US2255318A - Control apparatus for oil burners - Google Patents

Description

M 1941- J. R. HAWLEY 2,255,318

CONTROL APPARATUS FOR OIL BURNERS Filed Aug. 21, 1939 2 Sheets-Sheet l I t I as A 3 I I I l L-u-l K l l J 1 z/ I I 3/ L20 Pi 4 IIII'I ".ualll I INVENTOR JAMES HAM/45V Q ATTORNEY INVENTOR JAMES A? HA MEV 2 Sheets-Sheet 2 J. R. HAWLEY CONTROL APPARATUS FOR OIL BURNERS Filed Aug. 21, 1939 Sept. 9, 1941.

ATTORNEY Patented Sept. 9, 1941 CONTROL APPARATUS FOR OIL BURNERS James R. Hawley, Seattle, Wash, assignor to Mechanical Products Manufacturing Company, '(not incorporated), Seattle, Wash.

Application August 21, 1939, Serial No. 291,148

9 Claims.

This invention relates to heating systems and more particularly to improvements in oil burners designed for the heating of homes, for commercial plants and various other uses, and adapted to burn what is generally referred to as heavy fuel oil; it being the principal object of this invention to adapt the principle of atomization of heavy fuel oils, by applying heat and mechanical pressure to small capacity nozzles, thereby to render their operation satisfactory and free from coking or other fouling.

Explanatory to the invention, it will be here stated that it has been recognized in the use of heavy fuel oils that a greater heating efiicicncy can be obtained in the burning operation if the temperature of the fuel oil is raised to a degree near the temperature of combustion before it is atomized for ignition in the combustion chamber.

In some burners, provision has been made for such heating of the oil, but usually at some point remote from the actual point of atomization and burning.

There have been some disadvantages observed in such preheating of the oil at a point distant from the point of combustion; for example, in the resultant heat loss from the oil as it flows from the point of heating to the point of combustion, and the corresponding loss of burning efficiency. It has been particularly noted, however, that should the pre-heating be carried to a high degree suflicient to compensate for this drop in efiiciency due to heat loss, there will then be the objectionable feature of coking of the oil in the preheating coils and apparatus, requiring that they be periodically cleaned of such coke or carbon, or that the apparatus ultimately be replaced because of resultant deterioration.

Furthermore, small particles of this coke will be dislodged from the inside walls of the heater pipes, and will be carried to the atomizing nozzle, either partially or completely closing the orifice therein, rendering the burner inoperable and also presenting a serious hazard to safety. It is also possible that such particles of carbon or coke would clog or foul the valve plunger in its valve seat, holding it partially open, and allowing a slow drip or leaking of the oil, also creating a serious hazard to safety.

Another disadvantage incident to the preheating of the oil at a point remote from the point of ignition, is due to the long period of time required to bring the oil to a temperature for ignition.

In view of the above mentioned, and other disadvantages in systems as generally manufactured,

it has been an object to provide an oil burner 55 wherein the oil, delivered from a point remote from the burner, is preheated within the burner itself to a degree reasonably close to its vaporization temperature, and at a point substantially adjacent that where it is delivered in an atomized condition into the combustion chamber to avoid the previously mentioned heat loss, nozzle fouling and coking of the pipes.

It is also an object of this invention to provide a burner that will bring about a reduction in the cost of operation by reducing the amount of heat required to efiect proper atomization of the oil and by preventing overheating of the oil supply.

Still another object of the invention is to provide an oil burner wherein the time required for the preheating operation prior to starting the burner is reduced to a minimum.

Another object of the invention is to provide a substantially accurate means of controlling the temperature of the oil in the pre-heating tube or chamber adjacent to the point of atomization so as to prevent overheating of the oil.

A further object of the invention is to provide that, upon shutting off the burner, the oil temperature in the heating tube or chamber be reduced, thereby dissipating the heat in the coils and eliminating the undesirable results that are incident to allowing over-heated oil to stand in the heating coils.

A still further object of the invention is to provide an oil burner of the kind stated, that is relatively simple in construction and relatively inexpensive to manufacture, that is durable in use, reliable and efiicient in its operation, and otherwise well adapted for its intended uses.

Other objects of the invention reside in the details of construction of parts, in their combination and mode of operation as will hereinafter be fully described.

