GB1006897A - Improvements in or relating to telecommunications cables - Google Patents

Abstract

1,006,897. Cables. PIRELLI GENERAL CABLE WORKS Ltd. April 16, 1962 [May 11, 1961], No. 17172/61. Heading H1A. An electric cable comprises stranded insulated conductors 6, barriers 36 being formed across the cable at intervals to prevent fluid, leaking into the cable through the cable sheath 35, from migrating along the interstices between the conductors themselves and between the inductors and the sheath. Barriers 36 are formed, as described, Figs. 1a, 1b (not shown), during the process of manufacture of the cable. Fig. 1a shows a conventional stranding machine to which is added an injector head 4 for depositing a barrier forming material. A central insulated conductor 1 is continuously drawn from a supply drum 2 through injection head 4 where deposits are formed on the conductor at intervals, then through a carriage 5 supplying further conductors 6 which are laid on the first conductor. Conductors 1 and 6 are then passed through a shaping die 8 which presses the conductors 6 on to the conductor 1, tapelapping heads 9 wrapping up the thus formed core with tapes. A further embodiment is described, Fig. 1b wherein a second injection head is provided between the shaping disc and tape-lapping heads. Injection heads are synchronized so that barriers formed by the first are built up by the second. The injection head comprises, as shown in Fig. 2, a frustocone 18 with apertured apex through which passes the conductor or conductors, a cap 22 is fitted to the cone snugly so as to leave a passage 23 between them. The passage 23 communicates with a reserve 25 of a barrierforming liquid, which is a cold-setting thermoplastic material, through a hole 27 which is alternately opened and closed by a plunger 29 operated by a " bell and crank " system and a mechanism 15.