US2786158A - Tognola - Google Patents

Description

March 19, 19 57 T. TOGNOLA SPARKING DEVICE Filed April 17, 1951 HEL l-AEC WELD INVENTOR iQaZa Q. 6%

ATTORNEY SPARKING nnvrcn Tullio Tognola, Sidney, N. Y., assignor to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application April 17, 1951, Serial No. 221,435

21 Claims. (Cl. 315-46) This invention relates to electrical apparatus and more particularly to electrically energized devices adapted for creating electrical spark discharges between spaced electrodes in an electrical circuit.

One of the objects of the present invention is to provide a novelly constructed spark or igniter plug or device adapted for use in ignition systems for initiating the combustion of gaseous or other combustible charges such as in engines or the like.

Another object of the invention is to provide novel apparatus of the above character which is so constructed that low voltage high energy sparks or arcs may be created across a relatively wide gap considering the magnitude of the voltage. I

A further object is to provide a novel sparking device which will function with complete satisfaction-and reliability under severe adverse operating conditions which would cause certain failure of operation of most known types of sparking devices under corresponding conditions.

Still another object is to provide a spark or igniter plug, the mechanical construction of which is simplified without endangering the safety factor insofar as flashovers or the like are concerned by reason of the relatively low voltages which are required to be impressed across the electrodes to create a spark or arc.

A still further object is to provide a device of the above character which is constructed in a novel manner toinsure proper concentricity and locating of some of the parts in the assembled construction.

Another object is to provide a spark discharge device of novel construction which is adapted to initiate a spark or are discharge from a source of electrical energy such as a charged condenser or the like, the voltage of which i is lower than the normal breakdown or spark-over voltageof a gap having similar dimensions.

A still further object is to provide an electrical sparking device such as a sparking plug or igniter which embodies novelly constructed electrode means for forming a spark gap.

The above and further objects and novel features of the present invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a sectional elevation view of one form of spark gap device embodying the present invention; and,

Fig. 2 is a bottom view of said device.

The single embodiment of the invention illustrated in the accompanying drawings, by way of example, is in the form of a spark gap'or sparking device commonly known as an igniter plug or spark plug adapted for use in ignition systems for initiating sparks to ignite combustible mixtures, such as in combustion engines or the like. The engines may be of the reciprocating type or of ice - the so-called jet or direct-expansion type. As exemplielectrode of a spark gap to be later described.

I turn seated on shoulder 17 in the shell.

tied in the drawings, said device comprises a tubular metallic body or shell 10 which is fabricated, in a manner to be later described, from what may be conveniently referred to as a main or insulator shell 11 and an electrode shell 12. Threads 13 or other suitable means are provided on shell 13 for use in securing the device to an engine or other support, such as in the wall of a cylinder or other combustion chamber of an engine, The upper end of shell 10 is externally threaded at 14 or may be provided with other suitable known means for attachment thereto of a shielded supply cable or conductor (not shown) and the upper enlarged portion 15 of the bore through shell 10 serves as a receptacle or well for the terminal of said supply or input conductor. Inwardly of bore portion 15, a reduced bore portion of the shell is threaded as at 16 for a purpose to hereinafter appear and spaced inwardly from the threads 16 is an internal tapered shoulder 17. Although shell members 11 and 12 may be made of different metallic materials, it has been found suitable in one commercial embodiment to make both members of a nickel-steel alloy.

. Shell member 11 supports a central conductor assembly whereby leakage of gases is prevented and electrical current is conducted through the shell to the inner or center In the form shown, said assembly comprises a tubular insulator 18 made of ceramic, aluminum oxide or other suitable insulating material and having an external conical surface that rests. on a conical soft metal gasket 19 which is in Insulator 18 is secured in the shell by an externally threaded ring 20 which engages threads 16 in the shell. The lower end of said ring is internally tapered to engage a conical gasket 21 seated on an upwardly facing conical surface on insulator body 18.

