US3079984A

US3079984A - Burner ignition and control system

Info

Publication number: US3079984A
Application number: US781987A
Authority: US
Inventors: James A Wright; Jr Lee R Johnson
Original assignee: White Rodgers Co
Current assignee: White Rodgers Co
Priority date: 1958-12-22
Filing date: 1958-12-22
Publication date: 1963-03-05
Anticipated expiration: 1980-03-05

Description

March 5, 1963 J. A. WRIGHT ETAL 3,079,984

BURNER IGNITION AND CONTROL SYSTEM Filed Dec. 22. 1958 FIG. 2

I N V E N TO R JAM ES A. W LEE R. JOH N SO S RIGHT N JR TH E l R AGENT United States Patent ()filice,

3,079,984 Patented Mar. 5, 1963 3,079,984 BURNER IGNITION AND CONTROL SYSTEM James A. Wright, Webster Groves, and Lee R. Johnson, Jr., Kirkwood, Mo, assignors, by mesne assignments, to White-Rodgers Company. a corporation of Missouri Filed Dec. 22, 1958, Ser. No. 781,987 4 Claims. (Cl. 158125) This invention relates to ignition and control means for the fully automatic and safe operation of gaseous fuel burners and particularly to a system wherein the main burner is operated in an on-and-otf manner and is directly ignited by electrical ignition means each time operation thereof is initiated, the usual pilot burner being eliminated. 1 An object of the invention is to provide a fully automatic control system for the on-and-off operation of a gas burner which is particularly safe and reliable and in which considerable simplification and economy is achieved bydirect electric ignition of the main burner, thus eliminating the usual pilot burner and its control valve.

A further object is to provide a novel and reliable spark ignition device which is particularly economical in that it may be operated directly from the usual 115 volt A.C.- commercial power supply, thus eliminating the necessity of providing the usual step-up transformer.

Further objectsandadvantages will become apparent when readingthe' following description in connection with the accompanying. drawing.

In the drawing:

FIG.:1 is a diagrammatic view of a gas burner control system constructed in accordance with the present invention;

FIG. 2 is a top plan view of the spark igniter constructed in accordance with the present invention;

1 FIG. 3 is an end elevational view of the igniter shown in FIG. 2; and

FIG. 4 is a longitudinal cross-section view of the igniter shown in FIGS. 2 and 3 and is taken on line 4-4 of FIG. 2.

Referring to FIG. 1 of the drawing, the primary elements of the system are; a main gas burner which receives'fuel from a suitable source through a supply line 12, a normally closed, solenoid operated valve 14 interposed in supply line 12. having a solenoid winding 16, a spark igniter generally indicated at '18, a doublethrow, thermal time switch 20 having a resistance heater 21 and

contacts

23 and 25, a make-betore-break type, flame responsive switch 22, a thermostatic space temperature responsive switch 24,

resistors

26, 28, and 29, and a line switch 30.

Circuit lead terminals

31 and 33 are provided for connection with a suitable source of electrical power.

; Referring to FIGS. 2 to 4 of the drawing, the spark igniter 18 comprises a pair of

conductive legs

32 and 34 attached at one end to the opposite parallel sides of an insulator block 36 by screws 33. The outer free ends of

legs

32 and 34 are formed at a right angle toward each other and each has attached thereto a contacting element 49. The leg 34 is constructed of two lengths of material connected by a rivet 42. The inner length of material designated at 44 is thin and relatively flexible so that the leg 34 may be readily moved toward and away from leg. 32, which is constructed of a single length of thicker material so as to be relatively inflexible. The fiexibleportion -44 of leg 34 is preformed so as to normally hold the contact element thereon in a direction away from the contact .element on leg 32.

A tensioned, conductive wire conductor 46 attached at one end to a conductive terminal pin 48 and its other end to leg 34 near its outer end is of such length at normal temperatures as to hold contact elements 40 together in closed circuit contact. The terminal pin 48 is mounted for free rotation in a threaded insulator plug 50, which plug is in turn threadedly engaged in an internally threaded bushing 52 centrally disposed and rigidly mounted in the insulator block 36. The wire element extends from the end of terminal pin 48 through a central bore 54 in the insulator block, then angularly to its point of attachment with the outer end portion of leg 34. An inwardly formed tab 56 near the outer end of leg 34 is provided for the mechanical and electrical connection of the end wire 46, and a bushing 58 with a smoothly rounded internal edge positioned at the end of bore 54 prevents kinking or abrading of wire element 46.

