Patent GB-563805-A (GB)
Abstract: 563,805. Electric conductors. WILKOFF, H. M. May 6, 1943, No. 7202. [Class 36] An ignition harness, which is especially applicable in connection with carrying currents from magnetos 7 to sparking- plugs 5 on radial engines used on airplanes, comprises an annular member 1 in which are arranged a number of cables 6 connected respectively to junction members 3 fitted with similar cables leading to the plugs 5. The cables are individually insulated and disposed within a jacket which is tough, elastic, flexible and seamless, and is formed of water- and oil-resisting insulating material, enclosed in a flexible sheath of electrical conducting material housing the conductor assembly. One method of forming the harness is to take a number of cables 6 of different lengths containing conductors 8 and wrap these in helical form as in Fig. 4. To form a uniform annular member 1 the short cables may be supplemented by similar sized tubes of neoprene or the like to make a complete ring 1. The cables 6 are. covered with asbestos yarn or shaped strands of plastic material so as to fill the helical grooves 10, Fig. 4, and a thin metal ribbon is then wrapped round the assembled layers. The metal known under the Registered Trade Mark " Duralumin " may be used. Or the assembly could be drawn into a tubular metallic casing, and a cross-section of the assembly is shown in Fig. 9, 13 representing the metal casing. The casing 13 is now wound with two tapes of thermoplastic material such as vinyl chloride, or a vinyl acetate resin in overlapping helices of opposite thread, and these tapes are united by pressure under heat in such manner that the cables are not heated. As shown in Figs. 13 and 15, the assembly between the ends of two conductors is inserted in a wooden mould 17, 18 having a metal lining 20 which is connected by terminals 21 to form one condenser plate of a high frequency tuned circuit, and the casing 13 is connected to form the other plate of the circuit, which comprises a primary - coil 24, secondary coil 25, and primary coil 27 of a secondary coil 28 in the circuit of the condenser plates 20, 13 and also in a circuit containing a variable condenser 29 and auxiliary condensers 30, 31. The current is supplied for 45 seconds while the moulds 17, 18 are acted upon by a press 23. The tapes coalesce to form a tubular jacket which is waterproof, oil resistant, highly elastic, tough and unaffected by temperature conditions. The leads 4 for connecting the cables 6 to the spark plugs are treated similarly to cables 6 and are connected to the cables 6 by means of fittings 3, Fig. 1a, comprising a screw-threaded portion 3<x> engaging an internally screw-threaded connection 32b of the ignition wire conduit. A flange 3y on the member 3 is bound to the jacket 15 by a plurality of wrappings of thermoplastic tape, and this is consolidated in a mould and heated in a similar manner to the jacket 15. The fitting 3 is provided with a resilient contact for joining the wires 4a and 8. The cable and ignition wires are finally bound in a braded metallic tube 32 or 32a, Fig. 1a, which is preferably applied so as to exert a radial stress upon the enclosed assembly. In a modification, Fig. 20, the cables 6 are wound upon a core tube 33 of flexible material, e.g. of a synthetic resin such as neoprene. This core has a grooved external surface, and is' formed with a bore of less diameter than the cables 6 and one cable is passed through the bore while it is inflated. The other cables are laid in the grooves and the core is twisted so as to cause the cables to be in helical form. The core is deflated and the assembly is then mounted in a jig provided with a clamp for each end of the cable. The jig is also provided with means for supporting and holding terminal fittings 3m, Fig. 24, which receive the ends of the individual conductor wires 4, the wires 8 of the cables 6 being connected to spring contacts 43 in the fittings 3m. Neoprene saddle-shaped bridges 46 and tubes are used to complete the harness and then a winding of copper foil ribbon is applied after protective layers of neoprene are applied near the cable ends. The copper foil is soldered in place and is applied four layers in thickness. A jacket of neoprene or Vinylite (Registered Trade Mark) is then applied, and the jacket is moulded in a jig and heated by a high frequency current as in the first modification. The sparking-plug leads are constructed with terminal connections 58, Figs. 34, 35, formed with a knurled part 59 and a screw-connection 60 for receiving a fitting 67 which operates clamping rings 64 for compressing a gasket ring 68 which clamps the connection 58 to a tube 56 of neoprene or Vinylite covered with armour material 63. The connection 58 is inserted into the tube 56 which is of smaller internal diameter by inflating the tube. The conductor 57 is also inserted while the tube is inflated, a thimble 66 being placed ahead of the conductor as it is being inserted. The conductor passes through a ceramic sleeve 70 and is connected to a terminal 71. At the opposite end of the ignition lead the wire is pushed through the spark-plug elbow, and a lead gasket and clamping rings are applied to this end also.