GB501809A - Improvements relating to apparatus for moulding thermo-plastic material by injection - Google Patents

Abstract

501,809. Injection moulding. THERMOPLASTICS, Inc. Sept. 2, 1937, No. 24048. Convention date, Oct. 26, 1936. [Class 87 (ii)] Thermoplastic material is injected concurrently into a plurality of mould sprues through nozzles which are mounted for independent movement and which are initially seated in the sprues under yielding pressure to ensure concurrent full pressure engagement of all the nozzles. A two part mould has a movable upper part and a fixed lower part 2 containing a number of sprues 4. A number of nozzles 11 co-operate with the sprues 4, each nozzle being carried by a platen 10 containing an injection cylinder 13 supplied with material from a hopper 18 by a piston 19 through a heated head 17. The injection piston 51 is operated by hydraulic or pneumatic pressure through the pipe 25 and is returned by a spring 26. The platen 10 is raised by pistons 30 hydraulically or fluid operated through pipes 33. A number of platens 10 co-operate with the mould 2, the various pipes 25 and 33 being connected in parallel to two main conduits which may connect through valves with a main supply line. All the nozzles 11 are thus seated independently in the sprues 4 under equal pressure. Small booster pistons 40 may be provided, connected to the pipes 33, for closing particular platens 10 under increased pressure. With this apparatus a number of nozzles may co-operate with sprues at different levels in the same or a number of moulds, the closing pressure being independent of the distance of travel of the nozzles. Specification 477,398 is referred to.