Non-welding type thermocouple assembly

Abstract

A thermocouple assembly includes a first thermocouple wire and a second thermocouple wire. The body is configured to electrically isolate the first thermocouple wire and the second thermocouple wire from each other. The metallization cap is provided with an electrically conductive inner surface. The body is bonded within the metallization cap to cause the first thermocouple wire and the second thermocouple wire to contact the conductive inner surface of the metallization cap. The first thermocouple wire, the second thermocouple wire, and the conductive inner surface of the metallization cap form a thermocouple.

Description

Technical Field

[0001] The present invention relates to a thermocouple assembly, and more particularly to a non-welding thermocouple assembly. Background Art

[0002] A thermocouple is a temperature-sensing device consisting of two wires made of dissimilar metals, joined at one end. When the junction of the two metals is heated, a voltage is generated that is proportional to the temperature difference between the junction and the other end of the wires. Thermocouples are widely used in industry and science for temperature measurement and control.

[0003] Typically, a thermocouple is formed by welding the ends of thermocouple wires together. The type of thermocouple formed is determined by the type of wires that are connected together. For example, a J-type thermocouple is formed by welding iron (FE) thermocouple wire to copper-nickel (Cu-Ni) wire. The J-type thermocouple has a relatively small thermal mass, which allows it to react quickly to temperature changes and has an operating range of -210 degrees Celsius to 1200 degrees Celsius.

[0004] Thermocouples are used in a wide variety of industries and industrial processes. Examples include furnaces, kilns, ovens, food processing, plastics manufacturing, petrochemical refining, and many other applications. Many existing thermocouple assemblies require welding processes, which add complexity and cost to the manufacturing process. These processes involve specialized welding equipment, processes, and procedures to ensure the weld is of acceptable quality and robustness. Welding also causes metallurgical changes that reduce thermocouple accuracy and can cause drift due to alloy grain growth and alloy impurities. Moving to processes that eliminate welding offers a lower-cost solution while still maintaining accuracy.

[0005] Non-welded thermocouple assemblies are known, but still typically require complex machining processes and equipment. U.S. Patent 3,538,596 provides a method for preparing non-welded thermocouple junctions. In the description of the '596 patent, multiple swaging operations are used to form the non-welded thermocouple assembly. Swaging is a cold working process that uses a die to reduce the diameter, create a taper, or add points to a circular workpiece. Swaging can also impart internal shape to a hollow workpiece by using a mandrel (the shape must have a constant cross-section). However, the swaging operation is time consuming and still requires a swaging mechanism and / or tooling to perform the swaging operation. Summary of the Invention

[0006] A thermocouple assembly includes a first thermocouple wire and a second thermocouple wire. A body is configured to electrically isolate the first thermocouple wire and the second thermocouple wire from each other. A metallized cap is configured to have a conductive inner surface. The body is engaged within the metallized cap to force the first thermocouple wire and the second thermocouple wire into contact with the conductive inner surface of the metallized cap. The first thermocouple wire, the second thermocouple wire, and the conductive inner surface of the metallized cap form a thermocouple. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a cross-sectional view of a non-welded thermocouple assembly according to an embodiment of the present invention.

[0008] Figure 2 is a bottom perspective view of a main body of a thermocouple assembly according to an embodiment of the present invention.

[0009] Figure 3 and Figure 4 4 and 5 are bottom perspective and cross-sectional views, respectively, of a main body of a thermocouple assembly according to another embodiment of the present invention.

[0010] Figure 5 is a top perspective view of a main body of a thermocouple assembly according to an embodiment of the present invention.

[0011] Figure 6 is a perspective view of a main body of a thermocouple assembly according to another embodiment of the present invention.

[0012] Figure 7 is a cross-sectional view of a non-welded thermocouple assembly according to an embodiment of the present invention. DETAILED DESCRIPTION

[0013] The embodiments described herein generally utilize a body that isolates two separate thermocouple wires from each other but connects them to a metal or metallized cap, thereby forming a sensor junction without the need for welding. The thermocouple wires are typically held in constant pressure against the cap by a mechanical press fit around the body. This eliminates the need to purchase specialized welding equipment and specialized swaging equipment.

