US2616490A - Fuel burner safety control apparatus - Google Patents

Description

1952 J. M. WILSON EI'AL FUEL BURNER SAFETY CONTRQL APPARATUS Filed Fab. :5, 1949 INVENTOR. JOHN M. WILSDN 'RICHARD S- FEWN- Patented Nov. 4, 1952 UNITED STATES PATENT OFFICE FUEL BURNER SAFETY CONTROL APPARATUS corporation of Delaware Application February 26, 1949, Serial No. 78,592

Claims. 1

The present invention is concerned with an improved control apparatus for a fuel burner and more particularly an apparatus with greater flexibility to make the same readily adaptable for universal use on fuel burners, particularly those of the industrial type.

In many present day fuel burner installations, the burner is provided with an electric ignition device, a gas pilot valve, a blower motor, and a main fuel valve. To insure maximum safety with this type of burner, it is necessary to control the operation time or sequence in which the burner and its components become effective. This involves purge timing, opening the main fuel valve only after the pilot flame has been established, delaying opening of the main fuel valve until a timed period after the blower operates, and delaying the deenergization oi the ignition device and pilot valve until after the main feul valve has been opened, or any combination of the above as the specific installation may require. To obtain added safety, it is also necessary to provide shutdown upon a failure of components in the control apparatus or upon a failure of combustion at the burner.

The present invention contemplates accomplishing the above set forth type of control by a new and improved control apparatus that utilizes to best advantage electronic control devices to accomplish the desired timin and safety functions. The electronic devices are utilized in the timing circuit and in the flame detection circuits and this lends quick and positive response to the type of control desired. Three distinct timing periods are obtainable from the electronic timing device and these include delayed fuel valve opening, delayed ignition cutoff, and a blowout timing following burner operation. This is accomplished by utilizing a filament heater timing circuit and a resistance capacitance timing circuit, the former being utilized in the delayed fuel valve opening and the blowout timing while the latter is utilized for the ignition timing.

Checkin pilot and burner operation is an electronic flame detector that utilizes a flame rod for pilot flame detection and a photocell for main flame detection. Circuits of the timer and the flame detector are associated with a safety cutout device which is arranged to render the con trol apparatus inoperative whenever there is a flame failure, a false indication of flame when the apparatus is inoperative, or upon the electronic timer failing to operate when the apparatus comes into operation.

It is therefore an object of the present invention to provide an improved burner control apparatus having an electronic timing device for providing delayed fuel valve opening, delayed ignition cutoff, and blowout timing following burner operation.

A further object of the present invention is to provide a burner control apparatus having an electronic timer utilizing the time delay of heating and cooling of the timer for obtainin delayed fuel valve opening and blowout timing.

A still further object of the present invention is to provide an apparatus having a safety checking circuit which will render the apparatus inoperative upon a flame failure, upon a false indication of flame, or upon the timing apparatus failing to operate upon a demand for burner operation.

Another object of the present invention is to provide an improved burner control apparatus with a limit control device associated therewith having an electronic flame detection circuit and arranged so that when the limit control apparatus is operative, the burner is rendered inoperative by interruption of the power supply to a portion of the control apparatus but not that supplied to the flame detection circuit.

These and other objects of the present invention will be understood upon a consideration of the accompanying specification, claims and drawing of which:

The single flgure shows diagrammatically the control apparatus and the manner in which it is associated with a fuel burner and its associated operatin components.

Referring now to the single figure, the numeral I 0 represents a blower motor which may be used to supply air to the combustion chamber of the fuel burner. A solenoid valve II and a motor operated valve l2 control the flow of fuel through a conduit l3 which conduit may conduct the fuel to a point where it will be atomized by the air originating from the blower motor It. A pilot assembly l4 comprises a gas pilot nozzle IS, an ignition electrode l6 and a flame electrode I! for detecting the presence of the pilot flame. A flame stabilizer and grounding element in the form of a pair of crossed fins is mounted on the end of nozzle [5. These fins stabilize the pilot flame against cross drafts and allows the flame to' make a good electrical contact therewith. A projected end view is shown above the nozzle l5. Controlling the flow of fuel to the pilot nozzle 15 is a solenoid operated valve [8. The ignition potential for the ignition electrode i6 originates at an ignition transformer i9. Detecting the presence of the main burner flame is a photocell indicated by the numeral 20.

Located within a housing indicated generally by the numeral are the control circuits for the various components associated with the fuel burning device. These control circuits may be brought into operation by any suitable device which is operative upon the need for burner operation. This device may be a thermostat such as has been indicated by the numeral 2! and which may be located in a separate enclosure Whenever the thermostat 21 indicates a need for burner operation, the electrical circuits located within the housing 25 will be effective to energize the blower motor, energize the pilot assembly to establish a pilot flame, check the presence of the pilot flame, open the mainfuel valve after the pilot flame has been checked and a predetermined time has elapsed a primary winding 4! connected to a common inputsource of .power and a secondary-winding 42 wvhichis tapped at 43." The primary winding may 'be connected to the input power line through'a plurality of limit control devices that may be associated with the fuel burner," These limit control devices may be a low water-"cutoff 45,-a high limit cutoff lt and a fuel temperature responsive thermostat 31;

Whenever any oneof 1 these limit controls is operative it is impossible to complete an energizing circuit to the primary 4| of transformer 50. 'Obviously, any one or all of the limit controls could be dispensed with should a particularinstallation not-require such.

Associated with-the energizing circuit for-the main control relay 3!] is a safety cutoff device 53 which comprises a bimetallictiming element 5i, a pairof switch contacts 52 and 53, a resistance heater 54 and a reset actuator 55.] When the I heater -53has beenenergized for a predetermined length of time, the bimetal 5| will be warped from its normalposition so that the contacts 52 and 53 will break contact to open the energizing circuitand holding circuit for the main control relay 3ilj Depressing of the reset actuator 55 will close the contacts 52 and 53 if the bimetal 5| has returned to its normal position. A resistor 56 is associated with the safety cutout device-in the main control relay for current limiting .purposes."

