US2767355A

US2767355A - Thermoelectrically powered control apparatus

Info

Publication number: US2767355A
Application number: US341550A
Authority: US
Inventors: John A Wolff
Original assignee: Milwaukee Gas Specialty Co
Current assignee: Milwaukee Gas Specialty Co
Priority date: 1953-03-10
Filing date: 1953-03-10
Publication date: 1956-10-16
Anticipated expiration: 1973-10-16

Description

Oct. 16, 1956 l J. A. woLFF' 2,757,355

TRERMOELEOTRIOALLY POWERED CONTROL APPARATUS John ff'. BY

Oct. 16, 1956 J. A. woLFF 2,767,355

THERMOELECTRICALLY POWERED CONTROL APPARATUS Filed March l0, 1953 2 Sheets-Sheet 2 INVENTOR. rfc/fz j? (/lf United States Patent O THERMOELECTRICALLY POWERED CONTROL APPARATUS John A. Wolff, Milwaukee, Gas Specialty Company, tion of Wisconsin Wis., assigner to Milwaukee Milwaukee, Wis., a corpora- This invention relates to improvements in thermoelectrically powered control apparatus and more particularly to a safety shut-off system for fuel burners or the like having a thermoelectric generator as its sole source of power, said system being operable to shut off the ow of fuel to the burners upon occurrence of predetermined conditions.

Thermoelectrically powered safety devices have found wide application in the control of fuel flow to burners. These devices are operable to close a shut-E valve upon extinguishment of a pilot flame. It has been recognized as desirable to provide for safety shut-olf of the fuel supply in response to predetermined conditions rother than pilot failure, for example, in response to excessive te'mperature conditions in a heated space, such as in a water heater tank, a clothes drier, a space heater or the like; and it is particularly desirable to incorporate such a feature in a conventional therrnoelectrically powered safety shut-off circuit having a thermoelectric generator as its sole source of power.

Due to the fact that a thermocouple is capable of only limited power generation, frequently on the order of twenty millivolts, the resistance in a circuit powered thereby is critical. The mere formation of a film on a set of contacts in a circuit of this type can create a resistance high enough to prevent proper operation of a safety shut-olf device controlled by the circuit.

It is therefore a principal object of the present Vinvention to provide an improved control apparatus having embodied therein a thermoelectric safety device and-also having means for actuating said safety device in response to predetermined conditions other than pilot failure, the improved apparatus having a thermoelectric generator as its sole source of electric power.

Another object of the invention is to provide means for readily associating a condition responsive device with a presently installed pilot `flame controlled thermoelectric safety shut-off apparatus to provide for operation of the latter under the dual control of the condition responsive device and the pilot flame without requiring an additional power source.

A more specific object of the invention is to provide an improved control apparatus of the character described in which the condition responsive means takes the -form of a temperature responsive circuit interrupting device comprising a Ypair of coacting contacts mounted within an encapsulating enclosure and connected in series circuit relationship with the thermoelectric generator and the thermoelectric safety device.

Another specific object of the invention is to provide Van improved unitary junction block -and electromagnet assemblage which is readily interchangeable with the electromagnet and lead connector of a presently installed thermoelectricshut-oif device, vsaid assemblage alfording means for readily veffecting a series circuit connection of a separate condition responsive device between the electromagnet of said assemblage and the thermoelectric generator of said shut-olf device.

A further object of the invention is to provide an improved unitary junction block and electromagnet assemblage of the character described which is adapted to be embodied in a thermoelectric control apparatus wherein the thermoelectric generator is provided with a concentric type lead, said assemblage providing for series circuit connection of the condition responsive device between the inner conductor of said lead and the electromagnet of said assemblage.

A further object of the invention is to provide an improved unitary junction block and electromagnet assemblage for use in the improved control apparatus which assemblage is simple in construction and easy to manufacture, said assemblage being so compact that it occupies not substantially more space than the electromagnet and lead connector assemblies of prior safety shut-off devices.