[0014] Figure 1 1 is a cross-sectional view of a non-welded thermocouple assembly according to an embodiment of the present invention. The non-welded thermocouple assembly 100 includes a metallized cap 102, a body 104, and thermocouple wires 106, 108 (wire 108 is shown in FIG. Figure 2Thermocouple wires 106, 108 may be formed from any suitable thermocouple wire material, including, but not limited to, iron-constantan (J-type), chromium-aluminum (K-type), copper-constantan (T-type), platinum and rhodium in varying ratios (B-type, R-type, and S-type), nickel-chromium / constantan (E-type), and nickel-chromium-silicon / nickel-silicon (N-type).

[0015] The metallized cap 102 can be formed from any suitable conductor. Examples of suitable conductors include various metals, such as aluminum, copper, stainless steel, Inconel, and the like. Additionally, the metallized cap 102 can be formed on a non-conductive material, such as ceramic or glass, and then provided with a metallization on the inner surface 110. The metallization can be formed in any suitable manner, including electrophoretic deposition, physical vapor deposition, and other suitable techniques.

[0016] like Figure 1 As shown, the metallized cap 102 generally includes a cylindrical portion 112 having a hollow interior 114 and a shoulder 116 located adjacent the flange 118. The metallized cap 102 also includes a hollow interior cylindrical distal portion 120. A temperature sensing surface 122 forms part of the cylindrical distal portion 120.

[0017] Main body 104 Figure 1 108. The body 104 is shown as being generally cup-shaped, with a bottom surface 124, a cylindrical sidewall 126, and an interior 128. The body 104 is formed of any suitable material capable of electrically isolating the thermocouple wires 106, 108 from each other. However, the selected material must be able to withstand the operating temperature of the thermocouple assembly. Examples of suitable materials for the body 104 include refractory materials, including some ceramics (such as alumina, zirconium oxide, silicon nitride, aluminum nitride, silicon carbide, and magnesium oxide), certain polymers (such as polyphenylene sulfide), and glass. In some examples, the body 104 can be formed of metal, as long as the holes through which the thermocouple wires 106, 108 pass are made non-conductive (for example, using a non-conductive insert, coating, or other suitable structure). In one example, the body 104 is a non-conductive block. In addition, as described below, the structure of the body 104 must abut against the inner surface of the metallized cap 102 to create a sufficient press fit so that the body 104 remains in place within the metallized cap 102. In this embodiment, the body 104 engages a shoulder on the inner surface of the cap to secure the body so that the wires contact the bottom of the cap. The body 104 also includes a hole for each thermocouple wire from the interior 128 to the bottom surface 124. The thermocouple wires passing through the holes are bent ( Figure 1102 ), so that the end 132 of the thermocouple wire is pressed against the inner surface 110 of the metallized cap 102. When each of the two thermocouple wires is pressed into contact with the inner surface 110 of the metallized cap 102, a thermocouple assembly is formed.

[0018] Figure 2 1 is a bottom perspective view of a body of a thermocouple assembly according to an embodiment of the present invention. The body 104 includes a plurality of (six in the illustrated example) extruded ribs 140 configured to be compressed when the body 104 is axially pressed into the metallized cap 102 (e.g., Figure 1 144 ). In one embodiment, each extruded rib 140 is shaped to produce a higher extrusion force when it is axially extruded. For example, the extruded rib 140 includes a bottom or distal end 142 having a width that is less than the width of the extruded rib 140 near the top of its proximal end 144. The width varies approximately linearly, forming a triangle 146. In addition, to better orient the body during assembly, each extruded rib 140 preferably has a taper 148 near its bottom or distal end 142. The extruded ribs 140 are preferably arranged in diametrically opposed rib pairs (i.e., Figure 2 3 pairs of extruded ribs are shown in FIG.

