US3273019A

US3273019A - Direct spark ignition system

Info

Publication number: US3273019A
Application number: US314744A
Authority: US
Inventors: Russell B Matthews
Original assignee: Penn Controls Inc
Current assignee: Penn Controls Inc; Johnson Controls International Inc
Priority date: 1963-10-08
Filing date: 1963-10-08
Publication date: 1966-09-13
Anticipated expiration: 1983-09-13

Description

Sept. 13, 1966 R. B. MATTHEWS 3,273,019

DIRECT SPARK IGNITION SYSTEM Filed Oct. 8, 1963 2 Sheets-Sheet l T Z a 185 igagwgfiav 41d ilggdl 10 i v n I "L 32m 456 i 30 J ilg. Z. QUSSELL a w v i tws 31a lam/7 x1, "7", ax, 5 Mhd dltbys.

Sept. 13, 1966 R. a. MATTHEWS DIRECT SPARK IGNITION SYSTEM 2 Sheets-Sheet 2 Filed Oct. 8, 1963 TIMING 9 Z- DEVICE nun United States Patent 3,273,019 DIRECT SPARK IGNITION SYSTEM Russell B. Matthews, flconomowoc, Wis., assignor to Penn Controls, Inc., a corporation of Indiana Filed Oct. 8, 1963, Ser. No. 314,744 14 Claims. (Cl. 317-86) The present invention relates to direct spark ignition systems and more particularly to a fast responding spark ignition system.

Flame sensors are presently utilized to detect the absence of a flame at gas burners. However, after a flame is extinguished, these flame sensors require a period of time to detect the absence of a flame, during which unburned gases are admitted at the burner ports. Then, when a spark gap igniter is energized, the accumulation of gas could result in an explosion. This is especially true of enclosed combustion boxes that are gravity vented. Unburned gases may also collect in the stack and explode when the spark is reestablished. The present invention overcomes these d-ifficulties by providing an ignition system that locks out in a period of approximately four seconds after a flame-out condition or gas interruption has occurred and does not re-establish the ignition spark for another trial for ignition. In the former systems, the spark would automatically be reestablished in an attempt to re-ignite the fuel.

The present invention also provides for the re-establishment of simultaneous fuel flow and ignition spark at the termination of an electrical interruption, having kept the fuel oif for the duration of an electrical interruption regardless of the duration of that interruption.

Therefore, an object of the present invention is to provide a new and improved spark ignition system.

A principal object is to provide a spark ignition system that will recycle for electrical interrupt-ions of any type and will not recycle under flame-out or gas interruption conditions.

Another object of the present invention is to provide a spark ignition system that will lock-out in approximately four seconds.

An additional object is to provide a direct spark ignition system wherein the period of time during which a spark gap continues firing, as a trial for ignition, may be preselected from a wide range of values while the period of time for a flame sensor to react to the absence of the flame is extremely short.

A further object is to provide a spark ignition system which includes a manually resettable fuel valve which will automatically close only after a trial for ignition and when there has been, during the trial for ignition, either a flame ignition failure or, subsequent to the ignition of a flame, the occurrence of a gas interruption or flame-out.

An additional object is to provide a direct spark ignition system for igniting a pilot light which, in turn, ignites main fuel burners wherein fuel is not fed to the main fuel burners until after the pilot flame has been established and wherein gas to both the pilot flame and the main burners is cut off as soon as there is either an electrical or a gas interruption and the system becomes locked out.

Further objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic diagram of a preferred embodiment of the present invention;

FIGURE 2 is a schematic diagram of a modified version of the preferred embodiment illustrated in FIGURE 1;

FIGURE 3 is a further modified version of the pre- 3,273,019 Patented Sept. 13, 1966 ferred embodiment of the invention illustrated in FIG- URE 1; and

FIGURE 4 is a sectional view of a portion of the modified versions of the invention shown in F-IGU-RES 2 and 3.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail, embodiments of the invention with the understanding that the present disclosures are to be considered as exemplifications of the principles of the invention and are not intended to limit the invention to the embodiments illustrated. The scope of the invention will be pointed out in the appended claims.

A trial for ignition is a period of time during which a spark gap in a direct ignition system is continuously tiring. The lock-out of a spark ignition system refers to the fact that the system cannot commence a new trial for ignition'without the resetting of a manual control.

In the past, various types of heat and light sensing devices have been used as flame sensors to determine whether there is a flame present at a burner. When a flame is established, these sensors require a period of time before their electrical outputs can equal a value which gives a positive indication of the presence of a flame. The, when the flame is extinguished, the presence of light and heat at the sensor does not disappear immediately, but requires a period of time. This time, coupled with the reaction time of a particular sensor, makes the time required to positively indicate the absence of a flame at least as great as the time to indicate the presence of a flame after it is first established, and in most cases, considerably longer. The present invention overcomes this situation by utilizing an electrical voltage value to indicate the presence of a flame which increases as the period of time that the flame has been established increases and establishes another electrical voltage value which is indicative of a flame failure which also increases with the period of time the flame has been burning. Therefore, only a slight decrease in the electrical output of a flame sensor is required to indicate a flame-out. The system is extremely fast-acting to turn off both gas and spark after a flame-out or gas interruption. Thus, the present invention is not only faster responding to flame-out or gas interruption than present ignition systems, but it is also faster in insuring that raw fuel does not accumulate in undesired locations after the occurrence of a flame-out or gas interruption.

