IMPROVEMENTS IN OR RELATING TO MAKING 163 MOULDS

A series of expendable shell molds is formed in a permanent pattern having a series of connected mold cavities. A passage extends from outside the pattern into each end of the series. A suspension of parting agent is blown by gas or superheated steam into the cavities through one of the passages while the other is vented through an orifice of controlled size to maintain the desired pressure. To coat evenly the parting agent may then be blown in the opposite direction through the cavities. Thereafter molding sand is blown into the pattern through one or both of the passages. Imperfect closing of the separatable pattern is detected by blowing air into a third passage which ends at the parting plane. The air is supplied from a constant pressure source through an orifice of predetermined size and the pressure is measured on the down-stream side of the orifice. A blow box connected to a sand hopper is pivoted to be swung toward and away from the pattern. A sand valve and a vent valve cooperate to dump sand from the hopper rapidly into the blow box. Gas under pressure is distributed throughout the sand from below to fluidize the sand and simultaneously force is applied above the sand to flow the mass into the pattern.