US1067791A - Spark-plug. - Google Patents

Description

C. H. DUFFY.

SPARK PLUG,

APPLICATION funn PBB.5,1912,

Patented July 15, 1913,

2 SHEETSvSI-IEETI S n v01/Lto@ SPARK PLUG.

APPLwATIoN FILED m1101912.

Patented July 15. 1913.

2 SHEETS SHLBT Z,

CHARLES HUGH DUFFY, OF NORTH LAUREL, MARYLAND.

SPARK-PLUG.

Specification of Letters Patent.

Patented July 15, 1913.

Application med rebruary s, 19122. serial No. 315,780.

ing, atNc-rth Laurel, in the county of Howardand State of Maryland, have invented certain new and useful Improvements in Spark-Plugs; and I do declare the following to be a full, clear, and exact description of the invention, such as will enableothers 4' skilled' in the a'rt to which it apperta'ins vto make and use the same; reference being had to .the accompanying.drawings, and to the lettersl and'v figures of reference markedV thereon, which form a part of this specification.

This invention relates to spark plugs for inlcrnalcombustion engines and has for its object to'provide adevice of this class which will elfectually hold the current to cause same to jump the spark gap at the sparking points of the electrodes in such manner that grounding or short circuiting will be prevented.

' The current employed in connection with spark plugs for the ignition of internal 'com-' bustion engines being a high tension cur i rent is extremely diicult to hold, and spark plugs are prone .to short circuitthe current I to sucll an extent that said current instead of jumping across the spark gap follows along the central insulator or core to the metal shell of the plug. This condition invariably results when the central elect-rode r core becomes coated with a depositof carbon, soot or oil, and as-the spark plug enters the engine cylinder or combustion chamber and is constantly in contact with the products of combustion within the engine i cylinder it is practically impossibleto 'prevent a deposit of short circuiting material on` thel insulator 'orcore and thus short cir'- cuit the plug andvinterfere with, if not entirely prevent ignition. Still another dithculty'experienced with'spark plugs is due to tllc accumulation of a drop of oll in which carbon is suspended on the sparking points ullicll bridges the spark gap and acts as a conducmr for tllecurrcnt to flow from one electrode t@ the other across the spark gap instead of iunflping to produce a spark. This condition more frequently arises from lan excess of lubricating oi-l in the-en ine cylinder and is extremely annoying, an not infrequently results from waterentering the en ine cylinder from the water jacket.

his invention is designedto obvate and overcome the aboveditliculties and to produce a spark plug which is sov constructed and arranged that a short 'circuiting l the insulating core will not short circuit the further object of the invention/is to prevent the accumulation of short circuiting material on the sparking points and to maintain same in a clean serviceable; condition1 A further' object of the invention i'sl-to provide for cooling the central electrode and insulating core t0 prevent 'excessive heating, wllile. a further. objectl of the ine ventipr'i is to provide for quick and effective vpriming of the engine cyllnder.

With these and other objects in view, the invention Consists in the novel construction and arrangement of the insulating corev and insulating iacket therefor.

y The invention further consists .in the arraement for -insulating the central elec'- tf e from t-he-tletal shell of the, plug by providing a plurality of air chambers between the central electrode and the metal shell4 of the' plug.

Vhe invention further consists in the novel construction for guarding the insulating plug and insulating sleeve orv jacket against a deposit of short circuitingl material.

The invention further consists in the novel construction for packing the `parts of the plug to prevent leakage.

- The invention further consists in the novel construction for jetting atmospheric air sp'ark gap to clean the points.

The invention further consists in the novel construction of the central electrode so as to cool its insulating core.

Thev invention further consists in the arrangement and construction of the Aball check and its casing.

ing the physical force. or attractionl of upon the sparking points and through tlle y The invention further consists in apply aube against the force of gravitation and -which would pre vent capillarity in order to remove from thel sparking points any deposit of oil or water thereon in such manner that bridging of the spark gap is absolutely prevented.

