GB1333427A - Moulding - Google Patents

Abstract

1333427 Moulds; injection moulding GKN SANKEY Ltd 16 Feb 1972 [16 Dec 1970] 59675/70 Heading B5A The invention relates to a mould comprising three or more walls 10-13 arranged so that of each group of three adjacent walls, one edge of the centre wall engages the planar surface of one of the outer walls, and one edge of the other outer wall engages the planar surface of the centre wall, the walls being movable to vary the size of the mould cavity while maintaining inter-wall engagement. According to the invention the mould cavity is closed by first and second end members 25, 26, respectively, the second end member 26 being apertured to receive a core 28, and first and second means are provided for moving the core 28 and an insert 31 respectively away from the first end member 25 simultaneously with increase in the cross-sectional size of the cavity. The mould is used in a "sandwich moulding" process in which a non-foamable plastics material is first injected into the space 20 between the insert 31 and the mould walls, and then a foamable plastic is injected within the non-foamable plastic. Injection is effected with the parts in the positions shown in Figs. 1 and 2. The mould cavity is enlarged to the position shown in Fig. 3 and in dotted lines in Fig. 1 and the foamable material allowed to expand. The insert 31 is arranged to move half the distance moved by the core 28. The insert 31 may be a container. If not sufficiently strong to withstand the moulding pressure the container may be filled with e.g. a low m.p. alloy which is removed after moulding is complete. Alternatively the insert itself may be of a material which is removed from the plastic sandwich after moulding to leave a hollow container. The means 32 for holding the insert in position extends through an aperture in the plastic sandwich layer. As shown the insert is a container having a neck 35 received in an aperture 36 in the core.