The" numeral 60 represents the electronic timing' portion of J the subject control apparatus. Supplying power'to this timer-is an alternating current'transfo'rmer 6i having a primary winding- 62 and a plurality of secondary windings 63,

64 and 35.' Also includedin the timing apparatus are t'a' pair of electron discharge devices 66 and 61. The discharge device 66 comprises an anode 68, a control electrode 53, and a cathode 73 which is heated'indirectly to be electron emissive by a filament type heater "II. The discharge device 6! comprises an anode 12, a control electrode' 'l-3, a cathode 73, the latter being. heated to be electron emissive by a filament type heater I3. In the plate circuit of the discharge device 66 is a control relay having a relay winding BI, and switch blades 82, 83, 84, and 86 normally biased as shown by means not shown. The switch blade 82 is normall biased into engagement with an associated switch contact 31. The switch blade 83 is normally biased into engagement with switch contact 83 and when the relay winding 8| becomes energized the switch blade 33 moves into engagement with an associated contact 83. Switch blade 34 is normally biased into engagement with switch contact and, when the relay winding 8| becomes energized, the blade 84 will move out of engagement with contactiiil. Switch . blades 35 and 86 are associated with switch contacts ill and 92 respectively and are normally biased out of engagement with their respective contacts when the relay'winding 8| is deenergized.

Associated with the input of triode 61 are a potentiometer 33 and atiming condenser 94. Associated with the anode circuit of discharge device 37 is a further control relay- 96 having a relay winding el which-is by-passed" by a suitable bypass-"condenser- 98, and a plurality of switch blades 93, I30 and IllI. When the relay windin 31 1s deenergized, the switch blades 99; I00 and-19L are normally biased into engagement witlrcontacts I32, J03 and lfi ir respectively 'by' means-not shown. When the relaywinding '97 becomes energized-the switch" blade 39 "moves into engagement rwith an associated switch contact- I35.

The electronic-name I detection. portion of the. apparatus is indicated by the numerall II); This flame detection apparatus -is substantiallywthe same as the FlameDetection Apparatus shown in vRichard S.-Feigal-Patent-2,556,961. For a complete understanding of thecperation of the flame detection apparatus, reference should be made to thiscopendingapplication. This detection apparatus includes an alternating source of power comprising a transformer III having a primary windingv II2, connected to the common source of power, and a secondary winding --II3 which is tapped at II 3. I Also included. in the flame detection apparatus'area pair of electron I discharge devices H5 and I 9 I3. The discharge device II5 comprises an anode 1 ISA, a control electrode I I1, and a cathode III] which is heated to be electron-emissivelby a suitable filament type heater-II9, continuously connected to a source of power, not shown. Connected tothe input of this discharge device is a filter network comprising a resistor i223,- a condenser I2I,and' a further resistor I22. Also associated with the in put of this discharge device is a condenser I23 which is directly associated with the flame detecting elements of the apparatusiincludingthe photocell 23 and the flame rod I.'I.

'T'heelectron discharge-device I It comprises an anode'i'25, a control electrode I26, and a. cathode- I27 which is heated to be electron emissive by a suitable filament type heater I23, continuously connected to a source-of power, not. shown; Located on theinput'of triode I I6 are a pair of resistors I29 and I33. anode circuit of the discharge device H3 is a control relay- I35 having the relay winding I36, bypassed by a suitable by-pass condenser I31;

and a pair of switch blades I38 and I39 which are normally'biased out of engagement with their associated switch contacts ME) and MI respectively, and when so biased switch blade I38 will a be engaging a further switch contact I42.

Located in the output or Associated with the energizing circuit for the main control relay 30 is a switch operated by the motorized valve I2. This switch I45 is operated by a motor I46 whenever the motor has moved the valve assembly to the low supply position. The switch is utilized to ensure that the main control relay 30 cannot be energized until the motorized valve 12 is in the low fuel supply position.

In order that various modes of operation may be obtained from the subject apparatus, a switch I41 is provided. This switch comprises a blade I 48 and a plurality of contacts A, B and C certain of which are electrically connected to terminals in the control apparatus. The blade I48 connects to a terminal I56, the contact A connects to a terminal I52 and the contact connects to a terminal II. The switch I41 may be dispensed with if it is desired to make permanent connections between the terminal I50 and the terminals I5I or I52.

Operation In considering the operation of the subject apparatus it will be assumed that the controls and components associated with the fuel burner are all in the deenergized position as they are shown upon the drawing except with blade I48 of switch I41 engaging contact B. When in this position, there will be no pilot flame, main flame, or blower motor operation.

Assume now that the space wherein is located the thermostat 21 begins to cool and that the contacts 21W and 21B are engaging the switch blades of the thermostat 21. The switch contact 21W closes before the contact 21B. This arrangement of the contacts is arranged so that contact 21B is used only as a start circuit. Once the circuit it is designed to complete is complete, a holding circuit is established through contact 21R independent of contact 21B. Thus any chattering tendencies of contact 213 will not affect the circuit associated with the thermostat once that it has become energized.

The energizing circuit completed by the closing of the thermostat 21 is the energizing circuit to the main control relay 30. This energizing circuit may be traced from the upper terminal of the secondary 42 through conductor I60, relay winding 3|, switch contacts 21W and 2113, conductor I6I, end switch contacts I45, conductor I62, switch contact 90, switch blade 84, conductor I63, switch contact I42, switch blade I38, conductors I64 and I55, heater 54, switch contacts 52 and 53, and conductors I66 and I61 to the lower terminal of the secondary 42. It will be noted that this energizing circuit for the relay 30 was completed through deenergized contacts of the timing relay 80, the flame detection relay I35 and the low position indicating end switch of the motorized valve I2. As soon as the relay 30 becomes energized, a holding circuit is completed for this relay and this holding circuit may be traced from the upper terminal of secondary 42, conductor I60, relay winding 3|, switch contacts 21W, contact 21R, conductor I 68, switch blade 32, switch contact 33, conductor I69, voltage dropping resistor 55, conductor I65, heater 54, contacts 52 and 53, and conductors I66 and I61 to the lower terminal of secondary 42. This will mean that the control relay 30 will now be energized independently of contact 21B of thermostat 21 and will not be subject to any chattering tendencies of the thermostat contact 2113.

When therelay 30 has become energized, an

energizing circuit is completed to the blower motor I0 through contacts of the relay 30. This energizing circuit may be traced from the input power line I18, conductor I12, limit controls 45, 46 and 41, conductors I13 and I14, switch contacts 38, switch blade 34, conductor I15, switch blade 35, switch contact 39, conductors I16 and I11, blower motor I 0, conductors I18 and I19 back to the other input power line "I. With the energization of the blower motor, the blower will come into operation and will be forcing air into the combustion chamber of the burner. This air will be available for the combustion purposes in the associated furnace.

