US2276909A - Thermoelectric safety shutoff valve and thermally operated control therefor - Google Patents

Description

March 17, 1942. H. F. ALFERY 2,276,909

THERMO'ELECTRIC SAFETY SHUTOFF VALVE AND THERMALLY OPERATED CONTROL THEREFOR Filed Jan. 26. 1958 a Sheets-Sheet 1 March 17, 1942. ALFERY 2,276,909

THERMOELECTRIC SAFETY SHUT-OFF VALVE AND THERMALLY OPERATED CONTROL THEREFOR March 17, 1942. H. F. ALFERY 2,276,909

THERMO-ELEGTRIC SAFETY SHUT-OFF VALVE AND' THERMALLY OPERATED CONTROL THEREFOR Filed Jan. 26, 1958 3 Sheets-Sheet 3 lax/enforfferz ig jflqfiry lhiZ atented THERMOELECTRIC SAFETY SHUTOFF VALVE AND THERMALLY OPERATED CONTROL THEREFOR Henry F. Alfery, Milwaukee, Wis., assignor to Milwaukee Gas Specialty Company, Milwaukee, Wis., a corporation of Wisconsin Application Januar 26, 1938, Serial No. 186,967

(c1. ts-n35) 8 Claims.

This invention relates to a thermo-electric safety shut-off valve and thermally operated control therefor.

While the particular device which I shall describe hereinafter in connection with the drawings is a thermo-electric safety shut-off valve and thermally operated control adapted for use with water heaters and the like, it is to be understood that the invention is not limited to this particular use but may be employed in all equivalent or similar work, or elsewhere as suitable or desired.

One of the main objects of the invention is to provide a thermo-electric safety shut-oif valve for shutting off the supply of gaseous fuel to the main burner for the water heater when the pilot burner for said main burner is extinguished, and thermally operated means for rendering the thermo-electric means ineffective to hold the thermo-electric valve open by the heat of the pilot flame when the water is heated to the tem' perature at which said thermally operated means is operable.

Itiis also an object of the invention to provide means for shutting off, or substantially shutting off, the supply of gaseous fuel to the main burner during resetting of the armature of the thermoelectric device into contact with the pole faces of the magnetic frame and the thermo-electric valve to open position, and means for by-passing gaseous fuel for the pilot burner to said pilot burner while the means for shutting off, or substantially shutting off, the supply of gaseous fuel to the main burner is operable during the resetting operation and wherein, at the same time, the thermo-electric valve operates to shut oif not only the supply of gaseous fuel to the main burner but also the supply of gaseous fuel to the pilot burner when the pilot burner is extinguished.

Another object of the invention is to provide means for manually rendering the thermo-electric means ineffective to hold the thermo-electric valve open by the heat of the pilot flame.

Further objects and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a side elevational view of a water heater system, showing an embodiment of the present invention in connection therewith;

Figure 2 is a vertical section through the thermo-electric safety shut off valve and thermally operated control therefor;

Figure 3 is a fragmentary horizontal section taken on the line 3-3 of Figure 2;

Figure 4 is a fragmentary vertical detail sec-- tion showing a more compact arrangement of the Sylphon or currugated bellows which operates to render the thermo-electric means ineffective to hold the thermo-electric valve open by the heat of the pilot flame, and a more compact hood of reduced height therefor;

Figure 5 is a fragmentary vertical section similar to Figure 4, showing manual means for rendering the thermo-electric means ineffective to hold the thermo-electric valve open by the heat of the pilot flame;

Figure 6 is a vertical section through another form of valve and reset means therefor; and

Figure 7 is a vertical section similar to Figure 6 showing another form of valve and reset means therefor.

Referring to the drawings, the water heater system shown in Figure 1 may be of any existing or other suitable or preferred type. The par ticular system shown comprises a heating coil, indicated at 5, and a hot water tank 6. The top of the coil 5 is connected to the tank 5 near the top thereof by a pipe I which delivers the hot water from the coil 5 to the tank 5. The tank 6 is connected near the bottom with the lower portion of the coil 5 by a pipe 8 which delivers the cold water from the tank 6 to the coil 5. The tank 6 has a cold water inlet pipe S! for delivering cold water to the tank 6, and a hot water outlet pipe It! extends from the top of the tank 6 for delivering the hot water therefrom.

