US2981324A - Burner control apparatus - Google Patents

Description

April 25, 1961 F. T. DEZIEL BURNER CONTROL APPARATUS Filed Oct. 23, A958 INVENTORI FRED T. DEZIEL jYM 421w ATTORNEY United States BURNER CONTROL APPARATUS Filed Oct. 23, 1958, Ser. No. 769,153

5 Claims. (Cl. 158-125) The present invention is concerned with an improved control apparatus and particularly with an improved burner control apparatus which uses an electronic flame detector. In the structure of the present invention, an electronic flame detector is utilized in which stages of amplification are connected in cascade. The first of these stages of amplification is controlled by a flame sensing means. The output of this first stage of amplification includes a first relay. This output also controls the input of a second stage of amplification, whose output includes a second relay. The switch means of the first and second relays are interconnected to control the initial atent O energizing circuit for a main burner control relay such that this relay may not be initially energized unless both the first and second relays are in a condition indicating the absence of flame at a fuel burner unit which is being controlled. I

A burner control apparatus must provide safe and re liable operation of an associated fuel burner unit. It is desirable to accomplish this with a minimum amount of expense and yet safe operation is of prime importance. Electronic flame detectors have found wide acceptance due to the fact that these detectors are fast acting and will sense the presence or absence of flame in a very short time. This fast acting feature is particularly of importance in a fuel burner unit which has a high firing rate.

A number of safety features have been incorporated into electronic flame detectors to render them fail safe. That is, features have been provided to insure that the flame detector will fail in a condition indicating the absence of flame, should some component within the electronic circuitry fail. One of these features is the pro vision of inter-locking circuit means between a flame relay and a main burner control relay such that this main burner control relay is not initially energized unless the flame relay is in av condition indicating the absence of flame. Such a construction insures that the main burner control relay is not energized upon a call for operation of the fuel burner unit if the electronic flame detector at this time has failed such that the flame detector is falsely indicating the presenceof flame at the fuel burner unit.- i The present invention utilizes a feature of this type which is improved to provide safe and reliable operation 1 at a: minimum cost.

Specifically, the present invention provides an electronic flame detector having a firststage of electronic amplification which is controlled by flame sensing means such that this first stage is rendered conductive in the absence. of flame at the fuel burner unit. The output of this first stage of electronic amplification includes a first relay which is normally energized in the absence of: flame at the: fuel burner unit. The output of this first stage. of electronic amplification is connected to the input of a second stage of electronic amplification in such a manner as to render this second stage non-conductive in the absence of flame at the fuel burner unit; The output of the second stage of electronic amplification includes a. second relay which is normally tie-energized in the absence of flame in the fuel burner unit. The switch means of the first and second relays are so inter-connected in the initial energizing circuit of the main burner control relay that this relay may not be energized unless each of these two relays are in a condition indicating the absence of flame at the fuel burner unit. In this manner, both the first and the second stage of electronic amplification is checked to insure that in the event either of the stages is unable to respond to the absence of flame at the burner unit, the main burner control relay cannot be energized. In other words, a safe failure is insured.

Furthermore, with the apparatus of the present invention, a safe start is provided when operating voltage is initially applied to the burner control system, or, as a further example, when a power failure occurs and the power is then restored. In this case, it is necessary for the electronic flame detector to be placed in an operating condition; for example if the electronic amplifying stages include hot cathode discharge devices, these discharge devices must be heated to an operating condition. Upon operating the voltage being applied to the electronic flame detector, the first above mentioned relay must be energizedin response to the absence of flame at the fuel burner unit and the second above mentioned relay must be de-energized in response to this absence of flame. In the event that there was a call for operation of the fuel burner at this time, the fuel burner unit is not energized by the main burner control relay until the electronic flame detector has in fact properly sensed the absence of flame at the fuel burner unit.-

' The present invention will be apparent to those skilled in the art upon reference to the following specification, claims and drawing of which;

The single figure is a schematic representation of the present invention.

