US2662591A - Burner control apparatus - Google Patents

Description

Dec. 15, 1953 H. L. HANSON 2,662,591

BURNER CONTROL APPARATUS Filed April 5, 1950 K- IO IN VEN TOR. .HEN RY L. HANSON ATTORNEY Patented Dec. 15, 1953 2,662,591 BURNER CONTROL APPARATUS Henry L. Hanson, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application April 3, 1950, Serial No. 153,730 13 Claims. (Cl. 158128) The present invention is concerned with a new and improved burner control apparatus. More particularly this invention is directed to the provision of a combined burner ignition and flame detection apparatus arranged to insure maximum safety of operation of a controlled fuel burner.

In present day burner controls used with burners having igniting means and fuel flow controlling means it is often necessary that there be provided a control apparatus for checking separately each function of the fuel burner and its flame initiating means. It is also desirable to check the control apparatus itself to see that the burner is not brought into operation unless the control apparatus is functioning in the desired manner.

It is therefore an object of the present invention to provide a new and improved burner control apparatus for checking ignition and flame at a controlled fuel burner.

Another object of the present invention is to provide a new and improved burner control apparatus having ignition and flame detecting means combined in a single unit.

Still another object of the present invention is to provide a burner control apparatus having an ignition checking means which is effective in the absence of the detection of flame to periodically check the presence of ignition.

A further object of the present invention is to provide an electronic control circuit with an electron discharge device having a plurality of anode, cathode and grid electrodes with relays in circuit with at least two of those electrodes and each controlled by diflerent signal voltages applied to two other of said electrodes.

A still further object of the present invention is to provide a burner control apparatus having ignition checking means which periodically checks the presence of ignition in the absence of a burner flame and then shuts down completely the controlled burner if after the ignition check has been made a number of times no flame is detected.

These and other objects of the present invention will be understood upon considering the following specification, the attached drawing, and the appended claims.

Referring to the single figure, which is a wiring diagram of the apparatus, the numeral l represents a thermostatic device of any desired type which will indicate when there is a need for burner operation. This thermostatic device l0 comprises a pair of switch contacts H and I2 which are adapted to complete appropriate elec trical circuits in the control apparatus of the present invention which is located within the housing indicated generally by the numeral [5. The control circuits within the housing are effectve to energize an ignition device 20, a pilot valve 2| which controls the flow of fuel to a pilot burner 22 and a main valve 23 which controls the flow of fuel to a main burner 24. For detecting the presence of a flame at the pilot burner and at the main burner a photoelectric device 25 is provided although it is to be understood that other types of flame responsive means can'b'e employed, such as flame rods. Supplying power to the low voltage circuits controlled by the thermostatic device l0 within the housing 15 is a transformer having a primary 3! and a secondary 32 tapped at 33. In circuit with the secondary 32 is a safety switch device 35 and a control relay 40. Safety switch device 35 comprises a bimetallic element 36, a heater 3! therefor, a pair of switch contacts 38 and 38 normally held in engagement by bimetal 35, and a reset actuator 41. The relay 40 comprises a relay winding 42, and a pair of switch blades 43 and 44 normally biased out'of engagement with a pair of associated contacts 45 and 46. Connected to the tap 3.3. Of secondary 32 is a current limiting resistor 48. A

Supplying power to the detecting portion of the apparatus is a transformer having a pri mary winding 5| and a secondary winding 52 which is tapped at 53, 54 and 55. Connected in energizing relation to this secondary winding 52 is an electron discharge device having an anode 6|, cathode 62, and grid elements or electrodes 63, 64 and 65. Also associated with the cathode 62 is an anode 66 which cooperates with the cathode 62 to form a diode rectifier. Connected in circuit with the anode BI is a control relay 10 having a relay winding H, and switch blades 12, 13 and 14 which are normally biased out of engagement with associated switch contacts l5, l6, and H. The switch blade 13 is normally biased into engagement with a further contact 15. A condenser 19 is connected in parallel with the relay winding H to function in the normal manner to bypass alternating current flowing in the relay circuit. Connected in circuit with the grid electrode 54 is a further relay having a relay winding 8i, a switch blade 82 normally biased into engagement with a contact 83 and a switch blade 84 normally biased out of an en gagement with a contact 85. A condenser 86 is connected in parallel with the relay winding 8 3 and functions to by-pass alternating current flowing in the relay circuit.