Underlying the bottom of the coil 5 to heat the water in this coil is a main burner i2. The gas supply pipe for supplying gaseous fuel to the burner i2 is indicated at E3. The gaseous fuel supply line has connection to the burner it through a feed pipe, having at its outer end a mixing chamber It, to the outer end of which air is admitted, as well understood in the art. The main burner I2 is provided with a pilot burner l5 located in proximity thereto for maintaining a pilot flame in proximity to the main burner to ignite the same in case it is accidentally extinguished. This pilot burner assures that the main burner is ignited so long as there is a supply of gaseous fuel thereto.

A thermo-electric valve device, indicated at I6, is provided in the gaseous fuel supply line l3 for shutting off the supply of gaseous fuel to the main burner l2 when the pilot burner I5 is extinguished. This thermo-electric valve device l6 has thermally operated means connected thereto for rendering the thermo-electric means of the device I6 ineffective to hold the thermo-electric valve open by the heat of the pilot flame when the water is heated to the temperature at which the thermally operated device is operable.

The thermo-electric valve device I6 comprises a valve body 28 provided with an inlet chamber 2| and with an outlet chamber 22. The partition 23, intermediate these chambers 2| and 22, has a valve opening 24 provided on the inlet side with a surrounding valve seat 25. The flow of gaseous fuel through the valve opening 24 is controlled by a valve member 26 provided with a leather or other suitable valve seating member 21 which engages the valve seat 25 when the valve is closed. The seating member 21 is secured to the valve member 26 by a screw 28.

Mounted upon the top of the valve body 26 is a housing comprising a downwardly opening cupshaped bell 38, and an upwardly opening cupshaped shell 8|. The shell 86 has an enlarged lower end 32 fitting telescopically over the enlarged upper end 33 of the shell 3|. The lower end of the shell 88 has an outwardly extending annular flange 34; and the two shells are clamped in place to the top of the valve body 28 by' a nut member 35. a suitable sealing gasket being preferably provided as indicated at 36.

A generally U-shaped magnetic frame member 86 is mounted in the shell or hood member 38, and this magnetic frame member 46 is provided with an electromagnetic coil indicated at an. The coil 4| surrounds one of the legs of the magnetic frame member 48, and one terminal of the coil is connected to a terminal stud 43. The other terminal of the coil 4| is connected at 44 to a metallic terminal plate 45. The stud 43 has an enlarged upper end 46 and a reduced stem 41 depending therefrom. This stud fits in a correspondingly formed bushing member 48, which bushing member is externally threaded and clamped in place in an opening 49 in the top of the shell 36 by nut members 50 and The lower end of the bushing 48, which constitutes a terminal bushing, is reduced, and this reduced lower end of the bushing fits in an opening in the plate member 45. A second terminal plate 53 underlies the plate 45 and is secured with the plate 45 to the bushing 48 by extending the reduced lower end of the stud 43 through an opening in the plate 53 and heading the lower end of the stud over, as indicated at 54, or otherwise as desired. The stud 43 is insulated from the bushing 48, and the plate members 45 and 53 are insulated from each other by insulation indicated at 56 and 51. The terminal of the coil 4|, which is connected to the terminal stud 43, is clamped in place between the insulation at 5? and the plate member 53.

The plate member at has an opening 68 and is depressed at 60' to provide a support for the magnetic frame 46 which is secured thereto in any suitable or desired manner. The plate member 53 is depressed and -secured to the plate member 45 by a screw 6|, the plate members 45 and 53 being insulated from each other and from the screw 6| by insulation indicated at 62. The plate 53 also has 9. lug 63 struck up therefrom into the opening 68 in the plate 45 but out of contact with said plate 45. This lug 63 has a contact member 64 for a purpose which will presently appear.

The thermocouple, indicated at 10, may be of any existing or other suitable or preferred formfor example, of the general type more fully dis closed in-iOscar J. Leins Patent No. 2,126,564, issued August 9, 1938, or in the copendlng application of John H. Thornbery. Serial No. 37,276. filed August 22, 1935. The hot junction 1| thermocouple is disposed in proximity to the pilot burner l5 so as to be responsive to the heat of the pilot flame for the main burner l2 at all times. The internal element or the thermocouple is suitably joined to the lead wire 12 (Figure 2) which constitutes one part of the lead connection between the coil 4| and the thermocouple. The other part of this lead connection comprises a metallic tube I3 suitably connected to the external element or the thermocouple. The lead tube I3 is insulated from the lead wire 12 by the insulation on this wireas indicated at 14.