Further objects and advantages of the invention will appear from the following detailed description taken in connection with the accompanying drawings which illustrate one complete embodiment of the preferred form of the invention and in which:

Figure 1 is a semi-diagrammatic elevational view of the improved control apparatus as applied to a water heater;

Figure 2 is an enlarged fragmentary axial sectional view of the improved unitary junction block and electromagnet assemblage along with a thermocouple and the lead connections therefor;

Figure 3 is a reduced scale plan view of the improved unitary junction block and electromagnet assemblage as indicated by the line 3-3 of Figure 2;

Figure 4 is a reduced scale fragmentary axial sectional view indicated by the line 4 4 of Figure 3; and

Figure 5 is a fragmentary perspective view of a cupshaped insulator forming a part of the illustrated embodiment of the invention.

Referring now to Figure l of the drawings, the invention as illustrated is applied to a gas burning water heater indicated by the numeral 10. The heater 10 has a tank 11 provided with a main burner 12, the latter having a fuel supply pipe 13. A suitable thermostatic fuel control valve may be interposed in the pipe 13 as at 14. A pilot burner 15 is mounted adjacent the main burner 12, and a thermoelectric generator 16 which may take the form of a thermocouple is mounted adjacent the pilot burner. The thermocouple 16 is positioned so that its hot junction, indicated by the numeral 16', is subjected to the flame of the pilot burner 15 in a manner well known in the art. A coaxial lead 17 extends from the thermocouple 16 and comprises an inner conductor or wire 18 and a coaxial metallic tubular outer conductor 19 insulated from the wire 18 by insulation 20, 'as is most clearly shown in Figure 2. The end of the tube 19 opposite the thermocouple 16 is flared, as at 21 for engagement by the end of a coaxial externally threaded connector nut 22 positioned axially inwardly of saidflared end as shown. The inner conductor 18 is provided with a circular terminal lug 23 which is held in axially spaced relation with the ared tube end 21 by an annular insulator 24 of slightly larger diameter.

Referring again to Figure l, the numeral 25 indicates a control body, which in the illustrated embodiment takes the form of a fuel shut-olic valve body. Valve body 25 is provided with a fuel vinlet 6 to which a fuel supply pipe 27 is connected, and a fuel outlet 28 to which the pipe V13 is connected. The fuel supply pipe 27 may be provided with'a manual shut-off valve 27. A centrally apertured transverse partition 29 extends across the in terior of the valve body 25 between the inlet 26 and outlet 28 and .is provided with a pair of axially spaced annular valve seats .30 and 31. A passage 33 affords communication between a pilot burner fuel supply pipe 32 and the central aperture of partition 29 intermediate the valve seats 30 and 31. An outwardly spring urged reset pin 34 is axially slidably mounted in a Suitable aperture in an end wall 35 of the valve body 25, said pin having an external manually engageable button 36. A flow interruptor disc 37 is carried by the stern 34 within the valve body 25 and is adapted to sealingly engage the annular valve seat Slupon inward movement of said stem.

The end of the valve body 25 opposite the end wall 35 is open and may be internally threaded. In one well known type of safety shut-off apparatus which operates under the control of a pilot flame only, an electromagnet assembly is positioned in the open end of a valve body similar to the body 25 and is provided with connector means tor receiving the lead connector nut 22 and effecting a series circuit connection between the thermocouple 16 and the coil of the electromagnet. In the present invention, however, an improved unitary junction block and electromagnet assemblage 38 is removably threaded into the open end of the valve body 25.

The unitary assemblage 38 comprises an externally threaded cup-shaped connector head 39 having an apertured end wall 40 on the outer end of which is mounted a U-shaped magnet frame 41. A cup-shaped housing 42 is suitably iixed to the closed end of the connector head 39 for disposition within the valve body as shown in Figure l. The housing 42 has a centrally apertured end wall 43, and a stem 44 is mounted for axial sliding movement in the aperture of said end wall. An armature 45 is iixed to the end of the stem 44 within the housing 42, and valve member 46 is suitably connected to the end of the stem outwardly of the housing 42. A coiled compression Spring 47 surrounds .the stem 44 and is interposed between the valve member V46 and the end wall 43 of the casing 42 to urge the armature 45, stem 44 and valve 46 downwardly as viewed in Figure 1. It is apparent that reciprocation of the stem 44 causes alternate engagement of the armature 45 with the magnet frame 4l and sealing engagement of the valve member 46 on the annular valve seat 30.