Also energized at the same time that the blower motor I0 is energized are the pilot valves I8 and the ignition transformer I9. Inasmuch as the pilot valves I8 and the ignition transformer are effectively connected in parallel, the circuit to both of the components may be traced as follows: from input power line I10, through conductor I12, limit controls 45, 46, 41, conductors I13 and I14, switch contact 38, switch blade 34, conductors I80 and I8I, switch blade IBI, switch contact I04, conductor I82 to the pilot valve' and ignition transformer and conductors I83 and I19 back to the other input power line I1I. With the energizing circuit completed tothe pilot valve I8 and ignition transformer I9, the pilot valve will become energized and will open and the ignition transformer will be conditioned so that it will be able to energize the ignition electrode I6 through conductor I84. With the ignition electrode I6 energized, there should be a sparking at the end of the electrode between the electrode and the pilot nozzle I5. If there is gas coming to the pilot nozzle I5, this gas will be ignited and a pilot flame will be established.

Also established upon the energization of relay 30 is the energizing circuit to the filaments of the electron discharge devices of timer 60. The energizing circuit for these filament heaters of the discharge devices may be traced from the the flame detection device IIO will be operative to detect the presence of the pilot flame existing on the pilot assembly I4. In considering the operation of the flame detection device IIO, reference should be made to the above-mentioned copending application of Richard S. Feigal for a complete understanding of the same. Briefly, the apparatus is one which will detect the presence or absence of a flame by using the current rectifying characteristics of a flame. The apparatus is designed to indicate a flame only when there is a flame existing across the flame electrode I1 or a flame is being viewed by the photocell 20. Under a no flame condition, the discharge device Il5 will be normally conducting as the control electrode I I1 is effectively biased slightly positive with respect to the cathode since the resistor I20 and the parallel combination of the condenser HI and resistor I22 form a voltage divider across the lower half of secondary II3. With this, on the positive half cycle of the alternating power source'when the anode is positive, the control electrode I I! will be slightly positive with respect to the cathode I I9. Thiswill mean that the discharge device will be conductive and plate current will .flowin a circuit that may be traced from the center tap 'I'I I through conductor I9 I, resistor I30, conductor I92, anode IIISA, cathode H8 and conductor I93 to the lower terminal of the secondary I I3. With current flowing through the resistor I30, the. discharge device IIE will be biased to be effectively non-conducting since the upper terminal of the resistor I30 will be negative with respect to the lower terminal on the conductive half cycle of the discharge device IIS. With this negative bias on the discharge device IIB, there will be no current flow through the device-for energizing the flame detection relay I35.

When a flame is present, as when the flame electrode has a flame impinging thereon from the pilot nozzle I5, the discharge device II will be rendered non-conductive. This will occur since the existence of a flame between the pilot nozzle I5 and the flame electrode I1 forms a rectifying impedance which, with current flowing therethrough', may be used to charge a condenser associated with the input of discharge device I I5. The condenser that is charged is condenser I23 and the charging circuit for this condenser may be traced from the center tap I I4, through condenser -I23, conductor I98, conductor I99, flame electrode I1, pilot nozzle I5, ground 200, ground I ,andconductor I93 back to the lower terminal of secondary II3. The charge on this condenser will be such that the lower terminal of the condenser is negative while the upper terminal is positive. Since the lower terminal of condenser I23 is directly connected to the control electrode II1 of discharge-device II5 through the resistor I20, this control electrode III will be biased effectively negative'with respect to the cathode by reason of this negative charge on the condenser I23.- This will effectively stop the current flow through the discharge device II5 so that there will no longer be a current flow through the resistor I30. With no current flow through resistor I due to the discharge device I I5, the discharge device I I6 will be able to pass current and this current flow will besuificient to energize the relay I35. The energizing circuit for the relay I may be traced from the upper terminal of the secondary I I 3 through conductor 202, relay winding I36, anode I25, cathode I21, and conductors 203 and 204 back to the center tap I I4. Should a groundout condition occur; where the flame electrode H was touching the pilot nozzle I5, there would no longer be a rectifying impedance available to charge the condenser I23 and therefore discharge device I I5 would once again become conductive.- When so conductive, the current flow from this discharge device will flow through resistor .I30 and will bias the discharge device II6 to be nonconductive and the relay I35 will become deenergized.

Assuming now that the flame detection apparatus I I0 is operating properly and that the flame between the pilot nozzle I5 and the flame electrode. I I is acting in the normal manner described and contact MI are directly associated with the energizing. circuit of the main fuel valve and, if

an electrical circuit cannot be completed through switch blade I39 and contact MI, it will be'impossible to energize the main fuel valve. circuit utilizing this switch arm and contact will be considered when the operation of the timer 50 has been discussed. When the switch blade I38 and contact I40 come into engagement, a first portion of a shunt circuit around the safety switch heater 54 is completed. This shunt circuit will likewise be traced after operation of the timer 60 has been considered.

As mentioned above, when the main control relay 30 becomes energized, the energizing circuit to the filament heaters II and 15 is completed. After a predetermined time delay, the cathodes of the discharge devices will become electron emissive. When these cathodes are emissive, electrons will begin to flow between the cathodes and anodes. The current flow will initially be rather slow before the cathodes are up to full temperature and the current that does flow may be traced from the upper terminal of the secondary 63 through relay winding 8I, conductor 2I0, anode t3, cathode 10, and conductors 2H and 2I2 to the lower terminal of secondary 63. Some of the current flow for discharge device 66 may also be traced from the upper terminal of secondary 63 through conductor 2I3, potentiometer 93, conductor 2M, switch contact 81, switch blade 82, and conductor 2I5 to the anode 69. In other words, the winding 8i and the potentiometer 93 are eflectively connected in paralleL. With the current flowing in the last traced circuits, the

condenser 19, connected in parallel with winding SI, and condenser 94, connected in parallel with potentiometer 93 will become charge-d. When the condenser 19 has become charged sufiiciently, the current flow through the relay winding 8| will be sufficient to move the relay into the energized position. When the condenser 19 is so charged, the condenser 99 will be similarly charged and the polarities of their charge will be such that the lower terminal of condenser 93 is negative and the upper terminal of the condenser is positive. Since the control electrode I3 is directly connected to the lower terminal of condenser 94, the control electrode will be biased negative with respect to the cathode which is connected to the upper terminal of condenser 99. This will prevent any current from flowing through the discharge device 61 as long as this biasing potential remains on the condenser 99.

