Degassing apparatus for a metal mold

Abstract

Disclosed is a degassing apparatus incorporated with a molding apparatus having a mold cavity, which includes a spool having a bore formed therein. The spool further has formed therein a gas inlet opening adapted to be communicatively coupled to the mold cavity of the molding apparatus, and a gas outlet opening, the gas inlet and outlet openings being in selective communication and non-communication with each other. Means for selectively controlling the communication and non-communication between the gas inlet and gas outlet openings, are provided. Also provided is a flanged piston mounted in the bore and coupled to the communication controlling means, the piston being reciprocatingly slidable between a first position and a second position, the bore being further formed with an upper chamber and a rod-side chamber situated on opposite axial sides of the piston, and a lower chamber radially surrounding a portion of said piston. The spool further includes first, second and third fluid ports formed therein, the ports being in communication with the upper, rod-side and lower chambers respectively, the lower chamber being in communication with said rod-side chamber when said piston is in the second position, wherein the gas inlet and outlet openings are in non-communication, and the lower chamber being in non-communication with the rod-side chamber when the piston is in the first position, wherein the gas inlet and outlet openings are in communication.