CA1286124C - Repeating temperature sensing immersion probe - Google Patents
Repeating temperature sensing immersion probeInfo
- Publication number
- CA1286124C CA1286124C CA000522316A CA522316A CA1286124C CA 1286124 C CA1286124 C CA 1286124C CA 000522316 A CA000522316 A CA 000522316A CA 522316 A CA522316 A CA 522316A CA 1286124 C CA1286124 C CA 1286124C
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- Prior art keywords
- sleeve
- temperature sensing
- support tube
- tube
- sensing device
- Prior art date
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Abstract
REPEATING TEMPERATURE SENSING
IMMERSION PROBE
Abstract of the Disclosure A temperature sensing device suitable for repeated immersions into a molten metal bath. The invention in-cluding a protective refractory sleeve which encases a portion of a generally cylindrical cardboard support tube.
Within the support tube is mounted a temperature sensing unit including a body portion, which is positioned within the end of the support tube, and a thermocouple extension portion, which includes a U-shaped quartz tube and which extends through and projects away from the end of the protection sleeve. The cardboard support tube is wrapped with a reflective foil substantially over its end and its entire peripheral surface. The U-shaped quartz tube is provided with an alumina coating to prevent degredation of the quartz material during repeated immersions into the molten metal bath. The combination increasing the number of useful immersions of the sensing unit prior to failure.
IMMERSION PROBE
Abstract of the Disclosure A temperature sensing device suitable for repeated immersions into a molten metal bath. The invention in-cluding a protective refractory sleeve which encases a portion of a generally cylindrical cardboard support tube.
Within the support tube is mounted a temperature sensing unit including a body portion, which is positioned within the end of the support tube, and a thermocouple extension portion, which includes a U-shaped quartz tube and which extends through and projects away from the end of the protection sleeve. The cardboard support tube is wrapped with a reflective foil substantially over its end and its entire peripheral surface. The U-shaped quartz tube is provided with an alumina coating to prevent degredation of the quartz material during repeated immersions into the molten metal bath. The combination increasing the number of useful immersions of the sensing unit prior to failure.
Description
lZ861 ~4 REPEATING TEMPERATURE SENSING
IMMERSION PROBE
Background Of The Invention This invention relates generally to temperature sensing devices which are suitable for repeated immersions into molten metal. In particular this inventions relates to improvements to a molten metal temperature sensing device which includes a high temperature protection tube of a fiberous refractory material.
As shown by Kraus, U.S. Patent Number 3,816,183, and Falk, U.S. Patent Number 4,521,639, it is known to surround a ~emperature sensing device with a cylindrical sleeve of refractory ~aterial for aohieving repeated immersions into a molten metal bath. The oorresponalng U.g. Patent Number 4,645,865 referred to above shows a refractory ~leeve havlng a generally cylindrlcal bore lnitlatlng at one end and termlnatlng at an inwardly projectlng shoulder and a tapered or trunoated cone shaped cyllndrical bore whlch extends from the choulder through the opposlte end of the sleave.
The construction of the repeating device includes a support tube surrounding a thermocouple unit which is in-serted into the cylindrical bore of the refractory sleeve.
A projecting portion of the thermocouple unit extends through the cone shaped bore and away from the end of the sleeve by a predetermined distance. The refractory sleeve is secured to the support tube by filling the end of the sleeve with a refractory cement.
925-173 C ~
121~6~ '~
The invention described herein is an improvement over the structures shown and described in the previous mentloned patents and U.S. Patent 4,645,865 so as to further .
increase the number of immersions that the sensing device may be utilized prior to failure.
Summarv Of The Invention In accordance with the present invention, a pre-formed refractory sleeve, preferably having a generally cylindrical bore therethrough, is provided for receiving a support tube having a thermocouple unit inserted therein. This structure is further provided, first, with a reflective metal foil which is wrapped around the exterior of the support tube prior to insertion into the pre-formed refractory sleeve.
