US2290047A

US2290047A - Safety device for heating and other apparatus

Info

Publication number: US2290047A
Application number: US239799A
Authority: US
Inventors: Charles V Hildebrecht
Original assignee: Milwaukee Gas Specialty Co
Current assignee: Milwaukee Gas Specialty Co
Priority date: 1938-11-10
Filing date: 1938-11-10
Publication date: 1942-07-14
Anticipated expiration: 1959-07-14

Description

Jilly 1942- c. v. HILD EBRECHT 2,290,047

SAFETY DEVICE FOR HEATING AND OTHER APPARATUS Filed Nov. 10, 1938 Patented July 14, 194 2- UNITED- STATES PATENT OFFICE T SAFETY DEVICE FOR HEATING .OTHER AND Charles v. nusebmm, Chicago, 111., assigno'r to Milwaukee Gas Specialty Company, Milwaukee, Wla, a corporation of Wisconsin Application kovember 10, 1938, Serial No. 239,799

18 Claims.

This invention relates to safety devices for heating and other apparatus.

safety devices of the general character in which an electromagnet connected 'in circuit with a thermocouple is adapted to be energized by the thermo-electricvcurrent set up by the thermo- Further objects and advantages of the inven- 7 tion will appear from the following detailed de- More particularly, the invention relates to couple so long'as the burner to which the therf mocouple is" subjected, such as a pilot burner, is

lighted, and when so energized, maintains a valve or other controlling member for controlling the supply of fuel or'operative energy to the apparatus in open or operating position; cessation of the holding action of the electromagnet upon extinction of the burner or upon-opening of the thermo-electric circuit releasing the valve or controlling member formovement to closed or safety position, shutting off the supply of 'fuel or operative energy to the apparatus.

-Where the relatively weak thermo-electric current is not capable of actuating the valve or controlling member of devices generally of the character above set forth to open or operating position, reset means is required for resetting the device.

One of the main objects of my invention is to provide improved reset means for resetting the armature of the electromagnet to attracted position and the valve or controlling'memberg to open or operating position, in which position, it

is adapted to be maintained so long as the electromagnet is energized and the armature held in attracted position thereby. v

Another object of my invention is to provide,

in combination with means for tripping the eleo- 1 tromagnet to release the valve or controlling member for movement to closed or safety position when, for example, adesired temperature is exceeded or upon abnormal, defective, or insufllcient or non-functioning of the apparatus or other parts, of means for resetting the armature of .the electromagnet to attracted position and the valve or other controlling member to open or operating position--for example, upon a prede-' termined drop in temperature-although the re- .set means may be controlled by a pressure senscription taken in connection with the accomburner for certain types of ovens or other heatingapparatus, or any other burner.

A pipe, indicated diagrammatically at H, supplies gaseous or any other suitable fuel to the burner If). A valve body, shown fragmentarily at l2, isconnected into the fuel supply pipe ll.

The valve body l2 has a valve opening or port l3. Disposed in juxtaposition to the burner I0 is a pilot burner M which maintains a pilot flamefor igniting the main burner. The pilot burner I4 is supplied with fuel by a tube l5 preferably con nected to the pipe ll anterior of the valve opening or port I3, or through a by-pass in the valve body l2, or otherwise, to maintain a constant supply of fuel to the pilot burner, and thereby a constantly burning pilot flame.

The port or valveopening I3 is adapted to be I closed by a valve 18 to shut off the fuel-supply to sitive device or by a humidity sensitive device or other device. It is also an object of my invention to provide a tripping and resetting combination, generally such as above set forth, and of a characterautomatically to maintain the flow of fuel to the burnervso long as it is desired to supply heat therefrom, and automatically to shut off the fuel supply when heat from the burner is not desired.

the main burner l0, preferably, in the illustrated embodiment of the invention, without shutting, off the fuel supply to the pilot burner i l, although this may be varied within the scope of the pre ent invention. The valve I8 is connectedby a,

valve stem 20 to an armature 2|, and ahelical spring 22 surrounds the valve stem with oneend engaging the valve l8 and its other end engaging a fixed part 23 of the control device. The spring 22 is normally compressed when the armature is, in attracted position, but when the electromagnet, indicated generally at 25, is energized and the armature Ills held in attracted position thereby, the spring 22 is prevented from. moving the valve It to closed position engaging the valve seat surrounding the opening H to shut off the fuel supply to the main burner. Upon cessation of the holding action of the electromagnet 25, as, for example, upon extinction of the pilot light at the pilot burner II, or upon tripping of the electromagnet as will hereinafter appear, the

armature 2| and connected valve l8 are released, whereupon the. valve I8 is moved by the spring 22 into position closing the port or valve opening l3 to shut .off the supply of fuel to the' main burner.

