| 摘要 |
An open-center three-way hydraulic valve as applicable to hydraulic control circuits of electric circuit-breakers comprises an admission valve-head which is restored to the closed position by a first spring, a drain valve-head which is displaced toward the closed position by a pilot valve, a second spring which is more powerful than the first and tends to close the drain valve-head, and a resilient semi-locking mechanism for retaining the drain valve-head in the open position in opposition to the second spring when the pilot jack is not under pressure. |
