US2631656A

US2631656A - Combination gas and oil burner and control system therefor

Info

Publication number: US2631656A
Application number: US53951A
Authority: US
Inventors: Richard H Siemon
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-10-11
Filing date: 1948-10-11
Publication date: 1953-03-17
Anticipated expiration: 1970-03-17

Description

March 17, 1953 2,631,656

. R. H. SIEMON COMBINATION GAS AND OIL NER AND CONTROL SYSTEM THE FOR Filed Oct. 11, 1948 5 Sheets-Sheet l fly 1 I 202% m 9 2r; W"

w- -{I A?! 2 Q #4 07 zm- A M d @I If? w 2% 7% Z a}? 2% 1 "C 92 w w I x fi/thy/"d T5927? March 17, 1953 R. H. SIEMON COMBINATION GAS AND OIL BURNER AND CONTROL SYSTEM THEREFOR 5 Sheets-Sheet 2 Filed Oct. 11, 1948 v INVENTOR, Pic/bra 176M070.

March 17, 1953 R. H. SIEMON 2,631,656

COMBINATION GAS AND OIL BURNER AND CONTROL SYSTEM THEREFOR Filed Oct. 11, 1948 5 Sheets-Sheet 5 INVENTOR, Pithrd A? .SlWra/I.

March 17, 1953 R. H. SlEMON 2,631,656

COMBINATION GAS AND OIL BURNER AND CONTROL SYSTEM THEREFOR Filed Oct. 11, 1948 5 Sheets-Sheet 4 March 17, 1953 2,631,656

R. H. SIEMON COMBINATION GAS AND OIL BURNER AND CONTROL SYSTEM THEREFOR Filed Oct. 11, 1948 -5 Sheets-Sheet 5 JZLL" w j 1 we 1 Q 0 I J v INVENTQR,

4 Fla/9am Karma/7.

Patented Mar. 17, 1953 UNITED STATES TENT OFFICE COMBINATION GAS AND OIL BURNER AND CONTROL SYSTEM THEREFOR 10 Claims.

This invention relates to new and useful improvements in automatically controlled combination gas and oil burners, and relates particularly to a burner adapted to burn either gas or oil, and to switch automatically from one fuel to the other responsively to certain control conditions, such as the outdoor atmospheric temperature or the pressure in the gas supply line.

Due to the shortage of fuel gas for he t prevailing in many part of the country, numerous cities have conditioned permits to install household gas heating equipment on the provision of a stand-by fuel supply such as oil, said oil to be burned during the periods of peak gas load. It is therefore the principal object of this invention to provide a combination gas and oil burner arrangement adapted to burn gas as lon as the outside air remains above a predetermined temperature, but which will switch automatically to oil whenever the outside air falls below said predetermined temperature, and to switch automatically back to gas when the outside temperature again rises above said predetermined level. Since the gas load in a gas supply system is generally inversely proportional to the outside temperature, this control means is effective to turn off the gas during peak load periods.

Another object is the character described, of automatic pressure sensitive means for switching from gas to oil fuel whenever the pressure in the gas supply line falls below a predetermined level, re

less of the outside temperature.

A further object is the provision of a combination gas and oil burner system wherein the oil isignited by means actuated by an inside thermostat, and having means actuated by the oil flame to ignite the gas fuel and to shut off the oil burner whenever the outside temperature and the gas pressure are above predetermined levels, and automatic means for Switching to oil fuel whenever either the outside temperature or the gas pressure falls below said predetermined levels.

A still further object is the provision, in a combination gas and oil burner system of the character described, of independent draft means for supplying air for combustion to said gas and oil burners, the draft means for said gas burner being self-regulating according to the amount of gas being burned, and being adapted to close automatically when oil is being burned.

Other objects are simplicity and economy of construction, accuracy and dependability of pthe provision, in a device of side wall l and a floor partition 6.

oration, adaptability to include a standard untype oil burner, and adaptability to use only standard, commercially available control devices.

With these objects in view as well as other objects which will appear in the course of the specification, reference will be had to the drawing, wherein:

Figure 1 is a schematic layout of an automatically controlled combination gas and oil burner system embodying the present invention.