When the relay 39 becomes energized due to sumcient current flowing through the winding 8|, the switch blades will move from the position in which they are shown upon the drawin to the energized position where the switch blade 82 will move out of engagement with switch contact 81, switch blade 83 will move out of engagement with switch contact 88 and into engagement with con-.

tact 89, switch blade 94 will move out of engagement with switch contact 90 and switch blades 85 and 86 will move into engagement with their respective contacts 9i and 92. When the relay becomes energized, the energizing circuit through the main fuel valve I I is completed and this circuit may be traced from the input power line I 10 through conductor I12, limit control devices 45, 45 and All, conductor I13, conductor I'M, switch contact 38, switch blade 39, conductor I80, conductor 220, switch blade I39, switch contact I 4|, conductor 22I, switch contact 9i, switch blade 85, conductor 222, valve II, and conductors 223 and I19 back to the other input power line III With the. main fuel valve II energized, .a combustible The . 9 fuel such as oil will pass through the valve and conduit I3 into the fuel burner chamber where the air from blower I will atomize the oil and the atomized oil will be ignited by the presence of the pilot flame existing on the pilot nozzle I5.

Also completed by the energizati-on of the relay 80 is a shunt around the heater of the safety cutout device 50. This shun-t around the heater of the safety cutout device is provided to maintain the energizing circuit for the relay 30 while rendering the safety cutout device 50 ineffective. This energizing circuit for the relay 30 may now be traced from the upper terminal of secondary 42 through conductor I60, relay winding 3|, switch contact 21W, contact 21R, conductor I68, switch blade 32, switch contact 38, conductor I69, resistor 56, conductor I64, switch contact I49, conductor 225, switch blade 83, switch contact 89, conductor 226 and conductor I61 to the lower terminal of secondary 42. It will be noted that this last traced circuit included the resistor 56. The purpose of this resistor 56 is merel to keep the current flow in the last traced circuit for winding 3| below a predetermined value so that there will be no excessive heating in the winding. When timing switch blade 84 moved out of engagement with switch contact 90, the circuits through the originally traced energizing circuit for the main control relay 30 was broken. However, since the relay has its own holding circuit, the opening of switch blade from contact 99 will have no affect upon the apparatus at the moment.

Another circuit completed by the energization of the timer relay 90 is a shunt circuit for the blower motor I0 that is independent of the contacts of the main control relay. This shunt circuit may be traced from the input power line I through conductor I12, limit controls 45, 46 and 41, conductor I13, conductor I14, conductor 230, switch contact 92, switch blade 86, conductor Ill, blower motor I0, and conductors I18 and I19 back to the other input power line I'II. This last traced circuit will maintain the blower motor energized after the main control relay has become deenergized in a manner that will be discussed below.

When the timing relay 88 becomes energized, a further switch contact and blade, 8! and 82, are open circuited. As traced above, the switch blade 82 and contact 81 are in a portion of the anode circuit of the discharge device 96 and allow some of the anode current to pass through the potentiometer 93 and charge condenser 94 at the same time. Obviously, when the switch blade 82 moves out of engagement with switch contact 81, the charging circuit for the condenser 94 is no longer existing and the condenser will tend to discharge. This condenser will discharge through the potentiometer 93 at a rate determined by the amount of resistance existing in the potentiometer circuit. After a predetermined length of time the condenser 94 will have discharged through the potentiometer 93 sufliciently so that the control electrode will approach the same potential as the cathode I4 at which time the current flow through the discharge device 61 will be sufficient to energize the timing relay 99 in a circuit that may be traced from the lower terminal of the secondary 03 through conductor 2I2, conductor 230, relay winding 91, anode I2, and conductors 23I and 2I3 back to the upper terminal of secondary.

63. When the timing relay 96 becomes energized,

10 the switch blades 99, I00 and IOI move out of engagement with their respective contacts I02. I03 and I04. When switch blade 99 moves out of engagement with contact I02, it moves into engagement with switch contact I95. When switch blade IOI moves out of engagement with switch contact I84, the energizing circuit to the pilot valve I8 and the ignition transformer I9 is opened. With the opening of this energizing circuit, the pilot valve will become deenergi'zed and will stop the flow of gas to the pilot nozzle I5. Since the pilot flame has been operating a timed period after the main fuel valve II was operated, the need for the pilot flame is no longer existing and therefore it is desirable to shut the pilot flame off.

With the pilot flame cut off, it is necessary that the photocell 20 detect the presence of the main burner flame if the flame detection relay I35 is to remain in the energized position, Inasmuch as a photocell is a rectifying impedance in much the same manner that a flame is a rectifying impedance, the condenser I23 on the input of discharge device II5 will remain charged with the same polarity as occurred when the pilot flame was intersecting the flame rod H. The photocell 29 and the flame rod I! are efiectively connected in parallel and, therefore, both of the devices function in exactly the same manner as far as the electronic flame detecting circuit H0 is concerned and with the main burner flame present, the flame detection relay I35 will remain energized.

When the switch blade 99 is engaging switch contact I02, the control motor of the motorized valve I2 has been driven to an end position by an energizing circuit that may be traced from the upper terminal of secondary 65 through conductor 235, switch blade 99, switch contact i232, conductor 236, the lower winding of motor I43, ground 231 and ground 238 back to the lower terminal of secondary 65. When in this position, the motorized valve is in the low supply position and only a small amount of fuel may be sent through the valve to the combustion chamber. When the switch blade 99 moves into engagement with switch contact I55, a new energizing circuit is established to the motor I48 and this circuit may be traced from the upper terminal of secondary 65 through conductor E35, switch blade 99, switch contact I95, conductor 239, the upper winding of motor I43, ground I31, and ground 238 back to the lower terminal of secondary 55. With the motor I 46 so energized, the motor will move the motorized valve assembly in an upward direction so that the valve as sembly is moved to the high supply position where a large amount of fuel may pass through to the fuel burner combustion chamber.

The fuel burning control apparatus and the components associated therewith are. now in the normal operating position where the valve assembly I4, the pilot valve I3, and the ignition transformer I9 are no longer effective and the blower motor I0 is supplying air to atomize the fuel now flowing at a maximum, as governed by the motorized valve I 2, and the main burner flame is being detected by the photocell 20. As long as all components are operating properly, the apparatus will stay in this state of operation until such time as there is no longer a demand for such operation.

