| 摘要 |
1361039 Pressure casting machines IDRA-PRESSEN GmbH 26 Nov 1971 [2 Dec 1970] 54921/71 Heading B3F In a method of pressure diecasting in which pressure is applied to a press piston 2 in three phases, a multiplied pressure is applied to the metal in the mould during the third phase by a multiplier piston 5 which remains at rest during the first and second phases because of a restraining pressure in a chamber 25, said restraining pressure being reduced to permit the movement of the piston 5 after a time delay initiated by the position of the press piston. A pressure reservoir 6 is connectible to the piston 5 via a valve having a closure member 8. With a reversing valve 9 in the position shown, the member 8 is maintained in its closed position since the pressures in spaces 12 and 16 are equal, and a low pressure is applied to the piston 2 by means not disclosed. At the end of this first phase the valve 9 is reversed, the actuation of this valve being dependent on the position of the press piston 2, to cause a higher pressure to be applied to the piston 2. The reversal of the valve 9 also causes the closure member 8 to move to its open position thus enabling the pressure in the reservoir 6 to act on the piston 5. Immediate movement of the multiplier piston 5 is prevented by a counter pressure in the chamber 25 which is maintained until operation of a time delay valve 24 whose actuation is initiated by the reversal of the valve 9. |