Fig. 2 is an enlarged fragmentary section taken on line 11-11 of Fig. l, with parts left in elevation.

Fig. 3 is a fragmentary section taken on line III-III of Fig. 2, with parts left in elevation.

Fig. 4 is a fragmentary section taken on line IV-IV of Fig. 2, with parts broken away and other parts left in plan.

Fig. 5 is a fragmentary section taken on line V-'V of Fig. 4, with parts broken away and other parts omitted.

Fig. 6 is a fragmentary section taken on line VI-VI of Fig. 5.

Fig. 7 is a. fragmentary section taken on line VII-VII of Fig. 2.

Fig. 8 is a schematic wiring diagram of the burner controls.

Fig. 9 is a schematic wiring diagram of a modified form of the burner control system.

Fig. 10 is a view similar to Fig. 4, including I the principal modifications indicated in Fig. 9.

Like reference numerals apply to similar parts throughout the several views, and the numeral 2 applies to a furnace shown in Fig. 1 disposed in the basement of a building having an out- Said furnace may be of any common type such as warm air, hot water, or steam, and is provided with a suitable stack pip 8. The combination gas and oil burner includes a standard gun-type oil burner l0, said oil burner including a blast tube l2 disposed horizontally, said blast tube extending at its inner end flush with the inner surface I of the refractory combustion chamber wall H! of furnace 2, a fan housing It carried by and interconnected with said blast tube adjacent the outer end thereof, a fan wheel l8 carried in said housing and operable by a motor 20 mounted at one side of the fan housing to supply air under forced draft to blast tube l2, and an oil pump 22 mounted on the opposite side of fan housing 15 coaxially with motor 20, said pump also being driven by said motor through coupling 24, as shown in Fig. 3. Said pump is provided with a suction line 26 and a return line 28 connecting it with a Suitable supply of fuel oil. The delivery line 30 of said pump is interconnected with an oil tube 32 which passes through rear closure plate 34 of blast tube i2 and extends axially through said blast tube to a point adjacent the open inner end thereof. Said oil tube carries at its inner end a nozzle 36 adapted to direct a finely divided oil spray into the furnace combustion chamber. Said oil tube is supported intermediate its ends within blast tube 52 by means of spider 38, and the outer end portion of blast tube I2 is supported by a floor-engaging leg 46.

Oil emerging from nozzle 36 is ignited by an electric spark passing across spark gap 42 between electrodes 44 adjacent the tip of said nozzle. Said electrodes are disposed adjacent oil tube 32, and are supported from said oil tube by clamp 46. The electric leads 48 and 50 to said electrodes pass through insulating fittings 52 provided therefore in closure plate 34, and are respectively interconnected with the secondary terminals of ignition transformer 54, which is carried in a suitable housin mounted on fan housing I6.

'As best shown in Figs. 2, 3 and '7, a burner box 56 of sheet metal construction is disposed about the inner end portion of blast tube I2. Said box is substantially rectangular in transverse crosssection, and comprises a top wall 58, bottom wall 80, side walls 52 and 64, an outer end wall 66, and an inner end wall 58 flush with the inner surface of furnace wall i i and extending from the upper edge of box 56 to a point spaced apart from the lower edge thereof, as best shown in Fig. 5. An open-ended tube It extends horizontally between outer wall 65 and inner wall 68 through the upper portion of box 56, and blast tube I2 of the oil burner extends therethrough. The space between tube lb and blast tube I2 is filled with a heat insulating material I2.

A plurality of horizontally disposed, laterally spaced apart gas burner tubes I4 are carried in' the lower portion of burner box 58 parallel to blast tube I2, being secured rigidly to brackets "I6 extending between and fixed to side walls 32 and 6 tubes are flush with the inner surface of furnace wall I4 and beneath the lower edge of inner wall 68, and the outer ends of said tubes are fitted with apertured plates 58 which serve to center therein coaxially disposed pipe nipples 80, to the inner ends of which are carried nozzles 32, so disposed that when gas is supplied to said nozzles through said nipples, air will be drawn into tubes I4 through apertured plates I8 and intermixed with said gas. Pipe nipples 80 are externally threaded to receive thereon closure discs 84, which may be moved adjustably to and from the ends of tubes M to regulate the amount of air entering said tubes. All air which does not enter tubes I4 will pass around the outside of said tubes and be intermixed with the burning air-gas mixture emerging from the inner ends of said tubes, thereby providing a secondary supply of air for complete combustion. The outer ends of nipples 80 are interconnected with a common transverse header pipe 86. Said header is mounted on a bracket 88 fixed to bottom 60 of box 56, extends outwardly through side wall 64 of said box, and is interconnected at its outer end with a gas supply pipe 94].

