US2385530A

US2385530A - Thermoelectric device

Info

Publication number: US2385530A
Authority: US
Inventors: Paille Eugene
Original assignee: General Controls Co
Current assignee: General Controls Co
Priority date: 1942-04-18
Filing date: 1942-04-18
Publication date: 1945-09-25
Anticipated expiration: 1962-09-25

Description

Sept 25, 1945. E PALLE THERMOELECTRIC DEVICE Filed April 18, 1942 Bnnentor, [wf/VEQA/LLE /W if.

ad f Gttorneg Patented Sept. 25, 1945 THERMOELECTRIC DEVICE Eugene Paille, Los Angel es, Calif., assignor to General Controls Co., Glendale, Calif., a corporation of California Application April 18, 1942, Serial No. 439,494

Claims.

My present invention relates .to thermoelectric devices of the type adapted to generate electricity when a suitable temperature difference exists in the device.

A main object of this invention is the provision of a device of the character described which, upon the application of heat thereto, generates a relatively high initial E. M. F'. which is rapidly reduced to a constant lower value upon continued heating.

While not so limited, the device of the present invention has particular utility for the energization of the electromagnet employed in electromagnetic manual-reset control means for a uid control valve or electric switch. Such control means generally comprises an armature, movable to operate the valve member or switching mechanism, and an electromagnet adapted to magnetically hold the armature only when the same is first manually brought into engagement with the core of the electromagnet-the electromagnet being incapable of attracting the armature through space. When the energization of the electromagnet is interrupted, or suiliciently reduced, the armature, being biased away from the electromagnet, operates the valve member or switching means to render the system controlled thereby safe-manual-resetting of the control means then being required to reinitiate operation of the system, after the abnormal condition which caused the deenergization of the electromagnet has been corrected.

When the manual-reset control means is employed in connection with gas-burning apparatus, the thermoelectric generating device is preferably arranged to be heated by the pilot burner of such apparatus, so that if the same becomes extinguished, the control means acts to shut-off the supply of gas to the main burner. Obviously, it is desirable that such safety shut-01T should occur as promptly as possible. However, as is Iwell known, the energization necessary for initial magnetic holding of the armature in the resetting operation is considerably greater than that required to maintain it in its held position; an undesirably large period therefore elapsing after extinguishment of the pilot burner flame before the thermoelectric device can cool to a temperature at which its energization of the electromagnet is suiiciently reduced to permit release of the armature. The thermoelectric device of the present invention is adapted, upon heating, to generate initially the large amount of energy necessary for readily resetting the armature-,- continued heating of the device eiecting rapid reduction of its output of energy to a constant amount which is only slightly more than that required to maintain 'the armature in its reset position, so that upon extinguishment 1 of the pilot burner ilame the amature is promptly released.

Another object of this invention is the provision of a thermoelectric device, of the character described, ewherein the rate of reduction of generation upon cooling is greater than is its rate of increase upon initial heating.

Another object is the provision, in a thermoelectric device of the character described, of independent means for generating opposing E. M. Fs., and means for delaying the operation of one of said means upon initial heating of the device.

Other objects and advantages of the invention will be found in the description, the drawing, and the appended claims; and for complete understanding of the invention, reference may be had to the following detailed description and accompanying drawing wherein:

Figure 1 is a generally diagrammatic view of a iiuid control system including a thermoelectric device embodying my invention;

Figure 2 is a diagrammatic view of a modified form of thermoelectric device according to my invention;

Figure 3 is a longitudinal sectional view of a further modification o1' the device: and

Figure 4 is a graph illustrating typical generation characteristics of the devices shown in the other gures.

Referring iirst to Fig. 1 of the drawing, the numeral II indicates a valve casing having a passage I2 therethrough -provided with a valve seat I3. Mounted in a housing I4, covering an opening in the top wall of the valve casing, is an electromagnet comprising a U-shaped core I5, around one arm of which is wound an energizing coil I6. Cooperable with the core l5 is a disk-shaped armature I1 which also serves as a closure member for the valve by cooperation with the seat I3.