The invention further consists in the construction which provides for draining excess liquid from the capillary/ opening by gravity. v

The invention further consists in the construction of the central electrodewhich provides for priming the engine cylinder, and the invention further consists in certain other novel features of construction and in combinations of parts, all of which will be first fully described and afterward specilically pointed out in the appended claims.A

The bridging of the spark gap at the spa rking points of a spark plug by a drop of oil or water is due to the capillary attraction of the oil or Water for the surfaces of the sparking points, and when such a drop attracted to the surfaces of the points to bridge the gap the current flows through the drop and does not jumpyrto produce a spark.

v It is needless for the purposes of a full D description ci' this invent-ion to ,e0 further the Same will be readily apparentiuto the principle of capillarity other than Refel'lllll i0 the lccilmlmlylng dl'wlngsi to say that the attraction of a liquid in a Flgule l 1'3 a "Ql'tlcl SCCflUnal "16W 0f il ver); small bore, such as the bore of a. small I spark plug constructed in accordance with tubey is extremely great, so great in fact this invention, and Fig' is a vertical secthat when a small tube is immersed in water .tional View 0f a spark plug of different conthe water will rise in the bore otl the tube SIUCOIL :l Considerable distance above the Surface Like numerals of 'reference indicate the of the water which is a phenomenon apsame parts throughtiut the tivo figures in parently contrary to the law of gravitation. which` As a matter of fact the capillary attraction l indicates the spark plug which comot the water for the inner-Walls of the bore prises the metal shell 2 which is threaded ot' the tube is greater on thewater than the at 3 for threaded engagement 'with the cylforce oit gravitation thereon as this attracindcr or combustion chamber of an internal tion rais-rs the water within the bore of the combustion engine. The lower end of thc spark plug is provided with a relatively small cent-ral opening and the interior of the threaded portion 3 is chamber-ed out at 5` the bottom o't' the chamber'- being inclined at (3 toward the central opening 4l to drain ythe same. The chamber extends preferably the full length of the threaded portion 3 and at the point i7 an .inclined wall S is formed which meets the vertical wall 9 of the upper or enlarged chamber I0, said upper or enlarged chamber l0 terminating at ll at which point'an annular shoulder 12 is formed, said shoulder 12 meeting the vertical wall 13 of the top chamber, which'top chamber accommodates the insulating clearly shown in the drawings.

Referring now to the insulating sleeve or jacket 14 it will be seen that the same is provided with an annular shoulder 15 which meets the vertical wall 16 of the sleeveor jacket, said wall 16 extending downwardly to the point 17 vWhere it is turned inwardly this principle to a spark plug and arranging the bore in the lower electrode the capillary of thc electrode is further assisted by the force ot f ravitatirm` as in the present iustance the passage ot the liquid is in a downward direction and the force is therefore greater than it is when inserting a. small tube in water for the purpose ot' raising the water within the tube and above the surface of the water by capillary attraction.