The lower portion of burner box 56 is extended outwardly from the upper portion thereof, and is The open inner ends of said gas burner provided at its outer end with a damper door 92 hinged at 94, and. adapted normally to be retained closed by gravity. Said damper is operated by a pressure sensitive damper control 96 disposed in gas supply line 9%. As best shown in Fig. 6, said damper control comprises a housing 98 carrying a flexible diaphragm IE5 beneath which gas from pipe is adapted to enter. A lever N2 is pivoted adjacent one endto housing 98 at I04, and is pivotally connected at we intermediate its ends to a slide rod IE3 fixed to and operable by diaphragm Hit. The free end of lever 452 is connected by chain His with a pin II2 fixed to the free edge of damper door 92. Thus whenever there is gas pressure in gas supply line 86, the damper will be opened, and the amount it is opened will be proportional to the gas pressure. Hence the damper is automatically regulated and by selecting a damper control of the proper sensitivity, and by adjusting the length of chain III), damper 92 will open suihciently to permit the amount of air required for proper combustion of the gas being burned.

A solenoid operated gas valve 5 I4 is inserted in gas supply line 90 behind damper control 96, and a pilot gas tube H3 is interconnected with said supply line behind said main valve, said connection usually being made within the body of valve iI i itself. Said pilot tube is provided with a solenoid operated valve i !8, enters burner box 56 immediately beneath header 8t, and extends transversely beneath the inner ends of gas burner tubes M. That portion of said pilot tube adjacent the forward ends of the gas burner tubes is provided with a plurality of longitudinally spaced apertures I20. The gas escaping from said apertures is ignited by the flame of the oil burner as hereinafter described.

Within burner box 56, pilot tube I I 3 is provided with a branch tube I22 adapted to supply gas to a flame actuated switch device I24 best shown in Figs. 5 and 8. Said device is disposed in the upper portion of burner box 56 adjacent tube It, andcomprises a tube I25 fixed in outer wall 65 of said burner box and extending to a point adjacent the inner wall G8 thereof, a horseshoe shaped bimetallic element I26 fixed at one end to the inner end of said tube and fixed at its opposite end to one end of a rod I23 disposed within tube I25, and an electric switch 33% carried in a housing I32 disposed outside of burner box 56 and operable by the movement of rod E28. As shown in Fig. 5, tube I22 supplies gas to a jet I34 adapted to apply a flame against bimetallic element I26. Switch I3fl remains open so long as no flame is applied to the bimetallic element, but closes when the flame is so applied. Inner wall 68 of burner box 56 is provided with an aperture 536 adjacent bimetallic element !26, and gas supplied to jet I34 may be ignited directly through said aperture by the oil burner flame. However, in order to insure positive ignition of the jet, an auxiliary pilot tube i38 is interconnected at its lower end with pilot tube H6 and extends upwardly adjacent wall 68 and across aperture 535. Said auxiliary pilot tube is provided along its length with spaced apart holes it as shown. in Fig. 5. This device is known as a ladder pilot. When gas from pilot tube H6 is ignited by the oil burner, gas escaping from the lower holes I46 of tube I38 is ignited by said pilot. The flame then travels upwardly along tube I38, successively lighting gas from the next higher hole Mil until a flame is directed inwardly through aperture I36 to ignite jet I34.

enemas 'R r i g o Fig. 8 fora-wiri g dia ram of the control system, it will be seen that line Wires I42 and 5144 are connected by wires I48 and I48 with the primary terminalsof atrans rm r 5 suitable for stepping the line yoltage down to a level suitable for the operation of rel ys, etc. Amain switch A52 is disposed in wires I lfiand I48, and a limit ,control IE4 is disposed in series in wire I48. Said limit control comprises an electrical switch normally closed and adapted ,to he opened by a bimetallic element L58 whenever said element is h a d abov a pr d termine emp ratu Said bimetallic element is positioned in the furnace bonnet v{asindicated in Fig. l, and thus adapts the limit control to shut off the entire system whenever. {the bonnet temperature exceeds a safe level.

