Electro Hydraulic Actuators

An electrohydraulic actuator comprising: a hydraulic actuator comprising a piston secured to a member to be controlled and capable of moving in a cylinder under drive from a hydraulic fluid; a hydraulic pump feeding both faces of the piston with hydraulic fluid via channels integrated in the walls of the cylinder; an electric motor immersed in the hydraulic fluid, and controlled and powered electrically by an electronic control unit, driving the hydraulic pump in rotation; and a hydraulic accumulator for compensating variations in the volume of the hydraulic fluid; the hydraulic actuator, the hydraulic pump, the electric motor, and the hydraulic accumulator having a common axis of symmetry and being mounted in alignment in a common housing that is leaktight to the hydraulic fluid, thereby forming an axially symmetrical self-contained hydraulic assembly.

The electro-hydraulic actuator for turbine valves essentially includes a control valve, a rapid action stop valve, a hydraulic supply and an oil supply unit. In order to create a hydraulic actuator for turbine valves which, on the one hand, satisfies the stringent requirements with regard to adjustment force and adjustment speed and, on the other hand, avoids the problems associated with the transmission of hydraulic energy, at least one adjustment valve and at least one rapid action stop valve are allocated per turbine inlet valve. The actuators of these two valves are of the same design and are mutually interchangeable and integrated into a compact actuator unit located on the valve housing. The actuators are connected in pairs to a hydraulic supply located immediately adjacent to the actuators. In addition, the actuators are controlled by a volumetrically controlled oil supply unit integrated with the hydraulic supply, this oil supply unit containing an adjustment pump for controlling the adjustment valve and an auxiliary pump for controlling the rapid action stop valve.

The advantages of the invention are to be seen essentially in that, as a result of the proposed solution, the attachment of one control valve and one rapid action stop valve to each turbine inlet valve can be brought about without problems in terms of the space that is required and is available. Due to the fact that the two actuators are of the same design, the highest possible degree of interchangeability is attained. A further advantage of the invention is that each hydraulic supply serves one control valve and one rapid action stop valve. Due to the fact that the hydraulic supply is no longer restricted in terms of space, it can be made more sturdy, simpler and cheaper. A further advantage of the invention is that the hydraulic supply contains a volumetrically controlled oil supply unit which supplies the quantity of fluid necessary for action on the control valve. This oil supply unit also includes an auxiliary pump, which supplies the hydraulic quantity for action on the rapid action stop valve, for the electro-hydraulic valve and for the adjustment cylinder of the pump adjustment unit.