Connected by leads IB to the coil I6 is a thermoelectric device generally indicated at I9, a condition-responsive switching device 20 being inserted in one of the leads. The device I9 comprises a pair of thermocouples 2| and 22; the thermocouple 2l being composed of thermoelectrically dissimilar elements or wires 23 and 24 joined at their outer ends to form a. hot junction 25, and the thermocouple 22 being similarly comand 21 having a not Juncelement 25. For the sake of convenience it may be assumed that the two thermocouples are constructed of the same materials, such as the wellknown alloys Chromel and Copel, in which case elements 23' and 26 are of one of these alloys and elements 24 and 21 of the other. However, it is to be understood that for the purpose of my invention the thermocouples may be constructed of such different materials that, under the same conditions, the generation of one thermocouple is somewhat greater than that of the other. Since the thermocouples are in series-aiding relation to each other, maximum current ilows in the closed circuit consisting of

elements

23, 24, 26 and 21 when both of the hot junctions 25 and 28 are heated; however, under that condition, minimum current then ilows through leads I8 to the electromagnet coil I since the leads are connected to the

cold junction connections

29 and 30 of the thermocouples, and hence, effectively, the coil is energized by both of the thermocouples in parallel, the voltage delivered to the coil by one thermocouple being in a sense opposite to that delivered by the other.

The thermoelectric device I9 is shown arranged to be heated bythe ilame 3| of a burner 32, hot junction 28 being exposed directly to the flame and hot junction 25 being shielded from direct radtion from the ilame by an insulating bafile l In describing the operation of the system shown in Fig. 1, it will be assumed, by way of example, that the valve casing I is connected to supply gaseous fuel to a main burner, for which the burner 32 serves as a pilot, an automatically or manually operated valve being inserted between the casing I| and the main burner. 'I'he pilot burner 32 is preferably connected between the two valves so that its supply of fuel is controlled by the valve illustrated. The closure member I1 of that valve is shown in the gure in its open position, in which position it normally will remain while the pilot burner 3'2 is burning and the switch is closed, this switch being adapted to open only when some abnormal condition exists, such as an excess of the temperature or pressure to which it may be responsive. Let it be assumed that the pilot burner ilame 3| has been extinguished and that the resultant cessation of current generation by the thermoelectric device I9 has caused deenergization of the electromagnet so that the armature-closure member II has dropped by gravity into engagement with seat I3, obstructing fuel supply to the main burner and to the pilot burner 32. The closure member I1 is now raised from'its seat, and into engagement with the pole faces of core I5, by manual operation of a reset stem 34 through its externally extending button portion 35. While thus holding the armature-closure member I1 in engagement with the core I5, the fuel now flowing to the pilot burner is lighted by a, match. The temperature of the hot junction 28 of the lower thermocouple 22 is quickly raised by the flame (the hot junction of the upper thermocouple 2| being initially substantially unaffected on account oi! the baille 33) so lthat current ows to the electromagnet in an amount soon sumcient to cause the amature I1 to be magnetically held in engagement with the-core I5, whereupon the reset stem 34 may be released, the parts then being in the positions shown in Fig. 1. It will be understood that the current generated by thermocouple 22 also flows through the other thermocouple 2|, in parallel with the electromagnet coil I8, but this has no useful eiect. Continued heating of the baille 33, which is preferably of ceramicmaterlal, raises its temperature to a degree at which the hot junction 25 is affected by the heat then radiated by the baille, which causes the thermocouple 2| to generate current which tends to energize coil I6 in a sense opposite to that due to thermocouple 22, with the result that the power of the electromagnet is substantially reduced, but is still suillcient to maintain the armature in its attracted position.

If the pilot burner flame 3| should now be extinguished, both of the hot junctions 25 and 23 will rapidly assume the same temperature (or a temperature at which their individual eiects are equal and opposite) since, after removal of the ilame, they are substantially equally affected by radiation from the heat-retaining baille 33, and the resultant deenergization of the electromagnet elects immediate release of the armatureclosure member to render the system safe."

