Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1997-09-19
1999-06-01
Ryan, Patrick
Metal founding
Process
Shaping liquid metal against a forming surface
164337, 222590, 222593, 222595, B22D 100, B22D 3700, B22D 3506, B67D 104
Patent
active
059080663
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for charging casting machines with non-ferrous molten metals, according to which melt is supplied batchwise from a withdrawal chamber of a melting furnace having a gas atmosphere to the filling hole of a casting machine, and to an apparatus for carrying out this method.
2. Description of the Prior Art
For the batchwise charging of casting machines, melt has so far been discharged from a melting furnace by means of gas pressure conveyance (EP-A 0,252,318) or by means of piston pumps or spiral pumps (DE-B 1,134,183) via pump components extending beyond the cover of the melting furnace, so that long conveying distances along with the difficulties of an undesired premature slag formation and solidification have to be accepted and expensive holding and conveying means are required. The charging of the melt thus requires very much handling and maintenance above all in the case of easily oxidizable non-ferrous metals, impairs the availability of the machine, and there is also a poor metering accuracy.
SUMMARY OF THE INVENTION
It is therefore the object underlying the invention to provide a method as described above, which provides for an economic charging of the melt with a high metering accuracy and constancy. In addition, there should be created a comparatively inexpensive apparatus for carrying out the method.
This object is solved by the invention in that the metered melt is pumped up inside the withdrawal chamber and is drained towards the filling hole via a discharge pipe extending through the furnace wall, where for supporting the melt flow a pulsed supply of gas to the withdrawal chamber is effected. Thus, the flow path of the melt is at least partly integrated in the furnace space of the withdrawal chamber, and the discharge of the melt is effected on a comparatively short path by simply draining it along the discharge pipe, so that inexpensive pumping means and heating means are sufficient for a proper discharge of the melt. Due to the pulsed supply of gas to the withdrawal chamber the metering accuracy is improved in the desired sense, as the gas pulses ensure the complete and clearly limited discharge of the melt through the discharge pipe and can in addition provide a protective atmosphere for the melt in the discharge area when using a protective gas. Due to the pulsed supply of gas to the withdrawal chamber the discharge velocity of the gas through the discharge pipe is increased, and there is formed a discharging gas piston for the melt flow. This gas piston prevents that after the pump has stopped during the metered discharge of the melt, the boundary layers of the outflowing melt close to the wall stay back behind the melt particles more remote from the wall inside the discharge pipe, so that the final idling would take longer and involve an afterdripping. Due to the increase of the gas velocity inside the discharge pipe, however, the layers of the outflowing melt close to the wall can be accelerated and the metering process can thus be terminated more quickly, there is no afterdripping and the metering accuracy is increased. Despite the simple melt discharge measures a perturbation-insensitive and exactly dosable conveyance of the melt is ensured.
In the case of aluminum or the like, the withdrawal chamber could even be supplied with air or the like, but when oxygen-free protective gas, preferably a mixture of nitrogen or argon and sulfur hexafluoride, is supplied to the withdrawal chamber, melt oxidations can safely be prevented also in the discharge area and in the case of delicate metals such as magnesium or the like. Since the metered discharge of the melt is a turbulent melt flow, which does not cover the entire cross-section of the discharge pipe, and the melt surface is permanently torn up and newly formed, there cannot form a sealing protective layer as in the usual melt baths, so that special care should be taken that there is an oxygen-free protective gas atmosphere, and the usual protective g
REFERENCES:
patent: 4635706 (1987-01-01), Behrens
patent: 5407000 (1995-04-01), Mercer, II et al.
patent: 5411240 (1995-05-01), Rapp et al.
patent: 5477907 (1995-12-01), Meyer et al.
Light Metals and Metal Industry; vol. 27, No. 319, Dec. 64, p. 40 Volkswagen: "Nitrogen aids automatic metering of".
Ing. Rauch Fertigungstechnik Gesellschaft m.b.H.
Lin I.-H.
Ryan Patrick
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