Wire I48 is connected by wire I58 with the armature of a-relay .I88,, and the fixed terminal of said relay is connected by wire 'I 82 with oil burner motor 28, and by means of wires I82 .and I64 with one of the primary terminals of ignition transformer 54. The other primary terminal of said transformer, and the other terminal of said motor 28 are connected with wire I48 by wires I86 andv wire I58, thus completing the oil burner circuit. Relay I88 is normally open, and hence the -,oil burner can not function except when the coil of relay 'I 68 is energized. One of the secondary terminals of transformer 54 is connected to said relay coil by wire I18, and the other wire I72 fromsaid coil is connected with the armature of normally open relay H4. The other secondary terminal of transformer I58 is connected by wire I18 with a movable switch member of stack switch I18. Said movable switch member is operable by a bimetallic member I88 disposed in the stack pipe 8 of the furnace 2 to connect wire I'IB with either a wire I82 connected with the armature of a relay I14, when bimetallic member I88 is heated, or with a wire I84. Wire I84 is connected with a safety switch comprising in series a heater coil I86, a bimetallic switch element I88 adapted to be heated by said heater coil, and a fixed contact I98 connected with wire I82 by wire I9I. Said safety switch is norm-ally closed when heater coil I86 is not energized. Hence when relay I14 is closed by means hereinafter described, the secondary circuit of transformer I58 is closed to energize relay I68, thus completing the oil burner circuit and. starting it in operation. At the beginning of furnace operation, said secondary circuit flows through safety switch I88, energizing heater coil I88. If, within a predetermined number of seconds from the beginning of operation, stack switch I18 has not been operated by the heat of the cilcombustion products rising in stack pipe 8 to connect wire I'IIi directly with wire I82, heater coil will open switch I88, thus breaking the oil burner circuit. Safety switch I88 is retained in the open position by a latch I 89, which must be manually released, thus preventing starting of the oil burner till the defects therein have been corrected. Transformer I58, relay I68, stack switch I18, and safety switch I88 are normally encased ina single housing and designated as the rimary oil burner control I92, said control being disposed adjacent stack pipe 8 with bimetallic element I88 projecting into said stack pipe, as shown in Fig. 1.

The primary terminals of step-down transformer I94 are connected with wires I46 and I48 respectively by wires I98 and I88. One secondary terminal of said transformer is connected by wire 288 with an inside thermostat 282, which is n efie swit h adjustab e to c ose henever the. temperaturein the building to he heatedfa ls below the desired level. The other pole of thermostat is connectedby wires 284 and 288 with the armature of a double-throw relay 288. Said armature connectsnormally with a wire 2 I 8 connected to the coil of relay I'l4,-and the other terminal of said coil is connected by wire 2I2, and wire 2M with areturn wire 2 I6 to the secondary of transformer I84. Thus whenever thermostat 282 is closed, calling for heat, the circuit to the coil ofrelay I14 will be completed through wire 288, thermostat 282, wires 284- and 286, relay 288, wire 2I8, the coil of relay I14. and wires 2,I 2 2J4 andZ I6. Relay I'I4 will then close, actuatingthe oil burner circuit as previously described.

Wire 284 is connected by wire 2 I8 with an outdoor thermostat 228, which is set to close at and above some temperature representing the period of peak gas load, and to open when the outside temperature falls below said predetermined level. It is contemplated that this thermostat should be set and sealed by the public utility authorities. The other pole of said thermostat is connected by wire 222 with one terminal of solenoid operated gas pilot valve II8, and return wire 2I6 is connected to the other terminal of said valve. Thus whenever thermostat 282 is closed to actuate the oil burner circuit as previously described, and the outdoor temperature is above the setting of thermostat 228, the circuitto pilot valve IIB will be completed through wire 288, thermostat 282,

wires 284 and H8, thermostat 228,

wire

22,2, valve and thence to common return wire 2I8 by wire 2I4. Thus when switch I38 is closed by the action of jet I84, the circuitto the relay of coil 2.88 is completed through wires 288 and 224, switch 38, wire 22E, relay 288, and wires 2I4 and 218.

