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Publication numberUS2892591 A
Publication typeGrant
Publication dateJun 30, 1959
Filing dateNov 25, 1955
Priority dateNov 25, 1955
Publication numberUS 2892591 A, US 2892591A, US-A-2892591, US2892591 A, US2892591A
InventorsMatthews Russell B
Original AssigneeMinnesota Mining & Mfg
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Control apparatus using thermoelectric power
US 2892591 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

June 30; 1959 R. B. MATTHEWS 2,

CONTROL APPARATUS USING THERMOELECTRIC POWER Filed Nov. 25, 1955 IIIIIIIIIIIIIIIIIII IN VEN TOR: RUSSELL B. MATTHEWS BY Ai *ZW ATTORNEYS United States Patent CONTROL APPARATUS USING THERMO- ELECTRIC POWER Russell B. Matthews, Wauwatosa, Wis., assignor, by

mesne assignments, to Minnesota Minin and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Application November 25, 1955, Serial No. 549,074

11 Claims. (Cl. 236-9) This invention relates to improvements in control apparatus and more particularly to control apparatus powered from a low power direct current source, for example a thermoelectric generator.

One of the limitations of control circuits powered from low voltage sources, for example thermoelectric generators, is that transmission losses are relatively high and therefore the length of the circuit leads or conductors must be kept relatively short in order to be able to utilize this low voltage power in the performance of use- [ful work.

With this in mind it is a general object of the present invention to provide in a control apparatus powered from a low power source, means for changing the voltage of the electric energy available from said source to a higher voltage for the energization of a control circuit, the said higher voltage permitting extension of the leads of said circuit to a location remote from said source, for example to a remotely located thermostat.

More specifically, it is an object of the invention to provide an improved control apparatus of the aforementioned character having novel means for converting the output of a low voltage direct current source, for example, a thermoelectric generator to a pulsing direct current and for feeding said pulsing current into the primary winding of a step-up transformer for induction into the secondary Winding of said transformer of a higher voltage alternating current operable to energize the control circuit. 7

Another specific object of the invention is to provide an improved control apparatus of the class' described wherein the pulsing direct current is produced by a continuously cycling device for successively interrupting and remaking the low voltage direct current circuit, said device including temperature responsive contact actuating means and heating means energized by the current flow in said direct current circuit when the contacts are in circuit-making position, said contact actuating means being responsive to the heat produced by said heating means for moving the contacts to circuit-interrupting position and terminating said heating action for reengagement of the contacts and the beginning of a new cycle.

Another object of the invention is to provide means operatively'related to the temperature responsive contact actuating means for rendering the operation of the circuit interrupting and remaking device independent of changes in the ambient temperature.

Other and further objects of the invention will become apparent as the description proceeds, reference being had to the accompanying drawing illustrating one form of the invention, wherein:

Figure 1 is a semi-diagrammatic view of a fluid fuel burning apparatus equipped with control apparatus constructed in accordance with the invention; and

Figure 2 is an enlarged longitudinal sectional view showing the construction of the preferred thermoelectric generator for powering the control apparatus shown in Figure 1. l

Referring now to Figure l of the drawing, the numeral 10 indicates a mainfuel burner which is supplied with fluid fuel under pressure through a supply conduit 11 which has a cycling type electromagnetic valve 12 interposed therein. The electromagnetic operator of the valve 12 comprises an electromagnet 13 having an energizing winding 13a having a relatively large number of turns as compared with the number of turns usually found in the electromagnets of thermoelectrically powered cycling type valves. An armature 14 cooperates with pole faces of the electromagnet 13 and is can ied by a reversely bent pivotal arm 16 which also carries a valve member 15 as shown. The arm 16 preferably includes a resilient energy storing portion, and a spring 17, acting through the arm 16, biases the valve members 15 toward its seat 18 and the armature 14 towardretracted position with respect to the pole faces of the electromagnet 13.

