US2085577A - Burner control - Google Patents

Description

June 29, 1937. J. EATON BURNER CONTROL Original Filed July 14, 1934 2 Sheets-Sheet 1 Inventor: John Eaton b 5.

His Attorneg- June 29, 1937. J. EATON BURNER CONTROL Original Filed July 14, 1934 2 Sheets-Sheet 2 Inventor John Batch Hls Attorneg- Patented June 29 1937 UNITED STATES BURNER CONTROL John Eaton, Schenectady, N.,.Y., mignor to General Electric Company, a corpontion ot New York Original application- July 14, 1934. Serial No. 735,103. Divided and this application March 14, 1935, Serial No. 11,100

29 Claims. (01. 158-28) This application is a division of my application, Serial No. 735,103, filed July 14, 1934.

The invention relates to automatic fuel burner control systems and apparatus such as used with oil fired boiler furnaces for heating homes or in other similar service. v

The principal object is to provide improvements which insure the maximum safety in the automatic control and operation of the fuel burner as well as safe operation of the boiler furnace.

A specific object is to provide an improved control system and apparatus for obtaining a predetermined timed sequence of the operations involved in introducing and igniting oil in the furnace in which the introduction of unburned oil into the furnace is automatically limited to a predetermined safe value upon failure to establish combustion or upon failure of the oil burner mechanism and control apparatus to function properly.

Another specific object is to provide an automatic fuel burner control system and apparatus which insures detection of both the presence and absence of combustion with a minimum delay.

A still further object is to provide an improved .form of combined room thermostat and limit control for effecting operationof the fuel burner in accordance with both room temperature and certain other conditions such as boiler temperature, domestic hot water temperature, steam pressure or the like.

Another important object is to provide a fully automatic fuel burner control system and apparatus which effectively ensures against continued operation of the burner in case of accidental failure or faulty operation of-the important safety control elements, such as the flame detector, the

low water cutofi, the fuel supply control and the like.

It is also a special object to provide an improved unitary structural arrangement for the automatic fuel burner and boiler control mechanism whereby reliability, ease of installation, inspection and adjustment of the various automatic operating elements are obtained.

Apreferred form of automatic oil burner control system 3 and apparatus embodying the'improvements of the present invention is illustrated in the accompanying drawings. Fig. 1 is a schematic diagram showing the improved form of oil burner safety control system and apparatus applied to an electric motor driven oil burner mechanism adapted for use in combination with a vacuum vapor house heating boiler; Fig. 2 is a sequencediagram indicating the predetermined timed relations in which the various operations involved in starting the oil burner and establishing combustion are accomplished under the control of a room thermostat, a boiler thermostat or similar master control element, by the improved safety control system and apparatus shown in Fig. 1; Fig. 3 shows more fully the cooperating arrangement and detailed structure of the various elements of the oil burner timing control mechanism and certain of the safety control elements shown diagrammatically in Fig. 1; Fig. 4 is a top view of the timing and safety control mechanism shown in Fig. 3, and Fig. 5 is a view of the top part of the oil burner boiler showing more clearly the manner in which the oil burner mechanism and-timing and safety control mechanism therefor is mounted on the boiler.

As diagrammatically shown in Fig. 1 the boiler furnace III is of the improved type described and claimed in the copending application of Henry S. Woodruif, Serial No. 676,651, filed June 20, 1933, and assigned to the assignee of my present invention. It will be understood, however, that the improvements of my present invention are applicable to control any ordinary type of automtically fired boiler or furnace.

The oil burner nozzle ll supplies atomized oil which is ignited during the starting operation of the oil burner mechanism by an electric spark between electrodeslZ to establish combustion in the boiler combustion chamber iii, in the manner described in detail hereinafter. A quick acting flame detector i4 having a control switch l5 movable between the cold and hot positions is provided for detecting the presence or absence of combustion. As indicated the flame detector i4 is of the expansible heat responsive type although any quick acting type of flame detector may be employed.

An oil control valve l'his shown incorporated in the oil burner nozzle l I for starting and stopping the supply of oil into the combustion chamber i3. Oil valve I1 is normally closed and is opened only when the oil valve operating electromagnet i8 is energized. As pointed out hereafter electromagnet i8 is provided with a holding circuit for maintaining valve ll open after it is once opened independently of the initial energizing circuit. As shown in Fig. 5 oil and air are supplied under pressure to the burner nozzle II from the electric motor operated oil burner blower compressor mechanism 20.

The oil atomizing nozzle ii and oil valve l'l preferably are of the type described and claimed in my copending joint application, Serial No. 691,320, filed September 28, 1933, although the present invention is not limited thereto.

The oil burner motor compressor mechanism 20 preferably is of the type described and claimed in the copending application of Walter O. Lum,

Serial No. 737,063, filed July 26, 1934, and assigned to the assignee of my present invention.

The oil burner mechanism 20 has an electric.

driving motor II which .drives a suitable oil and air pumping means located inside of the tank 22 for pumping oil and air under pressure into the tank. The air under pressure is supplied from tank 22 directly to the burner nozzle through the pipe 23 and the oil under pressure is supplied to the nozzle upon opening of oil control valve I! through the pipe 24. Low pressure combustion air is supplied from the blower 25. As indicated diagrammatically in Fig. 1 the oil burner motor 2| is provided with a running winding 21 and a starting winding 28.