Experiments carried on with the construction 'in accordance with the accompanying drawings have shown conclusively that it is impossible to maintain a bridge ofoil or Water between the two electrodes ,of the spark plug for the very obvious reason that the capillary attraction of the oil or Water by reason of the bore in the lower electrode so far exceeds the attraction of the oil or water to the upper electrode that the bridge is instantly broken and the oil or water is attracted into and passes through the bore in the lower electrode. With this brief explanation of this principle as applied to this spark plug it is thought that the action ot' overcomes the same. Applylng lthis principle oit' capillarity to the sparking points of a spark plug it Will be apparent from an inspection of the accompanying drawings taken in connection with this specification that the lower electrode of the .sparkplUgr when formed with' a small cent-ral bore will so attract. a drop of oil or Water bridging the spark gap that the bridge will be broken and the drop of oil or water will be attracted into the bore of the lower electrode. This capillary attraction only exists when the bores ot' tubes and the like are very small, and consequently it is necessary in applying this principle lo the' present spark plug to construct the central bore in the lower electrode very small but large enough to insert a pin or small Wire for the purpose of clearing the same should it be obstructed by carbon or anyiother material a tree passage of oil same. In applying or Water through the attraction ot the water o1' oil in the bore y heredan-M125 from the end 26 to 2,7 in such manner that an air chamber 28 is l Surrounds the lower chambered portio-n of the central core 21, and itwill also be seen tof form a 'guard 18,l a-'relatively small centrol opening 19- bging-formed .in the guard 18 as is clearly sh y nin the'drawings. The upper: portion the insulating sleeve or jacket 14 ischamberedfout at 19 and forms an .annular shoulder 20, said chambered-out insulating-core- 21, said insulatingV core 21. being; provided about'ceutrally with an annular swell or enlargement 22 which enters the chambered portin'19 of the insulating sleeve or jacket 14, The insulating core 21v is provided centrally with, a bore 23 w reeeive the central electrode 24, the lower portion of thef'insulating core 21 bein chamt e point formed around the central electrode 24 as will be apparent from the accompanying drawings It will also be seen that when the insulating core 21 is entered into the insulating sleeve 14 that an annular air Lchamber 29 is :formed around and entirely 'that when the insulating sleeve or jacket 14 is entered into the metalshell 1 that an annular air chamber 30 entirely surrounds the lower chamberedportionof the insulating sleeve or jacket, while vthe guard 18 .formed on the lower end of the insulatingV sleeve or jacket extends inwardly and under the ends of the chambered portion of the insulating core 21. It will also be seen that the inclined wall 8 in the metal shell extends inwardly and under the insulating sleeve or jacket 174 to.guard the annular air chamber 30 which surrounds. the chamhered portion of the insulating sleeve or jacket. This arrangement" of a plurality of air chambers surrounding the central electrode 24 is very material to the pro-per operationA of this spark plug.l for the reason that a single chamber in the insulation of aspark plug is notl suiiicient to prevent the passage of the current over the surface of the insulation and ground itself. on the metal shell whenever a coating of short circuiting material hasl been deposited upon the insulai tion. It is extremely difficult to insulate a i high tension current of the character cmployed for spark plugs and this current uuiformly overcomes the resistance of a coating of short circuitng material on an insulator and grounds itself on the metal shell of the plug. By reason of'. the plurality of air chambers surrounding the central electrode the distance which the current must travel from the central electrode over the Walls forming the air chambers to the metal s nll of the plugr is so great that the currentcannot overcome the resistance to ground itself and must therefore jump at the spark gap to produce a spark.' As the resistance of 1 carbon, unlike that of metals, diminishes, as the temperature rises the heat conditions encountered in an internat combustion ena series of air chambers in order to greatly' increase the distance over the ywalls surf rounding the air chambers from the centralv electrode to the metal shell thecurrent will be very quickly and easily short circuited and grounded as soon as a deposit or-carbon of other short circuiting material collects upon the surface of the insulator. It is further seen from an inspection of thedrawings that the central core 2l isentirely insulated from the metalshell of the 'plug and that even though the chambered portion of the core 21 is etfectually coated with a short circuiting material such a condition could in no sense short circuit the current as said core 21 being insulated from the metal shell a short circuit of the core could not short circuit the current.

