An example valve includes: a first port, a second port, and a load-sense port; a valve piston configured to block fluid flow from the first port to the second port when the valve piston is in a neutral position; a reverse flow spring applying a first biasing force on the valve piston in a proximal direction; and a pressure compensation spring disposed in a spring chamber and applying a second biasing force on the valve piston in a distal direction, wherein when pressure level of fluid at the second port is higher than pressure level of fluid at the load-sense port, fluid flows from the second port to the spring chamber and the load-sense port, and wherein when pressure level of fluid at the load-sense port is higher than pressure level of fluid at the second port, fluid of the load-sense port is provided to the spring chamber.

A hydropneumatic suspension system for vehicles, at least consisting of an axle suspension (10) and a cabin suspension (12), which for supplying them with pressurized fluid, can be connected to a pressure supply source, is characterized in that both the axle suspension (10) and the cabin suspension (12) can be actuated jointly by means of an control device (14), and in that, by means of a priority detection system (16) involving a sensor device (18) for the respective suspension (10, 12), the supply with pressurized fluid of the one suspension (10, 12) takes precedence depending on demand over the other suspension (12, 10).

Disclosed is a hydraulic circuit for construction equipment for controlling to selectively supply a hydraulic oil from a hydraulic pump to a hydraulic cylinder for driving a boom. The hydraulic circuit for construction equipment, according to the present invention, comprises: a hydraulic cylinder driven by a hydraulic oil of a hydraulic pump; a direction control valve installed on the oil passage between the hydraulic pump and the hydraulic cylinder; an operating device installed on the oil passage between a pilot pump and the direction control valve; a center by-pass switching valve installed at the most downstream side of a center by-pass passage of the hydraulic pump; a pressure detection sensor that detects the pressure of a hydraulic oil at the large chamber side of the hydraulic cylinder; a jack-up switching valve installed on the oil passage between the operating device and the center by-pass switching valve; and a flow control valve installed in the spool of the direction control valve.

A pressure compensation valve comprises a valve body, a valve sleeve fixedly mounted on the valve body, and a spool disposed in a valve hole of the valve body and capable of moving. The pressure compensation valve can change the pressure compensation characteristic, that is, the pressure compensation valve can change the difficult degree of the pressurized oil liquid flowing by changing an effective pressure acting surface of the pressure compensation valve The structure is simple, requires low cost, and increases the utilization rate of a product.

When a fluid control valve is opened and closed, the port pressure of fluid control valve is guided to a main relief valve through a first passage, and its maximum pressure is controlled by the main relief valve. At the same time, the port pressure of fluid control valve is guided to pressure compensation valves of the respective fluid control valves. As a result, even when functions having different load pressures are simultaneously operated in the fluid control valves, constant operability can be always secured without depending on the load pressures. In addition, when the fluid control valve, which drives a tilt cylinder for a function of tilting a fork, is opened and closed, the port pressure of the fluid control valve is guided to a secondary relief valve through a second passage, and is also guided to the main relief valve and the pressure compensation valves of the respective fluid control valves through the first passage.

A fluid power system comprises a pump with multiple independently variable outlets, each of which is capable of delivering fluid in individually controllable volume units and a plurality of hydraulic loads. A system of switching valves is configured to create fluid connections between the pump outlets and the loads. A control system commands both the pump and the switching valves, so as to create valve state combinations to satisfy load conditions as demanded by an operator. The number of pump outlets connected to one or more of the loads is changeable to satisfy the flow required of the load due to the operator demand, each pump outlet being commanded to produce a flow depending on the status of other outlets connected a load to which the outlet is connected and the operator demand for that load.

When a fluid control valve is opened and closed, the port pressure of fluid control valve is guided to a main relief valve through a first passage, and its maximum pressure is controlled by the main relief valve. At the same time, the port pressure of fluid control valve is guided to pressure compensation valves of the respective fluid control valves. As a result, even when functions having different load pressures are simultaneously operated in the fluid control valves, constant operability can be always secured without depending on the load pressures. In addition, when the fluid control valve, which drives a tilt cylinder for a function of tilting a fork, is opened and closed, the port pressure of the fluid control valve is guided to a secondary relief valve through a second passage, and is also guided to the main relief valve and the pressure compensation valves of the respective fluid control valves through the first passage.

A hydraulic system includes a pump in communication with a fluid reservoir and powered by a motor. A pressure compensator is adapted to adjust a position of a variable displacement mechanism of the pump. A load sensing line is adapted to communicate a highest load sensing pressure from a plurality of valves to the pressure compensator. The pressure compensator adjusts the variable displacement mechanism of the pump based on the highest load sensing pressure for maintaining a constant pressure drop across one or more work ports in each of the plurality of valves. The plurality of valves each include a load sense port having an integrated check valve that includes a metering orifice.

An example valve assembly is configured: generate a valve load-sense pressure signal indicative of a pressure level at a workport of an actuator; generate a pilot fluid signal to be communicated to a worksection of a valve assembly to enable shifting a spool in the worksection; compare a first pressure level of the valve load-sense pressure signal to a second pressure level of the pilot fluid signal; and communicate the pilot fluid signal to a load-sense port fluidly coupled to a load-sensing source of pressurized fluid when the second pressure level of the pilot fluid signal exceeds the first pressure level of the valve load-sense pressure signal.

A control device for at least one hydraulic working section (A, B), which can be connected to a pressure supply source (P) and a return flow (T) via a hydraulic supply circuit and to a control valve (34) supplied with a pilot pressure. The device includes an emergency shutdown system (32) having a pilot solenoid valve (16) and an additional valve (14). Both the hydraulic energy flow from the pressure supply source (P) to at least one of the respective working sections (A, B) and the pilot pressure supply to the control valve (34) can be suppressed by the pilot solenoid valve (16) via the additional valve (14).