CA1076710A - Thermocouple element - Google Patents
Thermocouple elementInfo
- Publication number
- CA1076710A CA1076710A CA283,302A CA283302A CA1076710A CA 1076710 A CA1076710 A CA 1076710A CA 283302 A CA283302 A CA 283302A CA 1076710 A CA1076710 A CA 1076710A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- pins
- wires
- thermocouple
- junction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Temperature Or Quantity Of Heat (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The invention relates to an improved high tempera-ture (e.g. up to 1800°C) hot junction element for a thermo-couple circuit which comprises a vitreous silica tube enclosing the thermocouple wires and the hot junction thereof, and having contact elements (by which the wires are connected into the thermocouple circuit) protruding from one end of the tube. The thermocouple wires are loosely located within the tube but are separated by a barrier formed from the tube wall and defining a melt passage extending across the bore of the tube.
The invention also relates to a method of manufac-turing such a hot junction element.
The invention relates to an improved high tempera-ture (e.g. up to 1800°C) hot junction element for a thermo-couple circuit which comprises a vitreous silica tube enclosing the thermocouple wires and the hot junction thereof, and having contact elements (by which the wires are connected into the thermocouple circuit) protruding from one end of the tube. The thermocouple wires are loosely located within the tube but are separated by a barrier formed from the tube wall and defining a melt passage extending across the bore of the tube.
The invention also relates to a method of manufac-turing such a hot junction element.
Description
This invention relates to a hot junction element for a high temperature thermocouple measuring circuit. It is well known that the temperatures of molten metal baths can be determined by a thermocouple measuring circuit, which includes a hot junction element which is dipped into the bath, the element incorporating the dissimilar thermocouple wires which meet at the junction and contact members by which the thermo- -couple wires are electrically connected to the remainder of the measuring circuit. It is conventional to construct such junction elements as cheaply as possible since their service life under the extreme operating conditions is normally not more than a few dips and not infrequently a junction element of this type is used for just one dip and then discarded.
This invention relates to an improved disposable hot junction element which in its preferred embodiments enables reduced quantities of thermocouple wires to be used (and since these are usually made from very expensive metals, a small saving in the quantity used can significantly affect the cost of an element) reduces the response time of the element and reduces the unit cost of the element by reducing the number of reject elements produced.
U.K. Patent Specification 1,022,172 of Thermal Syndicate Limited, filed June 22, 1961 describes a hot junction element for a high temperature thermocouple which comprises a hollow tube of vitreous silica material, a pair of dis-similar thermocouple wires forming a thermocouple junction sealed within the tube and each connected to a different con-tact member extending from an end of the tube.
The junction element described in Specification 1,022,172 leaves the junction of the thermocouple wires exposed and tensions the thermocouple wires within the tube to keep them separated within the tube. This form of con-struction does not lend itself to automatic production .... . .
'''' ' ' ' ' '' ' "
:107~710 techniques, the manufacture being difficult and resulting in a high proportion of unsaleable junction elements, the cost of which adds to the unit cost of the saleable elements.
French Patent Specification 1,600,350 of Meci Materiel Electrique de Controle et Industriel, filed December 31, 1968, describes a hot junction element in which the thermocouple wires are dispose~d loosely within the tube but are separated between the thermocouple junction and the contact members by a dimple formed in the tube wall after the wires have been located therein.
To prevent the wires contacting the hot tube wall while the dimple is being formed, electromagnetic forces are utilized to urge the wires outwardly, away from each other.
However, even with the wires separated there is a risk of the wires being damaged during this dimple-forming operation -resulting in the production of unsaleable elements.
According to one aspect of the invention there is provided a method of manufacturing a hot junction element for a high temperature thermocouple circuit comprising the steps of ~ -forming between the ends of a vitreous silica tube a deformed region which includes a melt passage extending across the tube in said region and which leaves passages within the tube on either side of said region, forming an assembly from two com-pensating pins and two thermocouple wires with the wires elec-trically connected at a junction adjacent one end and each elec-trically connected at the opposite end to a respective pin, inserting the assembly, pins first, into said passages so that the ends of the pins remote from the wires project from one end ~ `
of the tube and the wires, intermediate the junction and the pins, are separated within the tube by said deformed region, securing the pins within the tube adjacent to said one end of the tube and closing the opposite end of the tube to complete the element.