Referring again tothe drawing, 31 indicates an insulating bushing which rests on the annular shoulder 32 of the central core 21, which annular bushing 31 is engaged by the threaded gland 33, which threaded gland eiects a Athreaded engagement with the threaded portion 34 of the metal shell 1 for the purpose of securing the parts rigidly together as will be apparent.; In order to etfectually pack the parts to prevent leakage through the plug I-provide under the fiange 15 of the insulating Asleeve or jacket 14 an annular tapered copper gasket 35 which engages the shoulder 12 of the metal shell 1 as is clearly Shown, and under the enlarged. central portionl 22 of the core 21 I provide a similar annular tapered'copper gasket 36 which engages the shoulder in the upper portion of the insulating sleeve or jacket 14. As the parts are drawn together these tapered gaskets are compressed inwardly to grip and engage the vertical sur- 3T and enters, the ccntral here of the core 21 iu order m effect an absolutely tight joint between thc electrodev 2i and the core 21.

t The upper end of the electrode 24 is threaded at 39 to receive a knurlediut 40 for holding the secondary terminal 41, while a nut 42 is threaded on the central electrodo 2i and against the core 2l to tightly hold i the central electrode-24 in position.

Referring now to the lower electrodes 43 `metal shell i.

, pass through the bore 46 and it will be seen that the same is preferably connected in the bottom of the threaded portion 3 of the shell which connection can beefected by able manner. The electrode being thus arranged is= bent or curved at 44 and is then bent to lie vertically the extreme end of the electrode being disposed directly under the central opening 4 in the threaded end of the The central vert-ical portion 45 o' the electrode 43 is provided centrally with a small bore"46 and is preferably cupped at 47 at vthe extreme' upper end there-A of, While the lower end of the bore 46 and the-metal shell of the electrode adjacent thereto are beveled off' at'48 in order to facilitate the passage of the liquid out of the bore 46 by gravity. The central electrode 24 passing through the chamber 5 within the threaded portion 3 of the shell is bent back upon itself near the end thereof at the point 49 and is again bent lback upon itself at the point 50, the lower end 51 of the electrode lying vertically within the chamber' 5 and entcndingfentrally through the opening 4 in the bottom ofthe shell terminating at which is just above the cupped end 47 of the lower electrode 43. The purpose of the bend 49 in the central electrode 24 is to provide an oil drip so that. any oil accumulating on the central electrode 24 will run down to the point 49 and drop therein-oni instead of passing to the point ofthe electrode which is the sparking point. This construction prevents any accumulation of oil at the sparking point 2 which might accumulate on the central electrode 24.

The ,operation of the construction justdescribed is follows: 'lhe current which is led to secondary wire is prevented from short circuiting or grounding itself on the metal shell of the plug by reason of the construction of the insulation as' heretofore described, and consequently the current must.

produce a spark at the spark gap which between the point 52 of the central electrode 24 and the cupped end of the lower electrade 43. When, however. a deposit of oil or water is toi-:ined on tbc points of the electrodes to bridge the spark gap, said oil resting in the cupped end 47 of the lower electrode and touching the point /52 of the upper electrode is quickly drawn into the small bore 46 in the lower electrode by capillary attraction governed by the principle as previously described, and as passes into the bore 46 it is assisted in its passage vthrough the bore by the force of c gravity, which together with .the capillary attraction of the oil or water for tle bore ,l trode 43,

2G causes the said oil or water to quickly onto the bevthreaiis or in any other suit# the central electrode 24 'from thev that an additional vand oil runs to the curved portion 44- of Athe lower electrode and drops therefrom backv into the combustion chamber. By means of this construction it is a physical impossibility to maintain a drop of oil between the sparking points of the electrodes as the capillary attraction for the oil for the bore 46 being very much greater than the attraction of the oil for the point 52 said oil will be'dra'wn into the bore 46 and instantly break the bridge. Should, however, in constant use the oil assing through the bore 46 become, carbonized the said bore can be instantly cleaned by inserting a pin or other smallwire through the bore 46 to remove any deposit therein and to thus maintain the bore open and in operative condition.