The electrically conductive portions of the central conductor assembly, in the form illustrated, includes a tubular connector 22 made of a nickel-steel alloy or other suitable conductive material and supports a bar or wire 23 that may be of similar material. The upper end of wire 23 may be enlarged or deformed to rest on an internal shoulder in recessed connector or adaptor 22 and the latter is provided with an external shoulder intermediate its ends for supporting engagement with an internal shoulder near I the lower end of insulator 18. The lower portion ,of

member 22 may be crimped around wire 23, if desired. A terminal member 24, which may be madeof stainless steel or other suitable metal, extends into the upper end of insulator 18 and has a flange 25 intermediate its'ends for engagement with the end of the insulator. The upwardly projecting pin or plug portion 26 of the terminal member may be designed for reception in the socket of an electrical connector of known construction for connecting the illustrated device to a source of electrical energy.

' The adjacent ends of terminal 24 and connector 22 within insulator 18 are preferably recessed for receiving the ends of a small wire 27 that may be made of molybdenum or the like for completing the central conductor through the insulator 18. The bent or hooked ends of W wire 27 are preferably silver soldered in recesses in membly against leakage of gases and for securing the conductive parts of the assembly in assembled relation. The

parts of the assembly are preferably assembled while the filling material 28 is heated to a temperature at which it is in a plastic or molten form. The material 28 enters the recesses in members 22 and 24 and serves as additional means to hold the wire 27 in conductive relation ween as with said members: The external surface of member 24 is irregular-- sot-hatit-will be gripped by'the filling'material 28 when the latter sets up as a rigid mass.

The invention comprehends a novelly constructed electrode or spark gap" assembly in; novelcombinationwith theshell and central conductor assemblies described above. In the formillustrated, the electrode assembly includes the-tubular electrode shell 12 having at its lowerend an internal'flange 30- which functions as a gap electrode. Thediameter of bore 31 atthe upper end of shell member 12 is somewhat greater than the diameter of thebore at the lower end of shell member 1-1- and a'portion 32 of-the' bore-adjacent the electrodeflange 30- is preferably slightlylarger than'bore 31. 'Ifhejaxially ex tending fir-cylindrical wal1 of-fiange 30 is-preferably concentric witli the bore 31 and the upper radial face of said flange ispreferably-squarewithsaid-bore, only slight tolerances being permittedi A centerelectrode 33' issnpported in a novel m'anner in shell member 12 in annular spark gap relation with electrode30; Said) center electrode, in-' the; formillus trated; is tubular and-ghas an enlarged cylindrical head portion of flange 341the diameter of'which is somewhat less than the inner diameter of" electrode flange 30: Electrode-'member 33 may be made of anickehsteeliallay, and is supported with head portion 34 thereof: in concentric relation with electrode 30' by an insulating ring 35fmade' of rigid ceramic material or the: like anda ring 36 which has a highresistance, to the, passage of electrical'current" and may be conveniently referred to as ajserni eon'ductor. One suitable, composition for fabri: cating ring'j36consists of 85 parts (by weight) of1silicon carbide, one partof'cobalt oxide, two parts of aluminum oxide and;.5ipart. of urea formaldehyde resin. Semiconductive ring 36 is seated on the upper surface of flange30' in conductive contact therewith and has an outside diameter slightly less than the diameter of bore 31;;32'so that the same will be in electrical contact with shell12 only at the surface of flange. 30. The inside di ameter of semi-conductive ring 36 is slightly greater than the diameter of the shank of electrode member 33 abovethe head'portion 34 so that the two will not be in electrical Contact along the bore surface of the semiconductive member. If'desired, the bore of ring 36rnay beglazedor coated with a thin-layer of insulation. The, ceramicor insulating ring 35. is seated on ring 36 and has: a sliding fitin bore 31 to insure, concentric'ity of'the. parts in, thesh'elI; Thebore through. ring 35. is. threadedxat 37'? for engagement with the externally threaded, portion .of; thesliank.ofilectrodermemberli Insider olredilce. erosionduring operation and hence, prglongtlie efullife ofthe dv'ice,.one .or more washers. 3810f nrresistant material, such as platinum, tang: t .I ,..11.' 1 :l ';el,v tantalum, .01 the like, are interposed. between, semicgindnic'torlifiandthe upper, f-aceof electrode head 34; "llwo washers, 38.11am ilustrated, the outside,diam-. eters thereofiheingthe same as-the diameter of electrode. head34l 'In' manufacture,,the parts 33,35, 36 and.38' are preferably made into a sub-assembly by first placing washers .3 8..-0.n.electrode. 33 and then putting semi-icon ductiyef ring-. 36, in p'osition against the washers. Preferably, agcoating of some suitable cement or thelike such as. sauereisemcement, may then be placed on the upper. endof semi-conductor or resistor 36 and on the threads. of electrode-spindle 373.. The. insulating ring 35, is'then. screwedjiiito placelon spindle'33 and with theparts held injconcentric relationin a-suitable fixture atorque. isapplied to, electrode, 34 to .effectthe desired tightening of axialpressure'. A torque ofrabrout, inch, pounds. has been foundsatisfactory inone embodiment.

