US2135240A - Spark plug - Google Patents

Description

Nov. 1, 1938. G PAULS'QN 2,135,240

SPARK PLUG Filed Sept. 12,, 1932.

' Fig.1.

1 v I INVENTOR- Patented Nov. 1, 1938 UNITED STATES SPARK PLUG.

George M. Paulson, New York, N. 1., assignor to The B. G. Corporation, New York, N. Y., a corporationof New York Application September 12, 1932, Serial No. 632,745 10 Claims. (01. 123-169) This invention relates to spark-plugs, and more especially to spark-plugs for use in aviation engines.

The object of the invention has been to provide a spark-plug which would give. superior, re-

liable and long service under the .conditions to. which aviation spark-plugs are subjected, and even when very high compressions, with extreme super-charging, are restarted to.

A further object has been to provide an"aviation spark-plug which, under most difficult conditions, would not heat up to the point of causing pre-ignition.

A further object has been to provide a. construotion which would protect the core and keep it relatively cool under such conditions.

A particular object of the invention is to provide an improved electrode construction or combination which gives the maximum length of service without adjusting or re-setting the gap. A further object is to provide a construction with which it is easyto adjust the gap when it does eventually burn away sufliciently to require resetting, and which can be re-set repeatedly, for

successive long periods of service.

Another particular object is to provide the maximum amount of metal to burn away at the gap and-a maximum amount of heat conduction to the body or shell of the plug.

Another object is to provide a spark-plug having the maximum amount of area ofmetal at the.

gap and which can stfll be easily adjusted.

Another object is to provide the maximum amount of metal at the gap with a comparatively small amount of metal exposed to. the high cylinder temperatures. v j

A-furtherobject is to provide a construction with which there is no danger of longitudinal expansion of the-electrode elements closing the 40 gap suiiiciently to produce a short circuit.

- Still another object'is to provide a construction which promotes the flow of gases intoand. out of the plug.

Another object is to provide a construction which is easy and economical to manufacture.

The invention relates to the type of sparkplug having several electrode prongs-extending from the body or shell into proximity "to a central electrode, and more especially to the kind of construction in which these prongs are cut or formed from a disc or baflle of a metal or alloy which is resistant to the spark in the presence of cylinder gases, this baiiie being united to the shell, which is usually of a different metal. The

is prongs or pronged baiiie provide a plurality Of spark gaps, and'by partly closing the chamber of the shell, into which the core projects, and by carrying heat off into the shell protect the core from too intense radiant heat and shield it more or less from lubricating oil. The shell electrode- 5 should not substantially close the inner end of the core chamber, since a comparatively large orifice area aids in preventing overheating. The construction disclosed herein provides ample orifice area. By properly proportioning the solid 10 area of the baffle ongroup' of prongs, the spaces between the prongs and the amount and distribution ofmetal in the baflle, and if there be enough heat conduction from the bailie into the shell, it is possible to shield the coresufilciently from 15 temperatures on the order of 2600"F. or higher, and still enable the multiple gap electrode to function satisfactorily and not superheat itself or the plug to a point of failure. The electrode. baflle, or the group of prongs, must be heavy in order to stand up and save itself and the'core from excessive heating, but not so heavy as to be an accumulator of heat.

In a prior application, now Patent No. 1,959,639,1ssued May 22, 1934, I have set forth the discovery of the cause of'failure of electrode baflie spark-plugs of ordinary construction when I subjected to severe conditions in aviation engines, and a solution of the "difliculty, which was to unite the baille to the shell by a thorough, fused joint. The prior practice was to clamp the edge of, the baflie in a groove of the shell by crimping the end of the shell under the baiiie, a plan which apparently produced a perfectlysolid construction, but which, I became convinced, di permit gases to enterthe joint and cause dete oration, reducing the capacity of the shell to draw oil. heat from the baflle until, after more or less service, the baflle would overheat sufliciently to cause pre-ignition, this in turn causing the .sparking 40 points to burn away quickly.

The'constructionclaimed in my former appli v cation is embodied in the spark plug disclosed herein, and is highly important incombination with thepresent improvements.

The other features of this invention relate'to the form and relation of a central electrode head and the opposed or surrounding electrode prongs. Briefly, the head of'the spindle or central electrode is rather like an inverted truncated cone, with its sides preferably incurved at the sparkg'ap in axial planes,'while the stout prongs; in stead of extending radially inward, or in a cupwise manner, from the baflie or shell, are directed inward and steeply downward and preferably on a convex curvature, substantially paralleling the lines of the head. The result is to produce a much deepened or vertically extended multiple sparkgap, with so much metal and surface at the gap both to the presence of a large amount of 'metal to burn away very slowly and to a maximum amount of heat conductivity.