Referring now to FIGURE 1, a spark gap 10 is connected across a secondary winding 11 of a high-voltage transformer 12 which has a primary winding 13 connected in series with a valve actuator in the form of a solenoid coil 14, a condenser 15,

switch contacts

16 and 17 bet-ween a pair of power leads 18 and 19. The coil 14, when energized, has a sufficient magnetic force to open a valve 20 which is inserted in a gas line leading to a set of burners (not shown), whose operation is controlled by the ignition system. The valve 20 has associated with it a holding coil 21 which has sufiioient magnetic force to hold the valve in its open position once it is placed in that position by the actuator 14, but it does not have sufficient magnetic force when energized to move the valve from its closed position to its open position. A magnetic amplifier generally indicated at 22 is composed of a pair of reactors. One reactor has a load coil 23, a control coil 24, and a bias coil 25. The other reactor has a load coil 26, a control coil 27, and a bias coil 28. The load coils 23 and 26 are connected in parallel in a two-arm parallel circuit which is, in turn,

nected to a terminal 31 through a fuse 32 and a thermo stat switch 33. The terminals and 31 are adapted to be connected across a source of alternating current (not shown). A pair of

rectifiers

34 and 35 are each placed in series with the respective load coils 23 and 26 in the respective arms of the two-arm parallel circuit so that current flows through alternate load coils on the alternate half cycles of the alternating current placed across the

terminals

30 and 31.

A thermocouple 36 is placed near the burner so that when the burner is ignited the thermocouple senses the presence of a flame. The thermocouple 36 is serially connected with the two

control coils

24 and 27 in the magnetic amplifier and a resistor 37 is connected in parallel with the thermocouple 36.

With the

switch contacts

16 and 17 closed, a third series resistance circuit between the power leads 18 and 19 is formed by a rectifier 38, bias coil 25, bias coil 28, a condenser 39, and a resistance 40. Condenser 39 and resistance 40 form a resistance capacitance circuit which combines with a voltage limiter in the form of an argon glow tube 41 serially connected with a relay coil 42 across the condenser 39 to form a timing circuit which, as will be explained in greater detail presently, determines the trial for ignition of the spark gap 10. The relay coil 42, together with the movable contact 17, fixed contact 16, and a fixed contact 43, form a conventional relay. A condenser 44 is connected across the relay coil 42, and a condenser 45 is connected across the resistor 40. When the relay coil 42 is energized,

contacts

16 and 17 are opened while contacts 43 and 17 are closed so that the bias coils 25 and 28 are connected to power lead 19 through relay coil 42 and a thermistor 46 which has a resistor 47 connected in parallel with it. A resistor 48 is connected between the fixed contacts 16 and 43.

The thermostat switch 33 is placed in an enclosure which is to be heated by the burner (not shown). When the thermostat 33 closes to call for additional heat, its closure energizes actuator 14 and spark gap 10 to simultaneously provide a flow of fuel and a spark. At this moment, the current flow through the holding coil 21 and the load coils of a magnetic amplifier 22, is negligible because the magnetic amplifier is partially biased or cut off by the current flow through the bias coils 25 and 28. The current flow provided to the bias coils 25 and 28 may be traced from power lead 18 through rectifier 38, bias coil 25, bias coil 28, relay coil 42, resistor 47, resistor 48, and

contacts

16 and 17 to power lead 19. Power lead 19 is connected to the terminal 31 through the fuse 32 and thermostat switch 33. When the spark gap 10 ignites the fuel, thermocouple 36 commences to heat and create a current flow through

control windings

24 and 27, arranged serially in opposition. This control current causes the impedance of the magnetic amplifier to decrease sufficiently to increase the current flow through the holding coil 21 so that the magnetic field it creates will hold valve 20 in its open position. Thus, in normal operation, spark gap 10 will ignite the burner during the trial for ignition, and the resulting flame will heat the thermocouple 36 until a sufiicient current flow is allowed through the holding coil 21 to make the coil capable of maintaining the valve 20 in its open position. Simultaneously with the energizing of the spark gap and holding coil current flow, current commences to flow through a third path consisting of the resistance-capacitance timing circuit, relay coil 42 and the argon glow lamp 41. Half-wave rectified current flows from power lead 18 to bias coil 25, bias coil 28, capacitor 39 and through resistor 40 to lead 19. The time required for capacitor 39 to charge to the'firing voltage of the argon glow lamp 41 is controlled by the value of resistor 40. When the voltage across the argon glow lamp 41 reaches its breakdown potential, the capacitor 39 will discharge its energy through relay coil 42 and the lamp 41 causing

relay contacts

16 and 17 to open and contacts 17 and 43 to close. The opening of

contacts

16 and 17 de-energizes the high voltage primary coil 13 and actuator 14. This terminates the trial for ignition by extinguishing the continuous firing spark across the spark gap 10 and simultaneously releasing the valve 20 to the control of valve hold coil 21. The opening of the

contacts

16 and 17 also disconnects the thermistor 46 from the bias circuit.