The above, described sub-assembly. consisting. of. rings. 35} 36' and1electrode, 33. may be secured in-.shel1'. mem ber ,(12 by ametallicring or sleeve 39 which ,is preferably made. of thesarne. metalas shellv 12. Ring or. retainer} .'a.dr ive;.fit .or. may be, threaded; in 1 shell 12%. and;

i holds resistor ring 36 in firm electrically conductive engagement with electrode flange 30. The sauereisen oement placed between rings 35 and 36 and on the threads 37, serves to cushion the pressure applied to said rings by sleeve 39 thereby preventing cracking or breakage of said rings during assembly. The electrode assembly may then be baked in an oven-for a suitable time and at a suitable temperature to cause the sauereisen cement therein to solidify.

After. retainer. sleeve. 39 has beenpressed into place inshell 1Z.the upper ends. ofthe shell and retainer sleeve are machined square with bore 31. The lower end' of shell member 11 is also machined, square and placed in abutting'relation with the electrode assembly. The engaging ends of shells.11-.and:12 are then heli-arc welded or otherwise suitably secured together. It will be noted that the end of shell 11 also engages the end of retainer sleeve 39 to prevent movement thereof out of shell 12.

' fullyappear hereinafter, the annular spark gap 40 formed on the one hand by electrode 34, 38' and on the other hand by electrode 30 is bridged at its inner end by the semi-conductive ring 36 which has surface contact with both, washers 38 and electrode flange 30. Thedesirable radialwidth. of gap 30 will differ in diiferent circuits, and in one suitable jet engine ignition system wherein the voltage rangesv from 800- to 1200 volts a spark plug having; an initial'gap about .Oll' inch wide has been found satisfactory. The width of the gap may be greater in the first instance'or may increase a very considerable amount. during operationwithout rendering the spark plug, defective, this being one of the important advantages of this type of construction.

When the device hereinabove described is connected in I an electrical circuit, such as in the ignition'system of a combustion engine, energy from a suitable source is supplied to terminal pin 26. The. device may ofcourse be. used in any electrical circuit in connection with a source of. electrical. energy capable of, impressing. approximately 500,volts or more across the gap 40, but the sameis'gpreferably. usedin conjunction with a.condenser whicdwhen operatively. connected. to terminal 26 and charged to the desiredyoltage will be capable, of dis-. charging acrossthe gap of the. illustratedstructuret The semiiconductorfor. resistor 36-whichhas surface engagementlwithih'e electrodesof the gap. and bridgesthe gap at one edge thereof makes it possible to create a high energy. arc. or spark across the air gap between the elec-' trodeswhenthe voltage. is very considerably less thanthevoltagewhich would be required to bridge the same airgap in the; absence of the-resistor. It is believed that whena voltage insufficient to bridge gap 40 with an arc is impressed acrossthe electrodes of the illustrated-device, a small amount ofv electrical energy passesthrough or along the lower. surface of resistor 36. between the electrodes and eflfectsionization of the gaseous medium in..the-; gap.40, thereby reducing the resistance ofsaid gaseous ;medium to a level, such thatv alow'voltage spark or arc will occur incthe. spacebetweenthe electrodes. In accordance-with the usual practice the terminal26, may be connected, to a storage condenser or. other source of electricalenergyand electrode.30 may be at sorcalled ground; potential. Successive sparks across gap 40-will of course-occur at the-points of least resistancealong the annular.gapwand,. hence; at points whichmay be bridged by. @BIbQU; lead: 01': other foreign matter. Any accumula agen as tion of this character which might otherwise create a permanent low resistance path between the gap surfaces, a condition known to the art as fouling, will be burned away by the high energy sparks, thereby increasing the efliciency and prolonging the useful operating life of the spark plug construction.

