US2441965A - Method of and apparatus for igniting fuel - Google Patents

Description

May 25, 1948. w, H 2,441,965

METHOD OF AND APPARATUS FOR IGNITING FUEL' Filed March 29, 1946 2 Sheets-Sheet 1 3 vweufoz Mil/am D. Hall 1 I f #4 M 3m f May 25, 1948. w. D. HALL 2,441,955

METHOD OF AND APIARATUS FOR IGNITING FUEL Filed March 29, 1946 2 Sheets-Sheet 2 Wf/l/am D. Ha

Patented May 25. 1948 METHOD OF AND APPARATUS FOR IGNITING FUEL William D. Hall, Elkins, W. Va.

Application March 29, 1946, Serial No. 658,195

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) 13 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to methods of and apparatus for igniting and burning combustible fuel and has several objects and advantages. The primary object is to provide starting methods and means which increases the probability of ignition and reduces the likelihood of explosions. Another object is to provide a switch which quickly cuts off the electrical igniter when combustion is established. Still other objects and advantages of my invention will appear as this description proceeds.

When the fuel valve of an electrically ignited burner is opened, the initial on rush of incombustible gases may so cool the igniter that combustion will not be effected. According to the invention now to he described, the supply of fuel is purposely decreased to a low steady quantity and then again increased to normal should it fail to ignite on the first efiort at ignition. When is done, the cooling effect on the igniter ceases for a short while and as the fuel again increases it will ordinarily ignite immediately. further advantage of this method is that should ignition he attempted when the main control valve is wide open and admitting a very large ly inside of the same prior to establishment of combustion and is already heated to some degree before the fliame heats it. This will be discussed in detail later.

I have illustrated the various parts of my invention rather diagrammatically in the accompanying drawings since my invention relates to methods and. systems generally rather than to specific details of design of a particular system. Figure 1 illustrates fuel burning apparatus on which my invention may be performed manually. Figure 2 illustrates schematically certain apparatus that will automatically operate in accordance with the principles of my invention.

Figure 3 illustrates schematically another form of the invention. Figures 1 and 2 of this application and the description applicable thereto are identical with corresponding figures and description in my now abandoned prior copending application S. N. 379,586, filed February'l 1941, entitled the same as the present case and of which the present case is a continuation-in-part.

In Figure 1 a source of electricity which may be a. six volt storage battery supplies power to wires it and ii. A. switch it is used to close the circuit and initiate operation of the system. A bimetallic strip is is supported in the vicinity of the burner is by the bracket i i. Strip it carries a contact point it which normally engages conquantity of gas, the supply of such'gas is reduced so tact po that is, it engages p t it when during the ignition period. A still further advantage of this idea resides in the fact that in event ignition actually takes place the instant prior to reduction in the quantit of fuel that the flame will not be extinguished but will con- 35 tinue to burn.

it is common in the art to deenergize an electrical igniter with a series connected thermo static switch. Such a switch does not instantly deenergize the igniter when combustion is esen tablished. During the interval when both the flame and the current are heating the igniter the latter deteriorates. For this reason it is desirable to reduce the time lag of response of the thermostatic switch as much as possible in order that at the burner is cool. When the strip it is heated, it moves contact point it to the right and breaks contact between that point and its complementary contact point it. Contact point it is carried by a stationary support ii and connects electrically to one end of the electrical resistance igniter coil iii, which coil may be directly above the burner iii and in thepath of the oncoming fuel. While the igniter coil is is shown in direct operative relation with the burner it I wish to state that such coil may be operatively associated with the burner in any of the well known indirect methods lrnown to the art. The gas issuing from the burner is is ignited by the coil iii, and such gas is fed to the burner through the fuel feed line it. A valve it is located in pipe ill but this valve is so constructed that it never completely closes the fuel feed line. Even when the valve ii is fully seated, a space 22 is open which permits some fuel to flow to the burner. A handle "it is controlled manually and it in turn controls the valve 2|. The valve 2! has enough friction in its operation that it will remain fully open or fully seated as the case may be when it rapidly because it receives heat generated direct- 56 is left in either of these positions. A main control valve V may be used to completely shut down the system or to regulate the quantity of fuel fed thereto. v

To carry out the invention manually with the system of Figure 1, the switch I2 is first closed. When this is done, the igniter coil I8 is immediately energized and at the same time current flows through the bimetallic strip l3 heating it. Valves V and 2| are then completely opened in turn to the desired degree If valve 2| is already completely open as would ordinarily be the case, only valve V need be opened. When these valves are opened the supply of fuel may increase either gradually or very rapidly depending on how fast they are opened. In either event the fuel may fail to ignite in which event the valve 2| should be fully seated for a few seconds or so and then again fully opened. It is Very probable that should the fuel fail to ignite on the first effort due to improper combustion conditions that it will ignite this second time. If the fuel ignited at precisely the instant that the supply of fuel was decreased, the flame will not extinguish because valve 2| does not fullv close. As has been stated there is an opening 22 below the valve 2| which permits some fuel to flow to the burner even when the valve is fully seated. Should the fuel fail to be ignited on the first or the second efforts. the valve handle 23 may be repeatedly operated up and down until the fuel does ignite. It may be operated up and down either fast or slow depending on which manner is found most effective under particular circumstances. During ll this time, the igniter coil l8 remains continuously energized.

As soon as the fuel ignites, the strip i3 is heated and tends to open the circuit at contacts 95 and IS. The prior art shows the same electrical circuit as I have shown in Figure 1, however, I contemplate a bimetallic strip |3 of such size and resistivity that it will be appreciably heated by the flow of current therethrough to the igniter. Therefore, prior to the time the thermostatic switch I3, l5 breaks the igniter circuit the bimetallic strip I3 is heated by the current and due to this heating breaks the circuit in less time than it otherwise would. This feature also permits the design to operate the switch I3 at a higher temperature without increasing the response time above that now used; hence the switch ill recloses the circuit quickly when the flame becomes extinguished. By generating the ore-heating directly inside of the bimetallic strip it the effect of the heating is much more rapid than it is when such pie-heating is accomplished by a series resistor near the strip. The degree to which bimetallic strip i3 is heated by the igniter current therethrough may be (a) sufiicient to actually break the circuit at contacts i5, i6 even if the fuel completely fails to ignite at any time, or (b) it maybe insufficient to actually break the circuit at |5, |6 until additional heat is supplied by the flame. Preferably the heating is sufficient to bring the temperature of the strip I 3 almost up to the point at which it breaks the circuit at contacts i5, i6. In this case only a slight additional heating is necessary from the flame. to break the circuit and deenergize the igniter and of course this small amount of heat will be supplied almost instantly after the fuel is ignited. Of course, my claims are not to be limited to this high degree of perfection but broadly cover the case where appreciable heat is generated inside strip l3.

The apparatus of Figure 2 will automatically accomplish the functions performed manually on the device of Figure 1. The various parts of Figure 2 that bear'reference numbers common to Figure 1 are identical in construction and operation to similar parts of Figure 1.

In Figure 2, the valve 2| is operated by a cam follower 26. The follower or roller 26 is held in contact with the cam 29 by a spring 24. The spring 24 is based upon pipe 20 and presses upward on arm 25 which arm is rigidly fastened-to the valve 2|. The cam 29 is pivoted off center at 28 and is driven by a motor 32. Contact points 3|] and 3| are separated when the valve 2| is open and the contacts are together when the valve 2| is fully seated. The parts are shown in the nor mal off position just prior to turnin it to the on position. To start the apparatus, the switch |2 is thrown "on thus establishing an igniter circuit as follows: I0|2-|4-|3-|5|6|l |8--| The igniter |8 begins to become hot and strip I3 is preheated due to the large igniter current flowing therethrough. The motor 32 is also energized by the following path: ||l|2--|3 |5|6-|'|-3332-| Resistor 33 is not large enough to prevent energization of the motor by this circuit. If the fuel ignites immediately, the switch 3 will break the igniter circuit as well as the motor circuit quickly, thereby leaving valve 2| fully open. If on the other hand the fuel should fail to ignite on the first effort, motor 32 will begin to rotate the cam 25 slowly (as the motor is provided with suitable mechanism whereby it rotates the cam only very slowly). It requires say twenty seconds or so to revolve the cam 29 a half revolution. When the valve 2| approaches a seated position, contacts Bil and 3| engage each other and thereby energize the motor as follows: |ll--|2--i |--|3fiexible lead 2'l 253il3|-- |9'32-l l. The motor is now energized independently of switch I5, l5 and will remain running until the valve 2| is unseated. If by that time the fuel has ignited and has broken the circuit at contacts I5, I6 the motor will stop in a valve-open position upon the breaking of contacts 3i! and Eli. It is noted that the motor can never stop in a valve-closed position. If the fuel fails to ignite, the cam 29 will continue to rotate thereby intermittently opening and seating the valve 211 and will therefore repeatedly decrease and increase the ilow of gas striking the igniter coil it which of course remains energized continuously. if switch it? opens while the valve is seated, the igniter it will. drop in temperature slightly below incandescence due to resistor but will still be heated by the circuit i@-i2 li32f|253i|3 |'ti3l8-l l, until finally the valve 2| is fully unseated at which time the igniter is completely deenergized due to the separation of contacts 30 and 3|.

If the self-heating of switch I3 is designed to be sufficient to actually break the circuit by reason of the heavy igniter current therethrough even in event the flame never is established; then the igniter IE will be intermittently increased and decreased in energization. Similarly the valve 2| will repeatedly open and reseat itself,

If the flame ignites, continues to burn for a while, then becomes extinguished, switch l5, l6 will close and cause the motor 32 to rotate cam 29 just as in the case of an initial ignition attempt. This will automatically attempt to make several new attempts to again establish combustion.

In Figure 3, a hot wire igniter I8 is connected to the center, tap 50 of the secondary of current transformer 5|. The ends 52 and 53 of the secondary winding connect to the U-shaped bimetallic member 54 which normally maintains contact with contact point 55 but bends upward and away from 55 when member 54 is heated. Contact 55 is in series with primary winding hi and with source 51, 58. The motor 32 across the igniter operates the cam 29, cam follower 26, and valve 2! as is more completely shown in detail in Figure 2.

Eu Figure 3, when the starting switch is closed, current flows as follows: 58--l9-5ll-52E3-- li l-llilfib-lil--tl. Flow of current through primary winding til causes a heavy current to ilow in the secondary which current circulates through the iJ-shaped member ti l. This heating causes member b l to be thoroughly heated and to greatly aid the heat of combustion in heating member 53 so as to break the circuit at After contact at is broken the member so is heated by the flame only. The principles of operation of Figure 3 can tently' increases and decreases the quantity of fuel fed through said feed line; a thermal switch comprising a bimetallic strip and. contacts associated with, and separated by, the strip when the strip is heated, and closed by the strip when the strip is cooled; one of said contacts being electrically connected to one end of said strip; a wire ciao-- trically connecting the other of said contacts to one of said terminals and also to one side oi said hot-wire igniter; a wire adapted for connection to a source of electrical supply and connecting the remaining terminal as well as the remaining end of said hct wire igniter to one side of such source; another wire also adapted ior connection to a source of electrical supply for connecting the remaining end of said bimetallic strip in such a n manner that current from said source flows directly throughout the length of said bimetallic strip before reaching said contacts; and means supporting said bimetallic strip to position the same responsive to the heat of combustion; said strip comprising materials of such size and resistivity that the flow of current directly therethrough to said igniter will generate appreciable heat directly inside the strip and raise the ternperature of the strip close to the actual temperature required by the strip in order to separate said contacts, whereby the strip will operate to quickly separate the contacts in response to combustion of fuel at said fuel burner.

2. in a fuel burning system, a burner, a hotwire ignite!" therefor, a thermal switch comprising a thermal element, said thermal switch being connected directly in series with said igniter and such that the current to the igniter flows directly through said thermal element, means supporting said thermal element responsive to combustion at said burner, and means operable to feed fuel to said burner; said thermal element and said igniter being composed of materials of such size and resistivity that when energized the heating generated directly inside of said thermal element by the igniter current fed therethrough will appreciably raise the temperature of said element.

3. The system of claim 2 wherein the resistivity of said element is so high that the heat generated directly in the thermal element is so great as to cause the switch to deenergize the igniter even in absence 0! heat of combustion.

4. The system or claim 2 in which the resistivity of the thermal element is sufilciently low that the heating thereof due to the current flowing therethrough will raise the temperature thereof above ambient to a lower value than is required to break the igniter circuit.

