GB527972A - Improvements in and relating to injection moulding machines - Google Patents

Abstract

527,972. Injection moulding-machines. HEMPEL, E. April 11, 1939, No. 11041. Convention date, April 11, 1938. [Class 87 (ii)] In injection moulding-machines for thermoplastic material the material, before entering the nozzle, is caused to flow around and past a heating-member provided with helical ribs which split the material into a plurality of helical strands. The material is forced by a piston 11 past the heating-member 13 to the nozzles 12. The member 13 comprises a tubular part 14 having a number of bores 15 containing heating-elements and having also four helical ribs 17 for deflecting the plastic material. An exchangeable mouth-piece 25 carrying the four nozzles 12 is attached to the cylinder 18 of the press by a cap 19 which engages the press frame 23 by bayonet slot connections 21 which have inclined surfaces to tighten the joint. Insulation 24 is provided between the cap 19 and cylinder 18 which may have additional heating recesses. The nozzle conduits 26 diverge upwardly to form mixing chambers which are separated by central partitions 27, Fig. 2, having acute edges and partitions 29 which form continuations of the ribs 17 and cause the helical strands of material to turn upon themselves and become mixed. The mouth-piece 25 and cylinder 18 are held against rotation by a key 31 and pin 32. The conduits 26 are provided with slide valves 34, Fig. 3, which are operated by inclined faces which engage corresponding faces 38 on the mould slide. As the mould is lowered the valves 34 are reciprocated. The valves 34 are hollow and are provided with electric heating elements 42 which are connected to contact strips 43. The contacts 43 slide on insulating bars 45 which contain contact members 47 carrying the current so arranged that the current only flows through the heaters 42 when the valves 34 are open. Specification 528,171 is referred to.