The armature of relay 288 thus breaks contact with wire 2I8, breaking the circuit to relay I14 and shutting off the oil burner, and establishes contact with wire 228, which is connected with main gas valve I I4. The returnwire 228 of said main gas valve is connected with common return wire 2I8. The circuit to the main gas valve is thus completed through-wire 288, thermostat 282, wires 284 and 288, the armature of relay 288, wire 228, main valve I I4, and wires 228 and 2I6. Main valve I I4 is thereby opened, permitting gas tooperate damper control 96, and to flow through header 88, nipples 88, nozzles 82, and burner tubes '54, where said gas is ignited by the pilot tube I I6.

If for any reason the pilot has-failed-to ignite, the oil burner will continue to operate, since then flame actuated switch I38 will not be closed to energize relay 288 to interrupt the circuit to the oil burner. If, while the gas burner is in operation, the outdoor temperature should fall below the setting of thermostat 228, said thermostat will has cooled sufiiciently, which requires only a few seconds, switch I38 will be opened, thereby brealsnc t circu to he .11 o re ay 2 8.- T ifirrfllay, thus de-energized, breaks the circuit to the main gas valve H4 and reestablishes the circuit to the coil of relay I74, and said relay closes the circuit to the oil burner as previously described. If, while the gas burner is in operation, the pressure in the gas supply line falls below a predetermined level, the flame at jet 34 of flame switch mechanism I24 will become too small to actuate bimetallic member I26, and switch I90 will open. This breaks the circuit to relay 208, which then operates to close the main gas valve and start the oil burner as described. above. This cycle will also occur in case of total gas failure. In this instance the gas pilot will continue burning after the oil burner is lit, but this is not considered obj ectionable. If, after the oil burner has been put back in operation, the outside temperature should again rise above the level at which thermostat 220 is set, said thermostat will again close to initiate the gas lighting cycle previously described. Likewise, if the oil burner has been put in operation by low pressure or failure of the gas supply, and the pressure is again restored, jet I34 will again function to close switch I36, and relay 208 will function to shut off the oil burner and open the main gas valve.

.As shown in Figs. 1 and 8, relays I14 and 208, and transformer I94, may be enclosed in a wall mounted housing 230. Line wires I46 and I48 from switch I52 pass to a junction box 232 through conduit 234. From said junction box, suitable connections are made to limit switch I54 through conduit 236, to primary oil burner control I92 through conduit 238, and to relay and transformer housing 230 through conduit 240. From said housing, connections are made to the oil burner through conduit 242, and to the gas control apparatus through conduit 244. A conduit 246 extends through floorpartition 6 into the rooms to be heated for connection with inside thermostat 202, and a conduit 248 extends through outside wall 4 for connection with outside thermostat 220.

In the modified form of control system shown in Figs. 9 and 10, substantially similar results are obtained in a simpler manner using fewer controls. The pilot tube II6, pilot valve IIS, flame actuated switch mechanism I24, and relays I14 and 208, which are present in the form shown in Figs. 1 to 8, are omitted. A pressure sensitive, diaphragm operated electric switch 250 is inserted in gas supply line 90 between main gas valve H4 and damper control 56, and an additional stack switch 252 is used, said stack switch being operable by a bimetallic element 254 adapted to be positioned in furnace stack pipe 8.

Referring to Fig. 9 for the wiring diagram of the modified control system, it will be noted that wires I46 and I48 are connected with main switch I52, limit switch I54, and the primary terminals of transformer I50 of primary burner control I92 just as in the preferred form. Said primary burner control is identical with the control used in the preferred form, however, the lead wires I12 and I82 of the secondary circuit of transformer I50 are connected directly to inside thermostat 202, and the line voltage lead wires I62 and I66 from said primary control are connected directly to the primary terminals of gas control transformer I94. Wire I62 is connected by wire 256 with one pole of pressure switch 256.