The oil burner mechanism is operated under the control of the room thermostat III to heat the water in the boiler II to supply steam or vapor to a room heating radiator system (not shown). In addition the oil burner mechanism is also operated under the control of the water thermostat Sl. As shown the water thermostat 3| is of the expansible bellows type having the bulb 32 responsive to the temperature of the water in the boiler Ill. The thermostat 3| serves to operate the oil burner mechanism to maintain the boiler water temperature above a predetermined value sufficient to heat an adequate supply of domestic hot water by means of the water heating coil 33 which is shown immersed in the boiler water.

A bellows 38 is responsive to the pressure in boiler II and serves to shut down the oil burner mechanism whenever an excessive pressure occurs. An improved form of electrically heated low water cutout switch mechanism 36 having a heater I4 is provided for preventing operation of the oil burner mechanism whenever the boiler water level falls to an unsafe value as described and claimed in the parent application.

A vacuum relief valve 31 is provided for venting the boiler in accordance with the invention described and claimed in the copending application of Walter O. Lum, Serial No. 735,128, flied July 13, 1934, and assigned to the assignee of my present invention. The improved arrangement whereby the vacuum relief valve 31 is operated directly by the domestic water temperature control thermostat II is an improvement of my present invention.

In order to obtain a predetermined timed sequence of operation of the various elements comprising the oil burner mechanism, a timing con-, trol device indicated generally by the reference numeral 40 is provided. In the preferred form indicated diagrammatically in Fig. 1 and shown more in structural detail in Figs. 3 and 4, a cam shaft 4i is driven by the electric timing motor 42 which preferably is of the alternating current constant speed type such as commonly used in electric clock's. The cam shaft 4i carries a seriesoi' timing cams indicated respectively as B I", O T and I, all of which are rotated in unison in a clockwise direction as indicated 1 by the arrow in Pig. 1 upon operation of the timing motor 42. kch of these cams has a corresponding cam operated switch contact mechanism arranged so that a definite series of switching operation is performed in timed sequence in the manner described more fully hereinafter in connection with the operation.

Cooperating with the timing cam operated switch mechanism are a series of electromagnetically operated switches indicated as A, B and C, each having a pair of circuit controlling switch contacts indicated respectively at A A B 13 and C C in Fig. 1.

As shown more in detail in Figs. 3 and 4. the cam shaft 4| is rotatably supported between the side plates 43 and 44 with the motor 4! driving the'cam shaft through the speed reducing gearing 45. The series of spring contacts operated by the cams B, F, 0 O, T and I are mounted between suitable blocks of insulating material 46 and 41. Likewise the spring switch contact mechanism of the electromagnetic switches A, B and C are mounted between blocks 41 and blocks 48, the operating electromagnets therefor being mounted below the contact mechanism as indicated in Fig. 3. The side plates 43 and 44 are secured to a cover plate 50. As indicated in Fig. 3 plate 50 is arrangedto cover an opening provided in the top wall 52 of boiler i0, being removably bolted in place with suitable gasket to seal the boiler wall.

The cover plate 50 carries the boiler water thermostat 3!, the boiler pressure responsive bellows 35 and the vacuum relief valve 31, all as a unitary structure with the oil burner timing control mechanism 40. With this improved unitary arrangement, the expansible bellows thermostat 3| is connected through the overcenter snap action spring operating mechanism 55 to mechanically operate the contact switch mechanism A of the electromagnetic switch A. At the same time the thermostat 3i operates the vacuum relief valve 31. Similarly the expansible bellows of the boiler pressure responsive device 35 operates the spring contact switch L through the agency of the overcenter spring snap action mechanism 56.

The operation of the improved burner control system and apparatus illustrated is as follows: When the room thermostatic switch 30 calls for heat, the running contact R is closed. When the room thermostat exceeds the temperature which it is adjusted to maintain, the contact 8 is closed to stop the oil burner. While not shown in detail it will be understood that the electrically driven clock 51 serves to vary the setting of the room thermostat 30 to provide different day and night temperature in home heating service in the customary manner. When the room thermostat 3|! closes the running contact R, the A electromagnetic switch or relay is energized. As shown in Fig. 1 the A relay is energized from the low voltage secondary winding of the control transformer CT having the primary winding thereof energized from a suitable alternating current power source L L with the contacts of the low water cutofi switch 36 and also the safety plug switch 58 connected in the primary circuit. The safety switch 58 is arranged to be opened by the pressure relief door 59 in case an excessive pressure should develop within the combustion chamber ll of the oil burner i0; Likewise the low,water cutoff switch 36 opens in case the water in boiler l0 reaches a dangerously low level. However, upon the occurrence of either of these abnormal and unsafe conditions, the primary oi the control transformer CT is deenergized thus eifectively preventing further operation of the oil burner.

Under normal conditionsthe secondary winding or the control transformer CT is continu-' ouslyenergized and therelay A is energized therei'rom througha circuit which may be traced from the intermediate point B through contact R oithermostat 30 and thence through conductor W and the energizing winding of the electromagnetic relay A to the terminal S of the transf-iormersecondary winding. This results in operation of relay A to close both contacts A and contactsA. Contacts .A shunt the room thermostat contact R and connect the energizing windingoi relay Adirectly to the terminals R and S of the transformer, thus maintaining relay A continuously energized independently of the room thermostat 30.

