GB1339712A - Injection moulding process - Google Patents

Abstract

1339712 Injection moulding P A WOINARSKI 21 Dec 1970 [29 Jan 1970] 60477/70 Heading B5A An article is injection or transfer moulded from molten thermoplastic material, e.g. high density polyethylene, between first male and female mould parts and is retained on the male or within the female mould part during movement thereof along a linear or circular path for a final shaping and solidification by compression moulding in co-operation with a further mould part which is at a lower temperature than the co-operating or each first mould part. The further mould part may be of the same or different shape from the corresponding first mould part, and may act over part only of the moulded article. The mould parts may be maintained at the required temperature by temperature control fluids circulating through mould part passages. In the Fig. 2A embodiment, the male mould part is transversely reciprocable, e.g. by hydraulic, pneumatic or mechanical means, along a platen 10 between positions in alignment with a first fixed female mould part 17 (into which the material is injected), and with a further similar shaped fixed female mould part 18 in each position whereof it is reciprocable upon the platen 10, e.g. by hydraulic, pneumatic or mechanical means, into and out of moulding engagement with the mould parts 17, 18. Ejection of the moulded article is effected from the male part 16 by mechanical and/or pneumatic means. The male mould 16 may alternatively be fixed, with a pair of female moulds mounted for transverse reciprocation upon the platen 11. The male mould 16 is preferably maintained at a temperature equal to or less than the crystalline melt temperature of the material being injected, the first female mould is maintained at a temperature equal to or in excess of the crystalline melt temperature, and the further mould 18 is maintained at a temperature lower than that of the other moulds, e.g. room temperature. In the Fig. 3A to 3F embodiment (not printed), a pair of first male mould parts are mounted for transverse reciprocation across their platen between positions in which each thereof is alternatively in alignment with a first female mould part into which injection is effected and then each with a different one of a pair of further female mould parts, which are of shorter length than the first female mould part, to effect the final compression moulding shaping along part only of the moulded article. Fig. 4 (not printed) shows a similar embodiment to the Fig. 3A embodiment, but wherein the further female mould parts are mounted to their platen at adjustable resilient mounts or cushions. In the Fig. 5 embodiment, which is also similar to the Fig. 3A embodiment, portions 21, 22 of the first female and male mould parts are cooler than the remainder, of the mould parts, so that, e.g. a rim of a pail, is more rapidly cooled than the remainder thereof, the further female mould parts being configured to extrude material to provide an external change of shape below the rim.