US1533308A - Spark plug - Google Patents

Description

April 1'4, DAVIS SPARK PLUG Filed y 7. 192

INVENTOR. 0A W ATTORNEYS,

Patented Apr. 14, 1925'.

UNITED STATES PATENT; orrlcu.

sn'nnnn s. Dawson scorn: PAsADENA,

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sranx 1 mm.

Application filed May 7,

States,

that will give a double spark and will thereobjects and advantages of the invention will illustrated in th fore he better adapted to ignite a charge even under unfavorable conditions. Further appear as the specification proceeds. v The preferred form of .my invention is e accompanying drawing, in which Figure 1 shows a vertical section throughthe spark tive view of an insulating element having v I one electrode and another element forming celain,

the principal part-otmy invention connected therewith; and Figure 3 a perspective detail view of the latter element. While I have shown only the preferred form'of the invention, I wish to have it understood that various changes or modifications may-be made within the scope of the claim hereto attached without departing from the spirit of the invention.

In its main structural features my spark plug does notess'entially differ from spark plugs now commonly used, and comprises a metallic shell 1) threaded at its lower end as shown at (2) adapted to be screwed into a registeringperforation in the cylinder, not shown in the drawing, and a bushing (3) made of insulating material, preferably porw'ith a gland (4) threadedly engaging the top of the shell as shown at (6) and hearing on a shoulder (7-) of the bushing with an asbestos packing (8) interposed between the gland and .the shoulder. metal shell has'a in (9) extending from its lower end, which 'atter is bent to extend into the vicinity of the rod (11) extending centrally through the porcelain bushing and pro'ectin from its lower end asshown at (12). T e upper end of this rod forms a plug; Figure 2 a perspec- The th 1923. Serial-R0. 637,378.

terminal to which a wire maybe attached be tween the two nuts (13) and (14). The pin (9) and the lower end of the rod (1l) form two electrodes of a circuit includinga source of power, the body of the cylinder to which the pin (9) is grounded and a wire connecting the source of power with the upper end of the rod (11). The two electrodes leave a gap between thesa e across which a spark is caused to jump when a high voltage current is .passedthrough the circuit.

Iy invention conslsts in its principal-few -'tures in the introduction of a third metal element (16) disposed in such a manner as to extend into the gap and to thus form a stepping-stone for the spark so that instead of asingle spark two sparks will be produced, one between the electrode (12) and the third element, and the other between the electrode (9) and the third element. The third element may assume manydifferent forms, and the preferred form is shown in the drawing as comprising a loop (17) adapted to engage an annular groove 18) in the insulating bushing from one end of which extends a projection (19) bent as shown at (21) to extend into the gap.

The double spark thus produced will be hotter than a single spark would be and therebyinsures proper ignition of a charge of lower grade. An arrangement of this character also allows a good spark to he produced from a comparatively weak source of energy. The electrode (9) might also be omitted and the spark caused to jump from the loop (17) directly to the shell '(1).

' I claim:

A spark plug comprising an insulating core, a metallic shell carrying the core, a main electrode projecting from the lower end of the core, a second electrode projecting inwardly from the lower end of the s ell to a point below and at one side of the main electrode, a metallic loop embracing e core, and a projection on the loop and extending across the lower end of the main electrode to provide a gap between the two and having its free end spaced from the second electrode to form a gap therebtween.

SELDEN s. DAVIS.

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