Method for controlling and damping the motion of a hydraulic actuator in an electro hydrostatic actuator (EHA) system comprising an electric motor, a hydraulic pump and a hydraulic fluid circuit connecting the hydraulic pump and the hydraulic actuator includes comprising: energising the electric motor to drive the hydraulic pump to supply hydraulic fluid to the hydraulic actuator through the hydraulic fluid circuit in an active mode of operation; providing a flow path between the hydraulic actuator and the hydraulic pump in a damping mode of operation such that hydraulic fluid can flow via the flow path through the hydraulic pump when the hydraulic actuator is driven by an external force; and determining a desired amount of damping to be applied to the hydraulic actuator in the damping mode of operation and providing the electric motor with one or more energy consuming means configured to provide the desired amount of damping.

A stability and control augmentation system (SCAS) actuator is operable for actuating a flight control surface of an aircraft. The SCAS actuator includes an actuator housing having a first aperture, a second aperture and a hydraulic chamber therebetween. A piston extends through the actuator housing. Fluid inlets are in fluid communication with regions of the hydraulic chamber. A first end portion of the piston is arranged to slide through the first aperture without a seal between the first end portion and the first aperture. A second end portion of the piston is arranged to slide through the second aperture without a seal between the second end portion and the second aperture. An intermediate portion of the piston is arranged to slide in the hydraulic chamber without a seal between the intermediate portion and the hydraulic chamber.

A hydraulic adjusting device, in particular for use in a power plant and/or a wind power plant, includes a double-acting adjusting cylinder that has an adjusting function for a working operation and for a special operation. The double-acting adjusting cylinder is configured to be pressurized with a working pressure medium. In order to satisfy the adjusting function in the special operation, the double-acting adjusting cylinder is further configured to be connected to a pressure medium reservoir that has a pressurized gas isolated from the working pressure medium. The adjusting cylinder has a working chamber configured for the adjusting function of the special operation, the piston area of which is coupled to a piston arrangement of the adjusting cylinder that is configured for the working operation or is configured to be coupled to the piston arrangement.

A hydraulic actuating device for a friction clutch and a gear setting element has a power unit for pressure generation by use of an electrically driven pump. Gear setting and clutch actuating sections are hydraulically connected to the power unit. A detenting device with a blocking element is associated with a piston of the clutch setting cylinder, which is operatively connected with the friction clutch and can be hydraulically loaded on opposite sides. The blocking element is resiliently biased into a blocking setting preventing piston movement and is movable by an actuator from the blocking setting into a release setting permitting piston movement. The pump is reversible in order to load the piston on one or the other side for an actuating movement. The control unit coordinates activation of the pump and actuator in order to disengage or engage the friction clutch.

A hydraulic system includes: a cylinder in which an interior of a tube is divided by a piston into a first pressure chamber and a second pressure chamber; a first bidirectional pump connected to the first pressure chamber by a first supply/discharge line; a second bidirectional pump connected to the second pressure chamber by a second supply/discharge line and coupled to the first bidirectional pump in a manner enabling torque to be transmitted between the first and second bidirectional pumps; a relay line connecting the first and second bidirectional pumps such that a hydraulic liquid discharged from one of the first and second bidirectional pumps is introduced into the other of the first and second bidirectional pumps; and an electric motor that drives the first or second bidirectional pump. At least one of the first and second bidirectional pumps is a variable displacement pump whose delivery capacity per rotation is freely variable.

A hydraulic system includes a hydraulic pump to output an operation fluid, first and second hydraulic devices to be operated by the operation fluid, first and second control valves to control the first and second hydraulic device, respectively, first and second communication tubes connecting the first hydraulic device to the first control valve, a supply fluid tube connecting the first control valve to the second control valve, the supply fluid tube being configured to supply the return fluid to the second control valve, first and second connection fluid tubes disposed on the first control valve, a discharge fluid tube connected to the first control valve, first and second branching fluid tubes branched from the first and second connection fluid tubes, respectively, first and second throttles disposed on the first and second branching fluid tubes, respectively, the second throttle being smaller than the first throttle.

A steering device includes: a cylinder demarcated into first and second chambers by a piston; a main valve having first and second shuttle chambers; a hydraulic source having first and second discharge ports; a first oil passage configured to connect the first chamber and the first shuttle chamber; a second oil passage configured to connect the second chamber and the second shuttle chamber; a third oil passage configured to connect the first shuttle chamber and the first discharge port; a fourth oil passage configured to connect the second shuttle chamber and the second discharge port; and a tank connected to the main valve via the third oil passage and the fourth oil passage. One of the first shuttle chamber and the second shuttle chamber of the main valve is in an opened state when the hydraulic source is stopped.

A cylinder with position feedback sensor, including a barrel (11), a piston rod (12) and piston (15). Markings (M) associated with a central portion of the piston rod (12C) are readable by a sensor (S). In practice, the freedom of slidable movement of the piston rod (12) is such that the markings are retained at all times entirely within the barrel (11) during use so that the external environment cannot influence (e.g. damage) the markings.

In a steam valve driving apparatus according to an embodiment, a control valve permits or blocks a flow of hydraulic oil from a supply port to an opening direction piston chamber. A dump valve blocks or permits the flow of the hydraulic oil from the opening direction piston chamber to a discharge port. A blocking valve permits or blocks a flow of the hydraulic oil from an accumulator to a closing direction piston chamber. The control valve permits the flow of control oil from the closing direction piston chamber to the discharge port in a state where the flow of hydraulic oil from the supply port to the opening direction piston chamber is permitted.

A hydraulic drive, preferably for a hydraulic press, having a first synchronized cylinder that comprises a piston between first and second pressure chambers; at least one hydraulic pump whereby the pump outlet is hydraulically connected with the first pressure chamber of the first synchronized cylinder and the pump inlet is hydraulically connected with the second pressure chamber of the first synchronized cylinder; at least a second synchronized cylinder that comprises a piston between first and a second pressure chambers; whereby the piston of the first synchronized cylinder is mechanically movably coupled with the piston of the second synchronized cylinder; whereby the first pressure chamber of the second synchronized cylinder is hydraulically connected with the pump outlet; and whereby the second pressure chamber of the second synchronized cylinder can be connected with the pump inlet when a pressure limit in the second pressure chamber of the second synchronized cylinder is exceeded.