US1707741A - Spark plug - Google Patents

Description

APil 2, 1929- H. RABEzzANA 1,707,741

SPARK PLUG A Filed July 20, 1925 3111x1114 oz atto: nu;

Patented Apr. 2, 1929.

UNITED STATES 1,707,141 PATENT oFr-icu.

\ HECTOR RABAEZZANA, F FLINT, MICHIGAN, ASSIGNOR TO A C SPARK PLUG COMPANY,

' OF FLINT, MICHIGAN, A COMPANY 0F MICHIGAN.

SPARK PLUG.

Application filed July 20, 1925. Serial No. 44,867.

Considerable difficulty has been experienced in maintaining the spark plugs used in internal combustion engines, particularly those operated at high compressions, at suiiiciently low temperatures for most effective operation. Thus, when the plugs become too highly heated, the electrical resistance of the insulators is reduced and the temperature of the latter may even be raised to a point TJ of redness and cause pre-ignition of the combustion mixture.

This application discloses one means which may be used to secure or to assist in securing the desired lower-working temperatures for the plug. This means consists primarily in forming the inner surface of the shell of the plug of such configuration that a considerable area is presented to the surrounding gases whereby the rate of transfer of heat therefrom is greatly increased. This increased transfer of heat results in a lowering of the temperature of these gases and as they also surround the insulator, the temperatures to which the latter are subjected are thereby reduced. Specifically, the configuration which I have preferred to employ consists of ridges upon the inner surface of the shell, the ridges extending either axially or circumferentially.

Referring now to the drawings:

Figure l is a side elevation ofa spark plug, parts being shown in section to better illustrate the invention;

Figure 2 is an enlarged sectional view of the shell shown in Figure 1;

Figure 3 is a section on line 3-3 of Figure 2;

Figure 4 is a. view corresponding to Figure 2 but showing a modified form; and

Figure 5 is a section on line 5-5 of Figure 4. Y v

I have illustrated in the drawing a spark plug of conventional type comprising a shell 2, insulator 4, center electrode '6 and side electrode 8. I have formed the interior of the shell with ridges which may extend either longitudinally of the shell as shown at 10 in v.Figures 1, 2, and 3 or circumferentially thereof as shown at l2 in Figures 4 and 5. I have found by actual experiment that a plug so constructed will be maintained at a lower temperature than a plug having a shell, the

i inner surface of which is a smooth cylinder. With a plug constructed as described the surface of the interior of the shell is greatly increased, giving a greater area for contact with the gases, with the result that there is an increased fiow of heat from the gases into the shell from whence it is effectively dissipated throughthe cylinder head. As these gases are pocketed in the shell there is very little opportunity for the operation of convection currents so that the heat thu-s lost is not readily replaced. Accordingly, the gases are maintained at a lower temperature. lVith the gases at a lower temperature,'the insulator receives less heat with the advantages above described.

lVhile I have described constructions in which ridges are provided upon the interior of the shell it is to be understood that my invention is not limited to these particular con-- fgurations for others may be employed to secure the desired increased area; thus the shell may be provided with protuberances'or the 75 like. 1 While I have given above the theory of operation Which seems to me now. to best explain the results obtained, it is to be understood that there may be other factors, such as radiation, which may have an important yeffect in securing the described results in a manner not now obvious, so that my invention is not to be understood as limited by the theory of operation disclosed.

What I claim and desire to secure by Letters Patent is:

l. A spark plug comprisingvan open ended metallic shell adapted to be secured in good heat conducting relation with cooled surfaces of the engine, an insulator in the shell extending approximately to the lower end vthereof, an electrode on the insulator, an electrode on the shell, the lower end of said shell and the lower end of said insulator defining an elongated chamber normally filled with hot combustion gases, substantially the entire surface of the shell exposed in said chamber being roughened to increase the area thereof to facilitate the conducting away of heat to prevent said insulator and its electrode from attaining sufficiently high temperatures to cause pre-ignition.

2. A spark plug comprising an open ended metallic shell adapted to be secured in good heat conducting relation with cooled surfaces of the engine, an insulator in the shell, an electrode on the insulator, an electrode on the shell, said electrode being arranged to provide a spark gap outside of the shell, 11 o the lower end of the shell cooperating with the insulator to form an elongated annular space extending substantially to the end of the shell, and normally filled with hot cornbustion gases, the portion of the shell eX- posed in said space being provided with corruwations to increase the area thereof to more ellectively conduct away the heat of said gases and prevent the center electrode and the insulator from attaining sutliciently high teniperatures to cause pre-ignition.

3. A spark plug comprising a metallic shell adapted to he secured in good heat conducting rela/tion with cooled surfaces of the engine, an insulator in the shell, the lower.

end of said shell and the lower end of said insulator being spaced from each other tlnoughout a considerable portion of their length and defining an annular dead air space normally lilled with-hot combustion gases, the surface of the shell opposite the insulator being formed to present greatly increased area to the said A.dead air space to fa cilitate conduction of'he'at away from said space, said plug being provided with the spaced electrodes arranged to provide a spark gap below the lower end ot the shell.

4. A spark plugY comprising.,r a metallic shell adapted to be secured in good heat conducting relation with cooled surfaces of the engine, an insulator in the shell, the lower ends of said shelland insulator being spaced to provide an elongated annular dead air space normally illed With combustion gases, said insulator being provided with a center electrode having its end extending below the shell, said plug being provided with an electrode cooperating with the end ot said eenter electrode to provide a spark gap, the interior of the shell surrounding said insulator being formed to provide greatly increased surface to increase the rate otl conduction ot heat away from said air space.

5. A spark plug comprising a metallic shell adapted to be secured in good heat conducting relation with cooled surfaces oit the engine, an insulator in the shell, the lower ends of said shell and insulator being spaced throughout a considerable portion of their length to form an elongated dead air space normally filled with combustion gases, the interior surface of the said last named portion of the shell being provided with vertical corrugations to increase the rate of conduction of heat away from said space.

ln testimony whereof l alix my signature.

HECTOR RABEZZANA.

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