Upon closure of contacts A an energizing circuit for the operating winding of relay C is closed provided the movable contact l5 of the flame detector I4 is in the cold position as indicated inFig. 1.

Normally the flame detector l4 operates its movable control contact 15 to the cold position quickly in response to the absence of combustion in the combustion chamber ill of the boiler I0. Relay C is energized from the supply line L through conductor l,the normally closed contacts of the pressure limit switch L,.conductor 2, contacts A conductor 3, the cold contacts of the flame detector l4, conductor 9, the winding of relay C and thence to the supply line L.

Upon the resulting operation of relayC, the normally open contacts C1 are closed and the normally closed contacts C2 are opened. -Contact C establishesan energizing circuit for the timing motor 42. This circuit is traced from conductor 3 which remains energized from the supply lineL as long as the contacts A and the limit contacts L remain closed, through contacts C and conductor 12, the energizingwinding of timing motor 42to the supply line L.

Thereupon the timing motor'42' begins to rotate the series of timing cams carried by theshaft 4|.

At the same time the opening of the normally closed contact C prevents energlzation of the holding circuit of the oil valve operating electromagnet I8, this circuit being traced from the supply line L through the safety door switch oil burner control.

As indicated in' the sequence chart of Fig. 2,. there is a considerable interval a of time after the starting of the timing motor 42 before the v sequential operation/oi the timing cam switches begins.

transformer closes it contacts to energize the primary winding of the ignition transformer IT, the circuit extending from the conductor 3 which remains energized as previously pointed out through the contacts of the'cam switch I, the primary of the ignition transformer to the supply line L. The cam contact I remains closed to maintain the spark ignition electrode l2 energized from the high voltage secondary winding of the ignition during almost the entire starting cycle oi the oil burner. This insures that any oil supplied from the nozzle II at any time during At the end of this interval a the cam I this cycle is ignited. This insures that ignition is always present to ignite any all delivered from the oil burner nozzle II at any time during the starting cycle. i a

After a relativelyishort timeinterval b, the cam F operates to close its contact and establish a circuit preparatory to. energizing the start winding of the oil burner motor. After a longer time interval 0, cam B operatesto close its con-- tact. Thereupon an energizing circuit for the relay B is established. This circuit is traced from conductor 3 which remains energized from the supply line L, as previously pointed out. through contact- C conductor 12, cam contact 12', and thence through conductor 13 and the energizing winding of the operating electromagnet of relay B. Relay B responds to close both of its contacts B}, B". Upon closure of contact B both the start and the run windings or the oil burner motor are energized. The circuit for the running winding is traced from the conductor 3 which remains energized from supply line L under normal conditions through the relay contact B conductor 4 and thence through the run winding to supply line L. The energizing circuit of the start winding extends from condoctor 4 through the-previously closed cam contact F, conductor 5, and thence through the start winding to supply line L. The oil burner driving motor immediately starts operation of the oil and air" pumping means to pump oil and air under pressure into the tank 22 and to supply air from the blower 25 to the combustion cham- During the interval (1 the oilburner motor comes up to speed and operates with both the running and the starting winding energized. At the end of interval d cam F opens its contact to deenergize the starting winding and the oil burner motor continues at full speed operation with the run winding energized alone.

During theintervals d and e, the operation of the oil burner motor serves to build up full pres sure of the oil and air in the tank 22, at the same time theignition electrodes are in operation to provide a spark for igniting the oil. At

the end of interval e, the cam T closes its conmains closed since the conductor 12 is connected to conductor 3 through the cam contact T.

All that remains to be done to establish combustion conditions is to open the oil valve l1 only a safe amount of unburned oil is projected into the combustion chamber of the boiler ill in case for some unknown reason there is failure to establish combustion. The opening of the oil valve for this predetermined limited interval g is accomplished by the joint action of V the two timing earns 0 0". Cam 0 serves to close the energizing circuit for the operating electromagnet I8 01 the oil valve at the end of interfor a predetermined limited interval such that v the cam is moved into'e'ngagement with the spring contact 0 and the cam!) is moved into engagementwith the spring contact 0. Upon continued rotation of cm shaft 4| during the time preceding the end of interval, f, cams 0 I contact 0, the snap contacts 0 and theme and 0' serve to move the spring contacts 0 and O downwardly without, however, bringing these contacts into engagement. At the end of interval/,the cam O disengagcs the contact 0 and the latter. springs with a snap action into encasement with the contact 0; lit the end of interval a, cam 0" disengages the contact 0 and the latter springj out-of engflsement with contact 0 Thus contacts .and 0 remain .in engagement only for predetermined limited int'ervala. v m

