US2526112A

US2526112A - Thermopile structure

Info

Publication number: US2526112A
Application number: US760606A
Authority: US
Inventors: Laurence C Biggle
Original assignee: General Controls Co
Current assignee: General Controls Co
Priority date: 1947-07-12
Filing date: 1947-07-12
Publication date: 1950-10-17
Anticipated expiration: 1967-10-17

Description

Oct. 17, 1950 L. c; BIGGLEI THERMOPILE STRUCTURE 2 Sheets-Sheet 1 Filed July 12, 1947 Gttorneg Oct. 17, 1950 C, BlGGLE 2,526,112

THERMOPILE STRUCTURE Filed July 12. 1947 ZASheetS-Sheet 2 Z0 9 E fg Gttomeg Patented Oct. 17, 1950 UNITED STATES. PATENT OFFICE THERMOPILE STRUCTURE Laurence C. Biggle, Altadena, Calif., assignor to General Controls Co., Glendale, Calif., a. corporation of California Application July 12, 1947, Serial No. 760,606

(Cl. 13G-4) 12 Claims. l

This invention relates to thermocouples, and especially to a structure in which a number of thcrmocouples are placed in series in order to increase the generated electromotive force.

The principle of operation of thermocouples is now well understood. Usually, one or more lengths of dissimilar metals or alloys are connected or joined as by welding, the two kinds of material alternating. Now if every other junction is heated, while the other junctions are unheated. an elcctromotive force is generated, which depends upon the temperature difference between the hot and cold junctions.

Such thermocouples are extensively used for control purposes, such as in safety systems for gas burners. In such instances, the pilot flame or the main burner flame is caused to heat the hot junctions. While the flame is in existence, a safety valve is maintained open by ald of the electrical control provided by the thermocouple or thermopile. When the flame goes out the thermocouple or thermopile is inactive, and the valve is caused to close.

lll

It is one of the objects of this invention to I improve in general, thermocouple structures of this character.

It is another object of this invention to provide a thermocouple structure that can be readily assembled within a protecting sheath, and that ensures excellent heat transfer from the sheath to the hot junctions.

It is still another object of this invention to provide a structure of this character to simplify the manner of supporting the thermopile on a pilot burner.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of one embodiment of the invention. For this purpose there is shown a form in the drawings accompanying and forming part of the present specication. The form will now be described in detail illustrating the general principles of the invention: but it is to be understood that this detailed description is not to be taken `in a limiti'w; sense. since the scope of this invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is an elevation of a thermopile and pilot burner assembly incorporating the invention;

Fig. 2- is an enlarged sectional view, taken along a plane corresponding to the line 2-2 of Fig. 1;

Figs. 3, 4, and are cross-sectional views, taken along planes corresponding to lines 3 3, 4-4, and 5-5 of Fig. 2;

Fig. 6 is a pictorial view of a spacer utilized in connection with the thermopile structure;

Fig. 'l is a pictorial view of a core and support utilized in connection with the thermopile;

Fig. 8 is a further enlarged pictorial view oi one of the hot junctions of the thermopile; and

Fig. 9 is a diagrammatic representation of the conducting elements of the thermopile structure.

The thermopile structure I, as shown in Figs. 1 and 2, has a cylindrical head 2 that is made of good heat conducting material, and within which are arranged the hot junctions. It may conveniently be made from thin stainless steel. This head 2 is telescoped within an aperture 3 in a pilot burner casting 9. The head 2 is arranged to be heated by a series of flames I4 arranged circumferentially around the head 2. These llames project through the jets 5 formed as slots in a spacer member 4. This spacer member 4 has a downwardly extending ilange which rests on a shoulder formed above the aperture 3. This ange defines an annular space around the head 2 into which fuel may be led. A fuel port I is shown as extending transversely into a vertical port 8 that extends downwardly through the pilot burner 9 for connection to an appropriate supply of fuel and air.

In order to hold the thermopile structure rmly in the pilot burner 9, a set screw I0 may be provided extending radially of the aperture 3, and extending through a wall of the burner.

The upper end of port 8 is arranged to support the pilot burner II. Fuel is led through the port 8 to this pilot burner which is ignited from the flames I4 at jets 5. This pilot burner has a helical slot I2 leading to a pilot burner opening I3. The lower end of the slot I2 is in sufficiently close proximity to the flames I4 to cause ignition of the pilot burner.

A projection I5, extending from the pilot burner 9, serves as a convenient means for attaching the pilot burner to any appropriate support in relation to the main burner.

The head 2 (Fig. 2) telescopes within a tube I6 and may be welded thereto. The lower end 0f tube I6 in turn is telescoped within a base member I1. The base member I'I terminates in an oval projection I8 Figs. 2I and 5) within which a metal armored cable structure I9 extends. This armored cable structure I9 includes the insulated terminal conductors 20 and ZI for the thermopile.

