GB703003A - Improvements in the manufacture of a metal tube which may form part of an electric cable - Google Patents

Abstract

703,003. Making tubular electrical conductors. BRITISH INSULATED CALLENDER'S CABLES, Ltd. Feb. 18, 1952 [Feb. 19, 1951 ; Sept. 26, 1951], Nos. 4040/51 and 22498/51. Classes 83 (2) and 83 (4) A method of making a metal tube, e.g. a tubular electrical conductor, by transversely bending a metal tape to a tubular form in which its edges abut and holding it in such condition by transversely bending a second metal tape over it and soldering this outer tape to the inner tape along a continuous strip on each side of the abutting edges of the inner tape, is characterized in that one of the tapes has a coating of solder metal on each of one or more narrow strips of the tape before transversely bending it and, as the outer tape is being applied to the inner tape flux is applied and the assembly is heated in the region of the solder coated strip or strips to effect the soldering. Figs. 1 to 9 show embodiments wherein' one or more narrow strips of solder 3, are employed to unite the transversely bent outer tape 2, to the tubular inner tape 1, having abutting edges 4. The solder strips may take a sinuous path along the length of the inner or outer tape and the coating may be produced by applying metal powder admixed with adhesive liquid consisting of or containing a flux and then heating the mixture on the tape. Alternatively, flux may be applied to the tape which is then heated and solder metal applied in the form of a wire or rod. Where a sinuous strip coating is required the solder wire is reciprocated laterally as the tape travels forward. The simultaneous deposition of solder and flux may be effected by passing the tape 2 (Fig. 12), under a roller 5, having projecting rubber rims 6, which are fed with the liquid solder-flux mixture by an applicator roller 7, dipping in a bath 8, containing the mixture 9. From the roller 5, the tape passes over a heated convexly-curved shoe 10, which melts the solder and drives off the liquid the solder being set by passing the tape over a water-cooled shoe. Alternatively, apparatus for applying flux and solder wire to the tape comprises a flux applicator 12 (Fig. 13), consisting of a number of wicks 16, one for each line of solder, each wick being held in a tube 17, leading from a flux container 18; a heater 13, consisting of a heated convex arcuate surface and a so'der feeding device comprising a pair of rubber feed rolls 22 for feeding the solder wires 23, from supply reels 24, through guides 25. The feed rolls are driven by a chain drive 26, from the tape-advancing means 15, which comprises a frame 27, supporting a pair of rolls 28, the lower of which is driven by an electric motor 29, through a gear box 30, and chain drive 31. The upper roll is spring-loaded on to the lower roll by a pair of springs 32. The tape is fed to the flux applicator from a reel 21, and it is rapidly cooled on leaving the heater 13, by passing over an arcuate cooling plate 35, cooled by a water spray or air blast or by immersion in a liquid coolant. From the rolls 28, of the advancirig means the tape passes on to a take-up reel 33, driven through the gear box 30, by the motor 29. In carrying out the invention the inner tape 1 is drawn from a supply reel 34, and guided by a pulley 35, towards a transverse bending device 36, comprising spaced metal plates 37, having apertures which progressively decrease in size. The prepared outer tape 2, drawn from a reel 39, and guided by pulleys 40 and 41, is applied to the underside of the transversely bent inner tape 1, and a second bending device 42, bends the outer tape around the tube 38, formed by the bent inner tape. Flux is applied by an applicator 43, consisting of a flux container 44, and a tube or tubes 45, carrying a wick or wicks 46. The wicks may be replaced by brushes or rollers. On leaving the second bending device 42, the tube 38, passes through a heating device 47, e.g. a hot die or hot rolls and then through a forced cooling device 48. The solder-applying apparatus may be inserted in the path of the tape 2, between the supply wheel 39, and the point of application of the tape 2, to the pre-shaped inner tape 1. When it is required to make transversely corrugated tubing the tape is corrugated after the application of the lines of solder. When either or both layers of the tubing are to be of a metal, e.g. steel which will not solder easily, both the inner and outer tapes are provided with juxtaposed solder strips. Tubes made according to the invention may form part of an electric cable, e.g. the outer conductor of a co-axial cable or screen or sheath which encloses the conductor and the insulating material of a cable.