Connected to the grid 63 is a grid resistor 96 having a filter condenser 9| connected in parallel therewith. A grid current limiting resistor 32 is also connected to the grid 63 and this resistor 92 with a further condenser 93 are connected in series parallel relationship with condenser iii. A filter network 95 is associated with the anode E56 and comprises a resistor 96 and a condenser 91?. Also associated with this anode 5G is a tuned resonant circuit 98 comprising a condenser es and a transformer I539 having a primary IiiI, which is energized by a selected harmonic frequency arising in ignition device 20, and a secondary I92. The harmonics may, for example, be coupled from the ignition device 23 by means of a current type of pickup transformer not which has one winding in series with one of the ignition electrodes.

Operation The apparatus as shown in the drawing is in the completely shut down position. When in this condition the thermostatic device ID will be open circuited and the control relays MB, III, and 8e, will all be deenergized. With the control relays deenergized the burner apparatus including the ignition device 28, pilot valve 2|, and main valve 23 will also be deenergized so that there will be no flame present at the pilot burner 22 or at the main burner 25. When there is no flame present at either of the two burners the control discharge device 50 will have a bias thereon which will maintain the current flow through the discharge device sufiiciently low that neither of the relays Iii nor 8% can become energized. The source of biasing voltage for the discharge device [it is obtained from the secondary winding 52. With the control grid 63 connected through resistor 95 to tap 53, with the cathode 52 connectedto tap 5 1 of secondary 52 and with the anode GI connected to the right-hand terminal of secondary 52 through conductor III], relay II, and conductor HI, there will be an A. C. bias which is negatively phased applied to the control grid whenever the right-hand terminal of secondary 52 is phased positive with respect to the lefthand terminal. While the current that does flow is insufficient to energize either of the relays ID r 89, there will be some current flow in the circuit when the anode is phased positive with respect to the cathode.

As soon as there is a demand for operation of the burner due to a drop in space temperature to some predetermined value, the thermostatic device I!) will operate to close the contacts I I and E2. The closing of these contacts will effect the energization of the relay it in a circuit that may be traced from the right-hand terminal of secondary 32 through conductor IIZ, relay winding 62, conductor H3, switch contacts II and I2, conductor Ih'i, safety switch contacts 38 and 39, safety switch heater 31, and conductors II5 and HE back to the left-hand terminal of secondary 32. With this energ'zing circuit for relay 4!) completed the relay winding will move the switch blades 43 and 6 1 into engagement with their associated switch contacts 45 and 45 respectively. When switch blade 33 engages contact 35 a circuit is completed from the lower end of resistor 43 through the switchconta'ct d5, switch blade 43, and conductor lid to the left-hand terminal of secondary 32. This connection will have no immediate effect upon the operation of the apmam paratus. When switch blade 44 engages switch contact 48 an energizing circuit is completed to the ignition device 20. This circuit may be traced from the input power line 28 through conductor lit, switch blade 41:, switch contact 46, conductor I2I, conductor I22, switch blade I3, switch contact 18, conductor I23, ignition device 20, and conductor I24 to the other input power line 21.