Referring to the single figure, the apparatus disclosed therein can be divided into three basic portions. The first portion is a control network identified bythe refer ence numeral 10. This control network includes means responsive to the need for operation of the fuel burner unit, in the form of a thermostat 11. The referencenumeral 12 identifies a main burner control relay having a winding 13 which is energized upon a need for opera tion of the fuel burner unit. The switches 14 and 15 of relay 12 are shown in the de-en'ergized condition wherein these switches are open. Energizat ion of winding 13 causes switches 14 and 15' to move to a closed position to perform control functions hereinafter described. The control network 10 also includes a safety lockout means 16 in the form of a conventional bi-- metal operated safety switch. The bimetal element of this safety switch is identified by the reference numeral 17 and this bimetal element is adapted to be heated by an actuating heater 18. The reference numeral 19 identifies a normally closed safety switch. In the operation of the safety cutout means 16, a: predetermined time period of heating of bimetal 17 causes the upper end thereof to move to the left to release the switch blades, holding switch 19 and to cause this switch to open. is' the safety lockout condition. In order" to reset the safety cutout. means 16 to the position shown, it is necessary to manually actuate a reset button 20.

The second basic portion of the apparatus disclosed in the single figure is an electronic flame detector identified by a reference numeral 100. This flame detector includes a first and a second controllable current conducting devicein the form of electron discharge devices 21 and 22, these devices and their associated circuitry-malt; ing up what may be defined as first and second stages-of;-

electronic amplification respectively. These discharge devices are provided with anodes 23 and 24, control electrodes 25 and 26, cathodes 27 and 28, and cathode heaters 29 and 30. The input of electron discharge device 21, that isthe control electrode 25 and the cathode 27, is connected to be controlled by a flame sensing means in the form of a photoemissive cell 31 having a cathode 32 and an anode 33. The output of discharge device 21, that is the anode 23 and the cathode 27, is connected to control the energization of a first flame relay 34 having a winding 35 and a single switch 36. This relay 34 is shown in the deenergized condition wherein its winding is de-energized and its switch is in an open condition.

The output of discharge device 21 is also connected to the input of discharge device 22, that is the control electrode 26 and the cathode 28. The output of this discharge device, that is anode 24 and cathode 28, is connected to control a second flame relay 37 having a winding 38 and switches 39, 40 and 41. Here again, the winding 38 is shown in a de-energized condition wherein switches 39 and 40 are closed and switch 41 is open.

The third basic portion of the apparatus disclosed in the single figure is a fuel burner unit identified by the reference numeral 42. This fuel burner unit includes a main fuel burner 43, a pilot burner 44, a main valve 45, a pilot valve 46, and ignition means inthe form of an ignition transformer 47.

The overall sequence of operation of the apparatus disclosed is such that the thermostat 11 senses a need for operation of the fuel burner unit 42 and causes the main burner control relay 12 to be energized, providing the electronic flame detector 100 and particularly the relays 34 and 37 are in a condition indicating the absence of flame at the fuel burner unit. Energization of the main burner control relay 12 causes the pilot valve 46 and the ignition transformer 47 to be energized and establishes a pilot flame at the pilot burner 44. This pilot flame is sensed by the electronic flame detector 100, including photocell 31, and causes relays 34 and 37 to move to a condition indicating the presence of flame at the fuel burner unit. This then causes the main valve 45 to be energized and the fuel flows to the main fuel burner 43 and is ignited by the pilot flame. The presence of this flame is continuously supervised by the electronic flame detector 21, to thereby provide safe operation. I Consideringthis operation in detail, operating voltage for the apparatus disclosed in the single figure is derived from a pair of power lineconductors 48 and 49 which are connected to a source of alternating voltage, not shown. The alternating voltage is applied to a transformer 50 by means of a master switch 51. In some cases it is desirable to eliminate the thermostat 11 and to'provide a pressure or temperature responsive device or the like to control switch '51 such that the closing of this switch indicates the need for operation of the fuel burner unit.

Upon the closing of switch 51, the primary winding 52 of transformer 50 is energized and'this in turn energizes the secondary windings 53, 54 and 55. Secondary 'wind ing 53 provides operating voltage for the control network 10 while secondary windings 54 and 55 provide operating voltage for the electronic flame detector 100 and the photocell 31. Secondary winding 54 is provided to energize the cathode heaters 29 and 30 of the electron discharge devices.

