GB768616A - Improvements in electric blasting initiators - Google Patents

Abstract

768,616. Blasting fuzes. CANADIAN INDUSTRIES (1954), Ltd. April 19, 1955 [June 10, 1954], No. 11216/55. Class 9 (1). An electric blasting cap similar to that described in Specification 768,486 is protected against accidental discharge by stray currents by filling the channels 9, 10 in the insulating plug 7 between the lead wires 5, 6 and the shell wall 2 with ionized air. Radio-active material 11, 12 is applied to the inner surfaces of the channels 9, 10 and may be dispersed in a paint or lacquer or porous material. The radio-active element is preferably one emitting beta-particles of energy 1 to 20 kv., such as tritium, the third isotope of hydrogen. initiator respectively by a weld between a nickel - zinc - copper alloy or a nickelcobalt-iron alloy and the high resistance wire and the tab or lead respectively. In making an electric match assembly for a blasting cartridge &c. brass tabs 1, 3 e.g. of composition 65-75 preferably 70 per cent. copper, 25- 35 preferably 30 per cent. zinc are bonded to an insulating material 2 e.g. resin impregnated paper or vulcanized fibre paper and a 0.0015 inch diameter high resistance wire 3 of composition 80 per cent. nickel, 20 per cent. chromium is laid over the tabs to form a bridge over a step in the material 2. A 0,005 inch diameter wire 4 of composition 29 per cent. nickel 18 per cent. cobalt 53 per cent. iron is laid across the wire 3 at an angle of 80-90 degrees above the tab 1. A welding