A coil 4S is wound around the poles of the magnet frame 4l and forms an electromagnet with said frame. One end of the coil is connected in circuit with the connector head 39, as at 49 (Figure 2), and the other end of the coil is connected to a terminal tip 50, as at 51, said tip being suitably insulated as shown'. Terminal tip 50 extends through a suitable aperture inthe magnet frame 41 and through the aperture in the connector head end wall 40, having a rusto-conically tapered lug 51 exposed within the connector head 39. Y

A terminal connector 52, which may take the form of a generally L-shaped metallic strip, is positioned within the connector head and is suitably insulated Vtherefrom as shown. The connector 52 has a transverse extension or arm 60 which is apertured, as at 53, to receive and electrically contact the tapered portion of the lug 51. The terminal connector 52 also has an axial extension or arm 6l provided with a laterally outwardly directed portion 54 outwardly of the connector head 39 and provided with an upstanding lug 55 having a screw 56 threaded thereinto. A similar terminal connector 58 is positioned within the connector head 39 and is insulated therefrom, said terminal connector being in a substantially diametrical alignment with the connector 52 and having a transverse arm 59 superimposed on and insulated from the arm 60 of the latter connector. The arm 59 may be apertured, as at 62. The terminal connector 58 also has an axial arm 63 formed with a laterally outwardly directed portion 64 outwardly of the connector head 39 and provided with an upstanding lug 65 having a screw 66 threaded thereinto.

A generally cup-shaped insulator 67, shown most clearly in Figure 5, is formed with a pair of diametrically opposite axially extending rectangular inwardly

oiset portions

68 and 69, and is also formed in its end Wall with a diametrically extending rectangular inwardly odset portion 70 connecting the

portions

68 and 69 and having a central aperture 7l. The insulator 67 is positioned within the connector head 39 with

ythe portions

68 and 69 enclosing the

arms

61 and 63 respectively and the portion 70 enclosing the superimposed

arms

59 and 60.

A metallic terminal sleeve or bushing 72 is positioned coaxially within the insulator 67 and is formed with a pair of diametrically opposed axially extending rectangular grooves '73 and 74 in which the

offset portions

68 and 69 of the insulator 67 are received, as shown most clearly in Fig. 3. The sleeve 72 is internally threaded to receive the connector nut 22 of the thermocouple lead i7 and thereby position the terminal lug 23 of said lead in electrical contact with-the arm 59 of terminal connector 5S.

The connector head 39 is formed near its open end with a pair of diametrically aligned radial

pin receiving bores

75 and 76, andthe terminal sleeve 72 is formed with a pair of similar radial bores 77 and 7S in registration with

bores

75 and 76. A pair of retaining pins 79 and 8() are press iitted into the bores 75 and 77 and bores 76 and 78 respectively 4to securely hold the sleeve 72 in place Within the head 39 and to also effect an electrical tank 11 as shown in Figure l.

connection between said sleeve and head.

A condition responsive device 87, which in the illustrated embodiment takes the form of a temperature responsive variable resistance device, is mounted on the The device S7 may comprise a pair of normally engaged electrical contacts 81 and 82 mounted within and insulated from a bellows 83 in which they are sealingly encapsulated. The bellows 33 has a pair of opposing end walls 88 and 89, each of which carries one of the contacts S1 and 82. A tube 90 aiords communication between a sensing bulb 84 and the interior of the bellows 83, and said bulb, tube and bellows are lilled with a volatile fluid which is adapted to expand and contract to cause corresponding expansion or contraction of the bellows upon changes in temperature at the bellows 83 or its sensing bulb 84. In Figure l the bulb 84 senses the temperature of the tank ll.

In the illustrated embodiment of the invention, the fluid employed in the bellows 83 and sensing bulb 84 prot vides a vapor pressure somewhat below atmospheric at normal operating temperatures. Thus, if a leak occurs in the bellows, the entry of the greater atmospheric pressure through the leak expands the bellows, separating the contacts 81 and 82, and opening the circuit in which the device 87 is connected. The device, therefore, always lls safe.