- The apparatus as shown in the single figure is in the condition wherein the switch 51 is open and in this case the apparatus is completely de-energized. However, upon this switch being closed, the cathode heaters 29 and 30 of the electron discharge devices are energized and after a time period the cathodes of these discharge devices are heated to an operating condition. Since a flame is 'not present at the fuel burner unit at this time, the electron discharge device 21 is rendered conductive. This conduction circuit can be traced from a tap 56 on secondary 4 V winding 55 to cathode 27, anode 23, winding 35 of relay 34, and conductors 57 and 58 to a transformer tap 59. From this circuit it can be seen that winding 35 is energized. It will further be noted that a capacitor 60 is connected in parallel with winding 35 to maintain this winding energized during alternate half cycles of the alternating energizing voltage. The voltage developed across winding 35 and across capacitor 60, is such that terminal 61 is negative with respect to terminal 62. Terminal 61 is connected by means of a conductor 63 to the control electrode 26 of discharge device 22 while terminal 62 is connected by means of conductors 57 and 64 to the cathode of this discharge device. In this manner, the output of discharge device 21 is connected in controlling relation to the input of discharge device 22 and biases discharge device 22 to be non-conductive. Therefore, relay 37 remains de-energized.

Energization of relay 34 as above described, causes switch 36 to move to a closed condition and this completes a portion of the initial energizing circuit for the winding of the control relay 12. The apparatus is now in the standby condition wherein the electronic flame detector is operative and is properly indicating the ab sence of flame at the fuel burner unit.

If thermostat 11 now indicates a need for operation to the fuel burner unit by closing its switch, the winding of relay 12 is energized through an initial energizing circuit which can be traced from the upper terminal of secondary winding 53 through thermostat 11, safety switch 19, winding 13, conductor 65, switch 36, conductor 66, switch 39, conductor 67, heater18, and conductor 68 to the lower terminal of winding 53. From this circuit it can be seen that in orderfor control relay 12 to be energized, it is necessary that relays 34 and 37 both be in a condition indicating the absence of flame at the fuel burner and furthermore the actuating heater 18 of the safety cutout means .must have electrical continuity. i

Energization of relay 12 causes switches 14 and 15 to be moved to a closed condition.

Switch 14 completes holding energizing circuits for both relay 12 and safety cutout means" 16. The holding energizing circuit for relay 12 can be traced from the upper terminal of secondary winding 53 through thermostat 11, safety switch 19, relay winding 13, switch 14, and conductor 69 to transformer tap 70 of secondary winding 53. The holding energizing circuit for heater 18 of the safety cutout means can be traced from a transformer tap 70 through conductor 69, switch 14, conductor '65, switch 36, conductor 66, switch 39, conductor 67, heater 18, and conductor 68 to the lower terminal of secondary winding 53. In this manner, the relay 12 is maintained energized so long as safety switch 19 remains in a closed condition and so long as the thermostat 11 continues to indicate the need for operation of the fuel burner unit. Furthermore, the actuating heater 18 of the safety cutout means is maintained energized so long as the electronic flame detector continues to indicate the absence of flame at the fuel burner unit;

. Energization of the relay 12 also causes switch 15 to move to a closed condition and this completes an energizing circuit for the pilotvalve 46 and the ignition transformer 47. The energizing circuit of the pilot valve 46 is controlled solely by the switch 15 and this circuit can be traced from the power line conductor line 48 through switch 51, conductor 71, switch 15, conductors 72 and 73, pilot valve 46 and conductors 74 and 75 to the power line conductor 49. The energizing circuit for the ignition transformer 47 is controlled jointly by switch 15 and switch 40. This circuit can be traced from power line conductor 48 through switch 51, conductor 71, switch 15, conductor 72, switch 40, conductor 76, ignition transformer 47, conductor 74 and conductor 75 to power line conductor 49.

A pilot flame is now normally established at pilot burner 44, and this flame is sensed by the photocell 31.

enemas Since this photocell is a photoemissive cell, the cell acts as. a rectifier and this current flow circuit can be traced from the upper terminal of secondary winding 55 through a capacitor 77, conductor 78, photocell 31, and conductor 79 to the transformer tap 56. This current flow circuit is such that capacitor 77 is charged to the polarity indicated in the figure. This charge placed on capacitor 77 due to the presence of the pilot flame is applied to a filter means including resistors 80 and 81 and capacitor 82. Capacitor 82 is charged from capacitor 77 to the polarity indicated in the figure and this charge places a negative voltage on control electrode 25 thereby biasing discharge device 21 to be substantially cutoif. The winding 35 of relay 34 is then de-energized and terminals 61 and 62 associated therewith are then placed at approximately the same electrical potential.

