JP2014178127A - Method for sealing tip of sheath thermocouple by welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for automatically performing sealing by welding using a simple device without an operator rich in experience and skilled in welding, in a working method for sealing a metal sheath tip of a sheath thermocouple by welding.SOLUTION: A method comprises: approximately vertically fixing a metal sheath 2 having thermocouple elements 5 and 6 and an inorganic insulation powder 4 placed therein, with a tip part directed upward, by one clamp 101b and 102b using an existing automatic tube welder having a welding head 105; placing a spherical solid metal ball 8 on an upper end thereof; fixing a hollow bar 91 by another clamp 101a and 102a in the state that an inserted presser rod 93 presses the metal ball 8 against the metal sheath 2 from above; and sealing the tip by welding after starting the automatic tube welder.

Description

  The present invention relates to a sheathed thermocouple that is generally used as an industrial temperature sensor, and more specifically to sealing a metal sheath tip in the process of manufacturing a sheathed thermocouple.

  Sheath thermocouples are generally widely used as industrial thermometer sensors. The structure is as shown in FIGS. 4 and 5. FIG. 4 is an axial sectional view, and FIG. 5 is a BB sectional view of FIG.

  In the sheath thermocouple 1, an inorganic insulating material powder 4 such as magnesia or alumina is filled in a metal sheath 2, and a pair of thermocouple wires (a plus-side thermocouple wire 5 and a minus-side thermocouple wire 6) are filled therein. ) Is housed. As is well known, the tips of the thermocouple wires are joined to form a temperature measuring point 7, and the temperature at the temperature measuring point 7 becomes the output temperature of the sheath thermocouple.

  The distal end of the metal sheath 2 is hermetically sealed by the weld sealing part 3. The terminal opposite to the tip is not shown, but is hermetically sealed with a sealing material such as epoxy, and the thermocouple wires 5 and 6 are exposed to the outside through this seal. The inside of the metal sheath 2 is cut off from the outside by the seal of this end and the weld seal 3 at the tip, and this cut-off occurs when the insulation is lowered due to moisture absorption of the inorganic insulating powder 4 or when it is used at a high temperature. The sheath thermocouple 1 is indispensable in order to prevent the occurrence of temperature measurement errors due to oxidation of the internal thermocouple wires 5 and 6.

  4 shows the sheath thermocouple 1 that accommodates a pair of thermocouple strands, but accommodates a plurality of pairs of thermocouple strands, and joins the tips of each pair to provide a plurality of temperature measuring points. There is also a formed sheath thermocouple. Hereinafter, a sheathed thermocouple containing a pair of thermocouple wires will be described, but the same applies to a case where a plurality of thermocouple wires are used.

  Next, the manufacturing procedure of the tip sealing portion of the sheath thermocouple will be described. FIG. 6 is a view showing a manufacturing procedure of the tip sealing portion of the sheath thermocouple.

  As shown in FIG. 6 (a), the metal sheath 2 is filled with a plus-side thermocouple element 5, a minus-side thermocouple element 6, and a temperature measuring point 7 where the ends of both elements are joined by welding or the like. Then, it is processed into a state in which the inorganic insulating material powder 4 is present, and the tip of the metal sheath 2 is sealed by welding as shown in FIG. Then, normally, the surplus produced by welding is removed by polishing using a belter or the like, and the outer diameter of the sealed tip is adjusted to the outer diameter of the metal sheath 2 as shown in FIG. By this polishing, if there is a gap exceeding at least the outer diameter of the metal sheath 2, the sheath thermocouple 1 can be inserted to measure the temperature.

  As described above, the procedure shown in FIG. 6 is performed for almost all of the sheath sealing portions of the sheath thermocouples. However, the method of welding and sealing the distal end of the metal sheath 2 shown in FIG. Various things are considered and implemented.

  Patent Document 1 discloses a method in which a spherical or plate-like lid is placed at the distal end of a metal sheath, and a weld is formed at the boundary between the lid and the metal sheath distal end. Then, a method of melting and filling a welding rod directly at the tip of the metal sheath and sealing and a method of driving a plug-like lid piece into the tip of the metal sheath and welding and sealing the tip of the metal sheath and the lid piece are shown. Has been. Further, in Patent Document 3, the diameter of the metal sheath tip is reduced as it goes to the tip by forging or the like to reduce the end opening area, and then the welding rod is melted and sealed in the reduced opening by arc welding. It shows how to stop. Furthermore, Patent Document 4 discloses a method in which the tip portion of a metal sheath is melted by TIG welding or the like that does not use a welding rod, and the tip opening is sealed with this melt.