A pilot burner 20 is disposed in igniting relation with respect to the main burner 10 and may be supplied with fuel through a conduit 19. A thermoelectric generator, which preferably takes the form of a thermocouple 31 having at least one semi-metallic element, is mounted adjacent the pilot burner 20, \for example by a bracket 32, with its hot junction subject to the heat of burning fuelat the pilot burner 20. One of the terminals of the generator 31, for example the lead conductor 55, is connected to one end of the primary winding of a step-up transformer 40, as by a conductor 34, and the other teminal of said generator, for example the lead conductor 54 is connected to the other end of said primary transformer winding, as by a conductor 33. One end of the secondary winding 42 of the transformer 4i) may be connected to one input terminal of a full wave rectifier as by a conductor 36, and the other end of said secondary winding may be connected to the otherinput terminal of the rectifier 70, as by conductors 37 and 38 which may extend to a remote location for connectionof 'a thermostat 39 in series circuit relation with respect to the winding 42 and rectifier 70. The output terminals of the rectifier 70 may be connected in circuit with the winding 13a by conductors 71 and 72 as shown.

Means in the form of a continuously cycling device 23 is interposed in the conductor 33 as shown for successively interrupting and remaking the electrical circuit between the generator 31 and the primary winding 41 at predetermined intervals to thereby supply said primary winding with a pulsing direct current. The device 23 comprises a metallic expansible and contractible hermetically sealed enclosure which may take the, form of a cylindrical bellows of relatively thin gauge brass or other suitable electrically conductive material. The bellows 24 has opposing end walls 25 and 26, and sealingly and insulatably extending through the end wall 25 is a contact 27 which is cooperable with a relatively movable contact 23 carried by and in circuit with the end wall 26. The mounting for the contact 27 preferably also provides for the mounting of a connecting lug 29 in circuit with the end wall 25 as shown. The lug 29 and the contact 27 are connected in circuit with contiguous sections of the conductor 33 as shown. The contacts 27 and 28 are preferably made of low resistance metal, for example silver, and disposed within the bellows 24 is a temperature responsive expansible and contractible fill which does not deleteriously affect the low resistance character of the contacts. Preferably the fill takes the form of a volatile fluid which is substantially non-conductive electrically, one example of which is pentane.

For a purpose which will hereinafter appear, a bellows 43, which may be identical with the bellows 24 and may contain the same fill, is provided with an end wall 68 which may fixedly abut a suitable fixed support 70,

Patented June 30, 1959.

stress on the bellows 24 and 43 to bias the contacts 27 and 28 toward circuit-making position, and said means may take the form of a compression spring 45 acting through an abutment member 44 engaging the bellows end wall 25. The bias of the spring 45 may be adjusted by means including a rotary cam 47 engaging a thrust plate 46 which coacts with end of the spring 45 opposite the abutment member 44 as shown.

Referring now to Figure 2 of the drawing, the thermoelectric generator 31 illustrated therein comprises a pair of thermocouple element means 48 and 49, the latter of which takes the form of an elongated generally cupshaped sheath member, preferably of stainless steel. The sheath 49 has a tubular sleeve portion 50 and a tip portion 51 which may serve as a heat probe means for the assembly. The opposite end of the member 49 is telescopically received within a counterbore formed within one end of an extension tube 52 of brass or other suitable material and is sealingly fixed therein, as by silver soldering or brazing at 67. The other end of the extension tube 52 is formed with a portion of reduced diameter to snugly receive one end of a coaxial type thermoelectric generator lead 53, comprising a metallic tubular outer conductor 54 and an insulated coaxial inner conductor 55. The sleeve 52 has an end recess adjacent the lead 53, and said tube and lead are sealingly and electrically connected, for example by silver soldering or brazing, at 56.

The thermocouple element means 48 preferably comprises a rod-like or cylindrical ingot of semi-metallic alloy or composition disposed in coaxial spaced relation within the sheath 49. Because the thermocouple element means 48 is of frangible material, the generator is constructed in a manner to provide shock resistant mounting means therefor. The element means 48 includes an iron contact electrode 57 having a stem portion 58 formed with a shoulder 59. The tube 52 is formed with an internal annular shoulder 60, and surrounding the contact electrode stem portion 58 is an insulating washer 61 engaging the shoulder 60. interposed between the insulating washer 61 and the stem shoulder 59 is a compression spring 62 which may take the form of a concavo-convex centrally apertured resilient disc also surrounding the electrode stem 58.