In accomplishing these objects, I have provided the improved details of construction, the pre ferred forms of which are illustrated in the accompanying drawings, wherein- Fig. l is a horizontal, sectional view, taken centrally of a burner embodied by the present invention.

Fig. 2 is a vertical sectional view taken substantially axially of the blast tube of the burner.

Fig. 3 is an enlarged, sectional detail, showing the solenoid actuated valve mechanism for controlling oil delivery to the burner nozzle.

Fig. 4 is an enlarged, sectional detail of the burner nozzle and valve mechanism.

Fig. 5 is a wiring diagram, illustrating one way in which the burner may be wired with electrical controls for automatic operation.

Briefly described, the present burner comprises a housing that contains a fan which is driven by an electric motor for the forcible delivery of air through a blast tube into the combustion chamber of the stove or furnace. Located coaxially within the blast tube is an electrically heated oil delivery tube which, at its outer end is connected to a source of oil supply and at its inner end is equipped with an atomizing nozzle for the derivery of the oil, in an atomized condition with the air blast, into the combustion chamber.

Automatic devices control the energizing of the electrical heating element, and also the delivery of oil to the atomizer in accordance with the obiects oi the invention as previously stated. The automatic means includes the usual room thermostat, that may be set to operate at a selected room temperature, a time delay switch for setting the pump and motor in operation after a predetermined time interval necessary for the oil heating and various relays later to be explained in detail.

Referring more in detail to the drawings- The present device, in a preferred form of con struction, comprises a rectangular base section l which mounts thereon a fan housing or casing H. The base member may be made in various sizes, and of various heights, to best adapt it for use with stoves, furnaces or boilers of different kinds, and it is equipped within its fourcorner portions with vertical legs Illa, with feet lb, and these legs are threaded through mounting brackets I00 fixed in the base, and they may be vertically adjusted therein to level the burner and maintain it at a set position.

The fan housing II rests upon and is rigidly fixed to the base member II). It is substantially rectangular in cross section and within its upper portion containing an air delivery fan l4. The fan I4 is of the squirrel cage type and has a hollow hub portion l4a whereby it is mounted upon the end of the drive shaft 15a of an electric motor i5 which, in turn, is fixedly mounted upon a side wall of the housing ll. Air enters the fan housing through a side wall opening Ha: opposite the motor.

Mounted on the side wall of the housing ll, about the wall opening llx, is a bracket l9, and supported by the bracket I9 is a fuel oil pump equipped with a drive shaft i 8a having a driving connection with the drive shaft of the electric motor l5.

Fixed to the pump housing is an oil filtering device, designated in its entirety by numeral 20, and this is connected by a pipe 2| with a source of supply of fuel oil, not shown. Upon operation of the pump, oil will be drawn through pipe 2| to the filter, and then delivered therefrom under pressure, to the oil heating tube, later to be de scribed.

The lower portion of the fan housing H is rectangular in cross section, and is slightly larger than the upper portion, converging at its forward side to a cylindrical neck lib from which a cylindrical air blast tube I3 extends for directing the air supplied by the fan l4 to the combustion chamber of the furnace with which the burner is used. At its delivery end, the tube is fitted with a nozzle member l3 for concentrating the blast and this may, if desired, be equipped with fins or deflectors, not shown, for causing a whirling or swirling delivery of the mixture into the combustion chamber.

Disposed horizontally within the housing H and coaxially of the blast tube I2 is the oil heating tube 25. The rearward end of this tube extends through the rearward wall of the housing ll and is there provided with a tubular fitting 26 to which an oil delivery tube 21 from the pump I8 connects for supplying oil to the heating tube. At its forward end, the tube 25 is equipped with an atomizing tip 28 and this is disposed, as noted in Fig. 2, just within and centrally of the delivery end of the blast tube.

Mounted on a side wall of the housing H, below the motor I5, is a transformer 22, and extending from this are circuit wires 33 and 24 leading into the housing and along the tube 25, terminating in ignition points 25 and 36 located adjacent the atomizing nozzle and between which points a spark may be caused to jump for igniting the combustible mixture as is the usual procedure.

' Mounted upon the fitting 26 and disposed vertically thereon, is a solenoid 30 designed for control and operation of an oil delivery valve within the delivery end of tube 25, as presently will be explained.