Microfilm of Japanese Utility Model No. 49-110891 (Japanese Utility Model Publication No. 51-38475) JP-A-53-109239 JP 55-33689 A JP 2007-187654 A

  As disclosed in Patent Documents 1 to 4, there are various methods for welding and sealing the metal sheath tip of the sheath thermocouple. The conventional methods are roughly classified on the basis of the description and drawings of Patent Documents 1 to 4. A method of melting and filling a welding rod in a tip opening of a metal sheath and sealing it, and welding a lid to the tip opening of the metal sheath all around. And the method of melting the tip of the metal sheath and sealing the tip opening with this melt.

  The weld seal at the tip of the metal sheath needs to be hermetically sealed as described above. In order to satisfy this condition, a welding operation in which an appropriate amount of the welding rod is melted and filled at the tip opening is filled in accordance with the conventional method. It is difficult for beginners of welding to gain experience by welding the entire circumference of the sheath and lid, and also performing the welding operation of melting the tip of the metal sheath within an appropriate range and sealing it with the melt. There was a problem that required a worker who was proficient in welding.

  The conventional method is also used to make a device that automatically welds and seals the tip of the metal sheath, with precise positioning of the welding rod and welding electrode, precise control of these non-simple movements, the amount of closed melt, In order to realize position control, etc., there is a problem that it is necessary to use a large-scale apparatus as a whole, although the degree depends on the welding sealing method.

The present invention has been made in view of the difficulty of work in such a conventional method of sealing and sealing a sheath thermocouple tip, and does not require an operator who is experienced in welding and has a simple apparatus. It is an object to provide a method for automatically performing welding sealing.

To achieve the above object, according to the first aspect of the present invention, a metal sheath is filled with at least one pair of thermocouple wires in which tips are joined and temperature measuring points are formed. In a sheathed thermocouple that is housed in a metal sheath with an inorganic insulating material powder interposed and the tip of the metal sheath is sealed by a weld seal, the tip of the weld seal at the tip is connected by two clamps connected to the ground. The sheath thermoelectric generator is used with an existing automatic tube welder that automatically welds and connects the two tubes by rotating the TIG welding electrode around the butting position of the two tubes that are fixed together. It is a welding sealing method at the tip,
Thermocouple wire and inorganic insulating material powder are accommodated, and the end surface of the inorganic insulating material powder has an opening at the tip of the metal sheath formed into a spherical shape having a diameter substantially the same as the diameter of the metal sphere described later. A metal sphere mounting step in which a solid sphere-shaped metal sphere having a diameter substantially the same as the outer diameter of the metal sheath is placed in the opening at the tip of the metal sheath. ,
A holding rod made of a material having a melting point higher than the melting point of the metal sphere is inserted into a hollow rod with a lid at the rear end, and the holding rod is inserted through the lid of the hollow rod with a hollow end and a spring. It is connected, its tip protrudes outside from the tip opening of the hollow rod, and the projection length is limited to a predetermined range by the stopper mechanism, at least from the hollow rod and its lid, presser bar, spring and stopper mechanism In the state where the metal ball placed on the tip opening portion of the metal sheath in the metal ball placing step is pressed against the metal sheath from above by the spring force of the jig holding the metal ball holding jig, A metal ball pressing step for fixing the hollow rod with the other one of the clamps;
And a contact welding process in which the TIG welding electrode rotates around the contact portion between the metal sheath and the metal sphere and welds the contact portion between the metal sheath and the metal sphere all around,
In the contact part welding process, in the metal ball holding jig, since the protruding length of the holding bar from the tip end of the hollow bar is limited to a predetermined range by the stopper mechanism, the melting of the metal ball has started. Due to the flat shape, the contact between the presser bar and the metal ball is lost, and thereafter, the contact portion between the metal sheath and the metal ball is welded without contact.