The sheath 49 is formed with a conical inner end wall surface 63, and the semi-metallic element 48 is formed with a complementary conical end wall surface 64 which is seated against the end wall surface 63. The spring 62 exerts compressive stresses on the element 48, which stresses substantially reduce the net tensile stresses to which said element is subjected during transverse acceleration or shock, said compressive stresses not being so high as to exceed the compressive strength of said element. The bias of the spring 62 also provides the pressure necessary for a satisfactory pressure contact between the element 48 and the sheath 49 at the surfaces 63 and 64. The pressure type contact is not deleteriously effected by deformation of the element 48, for example on bending under transverse shock, and the conical nature of the surfaces 63 and 64 tends to maintain the biased element 48 in centered relationship within the tubular portion 50 of the member 49. The compressive stress under which the member 48 is placed increases the magnitude of deformation which said element can withstand without fracture and affords the generator 35 substantial shock resistance.

A tube 65 of insulating material preferably surrounds the contact electrode stem 58, and a flexible conductor 66'. extends within the tube 65 and affords an electrical connection between the stem 58 and the inner conductor of the coaxial lead 63.

The thermocouple element 48 may, for example, be formed of a semi-metallic alloy or composition which may be characterized as a binary metallic compound of slightly imperfect composition, i.e. containing beneficial impurities constituting departures from perfect stoichiometry by reason of an excess of one of the metals over the other, and/or containing added beneficial impurity substances hereinafter referred to as promoters. Such semi-metallic compositions have semi-conductor like conductance, both electrical and thermal, and include mixtures of such binary metallic compounds, which may be denominated ternary metallic alloys or compositions. Certain of these alloys or compositions exhibit negative and certain exhibit positive electrical characteristics.

More specifically, the thermocouple element 48 may, for example, be formed of an alloy further described in the copending application of Sebastian Karrer, Serial No. 475,540, filed December 15, 1954, now Patent No. 2,811,570, and assigned to the assignee of the present invention, said alloy comprising lead and at least one member of the group tellurium, selenium and sulphur. For example, a thermoelectric element 48 of lead-seleniumtelluriurn composition could include a tellurium-selenium constituent in which the selenium is but a trace. In this case such constituent should constitute from 35% to 38.05% by weight of the composition, the balance (61.95% to by weight) being lead. At the other extreme, where the tellurium-selenium constituent con sists almost entirely of selenium with but a trace of tellurium, such constituent should comprise from 25% to 27.55% by weight of the final composition, the remainder (from 72.45% to by weight) being lead. Between these two extremes, the selenium-tellurium constituent varies linearly with the ratio of selenium to tellurium (expressed in atomic precent) in the selenium-tellurium constituent.

The thermoelectric element 48 may also be formed of an alloy of lead, selenium and sulphur. For example, a thermoelectric element 48 of the lead-selenium-sulphur composition consist of a selenium-sulphur constituent in which the sulphur is but a trace. In this case, such constituent should constitute from 25% to 27.55% by weight of the composition, the balance (75% to 72.45% by weight) being lead. At the other extreme, where the selenium-sulphur constituent consists almost entirely of sulphur with but a trace of selenium, such constituent should comprise from 12.8% to 13.37% by weight of the final composition, the remainder (from 87.2% to 86.63% by weight) being lead. Between these two extremes the selenium-sulphur constituent varies linearly with the ratio of selenium to sulphur (expressed in atomic percent) in the selenium-sulphur constituent.

With regard to the aforementioned compositions, it will be observed that in each case there is an excess of lead over and above the amount thereof necessary for satisfying the stoichiometric proportions of the compound formed in the second constituent or constituents, i.e. the tellurium, selenium or sulphur. For example, the composition consisting substantially of lead and selenium can contain up to 10.4% lead by weight of the total composition over and above the 72.14% by weight lead stoichiometrically necessary for combination with seleniurn.

The electrical characteristics of the aforementioned semi-metallic alloys, desirable, for example in thermoelectric elements, can be markedly and advantageously altered in a reproducible manner by the addition thereto of controlled amounts of matter other than the constituents of the base composition. Such additions may also be denominated beneficial impurities as distinguished from undesirable impurities. For convenience. these additions are hereinafter designated promoters,

3 since they tend to enhance the electrical characteristics desired for the particular application of the base composition.