The oil valve energizing; circuit .is traced from conductor 3, which'remainsenergized as before from-supply line H through the bottom spring through. directly the energizing winding of the valve operating electromagnetf ll to the supply linejL; Theelectromagnet it immediately oper- .atstn oa;ya1v II to admit oilunder pressure throughthe atomizlng nozzle" l'l into the combustionzchamber it, Under normal conditions u atomized; oil is. immediately ignited by the 'mally closed contact C. the electric heater 34 ;,.-.b'etwe en the ignition electrodes 12 thus m ms-mastic in the boiler. l4atonceresponds to the preeence'o'f oombu'stion and starts to operate its controlflcoritaetfifrom the cold'side to the hot side ;theinitial movement of the flame detectorfjeohtact from the cold-side, the energizing circuit of relay Cis' interrupted. Thereupon,

contact Ci opens and contact C is reclosed. I j Upon reclosure of'contact C the holding cir'J-L cuit for "the oil valve operating electromagnet I. is reestablished through the circuits previously as extending from the supply line L! throughthe safety door switch contact 50, the low water 'cutoi! switch 36, the conductor I, the limit switch L, the conductor 2, the contact A, conductor 3, the contact B conductor 4, the norof the low water cutoff switch and thence through the energizing winding of the valve operating electromagnet I. to the supply line U. It is important to note that the inclusion of the heater or resistor 84 in this holding circuit serves to .prevent effective reenergization of the electromagnet I 0 after a voltage failure. Due to the voltage drop in the resistor 34, the reenergization of electromagnet fl is not suflicient to attract the armature thereof and reopen the oil valve. Hence after such a voltage failure, the only way the valve can be reopened is to fully reenergize the magnet ll through the energizing circuit as previously'described.

The reestablishment of the holding circuit for the oil valve operating electromagnet I8 provides an additional period for maintaining the oil valve open simultaneously with operation of the other elements of the oil burner mechanism after the limited combustion establishing period provided by the closure of cam contacts 0 O and the reopening thereof. These contacts are opened by operation of the cam O to move the lower contacts 0 away from the upper contacts 0 at the end of the predetermined limited combustion establishing period a. In this way the mostat 3 I.

oil valve is maintained open while the contacts of the flame detector I4 is moving from the cold side' to the hot side as the flame detector continues to progressively respond to the presence of combustion in the combustion chamber I3. However, the movable contacts of the flame detector must reach the hot side before the expiration of the additional interval 71. during which the B cam contact is maintained closed. Since the flame detector i4 is of the'quick acting type, it is able under normal operating conditions to move from the cold side during the interval a and reach the hot side before the end of the additional interval h. As'soon as the movable contact of the flame detector I4 reaches the hot side, an entirely new and independent energizing circuit for relay B is established. This circuit is traced from conductor l which remains energized as before through the movable contacts of the flame detector. in the hot position, conductor 14, the contacts B which are closed upon initial closure of the relay B and the operating. winding of relay B to the supply line L. The independent energizing circuit for the relay B Just traced serves to insure continued operation of the oil burner motor and the oil valve opening independently.

This establishment of the independent energizing circuit for the relay B through the hot side .of the flame detector contacts as just traced serve to continue operation of the'oil burner motor with the oil valve opened independently, of-further operation of the timing control mechanism as long as combustion is maintained in the combustion chamber l3 and contact A remains closed. However, the timing control motor 42 continues to operate during the interval 2' at the end of which the ignition cam contact is open to deenergize the ignition transformer and at the end of the final interval 7' the cam contacts T open to vdeenerg'ize the. operating winding of the timing motor 42. with the timing shaft 4| and all of the timing cams thereon start" position.

returned to the initial Upon operation of the oil burner long enough to cause the boiler III to supply suflicient heat to the room heating radiator system to satisfy the room thermostat 30, the room thermostat operates to close on contact S and stop further operation of the oil burner. Upon closure of contact S the operating winding of relay A is short circuited and thereby deenergized. Thereupon the contacts A A are open. Upon opening of contact A conductor 3 is disconnected from the supply line L and all elements of the oil burner mechanism and control are deenergized. At the same time, the opening of contact A disconnects the relay winding A from the mid-terminal R of the control transformer CT. The flame detector l4 quickly returns its movable contact ii to the cold position in response to the absence of combustion in the combustion chamber I3. Thus the oil burner and control mechanism is in its initial condition ready for a new start whenever the room thermostat 30 again closes on contact R to run the oil burner.

The boiler water temperature thermostat 3| functions to mechanically close the contact A whenevertheboiler water temperature falls below a predetermined value. At the same time the vacuum relief valve 31 is opened by ther- Exactly the same sequence of the starting control operations are accomplished upon mechanical closure of the contact A as previously described when A was closed by enture thermostat 3 I.

ergizing the operating winding of the relay A under the control of the room thermostat 30. In this case the boiler water thermostat 3| mechanically opens the contacts A when the operation of the oil burnerv has been continued long enough to raise the boiler water temperature to the value at which the thermostat II is set to operate. As previously pointed out, water thermostat 3| permits the oil burner boiler to be operated in the summer time to supply all domestic hot water heating requirements under the control of the boiler water tempera- However, at any time, winter or summer, that the room temperature falls below the value at which the room thermostat is set to close the contacts R, the oil burner will automatically operate to supply heat to the house heatingradiator system. The operation of the vacuum relief valve 31 by the boiler water temperature thermostat 3| eiiectively prevents a supplyof heat in a vapor system to the house heating radiators when the oil burner is operated under the control of the domestic hot water control thermostat. It will be understood that the thermostat 3| may, if desired, be arranged torespond directly to the temperature of the water in the domestic hot water storage tank instead of the temperature of the water in the boiler.

