A MOLTEN METAL DISPENSING APPARATUS

Abstract: The apparatus includes a molten metal storage container (1) and a pouring passage (3) extending upwardly from the bottom of the storage container (1) and having an outlet in a position above the highest level (7) of molten metal (6) in the storage container. Compressed gas is introduced into a closed hollow space in the storage container (1) to apply pressure to molten metal (6) therein to discharge it through the outlet of the pouring passage (3). In order to avoid any oxidation of molten metal (6) means or to operate with a small quantity of compressed inert gas means are provided for recovering gas from the storage con­ tainer, compressing it and supplying the compressed gas into the storage container when any dispensation of molten metal is required.

Description: A molten metal dispensing apparatus This invention relates to an apparatus for dispensing molten metal into a mold or the like. It includes a molten metal storage container, and a pouring passage extending upwardly from the bottom of the storage container and having an outlet in a position above the highest level of molten metal in the storage container. Compressed gas is introduced into a closed hollow space in the storage container to apply pressure to molten metal therein to discharge it through the outlet of the pouring passage. A dispensing system of this type is described in the DE-OS 2433060. This known system employs air as a gas for compressing molten metal. When it is desired to discontinue dispensation of molten metal, the compressed air in the storage container is released into the atmosphere. If it is desired to dispense molten metal again, it is necessary to introduce a fresh supply of compressed air into the storage container. If fresh air is introduced into the storage container whenever it is desired to dispense molten metal, however, the storage container always remains filled with a gas containing a large quantity of oxygen. This gas oxidizes the molten metal contacting it, and disadvantageously brings about generation of a large quantity of slag, and the loss of effective constituents from molten metal. The apparatus is, therefore, unsuitable for use in the dispensation of easily oxidizable molten metal, or molten metal containing an easily oxidizable constituent, though it can relatively easily and accurately control the amount to be dispensed. Attempts have, therefore, been made to introduce compressed argon or other inert gas into the storage container in order to prevent such oxidation. However, such an inert gas is expensive, and disadvantageously increases the cost of operation, as it requires a large quantity of such gas. In view of the aforesaid disadvantages, it is an object of this invention to provide a molten metal dispensing apparatus which can be operated with compressed air without any oxidation of molten metal, or with a small quantity of compressed inert gas. This object is achieved in accordance with the present invention by a molten metal dispensing apparatus including a molten metal storage container and a pouring passage extending upwardly from the bottom of said container to a point above the highest level of molten metal in said container, and adapted for dispensing molten metal through said pouring passage when compressed gas is introduced into a closed hollow space above said molten metal in said container to apply pressure to said molten metal, characterized by a high pressure gas tank in which said compressed gas is stored before it is introduced into said storage container, a low pressure gas tank into which said compressed gas is recovered from said storage container, and a compressor for compressing said gas from said low pressure gas tank and returning it into said high pressure gas tank. The invention will now be described by way of example with reference to the drawing. Referring to the enclosed figure, there is schematically shown a dispensing system embodying this invention. The system comprises a storage container 1 lined with refractories. The storage container 1 defines a storage chamber 2 for storing molten metal 6 therein, and is provided with a pouring passage 3 extending upwardly from the bottom of the storage chamber 2 and having an outlet 31 at a point above the highest level 7 of molten metal 6, and a receiving passage 4 extending upwardly from the bottom of the storage chamber 2 and having an inlet 41 at a higher level than the outlet 31 of the pouring passage 3. Molten metal is received through the receiving passage 4, and stored in the storage chamber 2. The top opening of the storage chamber 2 is closed by a cover 5 in a gastight manner, so that a closed hollow space may be formed above the