A hydraulic control valve maintains the pressure at a control port at a desired percentage of the pressure at two other ports as the pressure at the two other ports varies. Upon the pressure at the control port reaching a predetermined pressure setting, a fourth port will open to maintain the control port at a second desired percentage of the two other ports.

An apparatus for controlling a hydraulic machine, for example a turbine, pump or pump turbine, using variable-speed driven fixed displacement pumps. The apparatus includes a device for carrying out an emergency shut-off that is characterized by low energy consumption and high efficiency while guaranteeing all the operation-relevant and safety-relevant requirements of a hydraulic machine.

A hydraulic drive for executing a linear movement includes a motor, a pump, a lifting cylinder having the one linearly movable piston and a cylinder housing with at least one first connection and at least one second connection, a spring arranged such that the piston can be extended or retracted when the spring is in the relaxed state, and at least one first valve with which the first connection and the second connection of the cylinder housing can be fluidly connected. At least one second valve connected in parallel with the first valve is further provided, wherein the first valve has a maximum volumetric throughflow which is greater than the maximum volumetric through-flow of the second valve.

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 valve system for use with a cylinder having an extensible rod, includes first and second valve assemblies, each including an inlet/outlet port configured to selectively be coupled with a source of pressurized gas, a check valve biased toward a closed state and having a check valve body at least partially receivable within a first port of the cylinder, a flow control valve positioned in series between the inlet/outlet port and the check valve, and an inlet pilot port connected with the check valve for opening the check valve when supplied with pressurized gas. First and second pilot lines extend to the respective inlet pilot ports from respective outlet pilot ports of the opposite ones of the first and second valve assemblies. When pressurized gas is supplied to the inlet/outlet port of a valve assembly, pressurized gas is also supplied to the opposite inlet pilot port.

A fluid pressure circuit for controlling a rod of a cylinder controlled in accordance with an operation command includes a tank, a fluid pressure actuator configured to pressurize fluid supplied from the tank for extending and retracting the cylinder, a flow control valve arranged between the fluid pressure actuator and the cylinder device configured to switch a flow passage of pressurized fluid and discharge via a first throttle return fluid from the cylinder, a variable regeneration switching valve configured to discharge return fluid from the cylinder to the flow control valve upon non-regeneration and upon regeneration, branch part of the return fluid and discharge via a second throttle the fluid branched, a regenerative motor configured for regeneration by fluid branched by the variable regeneration switching valve, and a third throttle connected in series with the first throttle upon the regeneration to limit flow of return fluid.

An apparatus for controlling a hydraulic machine, for example a turbine, pump or pump turbine, using variable-speed driven fixed displacement pumps. The apparatus includes a device for carrying out an emergency shut-off that is characterized by low energy consumption and high efficiency while guaranteeing all the operation-relevant and safety-relevant requirements of a hydraulic machine.

A boom cylinder drives a boom, and includes a head side oil chamber and a bottom side oil chamber. A first valve includes a first opening for discharging oil in the head side oil chamber to an oil tank, and supplies oil from a hydraulic pump to the head side oil chamber. A second valve includes a second opening for discharging oil in the bottom side oil chamber to the oil tank, and supplies oil from the hydraulic pump to the bottom side oil chamber. A controller individually controls an opening degree of the first opening and an opening degree of the second opening, during work including manipulation of the boom.

A failsafe vale provides Hole-In-The-Wall failsafe functionality for thin-wing aircraft control surface actuation systems having a geared rotary actuator powered by a hydraulic rotary motor. The failsafe valve is associated with the hydraulic rotary motor and mechanically connected to the control surface, and enables the flight control surface to return to an aerodynamically neutral failsafe position if electrical control and/or hydraulic pressure is lost. When the failsafe valve receives a normal command pressure from the hydraulic system, the valve is inactive and the actuation system operates normally. However, if there is a loss of electrical command capacity to control hydraulic valves and/or a loss of hydraulic pressure, the failsafe valve is activated and connects one of the motor hydraulic control lines to the case return line for the motor if the control surface is away from its failsafe position. Consequently, the control surface will be hydraulically powered or aerodynamically ratcheted to its failsafe position in the failure event.

A hydraulic cooler pressure isolation circuit for a header of an agricultural harvester equipped with a reservoir and a pump. The circuit comprises a hydraulic fluid cooler, a supply line extending from the hydraulic fluid cooler to the pump, a return line extending from the hydraulic fluid cooler to the reservoir, and a drain line operatively in fluid communication with the return line for connecting to the reservoir. A first valve, a second valve, a return valve, and a bypass valve of the circuit operate to direct hydraulic fluid flow through the cooler under normal system operating conditions, and direct hydraulic fluid flow to bypass the cooler when the system experiences high pressure operating conditions at the cooler.