US2031335A - Control for heat generators - Google Patents

Description

Feb. 1s, 1936. .Ji J. SLOYAN mamas ./Zfrome f jlogan/ ATTORN EYS Feb. 18', 1936. J. J. sLoYAN CONTROL FOR HEAT GENERATORS Filed July 2, 1952 4 Sheets-Sheet 2 INVENTOR .femme J .Slogan BY b bua/3, ATTORNEY-S mi l Feb. 18, 1936.- J. J. vSLOYAN CONTROL FOR HEATOENERATORS 4 Sheets-Sheet 5 Filed July 2, 1932 INVENTOR ./mme .lagan/ @MRL d` ATTORNEYS Feb. 18,1936. J; SLOYAN O 2,@3L335 CONTROL FOR HEAT GENERATORS Filed July 2, 1952 4 Shets-Sheet 4 LZal 342 225 zz@ L ;.`\r .V 53g azz l JDi555: sa] l amd 5 254 1 3M Z--'O&Q 335 j -516 INVENToR ATTORNEYS .femme f Siayfln/ Patented Feb. 18, 1936 UNITED STATES PATENT OFFICE ALl Claims.

-invention pertains to the general class of heating devices and particularly Lto automatic and semi-automaticcontrols for such devices. In copending application, Serial No. 502,055 med-December 13,- 1930.1 have shown and described a burner, together with electrical controls therefor. This application comprises a continuation in part of said copending application.

The invention will be-more fully understood upon reference tothe drawings in which like referen'ce characters have been appended to like parts in the-various figures, and in which A Fig. -l-is an elevation, chiefly in section, of a burner;-

Fig. 2 is an end View;

Fig. 4 is adiagrammatic illustration of one form of control;

Fig.l 5 isa diagrammatic illustration of another i form of control;

- Fig. 6 is a diagrammatic illustration of a further form of control particularly adapted to automatically control two burners, in simultaneous operation;

Fig.A 7 is a diagrammatic illustration of the location of the thermostatic switching devices for the form of control illustrated in Fig. 6.

Referring to Figs. l, 2 and 3, at I0 is shown a furnace wall through which extends a combustion chamber II. To the mouth of the combustion chamber is secured an ante-combustion chamber I2. Any means maybe employed for connecting the ante-combustion chamber I2 to the combustion chamber I I. Sheath I4 surrounds ante-'combustiorrcha-mber I2 and is spaced therefromso as to provide an air passageIS. l'

Sheath I4 is shown' formed so'as to provide an annular enlargement I'I which opens'at one side edge into the air-passage I5. Connection between a-blower I8 and the enlargement-Il is provided through an opening I9 in thesheath I4.

Other forms-of air passages are shown and described in mycopending application, Serial No. 620,595 led July 2, 1932. The particular description ofl an air passage Aherein is merely for the purpose of showing means for preheating air by meansl of heat derived from the sustained c'ombustion of fuel in the burner.

Ante-combustion chamber I2 is shown as merging into a straight Vportion 22.` Portion 22 is shown provided with a collar 23 for supporting one end of sleeve 25. The other end of sleeve 25 is shown'tted aboutfthe end- 26 of sheath I4, apacking nut 2l Ybeingprovided to form a tight connection. M 'i A tubularmember 30 leads froml opening 29 in sleeve 25 and opens into a heating chamber 32 containing an electrical heating element 45 having electrodes-48 'and-50. Heating chamber-32 opens into a conduit 34, which in turnleads to the air inlet of 'carburetor-39.- The outlet of carburetor 39 opens into the extended portion 22 of ante-combustion chamber I2.

The generalpath ofthe air and eventually of the combustible mixture is as follows: The air enters from blower I8 into blower pipe 20, then passes through opening I9- into enlargement I1 of air passage I5, then intothe more restricted portion of air passage -.I5, then in between sleeve 25 and extension 22, Vthen upwardly through tubular member 3|] into chamberv 32, thenthrough a conduit 34 into carburetor 39, where it is mixed with fuel. VFrom here theresultant combustible mixture passes through portion 22` into ante-combustion chamber I2 via a safety device 'I0 illustrated as a venturi.

The blower I8, of course, may be inserted at any other point in the set-up that is between the air passage I5 and the carburetor, or between the carburetor and the ante-combustion chamber, or might even be placed in the stack, the particular description of the burner and its associated parts being merely for the purposes of illustration.

The carburetor 39 is shown-provided with-an overow 60 leading to a-sealed receptacle 62 n which the` pressure is equalized with that of the float chamberY and that of conduit 34 by means of a pipe 56. Y f.

- Ignition is accomplished by means of electrodes 'I6 inserted into the path of the combustible mix- 3 ture through'apertures 'I'I in venturi "I9, the ends 'I5 of electrodes 'IB being; of course, spaced from each other.

As part of the automatic and semi-automatic startingand operating equipment, I insert a thermostatic switching device 'I8 of any suitable type in the air streamupstream from the' heating element 45 and'downstreamiromthe air Vpassage I5. The l temperature .responsive elementV of thermostatic switching device I8 is illustrated as extending into tubular member 30. The thermostatic switching device `'illustrated comprises two mercurytube switches mounted upon a rotating base. The arrangement is such that at low temperatures the mercury switches are in the positions shown' inFig. 1 with one switch closed and the other switch open. As the airflowing through air passage I5 increases in temperature due to sustained combustion in ante-combustion chamber I2, the Lrotating base'of thermostatic switch- CTI ing device 18 eventually rotates clockwise, as seen in Fig. l, whereupon the mercury switch which was formerly closed opens and the mercury switch which was formerly open closes.

A thermostatic switching device 19, in all respects similar to that shown at 18, is placed in the conduit 34 downstream from heating element 45.

Carburetor 39 is shown with a. fuel inlet pipe 8| provided with an electrically operated valve 82. Carburetor 39 is also provided with a drain pipe 83 having an electrically operated valve 84. Pipe 83 leads to any suitable receptacle, not shown.

Carburetor 39 is, of course, provided with the usual volume controlling mechanism illustrated as a butterfly 81.

Receptacle 62 is provided with a float 88 which controls a mercury switch 89 to which wires ||0 and |66 (see. Fig. 4) are connected, wire |66 leading to valves S2 and 84. The arrangement is such that when the iioat 88 is at the bottom of receptacle 62, switch 89 is closed, and when float 08 is raised by overflow from carburetor 39, switch 89 opens. Fuel valve 82 opens with a now of current and drain valve 84 closes with a flow of current, and vice versa.

Substantially automatic starting and regulatlng mechanism is shown diagrammatically in Fig. 4. At 95 is illustrated a single throw double pole switch which is connected to a suitable source of electrical energy. At 18 is diagrammatically illustrated the thermostat located in the tubular element 30 of Fig. 1. This thermostat has two mercury tubes 96 and 91. The tubes as illustrated in full line are in cold position. It will be noted that the mercury illustrated at 98 in tube 96 closes a circuit through conductors 99 and whereas the mercury |0| in tube 91 has flowed away from the electrodes on the ends of conductors |02 and |03 to open the circuit through the same.