The electromagnet 25 comprises a magnet frame 28 having an energizing coil 21 as more fully disclosed in'the copending application of John H. Thornbery and Theodore A. Wetzel, Serial No. 283,572, filed July 10, 1939, or it may be of any other suitable or preferred form. In the illustrated embodiment of the invention, the magnet frame 28 is of generally U-shaped form, and the coil 21 surrounds one of the legs of the magnet frame. The coil 21 is connected in circuit, as more or less diagrammatically illustrated at 28, with the thermocouple 88.

The thermocouple 88 is placed in position so that its hot junction 8| will be heated by the pilot light i4 when said pilot light is burning. Its construction may be similar to that more fully disclosed in Oscar J. Leins Patent No. 2,126,564, granted August 9, 1938, or it may be in the form of any of the thermocouples ormultiple thermocouple devices disclosed in the copending application of Guido Wunsch and Josef Schuppert, Serial No. 738,370, filed August 3, 1934, now Patent No. 2,189,829 granted Feb. 13, 1940, or of any other suitable or preferred form.

A trip coil 82 surrounds the other leg of the magnet frame 28. On terminal 88 of the coil 82 is connected through a conductor 84 to one side or one of the conductors 88 of a

circuit

88, 88. The

circuit comprising theconductors

88 and 88 is connected to a suitable source of current-for example, through a transformer 88 to an alterhating current circuit 48. The circuit 48 may,

for example, be an alternating current lighting ity responsive device, or a device responsive to some other condition for actuating the contact 88.

The reset means for resetting the armature 2i into attracted position and the valve i8 to open position comprises a reset stem 88. The resetting electromagnet 8| cooperates with the stem 88 for the purpose of actuating this stem inwardly to reset the device by engaging the valve l8 and movin the valve to open position and the armature 2| to attracted position. In the embodiment of the invention illustrated in the drawing, the reset electromagnet 8i has a magnet frame 82 with the magnet coil 88 surrounding the same. The stem 88 ispreferably formed of non-ferromagnetic material, and its outer end carries an armature 88'formed of suitable magnetic material. When the circuit through the coil 88 is closed, the electromagnet 8| isenergized and moves the armature 88 to attracted position, this movement of the armature 88 actuating the reset stem inwardly to reset the device.

A reset return spring 88, interposed between the armature 88 and, for example, a fixed part of the electromagnet 8|, returns the reset stem 88 and armature 88 to outwardly projected or retracted position, as shown. A stop 88, fixed on the stem 88, limits the outward projection of this stem and the armature 88 under the action of the spring 88. The particular reset electromagnet 8| shown in the drawing is illustrative and not limiting. Any other suitable form of circuit, or any other alternating current circuit supplied by a suitable source of alternating current (not shown), although, of course, a direct current tripping circuit as well as other tripping arrangements may be employed within the scope of the present invention. Moreover, omission of the tripping feature entirely is contemplated within the broader aspects of the invention.

The other terminal 42 of the trip coil 82 is connected by a conductor 48 in circuit with a fixed contact 44. A second fixed contact 48, positioned in spaced relation with respect to the contact 44, is connected through the winding of an electromagnet 48'and.a conductor 48 to the conductor 88 of the

circuit

88, 88.

A thermally sensitive member or thermostat 88 is fixedly supported at one end at 82 and carries, at its opposite end, contact means 88 for movement by the action of different temperatures upon the thermostat into engagement with the contact 44for example, upon a predetermined maximum temperature adjacent the thermostat,

and for movement into engagement with the conv,oif the electric circuit for conducting current from the

circuit

38, 88 to the contact 88. .smay be varied so that the bi-metal thermally sensitive member is removed from the electric This circuit. Moreover, the thermostat may be of any other suitableor preferred type, and, as heretofore pointed out, I contemplate other devices such as a pressure responsive device or a humidelectromagnet may be employed in conjunction with the reset stem for the purposes herein set forth. For example, the reset electromagnet may be of the swinging armature type, with the swinging armature cooperating with the reset stem in a manner to move same inwardly to accomplish the desired resetting of the device when the armature is attracted.