The aforedescribed base compositions exhibit negative thermoelectric power and negative conductivity. By the addition of certain promoters, such negative properties may be enhanced, While the polarity of the electrical properties of the base composition may be reversed by the addition of certain other promoters. The copending application of Robert W. Fritts and Sebastian Karrer, Serial No. 475,488, filed on December 15, 1954, now Patent No. 2,811,571, and assigned to the assignee of the present application, gives a complete description of the beneficial impurities, including both departures from perfect stoichiometry and promoters, which have been found to be efiective for improvement of the electrical properties of semi-metallic thermoelectric generator elements when added to the aforementioned base compositions in minor amounts, for example up to a maximum of 6.9% by weight of beneficial impurity, including 3.9% excess lead and 3.0% promoter.

The proportions and ranges of the various constituents aforementioned and particularly the minimum limits of the lead constituent in the compositions, must be regarded as critical if the composition is to have the electrical and physical properties desired. If the lead content is significantly less than the minimum amount indicated for any particular selenium-tellurium or seleniumsulphur proportion, the polarity of the Seebeck emf changes and the desired electrical and mechanical properties will not be reproducible. On the other hand, if the lead content of any composition appreciably exceeds the aforementioned maximum limits, the resulting composition is too metallic in nature to afford satisfactory energy conversion efliciencies.

Not only are the proportions and ranges aforedescribed to be considered critical, but so also is the purity. More specifically, the limit of tolerable metallic impurity in non-promoted final compositions has been found to be on the order of 0.01%, and the composition must be substantially oxygen free, if the mechanical and electrical properties desired are to be obtained and are to be reproducible. In the case of promoted compositions, however, the limit of tolerable impurity is 0.001%.

In order to utilize any of the aforementioned base alloy or promoted compositions in electrical devices, for example as thermoelectric generator elements, they must necessarily be electrically contacted. As previously pointed out, electrical contact with the ingot 48 is made at one end with the inner wall surface 63 by means of a pressure contact. The electrical contact with the ingot at the opposite end, however, is made by bonding of the contact electrode 57 with the end surface of the ingot 48, and if desired, the aforementioned pressure contact can be replaced by such a bonded contact. In the latter case the element-electrode interface must have a mechanical strength at least comparable to that of the alloy of which the element 48 is made. The contact electrode must be chemically stable with respect to the element 48 and provides the necessary means for connecting said element into its electrical circuit while at the same time chemically isolating said element from the other conductors making up said circuit. Iron is especially adapted for use as contact electrode material for elements 48 of lead-tellurium-selenium composition, and pressure type contacts of carbon are suitable for elements 48 of any of the aforedescribed compositions including those comprising lead and sulphur.

Since, as is well known in the art, the electrical and thermal resistance of the thermoelectric generator 35 are dependent upon the configuration thereof as well as on the electrical and thermal conductivities of the elements 48 and 49, the relationship between the dimensions of each element can be obtained which affords the highest thermal conversion efiiciency in such a mounting or assembly. In the embodiment described, the thermal con- 6 ductivity of the semi-metallic element 48 is low as com pared with that of the element 49 (for example .025 watt/cm./ C. as compared to .261 watt/cm./ C.).

For elements of any given thermal and electrical conductivities, the conversion efliciency depends strongly upon the ratio of thickness of the sheath 49 to the radius of the element 48, or more specifically, upon the cross-sectional area of the tube. In the embodiment illustrated, this ratio of the radius of the element 48 to the thickness of the sheath 49 is preferably about 6 to l or more.

