US2260399A - Spark plug - Google Patents

Description

Oct. 28, 1941. PETERS 2,260,399

SPARK PLUG.

Filed April 19, 1940 VENTOR I IN NELWLLE E PETERS 7 BY HENRY K. KING Maw Patented Oct. 28, 1941 UNITED STATES PATENT OFFICE Application April 19, 1940, Serial No. 330,5d6

10 Claims.

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) This invention relates to an improved spark plug, and specifically to a spark plug having a cause pre-ignition and without the electrical re-' 10 sistance becoming low enough to cause a shorting of the plug to ground. Reliable firing and--- long life is reasonably assured if a low temperature of the spark plug can be maintained.

It is anobject of this invention to provide a 15 spark plug utilizing the series gap principle and so constructed as to permit its use in modern high output engines.

It is a further object of this invention to provide a spark plug so constructed'that the tem- 20 perature over all portions of the plug will be maintained at'a low temperature under severe operating conditions.

It is a still further object of this invention to provide a construction which will permit the use 2 of smaller diameter plugs with a consequent increase in thermal eiliciency, but with no loss in mechanical ruggedness and strength.

It is well known that in a laminated mica core Fig. 3 is a view similar to Fig. 1, showing second embodiment of the invention; and

Fig. 4 is an enlarged view of a fragment of Fig. 3, showing the details of the lower end of the plug.

Referring now to the embodiment shown in Fig. 1, the plug is built up around the central spindle shank I, extending longitudinally thereof. A mica cigarette 2 surrounds the spindle shank throughout its length and protrudes for a certain distance below its lower end. A metal shell 3 contains the spark plug assembly. The upper portion of this shell is thin walled and spaced top of the shell. This space may be filled with a pile of mica washers, the upper end 8 of the shell 3 being spun over to maintain them in place. The space between the inner cigarette 2 and the outer cigarette 6 is filled with a pile of mica washers 2|, the upper end of the spindle shank I being flanged outwardly at 9. The mica washers 1 may be omitted, if desired. The thickened porconstruction the interspersing of metal washers 39. tion 4 of the shell is screw threaded to fit the between the mica washers provides an increased thermal conduction from the surface of the core in contact with the flames to the center shank which carries the heat away, but in such constandard threaded hole in the engine cylinder.

The lower end of the shell is partially closed by a member Ill having a hole extending through its center. Between the lower end of the spindle struction care has always been taken to prevent '88} shank I and the member I0 is located an aselectrical flashover, due to the use of the metal washers, and the regular spark gap was provided elsewhere. of gaps between pins, rings, or other intermediate characteristics. However, such devices are subject tolocal overheating and cause pre-ignition in high output engines. The device of this inven- 'tion successfully combines the advantages of both types and eliminates some of the electrical disadvantages of the parallel gap type while eliminating the thermal disadvantages of the series p yp Referring now to the drawing:

Fig. 1 is a cross-sectional view of one embodi- 0 and the cigarette 8. Into this space an insulating ment of the improved spark plug of this inven-' tion, taken along its longitudinal axis.

Fig. 2 is an enlarged view of a fragment of Fig. 1, showing the details of the lower end of the spark plug.

It is also well known that a series v metal washers I2. "metallic paths, gives certain desirable electrical- 9. central hole through each of the mica. washers sembly of washers forming a series of spark gaps. The assembly consists of a series of mica washers I I, between which are interspersed a series of It will be noted that the is of a larger diameter than that through the metal washers, thus providing a series of air gaps bridging the distance between the lower end of the spindle shank and the member I0, across 45 each of which sparking will occur.

The mica washers fit snugly against the cigarette 6. However, the outer diameter of the metal washers is small enough that a considerable annular gap is left between each metal washer compound I3 is placed. The lower outer corner of each metal washer is rounded at I4 to increase the distance between this portion ofthe washer and the upper corner of the adjacent at this edge, thus preventing the occurrence of any sparking at this point. The upper outer corner of each metal washer is smoothed oil and siightly rounded, so that the upper surface of v the washer is flat so as to provide the maximum amount of bearing surface for the superimposed mica washer, thus preventing breakage of the mica washer.

