Electric lamp and discharge devices – Spark plugs – Particular electrode structure or spacing
Reexamination Certificate
2008-12-19
2010-10-26
Guharay, Karabi (Department: 2889)
Electric lamp and discharge devices
Spark plugs
Particular electrode structure or spacing
C123S1690EL
Reexamination Certificate
active
07821186
ABSTRACT:
A spark plug includes an outer electrode including an outer electrode tip of which a distal end surface is spaced from an outer peripheral surface of a leading end portion of a center electrode to define a spark discharge gap. A protruding insulator portion of a cylindrical insulator protrudes at least 1.0 mm from a leading end surface of a cylindrical metal shell. A protruding center electrode portion of the center electrode protrudes at least 3.5 mm from the leading end surface of the cylindrical metal shell. A relationship (θ1+θ2)/2≧75 degrees is satisfied where the angle θ1is defined as a central angle (degrees) of a first circular sector having a point B1as a center thereof, and the angle θ2is an average value (degrees) of the central angles of two second circular sectors having the point B1as a center thereof.
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Kameda Hiroyuki
Nagasawa Satoshi
Nakayama Katsutoshi
Yoshida Kazumasa
Guharay Karabi
Haeberlin Jeffrey A.
NGK Spark Plug Co. Ltd.
Stites & Harbison PLLC
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