Second, the quartz tube of the thermocouple unit within the device, which surrounds the hot junction of the ther-mocouple wire, is provided with an alumina coating. These individual features on a repeating type sensing device or each feature, in conjunction with the other improvement, permit the device to be immersed into a molten metal bath for temperature measurements for an increased number of readings prior to failure, as compared to known structures.
The reflective foil wrap around the, typically, paperboard tube reflects radiant heat prior to and during immersion into the bath. Additionally, the foil wrap pro-tects the paperboard tube such that the temperature seen by the tube is substantially uniform across the length of the tube which is inserted within the refractory sleeve.
The foil wrap also seals the outer surface of the paper-board tube so as to limit the amount of oxygen that is in contact with the paperboard tube during immersion. Since the presence of oxygen is removed combustion of the tube at elevated temperatures in basically eliminated.
The alumina coating on the quartz sleeve of the thermocouple unit is provided to eliminate degradation of the ~uartz material after repeated immersions into the molten metal environment. A common mode of failure in the typical repeating type immersion sensing devices is the _ 12~36~f'4 failure of the quartz material of the thermocouple tube.
It was previously known to coat a thermocouple tube with an alumina coating in a non-repeating device for use in conjunction with a oxygen sensing electrochemical cell which was also mounted on the immersion end of the probe.
An examPle of this type immersion probe is described in Cure, U.S. patent Number 4,342,633. The coating found on the oxygen and temperature measuring type device is generally heavier than that contemplated by the present invention. The purpose of the alumina coating on this oxygen and temperature type probe is to prevent dis-sociation of the oxygen in the area of the oxyen sensing electrochemical cell from the quartz material such that the cell provides a more accurate reading of the oxygen content of the molten metal bath. An oxygen an~ temDerature sensing probe is not utilized repeatedly as in the p.esent invention. Additionally, the relatively heavier coating of alumina on the quartz material of the oxygen and tempera-ture type probe slows the time required to make an accurate temperature reading by the thermocouple and, therefore, is undesirable for purposes of a repeating ty~e temperature probe. A repetitive type probe must provide a temperatu.e reading as quickly as possible in order to prevent exces-sive degradation of its entire structure during a lengthy immersion. The faster the response time of the thermo-couple unit the more likely that the number of immersions of the probe will increase prior to failure.
Further advantages of the invention will become apparent to those skilled in the art by particularly pointing out and describing a preferred embodiment of the invention.
For the purpose of illustrating the invention, there is shown in the drawings a form which is presently pre-ferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumen-talities shown.
Brief Descrintion of The Drawings Figure 1 shows a cross sectional view of a reneating high temperature immersion probe of the invention.
Figure 2 shows a cross sectional view of the immer-sion probe in Figure 1 taken along line 2-2.
Detailed Description Of The Invention Referring to the drawings wherein like numerals indi-cate like elements, there is shown in Figure 1 a cross section of a temperature sensing device 10 which is adapted to be mounted on the immersion end of the lance ~not shown).
The structure of the device 10 is designed for repeated im-mersion into a bath of molten metal such as steel or iron.
The device 10 includes a support tube 12 which is typically made of a paperboard or like material. The SUD-port tube 12 is inserted into and surrounded by a high temperature protection sleeve 14. Positioned within the interior of the support tube 12 is a temperature sensing unit 16 having a body portion 18 and a thermocouple exten-sion portion 20. The bodv portion 18 is positioned within the interior of the support tube 12 while the thermocouple extension portion 20 projects through and out of the end of the protection sleeve 14.
The protection sleeve 14 shown in the drawings is simllar to that described in applicantl 6 U. S. Patent 4,645,865. The sleeve 14 i preferably vacuum casted from a fine refractory fiberous type material such as a ceramic type fiber as disclosed in U.S. Patent number 3,816,183. However, the sleeve 14 may take any specific form and is not limited to that shown by the drawing or by the patents discussed herein. The outer surface 22 of the protection sleeve -14 is preferably smooth. The interior of the protection sleeve 14 is provided with a generally cylindrical shaped bore 24 which extends from one end of the sleeve and terminates in a radial, inwardly projecting shoulder 26 which is formed adjacent to the immersion end . .. . . . . .......................... .. ..
lZ861 '~
., 28 of the protection sleeve 14. ~etween the shouid~r '~
and the immersion end 28 of the sleeve 14 is provi~ed an inwardlv tapering cylindrical surface 30 which ta~ers toward the immersion end ~8 of the sleeve 14. This surface 30 forms a generally truncated cone shaped bore. A second shoulder 32 may be provided on the sleeve 14 which is open to the immersion end 28. The second shoulder 32 is in communication with the narrow end of the cone shaped bore 30.