At its opposite end the metallic tube 13 enters and is connected at 15 to a metallic thimble 'member 16 having threaded engagement on the outer externally threaded end oi the terminal bushing 48. The adjacent end oi the lead wire 72' has metallic connection at 12' to a terminal member 11. This terminal member 11 has a conical end I8 which seats in a recess of corresponding conical form in the outer end of the terminal stud 43 and forms the metallic contact between the member 11 and the stud 43. The terminal member 11 may be held centered in the thimble member I6 at its outer end by a centering member 88 fitting within the thimble and engaging the upper end of the member Ti as shown. Suitable insulation is provided as indicated at 8|, and the conical end of the terminal I1 is clamped in contact with the conical recessed surface ofthe stud 43 by the thimble 16.

From the foregoing description and the drawings, it will now be apparent that the internal element of the thermocouple 10 is connected through lead wire 12, terminal member Tl, stud 43, and connection 42, to one terminal of the coil 4|, and that the external element of the thermocouple is connected through the thimble 16, terminal bushing 48, metallic terminal plate 45, and connection 44 to the other terminal of the coil 4|.

The free ends of the magnetic frame member 40 constitute pole faces, and the magnet armature 83 is held against these pole faces by the magnetic field produced in the frame 40 by the thermo-electric current set up in the coil 4| due to the action of the heat of the pilot flame on the hot junction 1| of the thermocouple when the pilot flame is burning. The armature 83' has attached thereto, by upwardly extending bent-over portions 84, a cradle 85 which, in turn, is connected to the upper end of the valve stem 86, preferably for limited universal movement, by means of U-shaped retainers 81 engaging in grooves in the upper end of the stem 86. The armature 83 is guided for reciprocating movement by an armature guide 88, and the valve member 26 is connected to the lower end of the stem 86, preferably for limited universal movement with respect to the stem. by means of a retainer 89 engaging in a groove in the valve stem.

The bottom wall of the shell 3| is depressed at 90 and provided with an opening 9| in which the stem 86 has reciprocating movement. The opening 9| is sealed against the leakage of gas from the valve body 28 and into the enclosure formed by the shells 30 and 3| by suitable packing indicated at 92. A washer is provided at 93, and surrounding the valve stem 86 and interposed between the washer 93 and the valve member 26 is a generally conically coiled spring 94. This spring 94 compresses the packing 92, and when ofthethe coil 4| is deenergized, the spring 34 moves the valve member 26 to closed position against the seat 25 to shut off the supply of gaseous fuel to the main burner I2 and pilot burner I5.

For the purpose of resetting the device after the coil 4| is deenergized and the valve 26 closed, a resetting stem I is mounted for sliding movement in the valve body in axial alignment with the valve member 26. Secured upon the lower end of the stem I00 is a resetting button IOI, and fixed upon the upper end of the stem is a valve member I02. The valve member I02 has a valve seating surface I03 which engages an annular valve seat I04 to prevent leakage of gas through the opening I05 in which the stem I00 operates. This opening I05 is additionally sealed against the leakage of gas by suitable packing indicated at I06. A washer is provided at I01,

and surrounding the stem I00 and interposed between the washer I01 and the resetting button IN is a coiled spring I08 which holds the valve member I02 against the seat I04 and the button IOI in the position shown.

The valve member I02 has upstanding lugs I I0 which, in the resetting operation, engage the valve member 26 and force the same to open position away from its seat and the armature 83 into engagement with the pole faces of the magnetic frame 40 against the tension of the spring 34. The lugs IIIl may have sliding movement in the valve opening 24 for the purpose of guiding the valve member I02 and resetting stem I00. When the resetting stem has been pressed upwardly sufficiently to bring the armature 83 into contact with the magnetic frame 40, the valve member I02 preferably shuts off, or substantially shuts off, the flow of gaseous fuel through the valve opening 24. This eliminates the flow of gaseous fuel from the main burner I2 until the pilot burner is ignited and the coil 4| is energized to hold the armature 83 against the magnetic frame 40 and the valve 26 in open position.

