METHOD FOR CONTROLLING BLOWING PRESSURE OF GREEN SAND WITH MOLDING MACHINE FOR GREEN SAND CORE

摘要

PURPOSE:To mold easily and surely a green sand core having required hardness, size, etc. by detecting the position of a plunging bar plunged into the green sand in a cavity part, controlling the blowing pressure for the succeeding green sand by said position. CONSTITUTION:Green sand is charged from a sand hopper 12 into a blow tank 7 and after a lower metallic mold 3 is risen to be mated with an upper metallic mold 5, a vent plate 15 is lowered down to the position of the opening 18 at the other end of the mated metallic mold. A plunging bar 19 is then projected and the plate 15 is pressed to the side face of the opening 18. A sand supply port 8 of the tank 7 is then closed and the blowing pressure corresponding to the prescribed insertion position of the bar 19 is calculated from the empirical correlation equation between the insertion position of the bar 19 and the blowing pressure stored preliminarily into an arithmetic device 25. The calculated blowing pressure is fed from the device 25 to a proportional electromagnetic pressure regulating valve 26 and is regulated to the above-described blowing pressure. The compressed air subjected to such pressure regulation is supplied 10 via a valve 26 and a conduit 27 to the inside of the tank 7 so that the green sand in the tank 7 is blown via a sand blow port 14 into the cavity 20 of the mated metallic mold.