The closing of contacts 17 and 43 energizes the bias circuit via resistor 47 in parallel with thermistor 46 to cause a bias current of approximately 10 milliamperes to flow through the relay coil 42 and bias coils 25 and 28. With the closing of contacts 17 and 43, thermistor 46 starts heating, and in approximately 5 seconds, it has dropped its resistance sufficiently to raise the negative bias current to approximately 20 milliamperes. The reason for delaying the application of the 20 milliamperes negative bias current by such an automatic variable current limiter is to allow the thermocouple time to generate enough voltage to cause the magnetic amplifier to pass sufiicient current to the valve holding coil 21 to keep the valve 20 open. If the 20 milliampere bias current were to be applied to the bias coil immediately on the termination of a five second trial for ignition period, the thermocouple would provide an insuflficient current to maintain the valve 20 in its open position, and the system would lock-out.

The reason that one-half wave rectification is suflicient for the biased series circuit is that, at the instant power lead 18 is positive with respect to power lead 19, current will flow through load winding 23 and through the bias winding 25. The flux generated by the bias winding 25 will oppose that of load winding 23. On the alternate half cycle of the alternating current, when lead 19 is positive with respect to lead 18, current flows through the load winding 26 with no current flowing to the bias winding 28. Current is not required in the bias winding 28 on this half cycle of the alternating current because current flow during the previous half cycle resets the core down the magnetizing curve because the load winding 26 was non-conducting. Thus, one core is biased, while load winding 23 is conducting, and one core is reset, While load winding 26 is not conducting. Therefore, when the trial for ignition is terminated and there is a current produced by the thermocouple 36, the control windings allow a sufiiciently large current flow through the load windings that the valve 20 remains in its open position. As the thermocouple 36 continues to heat, the current fiow in the bias windings also increases as the flow through the control windings increases. Therefore, the flow in both the bias windings and the control windings continues increasing until the flow in the bias circuit has reached a value of approximately 20 milliamperes. If there should be a flame-out or interruption in the gas flow, thermocouple 36 will immediately commence to cool. However, only a very small amount of cooling is required until the load windings, under the influence of the bias Windings, decrease the current flow through holding coil 21 sufficiently to allow valve 20 to close. Therefore, a lock-out time of approximately four seconds, commencing with the actual flame-out or gas interruption, is sufficient to lock out the system. Since the

contacts

16 and 17 remain open, there cannot be another trial for ignition until the system is recycled by manually opening and closing the contacts of thermostat switch 33. Thus, the system is non-recycling for a flame-out or a gas interruption.

If there should be an electrical interruption, contacts 17 and 43 will open with the de-energization of the coil 42, and at the termination of the electrical interruption, there will be a new trial for ignition because

contacts

16 and 17 are closed. Thus, the embodiment of the invention illustrated in FIGURE 1 is electrically recycling.

The trial for ignition may be selected from a large range of time periods by the proper selection of the time constant of the resistance capacitance circuit and the breakdown voltage of the lamp 41. Depending on the preselected value for the trial for ignition, the thermistor 46 and the resistor 47 are chosen so that there is a bias voltage that will allow coil 21 to hold valve 20 open when

contacts

16 and 17 are open and contacts 17 and 43 are closed. In this manner, a flame-out shortly after the closing of contacts 17 and 43 will be quickly detected because the voltage through the control windings combined with the voltage of the bias windings require only a small drop to increase the resistance in the load coils sufficiently to cause coil 21 to drop out the valve 20.

The resistor 48, in series with the

contacts

16 and 17, provides a small current through relay coil 42 and thereby reduces the amount of energy to be supplied by the resistance-capacitance circuit with resulting cost and size reduction. The resistor 48, in series with resistor 47, provides a discharge path for the condenser 32. This enables a full trial for ignition period for each time the system starts over. This discharge path may be traced from capacitor 39 through argon glow lamp 41, resistor 47, resistor 48, normally closed

contacts

16 and 17, power lead 19, magnetic amplifier 22, holding coil 21, power lead 18, rectifier 38, bias c-oils 25 and 28 to the other side of capacitor 39.

The capacitor 45 is a peaking capacitor to raise the voltage applied to the resistancecapacitance circuit to the peak value of the line voltage sine wave. The capacitor 44 is to keep relay coil 42 energized during the portion of the alternating current cycle that rectifier 38- is nonconducting.

The purpose of resistor 37 is to keep the magnetic amplifier 22 from holding the gas valve 20 open in case of an open circuit thermocouple. Without the resistor, the amplifier will conduct sufficient current to maintain the gas valve open. Under these conditions, the circuit would be operational without a flame detector and therefore, devoid of safety. If the resistor 37 and the thermocouple were disconnected, the valve would close under all conditions. Assuming an open circuit thermocouple, current will flow through the actuator 14, the primary coil 13, capacitor 15, and the

contacts

16 and 17. The normal ignition of gas should then take place, and at the end of the trial for ignition period when the

contacts

16 and 17 open, the valve will open and the spark will be shut off.