The valve body 20 has a passageway 2 connected to a tube or gas supply line II3 for dethe supply of gaseous fuel to the pilot burner I5 when the valve member 261s closed against its seat 25.

The thermally operated control for the thermoelectric shut-off valve comprises a corrugated metallic bellows 6 connected by a tube II'I with a bulb or chamber H8. The bellows IIB, tube III and bulb II8 contain a sensitive fluid, preferably a liquid, the expansion and contraction of which, whether by evaporation and condensation or otherwise, results in expansion and contraction of the bellows H6.

The bulbor chamber H0 is disposed where it is subject to the temperature of the hot waterfor example, in the tank 6 as. shown in Figure 1. The bellows II6 is located in a hood I20 mounted over an opening I2I in the top of the shell 30, with a gasket I22 interposed therebetween. The upper end of the bellows II6 has fluid-tight connection with the lower end of a sleeve member I23, the upper reduced and threaded end of which extends through an opening in the top wall of the hood I20 and is clamped thereto by a nut I24. The adjacent end of the tube II'I extends into the sleeve I23 and has communication withthe interior of the bellows II6 through an opening I25, and a suitable wiping or other means at I26 seals the joint between the tube III and the sleeve I23.

The lower end of, the bellows II6 has fluid tight connection with the outwardly extending flange on the thimble member I28. This thimble member I28 has an internally threaded recess in which a stud I20 has threaded engagement, and the stud I29 has an axial recess in which is I mounted a contact pin I30, the lower end of which, in the specific use of the device herein described, is adapted to be forced into engagement with the contact 64 by the expansion which results in the bellows II6 when the water in the tank 6 reaches the temperature, at which the thermally operated control is set to operate. The particular temperature at which the contact I30 engages the contact 64 may be adjusted by adjusting the stud I29 in the thimble I23, or otherwise as desired, there being some lost motion between the stud I20 and the contact stem I30 as shown at I32 in the particular setting illustrated.

An annular resilient sheet metal member I34 is clamped in place between the undersurface of the top of the shell 30 and the metallic plate 45. This member I34 has a resilient ear I35 in which the contact pin I30 is mounted. As the bellows ||6 expands, the thimble|28 moves downwardly and carries with it the stud I29 which slides upon the pin I30 until the lost motion at I32 is taken up and the stud I29 engages the upper end of the contact pin I30. The contact I30 is then moved downwardly, depressing the ear I35 with it, and when the water in the tank 6 reaches the temperature at which it is desired to render the therrno-electric device ineffective to hold the valve member 26 open by the heat of the pilot flame., the contact I30 engages the contact 54. This short-circuits the thermo-electric current before it reaches the coil 4|, i. e., from the lead tube I3 of the thermocouple through thimble I6, bushing 40, shell 30, metallic plate 45, member I34, contacts I30 and 64, and metallic plate 53, to the stud 43 and through terminal member 'I'I to the lead wire I2.

This short-circuiting of the thermo-electric current before it reaches the coil 4| deenergizes this coil, and the spring 94 moves the valve member 26 to closed position and the armature 83 downwardly away from the magnetic frame to the position shown in Figure 2. When the temperature of the water drops, the flexible metallic bellows ||6 contracts, and the ear I35, by its inherent resiliency, moves the contact I30 upwardly out of engagement with the contact 64.

It is to be understood that the fluid fill within the bellows II6, tube III, and bulb II8 may work the other way, i. e., it may contract and break contact thereby instead of expanding to make contact as described. In other words, the fill may operate to expand the bellows, or it may operate to contract or produce a contraction of the same. Where the fill operates to expand the bellows, such bellows may be contracted by its inherent resilience or by means of a spring, or a combination thereof, and where the fill operates to contract or produce a contraction of the bellows, such bellows may be expanded by its inherent resilience or by means of a spring, or a combinanetic frame 40 where'it is held by holding the button I in raised position. In this raised position of the resetting stem I00, the valve I02 shuts off, or substantially shuts off, the flow of gaseous fuel to the main burner I2 to prevent the escape of gaseous fuel from the main burner during the resetting operation.