According to a further aspect of the invention a hot junction element comprises a hollow tube of vitreous -~
- - . , . -, silica, a pair of dissimilar thermocouple wires forming a thermocouple junction wit~nthe tube and each connected to a different contact member extending from an end of the tube, the thermocouple wires being disposed loosely within the tube and separated between the junction and the contact members by a barrier means formed from the tube wall and is characteri- ;-zed in that the barrier means is formed, prior to the inser-tion of the wires in the tube, by the wall of a melt passage extending across the bore of the tube.
10The dissimilar thermocouple wires are conveniently very fine wires of metals or alloys of nickel, chromium, aluminium, tungsten, molybdenum, platinum, rhodium or platinum~
rhodium alloys which can be twisted together or welded to form the thermocouple junction. The use of a connecting conducting bridge between the ends of the thermocouple wires at the thermocouple junction is not ruled out.
The contact members may be'spaced-apart pins pro-jecting through the end of the tube, to which the end of the appropriate thermocouple wire is connected (e.'g. crimped or 20 weldedl. The contact members may also be'of dissimilar metals ' (e.g. copper and copper/nickel) to act as compensating leads in a manner well known in the art. Further the contact members may be physically distinguishable one from the other ~as by length or cross-sectional area) to ensure correct polarity connection to the rest of the measuring circuit. By making the deformed region into a melt passage the response time of the junction element is reduced.
One embodiment of hot junction element in accordance with the invention and a method in which it can be'constructed will now be described, by way of example, with reference to the accompanying drawing, in which:-Figure 1 is a side'elevation of the eIectrical com-ponents of the element prior to insertion in the vitreous ,~t~ - 3-... .
,~ ' ' ' ' ', ' 1076~0 silica tube, Figures 2 and 3 are, respectively, a side elevation and an end elevation of the vitreous silica tube used with the components of Figure 1 to make a complete junction element, and Figure 4 is a sectional view of the complete junc-tion element.
Referring to Figure 4, the complete junction element comprises a tube 1 of transparent vitreous silica closed by pinching at 2 and pinched around compensating pins 3 and 4 at the other end. The pins 3 and 4 are slightly flattened over regions-3a and 4a to enhance their securement in the pinched tube.
Thermocouple wires 5 and 6 connect the pins 3 and 4 to a thermocouple junction 7 which is located close to the pinch 2 but within the interior of the tube. Welding is used to bond the wires to each other at the junction 7 and to bond each wire to its pin.
The pins are of different gauge to ensure that the element can only be plugged into its receiving socket (and thus connected into the remainder of the measuring circuit) one way round. A refractory cement 8 fills the lower end of the tube 1 more securely to bond the pins to the tube and to thermally insulate the junctions between the wires and the pins.
To space the wires 5 and 6 apart in the region be-tween the pins and the junction 7, a hole 9 is provided through the tube 1 to define an insulating barrier 9a between -~
the wires 5 and 6.
The element shown in Figure 4 is manufactured from the parts shown in Figures 1 and 2 by lowering the pins 3 and 4 into the tube 1 from above until the junction 7 is disposed just above (or even resting on) the barrier 9a, pinching the _4_ ., ' , . ~.:
tube lightly around the regions 3_ and 4a, injecting the cement 8 into the lower end of the tube and finally pinching the end 2 to close the tube.
The element illustrated in Figure 4 is designed for temperature measurements in the range 500C to 1800C. Pin 3 is of 1.42 mm diameter and is made of copper/nickel alloy, pin 4 is of 1.63 mm diameter and is made of copper, wire 5 is of 0.075 mm diameter platinum and wire 6 of 0.075 mm diameter and is a 13% rhodium/87% platinum alloy. The overall length of the oval cross-section tube 1 is 45 mm and the undistorted bore is 8-9 mm in the direction of the major axis and 2-3 mm in the direction of the minor axis. The hole 9 has a bore of approximately 3mm and the cement 8 (e.g. Plaster of Paris) extends 3 mm beyond the upper ends of the pins 3 and 4.