molten metal in the storage chamber 2. A gas feed line 21 and an exhaust line 22 extend through the cover 5 into the storage chamber 2. The gas feed line 21 is connected to a high pressure gas tank 8, in which compressed gas is stored, through a device 9 for controlling the pressure of the gas to be intro duced into the storage chamber 2. The exhaust line 22 is connected through an exhaust valve 10 to a low pressure gas tank 11 into which exhaust gas is collected. The low pressure gas tank 11 has an outlet connected to the inlet of a gas compressor 15 through a primary cooler 12, a drain separator 13 and a filter 14. The gas compressor 15 has an oulet connected to the high pressure gas tank 8 through a secondary cooler 16. A pressure regulator 17 is provided for detecting the pressure of the gas in the high pressure gas tank 8, and maintaining it at a predetermined level of, 2 say, 3.5 kg/cm2 by causing the operation of the compressor 15 to be stopped if the gas pressure exceeds the predetermined level, while causing it to be started again if the gas pressure has dropped below the predetermined level. A suction valve 19 is connected to the low pressure gas tank 11 for drawing air thereinto. A pressure regulator 18 is connected between the suction valve 19 and the low pressure gas tank 11 for detecting the pressure of the gas in the tank 11 and maintaining it at a substantially equal negative 2 pressure of, say, - 0.3 kg/cm2 by causing the valve 19 to open if the gas pressure in the tank 11 has dropped below the aforesaid level, while causing it to be closed if the gas pressure exceeds the aforesaid level. In preparation for the pouring operation, the compressor 15 is started for drawing air from the low pressure gas tank 11, and compressing it, so that the compressed air may be stored in the high pressure gas tank 8. The pressure regulator 9 and the exhaust valve 10 remain closed. Until the pressure of the gas in the high pressure gas tank 8 2 reaches a predetermined level of, say, 3.5 kg/cm , the com- pressor 15 continues in operation, and draws air from the low pressure gas tank 11. Therefore, a gradual reduction takes place in the quantity and pressure of the air in the tank 11. If the pressure of the air in the tank 11 drops 2 below a predetermined level of, say, - 0.3 kg/cm2, the pressure regulator 18 causes the suction valve 19 to open, and draw a fresh supply of air into the tank 11. The compressor 15 stops its operation when the high pressure gas tank 8 has been filled with air to the extent that its 2 pressure reaches a predetermined level of, say, 3.5 kg/cm whereupon the apparatus is ready for the dispensing operation. The pressure of the air in the low pressure gas tank 11 is maintained at a predetermined negative pressure of 2 - 0.3 kg/cm2. In the operation of the apparatus for dispensing molten metal, the pressure regulator 9 is controlled to introduce compressed air from the high pressure gas tank 8 into the closed storage chamber 2 through the feed line 21 for raising the pressure of the gas in the storage chamber 2, whereby pressure is applied to the molten metal 6. The level 7 of the molten metal in the storage chamber 2 is lowered, and the levels of the molten metal in the pouring passage 3 and the receiving passage 4 are raised correspondingly. If the molten metal in the pouring passage 3 reaches its outlet 31, it is forced out therethrough into a mold not shown, or the like. As long as the pouring of molten metal continues, the pressure regulator 9 continues to introduce compressed air into the storage chamber 2 to maintain therein the pressure required for forcing molten metal out of the pouring passage 3. When it is desired to discontinue the pouring operation, the pressure regulator 9 is actuated in such a manner as to interrupt the supply of compressed air from the high pressure gas tank 8, and the exhaust valve 10 is opened. The high pressure air in the storage chamber 2 is drawn into the low pressure gas tank 11 in which a negative pressure is maintained, and reduces its pressure. The air in the storage chamber 2 ceases to apply pressure to the molten metal 6 therein, and its level 7 rises, while the level of the molten metal in the pouring passage 3 drops below its outlet 31, whereby the pouring operation is terminated. Upon termination of the pouring operation, the exhaust valve 10 is closed again, so that the apparatus may be ready for another cycle of pouring operation. As compressed air is supplied from the high pressure gas tank 8 into the storage chamber 2 for the pouring operation, the resulting reduction in the quantity and pressure of the air in the tank 8 causes the compressor 15 to be started. The air recovered from the storage chamber 