The assembly of the device 10 is such that the body 18 of the temperature sensing unit 16 is inserted into the support tube 12 with the thermocouple extension portion 20 of the unit projecting away from the end of the tube 12. The support tube 12 and sensing unit 16 are inserted into the cvlindrical bore 24 of the protection sleeve 14 such that the protection sleeve 14 and sensin~ unit 16 abut the inwardly projectiong shoulder 26. This arran~e-ment prepositions the projecting end of the sensing unit extension 20 beyond the immersion end 28 of the protection sleeve 14 by a predetermined amount. The cone shaped bore 30 and the second shoulder ~ortion 32 of the protection sleeve 14 are filled with a refractory cement 34. The combination of the shoulder 26 and the cement fill 34 in the tapered bore 30 provides a positive locking of the temperature sensing unit 16 and the support tube 12 within the protection sleeve 14. Additionally, this arrangement provides an increased insulation of the temDerature sensing unit 16 and permits the use of less refractory cement 34.
The refractory sleeve 14 is typically a better insulator than the refractory cement 34, therefore the thermocouple unit 16 may be embedded in the sleeve at a relatively shallower depth. Additional advantaqes of this type struc-ture are discussed in U.8. Patent 4,645,865.
In accordance with the present invention the support tube 12 is provided with a reflective foil wrap 36. The reflective wrap 36 is provided in substantially direct contact with the exterior surface of the support tube 12.
Additionally, the wrap 36 is folded over the end of the .
.... . . . . ...... . .
IZ861~ 4 support tube i2 and is ?ositioned around the leas ~2 of the thermocouple extension 20 and over the top of the tempera-ture sensing unit 16. The wrap 36 may be applied in any convenient manner and is preferably of an aluminum material approximately .004 inches thick, although other thicknesses may be utilized depending on design conditions. The out-side surface of the wrap 35 is reflective of heat radiated from the protection sleeve 14 prior to and during immersion.
The foil wrap 36 also acts as a heat sink for the heat transfered by conductin~ or convection from the sleeve 14 during immersion. The wrap 36, because of its relatively high conductivity, will also disperse absorbed heat from within the interior of the protection sleeve 14 substantially over its entire surface.
A common problem in the repeating temperature sensing devices 10 is the combustion of the paperboard material of the support tube 12 after a number of immersions. ~fter repeated immersion of the device, the paperboard material of the tube 12 reaches its combustion point and combines with the oxygen within the interior of the cylindrical bore 24 to cause the paper to smolder or char. By provid-ing a reflective foil wrap 36 of a non-combustible material in surrounding contact with the paperboard material the oxygen present within the cylindrical bore 24 is not directly exposed to the paperboard tube. Therefore, the wrap 36 prevents combustion of the tube 12 even at elevated temper-ature above its flash or burning point.
The body portion 18 of the temperature sensing unit 16 generally includes contacts 38 which extend from the end opposite from that of the thermocouple extension 20.
The contacts 38 are adapted to mate with corresponding contacts on a lance tnot shown) which is inserted through the support tube 12. The body portion 18 contains cold compensation joints between the thermocouple wire and the contacts 38 (structure not shown). In Figure 2, a cross section of the body portion 18 is shown including a refrac-tory cement fill 40. This refractory cement 40 acts to 121~ 4 support ~he ~lermocoup ~ e.Ytension portion 2n on he body portion 13 anc protect tne thermocouple lires and the cold joints ~ithin ~he body 18. Th2 refractorv cement fill 40 is, oreferably, of the same material as refractory cement 34.
