US2640920A - Safety fuel burner control system utilizing flame conduction - Google Patents

Description

June 2, 1953 F. E. CAIRNS, JR 2,640,920 SAFETY FUEL BURNER CONTROL SYSTEM Y j UTILIZING FLAME CONDUCTION Filed July 9. 1949 2 Sheets-Sheet l INVENTOR. 4,0, FEED E. cn/eA/s J- June 2, 1953 F. E. CAIRNS, JR 2,640,920

SAFETY FUEL BURNER CONTROL SYSTEM UTILIZING FLAME CONDUCTION Filed July 9,1949 2 Sheets-Sheet 2 *INVENTOR. F250 E. 9/2/15 I,

FTTOQNEV Patented June 2, 1953 SAFETY FUEL BURNER CONTROL SYSTEM UTILIZING FLAME CONDUCTION Fred E. Cairns, Jr., North Hollywood, Calif., as-

signor to General Controls 00., Glendale, Calif., a corporation of California Application July 9, 1949, Serial No. 103,768

2 Claims.

This invention relates generally to a system referred to in an application filed concurrently herewith, in the name of Fred E. Cairns, Jr.

Serial No. 103,767, and entitled Fuel Burner Safety Control Using Flame Conduction.

In that application, the flame of a pilot burner serves while it is in existence, to provide a conducting path between a pair of electrodes spaced within the flame and in the direction of flame propagation. While the flame is in existence, electric power is supplied to hold a fuel valve open. This power is supplied conveniently by the aid of an electronic emission device operat- 'ing to produce a controlling space current.

The flame conductivity is greater in one direction along the flame than in the opposite direction of current flow. This unilateral effect is utilized effectively in the system.

In accordance with the present invention herein described, the pilot flame is caused to 'be automatically ignited when the operation of the system is initiated. It is one of the objects of this invention to effect such automatic response, and yet ensure that the main burner cannot be placed into operation until after the pilot flame is ignited and in existence.

It is still another object of this invention to ensure that the ignition of the pilot burner and the main burner are definitely interlocked by the aid of the flame electrodes.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several forms in which it may be embodied. Such forms are shown in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a diagrammatic representation of .one embodiment of the invention;

Figs. 2 and 3 are views, similar to Fig. 1, of modified forms of the invention.

In Fig. 1 a main gas burner I is illustrated adapted to be supplied with fuel, as by aid of a pipe or conduit 2. A pilot burner 3 is also supplied from pipe I through 3.-T-C0llll80'tl0ll 4. A main shut-off valve 5 is interposed in the pipe 2.

Control of the flow of fuel to the main burner I is effected by an electromagnetically operated valve structure 6.

Power for operating the valve structure 6 is derived from a source of alternating current controlled by a switch I and connected to the primary winding 8 of a transformer 9. A secondary winding It of transformer 9 is arranged to energize an electric igniter II disposed near the burner 3 to light the pilot flame l2. This pilot flame I2 is shown in dot-and-dash lines to indicate that the system in the position shown is not in operation.

Power for the valve 6 is controlled by an electronic emission device I3 having an electrically heated cathode I4, a control electrode I5, and an anode IS. The heater I! for the cathode I4 is connected to a section of a main secondary winding I8 of the transformer 9.

While the pilot flame I2 is not in existence, the electronic emission device I3 is in such condition that it is incapable of causing energization of the valve means (3. The output circuit of the device I3 includes the upper section of transformer winding I8, a connection I9, valve means 6, automatic switching devices 20 and 2|, anode I6, cathode I4, and connection 22 to an intermediate point of the winding I8. The switching device 20 may be a thermostatic switch located in the medium to be heated, such as circumambient atmosphere in a room, or water heater, or the like. Automatic switch 2| may provide a limit as of temperature, or pressure, or the like. Either of these switching devices 20 and 2| may prevent energization of the electromagnetically operated valve means 6.

The control electrode I5 is connected, as by a large resistance, to the lower terminal of the winding I 8. This resistance thus imposes a negative potential upon the control electrode I5 when the anode I6 is positive, and no substantial space current can flow through the output circuit. A conventional grid leak condenser 24 may bridge the resistance 23. During those half cycles in which anode It is negative, it is impossible for any output current to flow between the anode I6 and cathode I4.

