A hydraulic lifting mechanism suspension has a main valve in the activation position whereof at least one hydraulic accumulator is connected to a connection line of the lifting mechanism suspension acting in the lifting direction or to working line of the lifting mechanism suspension acting in the lifting direction. The lifting mechanism suspension is deactivated via a deactivation position of the main valve, while at the same time a connection for recharging or filling the hydraulic accumulator is opened.

An apparatus for controlling a hydraulic machine, for example a turbine, pump or pump turbine, using variable-speed driven fixed displacement pumps. The apparatus includes a device for carrying out an emergency shut-off that is characterized by low energy consumption and high efficiency while guaranteeing all the operation-relevant and safety-relevant requirements of a hydraulic machine.

An energy regeneration device capable of controlling flow of a working fluid discharged from an actuator while regenerating energy from the working fluid, and a work machine including the foregoing device, include a boom cylinder, an inertial fluid container, an oil tank, an accumulator, a low-pressure-side opening/closing device, and a high-pressure-side opening/closing device. A calculation unit calculates a duty ratio for opening/closing the low-pressure-side opening/closing device and the high-pressure-side opening/closing device in accordance with a desired flow rate of a hydraulic fluid discharged from the boom cylinder. A regeneration control unit selects alternately the low-pressure-side opening/closing device and the high-pressure-side opening/closing device as a destination with which the inertial fluid container communicates in accordance with the calculated duty ratio, and supplies the discharged hydraulic fluid to an accumulator.

A work machine including: a hydraulic cylinder 20 configured to drive a work implement 3; a control valve 22 configured to connect a delivery line of a hydraulic pump 21 switchingly to a bottom fluid chamber and a rod fluid chamber of the hydraulic cylinder 20 and a tank; a pilot pump 23 configured to output a pilot pressure to drive the control valve 22; an engine 24 configured to drive the hydraulic pump 21 and the pilot pump 23; and an accumulator 26 configured to accumulate a return hydraulic fluid from the hydraulic cylinder 20 is provided with: a bypass line 41 configured to connect the bottom fluid chamber of the hydraulic cylinder 20 and a delivery line 21a of the hydraulic pump 21 by bypassing the control valve 22 and be provided with the accumulator 26 thereon; a pressure-accumulation control valve 27 provided between the bottom fluid chamber of the hydraulic cylinder 20 and the accumulator 26; a release control valve 28 provided between the accumulator 26 and the delivery line 21a; and a hydraulic system controller 30 configured to open the release control valve 28 if an engine revolution speed N becomes lower than a set value Ns.

A control system can include a resettable chamber and a bidirectional valve. The bidirectional valve can be switchable between (i) a first configuration for enabling fluid flow from the control line into a first port of a well tool and from a second port of the well tool into the resettable chamber, and (ii) a second configuration for enabling fluid flow from the control line into the second port of the well tool and from the first port of the well tool into the resettable chamber. The bidirectional valve can be switched from the first configuration to the second configuration in response to pressure being applied to the control line.

To provide a hydraulic control circuit for a construction machine capable of shortening a time duration from the start of an engine until the pressure of a pump oil passage reaches a required pressure. A hydraulic control circuit for a construction machine includes a hydraulic pump that is driven by an engine; a hydraulic actuator that is operated by hydraulic oil discharged from the hydraulic pump; a hydraulic pilot type control valve that controls an amount and a direction of supply of the hydraulic oil to the hydraulic actuator from the hydraulic pump; a pump oil passage that connects the hydraulic pump and a pump port of the hydraulic pilot type control valve; a bypass oil passage that branches from the pump oil passage and extends to a hydraulic oil tank; a bypass valve that is disposed in the bypass oil passage and controls an amount of the hydraulic oil returning to the hydraulic oil tank through the bypass oil passage; and a pilot oil passage that branches from the pump oil passage and extends to a pilot port of the hydraulic pilot type control valve; an electromagnetic proportional pressure reducing valve that is disposed in the pilot oil passage and controls a pressure acting on the pilot port; a controller that controls an operation of the bypass valve and the electromagnetic proportional pressure reducing valve; and an operation implement for outputting an operation signal to the controller in response to an operation applied from an operator. The controller sets the opening area A of the bypass valve to a second opening area A1 in a state where an operation signal is not output from the operation implement after the engine has been started and the pressure of the pump oil passage has reached a required pressure P0, and sets the opening area A of the bypass valve to a second opening area A2 which is smaller than the first opening area A1 during a time duration from the start of the engine until the pressure of the pump oil passage reaches the required pressure P0.

A hydraulic valve body, comprising two main lines for bringing pressurized hydraulic fluid into the body's channel system and further out of the channel system. The body further comprises at least two outlet fittings for conducting hydraulic fluid from the body's channel system to actuators and two respective inlet fittings for conducting hydraulic fluid from the actuators back into the channel system.

An actuator device includes two drive units for an actuator output element. The first drive unit has a first piston chamber and a first piston displaceable therein and also first hydraulic means for displacing the piston. The second drive unit has a second piston chamber and a second piston displaceable therein and also second hydraulic or pneumatic means for displacing the piston. The second piston is joined to the actuator output element for conjoint movement therewith and can be coupled to the first piston for thrust, so that the second piston is displaceable in an outward direction by the first piston. The first drive unit is configured for a larger thrust force than the second drive unit, while the second drive unit is designed for a greater stroke speed than the first drive unit.

A hydraulic hybrid system for rotatory applications has an actuator (49, 91) in the form of a motor pump unit (91). The motor pump unit is coupled to a rotatory-operating device (94) and works as a consumer of hydraulic energy in one operating state of the device (94) and works as a producer of hydraulic energy in another operating state of the device (94). A hydraulic accumulator (1) can be charged by the motor pump unit (91) for energy storage in the one operating state and can be discharged for energy release to the motor pump unit (91) in the other operating state. The hydraulic accumulator is an adjustable hydropneumatic piston accumulator (1) in which a plurality of pressure chambers (19, 21, 23, 25) are delimited by active surfaces (11, 13, 15, 17) of different sizes on the fluid side of the accumulator piston (5). An adjusting arrangement (51) connects a selected pressure chamber (19, 21, 13, 25) or a plurality of selected pressure chambers (19, 21, 23, 25) of the piston accumulator (1) to the actuator (49, 91) depending on the prevailing pressure level on the gas side of the piston accumulator (1) and at the actuator (49, 91).

A hydraulic system for a working machine includes a hydraulic actuator having a first fluid chamber and a second fluid chamber, an accumulator, an outputting fluid tube to output an operation fluid, and a switching valve to be switched between a first position and a second position. The first position allows the first fluid chamber and the second fluid chamber to be communicated with the outputting fluid tube and thereby allowing a floating operation. The second position allows the first fluid chamber and the accumulator to be communicated with each other, allows the second fluid chamber and the outputting fluid tube to be communicated with each other, and thereby allows an anti-vibration operation.