[0019] Figure 2 A pair of holes 150, 152 are shown through which the thermocouple wires 108, 106 are passed, respectively, from the interior 128 (e.g., Figure 1 108 , 108 ). Figure 1 104 to the bottom surface 124. The thermocouple wires 106, 108 are then bent 90 degrees on the bottom of the body 104. The thermocouple / body assembly is then press-fitted into the metallized cap 102. The crush ribs 140 located on the body 104 deform during the press-fit, thereby securing the body 104 into the metallized cap 102. The body 104 allows the thermocouple wires 106, 108 to be "smashed" onto the inner surface 110 of the metallized cap 102. The thermocouple wires 106, 108 are then electrically coupled to allow appropriate measurement electronics to monitor the voltage generated by the junction.

[0020] Figure 3 and Figure 4 2 are bottom perspective views and cross-sectional views, respectively, of a body of a thermocouple assembly according to another embodiment of the present invention. Body 204 is similar to body 104, and similar components are numbered in a similar manner. Like body 104, body 204 also includes six extruded ribs 240. The main difference between body 204 and body 104 is that body 204 includes four holes 250, 252, 254, and 256. With four holes, each thermocouple wire can be passed downwardly through a hole (such as hole 252) from the interior 228 of body 204, and then the end 260 of the thermocouple wire can be passed upwardly into an adjacent hole (such as hole 256) to capture or otherwise accommodate the end 260. Although Figure 3 The embodiment shown in FIG. 2 does not include channels shown with respect to the body 204 , but it is expressly contemplated that such channels may be used.

[0021] Figure 5 is a top perspective view of a main body according to an embodiment of the present invention. Figure 5 The relative positions of the various holes 250 , 252 , 254 , and 256 and the thermocouple wires 106 , 108 are shown.

[0022] Figure 6 304 includes a slot 306 in a side wall 308 that allows the thermocouple wires 106, 108 ( Figure 6 108). In addition, the narrow slot 306 allows the body 304 to deform slightly to allow the body 304 to be fitted into the metallized cap 102. The end 310 of the body 304 may include a taper to help the body 304 fit into the metallized cap 102 during assembly. In this embodiment, the narrow slot 306 allows the thermocouple wires 106, 108 to be fed from the side, which can facilitate manufacturing by allowing the thermocouple wires to be fed from both the side and the top.

[0023] Figure 7 is a cross-sectional view of a non-welded thermocouple assembly according to an embodiment of the present invention. Figure 7 Similar to Figure 1 The non-welded thermocouple assembly 100 is shown in FIG. Figure 7 In, with Figure 1Compared to the conventional, welded grounded thermocouple, the assembly is rotated 90 degrees. As can be seen, the ends 400 and 402 of the thermocouple wires 106 and 108 are shown as rounded. Line 404 indicates the circuit created when the thermocouple wires 106 and 108 contact the surface 110 of the metallized cap 102. The legs 406 of the wire 404 run along and / or through the surface 110 of the metallized cap 102. This not only creates a solid contact surface for the thermocouple, but also, if one or both of the thermocouple wires lose contact with the metallized cap 102, the thermocouple circuit is broken, thereby not reporting voltage / temperature. In conventional, welded grounded thermocouples, the thermocouple junction may have separated from the sheath but still provide voltage because the conductors are connected together. If the junction is no longer grounded to the sheath, this can lead to inaccurate measurements. The embodiments described herein can provide early detection of whether a thermocouple is about to lose contact with the cap.

[0024] The embodiments described herein can be used in a variety of applications requiring temperature measurement. This low-cost, simple solution will enable manufacturers to produce high-quality thermocouple solutions. The embodiments described herein also provide the accuracy benefits of a grounded thermocouple while avoiding capital equipment costs or laborious assembly techniques. It is clearly contemplated that the metallized cap 102 can be part of the thermowell. By removing material and forming the junction within the thermowell, response time will be improved, and diagnostics can be utilized to indicate that the thermocouple is maintaining good thermowell tip contact.

[0025] While embodiments have been provided showing thermocouple wires that are bent at their ends, it is also contemplated that the thermocouple / body assembly may include thermocouple wires that are overmolded into a conductive polymer without feeding the thermocouple wires through a hole and bending the thermocouple wires at 90 degrees.

