초록 ▼

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 hol

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.

대표청구항 ▼

[ Having thus described our invention, we claim:] [1.] A low pressure metal casting process in which molten metal is delivered from a master furnace to a molten metal holding chamber of a holding furnace of a low pressure casting machine having a housing within which said holding furnace is located

[ Having thus described our invention, we claim:] [1.] A low pressure metal casting process in which molten metal is delivered from a master furnace to a molten metal holding chamber of a holding furnace of a low pressure casting machine having a housing within which said holding furnace is located and a riser tube, said process comprising the steps of:providing a launder assembly between said master furnace and said holding furnace;providing a valve for controlling the flow of molten metal between said master furnace and said holding furnace, said valve including a valve closure member; andcasting metal parts by a sequence of operating steps comprising:a. opening said valve to permit the molten metal within said master furnace and said holding furnace to seek a substantially uniform level;b. preventing the flow of molten metal from said master furnace to said casting machine by closing said valve;c. while said valve is closed, introducing a gas under pressure into said holding furnace above the level of the molten metal so that molten metal will rise up the riser tube into a molten metal-receiving cavity located adjacent the top of said riser tube, while at the same time, applying a gas under pressure into a chamber above said valve closure member;d. reducing the pressure of the gas above the molten metal in the holding furnace and above said valve closure member to or near to atmospheric pressure; ande. after reducing the pressure of the gas above the molten metal, reopening said valve to permit the molten metal within said master furnace and said holding furnace to seek a substantially uniform level. [16.] A low pressure metal casting apparatus comprising:a master furnace that has a reservoir for holding a pool of molten metal;a low pressure casting machine comprising a metal holding furnace having a holding chamber for holding molten metal, a lid closing and sealing said holding furnace, and a riser tube extending through said lid downwardly into said molten metal and upwardly to a molten metal-receiving cavity;a launder assembly extending from said master furnace to said holding chamber and constructed to provide a molten metal conduit from said master furnace to said chamber, said master furnace, said launder assembly, and said low pressure casting machine metal holding furnace being constructed to receive a pool of molten metal;a valve assembly within said launder assembly comprising a valve having a passageway located within the molten metal and through which the molten metal can flow, said valve further having a valve closure member for closing said passageway, said valve when said passageway is closed providing a barrier to the flow of molten metal between said master furnace and said chamber;said valve assembly further comprising a valve chamber formed above said valve closure member and a valve operating mechanism operable to selectively move said valve closure member between two positions, one in which said passageway is open and one in which said passageway is closed;means for supplying gas under pressure into the holding furnace above the pool of metal within said holding chamber when said valve closure member closes said passageway to cause molten metal to rise up said riser tube; andmeans for supplying gas under pressure into said valve chamber above said valve closure member. The apparatus of claim 16 wherein said valve passageway comprises an inlet conduit and an outlet conduit centered around a horizontal axis. The apparatus of claim 17 wherein said valve comprises a valve body through which said conduits extend, and said valve closure member comprises a valve plug extending into said valve body between said inlet conduit and said outlet conduit and having a through bore, said valve plug being rotatable about a vertical axis to open said valve passageway by aligning said through bore with said inlet conduit and said outlet conduit and said valve plug also being rotatable to position said through bore out of alignment with said conduits. The apparatus of claim 16 wherein said valve passageway is located within said launder in a position in which it is in the pool of molten metal during normal operation of said casting apparatus.