A number of sub-atmospheric fills are available for use in the device 87, the particular till selected being dependent upon the desired high limit setting of the device. In the water heater application of the invention illustrated, the bellows 83 and bulb 84 may be lled with isopropyl alcohol for a 180 F. maximum setting. For other applications having appropriate high limit settings the following lls may be used for sub-atmospheric operation: N-propyl alcohol for a 200 F. maximum setting, isobutyl alcohol for a 220 F. maximum setting, N-butyl alcohol for a 240 F. maximum setting, isoamyl alcohol for a 260 F. maximum setting, N-xylene for a 280 F. maximum setting, of P-cymene for a 340 F. maximum setting. Other sub-atmospheric fills which may be used for appropriate applications are ether and isopentane.

It is desirable in certain applications to utilize a fill having a vapor pressure somewhat above atmospheric at normal operating temperatures. Illustrative of such fluid iills are sulphur dioxide, ethyl alcohol, and xylene.

A conductor 85 connects the contact 82 of the device 87 with the lug 55 and screw 56 of the terminal connector 52, and a conductor 86 connects the contact 81 of said device with the lug 65 and screw 66 of the terminal connector 58. It is apparent that in the improved control apparatus the condition responsive device 87 is connected in series circuit relation with the electromagnet coil 48 and the thermocouple 16. TheV contacts 81 and 82'. are immersed in the volatile fill in the bellows 83, and are thereby protected against fouling by foreign matter or by the formation of lms which might create undesirable resistance between said contacts. Due to the low voltage in the electrical circuit of the improved apparatus, there is no arcing at the contacts 81 and 82, and therefore there is no danger of breaking down the till;

During normal operation the pilot flame causes the thermocouple 16 to energize the magnet coil 48 through the series circuit provided by the innerl leads conductor 13, terminal connector 58, conductor 86, contacts 81 and 82, conductor 85, terminal connector 52, terminal tip 50, magnet coil 48, connector head 39, retaining pins 79 and 80, terminal sleeve 72, lead connector nut 22 and outer lead conductor 19. The armature 45 isthereby held in contact with the poles of the energized. electromagnet, and the valve member 46 is simultaneously held in the open position, both as shown in Figure l, Extinguishment of the pilot flame, of course, causes the thermocouple 16 to cool and stop generating power for energization of the coil 48. When this happens, the armature 45 is drawn away from the poles of the magnet frame 41 by the spring 47 as the valve member 46 simultaneously moves onto the annular seat 30 to stop all fuel flow.

If, during operation of the improved control apparatus, and while the pilot burner 1S is operating normally, the temperature of the tank 11 reaches that which is the upper limit setting of the device 87, the till within the bellows 83 expands sufficiently to causeA the contacts 81 and 82 to tend to separate at least sufficiently to reduce the contact pressure of one contact against the other contact in amount to increase the resistance therebetween to a point where the current which can ow through the electromagnet is insufcient to hold the armature 45 in the normal operative position shown. As a result, the armature drops away from the electromagnet, and the valve 46 closes to shut off all fuel tlow to the burners 12 and 15 and thereby prevent further heating of the tank.

It is thus apparent that in the improved control apparatus the safety shut-off valve is under the dual control of the pilot burner and the condition responsive device 87, which in the illustrated embodiment functions broadly as a thermostatic high limit switch. `Of particular importance is the fact that the improved apparatus can operate with a single thermocouple as its sole source of power. The encapsulation of the contacts 81 and 82 in an eX- pansible and contractible enclosure, such as the bellows 83, and the immersion of said contacts in the volatile fill provides an eiicient and sensitive condition responsive circuit interrupting device which is well adapted for use in a thermoelectrically powered circuit of the type disclosed erem.

The structure of the improved junction block and electromagnet assembly 38 is such that it can be readily interchanged with the electromagnet assembly of presently installed thermoelectric shut-off devices. By substituting the improved junction block and electromagnet assembly in the manner described, the condition responsive device 87 can be connected in series circuit relationship with the electromagnet of said assemblage and the thermoelectric generator of the shut-off device, thereby placing ythe latter under the dual control of the pilot llame and the condition responsive device. The improved dual control shut-ott device thus provided requires no power' source other than the single thermoelectric generator of the original pilot-controlled thermoelectric shut-off device.