The thermocouole extension portion 20 of the sensing unit 16 typically comprises a U-shaped quartz type tube ~2 which contains the hot junction of the thermocouple wire at the projecting end of the U-shape. A primary reason for failure of known variations of a repeating i~mersion device is due to the failure of the quartz material of this U-shaped tube 42. As part of the invention, the quartz tube 42 was modified by coating 44 the quartz ~aterial with an alumina (AL2~3) material which is then force-dried. The alumina coating 44 of the quartz tube '2 acts to strengthen t~e quartz material and prevent degreda-tion during repeated i~mersions. Typically, the environ-ment of the molten metal bath causes the quartz material to become soft and eventually fail. It has been discovered that by coating 44 the quartz material with the alumina in diluted strength (260 grams AL2O3 with 340cc of a polyvinyl alcohol solution) that the failure of the quartz ~-shaped tube is eliminated as a mode of failure of the device 10.
As stated previously, it was known to use an alumina coating on a quartz thermocouple tube on an oxygen and temperature type measuring device having an electro-chemical cell for measuring the oxygen content in the bath. The application of the alumina coating in this type temperature and oxygen device is to prevent dissociation of the oxygen from the quartz which may effect the measure-ments of the oxygen sensing cell. In the present applica-tion, the alumina coating is provided in diluted strength as compared to previous uses 1000 grams AL2O3 with 400cc polyvinyl alcohol) so that the alumina does not effect the response time of the thermocouple. By providing this coating on a repeating immersion temperature sensing device 1~, the molten metal bath will not cause degredation of ~Z861 '~
the quartz material after repeated immersions. The tempera-ture and oxygen sensing type probes are not utilized for repeated immersions.
The structure of the immersion device 10 as shown in the drawings and as described herein substantially increases the useful life of the temperature sensina devi~ described ln U.S. Patent 4,645,865. Each of the lmprove-ments as described herein substantially increase this useful life. However, each improvement may be utilized individually as desired.
Optional structure which may be added to the device 10 includes a cap located at the immersion end 28 of the sleeve to protect the thermocouple extension portion 20 during initial immersion of the device 10 through the slag on the top of the molten metal bath. Additionally, ribs 48 may be provided within the sleeve 14 which project inwardly from the cylind.ical bore 24 so as to maintain the support tube 12 and temperature sensing unit 16 within the protection sleeve 14 in a fixed relationship. The cylindrical bore end of the sleeve 14 ~ay be sealed by a refactory material (not shown). However, the device 10 contemplated by this invention is generaly not immersed into the bath beyond the level of the non-immersion end.
The invention as described herein substantially increases the useful life of a temperature sensing device such that the number of immersions, providing accurate temperature readings, may be increased. Testing has shown that the invention as described increases the number of immersions by two-fold.
The present invention may be embodied in other specific forms without departing from the spirit o essen-tial attributes thereof and, accordingly, refe.ence should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.
IMMERSION PROBE
Background Of The Invention This invention relates generally to temperature sensing devices which are suitable for repeated immersions into molten metal. In particular this inventions relates to improvements to a molten metal temperature sensing device which includes a high temperature protection tube of a fiberous refractory material.
As shown by Kraus, U.S. Patent Number 3,816,183, and Falk, U.S. Patent Number 4,521,639, it is known to surround a ~emperature sensing device with a cylindrical sleeve of refractory ~aterial for aohieving repeated immersions into a molten metal bath. The oorresponalng U.g. Patent Number 4,645,865 referred to above shows a refractory ~leeve havlng a generally cylindrlcal bore lnitlatlng at one end and termlnatlng at an inwardly projectlng shoulder and a tapered or trunoated cone shaped cyllndrical bore whlch extends from the choulder through the opposlte end of the sleave.
The construction of the repeating device includes a support tube surrounding a thermocouple unit which is in-serted into the cylindrical bore of the refractory sleeve.
A projecting portion of the thermocouple unit extends through the cone shaped bore and away from the end of the sleeve by a predetermined distance. The refractory sleeve is secured to the support tube by filling the end of the sleeve with a refractory cement.