One terminal of the reset coil 88 is connected to th conductor 88 of the

circuit

88, 88, and the other terminal of the coil 88 is connected through a conductor I2 to a contact 14 in juxtaposition to the electromagnet 48, A leaf spring 18, fixedly supported at I8 and connected at its fixedly support end with the conductor 88 of the

circuit

88, 88, carries a contact 18 which is adapted to engage the contact I4 for closing the circuit through the coil 88 of the reset electromagnet 8|, whereby the resetting operation is secured. The contact 14 may be carried by a leaf spring I8 fixedly supported at 88. v

The spring I8 is preferably tensioned normally to separate the contact I8 from the contact I4 and to snap the contact 18 away from the contact I4 to open the

reset coil circuit

88, 12 at the contacts 14, I8 upon completion of the resetting operation. A fixed stop may be provided at 82 for limiting the separation of the spring I8 and its contact I8 from th contact 14.

The free end of the spring 18 projects beyond the contact I8, and the electromagnet 48 is provided with an armatur 88 pivoted, for example, at 88, and which, upon completion of th circuit through the electromagnet 48, i actuated to attracted position and, by such actuation, engages the projecting end 81 of the spring 18 and moves the contact 18 into engagement with the contact 14 to close the

reset coil circuit

88, 12. To prevent holding of the contact I8 in engagement with the contact 14 during the entire period of contact of the thermally controlled contact means 88 with the contact 48, and particularly after the resetting operation is completed, the

armature 85. (or detent means associated therewith) is adapted to snap clear of or to move past the projecting end 81 of the spring 15 as it moves to attracted position.

, tact I4 continue only so long as necessary to complete the resetting operation, Continued energization of the electromagnet'lt snaps or.

moves th armature or detent means associated therewith past the projecting end of the spring 15, whereupon the tension of the spring I5 snaps the contact 18 to open position notwithstanding the fact that the armature 85 may continue in attracted position.

A spring 86', having one end connected to the armature 85 and its other end fixedly anchored at 88, returns the armature 85 to retracted position when the electromagnet 46 is deenergized, as, for example, by separation of the contact means 53 from the contact 45. The spring character of the projecting end 81 of the spring permits the cooperating end of the armature 85 or detent means associated therewithto snap past the same in its movement to retracted position as shown in the drawing.

Instead of theelectromagnet and armature arrangement as shown at 46 and 85, the electromagnet'fli may be provided with a movable core having at its lower end, as viewed in the drawing,

a detent pivoted thereto and adapted, upon the movement of the core which accompanies energization of the electromagnet, to press the contact 18 into engagement with the contact 15. The pivotal movement of such detent could be restrained in the switch closing movement, whereas the detent could swing in movement in the opposite direction to clear the projecting end of the spring 15,

The operation of the device is as follows:

When the pilot light It is burning, the heat thereof upon the thermal junction 3| of the thermocouple produces a thermo-electric current in thecoil 21. The magnet frame 26 and armature 2| are preferably formed of an alloy. of

are so wound and so connected that, when both coils are energized, the lines of force produced in the magnet by the respective coils will oppose one another, forming like poles at the free ends of the magnet frame. As a result, the energizetion of the trip coil by engagement of the contact 53 with the contact 54 produces lines of force opposed to the lines of force set up by the thermo-electric current, and the magnetic attraction produced by the thermo-electric current is canceled out or reduced so that the armature 2i is'released and the valve it moves to closed position. i

Where the temperature to which the them stat 50 is subject drops below the predetermined minimumtemperature, the contact means 53 is moved by the thermostat 50 into engagement with the contact 45 and by completion of the circuit for the electromagnet .46, closes the contacts 18, I4 as hereinbefore described. This closes the circuit for the resetting coil 63 which energizes the resetting electromagnet. The armature 65 is attracted and actuates the reset stem 60 inwardly to reset the armature2l to attracted position and the valve l8 to open position. If the pilot burner is lighted, the energization' of the electromagnet 25 thereby will retain the armature 2i in attracted position and the valve I 8 open.

