GB1370864A - Method and apparatus for making ceramic shell moulds - Google Patents

Abstract

1370864 Investment casting apparatus PRECISION METALSMITHS Inc 25 July 1972 [16 Aug 1971] 34721/72 Heading B5A Apparatus for investment casting multiple shell moulds comprises an array of pattern set-ups 11 mounted for rotation as a group about an axis 13 transverse to the vertical and radially spaced from this axis, e.g. on rods 24 in slots in end discs 12 so that when the array is rotated by a motor 39, each set-up in turn will dip into a refractory slurry 35. The assembly is preferably provided with a housing cover 45 sealed at 46 to the tank 36 and having an outlet 48 to apply a vacuum. In an alternative embodiment (Fig. 4 to 6, not shown) a set of gears and pinions is mounted on the end of the shaft 13 to rotate the set-up shafts 24 individually, the array then being rotated in step-wise fashion to bring each set-up in turn into the slurry tank, where it is then rotated about its own axis by the gearing which is driven by a separate motor. In this embodiment the set-up cylinder is only partially immersed in the slurry. In both embodiments the individual patterns are mounted on corrugated cardboard sleeves on wax or wax-coated cylinders around the reds 24 (Figs. 1 and 2, not shown). The central shaft 13 is located in a spring-loaded bearing 41 so that the array may readily be removed. Typically the patterns are coated with a slurry of zirconium silicate and fused silica in a colloidal silica sol binder with small amounts of an organic film former, a wetting agent and a defoaming agent; they are then stuccoed with coarse refractory material by rotating the set-ups to pass through an airfluidized bed; then forced-air-dried and additional coatings applied as desired.