The operation of the thermoelectric device I9 is graphically shown in Fig. 4: 'I'he line 36 indicates the initial generation of the device due to the effect of heating substantially only the thermocouple 22, the E. M. F. represented by the upper portion of this line being great enough to permit ready resetting of the armature; the line 31 indicates the subsequent reduction in energy (to about one-half the maximum value) due to the additional heating of thermocouple 2|; the broken line 38 indicates the constant reduced value of generation by the device; and the steeply inclined line 39 indicates the accelerated equalization of generation of the opposing thermocouples, described in the preceding paragraph.

In Fig. 2, I have shown a modified form of thermoelectric device, the effective operation of which is substantially the same as that of the device I9 shown in Fig. 1. This device, generally indicated at 40, comprises an upper thermocouple 4| having a hot junction 42, and a lower thermocouple 43 having a hot junction 44, the hot junctions being separated by the baille 33 as in the system of Fig. 1. The thermocouples are connected in series with each other (to form a cold junction 49) and with the load I6, element 45 of thermocouple 4| being of the same (or thermoelectrically-similar) material as the element 46 of thermocouple 43, and, likewise, the element 41 of `the same material as element 48. The thermocouples are thus in series-opposing relation to each other so that the energy delivered to the coil I6, when both of the hot junctions are heated, is equal to the difference between that generated by the individual thermocouples; maximum energy being produced in the coil when the hot junction 44, only, is heated.

The still further modified form of thermoelectric device shown in Fig. 3 comprises an elongated tubular member 50, within which is a short rod 5| which is secured at one end, as by fusion or welding 52, to one end of the tubular member, the remainder of the rod being spaced from that member. Welded to the inner end of rod 5| is a smaller rod 53, from the free end of which a lead 54 extends to one terminal of the coil I3,

the other coil terminal being connected by a lead 55 to the free end o! the member 50. The rod I is of metal having one .thermoelectric power, such as Chrome1, and the tubular member 50 of metal having a substantially diierent thermoelectric power, such as Alumel; the small rod 53 being of the same metal as that of member 50, or of some other metal which dilers thermoelectrically from that of rod 5| and in the same sense as that of member 50. The welded portion 52 forms the hot junction of the device, and the junction 56 between the rods 5I and 53 serves as an intermediate or secondary hot junction; the portions of the elements to which the coil leads are connected constituting the effective cold junction of the device. Upon initial heating, the-generation of the device is due solely to the rise in temperature at the hot junction 52, the intermediate junction 56 being thermally substantially unaffected since it is shielded from the name. Upon continued heating, the junction 55 becomes heated mainly by conduction through rod 5l and the E. M. F. thus produced opposes that generated at junction 52, with the result that the current through the coil is reduced. The device thus functions in a manner similar to that of the other devices shown in Figs. 1 and 2. l While I have herein shown and described specic embodiments of my invention, I wish it to be understood that modifications may be made without departing from the spirit of the invention and that I intend therefore to be limited only by the scope of the appended claims.

I claim as my invention:

1. In combination: an electromagnetically operated device comprising a core, a coil for said core, an armature adapted to be magnetically held in attracted position by said core only when it is first mechanically brought into engagement therewith and while the core is energized by current flow through said coil, said armature being biased to unattracted position, means for mechanically moving the armature into engagement with the core, and control means connected to said armature; a thermoelectric generating device for energizing said coil and connected thereto; and a source of heat for said thermoelectric generating device; said thermoelectric generating device being adapted to supply to said coil a predetermined amount of current upon initial heating by said source and a smaller amount after prolonged heating, and comprising a pair of thermocouples each having eiectively a "hot" junction and a cold junction; said thermocouples being so'electrically interconnected that the generation of the individual couples of the thermoelectric generating device, due to the heating of their hot junctions, is in opposition; one of said hot junctions being subjected directly to said source of heat; the other of the hot junctions being so arranged that it is only indirectly heated by said source, so that upon continued heating its temperature approaches but does not reach the temperature of said one of the hot junctions; the cold junctions of the generating device being so arranged that they are substantially unaiected by the heat of said source.

