US3462316A - Terminal construction - Google Patents

Description

1969 H. A. M INTOSH ETAL 3,462,316

TERMINAL CONSTRUCTION Filed Sept. 20, 1965 fws/wafis 29 I HAOLD A. M IWWSM,

5 flaw w M. WAG/reg,

United States Patent US. Cl. 136-230 4 Claims ABSTRACT OF THE DISCLOSURE A thermocouple terminal including a terminal member having a longitudinal passageway and a radially extending recess opening at one end of said passageway. A conductor received by said terminal member in locking engagement within said passageway and recess to prevent rotational and longitudinal movement of said conductor relative to said terminal member.

This invention relates to terminal construction and more particularly to an improved mechanical and electrical joint between a thermocouple conductor and the terminal member of the thermocouple.

Inner and outer coaxial conductors electrically insulated from each other are often used to electrically connect a thermocouple to an external circuit. The inner conductor is attached to a terminal member which in turn is secured to a contact of the external circuit. A suitable socket may be provided in the external circuit to receive the terminal member.

Problems have arisen in connection with the securing of the terminal member to the thermocouple conductor. In some instances, the terminal member and conductor joint have failed structurally, thereby destroying the electrical connection, while in other instances the structural connection has remained substantially intact but the electrical connection has deteriorated. In either instance, the thermocouple becomes substantially electrically isolated from the external circuit and is disabled from performing its important functions.

Accordingly, an object of this invention is to provide an improved electrical and mechanical joint between a terminal member and a thermocouple conductor.

Another object of this invention is to use interlocking means and conductive bonding material to secure a terminal member to a thermocouple conductor.

Another object of this invention is to provide an improved terminal construction which includes a terminal member having a passageway therethrough and a laterally extending locking recess opening at the passageway, an elongated electrical conductor in said passageway and having a locking portion extending laterally into the locking recess, and conductive bonding material for bonding the elongated electrical conductor to the terminal member. The locking portion of the conductor engages the walls of the locking recess to prevent relative rotation therebetween and the prevent relative translation therebetween in at least one direction. The conductive bonding material further strengthens the conductorterminal member joint and also forms a portion of the terminal for the thermocouple. Thus, the combination of structural interlocking means and conductive bonding material forms a strong joint having a long useful life.

Another object of this invention is to provide a locking recess which opens at the passageway of the terminal member and also at one of the end faces of the terminal member. This feature of the invention facilitates construction in that it permits insertion of the conductor through the passageway of the terminal member and then bending of the end portion of the conductor into the recess.

A further object of this invention is to provide a terminal construction in which one end of the passageway through the terminal member is enlarged so that the interior wall thereof is spaced from the elongated electrical conductor to define a cavity for receiving the conductive bonding material.

A particular object of this invention is to provide a thermocouple assembly including a thermocouple; inner and outer generally coaxial conductors, the outer conductor being connectible to a first contact of an electrical circuit, the inner conductor having a section extending axially beyond the outer conductor; a terminal member having first and second end faces and a generally longitudinal passageway extending therethrough to connect the end faces, the terminal member having wall surfaces defining a generally radially extending locking recess opening at the passageway, the section of said inner conductor extending into said passageway from the first end face toward the second end face, the section of the inner conductor terminating in a generally radially extending locking finger, the locking finger extending into said locking recess and being engageable with the wall surfaces thereof to substantially prevent relative rotation between the terminal member and the inner conductor; insulating means for electrically insulating the outer conductor from the terminal member; and conductive bonding material for bonding the inner conductor to the terminal member, the bonding material and the terminal member forming a terminal for the thermocouple.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a side elevational view of a thermocouple assembly embodying the novel terminal construction of this invention;

FIG. 2 is an enlarged bottom view of the terminal construction; and

FIG. 3 is an enlarged fragmentary sectional view taken along line 3-3 in FIG. 1 and showing the terminal construction secured to a socket of an external circuit.

Referring to the drawing and in particular to FIG. 1 thereof, reference numeral 11 designates a thermocouple which includes a tubular member 13 of a first metal, a wire 15 of a dissimilar metal within and coaxial with the tubular member, and a weld 17 for securing one end of the wire 15 to the end of the tubular member 13 to form the hot junction of the thermocouple. A tubular connector 19 is secured to the lower end of the tubular member 13. A tube or outer conductor 21 of a conductive metal such as copper and having a flared lower end 23 is secured to the connector 19. A second wire or inner conductor 25 is secured as by soldering to the wire 15 and extends within and coaxial with the tube 21. The tube 21 and the conductive wire 25 are electrically insulated from each other by insulation 26 (FIG. 3). Thus, the tube 21 and the wire 25 form inner and outer coaxial conductors for carrying the current developed by the thermocouple 11 to an external circuit.