Since the voltage present across winding 35 was previously used to bias discharge device 22 to be nonconductive, this discharge device now becomes conductive to energize the winding 38 of relay 37. This energizing circuit can be traced from a transformer tap 59 through conductors 58 and 64, discharge device 22, winding 38 and conductor 83 to the lower terminal of secondary winding 55. It will be appreciated that the de-energization of relay 34, as well as the energization of relay 37, has interrupted the holding energizing circuit for heater 18 of safety lockout means 16, thereby de-energizing the safety lockout means to insure that the safety switch 19 will remain in its closed condition.

Energization of relay 37 also causes switch 40 to be opened and switch 41 to be closed. It will be remembered that switch 40 is in the energizing circuit for the ignition transformer 47 and therefore the ignition transformer is de-energized. However, a flame has been established at the pilot burner 44 and pilot valve 46 re mains energized. The closing of switch 41 completes an energizing circuit for main fuel valve 45 which can be traced from power line conductor 48 through switch '51, conductor 71, switch 15, conductor 72, switch 41, conductor 85, main valve 45 and conductor 75 to the power line conductor 49. Therefore, fuel is admitted to the main fuel burner 43 and is ignited by the pilot flame.

Safe operation of the fuel burner unit 42 is insured by the electronic flame detector 100 since photocell 31 continues to supervise the presence of flame at the fuel burner unit during the running period. Should the flame fail, the photocell 31 senses this absence of flame to render discharge device 21 once again conductive and thereby render discharge device 22 non-conductive. This in turn causes relay 34 to be energized and relay 37 to be de-energized to once again complete the holding energizing circuit for heater 18 of the safety cutoff means. Furthermore, de-energization of relay 37 causes the main valve 45 to be immediately de-energized. The pilot valve 46 is maintained energized and the ignition transformer 47 is again energized in an attempt to reestablish flame at the pilot and main burners. If such a flame is successfully re-established, the electronic flame detector 100 senses the presence of the pilot flame and once again energizes the main valve 45 in an attempt to establish flame at the main fuel burner 43. However, if a flame is not established at the pilot burner 44, the safety cutout means 16 is effective in a relatively short period of time, for example 60 seconds, to open the switch 19 and thereby de-energize the burner relay 12, placing the apparatus in a safety lockout condition.

Also, should there be a failure to establish flame at the pilot burner 44 upon the initial energization of the pilot valve and the ignition transformer, the apparatus likewise is placed in safety lockout condition.

From the above it can be seen that I have invented an improved control apparatus which is utilized with and incorporates an electronic flame detector providing safe and reliable operation of a fuel burner unit. Other modifications of the present invention will be apparent to 6 those skilled in the art and it is intended that the scope of the present invention be limited solely by the appended claims.

I claim as my invention:

1. An electronic flame detector comprising; flame sensing means arranged to be positioned to sense the presence or absence of flame in a given area, a first electron discharge device having an input circuit and output circuit, circuit means including said input circuit connected to said flame sensing means to thereby control said first discharge device in accordance with the presence or absence of flame at the given area, a first flame relay having a winding connected in the output circuit of said first discharge device and having switch means, a second electron discharge device having an input circuit and an output circuit, means connecting the output circuit of said first discharge device in controlling relation to the input circuit of said second discharge device to thereby control said second discharge device in accordance with the presence or absence of flame in the given area, the operation of said second discharge device also being dependent upon proper operation of said first discharge device, a second flame relay having a winding connected in the output cir cuit of said second discharge device and having switch means, and control circuit means jointly controlled by the switch means of said first and second relays to perform a control function only upon said first and second flame relays jointly detecting the presence or absence of flame in the given area.