The other pole of said switch is connected by wires 258 and 260 with oil burner motor and the primary of ignition transformer 54. The return wires 262 and 264 of said motor and 8 transformer are connected with return Wire I66. Thus when thermostat 202 closes to complete the circuit to the coil of relay I60, said relay closes and completes the circuit to the oil burner through wire I48, the armature of relay I60, wires I62'and 256, pressure switch 250, wires 25B and 260, motor 20, transformer 54, wires 262, and 264, and wires I66 and I46, and the oil burner will be placed in operation.

Pressure switch 250 is adapted to remain closed when the pressure in gas line is below a predetermined level, and to open when said gas pressure reaches a predetermined higher level. For example, if the operating gas pressure is two ounces, switch 250 may be set to open when the gas pressure is 1 /2 ounces or more, and to close when the gas pressure drops to ounce.

When the oil burner is placed in operation, the primary coil of transformer I94 is energized. Connected in series in the secondary circuit of said transformer are a wire 26B, stack switch 252, Wire 266, outside thermostat 220, wire 210, main gas valve II 4, and wire 2'I2. Stack switch 252 is adapted to remain open when the furnace is cold, and to close when the stack temperature rises to some predetermined higher temperature. Thus when the oil burner is first placed in operation by thermostat 202 and transformer I94 is energized, and when the outside temperature is high enough to close outside thermostat 220, main gas valve H4 can not open immediately since stack switch 252 is open. After the oilburner has been in operation a few seconds, the stack temperature will become sufficiently high to close the stack switch 252, and the circuit to main gas valve II 4 will be completed thereby. Said valve, thus opened, allows gas to flow through pipe 90 to operate damper control 95 and to pass to burner tubes I4, where said gas will be ignited by the oil burner. When the gas pressure reaches the level required to open pressure switch 250, said switch will open, thus breaking the circuit to the oil burner. Valve H4 is solenoid operated and hence quick acting, while switch 250 is diaphragm operated and hence inherently slow operating. In this manner a sufficient time lapses between the opening of valve I I4 and the opening of switch 250 to insure that the gas burner will be ignited before the oil burner is turned off. Should the outdoor temperature fall below the setting of the thermostat 220, said thermostat will open, thus breaking the circuit to gas valve H4 and closing said valve. Switch 250 will then close the circuit to the oil burner, setting said oil burner in operation. Thus the gas burner can operate only when the outside temperature is above a predetermined level, as determined by thermostat 220.

However, if, while the gas burners are operating, the pressure in the gas line at any time falls below the closing pressure of switch 250, or if the gas supply fails completely, switch 250 will immediately close to set the oil burner in operation.

If the gas pressure is adequate, but the gas for any reason fails to ignite when valve H4 opens, bimetallic element 254 of stack switch 252 will immediately begin to cool, and within a few seconds opens said switch, thereby breaking the circuit to valve I I4 and closing said valve. Switch 255 will then be closed, starting the oil burner in operation. Stack switch 252 will normally open before stack switch I76 of the primary burner control I92 functions to throw safety switch I68 into the circuit and said safetyswitch rected.

While I have disclosed specific embodiments of my invention, it is apparent that many minor variations of construction and operation could be made without departing from the spirit of the invention, and it is therefore desired to be limited only by the scope of the appended claims.

What I claim as new and desire to protect by Letters Patent is:

1. A combination gas and oil burner and control system therefor comprising an oil burner, a gas burner, means for supplying fuel oil and gas respectively to said burners, automatic means responsive to the temperature of the space heated by said burners for setting said oil burner in operation to produce flame whenever heat is required, a" gas valve controlling said supply means for said gas burner, means operable by the heat of combustion of said oil burner for opening said valve to supply gas to said gas burner, said gas burner being positioned to deliver gas adjacent the delivery end of said oil burner so that said gas is ignited by said oil burner flame, automatic means responsive to the outdoor temperature for rendering said valve opening means operabl only when the outside atmosphere is above a predetermined temperature, and automatic time delay means operable by the pressure of the gas thus supplied to said gas burner to shut down said oil burner.

