A fluid pressure control device includes a neutral passage, a control valve provided in the neutral passage, a first supply passage, and a discharge passage, the control valve has, a switching valve configured to control a flow of a working fluid to the discharge passage from the first actuator in accordance with a pressure in a pilot chamber to which a part of the working fluid supplied from the first supply passage to the first actuator is led, and a throttle portion configured to throttle the flow of the working fluid supplied to the first actuator from the first supply passage, and the pressure on an upstream side of the throttle portion is led to the pilot chamber.

A hydraulic work machine is provided which can improve the finishing accuracy in a horizontally leveling work, a slope face shaping work and so forth by preventing sudden acceleration of an arm when the excavation load decreases suddenly. The hydraulic work machine includes an arm velocity-control valve device 22 capable of adjusting a meter-out opening of the arm cylinder independently of a first arm directional control valve 23. A controller 100 is configured to control, when correcting and increasing an operation amount instructed by the first arm directional control valve, the arm velocity-control valve device to decrease the meter-out opening of the arm cylinder in response to the increase of load pressure of the arm cylinder.

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 valve member having a supply pressure and a method of controlling the supply pressure in the valve member includes a valve body having a fluid inlet, a fluid outlet, and a controlled port. The valve member includes a spool moveable within the valve body to fluidly connect at least one of the fluid inlet and the fluid outlet with the controlled port. The spool includes an end in fluid communication with a control pressure port and a pin received within the end of the spool that is moveable relative to the spool. Fluid flow through the control pressure port acts against a cross-sectional area of the pin and an annular area of the spool to modulate the supply pressure through the valve member.

A flow control circuit for an actuator is provided. The actuator includes a first chamber and a second chamber, wherein the first chamber experiences a volume change that is larger than a volume change experienced by the second chamber upon actuation of the actuator. The flow control circuit includes a first port configured to be connected to the first chamber, a second port configured to be connected to the second chamber, and a flow control valve assembly including one or more valves configured to provide a flow of pressurized fluid from a pressurized fluid source to one of the first and second ports along a fluid supply path and further configured to provide a flow of fluid from the other of the first and second ports to a fluid sink along a fluid return path. The flow control circuit further includes a fluid bypass path comprising a bypass valve.

The invention relates to a method for controlling a hydraulically actuated drive unit (1-3), especially for a valve or control device, wherein at least on a part of the displacement of the drive unit the displacement speed (v) is detected and compared with a predetermined target displacement speed (v), whereupon in the case of a difference between actual value (v) and target value (v) of the speed, the controlling of the drive unit (1-3) is changed such that the displacement speed (v) of the drive unit is adapted to the target value (v).

A hydraulic drive including at least one hydraulic cylinder that includes a piston chamber, an annulus, and a piston that separates the piston chamber from the annulus. The hydraulic drive also includes a first hydraulic pump hydraulically connected with the piston chamber, a second hydraulic pump hydraulically connected with the annulus, a third hydraulic pump, and a directional control valve that has a first switching position and a second switching position. The third hydraulic pump in the first switching position of the directional control valve is hydraulically connected with the piston chamber, and the third hydraulic pump in the second switching position of the directional control valve is not hydraulically connected with the piston chamber.

An actuator controller for actuating an actuator which can be operated fluidically, having a feed line for an inflow of the working fluid to an actuator connector and having a discharge line for an outflow of the working fluid to a fluid outlet, wherein the feed line is assigned a feed line valve and the discharge line is assigned a discharge valve, which valves are configured in each case to influence a volumetric fluid flow at the actuator connector, and having a control device for actuation of the feed line valve and the discharge valve. A throughflow sensor is arranged in a line section between the discharge valve and the fluid outlet, which throughflow sensor is configured for determining a volumetric fluid flow in the discharge line and for providing a throughflow signal.

A method of controlling hydraulic fluid flow to an implement of a material handling vehicle includes coupling a boom arm to a vehicle frame for rotation about the vehicle frame, rotating a boom arm with respect to the vehicle frame with an actuator, coupling an attachment to the boom arm for rotation with respect to the boom arm, sensing a pressure of fluid in the actuator, communicating the sensed pressure to a control system, determining a baseline pressure of the attachment based upon the sensed pressure of the fluid in the actuator, and limiting fluid flow to the actuator with a control valve in response to the sensed pressure of the fluid in the actuator being above the baseline pressure.

The present invention relates to a control valve, for hydraulic lifters used on tractors, and having a body (10), at least one main inlet line (11) which transfers fluid into the body (10), and a check valve (23) for controlling the passage of fluid, coming from the main inlet line (11), to a cylinder line (14).