When it is desired to shut down operation of the oil burner for any considerable length of time, the main supply lines L L are disconnected from the source of power by means of a suitable disconnecting switch (not shown). This deenergizes all of the oil burner operating and control apparatus. During such a shutdown interval, ambient temperature changes may occur in combustion chamber l3 such that the contion.

detector l4. Thus upon closure of switch M relay C is energized and the normal cycle of operation previously described up to the end of interval g is accomplished. However, in case the switch M is maintained closed after the end of interval y, it will be impossible for the flame detector i l to effect deenergization of the relay C so as to return the contact C to the closed position and establish a holding circuit for the oil valve in the manner previously pointed out in case flame is established. Hence the oil valve holding circuit will remain open and the oil valve will close at the end of interval 9. This cuts off the supply of oil and stops combustion inthe furnace. However, upon release of the switch M after the interval g, the oil burner control mechanism will start a new cycle under normal conditions so that the next time combusagainst the following dangerous or abnormal conditions.

If the oil fails to ignite during the limited period g during which the oil valve is opened by operation of the cams O 0, the flame detector contact will not leave the cold position and the oil valve will reclose at the end of period g. The oil burner motor 2| will continue to run until disconnected by opening ,of cam contact B at the end of interval 11. which in turn opens the contact B The operation of the timing motor 42 continues to complete its cycle. In so doing the arm 80 which is carried by the cam shaft 41 engages with the upper tooth of the lookout ratchet member iii to lift this member .one notch. As long as the C relay remains energized due to the flame detector remaining in the cold position, the spring latch 32 serves to engage the first notch on the ratchet member ill and maintain it in the advance position. As

long as the contact A is maintained closed by either the room thermostat or by the water thermostat 3!, the cam motor 42 continues to operate and start a new cycle. If flame again fails to be established during the limited interval 9, the arm 80 engages the next tooth on the lockout ratchet 8| and advances this member another notch. Upon completion of the third cycle, the lookout ratchet 81 is advanced to bring the finger 83 into engagementwith the arm 84 extending from the contact C so as to open this contact. Thereupon the energizing circuit for the timing motor 42 as previously traced. is interrupted and the oil burner mechanism is rendered inoperative until the difliculty causing the failure of establishment of combustion is corrected.

In case combustion is established during either the second or the third attempt, the flame dej tector l4 moves from the cold position and thereby deenergizes the relay 0. This disengages the locking pawl 82 from the ratchet member 8| and permits the latter to return to its initial position. It is evident that the lookout ratchet mechanism may be reset at any time by interrupting the main power circuit L L Whenever the boiler pressure exceeds the value at which the pressure responsive device 35 is set to open the limit contact L, the conductor 3 is disconnected from supply line L thus deenergizing all parts of the oil burner mechanism andcontrol. When normal boiler pressure conditions are restored, a new starting cycle will begin whenever the room thermostat 30 or water thermostat 3| calls for heat.

Should the boiler water level fall below a predetermined value, the contacts of the low water cutoff device 36 will be operated to disconnect the conductor I from the supply line L and thereby deenergize all of the equipment.

In a normal starting cycle, if combustion should be established at any time before the interval g, as mightoccur due to a leaky oil valve, protection against continued operation of the oil burner mechanism is obtained as follows:

As soon as flame appears in the combustion chamber 13, the flame detector moves its contact from the cold side, thus deenergizing relay C. Thereupon contact C is opened which in turn causes the timing motor 42 to be deenergized. The opening of contact C also deenergizes relay B, thus allowing contact B to open and stop operation of the oil burner motor 2i. As a result combustion is extinguished and the flame detector [4 again moves its contact to the cold side. Thereupon relays C andB are again energized and the starting cycle is resumed at the point of interlishing name and operation of the flame detector to stop the oil burner mechanism in the manner just described will be repeated and the cycle will again be interrupted. However, as

soon as the cam contact I has opened, as will .eventually happen if it is not open at the first occurrence of premature combustion, the oil burner motor II will not start since the starting winding is disconnected. This permits the timing motor 42 to continue the timing cycle without the oil burner motor operating. Continuation of the cycle will advance the lookout ratchet mechanism one notch. During the second cycle flame detection due to a leaky oil valve will again cause an interruption of the cycle but will not resetthe lockout mechanism because the second tooth of the lockout ratchet member Ii is in engagement with the actuating arm 80. The second cycle is completed in the same way as in a the first. In case the oil valve has cleared itself of the dirt or other obstruction causing leaking during the second or third cycle, premature combustion prior to the interval a will not be obtained and the normal starting sequence will result. However, incase the oil valve continues to leak the control will automatically lock out after three unsuccessful cycles. In the normal starting cycle, the lookout ratchet member II is reset by deenergization of relay C only during the oil valve opening period 9 when the flame detector leaves the cold contact.

Beginning a starting cycle before the flame detector contact hasreset to the cold side is prevented since the cam motor cannot start until contact C closes and contact C cannot close unless the flame detector is in the cold position.

If the starting cycle is interrupted by either voltage failure or by a change in setting of the water thermostat or room thermostat, the starting cycle will be successfully resumed at the point of interruption unless the interruption occurs after the cam contact 1" has opened. In this latter case a complete new starting cycle will follow the completion of the interrupted cycle.

