A servo valve includes a fluid transfer valve assembly comprising a supply port and a control port; a 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 means configured to move the valve spool relative to the fluid transfer assembly in response to the control signal to regulate the fluid flow. The drive means is arranged to rotate the spool relative to the fluid transfer assembly, the spool provided with openings arranged to selectively align with or block flow channels in the fluid transfer assembly according to the direction and degree of rotation of the spool.

A hydraulic multi-way valve with independent oil-port control, includes a multi-way valve body, an A valve core and a B valve core. The multi-way valve body has an A oil port and a B oil port, and includes an A cavity and a B cavity independent from each other therein. The A oil port, a P high-pressure oil port and a T high-pressure oil port are all in communication with the A cavity, the B oil port, the P high-pressure oil port and the T high-pressure oil port are all in communication with the B cavity. The A valve core is arranged in the A cavity, and the B valve core is arranged in the B cavity.

A safety valve is provided with an electronic control unit for generating a control voltage. An electro-fluidic preliminary stage has a piezo bending actuator which can be actuated between a working position and a safety position by the control voltage and influences the flow of a secondary control fluid flow depending on its position. A fluid-mechanical main stage has an influencing device for influencing the flow of a primary working fluid flow. The influencing device can be actuated by means of the secondary control fluid flow which flows into a control chamber of the main stage. The control unit caries out a test of the preliminary stage repeatedly in an iterative manner after the expiration of a specified time interval. As part of the functionality test, the position of the piezo bending actuator is changed slightly by varying the control voltage.

A safety valve is provided with an electronic control unit for generating a control voltage. An electro-fluidic preliminary stage has a piezo bending actuator which can be actuated between a working position and a safety position by the control voltage and influences the flow of a secondary control fluid flow depending on its position. A fluid-mechanical main stage has an influencing device for influencing the flow of a primary working fluid flow. The influencing device can be actuated by means of the secondary control fluid flow which flows into a control chamber of the main stage. The control unit caries out a test of the preliminary stage repeatedly in an iterative manner after the expiration of a specified time interval. As part of the functionality test, the position of the piezo bending actuator is changed slightly by varying the control voltage.

A counter pressure valve arrangement for controlling a pressure level of a hydraulic fluid in a return line from a hydraulic actuator arrangement. The counter pressure valve arrangement comprises a counter pressure valve having: a moveable valve member; a counter pressure regulating port configured for being connected to the hydraulic actuator arrangement via the return line; a tank port configured for being connected to a tank or low pressure reservoir for storing low pressure hydraulic fluid; and a pump port configured for being connected to a source of pressurised hydraulic fluid. A first position of the valve member effects fluid communication between the pump port and the counter pressure regulating port for supplying pressurised hydraulic fluid to the return line, and a second position of the valve member effects fluid communication between the counter pressure regulating port and the tank port for discharging hydraulic fluid from the return line to the tank.

Passage forming blocks of a first pilot valve and a second pilot valve each include a supply passage, which opens in a first surface and a second surface and is connected to a valve chamber, a first output passage, which opens in the first surface and are connected to the valve chamber, and a second output passage, which opens in the first surface. Further, the passage forming blocks each include an output passage connecting recess. The output passage connecting recess is provided in a section of the second surface that overlaps with an opening region of the first output passage, which opens in the first surface, and is connected to the second output passage. The first output passage of the first pilot valve is connected to the second output passage of the second pilot valve via the output passage connecting recess of the second pilot valve.

A load sense pressure regulating system is provided. The load sense pressure regulating system can be operable between a flow regulation mode and a pressure limiting mode. When the load sense pressure control system is in the flow regulation mode, flow between a load sense inlet and a pilot vent are metered by a main poppet. The load sense pressure regulating system can also include a control valve downstream from the pilot vent that is configured to control a relief setting of a relief valve to regulate the load sense pressure within a desired operating range.

A plug for retaining a filter screen in a fluid port of a servovalve, the plug comprises an annular body. The annular body comprises opposed first and second axial annular end surfaces. A radially inner surface extends between the first and second axial annular end surfaces and a radially outer surface extends between the first and second axial annular end surfaces. At least one recess is formed in the radially inner surface for receiving a tool for removing the plug from the port. A plurality of slots is formed in the first axial annular end surface and extends into the at least one recess for providing access for the tool to the at least one recess.

A plug for retaining a filter screen in a fluid port of a servovalve, the plug comprises an annular body. The annular body comprises opposed first and second axial annular end surfaces. A radially inner surface extends between the first and second axial annular end surfaces and a radially outer surface extends between the first and second axial annular end surfaces. At least one recess is formed in the radially inner surface for receiving a tool for removing the plug from the port. A plurality of slots is formed in the first axial annular end surface and extends into the at least one recess for providing access for the tool to the at least one recess.

A coupler cylinder is driven between a locked state and an unlocked state of a bucket by being supplied with hydraulic oil. A main pump supplies the hydraulic oil to the coupler cylinder. A pressure increasing valve controls the supply of the hydraulic oil to the coupler cylinder. A controller controls drive of the pressure increasing valve. The controller instructs the pressure increasing valve to stop the supply of the hydraulic oil to the coupler cylinder based on pressure in an oil passage between the main pump and the coupler cylinder.