| 摘要 |
1361038 Pressure casting machines IDRA-PRESSEN GmbH 10 Nov 1971 [26 Nov 1970] 52221/71 Heading B3F In a method of pressure diecasting in which pressure is applied to the press piston 2 in three phases, the initiation of the intensified pressure applied to the press piston during the third phase is effected in dependence on the position of said press piston. The machine has a multiplier piston 5 movable in a cylinder 4, the chamber 7 formed in front of the piston 5 being connected to a pressure reservoir 8 via a valve 9. A second pressure reservoir 18 is connected to a chamber 16 which is opened or shut off in relation to the piston 5 by a valve having a closure piece 19. With a reversing valve 21 in the position shown, the pressures in the chambers 16, 32 and 33 are equal and the closure members 19 and 11 are maintained in their closed positions. After a first, slow movement of the press piston 2, the valve 21 is actuated by the press piston or by the rod 3 linking it to the injection piston. This causes the chamber 32 to be connected to a line 35 leading to a tank 34 so that atmospheric pressure now prevails in the chamber 32. This allows the member 19 to move to its open position thus causing the pressure in the reservoir 18 to be applied to the piston 5. An bydraulically operated time delay device 27 may be located in the line leading from the chamber 33 to the tank 35. The operation of this is initiated on the actuation of the reversing valve 21. After the valve 23 of said time delay device has moved from the position shown, the chamber 33 is open to atmospheric pressure and the valve 9 opens, thus allowing the fluid in the chamber 7 to pass to the reservoir 8 and the piston 5 to move to the left under the influence of the pressure of the fluid from the reservoir 18. This constitutes the third phase in the injection process and is arranged to take place after the mould has been filled with metal. The second phase begins on reversal of the valve 21 and is brought about by means not disclosed. |