In the present instance there are flfteen hot junctions 43 arranged annularly within the head 2 and adjacent the top thereof. 'I'hese hot junctions are formed by alternate conductors, such as 22 and 23 (Figs. 2, 3, 8, and 9). The conductors may respectively be made of Copel and Chromel. One set of alternate conductors, such as the Copel conductors 22, may be provided with a sleeve of insulation 24 made, for example, of braided fibre glass. Furthermore, the conductors are of strip form, the ends being superposed and welded together.

The

conductors

22 and 23 form a zig-zag pattern, with the hot junctions 43 at the top and the cold junctions 28 at the bottom, as indicated at Fig. 9. These conductors actually are arranged in generally parallel arrangement, the Chromel conductors 23 having extensions 28 that project below the cold junctions 28. The conductor 20 is joined to the end Copel conductor 21, and the other terminal conductor 2| is joined to the end Chromel conductor 28. In this way, a thermopile arrangement is eilected.

In order to hold and space the conductors within the shield or shell formed by the head 2, tube I8, and the base I1, use is made of the spacer now to be described.

Thus, a spacer 29 (Figs. 2, 3, and 6) made of refractory material, such as a ceramic, is inserted in the top of the head 2. It is of generally tapered construction, and is formed with a plurality of slots 30 corresponding in number to the number of hot junctions. These slots are quite shallow, and their inner surfaces engage the inner edges of the

conductors

22 and 23. Due to the tapered coniiguration of the spacer 28, the outer edges of these conductors are urged into rm contact with a thin layer of insulation 3|, such as mica. This insulation, in turn, is in contact with a glass sleeve 32 which is in close contact with the inner surfaces of the head 2 and tube I8. 'I'his glass tube extends substantially to the bottom of the base member I1, as shown in Fig. 2.

In order to provide a proper support for the extensions 25, use is made of a core member 33 (Figs. 2, 4, and 7). This core member 33 may also be made of a ceramic material that is provided with an upper cylindrical extension 34 around which the cold junctions 28 extend. The body portion 35 of the member is also cylindrical and provided with slots 36 to accommodate the ends 25. The lower extension 31 of the core member 33 rests upon a bottom insulation washer 38 (Fig. 2) such as of asbestos, through which the

conductors

20 and 2| extend. In order to permit these conductors to pass outwardly of the lower extension 31, this lower extension may be provided with a slot 39. Furthermore, an insulation strip 40 is inserted between the ends of the

thermopile conductors

21 and 28. These ends may be provided with short insulation strips 4| and 42.

Immediately below the top of the head 2 there is an insulation washer 44 disposed on top of the spacer member 28.

The width of the

conductors

22 and 23 is such that, when the core 28 is urged rmly into place in the head 2, the outer edges of these conductors are urged outwardly into firm contact with the insulation member 3| and, therefore, in good heat transmitting relation to the head 2. The tapered configuration of the core member 29 serves to provide this outwardly directed force. These conductors are sufficiently elongated so that the cold junctions 28 are maintained at a considerably lower temperature than the hot junctions 43. 'I'his ensures proper temperature differentials between the hot and cold junctions.

One manner of assembling the parts includes the insertion of all of the parts within the glass sleeve 32 in their proper relation, as is clearly evident from Fig. 2, with the exception of the wedge member 29. The upper end of the sleeve is provided with the thin layer of insulation 3|. 'I'he wedge member is then inserted into the upperl end oi the glass sleeve 32 and insulation 3|, each pair of conductors forming the hot junction being received within a groove 38 provided in the periphery of the wedge or conical member 28. Since the wedge member tapers downwardly and inwardly, its downward insertion forces the hot junctions outwardly against the inner surface of the thin layer of insulation 3| The tubular head 2 is then telescoped over the glass sleeve 32 until it meets the tube I8, to

'which it is welded. The upper end of the tube 2 engages the upper end of the wedge 23 holding it in its wedged position within the hot junctions, and securing their conductors in firmly wedged relation against the inner surface of the mica insulation 3|.

The inventor claims: .1.

l. In a thermocouple structure: a sheath made from heat conducting material; a plurality of conductors joined in series, adjacent conductors being oi thermoelectrically dissimilar metals to form an alternate series of hot and cold junctions, the hot junctions being entirely within the sheath; and wedging means disposed centrally within said hot junctions, the wedging portion of said means urging the hot junctions toward the inner surface of the sheath; said wedging means being separate from and movable within said sheath to exert a wedging force against said hot junctions.

2. In a thermocouple structure: a cylindrical sheath made from heat conducting material; a plurality of conductors joined in series, adjacent conductors being of thermoelectrically dissimilar metals to form an alternate series of hot and cold junctions disposed within said sheath, said conductors being in side by side relationship sc that the hot junctions are all adjacent; and tapered means disposed centrally in the sheath, the tapered portion of said means urging said hot junctions outwardly toward the inner surface of the sheath; said tapered means being separate from and movable axially within said sheath to exert a wedging force against said hot junctions.

