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.

The invention relates to a hydraulic device for driving an actuator to be hydraulically controlled or actuated, comprising a motor arranged in a motor housing, a compensating tank (31) for accommodating hydraulic fluid, and a hydraulic pump, which is arranged in a pump housing and driven by the motor, wherein the hydraulic pump is designed in such a way that the hydraulic pump permits conveyance of hydraulic fluid in two directions, namely in the forward direction and in the backward direction, wherein the hydraulic actuator comprises a drive cylinder, which has a first and a second cylinder chamber and a drive piston (3) arranged therebetween, to which drive piston a drive shaft (2) that can be displaced in the longitudinal direction is attached, wherein the device comprises a loading cylinder for an emergency closing spring (16), in which loading cylinder a loading cylinder chamber (12) and a loading piston (11) that can be coupled to the drive shaft (2) are arranged, wherein the emergency closing spring (16) can be loaded into a loaded or emergency-triggering readiness position by the loading piston (11), wherein the loading cylinder chamber (12) is connected to an outlet of the hydraulic pump in such a way that the loading cylinder chamber (12) can be filled with hydraulic fluid by means of the hydraulic pressure of the hydraulic pump and the loading piston can be transferred into a loading position as the emergency closing spring (16) is compressed and the loading piston can be locked there hydraulically by means of check valves (36, 37), and wherein a controlled seat valve (50) is connected to an inflow/outflow opening of the loading cylinder chamber, by means of which seat valve the emergency closing spring (16) can be transferred from the loaded readiness position into an emergency-triggering opening position, wherein both the hydraulic fluid that is contained in the loading cylinder chamber (12) and holds the emergency closing spring (16) in the readiness position and the hydraulic fluid contained in the first cylinder chamber can be discharged via the controlled seat valve (50).

A hydraulic system for a mobile rescue stretcher has a hydraulic cylinder, with first and second working chambers, a tank and pump. The first and second chambers are connected to the pump via first and second line arrangements, respectively, and can be pressurized by the pump. Hydraulic fluid flows out of the first chamber via the first line arrangement when pressure is applied to the second chamber. The first line arrangement has a first check valve which opens when pressure is applied to the second line arrangement. Hydraulic fluid flows out of the second chamber via the second line arrangement when pressure is applied to the first chamber. The second line arrangement has a first branch line connected to the pump and a second branch line connected to the tank. A pressure valve in the second branch line opens when pressure is applied to the second line arrangement.

The present disclosure relates to a hydraulic system for a construction machine, and more particularly, to a hydraulic system for a construction machine including a plurality of actuators, in which each of the actuators includes a pump/motor, is operated under a control of a corresponding pump/motor, and stores working oil in an accumulator or receives the working oil supplemented from the accumulator in accordance with a difference between a flow rate entering the actuator and a flow rate discharged from the actuator.

The present invention relates to a hydraulic system with a feed pump for feeding hydraulic fluid, wherein the feed pump is driven by a hydraulic drive motor. The invention furthermore comprises a method for feeding hydraulic fluid into a hydraulic system via a feed pump, wherein the feed pump is driven by a hydraulic drive motor.

A steering system for a trailing or leading axle of a vehicle includes a steering angle sensor for measuring a steering angle of wheels of a front axle of the vehicle, a driving speed sensor for measuring a driving speed of the vehicle, an electric motor that drives a hydraulic pump, and a working cylinder connected to the hydraulic pump for steering the wheels of the trailing axle. The system also includes a control device that determines a trailing angle of wheels on the trailing axle of the vehicle and actuates the electric motor in a corresponding manner. The working cylinder has a center position borehole via which hydraulic fluid is released from the working cylinder. A piston closes the center position borehole in the straight-ahead position of the wheels of the trailing axle. The center position borehole can only be closed by a piston seal of the piston.

The present invention relates to an electro-hydrostatic system (1) with a hydraulic machine (11) which is driven by an electric motor (10) and has a variable volume and/or rotational speed for providing a volumetric flow rate of a hydraulic fluid, a differential cylinder (20) with a piston surface and with an annular surface, and at least one equalization container (30, 37), wherein the drive system (1) has a closed hydraulic circuit and during operation has an overpressure relative to the environment by means of the hydraulic machine (11) and/or a pretensioning source (15, 37), and the drive system (1) provides a movement of the cylinder in a first direction by means of a volumetric flow rate of the hydraulic machine (11) and a volumetric flow rate from the equalization container (30, 37), and provides a movement in a second direction by means of a volumetric flow rate of the hydraulic machine (11) and a volumetric flow rate into the equalization container (30, 37), and a power operating mode and a speed operating mode are provided with the differential cylinder (20).

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.

Provided is a construction machine on which a hydraulic closed circuit for driving a single rod-type hydraulic cylinder and a swing hydraulic motor is mounted and that has good swing deceleration responsiveness. In this construction machine that drives each of a single rod-type hydraulic cylinder and a swing hydraulic motor in a closed circuit, a minimum passage area from a second flushing valve to a tank in a case the second flushing valve is fully open is smaller than a minimum passage area from a first flushing valve to the tank in a case the first flushing valve is fully open.