GB731038A - Die casting - Google Patents

Abstract

731,038. Casting-machines. DOW CHEMICAL CO. Aug. 18, 1953, No. 22773/53. Class 83 (1). A die-casting apparatus for making a succession of castings delivering shots of molten metal, particularly magnesium base alloys, to dies, comprises a onepiece body 33 enclosing a well 43 of a volume at least sufficient to hold a charge of molten metal for a casting and a shot-cylinder 39, a gooseneck 34 having its lower end in communication with the bottom of the shot cylinder and its upper end in communication with the dies, a metal discharging piston 45 operable in the shot-cylinder, a port 42 connecting the well and the cylinder when the piston is retracted, a molten metal reservoir 17 having a working level above the top of the shot-cylinder or connected by a conduit 26 with the well, a melting-pot 5 having a working level above that of the reservoir and connected thereto by a pipe 8 having a valve 9, and level-detecting means. 29, 30 responsive to the level of metal in the reservoir to operate said valve to maintain the metal in the reservoir at a level to fill the well to a depth above the top of the shot-cylinder. The pipes 7, 26, the gooseneck assembly and the reservoir assembly 17 are surrounded by refractory material containing electric heating elements. A gasholder 58 maintains an inert gas pressure above the metal in the wall 43 and the reservoir 17. In operation, when the level of the metal in the well is the same as that in the reservoir, the level detector 30 causes the valve 9 to be closed, the piston 45 is drawn upwardly by piston 51, and the ports 42 are covered, allowing metal to enter the shotcylinder, lowering the level in the well and causing metal to flow from the reservoir and causing the level-detector to open the valve 9 to restore the level in the reservoir. Downward movement of the piston 45 forces metal into the die and after solidfication of the casting, the die half 68 and casting are withdrawn, the piston 45 is drawn upwardly, and molten metal recedes in the nozzle 37 to a level corresponding to that in the well 43, just below the outlet 64. Dripping is thereby obviated and only a small quantity of contaminating air enters the die ahead of each shot.