US2448193A - Spark plug - Google Patents

Description

Aug. 31, 1948. D. E. REPLoGLE snnx gwn Filed Jan. 25. 1944 IIIIIIIIIII4IIJ f fin/474124,

INVENTOR.

Patented Aug. 31, 1948 UNITED STAT-ES PATENT GFFICE SPARK PLUG Delbert E. Replogie, Ridgewood, N. J., assignmto Global Spark Plug Co., Paterson, N. J., a corporation of New Jersey Application January 25, 1944, Serial No. 519,670

struction of the spark plug and a step in the method of formation;

Fig. 2 is a similar view illustrating a subsequent' step in the process of formation of this spark plug;

Figs. 3 and 4 are 'sectional views of a modied method of manufacture of a spark plug; and

Fig. 5 is a vertical sectional view of a special formation of the central part of the shell of the spark plug.

The spark plug of this invention comprises an outer shell IIJ preferably of cold rolled steel, an insulator II at the lower portion of the shell, a molded insulation I2 filling the shell above the insulator II, and a. central electrode I4 preferably of molybdenum with an end or sparking point I5 of nickel or similar resistant metal.

The shell I has a tapered seat I6 for the insulator II, a bushing I1 intervening between the insulator and the seat and being composed of copper or other soft metal providing an intimate sealing contact with the cooperating surfaces of the seat and insulator.

The insulation I2 is molded in place under heat and pressure in a manner giving a thorough leakproof seal While at the same time rigidly fixing all of the parts in place and insulating the rod or electrode I4 from the Ashell I0.

On the outside the shell I0 is provided with flange I 3, nut portion i9 and threads 2li for the fastening of the spark plug in place in the engine.

The sparking end of the plug is provided with a recess 22 around the lower end 23 of the insulator II and a plurality of sparking points 24 are arranged around the end I of the central sparking electrode.

The top of the shell I0 is provided with an overhangin-g flange ring forming a ledge around the recess 3| for the reception of the terminal connection, the inner end of which reaches and contacts with the head 32 at the top of the central electrode I4 at the bottom of 1 Claim. (Cl. 12S-169) the recess 3|. Screw threads 33 are cut around the outer end of the shell above the shoulder 34 to cooperate with the outer attaching sleeve of the standard terminal fitting in recess 3| and held therein by the screwing of the sleeve on to the threads 33.

As shown in Fig. 5 the head 320 on the electrode |40 may be specially shaped m'th a neck portion 35 between the ends 36, 31, the upper surface of the latter forming the bottom of the recess 3|0. The shell IllII may have its central portion 38 bulged outward in globular formation as shown to give additional thickness of insulation between the head and the -shell and to aid in anchoring the molded insulation |28 securely in place.

In the formation of the spark plug the shell III is assembled with the liner or bushing I1 in place on the seat I6 and insulator I I pressed into place. The rod I4 is then inserted with its lower end part way in the bore of the insulator (Figs. 1 and 3). The insulation I2 for molding is then supplied, preferably in powdered or granular form, substantially filling the shell I0 above the insulator II, and a plunger 40 having a sliding fit in the flange ring 30 is forced downward into the shell to compress the insulation, the whole plug with the insulation being heated to a high temperature to render the insulation I2 plastic and moldable. A's the plunger 40 descends, the pressure increases and the rod I4 moves downward with the plunger, the now plastic insulation flowing into all cracks and crevices of the shell and insulator parts and upward around the plunger 40 and under the flange ring 30 as indicated in Fig. 2. During this plunger action the lower end I5 of the rod I4 protrudes outward below the lower end of the spark plug an amount dependent upon the length of movement of the plunger 40, and at the end of the plunger movement the molded insulation I2 has completely and tightly filled the entire space within the shell and has formed a permanent leakage-proof seal. The plunger 40 is then removed leavin-g the recess 3| with the contact head 32 at the bottom and the lower end I5 of the central electrode I4 is cut off about even with the sparking points 24 as shown for instance in Fig. 5.

The cooling of the molded insulation I2 hardens the insulation into solid glassy formation, all of the parts being tightly bound together. Preferably, the outer shell I0 is of material, such as cold. rolled steel, having a. relatively high coemcient of shrinkage on cooling in comparison to aus, los

the material molybdenum, for instance, of the central rod M, the shrinkage of the molded mass i2 being intermediate between these so that the sleeve of molded material l2 tightly grips the rod M and in turn is tightly gripped by the shrinking of the shell i0.

As illustrated in Figs. 3 and (i, the molded plunger 50 may b of hollow formation with o, bore Iii sliding over the rod 0i! forming the central electrode and the periphery of the plunger 50 having a sliding it within the flange ring lit. The further depression of the plunger E0, for instance to the extent shown in Fig. 4, Will cause the heated insulating material i?. to ovv into all parts of the interior of the shell, and at the se time the electrode 03 will move downward with said material, in this case being received in the template @5, limiting its downward movement and positioning it relative to the sparking points 20. The plunger 00 isthen removed and the recess 0o is formed similar to the recess 0i to receive the conventional terminal connection.

The molded insulation i?. is preferably of the glass bonded mica type as set forth for instance in U. S. Patent 1,795,200 and Re. Patent 15,727 to Crossley or U. S. Patent 2,032,239 to Wedloclr, as

this will give a rrn bonding and sealing e`ect while at the same time providing a, superior type of insulation.

The completed sparlr plug is strong and durable, effectively insulating the central electrode l0 and also absolutely tight against the leakage of pressure through the plug so es to be permanently leakproof.

I claim: v

A shielded spark plug comprising a tubular ,rn/etal shell having one end portion provided with a seat for an insulator and the other end portion of cylindrical form with'an intermediate centralportion bulged outward to larger diameter in globular formation. a tubular insulator on said seat, an electrode passing through said insulator and connected at its inner end to a head member extending into said globular formation and having an intermediate narrow neck portion, and a molded insulation filling said globular formation and said shell behind said insulator and around said neck portion oi said head to retain said insulator against its seat and lock said head in place in said globular formatlonand retain the parts against relative axial movement in either direction.

DELBERT E. REPLOGLE.

REFERENCES (CNED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 960,784v Anderson Aug 0, 1910 1,361,562 Schmidt `met. 2, 101? 1,300,232 Landa May i0, 1020 1,035,100 Littleton July 12, 1027 1,848,312 Bruzzone Mar. 8, 1932 1,369,133 Bevers et al July 26, 1932 1,074,208 Case Sept.' 10, 1934 2,240,415 SchWartZWnlder et nl.-- July 1941 2,250,810 `Rabezzena et al Oct. 14, 1041 FQREIGN PA Number Country Date 3,085 Great Britain Feb. 21, 1000 106,037 Australia Mar. 16, 1030 230,037 Great Britain Aug. 2'?, 1025 France Apr. 27, 1022

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