Other advantages of the invention have already" been indicated, and to these should be added the .fact that the construction makes possible a spindle head of minimum length.

In the accompanying drawing, illustrating a plug the sparking surfaces of the prongs are conpreferred embodiment of the invention:

Fig. 1 is aview-of the spark-plug with the lower part in section and the rest of the plug in elevation; and i Fig. 2 is a bottom plan view lookingjat the innor end of. the plug.

The body or shell of the spark-plug is designated by the reference character 2, and 3 'is the central spindle. The spark-plug is preferably-and typically of themica-insulated class. .A known construction is shown in which the spindle is surrounded first by a sleeve 4 of rolled mica, this sleeve being compressed against the spindle by means, including a nut 5, to produce a leak-tight dam, and in which a stack 6 of mica washers in the chamber 1 of the plug is held under compression between the head 8 of thespindle andan abutment in the shell, and another stack 9 of mica discsis held under compression between the nut and the top piece In over which the upper end of the spindle is upset.

-' Heretofore the electrode or sparking end of the spindle of a spark-plug has usually been a com paratively narrow cylinder, and in a construction such as illustratedthe head or lower portionof the spindle has been rounded inward below the shoulder, with the cylindrical electrode projection extending downward from the convexity.

The spindle head 8 of the spark-plug shown in the drawing is relatively short as compared with truncated lower end ll.

a head and pin-like sparking projection such as shown in my Patent No. 1,959,639, for example,

and it tapers downward from a broad base to a The precise form may be varled,bu't the best results are secured by concaving the lines I! of the sides'of the head coextensively with the deep spark-gap l3. For the short distance above the gap, the curvature M of the head is preferably convex, this reverse curvature being advantageous.

The electrode baiile l5 may be understood to be of a nickelmanganese alloy or some other shell, and at the present time being more conmetal or alloy resistant to the spark, and which It. is

can be bent repeatedly without injury. placed in an open bottom seat in the lower end of the shell or body 2 and is secured in place by a fused bend it as in my patent aforesaid. This.

. bond may be made by welding. or brazing, the "latter bond, which involves a third metal, being adequateto resist the heat and insuring perfect heat conductivity as between the baiiie'and the venient for production purposes than welding.

f This disc and its set ofv sparking prongs 26 are of considerable thickness, a thickness on the order I of .080" being sufllcient (this being given by way of example). The prong'sare of substantial width and are preferably three or more in number (four being very satisfactory), symmetrically disposed about the center. The openings I1 between the prongs are relatively large. In the end view of the plug the prongs appear to be substantially radial, but seen in vertical section they turn downward quite precipitously, bringing their blunt end faces even with the end face ll of the.

head and their sloping inner side surfaces l9 into opposition to the sides J! of the head across the 'spark-gaplil. The prong surfaces I 9 are preferably conve'xly curved in axial planes on a curvature substantially corresponding to that of the lines l2 of the head, so that the spacing is virtually uniform throughout a gap of very considerable depth.

In planes at right angles to the axis of the the shell, and obviously the improvements may be applied to the mechanically locked or crimplock type of baiiie construction, with advantages as compared with prior practice but with considerable sacrifice of benefits as compared with the preferred embodiment of this invention.

v While a spark-plug constructed in accordance with my invention has been described in detail it will be understood that various changes may be made without departing from essentials.

I claim: 1. A spark-plug having a shell, a downwardly tapering central electrode, and a set of massive prongs united with the lower end of the shell and constituting ground electrodes, said ground elec- I trodes extending inward from the shell and being directed steeply downward around the central of the central electrode, so that there is a deep and large spark gap surface area between the central and ground electrodes, with a large se'ction in the ground electrodes to carry off heat into the shell, the ground electrodes being adjustable by-deflecting their downturned portionsinwardly, so that in such adjustment the large spark gap surface area may be maintalned .saidground electrodes being formed in a bailie which is cutout between the prongs, the periphery of said baflie being united to theshell by a fused, heat-conducting bond.

