Measuring and testing – Gas content of a liquid or a solid – Of metal
Reexamination Certificate
1999-02-03
2001-04-03
Williams, Hezron (Department: 2856)
Measuring and testing
Gas content of a liquid or a solid
Of metal
C702S024000
Reexamination Certificate
active
06209384
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to probes used in collecting and sensing the gas content of liquid, molten metal, and more particularly to a hollow probe providing efficient collection of gas contained in a liquid metal.
It is known that hydrogen dissolved in molten metal, such as aluminum and aluminum alloys, causes voids or pores to develop within an ingot cast from such molten metal, the voids forming during the process of solidification. The voids give rise to various problems in products produced from the solidified metal. There has, therefore, been increasing requirements that a so-called dehydrogenation process be performed, i.e., that hydrogen dissolved in molten metal be removed as an important step in metal casting processes.
Before any removal of hydrogen gas takes place, of course, it is necessary to determine whether or not a body or supply of molten metal contains sufficient amounts of hydrogen for the removal process. This determination can be made by hydrogen sensing apparatus, such as those disclosed in the following U.S. Pat. Nos.:
2,861,450—Ransley
4,454,748—Warchol et al
4,731,732—Terai et al
4,829,810—Anderson et al
4,907,440—Martin et al
The disclosures of these patents are incorporated herein by reference.
In the above references, the content of hydrogen dissolved in a body of molten metal is determined by directing an inert carrier gas into the molten metal, and circulating the carrier gas a substantial number of times in the metal. In the process, the carrier gas acquires hydrogen gas from the molten metal when it is first brought in contact with such metal, and the acquired hydrogen content in the carrier gas increases in each period of contact until the hydrogen partial pressure in the carrier gas equilibrates with the hydrogen partial pressure in the metal.
Generally, the number of contacts required between the carrier gas and the liquid metal is relatively large before equilibrium is reached. A pump is used for this process to circulate the mixture of carrier gas and hydrogen content to and through a hydrogen sensing device and to and from the liquid metal.
Carrier gases are conducted into liquid metals and removed therefrom by hollow probe devices, such as shown in the above-incorporated patent references using pumps, tubing and check valves that control the direction of carrier gas to and from the liquid metal.
SUMMARY OF THE INVENTION
The present invention uses a simple, hollow, heat-resistant tube and probe having one end located in a body or supply of liquid metal, and a piston located in said end for reciprocation in the end of the probe and in the liquid metal. The piston is reciprocated in the tube and metal by a solenoid plunger, and the hollow tube and probe are connected in fluid communication with a hydrogen gas sensor. Gas is forced up the hollow tube from the liquid metal and reciprocating piston to the sensor by action of the reciprocating piston. The piston is mechanically connected to the solenoid plunger by a shaft located in the hollow probe, and the hollow probe can be connected directly to a sensor housing such that the number of connections and fittings, which can be subject to leakage, is kept to the one connection between the sensor housing and the hollow probe.
Cyclic movement of the piston in the end of the probe located in the liquid metal disturbs only the surface of the liquid metal disposed within the probe, i.e., the metal surface located outside of the probe remains undisturbed. Disturbance of the metal surface outside the probe causes hydrogenation of the liquid metal, as water vapor from the atmosphere above the liquid metal easily enters the liquid metal. This, of course, adversely influences the measurement of gas content, as the sensor must deal with extraneous sources of hydrogen.
The volume of the hollow probe is small such that the reciprocating piston rapidly fills the hollow probe with a mixture of hydrogen and carrier gas. There is no separate pump and no interconnecting tubing to be filled with carrier and hydrogen gases. Thus, the time for making the measurement is quite short, i.e., on the order of several minutes.
In addition, no check valves are needed, which valves can also be subject to leakage and require maintenance.
The solenoid can be operated by a cyclic voltage supplied by a source of electrical energy. The source, for example, can provide repetitive electrical pulses having a magnitude sufficient to energize the solenoid to respectively raise the piston, and using the absence of pulses, to lower the piston, i.e., the piston falls under the force of its own mass.
REFERENCES:
patent: 4731732 (1988-03-01), Warchol et al.
patent: 5495746 (1996-03-01), Sigworth
patent: 5591894 (1997-01-01), Falk et al.
patent: 5850034 (1998-12-01), Hugens, Jr.
Jones Tullar & Cooper P.C.
Politzer Jay L.
Sullivan Jr. Daniel A.
Williams Hezron
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