If the ignition device 20 is operating properly there will be considerable harmonics present at the device and these harmonics are coupled to the tank circuit 98 by a pair of conductors I2? and IE8. With the tank circuit 93 tuned to a preselected harmonic of the ignition frequency there will be a relatively high voltage across the terminals thereof and this voltage will be rectified by the action ofanode 66 cooperating with cathode 62 in a circuit that may be traced from the right-hand end of the tank circuit 98 through the conductors I30 and i3I, anode E6, cathode 62, resistor 96, back to the left-hand end of the tank circuit 98. circuit rectified there will be a relatively high negative voltage appearing on the right-hand terminal of the tank circuit 98 and this negative voltage will also be applied to the grid 65 through the conductors I31] and I32. With a negative voltage applied to the grid 65 there will be an increase in the current which normally flows in the circuit which includes the grid 64. This current flow circuit may be traced from the secondary 52, assuming the right-hand terminal thereof is positive with respect to the left-hand terminal, from ta 55, through conductor I33, relay coil 8I, conductor I34, grid 84, cathode 62, to tap 5t on secondary 52. If the voltage on grid 65 is sufiiciently negative the electrons which were previously flowing to the anode SI are effectively driven back toward the cathode and are collected by the grid 65 so that thegrid ourrent will increase to a point where the relay BI] will be energized.

When the relay 8t becomes energize-:1 the switch blade 82 will move out of engagement with the associated switch contact 83 so that the circuit to the harmonic tank circuit 98 will be broken. This will have no immediate effect upon the apparatus because of the fact that the condenser 91 will have been charged at the same time that the current was flowing through the resistor 98 and the charge on this condenser 9? will remain for a length of time dependent upon the size of the condenser and the resistor 96. Also actuated when the relay 89 becomes energized is a switch blade 8 which moves into engagement with the switch contact 85. This latter switching operation efiects energization of the pilot valve 2| and this energizing circuit may be traced from the input power line 26 through conductor I29, switch blade ii switch contact 46, conductor I2I, conductor lei switch contact 85, switch blade 85, conductor IQI, pilot valve El, and con ductor I24 back to the other input power line 2?. When the pilot valve 2i becomes energized fuel will how to the pilot burner 22 and will be ignited by spark electrodes of the ignition device 25. 7

As soon as a flame appears at the pilot burner 22 this fiame will be detected by the photocell 25 which will be effective to place a direct current charge on the condenser The charging circuit for conenser it may be traced from the lefthand terminal of secondary 52 through conductor hi5, photocell conductor i l-3, condenser With the voltage on the tank aecasei 9'3, and conductor I41 back to the tap 53' on sec-- ondary 52. The photocell or photoelectric device 25 is of the typewhich passes current in only one direction and therefore the current flow will be efiective to charge the condenser 93. The charge on the condenser 93 will be such that its upper terminal will be positive and its lower terminal negative. Inasmuch as the upper terminal is positive the positive voltage will be applied to the control grid 63 by way of resistor 92'. This positive voltage on the condenser 93 at its upper terminal will be sufficient to overcome the negative biasapplied to the control grid 53' by reason of the connection of the control grid to tap 5-3 and the cathode 62 connected to tap 54. With this positive voltage applied to the control grid 63 the current flow in the tube 69 will be increased'sufficiently to a point where the control relay i is energized. As soon as the control relay I0 becomes energised the switch blades I2, I3 and 74 move into engagement with the respective switch contacts 75, I5, and 11. When the contact 14 engages contact I? an energizing cir cuit is'completed to the main valve 23. This circuit may be traced from the input power line 26 through conductor I 20, switch blade 44, switch contact 46, conductor I2 I, switch blade I4, switch contact Ti, conductor I 50, main valve 23, and conductor I! to the other input power line 21. As soon as the inain valve becomes energized the valve will open and fuel will flow to the main burner 24.

Upon the switch blade I3 engaging contact 18 a holding circuit is established to the pilot valve 2] which is independent of the operation of the :relay Bil. This holding circuit may be traced from the input power line 26 through conductor I29, switch blade 44, switch contact 43, conductor I2I, conductor I22, switch blade 13, switch contact I6, conductor I4I, pilot valve 2i, and conductor I24 back to the other input power line 27. When the blade 13 engages the contact IE it broke the circuit through the contact 18 and this caused the deenergization of the ignition device 20. With the ignition device no longer energized there is no possibility of any harmonic frequencies appearing in the resonant network 98 and so there will be no effective biasing voltage applied to the grid 65. However, inasmuch as there is a positive voltage applied to the control grid 13 there will be a relatively large amount of current flowing through the tube and there will be current flowing in the circuit which includes the grid 64 and relay 8%. This current is normally suff cient to maintain the relay energized. However, in view of the fact that this operation is marginal it is necessary that the pilot valve circuit, first completed through the circuits of the relay 89, be maintained energized by the flame detection relay 13.