Thermostatic switching device 19 which projects into conduit 34 has two mercury tubes |04 and |05. The thermostatic switching device 19 is also illustrated in full lines in cold position. In this position the mercury |06 in tube |04 closes a circuit between conductors |00 and |01. The mercury |08 in tube |05 is in the opposite end of the tube from the electrodes on the ends of conductors |09 and ||0. Tubes 96 and 91 of thermostatic switching device 18 and tubes |04 and |05 of thermostatic switching device 19 are mounted upon bases which are adapted to turn clockwise with increase in temperature and turn counterclockwise with decrease in temperature. I arrange tubes 96 and 91 so that when turning with their bases in a clockwise direction a circuit will be established through conductors |02 and |03 be.- fore the circuit through conductors 99 and |00 is broken.

A timing switch illustrated generally at |I2 is connected across conductors |00 and |01. The timing switch comprises a base ||3 mounted to rotate about an axis ||4. A handle on one side of base ||3 would cause the base to rotate clockwise except for the latch I I6 which engages a depression I I1 in the edge of base I I3. Mounted upon base ||3 is a tube ||8 containing mercury shown at ||9 as well as electrodes on the ends of conductors |20 and |2|. In the position shown, the mercury ||9 in tube ||8 is adapted to close a circuit through conductor |22, resistance element |23, conductor |20 and conductor |2|. This construction is merely diagrammatic in character and any approved structure may be substituted therefor. For instance, the resistance element |23 which expands and contracts responsive to temperature changes is conveniently filled with graphite resistance discs.

When a sufcient current flows through resistance element |23 for a predetermined time it eventually expands, thus turning latch ||6 about its axis |24 to release the base ||3 and permit the same to rotate clockwise, thus causing the mercury ||9 to flow to the other end of tube IB to break the circuit established by the mercury through the electrodes on the ends of conductors |20 and |2|. A stop |25 adapted to engage latch ||6 may be provided to limit the rotation of the base I3.

Conductor |01 leads to a relay |21 which is adapted to operate an armature |28. The construction of the relay |21 and armature |28 is such that when no current is flowing through the relay, the bar of the armature is spaced from contacts |30, |3|, |32 and |33. When a current ilows through relay |21, the bar of the armature is drawn into engagement with contacts |30, |3|, |32 and |33 to electrically connect the same. Conductor |34 connects relay |21 with binding post |35 on automatic starter |36 to be hereinafter described.

One pole of switch 95 is connected to binding post |35 and the other pole is connected to binding post |31.

Contact |30 is connected to binding post |38 on automatic starter |36 by means of conductor |39. Contact |30 is also connected to conductor |02.

Contact |3| is connected to binding post |40 on automatic starter |36 through conductor |4|` Contact |3| is connected to conductor |42 which leads to one end of tube |43 mounted upon a base |44 adapted to rotate about an axis |45. Adjacent the electrode on conductor I 42 is an electrode on conductor 99 and a circuit is established through these electrodes by mercury |46 when the tube |43 is in the position shown. Axis |45 has mounted on one of its ends butterfly 81 of carburetor 39 (see Fig. 1). Arm |48 secured to axis |45 is connected to a master thermostat shown diagrammatically at |49 by means of rod |50. A lever |5| pivoted at |52 is connected at |53 to rod |50. Thermostat |49 is located within the zone to be heated by the burner. For instance, thermostat |49 might be located in a room of a building or at any other point, its function being the control of butterfly valve 81 of carburetor 39 shown in Fig. l. A removable pin shown diagrammatically at |54 is adapted to be positioned in the path of lever |5| to prevent clockwise movement thereof.

Contact |32 is connected through conductor |56 to heating element 45 and transformer |51. The other terminals of heating element 45 and transformer |51 are connected to conductor |58 which in turn connects to conductor |59 which leads to terminal |60 on automatic starter |36.

Contact |33 is connected with conductor |03. Contact |33 is also connected with conductor |09 which leads to tube |05 of thermostatic switching device 19.

Switch 89 controlled by float 88 in receptacle 62 may conveniently comprise a base |62 mounted on a shaft |63 which in turn is controlled by float 88 referred to in connection with Fig. 1. Base |62 may carry a tube |64 having a small amount of mercury |65 and having in one end spaced electrodes on the ends of conductors ||0 and 68. The operation of the switch 89 is such that when the float 88 is in the bottom of receptacle 62 the mercury |65 electrically connects conductors ||8 and |66. As the float 88 rises, due to an overflow from the float chamber of the carburetor, base |62 rotates clockwiser causing the mercury |85 to flow to the other end of the tube |84 to disconnect conductors ||8 and |98.V This breaks the circuit through valves 82 and 84 connected in parallel between conductors |66 and |59.

Contact |33 is also connected to terminal |18 on automatic star+er |36 by means of conductor |1|. Spaced from terminal |18 is the terminal |12. TerminalsY |18 and |12 comprise a portion of an overload relay |13 having an armature |14 which opens and closes a circuit through the terminals |18 and |12.

A relay |15 having an armature |16 comprising a bar |11 of insulating material with contacts |18 and |19 is connected to the terminal |12 by means of the conductor |88. The other side of relay |15 is connected to the terminal |35 by means of conductor |8|.

Blower motor 82 is connected across contacts |18 and |19 through the overload relay |23, the arrangement being such that relay |13 opens the circuit through terminals |18 and |12 when the blower motor |82 becomes overloaded.

Terminal |83 is connected to terminal |49 by means of a conductor |84 and terminal |85 is connected to terminal |31 by means of a conductor |88. Terminals |83 and |85 may be connected by means of a push button |81.

The operation of the starting and stopping mechanism is as follows: Push button |81 is depressed, thus connecting terminals |83 and |85. This closes a circuit from terminal |31 through conductor |88, terminals |85, |83, conductor |84, terminal |88, conductor |4I, contact |3|, conductor |42, tube |43, conductor 99, tube 95, conductor |88, tube |84, conductor |81, relay |21, conductor |34, and terminal |35. Relay |21 draws armature |28 into engagement with contacts |38, |3|, |32 and 33, thus electrically connecting these contacts. Contact |33 is thus connected to contact |3|. This closes a circuit through terminal |31, conductor |86, terminals |85 and |83, conductor |84, terminal |48, conductor |4|, contact |3|, armature |28, contact |33, conductor 1| terminals |18 and |12 (relay |13 being normally closed), conductor |88, relay |15, conductor |8|, and terminal |35. Relay |15 moves its Varmature |18 so that contact |18 engages a contact |89 connected to terminal |31, and contact |19 engages a contact |98 connected to terminal |35. This in turn connects contact |38 with terminal |31 through wire |39, terminal |38, and contacts |89, |18 since terminal |38 is electrically connected to Contact |18. Push button |81 may now be released because contact |3| in the circuit of relay |21 and contact |33 in the circuit of relay |15 are connected to the contact |38 through the armature |28.

