US3150710A - Electrically ignited pilot burner - Google Patents

Description

Sept. 29, 1964 E. C. MILLER ELECTRICALLY IGNITED PILOT BURNER Filed June 27, 1961 EARLE 6. MILLER INVENTOR United States Patent 3,150,710 ELECTRICALLY IGNITED PiLOT BURNER Earle C. Miller, Worcester, Mass., assignor to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts.

Filed June 2 7, 1961, Ser. No. 127,781 8 Claims. (Cl. 158-115) This invention relates to an ignitor and more particularly to apparatus arranged to provide a continuous flame for the ignition of the burner of a furna'ce.

In the burning of fuel and particularly of pulverized coal, it is common practice to provide a small flame or pilot which burns continuously and which uses a fuel which is less likely to blow out. It is necessary to provide some means for igniting the pilot in turn and for maintaining it in a lighted condition at all times. At the present time, it is the usual practice to use an ignitable gasas the pilot fuel and to use an electric spark as the ignition means. Some of the problems presented by the provision of such a pilot are solved by the invention set forth in the patent of Thomasian et al. No. 3,007,084 issued October 31, 1961 and in the application of Miller, Serial Number 717,949 filed February 27, 1958, and now abandoned. Although these ignitors usually operate adequately, there are some conditions under which they are not entirely satisfactory. Among other things, the supporting of a high-voltage elongated electrode of the type shown in these applications presents a problem in that the supports are ceramic insulators and considerable diificulty has been experienced with the breakage of the insulators and shorting of the electrodes. Furthermore, having the electrodes at the end of the gun where they are exposed to the furnace radiation leads to some deterioration of the electrodes and subsequent shorting. These and other difficulties experienced with the prior art devices have been obivated in a novel manner by the present invention.

It is, therefore, an outstanding object of the present invention to provide an ignitor for use in a furnace burner wherein flame stability is maintained despite high air velocity. I

It is another object of this invention to provide an ignitor in which gas passing between electrical electrodes is maintained in a readily ignitable condition despite variations in air velocity passing over the outside of the ignitor.

Another object of the invention is the provision of a gas-electric ignitor in which the electrodes are supported in such a manner "that the gun may be subjected to rough usage without breakage of delicate parts.

Another object of the invention is the provision of a gas electric igntor which may be readily removed for inspection and maintenance.

It is a still further obectof the invention to provide a gas-electric ignitor having an electrode arrangement which is not subject to deterioration and shorting due to exposure to heat or due to being mounted in delicate insulating supports.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation, and the manner of its organization may be best understood by referring to the following description taken in 'connection with the accompanying drawing forming a part thereof in which: a V

The single figureis a longitudinal sectional view of an ignitor embodying the principles of the present invention.

The ignitor, indicated generally by the reference numeral 10, is shown as mounted on a wall llof a burner. The wall is formed with a circular aperture 12 in which 3,150,710 Sept. 29, 1964 is inserted an insulating plug 13 which, in turn, has a circular aperture 14. Residing in the aperture 14 is an outer tube 15 to which is fastened by welding a collar 16 which is bolted to the wall 11 on the outer surface thereof. The outer tube 15 extends well into the burner housing and has connected thereto, in the vicinity of the wall 11, a threaded fitting 17'; fastened in the fitting is a pipe 18 leading to a portion of the burner having a more or less constant air pressure. This portion would preferably be the burner ducting outside of the burner vanes, this being an area which has a continuously-high static air pressure. v

The outer tube 15 also extends "outwardly of the wall 11 a considerable "distance and its outer end is provided with diametrically-opposed ears 19 and 21 having hingedly connected thereto swinging bolts 22 and 23 provided with wing nuts 24 and 25, respectively. An annular sealing ring 26 fits snugly around an intermediate tube 27 which is slidable within the outer tube 15. The ring is provided with a longitudinal flange 28 which embraces a resilient seal or packing 29. The bolts 22 and 23 lie in slotted ears 31 and 32 extending outwardly from the ring 26 and the ring and its packing 29 are pressed tightly by wing nuts against the outer end of the outer tube 15 and inwardly against the outer surface of the intermediate tube 27. The intermeditae tube 27 has a length in the order of the length between the outer end of the inner tube 15 and the fitting 17; at its outer end the intermediate tube is provided with a fitting 33. The intermediate tube 27 is welded to the fitting 33; threaded into the fitting concentrically of the intermediate tube is an inner tube 34 which has an external diameterconsiderably smaller than the internal diameter of the intermediate tube 27, thus defining therebetween an annular space 35. Threaded into the fitting 33 concentric with and at the opposite side of the inner tube 34 is a spark plug 36 having an insulating neck 37 from which extends an elongated electrode 38.