When the switch blade 12 engages contact '15 a holding circuit is established for the control relay 49 which is independent of the safety switch device 35. This holding circuit may be traced from the righthand terminal of the secondary 32 through conductor II2, relay winding 42, conductor H3, switch contacts II and I2, conductor II4, switch contacts 38 and 39, conductor I 55, switch contact 15, switch blade 12, conductor I55, switch contact 45, switch blade 43 and conductors I51 and H5 back to the left-hand terminal of secondary 32. With this holding circuit completed independent of the heater 3? of the safety switch device 35 the heater will no longer be energized and will not attempt to warp the bimetal from its normal position where it holds the contacts 38 and 39 in engagement.

The apparatus as described thus far is now in the normally operative position with the thermostatic device In still indicating. a need for burner operation, the ignition device 20 deenergized and the main and pilot valves 23 and 2I both energized to supply fuel to their respective burners. The apparatus will stay in this condition until such time as there is no longer a demand for burner operation.

As soon as the thermostatic device I0 is satisfied the contacts II and I2 will be open circuited. This will cause the immediate deenergization of the relay 40. When the relay 40 becomes deenergized the switch blade 44 moves out of engagement with associated contact 46 and this will effect the deenergization of boththe main and pilot valves 23 and H as the energizing circuits for these valves is completed through this switch blade and contact. As soon as flame is no longer present at the pilot burner 22 and the main burner 24, there is no longer a flame to be detected by the photoelectric device 25 and the charge on the condenser 93 will leak off. The discharge circuit which may be traced from the upper terminal of condenser 93 through resistor 92, resistor 90 and conductor I4! back to the lower terminal of condenser 93. When the condenser has discharged suificiently the control electrode 63 will have a potential which will maintain the current flow through the discharge device 60 below that value necessary to maintain either of the relays 10 or energized. Thus, both relays I9 and 89 are moved to the deenergized position as they are shown upon the drawing and the apparatus will be in the completely shut down position ready for another operation when the need is indicated by the thermostatic device I0.

Operation upon ignition failure In the event that there should be a failure of operation of ignition device 20 it is desired that the present apparatus not cause any fuel to flow to either the pilot or main burners and that if ignition is not established within a predetermined time that the apparatus shut down. Assume that the thermostatic device ID has just indicated a need for burner operation and the control relay 40 is energized to complete an energizing circuit to the ignition device 20 through the switch blade 44 and contact 46. If the ignition device is not operating properly there Will be no harmonics arising in the ignition circuit and this will result in no voltage being applied to the resonant circuit 98 associated with the ignition checking circuit. When there is no voltage applied to the resonant circuit and the control electrode 83 has only the alternating current from secondary 62 applied thereto the current flow to the discharge device 60 will be insuflicient to energize relay 80.

It will be noted that the energizing circuit for the relay 40 is still being completed through the safety switch heater 3! in a circuit that may be traced from the right-hand terminal of secondary 32 through conductor II2, relay winding 42, conductor II3, switch contacts II and I2, conductor I I4, switch contacts 38 and 39, safety switch heater 31, and conductor I I5 and I I6 back to the left-hand terminal of secondary 32. If this last traced circuit remains in tact for a surficient length of time the heater 3'! will warp the bimetal 36 to the right and the contacts 39 and 39 will separate to break the energizing circuit for the control relay 40. When the relay 40' becomes deenergized the switch blade 44 will move out of engagement with contact 46 and the ignition device 20 will become deenergized. The apparatus will remain deenergized until such time as the safety switch device 35 is manually reset by pressing the reset button 4| to effect a closing of the contacts 38 and 39. As soon as this is done the apparatus will attempt to start in the normal manner by first checking the operation of the ignition device 26. If the fault has still not been removed the apparatus will again be shut down by the safety switch heater 31 warping the'bimetal 36 to the right and again opening the energizing circuit to the relay 43.