According to the present invention, a metal sheath containing a thermocouple wire and inorganic insulating material powder is fixed with a single clamp substantially vertically with the tip portion on the upper side, and a spherical solid metal sphere is formed on the upper end thereof. Next, after fixing the hollow rod with the other clamp, with the inserted pressing rod pressed the metal ball against the metal sheath from above, start the tube automatic welder to Since sealing by welding sealing is possible, there is no difficult work, and there is an effect that the work can be surely performed even if it is not a person skilled in the welding required in the past. In addition, the existing automatic tube welders that are commercially available are generally small in size that can be carried on the tube installation site, and by using this, it is possible to perform welding sealing without requiring a large-scale device.
Moreover, the metal sphere can be stably placed on the tip of the metal sheath by forming the end face of the tip of the inorganic insulating material powder into a spherical shape having a diameter substantially the same as that of the metal sphere. This inorganic insulating material powder is formed by rotating the end surface of the inorganic insulating material powder filled up to the tip of the metal sheath from the tip of the metal sheath to the tip hemisphere while rotating a semispherical pin whose tip is substantially the same diameter as the metal sphere. This is possible by inserting until the metal sheath comes into contact with the metal sheath, which is an easy operation and can be realized as a simple device that combines rotation and positioning even if it is automated.
Furthermore, since the presser bar is made of a material having a melting point higher than that of the metal sphere, the presser bar does not melt during welding. In addition, at the time of welding, after melting starts on a part of the metal ball and the shape becomes flat, the contact between the metal ball and the presser bar is limited by the limit of the protruding length from the hollow bar at the tip of the presser bar by the stopper mechanism. Therefore, there is no possibility that the molten metal ball adheres to the presser bar.
As described above, the present invention does not require difficult operations such as simultaneous handling of two welding electrodes and a welding rod, circumferential welding, or sealing with a molten welding rod or sheath in the present invention. Even if it is not an expert, reliable welding sealing can be easily performed with a small apparatus.

  According to the second aspect of the present invention, there is provided a method for welding and sealing a sheath thermocouple tip according to the first aspect, wherein the stopper mechanism of the metal ball pressing jig is provided on the side surface of the pressing bar. One or a plurality of rod-shaped protrusions provided at right angles to the axial direction, and stopper openings provided on the side surfaces of the hollow rods corresponding to the protrusions, the protrusions projecting from the stopper openings to the outside Therefore, the length of the presser bar protruding from the tip opening of the hollow bar is limited to a range determined by the axial length of the stopper opening and the thickness of the bar-like protrusion.

  According to the present invention, the stopper mechanism of the metal ball pressing jig includes one or more bar-shaped protrusions provided on the side surface of the pressing bar at right angles to the axial direction of the pressing bar, and a hollow bar corresponding to each protrusion. Therefore, the stopper mechanism can be easily realized as a simple mechanism.

  According to a third aspect of the present invention, there is provided a method for welding and sealing a sheath thermocouple tip according to the first or second aspect, wherein the material of the presser bar is ceramics. It is.

  According to the present invention, the presser bar is made of ceramic having a melting point higher than that of the metal sphere, so that it does not melt during welding. In addition, ceramics have a higher melting point than metals such as SUS that are widely used industrially at low cost, and there are economic advantages compared to using a metal having a higher melting point than the press bar.

  According to a fourth aspect of the present invention, there is provided a method for welding and sealing a sheath thermocouple tip according to any one of the first to third aspects, wherein the metal sphere is made of the same material as the metal sheath. It is characterized by being.

  In a sheathed thermocouple, if the material of the metal sphere used as the material is different from that of the metal sheath, normal TIG welding may be difficult due to dissimilar material welding. Since the service life is governed by the material with lower durability, there is no advantage over using different materials. According to the present invention, since the material of the metal sphere is the same material as that of the metal sheath, there is no waste associated with such welding difficulty and durability.

  According to a fifth aspect of the present invention, there is provided a method for welding and sealing a sheath thermocouple tip according to any one of the first to fourth aspects, wherein the diameter of the metal sphere is 0 of the outer diameter of the metal sheath. It is characterized by a magnification of 0.8 times to 1.2 times.

