(19)
(11) EP 1 026 447 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
25.08.2004 Bulletin 2004/35

(43) Date of publication A2:
09.08.2000 Bulletin 2000/32

(21) Application number: 99310206.0

(22) Date of filing: 16.12.1999
(51) International Patent Classification (IPC)7: F23Q 7/00
(84) Designated Contracting States:
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
Designated Extension States:
AL LT LV MK RO SI

(30) Priority: 04.02.1999 JP 2699499

(71) Applicant: NGK Spark Plug Co., Ltd.
Nagoya-shi, Aichi 467-8525 (JP)

(72) Inventor:
  • Yoshida, Mitsutaka, c/o NGK Spark Plug Co., Ltd.
    Nagoya-shi, Aichi-ken 467-8525 (JP)

(74) Representative: Nicholls, Michael John 
J.A. KEMP & CO. 14, South Square Gray's Inn
London WC1R 5JJ
London WC1R 5JJ (GB)

   


(54) Glow plug


(57) The metallic shell (20) of a glow plug has a cylindrical male-threaded portion (21) and a tightening portion (22). The tightening portion (22) is formed to have an outer circumferential surface of a shape corresponding to that of a 12-point nut. By virtue of this structure, the tightening portion (22) can have a greater wall thickness as compared with a conventional tightening portion which has a an outer circumferential surface of a shape corresponding to that of a hexagon nut. Therefore, it becomes possible to made the glow plug thinner, while maintaining the strength of the tightening portion (22).









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