In the second embodiment of the invention shown in Figs. 3 and 4, the central spindle shank I extends below the lower end of the shell and terminates at its lower end with a strong outwardly turned flange l5. The upper portion of the plug assembly is constructed in the same manner as previously described. The lower porfiguration found in the outer portions of the metal washers of the previous embodiment is here found in the inner portions of the washers. The outer diameter of the metal washers in this embodiment is larger than that of the corresponding mica washers. The mica washers fit snugly against the inner cigarette 2, whereas the central hole. through each of the metal washers is large enough to leave a central annular space between the cigarette and the metal washer, which space is filled with insulating compound l3, as in the previous embodiment. The lower inner edge ill of each metal washer is rounded off in the same manneras was the lower outer edge I in the previous embodiment.

The upper metal washer of the series fits snu ly against the metal of the shell to provide a good grounding connection.

Fitting snugly down upon the assemblage of washers is a conical member I! which fits with a driving fit around the inner cigarette 2.

was formed within the lower portion 1 of the shell.

' If desired, the pile of mica washers I may be omitted as well as the upper portion of the shell, the shell being reduced in this case to the lower part 4, which merely acts as a bushing and a means of connecting the plug to the cylinder wall 2|. I

The metal washers must resist the temperatures and gases inthe engine, but they should also possess sufliciently good heat conductivity and have such a coefficient of expansion that upon heating of the sprak plug good thermal contact will be maintained along the directions shown by the arrows in Fig. 4. In other words, the metal washers should have a coefficient of expansion relative to that of the surrounding mafactured and/or used by or for the Government of the United States of America for governmental The member I! fits into a correspondingly shaped repurposes without the payment of any royalties thereon or therefor.

We claim: 1. A spark plug assembly comprising a central spindle shank, a mica sheath completely enclosing the side Walls of said shank, an outwardly flanged head formed on the lower endof said shank, a plurality of ring shaped terminalscarried by the lower part of said shank, a plurality of insulating disks separating said terminals and spacing them to form spark gaps between each pair of adjacent terminals, a cone-shaped metal bushing fitted snugly around said mica sheath and against the upper one of said terminals, a metal bushing fitting snugly over said coneshaped bushing and threaded for connecting said assembly to the cylinder wall of an engine, a column of mica washers fitted snugly around said sheath and down upon the upper surface of said outer bushing and meansbinding all the above mentioned'elements into a compact unit.

2. A spark plug assembly comprising a central spindle shank, a mica sheath completely enclosing the side walls of said shank, an outwardly flanged head formed on the lower end of said shank, a plurality of ring shaped terminals carried by the lower part of said shank, a plurality of insulating disks separating said terminals and spacing them to form spark gaps between each pair of adjacent terminals, a cone-shaped metal bushing fitted snugly around said mica sheath and against the upper one of said terminals, a metal bushing fitting snugly over said coneshaped bushing and threaded for connecting said assembly to the cylinder wall of an engine, a column of mica washers fitted snugly around said sheath and down upon the upper surface of said outer bushing, and an outwardly turned flange formed upon the upper endof said shank and binding all the above mentioned elements into a compact unit.

3. A spark plug assembly comprising a cylindrical shell, a central spindle shank extending longitudinally of said shell and terminating short of the lower end thereof, an insulating sheath enclosing the side walls of said shank, a plurality-of ring-shaped terminals contained in the lower end of said shell and beneath said shank, a plurality of ring-shaped insulating disks interspersed between said terminals, said disks having larger central holes than said terminals and se ing to space said terminals apart so that sp rk gaps are formed. between the adjacent edges of the central holes of adjacent terminals, and means insulating "said terminals from said shell.

