US2643709A

US2643709A - Electrically ignited gas pilot

Info

Publication number: US2643709A
Application number: US157356A
Authority: US
Inventors: Frank J Haverland
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-04-21
Filing date: 1950-04-21
Publication date: 1953-06-30
Anticipated expiration: 1970-06-30

Description

J1me 1953 F. .1. HAVERLAND 2,643,709

ELECTRICALLY IGNITED GAS PILOT Filed April 21, 1,950

IN V EN TOR. .[Frmwr (1 H0 van, fl/YO WIMW *Wm flTTORIYEYS Patented June 30, 1953 UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to igniters, and more particularly to an igniter device for starting the flame of an oil, gas or powdered fuel burner.

A main object of the invention is to provide a novel and improved igniting device for starting the flame of an oil, gas or powdered fuel burner in the combustion chamber of a furnace or the like, said device being relatively simple in construction, being easy to install, and being arranged so that it will not produce feed-back action on the electronic flame-sensing device conventionally employed to control the operation of the furnace.

A further object of the invention is to provide an improved igniting device for starting the flame of an oil, gas or powdered fuel burner, said device being of the type employing a high voltage spark gap, but the device being provided with means for shielding the spark gap so that said gap is not located in the proximity of the main fuel jet Within the combustion chamber of the furnace with which the igniter is being used.

A still further object of the invention is to pro vide an improved igniter for starting the flame of an oil, gas or powdered fuel burner, the igniter being very rugged in construction, inexpensive to manufacture, easy to adjust for desired operation, providing a substantially reduced risk of explosion, and providing a means of observing whether a spark is being developed in the spark ignition space of the device, and for observing the nature of the action occurring in said spark ignition space.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure 1 is a top plan view of an improved burner igniter constructed in accordance with the present invention;

Figure 2 is a longitudinal cross-sectional view taken on the line 2-2 of Figure 1;

Figure 3 is a horizontal cross-sectional detail view taken on the line 3-3 of Figure 2;

Figure 4 is a bottom plan view of the left-hand end portion of the burner igniter of Figure l.

The device of the present invention is intended for the purpose of starting the flame of an oil, gas or powdered fuel burner by a spark gap, and to accomplish this Without the necessity of locating the spark gap near the main fuel jet within the combustion chamber of a furnace being fired. Practically all igniters in present usage develop the spark in the main combustion chamber, and difficulties are experienced by the effects of high temperatures on the materials of the sparking device, or by the short circuiting of the electrodes of the sparking device by carbon particles from the combustion of the fuel in the furnace. Furthermore, electronic flame sensing devices employing a metal rod element in the path of the fuel ignition flame or pilot are employed in present equipment, and experience shows that much difficulty is caused by the presence of the electric spark near the flame sensing rod, due to the electrical discharge which often occurs from the high voltage electrodes through the flame, said discharge affecting the operation of the flame sensing rod, and producing undesired stoppage of the burner. The igniter of the present invention is arranged so as to be absolutely free from electronic troubles, and is further arranged so that it may employ a conventional automobile spark plug instead of specially designed sparking devices such as those heretofore employed, whereby the device of the present invention is -inherently more rugged and is less costly to manufacture and to maintain than the prior devices.

Referring to the drawings, the device comprises a main or hollow body II open at one end and closed at the other end. A partition I0 extends transversely of and is spaced from the closed end of the body I I and forms with the closed end and adjacent portion of the body II a mixing space I8. A first tube I2 shaped to conformably fit the open endof the body I I has one end extending into the open end of the body and abutting the partition IB and secured to the body II by means of the set screw 9. A second tube I3 is disposed coaxially of and within and spaced from the first tube I2, the tube I3 extending through the partition I0 and the mixing space'l8 and having one end threaded into the closed end of the body II and having the other end [4 terminating at a point contiguous to and spaced from the other end of the tube I2. Connected to the body II is a fuel supply conduit I5, the body II adjacent the closed end being provided with a fuel admission passage I6 having one end connected to the fuel supply conduit I5 and having the other end in communication with the one end of the tube I3. Threaded into the body II opposite the passage I6 is an adjusting screw IT arranged to control the size of the passage, whereby the rate of admission of the fuel into the tube I3 may be conveniently regulated.

The partition II] intermediate the first tube I2 and the second tube I3 is provided with a passage extending longitudinally therethrough, such passage forming an ignition space I9. The ignition space is in communication with. the mixing space l8 and the space between the tubes 42 and it. The wall of the body ll intermediate the closed end and the partition it has an air port or vent 20 which is in communication with the mixing space It. The rate of entry of air through the port or vent 20 is controlled by a screw 2! threaded through the rear wall of the body I l and overlying the vent 20. From Figure 2, it will be apparent that the rate of entry of air into the space l8 may be readily controlled by adjusting the screw 2|.

The rear portion of the inner tube I3 is formed with apertures 22 opening into space l8, as shown in Figure 3, allowing a limited amount of fuel to enter space it from tube 13. A needle valve 22' isthreaded through the wall of body II and enters one of the apertures 22 to provide a range of control of the amount of fuel entering space l8. Threaded into the wall of body I I over space I9 is a conventional spark plug 23 having its electrodes located in space it, as shown in Figure 2. The rear wall of the body I! i is provided with a transparent window 24 of mica or other suitable fiame-resistant material, affording observation of the space it and of the space IS.

The inner tube I3 is formed forwardly of the spark plug 23 with a plurality of longitudinally spaced apertures, the apertures being arranged in a spiral path and consisting of a plurality of circular apertures 25, slots 25, circular apertures 25, and slots 25" in the sequence named, as shown, or may merely extend in a straight line along the length of the tube ill. The outer tube I2 is formed with air-admission openings 26 forwardly of the open end of tube 13, as shown in Figure 2, for a purpose to be presently described.

The operation of the igniter is as follows:

It will be understood that the igniter is mounted in a combustion chamber which is attached in the usual manner to a stack or chimney by which a draft or slight vacuum is produced in the combustion chamber. The igniter of the present invention is secured in the wall of the chamber and has its open end, namely, the open end of outer tube 12, subjected to said vacuum, whereby atmospheric air is drawn into the space I8 through the vent 20. When the burner is to be operated, fuel is admitted into the conduit 15 and into the passage It, a suitable high voltage i.

being simultaneously applied to the spark plug 23, whereby a spark is produced across the electrodes of the spark plug. The gas-control screw I1 is open, allowing gas to enter the tube [3 and to flow toward the open forward end l4 thereof. As the gas pressure builds up in the tube l3, gas issues from the openings 22 and mixes with the air passing through the space 88. The mixture of gas and air then flows into the ignition space I9, where ignition takes place, and the exploding mixture causes a tongue of flame to move rapidly toward the forward end of tube 12 in the space between the tubes I2 and It. At the same time, small amounts of gas have been issuing from the small openings 25 in tube It and mixing with the air from the leaner mixture produced in the space l9 by adjustment of the ratio-control screws I! and 2!. The progressively richer mixture provided in the tube l2 assists the flame moving forwardly to the end of tube l2 where raw gas from the end of tube I4 is issuing into the furnace combustion chamber. The main flame of the burner is ignited immediately forward of the open end 14 of the tube l3 by the aforementioned flame tongue, and after the main ignition occurs, the main burner of the furnace is set into operation and furnishes fuel and air mixture into the furnace combustion chamber.

It is to be noted that during the operation of the igniter, three distinct air-to-gas ratio mixtures are produced and employed, as follows: The first mixture is a lean gas, rich air mixture produced by the relatively small amount of gas issuing from the openings 22 under the gas pressure built up in tube 13 and the relatively large amount of air in the space l8. Some of this very lean mixture flows into the space between tube l3 and the inside surface of tube l2. As this mixture gradually becomes enriched, a point is reached where the mixture is highly combustible and ignites by the action of the spark plug 23. This is the beginning of the ignition cycle.

Since gas also is issuing from the various openings 25 along the length of tube l3 and mixes with the lean mixture, air flushed forwardly, as above mentioned, the mixture in tube 12 is of richer gas content and burns more slowly than the first-described mixture. This richer mixture is ignited by the sudden explosion of the first mixture, and the tongue of flame from the ignition chamber 19 is propagated forwardly by the richer mixture provided along the length of tube it in the space between tube l3 and the inside surface of tube 12. Meanwhile, raw gas is issuing from the open end M of tube l3 and is being mixed with air from the furnace combustion chamber which enters the forward end of tube l2 through the openings 26. This third mixture is ignited by the flame propagated to it in the space between tubes [3 and I2, and the third mixture continues to burn as long as gas is fed into the fuel-admission conduit [5.

As long as fuel is fed to the conduit l5 and a spark is maintained at spark plug 23, a highly explosive flame is maintained in the spaces l8 and ill, a richer and more sluggish and slowburning flame is provided in the space between tubes l3 and [2 from a point forwardly adjacent the electrodes of the spark gap to the end of tube l3, and a large hot flame is provided from the forward end of tube l2 outwardly into the combustion chamber of the furnace which ignites the main fuel burner of the furnace. It will be apparent that if the large flame issuing from the forward end of tube 12 is extinguished for any reason, as by a heavy blast of burner air, the flame of the igniter cannot be completely extinguished because of the slower, richer flame continually burning within the throat of the tube 2 which continuously relights the fuel mixture in the forward end of tube [2 and maintains it burning even though the spark at spark plug 23 is discontinued.

In conventional installations, a flame-sensing device is employed comprising a rod element positioned so that the end of same is enveloped by or touches the flame produced by the igniter. In almost all conventional igniter-s or pilot devices using a spark gap within the combustion chamber of the furnace, the gas flame is occasionally ionized to the extent that the electronic charge on the electronic flame rod is either neutralized or increased to an extent such that it unbalances the electronic control system of the furnace and causes a burner shut-down or even an explosion. The ignited of the present invention is substantially free from this type of hazard, inasmuch as the spark gap is located a relatively large distance from the sensing rod, and all gas flame within the tube 12 is in contact with the inside surface of the tube l2 and the outer surface of the tube l3, thus grounding any feed-back which might be caused by ionization of the flame. Inasmuch as the main flame of the igniter is a continuation of a flame produced within the space between tubes 13 and 52, the possible feed-back path between the electronic centering device and the electrodes of the spark plug 23 cannot fail to be well grounded.

A further important feature of the present invention is that the operator of the furnace can observe through the window 24 whether a spark is being produced or whether ignition of the gas mixture in the space I9 is being obtained before the main fuel burner of the furnace begins to blow fuel into the furnace. Proper adjustment of the ratio screws I? and 2! can also be accomplished while observing the ignition flame through the window 24. Observation of the isniter flame may also be made after the spark has been terminated while making adjustments of the screws i! and iii. The visibility of the flame for adjustment during the operation of the igniter can be a very important factor in the prevention of explosions. In present types of igniters using a spark gap in a gas stream, a too rich gas mixture will cause a thread of carbon to form by electrostatic action between the electrodes of the sparking device, and thereby cause a short circuit, whereby no spark will occur. This is a very dangerous situation and may result in an explosion. The present igniter provides a meansof observing the conditions in the spark ignition space, whereby the gas and air mixture in said space can be adjusted so as not to produce the above-mentioned carbon deposit.

While a specific embodiment of an ignition device for oil, gas or powdered fuel burners has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

1. An igniter for fuel burners comprising a hollow body open at one end and closed at the other end, a partition extending transversely of and spaced from the closed end of said body and forming with the closed end and adjacent portion of said body a mixing space, said body having an air port intermediate its closed end and said partition and in communication with said mixing space, a first tube shaped to comformably fit the open end of said body having one end extending into the open end of said body and abutting said partition and secured to said body, a second tube disposed coaxially of and within and spaced from said first tube, said second tube extending through said partition and said mixing space and having one end secured to the closed end of said body, the other end of said second tube terminating at a point positioned within and spaced from the other end of said first tube, said body adjacent the closed end thereof being provided with a fuel admission passage having one end adapted to be connectedto a fuel supply line and having the other end in communication with said one end of said second tube, there being a passage extending longitudinally through said partition intermediate said first and second tubes and forming an ignition space, said ignition space being in communication with said mixing space and the space between said first and second tubes, and spark means within said ignition space and supported in said body, said second tube in the portion within said mixing space being provided with a plurality of apertures for the discharge of fuel from said second tube into said mixing space andin the portion intermediate its other end and said partition being provided with a plurality of longitudinally spaced apertures.

2. An igniter for fuel burners comprising a hollow body open at one end and closed at the other end, a partition extending transversely of and spaced from the closed end of said body and forming with the closed end and adjacent portion of said body a mixing space, said body having an air port intermediate its closed end and said partition and in communication with said mixing space, a first tube shaped to conformably fit the open end of said body having one end extending into the open end of said body and abutting said partition and secured to said body, a second tube disposed coaxially of and within and spaced from said first tube, said second tube extending through said partition and said mixing space and having one end secured to the closed end of said body, the other end of said second tube terminating at a point positioned within and spaced from the other end of said first tube, said body adjacent the closed end thereof being provided with a a fuel admission passage having one end adapted to be connected to a fuel supply line and having the other end in communication with said one end of said second tube, there being a passage extending longitudinally through said partition intermediate said first and second tubes and forming an ignition space, said ignition space being in communication with said mixing space and the space between said first and second tubes, and spark means within said ignition space and supported in said body, said second tube in the portion within said mixing space being provided with a plurality of apertures for the discharge of fuel from said second tube into said mixing space and in the portion intermediate its other end and said partition being provided with a plurality of longitudinally spaced apertures, said first tube in the portion intermediate the other end thereof and the other terminating end of said second tube being provided with a plurality of longitudinally spaced openings for the admission of air into the interior of said first tube.

3. The igniter according to claim 2 including in addition means regulating the flow through said fuel admission passage, and means regulating the flow through said air port.

FRANK J. HAVERLAND.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 840,586 Rech Jan. 8, 1907 1,675,133 Rayfield June 26, 1928 1,739,161 McKee Dec. 10, 1929 2,332,210 Frank Oct. 19, 1943 2,439,609 Mittendorf Apr. 13, 1948