The subject matter of this specification can be embodied in, among other things, a fluid valve assembly that includes a first fluid port, a second fluid port, a third fluid port, a valve spool configured to be positioned at a first position, a second position away from the first position, a third position away from the first position opposite the second valve position, the valve spool defining a first fluid duct configured to fluidly connect the first fluid port to the second fluid port in the first valve position, a second fluid duct configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and a third fluid duct configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

The subject matter of this specification can be embodied in, among other things, a fluid valve assembly that includes a first fluid port, a second fluid port, a third fluid port, a valve spool configured to be positioned at a first position, a second position away from the first position, a third position away from the first position opposite the second valve position, the valve spool defining a first fluid duct configured to fluidly connect the first fluid port to the second fluid port in the first valve position, a second fluid duct configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and a third fluid duct configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

A servo actuator is provided which may comprise a controller configured to control a plurality of solenoid valves based upon an output signal. The plurality of solenoid valves may be used to control the position of the object. For example, a set of solenoid valves, of the plurality of solenoid valves, may be configured to conduct fluid from a tank into a first chamber of the cylinder, conduct fluid from the tank into a second chamber of the cylinder, conduct fluid from the second chamber of the cylinder into a first solenoid valve and/or conduct fluid from the first chamber of the cylinder into the first solenoid valve. The first solenoid valve, of the plurality of solenoid valves, may be configured to conduct fluid from the set of solenoid valves into a vent valve based upon a pulse width modulation (PWM) signal received from the controller.

A servo actuator is provided which may comprise a controller configured to control a plurality of solenoid valves based upon an output signal. The plurality of solenoid valves may be used to control the position of the object. For example, a set of solenoid valves, of the plurality of solenoid valves, may be configured to conduct fluid from a tank into a first chamber of the cylinder, conduct fluid from the tank into a second chamber of the cylinder, conduct fluid from the second chamber of the cylinder into a first solenoid valve and/or conduct fluid from the first chamber of the cylinder into the first solenoid valve. The first solenoid valve, of the plurality of solenoid valves, may be configured to conduct fluid from the set of solenoid valves into a vent valve based upon a pulse width modulation (PWM) signal received from the controller.

A hydraulic system is provided. The hydraulic system includes a pump, a load sense conduit, a tank conduit, a function workport, and a function control valve. The hydraulic system further includes a function poppet valve arranged between the function workport and the function control valve and having a function poppet vent passage, and a system control valve arranged downstream of the function control valve. The system control valve is biased into a first position where fluid communication between the function poppet vent passage and the tank conduit is prevented and fluid communication between the load sense conduit and the tank conduit is provided. The system control valve is selectively movable to a second position where fluid communication between the function poppet vent passage and the tank conduit is allowed and fluid communication between the load sense conduit and the tank conduit is prevented.

A hydraulic system is provided. The hydraulic system includes a pump, a load sense conduit, a tank conduit, a function workport, and a function control valve. The hydraulic system further includes a function poppet valve arranged between the function workport and the function control valve and having a function poppet vent passage, and a system control valve arranged downstream of the function control valve. The system control valve is biased into a first position where fluid communication between the function poppet vent passage and the tank conduit is prevented and fluid communication between the load sense conduit and the tank conduit is provided. The system control valve is selectively movable to a second position where fluid communication between the function poppet vent passage and the tank conduit is allowed and fluid communication between the load sense conduit and the tank conduit is prevented.

Provided is a rotation drive device that has a wide rotary driving range, e.g. a rotary driving range of 0-180. Disclosed is a rotation drive device comprising a crank member rotatable about a crank axis, a first cylinder having a first piston and rotatable about a first cylinder rotation axis, and a second cylinder having a second piston and rotatable about a second cylinder rotation axis. The crank member and the first piston are coupled for rotation about a first piston rotation axis spaced from the crank axis. The crank member and the first piston are coupled for rotation about a second piston rotation axis spaced from the crank axis.

Provided is a rotation drive device that has a wide rotary driving range, e.g. a rotary driving range of 0-180. Disclosed is a rotation drive device comprising a crank member rotatable about a crank axis, a first cylinder having a first piston and rotatable about a first cylinder rotation axis, and a second cylinder having a second piston and rotatable about a second cylinder rotation axis. The crank member and the first piston are coupled for rotation about a first piston rotation axis spaced from the crank axis. The crank member and the first piston are coupled for rotation about a second piston rotation axis spaced from the crank axis.

A hydromechanical linear converter has a cylinder, a piston unit and a seat valve unit. The cylinder and a piston of the piston unit delimit a hydraulic working chamber, into which a working connection and a further fluid connection open, and has a supply connection 10. The valve unit switches between a first position connecting the supply connection to the fluid connection and a second position blocking the fluid connection from the supply connection. The linear converter includes a valve housing with a valve seat 16, a valve body with a valve head cooperating with the seat, a spring unit preloading the valve body into a position corresponding to the first position and an electromagnetic actuator 14 acting on the valve body 12 by purely mechanical action, to move the valve body against the force of the spring unit into a position corresponding to the second switching position.

An actuator comprising: a piezo actuator; a drive having a drive chamber and a drive piston element driven by the piezo actuator; a first output having an output chamber and a piston element; and a second output having an output chamber and a piston element. At least part of the hydraulic fluid is conveyed out of the drive chamber by movement of the drive piston element and into the first output chamber. At least part of the hydraulic fluid is conveyed out of the drive chamber and into the second output chamber. The second output piston element has a hydraulically active second output face which is different in size from the first output face. There may be a coupling device mechanically coupling the first output piston element to the second output piston element.