As soon as there is no longer an indication for a need of continued operation of the burner,

I H the room thermostat 21 will open and the switch blades of the thermostat will move outof engagement with the contacts Z'EW and 2113. When the room thermostat opens, the energizing circuit to relay winding 3I is broken so that the relay will become deenergized. When this relay becomes deenergized, the switch blades 32, 33, 34 and 35 move out of engagement with their associated contacts 36, 37, 33 and 39. When the blade 32 moves out of engagement with switch contact 36, the holding circuit for the relay winding 3I is opened so that it is impossible to reenergize the winding 3i unless the circuits associated with the thermostat contact 213 are all .in the deenergized position. Also deenergized by the deenergization of the main control relay 3c is a main fuel valve II. This will occur when the switch blades 34 and 35 move out of engagement with contacts 33 and 39. When the main fuel valve iI becomes deenergized, there will no longer be fuel flowing into the combustion chamber and the main burner flame should become extinguished. With the main burner flame no longer present, the flame detection relay I35 should become deenergized because the photocell 29 will no longer be detecting the presence of a flame.

Also deenergized upon the deenergization of the main control relay 30 is the filament circuit for the electron discharge devices of the timer 63. This occurs when the switch blade 33 moves out of engagement with switch contact 37. The opening of the filament circuit initiates another important timing period in the operation of the apparatus. Inasmuch as the cathodes of the electron discharge devices will not cool immediately, there will be current flow through the discharge devices 63 and 61 for a length of time determined by the cooling time of the respective cathodes. In other words, the main timing relay 8t will remain energized for a certain period and will maintain the blower motor IE] energized since the switch blade 86 and switch contact 92 form a shunt circuit for the blower motor to keep the blower motor in an energized circuit as long as these contacts are engaging. In other words, a blowout timing is obtained to insure that all fuel in the combustion chamber is completely burned and this is accomplished by the cooling time of the cathode IQ of discharge device 66.

While the time delay relay 96 will remain energized for a time period after the opening of the filament circuit of the dischargedevices 63 and 6?, the only function this relay will have will be to maintain the pilot burner assembly inoperative until after the blowout timing has taken place. When the relay 98 has become deenergized, the switch blade 99 will engage switch contact I02 and this will energize the motorized valve I2 so that the motor I46 will drive the valve mechanism to the low fuel capacity position. When switch blade IBI moves into engagement with switch contact E63, it will be possible to complete an energizing circuit to the pilot valve I8 and ignition transformer I9 upon a subsequent demand for heat or burner operation when the main control relay 3!] becomes deenergized.

The apparatus is once again back in the position in which it is shown upon the drawing with all of the components deenergized. Upon a subsequent demand for further burner operation as indicated by the room thermostat 27, the apparatus will go through an operating cycle in the manner which has beendescribed directly above.

12 Operation upon flame failure Assume for the moment-that the burner control is in the full operating position with the i contacts Hit and HM.

blower motor operative, and fuel being supplied theretoat the maximum rate as dictated by the motorized valve I2 and the main valve II. Assume now that the oil line becomes clogged momentarily so that there is no longer fuel supplied to the combustion chamber. When this occurs, the photocell 20 will no longer detect the presence of flame and will be ineffective to maintain a charge upon the condenser I23 in the flame detector I Hi. When this occurs, the flame detection relay I35 will move to the deenergized position. so that the switch blades I38 and I39 move out of engagement with their associated switch When the switch blade I39 moves out of engagement with switch contact I4 I, the energizing circuit to the main fuel valve I I is interrupted and when so interrupted will effect the deenergization of the main fuel valve II so that fuel can no longer be delivered to the combustion chamber. When the switch blade I38 moves out of engagement with switch contact I40, the shunt circuit around the heater 54 of the safety cutout device 59] is broken so that now an energizing circuit through the safety switch heater may be traced from the upper terminal of secondary 42 with the conductor I69, winding 3|, switch contact 27W, contact 27R, conductor I63, switch blade 32, switch contact 33, conductor I59, resistor 56, conductor :65, heater 54, switch contacts 52 and 53, and conductors I 66 and I6? to the lower terminal of secondary 42.

With the heater 54 again connected in theenergizing circuit of the main control relay 33, the heater will begin towarp the bimetal BI towards the right and, after a predetermined time, the bimetal will have moved sufficiently farthat the contacts 52 and 53 will open. When these contacts open, the energizing circuit to the main control relay 30 is deenergized and the apparatus will go into the completely deenergized position inthe manner described above when the room thermostat 2! no longer indicates a demand for heat.

. As lOIlg as the contacts 52 and 53 are open circuited, it will be impossible to complete anenergizing circuit to the main control relay 36 should there be a subsequent demand for burner operation. As soon as the reset actuator 55 is depressed, assuming the bimetalhas cooled, it will be possible for the switch contacts 52 and 53 to close. As soon as the contacts 52 and 53 do close,

the apparatus will start its operating cycle in the manner disclosed under operation. If, on restarting, no flame was detected at the pilot assembly I4, the flame detector I It would not energize the flame detection relay E35 and the main oil valve I I would not become energized. Further, the energizing circuit to the heater 3:! of the safety cutout device 50 would be energized in a manner described above and, after a predetermined time, the safety cutout device would become operative to open switch contacts 52 and 53 to deenergize the main control relay 39. Obviously, the deenergization of the main control relay will deenergize the components including the pilot burner assembly I4, and the filament circuits of the timing device Sil-when the relay becomes deenergized. As soon as the trouble has been cleared from the fuel line, it should be possible to depress the actuator 55 on the safety cutout device 56, close the contacts 52 and 53 and initiate normal burner oper ation in the manner described above.