2, A combination gas and oil burner and control system therefor comprising an oil burner, a gas burner, means for supplying fuel oil and gas-respectively to said burners, automatic means responsive to the temperature of the space heated by said burners for setting said oil burner in operation to produce flame whenever heat is required, a quick-operating gas valve controlling said sup- "ply means for said gas burner, means operable by the heat of combustion of said oil burner for'opening said valve tosupply gas to said gas burner, said gas burner being positioned to deliver gas adjacent the delivery end of said oil burner so that said gas is ignited by said oil burner flame, a relatively slow-operating pressure sensitive means operable by the gas thus supplied to said gas burner for shutting down said oil burner, and automatic means responsive to the outdoor temperat'ure for rendering said valve operating means operable only when said outdoor temperature is above a predetermined level.

3. A combination gas and oil burner and control system therefor comprising an oil burner, a gas burner, means for supplying fuel oil and gas respectively'to said burners, automatic means responsive to the temperature of the space heated bysaid burners for setting said oil burner in operation to produce flame whenever heat is required, a gas valve controlling said supply means for said gas burner, means operable by the heat of combustion of said oil burner for opening said valve to supply gas to said gas burner, said gas burner being positioned to deliver gas adjacent the delivery end of said oil burner so that said gas is ignited by said oil burner flame, automatic means responsive to the outdoor temperature and operable to render said valve opening means operable only when said outside temperature is above a falls below a predetermined lower level.

4. A combination gas and oil burner and control system therefor comprising an oil burner, a gas burner, means for sup-plying fuel oil and gas respectively to said burners, automatic electrical means controlled by an indoor thermostat disposed in the space heated by said burners for setting said oil burner in operation to produce flame whenever heat is required, an electrically operated quick-opening gas valve whereby gas is supplied to said gas burner, automatic electrical means including a thermostatic stack switch operable by the heat of combustion of said oil burner to open said gas valve, said gas burner being positioned to deliver gas adjacent the delivery end of said oil burner so that gas supplied to said gas burner is ignited bysaid oil burner flame, an outdoor thermostat connected in series with said gas valve and said stack switch and adapted to render said valve opening means operable only when the outdoor temperature is above a predetermined level, and to close said gas valve whenever the outside temperature falls below said predetermined level, and a pressure sensitive time delay switch disposed between said gas valve and said gas burner, said pressure sensitive switch being adapted to break the circuit to said oil burner whenever the gas pressure is above a predetermined high level, and to reestablish the circuit to said oil burner whenever said gas pressure falls below a predetermined level.

5. A combination gas and oil burner and control system therefor comprising an oil burner, a gas burner, means for supplying fuel oil and gas respectively to said burners, a main valve controlling said gas supply, a gas pilot for said gas burner, a valve controlling the gas supply to said pilot, automatic means responsive to the temperature of the space heated by said burners for setting said oil burner in operation to produce flame whenever heat is required, automatic means responsive to the outside temperature for opening said pilot valve whenever said outside temperature is above a predetermined level and said oil burner is in operation, said gas pilot being positioned to deliver gas adjacent the delivery endof said oil burner whereby gas supplied to said pilot is ignited by said oil burner flame, and means operable by the flame of said pilot for shutting down said oil burner and opening said main valve, whereby gas is supplied to said gas burner and-ignited by said pilot.

6. A combination gas and oil burner and control system therefor comprising an oil burner, a gas burner, means for supplying fuel oil and gas respectively to said burners, a main valve controlling said gas supply, a gas pilot for said gas burner, a valve controlling the gas supply to said pilot, automatic means responsive to the temperatureof the space heated by said burners for setting said oil burner in operation to produce flame whenever heat is required, automatic means responsive to the outside temperature for opening said pilot valve whenever said outside temperature is above a predetermined level and said oil burner is in operation, said gas pilot being positioned to deliver gas adjacent the delivery end of said oil burner whereby gas supplied to said pilot is ignited by said oil burner flame, and

to close said pilot valve whenever said outside temperature falls below said predetermined level, and means actuated by the flame of said pilot for shutting down said oil burner and opening said main valve to supply gas to said gas burner, said flame actuated means bein dependent upon the continued supply of gas at a predetermined pressure to said pilot, whereby when said pilot gas falls below said predetermined pressure, said main valve will be closed and said oil burner set in operation.

