US2677712A - Thermopile structure - Google Patents

Description

May 4, 1954 L. c. BIGGLE THERMOPILE STRUCTURE Filed Feb. 18, 1952 2 mit 1 Patented May 4, 1954 THERMOPILE STRUCTURE Laurence C. Biggie, Altadena, Calif., assigner to General Controls Co., Glendale, Calif., a corporation of California Application February 18, 1952, Serial No. 272,055

6 Claims. l

This invention relates to therinoelectric de vices of the type adapted, when heated by a small flame such as that produced by an ordinary fuel-gas pilot burner, to generate electric energy in an amount suii'cient for 'operative tion of sensitive electric control devices such as pilot valves, switching devices, and the like; such generating 'devices comprising a therinocouple, or a plurality of 'thermocouples electrically interconnected in series to form a thermopile. The present invention is, in some respects, an improve-- ment on the invention disclosed in Patent No. 2,526,112.

An object of this invention is to provide a novel thermopile of the character described, and a protective sheath therefor.

Another object is to provide improved and sirnplifie means for so mounting the thermopile in the sheath that the hot junctions 'of the 'th-errnon pile are maintained in good thermal-transfer relation to the sheath.

For full understanding of the invention, and .farther appreciation of its features and advantages, reference is to be had to the folio ing detailed description 'and accompanying drawing, and to the appended claims..

In the drawing:

Figure 1 is a longitudinal sectional View of a thei'znopile structure embodying 'this invention;

(Cl, 13G-4) H-l joined together, 'as byiwelding, `at their upper ends; these conductors being of thermoeleetrically dissimilar metals such as an alloy (kn-own as Copel containing approximately Cu and 45% Ni and another alloy (known as Chromel, adapted for use in vconjtmetion with Copel) containing approximately 99% Ni and 10% Cr; the thermocouples being interconnected at their lower ends in electrical series to form the thermopile.

The conductors I-l are ribbon-like; `their width and thickness in an actual embodiment of the invention being 0.093 inch vand l0.014 inch refspectiveiy. The tops i9 'of the therrnocouples are conveniently considered as the hot junctions oi the tlierinopiie unitfsi'nc'e the temperature oi the unit, when in operation, is the highest at those ends are arranged in a common plane and are in virtual engagement with the-end wall i3 oi sheath il, from which they are electrically insulated by a thin disk 2li of mica.

The thermopile conductors are electrically insulated from each other by fil-ms oi oxide formed on their. by subjecting the unit, 'before assembly in the sheath, to high rteniperature infan oxidizing atmosphere; such'insnlation being sucient to withstand the low Voltagevinvol-ved which, in normal operation, is about 1GO rnv. across the whole four-couple thermopile'when the saine is the thermopile unit ill-i8 being shown in eleva- 5U constructed of they-alloys mentioned. tion; Around each of the end conductors of the Figure 2 is a transverse section, to enlarged thermopile unit is a thin sleeve 2l of material taken along the line 2 2. of Fig. 1; and woven from `glass liber which protects the oxide Figure 3 is an elevational View ci the thermo* film on these conductors from abrasion and propil-e unit per se. 3;, vides additional electrical insulation between the the drawing, the numeral il indicates a conductors and the sides of the sheath section sheath having an upper section i2 cf thin oori2 adjacent its upper end, as can beseen in Fig. 2; i'osioneresis'tant Ine-tal such as stainless steel, the the sleeves '2i also serving an additional purpose side wall of this section being circular in cross to be described. section and tapering inwardly in a direction tO- o For the salie 'of clarity the thermopile unit is Ward its top where it is provided with an integral shown in expanded condition in Fig. 3. Before it end-wall I3. The upper section i2 is joined is inserted in the sheath the unit is lightly at its bottom, as by welding, to a generally eylinn wrapped with fine glass-ber thread (not shown) drical lower section ii which serves as a base which holds the conductors together temporarily; for supporting the structure in a gas-burner deu s@ a pile 22 of the glass thread being ferr-:led around vice. auch as is shown in the aforementioned the lower end of vthe unit to centralise that end Patent No. 2,525,112, whereby the top portion of within the Sheath, the Structure may be heated; a groove Hi beine A pair of copper wires 23 are welded to the outer DlOVded in 13h@ periphery Of the IGWSX SGCOD conductors of the thermopile and extend from for fastening means Such as a snap-fine or the 5c the bottom of the sheath, within flexible armor tip of a set-screw. 2li, for connection to an electrical device to be Within the Sheath H iS a Ghmople unit energized; a strip 25 of electrical insulating mawhich is shown per se in Fig. 3 and comprises a terial being inserted between the inner ends plurality (four, as shown) of thermccouples iii of wires 23. The intermediate ones of conductors each of which is formed. by a pair of conductors ik? I8 are extended downwardly, as indicated at 2@ in Fig. 3, to aid dissipation of heat from the cold junctions at the lower end of each of the thermocouples.