The electrode is exactly concentric with the inner tube 34. At its outer end the spark plug 36 is fastened to a cable 39 by which it is connected to a high voltage alternating current source (not shown). The fitting 33 is provided with an inner chamber 41 into which the spark plug 36 extends and into which the inner tube 34 extends. A gas conduit 42 is threaded to the fitting at a right angle to the inner tube 34 and enters the chamber 41, the conduit being connected at the other end to a source of gas (not shown). A disc-like wall 43 extends across the inner tube 34 adjacent the fitting 33 and it is provided with a central aperture 44 through which the electrode 38 extends, the aperture being larger than the electrode to define an orifice therebetween. Closely adjacent the wall 43 and on the side thereof opposite the fitting 33 are located a series of apertures 45 through the wall of the tube. Further away from the wall are a set of three radial electrodes 46 which are fastened in the wall of the tube 34 and extend radially inwardly to Within a definite distance of the electrode 38; these are the ground electrodes, while the electrode 38 would normally be at a high voltage. V 7

At the end of the inner tube 34which lies close to the furnace it is provided with a cup 47 whichis considerably larger in diameter than the inner tube 34, but does not have an external diameter larger than the inner diameter of the outer tube 15. A perforated plate 48 extends across the cup. The inner tube is provided between the cup 47 and the outer end with a collar '49 which is capable of sliding smoothly within theouterft'ube 15 and which is provided with set screws for fastening it firmly to the inner tube 34. This collar is normally located closer to the furnace than the fitting 17, that is to say, farther away from the Wall 11. A set screw 51 extends through the outer" tube and presses against the intermediate tube 27 to lock it in place and prevent sliding therebetween. Also hingedly mounted in the ears 19 is an L-shaped rod 58 to which is welded a closure 59 which exactly fits over the outer end of the outer tube 15.

The operation of the invention will now be readily understood in view of the above description. Gas enters the ignitor through the conduit 42 passing into the chamber 41 and then out again into the tube 34. The gas passes through the aperture 44 of the wall 43 through the annular area between the edge of the aperture and the surface of the electrode 38. Air enters the ignitor through the pipe 18 and passes into the outer tube 15 and, then, into the annular space between the outside of the inner tube 34 and the inside of the intermediate tube 27. Air cannot leave in the direction of the furnace along the inside of the tube 15 because the collar 49 effectively closes that end of the tube. Air does pass outwardly to the space outside of the inner tube 34 in which the apertures are located. The air moves radially inwardly through these apertures toward the stream of gas surrounding the electrode 38. This gas moves axially while the air from the apertures 45 is moving radially inwardly. When they meet, thorough mixing takes place before they pass axially together along the electrode 38 and, eventually, between the electrode 38 and the radial electrodes 46. Now, the electrodes 46 are connected to ground voltage back through the frame of the gun ignitor; the electrode 38 is connected to the high-voltage alternating current source through the cable 39. Sparking takes place, therefore, between the electrode 38 and the electrodes 45. When the gas-air mixture passes between these electrodes and sparking takes place, the gas will be ignited. The ignited mixture passes downwardly through the inner tube 34, through the aperture plate 48 of the cup 47, and forms a flame at the end of the ignitor. The introduction of the air radially through the aperture 45 and meeting the gas at right angles promotes a thorough mixing which tends to make the ignitor flame more stable. The provision of a cup and apertured plate 48 at the outer end of the gun tends to prevent the flame from being blown out by the air in the main burner itself, since the cap 47 acts as a flame holder. When it is desired to remove the operating elements of the ignitor, this is done by loosening the set screw 51. The intermediate tube 27 and the inner tube 34 may be moved outwardly of the outer tube 15. Before they are removed, however, it is necessary to loosen the packing 29 by loosening the nuts 28. Then, the intermediate tube may be withdrawn, carrying the rest of the elements with it. In order to close the outer end of the outer tube 15 it is necessary to remove the ring 28 and the packing 29. For this purpose the bolts 22 and 23 are rotated laterally so that they and their nuts 24 and 25 are free of the ears 31 and 32, respectively. The ring is then free to be lifted away from the pipe and at that time the closure 59 may be moved into place to close the end of the pipe. In this way neither gas from the furnace nor air from the conduit 18 will flow into the boiler room.

While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the :spirit of the invention.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

1. An ignitor for furnace having a burner wall and an air box, comprising an outer tube adapted to extend through the burner wall and to be fastened thereto, an intermediate tube slidable within the outer tube and having a fitting attached to its outer end for introducing a combustible gas therein, the fitting also holding an electrode coaxially of the tubes, an inner tube held in the fitting and extending coaxially of the intermediate tube, the inner tube having an external diameter which is smaller than the internal diameter of the intermediate tube whereby a substantial space exists therebetween, means supplying the space with pressure air, electrodes extending radially inwardly of the inner tube to positions adjacent the electrode, and apertures through the inner tube adjacent the electrodes.

2. An ignitor for furnace having a burner wall and an air box, comprising an outer tube adapted to extend through the burner wall and to be fastened thereto, means for connecting the outer tube to the air box, a closure fastened to the outer tube so as to lie externally of the furnace wall and capable of closing the external end of the tube on occasion, an intermediate tube slidable within the outer tube and having a fitting attached to its outer end for inroducing a combustible gas therein, the fitting also holding an elongated electrode coaxially of the tubes, an inner tube held in the fitting and extending coaxially of the intermediate tube, the inner tube having an external diameter which is smaller than the internal diameter of the intermediate tube whereby a substantial space exists therebetween, a wall across the inner tube having a central aperture through which the elongated electrode extends, electrodes extending radially inwardly of the inner tube to positions adjacent the elongated electrode, and apertures through the inner tube adjacent the electrodes.

3. An ignitor for furnace having a burner wall and an air box comprising an outer tube adapted to extend through the burner wall and to be fastened thereto, means for connecting the outer tube to the air box, a closure fastened to the outer tube so as to lie externally of the furnace wall and capable of closing the external end of the tube on occasion, an intermediate tube slidable within the outer tube and considerably shorter than the outer tube, the intermediate tube having a fitting attached to its outer end for introducing a combustible gas therein, the fitting also holding an elongated electrode coaxially of the tubes, an inner tube held in the fitting and extending coaxially of the intermediate tube, the inner tube having an external diameter which is smaller than the internal diameter of the intermediate tube whereby a substantial space exists therebetween, a collar extending between the inner and outer tubes, electrodes extending radially inwardly of the inner tube to positions adjacent the elongated electrode, and apertures through the inner tube adjacent the electrodes.

4. An ignitor for furnace having a burner wall and an air box, comprising an outer tube adapted to extend through the burner wall and to be fastened thereto, the outer tube being adapted to have one end outside of the Wall and another end inside the wall, means for connecting the outer tube to the air box, a closure fastened to the outer tube so as to lie externally of the furnace wall and capable of closing the external end of the tube on occasion, an intermediate tube slidable within the outer tube and having a fitting attached to its outer end for introducing a combustible gas therein, the fitting also holding an elongated electrode coaxially of the tubes, a seal between the end of the outer tube which is adapted to lie outside the wall and the outer surface of the intermediate tube, an inner tube held in the fitting and extending coaxially of the intermediate tube, the inner tube having an external diameter which is smaller than the internal diameter of the intermediate tube whereby a substantial spacing exists therebetween, a cup-like flame holder on the inner end of the inner tube, electrodes extending radially inwardly of the inner tube to positions adjacent the elongated electrode, and apertures through the inner tube adjacent the electrodes.

5. An ignitor for furnace having a burner wall and an air box, comprising an outer tube adapted to extend through the burner Wall and to be fastened thereto, means for connecting the outer tube to the air box, a closure fastened to the outer tube so as to lie externally of the furnace wall and capable of closing the external end of the tube on occasion, an intermediate tube slidable within the outer tube and considerably shorter than the outer tube, the intermediate tube having a fitting attached to its outer end for introducing a combustible gas therein, the fitting also holding an elongated electrode coaxially of the tubes, an inner tube held in the fitting and extending coaxially of the intermediate tube, the inner tube having an external diameter which is smaller than the internal diameter of the intermediate tube whereby a substantial space exists therebetween, a collar extending between the inner and outer tubes, a wall across the inner tube having a central aperture through which the elongated electrode extends, electrodes extending radially inwardly of the inner tube to positions adjacent the elongated electrode, and apertures through the inner tube adjacent the electrodes.

6. An ignitor for furnace having a burner wall and an air box, comprising an outer tube adapted to extend through the burner wall and to be fastened thereto, the outer tube being adapted to have one end outside of the wall and another end inside of the wall, means for connecting the outer tube to the air box, a closure fastened to the outer tube so as to lie externally of the furnace wall and capable of closing the external end of the tube on occasion, an intermediate tube slidable within the outer tube and considerably shorter than the outer tube, the intermediate tube having a fitting attached to its outer end for introducing a combustible gas therein, the fitting also holding an elongated electrode coaxially of the tubes, a seal between the end of the outer tube which is adapted to lie outside the wall and the outer surface of the intermediate tube, an inner tube held in the fitting and extending coaxially of the intermediate tube, the inner tube having an external diameter which is smaller than the internal diameter of the intermediate tube whereby a substantial space exists therebetween, a collar extending between the inner and outer tube, a cup-like flame holder on the inner end of the inner tube, electrodes extending radially inwardly of the inner tube to positions adjacent the elongated electrode, and apertures through the inner tube adjacent the electrodes.

7. An ignitor for furnace having a burner wall and an air box, comprising an outer tube adapted to extend through the burner wall and to be fastened thereto, the outer tube having adapted to have one end outside of the wall and another end inside the wall, means for connecting the outer tube to the air box, a closure fastened to the outer tube so as to lie externally of the furnace wall and capable of closing the external end of the tube on occasion, an intermediate tube slidable within the outer tube and having a fitting attached to its outer end for introducing a combustible gas therein, the fitting also holding an elongated electrode coaxially of the tubes, a seal between the end of the outer tube which is adapted to lie outside the wall and the outer surface of the intermediate tube, an inner tube held in the fitting and extending coaxially of the intermediate tube, the inner tube having an external diameter which is smaller than the internal diameter of the intermediate tube whereby a substantial space exists therebetween, a wall across the inner tube having a central aperture through which the elongated electrode extends, a cuplike flame holder on the inner end of the inner tube, electrodes extending radially inwardly of the inner tube to positions adjacent the elongated electrode, and apertures through the inner tube adjacent the electrodes and on the inner side of the wall.

8. An ignitor for furnace having a burner Wall and an air box, comprising an outer tube adapted to extend through the burner wall and to be fastened thereto, the outer tube being adapted to have one end outside of the wall and the other end inside the wall, means for connecting the outer tube to the air box, a closure fastened to the outer tube so as to lie externally of the furnace wall and capable of closing the external end of the tube on occasion, an intermediate tube slidable within the outer tube and considerably shorter than the outer tube, the intermediate tube having a fitting attached to its outer end for introducing a combustible gas therein, the fitting also holding an elongated electrode coaxially of the tubes, a seal between the end of the outer tube which is adapted to lie outside the wall and the outer surface of the intermediate tube, an inner tube held in the fitting and extending coaxially of the intermediate tube, the inner tube having an external diameter which is smaller than the internal diameter of the intermediate tube whereby a substantial space exists therebetween, a collar extending between the inner and outer tubes, a wall across the inner tube having a central aperture through which the elongated electrode extends, a cuplike flame holder on the inner end of the inner tube, electrodes extending radially inwardly of the inner tube to positions adjacent the elongated electrode, and apertures through the inner tube adjacent the electrodes and on the inner side of the wall.

References Cited in the file of this patent UNITED STATES PATENTS 2,241,295 Clark May 6, 1941 2,880,792 Raskin Apr. 7, 1959 FOREIGN PATENTS 499,657 Germany June 14, 1930

Claims (1)

1. AN IGNITOR FOR FURNACE HAVING A BURNER WALL AND AN AIR BOX, COMPRISING AN OUTER TUBE ADAPTED TO EXTEND THROUGH THE BURNER WALL AND TO BE FASTENED THERETO, AN INTERMEDIATE TUBE SLIDABLE WITHIN THE OUTER TUBE AND HAVING A FITTING ATTACHED TO ITS OUTER END FOR INTRODUCING A COMBUSTIBLE GAS THEREIN, THE FITTING ALSO HOLDING AN ELECTRODE COAXIALLY OF THE TUBES, AN INNER TUBE HELD IN THE FITTING AND EXTENDING COAXIALLY OF THE INTERMEDIATE TUBE, THE INNER TUBE HAVING AN EXTERNAL DIAMETER WHICH IS SMALLER THAN THE INTERNAL DIAMETER OF THE INTERMEDIATE TUBE WHEREBY A SUBSTANTIAL SPACE EXISTS THEREBETWEEN, MEANS SUPPLYING THE SPACE WITH PRESSURE AIR, ELECTRODES EXTENDING RADIALLY INWARDLY OF THE INNER TUBE TO POSITIONS ADJACENT THE ELECTRODE, AND APERTURES THROUGH THE INNER TUBE ADJACENT THE ELECTRODES.

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