US2318440A - Spark plug - Google Patents

Description

Inventor: Alexander. C. Wall, b x af/MAW' y His 'Attorney.

SPARK PLUG Filed April 28, 1941 A. c. WALL May 4, 1943.

Patented May 4, i943 UNITED STATES- PATENT. OFFICE 2,310,440 Alexander 0. wa mi N. 1., assignor to General Electric New York Company, a corporation of Avplicatioithprll 28, 1941, Serial No. 390,664

2 Claims. (Cl. 123-169) My invention relates to spark plugs, such as those employed .with internal combustion engines for providing electric ignition.

Spark plugs 118113118 include an insulating body oi some material such as porcelain with a centrallv disposed conducting member having a high tension electrode at one end and a connection terminal at the other end. A shell surrounds the porcelain body and is adapted to be screwed into a port in a cylinder of an internal combustion en ine and the connection terminal is connected to a suitable source of power. Ithas been found that when conventional spark plugs are employed the differences in thermal expansion between the conventional central conducting metallic member and the surrounding porcelain may loosen the joint therebetween when such plugs become heated during operation of the engine and this may provide a path through which gases from the cylinder may leak.

It is, therefore, an object of my invention to provide an improved spark plug structure which will minimize the possibility of gas leakage between the electrical conductor and the surround-- ing insulating body.

Another object of my invention is to provide an improved and eflicient spark plug structure.

Further objects and advantages of my invention will become apparent from the following description referring to the accompanying drawing, and the i'atures oi. novelty which characteriz my invention will be pointed out with particularity in the claims annexed to and forming a part of-this specification.

The single figure in the drawing illustrates a spark plug which is provided with an embodiment of my invention.

The arrangement illustrated in the drawing includes a high tension terminal and an electrical connecticnterminal embedded in a fusible or vitriiiable insulating body, the portion of the body between the terminal and electrode having par-, ticles of conducting material interspersed-among have illustrated a spark plug including a body ill formed of any suitable insulating material, such as a fusible or vitrlflable insulating material, such as aceramic material or aluminum oxide with a suitable binder. When the last-named material is employed, the possibility of reaction between the insulating material and the products of combustion is minimized sothat the insulating properties of the body will not deteriorate. A high tension electrode II is provided with a portion l2 7 having a threaded engagement with a complementary opening in the insulating body land is embedded a suiiicient amount therein to secure the electrode tightly to the insulating body. A connection terminal I! is provided with a part it extending into a portion oi the body In remote or spaced from the electrode Ii, and this part it also threadedly engages an opening in the insulating body ll and is embedded therein a suillcient amount so as mechanically to hold the terminal ll rigidly therein. A metal cap I! is provided over the end of the body II and a plurality of nuts ll are threaded on the terminal ll so that a conductor may be tightly secured between the nuts to provide an electrical connection between the terminal and the conductor. An'elec a threaded portion ll adapted to be threaded'into particles of insulating material so as to connect the electrode electrically to the terminal. ,The body is fused or vitrified to form an integral'mass in order to provide a substantially gas tight bond between the conducting particles and insulating-v material. Thus. when su ch a spark plug construction is employed in an internal combustion engine the possibility of a passage being-formed in the insulating body of the spark plug through which gases from the cylinder may leak is min- Referring more particularly to the drawing. 1

which surrounds the body II and is provided with a complementary bore in an internal combustion engine. The shell il is also provided with an electrode portion II which is spaced from the high tension electrode Ii to form an air gap between which a spark passes for igniting a charge or combustible materials in an internal combustion engine. In'order to secure the electrodes Ii and I! in the desired spaced relationship a nut 20 is provided with an externally threaded portion in engagement with an internally threaded portion of the shell il remote from the electrode l9. Suitable gaskets II and 22 are arranged between cooperating portions on the insulating body I. and the shell i1 and nut 20 so that when the nut is tightly secured to the shell, the body portion II will be held through the gaskets 2 I and 22 between the nut 20 and the shell '11 and the desired relative relationship will result.

In order to provide an electrical connection between the high tension electrode I] and the 24 of suitable size and of suitable electrically conducting material are interspersed with insulating material is to form an electrically conductive core'in that portion of the body I indicated by the numeral 23, ch is between the portion i2 ofthe high tension electrode ii and the portion 84 of the connection terminal IS. The conducting particles may be or any suitable material such as electrically conductive metallic particles, graphite, or carbon. The body it with the conducting particles, high tension electrode, and terminal is solidified, as by fusion or vitrification, by heating to a suitable temperature, or by any other suitable method such as by pressure to form an integral mass. Also, it will be apparent that the body I'll may be formed into an integral mass before the terminals are put in place. ,In this manner the particles of conducting material-are suflicientlymlosely arranged to form a conductor between the high It. This will insure that physical properties such as thermal expansion will bethe same in the core as in the body of the plug.

It is to be understood that any suitable proportion of conducting and non-conducting ma terial may be provided in the core so as to term a suitable electrical connector between'the'high tension electrode and the connection terminal and still minimize the possibility of gas leakternal combustion ignition systems to provide a tension electrode and the connector terminal, but

they' are surrounded with insulating material having the same physical properties as that of the bodyportion i0. With this constructionvarying operating conditions, such as changes in temperature, will not cause the conducting material to move away from the insulating material and no passage will be formed through which gasses may pass through the plug. The conducting material may be formed in the portion 23 in any suitable manner, such as by forming the body portion ill with a hollow axial portion 23 in which conducting and non-com,

material and the core non-conducting material resistance element in the ignition cireuit between the spark plug and the distributor to minimize the possibility of oscillations in the circuit and consequent radio disturbance. It is, therefore, possible with my invention to provide .the core with suitable conductance or resistance characteristics to obtain a resistance of a suitable value'in the circuit between the high tension electrode and the source of power which is connected through the conventional distributor 'to the connector l3.

Although I have shown-and described a particular embodiment of my invention, 1 do not desire to be limited to the particular illustrated. embodiment, and I intend in the appended claims to cover all/modifications .which do not depart from the spirit and scope of my inven tion.

What I claim as new and desire to secure by Letters Patent of the United States is:

'1. A spark plug for an internal combustion engine including a core of particles of conductthroughout the normal operating temperatures range of the spark plug. In this manner a core is formed of conducting and non-conducting material which is surrounded by a body portion ill of insulating material having substantially the same physical properties as the non-conducting core material. Also the core and body It may be formed in one operation so that a suitable amount of conducting material is interspersed in the portion of the body I0 between the high tension electrode and the terminal. With this method of construction the particles of non-conducting-material which surround the conductlng particles will be of the same insulating material interspersed in a vitrifiable insulating material, and a body of material similar said vitrifiable insulating material surrounding said core so that the body insulating material and the core insulating material will have the same thermal expansion characteristics, said core and body being formed as a vitrified integral mass providing a, substantially gas tight bond between said core material and said body.

2. A spark plug for an internal combustion L engine including a body of vitrifiable insulating material, a high tension electrode, a connection terminal, said electrode and terminal extending from spaced parts of said body and having portions embedded in said body mechanically securing said electrode and terminal to said body,

ing material as that forming the body portion and conducting particles interspersed in said body between said electrode and terminal portions so as to connect electrically said electrode and terminal, said body being formed as a vitrified integral mass providing a substantially gas tight connection between said electrode and terminal.

ALEXANDER C. WALL.

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