The upper sheath-section l2 is so tapered, or constricted at its upper end, as to grip the side corners of the thermopile unit when, in assembly of the structure, the unit is pressed into Final position in the sheath with the hot-junction ends i9 of the unit in virtual engagement (through mica disk with the end wall I3 for eiective transfer of external heat through the sheath to the unit. 'Ihe material of the sheath-section i2 is resilient and so thin (0.007 inch in an actual embodiment) that the circular side wall of the sheath is easily deformed by the rectangular end of the unit to ensure frictional holding in place of the unit. The glass-nbre sleeves 2| also contribute to the gripping eiect since they are somewhat elastic and their upper ends bear against the sides of the sheath at points below the top of the sheath (see Fig. 2) at which points the structure is relatively yieldable.

.After the thermopile unit is in place, the lower interior of the sheath is filled with a thermosetting material, indicated at 2'?, which hermetically seals the structure and serves as additional support for the inner parts; the material being of a type `adapted to Withsand the temperatures involved and to adhere tightly even to the smooth inner surface of the sheath, the material being known in the art as glass sealing compound. Even although the thermocouple elements or conductors are already oxidized, it is advisable to prevent further oxidation (particularly of the Copel elements) by providing the hermetic seal. It is to be observed that after the thermopile unit (with cable '2S-2li attached) is inserted in the sheath and forced to nal position with its hot-junction ends l in tight engagement with the end wall I3, the only step remaining for completion of the structure is the sealing of the open end of the sheath.

The specific embodiment of my invention herein shown and described is susceptible of modification Without departing from the spirit of the invention, and I intend therefore to be limited only by the scope of the appended. claims.

I claim as my invention:

l. Ina thermopile structure: an elongated unit, generaly rectangular in cross-section, comprising a plurality of ribbon-like conductors arranged with their sides in abutting relation and their ends terminating generally in a plane at one end of the unit, said conductors being alternately of therinoelectrically dissimilar metals and interconnected electrically to form a thermopile havits hot junctions at said one end of the unit; a sheath enhousing said unit and having an end wall engaged by said hot-junction end of the unit, the portion of said sheath adjacent said end wall being generally circular in cross-section and of thin resilient material having good thermal conductivity, said sheath-portion being constricted so as to grip the side corners of the unit and thereby rictionally maintain the unit with its hot-junction end in engagement with the end vra-l1.

2. In a thermopile structure: a plurality of dat ribbon-like conductors arranged with their sides in abutting relation to form an elongated unit generally rectangular in cross-section and with the ends of the conductors terminating in a plane at one end of the unit, said conductors being alternately of thermoelectrically dissimilar metals and interconnected electrically to form a thermopile having its hot junctions at said one end of the unit; and a sheath enhousing said unit, said sheath having, in a plane at right-angles to its longitudinal axis, a flat end-wall engaged by said hot-junction end of the unit, the portion of said sheath adjacent said end wall being generally circular in cross-section and of thin resilient material having good thermal conductivity, said sheath-portion being constricted so as to grip the side corners of the unit and thereby frictionally maintain the unit with its hot-junction end in engagement with the end wall of the sheath.

3. A thermopile structure as defined in claim 2, and wherein the side walls of said sheath-portion taper inwardly in a direction toward said end wall and so as to grip the side corners of said unit tightly When said hot-junction end of the unit is in engagement with the end wall.

e. In a thermopile structure: a plurality of. flat ribbon-like conductors arranged with their sides in abutting relation to form an elongated unit generally rectangular in cross-section and with the ends of the conductors terminating in a plane at one end of the unit, said conductors being alternately of thermoelectrically dissimilar metals and interconnected electrically to form a thermopile having its hot junctions at said one end of the unit, said unit having a symmetricallyarranged lateral enlargement of its side corners adjacent to but spaced longitudinally from said hot-junction end of the unitfand a sheath enhousing said unit, said sheath having, in a plane at right-angles to its longitudinal axis, a flat end-wall engaged by said hot-junction end of the unit, the portion of said sheath adjacent to said end wall being generally circular in cross-section and of thin resilient material having good thermal conductivity, the side walls of said sheathportion tapering inwardly in a direction toward said end Wall and being arranged so as to tightly grip the corners of said unit-enlargement when said hot-junction end of the unit is in engagement with the end Wall of the sheath.

'5. A thermopile structure as dei-med in claim 4, and wherein said unit-enlargement is formed by elastic electrical insulating material.

6. A thermopile structure as defined in claim Il, and wherein said unit-enlargement comprises a sleeve of electrical insulating material encircling a portion of each of the end conductors of said unit.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,126,656 Pack Aug. 9, 1933 2,349,306 Ray May 23, 194e 2,361,215 Lamberger et al. Oct. 24, 194,4. 2,526,112 Biggle Oct. 17, 1950

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