4. In a spark plug, a terminal assembly comprising a plurality of ring-shaped metal terminals of generally rectangular cross section, a plurality of ring-shaped elements of insulating material, each separating a pair of said terminals by a distance sumcient'to create an eflicient 'spark gap between them, the diameter of the hole in each of the ring shaped elements being larger than that of each of the ring-shaped terminals, whereby an air-gap will be formed between the central portion ofadjacent terminals, an insulating sheath surrounding said terminals and elements and'annularly'spaced from said terminals, at least one of each pair of adjacent outer edges of each adiacent pair of terminals being rounded off and'insulating' material filling said annular space and means binding saidassembly together into a compact unit.

5. In a spark plug, a terminal assembly comprising a plurality of ring-shaped metal terminals oi generally rectangular cross section, a plurality ct ring-shaped elements of insulating material, each separating a pair of said terminals by a distance sufllcient to create an efllcient spark gap between them, the outer diameter of each oi. said terminals beinggreater than that of said ringshaped elements, whereby an air-gap will be formed between the peripheral portions of adjacent terminals, means'passing through each of said elements and terminals and binding the whole assembly into a compact unit, the inner diameter of each of said terminals being sufllcient to leave an annular space between it and said binding means, at least one of each pair of adjacent inner edges of each adjacent pair of terminals being rounded off and insulating material filling each of said spaces.

6. In a spark plug, an outer shell having a partially closed bottom formed with a central aperture, a lining of insulating material on the inside adjacent points on said adjacent terminals.

01' said shell, a terminal assembly carried therein, said assembly comprising a plurality of ring-, shaped metal terminals, a plurality of ringshaped elements of insulating material, each separating a pair of said terminals by a distance suflicient to create an efflcient spark gap between them, the diameter of the hole in each of the ring-shaped elements being larger than that of each of the ring-shaped terminals, whereby an air-gap will be formed between the central portions of adjacent terminals, the outer diameter or each of said ring-shaped terminals being such' as to leave an annular space .between said terminal and said lining, the lower outeredge of each of said terminals being rounded ofl, an insulating substance filling said annular space and means holding said terminals and said elements into a compact unit.

7. In a spark plug, a central spindle shank, a

terminal assembly comprising a plurality 'of ring- 40 shaped terminals, a plurality oi! ring-shaped elements of insulating material, each separating a pair of said terminals by a distance sumcien't to create an efllcient spark gap between them, the

outer diameter of each of said terminals being i terminals and elements, a sheath of insulating material interspersed between said spindle shank and said terminals and elements, the diameter of the hole in each of said terminals being such as to leave an annular space between said sheath and said terminal, the lower inner edge of each of said terminals being rounded oil, an insulating substance filling said annular space, and means comprising means on said spindle shank holding said terminals and said elements into a compact unit.

8. A spark plug terminal, comprising a metal annulus having a cross-section presenting two angular outer corners and at least one rounded inner comer, said cross-section being so shaped that when a plurality of, said terminals are stacked and separated from each other by waters of insulation, the distance between the adjacent outer corners of adjacent terminals will be at least as short as the distance between any two 9. A spark plug terminal, comprising a metal annulus having a cross-section presenting two angular inner corners and at least one rounded outer corner, said cross-section being so shaped that when a plurality of said terminals are stacked and separated from each other by waters of insulation, the distance between the adjacent inner corners of adjacent terminals will be at least as short as the distance between any two adjacent points on said adjacent terminals.

10. A spark plug assembly comprising a central spindle shank, a'mica sheath completely en- 'closing the side walls of said shank, an outwardly flanged head formed on the lower'end 01' said shank, a plurality of ring-shaped terminals carried by the lower part of said shank, a plurality of insulating disks separating said terminals and spacing them to form spark gaps between each pair of adjacent terminals, a cone-shaped metal bushing fitted snugly around said mica sheath above said terminals, 9. metal bushing fitting snugly over said cone-shaped bushing, a column of insulation fitted snugly around said sheath and down upon the upper surface of said outer bushing and means binding all the above mentioned elements into a compact unit.

MELVIILE F. PETERS. HENRY K. KING.

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