An example valve includes: a piston movable between a neutral position and an actuated position; a check poppet configured to be coupled to the piston, wherein in the neutral position, the check poppet is seated on a seat formed on an interior peripheral surface of the housing and blocks fluid at the first port; a solenoid actuator sleeve movable between an unactuated state and an actuated state, wherein in the actuated state, the solenoid actuator sleeve allows pilot fluid to apply a fluid force on the piston in a distal direction; and a feedback spring that applies a biasing force in a proximal direction on the piston against the fluid force, wherein the piston and the check poppet are configured to move axially to the actuated position based on a relationship between the fluid force and the biasing force.

A hydraulic drive system of a construction machine includes: a boom control valve connected to a boom cylinder by a boom raising supply line and a boom lowering supply line; a pump that sucks hydraulic oil through a suction line, and delivers the hydraulic oil through a delivery line; a regenerative valve that brings the boom raising supply line and the suction line into communication with each other through a regenerative line when a boom lowering operation is performed; and a controller that controls an accumulator switching valve. The controller: switches the accumulator switching valve to a pressure accumulation position when a pressure accumulation condition is satisfied; switches the accumulator switching valve to a pressure release position when a pressure release condition is satisfied; and switches the accumulator switching valve to a neutral position when neither the pressure accumulation condition nor the pressure release condition is satisfied.

A pneumatic claw-controlling apparatus includes a claw, an air supply, a high-pressure channel, a medium-pressure channel and a low-pressure channel. The claw is normally in an opened position and movable to a closed position by working air. The air supply releases the working gas according to an air-supply signal. The high-pressure channel is operable to adjust the working gas to a high pressure and communicate the air supply with the claw according to a high-pressure signal. The medium-pressure channel is operable to adjust the working gas to a medium pressure and communicate the air supply with the claw according to a medium-pressure signal. The low-pressure channel is operable to adjust the working gas to a low pressure and communicate the air supply with the claw according to a low-pressure signal. The releasing channel is operable to block the claw from the atmosphere according to a vent-stopping signal.

A linear actuator system includes a linear actuator and an integrated pump assembly connected to the linear actuator to provide fluid to operate the linear actuator. The integrated pump assembly includes a pump with two fluid drivers, each fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The linear actuator system also includes a controller that establishes the pump in a normal mode of operation in which the prime movers are independently driven and switches to a fail-safe mode of operation in which only one prime mover is operated.

An electrohydraulic system includes a hydraulic load and at least one closed hydraulic circuit. The hydraulic circuit includes at least one control mechanism, a hydraulic machine, and a closed hydraulic reservoir. The closed hydraulic circuit is filled with degassed hydraulic fluid. A method, in one embodiment, includes filling the electrohydraulic system with degassed hydraulic fluid. In one embodiment, equipment is provided for filling the electrohydraulic system with the degassed hydraulic fluid

A fluid pump for a linear actuator causes a rod in the actuator to extend or retract by controlling fluid flow to and from portions of a fluid chamber on either side of a piston disposed within the fluid chamber and supporting the rod. The pump includes check valves that control fluid flow between a driven pump element and each portion of the fluid chamber and a shuttle movable in response to fluid pressure along a shuttle axis extending through the valves. At least one valve includes a valve member movable between a closed position and an open position defining a fluid flow path between the driven pump element and fluid chamber and means for limiting movement of the shuttle towards the valve such that the shuttle may, depending on the position of the limiting means, move the valve member to an intermediate position between the closed and open positions.

A linear actuator system includes a linear actuator and at least one integrated pump assembly connected to the linear actuator to provide fluid to operate the linear actuator. The integrated pump assembly includes a pump with at least one fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The linear actuator system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover to exclusively adjust at least one of a flow and a pressure in the linear actuator system to an operational set point.

A pneumatic claw-controlling apparatus includes a claw, an air supply, a high-pressure channel, a medium-pressure channel and a low-pressure channel. The claw is normally in an opened position and movable to a closed position by working air. The air supply releases the working gas according to an air-supply signal. The high-pressure channel is operable to adjust the working gas to a high pressure and communicate the air supply with the claw according to a high-pressure signal. The medium-pressure channel is operable to adjust the working gas to a medium pressure and communicate the air supply with the claw according to a medium-pressure signal. The low-pressure channel is operable to adjust the working gas to a low pressure and communicate the air supply with the claw according to a low-pressure signal. The releasing channel is operable to block the claw from the atmosphere according to a vent-stopping signal.

A method and apparatus for remotely positioning a stabilizer wheel of a towable agricultural implement simultaneously, cooperatively and proportionally control the flow of hydraulic fluid to and from both the rod and base ends of the bore of a double-acting hydraulic cylinder, to hold the piston of the hydraulic cylinder at a target position determined from a desired position input signal corresponding to a desired position of the stabilizer wheel with respect to a frame of the agricultural implement.

A fluid pump for a linear actuator causes a rod in the actuator to extend or retract by controlling fluid flow to and from portions of a fluid chamber on either side of a piston disposed within the fluid chamber and supporting the rod. The pump includes check valves that control fluid flow between a driven pump element and each portion of the fluid chamber and a shuttle movable in response to fluid pressure along a shuttle axis extending through the valves. At least one valve includes a valve member movable between a closed position and an open position defining a fluid flow path between the driven pump element and fluid chamber and means for limiting movement of the shuttle towards the valve such that the shuttle may, depending on the position of the limiting means, move the valve member to an intermediate position between the closed and open positions.