925-173 C ~
121~6~ '~
The invention described herein is an improvement over the structures shown and described in the previous mentloned patents and U.S. Patent 4,645,865 so as to further .
increase the number of immersions that the sensing device may be utilized prior to failure.
Summarv Of The Invention In accordance with the present invention, a pre-formed refractory sleeve, preferably having a generally cylindrical bore therethrough, is provided for receiving a support tube having a thermocouple unit inserted therein. This structure is further provided, first, with a reflective metal foil which is wrapped around the exterior of the support tube prior to insertion into the pre-formed refractory sleeve.
Second, the quartz tube of the thermocouple unit within the device, which surrounds the hot junction of the ther-mocouple wire, is provided with an alumina coating. These individual features on a repeating type sensing device or each feature, in conjunction with the other improvement, permit the device to be immersed into a molten metal bath for temperature measurements for an increased number of readings prior to failure, as compared to known structures.
The reflective foil wrap around the, typically, paperboard tube reflects radiant heat prior to and during immersion into the bath. Additionally, the foil wrap pro-tects the paperboard tube such that the temperature seen by the tube is substantially uniform across the length of the tube which is inserted within the refractory sleeve.
The foil wrap also seals the outer surface of the paper-board tube so as to limit the amount of oxygen that is in contact with the paperboard tube during immersion. Since the presence of oxygen is removed combustion of the tube at elevated temperatures in basically eliminated.
The alumina coating on the quartz sleeve of the thermocouple unit is provided to eliminate degradation of the ~uartz material after repeated immersions into the molten metal environment. A common mode of failure in the typical repeating type immersion sensing devices is the _ 12~36~f'4 failure of the quartz material of the thermocouple tube.
It was previously known to coat a thermocouple tube with an alumina coating in a non-repeating device for use in conjunction with a oxygen sensing electrochemical cell which was also mounted on the immersion end of the probe.
An examPle of this type immersion probe is described in Cure, U.S. patent Number 4,342,633. The coating found on the oxygen and temperature measuring type device is generally heavier than that contemplated by the present invention. The purpose of the alumina coating on this oxygen and temperature type probe is to prevent dis-sociation of the oxygen in the area of the oxyen sensing electrochemical cell from the quartz material such that the cell provides a more accurate reading of the oxygen content of the molten metal bath. An oxygen an~ temDerature sensing probe is not utilized repeatedly as in the p.esent invention. Additionally, the relatively heavier coating of alumina on the quartz material of the oxygen and tempera-ture type probe slows the time required to make an accurate temperature reading by the thermocouple and, therefore, is undesirable for purposes of a repeating ty~e temperature probe. A repetitive type probe must provide a temperatu.e reading as quickly as possible in order to prevent exces-sive degradation of its entire structure during a lengthy immersion. The faster the response time of the thermo-couple unit the more likely that the number of immersions of the probe will increase prior to failure.
Further advantages of the invention will become apparent to those skilled in the art by particularly pointing out and describing a preferred embodiment of the invention.
For the purpose of illustrating the invention, there is shown in the drawings a form which is presently pre-ferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumen-talities shown.
Brief Descrintion of The Drawings Figure 1 shows a cross sectional view of a reneating high temperature immersion probe of the invention.
Figure 2 shows a cross sectional view of the immer-sion probe in Figure 1 taken along line 2-2.
Detailed Description Of The Invention Referring to the drawings wherein like numerals indi-cate like elements, there is shown in Figure 1 a cross section of a temperature sensing device 10 which is adapted to be mounted on the immersion end of the lance ~not shown).
The structure of the device 10 is designed for repeated im-mersion into a bath of molten metal such as steel or iron.
The device 10 includes a support tube 12 which is typically made of a paperboard or like material. The SUD-port tube 12 is inserted into and surrounded by a high temperature protection sleeve 14. Positioned within the interior of the support tube 12 is a temperature sensing unit 16 having a body portion 18 and a thermocouple exten-sion portion 20. The bodv portion 18 is positioned within the interior of the support tube 12 while the thermocouple extension portion 20 projects through and out of the end of the protection sleeve 14.
