| 摘要 |
PROBLEM TO BE SOLVED: To effectively seal an outside surface of a metal barrel by a cap without damaging a peripheral protrusion in the cap, by radially increasing an outer diameter of a cylindrical part of a coupling member as compared with an outer diameter of an end face of an opening of the barrel, and radially decreasing the outer diameter of the cylindrical part as compared with a base provided with the peripheral protrusion. SOLUTION: An outer diameter of an opening end face 3b of a coupling member 4 is 8.1 mm, while an outer diameter of its adjacent cylindrical part 4e is 8.3 mm. This is because, since an inscribing diameter of a protrusion 2b in a cap is 8.0 mm and an inner diameter of a base 2c of the protrusion 2b is 8.4 mm, if the outer diameter of the adjacent cylindrical part 4e is thicker than this, it is brought into contact with the base 2c of the protrusion. Accordingly, it becomes difficult to ride across the protrusion 2b, while it is excessively thin, a contact preventing effect to the end face 3b is reduced, and hence it is necessary to increase 0.1 to 0.3 mm than the outer diameter of the end face 3b. |
