US2388909A - Electric ignition system for gaseous fuel burners - Google Patents

Description

Nov. 13, 1945. B. c. DOUGLAS 2,388,909

ELECTRIC IGNITION SYSTEM FOR GASEOUS FUEL BURNERS Filed Au 25, 1942 2 Sheets-Sheet 1 NOV. 13, 1945. a c, DOUGLAS 2,388,909

ELECTRIC IGNITION SYSTEM FOR GASEOUS FUEL BURNERS Filed Aug. 25, 1942 2 Sheets-Sheet 2 ELECTRIC IGNITION SYSTEl/I FOR GASEOUS FUEL BURNERS Bradley 0. Douglas, Clayton, Mm, assignor to American Stove Company, St. Louis, Mo., a corporation of New Jersey Application August 25, 1942, Serial No.456,070

3 Claims.

This invention relates to an electric ignition system and pertains more particularly and specifically to such a system which although being susceptible for use in a very wide field, is particularly adapted for use with the gaseous fuel burners of a cooking range. The system has many points of similarity to the system disclosed in the pending patent application Serial No. 385,178 filed in the name of the present inventor as a joint inventor with Lester S. Kaufiman, and in many respects constitutes what is believed to be an improvement over the system of said mentioned application and embodies advantages over said system, but at the same time the present system is susceptible of being combined with certain features of said Douglas and Kauffman application and is also susceptible of having its exact mode of operation modified by combining with the inventions of Patent No. 2,275,998 issued to Arthur Stockstrom, dated March 10, 15242, and the A. H. Brodheck Patent No. 2,276,015 dated March 10, 19 i2.

The present invention has many advantageous. constructional features not found in the above mentioned patents or application as well as a mode of operation difiering from them. In its broadest aspect the invention of the present application differs from the Douglas and Kaufiman application in the utilization of what I have termed a controller coil in the electric circuit the provision of which gives to the present system attributes and advantages, the nature of which will specifically hereinafter appear, not present in said joint patent application.

Broadly expressed the primary object of the invention is to provide an improved electric ignition system for igniting gaseous fuel burners.

Other objects or" the invention are to provide such an ignition system which in comparison with systems of the same general type is comparatively cheap and simple of manufacture and assembly and so constructed as to make the system applicable to existing gaseous fuel burning devices, particularly cooking ranges, without alteration of the present constructions thereof, and to make the application of the system to ranges moving on an assembly line optional without any alteration of the design or construction of the ranges being assembled.

In the accomplishment of the foregoing objects the system is extremely compact and flexible which comprises a further advantage derived from the invention. Th invention has many other objects and advantages among which are the provision of an ignition system of the type named wherein the system operates satisfactorily on an extremely low current voltage and amperage; a system which stands ready to cause re-ignition should it be necessary; a system which operates at small cost because of the low current consumption; a system in which ignition is caused by an electrically heated coil the life of which is lengthened and which has a long life notwithstanding the fact that electric current is delivered to said coil throughout the entire period of the operation of the range; and a system which causes extremely quick ignition.

Another and very important object is to p ovide a system of the type named which operates satisfactorily irrespective of variations in current supply which when occurring with a system of the present type as now known tends almost invariably to cause failure of operation of said system.

Other objects and advantages pertaining to the construction of the controller coil and the treatment of the ignition coil, as well as novel constructional features all of which contribute their part to the production of an improved electric ignition system, appear from a reading of the hereinafter following description when read in the light oi the accompaning drawings which illustrate the application of the inventive concept to a gaseous fuel burning cooking range.

In the drawings:

Fig. 1 is a horizontal sectional view through a range illustrating the application of the present improved ignition system thereto.

Fig. 2 is a vertical sectional View through the igniter assembly and pilot light and a portion of the oven burner.

Fig. 3 is a longitudinal horizontal sectional view through the igniter assembly, the current providing conductors being shown in full line.

Fig. 4 is an end view of the igniter assembly.

An easier and more comprehensive understanding of the invention will be had b an understanding of the ignition system arrangement and general construction, which will now be given by descriptive reference to the drawings, and particularly Figure 1 thereof which illustrates the system in its entirety in combination with a conventional domestic gas range.

Referring to Figure 1, A designates an insulated oven chamber positioned at one end of the range, and B designates a chamber adjacent the oven and at the opposite end of the range and which is commonly referred to as the cooking top burner chamber for the reason that the cooking top burners, which in the drawings are not illustrated for the reason that they would complicate the illustration -of the invention, are positioned in this chamber below suitable utensil supporting grids or a solid cooking top lid.

The burner C is positioned in the oven and is of conventional form in that it comprises a burner arm 5 having a plurality of burner ports 8. An air-gas mixture is fed to the burner arm through an inlet manifold I the outer flared end 8 of which is in communication with a chamber 9 formed by a tubular member lo the outer end of which extends through one oven wall and is provided with a plurality of primary air inlet openings Ii through which air is admitted under the control of a suitable shutter or valve l2.

' One side wall of the burner arm 5 is provided with a plurality of lighter ports i3, see Figure 2 of the drawings, which operate as a chain lighter after the fuel escaping from them has been ignited by the constant burning let M of the pilot light D, to ignite the main burner ports 6.

The range illustrated is of the type wherein a predetermined temperature is attained and maintained automatically by thermostatic control. The thermostatic control i not illustrated in detail as such controls-are common and 01' varying well known constructions. The thermostat for automatically maintaining a predetermined oven temperature is designated as an entirety at E and is provided exterior of the front of the range with a temperature setting dial and handle F. In a construction of this kind a thermo-responsive element is disposed within the oven and in any one of the. numerous well known manners controls the flow of gas to the oven burner to accomplish the maintenance of a predetermined temperature within the oven, Inasmuchas this specific construction forms no part of the present invention and is well .understood by those skilled in the art the thermo-responsive element of the heat control unit is not illustrated and further description of this unit is considered unnecessary.

