Combination of spark plug and combustion chamber having connected conical and cylindrical sections

Claim 1

For a rotary engine, the combination of a casing having an ignition opening extending to a combustion chamber which is formed in the casing, and a spark plug in said ignition opening, said spark plug including a shell detachably mounted in said ignition opening and having a lower end, an insulated center electrode mounted in said shell, and an outer electrode mounted at said lower end of the shell and projecting into spaced relation with said center electrode to form a spark discharge gap therewith, said ignition opening having a conical surface which narrows in a direction away from said lower end and towards said combustion chamber, said ignition opening having a cylindrical portion extending from said conical surface into said combustion chamber in substantial axial alignment with said center electrode said lower end of the shell being of slightly reduced diameter compared to the remainder of the shell to form a space with said casing which extends into the ignition opening at said conical surface said outer electrode including a portion extending from said lower end substantially parallel to said conical surface in closely spaced relation therewith, the latter portion projecting towards said center electrode.