Thermal measuring and testing – Temperature measurement – Combined with diverse art device
Reexamination Certificate
2000-05-03
2004-01-20
Verbitsky, G. (Department: 2859)
Thermal measuring and testing
Temperature measurement
Combined with diverse art device
C374S179000, C374S139000, C374S140000
Reexamination Certificate
active
06679627
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a device for supporting a temperature sensor in the interior of a liquid, to a temperature sensor assembly incorporating such a device and to a method of determining the temperature of a liquid; more especially the invention is concerned with such a device, sensor assembly and method in which the temperature sensor is an immersion pyrometer for measuring the temperature of a molten metal, molten salt or other high temperature liquid.
In particular the invention is concerned with such a device, sensor assembly and method in which the device supports a hot thermocouple element, and the device floats in the liquid, whereby the hot thermocouple element may be disposed at a predetermined, desired or selected position within the liquid.
BACKGROUND OF THE INVENTION
Immersion pyrometers for measuring the temperature of a molten metal or other high temperature liquid are typically immobile and are located at a fixed position in the liquid. For example, the pyrometer may extend into the liquid through a wall of a vessel holding the liquid.
The immersion pyrometer is housed or supported in a device which protects the pyrometer from the liquid. Examples of protective devices are described in U.S. Pat. No. 5,474,618 C. Allaire; U.S. Pat. No. 5,577,841 Cowall; U.S. Pat. No. 4,692,556 T. Bollen et al and U.S. Pat. No. 5,456,761 M. Auger et al.
Since the immersion pyrometer is immobile, different parts of the pyrometer are exposed to the liquid as the level of liquid rises or falls in the vessel in which it is housed. Likewise, in the case where the liquid is a molten metal, and a slag is formed on the surface of the molten metal, rise and fall of the level of molten metal results in different parts of the pyrometer being exposed to the slag. In addition the portion of the pyrometer not immersed in the liquid and which is exposed to possible attack by the atmosphere above the liquid, varies with the rise and fall of the liquid. A further problem is that these prior pyrometers are subject to a fluctuating thermal gradient in the liquid, as well as a fluctuating liquid line level.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a device for supporting a temperature sensor such as a thermocouple element for determination of the temperature of a liquid, which floats in the liquid.
It is a further object of the invention to provide a temperature sensor assembly employing a device for supporting a temperature sensor of the assembly, which device floats in a liquid, the temperature of which is to be detected.
It is yet another object of the invention to provide a method of determining the temperature of a liquid in which a device supporting a temperature sensor floats in the liquid with the temperature sensor disposed beneath the upper surface of the liquid.
According to the invention there is provided a device for supporting a temperature sensor within the interior of a liquid comprising: a sheath having an interior cavity extending from an open end to a closed end for receiving the temperature sensor, said device being adapted to float in the liquid with said closed end immersed in the liquid.
According to another aspect of the invention there is provided a temperature sensor assembly for determining the temperature of a liquid comprising: a) a temperature sensor, b) a device for housing the temperature sensor for supporting the sensor within the interior of the liquid, said device comprising a sheath having an interior cavity extending from an open end to a closed end, said temperature sensor being housed within said cavity, said device being adapted to float in the liquid with said closed end immersed in the liquid.
According to yet another aspect of the invention there is provided a method of determining the temperature of a liquid comprising: providing a bath of liquid having an upper surface, floating in said liquid a device supporting a temperature sensor, said device comprising a sheath having an interior cavity extending from an open end to a closed end, said temperature sensor being housed in said cavity at said closed end, and said closed end being immersed in said liquid, allowing the temperature of the sensor to adjust in response to the temperature of the liquid, and determining the temperature of the liquid from the adjusted sensor.
DESCRIPTION OF PREFERRED EMBODIMENTS
The invention is applicable to sensing the temperature of liquids generally, but has particular application in the sensing of the temperature of materials which are solid at normal temperatures and liquid at elevated temperatures.
In preferred embodiments the invention relates to the sensing of the temperature of molten metals and salts and is more particularly described hereinafter by reference to an especially important embodiment in which the temperature of a molten metal is to be determined.
i) Supporting Device
The supporting device of the invention, which supports a temperature sensor, for example, a hot thermocouple element, is constructed of materials and/or has design parameters such that it floats in the molten metal, with a lower portion of the device, housing the hot thermocouple element, immersed in the molten metal. In this way an upper end of the device extends above the upper surface of the molten metal, and a lower end of the device extends below the molten metal surface.
Alternatively if the device is not of a material or constructed with parameters such that it floats in the molten metal, it may employ a separate component or member which renders it floatable.
The sheath is suitably formed of a refractory material which will withstand the molten metal, and retain its structural integrity when floating in the molten metal with its lower end immersed in the molten metal.
The sheath has an internal cavity defined by an elongate bore which is closed at the lower end of the sheath and open at the upper end of the sheath.
A hot thermocouple element and its connecting lead may thus be inserted along the cavity to locate the hot thermocouple element at the closed end of the bore.
The refractory sheath thus protects the hot thermocouple element and its connecting lead. The refractory material may be a mixture of Al
2
O
3
, SiO
2
, CaO, MgO, ZrO
2
, AlN, SiC, Si
3
N
4
, C and the like. The selected composition is such that it confers to the refractory sheath the required resistance to corrosion by the liquid whose temperature is to be measured, as well as the required thermomechanical properties, including mechanical strength and thermal shock resistance.
The device also includes an outer protective shield surrounding the refractory sheath, for example, a metallic shield and particular reference will be made hereinafter to a metallic shield. This metallic shield is suitably in the form of a cylinder with one open end (toward the bottom part of the device) and one closed end (toward the top part of the device) through which is inserted the thermocouple element and its lead. The length of this metallic shield is at least equal to the length of the non-immersed part of the refractory shield after the later has been introduced into the liquid whose temperature is to be measured.
The metallic shield is suitably made of a pure metal or an alloy whose melting temperature should be higher than the temperature of the atmosphere located above the liquid whose temperature is being measured. If the atmosphere is oxidizing, the use of a metal or alloy having a high resistance to oxidation is preferred, such as Ni—Cr or Ni—Co alloys.
The inner diameter of the metallic shield is greater than the outer diameter of the refractory sheath. This creates a gap between the shield and the sheath. This gap, whose width or thickness is preferably less than 5 mm, is closed at one end by the closed end of the metallic shield, and at the other end by the liquid in which the device is immersed.
The metallic shield provides a number of functions including:
a) It prevents the deterioration of the refractory sheath by the action of the atmosphere above the liquid level;
(Ogilvy Renault)
Houle Guy J.
RDC Controle LTEE
Verbitsky G.
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