Operation upon failure to establish combustion If the ignition device 25.] should be operating properly but flame is not established at the pilot burner 22 the present apparatus will periodically check the ignition operation a number of times and if combustion is not established the apparatus will be completely shut down. Assume again that the thermostatic device W has just closed to indicate a need for burner operation. As under starting conditions with normal operation the relay do will become energized and the contacts 44 and 46 will close to complete the energizing circuit to the ignition device 2H. Assume that there is proper ignition and that the harmonics therefrom are coupled into the resonant tank circuit 98 and a voltage is developed across this tank circuit and across the condenser 97 which is effective to apply a negative voltage to the grid 35. With this negative voltage appearing on grid 65 the current flow in the grid circuit 64 and relay to will increase sufficiently to energize the relay 8% When the relay es becomes energized the energizing circuit to the pilot valve is completed by the closing of the switch blade 84 with contact 85. If there should be no flame established at the pilot burner 22 within a predetermined time the apparatus will shut off the pilot valve 2! and again check to see if the ignition device 2!! is operating properly. This operation will be understood when it is noted that when the relay to becomes energized, the switch blade 82 moves out of engagement with contact 83 to open the energizing circuit to the harmonic tank circuit 98. circuit 98, the condenser so will discharge effectively immediately through secondary I02 and the condenser 9'! will discharge through the resistor 98. The length of time that it takes for the condenser 91 to discharge through the resistor 9% will determine the length of time that the relay 80 will be energized without a further voltage being applied to the harmonic network 98. Thus, after the condenser 97 has discharged the potential on grid 65 will drop and the relay 80 will become deenergized. When the relay becomes deenergized the switch blade 84 will move out of engagement with contact 85 and will deenergize the pilot valve, and th switch blade 82 will engage contact 83 to again complete the energizing circuit to the tank circuit Q3. When the energizing circuit to the tank 98 is again completed a check will be made to see if the ignition device 23 is operating properly and if it is a voltage will be built up across the tank circuit and the condenser 9'! which will again bias the electrode 55 in a negative direction to effect energization of the relay 8B. vhen the relay again becomes energized the pilot valve 2i will again When no signal is applied to the tank 8 be energized and a further attempt will be made to establish combustion at the pilot burner 22.

If iiame is still not established at the pilot burner 22 the apparatus will again shut down to check the operation of the ignition device and this process will continue for a number of times until such time as the heater 31 associated with the safety switch device 35 warps the bimetal 38 toward the right and opens the contacts 38 and 39. The opening of the contacts 38 and 39 will cause deenergization of the control relay G0 and a complete shut down of the apparatus will result until such time as the reset device M is again actuated.

Thus it will be seen that the apparatus will check the ignition and if there is ignition the pilot valve will be opened. If no flame is established the apparatus will again check the ignition and if still operating properly a further attempt will be made to establish combustion at the pilot burner with this checking and igniting attempt being carried on until the safety switch device 35 opens to the energizing circuit to the main control relay 40. This arrangement has the advantage of maintaining the amount of unburned fuel injected into a combustion chamber at a minimum when there is no flame present to consume this fuel.

As soon as the fault causing the failure of combustion at the pilot burner has been cleared the apparatus will start in the normal manner as described above.

If there should be a failure of combustion during normal operation, the flame detection relay ill will become deenergized and will reconnect the ignition device 29 into an energizing circuit. If combustion is not established within a predetermined time the safety cut oif device will be effective to shut down the apparatus. During the period between the flame failure and the shut down by the safety switch 35 the apparatus will periodically check the operation of the ignition device 2!! as explained above and if the ignition device 20 fails for any reason the pilot valve will be retained in the deenergized position so that no further fuel can be fed into the combustion chamber.

