US1790445A - Assiqnob to the stztt ignition comfany - Google Patents

Description

Jan. 27, 193 D. scHAAF SEAL FOR SPARK PLUGS Filed May 1'7, 1929 3mxnbr DOWNS SGHAAF G Patented Jan. 27, 1931 UNITED STATES PATENT OFFICE- DOWNB SCELAI', OF OOLUKBUS, OHIO, ASSIGNOR TO THE STI'IT IGNITION comm, I OF COLUMBUS, OHIO, A CORPORATION 01' OHIO smnroa srnzax rnues Application filed Kay 17, 1929. Serial No. 863,770.

According to the common practice at present the battery or generator electrode of a spark plug is mounted in a porcelain insulator, the sealing between the electrode and theinsulator being effected by means of a cement of silica and silicate of soda. The cement referred to contains more orless water and such a sealing is not uniformly successful because of the creepa e of the cement anda resultant leakage 0% cylinder gases and crackin of the porcelain.

It is therefore, t e aim of this invention to provide a seal that shall not be subject to such objections. Because the metal bismuth has the property of expanding when changed from a liquid to a solid state and because the melting point of that metal is 518 Fah. and such temperature is not reached in the porcelain insulator of a spark plug at the exposed portionwhere the seal is to be applied I use that metal or a suitable alloy thereof to effect the sealing.

In the accompanying drawings Figure 1 is a sectional view of the shell of a spark plug with the porcelain insulator containing my improvement shown in full. p, Fig. 2 is a sectional view of the porcelain insulator showing my seal applied to the electrode wire.

In the views 5 designates the metallic shell which is of ordinary form and construction; 6 the porcelain insulator, and 7' the electrode wire, the latter bein provided with an enlarged and threadetf end for the electrical connections.

On the electrode wire 7 just below the threaded end thereof I molda sleeve 8 of bismuth or a suitable alloy of bismuth. This molding is effected by pouring the molten bismuth or an alloy thereof into the insulator while the electrode is positioned therein.

The porcelain,-\in the instance shown is at its upper end and before baking formed with an internal threaded socket of larger diameter than the diameter of the wire of the electrode and into this socket around the wire the bismuth or alloy thereof is poured as before stated. However the seal may be ap lied inother obvious ways. The wire I at t e portion' wherethe seal is applied is roughenedor ment.

Particular advantages, among others, of a metallic seal such as described is that, first, it is gas'tight as compared with a ceramic seal, second, it remains in the position applied whereas a ceramic seal such as referred to creeps toward the nose of the insulator and on expansion at such point of the seal often causes cracking of theinsulator, third, economy of time and labor in manufacture of the seal.

A further decided advantage of bismuth as compared with the cement as the sealing material is that the metal has no corrosive effect whereas with cement the wire is sometimes destroyed and rendered useless by the corrosive action of the cement.

The' forms and assembling of the parts can be changed without departing from the gist of the/invention as claimed.

What I claim is:

1. The combination of a spark plug whose electrode and insulator are secured in gas tight relation by a bismuth seal.

2. The combination of a spark plug whose electrode and insulator are secured in gas tight relation by a bismuth seal located in ing of bismuth or an alloy thereof that ex- 1 pands on solidification.

DOWNS SCHAAF.

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