Patent GB-1170558-A (GB)
Title: Moulding Method and Apparatus
Inventor: WAID GEORGE REUBIN
IPC: B29C45/03
Filed: 1968-07-09
Abstract: 1,170,558. Injection moulding. EATON YALE & TOWNE Inc. 9 July, 1968 [23 Aug., 1967], No. 32659/68. Heading B5A. [Also in Division F2] In a method of moulding articles, a plurality of article forming cavities of a multi-part mould assembly are filled with fluent moulding material, with some of the material flowing between said parts to form a continuous mat of material, which mat has thin film-like portions contiguous with the material in the cavities and relatively thick portions, and after solidification of the material one of the mould parts is removed from the mould assembly and the film-like portions are severed from the articles by stripping the mat from the assembly after which the articles are removed from the cavities. An injection mould for the simultaneous production of a number of tyre valve stems, each comprising a valve receiving metallic sleeve 26, Fig. 3, about which a body of rubber-like material is moulded, includes mould plates 16, 17 providing a number of mould cavities C therebetween which communicate with runners 19 in a plate 15 and sprues 20 for the supply of moulding material to the cavities. Each cavity includes a cavity part 45a located in an insert 53 positioned in a bore 50 of the plate 16, and a cavity part 45b in an insert 71 within a bore 70 of the plate 17. The lower end of each cavity part 45b is closed by a further insert 72 in a spacer plate 18 and bored at 85 and supporting a flange 26a of the sleeve 26. Air venting from each cavity is provided by score lines, located between abutting surfaces 83, 84 of the inserts 71, 72. A core 61 extends from each insert 53 and abuts the sleeve to provide an axial passage in the enlarged head of the valve stem. Each pair of inserts 53, 71 has circumferential cavities 66, 77 respectively which co-operate to provide a semicircular recess; each recess co-operates with similar recesses in adjacent pairs of inserts and with the plate 16 to form secondary cavities 80 which surround abutting surfaces 65, 76. When moulding material is fed at high pressure to the cavities, material is also forced between the surfaces 65, 76 to form a thin film-like flash 102, Fig. 9, and fills the cavities 80 providing annular parts 101 joined by a film 103 formed between the plates 16, 17. On completion of the moulding, the plate 15 is removed and the moulding material in the runners 19 and sprues 20 is removed; the plate 16 is then withdrawn from the plate 17, and the flash 102 and the parts 101 and 103 which form a " mat " are pulled away from the moulded articles whilst they remain in the plate 17. The lower ends of the parts 26 are engaged by members, not shown, to force the articles upwardly, after which a rake-like member, not shown, engages below the enlarged parts of the valve stems to completely remove them from the plate 17. The cavities are arranged in a square array which is fed centrally and downwardly from injection means, not shown, and the runners 19 extend radially therefrom to the sprues 20. The mould plates are compressed between hydraulically driven platens, not shown.