As seen in Fig. 3, the solenoid 30 comprises a coil 30' that is enclosed within a housing 28, and is disposed about a cylindrical, liquid-tight, tubular dome 40, which is threaded into the fitting 26. I'he dome 40 contains a steel block 4| which operates as a solenoid core, and, as here shown, will be drawn upwardly upon energization of the coil.

A link 42 is pivotally connected to the lower end of the core, as at 43, and at its lower end, the link is pivotally attached, as at 44, to a lever 45 used in control of the oil valve in the tube, as presently will be explained.

The tube 25, as noted in Fig. 3, is threaded into a nipple 46 which is fixed to the fitting 26 by a coupling union 41. A tubular fitting 48, is inserted in the fitting 4S and is held in place by the nipple 46 and the union 41. This fitting 48 is shouldered to limit its insertion in part 26 and forms a leak-tight connection with the nipple 46 and it-coaxially contains a rod 50, slidable therein within a coaxial bore 5|. It will be noted that the fitting 48 is slotted at its inner end within part 26, as at 52, to receive the end of the lever 45, and this lever 45 is pivotally mounted in the slot 52 by a pin 53. Also, it will be noted that the rearward end of the rod 50 is slotted as at 54, and receives the pivoted end portion of the lever 45. Also, it is seen that a pin 55 is fixed. in the rod 50 and extends through the slot, and that a notch or recess 56in the lower edge of the lever receives the pin 55 therein. Ports 5'! in the fitting 48 open into an enlarged central bore 58 for an unrestricted passage of oil therethrough to tube 25.

With this arrangement of parts, energization of the solenoid 30 causes an actuation of the lever 45 whereby the rod 50 will be pulled outwardly.

Disposed lengthwise within the tube 25 is a filler or spacer tube 50, provided at opposite ends with closure fittings 6l-6l' which seal the tube liquid-tight. These closure fittings 6| are provided with outer end portions 52-62' of a diameter slightly greater than that of tube 60, and they have an easy sliding fit within the tube 25. These enlarged portions 62-82 are provided with a plurality of notches or grooves 63-63 to allow a free and unrestricted passage of oil therethrough and about the tube 60. Furthermore, the closures at the outer end of the tube 60 are counterbored, as at 65-45 from the outer end, to a diameter and depth suitable to loosely receive an end portion of the rod 50, and the valve plunger, as will presently be explained, which are fixed therein by pins 66-66 in a. free or flexible connection.

The narrow passage between this filler or spacer tube 60 and the outer tube 25 provides for quicker and easier application of heat to the oil flowing therebetween, and these tubes, due to their construction, preferably copper, conduct the heat to the oil very readily. It is obvious that the oil may be heated quicker, more economically, and more uniformly in this manner.

Referring to Fig. 4, it will be seen that there is a sleeve tightly pressed into the outer end of tube 25, and the tube is threaded into a cap II, into which cap an atomizer spray tip or nozzle 28 is threaded. Flow of oil to the atomizer or nozzle 28 is under control of-a valve device that is located in the forward end of the tube 25, within the cap II and adjacent to the spray tip 28.

The valve device comprises a valve seat member I5 which is threaded in a liquid-tight joint, into an inner end opening provided in the spray tip 28. A valve stem or plunger I6 has an outer end portion slidably contained in a counterbore within an inwardly extending portion of the valve seat member and has its other end portion loosely contained within the counterbore 65 within the closure fitting 6| at that end of the spacer tube 60. A pivot pin 66' connects the parts 16 and 61 in a free or flexible manner. The valve stem or plunger I6 has a tapered forward end portion 16a adapted to close against a valve seat formed by a tapered bore a in the valve seat I6 to cut off the oil flow through the part I6 to the atomizing nozzle. It will be understood that upon energization of the solenoid, the core 4| will be lifted, and the lever 45 will be actuated to pull the tube 60 outwardly, thus to unseat the valve plug from seat I5. Also, upon de-energization of the solenoid, the core 4| will drop. and this action will move the valve to its closed position. Flow of oil to the nozzle through fitting I5 is permitted by reason of a plural ty of ports 15b in the inner end portion inside the valve seat, as noted in Fig. 4. A screen 153 is wrapped about the member to catch any foreign matter that might be apt to clog the valve or nozzle, or prevent the valve from seating.

