Explosive charge with annular ignition gap

Claim 1

An explosive device comprising a generally cylindrical explosive charge in a container having one end closed, an inert conical member having its major base in contact with the open end of said explosive charge and being slightly smaller in diameter than said explosive charge so as to leave exposed an annular surface of uniform width forming with said conical member and said container an annular ignition gap, said container being spaced uniformly from the conical surface of said conical member to form an annular initiation space, and propagation charge means disposed in said annular initiation space and filling said ignition gap for ensuring symmetrical propagation of the detonation waves around the major base of the inert conical member, said annular ignition gap having a predetermined width and said propagation charge means having a predetermined thickness, at least one of the predetermined width of said ignition gap and the predetermined thickness of said propagation charge means exceeding the respective minimum width and minimum thickness absolutely necessary to effect sure and safe propagation of the detonation by 0.5 to 1 mm.