liquid or semi-liquid state through a bore in the guide and into the tube and extruding around the tube a sheath of electrically insulating material.

Abstract: An electrical press-fit contact includes a compliant section (3) of substantially C-shaped cross-section and comprising first and second arm portions (4)(5) with a base portion (8) therebetween. The thickness of the compliant section increases steadily from the base portion (8) to the arm portions (4)(5) such that the center of the base portion is of least thickness to form a hinge about which the first and second arm portions may be preferentially deflected. The contact is formed by coining a portion of stock etc such that it has a planar first surface and an arcuate second surface sloping away from the first surface towards its edges. The coined portion is then folded to form the C-shaped compliant section with the first surface being the outer surface and the second surface the inner surface thereof.

Abstract: Apparatus for winding cable on to a spool comprises a movable table (11) on which at least three spools may be located. The table is mounted substantially horizontally such that the spools may be located thereon with their longitudinal axes substantially vertically upright. The table is movable between three positions; a loading position (12) where an empty spool is loaded on to the table; a winding position (13) where a spool is rotated and cable (2) is wound on to the spool; and an unloading position (14) where a wound spool is removed from the table. There is also provided first lifting means (15) for loading a spool on to the table, second lifting means (16) for removing a spool from the table, means (30) for loading the cable on to a spool, means (38) for cutting the cable, and a programmable controller adapted to control the sequence of operations.

Abstract: A rugged pressure actuated cable switch especially suitable for use in road vehicle detection comprises a central elongate conductor; a flexible insulating element helically wound around central conductor; a flexible tubular body of electrically conductive plastics material surrounding the central conductor; two elongate conductors in electrical contact with the outer surface of the flexible tubular body, and an overall insulating sheath of a transverse cross-section of approximately semi-circular shape having a flat surface for supporting the cable switch on the ground. Each outer conductor is embedded in the sheath alongside the flexible electrically conductive tubular body at a position intermediate of the flat surface and the longitudinal axis of the central conductor.

Abstract: An extrusion process is controlled by feeding the material to be extruded from a supply station (5) to an extruder (1) and repeatedly weighing the supply station to calculate the throughput of the extruder. The initial line speed necessary to produce a predetermined weight/meter of extrudate is calculated and the line speed is adjusted accordingly. Subsequently, the throughput and the line speed are increased simultaneously, such that the weight/meter is maintained substantially constant until any one of a plurality of parameters such as line speed, screw speed, motor load current, extrudate temperature, melt pressure, etc reaches a predetermined maximum value. Thereafter either the line speed or extruder throughput is adjusted such as to maintain the weight/meter of the extrudate substantially constant at the desired value.

Abstract: A simple and inexpensive elongate pressure-actuated electrical switch especially suitable for security purposes comprises a flexible tubular body of insulating material having air within its bore and incorporating at opposed locations around its periphery two sectoral portions of electrically conductive material. Two elongate conductors extend lengthwise in electrical contact with the conductive sectoral portion and two electric conductors extend lengthwise in contact with the conductive sectoral portion. The sectoral portions have a conductivity less than that of the conductors. An overall outer sheath surrounds the tubular body and conductors and has a flat surface which is suitable for supporting the switch on the ground and which is so positioned with respect to the sectoral portions that one conductive sectoral portion is at a position intermediate of the flat surface and the other conductive sectoral portion.

Abstract: Optical fibre splice mechanical testing apparatus for use with optical fibre splicing equipment comprises two optical fibre clamping devices for mounting on splicing equipment at spaced positions spaced lengthwise of the two optical fibres to be spliced and located on opposite sides of the splicing station. One clamping device is constrained to move towards or away from the other clamping device in a direction lengthwise of the optical fibres between a first position nearer the splicing station and second position remote from the splicing station and is urged towards the second position by a coil spring. The movable clamping device can be temporarily maintained in the first position against the action of the coil spring.