Referring .to the construction illustrated in Fig. 2 it will be seen that the same di'ers from the construction shown in Fig. 1 in expedient is employed to clean the sparking points of a deposit of oil, water or the like. In the construction shown in Fig. 2`the central electrode r24 is provided throughout its length with a. central port 53, While the nut 54 at the upper end of the electrode 24 is provided with a seat 55 and houses a ball check 56 which is normally in open position Ashown inv dotted lines in Fig. 2, the upper end of the central electrode 24 being beveled at 57 or otherwise conveniently formed to prevent the said ball check 56 from closing the central port 53 in the electrode 24 when the said ball .is in position shown in dotted lines in Fig. 2. The upper end of the nut 54 is threaded at 58 and is provided centrally with a port 59 which communicates with the interior of the nut 54 which port 59 is closed when the ball check 56 is in position shown in full lines in F ig. 2` The terminal retaining nut 6 0 is cupped at the top as shown at 6l in such manner that a priming charge can be conveniently introduced into the nut 60 which passes through the nut 54 and through the central electrode 24 thus into the combustion chamber. Near the lower end of the central electrode 24 I provide a. guard 62 to act as an oil drip to prevent oil deposited on the central electrode 24 from reaching the end or sparking point of the central electrode 24 as any oil passing downrthe central electrode 24 runs over the guard 62 and drops oil' of the depending -wall 63.

As far as the construction of the lower the Oil 01 Watl' electrode A23 isconcerned it is the same as l the construction -irst described. While the lower end of the electrode 24terininates just above'the cupped end 47 of the lower elec the spark gap being formed between the ends of the two electrodes,the re-J moval of the oil by capillary,` attraction` from the two sparking points is'lpreoi-se'ly the aire as described in theyforegoing de seription. v

It wi'lilhe noted from an inspection ofthe aeeompan'ving drawings that inasmuch as Athe central electrode insulation is arranged and loeated in the enlarged chamber 10, which is above the threaded portion 3 of the plug, thatsaid insulation does not extend inteI the engine cylinder or combustion ehamher and is at. all times on the outside of the said cylinder or emnbustion chamber as the outer line of the engine eyliruler or combustion chamber is indicated by the line A-B in the two figures; consequently the insulation being arranged as shown is i'elieved from the excessive heat which it would be subjected to if the insulation extended down into the threaded portion of the plug as is usual in plug eonstruetions. further advantage of this arrangement is that e 'large ehamher 5 is provided under the insulation and within the threaded portion 3 of the plug so that upon.ignition of the gas within the engine e'vlinder the gases under eompression within the eliamber 5 rush out through the hottom otl the plug and through the relatively small opening t therein, which relatively small opening inereases the speed ot' the gases at that point and assists in maintain lng the spark gap free. and elear ot' any troublesome deposit.

ln the operation ot' they ronstruetion shown in Fig. Z the hall eheek 5t, is seated as shown in full lines in Fig. 2 during the compression within the engine evlinder and during the power stroke of they piston. but on the intake stroke of the piston the pressure with` in the engineeylinder being less than atmos` pheritl the hall eher-k 5t? moves into position shown in dotted lines in Fig. and causes a drat't ot' atmospherie air to be drawn through the ported electrode 2,4 and jetted or impinged across the spark gap between the ysparking points of the elta'trodes. thus assisting in keeping the spark gap free from an)y injurious deposit. This relatively infinitesimal ouantitv of air whieh is drawn into thev enginey eylinder together with the romlmstihle mixture is benet'zeial to the mixture. while at the .same time this draft' of air pas ing through the ventral eleetrode has tendriav to eool the saure and to prevent undue and dangeWTts heating oi' its insulating eore, ,\s the illustrationsr are greatly enlarged over thtI :it-tual size-1 ot the plug in order to taeilitate the showing ot" the same it is thought that the eoustrnetion and oper- .L t

ation (.l' the plug will he elearlv apparent from the said drawings taken in Conner-tion with tthe 'foregoing .speeieatiolr Having thus fully de-erihed the emi-:trieA4 tions it is apparent that' numherless ehanges eould be made therein ywhich would fall within the limit and seope of this invention and I consider myself eleuiilv entitled to all I-sueh elianges and modifications as fall within tlhe limit andscope of the appended elaims.