When electrical current is passed through the wire conductor 46, it will expand and permit the contact elements 40 to open under the bias of preformed, flexible leg portion 44. Upon opening of the contact elements 40 an electric are or spark will occur between them and the current flow through the wire conductor 46 will be cut off, thereby permitting it to cool and contract and to move the contacting elements 40 to a closed position. While various lengths, diameters, and materials may be employed in constructing wire conductor element 46 so as to achieve the required expansion and response time for any given current flow therethrough, it is our preference to employ a wire element of such diameter, length, and material that it will burn out in a relatively short period of time if the contacts stick or fail to open for any reason. The purpose of this arrangement is to provide means in the form of a fusible link to break the circuit and assure the cutoff of fuel supply to the burner if ignition tails due to the contacts sticking closed.

Any growth in length of the wire element 46 due to stress at high temperatures may be readily compensated for by adjustment of the threaded plug 50. Inasmuch as the terminal pin 48 is mounted for rotation in plug 50, the plug may be rotated outwardly to precisely adjust contacts 4% without twisting the wire element. The contacts 40 may be constructed of any suitable material. While we have disclosed a reliable and operative arrangement which may be operated in such manner that the contacting elements 4%) are moved toward closed and open positions at the speed of contraction and expansion of the wire element 46, the addition of any suitable expedient to achieve a snap-action movement in making or breaking the contacts 40 is contemplated.

Operation The igniter and other elements of the control system are shown in a cold, de-energized position. Under these conditions when the line switch 30 is closed, the igniter 18 and solenoid valve winding 16 will be energized through a circuit which may be traced as follows: from terminal 31 through a lead 60, line switch 30, a lead 62, space thermostat 24, a lead 64, flame sensitive switch 22 (in its cold, solid line position as shown), a lead 66, thermal time switch heater 21 and contact 23, a lead 68, a lead 70, through igniter 18, a lead 72, solenoid valve winding 16, a lead 73, and a lead 74 to terminal 33. In order to maintain continuous and sufficient energization of solenoid winding 16 to hold valve 14 open during circuit interruptions occasioned by the repetitive parting of igniter contacting elements 40, a parallel connected across the igniter 18 is provided consisting of a lead 76, a resistor 26, and a lead '73. The value to resistor 26 is such that it effects a drop in the current fiow through solenoid winding 16 to a point wherein there is insufficient electro magnetomotive force developed in winding 16 to pull the solenoid valve open from a closed position, but wherein sulficient curent flow through winding 16 remains to hold the valve open once it is open.

Energization of solenoid winding 16 opens valve 14 and fuel flows to burner 10. Energization of igniter 18 causes the'wire-element 46 to alternately expand'and contract sutficiently to repetitively break and make the contacting elements 40 and thereby produce an intermittent spark'for igniting the fuel. The relay winding 16 provides a substantial inductance load in series with the contacting element 40 which considerably increases the voltage available to produce sparking at the contacting elements. When the burner is ignited the flame sensitive switch 22 responds, moving from its cold (solid line) position to its hot (dotted line) position. The flame sensitive switch 22 is a double-throw, make-before-break type switch. That is to say, it is so constructed that it completes one circuit before breaking the other when responding to either a condition of flame or absence of 'flame. '.'Such switch construction is'well known, and in the interest of simplicity, detail is omitted.

-When switch' 22 completesits response to flame, the above-described circuit for the igniter' and solenoid valve is broken at' thatpointand a second circuit for energizetion of solenoid winding'16'is completed through the hot side contact'of switch '22 which may be traced as followsz'from terminal 31' through'lead 60, through line switch 30, lea'd'62, space thermostat 24, lead 64, flame sensitive switch 22 (in its dotted line'position), a lead 80, resistor 28, a lead 82, leads 78 and 72, the winding 16, a lead 73,- and the lead 74 to terminal33. The resistor 28, like resistor 26, is of such value as to reduce the current flow through solenoid winding 16 to a point wherein it is sufficient to hold'valve 14 open once it is open, but is insuflicientto open the valve from a closed position.