Component checking features In the operation considered thus far the apparatus within the housing 15 has been considered to be operating properly. If, for any reason, the apparatus was not operating properly, and such lack of operation is apt to create an unsafe condition, it is desired that the apparatus be shut down.

One function where it would be desirable to maintain the apparatus inoperative would be where there is an open or a short circuit condition existing at the photoelectric device 25. In the event there is an open or a short circuit in the photocell circuit there will be no rectification present and. it will be impossible for the condenser 33 to charge to attempt to establish an effective control signal on the grid 63 for causing energization of the relay 10. Further, with a short circuit condition existing at the photoelectric device 25 the grid 63 would be effectively connected to the left-hand terminal of the secondary 52 by a connection through the resistor 92, conductor hi3, photo-electric device 25, and conductor M5. This would have the effect of applying a further negatively phased biasing voltage to the control grid 63 which would limit even more the flow of current through the discharge device 68. With the relay 1 deenergized for a predetermined length of time, with the relay il energized, the safety switch device 35 will become effective to shut the entire apparatus down.

In the event that the flame detection relay should stick in the operating position with the switch blade 12 engaging contact 15 an energizing circuit will be completed to the safety switch heater 3! whenever the main control relay do is deenergized. This circuit may be traced from the tap 33 on secondary 32 through resistor 48, conductor H50, conductor I56, switch blade 12, contact I5,conductor 155, heater 31, and conductors H and H6 back to the left-hand terminal of secondary 32. As soon as the heater has warped the bimetal 36 toward the right the contacts 38 and 39 will open to make it impossible to energize the relay 40 upon a subsequent closing of the thermostatic device 16.

Under these conditions it Will be impossible to reset the safety switch device until such time as the fault causing energization of the heater 3'! is removed. This will be understood when it is noted that the heater 31, circumstances, is energized independently of any relay contacts of relay 4'0 and the opening of the contacts 38 and 39 does not effect the deanergization of the relay 10. Thus, heater 3'! holds bimetal 36 in the warped position. Such an ar- 5 rangement as this enables the operator to determine whether or not the cont-r01 apparatus is not functioning properly or whether the controlled burner is not functioning properly.

When the apparatus is not functioning the apparatus cannot be put back into operation but when the burner fails the apparatus can be put back .into operation by the actuation of the reset actuator M.

Conclusion In conclusion it will be noted there has been provided a burner control apparatus with a new and improved circuit which checks the presence of ignition, introduces a minimum of fuel into the burner in the absence of combustion, and which shuts down in the absence of ignition or combustion or upon a component failure within the apparatus. While many modifications will be apparent to those skilled in the art it is to be understood the invention is limited solely by the scope of the appended claims.

I claim as my invention:

1. Burner control apparatus for use with a burner having .igniting means, a pilot valve and a main control valve, the combination comprising, a first control relay, a source of power, an energizing circuit for said relay "including said source adapted to be completed by means indicating a need for burner operation, means controlled by said first relay arranged to connect the igniting means to said source of power, control means comprising a second relay adapted to respond to the proper operation of said igniting means, said control means arranged to effect operation of the pilot valve, flame responsive means comprising a third relay adapted to respond to a burner and pilot flame, means including said flame responsive means rendering said main valve operative and maintaining the pilot valve operative upon the presence of a pilot flame, timing means connected to said control means for energizing the pilot valve for a number of relatively short periods in the absence of a flame, and further timing means connected in controlunder the assumed l0 ling relation with respect to said control relay for rendering said relay ineffective after said first named timing means has operated a number of times.