The valve member 26 is open, however, at this time, and the passageway I I 2 by-passing the valve I02 sets up the desiredsupply of gaseous fuel to the pilot burner I5 where it can be ignited as it issues from the pilot burner by applying a match or-otherwise as desired. The resulting pilot flame energizes the thermocouple I0, creat= ing a thermo-electric current which energizes the coil 4| and causes the armature 83 to be held against the magnetic frame 40 and the valve 26 to be held in open position against the tension of the spring 94. When the coil is so energized to hold the valve 26 open, the resetting button IOI is released and the spring I08 moves the resetting stem I00 downwardly to the position shown in Figure 2, and with it the valve I02 to open position.

The gaseous fuel then flows through the valve opening 24 and out through the fuel supply line to the feed pipe to which air is admitted, and the gaseous mixture enters the main burner I2 where it is ignited by the pilot burner I5 as it issues from the ports of the main burner. In case the main burner I2 is accidentally extinguished, the pilot burner I5 will reignite the same, and thereby assures that the main burner is lighted so long as the valve 26 is open.

If the pilot burner is extinguished, the thermoelectric current through the coil 4I diminishes to such a degree that the armature is released, whereupon the spring 94 forces the valve member 26 into engagement with the valve seat 25, thereby shutting off the flow of fuel to the main burner I2 and to the pilot burner I5.

If, on the other hand, with the pilot burner I5 ignited and the valve 26 held open by the thermo-electric current developed by the pilot burner, the water in the tank 6 is heated to the temperature at which the thermally operated control is operable, the expansion of the metallic bellows II6 engages the contact I30 with the contact 64, and thereby short-circuits the thermoelectric current before it reaches the coil 4|. The coil is thus deenergized and the spring 94 forces the valve 26 to closed position. I

While the fluid type thermostat, with its bulb in the tank 6 and the connected corrugated bellows at the thermo-electric shut-off device as indicated in the drawings, is preferred, it is understood that the thermostat or thermally operated control for the thermo-electric shut-off valve may be of any other suitable or desired type, such as the bimetallic or rod and tube type thermostats well known in the art.

The corrugated metallic bellows arrangement shown in Figure 4 is similar to the corrugated metallic bellows arrangement shown in Figure 2 except that the supporting sleeve I23 and the hood I20 are shortened to provide a more compact arrangement. The other parts are designated by primed reference characters corresponding to the reference characters used in Figure 2.

The manually operable device shown in Figure 5 for rendering the thermo-electric device ineffective to hold the thermo-electric valve open by the heat of the pilot burner comprises a plunger I50 recessed to engage over the contact pin I30. The plunger is mounted for sliding movement in a sleeve member I5I secured at I52 in the top of the hood I53, and the outer end of the plunger has a button I 54 fixed thereon. The opening I55 in which the plunger I50 has sliding movement is sealed by suitable packing I56, and this packing is compressed by a coiled spring. I57 which is interposed between the washer I58 and the button I54 and holds the button in its upper projected position.

In this embodiment of the invention, by manually pressing the button I54 downwardly, the

contact I30 is engaged with the contact 64' to short circuit the thermo-electric current ahead of the coil ii at will. This short-circuiting of the thermo-electric current ahead of the coil 4| deenergizes this coil, and the spring 94 moves the valve 26 to closed position as before.

The valve body 200 shown in Figure 6 has an inlet chamber 20I, an outlet chamber 202, and an intermediate partition 203 provided with a valve opening 204. On the inlet side, the valve opening 204 has a surrounding valve seat 205.

The flow of fuel through the valve opening 204 is controlled by a valve member 206 provided with a leather or other suitable valve seating member 201 which engages the valve seat 205 when the valve is closed. The valve member 206 is connected to valve stem 208 which, in turn. is connected at its upper end to an armature which, as in Figure 2, when held attracted to an electromagnet within the shell 209, holds the-valve member 206 open. Whenv the pilot burner is extinguished the thermo-electric current which passes through the coil means of the electromagnet diminishes to such degree that the armature is released and the spring 2I0 moves the valve member 206 to closed position. The nut member 2I2 corresponds with the nut member 35 in Figure 2.