The hole allows molten metal to come close to the junction 7 and thereby reduces the time taken for the element to record the true temperature of a melt after having been first dipped into the melt.
The volume within the tube may be sealed but a small gas vent can be provided (to reduce pressure rise on dipping) and this may be incorporated in the cement 8.
When the wires 5 and 6 become very fine, welding them to the more robust pins 3 and 4 may pose problems. Crim-ping is an alternative fixing means which can be used.
Although the embodiment illustrated employs a tube 1 of oval cross-section as the starting material this is not essential and other cross-sectional shapes can be employed.
_5_ `"'' , , ` '
This invention relates to an improved disposable hot junction element which in its preferred embodiments enables reduced quantities of thermocouple wires to be used (and since these are usually made from very expensive metals, a small saving in the quantity used can significantly affect the cost of an element) reduces the response time of the element and reduces the unit cost of the element by reducing the number of reject elements produced.
U.K. Patent Specification 1,022,172 of Thermal Syndicate Limited, filed June 22, 1961 describes a hot junction element for a high temperature thermocouple which comprises a hollow tube of vitreous silica material, a pair of dis-similar thermocouple wires forming a thermocouple junction sealed within the tube and each connected to a different con-tact member extending from an end of the tube.
The junction element described in Specification 1,022,172 leaves the junction of the thermocouple wires exposed and tensions the thermocouple wires within the tube to keep them separated within the tube. This form of con-struction does not lend itself to automatic production .... . .
'''' ' ' ' ' '' ' "
:107~710 techniques, the manufacture being difficult and resulting in a high proportion of unsaleable junction elements, the cost of which adds to the unit cost of the saleable elements.
French Patent Specification 1,600,350 of Meci Materiel Electrique de Controle et Industriel, filed December 31, 1968, describes a hot junction element in which the thermocouple wires are dispose~d loosely within the tube but are separated between the thermocouple junction and the contact members by a dimple formed in the tube wall after the wires have been located therein.
To prevent the wires contacting the hot tube wall while the dimple is being formed, electromagnetic forces are utilized to urge the wires outwardly, away from each other.
However, even with the wires separated there is a risk of the wires being damaged during this dimple-forming operation -resulting in the production of unsaleable elements.
According to one aspect of the invention there is provided a method of manufacturing a hot junction element for a high temperature thermocouple circuit comprising the steps of ~ -forming between the ends of a vitreous silica tube a deformed region which includes a melt passage extending across the tube in said region and which leaves passages within the tube on either side of said region, forming an assembly from two com-pensating pins and two thermocouple wires with the wires elec-trically connected at a junction adjacent one end and each elec-trically connected at the opposite end to a respective pin, inserting the assembly, pins first, into said passages so that the ends of the pins remote from the wires project from one end ~ `
of the tube and the wires, intermediate the junction and the pins, are separated within the tube by said deformed region, securing the pins within the tube adjacent to said one end of the tube and closing the opposite end of the tube to complete the element.
According to a further aspect of the invention a hot junction element comprises a hollow tube of vitreous -~
- - . , . -, silica, a pair of dissimilar thermocouple wires forming a thermocouple junction wit~nthe tube and each connected to a different contact member extending from an end of the tube, the thermocouple wires being disposed loosely within the tube and separated between the junction and the contact members by a barrier means formed from the tube wall and is characteri- ;-zed in that the barrier means is formed, prior to the inser-tion of the wires in the tube, by the wall of a melt passage extending across the bore of the tube.
10The dissimilar thermocouple wires are conveniently very fine wires of metals or alloys of nickel, chromium, aluminium, tungsten, molybdenum, platinum, rhodium or platinum~
rhodium alloys which can be twisted together or welded to form the thermocouple junction. The use of a connecting conducting bridge between the ends of the thermocouple wires at the thermocouple junction is not ruled out.
