GB1346892A - Injection moulding method and tool for plastics articles - Google Patents

Abstract

1346892 Moulding hinges TWINLOCK Ltd 19 April 1971 [7 Nov 1969] 54752/69 Heading B5A [Also in Division B6] An article comprising two portions 13 (Fig. 3) interconnected by a web of reduced thickness 17 is made by injecting plastics material into a mould and compressing the material at the desired location of the web 17 while still in the mould. Articles include leaf hinges for stationery binders, automobile components, container lids, plastics blanks for packaging containers, and tear-open bottle tops. High melt index (low density) polypropylene is injected into a mould either across or along the web, which may be of non-uniform thickness. As described, a plurality of leaf hinges are simultaneously moulded in injection moulds 3 (Fig. 6). As the injected material begins to set around the gates (4) (Fig. 1, not reproduced) a wedge 10a (Fig. 6) is reciprocated by an hydraulic or pneumatic cylinder and piston 22, to raise a bar 23 which lifts a plurality of rods 9 and an attached blade or plate 8. The blade 8 compresses the plastics material against an upper mould part at the desired locations of the webs. The blade 8 is retracted pneumatically, hydrau. lically or by springs 11a and is laterally adjustable; it may comprise a plurality of aligned blades for producing webs of non-uniform thickness. The wedge 10a may be replaced by a cam roller (10) (see Fig. 1, not reproduced). The flash is automatically severed on opening the mould (not further disclosed).