Where a thermally responsive control is provided at 50, the thermostat thereof may, as alrelatively low magnetic reluctance and, as a result, with the contact means 53 out of engagement with the contact 44, the relatively weak thermo-electric current produces a magnetic 4 force of sufficient strength so that when the armature 2i is placed in contact with th pole ends of the magnet frame, the magnetic attraction holds the armature in attracted position with a force reater than the force exerted by the spring 22, thereby holding the valve l8 open so long asthe pilot flame is burning and the contact means 53 is out of engagement with the contact 44, I y

Ifthe pilot flame is extinguished, the holding actionof theelectromagnet 25 ceases to be sufiicient to hold the armature 2| andvalve l8 in ready pointed out, be of any suitable or preferred form. Where the apparatus is employed in connection with a water heater, the thermostat may besubject to the temperature of the water in the tank, and where the apparatus is employed in connection with a space or room heater, the thermostat may be subject to the temperature of the space or room which is heated. Other controls at will be subject to the other conditions at which it is desired to trip and reset the device as herein described.

,With the present invention, the valve I8 is tripped and resetautomatically upon the occurrence of predetermined conditions. Where the device is reset automatically, the pilot burner i4 preferably provides a constantly burning pilot light, so that when the device is automatically reset it will be retained in reset position by energization of the electromagnet 25 by the heat of the pilot flame on the thermocouple. Where the automatic feature is not necessary or desired,

the fuel supply for the 'pilot light may be arranged to be shut off by the valve l8 which shuts off. the fuel supply to the main burner.

Other modifications are contemplated within the scope of the present invention and, therefore, I do not intend to be limited to the precise detailsshown or described.

I claim:

1. Safety device for heating and other apparatus comprising, in combination, means to control the supply of operative energy to the apparatus, heat generating means, pilot means for said heat generating means, a thermocouple subject to the heat of said pilot means, an electromagnet connected in circuit with said thermocouple and adapted to cause said controlling means to supply operative energy to the apparatus whilesaid pilot means is operative and to shutoff the supply of operative. energy to the apparatus when said pilot means becomes" inoperative, a circuit connectedto a source of current other than said thermocouple, and means in said last mentioned circuit for resetting said Cir means to supply operative energy to the appat ratus while said pilot means is operative and to shut off the supply of operative energy to the apparatus when said pilot means becomes inoperative, a reset electromagnet for resetting said first electromagnet and said controlling means to operative position to supply operative energy to the apparatus, a circuit for said reset electromagnet and having a source of current other than said thermocouple, a switch in the circuit for said reset electromagnet, and thermally responsive magnetic means for closing-said switch when the temperature adjacent said thermally responsive means falls below a predetermined minimum, said switch being. self-opening upon completion of the resetting operation.

3. In a device of the character described, in combination, a control device having an electromagnet provided with an armature connected.

to a controlling member and adapted when energized to hold said member in operating position and when deenergized to release said member for movement to a safety position, a second elec-' tromagnet adapted for resetting said armature to attracted position and said controlling member to operating position, a circuit having a source of current for energizing said second electromagnet; and means for closing said circuit to reset said armature and said controlling member and for interrupting said circuit upon completion of the resetting operation.

4. In a device of the character described, in combination, a control device having an electromagnet provided withan armature connected to a controlling member, and adapted when enmagnet connected incircuit with a source of current other than the thermoelectric current and cooperating with said reset stem for resetting said controlling member from safety position to operating position, a switch connected in circuit with said second electromagnet, and thermally responsive means located in a position the temperature of which is controlled by said safety device and operable to close said switch to energize said second electromagnet and reset said controlling member from safety position to operating position upon a drop in temperature adjacent said thermally responsive means, said thermally responsive means being operable. also to disable the holding action of the thermoelectrically energized electromagnet to release said controlling member for movement to safety position upon a rise in temperature adjacent said ergized to hold'said member in operating position and when deenergized to release said. member for movement to a safety position, a reset stem, a second electromagnet cooperating with said reset stem for resetting said armature to attracted position and said controlling member to operating position, a circuit for said electromagnet, and a switch for closing the circuit through said second electromagnet to reset said armature and said controlling member and operable to open the circuit through said second electromagnetupon completion of the resetting operation.

