GB982364A - Improvements in or relating to a blasting assembly - Google Patents

Abstract

982,364. Blasting-detonators. CANADIAN INDUSTRIES Ltd. Oct. 31, 1963 [Nov. 13, 1962], No. 43057/63. Heading F3A. A blasting-detonator, primarily intended for the detonation in bore holes of mixtures of ammonium nitrate and non-explosive fuels, comprises a metal casing 1, a compressed charge 2 of explosive such as P.E.T.N., a primer 3, a sealing element 6 consisting of a solid cylinder of deformable metal having a core of an essentially gasless combustible composition, and an explosive connecting cord 8 crimped in position to abut the sealing element 6 and having a core containing from 0À1 to 18 grains of high explosive per foot of length. The casing may be of aluminium or copper, the primer 3 of lead azide and the core of sealing element 6 of compositions which fuse on burning, such as mixtures of lead dioxide and silicon or red lead and silicon. The element 6, held in casing 1 by crimping or be adhesive, is conveniently made by charging and compacting the combustible composition into a lead tube, swaging the ends of the tube, drawing the tube down to the required diameter and cutting the tube to give elements of the desired length. A method of forming a sealing element having a helical core is also described. The connecting cord 8 is preferably one having a core-confining sheath of braided textile surrounded by a mantle of thermoplastics such as polyethylene or polyvinyl chloride and a core containing from 3À5 to 4À5 grains of high explosive per foot of length. As shown, the detonator is also provided with a delay train comprising a lead tube 4 containing delay mixtures such as silicon, selenium, red lead, lead chromate and barium chromate or red lead and silicon and a lead tube 5 containing a booster charge. In a second embodiment the primer is covered by a relatively insensitive ignition composition such as ground smokeless powder or a mixture of red lead and boron and the connecting cord, of smaller diameter than the casing, is held by a rubber plug crimped in the casing. Specifications 815,532 and 815,534 are referred to.