2. A spark-plug having a shell, a'downwardly and concavely tapered central electrode, and a set of stoutprongs united with the lower end of the shell and constituting ground electrodes, said ground electrodes extending inward from the shell and being directed steeply downward in a convex curvature and having broad inner surfaces which substantially follow the curvature of the central electrode, the formation of said ground electrodes and their relation to the central electrodes being such that there is a large spark gap surface area between the central elec-- trode and the ground electrodes. a

3. A spark plug having a shell, a downwardly and'concavely tapered central electrode, and a set of stout prongsunited with the lower end of the shell and constituting ground electrodes, said I and extending inward having inner side surfaces cross-axially curved concentrically with and extending downwardly spindle head to circumferen-' tially and, longitudinally conform thereto and ground electrodes extending inwardffrom the shell and being directed steeply downwardin a convex curvature which substantially follows the curvature of the central electrode, the formation of said ground electrodes and their relation to the central electrodes being such that there is a large spark gap surface area between the cen-, tral electrode andthegroundelectrodes, the inner side surfaces of said prongs being convexly curved in axial planes and concavely curved-in transverse planes.

1 4. A spark plug having a shell, a central electrode with a substantially cone shaped head and a set of massive prongs united with the lower end of the'shell and constituting ground electrodes, inner side surfaces of to the shape of the center electrode head, so that there is a deep and large spark gap surface area between the center and ground electrodes, which said gap may easily and by a narrow strip or wire gauge feelers, with a large section in the ground of! heat into the shell, the ground electrodes being adjustable by deflecting their down turned portions inward, so that in such adjustment the large spark gap surface area may be maintained' 5. A spark plug having a shell,-a downwardly and substantially uniformly tapering center electrode head and a set of prongs united with the lower end of the shell constituting the ground electrodes, 'saidgrou'nd electrodes being flattened from the shell and being shaped concentrically around and directed down the tapered center electrode head so as to furnish large surface areas for the spark gap and a large section in the electrodes for conducting heat to the shell, as well as to be flexible enough for adjustment of the gap. I

6. A spark plug having a shell, a downwardly tapering circular spi dle head, and a set of stout ground electrodes su ported by the shell and extending inwardly and downwardly therefrom and along the circular collectively surround the greater part of the circumference of thecomplementai y-portion of the spindle'head at the gap, so as to furnish a plu rality, of large surface areas for the spark gap,-

with a large section in each ground electrode for conducting heat' to the shell, said ground electrodes being adjustable by bending them radially of the plug, so that, by such adjustment, thelarge surface areas for the spark gap may be maintained.

. 7. A spark plug having a shell, a-downwar'dly tapering circular spindle head, and a set of stout,

ground electrodes supported by the shell and extending inwardly and downwardly therefrom and having inner side surfaces cross-axially curved concentrically with and extending downwardly.

along the circular spindle head to circumferentially and longitudinally conform thereto, with the said prongs conforming 1 accurately be measured electrodes to carry spark gap, with a large section in each ground constituting ground I electrodes, said gr able by deflecting their downturned portions in- "is out at least the lower end portions of said surfaces collectively surrounding the greater part of the circumference of thejuxtaposed portion of the spindle head,-so as to furnish a plurality of large surface areas for the spark gap, with a large section in each ground electrode for conducting heat to the shell, said ground electrodes being adjustable by bending them radially of the. plug so that, by such adjustment, the large surface areas for the spark gap may be maintained.

8. Aspark plug having a shell, a downwardly tapering circular spindle head, and a set of stout ground electrodes supported by the shell and ex- I tending portions thereof, inner side surfaces cross-axially curved concentrically with and ex-' tending downwardly along the circular spindle head to circumferentiallyand longitudinally conform thereto, with at least the lower end portions of said surfaces collectively surrounding the greater part of the circumference of 'the juxtaposed portion of the spindle head, so as to furnish a plurality of large surface areas forthe electrode for conducting heat to the shell, said ground electrodes their downwardly extending portions radially of the plug so that, by such adjustment, the large surface areas forthe spark gap may be main'. tained. I

9. A spark-plug having a shell, a downwardly tapering central electrode, and a set of massive prongs unitedwiththe, lower end of the shell and mm electrodes extending inward from the shell, and being directed steeply downward around the central electrode and so formed that their inner side surfaces substantially follow the lines ofthe sides of the central, electrode, so that there is a deep and large spark gap surface area between the central and ground electrodes, with a large section in the ground electrodes to carry off heat into the shell, the ground electrodes being adjustwardly, so that in such adjustment the large spark gap surfacev area may be'maintained, said ground electrodes being formed in-a baflle which out between the prongs, the said baille being supported at its-periphery adjacent the, lower end of the shell and making good heat-conducting and electrical connection therewith.

10. A spark-plug having a shell, a downwardly tapering central electrode head, and a set of prongs united with the lower end of the shell furnish large surface areas being adjustable" by bending constituting ground electrodes, said ground elec- I I the ground electrodes being likewise of large section for conduction of heat to the shell, yet flexible enough for adjustment of the gap.

GEORGE M. PAUL-SON.

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