2. Control apparatus, comprising in combination, a source of power, an electron discharge device having an anode, cathode and a plurality of grid electrodes, means connecting said cathode and anode and one of said grid electrodes to said source, a first relay connected in circuit with said anode, a second relay connected in circuit with said one grid electrode, a source of biasing voltage connected to another of said grid electrodes, said last named source when of a predetermined magnitude effecting operation of said second relay, and a control signal source connected to a further of said grid electrodes and effective when of a predetermined magnitude to efiect operation of said first relay.

3. Control apparatus, comprising in combination, a source of power, an electron discharge d vice having an anode, cathode, control grid, screen grid and suppressor grid, means connecting said cathode, said screen grid and said anode to said source, a first relay in the anode connection, a second relay in the screen grid connection, a source of biasing voltage connected to said suppressor grid and efiective when of a predetermined magnitude to effect operation of said second relay, and a source of control signal connected to said control grid, said control signal when of a predetremined magnitude effecting operation of said first relay.

4. Control apparatus, comprising in combination, a source of power, an electron discharge device having an anode, cathode, control grid, screen grid and suppressor grid, means connecting said cathode, said screen grid and said anode to said source, a first relay in the anode connection, a second relay in the screen grid connection, a source of biasing voltage connected to said suppressor grid and eflective when of a predetermined magnitude to effect operation of said second relay, a source of control signal connected to said control grid, said control signal when of a predetermined magnitude effecting operation of said first relay, and means actuated by said first relay for rendering ineflective said source of biasing voltage.

5. Burner control apparatus for use with a burner having electrical ignition; a relay, electronic means for checking the presence of proper ignition, said means comprising an electrical circuit adapted to be coupled by said relay to an ignition device, rectifying means connected thereto and adapted to produce an output voltage indicative of the presence of electrical ignition, an electronic discharge device having a plurality of grid electrodes, means connecting said relay in circuit with one of said grid electrodes, and means connecting another of said electrodes to said rectifying means to control the current flow through said relay; said relay thereby normally controlling said electrical circuit in accordance with the presence or absence of electrical ignition, and flame responsive means connected to render said relay ineffective to respond to the presence or absence of electrical ignition'when a burner flame is present.

6. Control apparatus, comprising in combination, a source of power, an electron discharge device having an anode, cathode, control grid, screen grid and suppressor grid, means connecting said cathode, said screen grid and anode to said source, a first relay in the anode connection,

a second relay in the screen grid connection, a source of biasing voltage connected to said suppressor grid and effective when of a predetermined magnitude to effect operation of said second relay, a source of control signal connected to said control grid, said control signal when of a predetermined magnitude effecting operation of said first relay, and means actuated by said second relay for rendering ineffective said source of biasing voltage.

'7. Burner control apparatus, comprising, an electron discharge device having an anode, cathode and a plurality of grid electrodes, a source of power, a first relay connected to said anode, a second relay connected to one of said grid electrodes, means connecting said device to said source of power so that normally the current flowing therethrough is insufficient to operate said first or second relays, a first electrical circuit connected to a second of said grid electrodes and including means effective to apply a voltage thereto upon exposure to a properly operating ignition means, said circuit effecting operation of said second relay when said last named voltage is present, and a second electrical circuit connected to a third of said electrodes and including means to apply a voltage thereon indicative of the presence or absence of a burner flame, said second electrical circuit effecting operation of said first relay upon said voltage indicating the presence of flame.

8. Control apparatus, comprising, a source of power, an electron discharge device having an anode, cathode and three grid electrodes, means connecting said device in energizing relation to said source, a first relay connected in circuit with said anode, a second relay connected in circuit with one of said grid electrodes, a first control signal source connected to said device at a second of said grid electrodes to effect operation of said second relay, a second control signal source connected to said device at a third of said grid electrodes to effect operation of said first relay, and circuit means controlled by said secondrelay for rendering said first source inefiective and said second source effective.

9. Control apparatus, comprising, a source of power, an electron discharge device having an anode, cathode and three grid electrodes, means connecting said device in energizing relation to said source, a first relay connected in circuit with anode, a second relay connected, in circuit with said one of said grid electrodes, a first control signal source connected to said device at a second of said grid electrodes to effect operation of said second relay, a second control signal source connected to said device at a third of said grid electrodes to effect operation of said first relay, and circuit means controlled by said first relay for rendering ineffective said first source.