When the metal sheath tip is welded and sealed, as shown in FIG. 6 (c), the welded portion is removed by polishing, and the outer diameter of the sealed portion is adjusted to the outer diameter of the metal sheath. If the diameter is too large compared to the outer diameter of the metal sheath, the polishing operation increases. Further, if the diameter of the metal sphere is too small compared to the outer diameter of the metal sheath, the welding depth may become shallow and the mechanical strength may be insufficient. According to the present invention, since the diameter of the metal sphere is 0.8 to 1.2 times the outer diameter of the metal sheath, there is no increase in polishing work and insufficient mechanical strength.

  According to the present invention, there is no need for difficult work such as simultaneous handling of two welding electrodes and a welding rod, circumferential welding, or sealing work with a molten welding rod or sheath, which has been necessary in the past. Even if it is not, welding sealing can be performed automatically and reliably with a small and simple device.

It is a perspective view which shows an example of the head part external shape of a commercially available tube automatic welder. It is sectional drawing which shows an example of the main components structure of the head part of a commercially available tube automatic welder. It is a figure explaining the work procedure of the welding sealing of the sheath thermocouple tip by this invention. It is an axial sectional view of a sheath thermocouple. It is a figure which shows the AA cross section of FIG. 3, and the BB cross section of FIG. It is a figure which shows the manufacture procedure of a sheath thermocouple front-end | tip sealing part.

Hereinafter, an embodiment of a method for welding and sealing a sheath thermocouple tip according to the present invention will be described with reference to the drawings.
First, a commercially available tube automatic welder used in this method will be described.

The tube automatic welder used in this method is a TIG welding electrode that rotates around the butting position of two welded tubes that are fixed at the tip by two clamps connected to ground. Two tubes are automatically welded and connected, and many companies are commercially available. For example, international application WO 2008/3339 is published as a patent.

FIG. 1 is a perspective view showing an example of the outer shape of the head portion of such a commercially available automatic tube welder. The welded tube is indicated by a broken line.
As shown in FIG. 1, there is a head portion 10 at the tip of an arm 11 of an automatic tube welder, and the head portion 10 is provided with a welding head 105 sandwiched between two clamps 101a, 102a and 101b, 102b. ing. Each of the clamps 101a and 102a and the clamps 101b and 102b has an opening for fixing the welded tube 12a and the welded tube 12b at the center, and each clamp is divided into two by a line passing through the approximate center of the opening. 101a and 101b can be opened and closed with pivots 103a and 103b as rotation axes, respectively. The state in which the clamp 101a is opened is as shown by a dotted line in FIG.

  When fixing the welded tube 12a to the clamps 101a and 102a, remove the set screw 104a, open the clamp 101a, place the welded tube 12a in a predetermined position, then close the clamp 101a and tighten the set screw 104a. The welded tube 12a is fixed by a central opening having a diameter slightly smaller than the welded tube 12a. This is the same as fixing the welded tube 12b with the clamps 101b and 102b.

  FIG. 1 shows an example of an automatic tube welding machine, in which there is a welding head sandwiched between two clamps, and the clamp is divided into two by a line passing through the center of the center opening, The tip side can be opened and closed, and the opening fixes the welded tube when closed, which is common to almost all commercially available automatic tube welders. It is also common to be small and portable at the site of tube placement.

  FIG. 2 is a cross-sectional view showing an example of the configuration of main components of the head unit 10 of the automatic tube welder. In addition to this, there is usually a line for supplying seal gas during welding, but it is omitted. The two clamps 101a, 102a and 101b, 102b are arranged in the welding head 105 around the butting position of the two welded tubes 12a and 12b, which are fixed with their tips butted at the same height as the TIG welding electrode 106. As the TIG welding electrode 106 rotates, the butt portion is welded all around.

  When the TIG welding electrode 106 rotates around the welded tube butting position, the electrode rotating drive wheel 107 that is connected to this electrode and also serves as the electric path for the TIG welding current rotates inside the electrode rotating drive wheel frame 108. Thus, the mechanism for rotating the electrode rotation drive wheel 107 is provided in the arm 11 of the automatic tube welder of FIG. The construction of such a welding head is also generally common to commercially available automatic tube welders.

