| 摘要 |
PURPOSE:To absorb a small variation in fluid pressure at an inlet of a valve seat for stabilizing operation by providing a minimum throttling portion of a fluid path until a ball is opened and then reaches the maximum lifting position. CONSTITUTION:A side wall 4'a is constituted close to a ball 2' such that a path 8b formed of the ball 2' and side wall 4a' of a ball valve V1' provides a minimum throttling portion of fluid path until the ball 2' is opened and then reaches the maximum lifting position. As the displacement of the ball 2' becomes large, area of a path 8a is enlarged and area of the fluid path 8b is reduced so that pressure in an inlet 1 will act on the whole section of the ball 2'. Thus, when differential pressures in the inlet 1 and the ball chamber 4' are equal, a force pushing up the ball 2' becomes larger than that when the ball 2' is closed. That is, as shown by the curve B, the ball 2' is not operated even when the pressures in the inlet 1 and ball chamber 4' vary somewhat after the ball 2' is completely opened. |