The inner conductor 25 has a section 27 (FIG. 3) which extends axially beyond the flared end 23 of the outer conductor 21. A cylindrical insulating washer 29 is mounted on the section 27 of the inner conductor 25 in abutting relationship with the flared end 23.

A terminal member 31 having a first end face 33, a second end face 35, and an interior wall defining an axial longitudinally extending passageway 3-7 is mounted on the section 27 as show in FIG. 3. The terminal member 31 has a radially extending locking recess or slot 39 which opens at the passageway 37 and at the end face 35.

The section 27 of the inner conductor 25 extends into the passageway 37 from the end face 33 toward the end face 35. An end portion 41 of the inner conductor 25 is bent through approximately a 90 angle so that it extends radially into the locking recess 39 to define a locking finger which terminates within the locking recess. The locking recess 39 has generally opposed spaced surface areas 43 and 45 which the locking finger 41 engages to prevent relative rotation between the terminal member 31 and the inner conductor 25. The surface areas 43 and 45 may be planar or partially rounded to conform to approximately the upper one half of the periphery of the locking finger 41. The terminal member 31 also has an upper wall or surface means 47 which defines at least a portion of the locking recess 39 and engages the locking finger 41 to prevent longitudinal movement of the locking finger toward the end face 33. The upper wall 47 may be planar or rounded to mate with the portion of the locking finger 41 which is engageable therewith.

The passageway 37 includes a frusto-conical counterbore 49 extending inwardly from the end face 35. The walls of the counterbore 49 and of a portion of the passageway 37 are spaced from the inner conductor 25 to define a cavity 51. Conductive bonding material 53 such as solder is disposed in the cavity 51 to bond the inner conductor 25 to the terminal member 31. Alternatively, the inner conductor 25 may be directly bonded to the terminal member 31 as by resistance welding or cold pressure forming. Regardless of the method used to make the bond, the material which flows or is worked to secure the conductor 25 and the member 31 together is referred to herein as the conductive bonding material or bonding material. As shown in FIG. 3, some of the bonding material 53 may enter the locking recess 39. The bonding material 53 and the terminal member 31 form a terminal for the thermocouple 11.

The terminal member 31 is preferably generally cylindrical and constructed of a conductive metal such as brass. The end face 35 is provided with a protruding peripheral frusto-conical surface 55. When the terminal member 31 is secured to the inner conductor 25, the end face 33 abuts the insulating washer 29 thereby sandwiching the washer between the terminal member and the flared end 23.

The terminal structure described hereinabove may be electrically connected to an external circuit by a variety of devices. One suitable arrangement for securing the terminal structure to an external circuit is illustrated in FIG. 3. A conductor 57 having three axial bores 59, 61, and 63 of progressively decreasing diameter is suitably secured to a supporting structure 65 by an electrically conductive terminal stem 67 and an electrically conductive terminal nut 69. The terminal nut 69 has a frusto-conical recess 71 at the upper end thereof. A terminal insulator 73, an insulator bushing 75, and a terminal washer 77 all constructed of insulating material electrically insulate the terminal stem 67 and the nut 69 from the conductor 57. A nut or tubular securing means 79 of a conductive material such as brass is slidably mounted on the outer conductor 21. As shown in FIG. 3, the nut 79 engages the flared end 23 of the outer conductor 21 and is threadedly received by the bore 59. Thus, the nut 79 electrically connects the outer conductor 21 and the conductor 57.

The conical surface 55 on the terminal member 31 is received by the frusto-conical recess 71 of the terminal nut 69 thereby electrically connecting the inner conductor 25 and the terminal stem 67. This relationship is maintained by the nut 79 and the threaded bore 59. The conductive bonding material 53 may also contact the terminal stem 67.

It is apparent therefore that an improved electrical and mechanical joint between the terminal member 31 and the inner conductor 25 has been provided. The locking finger 41 and the locking recess 39 prevent all relative movement between the inner conductor 25 and the terminal member 31 except translation of the locking finger toward the end face 35. Such translation is prevented, however, by the conductive bonding material 53 which rigidly holds the locking finger within the locking recess. Thus, without the addition of separate fastening means, a strong mechanical joint is obtained.

To facilitate construction and assembly, it is preferred that the locking recess 39 open at the end face 35. Thus, the section 27 is inserted through the passageway 37 and then the end portion of the section 27 is bent through approximately to form the locking finger 41 which may then be slid into the locking recess. The counterbore 49 provides additional volume into which the conductive bonding material 53 may be deposited.