Gas from a suitable source is brought to the range and into the cooking top burner chamber 3 by a supply manifold pipe I. It will be understood that the cooking top burners receive their gas from this supply manifold. The oven burner also is supplied with gas or fuel by this pipe and the supply thereof is primarily under the control of a manually operated valve It. When this valve is opened gas flows through the pipe I! to the temperature regulator E and from said resulator is conveyed by a pipe i8 to a safety valve G.

This safety valve can be constructed in any one of many well known constructions and includes a normally closed valve to prevent gas passing from the control valve through the pipe 19 to the oven burner fuel supply jet 20.

The pilot burner D is in the form of an elongated metallic base 2| and is supported by having one end connected to the safety valve G by a pipe 22. Gas is delivered to the base 2i by a pipe 23 which is connected as at 24 to the gas pipe I! at a point in front of the thermostatically operated heat control E so that immediately upon the manual opening of the valve i8 gas will flow through the pipe 23 to the pipe 22. In the pipe 23 is a suitable manually adiustable valve 25 by which the size of the flame burned by the pilot light may be controlled.

The base 2| of the pilot light is provided with an internal bore 28 having communication with the pipe 22 and the pilot jet housing 21 has its lower end 28 communicating with said bore 26 to convey gas to the pilot burner orifices 29, 30 and aseasoo 3| which are positioned at the opposite sides and top respectively of the jet'housing 21.

The pilot light D is associated with and in responsive element, through suitable connection the nature of which is well understood by those in the art, operates, when heated by the constant burning pilot flame iet II, the normally closed valve in the safety valve unit G so as to permit gas to flow through the pipe l9, jet 20, and burner manifold l to the main burner orifices I of the burner C and also to the chin lighter ports or oriflces I! with the result that the oven burner C will be automatically ignited,

When the manually operable gas cook it is opened gas is permitted to flow to the housing of the-automatic thermostatically operated temperature control unit, E and a portion of this gas flows from said housing through a pipe 34 to a pressure operated electric switch designated as an entirety at K. The exact construction of this switch is not illustrated'nor will a detailed description of it be given for the reason that any number of pressure operated switch controls well known and in common use could be satis-.

factorily utilized. As an example however of a switch which would be satisfactory, it could be a mercury type switch wherein the electric circuit is made and broken through a body of mercury the position of which, in respect to the electric contacts which it is adapted to connect, is changed by the pressure exerted by the gas entering the switch. The construction should be one wherein the switch is normally in an open position and biased toward that position so that the switch would be colsed only when gas is admitted to the switch and the pressure thereof overcomes the bias so as to move the switch parts to a position where the mercury bod will close the circuit. Upon the failure of pressure within the switch which would occur when gas delivery to the switch ceases; the bias would act automatically to open the switch.

The pilot has been referred to as constant burning but in a sense this is misdescriptive because the pilot burns, or is intended to burn. only so long as the oven burner is in operation which of course is throughout that period during which the manually operated fuel control valve is is open. Ordinarily the heat regulator E does not operate at any time to cut oil all the fuel delivery to the oven burner but only throttles it to a very small amount when the heat within the oven has reached the predetermined temperature. However should the heat regulator for any reason, such as being improperly adjusted, stop the flow of fuel to the oven burner fuel would still continue to now to the pilot light so that when the heat regulator again permitted fuel to flow to the oven burner the burner would be automatically ignited, or if through accident or some other cause the pilot were not ignited at the moment fuel reached the main burner the automatic electric igniter, designated as an entirety by M and hereinafter fully described, would cause re-ignition of the pilot light which would in turn cause manufacture is supported upon the elongate"' base El of the pilot burner by a bracket or the like. One open end 3'3 of the tube is hosi tioned adiacent but in spaced relationship to the pilot burner and particularly the fuel or burner orifice 30 thereof so that fuel issuing from the orifice will be directed into the open end of the flash tube and when said fuel is ignited the flame burned at the orifice and the heat generated by said flame will be directed toward and into the open end of the flash tube. The arrangement is such that as fuel escapes from the orifice 30 and enters the flash tube, to be ignited a will be hereinafter described, air is entrained into the flash tube with fuel so that there will be a combustible mixture within the flash tube to be ignited therein and flash back and burn at the burner orifice 30.

Detailed description of the flash tube method of ignition is unnecessary as it is well understood by those skilled in this art.

Referring to the electric igniter unit M and particularly Figures 2 to 4 of the drawings, a ceramic insulator block 38 extends throughout the length of the flash tube adjacent the bottom thereof and upon the upper and lower faces of this block at that end of the flash tube remote to the pilot burner there are suitably secured, as by bolts or rivets 39, 40 and 4!, a plurality of metallic contact plates 42, 43 and 44. The two first named plates are upon the top of the block and arranged in spaced parallel relationship while the plate 44 is on the bottom of the block and is disposed within a channelway 45 which is positioned to place the contact plate 44 intermediate the contact plates on the upper face of the block. All the contact plates have ends which extend outwardly beyond the flash tube. Each of the upper contactplates 42 and 43 is provided with an upwardly extending L-shaped arm 46 and to the horizontal leg portions of these arms is welded an electric igniter coil 41. This coil extends transverse the open end 48 of the flash tube but is disposed within the tube. This coil is of a specific construction the exact nature of which will hereinafter appear;

A second electric coil 49 is disposed within the flash tube and extends longitudinal thereof so that its longitudinal axis is at right angles to that of the igniter coil 41. Thi coil has one of its ends welded to the contact plate 32 as at 59 while at its other end the coil is provided with an extending portion which passes downwardly through a suitable opening 52 in the ceramic block and extends along under said block and is welded for electrical connection to the contact plate 44 as at 53. This coil I have termed a controller coil and it is supported by the two wires or elongated conductors which form a continua-v tion of its front and rear ends respectively. This coil, like the igniter coil 41, is of a special construction the exact nature of which will hereinafter appear, as will also the purpose for making both of said coils in the specific manner which will be hereinafter described.

