GB1505102A - Method of and apparatus for control of finishing pressure in the die-casting of metals - Google Patents

Abstract

1505102 Pressure die casting machines BUEHLER AG Gebr 20 May 1975 [22 May 1974] 21538/75 Heading B3F In a pressure die casting machine in which the pressure applied by an hydraulic fluid to the injection piston.during the mould filling phase is determined by a predetermined gas pressure, adjustment of the gas pressure automatically results in adjustment of the increased pressure applied to the injection piston during solidification of the casting. In the embodiment shown, a pressure gas container 20 is connected to the inlet of a piston accumulator 17 whose outlet communicates with a line 42, 23, 15 extending from a pump 43 for the hydraulic fluid to a multiplier cylinder 9. A valve 25 is located in the line 42, 23, 15 and has a slidable member 27 provided with a bore 29. The member 27 is biased to its open position by a spring 34. During the mould filling phase, the hydraulic pressure in the line 15, 23 acts on a piston 6 via a bore 10 in the multiplier piston 8, the pressure exerted on the piston 6 being determined by the gas pressure in the container 20. If it is required to change the pressure during the mould filling phase, e.g. to reduce it, the pressure in the container 20 is reduced by means of a valve 22. This results in a piston 101 in a cylinder 100 moving to the left under the influence of the hydraulic pressure in the chamber 108. This causes a control cone 37 to move further off its seat 36 and permits an increased flow of hydraulic fluid from a pressure chamber 33 to a tank 45 resulting in a movement of the member 27 in its closing direction and thus a proportional pressure reduction at the outlet 24 of the valve 25. Thus the hydraulic pressure applied to the multiplier piston 8 during solidification of the casting is reduced.