lvhat l elaim as new and desire to seeuro b v Letters Patent ot' the United States is:d

l. A spark plug comprising a metal shell elosed at one end and provided thereat with a relatively-small opening. said plug being provided in its lower portion with a ehamher and provided with an enlarged chamber above' said firstfmentioned rhamber. an insulating sleeve arranged in said enlarged Chamber `and shaped to form a guard at its lower end, said lower end being provided with a relatively small opening therein. an insulating eore arranged in said insulatingr sleeve and extending down near the bottom ing eore heilig provided `with a bore to reeeive the central eleetrode and provided in its lower portion with a chamber, a central electrode arranged in said insulating,eo1'e and extending through the said chamber; through the said opening in the bottom for said insulating sleeve, through the lower chamber in the said metal .shell and l.terminating adjacent the said opening in 'the elosed bottom end of the said metal shell, a lower electrode having its end terminating adjacent the end of the Central electrode to t'orm a spark gap between the two electrodes, said lower eleetrode being provided with a small here extending from the said end thereof and terminating at a Apoint in said electrode in sueh manner as to provide a passage, open at both ends vbelow the said ventral electrode, said small bore being artbe central eleetrode as tohreak a bridge ot' liquid aeross the'spark gap by capillary attraction. an oil drip on the said central eleetrode near the lower end thereof. means for paeking the, central electrode, insulating eore and insulatingr sleeve, and means for seeuring and holding the parts within the metal shell.

2. A spark plug eomprising a metal shell havingr a ehamher in the lower portion thereof and having an enlarged ehamber in the upper portion thereof. an insulating.- sleeve arranged in the said upper ehamher and ternliiulting at a point above the lower ehamber. an insulating eore arranged in said insulating sleeve and terminating at a point radjaeent the lower end of said insulating sleeve. said insulating eore being bored to reeeive the central eleotrode and provided in its lower portion with a eliamber. a central electrode, arranged in said insulating core. l the said elerftrode being surrounded h v said chamber`r the outer lower wall ot' said eentral eore and the inner lower wall ot said inranged in close association AWith the 'end ofend of said Ainsulating sleevev` said insulatf l :al lilflzlrallmi' 1911 Meer of slid vn'zugvfn fl' vili@ im zzl" latini! fill-vw :unl the inner sur? m I an insulating ffurv Mmmm lug ware f will Central ele-0 Erl( gap lmiwvvn "nme of liquid mls in lwalf.' Saul gm PW Uumilnr'y i arranged in @nifl 11m msu- -umm in lle will m31 Sail! vmlral @lodi-ode from lw metal SlwlL Said insulating menmilmving a pluralilv 5' wir cl'lambers W'llln the .fiume :mil (nl lwtfvven lle? smid @Html'elmrtrifrlm 5 :m-Cl lll# izfa, slwfll, as, lower electrode hav Spark flap.

noemvel a spark .gap betweenthe two electrodes, and

an electrode therein insulated from the. metal shell, a fellow electrode arranged in relation to the first mentioned electrode so as to provide a spark gap between the two electrodes, one of said electrodes being pro- I vided with a small bore extending` from the spark gap end thereof and terminating in termediate said spark'gap end and the other end of the electrode to providean open passage. throughthe same, saidsmall bore being arranged in relation tothe end of the first mentioned electrode so as to exert a capillary attraction for liquid bridging the spark gap to break the bridge.

- 9. A spark plu comprising a metal shell,V van electrode Wit in the same, means for insulating the electrode from the metal shell, a fellow electrode arranged in relation to the first' mentioned electrode so as to provide a spark gap, vand means for exerting a capillary attraction for liquid at the end of one electrode to break a bridge of liquid attlie spark gap.