2. An electronic flame detector comprising; flame sensing means arranged to be positioned to sense the presence or absence of flame in a given area and to derive a signal voltage in response thereto, a first electron discharge de vice having a pair of input electrodes and a pair of output electrodes, a first flame relay having a winding and switch means, circuit means connecting said first flame relay winding in series with the output electrodes of said first discharge device, circuit means connecting said flame sensing means in controlling relation to the input electrodes of said first discharge device in a manner to render said first discharge device nonconductive in the presence of flame in the given area, a second electron discharge device having a pair of input electrodes and a pair of output electrodes, a second flame relay having a winding and switch means, circuit means connecting said second flame relay winding in series with the output electrodes of said second discharge device, further circuit means connecting the input electrodes of said second discharge device to the winding of said first flame relay in such a manner as to render said second discharge device nonconductive upon said first discharge device being conductive, said first flame relay thereby being energized in the absence of flame in the given area and said second relay thereby being deenergized in the absence of flame in the given area, and control circuit means included in series therewith the switch means of said first and second relays.

3. Burner control apparatus for use with a fuel burner unit, comprising; a control relay having switch means adapted to be connected to the fuel burner unit, an electronic flame detector having a pair of controllable current conducting devices each having an input and an output, flame sensing means adapted to be positioned to sense the presence of flame at the fuel burner unit, means connecting said flame sensing means in controlling relation to the input of one of said controllable current conducting devices, a first flame relay connected to the output of said one controllable current conducting device to be controlled thereby and having switch means, means connecting the output of said one controllable current conducting device in controlling relation to the input of the other of said controllable current conducting devices, a second flame relay connected to the output of said other controllable current conducting device to be controlled thereby and having switch means, and energizing circuit means for said control relay including the switch means of said first and second flame relays adapted to energize said control relay and thereby the fuel burner unit only upon the switch means of said first and second flame relays being in a condition indicative of the absence of flame at the fuel burner unit.

4. Burner control apparatus for use with a fuel burner unit, comprising; a control relay having a winding and having switch means adapted to be connected to the fuel burner unit such that energizing of said control relay winding causes energization of the fuel burner unit, flame sensing means arranged to be positioned to sense the flame at the fuel burner unit, a first stage device of electronic amplification having input terminals and output terminals, circuit means connecting said flame sensing means to the input terminals of said first stage device, a first flame relay having a winding and switch means, circuit means connecting said first flame relay winding to the output terminals of said first amplifying stage device, a second stage device of electronic amplification having input terminals and output terminals, circuit means connecting the input terminals of said second stage device to said first flame relay winding such that the voltage across said first flame relay winding controls said second stage device, a second flame relay having a Winding and switch means, circuit means connecting said second flame relay winding to the output terminals of said second stage device, and further circuit means including the switch means of said first and second flame relays and the winding of said control relay to allow initial energization of said control relay winding only in the event that said first and second flame relay windings are in-a state indicating the absence of flame at the fuel burner unit.

5. Burner control apparatus for use with a fuel burner unit comprising; a control relay having a winding and switch means adapted to be connected to a fuel burner unit to energize the fuel burner unit upon energization of the control relay, winding, an electronic flame detector having a pair of electron discharge devices, each having a control electrode, an anode, and a cathode, flame sensing means adapted to be positioned to sense the presence or absence of flame at the fuel burner unit, means connecting said flame sensing means to the control electrode and cathode of said first discharge device in a manner to render said first discharge device nonconductive in the presence of flame at the fuel burner unit, said first discharge device being conductive in the absence of flame at the fuel burner unit, a first flame relay having a winding connected in series with the anode and the cathode of said first discharge device to thereby be energized in theabsence of flame at the fuel burner unit, circuit means connecting the winding of said first flame relay to the cathode and control electrode of said second discharge device in a manner to render said second discharge device nonconductive in the absence of flame at the fuel burner unit, a second flame relay having a winding connected in series with the anode and the cathode of said second discharge device to thereby maintain said second flame relay winding de-energized in the absence of flame at the fuel burner unit, and energizing circuit means for said control relay winding adapted to energize said control relay winding upon a need for operation for said fuel burner unit, said energizing circuit means including switch means of said first and second flame relays such that said control relay winding may be energized only upon said first and second flame relays being in a condition indicative of the absence of flame at the fuel burner unit.

References Cited in the file of this patent UNITED STATES PATENTS 2,386,648 Aubert Oct. 9, 1945 2,775,291 Wilson Dec. 25, 1956 2,839,132 Blackett et al June 17, 1958

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