5. In a safety device for fuel burners of the self-contained type employing thermoelectric actuation, a controlling member having an operating position for the flow of fuel to the burner and a safety position for shutting off the flow ,of fuel to the burner, an electromagnet adapted to be energized by a thermocouple subjected to the heat of a flame at said burner and holding said controlling member in operating position by the thermo-electric current generated by the heat of the flame on the thermocouple but'incapable of actuating the controlling member from safety position to operating position by the thermoelectric current, a reset stem, a second electrothermally responsive means. i

6. In a device of the character described, in

combination, a burner, a fuel supply pipe leading to said burner, a valve in said pipe, a supply pipe for a pilot light; in juxtaposition to said burner, an electromagnet, an armature for said electromagnet which, when attracted, maintains said valve in open position and, when retracted, compels closing of said valve, a thermocouple placed in position to be heated by said pilot light and connected in circuit with said electromagnet, a second electromagnet connected in circuit with a source of current and adapted for resetting said. armature to attracted position, and means subject to the heat supplied by said burner for closing the circuit through said second electromagnet at a predetermined temperature and for interrupting the circuit through said second electromagnet upon completion of the resetting operation.

7. In a device of the character described, in

combinatioma fuel supply pipe, a valve in said pipe, an electromagnet having an armature and a winding which, when energized, holds said armature in attracted position and maintains said valve in open position and, when deenergized, releases said armature for movement ofsaid valve to closed position, a trip coil'fgi stripping said electromagnet to release said valve for movement to closed position, a second electromagnet adapted for resetting said valve to open position and said armature to attracted position, and thermally responsive means adapted to close the circuit for said trip coil and said resetting electromagnet at predetermined different temperatures.

8. In a device of the character described, in combination, a fuel supply pipe, a valve in said pipe, an electromagnet having an armature and a winding which, when energized,, holds said armature in attracted position and, maintains said valve in open position and, when deenergized, releases said armature for movement of said valve to closed position, a trip coil for tripping said electromagnet to release said valve for movement to closed position, a second electromagnet adapted for resetting said valve to open position, and thermally responsive means adapted to close the, circuit for said trip coil and said resetting electromagnet at predetermined temperatures, the circuit for said resetting-electromagnet being self-opening upon completion of the resetting operation irrespective of said thermally responsive means.

9. Safety device for heating or other apparatus comprising, in combination, a burner, a fuel supply pipe leading to said burner, control means having an operative position permitting fuel to be supplied to the burner and a safety position shutting off the supply of fuel to the burner, an electromagnet having an armature connected'to said control means, a thermocoupleplacedin' position to be heated by a flame and connected in circuit with said electromagnet to energize same and hold said armature in attracted position and thereby said control means in operative position, means for rendering said electromagnet ineffective to hold said armature in attracted position and said control means in operative position, a reset electromagnet for reset- I ting said armature to attracted position and said control means to operative position, a circuit having a source of current other than said thermocouple, and. means subject to the condition of the apparatus for closing said last circuit through the means for rendering said first electromagnet ineffective upon the occurrence of one predetermined condition in the apparatus and for closing said last circuit through said reset electromagnet upon the occurrence of a different predetermined condition in the apparatus.

10. Safety device for heating or other apparatus comprising, in combination, a burner, a fuel supply pipe leading to said burner, control .said last circuit through said reset electromagnet at a predetermined minimum temperature 12. In combinationfa main burner, a pilot burner therefor; a fuel supply pipe leading to said main burner, a valve in said pipe, a thermocouple subject to the heat of the pilot burner and connected in circuit with an electromagnet,

for maintaining said valve open as long as the pilotbumer is ignited and for releasing said sure of the fuel in the fuel supply pipe leading to the main burner for resetting said valve to open position, and mea s under the control of the heat of the main burner and operative at a predetermined-maximum temperature to operate said tripping means and at a predetermined means having an operative position permitting fuel to be supplied to the burner and a safety position shutting off the supp y of fuel to the burner, an electromagnet having an armature connected to said control means, a thermocouple placed in position to be heated by a flame and connected in circuit with said electromagnet to energize same and hold said armature in attracted-position and thereby said control means in operative positiommeans for rendering said electromagnet ineffective to hold said armature in attracted position and said control means in' operative position, a reset electromagnet for resetting said armature to attracted position and said control means to operativeiposition, a circuit having a source of current other than said thermocouple, and a thermostat subject to heat supplied by said burner for closing said last circuit through the means forrendering said first electromagnet ineffective at a predetermined maximum temperature and for closing said last circuit through said reset electromagnet at a predetermined minimum temperature.

