| 摘要 |
PROBLEM TO BE SOLVED: To provide a straight mold body for an insulator for a spark plug having an axial line formed into a straight line, and also to provide a park plug having excellent durability without impairing ignitability. SOLUTION: This mold body 1 for an insulator includes: a large-diameter tube part 3 formed into a flange-like shape projecting in a direction perpendicular to the axial direction and having an axial length of 6-12 mm; a first small-diameter tube part 2 formed in a diameter smaller than that of the large-diameter tube part 3 on the side of one end of the large-diameter tube part 3 and having its outside diameter not larger than 10.8 mm; and a second small-diameter tube part 4 formed in a diameter smaller than that of the large-diameter tube part 3 on the side of the other end of the large-diameter tube part 3 and having its axial length not smaller than 30 mm. This mold body 1 for an insulator is formed into an insulator 11 of a spark plug 30 by baking a plurality of the mold bodies by erecting and aligning them in a sheath 20. The mold body 1 for an insulator is so formed that the large-diameter tube parts 3 of the plurality of the mold bodies 1 for insulators are brought into contact with one another when they are erected and aligned by setting the first small-diameter tube parts 2 lower than the second small-diameter tube parts 4 while tilting the sheath 20. COPYRIGHT: (C)2006,JPO&NCIPI
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