Patent GB-1339443-A (GB)
Title: Production of laminar articles
IPC: B29C44/04
Filed: 1970-11-30
Abstract: 1339443 Injection moulding IMPERIAL CHEMICAL INDUSTRIES Ltd 22 Nov 1971 [30 Nov 1970] 56695/70 Heading B5A Articles having dissimilar core and skin materials are formed by injecting both skin and core materials through a first sprue channel and a further quantity of skin and/or core material through a second sprue channel. If skin material 3 only is injected through the second channel, the skin material may be injected through the second sprue channel, e.g. 2, before, during or after injection of the skin material through the first channel, e.g. 1, and during or after injection of the core material, e.g. 5, through the first channel. The skin material injected through the second channel may or may not penetrate to within the core material injected through the first channel. If core material only is injected through the second channel, it may be injected before, during or after core material is injected through the first channel so long as skin material has extended to beneath the second channel from the first or another channel. If skin and core materials are injected, as shown, through the second channel, the skin material may be injected before, during or after skin material is injected through the first channel or during or after injection of the core material through the first channel. Core material, e.g. 7, may be injected through the second channel before, during or after injection of the skin or core materials through the first channel. The core materials may become integral or remain separated, as shown, by skin material. Further skin material may be injected after injection of core material to reduce surface exposure of core material (see Fig. 8). The sprue channels may be of different sizes and may be heated by movable probes. Taps, e.g. 4, 6, which may have single or multibores may be provided on the injection barrels to prevent back flow of material. More skin material than is desired in the moulded article may be injected with the excess material being forced back through the respective sprue channel by the injection of core material (see Specification 1,339,445). To permit a foamed core either less than a filling amount of material may be injected or the mould may be enlarged after injection either by retraction of a mould member by an external force or by reducing the clamping pressure in a vertical flash mould (see Fig. 6). Vents may be provided in the mould cavity to allow escape of air trapped between advancing fronts of skin material. Numerous examples of suitable thermoplastic and thermosetting materials are given. If skin material is injected through more than one channel, the skin materials may be different or the same but having different additives, e.g. pigments; plasticized P.V.C. and nitrile rubber modified plasticized P.V.C. Similarly, different core materials may be injected. The core material may be the same as the skin material, but having different additives or different proportions of the same additives. At least part of one or more walls of the mould cavity may be provided with a removable rigid or flexible lining which subsequently forms part of the article. The lining may be wooden sheet e.g. plywood or hardboard, metal sheet, thermoplastic sheet or the upper parts of shoes or boots. The articles may have rigid and/or flexible plastics skins and may form body or trim panels of furniture, motor vehicles, caravans, aeroplanes, trains or buildings or may form shoe soles and heels.