GB903520A - Vacuum die casting process and apparatus - Google Patents

Abstract

903,520. Casting-machines. OHSE, C. W. Nov. 14, 1960, No. 39053/60. Class 83 (1). In a die-casting process, the feed chamber 27 is fed with a charge which is of such a size as to leave a free space above it in the chamber, the charge is then moved slowly towards the die cavity 32 while maintaining the free space in the chamber and closing the feed opening 29, the die cavity and the communicating free space are subjected to a vacuum while maintaining the charge in the feed chamber momentarily stationary, and the charge is then moved into the die cavity while maintaining the vacuum. The movement of the injection plunger 33 is controlled by valves 51, 52, 55, 56, 57 and the vacuum is applied through a valve V operated by a piston 45 controlled by a valve 44, the operating sequence being controlled by a series of timers. During the initial slow forward movement of the injection plunger the pressure fluid supply to the plunger operating cylinder 35 is throttled by a valve 67, while during its subsequent movement the valve 67 is by-passed. A sealing gasket is mounted on the face of the cover die 23, and exhaust vents of a crosssectional area not more than about 0.006 square inches connect the runner 31 and various parts of the die cavity to exhaust channels connected to the vacuum line, several arrangements of such vents and channels being shown.