Three-way hydraulic valve

An open-center three-way hydraulic valve in particular for the hydraulic control circuit of an electric circuit-breaker in which the moving contact is actuated by a differential jack, comprising an admission valve-head and a drain valve-head which are physically independent but interact with each other in a movement of thrust, said admission valve-head being urged toward the closed position by a spring and said drain valve-head being actuated toward the closed position by pressurization of a hydraulic pilot jack, wherein said valve has a second spring which produces action on the drain valve-head so as to urge said valve-head to the closed position, wherein said second spring is more powerful than the first spring and wherein provision is made on the drain valve-head for a resilient semi-locking mechanism having limited resistance which is adapted to retain the drain valve-head in the open position in opposition to the action of the second spring in the absence of hydraulic pressure within the pilot jack and which is adapted to release said valve-head up to its closed position when said valve-head is subjected both to the action of said second spring and to the action of the pressurized pilot jack.