While I have illustrated and described the improvements of the present invention embodied in a control adapted for steam or vapor oil fired boiler, it will be evident that substantially the samecontrol may be applied to a hot water boiler. The only variations are that the low water cutofi' is omitted and the pressure limit control II is replaced by a boiler water temperature limit control which functions to open the limit switch L in case the boiler water temperature reaches a dangerous value. In hot water systems, the heater of the low water cutoff device is replaced bya similar resistor which prevents reopening of the oil valve with the holding circuit energized upon a momentary voltage failure.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. In combination with an oil burner having an electric oil and air supply motor and an electric igniter, of a normally closed electromagnetic oil valve for preventing combustion and having an energizing circuit for opening the valve and a holding circuit for maintaining the valve open, an electric motor driven timing switch mechanism for operating said motor and igniter for a predetermined period of time and for closing the said energizing circuit of said electromagnetic oil valve for a limited period of time intermediate the period of operation of said motor and igniter, and combustion responsive switching means effective during absence of combustion to render' v said electric motor driven switch mechanism operative and effective upon establishment of combustion during said limited period of time for closing said holding circuit of the said electromagnetic oil valve and for maintaining said oil and air supply motor in operation independently of said timing switch mechanism.

2. In combination with an oil burner mechanism, of controlmeans for operating the oil burner mechanism for a limited period to attempt to establish combustion, combustion responsive means having a movable control member operable from one position to another position upon establishment of combustion, and means controlled by said member for continuing operation of said oil burner after said limited period and having one element rendered effective upon. the initial movement of said movable control member from said one position during said limited period to continue operation of said oil burner for an additional interval and another element rendered eifective upon the final movement of said movable control member to said other position during said additional interval for continuing operation of said oil burner mechanism thereafter.

3. In combination, an oil burner having a plurality of elements operable to establish combustion, a portion only of said elements being operable to continue combustion thereafter, control means for effecting concurrent operation of said elem'ents only for a predetermined limited period to attempt to establish combustion, means responsive to combustion, means rendered effective upon the initial response of said combustion responsive means to establishment of combustion during said predetermined period for thereafter maintaining simultaneous operation of said elements for an additional period, and means rendered effective upon response of said combustion responsive means to combustion during said additional period for maintaining said portion of said elements in operation to continue combustion thereafter.

4. In combination with an oil burner mechanism, of control means for operating the oil burner mechanism for a limited period to attempt to establish combustion, means responsive to combustion, means rendered effective upon the initial response of said combustion responsive means to establishment of combustion during said limited period for continuing operation of said'oil burner after said period and means rendered eifective upon response of said combustion responsive means to combustion after said period for stopping operation of said oil burner in response to failure of combustion.

5. In combination with a burner mechanism, of timing means for initiating operation of said burner mechanism and continuing operation thereof for a predetermined limited period to attempt to establish combustion, means responsive to combustion and having a movable control member operable from one position to another position in response to the presence of combustion and operable from said other position to said one position in response to absence of combustion, means rendered effective upon the initial movement of said movable control member from said one position in response to establishment 01' combustion during said predetermined period for thereafter maintaining said burner mechanism in operation for an additional period, and means rendered effective upon movement of said movable control member to said other positionwithin said additional period for thereafter maintaining said burner mechanism in operation and for stopping operation of said V burner mechanism upon the initial movement of combustion during said limited period for continuing operation of said devices to continue combustion only for an additional limited period of time, and cooperating control means depend ent upon maintenance of combustion during said additional period and thereafter for continuing operation of said devices to continue combustion.

7. In combination with an oil burner mechanism, of timing control means for operating the oil burner mechanism for a limited period, a

-normally closed oil valve for preventing combustion, control means associated with said timing control means for opening said oil valve and maintaining said valve open only for a predetermined limited interval during the period of operation of said oil burner mechanism, means responsive to combustion, means rendered effective upon the initial response of said progressive means to establishment of combustion during said limited interval for maintaining said oil valve open for an additional interval during the period of operation of said oil burner mechanism, and means rendered effective upon response of said combustion responsive means to the continuance of combustion during said additional interval for maintaining said oil burner in operation and said valve open to continue combustion thereafter.

8. In combination with anoil burner having electric motor driven oil and air pumping means, of control means including a timing device for operating said pumping means for alimited period, a, normally closed oil valve for preventing the supply of oil to the burner, control means associated with said timing device for opening saidoil valve and maintaining said valve open only for a predetermined limited interval during said limited period of operation of said pumping means, combustion responsive means having a movable control member operable from other position to said one position upon extinguishment of combustion, means rendered effective upon the initial movement of said movable control member from said one position during said predetermined limited interval to maintain said oil valve open for an additional interval during said limited periodof operation of said pumping means, and means rendered effective upon the final movement of said movable control member to said other position during said additional interval for maintaining said pumping means in operation and said valve open after said period and for reclosing said valve upon the initial movementof said member from said other position in response to failure of combustion.

9. In combination with an electric motor oper guishment of ated oil burner mechanism, a control system including in circuit said mechanism, a main control switch closed in response to a demand for heat, a switching means including an electric motor driven timing mechanism for operating the oil burner mechanism at recurring intervals to at tempt toestablish combustion upon closure of said main switch, combustion responsive means having a movable switch member operable from one position to another position upon establishment of combustion to stop said timing mechanism and to continue operation of said oil burner I mechanism thereafter and operable from said other position to said one position upon extincombustion, electroresponsive switching means normally dependent upon oper ation of said switch member to said one position for initiating operation of said electric motor driven timing mechanism, and a normally open manually operable switch forcontrolling said electroresponsive switching means to initiate operation of said electric motor driven timing mechanism independently of the position of said movable switch member.

