GB1336714A - Methods of making shell-moulded articles and apparatus therefor - Google Patents

Abstract

1336714 Moulds; casting-machines POLYGRAM CASTING CO Ltd 26 Nov 1970 [1 Dec 1969] 58657/69 Heading B3F Shell moulds (13) are backed by immersion in a fluidized bed of particles 2. The shell moulds or fluidized bed are first treated so that the permeability of the moulds to the fluidizing gas is less than that of the fluidized bed. This is accomplished by (a) enveloping the mould in a bag, container or sheet of a substance, impermeable to the fluidizing gas and destroyed by the metal on pouring (b) coating the mould external surface with such a substance (e.g. wax), (c) coating the mould external surface with a substance (e.g. bentonite) that decreases the permeability of the mould without rendering it completely impermeable so that gases produced in the mould after casting can escape, (d) provided the mould sprue with a stopper or (e) using fluidized particles of such a size that their permeability when fluidized is greater than that of the mould. In the Fig. the moulds 13 surrounded by PVC bags 14 are held in members 11 of a frame 7 having a perforated base-plate 12. The particulate material 2 in the flask 1 is fluidized by passing air from a plenum chamber 4 upwards through a perforated tile 6. The frame 7 is lowered into flask 1 and fluidization is ceased leaving the shell moulds backed by the particulate material 2. The flask may be electrically vibrated to further pack the particulate material. After pouring the moulds they are allowed to cool, the bed refluidized and the frame withdrawn from the flasks 6. Costinq machines.-In Fig. 3 shell moulds are supplied to a rotating turntable 19 at a station 24 and immersed in the fluidized beds within flasks 20. They rotate through a pouring zone and cooling zone, as shown, and the moulds are withdrawn from the flasks at a station 25. A central plenum chamber 23 supplies air to each flask through pipes 21.