As the present system has been devised so as to be readily attachable to ranges already in use or to be applied to ranges in the course of production without altering the constructions thereof, the system is devised also to operate from the electric system found and in common use in homes or in other buildings where illumination A PI! u. bu

transformer extends a conductor 548 which leads to a terminal block 51 which is positioned exterior of the range oven so that it and its terminals 58 and 59 are not subjected to the high heats prevalent in the oven. The conductor 540 is connected to the block terminal 58. A second conductor 550 leads to one of the terminals 69 of the pressure switch K. The second terminal 6| of the pressure switch is connected to the connector block terminal 59 bya conductor 55L The connector block terminals 58 and59 are connected by extension conductor leads 82 and 63 to the contact plates 44 and 43 respectively and as their connections to the plates are within and subjected to the high temperatures within the oven these conductors are welded to their respective connector plates as indicated at 64. To withstand the high temperatures encountered these leads should be made of nickel or nickel alloy.

From the foregoing the mechanical and electrical construction and apparatu constituting the present improved system and the essential parts of a gaseous fuel burner and of a range with which said system is utilized has been described. Description will now be given of essential features of construction and arrangement knowledge of which is necessary to a complete understanding of the mode of operation of the system, description of which will also follow.

In the present system current is delivered to the ignition coil and the ignition coil remains on throughout the period of operation of the range, and in this respect the present system differs basically from that of the hereinbefore mentioned pending patent application and issued patents. Nevertheless, the present igniter unit could be used to good advantage with the system disclosed in said application and patents notwithstanding the fact that in them the ignition coil is on only for a short time after the ranges with which those systems are illustrated as being associated are brought into operation. Other differences and advantages of the present system over the systems of said application and patents will appear to those skilled in the art from the following description and in many instances they will be directly pointed out.

To be practical an electric ignition system must operate satisfactorily notwithstanding the nu merous variables which are encountered, and it also must have a life sufficiently long to not require frequent replacement of the igniter unit and to comply as a minimum with standards of approval set up by the American Gas Association which are that the igniter coil must withstand 25,000 cycles of operation, and furthermore the system must not be so complicated as to be impractical in the hands of the ordinary user or difficult to service in the field by those who ordinarily service gas ranges and are not familiar with electrical apparatus. Furthermore the system must be absolutely safe and must be highly efficient in providing positive and rapid ignition when the manually operated fuel valve is open. To these requirements is added the necessity that I with different kinds of gases.

the ignition system will ignite all kinds of gaswhether it be natural or one of. the numerous type of artificial gases the ignition temperatures of which vary widely. Obviously it would be impractical from a manufacturing standpoint to have to install ignition systems having differing VARIOUS Gases Both natural and artificial gas are widely used in this country as are also such gases as propane and butane. The ignition temperature of natural gas is approximately 1400" F. but it has been foundthat the temperature of the ignition coil must be considerably higher than the ignition temperature of the gas to successively ignite the gas. The coil temperature must be in the neigh- "borhood of from 400 to 500 F. higher than the ignition temperature of the gas to assure ignition. As far as I can determine the foregoing is necessary due to the fact that the conductivity of the gas results in a decrease of temperature in the atmosphere immediately surrounding the coil.

Most commercial or artificial gases have a lower ignition temperature than doe natural gas, but even so to be on the safe side the ignition coil should reach a temperature between 1800 and IGNITION COIL The ignition coil of this system, like that of the systems of the application and patents hereinbcfore referred to, is made of platinum wire and this coil is pretreated as is described in said application so that the coil can be raised to the critical ignition temperature with the use of as little as 2.7 amperes.

The pretreatment of the coil comprises the operation of the coil through a few thousand cycles and not less than 30 minutes with 2% volts and with three to four amperes impressed thereon. This pretreatment is by actually repeatedly igniting gas and has been found to cause the coil to thereafter reach a higher temperature with the very low amperage of 2.7 and is apparently due to the fact that irrespective of whether natural or manufactured gas is ,used in the pretreatment the platinum coil became a more active catalyst. Coils so pretreated have been found upon examination to have the surface of the wire of which thy are composed etched or eroded and as a consequence the surface area has been materially increased and this has, it is believed, helped to increase the catalytic action which results in the possibility of employing a lower voltage.

Although the igniter coil is described as being composed of platinum wire, obviously other material could be used and the voltages and amperages could be varied in accordance with the size of the wire used and the particular nature of the material of which the wire making up the coil is composed, as well as the size of the coil both as to diameter and len th- Additionally although the disposition of the ignition coil as illustrated in the drawings has been found to operate highly satisfactorily the coil could be disposed with its length longitudinal of the flash tube or in some other position in the flash tube, as is made clear in the aforementioned pending application Serial No. 385,178.

Platinum wire has been found to be highly satasaaaoe the ignition coll because it has great resistance to the high temperatures to which it is subjected and also because it is an active catalyst, but there are other metals having similar characteristics which could be satisfactorily used;

Comnotua Con.

The life of the ignition coil when operated with the amperage mentioned is relatively of short duration, and it is for this reason that in devices of the present character the operation or the ignition coil is stopped as quickly as possible after ignition of the burner is obtained, as is the case in the aforementioned application and patents.

. My controller coil makes it possible for the ignition coil to remain in operation throughout the entire period of the operation of the range without unduly shortening the life of the ignition coil and this has the decided advantage of the ignition coil standing ready to re-ignite the burner or pilot should either of them become accidently extinguished, which is not the case where the ignition coil operation ceases immediately after ignition is originally accomplished.

The primary reason for the shortness of life of the ignition coil in devices as heretofore known and as disclosed in the aforementioned 'applica-' tion and patents is due to the fact that the amperage increases to a predetermined amount and remains constant at that value and when said constant value is reached the heat of the coil is such that it will break down the coil over a comparatively short period of time.

The present arrangement contemplates the subjection of the ignition coil to the amperage which will raise the coil to the ignition temperature of the gas for only a very short period of time and will thereafter automatically reduce the amperage, and consequently the temperature of the ignition coil which has been found to give the coil, even with the coil in constant operation,

a life duration suillcient to meet with required a very high temperature co-eflicient of electrical standards and to make the system commercially practicable. f

The controller coil is made of a material having resistance. This coil, as is clear from the drawings, is connected in series with the ignition coil with the result that a reduction of current flow .through the controller coil, even though it be behind the ignition coil in the electric circuit, reduces the amount of current flowing through the ignition coll.

When current is first permitted to flow in the ture of the varying kinds of gases with which the system may be used. For convenience I refer to this original current flow as a surge and do so because shortly thereafter the controller coil acts as a resistor to materially reduce the current flow through the circuit so as to reduce the temperature of the ignition coil and thus prolong its life. This reduction in current flow by the controller coil does not take place until after ignition has occurred.

The resistance of the controller coil will commence to build up immediately. It will build up first because the passage of current through the controller coil will itself heat the coil and thereby increase its resistance. Secondly, immediately ignition occurs the controller coil is subjected isfactory as the material of which to compose 7 to the heat of that flame burned at the burner oriflce opposite the flash tube, and thirdly the resistance of the coil will be further increased by the heat built up in the oven chamber itself due to the continued operation of the main oven burner provided said heat reaches a degree greater than the degree of heat directed to and around the controller coil by the aforementioned pilot burner. flame.

It is intended and it has been found that within three or four seconds after the system is put into operation ignition of the gas occurs. The time duration before the controller coil begins to reduce the current flow can be varied practically at will by varying the dimension or gauge of the wire of which the coil is made; by varying the length of the coil; or by letting the pilot flame actually impinge upon the coil. Variance could also be obtained or controlled through the use of wires having different temperature co-eflicients of electrical resistance.

I have found Hytemco wire to be highly satisfactory as a material for the controller coil. Hytemco is an alloy of nickel and iron composed approximately of 70% nickel and 30% iron. The chief characteristic of wire made of this material is its high co-eiilcient of electrical resistance, which resistance co-eflicient rapidly increases with increased temperature.

There are unquestionably other materials out of which the controller coil could be made and would operate satisfactorily. These materials would probably be found aniong those alloys made up of nickel and iron or nickel, chromium and iron such for instance as those going under the trade names of Nichrome, Manganin, or Midohm.

Obviously the selection'of material out of which the controller coil is to b-made and control of the other variables of the controller coil would be suchthat the controller coil would permit the ignition coil to remain at the ignition temperature of the gas only so long as would be necessary to cause ignition so that the life of the ignition coil would be lengthened. As ignition occurs within three to four seconds after the system is put into operation the controller coil can be coordinated to permit the current surge period to be only slightly longer than six seconds.

Although it is stated that reduction in current flow due to its heating up by reason of its resistance, does not take place until after ignition has occurred, this statement should be qualified. Actually the controller coil starts immediately to reduce the current flow but the coil is so made that it will not reduce the current flow sufliciently to reduce the ignition coil temperature below the ignition temperature of gas until more than sumcient time has expired for ignition to have taken place. Actually, as will hereinafter appear, the coil can be so made that its resistance will not besuflicient to reduce the current flow at all and the current flow reduction will not occur until after the pilot light has been ignited and the controller coil has been subjected to the heat or flame of .the pilot light.

11' reduction of current flow is made to be dependent upon heating of the controller coil by the pilot light only the successful and eflicient opera- .tion of the system is in no way detrimentally affected. The point is, the controller coil can be made to reduce the current flow, due to its rise in temperature caused by electrical resistance, in any amount desired and within any time period desired, and equally as well the controller coil can be made so that it will not reach a temperature to reducegthe current at all until it, has been heated by the flame of the pilot light.

With the system made to operate in either of the manners mentioned there is of course an initial surge which in one instance is first reduced by the heat generated by the resistance of the controller coil and then a further current reduction is caused by the controller coil being heated by the pilot light.- In the second instance the heat of the pilot light alone causes the heating of the controller coil and a consequent current flow reduction; which current flow reduction would be further reduced should the oven temperature exceed the temperature generated on and about the controller coil by the pilot light flame.

What I term initial surge should be understood from the description immediately preceding. The initial "surge is the flow through the circuit of full voltage and amperage which follows turning on the current. From the preceding description it will be understood that the initial surge is directly related to and dependent upon, in the first instance the resistance of the controller coil, and in the second instance the amount of heat to which the controller coil is subjected by the flame burned by the pilot light or by the heat of such other flame or flames to which the controller coil may be subjected.