10. In combination with an oil burner-mechanism, of combustion responsive means having a movable control member operable from one position to another position upon establishment of combustion and operable from said other position to said one position upon extinguishment of combustion,.control means for the oil burner mechanism including timing means normally dependent upon operation of said member to said one position for effecting operation of the oil burner mechanism at recurring intervals to attempt to establish combustion, an auxiliary control member operable from one position to a second position for: effecting operation of said timing means independently of the position of said first member to attempt to establish combustion for an interval, and means dependent upon return of said auxiliary control member to said second position for continuing operation of said timing means after said interval.

11. In combination with an oil burner, of combustion responsive means having a movable control member operable from one position to another position upon establishment of combustion and operable from said other position to said one position upon extinguishment of combustion, control means for the oil burner including timing means normally dependent upon operation of said member to said one position for effecting operation of the oil burner for a. limited period to attempt to establish combustion, an auxiliary movable control member operable from one position toa second positionfor initiating operation of the controlmeans to attempt to establish com bustion when said first control member is away from said one position, and means cooperating with said timing device and dependent upon return of said first member to said one position and return ofsaid auxiliary controlmember to said one position for continuing operation of said oil burner mechanism when combustion is estab- Jished in response to operation of said auxiliary control member.

12. In combination with an oil burner having electric motor operated means for supplying oil and a normally closed oil valve for preventing the supply of oil, of control means operable for starting and stopping operation of said electric motor driven means and having a timing device for opening said oil valve and maintaining said valve open only for a predetermined limited period during operation of said first means and combustion responsive means for controlling operation of said control means to stop said electric motor operated means upon establishment of combustion due to leaking of said oil valve prior to said limited period.

' 13. In combination, an electrically operated oil burner mechanism including a plurality of sepathe energization of said separately operable elements of the burner mechanism in a predetermined sequence, and connections whereby said electrically operated timing. switch mechanism is energized under the control of said plurality of automatically operable master control and safety switches to start combustion and said electromagnetic switch is maintained energized thereafter independently'of said timing switch to continue combustion under the control'of said plurality ofautomatically operable master control and safety switches.

14. In combination with an automatic burner having a plurality of electrically controlled elements jointly operable for establishing combustion, of means including a timing control switch mechanism having an electric driving motor controlled by said switch mechanism after a predetermined operation thereof from an initial position for insuring continued operation of said switch mechanism through a complete cycle to elect operation of said burner elements in a predetermined sequence-providing a limited period of joint operation thereof, combustion responsive circuit controlling means, master circuit controlling means operating jointly with said combustion responsive means for energizing said electric motor to operate said switch mechanism from said initial position in response to predetermined conditions dependent upon the absence of combustion, and circuit connections controlled by said combustion responsive means for stopping saldjtiming control means in said initial position when combustion isestablished and for maintaining a predetermined portion of said elements in operation to continue combustion thereafter.

15. In combination with an automatic burner of timing control means operable from an initial position through a complete cycle for electing operation of said burner mechanism toestablish combustion, combustion responsive means, master control means operating jointly with said combustionresponsive means for starting said timing control means to operate from said initial position in response to predetermined conditions dependent upon the absence of combustion, and means controlled by said combustion responsive means for stopping said timing control means in said initial position when combustion is established and means controlled by said combustion responsive means for maintaining said burner mechanism in operation to continue combustion thereafter.

16. In combination with an automatic burner mechanism, of means including a master control and a timing device operable by said master conposition through a complete cycle for starting the burner to attempt to establish combustion, combustion responsive means electiveupon establishment of combustion to maintain the burner in operation to continue combustion thereafter independently of said timing device and a plurality of means for stopping said timingdevice in said initial position, one dependent upon establishment of combustion and another dependent upon failure to establish combustion,

17. In combination with a burner device having a plurality of electrically controlled elements jointly operable for establishing combustion, of means including a master control and an electric -motor driven timing switch mechanism having the motor energized in an initial position under the control of said master control switch to operate the timing control switch mechanism from said initial position through a complete cycle for electing operation of said elements in a predetermined timed sequence providing a limited period of Joint operation thereof to establish combustion,

combustion responsive means elective upon establishment of combustion to maintain a portion of said elements in operation to continue combustion thereafter independently of said timing switch mechanism, and a plurality of means for deenergizing said motor with said timing control switch mechanism in said initial position, one dependent upon establishment of combustion and another dependent upon failure to establish combustion.

18. In combination with an automatic burner having a plurality of electrically controlled elements jointly operable for'establishing combustion, of means including a master control and an\ electric motor driven timing switch mechanism having the motor energized in an initial position under the control of said master control switch to operate the timing control switch mechanism from said initial position through a complete. cycle for electing operation of said elements in a predetermined timed sequence providing a limited period of joint operation thereof to establish combustion, combustion responsive means for maintaining a portion of said elements in operation to continue combustion independently of said timing switch mechanism upon establishmentthereof, and a plurality of means for deenergizing said motor with said timing control switch mechanism in said initial position, one dependent upon failure to establish combustion during a predetermined number of cycles of operation of said timing switch and the other dependent ,upon establishment 'of' combustion during said predeterminned number of cycles.