The contact members may be'spaced-apart pins pro-jecting through the end of the tube, to which the end of the appropriate thermocouple wire is connected (e.'g. crimped or 20 weldedl. The contact members may also be'of dissimilar metals ' (e.g. copper and copper/nickel) to act as compensating leads in a manner well known in the art. Further the contact members may be physically distinguishable one from the other ~as by length or cross-sectional area) to ensure correct polarity connection to the rest of the measuring circuit. By making the deformed region into a melt passage the response time of the junction element is reduced.
One embodiment of hot junction element in accordance with the invention and a method in which it can be'constructed will now be described, by way of example, with reference to the accompanying drawing, in which:-Figure 1 is a side'elevation of the eIectrical com-ponents of the element prior to insertion in the vitreous ,~t~ - 3-... .
,~ ' ' ' ' ', ' 1076~0 silica tube, Figures 2 and 3 are, respectively, a side elevation and an end elevation of the vitreous silica tube used with the components of Figure 1 to make a complete junction element, and Figure 4 is a sectional view of the complete junc-tion element.
Referring to Figure 4, the complete junction element comprises a tube 1 of transparent vitreous silica closed by pinching at 2 and pinched around compensating pins 3 and 4 at the other end. The pins 3 and 4 are slightly flattened over regions-3a and 4a to enhance their securement in the pinched tube.
Thermocouple wires 5 and 6 connect the pins 3 and 4 to a thermocouple junction 7 which is located close to the pinch 2 but within the interior of the tube. Welding is used to bond the wires to each other at the junction 7 and to bond each wire to its pin.
The pins are of different gauge to ensure that the element can only be plugged into its receiving socket (and thus connected into the remainder of the measuring circuit) one way round. A refractory cement 8 fills the lower end of the tube 1 more securely to bond the pins to the tube and to thermally insulate the junctions between the wires and the pins.
To space the wires 5 and 6 apart in the region be-tween the pins and the junction 7, a hole 9 is provided through the tube 1 to define an insulating barrier 9a between -~
the wires 5 and 6.
The element shown in Figure 4 is manufactured from the parts shown in Figures 1 and 2 by lowering the pins 3 and 4 into the tube 1 from above until the junction 7 is disposed just above (or even resting on) the barrier 9a, pinching the _4_ ., ' , . ~.:
tube lightly around the regions 3_ and 4a, injecting the cement 8 into the lower end of the tube and finally pinching the end 2 to close the tube.
The element illustrated in Figure 4 is designed for temperature measurements in the range 500C to 1800C. Pin 3 is of 1.42 mm diameter and is made of copper/nickel alloy, pin 4 is of 1.63 mm diameter and is made of copper, wire 5 is of 0.075 mm diameter platinum and wire 6 of 0.075 mm diameter and is a 13% rhodium/87% platinum alloy. The overall length of the oval cross-section tube 1 is 45 mm and the undistorted bore is 8-9 mm in the direction of the major axis and 2-3 mm in the direction of the minor axis. The hole 9 has a bore of approximately 3mm and the cement 8 (e.g. Plaster of Paris) extends 3 mm beyond the upper ends of the pins 3 and 4.
The hole allows molten metal to come close to the junction 7 and thereby reduces the time taken for the element to record the true temperature of a melt after having been first dipped into the melt.
The volume within the tube may be sealed but a small gas vent can be provided (to reduce pressure rise on dipping) and this may be incorporated in the cement 8.
When the wires 5 and 6 become very fine, welding them to the more robust pins 3 and 4 may pose problems. Crim-ping is an alternative fixing means which can be used.
Although the embodiment illustrated employs a tube 1 of oval cross-section as the starting material this is not essential and other cross-sectional shapes can be employed.
_5_ `"'' , , ` '
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A hot junction element for a high temperature thermocouple comprising a hollow tube of vitreous silica, a pair of dissimilar thermocouple wires forming a thermocouple junction within the tube and each connected to a different contact member extending from an end of the tube, the thermo-couple wires being disposed loosely within the tube and separated between the junction and the contact members by a barrier means formed from the tube wall, wherein the barrier means is formed, prior to the insertion of the wires in the tube, by the wall of a melt passage extending across the bore of the tube.