While the illustrated embodiment of the invention is applied to a hot water heater, it may be applied to any other suitable equipment in which it is desired to have a thermoelectrically powered safety device under the control of a condition responsive device as well as under that of a pilot tlame. The specific structure of the condition responsive device 87 may vary, as may the volatile till used therein, depending upon the particular ap- 6 plication of the invention. Various changes and moditications may be made in the specific structural details of the combination junction block and electromagnet assemblage without departing from the spirit of the invention. All of such changes are contemplated as may come within the scope of the appended claims.

What I claim as the invention is:

1. The combination with a control body and a concentric thermoelectric generator lead having a connector nut in circuit with the outer conductor thereof and a terminal connector in circuit with the inner conductor thereof, of a unitary low-resistance junction block positioned within said control body and comprising, a.

cup-shaped connector head, a terminal tip insulatably disposed centrally within said cup-shaped head, a first terminal member having a portion insulatably disposed within said connector head and in circuit with said terminal tip, a second terminal member having a portion insulatably disposed within said cup-shaped connector head in overlapping relation with said tirst terminal member portion, and an internally threaded terminal sleeve xed coaxially within and in circuit with said cup-shaped connector head, said second terminal member portion being exposed at the inner end of said terminal sleeve for engagement by the terminal connector of the thermoelectric generator lead, threading of said connector nut into said terminal sleeve effecting low-resistance electrical connections between said nut and said sleeve, between said terminal connector and asid second terminal member portion, and between said first terminal member portion and said terminal tip.

2. The combination with a control body and a concentric thermoelectric generator lead having a connector nut in circuit with the outerv conductor thereof and a terminal connector in circuit with the inner conductorA thereof, of a unitary low-resistance junction block and control assembly removably positioned within said control body and comprising, a cup-shaped connector head having an end wall, a terminal tip insulatably disp-osed centrally of said end wall within said cup-shaped head, electrical control means carried by said connector head and in circuit with said terminal tip and said connector head, a first terminal member having a portion insulatably disposed within said connector head and in circuit with said terminal tip, a second terminal member having a portion insulatably disposed within said cup-shaped connector head in overlapping relation with said first terminal member portion, and an terminal sleeve xed coaxially within and in circuit with said.` cup-shaped connector head, said second terminal member portion being exposed at the inner end of said terminal sleeve for engagement by the terminal connector of the thermoelectrie generator lead, threading of said connector nut into said terminal sleeve effecting low-resistance electrical connections between said nut and said sleeve, and said second terminal member portion, and between said first terminal member portion and said terminal tip.

3. The combination with a control body and a con,- centric thermoelectric generator lead having a connector nut in circuit with the outer conductor thereof and a tapered terminal connector in circuit withV the inner conductor thereof, of a unitary low-resistance junction block and control assembly removably positioned within said control body and comprising, a cup-shaped connector head having a centrally apertured end wall, a terminal tip insulatably disposed within the aperture of Said end wall and having a tapered portion within said cup-shaped head, electrical control means carried by said connector head and having a winding in circuit with said terminal tip and said connector head, a rst terminal member for circuit connection having a portion insulatably disposed within said connector head and formed with an opening the periphery of which engages the tapered portion of said terminal tip, a second terinternally threaded between said lead terminal connectorminal member for circuit connection having a portion insulatably disposed within said cup-shaped connector head in overlapping relation with said first terminal member portion and formed with an opening in alignment with the opening in said tirst terminal member prtion, and an internally threaded terminal sleeve xed coaxially within and in circuit with said cup-shaped connector head, said second terminal member portion being exposed at the inner end of said terminal sleeve for engagement of the periphery of the opening therein by the tapered terminal connector of a thermoelectric generator lead, threading of said connector nut into said terminal sleeve effecting low-resistance electrical connections between said nut and said sleeve, between said lead terminal Aconnector and said second terminal member portion and between said rst terminal member portion and said terminal tip.