10. A spark plug having electrodes arranged in relation to cach other so as to provide a spark gap between the electrodes, .and means for exerting acapillarv attraction for liquid at one electrode sutlicient to break a bridge of vliquid across thev spark P- l 1l. A spark plug comprising a plurality of electrodes arranged to form a spark gap,

and means at the spark gap for exerting on a liquidbridgingthe spark gap a capillary attraction sufficient to break the said bridge.

12. Ajvspark plug comprising a metal shell closed at one ond and provided thereat with a relatively small opening, said plug being provided in its lower portion with a chamber and provided with an enlarged chamber above said first mentioned chamber, an 1nsulating sleeve arranged lin said enlarged chamber and sha ed to form a guardat its lower end,y said ower end being provided with a relatively` small opening therein. an insulating core arranged iny said insulating sleeve and extending ldown near the bottom end of said insulating sleeve, said insulating coro being provided 'with a bore to receive thc central electrode and provided in its lona-r portion with a chamber, a central-elecf in the said metal shell and. terminating ad- ,iacentthe said opening in the closed bottom 'end of the said metal shell, a lower electrode having its end terminating adjacent the end of the central electrode to form a spark gap between the two electrodes, said lower electrode being provided with asmall bore extending from the said end thereof and terminating at a' point in said electrode in suclf manner as to provide a passage. open at both ends below the said central electrode, said small bore being arranged in close association with the end ofthe central electrodehs tobreak a bridge of liquid across the spark, gap by capillary attraction, an oil drip on the said central electrode near the lower end thereof, means for introducing a draft of atmospheric air on the spark gap, means for packing the central electrode, insulating core and insulating sleeve, and mea-ns or secnrin and holding the parts within the metal s ell.

13. A spark plug comprising a met-al shell havin a chamber in the lower portion there# of an'( having an enlarged chamber in the upper portion thereof, an insulating sleeve arranged in the said upper chamber and terminating -at a point above the lower chamber, an insulating core arranged in said insulating sleeve and terminating at a point adjacent the lower end of said insuating sleeve, said insulating core being bored to receive the central electrode and provided in its lower portion with a chamber. a central electrode arranged in said insulating core, the said electrode being surrounded by said chamber, the outer lower wall of said central core and t-he inner lower ranged to form an air chamber surrounding Quid chambered portion of the insulating lower electrode being provided with a small bore extending from the end thereof at the said sparkigapand terminating at a 'point below the same in such manner as to provide. a passage through the same, said small bore being arranged in relation to the end of the central electrode so as to draw liquid therefrom into the said small bore by capil-l larv attract-ion to break a bridgeacross the said spark gap.'means for introducing a draft of atmospheric air on the spark gap, means for packing the central electrode, irisulating sleeve and insulating core. and means -for securing the partsl within the metal shell. v'

'14. A spark pl ug comprising a metal shell having a Chamber in the lower portion thereof and having an enlarged chamber in the upper portion thereof, an insulating Tse" arranged in said enlarged chamber and .er-

wall of saidv insulating sleeve being uron the spark minating adjacent the end thereof, the diameter of said insulating sleeve being less electrodes, means than thefinternal diameter of said enlarged ehamberffso as to-provide an air chamber surrounding-said insulating sleeve between said insulating sleeve and the inner surface vof the metal shell, an insulating core arranged in said insulating sleeve and extending down into the same, the external diameter of fsaid;-insut1`ig'core being less than the internal diameter of the insulating sleeve so as to provide an air chamber surrounding said insulating core bet-Ween said insulatingr core and the said insulating sleeve, a central electrode Within said insulating core, said insulating core being provided in its lower portion with a chamber surrounding said central electrode, alotver e1 'actrode having its end arranged in relation to the said central electrode so as to provide a spark gap between the two electrodes, means for introducing a draft of atmospheric air on the` spark gap, and means in the said lower electrode to draw a bridge of liquid from the said upper electrode to break said bridge at the said spark gap Ly capillary attraction.