It is understood, of course, that the conversion efiiciency of the thermocouple is also dependent upon the difference between the hot and cold junction temperatures. For thermocouples utilizing a semi-metallic inner element having a low thermal conductivity, high temperature differences can be achieved by selecting for the semi-metallic element a ratio of length to diameter, which in the exemplary embodiment herein disclosed is about 4 to 1, such that radiation transfer of heat from the surface of the inner element to the sheath establishes substantial temperature gradients within the inner element, particularly near the hot junction. When this is done, the heat flux into the inner element through the hot junction, i.e. the juncture of the faces 63 and 64 is exhausted to the case over the entire side wall surface of the inner element, allowing the inner cold junction, i.e. the juncture of the element 48 with the contact electrode 57, to assume a temperature only slightly greater than that of the outer cold junction, i.e. the juncture of the element 49 and sleeve 52. A further consequence of such radiative cooling is the reduced electrical resistance of the semimetallic element 48, said element having a positive temperature coefficient of resistance. The radiation responsible for the removal of the heat transmitted across the hot junction takes place between the element 48, its cold junction electrode 57, and the metal walls of the element 49 and extension tube 52. Since the cold junction temperature under such circumstances is dependent upon the temperature of its environment, it is desirable to keep the ambient temperature low. The extension of the sheath to a cooler Zone, as by the extension tube 16, provides a heat sink which aids in cooling the casing around the cold junctions.

In the operation of the improved control apparatus, the thermoelectric generator 31 produces a relatively low voltage, for example less than a volt, direct current in response to heating of the tip portion 51 thereof by the flame of the pilot burner 20, and this current flows through the primary circuit afforded by the conductor 34, primary transformer winding 41, conductor 33, contacts 2'7 and 28, end wall 26, the side wall of the bellows 24, end wall 25, lug 29 and conductor 33. By reason of the electrical resistance of the bellows walls, the flow of thermoelectric current therethrough, which occurs when the contacts 27 and 28 are in circuit-making position, produces a small amount of heat to which the fill within the bellows 24 is responsive to effect expansion of said bellows and movement of the contacts 27 and 28 in a separating direction to circuit-interrupting position. This, of course, interrupts the current flow through the primary winding 41 of the transformer and also terminates the heating action produced by the aforementioned current flow through the bellows walls. The bellows 24 and its fill thereupon, cool and the cooling of said fill effects contraction of the bellows to return the contacts to circuit-making position for the beginning of another cycle.

The device 23 continuously cycles with preferably equal periods of current flow and current interruption. As a result of the successive interruption and remaking of the aforementioned primary circuit, a pulsing low voltage direct current is supplied to the primary winding 41 of the transformer 40. This low voltage pulsing direct current induces in the secondary winding 42 of the transformer 40, an alternating current which, by virtue of the step-up character of the transformer, is of much higher voltage than that of said pulsing current for example 10 to volts or higher if desired, said alternating current having, however, substantially the same frequency as the aforementioned pulsing direct current. The alternating current from said secondary winding is supplied to the input terminals of the rectifier '70 which rectifies said current for delivery to the operator 13 as a direct current under the control of the thermostat 39. The thermostat 39 may be disposed in a space heated by the heat produced by the main burner 10 for control of the flow of fuel to the main burner in accordance with the requirements for which the thermostat is set. The relatively high voltage supplied by the secondary winding 42 permits the thermostat 39 to be located remotely from the transformer 40 if desired, since transmission losses at the higher voltage are relatively low as compared with those at lower voltages, for example those produced by the generator 31.

The response of the bellows 43 and its fill to changes in ambient temperature, opposes the response of the bellows 24 and its fill to said changes, so that operation of the cycling device 23 is independent of changes in the ambient temperature, and a relatively constant cycling frequency is thereby maintained.

The improved cycling device 23 is characterized by its high sensitivity and low differential which permits quick response to the presence or absence of thermoelectric current flow through the bellows walls. The low resistance character of the primary circuit including the walls of the bellows 24 and the contacts 27 and 28 provides for the most efficient use of the current supplied by the generator 31, and as a result, the device 23 cycles relatively rapidly, and the maximum amount of thermoelectric energy is supplied to the primary winding 41 for conversion to higher voltage alternating current by the transformer.

Having thus described one embodiment of the present invention, it is to be understood that the illustrated form was selected to facilitate the disclosure of the invention, rather than to limit the number of forms which it may assume. Various modifications, adaptations and alterations may be applied to the specific forms shown to meet the requirements of practice without in any manner departing from the spirit or scope of the present invention, and all of such modifications, adaptations and alterations are contemplated as may come within the scope of the appended claims.