The protection sleeve 14 shown in the drawings is simllar to that described in applicantl 6 U. S. Patent 4,645,865. The sleeve 14 i preferably vacuum casted from a fine refractory fiberous type material such as a ceramic type fiber as disclosed in U.S. Patent number 3,816,183. However, the sleeve 14 may take any specific form and is not limited to that shown by the drawing or by the patents discussed herein. The outer surface 22 of the protection sleeve -14 is preferably smooth. The interior of the protection sleeve 14 is provided with a generally cylindrical shaped bore 24 which extends from one end of the sleeve and terminates in a radial, inwardly projecting shoulder 26 which is formed adjacent to the immersion end . .. . . . . .......................... .. ..
lZ861 '~
., 28 of the protection sleeve 14. ~etween the shouid~r '~
and the immersion end 28 of the sleeve 14 is provi~ed an inwardlv tapering cylindrical surface 30 which ta~ers toward the immersion end ~8 of the sleeve 14. This surface 30 forms a generally truncated cone shaped bore. A second shoulder 32 may be provided on the sleeve 14 which is open to the immersion end 28. The second shoulder 32 is in communication with the narrow end of the cone shaped bore 30.
The assembly of the device 10 is such that the body 18 of the temperature sensing unit 16 is inserted into the support tube 12 with the thermocouple extension portion 20 of the unit projecting away from the end of the tube 12. The support tube 12 and sensing unit 16 are inserted into the cvlindrical bore 24 of the protection sleeve 14 such that the protection sleeve 14 and sensin~ unit 16 abut the inwardly projectiong shoulder 26. This arran~e-ment prepositions the projecting end of the sensing unit extension 20 beyond the immersion end 28 of the protection sleeve 14 by a predetermined amount. The cone shaped bore 30 and the second shoulder ~ortion 32 of the protection sleeve 14 are filled with a refractory cement 34. The combination of the shoulder 26 and the cement fill 34 in the tapered bore 30 provides a positive locking of the temperature sensing unit 16 and the support tube 12 within the protection sleeve 14. Additionally, this arrangement provides an increased insulation of the temDerature sensing unit 16 and permits the use of less refractory cement 34.
The refractory sleeve 14 is typically a better insulator than the refractory cement 34, therefore the thermocouple unit 16 may be embedded in the sleeve at a relatively shallower depth. Additional advantaqes of this type struc-ture are discussed in U.8. Patent 4,645,865.
In accordance with the present invention the support tube 12 is provided with a reflective foil wrap 36. The reflective wrap 36 is provided in substantially direct contact with the exterior surface of the support tube 12.
Additionally, the wrap 36 is folded over the end of the .
.... . . . . ...... . .
IZ861~ 4 support tube i2 and is ?ositioned around the leas ~2 of the thermocouple extension 20 and over the top of the tempera-ture sensing unit 16. The wrap 36 may be applied in any convenient manner and is preferably of an aluminum material approximately .004 inches thick, although other thicknesses may be utilized depending on design conditions. The out-side surface of the wrap 35 is reflective of heat radiated from the protection sleeve 14 prior to and during immersion.
The foil wrap 36 also acts as a heat sink for the heat transfered by conductin~ or convection from the sleeve 14 during immersion. The wrap 36, because of its relatively high conductivity, will also disperse absorbed heat from within the interior of the protection sleeve 14 substantially over its entire surface.
A common problem in the repeating temperature sensing devices 10 is the combustion of the paperboard material of the support tube 12 after a number of immersions. ~fter repeated immersion of the device, the paperboard material of the tube 12 reaches its combustion point and combines with the oxygen within the interior of the cylindrical bore 24 to cause the paper to smolder or char. By provid-ing a reflective foil wrap 36 of a non-combustible material in surrounding contact with the paperboard material the oxygen present within the cylindrical bore 24 is not directly exposed to the paperboard tube. Therefore, the wrap 36 prevents combustion of the tube 12 even at elevated temper-ature above its flash or burning point.
The body portion 18 of the temperature sensing unit 16 generally includes contacts 38 which extend from the end opposite from that of the thermocouple extension 20.
