| 摘要 |
PROBLEM TO BE SOLVED: To form a cap to smoothly mesh with a male screw of an opening at the initial stage of capping, by forming the pitch of an incomplete screw part to have the same width with the pitch of a complete screw part and forming a slope from the crest of the screw thread of the incomplete screw part to the outer peripheral face of the opening. SOLUTION: A length Y of an incomplete screw part 4 formed at a male screw part 3 of an opening 2 is formed shorter than 15% of the outer peripheral length of the opening 2. And a complete screw part 6 is formed continuously and immediately after the short incomplete screw part 4. The pitch of the screw thread is made equal in both complete screw part 6 and incomplete screw part 4. And all outer diameters of the screw thread from the upper side to the lower side are made equal. In this way, such an inconvenience that the screw thread of the male screw 3 is caught by the female screw, can be eliminated. |