The bias circuit failures will now be considered. Assuming that bias coil 25 or 28 is open or rectifier 38 is an open circuit, the resistance-capacitance timing circuit will not function and the spark gap and the actuator 14 will remain energized until the relatively heavy current drawn by these devices causes the fuse 32 to open.

If the rectifier 33 became shorted, an alternating current would be placed upon the resistance-capacitance timing circuit, and the capacitor 39 would not collect a charge. Therefore, the relay coil 42 will remain de-energized and the spark gap 10 and the actuator 14 will cause the fuse 32 to open by drawing a relatively heavy current.

Now, assuming that the relay coil 42 might have an open circuit, the

contacts

16 and 17 will again remain closed with the result that the heavy current drawn by the spark gap 10 and the actuator 14 will cause the fuse 32 to open shortly after the preselected time for ignition.

If the resistor 48 should become open, the relay coil 42 will not be energized and fuse 32 will open because of the current drawn by the spark gap 10 and the actuator 14 shortly after the termination of the trial for ignition.

Should the resistor 48 become short circuited, the relay coil 42 will be energized as soon as the thermostat switch 33 closes. This causes the

contacts

16 and 17 to open which de-energizes the spark and closes the gas valve 20.

Turning now to the resistor 47 and considering its effect if it should become open circuited, it can be seen that, under this condition, the relay coil 42 will not energized, and the current required by the spark gap 10 and the actuator 14 will cause fuse 32 to open shortly after the termination of the trial for ignition.

Assuming that resistor 47 has become short circuited, a high bias current will appear through the bias coils 25 and 28 as soon as the contacts 17 and 43 close at the termination of the trial for ignition period. This high current prevents the current in the load windings 23 and 26 from becoming sufficiently high for the coil 21 to maintain the valve 20 in its open position after the actuator 14 is de-energized. Thus, the system will be locked out under this condition.

If the thermistor 46 should become open circuited, the bias current through the bias coils could not rise above the value of the current allowed by the resistor 47 which, in the embodiment illustrated in FIGURE 1, is 10 milliamperes. If the open circuit occurred while 20 milliamperes was being allowed by the thermistor 46, the bias current would immediately drop to the 10 milliampere level. This would increase the time for the thermocouple 36 to cool and thereby reduce the current flow in the control coils 24 and 27 sufficiently. The time to increase the resistance of the load coils to a point that they would cause the holding coil 21 to release the valve 20 to its closed position would be changed to a period of approximately 12 seconds from a period of approximately 4 seconds. Although the response time to a flame-out or gas interruption would be about tripled, the response would still be sufiiciently fast to prevent an explosive condition from arising should the spark be again brought on.

Assuming now that the thermistor 46 was short circuited, there would be a high current flow in the bias circuit through the bias coils 25 and 28 in the same manner as would occur if resistor 47 was short circuited so that the current flow through the load coils is reduced to a point below which coil 21 can maintain the valve in its open position.

If the

contacts

16 and 17 are welded together in a closed position, the high current drawn by the spark gap 10 and the actuator 14, will cause the fuse 32 to open shortly after the normal trial for ignition period.

Assuming now a situation wherein the contacts 17 and 43 have not closed, even though

contacts

16 and 17 have opened, since there is no bias current flowing in the bias coils 25 and 28, the current to the load coils 23 and 26 and the holding coil 21 will be sufliciently large to cause fuse 32 to open after a short period.

If the contacts 17 and 43 should become welded together in a closed position, the system cannot start up the next time that the thermostatic switch 33 closes, for there cannot be a closed circuit through either the primary coil 13 of the ignition transformer 12, or the actuator 14.

Therefore, the system illustrated in FIGURE 1 is a fail-safe, a safety shut-off, and an extremely fast responding direct spark ignition system. All safety devices for the circuits in the system are devoid of contacts that could weld in an unsafe condition.

Capacitor 15 cancels out a portion of the circuit inductance in order to raise the current through the primary coil 13 of the high voltage transformer 12 to a level sufficient to maintain a spark at volts. The voltage at the spark gap 10 in this circuit is stepped up to approximately 7,000 volts by the transformer 12.

The amount of energy required to activate an electromagnetic device such as a gas valve is greater than that required to hold the device energized. The magnetic amplifier supplies only the energy required to hold the electromagnetic valve 20 energized. The opening of the valve is accomplished by a separate start circuit so that the system has inherent high efficiency and may be made of the smallest possible size components.

Referring now to FIGURE 2, a modification of the direct spark ignition system is illustrated which is particularly designed for use with remotely controlled heating plants. In remotely controlled heating plants, it has been found particularly desirable to incorporate a manually resettable lock-out device which is actuated to an off position whenever an ignition failure occurs. To place the system in operation, it is then necessary for the operator to manually reset the lock-out device while in the immediate physical proximity of the heating plant. In this manner, any malfunction can be quickly noted by the operator. Corresponding elements illustrated in FIG- URE 2 have been given corresponding identification numerals to the numerals in FIGURE 1 with a suflix a. The operation of the modified embodiment of the invention illustrated in FIGURE 2 is exactly the same as previously described for the embodiment shown in FIG- URE 1, except as hereinafter stated. Therefore, corresponding elements and functions of the elements will not be repeated here, except as affected by the addition of a manually resettable lock-out device which is actuated to an off position by an ignition failure. The system illustrated in FIGURE 2 differs essentially from the system illustrated in FIGURE 1 in that a valve 50 has been connected in series with a main fuel valve a which corresponds to main fuel valve 20 in FIGURE 1 in order that either the closure of valve 20a or the valve 50 will shut off the supply of fuel to a burner. For the purpose of operating valve 50, three

solenoid coils

51, 52 and 53 are included in the system shown in FIGURE 1 as indicated in FIGURE 2. The solenoid coils 51 and 52 are each connected in a different arm of a parallel load coil coil circuit of a magnetic amplifier 22a so that alternate coils are energized on the respective alternate half cycles of an alternating current supplied by a pair of

terminals

30a and 31a. The third coil 53 is connected in series with a resistor 54, a relay coil 42a, a bias coil a, and a bias coil 28a of the magnetic amplifier 22a, and a rectifier 38a between a fixed contact 43a and a power lead 18a connected to terminal a. Therefore, the coil 53 is energized only at the termination of a trial for ignition when the relay coil 42a closes a movable contact 17a with fixed contact 43a.

The system shown in FIGURE 2 does not include a thermistor such as 46 shown in FIGURE 1 because all circuits associated with valve are unidirectional. At the moment of termination of a trial for ignition, when contacts 170 and 43a close, if the output of a thermocouple 36a is not sufiiciently high, the gas valve 20a will close because the bias winding has direct current flowing therein, and during the instant the alternating current applied to a holding coil 21a passes through zero, the armature will release. The result is erratic operations on applications where the thermocouple heats at a slow rate.

The purpose of resistor 54 is to set the bias current to a correct value, and in this manner, serves a function similar to that of resistor 47 in FIGURE 1.

Referring now to FIGURE 4, the structure of valve 50 and the magnetic-mechanical connections of the coils 5153 are shown in detail. A valve housing 55 has an inlet passage 56 and an outlet passage 57 with an aperture 58 joining the passages. An annular valve seat 59 is formed at one end of the aperture 58 and cooperates with a movable valve head 60 mounted on a shaft 61. A circular threaded disc 62 is threaded onto the shaft 61 and is secured to a disc spring 63 which, in turn, is secured to a mounting 64. The mounting 64 is secured to the valve housing 55 in order to provide a gas-tight closure which prevents the escape of gas. Secured to the mounting 64 by a support disc 65 is a pair of

ferromagnetic bars

66 and 67 around which, on corresponding

insulated spools

68, 69 and 70, are wound the

coils

51, 52 and 53. A permanent magnet 71 joins the top of the two

bars

66 and 67. A ferromagnetic armature bar 72 is slidably secured to the top end of shaft 61 in order that it may be magnetically attracted to engage the

bars

66 and 67. As illustrated in FIGURE 4, the range of travel of the disc 72 on shaft 61 is limited by a pair of

annular abutments

73 and 74.

For the purpose of manually raising the valve head 60, a plunger 75 is slidably mounted in a holder 76 that is threaded into the housing 55. A spring 77 surrounds a neckdown portion of the plunger 75 and is positioned between an annular abutment 78 on the holder 76 and an annular abutment 79 on the plunger 75. The upper end of the plunger 75 has an undercut portion which receives a spring 80 which normally extends beyond the upper end of the plunger.

The direction of the flux of the permanent magnet 71 is indicated in FIGURE 4. The flux produced by coil 53 opposes the flux Coils 51 and 52 are connected so that the flux generated by each coil is in the same direction and of the same magnitude, but is produced electrically out of phase with each other. This, in effect, produces a fullwave rectified unidirectional flux o proportional to the flow of current through the holding coil 21a. The current flow is proportional to the output of thermocouple 36a. When a thermostatic switch 33a is closed, current flows through

contacts

17a and 16a, through a primary winding 13a of a high voltage transformer 12a and through a valve actuator 14a. De-energization of coil 140, as previously described in the discussion of the system illustrated in FIGURE 1, will open the valve 20.7. At the end of a trial for ignition period, the

contacts

16a and 17a open and contact 17a closes with contact 43a de-energizing primary winding 13a and actuator 14a and energizing solenoid coil 53, in addition to the biased coils 25a and 28a. If the trial for ignition was successful, thermocouple 3601 will be heated and will be producing sufficient current in the

control coils

24a and 27a to hold the valve 20a open by the magnetism produced by the coil 21a. The same current flowing through coils 51 and 52 produces the flux which acts in a direction shown in FIGURE 2 to aid produced by the permanent magnet 71. At this time, the flow of bias current through coil 53 produces a half wave rectifier unidirectional flux 952 which, as shown in FIGURE 2, opposes o and Flux is always less than the sum of and and therefore, the armature 72 is attracted to the

vertical bars

66 and 67.

If, at the termination of a trial for ignition, the thermocouple 36a has not been heated, current will not flow in the control windings 24a and 25a and therefore, current through load windings 23a and 2611 will be negligible. In this situation, when the trial for ignition is terminated and

contacts

17a and 23a close, the negative bias current through coil 53 will generate the flux Flux is always greater than so that with negligible, 5 is greater than and the disc spring 63, causes the disc 72 to separate from the

vertical bars

66 and 67 in order to close off the supply of fuel to a burner. Once the valve head 60 closes against the valve seat 59, the armature 72 will slide down the shaft until it engages abutment 74. With the armature in this position, the combined flux and with no flux 5 being produced, is not suflicient to attract the armature back to the vertical bars. Thus, once the valve has closed, due to insufficient current fiow through the load windings of the magnetic amplifier, it remains closed or locked out so that it must be manually reset before gas can again How through the valve 50. In a locked out position, any recycling of thermostatic switch 33a will not admit gas to the burner, thereby preventing an accumulation of unburned gas due to haphazard cycling of the thermostat.

In order to restart the system, it is necessary to reset the armature by manually pressing the plunger 75 upward until the spring 80 bears against the lower side of a valve head 60 and forces it upward until the disc 72 comes sufiiciently close to the

vertical bars

66 and 67 that it is magnetically attracted to these vertical bars.

Referring to FIGURE 2, a switch 81 interposed in the power lead 18a is mechanically connected to the armature 74 of valve 50 so that when the valve is closed, the power lead 18a is open circuited. Thus, when the valve 50 is closed and locked out, the electrical power to the system is also opened and locked out in an open position. The valve 50 is always placed close to the combustion chamber so that an operator must manually reset from its off position while he is in the immediate proximity of the heating device so that he will quickly observe any malfunction that might occur.

Referring now to FIGURE 3, another modification of the embodiment of the invention shown in FIGURES 1 and 2 is illustrated in which the corresponding elements are similarly numbered with a suffix b. It will be noted that all of the circuit components found in FIGURE 2 appear in FIGURE 3, except that the valves 50b and 2% are connected to supply a pilot burner rather than a main burner. Thus, the circuits shown in FIGURE 3 may be utilized to provide a pilot flame for large industrial burners of 500,000 B.t.u. capacity and larger. In such applications, the pilot rather than the main burners is controlled by the circuit. A timing device 90 of any conventional design is electrically connected across

terminals

31b and 32b to a thermostatic switch 33b and mechanically connected to a switch at for the control thereof. The main burners (not shown) are controlled by a solenoid operated valve 92 which is actuated from a normally closed position to an open position by an actuator 93 in the form of a solenoid coil. The coil 93 and switch 91. are connected in series with thermostatic switch 3312 between terminals 3% and 31b.

When the thermostatic switch 331) closes to energize the system through a normally closed lock-out switch 81b, the ignition system ignites a pilot flame in the same manner as previously described for the burners controlled by the systems specifically illustrated in FIGURES 1 and 2. The closing of thermostatic switch 331) also energizes the timing device 90 which proceeds to measure time intervals greater than the trial for ignition period. At the termination of this time interval, the time delay device will close switch 91, energizing valve actuator 93, which opens valve 92 and allows fuel to reach the main burners and be ignited by the pilot flame. If, however, the trial for ignition was unsuccessful, a thermocouple 36b will not have heated sufliciently to provide other than a negligible current through control coils 24b and 27b so that the valve 20b and the valve 5012 will both close at the termination of the trial for ignition period. As previously described, the closure of the valve 50b will open switch 811) to de-energize timing device 90. Deenergization of the timing device 90 at the termination of the trial for ignition period which is prior to the end of the timing interval measured by device 90, de-energizes the device so that it does not close switch 91 and thereby prevents the main fuel valve 92 from opening. The timing device 90 is of the recycling type upon de-energization so that each time it is de-energized, it is reset in preparation for measuring a full time interval when it is again energized. Should there be a gas interruption or a flame failure after the burner and pilot valve have been in operation for some time, the closure of valve 5012 will also bring about the opening of switch 81b which, in turn, cuts off electrical power to actuator 93 and the timing device 90. As previously described, the system is then locked out and cannot be operated again until the valve 5% is manually reset to its open position, which operation also closes switch 811). Thus, the system illustrated in FIGURE 3 verifies the existence of a pilot flame before allowing fuel to flow to the main burner, and in the event of the extinguishing of the pilot flame, shuts down and locks out the entire combustion at the burners.

Those skilled in the art will recognize that the embodiments disclosed may be applied to fuel burners other than gas and that variations may be constructed which are within the scope of the invention as set forth in the appended claims.

I claim:

1. A spark ignition system comprising:

a spark gap,

energizing means connected to the spark gap to cause a continuously firing alternating current spark to appear across said gap,

a resistance-capacitance circuit connected to said energizing means to limit a period during which said spark gap continuously fires to a preselected value,

actuation means for opening a fuel valve connected to said energizing means for energization only during said spark firing period,

valve holding means,

flame sensing means, and

a magnetic amplifier comprising a pair of magnetic reactors, each said reactor having a load winding, a bias winding, and a control winding, said load windings being connected to said valve holding means, said bias windings being connected to said energizing means in order to have said energizing means increase the current flow in the bias winding after said spark firing period, and said control winding being connected to said sensing means to produce a current in said control winding whose magnetic field opposes a magnetic field of current flowing in said bias windings.

2. In combination with the spark ignition system specified in claim 1, an automatic variable current limiter connected to said energizing means to gradually increase the current through said bias windings after said spark firing period.

3. A spark ignition system comprising:

a spark gap,

a timing circuit connected to said energizing means to limit the period during which said spark gap continuously fires to a preselected value,

valve holding means,

flame sensing means,

an actuator movable between an open and a closed position,

means for holding said actuator in the open position,

first control means connected to said flame sensing means, to said valve holding means, and to said actuator holding means to activate said valve holding means to aid said actuator holding means during said spark firing period only if a flame is sensed by the sensing means and to deactivate said holding means whenever said sensing means does not sense a flame, and

a second control means for opposing said actuator holding means after said firing period which is capable of overcoming said actuator holding means when unaided by said first control means.

4. A spark ignition system in accordance with claim 3, wherein said actuator moves a fuel valve between open and closed positions.

5. A spark ignition system in accordance with claim 3, wherein said actuator moves an electrical switch between open and closed positions, said switch being connected to control electrical current for said energizing means.

6. A spark ignition system comprising:

a spark gap,

energizing means connected to the spark gap to cause a continuously firing. alternating current spark to appear across said gap,

a first timing circuit connected to said energizing means to limit the period during which said spark gap continuously fires to a preselected value,

actuation means for opening a pilot light fuel valve connected to said energizing means for energization only during said spark firing period,

valve holding means,

flame sensing means,

an actuator movable between an open and a closed position,

means for holding said actuator in the open position,

a first control means connected to said fiame sensing means, to said valve holding means, and to said actuator holding means to activate said valve holding means to said said actuator holding means during said spark firing period only if a flame is sensed by the sensing means and to deactivate said holding means whenever said sensing means does not sense a flame,

a second control means for opposing said actuator holding means after said firing period which is capable of overcoming said actuator holding means when unaided by said first control means,

switch means connected to said energizing means to supply electrical power thereto and connected to said actuator to be controlled thereby,

a timing device connected to said switch means and measuring a period of time greater than said spark firing period, and

a main valve actuator connected to said timing device to be actuated thereby at the end of its timing period.

7. The combination of:

a valve mechanism including a ferromagnetic path having an air gap therein, an actuator movable between a first and a second position which acts as a keeper across said air gap in its first position, a magnetic means providing a first magnetic field, a first, a second and a third magnetic coil to produce fields therein when energized,

a magnetic amplifier consisting of a pair of magnetic reactors, each said reactor having a load winding, and a control winding,

a sensing device connected with said control windings,

a parallel two arm circuit adapted to be connected across an alternating current source and having each of said load windings and each of said first and second coils connected in series with a rectifier in each arm, said first and second coils being connected to produce a second magnetic field in said path aiding said first magnetic field, and

means for energizing said third coil connected to said third coil to produce a third magnetic field in said magnetic path which opposes said first and second fields to cancel the effect on the actuator of said first field alone in order that it may move to its second position when said first field is opposed by the third field and unaided by the presence of the second field.

8. The combination of:

a valve mechanism including a ferromagnetic path having an air gap therein, an actuator movable between a first and a second position which acts as a keeper across said air gap in its first position, a permanent magnet forming a portion of said magnetic path and providing a first magnetic field, a first, second and third magnetic coil, each wound around portions of said path to produce fields therein when energized,

a thermocouple connected in series with said control windings,

9. A spark ignition system comprising:

a transformer having a primary and a secondary winda spark gap connected across said secondary winding,

an electrical valve actuator coil,

a valve holding coil,

a magnetic amplifier consisting of a pair of magnetic reactors, each said reactor having a load winding, a bias winding and a control winding,

a thermocouple connected in series with the control windings of said magnetic amplifier,

a first series circuit adapted to be connected across an alternating current source including said electrical valve actuator coil, and said primary winding of the transformer,

a second series circuit adapted to be connected across an alternating current source including a parallel two arm circuit having each of said load windings connected in a different arm and said valve holding coil,

a third series circuit adapted to be connected across an alternating current source including said bias coils,

a second series circuit adapted to be connected across an alternating current source including a parallel two arm circuit having each of said load windings connected in series with one of the rectifiers in each arm and said valve holding coil,

a third series circuit adapted to be connected across an alternating current source including one of said rectifiers,

said bias coils, said resistance and said second condenser,

a voltage sensitive discharge device serially connected with said relay coil in parallel with said second condenser,

electrical relay holding means connected to said relay coil,

a fourth series circuit adapted to be connected across an alternating current source including said main valve actuator and said switch, and

a switch mechanism electrically connected in series with said four series circuits and in series with timing device and mechanically connected to said pilot valve actuator.

10. A spark ignition system comprising:

an electrical val-ve actuator coil,

a valve holding coil,

a condenser,

a resistance,

a rectifier,

a relay having contacts and an actuating coil,

a first series circuit adapted to be connected across an alternating current source including said electrical valve actuator coil, said primary winding of the transformer, and a pair of said relay contacts,

a second series circuit adapted to be connected across an alternating current source including a parallel two 1?- arm circuit having each of said load windings connected in a different arm and said valve holding coil,

a third series circuit adapted to be connected across :an alternating current source including said rectifier, said bias coils, said resistance and said condenser,

a voltage sensitive dis-charge device serially connected with said relay coil in parallel with said second condenser, and

electrical relay holding means connected to said relay coil.

11. A spark ignition system comprising:

a transformer having a primary and a secondary Winding,

a spark gap connected across said secondary winding,

an electrical valve actuator coil,

a valve holding coil,

a thermocouple connected in series with the control windings of said magnetic amplfier,

a first condenser,

a second condenser,

a resistance,

three rectifiers,

a relay having contacts and an actuating coil,

a first series circuit adapted to be connected across an alternating current source including said electrical valve actuator coil, said primary winding of the transformer, said first condenser, and a pair of said relay contacts,

a third series circuit adapted to be connected across an alternating current source including one of said rectifiers, said bias coils, said resistance and said second condenser,

a voltage sensitive discharge device serially connected with said relay coil in parallel with said second condenser, and

electrical relay holding means connected to said relay coil.

12. In combination with the spark ignition system specified in claim 11 a fuse means connected in series with the three series circuits.

13. A spark ignition system comprising:

a transformer having a primary and a secondary winding,

a spark gap connected across said secondary winding,

an electrical valve actuator,

a valve holding coil,

a condenser,

a resistance,

three rectifiers,

a relay having contacts and an actuating coil,

a valve mechanism including a valve actuator movable between an open and a closed position, means for moving said actuator to its closed position, means for producing a first magnetic field capable of holding said actuator in a closed position, a pair of coils, each producing a second magnetic field when energized to aid said first magnet field, a third coil producing a third magnetic field when energized 0pposing said first and second magnetic fields,

a first series circuit adapted to be connected across an alternating current source including said electrical valve actuator, said primary winding of the transformer, and a pair of said relay contacts,

a second series circuit adapted to be connected across an alternating current source including a parallel two arm circuit having each of said load windings and each of said pair of coils connected in series with one of the rectifiers in each arm and said valve holding coil,

electrical relay holding means connected to said relay coil, and

a fourth series circuit adapted to be connected across an alternating current source including said third coil and a pair of said relay contacts which are closed when said pair of contacts in said first series circuit are open.

14. A spark ignition system comprising:

a transformer having a primary and a secondary winding,

a spark gap connected across said secondary winding,

an electrical pilot valve actuator,

a valve holding coil,

a first condenser,

a second condenser,

a resistance,

three rectifiers,

a relay having contacts and an actuating coil,

a valve mechanism including a valve actuator movable in an open and a closed position, means for moving said actuator to a closed position, a pair of coils, each producing a second magnetic field when energized to aid said first magnetic field, a third coil producing a third magnetic field when energized opposing said first and second magnetic fields,

a timing device adapted to be connected across a source of alternating cur-rent,

an electrical main valve actuator,

a switch connected to said timing device to be closed thereby at the end of a preselected time period after the timing device is energized, and

a first series circuit adapted to be connected across an alternating current source including said electrical valve actuator, said primary winding of the transformer, said condenser, and a pair of said relay contacts.

References Cited by the Examiner UNITED STATES PATENTS 1,982,561 11/1934 Williams 317-85 2,789,632 4/1957 Smits 317-96 X 2,869,633 1/1959 Schaaf et al. 158l28 3,204,149 8/1965 Vance 31783 RICHARD M. WOOD, Primary Examiner.

V. Y. MAYEWSKY, Assistant Examiner.

Claims

1. A SPART IGNITION SYSTEM COMPRISING: A SPARK GAP, ENERGIZING MEANS CONNECTED TO THE SPARK GAP TO CAUSE A CONTINUOUSLY FIRING ALTERNATING CURRENT SPARK TO APPEAR ACROSS SAID GAP, A RESISTANCE-CAPACITANC CIRCUIT CONNECTED TO SAID ENERGIZING MEANS TO LIMIT A PERIOD DURING WHICH SAID SPARK GAP CONTINUOUSLY FIRES TO A PRESELECTED VALUE, ACTUATION MEANS FOR OPENING A FUEL VALVE CONNECTED TO SAID ENERGIZING MEANS FOR ENERGIZATION ONLY DURING SAID SPARK FIRING PERIOD, VALVE HOLDING MEANS, FLAME SENSING MEANS, AND A MAGNETIC AMPLIFIER COMPRISING A PAIR OF MAGNETIC REACTORS, EACH SAID REACTOR HAVING A LOAD WINDING, A BIAS WINDING, AND A CONTROL WINDING, SAID LOAD WINDINGS BEING CONNECTED TO SAID VALVE HOLDING MEANS, SAID BIAS WINDINGS BEING CONNECTED TO SAID ENERGIZING MEANS IN ORDER TO HAVE SAID ENERGIZING MEANS IN-