In order tomakeit possible to energize the valve means 6, the control electrode 15 must have its potential raised. This is effected in response to the energizatlon of the flame l2 by the aid of a pair of flame electrodes 25 and 26. These two electrodes are spaced in the direction of flame propagation, and the flame serves, as a substantially. unilateral conductor-,electrically to connect these two electrodes; Electrode 2'5 is connected to the control electrode l5 through a resistor 22'. of higher potential than the cathode l4. Accordingly, the control electrode then. permits the passage of an operative space current that on of the valve neans should both or" The elcc 25 obtains its potential from the upper terminal of the winding l8 through. connection l9 and a relay 28. When the upper terminal of the winding 18 is positive, the electrode 25 is also positive, and transmits positive potential to the'electrode [5. Accordingly, during those half cyclesin which the upper terminal or. winding i3 isposltive, an operative space current can flow to energize the valve means 6. This, of course, can: only occur when the flame i2 is in existence, since the flame is in series with the circuit through resistor 21 that imposes the operating potential upon the control electrode 15.

The relay 28, when the system is inactive, is in deenergized position. Accordingly, the back contact 29is closedby the movable arm 30. In this position, the igniter H is energized through the secondary winding l and the relay contacts 29 and 30.

However, as soon as the flame I2 is inexistence, the relay 28- is energized and the igniter circuit is interrupted. The:energization of this relay 2211s effected by the aid of another electronic emission device 3| having a cathode. 32,

a control electrode 33, and an anode 34-. An electric heating means 35 is used for heating cathode 32, and is connected in parallel with the. heater I E of the device I3.

The relay 23' is included in the output. circuit between the anode 34 and cathode 32 through the upper portion of the. winding IS. The control electrode 33, while flame I2 is not in existence, isimpressed with a potential from the lowerzterminal of winding [8 through aresistor 38 which is bridged by a grid leak condenser 31. This control electrode thus has a negative potential while anode 34 is positive. However, when the flame I 2 is in existence, the control electrode 33 is connected by way of connection 38.and the flame l2 to the upper termin'al'of'the winding i3. Accordingly, for those half cycles in which the upper terminal of secondarywinding 18. is positive, a space current can. flow through the output circuit and the relay [8.

In operation, the switch I is closed andv the shut-oil valve is opened. The igniter H is energized and stays energized until theflame I2 is established. As soon as the flame I2 is established, the electronic'emission device 13 permits flow of energy to the electromagnetically operated valve means 6.

At the same time, the electronicemission device 3| permits flow of energy to the relay 2-8 andthe igniter H is automatically deenergized.

Upon flame failure, the system returns to in active position. The valve means fi closes, since control electrode I5 prevents passage of a substantial output current.

In" the form of the invention illustrated in Fig.

Electrode is connected to a. point t ling devices 2 l. and Hzbc closed.

2, the pilot burner 3 and the main burner I are arranged as before. In this case, however, the valve means 6 is adapted to be operated by alternating current obtained from the secondary winding 39 of a transformer 40.

The primary winding 4| is controlled by a circuit: controlling device 42.

An electronic emission device 43 for controlling the passage of current to the igniter H and the valve means 6 is shown as having a cathode 44, a control electrode 45, and an anode 46. Heater 41: forthe cathode 44 is shown as connected across a section of a secondary winding 48. The right-hand portion of the secondary winding 48 is included: in the output circuit of the device 43, by way of a relay 49. The left-hand end of. the winding, 48. is connected by high resistance 53 to the control electrode 45. The usual grid leakcondenser Si is placed in parallel with the resistors 50.

When the pilot'ilame is not in existence, the control electrode 45 attains a potential which prevents flow of a space current during those half cycles in which the right-hand. terminal of the winding 48 is positive. Thisis due to the connection 5%] between the left-hand terminal of winding 48 and the electrode 45. Of course, during the alternate half-cycles in which anode 43 is negative, it is not possible under any. oilcumstances-for any current to flow in theoutput circuit.

When the flame I2 is in existence, electrodes 5 and 26 are electrically connected through the flame i2, acting as unilateral conductor. Electrode is directly connected to anode 46 and electrode 28 is connected to the. control electrode 425. Accordingly, a positive potential is-impressed in this manner upon the electrode for the half cycles in which the right-hand terminal of winding 48 is positive.

