GB809622A - Blasting initiator - Google Patents

Abstract

809,622. Blasting fuzes. DU PONT DE NEMOURS & CO., E. I. Sept. 25, 1956 [Jan. 13, 1956], No. 29235/56. Class 9(1) An electric delay igniter comprising a metal casing closed by a plug through which extend the leg wires of the igniter is provided with a shunt to prevent arcing, the shunt being within the plug and consisting of a layer of fuzible resistance film contacting the bared portions of the leg wires and a metal layer superposed on the first-mentioned layer. The casing 1, Fig. 1, may be of aluminium or gilding metal and contains a base charge 2, e.g. PETN or RDX, a primer charge 3, e.g. lead azide or a fulminate, a delay element and an ignition composition 6 such as boron with red lead or a mixture of bismuth, selenium and potassium chlorate. The delay element may be a lead tube 4 containing a gasless composition such as a barium peroxide-selenium mixture or a boron-red lead mixture. The shunt 11 consisting of a metal layer 11A and a fuzible resistance layer 11B, Fig. 4, may be folded about the bared wires with the film 11B in contact with the wires in various ways, e.g. the two layers may span the wires twice. The plug 9 may be of natural or synthetic rubber. The shunt may be a conducting rubber vulcanized to the metal, which may be shim brass, steel, nickel-chromium alloy, copper or aluminium. The rubber film may be a standard commercial product consisting of carbon particles in a rubber matrix with a resistance of 30 ohms/sq. cm. Instead of rubber a conducting vinyl resin may be used.