GB795271A - Delay compositions - Google Patents

Abstract

795,271. Blasting fuzes and delay compositions therefor. CANADIAN INDUSTRIES, Ltd. April 3, 1956 [Aug. 3, 1955], No. 10116/56. Classes 9(1) and 9(2) A gas-less, slow-burning delay composition comprises silicon, solid mon-metallic material from the group consistirig of selenium and tellurium, and oxidizing material from the group consisting of lead oxides and water-insoluble metallic chromates. Preferably not more than 65 per cent by weight of the composition is silicon and when the oxidizing 'material consists only of chromates, the silicon fraction is not more than 40 per cent. A ventless delay electric blasting cap, in which the delay composition 5 is used has a solid drawn metal shell 1 containing a detonating charge 2, e.g. of tetryl or pentaerythritol tetranitrate into which is pressed a priming charge 3, e.g. lead azide mixed with lead styphnate. The delay composition is housed in a lead tube 4 above which is an ignition charge 10, such as a mixture by weight of 98 per cent red lead and 2 per cent boron, surrounding a bridge wire 6. The delay element may be prepared by tamping the composition into a large diameter tube which, when full, is sized down by rolling, drawing or rotary swaging and then cut into suitable lengths to give the required delays.