| 摘要 |
PROBLEM TO BE SOLVED: To prevent sealing deterioration when fully closed while preventing wear.SOLUTION: The position α of a gap 7 regulated by a detent means 8 is set in a "range from 198.1 to 209 degrees". Consequently, even if a shaft 9 is rotationally operated, the gap 7 does not pass through moving ranges of contact points, thereby preventing wear to be caused when the gap 7 move on "the inner peripheral wall of a nozzle". Interference between a "seal ring 6" and the "nozzle" due to radial displacement of the seal ring 6 can be prevented when the shaft 9 is rotationally operated, thereby preventing wear due to the interference. The position &bgr; of a recess 8a is set in a "range from 5.4 to 8.1 degrees". In a range in which the rotation angle of the shaft 9 is at least ≤20 degrees, the recess 8a and the gap 7 are formed separately in different circular arcs divided by the contact points. When the rotation angle of the shaft 9 is an almost fully closed angle, the surface pressure applied to the contact points can be reduced, thereby preventing wear. |
