GB570361A - Improvements in protecting tubes for electrical mains and wiring installations - Google Patents

Abstract

570,361. Paper tubes &c. ALONSO, E: L. Jan. 8, 1942, No. 305. [A Specification was laid open to inspection under Sect. 91 of the Acts, May 30, 1942] [Class 99 (ii)] Protecting tubes for electric mains or wiring installations are made by simultaneously winding a number of paper or linen strips one upon the other to form tubular cone on which is wound a flexible conductive covering of non- magnetic metal which is then provided with a cover of insulating material. The core may be formed from strips of rag, blotting or other paper, or of linen of a width equal to the required length of the core, which are wound on a rotating and endwise movable mandril, alternatively the strips may be wound helically one upon the other. Each strip may be first passed through a heating device, and before reaching the winding machine, each strip but the first may pass through a device in which it is impregnated with insulating and adhesive material. Alternatively the strips may be wound with the use of adhesive only, the finished core being impregnated under vacuum. The non-magnetic metal covering may be copper, brass, aluminium &c. in the form of a ribbon, fabric, or groups of wires helically wound on the core before or after the latter has dried. The outer insulating cover may be of material similar to the core, and applied in the same way, or it may be of vulcanizable rubber, or a fabric may be woven in situ either to form the insulating cover or over such cover; further the whole may be dipped in vulcanizable rubber or phenolic compositions. A further outer covering of sheet or strip metal maybe provided.