GB1247341A - Improvements in or relating to the casting of metals - Google Patents

Abstract

1,247,341. Casting-machines; moulds. R.T.Z. METALS Ltd. 1 Oct., 1968 [6 Oct., 1967 (4)], Nos. 45907/67, 45908/67, 45909/67 and 45910/67. Heading B3F. Castings of Al, Mg, Zn, Pb, Cu or their alloys, e.g. slugs for extrusion, coining or forging, are formed in a series of movable mould plates 1, Figs. 1, 2, each co-operating in turn, so that a succession of moulds is formed, with both a cooled plate 31, Fig. 2, and a feed plate 1, 2, Fig. 3 (e.g. having an ingate 4 for feeding in the molten metal by means of vacuum or pressure), towards which feed plate the cast metal solidifies before the mould plate 1, moved sideways by a following mould plate, shears the casting from solidified metal in the ingate 4, there being a clearance 40 for evacuation or venting of the mould cavity 46 in each plate 1. There may be a pre-casting purge with N or Ar. The top plate 31 of the moulds, e.g. surrounded by a vacuum chamber 41, forms part of a casting head 5 (with coolant ducts 27, 28) movable vertically by a rocker arm 6, Fig. 1, and the mould plates 1 are moved by four pusher plates (4) around a rectangular track of guides 2 beneath at least one casting head. The various parts are moved by cylinders. The axis of the casting head 5, mould plate and bottom feed plate need not be vertical. After casting, the casting head 5 and mould plate 1 are slightly separated, the mould plate moved sideways (it eventually reaches a position in the track where a rod (9) descends to eject the cast slug) and a sprue-clearing pin 17, 36 descends through the top plate 31 and next mould cavity 46 into the ingate (4) in the bottom (feed) plate if the ingate is not cleared by arranging to reheat it. The top plate may be moved aside and a separate sprue-clearing pin lowered. The mould plates 1 may be of different thicknesses and cavity sizes to cast slugs of different sizes. They may have a vacuum groove (51), Fig. 8 (not shown), in the lower face and connected to the vacuum chamber 41, to assist sealing to the bottom plate. By replacing the sprue-clearing pin by a core or by attaching a core to each plate by a bridge above the plate, hollow slugs may be cast, in which case one or more off-centre ingates are provided in the bottom plate. The top and bottom plate surfaces may be curved, to produce domed slugs. The temperature gradient in the metal in the mould cavity 46 is controlled by heating of the bottom (feed) plate 1, 2, Fig. 3, and the ingate 4 heated for sprue-clearing, by an electric element 13 or by the circulation in a chamber (6) between upper and lower portions 1, 2 of the plate of molten lead or hot gas. Hot combustion gases may be used, with further combustion in the chamber (6). A stub-pipe 14 of silicon nitride or carbide from the bottom plate 1, 2 extends into a horizontal molten metal feed pipe 9, or the plate may be sealed directly on the pipe 9. A horizontal feed pipe 1 of silicon nitride or carbide (Figs. 1, 2 of provisional Specification 43909/67, not shown) has outlets (2) in thickened portions of its top surface and heating coils (4) around it beneath insulation (5). Instead of coils (4), the heating may be by immersion in a liquid or by combustion of gas or oil.