What is claimed as the invention is:

l. A continuously cycling device for successively interrupting and remaking an electric circuit at predetermined timed intervals, comprising relatively movable solid metal contacts normally biased toward circuit-making position, an hermetically sealed expansible and contractible enclosure for said contacts having an electrically conductive portion of predetermined electrical resistance, a temperature responsive expansible and contractible fluid fill for said enclosure substantially non-conductive electrically and responsive to a predetermined temperature for actuation of said contacts to circuit-interrupting position, a source of electrical energy, and means connecting said enclosure portion and contacts in circuit with said source to effect current flow from said source through said contacts and enclosure portion when said contacts are in circuit-making position, current flow through said enclosure portion producing heat in response to which expansion of said fill, after a predetermined time interval following making of said circuit at the contacts, moves said contacts to circuit-interrupting position for interruption of said current flow and termination of said heat generation to permit cooling of said enclosure portion and fill in response to which contraction of said fill, after a predetermined time interval following interruption of said circuit at the contacts, returns said contacts to circuitmakiug position for the beginning of another cycle.

2. A continuously cycling device for successively. interrupting and remaking an electric circuit at predetermined timed intervals, comprising relatively movable low resistance solid metal contacts normally biased toward circuit-makiug position, and hermetically sealed expansible and contractible enclosure for said contacts having an electrically conductive portion of predetermined electrical resistance, a temperature responsive expansible and contractible fluid fill for said enclosure substantially nonconductive electrically and responsive to a predetermined temperature for actuation of said contacts to circuit-interrupting position, a thermoelectric generator having at least one semi-metallic element, and means connecting said enclosure portion and contacts in circuit with said generator to effect thermoelectric current flow from said generator through said contacts and enclosure portion when said contacts are in circuit-making position, said current flow through said enclosure portion producing heat in response to which expansion of said fill, after a predetermined time interval following making of said circuit at the contacts, moves said contacts to circuitinterrupting position for interruption of said current flow and termination of said heat generation to permit cooling of said enclosure portion and fill in response to which contraction of said fill, after a predetermined time interval following interruption of said circuit at the contacts, returns said contacts to circuit-making position for the beginning of another cycle.

3. A continuously cycling device for successively interrupting and remaking an electric circuit at predetermined timed intervals, comprising relatively movable solid metal contacts normally biased toward circuitmaking position, an hermetically sealed expansible and contractible enclosure for said contacts having an electrically conductive portion of predetermined electrical resistance, a temperature responsive expansible and contractible fluid fill for said enclosure substantially nonconductive electrically and responsive to a predetermined temperature for actuation of said contacts to circuitinterrupting position, a source of electrical energy, means connecting said enclosure portion and contacts in circuit with said source to effect current flow from said source through said contacts and enclosure portion when said contacts are in circuit-making position, current flow through said enclosure portion producing heat in response to which expansion of said fill, after a predetermined time interval following making of said circuit at the contacts, moves said contacts to circuit-interrupting position for interruption of said current flow and termination of said heat generation to permit cooling of said enclosure portion and fill in response to which contraction of said fill, after a predetermined time interval following interruption of said circuit at the contacts, returns said contacts to circuit-making position for the beginning of another cycle, and ambient temperature responsive means operatively related to said enclosure for opposing expansion and contraction thereof in response to changes in ambient temperature, thereby rendering the operation of said device independent of changes in ambient temperature.

4. In combination, a thermoelectric generator having at least one semi-metallic element, a step-up transformer having primary and secondary windings, relatively movable low resistance solid metal contacts having circuitmaking and circuit-interrupting positions, temperature responsive contact actuating means for continuously cycling said contacts between said circuit-making and circuitintermpting positions, said means comprising an expansible and contractible hermetically sealed enclosure for said contacts having an electrically conductive portion of predetermined electrical resistance, a thermally expansible and contractible fluid fill for said enclosure substantially non-conductive electrically, and means conmeeting said contacts and enclosure portion in circuit with said generator and the primary widing of said transformer to effect thermoelectirc current flow through said enclosure portion and primary winding when said contacts are in circuit-making position, said current flow producing heat in said enclosure portion for expansion of said fill and actuation of said contacts to circuit-interrupting position to produce interruption of said current flow, said current interruption terminating said heating action for contraction of said fill and return of said contacts to circuit-making position and the beginning or" another cycle, the pulsing flow of said thermoelectric current through said primary winding produced by continuous cycling of said contacts being effective to induce an alter nating current of higher voltage in said secondary windmg.