Operation upon false indication of flame In order to render the control apparatus a completely safe one, it is necessary that the control apparatus fail to energize any of the key burner components when any portion of the control apparatus is not operating properly. In the event that the flame detection relay I35 should remain in the energized position after the room thermostat 21 is no longer indicating a need for heat and the main control relay 3!! is deenergized, it is desired to prevent further operation of the control apparatus. When the main control relay 30 becomes energized, it will be recalled that the energizing circuits of the filament heaters of the discharge devices in timer 60 are open. When this filament heater circuit is open, the timer relay 8!) will move to the deenergized position after a predetermined time. With the timer relay in the deenergized position and the flame detection relay I35 in the energized position, an energizing circuit can be traced to the heater 54 of the safety cutout device 50. This energizing circuit may be traced from the tap 43 of secondary 42 through conductor 245, switch contact 88, switch blade 83, conductor 225, contact I45, switch blade I38, conductors I54 and IE5, heater 54, switch contacts 52 and 53 and conductors I63 and I61 to the lower terminal of secondary 42. With this new energizing circuit to heater 54, the bimetal 5| will again be warped toward the right and after a predetermined time the contacts 52 and 53 will open to open the energizing circuit to the main control relay 35. Upon a subsequent demand for burner operation by the room thermostat 21, it will be impossible to complete an energizing circuit for the main control relay as the contacts 52 and 53 are open. As long as the flame detection relay remains in the energized position, it will be impossible to initiate operation of the apparatus even though the safety switch contacts are subsequently depressed and the contacts 52 and 53 are closed. This is true since the energizing circuit for the main control relay 30 is completed through deenergized contacts of the flame detection relay I35, switch blade I38 and switch contact I42, before the energizing circuit for the main control relay can be completed.

Operation upon faulty operation of timer In the event that the timer should fail to operate or should continue to operate after there is no longer a need for such operation, it is desired that the control apparatus be rendered inoperative. Assume, for example, that the timer filament circuit should open or some other fault should occur so that the relay 83 could not become energized after the control apparatus has been started up in its normal manner by a demand for burner operation by the room thermostat 21. Under this situation, the blower motor ID, the pilot valve I8 and the ignition transformer I9 will all be energized as upon a normal starting cycle. When so energized, a flame will appear at the pilot nozzle I5 and the same will be detected by the flame electrode I'I so that the flame detection relay I35 will move to the energized position. If, after a predetermined time the timer relay 83 does not become energized, the safety cutout heater 54 will have been energized for a sufficient length of time to move the bimetal 5I toward the right and open switch contacts 52 and 53. This energizing circuit may be traced from the center tap 43 through conductor 245, switch contact .j 14 88, switch blade 83, conductor 225 switch contact I40, switch blade I33, conductors I64 and I65, heater 54, switch contacts 52 and 53, and conductors I66 and I6! to the lower terminal of the secondary 42.

The timing period for the safety cutout heater to operate the bimetal is considerably longer than the period required for the timer relay 8!] to come into operation. Therefore, on the normal starting cycle, while the last traced energizing circuit is temporarily completed, the timer relay normally comes into operation to shunt out the safety cutout heater. When the timer does not come into operation, the last traced energizing circuit to the safety cutout heater 54 will be maintained and the apparatus will be shut down upon the circuit opening of the contacts 52 and 53.

Should the timing apparatus 65 remain in operation after the main control relay 39 has become deenergized, it is also desired to prevent any further operation of the apparatus which might possibly cause damage. This safety feature is accomplished by utilizing the deenergized contacts of the timer relay in the starting circuit for the main control relay 30. If the timer remains in the energized position, switch blade 84 will be out of engagement with switch contact 93 so that the initial starting circuit for relay 3% cannot be completed. It will be noted that the switch contact 85 will be engaging switch contact 92 in which case the blower motor It will remain energized. Obviously, no damage can be done by running the blower motor when there is no fuel being supplied to the combustion chamber..

Power failure In the event there should be an extended power failure, that is a power failure over a period of several minutes, the apparatus will of course be completely deenergized. As soon as power is returned, the apparatus will start up in its normal operating cycle, as explained above under the section entitled Operation.

Under conditions of momentary power failure, the dangers of explosion in the combustion chamher are quite great unless some steps are taken to shut the apparatus down and start it up from its initial starting position. Assume that the apparatus is operating normally under the condition of full operation with the pilot assembly l4 deenergized and the motorized valve I2 operated to the high supply position. Should a momentary power failure occur under these conditions, the main burner control relay 30 will become deenergized and will disrupt or open its holding circuits through switch blade 32 and switch contact 36. Should the power be immediately restored, it will be impossible to reenergize the burner control relay 30 through this holding circuit and it must be energized through the starting circuit which includes switch blade I38 and switch contact I42, engaging when the flame detection relay I35 is deenergized-switch blade 84 and switch contact 90, deenergized when timer relay 80 is deenergized, and the end switch I45 on the motorized valve I2. Inasmuch as all of the above mentioned switch contacts are in the energizing circuit for the burner control relay 30, it is necessary that they all be completely in the deenergized position before it is possible to energize the burner control relay.

This will mean that the timer relay 80 must go through a timing period dependent upon the cooling time of cathode loin-the discharge de- .vice .66. It furthermeans that the flame detec- :tion relay 135 cannot beenergized indicatingthe presence of a flame in the combustionchamber.

Further, the timer relay 96 must become deenergized sothatvtheswitch blade 99 moves into engagement with-switch contact I02 so that the motorized valve l2 willbe driven tothelow supply. position at which'position the end switch I45 will become closed. 'As soon as all "these switcheshave gbeen moved to the closed position', it will be-po'ssible to initiate burneroperation in the normal manner with the :burner M control relay 30 becoming energized first, which energization completes an energizing circuitto theblower motor I and the components of the pilot burner assembly M in the manner described above under the portion entitled Operation.

. Alternative. uses Obviously the above described control apparatus is one'with a great deal of flexibilityand there are many .ways in which the control apparatus may be adapted to varioustypes' of burner installationsl" For example, assume that adirect connection be made from terminal I50 to, terminal "I52 as shown upon the drawing by moving switch blade I48 into engagement with contact A.

' If such a connection were made, the timing delay of relay 80 obtained in the control apparatus as it is shown upon the drawing and as obtained by the closing of the switch blade" 85 and switch contact 9| would be effectively by-passed so that there would be no delay in the opening of the electrode H.

In the event that a direct connection should 'be'made between the terminal I50 and terminal If, by moving switch blade- M8 into'engagement with contact 0, it would be possible to-have an arrangement where there would be direct ignition of thef-u'el through the main valve H as the valve I l'will become energized immediately upon the'ene'rgization of theburner control relay 36. The energizing-circuit to the fuel'valve may be traced from the input power line' l'lfl -through "conductor 112, limit control devices 45; 45 and 41, conductors l'l3-and-I14,"switch contact 38, switch blade 34, conductor -18 0, switch-blade 1G0, switch contact 1 03, conductor 2 60; switch blade I48, conductor 26f, terminal liill, conductor: 222, va1ve H and conductors 223 and 119 back to the other "While the end" switch M5 is operated by. the movement of a'moto-rized valve to the low: fire or "low -supply position; that end I switch .could be eliminated in'certain situations where such a motorized valve is not used. Furthenthetend switchl lli could be operated by a: similar type of motor which would be driving adamperassoci- -ated with a the combustion =chamber and would not beeffective-untilthe damperwas in the desired position.

