| 主权项 |
1. A double hydraulic valve of a servo-control for feathering the blades of a rotorcraft rotor, the hydraulic valve comprising:
a valve cylinder having A ducts dedicated to providing a hydraulic connection between the hydraulic valve and a source of fluid under pressure, the A ducts comprising at least an admission A duct providing fluid admission from the outside to the inside of the hydraulic valve and at least one discharge A duct providing fluid discharge out from the hydraulic valve, the valve cylinder having B ducts dedicated to providing a hydraulic junction between the hydraulic valve and a cylinder of a hydraulic actuator of the servo-control, referred to as the actuator cylinder, the B ducts comprising a pair of B ducts providing fluid flow between the inside and the outside of the hydraulic valve; a main valve member movably mounted inside the valve cylinder and controllable by a control member, the main valve member providing A channels dedicated to fluid flow through the hydraulic valve between the A ducts and the B ducts, the admission A duct and the discharge A duct being in fluid flow communication via A channels selectively with one or the other of the B ducts depending on the respective positions of the main valve member inside the valve cylinder; an emergency valve member interposed between the valve cylinder and the main valve member, the emergency valve member movably housing the main valve member and being movably mounted inside the valve cylinder, the emergency valve member having B channels that are dedicated to fluid flow between the A channels and either the A ducts or the B ducts, selectively depending on the respective positions of the main valve member; and positioning means for positioning the emergency valve member in a predefined position inside the valve cylinder, in which predefined position the emergency valve member, the A channels, and the B channels are in fluid flow communication in pairs, the positioning means making use at least of elastically deformable means bearing against the valve cylinder, the emergency valve member being authorized to move inside the valve cylinder together with the main valve member under the effect of the emergency valve member being entrained by friction from the main valve member in the event of it seizing inside the emergency valve member against thrust exerted by the elastically deformable means; wherein said positioning means are means for blocking the emergency valve member against the valve cylinder by a pin mounted to move relative to the valve cylinder and co-operating by sliding thrust engagement with a cavity of the emergency valve member, the pin being movable between an engaged position in which a head of the pin is received in the cavity under the effect of the thrust exerted against the pin by the elastically deformable means, and a disengaged position in which said head is totally disengaged from the cavity by mover means for causing the pin to move against the thrust exerted on the pin by the elastically deformable means, operation of the mover means depending on relative movement between the emergency valve member and the valve cylinder serving to release at least in part said cavity by the head of the pin sliding inside the cavity; wherein the mover means for moving the pin are means for applying fluid thrust to the pin, which is provided with a piston having applied thereagainst the fluid that is admitted under pressure into the inside of the hydraulic valve. |