5. Control apparatus, comprising in combination, a thermoelectric generator, a step-up tansformer having primary and secondary windings, relatively movable low resistance solid metal contacts having circuit-making and circuit-interrupting positions, temperature responsive contact actuating means for continuously cycling said contacts between said circuit-making and circuit-interrupting positions, said means comprising an electrically conductive heating member of predetermined electrical resistance, means connecting said contacts and heating member in circuit with said generator and the primary winding of said transformer to effect current flow from said source through said member and primary winding when said contacts are in circuit-making position, said current flow producing heat in said member for actuation of said contacts to circuit-interrupting position and interruption of said current flow, said current interruption terminating said heating action for return of said contacts to circuitmaking position and the beginning of another cycle, the pulsing flow of said thermoelectric current through said primary winding produced by continuous cycling of said contacts being eifective to induce an alternating current of higher voltage in said secondary winding, a control circuit energized by said alternating current, and a circuitcontrolling device in said control circuit, the higher voltage of said secondary Winding permitting location of said'cir'cuit controlling device remote from said transformer and control device.

6. Control apparatus for fluid fuel burning apparatus having main and pilot burners, comprising in combination, a thermoelectric generator having at least one hot junction subject to the heat of burning fuel at said pilot burner, a transformer having primary and secondary windings, an electroresponsive fuel flow control device connected in circuit with said secondary Winding for control of the flow of fuel to said main burner, relatively movable contacts having circuit-making and circuit-interrupting positions, temperature responsive contact actuating means for continuously cycling said contacts between said circuit-making and circuit-interrupting positions, said means comprising an electrically conductive heating member of predetermined electrical resistance, means connecting said contacts and heating member in circuit with said source and the primary winding of said transformer to eifect thermoelectric current flow through said member and primary winding when said contacts are in circuit-making position, said current flow producing heat in said member for actuation of said contacts to circuit-interrupting position and interruption of said current flow, said current interruption terminating said heating action for return of said contacts to circuit-making position and the beginning of another cycle, the pulsing flow of said thermoelectric current through said primary winding produced by continuous cycling of said contacts being eifective to induce an alternating current in said secondary winding for energization of said electro-responsive control device.

7. Control apparatus for fluid fuel burning apparatus having main and pilot burners, comprising in combination, a thermoelectric generator having at least one hot junction subject to the heat of burning fuel at said pilot burner, a transformer having primary and secondary windings, an electro-responsive fuel flow control device connected in circuit with said secondary winding for control of the flow of fuel to said main burner, relatively movable contacts having circuit-making and circuit-interrupting positions, temperature responsive contact actuating means for continuously cycling said contacts between said circuit-making and circuit-interrupting positions, said means comprising an electrically conductive heating member of predetermined electrical resistance, means connecting said contacts and heating member in circuit with said source and the primary winding of said transformer to effect thermoelectric current flow through said member and primary winding when said contacts are in circuit-making position, said current flow producing heat in said member for actuation of said contacts to circuit-interrupting position and interruption of said current flow, said current interruption terminating said heating action for return of said contacts to circuit-making position and the beginning of another cycle, the pulsing flow of said thermoelectric current through said primary winding produced by continuous cycling of said contacts being effective to induce an alternating current in said secondary winding for energization of said electromesponsive control device, the circuit connecting said secondary winding to said electroresponsive device including a full wave rectifier for changing said alternating current to direct current for delivery to said electroresponsive device.

