US2349306A - Thermoelectric device - Google Patents

Description

Mayr 23, .1944. W, A RAY 2,349,305

THERMOELECTR'IC DEVICE Filed sept, 12. 1941' Jg/ /a Snventor, 50 h//LL/AMA. /QAV l Cttorneg Y Patented May 23, 1944 -THERMOELECTRIC DEVICE William A. Ray, Los Angeles, Calif.

Application September 12, 1941, Serial No. 410,545 l (Cl. 13G-4) 4 Claims.

My present invention relates to thermoelectric generating devices, and particularly to those of the type adapted for the energization of sensitive 'control devices, such as electromagnetically operated valves or switches, in distinction to those of the type employed for the measurement of v temperature differences.

Devices of the type indicated are commonly employed for the control of gas-burning systems, the device usually being arranged so as to be heated by the flame of a pilot burner provided for the ignition of the main burner of the system.

' so that the device serves not only as a convenient source of eltrical energy independent of'the utility service, but also as safety means which, due to the resultant cessation of generation, acts to renderthe system inoperative upon accidental extinguishment of the pilot burner ame.

When the device is heated by a gas name, the dissimilar metals of which it is composed are subject only to oxidation but also to the corrosive action of the burnt and unbumt gases, and for this reason means. such as a. cap of stainless steel, have been proposed for protecting the hot junction or juncnons of the device from the flame. However, it has been found that such means are inadequate, particularly' when relatively high direct and/or ambient temperatures are involved. due to the action of the gases which penetrate beneath the shield and affect the thermocouple elements. It is therefore an object of my invention to provide means for hermetically sealing the heated portions 'of the thermoelectric device from the atmosphere without, however, materially reducing the transfer of the heat of the flame to the hot junction.

Other objects and advantages of my invention will be found in the description, the drawing, and the appended claims.

For complete understanding of the invention, reference may be had to the following detailed description and accompanying drawing, wherein:

Figure 1 is a side elevation of a thermoelectrc Y device embodying my invention, the device being shown mounted in a gas burner, by the flame of which it is heated;

Figure 2 is an enlarged longitudinal section of the thermoelectric device i3 shown in Fig. 1, taken generally along the line 2--2 of Fig. 3;

Figures 3 and 3a are enlarged transverse sections taken respectively along the lines 3 3 and 3a-3a of Fig. 2; and

Figure 4 is a developed view of the thermocouple arrangement of the device shown in the other figures.

Referring first to Fig. 1 of the drawing, the

numeral Il generally indicates a gas burner ofv sheet-metal construction, the halves of which are joined together as by stitch-welding l2. A thermoelectric generating device I3, oi the same construction as that shown in section in Fig. 2, is mounted in a screw socket i4 carried in the lower end of a dependent tubular portion l5 of the burner and extends through a clearance opening in the top of the burner. Gas is supplied to the burner by a pipe I6 and passes upward through a mixing chamber Il and branch I8 to issue around the tip 34 of the thermoelectric device as a flame I9 which heats the same. Provision is also made for a main-burner igniting name 20. The general type of device-supporting burner shown by way of example is more particularly disclosed in the copending application of William R. Ray, Serial No. 387,591, led April 9, 1941.

Referring now to Figs. 2-4, the numeral 2| indicates a cylindrical tubular member or envelope of vitreous material, such as glass, having a closed upper end. Integral with and dependent from the underside of the top wall of the member is a cylindrical glass boss 22 (see Fig. 3a) which defines, with the adjacent side wall of the member, an annular recess for receiving a circular group of the twisted upper end portions 23'of a series of pairs of thermocouple wires or elcments, better seen in the developed view of Fig. 4. Each pair of elements consists of a wire 24 of one metal and another wire 25 of a diierent metal, the wires being threaded through openings formed in a circle in a disk 26, of ceramic material such as porcelain, and twisted together at opposite sidesof the disk to form the upper portions 23 and lower portions 21, 'Ihe wires are welded or fused together at their points of rst contact to form hot" junctions 23 and cold" junctions 29. It will be understood that the terms hot and "cold are employed merely to conveniently indicate the opposite junctions of a thexmocouple, the hot junction being the one whuh is subjected to heat or cold, while the other or r;old" junction is subjected to the ambient temperature; The material of the thermocouple elements may be selected from any of the well known alloys having high opposite thermoelectric powers, such as Chromel and Copel; or, when relatively low temperatures are involved, may be of such metals as bismuth and antimony. The series of pairs of elements form a series-connected thermopile, the E. M, F. of which equals the sum of the E, M. F.s of the several pairs. For the sake of clarity, only six pairs of elements have been shown, but in actual construction a considerably higher number is preferably provided, the elements being of wire 0.010 inch diameter or smaller.

The end elements of the thermopile are each inserted in and welded to one end of a pair of thin-walled tubes 30, of good electrically-conductive metal such as copper. Each of the coldjunction lower portions 21 of the thermopile is similarly connected to one of a series of tubes 3|, which may also be of copper or other metal having good thermal conductivity. The tubes 30 and 3l extend through openlngsjin a pair of insulating disks 32 which are maintained inV spaced relation by a Vrod 33 which passes through central openings in these disks and also in disk 26, the rod after assembly being pinched-out on either sides of the disks to hold them in position.

