US1761865A - Spark plug - Google Patents

Description

June 3, 1930. G. H. E BERTHOLD SPARK PLUG Filed Feb. 26, 1927 ATTORNEY Patented June 3, 1930 UNITED STATES PATENT, OFFICE GEORGE E. E. IBERTHOLD, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO THE RAJAH GOMIANY, OF BLOOMFIELD, NEW JERSEY, A CORPORATION OF NEW JERSEY SPARK PLUG Application filed February 26, 1927. Serial No. 171,188.

cylinder of an internal combustion motor.

Due partly to the extreme differences in temperature to which the several parts of a spark plug are subjected when in operation, and partly to the difierence of the coefficients ofexpansion of the several materials used, great difliculty has been experienced in the manufacture of a spark plug in which certain of the parts would stand up under continued hard use. A further ditliculty experienced has been failure to obtain tight joints between the several parts which results, especially when used in the modern high compression type motor, in loss of compression of the combustion charge, and a consequent loss of power of the motor.

One of the disadvantages in a spark plug for use in a high compression engine is the difliculty of keeping'tight the joint between the core or porcelain of the plug and the central electrode. This electrode usually runs through an elongated hole and is cemented in place. The longitudinal expansion of the electrode, aggravated by its radial expansion also, serves to break and disintegrate the cement which works its way out through the lower end of the core. It is well known that the gases under high compression work their way through minute openings. The plug therefore leaks and the engine loses some-of its compression. One of my objects is to provide a construction for adequately scaling in the central electrode which shall not be open to these objections.

. With the above and other objects in view, reference is had to the accompanying drawings in which the'figure is a longitudinal sectional view of a spark plug illustrating the improvements of the present invention.

In the drawings, 10 designates the shell which may be of any preferred type and 12 designates the shell electrode. The shell is externally threaded as at 14 in the usual mannerto provide for its attachment in operating position, and is further provided with an internally threaded recess 16' for the reception of a threaded bushing or collar 18 employed to retain the core 20 in position in the shell. A gasket 22 is employed and placed under compression by the bushlng or collar 18 in the usual manner to provide a gas-tight joint between the shell 10 and the core 20.

The core 20 has a passage extending entirely therethrough, and this passage is preferably formed with an enlarged internally screw threaded portion providing an internally screw threaded recess 24 and a constricted portion forming an electrode passage 26. The bottom of the recess 24 is preferably formed with a seat 28.

The center electrode 30 is preferably carried by a plug 32 which is externally threaded for engagement with the interior thread of the recess 24, and when said plug 32 is secured in position, the electrode 30 projects through the electrode passage at the lower .end of the core 20 and into proximity with the shell electrode 12 but slightly spacedtherefrom.

Surrounding the center electrode 30, and adapted to be received upon the seat 28 of the recess 24, there is a washer 34. This washer 34 closely fits the electrode, whereby it prevents the cement from, being carried below it, and is preferably of a pliable nature, and when forced inward conforms to the seat and exterior of the electrode and forms an additional sealing means.

To provide an effective seal for the center electrode 30 and the plug 32, cement is employed, and said cement is interposed'beftween theinner end of the plug 32 and the washer 34 as designated at 36. This cement is of sucha nature that when the plug 32' is screwed into the recess 24 to position the electrode 30 in, the core 20, the cement willbe placed undercompression against the washer 34 and the seat 28, andwill alsobe forced into intimate contactwith the electrodeand certain of "the threadsiof the recess andthe seals the central electrode 30 and the plug 32 and prevents the leakage of gas there- .plug. l The setting of the cement completely I I to receive an electric conductor terminal, and uponlts under face, the head 40 is formed or provided with an annular flange 42 providing a recess 44 for the reception of a suitable packing 46. This packing 46 is placed under compression upon screwing the plug 82 into the recess 24 of the core 20, and also serves in combination with the cement 36, as a sealing means for preventing the escape of gas around the center electrode 30.

The central electrode 30 has at least a loose fit 1n the passage 26 and preferably is sufliclently smaller in diameter than the passage so that it will not contact therewith. It is sealed at its upper end by the cement and washer which are obviously held under high compresslon by the screw plug 32. The electrode may therefore expand and contract without danger of rupturing the gas seal.

From the foregoing, it will be apparent that the present invention provides a new and improved spark plug in which the several parts are so constructed and assembled as to withstand without rupture, the various temperatures to which they are subjected in use. Furthermore, a spark plug constructed in accordance with the present invention is thoroughly gas-tight, thus insuring greater efficiency in motors of the'high compression While in the present instance but one form of the invention has been illustrated, it is to be understood that the invention is not limited to the form shown, but may be practiced in various other forms within thescope of the appended claims.

What is claimed is:

1. A spark plug comprising an insulating core having a longitudinal bore therethrough,

a central electrode mounted in said bore being 5 of a size and shape relative to the bore such that that portion of the electrode which is within the part of the insulating core exposed in use to the heat of burning gases will be free to expand and contract radially and longitudinally without interference from said core,

said core being formed with a recess into which the bore opens substantially above that part of the core which is exposed to the extreme temperature changes, a washer in the bottom of said recess fitting tightly about the electrode and into the bottom of the recess and a narrow band of a sealing material within said recess compressed into intimate sealing contact with the electrode and with the insulating'core and which serves to press said washer into a closer sealing contact with the electrode and the core.

2. A spark plug comprising an insulating core having a longitudinal bore therethrough, a central electrode mounted in said bore being exposure to the free to expand and contract radially and longitudinally without interference from said core, said core being formed with a recess into which the bore opens substantially above that part of the core which is exposed to the extreme temperature changes, a washer of a material adapted to resist crumbling when subjected alternately to abrasive and tensile stress at high temperatures fitting tightly about the electrode and into the bottom of the recess, and a narrow band of a refractory hardened plastic cement compressed in said recess into intimate sealing contact with the electrode and with the insulatin core and which serves to press said was or into a closer sealing contact with the electrode and the core.

3. A spark plug as defined in claim 1 in which the bore through the core is not sufliciently larger than the electrode to permit free access of burning or combustible gases therein.

4. A spark plug comprising an insulating core having a longitudinal bore therethrough, a central electrode mounted in said bore being of a size and shape relative to the bore such that that portion of the electrode which 1s within the part of the insulating core exposed in use to the heat of burning gases will be free to expand and contract radially and longitudinally without interference from said core, said core being formed with a recess into which the bore opens substantially above that part of the core which is exposed to the extreme temperature changes, a washer of a material adapted to resist crumbling when subjected alternately to abrasive and tensile stress at high temperatures, fittlng tightly about the electrode and into the bottom of the recess and a narrow band of a refractory hardened plastic cement compressed in said recess into intimate sealing contact with the electrode and .;with the insulating core and which serves to press said washer into a closer sealing contact with the electrode and the core, the band by which the electrode is cemented into the corebeing within that portion of the core which is cooled by atmosphere, and the space between the core and the electrode at normal temperatures of continuous operation being not substantially in excess of that required to permit radial expansion of the electrode at maximum temperatures which may be expected under conditions of operation.

Signed at New York, N. Y., this 24th day of February, 1927.

GEORGE H. E. BERTHOLD.

of a size and shape relative to the bore such

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