Patent GB-810030-A (GB)
Title: Vacuum die casting method and means
IPC: B22D17/14
Filed: 1956-09-11
Abstract: 810,030. Injection-moulding machines. MORGENSTERN, D. M. Sept. 11, 1956 [Oct. 31, 1955], No. 27773/56. Class 87(2). [Also in Group XXII] A die-casting machine comprises an enclosure surrounding the die members that is capable of being closed in advance of the closing of the mould cavity and of being opened to afford access to the interior, evacuating means connected to the enclosure, a charging chamber in communication with the die cavity, a container for molten material separated from the charging chamber, a conduit extending from below the minimum molten material level in the container and communicating with the charging chamber, and means for impelling molton material from the charging chamber to the die cavity. The machine comprises a stationary die member 5 and a movable die member 6, ejecting pins 11, push rods 12 which restore the ejecting pins as the dies close, a die-closing piston 25 working through a toggle linkage 20-23, and a charging chamber 40 from which metal is forced into the die cavity by a ram 75. The chamber is charged through a metering plug 47 and a conduit 49 dipping into a heated crucible 50. Inert gas from a bottle 60 may be supplied to the crucible through a valve 62. The parts 87, 86 of the two-part enclosure 85 are carried by the stationary die plate 1 and movable die plate 2 respectively, a flexible gasket 94 on the enclosure part 86 sealing the enclosure in the closed position. The enclosure part 86 has an extensible, bellows-like wall section 97, biassed towards the extended condition by springs 100, and cooled by coolant in a conduit 106. The enclosure is connected to a vacuum tank 130, through a valve 141, by a conduit 110. The volume of the enclosure to be evacuated is reduced by displacement elements such as 117 placed in the hood. In an operating cycle, movement of the die-closing piston 25 is initiated by a push button 170, and when the enclosure parts first engage, sealing enclosure against the admission of air, a switch 31, closed by movement of the piston causes evacuation of the container to commence, the gas valve 62 being simultaneously opened to admit gas to the crucible 50 and, with the suction in the charging chamber 40, causing molten material to be impelled to the charging chamber. The time of evacuation and delivery of the charge to the chamber, is controlled by a timer T<SP>l</SP>, thereafter, the enclosure and die members being fully closed, the enclosure connection to the vacuum tank 130 and the gas valve 62 are closed, and the ram 75 is advanced to force the molten material into the die cavity, the movement of the ram also uncovering a port 48 to open the conduit 49 to atmosphere and allow the molten material in the conduit to fall back into the crucible. The solidification period is timed by a timer Tz, whereafter a valve 155 opens to admit atmospheric air to the enclosure, and cause retraction of the piston 25. Actuation of a limit switch 30 by movement of the piston resets the circuits for commencement of another cycle. Accumulation of fugitive metal, or other electrically conductive material will bridge contacts 111, 112, and stop the machine. Specification 780,126 [Group XXII] is referred to.