Othermodifications will readily suggest them- 1 selves to" anyone skilled inothe art.

' Conclusion "detector and "have provided therewith a com i6 bination of" safety circuits which will prevent operation should any component. fail to "operate or operate falsely, Further, weahave pr.ovi(led,,-an

l apparatus which will enable the controlledburner installation to be brought into operation, inthe desired safestsequenca Manymodifications, of

;the above control. apparatus will suggest. themselves tothoseskilled in-the art and gwetherefore intend, to-belimited :solely. by the scope of the appendedclaims.

-* Wei-claim as our invention:

1.- Control apparatus for a fuel burnerrhaving a fuel valve and a bloweramotor, comprising in combination, anelectrondischarge device-having a heater therefor, firstswitchameans operated upon a demand forburner:ope1'ation,-rmean -lneluding said first switch means-adapted to complete an energizing electrical circuit to -the;blower motor and to said heater second switch means actuated by said discharge device when said heater has been energized for a predetermined length ofytime, means including said S. i0nd-vvitch means adapted ;with said first -svvitch; means; to

energize thefuel valve and establish independv.ently of, said first switch means a;further:electrical, circuit toqthe blower motor, said; further electrical 1; circuit. remaining. :established; for a length of time dependentonthe cooling :time of said heater. after. said first. switch. means iSiIlO longeroperative to indicate a demand-forburner operation.

- which is effective when energized for-apredetermined length of time to deenergizethe burnen. an energizing circuit for said firstrelay means-including said safety cutout device and connections adapted to be completed by means indicative of the need for burner operation, a shunt circuit around said cutout device including a switch .contact of said second relay means and a switch contact of vsaid timing device when operated, and a further energizing circuit for said-cutout -device comprising said one switch of said second .re-

lay means whenenergized anda further; switch of said timing means when deenergized.

3. Control apparatus for a fuelburner having ignition -mean s,-ablowerjnotor and a fuelvalve, comprising in combination, first relaymeanehaving'a plurality of switchcontactsadapted to be actuated on a; demand for burnerpperation, means includingsaid first relay neans cornpleting an energizing circuit to 'lihfiiblOWGljlllQfiQIf, and ignition meanson demand for heat, second relay means having a plurality of switchcontacts operated upon the. ignition means being in condition to sustain combustion,v firsttiming, means. for completing an energizing circuit to the fuel valve a predetermined time after the blowerumotor. operates, said timingmeans having a plurality of switch contacts, second timing'means for deenergizing the ignition means a-predetermined time aftersaid first timing means operates, a safety 17 cutout device which is effective when energized for a predetermined length of time to deenergize the burner, an energizing circuit for said first relay means including said cutout device and a thermostat circuit adapted to be completed upon a demand for burner operation, a shunt circuit around said cutout device includin a switch contact of said second relay means and a switch contact of said first timing means when operated, and a separate energizing circuit for said cutout device comprising said one switch of said second relay means when energized and a further switch of said first timing means when deenergized, said separate energizing circuit being effective to actuate said cutout device if maintained for a predetermined length of time.

4. A control for a fuel burner having igniting means, a fuel valve, and a blower motor, comprising in combination, first relay means adapted to be energized by means indicating a need for burner operation, means including said first relay means adapted to energize the blower motor and ignition means upon energization of said relay means, time delay relay means, flame detection relay means, a first circuit for connecting the fuel valve in an energizing circuit, said circuit comprising said first relay means when operated, a second circuit for connecting the fuel valve in an energizing circuit, said second circuit comprising said first relay means when op- 2 erated and said flame detection means when indicating the presence of an igniting flame, a

third circuit for connecting the fuel valve in an energizing circuit, said third circuit comprising said first relay means when operated, said time delay means when operated, and said flame detection means when indicating the presence of an igniting flame, and manuall operable switching means for selecting one of said circuits.

5. A control for a fuel burner having igniting means, a fuel valve, and a blower motor, comprising in combination, first relay means adapted to be energized by means indicating a need for burner operation, means including said first relay means adapted to energize the blower motor and ignition means upon energization of said relay means, time delay relay means, flame detection relay means, a first circuit for connecting the fuel valve in an energizing circuit, said circuit comprising said first relay means when operated,

a second circuit for connecting the fuel valve in an energizing circuit, said second circuit comprising said first relay means when operated, and

said flame detecting means when indicating the presence of an igniting flame, a third circuit for connecting the fuel valve in an energizing circuit, said third circuit comprising said first relay means when operated, said time delay means when operated, and said flame detecting means when indicating the presence of an igniting flame, manually operable switching means for selecting one of said circuits, and means including said time delay means for rendering said igniting means inoperative a timed period following energization of said first relay means.

6. A control for a fuel burner having igniting means, a fuel valve, and a blower motor, comprising in combination, first relay means adapted to be energized by means indicating a need for burner operation, means including said first relay means adapted to energize the blower motor and igniting means upon energization of said relay means, time delay means, flame detection relay means, a first circuit for connecting the fuel valve in an energizing circuit, said circuit comprising said first relay means when operated, a second circuit for connecting the fuel valve in an energizing circuit, said second circuit comprising said first relay means when operated and said flame detection means when indicating the presence of an igniting flame, a third circuit for connecting the fuel valve in an energizing circuit, said third circuit comprising said first relay means when operated, said time delay means when operated, and said flame detecting means when indicating the presence of an igniting flame,

manually operable switching means for selecting one of said circuits, and means including said following energization of said ignition means,

means including one of said pair of discharge devices with its associated relay for energizing the fuel valve following a first time interval, and means including the other of said devices with its associated relay for deenergizing the igniting means a timed interval following energization of the fuel valve.