  In this embodiment, the existing sheathed automatic tube welder described above is used to weld and seal the distal end portion of the metal sheath of the sheath thermocouple. A procedure for welding and sealing the metal sheath tip will be described below with reference to FIG. Here, FIG. 3 is a longitudinal sectional view for explaining the working procedure of the tip welding sealing of the sheath thermocouple 1 according to the present invention, and the shape of the AA section of FIG. 3 is the same as that shown in FIG. . Moreover, since the code | symbol common with another figure represents the same thing, description may be abbreviate | omitted below.

  As shown in FIG. 3, a pair of thermocouple strands (plus-side thermocouple strand 5 and minus-side thermocouple strand 6) whose tips are joined to form a temperature measuring point 7 are inside the metal sheath 2. A shape in which the tip end face of the inorganic insulating material powder 4 is recessed into a spherical shape having substantially the same diameter as the diameter of the metal ball 8 placed on the metal sheath 2 with the inorganic insulating material powder 4 filled in 3 (a) processed in FIG. 3 (a) is installed approximately vertically with the tip of the metal sheath 2 as shown in FIG. 3 (b), and automatic tube welding is performed as shown in FIG. 3 (b-1). The upper end of the metal sheath 2 is fixed at the same height as the TIG electrode 106 by the clamps 101 b and 102 b of the machine head unit 10.

  Thereafter, a solid sphere-shaped metal ball 8 made of the same material as the metal sheath 2 and having the same diameter as the outer diameter of the metal sheath 2 is placed on the front end of the metal sheath 2 at the approximate center of the upper surface of the metal sheath 2. Since the tip end surface of the inorganic insulating material powder 4 is processed into a spherical shape having a diameter substantially the same as the diameter of the metal sphere 8, the metal sphere 8 can be stably placed on the upper surface of the metal sheath 2. Yes (metal ball placement process).

  Subsequently, the metal ball pressing jig 9 is fixed by the upper clamps 101a and 102a as shown in FIG.

  The metal ball holding jig 9 is made of a ceramic having a melting point higher than that of the metal ball 8 on a hollow rod 91 (hereinafter referred to as a cylindrical frame in this embodiment) having a cylindrical frame shape and a rear end covered. Is inserted, and the rear end of the presser bar 93 and the lid of the rear end of the cylindrical frame 91 are connected via a coil spring 92. The front end of the presser bar 93 protrudes outward from the front end of the cylindrical frame 91, and the protruding length of the presser bar 93 includes two bar-shaped protrusions 94 a and 94 b provided at right angles to the axial direction of the presser bar 93. It is limited to a certain range by a stopper mechanism that protrudes to the outside from the stopper openings 95a and 95b corresponding to the protrusions provided on the surface. That is, the state in which the protrusions 94a and 94b are in contact with the upper ends of the stopper openings 95a and 95b is the shortest protrusion length, and the state in which the protrusions 94a and 94b are in contact with the lower ends of the stopper openings 95a and 95b is the protrusion length. In this state, the protrusion length is limited to a range determined by the axial length of the stopper openings 95a and 95b and the thickness of the rod-like protrusions 94a and 94b. As described above, the metal ball pressing jig 9 of the present embodiment includes at least a cylindrical frame 91 with one end covered, a columnar pressing bar 93, a coil spring 92, and a bar-shaped protrusion provided on the pressing bar 93. 94 and 94b and a stopper mechanism comprising stopper openings 95a and 95b provided in the cylindrical frame 91. Each of the rod-shaped protrusions 94a and 94b is attached by cutting a male screw at one end thereof, passing it through the stopper openings 95a and 95b from the outside, and screwing into a female screw previously cut by the holding rod 93.

  The metal ball pressing jig 9 is fixed by the clamps 101a and 102a in a state where the pressing bar 93 presses the metal ball 8 against the metal sheath 2 from above (metal ball pressing step).

  Next, when automatic welding of the automatic tube welder is started, the TIG welding electrode 106 circulates around the contact portion between the metal sheath 2 and the metal ball 8, and these two are welded all around (contact portion welding step).

  The presser bar 93 is made of a ceramic having a melting point higher than that of the metal ball 8. For this reason, it does not melt at the time of welding. In addition, at the time of welding, after melting starts on a part of the metal ball 8 and the shape becomes flat, as shown in FIG. Since the protrusion length from the cylindrical frame 91 at the tip of the presser bar 93 is limited, the contact between the metal ball 8 and the presser bar 93 is eliminated, and there is no possibility that the molten metal ball 8 adheres to the presser bar 93. Here, the ceramic used as the material of the presser bar 93 has a higher melting point than a metal such as SUS widely used industrially at a low cost, and has an economic advantage compared to the use of a high melting point metal. In addition, illustration of the tube automatic welder head part is abbreviate | omitted in FIG.3 (b-2).