The resetting stem 2I4 and its button 2I5, as well as the spring 2I6 and packing 2I1, are similar to corresponding parts in Figure 2. The valve member 2| 8, instead of being formed and provided with upstanding lugs as shown in Figure v the resetting stem is 2, is formed to enter the valve opening 204 when projected upwardly in the resetting operation. To guide the valve member 2I8 into the opening 204, the bottom of the valve openingis' preferably chamfered at 220 and the top of the valve member 2I8 is similarly chamfered at 22 I The valve member 2I8 preferably fits relatively loosely in the opening 204 so that when it is positioned in the opening 204 upon projecting the resetting stem upwardly to move the armature into attracted position and the valve member 206 to open position, a restricted supply of fuel for maintaining the pilot flame may flow past the valve member 2I8. The pilot connection for delivery of this restricted supply of fuel to the pilot burner is shown more or less diagrammatically at 222. It is to be understood that the pilot connection shown is diagrammatic and that the connection for delivering the restricted supply of gas which passes the valve 2"! when it is positioned in the valve opening 204 may be of any suitable or preferred form.

In Figure 7 the valve member 2 l8, which shuts off the supply of fuel to the main burner during the resetting operation, seats upwardly against a valve seat 230 on the outlet side of the valve opening 204'. The valve member 2l8', instead of being fixed upon the resetting stem 2M as in the preceding embodiments of the invention, is loose on the resetting stem 2M so that the stem may slide upwardly therethrough in the resetting operation. A spring 23!, interposed between the valve member 2l8 and the gland member 232, moves the valve member 2!!! yieldingly to closed position when the stem 2 I 4 is projected upwardly stronger than the spring 23| to provide this ac-.

tion.

When the valve member 2|8 is closed, a passageway 235 by-passes the valve member M8 to provide a restricted supply of fuel for the pilot burner. This by-pass passageway 235, instead of being formed in the partition 203' pf the valve body 200', may open through the valve member 2| 8', or may be arranged otherwise as suitable and desired.

I do not intend to be limited to the precise details shown or described.

I claim:

1. In a device of the class described, in combination, a thermoelectric generator, a hood, a first conducting member disposed within said hood and connected in circuit with one side of said thermoelectric generator, a second conducting member disposed within said hood and insulated from said first conducting member and connected in circuit with the other side of said thermoelectric generator, an electromagnet disposed within said hood and having a magnet frame supported by said first conducting member, and a coil for said magnet frame, said coil having its terminals connected in circuit with the opposite sides of said thermoelectric generator, a contact on one of said conducting members, a resiliently supported contact connected, within said hood, in circuit with the other conducting member, and means for moving said resiliently supported contact into engagement with the other contact for closing the thermoelectric circuit ahead of said eiectromagnet to short circuit the electromagnet.

2. In a device of the class described, in combination, a thermoelectric generator, a hood having an end wall, a first conducting plate disposed within said hood adjacent the end wall thereof and connected in circuit with one side of said thermoelectric generator, a second conducting plate disposed within said hood adjacent said first plate and insulated from said first plate and connected in circuit with the other side of said thermoelectric generator, an electromagnet disposed within said hood and having a magnet frame supported by said first conducting plate, and a coil for said magnet frame, said coil having its terminals connected in circuit with the opposite sides of said thermoelectric generator, 9, first contact on one of said conducting plates, 9. spring contact arm clamped between the other conducting plate and the end wall of the hood and in circuit with said other conducting plate, a second contact carried by said spring arm and normally held yieldingly out of engagement with said first contact, and means operable through the end wall of said hood for moving said second contact into engagement with said first contact for closing the thermoelectric circuit ahead of said electromagnet to short circuit the electro magnet.

3. In a device of the class described, in combination, a thermoelectric generator, a hood having an end wall provided with an opening, a first conducting plate disposed within said hood adjacent the end wall thereof and connected in circuit with one side of said thermoelectric generator, a second conducting plate disposed within said hood adjacent said first plate and insulated from said first plate and connected in circuit with the other side of said thermoelectric generator, an electromagnet disposed within said hood and having a magnet frame supported by said first conducting plate, and a coil for said magnet frame, said coil having its terminals connected in circuit with the opposite sides of said thermoelectric generator, a first contact on one of said conducting plates, a spring contact arm clamped between the other conducting plate and the end wall of the hood and in circuit with said other conducting plate, a supplementalhood attached to the end wall of said first hood over the opening therein, a thermostat bellows disposed within said supplemental hood, a tube opening into said bellows at one end and extending to a temperature sensitive bulb, a thimble member having fiuid tight connection with the opposite end of said bellows and disposed within said supplemental hood, and a second contact carried by said spring arm adjacent the opening in the end wall of said hood, said second contact being normally held yieldingly out of engagement with said first contact and cooperable with said thimble member to be moved by said thimble member upon expansion of said bellows into engagement with said first contact for closing the thermoelectric circuit ahead of said electromagnet to short circuit the electromagnet.