There is thus provided a novel spark plug or igniter adapted for use in combustion engines and particularly for uses requiring a high energy spark or are and in installations where low voltages are desirable, such as at high altitudes, and where radio interference is a hazard. The novel construction is such that operational advantages are attained while the probability of damage to the parts during assembly is minimized. The device comprehended may be assembled in a novel manner from parts of relatively simple construction whereby the cost of production is relatively low. The spark gap construction provided is self cleaning and is novelly constructed to minimize erosion from heat and sparking, thereby providing greater life and more. eflicient operation. Additionally, the construction is such that the parts subject to greatest wear during operation may be removed and replaced without the necessity of substituting a complete new device, thereby reducing operational costs.

Although only a limited number of embodiments and modifications of the invention have been illustrated in the drawings and mentioned or described in the foreging specification it is to be expressly understood that the invention is not limited thereto. For example, the terminal 26 may be in the form of a socket for receiving a pin contact or in the form of any other known type of terminal. The filling or sealing compound 28 may, if desired, be electrically conductive thereby eliminating the necessity for wire 27. Connector member 22 and wire 23 may be integral and electrode 30 may be of different metal than shell 12 and suitably secured thereto or mounted therein. Although the sides of gap 40 are shown as being parallel to each other and parallel to the longitudinal axis of the structure, either or both sides of the gap may extend at an angle to provide a gap with converging or diverging sides and in still another modification the sides of the gap may be parallel to each other but extend at an angle to the longitudinal axis of the structure. It may be desirable in some installations to eliminate Washer 38 in which instance the resistor or semi-conductor will directly engage the head portion 34 of the center electrode member. It might also be desirable in some constructions to eliminate the threads in insulator 35 and provide a nut on the upper end of electrode member 33 to hold the parts in assembled relation. The various parts may be made of materials other than those suggested by way of example as being suitable. Various other changes, including changes in the relative sizes, design and arrangement of the parts illustrated, may be made without departing from the spirit and scope of the invention as will now be understood by those skilled in the art.

What is claimed is:

1. In an electrical sparking device, a tubular shell, an electrode within one end of the shell, a center electrode in spark gap relation with said shell electrode, a resistor bridging said gap in said shell, an insulator slidably fitting into said shell and having threaded engagement with said center electrode, and means within the shell for clamping said resistor between said insulator and said shell electrode to retain the insulator and resistor in the shell and to hold said resistor in contact with said shell electrode.

2. A sparking device as defined in claim 1 wherein the resistor surrounds a reduced portion of said center electrode and is clamped between said insulator and an enlarged portion of said center electrode by threading said insulator onto said reduced portion into clamping engagement with said resistor.

3. A sparking device as defined in claim 2 compris- 6- .t ing at least one ring of erosion resistant material, such as platinum, tungsten or the like, interposed between said resistor and said enlarged portion of the center electrode in spark gap relation with said shell electrode.\

4. In an electric sparking device, an annular electrode, a center electrode having aspindle and a head portion forming an annular spark gap with said annular electrode, at least one washer of erosion resisting conductive material seated on said head portion around said spindle, a ring of material having a high resistance to the flow of electrical current bridging said gap with one end surface thereof in surface engagement with said annular electrode and washer, and means including an insulator for securing said electrode, washer and resistor in assembled relation as a sub-assembly for mounting in relation to said annular electrode.

5. A sparking device as defined in claim 4 wherein said insulator has threaded engagement with said center electrode spindle for securing the parts of said sub-as sembly in assembled relation. 7

6. In apparatus of the class described, a shell having an electrode thereon, a center electrode assembly in said 7 shell having a tubular center electrode in spark gap relation with said shell electrode, means for retaining said assembly in said shell, a shell member secured to said shell in end-to-end abutting relation therewith for holding said retaining means in said shell, a separate central conductor assembly supported in said shell member independently of said center electrode assembly and comprising central conducting means and means for insulating the latter from said shell member, said conducting means extending into said center electrode and being connected thereto.