The contacts 38 are adapted to mate with corresponding contacts on a lance tnot shown) which is inserted through the support tube 12. The body portion 18 contains cold compensation joints between the thermocouple wire and the contacts 38 (structure not shown). In Figure 2, a cross section of the body portion 18 is shown including a refrac-tory cement fill 40. This refractory cement 40 acts to 121~ 4 support ~he ~lermocoup ~ e.Ytension portion 2n on he body portion 13 anc protect tne thermocouple lires and the cold joints ~ithin ~he body 18. Th2 refractorv cement fill 40 is, oreferably, of the same material as refractory cement 34.
The thermocouole extension portion 20 of the sensing unit 16 typically comprises a U-shaped quartz type tube ~2 which contains the hot junction of the thermocouple wire at the projecting end of the U-shape. A primary reason for failure of known variations of a repeating i~mersion device is due to the failure of the quartz material of this U-shaped tube 42. As part of the invention, the quartz tube 42 was modified by coating 44 the quartz ~aterial with an alumina (AL2~3) material which is then force-dried. The alumina coating 44 of the quartz tube '2 acts to strengthen t~e quartz material and prevent degreda-tion during repeated i~mersions. Typically, the environ-ment of the molten metal bath causes the quartz material to become soft and eventually fail. It has been discovered that by coating 44 the quartz material with the alumina in diluted strength (260 grams AL2O3 with 340cc of a polyvinyl alcohol solution) that the failure of the quartz ~-shaped tube is eliminated as a mode of failure of the device 10.
As stated previously, it was known to use an alumina coating on a quartz thermocouple tube on an oxygen and temperature type measuring device having an electro-chemical cell for measuring the oxygen content in the bath. The application of the alumina coating in this type temperature and oxygen device is to prevent dissociation of the oxygen from the quartz which may effect the measure-ments of the oxygen sensing cell. In the present applica-tion, the alumina coating is provided in diluted strength as compared to previous uses 1000 grams AL2O3 with 400cc polyvinyl alcohol) so that the alumina does not effect the response time of the thermocouple. By providing this coating on a repeating immersion temperature sensing device 1~, the molten metal bath will not cause degredation of ~Z861 '~
the quartz material after repeated immersions. The tempera-ture and oxygen sensing type probes are not utilized for repeated immersions.
The structure of the immersion device 10 as shown in the drawings and as described herein substantially increases the useful life of the temperature sensina devi~ described ln U.S. Patent 4,645,865. Each of the lmprove-ments as described herein substantially increase this useful life. However, each improvement may be utilized individually as desired.
Optional structure which may be added to the device 10 includes a cap located at the immersion end 28 of the sleeve to protect the thermocouple extension portion 20 during initial immersion of the device 10 through the slag on the top of the molten metal bath. Additionally, ribs 48 may be provided within the sleeve 14 which project inwardly from the cylind.ical bore 24 so as to maintain the support tube 12 and temperature sensing unit 16 within the protection sleeve 14 in a fixed relationship. The cylindrical bore end of the sleeve 14 ~ay be sealed by a refactory material (not shown). However, the device 10 contemplated by this invention is generaly not immersed into the bath beyond the level of the non-immersion end.
The invention as described herein substantially increases the useful life of a temperature sensing device such that the number of immersions, providing accurate temperature readings, may be increased. Testing has shown that the invention as described increases the number of immersions by two-fold.
The present invention may be embodied in other specific forms without departing from the spirit o essen-tial attributes thereof and, accordingly, refe.ence should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.
Claims (11)
1. A temperature sensing device suitable for repeated immersion into a molten metal bath comprising: a protection sleeve capable of withstanding repeated immersions into a molten metal bath having a central longitudinally extending bore therethrough; a support tube within the bore of the protection sleeve; and a thermocouple unit having a body portion supported by the support tube within one end thereof and a thermocouple extension portion extending from the body portion through the end of the protection sleeve, the support tube wrapped with a reflective foil material which substantially covers the entire surface of the support tube within the protection sleeve.