19. The combination with a burner having a fuel supply means, an igniter and a normally closed fuel supply valve, of control means including a timing device for operating said fuel supply means and igniter for a predetermined interval and for opening said fuel supply valve and maintaining said valve open to establish combustion. conditions only for a predetermined limited:

supply means, means for igniting fuel supplied to the burner and separately operable means for controlling the supply of fuel from said fuel supply means to the burner, of means including a timing device for rendering said fuel supply means andsaid igniting means operative for a predetermined interval of time and for effecting the operation of said fuel control means during a predetermined intermediate part of said predetermined interval to establish combustion conditions, and combustion responsive means effective upon establishment of combustion during said intermediate part of said interval for thereafter maintaining both said fuel supply means and said fuel control means operative to supply fuel to the burner independently of said timing device.

21. The combination with an oil burner having an electric motor driven oil and air pumping means, an electric igniter for the oil, and a normally closed electrically controlled oil valve for preventing the suppy of oil from said pumping means to the burner, and automatic control means including a main control switch operable in response to predetermined conditions, and an electrically operated time switch mechanism controlled thereby for energizing said oil and air pumping means and said igniter for a limited period and for energizing said oil valve for a predetermined part of said limited period after said oil and air pump means and ignition means have been energized, and combustion responsive switching means effective upon establishment of combustion during said part of said limited period for maintaining said motor driven oil and air pumping means and said oil valve energized indecombustion responsive means effective upon establishment of combustion during said limited period for closing said holding circuit.

23. The combination with an oil burner having an electric motor driven oil supply pump and an igniter. of a normally closed electromagnetic oil valve for preventing the supply of oil to the burner and having an energizing circuit for opening the valve and a holding circuit for maintaining the valve open, a resistor in said holding circuit for preventing reopening of the valve after a temporary voltage failure, circuit controlling means for energizing said oil supply motor and igniter and having a timing circuit control means for closing said energizing circuit only for a limited period after the initial energization of said oil supply motor and igniter, and combustion responsive means effective upon establishment of combustion during said limited period for closing said holding circuit.

24. In combination with a burner mechanism operable to establish combustion, of combustion responsive means operable in response to both the presence and absence of combustion, control means normally dependent upon operation of said combustion responsive means in response to the absence of combustion for initiating operation of said burner mechanism, and an auxiliary control means for effecting operation of the first control means to initiate operation of said burner mechanism upon failure of said combustion responsive means to respond to the absence of combustion.

25. In combination with a burner having fuel supply means and a normally closed valve for preventing the supply of fuel to the burner, of control means including a timing device for operating said fuel supply means and for opening said fuel valve and maintaining said valve open only for a predetermined limited period during operation of said first means, and means including a combustion responsive-device for controlling said control means upon establishment of combustion due to leaking of said fuel valve prior to said limited period to prevent continued operation of said fuel supply means.

26. In combination with a burner having electrically operated fuel and air supply means and an electrically operated ignition means, of a control system therefor including an automatic control switch responsive to predetermined conditions'controlled by the burner, an electromagnetic switch, an electric motor driven timing switch having a plurality of contacts operated in a predetermined timed sequence, a combustion responsive switch, and circuit connections whereby said electric motor driven timing switch is energized under the control of both said automatic control switch and said combustion responsive switch to operate one of its contacts to effect operation of said electromagnetic switch and other of its contacts to effect jointly with said electromagnetic switch operation of said fuel and air supply means and ignition means for overlapping definite time intervals to establish combustion and whereby both said combustion responsive switch and said automatic switch controls said electromagnetic switch independently of said timing switch to continue only operation of said fuel and air supply means after said intervals upon establishment of combustion until either combustion fails, said automatic switch operates or voltage fails.

27. In combination with an electrically operated oil burner having an igniter, an electromagnetic oil valve and a burner motor provided with, a starting and a running winding, of an electromagnetic switch for controlling energization of said running winding, an electrically operated time switch-having contacts operated in a predetermined sequence for controlling energization of said electro-responsive switch, said igniter, said oil valve, and said starting winding, a combustion responsive device, and means automatically responsive to a predetermined condition control by the burner cooperating with said combustion device for controlling the energization of said time switch to operate the burner to start combustion and for controlling energization of said electromagnetic switch independently of said time switch to maintain the running winding of said motor energized after combustion is established.

28. In combination with an oil burner having an igniter and a burner motor provided with a giaingthe driving motor ofsaidtime switch to start operation of the burner and effective in the presence of combustion to maintain said electromagnetic switch energised independently of said time switch, and means preventing reenergimtion .of said electromagnetic switch independently of said time switch after a voltage failure during the presence of combustion. v

29. In combination with an oil burner having electrically controlled fuel supp y means and an electrically controlled igniter, of an electrically operated timing switch mechanism having a separately operable electro-responsive switch energined thereby and cooperating therewith for con-. trolling operation of said fuel supply means and igniter to attempt to establish combustion during a limited time interval, means including a combustion responsive switch and a thermostatic switch for controlling said electrically controlled timing switch mechanism to energize said electrically controlled fuel supply means and igniter to establish combustion, connections whereby upon establishment of combustion said combustion responsive switch and said thermostatic switch JOHN EATON.

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