GB647145A - Improvements in or relating to electric detonators and the production thereof - Google Patents

Abstract

647,145. Electric blasting detonators. ATLAS POWDER CO. July 29, 1947, No. 20408. Convention date, May 29, 1946. [Class 9 (i)] An electric detonator shell is sealed with a resilient plug by precompressing the plug from a diameter greater than the interior diameter of the shell to a diameter: smaller than that of the shell, inserting the plug while compressed into the shell where the plug expands and is held in place by the remaining lateral compression. A detonator shell 25 contains a charge 28 of high explosive, e.g. tetryl, and a primer charge 29 of lead azide or nitromannite together with an electric ignition assembly 30 of conventional type. In Fig. 4, a match-head 31 is connected to leg-wires 36 extending through a dielectric plug 39 of resilient material such as rubber or a synthetic rubber, e.g. neoprene, butyl and polyvinyl chloride or polyvinyl chloride-acetate. The plug before insertion in the shell has a diameter substantially greater than the internal diameter of the shell (from 5 to 40 per cent greater). For a shell of internal diameter 0.260 in. it is stated that the plug may advantageously be 0.310 in. in diameter: The plug may be moulded on to the leg wires or formed by extrusion with through passages to pass the leg wires freely. To assemble the detonator the shell is inserted in a holder 54, Fig. 9, mounted in a base 55 resting on a bed-plate (not shown). A female die holder 59 is placed on the holder 54 to abut against a shoulder 58. Into the die holder is placed a female die 60 resting on the holder 54, Fig. 14. The internal diameter of the die, which is greater than the diameter of the plug at the outer end, is tapered at the inner end so that at the exit it is less than that of the plug. The plug is threaded on to the leg wires and inserted in the die. A hollow plunger 61 longitudinally split or grooved to receive the leg wires is placed in the die and pressure is then applied to force the plug 39 into the shell where it is held-under pressure in sealing engagement with the shell and the leg wires (Fig. 15). Modified shapes of plug are described and the shell if metallic may be crimped to the plug or bent over the plug. The shell may be formed of thermo-setting plastic materials. Fluid means may be used to introduce the ignition assembly into the shell.