A thermostat bulb, designated by reference numeral 80, is disposed against the tube 25 near its forward end, and within a shallow, longitudinal groove 8|. This bulb is covered by thin, formed shell 62. A small tube 83 leads from the bulb 80 to transmit pressure of expandable medium used in the bulb to a cut-out switch 84 to provide for control of the latter, as will be expla ned in connection with the wiring diagram illustrated in Fig. 5.

A heating coil or element 85 of resistance wire is formed about the tube 25, being electrically insulated therefrom by a sheet of suitable material, such as sheet mica, or the like, as indicated at 86, and a substantially thick covering 81, such as plastic asbestos or the like, is applied to the tube 25 and over the element 85, functioning both as an insulation for the said element and as a means of confining the heat of the element to the tube 25, thereby obtaining the maximum efiiciency from the heating element in heating the oil within the tube.

It will be noted that there is a circuit wire 88 leading to the forward end of the heating coil, and this is embedded in the asbestos cover 81; the other circuit wire 89 connects to the rearward end of the coil; current being supplied, as presently described.

It will be stated that a much lower voltage is here desirable to operate the relay switch through the room thermostat, and to close the relay in the stack switch, than is necessary to operate the motor, ignition, heater and valve solenoid; therefore, two sources of current or circuits are utilized in the present instance.

In the wiring diagram shown in Fig. 5, 90 and 9| designate power lines leading from a source of low voltage current, while 92 and 93 designate power lines supplying high voltage current. The electric motor I5 has one side connected by a line 94 with line 93 and its other side connected by a line 95 with a contact 96 on the stack switch 91. The transformer 32 has one side connected by a wire 98 with the circuit line 93 and its other side connected by a wire 99 with a contact I00 of the stack switch 9'1. The switch 9! has a switch arm connected by a line |0| with line 92, and this arm comprises parts I02 and I03 adapted to open or close as a unit, and on closing to engage the contacts 96 and I00, and simultaneously close the high voltage circuit through motor I5 and the transformer 32. The switch members I02 and I03 are operable to closed position under control of a solenoid I05 having a circuit connection I06 with line 90 and a connection I01 through a time delay switch I08 and wire I09 from the switch to the line 9|. The solenoid I05 is energized upon closing of switch I08 which will electrically connect wires I01 and I09.

The room thermostat, which is generally the instrument under which automatic control of the burner is placed, is designated at II 0 and this has one side connected by a line III with circuit line 9| and its other side connected through a wire 42 to a solenoid coil 3, and then through a wire N20. to a lockout switch H4 and has a wire |I5 connecting with the line 90.

The time delay switch I08 includes a heating element I20 which functions when current is passed therethrough, to heat a bi-metal strip to effect the closing of switch I08 and thus connect the lines I01 and I09, and energize the solenoid coil I 05 in the stack switch 91. This solenoid coil I05 upon being energized closes the switch elements I02 and I03 in the stack switch, to energize the ignition transformer 32, and simultaneously operate the valve solenoid 30, and start the motor I5, It is shown in Fig. 5 that the valve solenoid 30 has a connection I2| with line 93 and a connection I22 with line 95. It is contemplated that the ignition transformer 32 and its circuit may be of the intermittent operation type as well as the continuous operation type; it being understood that the operation of the stack switch 91 is to open the circuit to the ignition transformer upon the establishment of combustion of the fuel oil through the expansion of a spiral bimetal coil 91a by the heat of combustion. Furthermore, in case of flame failure, for any reason, the lookout switch I|4 will be opened and the entire system will close down automatically. In such cases the stack switch is manually rest, by closing the lockout switch H4. This is the conventional operation of most standard stack switches now on the market, as is well known in the art, but for a better understanding of the operation of the system, it might be well to state here that the opening of the lockout switch H4 is accomplished by a bi-metal strip which is heated by a heating element connected in the stack switch which will open the lookout switch II4 a short predetermined interval of time after the closing of the switches I82 and I88 if the spiral bi-metal element 81a is not ail'ected by the heat of combustion.

In heating a home, when the room temperature falls below that for which the room thermostat III) is set, the switch IIIIa. therein is closed, thereby energizing the solenoid coil I I5 in the relay I24, which causes the closing of the switches I25 and I25. These latter switches close the circuit to the burner thermostatic switch 84 through the lines I28 and I88, and to the time delay relay switch through the lines I82 and I88.