2. In combination: an electromagnetically operated device comprising a core, a coil for said core, an' amature adapted to be magnetically held in attracted position bysaid core only when it is iirst mechanically brought into engagement therewith and while the core is energized by current ow through said coil, said armature being biased to unattracted position, means for mechanically moving the amature into engagement with the core, and control means connected to l.

`a predetermined amount of current upon initial heating by said source and a smaller amount after prolonged heating, and comprising a pair of thermocouples each having effectively a hot junction and a cold junction; said thermocouples being so electrically interconnected that the generation of the individual couples of the thermoelectric generating device, due to the heating of their hot junctions, is in opposition; one of said hot junctions being subjected directly to said source of heat; and means for shielding the other of the hot junctions from direct radiation of heat from said source; the cold junctions of the generating device being so arranged that they are substantially unaffected by the heat of said source.

3. In combination: an electromagnetically operated device comprising a core, a coil for said core, an armature adapted to be magnetically held in attracted position by said core only when it is first mechanically brought into engagement therewith and while vthe core is energized by current ow through said coil, said armature being biased to unattracted position, means for mechanically moving the armature into engagement with the core, and control means connected to said armature; a thermoelectric generating device for energizing said coil and connected thereto; and means for producing a flame for heating said thermoelectric generating device; said thermoelectric generating device being adapted to supply to said coil a predeterminedI amount of current upon initial heating by said flame and a smaller amount after prolonged heating, and comprising a pair of thermocouples each having effectively a hot and a cold" juncs a bailie interposed between said hot junctions and serving to screen one of the hot junctions from direct radiation from the ame while permitting direct subjection to the ilame of the other of the hot junctions; said thermocouples being so electrically interconnected that the generation of the individual couples of the thermoelectric generating. device, due to the heating of their hot junctions, is in opposition.

4. In combination: an electromagnetically operated device comprising a core, a coil for said core, an armature adapted to be magnetically held in attracted position by said core only when it is rst mechanically brought into engagement therewith and while the core is energizedby current ow through said coil, said armature being biased to unattracted position, means for mechanically moving the armature into engagement with the core, and control means connected to said armature; a thermoelectric generating device for energizing said coil and connected thereto; and means for producing a flame for heating said thermoelectric generating device; said thermoelectric generating device being adapted to supply to said coil a predetermined amount of current upon initial heating by said flame and a smaller amount after prolonged heating, and comprising a pair of thermocouples each having a hot and, effectively, a "cold junction; said hot junctions being located adjacent each other for heating by said ilame; a baille interposed between said hot junctions and serving to screen one of the hot junctions from direct radiation from the ilame while permitting the other of the hot junctions to be exposed directly to the flame; said thermocouples being joined together at one of their respective cold-junction ends in seriesaiding relation to each other, the other of the respective cold-junction ends of the thermocouples being likewise joined together; and a lead extending to said coil from each o1' said junctions of the cold-junction ends of the thermocouples.

5. In combination: an electromagnetically operated device comprising a core, a coil for said core, an armature adapted to be magnetically held in attracted position by said core only when it is ilrst mechanically brought into engagement therewith and while the core is energized by current flow through said coil, said armature being biased to unattracted position, means for mechanically moving the armature into engagement with the core, and control means connected to said armature; a thermoelectric generating device for energizing said coil and connected thereto and means for producing a name for heating said thermoelectric generating device; said thermoelectric generating device being adapted to supply to said coil a predetermined amount of current upon initial heating by said flame and a smaller amount after prolonged heating, and comprising-a pair of thermocouples each having a hot junction and, eiectively, a "cold Junction; said hot Junctions being located adjacent each other for heating by said flame; a baille interposed between said hot junctions and serving to screen one of the hot junctions from direct radiation from the -ilame while permitting the other of the hot junctions to be exposed to the flame; said thermocouples being Joined together at one of their respective cold-junction ends in series-opposing relation to each other; and a lead extending to said coil from each of the other cold-junction ends oi! the thermocouples; the cold Junctions of the generating device being so arranged'that they are substantially unaffected by the heat o! said ame.

EUGENE PAILLE.