  Subsequently, the surplus generated by the above-described TIG welding is removed by polishing with a belter or the like, and the outer diameter of the weld sealing portion 3 is adjusted to the outer diameter of the metal sheath 2 as shown in FIG. End processing of the sheath thermocouple 1 is completed.

  As described above, the present embodiment does not require difficult work such as simultaneous handling of two welding electrodes and a welding rod, circumferential welding, or sealing work with a molten welding rod or sheath, which has been necessary in the past. In addition, reliable welding sealing is easily possible.

  The end opposite to the tip of the sheath thermocouple 1 is hermetically sealed with a sealing material such as epoxy, and the thermocouple wires 5 and 6 are exposed to the outside through the seal. The inside of the metal sheath 2 is cut off from the outside by this seal and the weld seal 3 at the tip, and the insulation is lowered due to moisture absorption of the inorganic insulating material powder 4 and the thermocouple wires 5 and 6 are oxidized when used at high temperatures. Prevents temperature measurement errors from occurring. The terminal portion of the sheath thermocouple according to the present embodiment is the same as the conventional one, and is not directly related to the present embodiment, so that a detailed description thereof will be omitted.

  The solid metal ball 8 can be manufactured from a bar by existing manufacturing technology for producing bearing balls, pachinko balls, etc., and the economic impact of using the metal balls is limited.

  As specific examples of the material and dimensions of the sheath thermocouple 1 according to the present embodiment, the material of the metal sheath 2 is SUS316, the inner diameter is 2.4 mm, the outer diameter is 3.2 mm, the material of the metal ball 8 is SUS316, and the diameter is The material of 3.2 mm and the material of the inorganic insulating material powder 4 is magnesia.

  Note that the materials and dimensions of the metal sheath 2 and the metal sphere 8 are not limited to those described above. In the present embodiment, the thermocouple element is described as having a single pair, but the same applies to a plurality of pairs. Applicable to.

  However, if the material of the metal ball 8 is different from that of the metal sheath 2, it may be difficult to perform normal TIG welding because of dissimilar material welding, and even if welding is possible, the service life of the sheath thermocouple Is controlled by the material having lower durability, and therefore it is less meaningful to make the material of the metal sphere 8 different from that of the metal sheath 2, so it is desirable to use the same material.

  As for the size of the metal sphere 8, a diameter equivalent to the outer diameter of the metal sheath 2 is necessary, but if it is too large, the polishing operation from FIG. 3 (b-2) to FIG. 3 (c) is increased. The diameter of the metal sphere 8 is desirably 1.2 times or less of the outer diameter of the metal sheath 2, and is desirably 0.8 times or more in order to ensure the welding depth. In addition, the polishing operation is performed in order to make it possible to measure the temperature by inserting the sheath thermocouple 1 if there is a gap exceeding at least the outer diameter of the metal sheath 2, but there is no such requirement. This polishing is unnecessary.

  Furthermore, the spring 92 is not limited to a coil spring, and may be a plate spring, an air spring, or the like. Also, for the metal ball pressing jig 9, the shape of the cylindrical frame 91 is not limited to this, What is necessary is just the shape of the hollow stick | rod, and the shape of the holding | maintenance stick | rod 93 is not restricted to a column shape, What is necessary is just a rod-shaped thing which can be inserted in the said hollow stick | rod. Moreover, the stopper mechanism provided in this is not a combination of the two protrusions 94a and 94b and the two stopper openings 95a and 95b, as long as the movement range of the tip of the presser bar 93 can be limited to a certain range. Good.

(Application to other fields)
Micro heaters and sheath heaters that are widely used as industrial heaters have a structure similar to sheath thermocouples as described later, so this is used to weld and seal the metal sheath tip of micro heaters and sheath heaters. By applying the weld seal of the metal sheath tip in the form, the same effect as the above-described sheath thermocouple can be obtained.