The oil heating element 85 has its ends connected to the burner thermostatic switch 84 by the wires 88 and 89, and the circuit is completed through the normally closed switches 84a and 84b, to energize the heating element. Upon the heating element 85, the heater tube 25 and the oil contained therein reaching a certain predetermined temperature, the thermostat bulb 88 operates through the tube 88 to open the switches 84a and 84b in the thermostatic switch 84, and when these parts fall below a certain predetermined temperature, the thermostat bulb 88 operates to close the switches 84a and 84b, thereby maintaining the oil at a substantially constant temperature.

Simultaneously with the energization of the oil heater element 85, the time delay relay heater element I28 is energized, and after a predetermined period of time, which has been found to be approximately two minutes for most moderate climates, the switch I88 is actuated to a closed position, thereby closing the circuit to the solenoid coil I85 in the stack switch. During this period of time, the heater element 85 is heating the oil in the tube 25 to the point where atomization for combustion is most readily established and maintained most efliciently and economically. This period of time, of course, may vary in some cases and then it is necessary to make adjustments in the operation of the time delay relay, and also in the adjustable burner ther mostatic switch 84.

When the solenoid I85 in the stack switch 81 is energized, it operates to close the switches I82 and I08. Upon these switches I02 and I83 being closed, the circuits are closed both to the valve operating solenoid 88, thereby opening the valve, and-to the motor I5, starting the motor which drives the fan II and the pump 20, thereby delivering fuel oil under pressure through pipe 25 and a blast of air through tube I3 to support combustion, and also at the same time furnishing current to the ignition transformer 32, for effecting ignition oi the fuel mixture.

If, for any reason, the ignition should fail, and there occurs what is termed a flame failure, the lock-out switch will operate to close down the entire electrical circuit, as previously stated.

Upon combustion being established, it will continue, the burner operating until one of the controls automatically calls for a shut-down. The heating element 85 will remain energized to heat the oil to a predetermined temperature, or will be turned oil. and on intermittently to maintain a substantially constant heat under control of the thermostat bulb l8 and the switch 54.

In normal operation, when the room thermostat IIII is satisfied, the switch IIlla is opened, thereby de-energizing the solenoid coil III for opening the switches I25 and I25 in the relay I24. This opens the circuit to the heater 55, and the time delay relay element I28. However, a feature of this construction resides in the fact that the time delay relay switch III will not open for a predetermined interval of time, thereby maintaining the operation of the motor I5, the pump 28, and holding the valve solenoid energized until the circuit is opened. This allows the burner to scavenge itself of hot oil in the heater tube 25, and dissipate the heat of the tube itself, in that the burner will continue to operate until the time delay relay switch I05 is opened. This provides that the oil temperature in tube 25 be reduced, and that the tube itself will be cooled to a safe temperature below which coking of the oil therein will not take place.

The primary control switch has been described as a room thermostat IIII, operated by air temperature, but it may be replaced by a switch operated by water temperature or steam pressure, such as in commercial applications 01' the oil burner, or in a plurality of them, rather than in a home installation, as herein described. It

is thought obvious that with an oil burner in accordance with the invention as herein disclosed and described, all of the faults of previously used burners are eliminated.

It is not intended that the claims be limited to the details of construction of parts, but that they be given an interpretation commensurate with the spirit and scope of the invention disclosed.

Having thus described my invention what I claim as new therein and desire to secure by Letters Patent is:

1. In an oil burner an oil delivery tube equipped with an atomizing nozzle at its delivery end, a valve in the tube for controlling the flow of oil therefrom to the nozzle, an electric heating element associated with the tube for heating the oil contained therein, an electric circuit for the heating element including a cut-out switch, a device adapted to be electrically energized to open the control valve, an electrically energized time delay switch operable to energize said device after a predetermined time interval with reference to energization of the time delay switch, and a control switch common to the circuits of the heating element and the time delay switch.

2. In an oil burner, an oil delivery tube, a valve in the tube for control of the discharge of oil therefrom, an electric heating element associated with the tube for heating the oil delivered therethrough, a circuit for the heating element, a time delay switch, a circuit for the time delay switch, a thermostatic switch common to the heating element circuit and time delay switch circuit, and means under control of the time delay switch for actuating the said control valve to open and closed positions respectively, at predetermined time intervals following the energizing and deenergizing of the heating element by the actions of the thermostatic switch.

