GB1290015A - - Google Patents

Abstract

1290015 Injection-moulded cartridge IMPERIAL METAL INDUSTRIES (KYNOCH) Ltd 9 April 1970 [13 May 1969] 24269/69 Heading B5A [Also in Division F3] A method of manufacturing a shot concentrator for a shotgun cartridge comprises injection moulding a cylindrical side wall 11 of substantially unfoamed plastics material and a base wall 12 at least partly of unfoamed plastics material, injecting foamable plastics material into the mould and allowing the foamable plastics to foam and form a compressible wad 13, and allowing the unfoamed and foamed plastics material to set. The mould 18 is cooled by water flowing in channels 23 and suppresses foaming if foamable plastics material is used to foam the cylindrical side wall 11. The central core for forming the shot cavity in the concentrator comprises an optional sleeve 33 and a pin 34. During the injection moulding of the cylindrical wall 11 and the base wall 12 the pin is in the position A. The pin is moved to the position B to permit further injection of plastics material and is finally moved to position C to permit the wad 13 to be formed by foaming of the plastics material. The wad 13 can be formed of the same or from a different plastics material to the cylindrical and base walls 11 and 12. The plastics material comprises polyethylene with a blowing agent such as azodicarbon-amide, ethylene/vinyl acetate co-polymer or plasticized polyvinylchloride. The mould 18 is fitted within a block 21 mounted in an annular bolster 22 axially located between a bearing plate 24 and sprue plate 26. A sprue bush 27 is mounted on a reciprocating screw type injection machine, the sprue channel 29 opening into a cavity 30 which receives the injection nozzle which is fitted with a spring- loaded valve to maintain pressure on the material at about 2000 p.s.i.