The closing of relay |15 starts blower motor |82. Blower |82 is connected across terminals |38 and |58 by means of the conductors shown. The conductor between blower |92 and terminal |68 has interposed therein overload relay |13. It can be seen that closing of relay |15 connects blower |82 directly across the line. Butterfly 81 of carburetor 39 is attached to axis |52 and, with the thermostat |49 and its associated mechanism locked in the position shown by the stop |54, the buttery 81 is slightly open so as to permit a small flow of air from blower 8 through air passage |5, tubular member 38, past thermostatic switching device 18, over heating element 45, through air conduit 34 past thermostatic switching device 19, carburetor 39, venturi 18, into the ante-combustion chamber 2.

Contact |32 being engaged by armature |28,

' a circuit is closed through contact |32, conductor |58, heating element 45, transformer |51, conductors |58 and |59, terminal |68, contacts |19 and I 98 and terminal |35, terminal |68 being electrically connected to contact |19. A spark is thus established across electrodes 16. Heating element 45 heats the air passing around it, which is, of course, small in quantity. When the flowing air and the associated parts reach a temperature suitable for Vaporization of the fuel, ther'- mostatic switching device 19 in air conduit 38 moves clockwise as seen in Fig. 4, moving the tubes |84 and |85 to the positions shown in dotted lines. Movement of the thermostatic switching device 19 closes a circuit through contact |33, conductor |89, conductor ||8, conductor |86, valves 82 and 84, conductor |59, terminal |58, contacts |19 and |98 and terminal |35. Feed valve 82 opens to permit fuel to enter carburetor 39 and drain valve 84 closes to prevent draining of such fuel from the carburetor. As will hereinafter appear, opening of switch |84 connects resistance element |23 in series across the line instead of in parallel with the ends of conductors |98 and |81, which condition obtains when switch tube |84 is closed.

After the fuel reaches the proper level in carburetor 39 it begins to flow up into jet or jets 58 and is vaporized by the flowing air. The resulting combustible mixture is ignited as it passes through venturi 18 by the spark passing between electrodes 16.

The flame begins to heat ante-combustion chamber I2 which in turn begins to heat the air passing thro-ugh air passage I5. When the air passing through the air passage i reaches a desired temperature, suitable in itself for proper vaporization of fuel, it actuates thermostatic switching device 18 causing it to turn clockwise bringing the tubes 95 and 91 into the positions shown in dotted lines. The opening of switch tube 96 opens the circuit through relay |21, causing armature |28 to disengage contacts |38, |3|, |32 and |33. This opens the circuit through heating element 45 and transformer |51 and deenergizes resistance element |23. The closure of switch tube 91 closes a circuit from contact |39, through conductor |82, tube 91, conductor |03 and contact |33 so that fuel Valve 82 remains open and drain valve 88 remains closed. Relay |15 also remains closed.

The turning of the thermostatic switching device 18 signies that the device is properly warmed up and that the rate of combustion may be increased to meet requirements. Stop |54 holding lever |5| may be released at this time so as to permit normal operation of the thermostat |49. This may be done manually or automatically, for instance by some mechanism connected to thermostatic switching device 18 to be actuated by the clockwise movement thereof.

'I'he timing switch |2 acts merely as a safety device. Before the thermostatic switching device 19 turns clockwise practically no current flows through the timing switch in view of the small drop between its terminals. However, when the circuit through the tube |84 is open, the timing switch ||2 is placed in series with the circuit through conductors |00 and |01. The timing switch permits suiicient current to flow to hold relay |21 closed. The resistance element |23 of timing switch |2 is set so as to release ylatch ||6 to permit clockwise movement of the base ||3 after a desired time interval, say, for instance, ten minutes. Clockwise movementl of the timing switch opens the circuit through its tube ||8 and through the relay |21.

Under normal starting conditions the circuit through relay |21 will be broken by the tilting of tube 96 of thermostatic switching device 18 before the circuit is broken by the timing switch ||2. However, should the mixture coming from the carburetor fail to ignite for any reason, the air passing about ante-combustion chamber I2 will not be heated, and, therefore, will not cause thermostatic switching device 18 to operate to open relay |21. In this event relay |21 is opened by the timing switch H2 after the expiration of the predetermined time interval and the burner is shut down.

If, after the burner is in operation, the flame should become extinguished for any reason, antecombustion chamber I2 will begin to cool, thus failing to heat the air passing about it to the required temperature to hold thermostatic switching device 18 in its` clockwise position. Thermostatic switching device 18 will then turn counterclockwise back to its starting position, opening the circuit through tube 91 which in turn breaks the circuits through fuel valve 82 and drain valve 84 causing the fuel valve 82 to close and the drain valve 84 to open. Opening of the circuit through tube 91 also breaks the circuit through relay |15. This shuts off blower motor |82. All of the parts return to their original positions except tube |43. Flame extinction will simultaneously cause thermostatic switching device 18 to return to its original position which will also break the circuit through valves 82 and 84.

Any irregularities in the float chamber of the carburetor causing excess fuel to overflow through pipe 60 into receptacle S2 will cause float 88 to rise, turning switch 99 clockwise as seen in Fig. 4, which in turn tilts tube |64 to the position shown in dotted lines. This opens the circuit through valves and 84 to shut oil the supply of fuel and to drain the carburetor. The shutting off of the fuel supply extinguishes the name and the device shuts down as described in the previous paragraph.

Tube |43, which is connected to thermostat |49, must be re-set before re-starting because the thermostat |49, when the device shuts down, will normally hold the arm |48 to the right in Fig. 4, holding the tube |43 in the position shown in dotted lines. When the tube |43 is in this position, it is impossible to close the circuit through the relay |21 to start the device.

It is, of course, also necessary to re-set the timing switch ||2 if it has operated. If the timing switch I |2 is not re-set, the relay |21 will be opened when thermostatic switching device 19 turns counterclockwise, which in turn will shut down the device.

It can be readily seen that it is impossible to start and operate the device except under normal conditions. vIf any difiiculty should arise, such difficulty must be entirely removed before the burner can be restarted. For instance, fuel difficulties causing the float 88 to rise in receptacle 62 requires the receptacle to be drained before switch 89 will be returned to normal position.

The operator, of course, will at once realize that the cause of the overflow of fuel must also be immediately corrected.

Ignition difficulties will prevent thermostatic switching device 18 from turning clockwise or will cause this thermostat to return to its original position, in either event the device will be shut down.

Failure of the heating element 45 will prevent thermostatic switching device 19 from turning clockwise. This will prevent fuel from being delivered to the carburetor 39.

