An example valve includes: a piston movable between a neutral position and an actuated position, wherein in the neutral position: a second port of the valve is fluidly coupled to a first port, and a third port is fluidly decoupled from the second 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 a piston in a distal direction; a first feedback spring; and a second feedback spring disposed in series with the first feedback spring, wherein the first feedback spring and the second feedback spring cooperate to apply a biasing force in a proximal direction on the piston against the fluid force, wherein the piston is configured to move to the actuated position based on a relationship between the fluid force and the biasing force.

An example valve includes: a piston movable between a neutral position and an actuated position, wherein in the neutral position: a second port of the valve is fluidly coupled to a first port, and a third port is fluidly decoupled from the second 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 a piston in a distal direction; a first feedback spring; and a second feedback spring disposed in series with the first feedback spring, wherein the first feedback spring and the second feedback spring cooperate to apply a biasing force in a proximal direction on the piston against the fluid force, wherein the piston is configured to move to the actuated position based on a relationship between the fluid force and the biasing force.

An example valve includes: a piston movable between a neutral position and an actuated position, wherein in the neutral position: a second port of the valve is fluidly coupled to a first port, and a third port is fluidly decoupled from the second 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 a piston in a distal direction; a first feedback spring; and a second feedback spring disposed in series with the first feedback spring, wherein the first feedback spring and the second feedback spring cooperate to apply a biasing force in a proximal direction on the piston against the fluid force, wherein the piston is configured to move to the actuated position based on a balance between the fluid force and the biasing force.

An apparatus for monitoring the pressurisation of a control valve for a hydraulic actuator and a control valve. The apparatus including a spool movable along an axis (X), wherein the spool is configured to control the flow of hydraulic fluid through the control valve based on its position along the axis (X), and wherein in an unpressurised state of the control valve the spool occupies a first axial position, and in a pressurised state of the control valve the spool occupies a second, different axial position. The apparatus also including a position sensor configured to monitor the position of the spool within the control valve and detect whether the spool occupies the first axial position or the second axial position, wherein the first axial position and the second axial position correspond to neutral positions of the spool.

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 apparatus for monitoring the pressurisation of a control valve for a hydraulic actuator and a control valve. The apparatus including a spool movable along an axis (X), wherein the spool is configured to control the flow of hydraulic fluid through the control valve based on its position along the axis (X), and wherein in an unpressurised state of the control valve the spool occupies a first axial position, and in a pressurised state of the control valve the spool occupies a second, different axial position. The apparatus also including a position sensor configured to monitor the position of the spool within the control valve and detect whether the spool occupies the first axial position or the second axial position, wherein the first axial position and the second axial position correspond to neutral positions of the spool.

[Object] To make it possible to detect, with a single pressure sensor, a malfunction of two solenoid valves for switching flow paths and to quickly and reliably exhaust residual pressure in an air device through a solenoid valve.

[Solution] A residual pressure exhaust air circuit 1 includes: a main flow path 9 through which air from an air source 2 is supplied to an air cylinder 100; an exhaust flow path 10 through which air in the air cylinder 100 is exhausted; a first sensor 8 for detecting a malfunction of solenoid valves 12, 13; a detection flow path 11 through which air from the air source 2 is supplied to the first sensor 8; and the two solenoid valves 12, 13 that switch communication states among the main flow path 9, the exhaust flow path 10, and the detection flow path 11. The two solenoid valves 12, 13 are formed of two-position valves having first positions 12a, 13a at the time of OFF and second positions 12b, 13b at the time of ON and are synchronously ON/OFF controlled. When the two solenoid valves 12, 13 do not operate in synchronization with each other, the air from the air source 2 is supplied to the first sensor 8 to detect a malfunction of the two solenoid valves 12, 13, and at the same time, the air in the air cylinder 100 is exhausted through the solenoid valve 12, 13.

An assembly for a fluid-filled piston-cylinder unit comprises a main body having an assembly longitudinal axis (24), a valve unit integrated in the main body and having an overflow channel, which valve unit seals the overflow channel when the assembly is moved along the assembly longitudinal axis in a first direction and releases the overflow channel, in dependence on the fluid pressure, when the assembly is moved along the assembly longitudinal axis in a second direction. Furthermore, the assembly comprises an outer seal element that is arranged on the main body so as to be moved along the assembly longitudinal axis, for abutting in a sealing manner against an inner surface of the housing, and at least one undercut element formed on the main body for engaging in an interlocking manner behind a mating element of the piston-cylinder unit.

A return manifold includes a housing having a first workport, a second workport, a third workport, and a fourth workport, and defining a first chamber and a second chamber. The return manifold includes a back-pressure disk arranged between the first workport and the first chamber, a bypass disk arranged between the first chamber and the second chamber, a back-pressure spring biased between the back-pressure disk and the bypass disk, and a bypass spring biased against the bypass disk. The back-pressure disk and the bypass disk are hydro-mechanically coupled so that movement of the bypass disk alters a force on the back-pressure disk and movement of the back-pressure disk alters a force on the bypass disk.

A servo valve is provided with a first elastic portion, a second elastic portion, and a connecting portion. The first elastic portion extends in an X direction inside a valve body and has a first elastic force exerted on a movable element toward an X2 direction. The second elastic portion extends in the X direction inside the valve body and has a second elastic force exerted on the movable element toward an X1 direction.

The connecting portion is connected to the first elastic portion and the second elastic portion inside the valve body, and is in abutment against a step portion of the valve body and a spool of the movable element at a neutral position of the movable element.