10. Burner control apparatus, comprising, an electron discharge device having an anode, cathode and a plurality of grid electrodes, a source of power, a first relay connected to said anode, a second relay connected to one of said grid electrodes, means connecting said device to said source of power so that normally the current flowing therethrough is insufficient to operate said first or second relays, a first electrical circuit connected to a second of said grid electrodes and including means effective to apply a voltage thereto upon exposure to a properly operating ignition means, said circuit effecting operation of said second relay when said last named voltage is present, a second electrical circuit con- 12 nected to a third of said electrodes and including means to apply a voltage thereon indicative of the presence or absence of a burner flame, said second electrical circuit effecting operation of said first relay upon said voltage indicating the presence of flame, and means connecting said of ignition, and flame second circuit to said source at a point where said device will be rendered inoperative upon an open or short circuit condition occurring in said second circuit.

11. Burner control apparatus for use with a burner having electrical ignition means, a pilot burner, and fuel fiow control means, comprising in combination, an electron discharge device having an anode, cathode, control grid, screen grid and suppressor grid, a source of power, means connecting said cathode, said screen grid and said anode to said source, a first relay in the anode connection adapted when energized to actuate the fuel flow control means, a second relay in the screen grid connection arranged when energized to indicate the presence of elec-' trical ignition, a first control signal source connected to said suppressor grid and having a signal indicative of the presence or absence of electrical ignition, said suppressor grid when a predetermined signal is applied thereto effecting energization of said second relay, means including said second relay for initiating operation of the pilot burner, and a second control signal source connected to said control grid and having a signal thereon indicative of the presence or absence of a burner flame, said control grid efi'ecting operation of said first relay when said second source indicates a burner flame.

l2. Burner control apparatus for use with the burner having electrical ignition; a relay, electronic means for checking the presence of proper ignition, said means comprising an electrical circuit adapted to be coupled by said relay to an ignition device, rectifying means connected in said electrical circuit and adapted to produce a direct current output voltage indicative of the esablishment of ignition, a capacitor associated with "i said rectifying means to be charged by the direct current output of said rectifying means, a resistor forming a discharge path for said capacitor, and an electronic discharge device having said relay in circuit therewith and connected to said capacitor to be controlled by the direct current output of said rectifying means so long as said capacitor remains charged; said relay thereby normally controlling said electrical circuit in accordance with the presence or absence responsive means connected to render said relay inefiective to respond to the presence or absence of ignition when a burner flame is present.

13. Burner control apparatus for use with a burner having electrical ignition and fuel flow controlling means, comprising; a source of power;

a control relay having a first and second posi tion; electrical means, first circuit means controlled by said relay connecting said electrical 1 means to respond to the establishment of electrical ignition when said relay is in said first position, said electrical means adapted to energize said relay by said source when said relay is in said first position and electrical ignition is established to cause said relay to move to said second position and hence to disconnect said electrical means so that said electrical means no longer responds to the establishment of electrical ignition and said relay tends to return to said first position; eletrical timing means 13 connected in controlling relation to said electrical means to maintain said relay in said second position for a predetermined length of time after the establishment of electrical ignition; second circuit means adapted to control fuel flow controlling means, means including said relay for energizing said second circuit; and combustion responsive means connected to said electrical means and operative upon the establishment of combustion to render said electrical means inefiective to respond to the establishment of electrical ignition.

HENRY L. HANSON.

Number UNITED STATES PATENTS Name Date Huber July 7, 1936 Vaughan Aug. 2, 1938 Draper June 13, 1939 Maynard Apr. 9, 1940 Jones Dec. 8, 1942 Crews Oct. 30, 1945 Aubert Sept. 9, 1947 Rosche May 4, 1948 Gaddis Jan. 8, 1952

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