Any abnormal condition causing an abnormal load upon blower motor |82 will cause relay |13 to open the circuit through relay |15 which in turn will disconnect the whole device from the line.

It can be readily seen that the hook-up shown in Fig. 4 makes the device substantially automatic, fully safe and foolproof. When the system operates normally, operation may be stopped by opening switch 95, by shutting off the fuel supply or by any other means which might suggest itself to persons skilled in the art.

My invention, however, is not limited to the hook-up shown in Fig. 4. The invention broadly covers the control of a burner by means of the temperature of the air flowing to the carburetor.

In Fig. 5 I have shown a hook-up in which thermostatic switching device 19 has been eliminated as well as the thermostat |49 and its associated mechanism. Timing switch ||2 has also been eliminated. Contact |3| is connected directly to relay |21 through tube 96 by means of conductors and |96. Tube |05 has been eliminated from the circuit passing through contact |33 and tube |64. Otherwise, the parts are exactly similar to those shown in Fig. 4.

In operation the depression of the push button |81 operates relay |21. This in turn closes relay |15. Blower |82 is started, current is supplied to the heating element 45, and the flowing air is raised in temperature. Current is supplied to magnetic fuel valve 82, thus causing it to be held in open position and to drain valve 94, thus closing the same. A spark is established between electrodes 1G. After the flowing air has reached a proper temperature, a manually operated fuel valve 200 is opened permitting fuel to ow from the source of supply through valve 82 to the carburetor. The heated flowing air now Vaporizes and mixes with the fuel in the carburetor and the resulting mixture is delivered into ante-combustion chamber |2 where it is ignited by the spark between electrodes 16. After the ante-combustion chamber |2 begins to heat up so as to heat the air flowing through air passage I5, thermostatic switching device 18 will turn clockwise as seen in Fig. 5, thus opening the circuit through relay |21 and closing the circuit through contact |30, conductor |02, tube 91, conductor |03, contact |33, etc., which holds the relay |15 closed, fuel valve 82 open and drain valve 84 closed. The opening of relay |21 disconnects heating element 45 and transformer |51.

A form of the invention adapted more particularly for the control of a plurality of burners is disclosed in Figs. 6 and 7.

Fig. '1 discloses two burners 2|0 and 2| Burners 2|0 and 2| have throttle valves 2 |2 and 2|3 connected to a common control arm illustrated at 2|4 in Fig. 6.

Burners 2|0 and 2|| may be of any design. The burner illustrated comprises an ante-combustion chamber 2|5 surrounded by an air heating chamber 2I6 which opens into a conduit 2|1 leading to a preliminary air heating chamber 2|8. Chamber 2|8 leads into a conduit 2|9 leading to carburetor 222, the outlet 22| of which delivers a combustible mixture'which is eventually burned in ante-combustion chamber 2|5 after passing through venturi 222.

The burners illustrated are similar in all respects and are positioned with respect to each other as shown in Fig. 7 merely for clarity in the description of the automatic control.

In burner 2|() thermostatic switching device 224 having three mercury switches 225, 226 and 221 is positioned with its temperature reactive element in the air stream, downstream from the air heating chamber 2|6 and upstream from the preliminary air heating chamber 2|8. As shown, the thermostatic switching device 224 is inserted in the conduit 2|1.

A second thermostatic switching device 228 is positioned in the air passage between the preliminary a'ir heating chamber 2| 8 and the ante-combustio'nl chamber 2| 5 so as to be downstream from the preliminary heating chamber 2|8. Thermostatic switching device 228 has two mercury'switches 229 and 236.

Burner 2| has merely one thermostatic switching device 23| having mercury switches 232, 233 and 234'; Thermostatic switching device 23| has its temperature reactive element inserted in the air stream, downstream from the air heating chamber 2|6 and upstream from the preliminary air heating chamber 2|8.

Thermostatic switching devices 224, 228 and ,23| may be of the Vconventional bi-metal type 1 cooling of the air below the setting of the individual thermostatic switching device, it returns to its original position.

Preliminary heating chamber 2|8 of burner ZIB contains an electrical heating element illustrated at 233 in Fig. 6. Heating element 236 has electrodes 231 and 236 connected in the control circuit.

Preliminary heating chamber 2 8 of burner 2| contains an electrical heating element illustrated at 239 having electrodes 228 and 24| connected in the control circuit.

Delayed action switch 243 consists of a cylinder 222 which is filled with graphite discs 245. An adjustment screw 255 may be employed to increase or decrease the pressure on the discs to change the resistance characteristic. A bi-metallic element 22? is so positioned with respect to the graphite discs 245 that expansion of the element 241 in response to the heat generated in discs will cause arm to rotate counterclcckwise about its pivot 243. Cooling of the element 241 will return the arm 22B to the position shown in Fig. 6. Arm 258 when in the position shown is adapted to engage a notch 255 in block 25H pivoted at 252 on base 253 and carries a mercury switch 255 illustrated in closed position.

Expansion of element 241 in response to heatof discs 255 will, if the expansion is sufficient, move arm 228 out of notch 25B thereby permitting block 25i to move counterclockwise in response to resilient member 255, thereby opening mercury switch 254.

It is, of course, understood that the quantity of heat generated in discs 245 will depend upon, first, the rate of current iiow, second, the resistance to the flow, and third, the duration of the flow.

As illustrated in Fig. 6, discs 225 are in series with heating elements 236 and 239, and the rate of current ow will be the same as that throughout this part of the circuit under certain conditions to be described hereinafter. The duration of the flow is the factor intended to be employed, and the duration of flow may be adjusted by adjusting the resistance through discs 245, as will be seen hereinafter.

The function of delayed action switch 243 is to cause a complete shutdown by opening mercury switch 254, in the event that either burner is incapable of heating the air in its air heating chamber 2|6 to a predetermined temperature within a predetermined time interval after fuel has been supplied and ignited. Ignition failure will also cause its operation.

Should delayed action switch 243 be operated, it is so constructed that it will be necessary to manually reset the same before the device can be restarted. This would be done, of course, after previously removing the cause for the shutdown.

On the other hand, switch 243 is intended to remain in closed position as long. as combustion in both burners is taking place properly.

Transformers 258 and 259, comprising primaries 26D and 26| and secondariesV 262 and 253 respectively, are employed for ignition purposes, the primaries 260 and 26| being supplied with current of proper voltage by the circuit and secondaries 262 and 263 being connected across electrodes illustrated generally at 264 and 265 respectively. Of course, it is understood that the electrodes 264 and 265 will be positioned in the path of the combustion mixture at proper points and for convenience in description electrodes 2612 will be regarded as inserted in the burner 2H! and electrodes 265 as inserted in burner 2| i.

Of course, it is understood that any other form of ignition may be employed, provided it can be controlled in a manner similar to transformers -258 and 259, as hereinafter described.