Breaking the originally described circuit through switch '22 in a cold position'de-energizes the thermal time switch heater 21 and the igniter18. Operation of the burner 10 will now normally continue until suflicient heat is produced to effect opening of space thermostat 24. If, during normal operation of'the burner, energization of valve winding 16 is interrupted for any reason, as by interruption ofthe power source or opening of the line switch, the fuelvalve 14 will close and Will not be reopened upon recompletion of the last-described circuit due to resistor 28. Under these conditions operation will be resumed only after flame switch 22 has responded to loss of flame at the burner and again completed a pull-in circuit for winding 16 through the first-described circuit, which includes the thermal time switch 20 and igniter 18.

If upon starting from a cold condition the igniter contacting elements 40 fail to open'due to sticking, the wire element-46 is so constructed that it will burn out when subjected to full current flow through the closed contacting elements for a short period of time. If this occurs it will break the pull-in circuitfor winding 16 and prevent any subsequent openingiof thefuel valve 14 until the igniter is repaired and again in operating condition. If, however, the valve.14 .hasbeen opened through the pull-in circuit. including wire element 46, the valve will remain openeven though the wire element 46 burns out due to the parallel holding circuit which includes the resistor 26. This limited holding circuit is broken, however, in a short period of time at thermal timeswitch 20. Thermal time switch 20 is arrangedto break the pull-in circuit at contact 23' after a predetermined interval in which its heater 21 is in "circuit, thereby cutting off the'fuel'supply after a predetermined trial period if flamefails to occur at the burner for anyreasbn. In orderto prevent recycling of thermal time switch 20, a second contact 25 is provided and is arranged to be closed to complete a holding circuit for heater 21 just prior'to the breaking "of contact 23. This holding circuit extends from contact 25 through a lead 84, the resistor 29, a lead 86 and lead 74 to terminal 33. The resistor 29 has the purpose of preventing excessive current flow through heater 21.

-The foregoing is intended to be illustrative and not limiting, the scope of the invention being set forth in the appended claims iv We claim:

1. A spark ignition device comprising a pair of electrical contacting elements, means biasing at least one of said contacting elements in a direction to separate it from the other, a tensioned wire conductor arranged to hold said contacting elements in a closed position against said'bias at normal temperatures, said Wire conductor being thermally expansible .to elongate sufli'ciently and at such rate due to thermal expansion when a predetermined electrical circuit is passed therethrough as to permit the opening'of said contacting'elements by said biasing means thereby to draw an are between said elements and to break thecircuit, and said wire'conductor having such electrical resistance as to attain the temperature of fusion when'said predetermined current is passed therethro'ugh for aninterval'longen than that normally required for itto expand sufficiently to efiect the/opening of said contacting'-elerr're'n'ts, and means for passing said predetermined electrical current through'said wire conductor when said'conta-cting elements are closed and for increasing the 'voltageavailable'to intensify the are when said contacting elements separate comprising a source of electrical power, an inductance wadgand circuit connections 'connecting' said wire conductor; said contacting elements, and said inductance load m series relationship across said's'our'ce of power.

' 2. In a burner control system, a burner, means in cluding a'normally closed valve for controlling the supply of fuel to said burner, an electrically operated actuator including an inductance winding which when'energized opens said valve, a spark ignition device arranged to ignite said burner, said ignition device comprising a pair of electrical contacting elements, means'normally biasing at least one of said contactingelements in a direction to separate it'from the'other, a tensioned wire conductor arranged to hold said 'contactingelements in a closed circuit position against said bias at noima'l temperatures, said wire conductor being thermally expansible to elongate sufficiently andat such ratedueto thermal expansion when a predeterminedelectricalcurrent is passed therethrough to permit separation of said contacting elements to produce a spark, a source ofelectrical'energy, and means including circuit connections connecting said tensioned wire conductor, said contacting elements, and said valve actuator inductance winding in series relationship across said source of energy,'wliereby an intermittent spark of high intensity is achieved as said tensioned wire alternately expands upon being heated to break its circuit which includes said inductance winding and then contracts upon cooling to again complete its cir-cuitj 3. In a burner control system, a burner, a normally closed valve for controlling the flow of fuel to said burner, an electromagnetic actuator including an induc' tance winding which when energized opens and maintains said valve'in' an open position, a spark ignition device arranged to ignite said burner, said ignition'device comprising a pair of electrical contacting elements, means biasing at least one of said contacting elements in a direction to separate it from the other, a tensioned wire conductor arranged to hold said contacting ele} ments in a closed position against said bias at normal temperatures, said wire conductor being thermally ex pansible to elongate sufliciently due to thermal expansion and permit the opening of said contacting elements when a predetermined electrical current is passed therethrough thereby to produce an arc, a source of electric'al energy, circuit connections connecting said wire conductor, said contacting elements, and said valve ac tuator inductance winding across said source of energy, whereby said wire conductor alternately expands to eflect the opening of said contacting elements and produce an arc and then contracts to again establish the'circuit, and means for maintaining suflicient energization of said valve actuator inductance winding to hold said valve in an open position when said contacting elements are in an open position comprising a shunt circuit around said wire conductor and said contacting elements and including a current-dropping resistor having such value as to limit the flow of current through said inductance winding to a value wherein the electromagnetomotive force is insufiicient to open said valve from a closed position, but is yet sufiicient to hold said valve open once it is open.

