US2164578A - Spark plug - Google Patents

Description

P. A. DOYLE SPARK PLUG Filed July 24, 1937 Ava furor: Pfizer A. Dan:

J/ wav/w flrronvex July 4, 1939.

Patented July 4, 1939 UNITED STATES PATENT OFFICE SPARK PLUG Application July 24, 1937, Serial No. 155,397

1 Claim.

My invention relates to spark plugs, and has for its principal object to produce a spark plug particularly adapted to high compression, high speed, gasoline engines, and in which the spark is always operative in its full intensity. Another object is to produce a spark plug in which the negative electrode is provided with a disk-shaped member adjoining its free end, whereby the movement of the turbulent gases in the upper portion of the engine cylinder adjacent such diskshaped member is lessened and the sparking between the positive and negative electrodes is not substantially interfered with by reason of such turbulence.

The high compression generally developed in gasoline engines for automobiles is partly responsible for the inefficiency of spark plugs of the usual type now on the market. By my new spark plug with the disk-shaped member adjoining the free end of the negative electrode I overcome such inefficiency and produce a spark between the positive and negative electrodes that is of full intensity and delivered at regular intervals. For the smooth operation of a high speed gasoline motor it is essential that the spark delivered by the spark plug be absolutely regular and of such intensity as to ignite the gases entering the engine cylinder from the manifold, and in some types of spark plugs with which I have had experience, as the compression in the motor increases the efficiency of the spark plug decreases.

Fig. l is a cross-sectional view of my improved spark plug.

Fig. 2 is an enlarged side elevation of the lower portion of my spark plug.

Fig. 3 is an enlarged bottom plan view of my improved spark plug.

Fig. 4 is an enlarged side elevation, similar to Fig. 2 but taken from a different angle.

Fig. 5 is a perspective view of a negative electrode element.

In the invention as illustrated in the drawing, the detachable shell Ii] is provided with the usual longitudinal bore II to receive the porcelain insulated, cylindrical positive electrode-carrying member I2, in which is centrally located longitudinally of said member I2 the positive electrode I3. On a shoulder I4 in the bore II of the shell I0 is located a packing washer I5 against which a shoulder I6 on the lower portion of the porcelain member I2 is adapted to seat. The porcelain member I2 has another shoulder II on which a packing washer I8 is adapted to seat and on which a cylindrical plug I9 is seated by virtue of the screw-threaded portion 20 on the plug I9 and the screw-threaded portion 2| in the shell I0. By these means the member I2 is firmly and positively seated in the shell I0.

At the top of the porcelain member I2 and contacting with the electrode I3 is a copper element 22 exteriorly screw-threaded, as at 23, to receive an interiorly screw-threaded member 24, whereby electrical contact with the battery (not shown) is made. The structure which has just been described is substantially common to all spark plugs ordinarily employed for use in gasoline engines for automobiles.

The shell l!) acts as a negative electrode for the spark plug and is grounded through the engine and frame of the automobile or other device supporting the engine, as is now commonly done. To the lower end of the shell I0 a negative electrode extension piece 25 is secured, preferably by welding 25'. The negative electrode extension piece 25 is a continuation of the shell I0, and the free end 26 of said negative electrode extension piece 25 is separated from the positive electrode I3 by approximately 7 of an inch. Near the end 26 of the negative electrode extension piece 25 is a disk-shaped portion 21, which may be formed on the electrode extension piece 25 as an integral part thereof, or it may be provided with a central perforation 28 of a size sufficient to slip over the circular electrode extension piece 25 and be secured thereto by welding.

The shell ID at the lower portion thereof is provided with screw-threads 29 adapted to engage with screw-threads in the upper portion of the gasoline engine cylinder (not shown). When my improved spark plug is positioned in a gasoline engine cylinder, the disk 2'! acts as a barrier to the flow of gases and tends to break up such flow so that there is a relatively unobstructed flow of electric current between the positive electrode I3 and the negative electrode 25. This is highly important in order that the passage of the spark produced by the electric current passing from the positive electrode I3 to the negative electrode 25 be permitted to take place when contact with the battery is established, and that such sparking be regular and of full electrical intensity, particularly in high speed motors.

In the use of my improved spark plug I ignite all of the gases, and by reason thereof I produce increased mileage for the gasoline consumed in the operation of an automobile. I also decrease the formation of carbon by my improved spark plug.

If a spark gap consisting of two more or less pointed electrodes is subjected to a high voltage,

an electrostatic field is set up in the gap. The distribution of this field is not uniform throughout the length of the gap, as the electrostatic lines of force will be crowded together very closely in the immediate vicinity of the electrodes and spread out to a maximum separation in the gap midway between the two electrodes. The concentration of these electrostatic lines of force is a measure of the degree of electrical stress to which the air in the gap is subjected. If the concentration exceeds a certain amount, the air breaks down (ionizes) and becomes conducting. This break-down manifests itself by a bluishviolet glow, known as corona.

When a high voltage is applied to agap of the type being discussed, corona is first formed around the tips of the electrodes. This, in effect, shortens the gap between the electrodes, the ionized air where the corona occurs being equivalent to an extension of the electrodes. The effective length of the air gap having thus been shortened, the remaining length of air column is unable to withstand the impressed voltage and breaks doWn with the characteristic spark discharge.

In the case of electrical ignition, the initial production of corona (which has no igniting properties because of its relatively low temperature) represents a dissipation of electrical energy and thus reduces the amount of energy available to produce the spark, reducing the calorific value of the latter accordingly.

In my invention, the disk 21 serves to reduce the concentration of the electrostatic lines which would otherwise have taken place around the tip of electrode 26, and allows these lines to fringe outward and distribute themselves over the surface of the disk. While the electrostatic field will still have its greatest density at the tip of electrode 26, the concentration will be much lower. This serves to reduce the initial production of corona, resulting in a reduced time lag and a more intense spark of higher ignition properties.

While I have illustrated and described the positive and negative electrodes generally employed in spark plugs, it will be understood that these polarities may be reversed without in any Way altering theoperation of my invention.

I claim:

A spark plug comprising a shell constituting a negative electrode, a positive electrode extending centrally and longitudinally through a porcelain insulated member positioned in said shell, said shell having an electrode extension piece extending beyond one. end thereof, said positive electrode and said extension piece on said negative electrode being separated to provide a sparking gap, said extension piece being bent at a right angle to itself, and a disk-shaped piece on said angular portion of said extension piece adjacent the free end of said angular portion of said extension piece for the purpose of reducing the concentration of the electrostatic field at the tip of said extension piece.

PERCY A. DOYLE.

Images