  Microheaters and sheath heaters are those in which an electric resistance wire serving as a heating wire is contained in a metal sheath with an inorganic insulating material powder. Generally, the heating wire of a microheater is a straight wire, whereas the heating wire is a heating wire. A sheath heater is formed by increasing the heat generation amount by spiraling.

  In microheaters and sheathed heaters, when the electrical resistance wire is reciprocated in the same manner as the thermocouple wire of the sheath thermocouple in the metal sheath, it is sealed by welding at the tip of the metal sheath as in the case of the sheath thermocouple. The metal sheath is shut off from the outside by sealing and a sealing mechanism through which the lead wire for supplying electricity to the heating wire at the end is penetrated, insulation deterioration due to moisture absorption of the inorganic insulating material powder, disconnection due to oxidation of the heating wire Etc. are prevented.

  By applying the weld seal at the tip of the metal sheath of the sheath thermocouple of the present embodiment to the weld seal at the tip of the metal sheath of the microheater and sheath heater, work by a skilled person that has been conventionally required is unnecessary. can do.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Sheath thermocouple 2 Metal sheath 3 Welding seal part 4 Inorganic insulating material powder 5 Positive side thermocouple element 6 Negative side thermocouple element 7 Temperature measuring point 8 Metal ball 9 Metal ball holding jig 91 There is a lid on one side Cylindrical frame 92 Coil spring 93 Presser bar 94 Protrusion 95 Stopper opening 10 Head of automatic tube welder 11 Automatic tube welder arm 12 Welded tube 101 Clamp (fixed side)
102 Clamp (movable side)
103 Pivot 104 Set Screw 105 Welding Head 106 Tig Welding Electrode 107: Electrode Rotation Drive Wheel 108: Electrode Rotation Drive Wheel Frame (Suffixes a and b in 101 to 104 distinguish two clamps, and 12 suffixes a and b Is for distinguishing two welded tubes fixed by two clamps, respectively, and suffixes a and b of 94 and 95 are for distinguishing two pairs of protrusions and stopper openings. )

The present invention has been made in view of the difficulty of work in such a conventional method of sealing and sealing a sheath thermocouple tip, and does not require an operator who is experienced in welding and has a simple apparatus. It is an object to provide a method for automatically performing welding sealing.

To achieve the above object, according to the first aspect of the present invention, a metal sheath is filled with at least one pair of thermocouple wires in which tips are joined and temperature measuring points are formed. In a sheathed thermocouple that is housed in a metal sheath with an inorganic insulating material powder interposed and the tip of the metal sheath is sealed by a weld seal, the tip of the weld seal at the tip is connected by two clamps connected to the ground. The sheath thermoelectric generator is used with an existing automatic tube welder that automatically welds and connects the two tubes by rotating the TIG welding electrode around the butting position of the two tubes that are fixed together. It is a welding sealing method at the tip,
Thermocouple wire and inorganic insulating material powder are accommodated, and the end surface of the inorganic insulating material powder has an opening at the tip of the metal sheath formed into a spherical shape having a diameter substantially the same as the diameter of the metal sphere described later. A metal sphere mounting step in which a solid sphere-shaped metal sphere having a diameter substantially the same as the outer diameter of the metal sheath is placed in the opening at the tip of the metal sheath. ,
A holding rod made of a material having a melting point higher than the melting point of the metal sphere is inserted into a hollow rod with a lid at the rear end, and the holding rod is inserted through the lid of the hollow rod with a hollow end and a spring. It is connected, its tip protrudes outside from the tip opening of the hollow rod, and the projection length is limited to a predetermined range by the stopper mechanism, at least from the hollow rod and its lid, presser bar, spring and stopper mechanism In the state where the metal ball placed on the tip opening portion of the metal sheath in the metal ball placing step is pressed against the metal sheath from above by the spring force of the jig holding the metal ball holding jig, A metal ball pressing step for fixing the hollow rod with the other one of the clamps;
Subsequently , a TIG welding electrode rotates around the contact portion between the metal sheath and the metal sphere, and a contact portion welding step for welding the entire circumference of the contact portion between the metal sheath and the metal sphere,
In the contact part welding process, in the metal ball holding jig, since the protruding length of the holding bar from the tip end of the hollow bar is limited to a predetermined range by the stopper mechanism, the melting of the metal ball has started. Due to the flat shape, the contact between the presser bar and the metal ball is lost, and thereafter, the contact portion between the metal sheath and the metal ball is welded without contact.