This initial surge of current is of great importance, as will hereinafter appear, for assuring satisfactory performance under very wide ranges of voltage variation because the ignition coil can safely be subjected to voltages and amperages higher than that absolutely necessary to raise the temperature of the ignition coil to the ignition temperature of the gas to be ignited.

LIFE or rat: IGNITION 0011.

The life of the ignition coil in a two coil system such as the present one has been already touched upon in the foregoing description. On this phase of the invention attention is called to the fact that there are several features which affect the life of the platinum ignition coil and that the controller coil either modifies or eliminates the detrimental effects to the life of the ignition coil.

The life of the ignition coil is affected by the temperature to which it is raised and the number of cycles it must operate. Another important factor is the catalytic action of the coil. Catalysis occurs when the gas-air mixture envelopes or strikes the coil or lighted gas envelopes or strikes the coil as this causes the temperature of the coil to be raised considerably. On occasion the lighted gas within the flash tube may not flash back immediately to the pilot light and as a consequence catalytic action is prolonged and the temperature of the coil is raised considerably above normal. This condition can be eliminated by using a higher amperage in the electric circuit but if this is done without means to provide an initial surge and a prompt reduction of amperage, as for instance is the case in devices now known and used and in respect to the system of the identified application and patents,the life of the coil, by reason of the coil reaching a very high temperature due to the high amperage, is materially shortened. However the provision of a controller coil allows the use of higher amperage without shortening the life of the coil because the initial surge can be held to a very short period of time and the amperage thereafter reduced and the ignition coil temperature correspondingly decreased.

Delayed ignition, that is delayed flash back of ignited gas in the flash tube, may occur only for five or ten seconds but even such a short period has been found to be enough to aid or cause the development of intercrystalline weakness in the ignition coil which occurs at elevated temperatures.

The foregoing explanation will make it understandable why the inventive concept of the provision of a controller coil could be used advantageously in combination with the ignition system of application Serial No. 385,178 and the systems illustrated and described in the aforementioned patents.

Stated in broad terms, the controller coil permits the use of higher amperages without shortening the life of the ignition coil and the higher amperage assures instantaneous ignition and thereby obviates injury to the ignition coil which occurs when ignition is delayed, as explained above. Consequently the use of a controller coil is a highly important feature in lengthening the life of the ignition'coil regardless of whether or not the ignition coil remains constantly on throughout the operation of the range or whether the ignition coil operation is stopped after it has caused initial ignition.

It will be seen that where no controller coil is used amperage in the circuit remains constant and this amperage is suflicient to raise the temperature of the ignition coil to the ignition temperature of gas. This ignition coil temperature is sufliciently high to gradually break down the coil and thus shorten its life. Cotly it would be impossible to let the ignition coil remain constantly on when no controller coil is provided aseacoc voltage which will produce3.5 amperes at equilibriums without the pilot light in operation. With a pretreated coil satisfactory re-ignition can be obtained with a reduced voltage which will produce only 3 amperes of current.

To produce an initial surge" in the ignition coil the controller coil should have a resistance,

' at room temperature of at least 0.3 to 0.4 ohm.

Should the resistance of the controller coil be less than 0.15 or 0.20 ohm it has been found that the initial "surge is not appreciable. This fact however, will not affect the emciency of the controller coil insofar as current reduction due to the heating of the coil by the pilot is concerned.

For the controller coil it has been found de-' sirable to use an alloy of 70% nickel and 30% iron hown in the trade as Hytemco. This material at 400 F. has an electrical resistance two times its resistance at room temperature. At 800 F. the resistance factor is three and onehalf times its resistance at room temperature.

at 1200 F. this factor has risen to 4.7 times its resistance at room temperature.

The above figures have been found in respect to a controller coil composed of two lineal feet of No. 22 gauge Hytemco wire.

' flowing in the circuit at equilibrium with no varying degrees the temperature to which they must be raised to successfully ignite the various kinds of gases. It is my intent to use platinum as this metal has the attribute of withstanding for a longer time duration, than do most metals, the high temperature to which it must be raised to cause the ignition of various types of gases Example The following example is informative and not to be considered as a limitation of the invention. A system built in accord with the example given has been found to be highly satisfactory inoperation but satisfactory systems can unquestionably be built without adhering to the specifications enumeratedin the example.

The ignition coil may be pretreated or not as is desired. With an untreated platinum ignition coil 2 inches in length and composed of No. 30 gauge it has been found that in order to obtain pilot in operation the voltage drop across the ignition coil is 1.5 and the voltage drop across the controller coil is 2.2.- With the pilot in operation there is a one volt drop across the ignition coil and a drop of 3.l5-volts across the controller coil.

The pilot flame causes the amperage in the circuit to drop from 3 amperes to 2.50 amperes.

It has been found that the ignition coil will dissipate approximately 4.50 watts at equilibrium without the pilot in operation while at equilibrium with the pilot in operation the ignition coil dissipates approximately 2.50 watts.

Obviously the above specifications can be varied to obtain the specific operation desired. The important feature is that by the use" of a controller coil any voltage and amperage desired can be obtained after equilibrium conditions have been reached and this is true in respect to equilibrium without the operation of the pilot and equilibrium with the operation of the pilot.

It is intended that approximately .5 ampere drop be obtained in the circuit due to the heat generated by the pilot. By imposing a voltage on the circuit which will permit. for instance, passage of 3.25 amperes after equilibrium conditions have been reached without the pilot in operation and with ignition or re-ignition occurring at 3 amperes it will be seen that the coil -will ignite or ire-ignite the gas satisfactorily because with the pilot out of operation 3.25 am peres will be flowing in the circuit and thi is more than suflicient to raise the temperature of the ignition coil to the ignition temperature of thegaseous fuel.

Should the ignition coil be pretreated so that. ignition and re-ignition will occur at 2.7 amperes satisfactory re-ignition it is desirable to'use a then a correspondingly lower voltage could be used and satisfactory operation and performance could be obtained at a lower amperage.

It is not necessary to calibrate the current so closely as above described. A higher voltage and amperage could safely beused so as to assure ignition under all variables and the controller coil could be constructed so as to reduce the amperage suflicientl to prevent the ignition coil from being maintained at a critical temperature.

RE-IGNITION 'It has been pointed out that the ignition coil could be pretreated as is described in the aforementioned pendin application Serial No. 385,178 and that when so treated the coil would reach the ignition temperature of the gases to be ignited with a current flow of as little as 2.7 amperes. It is not intended however to operate the present system so that only 2.7 amperes reach or flow as a maximum current through the ignition coil because then the system would not operate to cause re-ignition should the pilot light or main burner be accidentally extinguished. Re-ignition at such a maximum current flow through the ignition coil would not take place because even with the failure of any heat from either or both of these burners being directed to and around the controller coil to increase its resistance the controller coil would still be exerting a resistance in the circuit because of the heat generated in it by the flow of current and this resistance causes a sufficient reduction in the flow of current through the ignition coil that the amperage thereof is less than 2.7 and therefore the temperature of the ignition coil is below the ignition temperature of the gas.

Consequently it is intended, if the ignition coil has been pretreated, to use a voltage in the circuit which will produce 3 amperes, at equilibrium, without the pilot flame and if the ignition coil has not been pretreated to use a voltage which will produce 3.2 amperes under the same conditions. Thus if the pilot flame should become extinguished the controller coil temperature will cool sufficiently to reach equilibrium within a short time and thereupon 3 amperes or 3.2 amperes, in accord with whether an untreated or pretreated ignition coil is used will be permitted to flow in the ignition coil and this will be suflicient to raise the temperature of said coil to the ignition temperature of gas and cause reignition of the pilot which in turn will cause reignition of the main burner as the main burner would be extinguished due to the closure of the safety valve, which would occur upon the cooling of the thermal element which operates it and which is dependent upon the heat of the pilot flame for its operation.

From the foregoing it will be seen that if gas ignition temperature can be reached by the ignition coil only when the full initial current "surge flows in this coil, then satisfactory re-ignition would be impossible. However with a two-coil system, that is with a controller coil, it is not so important to keep the amperage close to the amperage which will cause the ignition coil to reach gas ignition temperature so as to lengthen the life of the coil which would be shortened were a higher amperage permitted to flow in it. This is due to the fact that if a higher amperage flows it is promptly reduced automatically by the controller coil. The prompt reduction of the current flow in the ignition coil upon the controller coil being subjected to the heat of the pilot light makes it possible to operate the present system with a current such that reasonable variances, particularly droppage, in voltageidoes not so adversely affect the operation of the system as to be sufficiently critical to make the system inoperative, as will be pointed out under the heading of Voltage variance.

The foregoing described mode of operation stated to be theintended mode of operation need not however be necessarily followed. Under the heading of fController coil, herein preceding, it has been pointed out that the controller coil could, if desired, be so constructed that no appreciable temperature within the coil would be built up by the flow of current through the coil. Such a coil could be successfully used in the ignition system. To do so, the proper voltage and amperage necessary to raise the ignition coil to a temperature sufliciently high to ignite the gas would be imposed on the circuit and would quickly build up to its highest value and cause the initial ignition. Ignition having taken place the current flow would quickly be reduced, due to the controller coil being heated by the burning pilot light, and the reduction of current flow would be sufficiently great to reduce the temperature of the ignition coil below the ignition temperature of gas. Now, upon the pilot being extinguished for any reason the controller coil would cool and the initial highest value of current flow would be permitted and thereupon reignition of the pilot light would occur as should be understood from the foregoing description,'and will more clearly appear from the following description of the operation of the system. The advantage of assured operation even with voltage variances would not be lost if the system were caused to operate as immediately above described because the initial surge supplies suflicient current to take care of voltage variance.

OVEN HEAT CONTROL ELIMINATED The temperature regulator for providing oven heat control is one of the refinements of better gas ranges but forms no part of the present invention, and operation of the present ignition system would not in any way be affected by the elimination of an oven heat regulator,

Two Con. Svsrnm with the flash tube, current drop due to poor contacts atswitch points or other connections in the circuit, is assured.

Likewise it makes possible the use of some metal other than platinum for the ignition coil. These metals would probably be of the nickel-chromium alloys which are ordinarily recommended for useat working temperatures lower than that of platinum. Although these other metals would be raised to a temperature above that recomended, as they would have to be to reach gas ignition temperature, their life would be prolonged because of the very prompt current reduction made in the circuit by the controller coil.

Additionally the two coil system is desirable and advantageous for'use whether the system be an intermittent "one, that is, one in which the current is-cut oil in the circuit after initial operation or whether the system is one in which the current remains on in the circuit constantly as long as the range'is in operation. In the first type of system there is of course no provision for re-ignition. In either type of system the life of the ignition coil is prolonged and a satisfactory operation is assured irrespective of the existence of any of the adverse conditions herein immediately before enumerated.

It is recognized that fluctuation in voltage in the electric circuit could be eliminated by the provision of a constant voltage transformer but the cost of such a transformer is much greater than that of a standard transformer which latter type can be successfully used with the present system by reason of the controller coil.

Vom'ssn Vacuums It is not only possible but quite probable that when in practical use there will be voltage varishoes which will reflect itself in the electric circuit of the present system. This is one of the variables which must be taken into consideration in the production of a satisfactory device.

The present two-coil system is designed to meet and successfully overcome voltage variances and to do so with a greater degree of emciency than is the case in single coil systems such as for instance those disclosed in the aforementioned application and patents. I This is due to the fact that a higher amperage and consequently a higher voltage than the minimum required to raise the ignition coil to gas isnition temperature can be used without unduly shortening the life of the ignition coil. COME,

quently even though the voltage may be below normal, that is below that intended to flow in the circuit, the initial "surge" would cause sufliclent amperage to flow in the ignition coil to raise the same to gas ignition temperature, which would not be the case with a single coil where normal voltage flow is essential to raising the ignition coil to gas ignition temperature.

Actually by test I have found that satisfactory ignition with the system can be obtained at voltfull voltage the amperage permitted to flow is con siderably in'excess of the critical amperage necessary for ignition.

Passsims Bwrrcn The primary purpose of using a switch of the type described is to avoid the use of mechanical "electric contacts in the oven where they would be subjected to high temperatures which could cause corrosion and otherwise increase resistance in the circuit and thereby bring about a voltage drop in the circuit. A mercury filled switch avoids these difliculties. Additionally such a switch, when pressure operated, is very flexible in that it can be located anywhere whatsoever on the range, whereas the position of a manually operated switch is controlled by the necessity of the switch operating lever being disposed for convenient operation by the range operator.- This flexibility is aseaeoo ranges embodying the present ignition system and in incorporating the ignition system in ranges already built and in use.

This flexibility of course plays a part in the compactness of the system and in rendering the system one which will permit its installation without the use of special parts or fittings. This is highly important from the manufacturing standpoint Where some ranges will be and some will not be equipped with electric ignition.

A pressure operated switch has been found to be highly eficlent as the gas pressure is always sumclent to move the switch to a closed pomtion and of course means is provided for returning the switch to an open position immediately upon the discontinuance of gas delivery to the burner.

It is to be understood however that the particular type of manually or automatically operated switch provided with the system is limited only by the desire of the builder as the system will work as long as means is provided for opening and closms the electric circuit.

Iom'rroN Um The ignition unit need not necessarily be of the exact construction illustrated. As an example the ignition coil and the controller coil need not of necessity both be in-the same unit or in the flash tube. The controller coil could be placed anywhere it might be desired, as for instance, at the opposite side 01 the pilot burner from the flash tube and ignition coil. In such a construction it would be only necessary to have the controller coll near a pilot burner flame or in a position to be impinged by a pilot burner flame if very rapid controller coil current reduction is desired.

To those skilled in the art many variable arrangements will readily occur because it will be understood that it is only necessary that the controller coil be subjected to the heat generated by a flame the ignition of which is under the control of the ignition coil.

As a matter of fact even more than one flame for heating the controller coil could be used to cause a more rapid and greater reduction of flow of current in the electric circuit if this were found to be advantageous.

Should the ignition unit fail for any reason it can be quickly and cheaply replaced, which is of course advantageous. The simplicity of replacement is of major importance in servicing ranges as the service man has only to disconnect the conductors 82 and B3 and the brackets 38. This the service man can easily and readily do even if he is not an electrician by trade and the average gas range service man knows little about electricity or electric circuits. Replacement which can be made by gas range service men is therefore highly advantageous.

Enigma-non or PILOT Lmar A pilot light is not essential to the present system. The pilot light is used solely for the purpose of providing an ignition system having the greatest possible degree of-safety in operation. This safety is assured by the provision of the safety valve G and when this safety valve is used some means, such as a thermal responsive element, must be used to operate the safety valve and the thermo responsive means calls for the provision of a pilot light or some other heating means.

If the pilot light were eliminated the flash tube could be placed in proper gas receiving and ignition relationship with one of the chain lighter of material importance in fabrication of ports It or even the chain lighter ports could be eliminated and the flash tube put in gas receiving and ignition relationship with one of the burner ports of the main burner.

The present invention is primarily and solely an ignition system for any gaseous fuel burner and is capable of performing its ignition operation in any kind of setup or combination. That is to say, a pilot light can be used or eliminated; when used with a gas range the range can be equipped with or without automatic oven temperature control;

the current can be turned on simultaneously with the turning on of the fuel supply or can be turned on as a separate operation; the controller coil can be heated by that particular flame which is ignited by the ignition coil or can be heated by some other separate and distinct flame. Other numerous variations will readily occur to those skilled in this art, and all would fall within the present inventive concept.

OPERATION The specificconstruction making up the present ignition system having been described in detail and the advantages and improvements thereof having been pointed out, an understanding of the operation of the system can be had from a very short and general description thereof.

Assuming that the range oven is not in operation and it is desired to cook something therein, the operation of doing so is as follows: The heat regulator is set at the temperature it is desired to obtain and maintain in the oven. This is done by setting the dial handle at the desired temperature. The manually operable fuel valve I6 is then moved to an open position whereupon gas flows through the pipe l1, the heat regulator E and pipe 18 to the safety control valve G where further travel of the gas is prevented by reason of the normally closed valve of said safety valve. Simultaneously the gas flows also to the pilot light burner D through the pipe 23 and to the pressure switch K through the pipe 3L The gas flowing to the pilot light escapes through the burner ports 29, 30 and 3| thereof while the gas which flows to the pressure switch immediately closes said switch and closes the electric circuit.

