A servo valve includes a valve housing, a cavity formed in the valve housing defining an axis (X) and an axially moveable member disposed in the cavity. The member comprises flat surfaces parallel to the axis (X). A channel is formed within the cavity and a plurality of ports each forming a fluid passage through the valve housing in fluid communication with a spool and with the channel. The plurality of ports include first and second nozzles with nozzle openings, wherein in a first axial position of the member the first nozzle opening is at least substantially obstructed by the first flat surface, and in a second axial position of the member the second nozzle opening is at least substantially obstructed by the second surface, the member controlling fluid between the spool and the channel.

A pilot device for a hydraulic directional valve includes a displacement sensor, a pilot valve, an actuating device, a coil assembly, and a circuit board. The displacement sensor has a sensor axis and the pilot valve has a valve axis. The valve axis and the sensor axis are arranged substantially parallel to one another so as to lie in a reference plane. The actuating device and the coil assembly are arranged adjacent to one another. The circuit board is arranged parallel to the reference plane. In each case, to establish an electrical contact, the coil assembly, the actuating device, and an electrical plug connection are either soldered directly to the circuit board or are in breakable electrical contact with a respectively associated, rigid contact assembly. The contact assembly is soldered directly to the circuit board.

An example solenoid tube of a solenoid actuator for a valve includes: (i) a cylindrical body includes: a first threaded region formed on an exterior peripheral surface of the cylindrical body, and a second threaded region formed on an interior peripheral surface of the cylindrical body; and (ii) a pole piece formed as a protrusion from the interior peripheral surface of the cylindrical body and configured to divide a hollow interior of the cylindrical body into a first chamber and a second chamber, where the pole piece defines a channel therethrough, such that the channel fluidly couples the first chamber to the second chamber, where the first chamber is configured to receive an armature of the solenoid actuator therein, and where the second chamber is configured to a component such as a sensor or a manual actuator therein.

A servo valve comprising first and second nozzles and first and second piezoelectric actuators arranged to control fluid flow through the first and second nozzles respectively. A first fluid flow path is defined between the first nozzle and the first piezoelectric actuator and a second fluid flow path is defined between the second nozzle and the second piezoelectric actuator. The first and second piezoelectric actuators are arranged such that applying a voltage to the first and second piezoelectric actuators causes a change in dimension thereof, which acts to open or restrict said first and second fluid flow paths respectively.

A hydraulic cylinder spool valve device, which extends and retracts a cylinder rod of a hydraulic cylinder, includes: a first spool valve having a first dead band and a first opening characteristic; a second spool valve having a second dead band and a second opening characteristic; and a controller performing communication with the hydraulic cylinder by using the first spool valve and positioning the second spool of the second spool valve within the second dead band and performing communication with the hydraulic cylinder by using the second spool valve and positioning the first spool of the first spool valve within the first dead band, and adjusting a characteristic of a switching dead band between the first opening characteristic and the second opening characteristic.

For the purpose of providing a valve arrangement for controlling pneumatic drives with protection against a sudden automatic change in the initial switching position without an input signal in the event of a fault in a resetting device of a pilot stage and, for this situation, effective fault identification by purely pneumatic means, said valve arrangement comprises a first and a second working connection (1; 2), which can be connected to a drive, and a first and a second electropneumatically pilot-controlled directional valve, in which valve arrangement one or both directional valves is or are arranged upstream of the working connections (1; 2) for the purpose of influencing and venting said working connections, wherein the pilot stages of both directional valves are of automatically resetting design and the second directional valve is designed for alternately assuming an inoperative position and a switching position and the pilot stage of the first directional valve has an external control connection (8; 8) which can be influenced by means of the second directional valve in its switching position and can be vented by means of said second directional valve in its inoperative position, wherein the second directional valve has, as a resetting device for the main stage (14), an air spring (19) which can be influenced and can be vented externally by means of the first directional valve, and a change in state between influencing or venting of the air spring (19) after the first directional valve assumes a switching position takes place only depending on the change in the switching state of the first directional valve, and a change in state between influencing or venting at one working connection (1; 2) after previous influencing or venting which took place with the second directional valve assuming the switching position takes place only depending on the second directional valve assuming the inoperative position.

A pulse valve assembly including a main valve and two pilot valves. The main valve includes a main valve body, main valve bore, and main valve spool. The main valve body includes an inlet port, an outlet port, and a pressure chamber at one end of the main valve bore. A first pilot valve selectively supplies pressurized fluid to the second pilot valve depending on the position of a poppet, which is controlled by a solenoid. A second pilot valve includes a spool that is driven by pressurized fluid from the first pilot valve. The second pilot valve selectively supplies pressurized fluid to the pressure chamber in the main valve causing the main valve spool to move towards the open or closed position. When the main valve spool is in the open position, pressurized fluid can flow through the main valve from the inlet port to the outlet port.

In a closed loop control method for an electropneumatic field device, an electronic target value input of a command variable corresponding to a target value of a control center is received by the open loop and/or closed loop control electronics, an electronic output for a manipulating variable to pilot the electropneumatic converter is generated by the open loop and/or closed loop control electronics; and, in a predetermined operating condition of the field device, the manipulating variable is determined by a closed loop control algorithm based on the command variable and on another controlled variable different from an actual control member position measurement value.

A servovalve comprising: a fluid transfer valve assembly comprising a supply port and a control port; a moveable valve spool arranged to regulate flow of fluid from the supply port to the control port in response to a control signal; and a drive member configured to axially move the valve spool relative to the fluid transfer assembly in response to the control signal to regulate the fluid flow.

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.