Fuel valve 251 is electrically operated, such as by a solenoid, and controls the flow of fuel in fuel line shown broken at 268, which supplies fuel to each of the burners 2|@ and 2| Fuel valve 261 is so constructed that it is opened by the ow of current through its solenoid 269 and automatically closed on discontinuance of such iiow.

Carburetors 220 are provided with overflows illustrated at 21D, which lead to a container 21| having a float 212 connected to a mercury switch 213 in a manner so that when the float is at the bottom of the container as illustrated in Fig. 6 the mercury switch is closed, and when it is raised by overflow of fuel in carburetors 225 the mercury switch is opened.

If there is a positive pressure on the fuel in the float chambers of carburetors 228, container 21| is preferably sealed and means provided for an equalization of pressure between container 21| and the float chambers of carburetors 228 in order to facilitate the flow of excess fuel from carburetors 220 to the container 21|.

Mercury switch 213 is connected in the control circuit in a manner so that if and when it is opened by the overilow of fuel from carburetors 220 the burners 2I0 and 2| I are shut down.`

Additional mercury switches 214 and 215 are illustrated in series with the mercury switch 213 and may be operated by any means which may be used to register the existence of unsafe operating conditions which demand correction before operation can be resumed, such as failure of the butterfly valves 2I2 and 2I3 to close and reduce the rate of combustion in response to regulator 216, or the existence of low water in the boilers etc., or a time switch may be installed at this location to effect starting and stopping of the burners at predetermined intervals. These switches are connected in series so that the opening of any or all will cause they furnace to become inoperative.

This specific regulator in substance comprises a temperature, or pressure, speed or other responsive element 211, which is adapted to rotate arm 218 against the action of a resilient member shown in 219. At the end of arm 218 is hinged a fulcrum of bell crank 280 having one arm 28| connected to rod 282 through a slot 283. Rod 282 is connected to butterfly control arm 2|4. A resilient member 284 tends to hold the butterily valves of burners 2I0 and 2| I in minimum operating position, the amount of combustion taking place under minimum operation being made adjustable by the conventional adjustment illustrated at 285.

The other arm 281 of bell crank 290 is pivoted on leg 288 of U-shaped member 289. The other leg 290 of U-shaped member 289 is connected to core 29| of solenoid 292 secured to arm 218.

Solenoid 292 is connected in the control circuit and the operation of regulator 216 is such that movement of arm 218 is not reflected in rod 282 unless armature 29| is drawn up into solenoid 292 by the ow of current therethrough, in which case rod 282 is directly responsive to movements of arm 218.

As illustrated in Fig. 6, arm 218 is in the position of maximum operation of burners 2I0 and 2| I; therefore, if armature 29| were drawn up into solenoid 292 with arm 218 being in the position shown, the burner would be thrown wide open almost momentarily from a position of minimum operation. In order to avoid any possible dire results of such a rapid change in rate of combustion, I provide means for causing the change in combustion rate to take place gradually on connecting the butterily valves to the regulator 216, but at the same time preserving the function 0f rapid disconnection on failure of the current in solenoid 292.

The means illustrated comprises an inverted cylinder 294 having a piston 295 resting upon leg 288 of U-shaped member 289, so as to move with leg 288 in its upward movement in response to solenoid 292. A ball 296 for contacting piston 295 may be provided on leg 288 if desired.

Piston 295 ts sufliciently loosely in cylinder 294 to permit the escape of air around the piston at a desired rate depending upon the character of the delayed action desired.

Inasmuch as the pressure in cylinder 294 will be atmospheric at the beginning of the upward movementl of piston 295 and is, therefore, insuilicient to substantially retard the movement of piston 295, slot 283 is provided at the end of rod 282 so that arm 28| of bell crank 280 in moving clockwise, as illustrated, will not cause the movement of rod 282 until piston 295 has moved upwardly to a sufiicient extent to create a pressure in cylinder 294 sufllcient to materially retard the rate of clockwise movement of arm 28 I., and consequently the rate of increase of the rate of combustion.

It will be seen from the above that the ow of current in solenoid 292 will connect regulator 216 gradually to the butterfly valves 2| 2 and 2I3 of burners 2I0 and 2| I, and failure of current in solenoid 292 will substantially instantaneously disconnect regulator 216 and permit the butterfly valves to return to positions of minimum operation.

A double pole relay is shown at 298. Relay 298 has contact bars 299 and 300, which are insulatedly mounted on mechanism illustrated conventionally at 30|, which is operated by movement of armature 302 of solenoid 303.

Contact bar 299 is adapted to contact spaced terminals 304 and 305, and contact bar 300 is adapted to contact spaced terminals 306 and 301. The contact movements of contact bars 299 and 300 takes place simultaneously, contact of contact bar 299 with terminals 304 and 305 and contact of contact bar 300 with terminals 306 and 301 taking place by movement of armature 302 into solenoid 303 by virture of the ow of current through solenoid 303, and the contact of contact bars 299 and 300 being broken upon failure of current supply to solenoid 303. Solenoid 303 is connected in the control circuit.

A blower motor is shown at 3I0.

At 3| I is shown a conventional across the line A-C starter equipped with thermal-overload coils 3I2 and 3I3.

Solenoid 3| 4 of starter 3II has an armature 3I5 to which is attached a contact bar 3I6 of insulating material carrying the conventional four contacts.

Contacts 3| 1 and 3| 8 on bar 3I6 engage stationary contacts 3I9 and 320 respectively upon a flow of current in solenoid 3I4 to, among other things as will hereinafter appear, close a circuit through the blower motor 3 I 0.

The circuit through the solenoid 3| 4 includes a switch-button 322 which forms a switch with contacts 323 and 324. The circuit continues through a bi-metallie element 325 having a fixed pole 326 and a movable pole 321 adapted to form a switch with contact 328. Any abnormal current demand by the motor is registered by an increase in temperature of the thermal-overload coils 3 I 2 and 3 I3. Such rise in temperature causes the bi-metallic element 325 to change in shape in a manner so as to move pole 321 away from contact 328 to break the circuit through solenoid 3I4 and permit bar 3I6 to fall so as to open the switches formed by contacts 3 I1 and 3| 9 and contacts 3I8 and 320.

Button 322 has attached thereto the conventional frustro-conical member 330 whichis adapted to be depressed to break the circuit between contacts 323 and 324 and at the same time to facilitate the return of pole 321 to its contacting position with contact 328. Upon release of the button 322 the circuit is again closed through solenoid 3| 4.

A conventional single phase supply line, having one side grounded at 335, is shown at 332. That one side of the line should be grounded is obviously not necessary. Fuses are shown at 333 and a double pole switch at 334. An additional wire for a three phase connection is shown dotted at 336, in which case switch 334 would be of a triple pole type. Wire 336 continues to motor unit 310 and contains a switch comprising contacts 331 and 338 operated by bar 316.