8. Control apparatus for a fuel burner having a blower motor, ignition means, and a fuel valve, comprising in combination, first switch means for energizing the blower motor and ignition means upon a need for burner operation, a first timing device, means including said first switch means for energizing said first timing device, said first timing device having a plurality of switch means, means including said first switch means and one of said plurality arranged to energize the fuel valve a timed period after the energizing of the blower motor and ignition means, and a second timing device for deenergizing the ignition means, said second timing device comprising another of said plurality of switch means operated by said first timing I device and an electron discharge device, said other of said plurality of switch means controlling the energization of said discharge device, said second timing device including a further switch switch means for energizing the blower motor and ignition means upon a need for burner operation, a first timing device energized by means including said first switch means, said first timing device comprising an electron discharge device and a plurality of switches actuated thereby a timed period following energization and deenergization by said first switch means, means including one of said plurality of switches and said first switch, means arranged to energize the fuel valve a timed period after energization of the blower motor, a second timing device for deenergizing the ignition means, said second 19 timing device comprising a control switch operated by said first timing means when energizing the fuel valve and a second electron discharge device which is energized a predetermined time after the operation of said control switch, and means including said second electron discharge device for controlling said further switch, said second electron discharge device controlling a further switch in the ignition circuit a predetermined time after said first timing means operates said control switch.

10. Burner control apparatus for a burner having an initiating sequence and a running sequence, comprising in combination, a control circuit for initiating burner operation arranged to be completed by means indicative of the need for burner operation, a safety cutout device for rendering the burner inoperative when energized for a predetermined length of time, said safety cutout device having an actuator normally energized upon completion of said control circuit,

timing means for effecting a running condition of burner operation, said timing means having an energizing circuit therefor completed upon completion of said circuit control, combustion responsive means operative upon the presence of combustion at the burner, and means including switch contacts of said timing means and switch contacts of said responsive means to alter said control circuit to thereby render said device ineffective when both said timing means and said responsive means switch contacts are in an energizing position and to render said device effective upon either said timing means switch contacts or said responsive means switch contacts moving to a deenergized position while the other remains in the energized position.

11. Burner control apparatus for a burner having an initiating sequence and a running sequence, comprising in combination, a safety cut out device for rendering the burner inoperative when energized for a predetermined length of time, timing means including switch contacts for effecting a running condition of burner operation, combustion responsive means including switch contacts and operative upon the presence of combustion, means including relay means for initiating burner operation, a first energizing circuit for said cutout device, said circuit including said relay means when energized, mean for shunting said cutout device comprising switch contacts of said timingmeans and said combustion responsive means when in an energized position, a second energizing circuit for said cutout device, said second circuit comprising switch contacts of said timing means when in a deenergized position and switch contacts of said responsive means when in the energized position.

12. Burner control apparatus having means for establishing an initiating period and a running period and having limit control switching apparatus associated therewith, comprising in combination, relay means for initiating burner operation, electronic timing means comprising a thermionic discharge device for effecting a running condition of burner operation, electronic flame detection means for ascertaining proper operation of the burner, said detection means comprising a thermionic discharge device, switching means controlled by said flame detection means and assuming a first or a second operative position depending upon the presence or absenc of combustion at the burner, an initial energizing circuit for said relay including'said flame detection switching'means in saidseco'nd operative position, asource of power for said'relay means said timing means and said fiame detection means comprising separate transformers, input power terminals for said apparatus, means directly connecting said transformers for said timing means and said detection means to said terminals, and circuit means for that transformer associated with said relay means adapted to be completed to said terminals through the limit control switching apparatus.

13. Burner control apparatus having limit control apparatus associated therewith, comprising in combination, first relay means for initiating burner operation, an electronic flame detector having an electron discharge "device with a thermionic heater therefor, a second relay-controlled by said discharge device, a source of power, a first circuit including said second relay when deenergized connecting said first relay means to said source of power and arranged to be comp'letedby means indicative of a need for burner operation, a second circuit continuously connecting said flame detector to said source of power, and electrical terminals connected in series with said first circuit only arranged for connection to the limit control apparatus for rendering only said first relay means ineffective upon actuation of the limit control apparatus.

14. Burner control apparatus having limit control switching apparatus associated therewith, comprising in combination first relay means for initiating burner operation, said relay meanshaving an energized and a deenergized condition, electronic flame detection means forascertaining proper operation of the burner, said detection means comprising a thermionic discharge device having a heater therefor, second relay means controlled by said discharge device and assuming an energized or a deenergized condition dependent upon said detecting means detecting the presence or absence of combustion at the burner, safety cutout means having an actuator; transformer means comprising a first primary having "a first secondary winding associated therewith for said apparatus, means directly connecting said second primary winding to said input terminals, circuit means connecting said first primary winding to said power terminals and adapted to be completed'through switch contacts of the limit control apparatus; an energizing circuit for said first relay means including said second relay means in said deenergized condition and arranged to be completed by meansindicative of the need for burner operation, and a component checking energizing circuit for said safety cutout means actuator including said first relay means in said deenergized condition and said second relay means in said energized condition.

15. Burner control apparatus having limit control apparatus associated therewith, comprising in combination, first relay means for initiating burner operation when said relay means is energized, an electronic flame detector having .an electron discharge device with'a thermionic heater therefor, a second relay controlled, by said discharge device toassume a first or alsecond position depending upon said detector detecting. the presence or absence of combustion, terminals adapted to be connected to a sourceofpowena "first and a second transformer each havinga primary anda secondary winding, meansincluding means adapted to be connected to the limit control apparatus connecting the primary of said first transformer to said terminals, a first circuit including said second relay when deenergized connecting the secondary of said first transformer to said first relay means and arranged to be completed by means indicative of a need for burner operation, a second circuit continuously connecting the primary of said second transformer to said terminals, and third circuit means connecting the secondary of said second transformer to said flame detector, said apparatus functioning to cause deenergization of the primary of said first transformer upon limit control operation and to maintain said electronic flame detector energized such that a fault within said flame detector will maintain said first circuit open circuited so long as said flame detector falsely detects flame.

JOHN M. WILSON. RICHARD S. FEIGAL.

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

UNITED STATES PATENTS Number Name Date 2,021,647 De Lancey Nov. 19, 1935 2,075,289 Judson Mar. 30, 1937 2,102,618 Francis Dec. 21, 1937 2, 02,691 Francis Dec. 21, 1937 2,181,970 Fallon -1 Dec. 5, 1939 2,214,912 Valjean Sept. 17, 1940 2,313,943 Jones Mar. 16, 1943 2,370,205 Tate Feb. 27, 1945 2,370,847 Dempster Mar. 6, 1945 2,375,900 De Lancey May 15, 1945 2,388,124 Crews Oct. 30, 1945 2,388,666 Bower Nov. 13, 1945 2,440,700 Rosche May 4, 1948 2,519,889 Crawford Aug. 22, 1950 2,537,293 Peterson Jan. 9, 1951

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