'7. A combination gas and oil burner and control system therefor comprising an oil burner, a gas burner, means for supplying fuel oil and. gas respectively to said burners, a main valve controlling said gas supply, a gas pilot for said gas burner, a valve controlling the gas supply to said pilot, automatic means responsive to the temperature of the space heated by said burners for setting said oil burner in operation to produce flame whenever heat is required, automatic means responsive to the outside temperature for opening said pilot valve whenever said outside temperature is above a predetermined level and said oil burner is in operation, said gas pilot being positioned to deliver gas adjacent the delivery end of said oil burner whereby gas supplied to said pilot is ignited by said oil burner flame, and to close said pilot valve whenever said outside temperature falls below said predetermined level, an auxiliary gas jet adapted to receive gas through said pilot valve and positioned so that gas delivered thereto is ignited by the primary pilot flame, and thermostatic means operable by the heat of said auxiliary jet to shut down said oil burner and open said main valve, whereby gas is supplied to said gas burner and ignited by said pilot, said thermostatic means being operable whenever the flame of said auxiliary jet is extinguished or reduced by failure of the gas supply or reduction of the gas supply below a predetermined pressure to close said main gas valve and set said oil'burner in operation.

8. A combination gas and oil burner and control system therefor comprising an oil burner, a gas burner, means for supplying fuel oil and gas respectively to said burners, means controlled by a thermostat disposed in the space to which heat is supplied by said burners for automatically setting said oil burner in operation to produce an oil flame whenever heat is required, means rendered operable by the heat of combustion of said oil burner for shutting down said oil burner and supplying gas to said gas burner, said last named means including a time delay means whereby said oil burner is continued in operation for a short time after the gas supply is initiated, said gas burner being positioned to deliver gas adjacent the delivery end of said oil burner whereby said gas is ignited by the oil flame, and automatic means responsive to the temperature of the outdoor atmosphere and operable to render said last named means inoperative to shut down said oil burner and inoperative to supply gas to said burner when said outdoor atmosphere falls below a predetermined temperature.

9. A combination gas and oil burner and control system therefor comprising an oilburner, a gas burner, means for supplying fuel oil and gas respectively to said burners, means controlled by a thermostat disposed in the space to which heat is supplied by said burners for automatically setting said oil burner in operation to produce an oil flame whenever heat is required, means rendered operable by the heat of combustion of said oil burner for shutting down said oil burner and supplying gas to said gas burner, said last named means including a time delay means whereby said oil burner is continued in operation for a short time after the gas supply is initiated, said gas burner bein positioned to deliver gas adjacent the delivery end of said oil burner whereby said gas is ignited by the oil flame, and automatic means responsive to the pressure of the fuel gas supply and operable to render said last named means inoperative to shut down said oil burner and inoperative to supply gas to said burner when said pressure falls below a predetermined level.

10. A combination gas and oil burner and control system therefor comprising an oil burner, a gas burner, means for supplying fuel oil and gas respectively to said burners, means controlled by a thermostat disposed in the space to which heat is supplied by said burners for automatically setting said oil burner in operation to produce an oil flame whenever heat is required, means rendered operable by the heat of combustion of said oil burner for shutting down said oil burner and supplying gas to said gas burner, said last named means includin a time delay means whereby said oil burner is continued in operation for a short time after the gas supply is initiated, said gas burner being positioned to deliver gas adjacent the delivery end of said oil burner whereby said gas is ignited by the oil flame, and

automatic means responsive to the temperatureof the outdoor atmosphere and to the pressure of the fuel gas supply and operative to render said last named means inoperative to shut down said oil burner and inoperative to supply gas to said burner whenever either said outdoor temperature or said gas pressure falls below a predetermined level.

RICHARD H. SIEMON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,394,807 Blanchard Oct. 25, 1921 1,596,836 Hoff Aug. 17, 1926 1,722,253 Sherwood July 23, 1929 1,786,900 Doherty Dec. 30, 1930 1,840,744 Scott Jan. 12, 1932 1,938,335 Hubbard et al Dec. 5, 1933 2,003,624 Bower June 4, 1935 2,065,533 Leahy Dec. 29, 1936 2,081,091 Kuempel May 18, 1937 2,407,973 Beckstrom Sept. 24, 1946 2,451,661 Cochrane Oct. 19, 1948