GB614761A - Improvements in or relating to blasting assemblies - Google Patents

Abstract

614,761. Blasting devices. THOMSON, T., REID, K. C., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. July 26, 1946, No. 22299. [Class 9 (i)] Relates to blasting devices of the type in which a pressure-resisting container is separated from a perforated dischargehead by a closure adapted to yield at a predetermined internal gas pressure produced by a non- detonating gas - evolving charge the gases being evolved without flame as in Specification 431,935. According to the invention such a device containing a granular charge of a mixture of sodium nitrite and ammonium chloride stabilised by an alkaline is actuated by electrically fired local heating means comprising an electric black powder fuze having a sheathing of a perchlorate. A pressureresisting container 1 having a firing head 2 is separated from a discharge head 3 by a rupturable disc 4. A 460 gm. charge 7 of a stabilised mixture of sodium nitrite and ammonium chloride in the container 1 is initiated by an electric fuze 6. Insulated leads 5 of the fuze 6 are connected through terminals in the firing head to the electric circuit. The fuze 6 consists of a paper tube closed by plugs 8, 9 and 17 and containing a 20 gm. charge 11 of ammonium perchlorate surrounding a 60 grain charge 16 of black powder in a paper tube 12. A low-tension electric fuze-head 15 is embedded in the black powder. The charge of ammonium perchlorate acts as a booster, reducing the delay between closing of the firing circuit and venting of the gases from the initiated charge 7 to about 30 millisecs. Thus an assembly of a plurality of these devices may be electrically connected for simultaneous shot firing. Specification 461,647 also is referred to.