A hydraulic system includes: a solenoid valve that includes a valve spool configured to slide within a housing, and moves the valve spool to a position corresponding to an operation command input to the solenoid valve; and a control device that outputs the operation command to the solenoid valve. When a predetermined condition is satisfied, the control device outputs a continuously or intermittently changing operation command to the solenoid valve to reciprocate the valve spool from a full open position or a full closed position.

A quick coupler circuit includes a cylinder to attach and/or detach an attachment to and/or from a construction machine by expansion and/or contraction, a flow pump to supply fluid to the cylinder, a valve through which fluid for operating the cylinder passes, a spool valve which includes a spool, to move along an axial direction, and to form a pressure at a node of the flow pump according to movement of the spool, an electronic proportional pressure reducing valve to control the spool valve, a switch to perform an ON/OFF operation, and a controller to output a control current to the electronic proportional pressure reducing valve in response to the operation of the switch. The controller is maintains control current which it outputs during the switch's ON operation for a predetermined period of time after the switch's OFF operation.

A hydraulic machine unit that can be operated with various working forces, in which working medium is selectively delivered, via a pump-piston accumulator system, to a main cylinder and at least one driving cylinder, wherein at least for one working stroke a pump system of the pump-piston accumulator system is used to provide working medium to a piston accumulator of the pump-piston accumulator system, and then at least for the working stroke at least the main cylinder is charged with a working pressure from the piston accumulator, and wherein at least for a return stroke the at least one driving cylinder is charged with a return stroke pressure from the pump-piston accumulator system, can be of structurally simple configuration if, at reduced working forces, the working pressure is reduced with respect to the piston accumulator pressure prevailing in the piston accumulator.

An electric-powered fail-safe actuator for use with a valve, where the actuator stores potential energy for conversion to kinetic energy to close or open the valve to the fail-safe position.

An electric-powered fail-safe actuator for use with a valve, where the actuator stores potential energy for conversion to kinetic energy to close or open the valve to the fail-safe position.

A hydraulic system includes: a solenoid valve that includes a valve spool configured to slide within a housing, and moves the valve spool to a position corresponding to an operation command input to the solenoid valve; and a control device that outputs the operation command to the solenoid valve. When a predetermined condition is satisfied, the control device outputs a continuously or intermittently changing operation command to the solenoid valve to reciprocate the valve spool from a full open position or a full closed position.

A vehicle brake system may include: two hydraulic brake circuits, each having at least one hydraulically operating wheel brake; first and second pressure supply devices; at least one valve assembly for adjusting the brake pressure for each wheel individually and/or for separating/connecting the wheel brakes from/to at least one of the pressure supply devices; at least one electronic control and regulating unit; and a hydraulic connection line connecting the two brake circuits. Each wheel brake is paired with a dedicated switch valve, and each brake circuit has a hydraulic main line via which the switch valves may be connected to the pressure supply devices. The connection line has two connection switch valves connected in series and open when unenergized via pressure present in the respective hydraulic main line and/or an inner section of a connection line connecting two connections of the connection switch valves directly together.

A balancing valve includes four ports. While the pressures at a pair of balancing ports of a hydraulic balancing valve are equal, the valve maintains two other ports in a closed position. Upon a pressure differential between the balancing ports, fluid communication can occur between one of the balancing ports and either of the other ports based upon the direction of the pressure differential. A hydraulic ride control system utilizes the balancing valve together with other control valves to provide ride control functionality.

A regulator valve has a check valve manifold for use in subsea control circuits. For example, the regulator valve having the check valve manifold can be used in a circuit between a directional control valve and an actuator for a gate valve. The check valve manifold can be a flange that attaches to the regulator valve to communicate with the supply and outlet of the regulator valve. Internal communication inside the manifold includes a check valve. If the pressure in the circuit downstream of the regulator valve needs to be vented, the check valve can open to allow the pressure to bleed from the outlet back to the supply without needing to pass through the internal pressure control valve of the regulator.

Disclosed are a fork leveling system and a method thereof, and a telescopic boom forklift. The fork leveling system includes an active leveling oil cylinder, a passive leveling oil cylinder and an electric control oil supplement valve, where a rodless cavity of the active leveling oil cylinder is communicated with a rodless cavity of the passive leveling oil cylinder, and a rod cavity of the active leveling oil cylinder is communicated with a rod cavity of the passive leveling oil cylinder; and an oil inlet of the electric control oil supplement valve is connected to an oil pump, and an oil outlet of the electric control oil supplement valve is connected to the rodless cavity of the active leveling oil cylinder and the rod cavity of the active leveling oil cylinder.