Now let us suppose that thermostatic switching devices 224, 228 and 23| are in cold position. The mercury switches of these thermostats are,

therefore, in the following positions: 225` is closed,

221)l is open, 221 is open, 229 is closed, 238 is open, 232 is closed, 233 is open, and 234 is open.

In delayed action switch 243, arm 248 is in notch 250 and, therefore, mercury switch 254 is closed.

Fuel valve 261 is closed.

Throttle valves 212 and 213 are in positions of minimum fuel consumption, being retained in these positions by spring 284.

Regulator 2113 is disconnected from rod 282 and, therefore, from throttle valves 212 and 213 inasmuch as no current is owing through solenoid 292.

Contact bars 299 and 38|) are in open positions because no current is flowing through solenoid 383.

Bar 316 is in open position because no current is flowing through solenoid 314.

Push button switch 322 is closed.

The bi-metallic element switch comprising parts 325, 326, 321 and 328 is in closed position.

Let it be assumed that no abnormal conditions exist which would cause mercury switches 213, 214 and/or 215 to be open.

Switch 334 is open.

Now let us close switch 334. Following the current from? the hot side ofl line 332 for the purposes of simplicity in description, the current ilows to contact 319 over wire 339; to contact 3114 over wire 340 which is connected to wire 339; from contact 304 over wire 34| which divides into wires 342 and 343; over wire 342 through mercury switch 225; over wire 344 through mercury switch 254; over wire 345 through solenoid 303; over wire 341i and then over wire 400 back to the opposite side of line 332.

Mercury switch 232 is connected in parallel with mercury switch 225, and inasmuch as it is closed, current will flow between wires 341 and 344 over wire 343, mercury switch 232 and wire 341. Consequently, as long as either mercury switch 225 or mercury switch 232 is closed, current will flow as indicated.

Y Relay 293 is now closed in View of the flow of current through solenoid 303. This connects contacts 3134 and 335 as well as contacts 38B and 3131.

Current will now flow from contact 3135 over wire 349 and through mercury switch 213; over wire 3513 and through mercury switch 214; over wire 351 and through mercury switch 215; over Wire 352 to contact 328; from pole 321 over element 325, through contact 336, contact 324, switch element 322, contact 323, solenoid 314, over wire 353 and then over Wire 433 back to the opposite side of line 332.

Solenoid 3111 operates and raises bar 3115 as seen in Fig. 6 so as to close the switches formed by contacts 311 and 319 and contacts 318 and 3211.

Current may now flow from contactl 313 through contact 311 to terminal 355. From terminal 355 current may flow over wire 355, through thermal-overload coil 312, over wire 351, through motor 3113, over wire 358, through thermal-overload coil 313, over wire 359, and through terminal 331), contacts 318 and 32|] to the opposite side of line 332.

The blower starts and flow of air is established through burners 2111 and 2| 1 through paths above described. The amount of air thatY is permitted to flow is small because throttle valves 212 and 213 are substantially closed.

Current may now flow from terminal 355 to contact 3111i over wire 332. Contact bar 3113 is closed. Current may, therefore, flow to contact 3111, then over wire 333 through graphite discs 235, and over wire 3153 to terminal 365.

Current may also ilow from contact 331 over wire 355, through mercury switch 223, over wire 351 to terminal 3135.

The resistance oiered by the graphite discs 245 is so high as compared to the negligible resistance et wires 31515, 'entry switch and wire 3111 that practica Ly no current ilows through the graphite discs at this time.

From terminal 335 current continues over wire 31513 to electrode 233, through heating element 233 in preliminary air heating chamber 218 or burner 2111 to electrode 231, over wire 311) to electrode 241i, through heating element 233 in preliminary air heating chamber 218 of burner 211 to electrode 2511, over wire 311 to terminal 3311, through contacts 313 and back to the opposite side of line 332.

The iiowing air in each of burners 213 and 211 is now being heated it passes through prelirni nary air heating chamber 213.

' Going hack to contact 331 of relay 293, current flows over wire 313, through the primaries 233 and 231 of transformers 253 and 253 respectively, over wire 314, wire 311, and through terminal 333, contacts 18 and back to the opposite side of l-ne 322.

A spark is, therefore, established across electrodes and 235 of burners 313 and 211 respectively.

When te air passing over heating elements 236 and 239 of burners 2111 and 211 respectively becomes heated to a predetermined desired temperature, the temperature reactive element of thermostatic switching device 223 which is downstream from preliminary air heating chamber 213 of burner 213 (a similar thermostatic switching device may be positioned downstream from the preliminary air heating chamber 218 of burner 21 1 and its mercury switches connected in series with the mercury switches 2211 and 233 respectively, if desired) will tilt the mercury switches 229 and 233 so as to open mercury switch 229 and close mercury switch 233.

The current iowing to the heating elements 233 and 233 must now ow entirely through graphite discs 2115, because of the opening of mercury switch 223.

The closing of mercury switch 233 causes rent to ow from contact 335 over wire 316, through mercury switch 33B to terminal 311. From terminal 311 current flows over wire 318, through solenoid 2G51, over wire 319, wire 311, through terminal 353, contacts 313 and 32@ back to the opposite side of line 332.

This opens fuel valve permits fuel to flow to carburetors 221i of burners 213 and 211. The fuel so delivered is metered and mixed with the small quantity of heated air that is passing through the carburetors. rhe heat of the air assists in vaporizing the fuel and a combustible mixture is delivered through each throttle valve 212 and 213 of the respective burners, is ignited by electrodes 233 and 235 of the respective burners, and is burned in the ante-combustion chambers 215 of the respective burners.

Combustion, of course, will take place at the minimum rate, and the igniters as well as the Cul."-

heating elements 236 and 239 will function continuously.

The iiame in each burner heats the inner wall of its adjacent air heating chamber 2 I6, and heat is thus transferred to the owing air. After the burners have become suiciently warm to safely operate in accordance with the demand, which is evidenced by the ability of ante-combustion chambers 2I6 to continuously heat the air to a predetermined temperature, thermostatic switching devices 224 and 23I oscillate in response to the temperature of such heated air.

It is quite probable that thermostatic switching devices 224 and 23| will not as a practical matter be adjusted so accurately as to turn simultaneously. However, since mercury switches 225 and 232 are connected in parallel, the opening oi one of these switches in itself will not affect the circuit.

Since mercury switches 226 and 233 are in series and mercury switches 221 an-d 234 are in series, the closing of only one switch in each series arrangement will not aiect the control circuit. It requires oscillation of both thermostatic switching devices 224 and 23| to close the circuits controlled by mercury switches 226, 233, 221 and 234.

Let us assume, therefore, that both thermostatic switching devices 224 and 23| have oscillated. This indicates that the iiame in each burner is operating properly since it is heating the air passing through its air heating chamber 2 I 5 to a predetermined .desired temperature.

