GB1401239A - Casting method - Google Patents

Abstract

1401239 Moulds AKITA KK 27 Oct 1972 [14 Dec 1971 25 Dec 1971 3 July 1972 13 July 1972] 49728/72 Heading B3F A method of casting comprises surrounding a readily-combustible pattern 6, Fig. 1 (of foamed polystyrene) (or pattern part 57, Fig. 5) in a moulding box with heat-resistant air-pervious particulate material, closing the box with a synthetic resin film 13, reducing the pressure in the box to seal the film against the box and thus compact the material, and pouring in molten metal, while maintaining the reduced pressure, to burn the pattern or pattern part. A perforated evacuation pipe 2 is surrounded with a wire-netting filter 4. The box 1 is vibrated, for packing, before the film 13 is fitted. The openings 8 and 9 in the pattern 6 may be filled with the material 12 or by separate cores. In a modification, the pattern 27, Fig. 3, is covered with a layer 30 formed either by a synthetic resin film, preformed or applied initially in liquid form, or by plaster or clay. A gas vent 34 may be provided. In a further modification, a resin film 56, Fig. 5, 20 to 50 microns thick, is heated or treated with a solvent and sucked into contact with a wooden pattern 49 by suction through passages 53, 54 and an opening 55. A runnerforming member 57 of combustible synthetic resinous material is mounted on a pattern rib 52 and a similar polystyrene or polyethylene gas-vent-forming member 58 communicating with a further vent is also provided. A box half 41 is then placed on the pattern, and sand &c. 59 poured in. The box is vibrated, covered with a film 60 and evacuated, e.g. through openings 42 in the walls and a surrounding passage 44. The evacuation means is then disconnected and air under pressure is supplied to the pattern passages 53, 54 causing the film 56 to separate from the pattern (which is removed) and remain with the box half 41. The above procedure is repeated with a second box half 41 and the halves brought together, Fig. 6, with an interposed core 61 in the mould cavity 62. The metal is poured on the member 57 to burn it.