3. In a thermocouple structure: a sheath made from heat conducting rmaterial; a plurality of annularly disposed longitudinally extending conductors joined in series, adjacent conductors being of thermoelectrically dissimilar metals to form an alternate series of axially spaced hot and cold junctions, the hot junctions being entirely within the sheath; and a wedge member within the sheath and centrally of the annularly disposed conductors adjacent the hot junctions, the wedged portion of said member urging the hot junctions toward the inner surface of the sheath; said wedge member being separate from and movable within said sheath to exert a wedging force against said hot junctions.

4. In a thermocouple structure: a sheath made from heat conducting material; a plurality of annularly disposed longitudinally extending conductors joined in series, adjacent conductors being of thermoelectrically dissimilar metals to form an alternate series of axially spaced hotand cold junctions, the hot junctions being entirely within the sheath; and a tapered member formed of insulation material and disposed within the sheath and centrally of the annularly disposed conductors adjacent the hot junctions, the tapered portion of said member urging the hot junctions toward the inner surface of the sheath; said tapered member being separate from and movable axially within said sheath to exert a wedging force against said hot junctions.

5. In a thermocouple structure: a cylindrical sheath made from heat conducting material; a plurality of conductors joined in series, adjacent conductors being of thermoelectrically dissimilar metals to form an alternate series of hot and cold junctions, said conductors being in side by side relationship so that the hot junctions are all adjacent; said hot junctions being annularly spaced and disposed within the sheath; and a conical member disposed within the sheath and centrally of the hot junctions, the conical portion of said member urging the hot junctions outwardly toward the inner wall of the sheath; said conical member being separate from and movable axially within said sheath t0 exert a wedging force against said hot junctions.

6. In a thermocouple structure: a cylindrical sheath made from heat conducting material; a plurality of conductors joined in series, adjacent conductors being of thermoelectrically dissimilar metals to form an alternate series of hot and cold junctions, said conductors being in side by side relationship so that the hot junctions are all adjacent; said hot junctions being annularly spaced and disposed within the sheath; and a conical member disposed within the sheath and centrally of the hot junctions, the conical portion of said member urging the hot junctions outwardly toward the inner wall of the sheath; said member having slots in its periphery to accommodate the inner edges of the conductors forming the hot junctions; said conical member being separate from and movable within said sheath to exert a wedging force against said hot junctions.

7. In a thermocouple structure: a sheath made of heat conducting material; a plurality of conductors joined in series, adjacent conductors being o! thermoelectrically dissimilar metals to form an alternate series of hot and cold junctions, the hot junctions being entirely within the sheath; and a tapered member disposed centrally of said conductors and having a tapered portion wedging the said hot junctions between the member and the inner surface of said sheath; said tapered member being separate from and movable within said sheath to exert a wedging force against said hot junctions.

8. In a thermocouple structure: the combination of a plurality of pairs of elongated thermocouple elements annularly disposed in substantially parallel axial relation to each other and electrically joined in series to form a thermopile having axially displaced hot and cold junctions; a cylindrical sheath enclosing the said thermopile; a wedge shaped member disposed axially of said thermopile and having a wedge portion exerting an outward radial thrust on said hot junctions; said wedge-shaped member being separate from and movable axially within said sheath to exert a wedging iorce on said hot junctions; and a thin cylindrical cover member having one closed end telescoping over said sheath and said thermopile.

9. In a thermocouple structure: the combination of a plurality of pairs of elongated thermonation of a plurality of pairs of elongated thermocouple elements annularly disposed in substantially parallel relation to each other and electrically joined in series to form a thermopile having axially displaced hot and cold junctions; a sheath enclosing the said thermopile; and a wedge-shaped member in the form substantially of a frustum of a cone disposed axially oi said thermopile and having a frusto-conical portion exerting an outward radial thrust on said hot junctions.

1l. In a thermocouple structure: the combination of a plurality of pairs of elongated thermocouple elements annularly disposed in substantially parallel relation to each other and electrically joined in series to form a thermopile having axially displaced hot and cold junctions; a sheath of heat conducting material; and a wedgeshaped member in the form substantially of a frustum of a cone disposed axially of said thermopile for exerting a radial thrust on said hot junctions and having a frusto-conical portion urging said hot junctions toward said sheath.

12. In a thermocouple structure: the combination of a plurality of pairs of elongated thermocouple elements annularly disposed in substantially parallel relation to each other and electrically joined in series to form a thermopile having axially displaced hot and cold junctions; la sheath of heat conducting material; and a Wedgeshaped member disposed axially of said thermopile and having a wedge surface tapering toward the axis of the thermopile, said wedge surface of said member exerting a radial thrust on said hot junctions and urging said hot junctions toward said sheath; said wedge-shaped member being separate from and movable axially within said sheath to exert a wedging force on said hot junctions.

LAURENCE C. BIGGLE.

REFERENCES crrnn The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,197,818 Tozier Apr. 23, 1940 2,202,533 Mason May 28, 1940 2,266,416 Duclos Dec. 16, 1941 2,349,306 Ray May 23, 1944 2,374,701 Ray May 1, 1945 2,407,517 Bay Sept. 10. 1946 2,416,455 Ray Feb. 25, 1947