Many changes, modifications, and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.

What is claimed is:

1. In a thermocouple assembly connectible to first and second contacts of an electrical circuit, the combination of:

a thermocouple;

a first elongated electrical conductor electrically connected to said thermocouple and connectible to the first contact of the electrical circuit, said elongated electrical conductor having an end portion;

a second electrical conductor electrically connected to said thermocouple and connectible to the second contact of the electrical circuit;

a terminal member having first and second end faces,

said terminal member having an interior wall defining a longitudinal passageway extending through said terminal member and connecting said end faces, said terminal member having a radially extending locking recess opening at said passageway, said locking recess having generally opposed spaced surface areas;

said first elongated electrical conductor extending into said passageway from said first end face toward said second end face, said end portion of said first elongated electrical conductor extending radially into said locking recess to define a locking finger which terminates within said locking recess, said locking finger being engageable with said generally opposed spaced surface areas to prevent relative rotation between said terminal member and said first elongated electrical conductor, at least a portion of said first elongated electrical conductor being spaced from said interior wall of said passageway adjacent said second end face of said terminal member to define a cavity;

surface means on said terminal member defining at least a portion of said locking recess for engaging said locking finger to prevent longitudinal movement of said locking finger toward said first end face of said terminal member; and

means within said cavity for securing said first elongated electrical conductor to said terminal member.

2. A combination as defined in claim 1 wherein said passageway includes a counterbore extending inwardly from said second end face of said terminal member, the Wall of said counterbore being spaced from said elon gated electrical conductor to define at least a portion of said cavity.

3. In a thermocouple assembly connectible to first and second contacts of an electrical circuit, the combination of:

a thermocouple;

inner and outer generally coaxial conductors electrically connected to said thermocouple, said outer conductor being connectible to the first contact of the electrical circuit, said inner conductor having a section extending axially beyond said outer conductor;

first insulating means for insulating said inner conductor from said outer conductor;

an insulating washer on said section of said inner conductor, said washer engaging said outer conductor;

a terminal member having first and second end faces,

a terminal member having first and second end faces,

said terminal member having an interior wall defining a longitudinal passageway extending through said terminal member and connecting said end faces, said terminal member having a radially extending said terminal member having an interior wall defin- 5 locking recess opening at said passageway and at ing a longitudinal passageway extending through said said second end face, said locking recess having genterminal member and connecting said end faces, said erally opposed spaced surface areas; terminal member having a radially extending locksaid elongated electrical conductor extending into said ing recess opening at said passageway and at said sec- 10 passageway from said first end face toward said end end face, said locking recess having generally second end face, said end portion of said elongated opposed spaced surface areas; electrical conductor extending radially into said locksaid section of said inner conductor extending into ing recess to define a locking finger which terminates said passageway from said first end face toward said within said locking recess, said locking finger being second said end face, said first end face abutting engageable with said generally opposed spaced sursaid insulating washer, said section of said inner conface areas to prevent relative rotation between said ductor having an end portion which extends radially terminal member and said conductor, at least a porinto said locking recess to define a locking finger tion of said conductor being spaced from the interior which terminates within said locking recess, said Wall of said passageway adjacent said second end locking finger being engageable with said generally face of said terminal member to define a cavity; opposed spaced surface areas to prevent relative rosaid passageway including a counterbore extending intation between said terminal member and said in- Wardly from said second end face of said terminal ner conductor; member, the wall of said counterbore being spaced said passageway being enlarged adjacent said second from said elongated electrical conductor to define at end face to define a cavity between said interior wall least a portion of said cavity; and said inner conductor; surface means on said terminal member defining at surface means on said terminal member defining at least a portion of said locking recess for engaging least a portion of said locking recess for engaging said locking finger to prevent longitudinal movement said locking finger to prevent longitudinal movement of said locking finger toward said first end face of of said locking finger toward said first end face of said terminal member; and said terminal member; conductive bonding material within said cavity for a deposit of solder within said cavity for bonding said bonding said conductor to said terminal member.

inner conductor to said terminal member, said de- References Cited posit and sald terminal member forming a terminal for the thermocouple; and UNITED STATES PATENTS tubular securing means on said outer conductor for 1,190,524 7/1916 Douglas.

securing said terminal to the second contact of the 2,691,056 10/1954 Wolff 13 223 electrical circuit. 2,755,451 7/ 1956 Smyers, 4. Terminal construction adapted for connection to a 2,992,402 7/1961 Thoma 13 .435

contact of an electrical circuit comprising:

an elongated electrical conductor having an end portion;

WINSTON A. DOUGLAS, Primary Examiner M. J. ANDREWS, Assistant Examiner

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