US2208668A - Aviation spark plug - Google Patents

Description

July 23, 1940. J. DEVINE 2,

AVIAT ION SPARK PLUG Filed Feb. 16, 1940 l N VENTOR.

Patented July 23, 1940 UNITED STATES PATENT OFFICE 4 Claims.

My invention relates used in aeroplanes. I

The fundamental object of this invention is most particularly directed to the novel means of regulating the flow of heat, and to maintain a normal operating temperature of the plug under all conditions in low and high compression motors. In this connection, I employ a construction for illustration, showing some features of my previous patent and pending patents for the purpose of better defining my invention and its relationship in connection with this construction.

In spark plugs used for aircraft engines, the lower end of the insulation surrounding the electrode and being directly exposed to the continuous explosive charge of the gas chamber, results in overheating of the insulation, causing the insulator to become partly conductive, thus electrifying the lower end of the plug and creating excessive heat in the gas chamber, while at the same time causing interferences with the proper flow of current. Likewise the uninsulated firing end of the electrode which is exposed to the gas chamber, adds additional heat, which often results in preignition of the gases in the cylinder head.

Much has been experimented with in connection with materials to be used forelectrodes from the standpoint of eliminating scaling, corrosion, and erosion, likewise, much has been experimented with electrodes from the standpoint of heat conduction.

I have found that the best results may be obtained by the use of a central electrode, being of an excellent heat conductor, having a slow oxidizing massive firing head and in which the lower end of the electrode above the firing head has a spiral worm cut around its shank, and either a filler of copper or any other filler of high heat conduction, and of differential expansion than the shank surrounding the spiral worm cut, and spaciously spaced apart in round relation to the main shank, forming only three, four, or five diagonal steps, will insure rapid heat conduction.

With this type electrode, the heat traveling the short spiral path of least resistance, conducts, transfers, and regulates the flow of heat through the insulator at a pace many times the speed of a straight shank encased in a copper sleeve in which the heat becomes stagnant and trapped between the insulator and the copper. invention, due to the higher heat conducting spiral filler spaciously spaced apart in the worm to spark plugs of the type cut of the shank, and in combination with the other illustrative features of this drawing from the standpoint of the unique method of sealing the plug without damage to the insulator by the easy spreading action of the annular housing member, and the sealing of the lower ends of the insulator in the electrode head, as in claim 4 of my previous Patent 2,098,934 which keeps the hot gases out of the lower end of the insulator. The plug will then automatically be free from excessive heat, leaving the spiral filler to act more or less as a heat distributor.

It is understood that the drawing is for the purpose of illustration only, reference being had for the purpose of this invention to the appended claims, and will describe only those parts of the plug as will be necessary to understand this invention.

Referring now to the drawing:

Fig. 1 is a central section of a spark plug in longitudinal central section embodying the invention in its preferred form.

Fig. 2 is a view taken on Fig. 1 showing a modified form of massive electrodes in gas and gap space relationship.

Fig. 3 is a section of the central electrode embodying the invention.

Referring now to Fig. 1, 4 is the central electrode made of pure nickel, 5 is the hollow square ground electrode also made of pure nickel, 6 shows the nickel firing head in gap space relationship as at l, forming a large uniform burning area to eliminate gap setting. 8 shows the spiral worm cut surrounding lower end of central electrode 4, 9 shows the high conducting filler which is mounted in by a heating process, or by a molding operation. III shows the spiral steps of the main electrode 4 spaciously spaced apart in round relation-to the worm cut 8 and filler 9, insulator ll surrounding lower end of electrode 4, and insulating washers surrounding lower end of insulator H. The lower end of the insulation II is securely wrapped in close contact with the spiral steps 8, l0, and filler 8, of th electrode 4, I3 is a recessed annular member surrounding the middle part of the insulator H, l4 shows the W shaped recess and the metal filler l5 which seals the plug against the leakage of gases by the easy spreading action of the W shaped recess ll of the annular member H.

The shell I6 is threadedly engaged with cylindrical nut 11. The annular member l3, and the wedge IS in the recess I4, is supported and held in place by the cylindrical nut ll. l8 shows the gas chamber, I9 shows the thread on the shell.

In Fig. 2, 20 shows the brazed corners of the square ground electrode 5 securely fastened to the lower end of the shell Hi. In Fig. 2, 2| shows the separate gas entrances relating to the lower end of Fig. 1, to eliminate fouling of the gap.

Having described my invention in connection with the accompanying illustrative drawing, I claim as new in connection with the cooling and regulation of heat for which I desire to secure by Letters Patent:

1. In combination a spark plug comprising a shell, a central electrode insulated from said shell by wrappings of mica around said electrode, and retention means comprising an annular means of high heat conducting metal interposed between said shell and said insulation, said central electrode having a sparking terminal cooperating with a ground electrode on said shell, and having on its lower portion a spiral square sectional strip of good heat conducting metal embedded therein, the pitch of said spiral being approximately equal to the width thereof, and flush with the surface of said electrode spiral and retention means, enabling a cooling of said central electrode.

2. In a spark plug a central electrode having a. sparking terminal cooperating in gap space with a ground electrode on said shell, said central electrode having on its lower portion a spiral square sectioned strip of high heat conducting metal embedded therein, the pitch of said spiral being approximately equal to the width thereof,

and diagonally in round relation to the spiral and flush with the surface of said electrode spiral,

' and fiush with said spiral strip and said electrode being of differential rates of expansion and heat conductivity, enabling a regulating and cooling means of said electrode.

3. In a spark plug a central electrode embodying around its gap end a shell having a hollow gas chamber, said central electrode having a sparking terminal in cooperation with a ground electrode on said shell, and having on its lower end above the sparking terminal a metallic spiral square sectioned strip of higher heat conductivity than the said sparking terminal embedded therein to quickly transfer and distribute the heat from said gas chamber.

4. In combination a spark plug comprising a shell, a central electrode insulated from said shell by wrappings of mica around said electrode and retention means comprising an annular member of high heat conducting metal interposed between said shell and said insulation, said central electrode having on its lower portion a spiral square sectioned strip of high heat conducting metal embedded therein, the pitch of said spiral being approximately equal to the width thereof, the surface of said electrode spiral, said central electrode having a sparking terminal cooperating in gap space with a ground electrode on said shell, and retention means in cooperation with said electrode spiral enabling a fast distribution and transference of heat from the said sparking terminal upwards and through the said insulation enabling a cooling of the plug.

JULIUS DEVINE.

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