2. A temperature sensing device as claimed in claim sensing device as claimed in claim 1 wherein the thermocouple extension portion of the sensing unit includes a U-shaped quartz tube, the U-shaped quartz tube having a coating over at least its surface area to be exposed to the molten metal upon immersion, the coating comprising an alumina material.
3. A temperature sensing device as claimed in claim 2 wherein said alumina material coating is made of a mixture in solution of approximately 260 grams AL203 and 340 cc of polyvinyl alcohol.
4. The temperature sensing device as claimed in claim 1 wherein the body portion of the sensing unit includes a refractory cement fill.
5. A temperature sensing device as claimed in claim 1 wherein the reflective foil wrap is an aluminum material.
6. A temperature sensing device as claimed in claim 5 wherein the aluminum foil wrap is approximately 0.004 inches in thickness.
7. A temperature sensing device as claimed in claim 1 wherein the reflective foil wrap encases the end portion of the support tube and the body portion of the sensing unit.
8. A temperature sensing device suitable for repeated immersion into a molten metal bath comprising: a generally cylindrical inert refractory protection sleeve; a cylindrical support tube within a generally cylindrical bore through the protection sleeve; and a thermocouple unit having a body portion supported by the support tube within one end thereof and a thermocouple extension portion extending away from the body portion through the end of the protection sleeve, the thermocouple extension portion including a U-shaped tube, and the U-shaped tube encasing the hot junction of the thermocouple unit, the U-shaped tube being made of a quartz material, and the quartz material being coated with an alumina type material over its surface area to be exposed to molten metal during immersion.
9. The temperature sensing device as claimed in claim 8 wherein the body portion of the sensing unit includes a refractory cement fill.
10. The temperature sensing device as claimed in claim 8 wherein the alumina material is made of a mixture in solution of approximately 260 grams of AL203 and 340 cc of a polyvinyl alcohol.
11. A temperature sensing device suitable for repeated immersion into a molten metal comprising: a generally cylindrical inert refractory sleeve, a generally cylindrical bore beginning at one end of the refractory sleeve and terminating at an inwardly projecting shoulder formed within the sleeve, a generally truncated cone-shaped bore within the sleeve being in axial alignment with the cylindrical bore and initiating at the inwardly projecting shoulder within the sleeve with the base of the truncated cone being adjacent to and in communication with the generally cylindrical bore and the opposite end of the truncated cone-shaped bore being in communication with the opposite end of the sleeve; a cylindrical support tube positioned within the generally cylindrical bore, one end of the support tube abutting the shoulder within the sleeve; a thermocouple unit having a body portion supported by said support tube within the end abutting the shoulder portion of the sleeve and projecting member which extends from the body portion through the generally truncated cone-shaped bore of the sleeve, the projecting member extending beyond the end of the sleeve by a predetermined amount, the projecting member including a generally U-shaped quartz tube having a hot junction of the thermocouple contained therein, the quartz tube having a dilute alumina coating over its surface area to be exposed to molten metal upon immersions, the body portion supporting the U-shaped tube by means of a refractory cement fill; a refractory cement surrounding a portion of the projecting member of the thermocouple unit within the truncated cone-shaped bore and filling the truncated cone-shaped bore; and a refractory foil wrap surrounding the periphery and the end of the cylindrical support tube within the generally cylindrical bore of the protection sleeve; whereby the temperature sensing device may be immersed into a molten metal bath repeatedly while providing an increased number of temperature readings.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3541326 | 1985-11-22 | ||
| DE19853541326 DE3541326A1 (en) | 1985-11-22 | 1985-11-22 | Measuring and/or sampling probe for metal melts |
| US843,436 | 1986-03-24 | ||
| US06/843,436 US4692556A (en) | 1984-06-29 | 1986-03-24 | Repeating temperature sensing immersion probe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1286124C true CA1286124C (en) | 1991-07-16 |
Family
ID=25838092
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000522316A Expired - Lifetime CA1286124C (en) | 1985-11-22 | 1986-11-06 | Repeating temperature sensing immersion probe |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1286124C (en) |
-
1986
- 1986-11-06 CA CA000522316A patent/CA1286124C/en not_active Expired - Lifetime
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |