US3319130A - Electrical ignitors - Google Patents

Description

May 9, 1967 c. a. BE TTERID GE ELECTRICAL IGHITORS Filed July 22, 1964 3 Sheds-Sheet l Cecil j A tlqrneyS y 1967 c. e. BETTERIDGE I 3,319,130

ELECTRICAL IGNITORS' F iled July 22. 1964 I s Sheets-Sheet 2 BURNER CONTROL M4//V /G/v/7oR TRANSFORMER Cr IIZT 7o RELAY SW/TCH/NG I SOLE/v00 J: OPE/PA r50 FUEL l44Ll/E Inventor MQMW 3 A ttorneys y 967 c. a. BETTERIDGE 3,319,130

ELECTRICAL IGNITORS Filed July 22, 1964 r 5 Sheets-Sheet 3 Inventor A Horn 2315 United States latentOfiice 3,319,130 Patented May 9, 1967 3,319,130 ELECTRICAL IGNITORS Cecil George Betteridge, Woodley, near Reading England,

assignor, by mesne assignments, to Fuel Ignition 1mited, Reading, England, a company of Great Britain Filed July 22, 1964, Ser. No. 384,487 6 Claims. (Cl. 317-87) This invention relates to electrical ignitors for lightingup liquid, gaseous, or pulverised fuel burners.

The primary object of the invention is to provide an ignitor which is not affected by draught or moisture and will even light under water.-

A further object of the invention is to provide an 1gnitor with a readily-detachable head assembly.

A further object of the invention is to provide an ignitor capable of having an electrode of substantial length relative to those of ignitors of comparable size heretofore provided in order to give a considerably increased working life before the electrode requires to be replaced.

Yet another object of the invention is to provide for ready and speedy replacement of the electrode.

A still further object of the invention is to enable electrical cable material to be remote from the hot zone of the ignitor.

It is a further object of the invention to provide an ignitor of small size suitable for lighting-up gas turbines and the like and adapted to be operated, switched, and inserted solely by combustion chamber pressure.

It is yet another object of the invention to provide for control of the fuel supply to the burner in such a way that fuel is not supplied or fed until the ignitor element is actually glowing hot enough for the ignition of fuel.

Other objects and advantages of this invention will become apparent as this description proceeds with reference to the accompanying drawings, wherein:

FIG. 1 is a sectional elevation of an ignitor head assembly;

FIG. 2 is a sectional elevation of an ignitor body and handle assembly, this together with the head assembly of FIG. 1 making up a complete ignitor according to the invention;

FIG. 3 is a sectional elevation of a modified ignitor;

FIG. 4 is a wiring diagram for the FIG. 3 ignitor in use; and

FIG. 5 is a diagram of part of the ignitor return circuit.

Referring now to the drawings, throughout which similar reference numerals denote like parts, and firstly to FIG. 1, the ignitor head assembly comprises a tubular metal casing or housing plugged at one end 13 by a carbon plug 11, the end 13 being closed ofl by an end cap 12. A liner 14, having two bayonet slots, is engageable by a pin 12a on the cap 12 and releasably holds the cap and other parts of the ignitor in place.

The plug 11 abuts the annular end 15 of a liner 16 against the other end of which abuts an insulating guide block 17 having an axial bore 18. The housing 10 and liner 16 are correspondingly apertured at 19 and 20, respectively, to provide intercommunication between the housing exterior and the liner interior 21.

At its other end, the housing 10 is plugged by an assembly comprising a pair of insulating guide blocks 22 and 23 spaced apart by a metal sleeve 24 and having axial bores, the blocks having moreover peripheral external flanges 25 and 26, respectively, at their mutually remote ends and against which the sleeve 24 abuts. A pair of spaced peripheral external flanges 27 and 28 are provided in spaced relationship intermediate the length of the sleeve 24 and the flange 27 abuts the end 29 of the tubular housing 10. The sleeve 24 is externally screwthreaded between the ends thereof and the flanges 27 and 28 as shown at 30 and 31, respectively, and the housing 10 is threaded onto the sleeve. A metal pin 32 is tightly fit in the bores in the blocks 22 and 23, the outer end of the pin being flush with the outer end of the block 23 and the inner end 33 of the pin projecting into the housing interior 34 beyond the block 22. The outer end of the pin has an axial tapped opening which is engaged by the threaded end 35 of a connector plug 36 of conducting material, the latter having a longitudinal split 46 for flexure purposes and a chamfered lead-in end 47.

A longitudinal sleeve 37 providing a forward part of conducting means extends axially of the casing or housing It) for the greater part of the length of the latter and is brazed to the projecting end 33 of the pin 32. At its other end the sleeve 37 fits into the bore 18 of the block 17 and is provided with an external peripheral flange 38 which abuts the adjacent end face 39 of the block 17. A copper-coated carbon electrode 40 is a sliding fit in the bore 41 of the sleeve 37 and is pressed into engagement with the carbon plug 11 by a spring 42 accommodated in the bore 41 between the end face 43 of the electrode 40 and the end face 44 of the projecting end 33 of the pin 32. The plug-abutting end of the electrode is nosed as shown at 45.

Referring now to FIG. 2, a tubular metal housing 50, of the same diameter as the housing 10, is plugged adjacent its leading end 51 with an insulating block 52 having a socket 53 with a metal surround or liner 54 which is adapted to engage the connector plug 36. The end 51 is internally screw-threaded as shown at 55 to engage the screw-threaded surface 31 of the sleeve 24. The block 52 is secured in position by self-tapping screws 56 and is bored for through-passage of a conducting rod 57 tapped at both ends and engaged at one end by nuts 58 and 59, a washer being shown at 60. The conducting rod 57 has a glass wool sheath 63. Atits other end, the rod 57 penetrates the bore of an insulating guide plug 64 and its tapped end is secured by a threaded nut 66 and washer 68 to the guide plug 64. The plug 64 is peripherally flanged externally at its outer end at 69 to abut on the end of the housing 50.

A pistol-type hand-grip 70 is fitted on the end of the housing 50 and abuts against an adjustable locating piece- 71 secured on the housing by a set screw 72, the hand-grip facilitating proper location of the glowing electrode in a fuel spray at a burner. The hand-grip 70 is of split const'ruction to enable assembly and maintenance of parts contained therein. 7

A four-core cable 73, connected to a supply of voltage, for example of the order 10-30 volts, enters the butt portion 78 of the hand-grip through an aperture in the base thereof. The four conductors 74, 75, 76 and 77 of the cable 73 are encased in insulating sheaths 79, 80, 81 and 82 respectively. The conductor 74 is electrically connected by a terminal 83 on the conducting rod 57 and locked in position by a nut 65. A conducting member 84- is fixed to the housing 50 and provides at its free end 85 a terminal for the conductor which is connected to ground. Conductors 76 and 77 are connected across a switch 86. The switch-actuating member 87, forming the trigger of the pistol-like hand-grip 70, projects through a slot 88 in the hand-grip.

The ignitor head assembly may be remotely-controlled or hand-operated. In the former case, conductors 74and 75 are connected across the voltage source and the current supply to the carbon electrode 40 is made and broken at some point outside the assembly, the switch not being in circuit. In the latter case, the switch 86 is connected in series with the conducting rod 57 by the tab 89 being brought into contact with the switch-actuating member.

When the member 87 is actuated and current flows to the terminal 83 and through the conducting rod 57, the metal liner 54, the connector plug 36, the metal pin 32 and the longitudinal sleeve 37 to the carbon electrode, the electrode is heated due to the electrical resistance thereof and glows to ignite fuel in the combustion chamber of'a burner into which the forward end of the ignitor is thrust. The electrode 40 glows white hot along its length for some distance from the tip, the distance depending on the length of time current is switched on and generally being of the order of about The ignitor head assembly is readily detachable from the body and handle assembly. The electrode element is long relative to the length of the head assembly and is subject to direct spring pressure to maintain contact with the carbon plug. The electrode element being of such length has a longer life than in ignitor constructions heretofore proposed and can be replaced very quickly by unthreading the housing from the sleeve 24 at the end 29. All cables, which are liable to be affected by heat, are in the cool zone of the i gnitor.

The ignitor just described would normally be of a length not less than 2 feet, but a much smaller size of ignitor can be provided for use with furnaces having combustion chambers in which pressure rises when ignition is effected, for example a gas turbine. An example of such a smaller ignitor is shown in FIG. 3 in which reference numeral 100 denotes a tubular metal housing closed at its front end, 101 a carbon cap, 102 a carbon electrode, 103 and 104 insulating guide blocks, 105 a longitudinal metal sleeve connecting to supply at 106, and 107 a sliding block housed in the sleeve between the electrode and a spring 108. Apertures 99 (one shown) are provided in the housing wall adjacent the cap-contacting end of the electrode 102.

A member 109 is mounted about an opening in the combustion chamber and has a inwardly-projecting axially-situated collar. The tubular metal housing is a loose fit in the collar, and gas from the chamber can pass between the housing and the collar into a cavity 110 beyond. A domed cover 111 is fixed, by means of bolts 112 to the member 109, insulating washers 113 being placed between the heads of the bolts and the cover.

An insulator 114 is fixedly mounted about the longitudinal sleeve 105, and the downwardly extending axial collar of a metal cup 115 is fixedly mounted about the insulator. The cup is connected to ground by a conductor 116 which passes through a hole in the cover 111.

The housing 100 has an annular flange 117 at its upper end and a flexible insulator 118 is held between the flange and lower side of the cup 115. This insulator follows the outer surface of the cup. At the top of the cup it 'bends upon itself to close the cavity 110 and is fixed to the inside wall of the cover 111 and is held between the cover and the member 109 by means of the bolts 112. g The cover has an axial hole wherein is fixed an insulating member 119 having an axial bore in which the sleeve 105 is a sliding fit. The member has an annular flange 120 which is fixed to the underside of the cover 111 and extends in two collars 121 and 122 along the length of the sleeve. A contact 123 is attached to the upper end of the collar 121.

The upper end of the sleeve 105 is capped with an insulating member 124 whereon is mounted a contact 125 in opposition to the contact 123.

A helical spring 126 bears at one end against the inside of the cup 115 and tapers to its other end where it is mounted about the collar 122 and bears against the underside of the flange 120. The spring 126 keeps the contacts 123 and 125 closed until the :force of the spring 126 is overcome by combustion chamber pressure building up in the cavity 110, by passage thereof from the chamber through the apertures 140.

In FIG. 4, which depicts the wiring diagram of the ignitor of FIG. 3, the reference numeral 132 denotes a solenoid contactor with a coil 130, 136 denotes an on/ofi switch, and 131 a battery.

At the beginning of the operation fuel is fed into the chamber, the contacts 123 and 125 are closed and the coil of the contactor is energized which closes the main points permitting a heavy current, say amps, to flo'w directly from the battery through the ignitor. The carbon electrode 102, which glows white hot for a distance of about /2" from the tip thereof, ignites the fuel in the chamber causing a rapid expansion of pressure in the chamber. The increase in pressure in the cavity acts on the flexible member 118, compresses the spring 126 and opens the contacts 123 and which cuts off the supply to the carbon electrode.

If pressure drops in the chamber and the cavity, the spring relaxes and the contacts are re-made, once more causing the carbon electrodes to become hot and the gas to ignite. Therefore, this arrangement provides for automatic re-lighting of the fuel.

FIG. 5 diagrammatically shows part of the ignitor return circuit which is connected to a solenoid-controlled fuel valve through a preset current transformer thus preventing fuel being turned on at the burner until the ignitor element is glowing hot enough for the ignition of fuel.

While certain preferred embodiments of the invention have been shown and described, it will be understood that various modifications may be effected within the scope of the claims.

I claim:

1. An electrical ignitor for lighting fuel burners, comprising a tubular metal casing having front and rear ends, a plurality of insulating blocks disposed within said casing and having bores coaxial with said casing, conducting means of substantially the length of said casing extending into said bores to mount said conducting means coaxially in said casing, said conducting means having a bore extending through at least a portion of its length, a carbon rod electrode disposed Within said conducting means bore, resilient means in said conducting means bore urging said electrode towards the front end of said casing, a carbon plug in said casing at said front end thereof in electrical connection with said casing and contacted by said electrode, means closing said front end of said casing, said casing having aperture means adjacent the plug-contacting end of said electrode for entry of fuel to be ignited, and means to supply electric current to said conducting means and said casing.