Upon the opening of mercury switches 225 and 232, the current flow through solenoid 303 ceases thereby releasing armature 302 and opening relay 29S. Contact 301 is no longer connected to the line, hence no longer furnishes current to transformers 258 and 259 which now become inoperative. Heating elements 236 and 239 become inoperative since they have been receiving their current irom contact 301 through wire 363, .graphite discs 245, terminal 365 and over wire 369, wire 310 and wire 31 I. Delayed action switch 243, of course, also becomes inoperative.

Solenoids 3I4 and 269, which previously received current from terminal 305, now receive current from terminal 306 over wire 382, through mercury switch 221, over wire 383, through mercury switch 234, and over wire 384 which is connected to terminal 311 from which solenoid 269 previously received its current, since terminals 311 and 305 are connected by wire 380, mercury switch 230 and wire 316. Terminal 311, instead of receiving current from contact 305, now supplies contact 305 with current. Therefore, solenoid 3 i4 which receives its current from contact 305 remains energized.

From the foregoing it will be seen that mercury switches 221 and 234 should close just prior to the opening of mercury switches 225 and 232 during the clockwise movement of thermostatic switching devices 224 and 23| or the opening and closing should at least be simultaneous so that solenoid 3 I4 will always be energized.

Solenoid 292 of regulator 218 is also energized by virtue of they closing of a circuit through wire 365 which is connected to wire 382, mercury switch 226, wire 386, mercury switch 233, wire 361, solenoid 292 and wire 388 which connects to wire 31 I.

Upon solenoid 292 becoming energized, its armature 29| is drawn upwardly into its winding to connect regulator 216 tov throttle valves 2I2 and 2 I3 as previously described. The positions of throttle valves 2I2 and 2I3, which control the rates of combustion, are now determined by the expansion and contraction of the element 211 of the regulator 216.

The burners are now in full operation.

A discussion of the diiiiculties which might prevent the normal starting cycle follows.

The essentials for starting are:

Mercury switch 229 must be closed. Either thermostatic switching device 224 or thermostatic switching device 23| must be sufficiently cool so that either mercury switch 225 or mercury switch 232 will be closed. This is necessary so that relay 298 may be closed by flow of current through its solenoid 303. Mercury switches 254, 213, 214 and 215 must be closed. Pole 321 must engage contact 328. Switch 322 must be closed.

Should relay 29S close without the closing of starter 3| I, nothing is accomplished. Starter 3| I must be closed before current can flow in any circuit save that which effects the closing of relay 298. Before a start can be made, it is necessary that at least one of the burners be out of operation a suiiicient length of time to permit its thermostatic switching device upstream from its preliminary heating chamber 2 I 8 to have cooled and to: have returned to cold position. Let it be assumed that there are no unsafe conditions which would have opened mercury'switches 213, 214 or 225.

Let it be assumed for purposes of illustration that thermostatic switching device 224 has reverted to cold position and that thermostatic switching device 23I is still in hot position and that the safety switches 213, 214 and 215 are closed. Relay 298 will close as well as starter 3| I because mercury switch 225 is closed. The blower will start operating.

inasmuch as mercury switch 226 is open, regulatcr 216 is disconnected from throttle valves 2I2 and 2I3, and these valves are in their positions of minimum combustion. Both heating elements 236 and 239 will be energized and if thermostatic switching device 228 was also in cold position, it will soon oscillate to hot position and fuel valve 261 will open. Fuel valve 261 was formerly closed because both mercury switches 230 and 221 were open. Inasmuch as mercury switch 229 is now open, current for the heating elements 236 and 239 will have to pass through graphite discs 245.

Since relay 298 is closed, the transformers 258 and 259 are operating and upon the opening of the fuel valve 261, combustion should be reestablished in both burners.

Let it be assumed that the adjustment of 246 is such that the heat generated in graphite discs 245 is sufficient to expand element 241 to force arm 248 out of notch 250 to permit the opening of mercury switch 254 at the end of six minutes.

If thermostatic switching device 224 fails to oscillate to hot position within six minutes, mercury switch 254 will open, relay 298 will open and inasmuch as mercury switch 221 is open, starter 3I I will also open and all of the parts will return to their original positions except, ofcourse, switch 243 which must be manually reset. The necessity of resetting delayed action switch 243 is indicative of. trouble which should be corrected before another attempt is made to start.

Let us assume on the other hand that thermostatic switching device 224 oscillates to hot position in response to combustion in burner 2I0, but that combustion in burner 2II has failed or is not up to par. -'ihermostatic switching device 23| will then eventually return to cold position, thereby opening mercury switch 234 which in turn 'such lengths as to make operation unsafe.

causes starter V3|| to open and "all .'of the parts returned to their original positions.

If thermostatic switching device 123| .'returnsto 'cold position before thermostatic switching device 224 oscillates to hot position, the same cycle of operations follows as under normal starting 'conditions with both burners cold and unless ther-V mostatic switching device 23| returns vto hot kposition, mercury switch 254 will opento shut down `the burners.

Itis, of course, understood that, upon ashutvting down, blower 3||! stops, fuel valve 251-closes,

regulator 21%:` is disconnected lfrom throttle valves ZI2 and 2|3, heating elements 236 and 233 are deenergiz'ed, and transformers 253 and 259 become inoperative.

If the flame in either burner should fail during continuous operation, either thermostatic switching device 224 or 23| will return to its vcold'posi- `tion, thereby opening either mercury switch ,221

or mercury switch 234 resulting in the breaking of current through solenoid S24-and starter 3|! opens to shut down the device.

It will be seen that the burners vwill shut down regardless of the type of trouble 'which .might occur, such as improper supply of'fuel, improper mixture of fuel, failure to ignite, improper burning, etc.

The delayed action switch 243 may be setfor any time interval. Experience has vshown that intervals up to six or even ten minutes are long enough to permit the flames to evidence their ability of being of good quality and are not of The latter is due to the fact that valves 2|2 and 2|3 are in their minimum positions and consequently only a very small quantity of fuel Will be delivered during this period.

The novel control is particularly useful when two or more burners are connected to separate combustion chambers which communicate with a common set of tubes or common stack. Failure of any burner so connected demands the `shutdown of all the burners in the battery and the correction of that fault which caused the shutdown before a permanent recycling will result.

In the case of two or more burners being connected to a common combustion chamber, the passage of free air into the chamber without its being mixed with the proper proportion of fuel is prevented also.

During normal operation the most likelyreason for a shutdown will be failure of current supply from the line 332. VThis would cause a complete shutdown as will be seen from the above. In order for a yre--start to occur after re-establishment of the current supply at line 332, it will be necessary for either thermostatic switching device 224 or thermostatic switching device 23| to return to cold position. This is because contacts 3|1 and 3|9 will have separated upon de-energization of solenoid 3|4 by the failure of current in the line 332, and their Contact is necessary in order for a flow of current through solenoid 3|4 to take place when relay 298 is open. Relay 298 is always open during normal operation.