11. In combination, a burner, a fuel supply pipe leading to said burner, a valve member having an operative position permitting fuel to be supplied to said burner and a safety position shutting off the supply of fuel to the burner, an electromagnet having a winding and an armature connected to said valve member, a thermocouple placed'in position to be heated by a flame and connected in circuit with said electromagnet to energize and hold said armature in attracted position and thereby said valve member in operative position, an auxiliary winding for said electromagnet having a differential effect relative to said first winding and adapted, when energized,

to release said armature for movement of the armature to retracted position and movement of minimum temperature to operatesaid resetting means.

13. In a thermoelectric control apparatus for a burner, the combination with a burner, a fuel supply pipe leading to said burner, a valve in said pipe, a pilot light in position to ignite said burner, a first electromagnet, an armature for said electromagnet which, when attracted, maintains said valve in open position, and, when retracted, frees, said valve from movement to closed position, a thermocouple placed inposition to be heated by said pilot light and connected in circuit with said electromagnet so as to energize said electromagnet sufllciently to.

hold said armature in attracted position and said valve in open position, said valve being incapable of being actuated to open position by the thermoelectric current "generated by the heat of the pilot light on said thermocouple, of a second electromagnet connected in circuit with a source of current other than said thermocouple and adapted for resetting said armature to attracted position and said valve to open position, a switch connected in circuit with said second electromagnet, and thermally responsive means located in a position the temperature of which is controlled by said control apparatus and operable to close said switch to energize said second electromagnet and reset said valve from: closed position to open position upon a drop in temperature adjacent said thermally responsive means, said thermally responsive means being operable also to' disable the holding action of's'aid first thermoelectrically energized electromagnet to release said valve for movement to .closed position upon a rise in temperature Iadjacent said thermally responsive means. i

14. A-safety device for heating and other apparatus comprising, in combination, means to control the supply of operative energy to the apparatus, heat generating means, pilot means for said heat generating means, a thermocouple sub ject to the heat of said pilot means, an electromagnet connected in circuit with said thermocouple and adapted to cause said controlling means to supply operative energy to the apparatus while said pilot means is operative and to shut off the supply of operative energy to the apparatus when said pilot means becomes inoperative, a reset electromagnet for resetting said first electromagnet and said controlling means to operative position to supply operative energy'to the apparatus, a circuit for said reset.

electromagnet and having a source of current other than said thermocouple, a switch in the circuit for said reset electromagnet, and condition responsive means for closing said switch upon the occurrence of a predetermined condition, said switch being self-opening upon completion of the resetting operation.

15. In a device of the character described, in combination, a'fucl supply pipe, a valve in said pipe, an electromagnet having an armature and a winding which, when energized, holds sald armature in attracted position and maintains said valve in open position and, when deenergized, releases said armature for movement of said valve to closed position, a trip coil for tripping said electromagnet to release said valve for movement to closedposition, a second electromagnet adapted for resetting said valve to open position and said armature to attracted position, and condition responsive means adapted to close the circuit for said trip coil and said resetting electromagnet.

16. In a device of the character described, in combination, a fuel supply pipe, a valve in said pipe, an electromagnet having an armature and a winding which, when energized, holds said armature in attracted position and maintains said valve in open position, and, when deenergized, releases said armature formovement of said valve to closed position, a trip coil for tripping said electromagnet to release said valve for movement to closed position, a second electromagnet adapted for resetting said valve to open' connected to said control means, a thermocouple placed in position to be heated by a flame and connected in,circuit with said electromagnet to energize same and hold said armature in attracted position, and thereby said control means in operative position, means for rendering said electromagnet ineffective to hold said armature in attracted position and said control means in operative position, a reset electromagnet for resetting said armature to attracted position and said control means to operative position, and a circuit having a source of current other than said thermocouple for energizing the means for rendering said first electromagnet ineffective upon the occurrence of one condition and for energizing said reset electromagnet upon the occurrence of a different condition.

18. In a safety device for fuel burners of the self-contained type employing thermoelectric actuation, a controlling member having an operating position for the flow of fuel to the burner and a safety position for shutting off the flow of fuel to the burner, an electromagnet adapted to be energized by a thermocouple subject to the heat of a flame at said burner and holding said controlling member in operating position by the thermoelectric current generated by the heat of the flame on the thermocouple but incapable of actuating the controlling member from safety cooperating with said reset stem for resetting CHARLES v. HILDEBRECHT.