GB947831A - Electrical delay blasting device - Google Patents

Abstract

947,831. Electric blasting devices. CANADIAN INDUSTRIES Ltd. June 15, 1962 [June 24, 1961], No. 23107/62. Heading F3A. A blasting device for closing an electrical circuit comprises a casing 1 closed at its ends by rubber plugs 2, 3, leads 4 connected by a bridgewire 5, leads 6 with bared ends 7 and an apertured electrically conducting piston 10. The bridgewire 5 is surrounded by an ignition composition 9 housed in a plastics cup 8 which ignites a delay composition 13, which may, for example, be a silicon and red lead mixture or a selenium, silicon, red lead, lead chromate and barium chromate mixture. The delay 13 ignites in turn a gas-producing composition 14, which in a preferred form is a 40: 20: 40 parts by weight mixture of ground cellulose, potassium chlorate and lead sulphocyanate, thereby driving the piston 10, hitherto wedged in the casing, into contact with the ends 7 to complete the circuit of which leads 6 form part. The piston may be made of lead, the soft alloys of copper, zinc and iron or of a conducting non-metallic material. The aperture 11 is preferably less than 0.1 cm in diameter and more than one such aperture may be provided. In a second embodiment, the delay 13 is dispensed with and the ignition composition 9 is a gas-producing composition having a preferred form as given above. Specifications 728,598 and 744,530 are referred to.