4. In a burner control system, a burner, means including a normally closed valve for controlling the supply of fuel to said burner, an electromagnetic actuator including a winding which when energized opens said valve, a spark ignition device arranged to ignite said burner, said ignition device comprising a pair of electrical contacting elements, means normally biasing at least one of said contacting elements in a direction to separate it from the other, a tensioned wire conductor arranged to hold said contacting elements in a closed circuit position against said bias at normal temperatures, said wire conductor being thermally expansible to elongate sufiiciently due to thermal expansion when a predetermined current is passed therethrough to permit the opening of said contacting elements thereby to draw an are between them, said wire conductor having such electrical resistance as to attain the temperature of fusion when said predetermined current is passed therethrough for an interval longer than that required for it to expand, sufficiently to efiec-t opening of said contacting elements, means for passing a predetermined current through said wire conductor comprising a source of electrical power, and circuit connections connecting said wire conductor, said contacting elements, and said actuator winding in series relationship.

References Cited in the file of this patent UNITED STATES PATENTS 346,430 Cutten July 27, 1886 761,379 Heany May 31, 1904 2,270,722 Beam Jan. 20, 1942 20 2,500,663 Cleveland Mar. 14, 1950 2,874,762 Dunstan Feb. 24, 1959

Claims

1. A SPARK IGNITION DEVICE COMPRISING A PAIR OF ELECTRICAL CONTACTING ELEMENTS, MEANS BIASING AT LEAST ONE OF SAID CONTACTING ELEMENTS IN A DIRECTION TO SEPARATE IT FROM THE OTHER, A TENSIONED WIRE CONDUCTOR ARRANGED TO HOLD SAID CONTACTING ELEMENTS IN A CLOSED POSITION AGAINST SAID BIAS AT NORMAL TEMPERATURES, SAID WIRE CONDUCTOR BEING THERMALLY EXPANSIBLE TO ELONGATE SUFFICIENTLY AND AT SUCH RATE DUE TO THERMAL EXPANSION WHEN A PREDETERMINED ELECTRICAL CIRCUIT IS PASSED THERETHROUGH AS TO PERMIT THE OPENING OF SAID CONTACTING ELEMENTS BY SAID BIASING MEANS THEREBY TO DRAW AN ARC BETWEEN SAID ELEMENTS AND TO BREAK THE CIRCUIT, AND SAID WIRE CONDUCTOR HAVING SUCH ELECTRICAL RESISTANCE AS TO ATTAIN THE TEMPERATURE OF FUSION WHEN SAID PREDETERMINED CURRENT IS PASSED THERETHROUGH FOR AN INTERVAL LONGER THAN THAT NORMALLY REQUIRED FOR IT TO EXPAND SUFFICIENTLY TO EFFECT THE OPENING OF SAID CONTACTING ELEMENTS, AND MEANS FOR PASSING SAID PREDETERMINED ELECTRICAL CURRENT THROUGH SAID WIRE CONDUCTOR WHEN SAID CONTACTING ELEMENTS ARE CLOSED AND FOR INCREASING THE VOLTAGE AVAILABLE TO INTENSIFY THE ARC WHEN SAID CONTACTING ELEMENTS SEPARATE COMPRISING A SOURCE OF ELECTRICAL POWER, AN INDUCTANCE LOAD, AND CIRCUIT CONNECTIONS CONNECTING SAID WIRE CONDUCTOR, SAID CONTACTING ELEMENTS, AND SAID INDUCTANCE LOAD IN SERIES RELATIONSHIP ACROSS SAID SOURCE OF POWER.