When the metal sheath tip is welded and sealed, as shown in FIG. 6 (c), the welded portion is removed by polishing, and the outer diameter of the sealed portion is adjusted to the outer diameter of the metal sheath. If the diameter is too large compared to the outer diameter of the metal sheath, the polishing operation increases. Further, if the diameter of the metal sphere is too small compared to the outer diameter of the metal sheath, the welding depth may become shallow and the mechanical strength may be insufficient. According to the present invention, since the diameter of the metal sphere is 0.8 to 1.2 times the outer diameter of the metal sheath, there is no increase in polishing work and insufficient mechanical strength.

The tube automatic welder used in this method is a TIG welding electrode that rotates around the butting position of two welded tubes that are fixed at the tip by two clamps connected to ground. Two tubes are automatically welded and connected, and many companies are commercially available. For example, international application WO 2008/3339 is published as a patent.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (5)

At least one pair of thermocouple wires in which the tips are joined to form a temperature measuring point are accommodated in the metal sheath via an inorganic insulating material powder filled in the metal sheath, and the tip of the metal sheath In a sheathed thermocouple sealed with a weld seal, the weld seal at the tip of the tube is connected to the corresponding position of the two tubes where the tips are butted together by two clamps connected to ground. A sheath thermocouple tip welding sealing method that is performed using an existing automatic tube welding machine that automatically welds and connects the two tubes by turning a TIG welding electrode around the electrode,
The thermocouple wire and the inorganic insulating material powder are housed, and the end surface of the inorganic insulating material powder is formed into a concave shape in a spherical shape having a diameter substantially the same as the diameter of the metal sphere described later. The tip opening is fixed upward with one of the clamps approximately vertically, and a solid spherical metal ball having the same diameter as the outer diameter of the metal sheath is placed on the opening of the metal sheath. A metal ball placing process,
A presser bar made of a material having a melting point higher than the melting point of the metal sphere is inserted into a hollow bar with a rear end covered, and the rear end of the presser bar is connected to the cover via a spring. The tip of the hollow stick protrudes to the outside from the tip opening of the hollow stick, and the length of the protrusion is limited to a predetermined range by a stopper mechanism. At least the hollow stick and its lid, the presser stick, the spring And a metal ball holding jig comprising the stopper mechanism, and the metal ball placed on the distal end opening of the metal sheath in the metal ball placing step in the metal ball placing step by the force of the spring. A metal ball pressing step of fixing the hollow rod with the other one of the clamps while being pressed against the sheath;
Subsequently, the TIG welding electrode rotates around the contact portion between the metal sheath and the metal sphere, and a contact portion welding step for welding the contact portion between the metal sheath and the metal sphere all around. ,
In the contact part welding step, in the metal ball holding jig, the protruding length of the holding bar from the tip opening of the hollow bar is limited to a predetermined range by the stopper mechanism. Due to the start of the melting of the sphere and the flattening of the shape, the contact between the presser bar and the metal sphere is lost, and thereafter, the contact portion between the metal sheath and the metal sphere is welded without the contact. A method for welding and sealing a sheath thermocouple tip. The stopper mechanism of the metal ball holding jig is:
One or more bar-shaped protrusions provided on the side surface of the presser bar at right angles to the axial direction of the presser bar;
A stopper opening provided on the side surface of the hollow rod corresponding to each projection, and
By projecting the protrusion from the stopper opening to the outside, the length of the presser bar protruding from the tip opening of the hollow bar is equal to the axial length of the stopper opening and the rod-like shape. The method for welding and sealing a sheath thermocouple tip according to claim 1, which is limited to a range determined by the thickness of the protrusion.   The method for welding and sealing a sheathed electrothermal pair tip according to claim 1 or 2, wherein a material of the presser bar is ceramics.   The method for welding and sealing a sheath thermocouple tip according to any one of claims 1 to 3, wherein a material of the metal sphere is the same material as that of the metal sheath. The sheath thermocouple tip welding according to any one of claims 1 to 4, wherein the diameter of the metal sphere is 0.8 to 1.2 times the outer diameter of the metal sheath. Sealing method.

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