A hydraulic system includes first and second valve assemblies connected to a common pump. The first valve assembly includes a main valve housed inside a manifold. A pressure compensator valve maintains a constant pressure drop across a variable orifice of the main valve. A pressure limiter valve is in communication with the main valve and the pressure compensator valve, and allows an actuator connected to the first valve assembly to operate independently of the second valve assembly so that fluid flow to a work port of the first valve assembly is not interrupted by operation of the second valve assembly.

The present invention discloses a load-sensing multi-way valve with a variable differential pressure, where each valve group uses a new element: an electro-hydraulic pressure compensation valve, so as to implement continuous real-time adjustment and control of compensated differential pressure and real-time position feedback and monitoring of a compensation valve trim, and overcome a flow mismatch problem of a conventional LS system in a flow saturation working condition and problems of a fixed shunting proportion of an LUDV system and poor operation coordination of actuators. The load-sensing multi-way valve with a variable differential pressure disclosed in the present invention has advantages such as strong working condition applicability, high flow distribution accuracy, and strong technicality.

A monitoring device for determining a position of a displacement piston (1) guided longitudinally movably in a housing (7) and, in the housing (7) and delimits a fluid chamber (3, 5) with a variable volume and connected via a pressure supply connector (9, 11) to a pressure fluid control device (13). A volumetric flow regulating device (45) and a pressure determining device (47) are connected between the pressure fluid control device (13) and the measuring connector (15, 17) of the fluid chamber (5, 3). The pressure determining device (47) outputs a measuring signal when the displacement piston (1) reaches an end position.

A hydraulic drive device for a cargo vehicle includes a hydraulic cylinder supplying and discharging of hydraulic oil, an operation member that operates the hydraulic cylinder, a hydraulic pump, a lowering oil path connecting the hydraulic cylinder and the hydraulic pump, an operation valve disposed in the lowering oil path, a bypass oil path that branches off from the lowering oil path, a bypass flow rate control valve disposed in the bypass oil path and that controls a bypass flow rate, and a resistance element that is disposed closer to the hydraulic cylinder than the operation valve in the lowering oil path and that increases a fluid resistance. A pilot flow path of the bypass flow rate control valve is connected to a part of the lowering oil path between the hydraulic cylinder and the resistance element.

A hydraulic system for a working machine includes a variable displacement hydraulic pump, a plurality of hydraulic actuators, and a plurality of control valves. Each of the control valves includes an input port, an output port, and a flowrate reduction section. At least one of the control valves includes a flowrate increase section. The hydraulic actuators are a boom cylinder, a working tool cylinder, and an auxiliary actuator. The control valves are a boom control valve for controlling the boom cylinder, a working tool control valve for controlling the working tool cylinder, and a first auxiliary control valve for controlling the auxiliary actuator. The boom control valve and the working tool control valve each include the flowrate reduction section, and the first auxiliary control valve includes the flowrate reduction section and the flowrate increase section.

A hydraulic drive device for a cargo vehicle includes a first hydraulic cylinder for raising and lowering, a second hydraulic cylinder for performing an operation different from the first hydraulic cylinder, a first operation member, a second operation member, a hydraulic pump, an electric motor, a lowering oil path, an operation valve, a bypass oil path that branches off from the lowering oil path, a bypass flow rate control valve in the bypass oil path, a command rotational speed setting unit that sets a command rotational speed of the electric motor, and an electric motor control unit. A command rotational speed deceleration which is a deceleration of the command rotational speed set by the command rotational speed setting unit is larger than an actual rotational speed deceleration which is a deceleration of an actual rotational speed of the electric motor by the controlling output of the electric motor control unit.

The invention relates to a discharge pressure scale (30) consisting of at least one valve housing (41) having at least three fluid connection points in the form of a functional connector (A), a return flow connector (T) and a control connector (28), wherein a valve piston (52) is guided such that it moves longitudinally against the effect of an energy accumulator (42), moving from a respective opening or regulating position, against a valve seat (94), into a closed position, wherein the control (28) and return flow connectors (T) are separated from one another, characterised in that the fluid pressure present at the control connector (28) can be guided onto a pressure-active surface (A.sub.1*) of the valve piston (52) by means of a pressure compensation device (70) in such a way that it moves into its respective opening or regulating position in a pressure-compensated manner due to the force of the energy accumulator (42).

A hydraulic system includes first and second valve assemblies connected to a common pump. The first valve assembly includes a main valve housed inside a manifold. A pressure compensator valve maintains a constant pressure drop across a variable orifice of the main valve. A pressure limiter valve is in communication with the main valve and the pressure compensator valve, and allows an actuator connected to the first valve assembly to operate independently of the second valve assembly so that fluid flow to a work port of the first valve assembly is not interrupted by operation of the second valve assembly.

The aerial work platform includes a chassis, a basket, a hydraulic lifting structure and a hydraulic system. A control unit includes a circulation circuit, an electric motor pump and a flow regulator. To simultaneous displace two different parts of the lifting structure, the actuators are divided between first and second groups and the control unit determines first and second target flow rates, while controlling the motor pump with a delivery flow rate greater than or equal to the sum of the target flow rates. The control unit controls the flow rate controller to send toward the groups a regulated proportion of the fluid from the motor pump, presenting a flow rate equal to the sum of the target flow rates, and then to divide this regulated proportion into two adjusted parts, respectively presenting the first and second target flow rates and respectively sent to the first and second groups.

To keep operability of a hydraulic actuator excellent even in a state pressure has been sufficiently accumulated in a pressure accumulator. In a hydraulic driving device of a work machine including a hydraulic actuator, a tank, a flow control valve, and a pressure accumulator, there are further provided with a first pressure compensation valve that is for controlling difference between front and back pressures of the flow control valve constant and a second pressure compensation valve that is arranged between the pressure accumulator and the tank and is for controlling difference between front and back pressures of the flow control valve and the first pressure compensation valve constant.