2. A hot junction element as claimed in Claim 1, in which the contact members are pins pinched into the tube.
3. A hot junction element as claimed in Claim 2, in which the pins are of dissimilar metals and act as compensating leads for the thermocouple wires.
4. A hot junction element as claimed in Claim 3, in which the pins are physically distinguishable one from the other.
5. A method of manufacturing a hot junction element for a high temperature thermocouple circuit comprising the steps of forming between the ends of a vitreous silica tube a deformed region which includes a melt passage extending across the tube in said region and which leaves passages within the tube on either side of said region, forming an assembly from two compensating pins and two thermocouple wires with the wires electrically connected at a junction adjacent one end and each electrically connected at the opposite end to a respective pin, inserting the assembly, pins first, into said passages so that the ends of the pins remote from the wires project from one end of the tube and the wires, intermediate the junction and the pins are separated within the tube by said deformed region, securing the pins within the tube adjacent to said one end of the tube and closing the opposite end of the tube to com-plete the element.
6. A method as claimed in Claim 5, in which the pins are secured in place by pinching the tube around them and allowing a refractory cement to set in the tube around the pins and around a few millimetres of the wires closest to the pins.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3077876A GB1585077A (en) | 1976-07-23 | 1976-07-23 | Thermocouple element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1076710A true CA1076710A (en) | 1980-04-29 |
Family
ID=10313005
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA283,302A Expired CA1076710A (en) | 1976-07-23 | 1977-07-21 | Thermocouple element |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5315180A (en) |
| CA (1) | CA1076710A (en) |
| DE (1) | DE2732984A1 (en) |
| FR (1) | FR2359407A1 (en) |
| GB (1) | GB1585077A (en) |
| IT (1) | IT1083028B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013091115A1 (en) * | 2011-12-23 | 2013-06-27 | Bruce Wilnechenko | Temperature probe for a temperature control unit |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2508236A2 (en) * | 1981-06-17 | 1982-12-24 | Mecilec Sa | THERMO-ELECTRIC TORQUE ELEMENT |
| GB2129210A (en) * | 1982-10-18 | 1984-05-10 | Atomic Energy Authority Uk | Thermocouples |
| DE3528161C1 (en) * | 1985-08-06 | 1986-10-23 | Degussa Ag, 6000 Frankfurt | Thermocouple for measuring temperatures in vacuum furnaces |
| JP2578610Y2 (en) * | 1992-05-26 | 1998-08-13 | 耕路 浅野 | Prefabricated tombstone |
| JP2858220B2 (en) * | 1994-09-13 | 1999-02-17 | 川惣電機工業株式会社 | Temperature sensor element in temperature measuring device |
| DE19715080C1 (en) * | 1997-04-11 | 1998-10-15 | Hartmann & Braun Gmbh & Co Kg | Temperature sensor for remote operation employing thermocouple |
| DE102012105547A1 (en) * | 2012-06-26 | 2014-01-16 | Endress + Hauser Wetzer Gmbh + Co. Kg | Temperature measuring device, measuring element for a temperature measuring device and method for producing the temperature measuring device |
-
1976
- 1976-07-23 GB GB3077876A patent/GB1585077A/en not_active Expired
-
1977
- 1977-07-21 DE DE19772732984 patent/DE2732984A1/en not_active Withdrawn
- 1977-07-21 CA CA283,302A patent/CA1076710A/en not_active Expired
- 1977-07-22 IT IT6871077A patent/IT1083028B/en active
- 1977-07-22 JP JP8822977A patent/JPS5315180A/en active Pending
- 1977-07-25 FR FR7722724A patent/FR2359407A1/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013091115A1 (en) * | 2011-12-23 | 2013-06-27 | Bruce Wilnechenko | Temperature probe for a temperature control unit |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2732984A1 (en) | 1978-01-26 |
| GB1585077A (en) | 1981-02-25 |
| FR2359407A1 (en) | 1978-02-17 |
| IT1083028B (en) | 1985-05-21 |
| FR2359407B1 (en) | 1981-02-27 |
| JPS5315180A (en) | 1978-02-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |