US2628676A - Spark responsive safety control system for gas burners - Google Patents

Description

Feb. 17, 1953 R. SHOTTENFELD 2,628,676

SPARK RESPONSIVE SAFETY CONTROL SYSTEM FOR GAS BURNERS Filed Aug. 26, 1950 INVENTOR ATTO R Y Patented Feb. 17, 1953 SPARK RESPONSIVE SAFETY CONTROL SYSTEM FOR GAS BURNERS Richard Shottenfeld, Jamaica, N. Y., assignor to Ensign Ribbon Burners, Inc., Pelham Manor, N. Y., a corporation of New York Application August 26, 1950, Serial No. 181,645 7 .2 Claims.

This invention relates to gas burners provided with ignition by electric spark for currently insuring ignition of the gas; more specifically this relates to safety devices for automatically shutting off the gas supply to the burner when the ignition spark fails for example due to power failure. Normally the spark is produced by current from a so-called ignition transformer which delivers an alternating currentof high enough voltage to cause a spark to jump the air gap between a pair of electrodes as long as such current is being delivered to the electrodes.

According to one aspect, this invention relates to what may be termed interrupted spark operation, namely a mode of operation in which the spark-producing current is interrupted rhythmically as by an interrupter for the current that feeds the ignition transformer. In this way,- brief periods during which the spark is alive alternate with similarly brief periods during which the spark is dead. These periods will herein be termed the on-periods and the off-periods or the liveand the dead-periods of the spark. v

The purpose of interrupted spark operation is to reduce power consumption,.reduce wear of the electrodes, and to reduce the average load on the transformer 50 that smaller electrical condoctors may be employed. To be thus effective the lengths of the oiland on-periods are so proportioned that the off-period is too short to allow for the escape of a dangerous amount of gas from the burner in the absence of a flame, while the on-period is long enough to provide a reasonable length of time for ignition yet short enough to minimize, power consumption and load. To meet these requirements suitable proportions are of the order of 3 seconds for the elf-periods and of the order of 3 seconds for the on-periods.

While a variety of automatic safety devices or safety control systems in general are known for shutting off the gas in case of spark failure, a problem lies in rendering such devices properly responsive where a system of interrupted spark operation is employed. The problem lies in devising means for rendering vthe safety "device nonresponsive during the off-periods, but responsive to shut off the gas whenever the spark remains off longer than the normal off-period provided for by the interrupter.

Another problem lies in devising such a safety control system that will be secure against rendering an erroneous or uncalled for response i case of any fault within the system itself. That is to say, if any component or element of the safety control system should fail, the response should invariably be on the safe side, namely to shut off the gas.

It is among the objects of this invention to provide a safety control system which is simple and inexpensive to manufacture, for preventing gas shut-off during the off-periods of the spark, yet to shut off the gas promptly when the spark remains off for a length of time appreciably in excess of the normal off-period; to provide such a system that is'fool proof in the sense that it is safe against rendering uncalled for response in case a fault develops in the system, in other words to provide a system in which any fault in thesystem itself will assuredly'cause the gas to be shut off; to provide such a system in which the spark must be restored manually as by push button operation; and to provide a system that is fool proof in regard to the push button operation, in the sense that irrespective of the length of time the push button is held pressed for opening the gas valve the closure of the gas valve willnevertheless be assured when the spark is absent.

According to the invention these objects are attained by providing a system in which an alternating current detector or monitor circuit is dependent upon and coupled through a step-down transformer, herein termed the detector transformer, with the spark-producing high voltage circuit. The term detector or monitor circuit is herein used to mean that it is energized while the spark is functioning properly and is dead when the. sparkis dead. This detector circuit, according to the invention, carries an alternating current which is rectified for energizing the solenoid of a direct-current operated relay switch for opening and closing an independent energizing circuit foractivating a solenoid that opens and closes the gas supply valve for the burner in accordance withthe opening and closing of the independent energizing circuit.

Associated with the solenoid of the relay switch is a condenser so dimensioned as to store up, during each on-period of the spark, sufficient energy adapted in turn to discharge from the condenser ma solenoid-energizing direction for holding the relay solenoid energized and the relay switch closed during the off-periods of the spark, but

switch is provided and operable to close the detector circuit, and the relay switch comprises switch contacts which close when the relay switch is energized to close, so as to hold the detector circuit closed as long as the spark is operating normally although with the prescribed interruptions.

A safety control system. embodying the invention comprises a primary power supply circuit with interrupter; a high voltage spark-producing circuit with spark electrodes for the gas burner and coupled through the ignition transformer with the supply circuit; a detector circuit coupled through the detector transformer withthesparkproducing circuit, and having a rectifier in circuit with the solenoid of the relay switch. as" well as a condenser connected in parallel with the solenoid coil; and a relay controlled power supply for energizing the solenoid that operates the gas valve for the burner by the closing and opening of the. relay switch of the detector circuit.

As this invention may be embodied in several forms withoutdeparting-from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding. them, and all changes that fall within the metes and bounds of the. claims are-therefore intended to be embracedby those claims.

The drawing figure shows the. burner with solenoid-actuated gas. supply valvediagrammatically, as wellas an associatedlwiring. diagram embodying the invention.

A tube-shaped gas burner. I0. is. indicated by a burner tube having a longitudinal gas port l2 producing a ribbon-like flame when theburner is lit. The burner tube. is. closed atone end l3 and is supplied with. gas. at. the other end from a gas nozzle. I4: surrounded. by an annular passage |5 through. which. the gas jet from. the nozzle draws combustion air. Associated with the burner is a pair of spark electrodes E1 and E2 presenting. between them a spark gap G.

The gas supply to the nozzle I4 is by way of a solenoid-controlled valve |5 provided in a gas supply pipe l6 having a hand-operated. main shut-off valve H. An electromagnetically operated mechanism, for example solenoid. l8 for opening and closing valve l5 comprises an armature |8 and a solenoid. coil l9 having terminals I 9 and la the armature engaging a. valve-actuating arm 28. The valve. I5 is held closed by a spring 2| acting upon the. armature in a valve closing. direction when the solenoid coil. I8 is deenergized, while energization of the solenoid coil IE will pull the armature upwardly against the tension of spring 2| to open the valve and to keep it open as long as the solenoid coil remains energized- The system is supplied with operating current from supply lines 22 and 23 furnishing, a suitable alternating current, for example of 110 volts. In terms of a general outline the system for producing the control effects comprises a primary power supply circuit 24 with an interrupter 25, a spark-producing circuit 26 with electrodes E1 and E2 and supplied from circuit 24 through a step-up transformer 21 herein termed the ignition transformer having a step-up ratio of the order of 110 volts to about 5000 volts for Jumping the spark gap G; a detector circuit 28 coupled with the spark producing circuit 26 through a step-down transformer 2!! herein termed the detector transformer, this circuit having a rectifier 38 in circuit with the solenoid coil 3| of a relay switch 32, and a condenser 33 connected across the solenoid coil 3|, which detector circuit may be closed by a starting switch shown in the form of a push button 34 adapted to close and open a pair of contacts 88 and 82, which starting switch is in. parallel with a. pair of. contacts 35 and 36 adapted'tobe closed and to be held closed by relay switch 32; and a relay-controlled supply circuit 31 for energizing solenoid H! which circuit is adapted to be closed and to be held closed by the relay switch 32 closing a pair of contacts 38 and 38. When the spark across gap G functions normally although. rhythmically interrupted, the relay switch 32. will; be held closed so that solenoid coil. I8 is energized without interruption and armature l8 held constantly in valve-closing position.

The relay switch 32 comprises an armature 48 actuated'by the solenoid coil 3| and has a pair of switch. members 4|. and 42 whereby it simultaneously'closes. and openscontacts, 35 and 36 as Well as. contacts. 38 and 39. A. spring 43 acting upon armature 40 holds these contacts open when coil. 3| is de-energized'.

The interrupter 25 comprises a pair of contacts 44 and 45, contact 44 stationary and contact 45 movable. These contacts. are rhythmically opened and closedby a rotary cam member 46 engaging, the movable. contact. 45, the cam member 46. being. rotated as by a motor 41 supplied with current through. conductors 48 and 49 leading. to points5|i and. 5|. respectively on supply lines 22 and 23.

Now follows a more detailed description of th safety control. system in. terms. of the circuits just. outlined. namely the. primary power supply circuit 24., the sparks-producing circuit 26, the detector circuit 38. and the relay-controlled power supply circuit 31.

The primary power supply circuit, 24 comprises a conductor 52 leading from a point 53 on power line 22 to a terminal 54 of a primary transformer coil 55' of the ignition transformer 21, a conductor 58 leading from a terminal 51 of transformer coil 55 to movable interrupter contact 45, a conductor 58 leading from stationary interrupter contact 44 to a point 59 on power line 23.

The spark-producing circuit 26 comprises a conductor 68. leading from a terminal 6| of secondary coil 62 of ignition transformer 21 to spark electrode E1; a conductor 63 leading from spark electrode E2 to a terminal 64 of primary coil 65 of detector transformer 28; a conductor 66 leading from a terminal 61 to a terminal 68 of secondary coil 62 of ignition transformer 21, conductor 68 being grounded as at 68. The characteristics of the ignition transformer 21 are such that when a spark is maintained across gap G then the spark producing circuit 26 operates substantially as a constant current circuit in which variations of impedance do not effect appreciable changes in the magnitude oi the spark producing current. Therefore the term ignition transformer herein connotes a transformer having the characteristics just defined.

The detector circuit 28 comprises a conductor 10 leading from a terminal 1| of secondary coil 12 of detector transformer 29 to a terminal 13 of rectifier 38 which may be in the nature of a selenium rectifier; a conductor 14 leading from a terminal 15 of the rectifier by way of point 16 to a terminal 11 of relay solenoid coil 3 I; a conductor 18 leading from a terminal 19 of solenoid coil 3| to a contact of push button switch 34; a

conductor 8| leading from a contact 82 of the push button switch by way of point 83 to a terminal 84 of secondary coil 12 of detector transformer 29, a conductor 85 leading from point 19 to relay switch contact 36 and a conductor 86 leading from relay switch contact 35 to point 83, so that relay switch contacts 35 and 36 can be closed in parallel with push button contacts 80 and 82; a conductor 81 leading from point 19 to a terminal 88 of condenser 33 and a conductor 89 leading from a terminal 90 of the condenser to point 16.

Th relay-controlled power supply circuit 31 comprises a conductor 8| leading from a point 92 on power line 22 to relay switch contact 39; a conductor 93 leading from relay switch contact 38 to terminal I9 of solenoid coil l9; and a conductor 94 leading from terminal Ill of solenoid coil l9 to a point 95 on power line 23. A signal light 98 connected across solenoid coil I3 is lit to indicate the gas valve being open with spark operation being in order, the light being extinguished when due to failure of the spark to operate normally or due to any fault in thesystem the solenoid I9 is de-energized and the gas valve I is shut.

Operation In order to start the burner as well as the spark, with the main gas valve I! open, the 110 volt power from lines 22 and 23 is fed to the ignition transformer 21 by way of interrupter 25 so that a spark will appear across gap G between electrodes E1 and E2 at rhythmic intervals. For example the function of the interrupter 25 may be such as to produce alternating onand offperiods of the spark with on-periods of about 3 seconds and off-periods of about 3 seconds duration.

The spark-producing current derived from the ignition transformer 2'! energizes the primary coil of detector transformer 29, while the detector circuit 28 is open due to the then open condition of relay switch 32 and the open condition of push button switch 34, 88, 82. This push button switch represents a switch device for holding a pair of contacts normally open and for momentarily closing them through manual operation. Hence, even though the spark is functioning in its normal rhythmically interrupted manner, the gas valve I5 still remains closed because of the then tie-energized condition of solenoid coil I9, as indicated by the full-line closed position of valve lever 20 thus held by spring 2|.

In order to light the burner the operator must press the push button 34 normally held open by a spring, to effect the closing of contacts 88 and 82 to establish the detector circuit 28 from contact 82 through conductortl, secondary coil E2 of detector transformer 29, conductor 10, rectifier 30, conductor 14, relay solenoid coil 3|, point 19, and conductor 18 to terminal 8|).

The closing of push button switch 34, 80, 02 energizes relay solenoid coil 3| pulling in the armature 48 against the tension of the spring 43, thereby closing switch member 4| upon contacts 35 and 36 and switch member 42 upon contacts 38 and 39. Push button 34 may then be released as relay coil 3| remains energized by reason of the closing of contacts 35 and 36, while simultaneously solenoid coil I9 is energized by the closing of contacts 38 and 39, and draws in o r'pullsup the armature 18* against tension of spring 2|, thus opening the gas valve l5 as is indicated by the dot-and-dash line position of the valve actuating lever ML The condenser 38 connected across the relay solenoid coil 3| is provided to store up energy while the relay solenoid vcoil is energized, and to discharge the stored up energy in a, coil-energizing direction so as to continue the energization of coil 3| even after current in the detector circuit proper will have ceased to flow during the ofi-period of the spark when the spark producing circuit 26 as well as the power supply circuit 24 is dead. The capacity of the condenser is so dimensioned as to store during a singl on-period and to discharge durin a single off-period sufficient energy for holding relay solenoid coil 3! energized and relay switch 32 closed until another on-period of the spark will have started due to the closing of interrupter contacts 44 and 45. In this way, even though the spark is operated with rhythmic interruptions, the gas valve I5 will nevertheless remain open continuously that is through the on-periods as well as the off-periods of the spark. I

Yet, the capacity of condenser 33 is so dimensioned that it requires only a moderate extension of the off-period of the spark to allow the relay solenoid coil 3| to become de-energized allowing spring 43 to open the relay switch 32 and thereby to open both the detector circuit 28 as well as the power supply circuit 31, thereby de-ener gizing the solenoid coil l8 and allowing spring 2| to close the gas valve I5 Thus, if the oilperiod of the spark is unduly extended, the gas valve will shut and will not open again irrespective of whether or not normal operation of the spark is re-established. However, if such normal spark operation has become re-established, it is necessary to initiate the opening of the gas valve again by pressing the push button 34.

While the embodiment so far described requires manual operation as of the push button switch [34 to reestablish the spark and to re-light the gas burner once the gas valve has been shut, for instance when the power supply has failed, it may be desired to have the spark restored automatically to re-open the gas valve directly when the power supply is restored. To this end there is shown a switch 91 which may be closed to bridge the normally open push button switch contacts 80 and 82. With switch 9'! closed the restoration of the power supply from lines 22 and 23 will at once restore the spark operation. energize relay solenoido3l, and thus close relay switch 32 causing solenoid l9 to be re-energized and thus gas valve |5 to be opened.

Since it is one of the features of this invention that the system is fool proof against rendering false control effects with respect to the gas valve irrespective of any fault that may develop within the system itself, there will now be presented a discussion of possible break-downs or faults in the system along with reasons why such breakdowns or faults will in any instance assure the automatic closing of the gas valve irrespective of whether the starting push button switch 34 is being held closed.

Such possible break-down or faults are present (a) If the primary coil 55 of ignition transformer 21 be open; then no energy enters the secondary coil 62, and the system is dead causing gas valve l5 to be closed by spring 2|.

(1)) If the primary coil 55 be shorted, then the effect is the same as in (a). k

(c) If the secondary coil 62 0f ignition transformer 21 be open, then no current is supplied to primary coil 55 of detector transformer 29, and

a'eaaevs relay circuit through secondary 'coil 12 is dead, allowing relay switch, 32 to be opened by spring 43, thus causing gas valve I to close.

(d) If the high tension conductor 60 leading to the spark electrode E; be grounded, then there is no spark at the gap G and no current in conductor 63 and coil 65 of detector transformer 29, so that the system beyond the spark producing circuit 26 is dead causing gas valve l5 to close.

(e) If low tension conductor 63 be grounded, then whether or not a spark exists across spark gap G, the detector transformer 29 will nevertheless subsequently remain de-energized causing gas valve If: to be closed by spring 2|.

(f) If primary coil 65 of detector transformer 29 be shorted, then the effect is the same as in (e) when conductor 63 is grounded.

(g) If conductor 60 or 63 or transformer coil 65 or conductor 66 be open, or if the spark gap G becomes too wide to allow a spark to jump, then the detector transformer 29 will be de-energized, causing the gas valve l5 to be closed by spring 2|.

(It) If any one of the elements of relay circuit 28 (that is transformer coil 12, conductor 13, rectifier 30, conductor 14, solenoid coil 3|, conductor 13, contacts 80 and 82, or conductor 8|) be open, then relay solenoid 3| receives no current, the relay switch 32 opens, and consequently the gas valve I5 is shut by spring 2|.

(1) If secondary coil '12 of detector transformer 29 be shorted, no energy is delivered to the de tector circuit 28, so the relay solenoid 3| is deenergized causing as valve l5 to be closed by spring 2|.

(7') If rectifier 30 be shorted, then alternating current is impressed across condenser 33 in parallel with relay solenoid coil 3|, but solenoid coil 3| being built for direct current operation does not respond to alternating current, and condenser 33 now represents in effect a short circuit across solenoid coil 3| for this impressed alternating current, so that solenoid coil 3| remains de-energized causing gas valve I5 to be closed by spring 2|.

(k) If condenser 33 be short-circuited, then the relay solenoid 3| receives no energy, causing spring 43 to open relay contacts 35 and 36, and gas valve l5 to be closed by spring 2|. No damage can result to the system, as a result of operation with shorted condenser 33, since the very shorting of the condenser acts to choke off any supply of energy from detector transformer 29. In other words, with a shorted condenser 33 the rectifier 30 being placed directly as an excessive load across transformer coil 12 has the effect of lowering the impedance of primary coil 65 so that less energy is abstracted from the spark pro ducing circuit 26, since the spark producing current in that circuit is maintained substantially constant by virtue of the characteristics of ignition transformer 21.

i Z) If condenser 33 be open, then relay solenoid coil 3| receives pulsating direct current in the form of half-wave impulses, which is insufficient and ineffective for keeping relay contacts 35, 30 and 38 and 39 closed, thus causing gas valve l5" to be closed by spring 2|.

(m) Or if any one or more of the foregoing faults occur, then the gas valve IE will be closed due to de-energization of relay solenoid coil 3|.

(a) If relay solenoid 3| be shorted or open, then relay contacts 35, 36 and 38, 39 will remain open, causing gas valve l5 to be closed by spring 2|.

ground.

What I claim is:

1. In combination with a gas burner having a gas valve operable to open and close the gas supply to the burner, a pair of ignition spark electrodes, a solenoid coil controlled armature for'so operating the valve, 2. power supply circuit for controlling the solenoid coil, a step-up ignition transiormer the secondary coil of which supplies alternating current to the spark electrodes for sustaining a spark passing between the electrodes, current interrupting means for intermittently supplying current to the primary coil of the ignition transformer whereby spark onperiods of a controlled length alternate with spark off-periods of a controlled length; a safety control system for shutting the gas valve when the spark fails for a length of time appreciably in excess of the length of its off-period, which system comprises a step-down detector transformer having a primary coil in circuit with the secondary coil of the ignition transformer as well as in circuit with said electrodes to constitute a spark circuit, a detector circuit comprising the secondary coil of said detector transformer, a rectifier, a relay solenoid coil and a starting switch, a condenser connected in parallel with said relay solenoid coil, a current holding connection including a pair of switch contacts in parallel with said starting switch and adapted to be opened or closed, an armature controlled by said relay solenoid coil to close said current holding switch contacts when the solenoid is energised and to open said current holding switch contacts when the solenoid is de-energized, a second pair of switch contacts disposed to be closed and opened by said last mentioned armature for thereby closing and opening said power supply circuit concurrently with the closing and the opening respectively of said current holding switch contacts, said condenser being dimensioned and adapted to receive a charge of enerry by said rectified current during the on-period of the spark, which energy is adapted to discharge through the relay solenoid coil in a solenoid energizing direction and is sufficiently large and effective to hold both said pairs of contacts closed at least until a subsequent on-period of the spark has started and is insufliciently large to keep the solenoid energized appreciably longer than the length of the off-period of the spark, so that said when the spark remains off for a length of time appreciably in excess of the length of the 01L period of the spark.

2. The combination according to claim 1, with the addition of a ground connection in the spark circuit, said ground connection being disposed directly between the secondary coil of the ignition transformer and the primary coil of the detector transformer whereby the primary of the detector transformer is placed at low potential to RICHARD SHOTTENFELD.

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

UNITED STATES PATENTS Number Name Date 2,154,041 Gille Apr. 11, 1939 2,209,410 Lowrey July 30, 1940 2,506,913 Baker May 9, 1950

Images