7. Apparatus as defined in claim 6 wherein said retaining means comprises a tubular sleeve having a drivefit in said shell.

8. In apparatus of the class described, a tubular shell member, a center electrode assembly operatively mounted in said shell member, means including a ring fitted into said shell for retaining said assembly in said shell, one end of said ring being flush with the end of said shell, and a second tubular shell member secured in end-to-end abutment to said first-named shell member and having end-to-end abutment with said retaining ring.

9. In apparatus of the class described, upper and lower shell members, a center electrode assembly operatively mounted in said lower shell member with electrodes on the latter and said assembly in spark gap relation, a central conductor mounted in and insulated from said upper shell member, said shell members being secured together in end-to-end abutment and said conductor extending through a bore in the electrode of said assembly and being connected thereto.

10. Apparatus as defined in claim 9 wherein said shell members are secured together by welding at the abutting ends thereof.

11. A sparking device comprising a tubular shell, an electrode on the shell, a center electrode assembly in said shell having a tubular center electrode in spark gap relation with said shell electrode, a rigid central conductor, means supporting said conductor in said shell and insulating the same therefrom independently of said center electrode assembly, said conductor extending through the center electrode and being electrically and mechanically connected therewith.

12. In an electric sparking device, a tubular metallic shell having an annular internal flange at one end thereof constituting an electrode, a center electrode having an enlarged head forming an annular spark gap with said flange and a threaded spindle, a ring of semi-conductive material in said shell around said spindle and seated on said flange and head to bridge said gap, a ring of insulating material having a sliding fit in said shell and threadedly engaging said spindle to hold said first-named ring against said head, and a sleeve having operative engagei in engage ent W ths'ai'd fla ge 13, In ,apparatusofthe clas's described, a sub-assembly comprising an,- electrodje haying an externally threaded spindlfe a'nd'an enlarged head portion, an insulator threaded onto said spindle andfa slightlyconductive electrical resistor interposed-between said insulator and head portion and pressed againstthelatter by said insulator, a shell closely surrounding said insulator andhaving electrode means, in,, spark gap relationwith said head portion, and meansjfor, securing.said,-sub assernb1y in said shell with saidresistorpengaging. said electrode means and bridging said gap. 7

-14.v In apparatus-of the classdescribeda sub-assembly comprising a, center: electrode having .a spindle and a headat one end of the spindle, a ring o i semi-conductive materialsurroundingjthespindle, and engaging said head, a separate: ring, of insulating material surrounding said spindie, andameans for holding said electrode and rings in assembled relation with said-semi-conductive ring pressedghetween said, head andsaid insulatingring.

1.5. Apparatus as defined-in claim -14 comprising at least one washer of'corrosion resistantmaterial, such as platinum, tungsten or the like, interposed between said semi conductive-ring and said head, said washerhaving substantially the-same:externaLdiarneteras said head;

:16; Apparatus as defined in claim 14 wherein said holding-means, comprises cooperating "screw threads on said spindle and insulator.

1;7,. vApparatusas definedin claim 14 including-a coating, of cement between l said, rings.

'18, Apparatus asdefined in claim 14 wherein said Td she11,an,.d nsulati gi na r h l in a semi conductive ring stn'rounds said spindle inspaced,

relation thereto.

19; Apparatus "as defined in claim 14'compri'singashell cl'os'el'y surrounding said insulator, an electrodein the shell in spark gapreiatiomwitbsaidcenter electrode head; and means for securing thesub-asserrilz'ly saidshell with said semi-conductive ring I engagingysaid sh ell electrode and'bridgingthe gap between said electrodes.

20; Apparatus 'as'defin'ed claim :19 wherein said securingrn'eans comprisesa sleeve operat ively engaging the shell;

1- App atus asfle e 'i nj a m her he t circumference off 'the semigconductive ring. is in spaced relation to said shllg References (Zited in the file of this patent UNTIED zrATes ATENTL

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