4. The combination with a control body and a concentric thermoelectric generator lead having a connector nut in circuit with the outer conductor thereof and a tapered terminal connector in circuit with the inner conductor thereof, of a unitary low-resistance junction block and control assembly removably positioned within said control body and comprising, a cup-shaped connector head having an end wall, a terminal tip having a tapered portion insulatably disposed centrally of said end wall within said cup-shaped head, electrical control means carried by said connector head and in circuit with said terminal tip and said connector head, a tirst terminal member for circuit connection having a portion insulatably disposed within said connector head and formed with an opening the periphery of which engages the tapered portion of said terminal tip, a second terminal member for circuit connection having a portion insulatably disposed within said cup-shaped connector head in overlapping relation with said rst terminal member portion and formed with an opening, and an internally threaded terminal sleeve xed coaxially within and in circuit with said cup-shaped connector head, said second terminal member portion being exposed at the inner end of said terminal sleeve for engagement of the periphery of the opening therein by the tapered terminal connector of the thermoelectric generator lead, threading of said connector nut into said terminal sleeve effecting low-resistance electrical connections between said nut and said sleeve, between said lead terminal connector and said second terminal member portion, and between said rst terminal member portion and said terminal tip.

5. In a control apparatus wherein a control member is positioned within a cont-rol body and movable between operating and safety positions in response to a given condition sensed by a condition responsive device and wherein the sole source of power is a therrnocouple having -a concentric lead the outer conductor of which is in circuit with a connector nut and the inner conductor of which -is in circuit with a terminal connector, of a unitary junction block and control assembly removably positioned within said control body and comprising, a cupshaped connector head having an end wall, a terminal tip linsu-latably disposed centrally within said cup-shaped head, electrical control means for said control member carried by said connector head .and in circuit with said terminal tip and said connector head, a tirst terminal member for connection with said condition responsive device and having a portion insulatably disposed within said connector head and in circuit with said terminal tip, a second terminal member also Yfor connection with said condition responsive device and having a portion insulatably disposed within said cup-shaped connector head -in ovenlapping relation with said lirst termina-l member portion, and an internally threaded terminal sleeve xed coaxially within and in circuit with said cup-shaped connector head, said second terminal member portion being exposed at the inner end of said terminal sleeve for engagement by the terminal connector of the concentric lead, threading of said connector nut into said terminal sleeve effecting low-resistance electrical connections between said nut and said sleeve, between said terminal connector and said second terminal member portion, and between said rst terminal member portion and said terminal tip, whereby to eiect a series circuit connection between said thermocouple, said condition responsive device and said control means.

6. In a control apparatus wherein a control member is positioned within a control body and is movable between operating and safety positions in response to a given condition sensed by a condition responsive device and wherein the sole source of power is a thermocouple having ya concentric 'lead the outer conductor of which is in circuit with a connector nut and the inner conductor of which is in circuit with a tapered terminal connector, of a unitary junction block and control assembly removably positioned within said control body and cornprising, a cup-shaped connector head having a centrally apertured end wall, a terminal tip insula-tably disposed within the aperture of said end wall and having a ltapered portion within said cup-shaped head, electrical control means carried by said connector head including a windingin circuit with said terminati tip and s-aid connector head, a irst terminal member for connection with said condition responsive device and having a portion insulatably disposed within said connector head and formed with an opening the periphery of which engages the tapered portion of said terminal tip, a second terminal member also for connection with said condition responsive device and having a portion insulat-ably disposed within said cup-shaped connector head in overlapping relation with said rst terminal member portion and formed with an opening axially aligned with the opening in said iirst terminal member, and an internally threaded terminal sleeve fixed coaXia'lly within and in circuit with said cup-shaped connector head, said second terminal member portion being exposed at the inner end of said terminal sleeve for engagement of t-he periphery of the opening therein by the tapered portion of the terminal connector of the concentric lead, threading of said con- Inector nu-t into said terminal sleeve effecting lowresistance electrical connections between said nut and said sleeve, between said terminal connector and said second terminal member portion, and between said rst terminal member portion and said terminal tip, whereby to effect a series circuit connection between said thermocouple, said condition -responsive device and said control means.

References Cited in the le of this patent UNITED STATES PATENTS 2,276,909 Alfery Mar. 17, 1942 2,414,236 McCarty Ian. 14, 1947 2,503,459 Thornbery Apr. 11, 1950