Improved detonating explosive charges and method of using said charges to impress surfaces

摘要

637,332. Blasting charges. COOK, J. H., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Oct. 6, 1947, No. 26791. [Class 9 (i)] [Also in Group XXII] A composite explosive charge giving a plane detonation wave-front and used to transfer a design from a stencil to a metal plate has a conical core with a plane base, the curved surface of the cone being covered by a uniform layer of explosive of higher detonation velocity than the core, the sine of the base angle of the cone being equal to the quotient of the detonation velocities of the two explosives. A cardboard container 3 with a base 6 contains a composite explosive charge over a cylindrical charge 52, the composite charge being a conical charge 51 covered by a charge 5 of uniform thickness, the respective detonation velocities being 3600, 2300 and 5800 ms. per sec. and the base angle of the cone 23‹ 221. On firing the composite charge by an electric detonator 12 in a tetryl primer 11, a plane detonation wavefront is set up, so that a design on a hard cardboard stencil 1 will be embossed on a brass plate 8 without distortion. Partitions 4, 41 of stiff paper cover the conical surfaces and cushioning material 9 is placed between the brass plate and a steel anvil 10. The composite charge may be truncated towards the base by a surface or surfaces perpendicular to the base. The cylindrical charge may be an 80: 20 mixture of trinitrotoluene and sodium chloride, while the core of the conical charge may be a commercial powder and the outer thickness cyclotrimethylene trinitramine.