4. In a device of the class described, in combination, a thermoelectric generator, a hood having an end wall provided with an opening, a first conducting plate disposed within said hood adjacent the end wall thereof and-connected in circuit with one side of said thermoelectric generator, a second conducting plate disposed within said hood adjacent said first plate and insulated from said first plate and connected in circuit with the other side of said thermoelectric generator, a first contact on one of said conducting plates, a spring contact arm clamped between the other conducting plate and the end wall of the hood and in circuit with said other conducting plate, a supplemental hood attached to the end wall of said first hood over the opening therein, a thermostat bellows disposed within said supplemental hood, a tube opening into said bellows at one end and extending to a temperature sensitive bulb, a thimble member having fluid tight connection with the opposite end of said bellows and disposed within said supplemental hood, 9. second contact carried by said spring arm adjacent the opening in the end wall of said hood and normally held yieldingly out of engagement with said first contact, and a stud having threaded engagement with said thimble member and cooperable with said second contact for moving said second contact into engagement with said first contact for closing the thermoelectric circuit ahead 01 said electromagnet to short circuit the electromagnet upon expansion of said bellows.

5. In a device of the' class described, in combination, a thermoelectric generator, a hood, a first conducting member disposed within said hood and connected in circuit with one side of said thermoelectric generator, a second conducting member disposed within said hood and insulated from said first conducting member and connected in circuit with the other side of said thermoelectric generator, an electromagnet disposed within said hood and having a magnet frame supported by said first conducting member, and a coil for said magnet frame, said coil having its terminals connected in circuit with the opposite sides of said thermoelectric generator, a first contact on one of said conducting members, a second contact connected within said hood with the other conducting member and normally held yieldingly out of engagement with said first contact, and means for moving said second contact relative to said first contact to disable the thermoelectric circuit.

6. In a device of the class described, in combination, a thermoelectric generator, a hood having an end wall, a first conducting plate disposed within said hood adjacent the end wall thereof and connected in circuit with one side of said thermoelectric generator, a second conducting plate disposed within said hood adjacent said first plate and insulated from said first plate and connected in circuit with the other side of said thermoelectric generator, an electromagnet disposed within said hood and having a magnet frame supported by said first conducting plate, and a coil for said magnet frame, said coil having its terminals connected in circuit with the opposite sides of said thermoelectric generator, a first contact on one of said conducting plates,

- a second contact connected within said hood with the other conducting plate and normally held yieldingly outof engagement with said first contact, and means operable through the end wall of said hood for moving said second contact bination, a thermoelectric generator, a hood, a.

first tubular terminal member mounted in the wall of said hood, a second terminal member mounted in said first terminal member, said second terminal member being insulated from said first terminal member and extending at its inner end into the hood inwardly from said first terminal member, a first conducting plate mounted on said first terminal member in position within the hood, a second conducting plate mounted on the inwardly extending end of said second terminal member in position within the hood and insulated from said first plate, an electromagnet disposed within said hood and having a magnet frame supported by said first conducting plate, and a coil for said magnet frame, said coil having its terminals connected in circuit with the opposite sides of said thermoelectric generator, a first contact on one of said conducting plates, a resiliently supported contact connected within said hood in circuit with the other conducting plate, and means for moving said resiliently supported contact into engagement with said first contact to disable the thermoelectric circuit.

8. In a device of the class described, in combination, a hood, a first tubular terminal member mounted in the wall of said hood, a second terminal member mounted in said first terminal member, said second terminal member being insulated from said first terminal member and extending at its inner end into the hood inwardly from said first terminal member, a first conducting plate mounted on said first terminal member in position within the hood, a second conducting plate mounted on the inwardly extending end of said second terminal member in position within the hood and insulated from said first plate, an electromagnet disposed Within said hood and having a magnet frame supported by said first conducting plate, a coil for said magnet frame, a first contact on one of said conducting plates, 2. resiliently supported contact connected within said hood in circuit with the other conducting plate, and means for moving said resiliently supported contact into engagement with said first contact.

HENRY F. ALFERY.

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