2. The electrical ignitor as claimed in claim 1, wherein said casing is formed by two mutually continuous parts defining a head assembly and a body and handle assembly, and further comprising plug and socket means interconnecting said assemblies and being readily detachable from one another, readily fitted together, and providing insulation from said casing, said insulating blocks being spaced apart lengthwise within each of said casing parts, said conducting means consisting of a first conducting member and a second conducting member, mounted by said blocks in said head assembly and in said body and handle assembly parts, respectively, said first conducting member having the bore in which said carbon rod electrode extends.

3. The electrical ignitor as claimed in claim 2, wherein said plug and socket means comprise a metal sleeve, a pair of spaced peripheral external flanges on said sleeve intermediate the length thereof, said sleeve being screwthreaded into the adjacent ends of said casing parts with said flanges abutting the ends thereof.

4. The electrical ignitor as claimed in claim 2, wherein said means to supply electric current comprises a trigger actuated switch adapted to connect a source of electrical current to said conducting means.

5. The electrical ignitor as claimed in claim 1, wherein said conducting means is slidably mounted in said bores, and further comprising cooperating electrical contacts mounted on the other end of said electrode and the rear end of said casing, one of said contacts being spring loaded to move relative to the other contact in response to pressure fluctuations to open or close the electrical contacts, one of said contacts being connected to said means to supply electric current, so that current is supplied to the electrode automatically with a decrease in pressure in the combustion chamber of a gas turbine in which the ignitor is placed.

6. The electrical ignitor as claimed in claim 5, further comprising a solenoid controlled fuel valve, a preset current transformer, and means connecting the ignitor return circuit to the solenoid controlled fuel valve through the preset current transformer to prevent fuel being turned References Cited by the Examiner UNITED STATES PATENTS 2,178,659 11/1939 White 123-145 2,424,848 7/1947 Reitan 219-233 2,430,666 11/ 1947 Burger 219233 2,933,896 4/1960 Ferrie 6039.82

FOREIGN PATENTS 1,146,330 5/1957 France.

1,099,796 2/ 1961 Germany.

RICHARD M. WOOD, Primary Examiner.

on at the burner until the ignitor element is actually 15 V. Y. MAYEWSKY, Assistant Examiner.

glowing.

Claims (1)

1. AN ELECTRICAL IGNITOR FOR LIGHTING FUEL BURNERS, COMPRISING A TUBULAR METAL CASING HAVING FRONT AND REAR ENDS, A PLURALITY OF INSULATING BLOCKS DISPOSED WITHIN SAID CASING AND HAVING BORES COAXIAL WITH SAID CASING, CONDUCTING MEANS OF SUBSTANTIALLY THE LENGTH OF SAID CASING EXTENDING INTO SAID BORES TO MOUNT SAID CONDUCTING MEANS COAXIALLY IN SAID CASING, SAID CONDUCTING MEANS HAVING A BORE EXTENDING THROUGH AT LEAST A PORTION OF ITS LENGTH, A CARBON ROD ELECTRODE DISPOSED WITHIN SAID CONDUCTING MEANS BORE, RESILIENT MEANS IN SAID CONDUCTING MEANS BORE URGING SAID ELECTRODE TOWARDS THE FRONT END OF SAID CASING, A CARBON PLUG IN SAID CASING AT SAID FRONT END THEREOF IN ELECTRICAL CONNECTION WITH SAID CASING AND CONTACTED BY SAID ELECTRODE, MEANS CLOSING SAID FRONT END OF SAID CASING, SAID CASING HAVING APERTURE MEANS ADJACENT THE PLUG-CONTACTING END OF SAID ELECTRODE FOR ENTRY OF FUEL TO BE IGNITED, AND MEANS TO SUPPLY ELECTRIC CURRENT TO SAID CONDUCTING MEANS AND SAID CASING.

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