GB619315A - Improvements in or relating to blasting cap manufacture - Google Patents

Abstract

619,315. Blasting-cartridges. HERCULES POWDER CO. Dec. 2, 1946, No. 35664. Convention date, May 18. [Class 9 (i)] Relates to electric ignition devices for blasting caps, and consists in moulding a plug 10 of dielectric material with a recess 11 at one end from which two openings 12, 13 extend to the other end of the plug, two pins 16,17 being accommodated in the openings. In addition, leg wires 18, 19 are welded to the pins 16, 17, the pins then being drawn through the plug until the welded joints are embedded in an insulating compound in the recess 11 and abut against the openings 12, 13, a bridge wire 25 being affixed to the free ends of the pins and the completed device inserted into the casing of a blasting cap. Ears 23, 24 are formed in the pins to increase the anchorage of the leg wires in the plug. Thermoplastic and thermosetting resins suitable for moulding such plugs are given. The pins 16, 17 may be of steel, copper, nickel or the like. The leg-wires may be copper or iron and are insulated in a known manner. Waxes, asphaltic compounds, thermoplastic compounds or combinations of these may be used as the insulating compound in the recess 11. The bridge wire may be of platinum, nichrome, copper-nickel or other alloys. The casing 26 of the cap is of ductile metal so that the plug which has a slightly larger diameter can be forced into the casing to form a watertight assembly. An additional waterproof coating of wax such as stearin, ceresin, beeswax, may be applied to the plug. These substances may also be incorporated in the plug. Suitable explosive fillings 27 are given. Instead of being moulded the plugs may be formed by an extrusion method. When extruded wires to form pins may be embedded in them, the oxtruded material being subsequently cut into the appropriate lengths.