GB1384434A - Injection moulding machinery - Google Patents

Abstract

1384434 Injection moulding IMPERIAL CHEMICAL INDUSTRIES Ltd 1 Oct 1973 [2 Nov 1972] 50479/72 Heading B5A The invention relates to an injection moulding process for making laminar articles comprising a core of a synthetic resin composition substantially totally enclosed in a skin of a dissimilar synthetic resin composition wherein the skin composition is injected into a mould cavity from a first source through a passage 3 and a sprue channel 2 having an inlet of circular crosssection and, before the skin composition has solidified, the core composition is injected from a separate source through a passage 4 and the sprue channel 2 such that it tends to be first injected offset from the axis of the sprue channel towards one side thereof. According to the invention, a slidable member 5 is provided in a housing 1, the member 5 having a passage 6 of circular cross-section for communication with the inlet of the sprue channel 2, the outlet of the passage 6 being the same size as the inlet of the sprue channel, and the skin composition is injected through the passage 6 while the member 5 is in a position wherein the axis of the passage 6 lies on the axis of the sprue channel 2 and, before injection of the core material the member 5 is moved in a direction opposite to that side of the channel 2 to which the core material tends to be first injected until a line on the surface of the passage lies on the axis of the sprue channel, and then commencing injection of the core material whereby the core material is first injected along said line (Fig. 2). The member 5 is then returned to the position wherein the axis of the passage 6 lies on the axis of the channel 2 as the injection of core material builds up. The member 5 may be moved to a position (Fig. 7, not shown), wherein the passage 6 is isolated from the sprue channel after completion of injection. A further quantity of skin material may be injected after the core material, and the member 5 may accordingly be moved in the opposite direction before commencement of this injection (Fig. 6, not shown), and then retracted as before as the injection of skin material builds up. Fig. 8, shows a modification in which the sliding member 5 comprises a cylindrical sleeve surrounding a rotary multiway tap body 12. The sleeve 5 is rotatably mounted in a housing 1 having a channel 3 for supplying skin material through passages 13, 15 in the sleeve 5 and tap body 12 respectively. A channel 14 in the housing supplies core material through passages 14, 16 in the sleeve 5 and tap body 12 respectively. Figs. 8 to 15 (only Fig. 8, shown), show the sequence of positions of the sleeve 5 and tap body 12 during the injection cycle, Figs. 8 and 16 (not shown), showing alternative cut-off positions. In a further modification (Figs. 17, 18, not shown), the passages 15, 16 in the tap body are "skewed" so that the axes of channels 2, 3, 4, all lie in the same plane as the axis of rotation of the tap body 12.