5. In a heating system, a space wherein fuel is burned, electrical energized ignition means adapted to ignite the fuel when such means is energized, a circuit ior energizing said ignition means and including a control means in series with the circuit, said control means including a thermal element for operating the same to break the circuit when said element is heated and to close the circuit when said element is cooled, said control means comprising means for effecting flow of sufiiicent current directly through said element when and only when the igniter is energized to appreciably heat said element and provide at least ten percent of the amount of heating that is required to be supplied to said element in order for the circuit to be broken by said element, whereby to reduce the time lag of response thereoi to combustion, and supporting means positioning the thermal element responsive to the heat oi" combustion.

6. The method of utilizing an igniter oi the hot-member type to establish combustion of fuel at a burner which includes heating the igniter, establishing a flow of fuel operatively near the ignlter. and maintaining the igniter continuously energized while the supply of fuel is decreased to a low but substantial value at which it will sustain combustion ii a flame was established on the first effort and subsequently increased.

'7. The method of utilizing an igniter of the hot-member type to establish combustio at a burner which includes varying the fuel flow rate across the igniter between a high rate and a low substantial rate while maintaining the igniter continuously energized.

8. "in a heating system, a burner, a hot-mern ber type igniter therefor, iuel feeding means, means for energizing the igniter and maintaining the same continuously energized until combustion is established, and means for making more than one effort to effect combustion of the fuel at the burner, the last-named means comprising means for initially increasing the flow or fuel so as to make a first effort and in event that effort fails to reduce such flow to a lower but appreciable quantity and subsequently again increase such flow.

9. The method of utilizing an igniter oi the hot-member tyne to establish combustion of fuel at a burner which includes heating the ignlter, establishin a flow of fuel operatively near the igniter so as to cool the igniter if ignition is not effected, reducing the quantity of fuel fed near the igniter so that the igniter can rise in temperature yet maintaining at all times suificient flow of fuel that if combustion is established that it will sustain itself, and subsequently again increasing the flow of fuel.

10. In a heating system; a burner, a hot wire igniter that consumes a large current when operating; said igniter being positioned near the burner so as to ignite fuel thereat; a thermal element composed of a high resistivity bimetallic strip; a stationary supporting current connection at one end of said. bimetallic strip; a contact point carried by the other end of said bimetallic strip; a stationary current connection having a complementary contact point for the first-named contact point; wires energized by a low voltage large current supply for forcing the large current through said strip and igniter; said wires forming a series circuit from the source to and through the igniter, to one of said stationary current connections, through said strip to the other stationary current connection, and back to the source; said bimetallic strip being positioned in the region of heat from the burner and operable upon establishment of combustion to rise in temperature and move said contacts to a separated position to thereby break the igniter circuit and deenergize the hot wire igniter in a predetermined time interval after combustion is established, and said bimetallic strip comprising means whereby the large igniter current/flowing therethrough generates sufllcient heat directly inside of said bimetallic strip as to materially and substantially reduce the time required to break the ignlter circuit below the time that would be required in event there was no heat generated in the bimetallic strip by the igniter current; and switching means operable to control the igniter circuit to close the same, activate the igniter. and effectuate the said heating in said bimetallic strip.

11. The heating system defined by claim in which the igniter is a hot-wire type igniter, and in which the thermal element consists of high resistivity material.

12. The device defined by claim 5 in which said control means comprises a current transformer havingits primary in series with said circuit and its secondary connected across at least a portion of said element so as to pass a heavy current through the latter.

13. In a burner control system, a hot-wire igniter, a circuit energizing the igniter, a transformer having a primary winding in series with said circuit, said transformer having a secondary winding, and thermostatic means comprising a bimetallic strip a portion of which is shunted across said secondary winding and thereby is heated by current from said secondary winding.

means supporting said thermostatic means near the flame so as to be heated thereby, and a switch in series with said circuit and operated by said thermostatic means to break said circuit when said thermostatic means is hot and to close said circuit when said thermostatic means is 0001; said bimetallic strip and said igniter circuit being of such impedances that when energized the heating in said bimetallic strip by the current passing therethrough will appreciably raise the temperature of said bimetallic strip and thereby cause the igniter to be deenergized more promptly than it would have been deenergized had the bimetallic strip been heated solely by heat from the flame.

WILLIAM D. HALL.

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

UNITED STATES PATENTS Number Name Date Re.19,235 Phelan July 10, 1934 1,575,170 Knopp Mar. 2, 1926 1,735,834 Mayo Nov. 12, 1929 2,149,853 McCabe Mar. 7, 1939 2,268,229 Walle Dec. 30, 1941

Images