' The disks are a free iit in the Vtubular member 2l, into the initially-open bottom end of which the envelope andthe hot junctions, while protecting the same fromrthe harmful effect of air and other gases.

While I have herein shown and Ydescribed aY speciiic embodiment of my invention, I wish it to be understood that modifications may be -made i without departing from the spiritof the Vinventhe thermople assembly is inserted as a unit so that its upper end hot-junction portions 23 are within the recess dened'by the boss 22 and the adjacent wall of the tubular member, as was mentioned above. After such assembly, the upper portion or tip 34 of member 2|, surrounding the' tion, and that I intend therefore to be limited only by the scope of the appended claims.

`I claim as my invention: 1 1. VA thermoelectric generator 'comprising a, plurality of'pairs of elongated thermocouple elements annularly arranged insubstantially parallel axial relation to each other and joined in electrical sethermocouple hot-junction portions v23, is soff account of its strength may be provided in thinlwalled form-but also to synthetic organic plastics when relatively low temperatures areinvolved. It is to be noted that plastics are now available which are claimed to withstand the diries to form a thermoplel having hot and cold junctions at its opposite ends, and an elongated hollow cylindrical member of vitreousrmaterial having a closed end provided with an internal annular recess for so closelyreoeiving thehotjunction portions-of said elements that they are maintained in Agood heat-transferv relation to the member.

rect action of flame and hence would be well adapted'for use in the present invention. 'Ihese vplastics are known as poly-silicone resins, and

contain silicon as well as carbon. Y

After the assembly of the thermople' unit in the member 2|, the same is sealed-off at its lower end as by fusion and provided with a screw-shell connecting-base 35 to which the terminal tubes 2. A thermoelectric generator comprising a plurality of pairs of elongated thermocouple elements annularly arranged in substantially parallel axial relationY to each other and joinedin electrical series to form a thermople having hot'and cold junctions at its opposite4 ends, and an elongated hollow ,cylindrical member `of vitreous material having aclosed end provided with an internal annular recess for so closely receiving the Vhot-junction portions of said elementsthat they are maintained in good heat-transfer relation to the member, the other end of said member also being closed so as to isolate the hot junctions from the atmosphere. Y Y

3. A thermoelectric generator comprising a plurality of pairs of elongated thermocouple ele- 3E are'electrically connected by wires 36. Before` Y sealing-oil, the member 2| may be evacuated. or. preferably, filled with an inert gas such as nitro- Een to aid'the conduction of heat away from theV cold junctions 29. The purpose of the tubes- 3|, connected to the intermediate cold-junction pore tions21 of the thermople, is also to dissipate the heat which is conducted from the hot junctions. to the cold junctions through the short portions oi.' the elements which interconnect them. This feature is covered in the copending application of wimam R. Ray, serial No. 265,974, med April 4,.

1939. Due to the shortness of the thermocouple elements, the total electrical resistance of the Y thermople is held 'at a low value, although the materials of which the elements are usually .constructed have high specific resistance. The bottom end of rod 33 may extend into abutting relation to the base 35 to serve as support for the thermople additional to that Vprovided by theY rolled-in portion 34 of member 2l. To increase their effect, the cooling tubes 3J may, in some embodiments of the invention, extend to the atmosphere through the bottom of the glass enV velope.

In the prior art. there are found examples of thermocouples, usually employed for electrical measurements, which are mounted in evacuated glass vessels and heated by electrical means adjacent their hot junctions. However, the purpose of such an arrangement is to thermally insulate the hot junctions from the atmosphere, whereas the main object of my present invention is to effect good heat-transfer between the exterior of ments annularly arranged in .substantially parallel axial`re1ation' to each other and joined in electrical `series to form a thermople having a. plurality of hot and ofr cold jnctions at its o'pposite ends, heat-conducting and -collectingmetallic means joined to Vand extending from each of said hot junctions, and an elongated hollow cylindrical member of vitreous material having a Y closed end provided will an internal annular recess for so closely'receiving said heat-conducting means that they are maintained -in good heattransfer relation tothe member, the other end of said member also being closed so as to isolate the hot junctions and the heat-conducting means from the atmosphere.

4. A thermoelectric genera rality of pairs of elongated thermocouple elements annularly arranged in substantially parallel axial .relation to each other and joined in electrical series to form a-thermopile having a plurality of hot and of cold junctions at its opposite ends, heat-conductingrand -collecting metallic means joined to and extending from each of said hot junctions, heat-conducting and -dissipating metallic means joined to and extending from each of said V,cold junctions, and an elongated hollow vcylindrical member of vitreous Ymaterial having a closed end provided with an internal annular recess for so closely receiving said heat-collecting means that they are maintained in good heattransfer Yrelation ,to the member, said thermocouple elements being relatively short so that their cold junctions and at least a portion of said heat-dissipating means are Within the member and toward the other end thereof.

WILLIAM A. RAY.

tor Ycomprising a plu-

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