2 into the low pressure gas tank 11 is compressed and recycled into the high pressure gas tank 8. The aforesaid sequences of operation are repeated for dispensing molten metal, and discontinuing any such dispensation. The quantity of the molten metal to be dispensed can be controlled by the pressure regulator 9 which controls the duration of pressure application into the storage chamber 2. According to the system of this invention, the compressed gas supplied from the high pressure gas tank 8 into the storage chamber 2 is never released into the open atmosphere, but is recovered into the low pressure gas tank 11, so that it may be compressed by the compressor 15 again, and recycled into the high pressure gas tank 8. In other words, the gas is circulated along a closed loop. The closed loop circulation of the gas provides a number of advantages. If air is used, for example, as such gas, oxygen, which is present in a large quantity in the air during the initial stage of operation, is gradually reduced by reacting with molten metal in the storage container 1 during its recirculation in the closed loop. Accordingly, the oxidation of the molten metal 6 in the storage container 1 can be effectively prevented. If an inert gas is used, the closed loop prevents any substantial loss thereof except for a very small amount of leakage. Therefore, the system requires only a very small quantity of inert gas, and is very economical to operate. Should there develop any deficiency in the quantity of the gas in the closed loop due to leakage, however, the pressure of the gas in the low pressure gas tank 11 drops below a predetermined level. The pressure regulator 18 detects any such pressure drop in the tank 11, and causes the suction valve 19 to open to draw air therethrough to supply a satisfactory amount of additional air into the tank 11. In the event an inert gas is used, a bottle of such gas may be connected to the inlet of the suction valve 19 to supply additional gas into the tank 11 when the valve 19 has been opened. Even if air is used, there is virtually no fear of molten metal oxidation, since the amount of any such additional air is very small, and does not bring about any appreciable increase in the quantity of oxygen in the closed loop. The primary cooler 12 provided on the inlet side of the compressor 15 cools the gas from the low pressure gas tank 11 before its transfer into the compressor 15 to thereby protect the compressor 15 against overheating, since the gas recovered from the storage container 1 remains hot due to the high temperature of the molten metal therein. The secondary cooler 16 provided on the outlet side of the compressor 15 cools the gas heated during its compression. The drain separator 13 and the filter 14, which are provided on the inlet side of the compressor 15, remove moisture and dust, respectively, from the gas to be supplied from the low pressure gas tank 11 to the compressor 15 to protect the compressor 15 against damage by any such moisture or dust.

Claims: CLAIMS 1. - A molten metal dispensing apparatus including a molten metal storage container (1) and a pouring passage (3) extending upwardly from the bottom of said container (1) to a point above the highest level (7) of molten metal (6) in said container (1), and adapted for dispensing molten metal through said pouring passage (3) when compressed gas is introduced into a closed hollow space above said molten metal in said container (1) to apply pressure to said molten metal (6), characterized by a high pressure gas tank (8) in which said compressed gas is stored before it is introduced into said storage container (1), a low pressure gas tank (11) into which said compressed gas is recovered from said storage container (1) and a compressor (15) for compressing said gas from said low pressure gas tank (11) and returning it into said high pressure gas tank (8). 2. - A molten metal dispensing apparatus as claimed in claim 1, wherein a substantially constant negative pressure is maintained in said low pressure gas tank (11). 3. - A molten metal dispensing apparatus as claimed in claims 1 or 2, wherein said compressor (15) is operated in such a manner as to maintain a substantially constant positive pressure in said high pressure gas tank (8). 4. - A molten metal dispensing apparatus as claimed in any of claims 1 to 3, wherein said compressed gas is air. 5. - A molten metal dispensing apparatus as claimed in any of claims 1 to 3, wherein said compressed gas is an inert gas.

Inventors: OHMORI, TSUGUHARU KOHGYO-DENNETSU-BU GIJUTSU-KA, UENO, SADAUMI KOHGYO-DENNETSU-BU GIJUTSU-KA
Applicants: FUJI ELECTRIC CO., LTD.
Application year: 1981
Main classification: B22D39
IPC codes: B22D37, B22D39, B22D18