3. In an oil burner, an oil delivery tube equipped at its discharge end with a control valve, a solenoid operatively connected with the valve and adapted, upon being energized, to open the valve and when de-energized, to close it, a circuit for the'solenoid, an electrical element for heating the oil in the delivery tube, a circuit for the said element including a cut-out switch, a time delay switch controlling the energization and deenergization of the solenoid circuit, a circuit for the time delay switch, a thermostatic switch operable to control both the heating element and time delay switch circuits and a thermostatic control for said cut-out switch operable under influence of temperatures of oil in the tube.

4. In an oil burner, an oil delivery tube equipped atits discharge end with a control valve, a solenoid operatively connected with and adapted, upon being energized, to open the valve, a circuit for the solenoid, an electrical element for heating the oil in the delivery tube, a circuit for said element, a time delay switch, a circuit for the time delay switch, a thermostatic switch for the Joint control of the circuit of the heating element and or the time delay switch; said time delay switch being operable for effecting a delayed energization and delayed de-energization of the solenoid circuit, and a temperature responsive means associated with the delivery tube and oil contained therein for opening the heating element circuit independently of the action of the thermostatic switch.

5. In an oil burner, a tube for delivery of oil into a combustion chamber, an atomizing nozzle at the delivery end 01' said tube, a control valve in the tube adjacent the nozzle, a solenoid having operative connection with the valve to move it between open and closed positions, a circuit for the solenoid, an electrical element for heating oil in the tube, a circuit for the element, a timedelay switch for control of the solenoid circuit, a circuit for the time delay switch, a thermostatic switch operable to control the circuits for the heating element and time delay switch; saidtime delay switch being arranged to control the solenoid-circuit for opening and closing the valve at predetermined time intervals after the energize.- tion and de-energization or the heating element by the action or the thermostatic switch, and a temperature responsive element associated with the tube and operable in accordance with temperature of the oil therein for controlling the heating element circuit independently of other circuits while the control valve is open.

6. In an oil burner, the combination with an air blast tube and means for delivering a blast of air therethrough into a combustion chamber, 01' an oil delivery tube equipped at one end for delivering oil therefrom in an atomized condition into the air from the blast tube, to form a combustiblemixture, a valve in the oil delivery tube at its discharge end, a heating circuit for the oil tube, a pump for delivering oil under pressure into the tube, an electric motor for operating the pump, a motor circuit, a solenoid tor actuating the valve, a circuit for the solenoid, a time delay switch operable to control the solenoid circuit, a thermostatic swimh for control of the time delay switch circuit and the heating circuit, and means under control of the time delay switch to open the motor circuit.

7. In an oil burner, an air blast tube, a fan operable to supply air under pressure to the tube for discharge into a combustion chamber, an oil delivery tube disposed within the air blast tube and equipped at its discharge end with means for discharge of oil from the tube in an atomized condition for mixture with the delivered air, a control valve in the tube adjacent the atomizing means, a pump operable to supply oil under pressure to the oil delivery tube, an element for heating oil in the tube, a circuit for the heating element a motor for operating the fan and pump an electric circuit for the motor, a solenoid for ment, a time delay switch, a circuit therefor, a-

thermostatic switch for control of the circuit of the time delay switch and heating element, and a relay operated by the time delay switch, and controlling the motor and solenoid circuits.

8. In an oil burner, an electric power circuit, an oil delivery tube, a valve for controlling the discharge of oil therefrom to a combustion chamber, electrically operated mechanism for actuating the valve, a heating element associated with the tube, for heating the oil therein, a time delay switch for control of the valve actuating mechanism, a control switch controlling the energization of the heating element and time delay switch from the power circuit, an electrically operable pump for delivery of oil to the chamber, a second power circuit for said pump, and a switch in the latter circuit operable under control or the time delay switch to delay the de-energization of the pump for a predetermined interval after the heating means has been de-energized by the opening of the said control switch.

9. In an oil burner of the character described, an oil delivery passage, an atomizing nozzle at the discharge end of the passage, a control valve adjacent the nozzle, electrically energized means for actuating the valve, a source of electrical power, an electrical heating element for the passage, a time delay switch for controlling the valve actuating means for the opening and closing action of the valve in time delay to the energizing and de-energizing of said switch, and a thermostatic control switch and means electrically connecting said heating element and said time delay switch to the power circuit through the said thermostatic control switch.

JAMES R. HAWLEY.

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