8. Control apparatus for fluid fuel burning apparatus having main and pilot burners, comprising in combination, a thermoelectric generator having at least one hot junction subject to the heat of burning fuel at said pilot burner, a step-up transformer having primary and secondary windings, an electroresponsive fuel flow control device connected in circuit with said secondary winding for control of the flow of fuel to said main burner, a condition responsive circuit-controlling device in circuit with said flow control device for controlling energization of the latter, relatively movable contacts having circuit-making and circuit-interrupting positions, temperature responsive contact actuating means for continuously cycling said contacts between said circuit-making and circuit-interrupting positions, said means comprising an electrically conductive heating member of predetermined electrical resistance, means connecting said contacts and heating member in circuit with said source and the primary Winding of said transformer to eflect thermoelectric current flow through said member and primary winding when said contacts are in circuit-making position, said current flow producing heat in said member for actuation of said contacts to circuit-interrupting position and interruption of said current flow, said current interruption terminating said heating action for return of said contacts to circuit-making position and the beginning of another cycle, the pulsing flow of said thermoelectric current through said primary winding produced by continuous cycling of said contacts being efiective to induce a higher voltage alternating current in said secondary winding for energization of said electroresponsive control device, said higher voltage permitting location of said circuit controlling device remote from said transformer and flow control device.

9. In combination, a direct current source, a transformer having primary and secondary windings, relatively movable solid metal contacts having circuit-making and circuit-interrupting positions, an hermetically sealed expansible and contractible enclosure for said contacts having an electrically conductive portion of predetermined electrical resistance, a temperature responsive expansible and contractible fluid fill for said enclosure substantially non-conductive electrically and responsive to variations in temperature for moving said contacts between said circuit-making and circuit-interrupting positions, and means connecting said contacts and enclosure.

portion in circuitwith said source and the primary winding, of, said transformer to effect current flow from said source through said enclosure portion and primary winding when said contacts are in circuit-making position, said current flow producing heat in said enclosure portion for actuation of said contacts to circuit-interrupting position and interruption of said current flow, said current interruption terminating said heating action for return of said contacts to circuit-making position and the beginning of another cycle, the pulsing. current flow through said primary winding produced by continuous cycling of said contacts being effective to induce an alternating current in said secondary winding.

10. In combination, a thermoelectric generator having at least one semi-metallic element, a step-up transformer having. primary and secondary windings, relatively movable solid metal contacts having circuit-making and circuit-interrupting positions, an hermetically sealed expansible and contractible enclosure for said contacts having an electrically conductive portion of predetermined electrical resistance, a temperature responsive expansible and contractible fluid fill for said enclosure substantially nonconductive electrically and responsive to variations in temperaturev for moving said contacts between said circuit-making and circuit-interrupting positions, and means connecting said contacts and enclosure portion in circuit with said generator and the primary winding of said transformer to effect current flow from said source through said enclosure portion and primary winding when said contacts are in circuit-making position, said current flow producing heat in said enclosure portion for actuation of said contacts to circuit-interrupting position and interruption of said current flow, said current interruption terminating said heating action for return of said contacts to circuit-making position and the beginning of another cycle, the pulsing flow of thermoelectric current through said primary winding produced by continuous cycling of said contacts being effective to induce an alternating current of higher voltage in said secondary winding.

11. In combination, a direct current source, a transformer having primary and secondary windings, relatively movable contacts having circuit-making and circuit-interrupting positions, an hermetically sealed expansible and contractible enclosure for said contacts having an electricaily conductive portion of predetermined electrical resistance, a temperature responsive expansible and contractible fluid fill for said enclosure responsive to variations in temperature for moving said contacts between said circuit-making and circuit-interrupting positions, and means connecting said contacts and enclosure portion in circuit with said source and the primary winding of said transformer to eiiect current fiow from said source through said enclosure portion and primary Winding when said contacts are in circuit-making position, said current flow producing heat in said enclosure portion for actuation of said contacts to circuit-interrupting position and interruption of said current flow, said current interruption terminating said heating action for return of said contacts to circuit-making position and the beginning of another cycle, the pulsing current flow through said primary winding produced by continuous cycling of said contacts being efiiective to induce an alternating current in said secondary Winding, and ambient temperature responsive means opposing the response of said fluid fill to changes in ambient temperature, thereby rendering cycling of said contacts independent of changes in the ambient temperature.

References Cited in the file of this patent UNITED STATES PATENTS.

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US3022361 *Oct 24, 1956Feb 20, 1962Minnesota Mining & MfgElectrical device
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Classifications
U.S. Classification236/9.00R, 236/75, 136/217, 337/2, 136/228, 337/117
International ClassificationF23N5/02, F23N5/10
Cooperative ClassificationF23N5/105
European ClassificationF23N5/10D