Thus simultaneously the electric circuit is closed and gas is discharged through the pilot light burner port 30 which is positioned opposite the open end 31 of the flash tube M. The closed electric circuit causes a full flow of the maximum current in the circuit which raises the ignition coil 41 to a temperature sufliciently high to ignite the gas-air mixture which flows through the flash tube by reason of the injection of gas into said tube by the passage of said gas through the pilot burner port 30. Immediately this ignition takes place there is a flash back through the tube which will cause ignition of the pilot light burner.

The full flow of current, or initial surge of current through the electric circuit and the ignition coil is quickly reduced due to the rise in temperature of the controller coil 49 by reason of this coil being composed of a material which has a very high temperature coefllcient of electrical resistance, which resistance increases rapidly with the increase in the controller coil temperature. It is of course understood that the controller coil constitutes a resistor in the circuit and as such the current passing through the coil causes a rise in temperature of the coil. The initial surge or full current flow is further promptly reduced by reason of the temperature of the controller coil being raised due to the heat from the flame burned at the pilot light burner Within a short period of time the flame burned I at the pilot light 3| heats the thermo-responslve element 33 sufficiently to cause said element to expand and open the normally closed safety valve G which upon opening permits gas to flow through the pipe l9 to the oven burner C. This gas finds its way not only to the main burner ports 6 of this burner but also to the chain lighter ports l3 thereof. The gas passing through the chain lighter ports I3 is ignited by the flame ll burned at the pilot light port 29 and in turn cause ignition at the main burner port 6 as is well undesrtood by those skilled in this art.

Throughout the further operation of the range the current continuously flows in the electric circuit but through the ignition coil at a much lower amperage than the amperage imposed upon the circuit at its source of supply. This reduction in amperage is sufilcient to reduce the temperature of the ignition coil to a point where its temperature is not sufliciently high to be injurious and is much below the ignition temperature of gas. 1

Should the pilot light fail for any reason the temperature of the control coil will quite promptly be reduced and within a short period the control coil will have cooled sufliciently to permitvsufficient current to flow in the circuit to raise the temperature of the ignition coil to the ignition temperature of the gas. Thereupon re-ignition of the pilot light burner and, of course been said under the preceding heading of Elimination of pilot light.

The operation of the system when not used in combination with an oven heat control is in no way altered, as has been pointed out under the preceding heading of Oven heat control eliminated.

The preceding description under the heading of "Controller coil will enable an understanding of the operation of the system when the controller coil is made so that it is not heated up by reason of the flow of current in the circuit.

If, as has been previously explained under the heading of Pressure switch th current is not turned into the circuit simultaneously with the turning on of the gas but is controlled separately and independently, the operation with such a modification should be clearly understood from the description already given. Such a modified construction would merely require that the operator separately turn on the gas and electricity. There would be no possibility of accident if the gas was turned on and the electricity was not turned on because in such an event although gas would flow to the pilot light no gas would flow to the main burner as the flow of any fuel to this burner is absolutely dependent upon an ignited pilot light. It is true that the small amount of gas being emitted by the pilot light would not be ignited and this of course would not be desirable and as a consequence automatic simultaneous end positioned remote to said port, an electric circuit and a source of current supply therefor, an electric ignition resistance element insaid circuit and adapted to be heated by the normal new or current in said circuit to a temperature sufliciently high to ignite gas, said resistance gas ignition element being positioned in said flash tube, a resistance controller element in said circuit with said resistance ignition element, said controller resistance element comprising an electricity resistance device and having a rapid increase of electrical resistance in response to an increase in its temperature and acting to reduce the current flow in said circuit in response to its increase in temperature, and said controller resistance element being positioned in said flash tube and subject to the heat generated by the flame burned at said burner port.

2. An electric ignition arrangement comprising a ported gaseous fuel burner to be ignited and a source of fuel supply therefor, an electric circuit and a source of current supply therefor, an electric ignition resistance element in said circuit, said source of current supply normally initially imposing on said circuit suflicient electric cur rent to heat said ignition resistance element to a temperature sufllciently high to ignite an airgas mixture, said ignition resistance element being positioned in spaced relationship to a port of said burner and in the path of travel of fuel emitted from said port, a controller element connected in said circuit with said ignition element, said controller element having the characteris-- tic of an increase electrical resistance upon an increase in temperature, means to turn on andoflthesupplyotfueltosaidbumerandthe supply of electric current to said circuit, electric current passing through said controller element after the closure of said circuit acting to cause a rise in temperature of said controller element to cause said element to reduce the current flow in said circuit, an open ended flash tube positioned to receive through one end the fuel emitted from said burner port, said ignition resistance element being positioned within said tube, and said controller element being positioned within said tube and subjected to the heat of the flame burned at said burner port.

3. An electric ignition arrangement comprising a ported gaseous fuel burner to be ignited and a source of fuel supply therefor, an electric circuit and a source of current supply therefor, an electric ignition resistance element in said circuit, said source of current supply normally imposing on said circuit sumeient electric current to heat said ignition resistance cement to a temperature sufliciently high to ignite an airgas mixture, said ignition resistance element being positioned in spaced relationship to a, port of said burner and in the path of travel of fuel emitted from said port, a controller element connected in said circuit with said ignition element, said controller element having the characteristic of an increase of electrical resistance upon an increase in temperature, means to turn on and oil! the Supp y of fuel to said burner and the supp y of electric current to said circuit, electric current through said controller element after the closure of said circuit acting to cause a rise in temperature of said controller element to cause said element to reduce-the current flow in said circuit, an open ended flash tube positioned to receive in one end the fuel emitted from said burner port, said ignition resistance element beingpositioned in ignition re- 40 lationship to the fuel within said tube, and said controller element being positioned within said tube and subjected to the heat of the flame burned at said burner port.

BRADLEY C. DOUGLAS.

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