GB458257A - Improvements in or relating to the manufacture of electric cables or other insulated conductors having mineral powder insulation - Google Patents

Abstract

458,257. Cables. CONDUCTEUR ELECTRIQUE BLINDE INCOMBUSTIBLE, 54, Avenue Marceau, Paris. March 12, 1935, No. 7692. Convention date, March 12, 1934. [Class 36] Electric cables of the kind comprising one or more conductors insulated with a mineral powder, such as magnesia, are formed by passing the conductor or conductors through a die through which the powdered insulating material is forced under pressure in a dry condition, a protective cover, in the form of an extruded sheath or a permeable tube consisting of braided or wound textile threads or metallic wires, being applied to the insulated conductor or conductors as they emerge from the die. When the protective cover is in the form of a permeable tube the cable may be subjected to heat treatment to remove any residual moisture in the powdered insulation, after which an impermeable covering may be applied. As shown in Fig. 1, a conductor 4 to be insulated passes through the die 3 of a forcing machine comprising a container 2 from which dry mineral insulating powder is forced through the die 3 by a screw 7. A braided tube 6 is formed. about the conductor as it and its coating of powder emerges from the die 3. Powdered insulation is fed to the container 2 from a hopper 11, excess powder falling into a tray 12 and being transferred back to the hopper by a conveyer 13. The apparatus may be vibrated to facilitate the downward movement of the powder through the container 1. In the construction shown in Fig. 2, the die 3 is surrounded by a second die 14 through which rubber, lead or other thermoplastic material is extruded to form a sheath 16 surrounding the insulated conductor. The Specification as open to inspection under Sect. 91 comprises also the subjectmatter of Specification 458,254, [Group V]. This subject-matter does not appear in the Specification as accepted.