| 摘要 |
Molten metal is delivered from a master furnace to the molten metal holding chamber of a low pressure casting machine by a launder assembly having a unitary, quickly replaceable, valve assembly including a valve which, when closed, prevents flow of the molten metal from the master furnace to the holding vessel. The valve has a plug mounted for rotation in a valve body which may be made from graphite. In a modification, the valve has a port centered in a valve plate and a movable plug which may be made from aluminum titanate. In operation, the valve is opened to permit the molten metal within the master furnace and the holding vessel to seek a substantially uniform level and closed when the low pressure casting process is initiated. While the valve is closed, a pressurizing gas is introduced into the holding vessel above the level of the molten metal therein so that molten metal will rise up a riser tube into the cavity of a mold or other molten metal-receiving member. After the cavity is filled and before the next molding operation is begun, the pressurizing gas is exhausted so the pressure above the molten metal in the holding vessel is lowered to or near to atmospheric pressure and the valve opened so that the molten metal in the holding vessel and the master furnace again begins to seek a substantially uniform level. This process can be repeated indefinitely to produce plural molded parts.
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