The relay 49 is thus energized and alternating current-power may be transmitted to the valve means sthrough the secondary winding 39, front contact 52 of relay 49, and connection 53. At the same time, connection is broken at tliTbEck contact 54' of the relay 49. This interrupts energization of the igniter H. The igniter circuit 1 I, while the flame IZisnot in'existence, is completedthrough secondarywinding. 39 and through back contact 54- anda. manual reset thermal cut-off device 55;. This thermal cut-off. device is:included in the ignition circuit to ensure interruptionoi this circuit should the pilot burner 3. remain unignited; Such devices are now well known, and require manual resetting in order to start the. series of operations. This. manual reset device. thus ensures against continuousenergization of the ignition circuit, permitting this circuit to becompleted for only a relatively short interval.

As before, upon failure of the pilot flame H, the control electrode 45-returns to a condition in whichno substantial output current can flow in the'output circuit and, accordingly, relay 49 is'deenergized, opening the circuit through which electrical'encrgym'ay be passedto valve means 6.

In the" form of" the invention illustrated in Fig. 3, the ignition circuit is arranged in the samelmannerasbefore, and includes the manual reset thermal cutoff 55; The electronic emission'. device 43has'an output circuit substantially identical withxthatl described. in connection with Fig. 2. The input. circuit; however, is'mo'dlflad in a manner now to be described.

A saturable core reactor device 56' isiillustrsted having the saturating direct current coil 51 and a reactor coil 58. With the pilot flame [2 extinguished, the resistance 50, as before, maintains the input circuit in such manner as to prevent substantial flow of output current through the relay 49. However, when the flame I2 is in existence, a direct current can flow through the saturating coil 57 by way of the flame I2 and electrodes 25 and 26. This direct current is derived from the right-hand terminal of winding 43, relay 49, to the cathode tap on the winding 48. Unilateral current is produced because of the rectifying function of the flame l2. Accordingly, with the flame l2 in existence, the reactance of the coil 58 is greatly reduced. Since this coil is connected directly between the cathode 44 and control electrode 45, the potential of the control electrode 45 is correspondingly raised and an output current can flow. In this case, the electronic emission device 43 is of such type as to permit the flow of space current unless control electrode. has a considerable negative potential with respect to cathode 44.

It is apparent that the coil 58 and the resistor 50 are in a series circuit across the left-hand section of winding 48. As the reactance of coil 58 is reduced, the diiference in potential across it is correspondingly reduced, permitting a space current to flow.

What I claim is:

1. In a control device: an electronic emission device having a cathode, a control electrode and an anode; means impressing an alternating electromotive force between the cathode and anode; means supplying an alternating electromotive force between the cathode and the control elec= Mode in such direction as to reduce the output current between the anode and the cathode; said latter means including a resistor; a saturable core reactor paralleling said latter means that supplies an alternating electromotive force between the cathode and the control electrode; a circuit responding to a condition for saturating 6 the reactor core, said circuit including a pair of electrodes between which a current may pass; and load moans operated by the space current of electronic emission device.

2. In a control device: an electronic emission device having a cathode, a control electrode and an anode; means impressing an alternating electromotive force between the cathode and anode; means supplying an alternating electromotive force between the cathode and the control electrode in such direction as to reduce the output current between the anode and the cathode; said latter means including a resistor; a saturable core reactor paralleling the said latter means that supplies an alternating electromotive force between the cathode and the control electrode; a pair of electrodes adapted to be spaced in thepath of a flame; a saturating coil for the reactor and in series with the electrodes, said electrodes and saturating coil being connected between the cathode and anode; and load means operated by the space current of the electronic emission device.

FRED E. CAIRNS, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,809,280 Knowles June 9, 1931 2,112,736 Cockrell Mar. 29, 1938 2,138,796 Sparrow Nov. 29, 1938 2,170,497 Gille Aug. 22, 1939 2,225,700 Laing Dec. 24, 1940 2,245,730 Sparrow June 17, 1941 2,260,977 Jones Oct. 28, 1941 2,263,430 Wannamaker Nov. 18, 1941 2,343,001 Cohen Feb. 29, 1944 2,374,610 McLaren Apr. 24, 1945 2,379,872 Gille July 10, 1945 2,379,873 Lange July 10, 1945 2,435,940 Jones Feb. 10, 1948 2,455,350 Beam Dec- 7. 1

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