15. A spark plug comprising a metal shell hav'ng a chamber in its lower portion and having an enlarged chamber in'i'ts upper portion, an insulating sleeve arranged in said enlarged chamber to provide anr air chamber surrounding said insulating sleeve between said insulating sleeve and the wall of said enlarged chamber, an insulating core arranged in said insulating sleeve to provide an air chamber surrounding said insulating core between said insulating core and the wall of said insulating sleeve, a central electrode arranged in said insulating core, a lower electrode having its end arranged in relation to the end of the central electrode to provide a spark gap, means for introducing a draft of atmospheric air gap to cool the electrodes, and means at the spark gap for exerting on a liquid bridging the spark gap a capillary attraction sufficient to break the bridge.

16. A spark plug comprising a metal shell having a chamber in the lower portion thereof and an enlarged chamber in the Lipper portion thereof, an insulating core, means for insulating said core from the metal shell. saidcore being arranged in such manner as to provide an air Vchamber surrounding thesame, the said insulating means being arranged in the metal shell in such manner as to provide an air chamber surrounding said insulating means between said insulating means and the metal shell, a central electrode arranged in the insulating core and insulated from the metal shell by said insulating core and said insulating means, a lower electrode having its end arranged in relationto the end of the lcentral electrode so as'to provide a spark gap between the two for introducing a draft of atmospheric air on the spark gap to cool the electrodes, and means for exerting a capillary attraction at the end of one electrode to break a bridge of liquid across the said spark gap.

17. A'spark plug comprising a metal shell having a chamber in the lower lportion thereof and having an enlarged chamber in the upper portion thereof, a central electrode within said metal shell, means for insulating said central electrode from the metal shell, said insulating means comprising a plurality of air chambers Within the same and lated between the said central electrode and the metal shell, a lower electrode having its end terminating in relation to the end et the central electrode so as to provide a spark gap between the two elecas to provide a spark gap between the two electrodes, one of said electrodes being provided with a small bore `extending from the spark gap end thereof and terminati terinediate said spark gap end and the other end of the electrode to provide an open passage through the same, said small bore being arranged in relation to the end of the first i mentioned electrode so as to exert a capillary attraction for liquid bridging the spark gap to break the bridge, an means for intro during at the spark gap a draft of atmospherie air to clean and cool the points of the electrodes.

19. A spark plug eomprismg two electrodes, one of which is provided with an oll drip near the end thereof to prevent an accumulation of oil at the point thereof, and means for exertingr a eapillaryatt-raction at one electrode suicient to break a bridge of v liquid connecting the electrodes.

' 20. A spark plug c .mprismg two electrodes, one of which is irovided with an oil drip near the end thereof to prevent an accumulationof oil at the point thereof, means for breaking a bridge of liquid connecting the electrodes, and means for introducing a draft of atmospheric air at the to eoolthe points of the electrodes.

21. A spark plug comprisingametal shell, an electrode within the same, means for insulating the electrode from the metal shell, a fellow electrode arranged in relation to the first mentioned electrode so as to pro- Spark gap vide a spark gap7 and means; for exerting acapillary attraction for liquid at theendiof one electrode to break a bridge of liquid at the Spark gap; said means being positioned to drain excess liquid therefrom by gravity.

22. A spark lng having electrodes ar.- ranged in relation to each other so as to provide a spark/gap between the electrodes, and ,means for.) exerting a capillary attraction. for liquid at one electrode suflicient to break *bridge of-lquid across the spark gap, said 'means being positioned to drain excess liquid therefrom by gravity.

23. A spark plug` comprising a plurality of electrodes arranged to form a spark gap, and meansl at the spark gap for exerting on a liquid bridging the spark gap al capillary attraction stilicient to break the said bridge, said means being positioned to drain excess liquid therefrom bv gravity.

In testimony whereof, I alix my signa-l ture, in presence of two witnesses.

CHARLES HUGH DUFFY.

Witnesses:

T. P. BRUT,

C. MAE GOULD.

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