Should the flame in either heat generator becomeextinguished for any reason whatsoever, this Will cause a temporary shutdown that will be follo-wed most likely by an incomplete starting cycle and a permanent shutdown will then take place by opening of the mercury switch 254.

Failure of flame might be caused by fuel stoppage in either carburetor 220. 'I'he thermostatic switching device upstream from the preliminary fairheating Vchamber 2 8 of. the particular burner affected will cool and return to cold lposition.

' This will be followed vby a temporary set of `shut- .down operations as above described. VAre-'start will immediately follow. The starting cycle will l,

proceed normally. Should the aected .burner fail to frefignite or should 'the ignition be imperfect, or'the flame poor, this will, as described above, cause a complete shutdown by opening :switch 254.

A .uniquefeature of the circuit is that an overload on the blower motor will cause ashutdown by the abnormal heating of elements 3|2 and 3|?, which will cause pole 321 to leave 4contact '323 'and break the circuit through solenoid 3|4.

It 'will benoted that to start the burnersit is lnecessary that at least one is cold or cooled. This provision is made for tworeasons, iirst, to permit any uncombusted inflammable vapor which may have been delivered into any combustion chamber prior to the shutdown to be condensed or dispelled from the burner, thereby lessening the hazard of an explosion on arestart, and, second, to insure that a spark for ignition'purposes'will accompany the re-start.

.By sealing the relay 298, starter 3H and thermostatic switching devices 224 and 23|, it will be impossible for anyone to tamper with the starting mechanism to cause the igniters to function except as called for by the starting cycle. This will prevent explosions inasmuch as Vthe igniters will not operate after a shutdown until after inammable vapors have either condensed or have been dispelled.

If either of the heating elements 236 or 239 should be out of o-rder, thermostatic switching device 228 will not oscillate to hot position, consequently fuel will not be supplied and, therefore, combustion cannot take place. Although vthe blower 3|0and the transformers 258 and 259 willI continue to operate, there is'no danger in such continuous operation. However, means may be provided tot stop both, for instance, insertinga device in wire 313 or in wire 314 similar to delayed action switch 243 which would cause a com plete shutdown. Such provision, however, unnecessarily complicates the circuit.

It is to be strictly understood that the particular description herein is purely for the purposes of illustration and that the invention is in no way limited to the specific parts or descriptions set forth.

While the invention has been described in connection with heat generators, oil burners, etc.,it is in no way limited thereto but may have man other applications.

It is, of course, obvious that many modifications may be made within the scope of the claims without departing from the spirit of the invention.

It is, of course, understood that the regulator shown .at 216 may be inserted in the control circuit shown in Figs. 4 and 5. For instance, in Fig. 4 the regulator 216 might be substituted in place of the lever |5|, stop |54 and thermostat |49, with similar circuit connections.

It is also understood that the form of control circuit shown in Fig. 6 might be adapted for one burner 2||l only by eliminating the duplications made necessary by the second burner 2| or may be adapted to any number of burners by increasing the number of the parts which have been duplicated.

It is also understood that the fuel drain valve 84 might be added to the form shown in Fig. 6

and may be controlled in the same manner as in the form shown in Figs. 4 and 5.

Many other additions or modifications may be made without departing from the spirit of the invention.

I claim:

1. In combination with a burner having ignition means, a fuel feeding means and an air supply means, including an air heating chamber operatively associated with said burner to be heated thereby and an auxiliary air heater positioned intermediate said chamber and burner for initially heating the air; a control system comprising circuits including a main control switch closed in response to a demand for heat, a rst temperature responsive switching mechanism in said air supply means intermediate said auxiliary heater and burner and having contacts closed when hot controlling initiation of fuel feed, a second temperature responsive switching mechanism in said air supply means intermediate said chamber and auxiliary heater and having contacts closed when cold controlling operation of said auxiliary heater and ignition means and initial operation of said air supply means and contacts closed when hot prior to the opening Of the cold contacts maintaining operation of said blower and fuel feeding means whereby upon a demand for heat, fuel feed is delayed until the temperature of the carbureting air reaches a determined Value.

2. In combination with a burner having a fuel supply means, ignition means and air supply means provided with an air heating chamber cperatively associated with said burner to loe heated thereby, an auxiliary air heater arranged between said chamber and said burner for initially heating said air, a control system comprising circuits including a main control switch adapted to be closed in response to a predetermined demand for heat, a temperature responsive switching mechanism in said air supply means intermediate said auxiliary heater and burner having contacts closed when cooled to a predetermined degree to initiate the control of said air supply means, said ignition means and said auxiliary heater and having contacts closed when heated to a predetermined degree to control the flow of fuel, a second temperature responsive switching mechanism in said air supply means intermediate said air heating chamber and said auxiliary air heater having contacts closed when cooled to a predetermined degree controlling the operation of said auxiliary heater and ignition means and initially controlling the operation of said air supply means and contacts closed when heated to a predetermined degree maintaining the operation of said air supply, a thermal time-limit cut out switch having a resistance heater connected in shunt around the contacts of said rst temperature responsive switching mechanism that are closed when cooled to a predetermined degree, whereby when such contacts are opened, said switch heater will be energized to thereafter open said cut out switch.

3. In combination with a burner having ignition means, a fuel feeding means and a carbureting air supply means including an air heating chamber operatively associated with said burner to be heated thereby and an auxiliary air heater positioned intermediate said chamber and burner for initially heating the air; a control system comprising circuits including a main control switch closed in response to a demand for heat, a. first temperature responsive switching mechanism in said air supply means intermediate said auxiliary heater and burner controlling initiation of fuel feed, a second temperature responsive switching mechanism in said air supply means intermediate said chamber and auxiliary heater controlling the operation of said auxiliary heater and ignition means and the initial operation of said air supply means and cooperating with said rst switching mechanism to maintain operation of said blower and fuel feeding means whereby upon a demand for heat, fuel feed is delayed until the temperature of the carbureting air reaches a determined value.

4. In combination with a burner having a fuel supply means, ignition means and air supply means provided with an air heating chamber operatively associated with said burner to be heated thereby, an auxiliary air heater arranged between said chamber and said burner for initially heat-- ing said air, a control system comprising circuits including a main control switch adapted to be closed in response to a predetermined demand for heat, a temperature responsive switching mechanism in said air supply means intermediate said auxiliary heater and burner controlling said air supply means, said ignition means, said auxiliary heater and the ow of fuel, a second temperature responsive switching mechanism in said air supply means intermediate said air heating chamber and said auxiliary air heater controlling the operation of said auxiliary heater and ignition means and cooperating with said first switching mechanism to control the operation of said air supply means and fuel feed, and an electrically actuated time limit cut out switch jointly controlled by said first and second switching mechanisms to energize said cut out switch with the initiation of said fuel feed.

JEROME J. SLOYAN.

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