[0026] Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. Although embodiments have been described with respect to a press fit between the body 104 and the metallized cap 102, those skilled in the art will recognize that other forms of mechanical fastening or mounting may be used to retain the body 104 within the metallized cap 102. Embodiments include the use of a snap ring in the body 104 that mates with a groove in the metallized cap 102. Additionally, adhesives may be used to secure the body within the metallized cap. In yet another example, a threaded member may be engaged with the internal threads of the metallized cap 102 and driven into engagement with the body 104.

Claims

1. A thermocouple assembly, comprising: a first thermocouple wire; a second thermocouple wire; a body configured to electrically isolate the first thermocouple wire and the second thermocouple wire from each other; a metallized cap having a conductive inner surface; and wherein the body is engaged within the metallized cap to force the first thermocouple wire and the second thermocouple wire into contact with the conductive inner surface of the metallized cap, and wherein the first thermocouple wire, the second thermocouple wire, and the conductive inner surface of the metallized cap form a thermocouple.

2. The thermocouple assembly according to claim 1, wherein The thermocouple is selected from the group consisting of: J-type, K-type, T-type, B-type, R-type, S-type, N-type, and E-type.

3. The thermocouple assembly according to claim 1, wherein The metallized cap is formed entirely of metal.

4. The thermocouple assembly according to claim 3, wherein: The metal is selected from the group consisting of aluminum, copper, stainless steel, and Inconel.

5. The thermocouple assembly according to claim 1, wherein The metallized cap is formed of a non-conductive material with metallization formed on the non-conductive material to provide the conductive inner surface.

6. The thermocouple assembly according to claim 5, wherein The non-conductive material is selected from the group consisting of: ceramics, polymers, and glass.

7. The thermocouple assembly according to claim 1, wherein The metallized cap forms part of a larger structure.

8. The thermocouple assembly according to claim 7, wherein: The larger structure is a thermowell.

9. The thermocouple assembly according to claim 1, wherein: The metallized cap includes a shoulder and a flange, wherein the shoulder is on an inner surface of the metallized cap and the flange is disposed around an outer surface of the metallized cap and adjacent to the shoulder.

10. The thermocouple assembly according to claim 9, wherein The shoulder is configured to engage and secure a portion of the body.

11. The thermocouple assembly according to claim 1 , wherein: The body includes a plurality of apertures, each aperture having a corresponding thermocouple wire passing therethrough.

12. The thermocouple assembly according to claim 11, wherein Each of the first thermocouple wire and the second thermocouple wire includes a bend after passing through the corresponding hole.

13. The thermocouple assembly according to claim 11, wherein The body includes a plurality of channels on a distal surface of the body, each channel communicating with a corresponding aperture, and each channel configured to receive at least a portion of one of the first thermocouple wire and the second thermocouple wire therein.

14. The thermocouple assembly according to claim 11, wherein The plurality of holes includes four holes, and wherein the first thermocouple wire includes a u-shaped end, and wherein the first thermocouple wire passes through a pair of holes in the body.

15. The thermocouple assembly according to claim 14, wherein The second thermocouple wire includes a u-shaped end, and the second thermocouple wire passes through a different pair of holes than the first thermocouple wire.

16. The thermocouple assembly of claim 1, wherein: The body includes a slot configured to receive the first thermocouple wire and the second thermocouple wire.

17. The thermocouple assembly of claim 1, wherein: The body is press-fit into the metallized cap to secure the first and second thermocouple wires in contact with the inner surface of the metallized cap.

18. The thermocouple assembly of claim 1, wherein: The body includes a plurality of extruded ribs configured to engage a portion of the metallized cap to secure the first and second thermocouple wires in contact with the inner surface of the metallized cap.

19. The thermocouple assembly of claim 18, wherein: A first extruded rib of the plurality of extruded ribs is radially opposite a second extruded rib of the plurality of extruded ribs.

20. The thermocouple assembly of claim 18, wherein: Each of the plurality of crush ribs is tapered such that a distal end of the body is narrower than a proximal end of the body.

21. The thermocouple assembly of claim 18, wherein: Each of the plurality of extruded ribs includes a tapered end surface configured to engage the metallized cap.

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