A valve assembly and a hydraulic circuit including the valve assembly are provided. The valve assembly comprises a hydraulically actuated valve configured to be biased from a first control position to a second control position by a hydraulic pressure applied to a first fluid port of the hydraulically actuated valve. A first switching threshold pressure required to switch the hydraulically actuated valve to its second control position when applied to the first fluid port of the hydraulically actuated valve in its first control position differs from a second switching threshold pressure required to keep the hydraulically actuated valve in its second control position when applied to the first fluid port of the hydraulically actuated valve in its second control position.

A control valve assembly for indirect pneumatic control and method for controlling a working fluid pressure, which enable precise, sensitive and speed-variable controlling. The assembly includes two valve units, a working fluid inlet, and a control fluid inlet. A working fluid channel connects the working fluid inlet through the two valve units to an outlet. A valve piston arranged within a valve cylinder of the valve units is movable between open and closed positions. A spring element biases the valve piston toward the closed position, and a control pressure chamber applies a control pressure counteracting the spring element's bias. When a control pressure is applied in the first chamber, the first valve piston is moved to the open position. Two opposite valve surfaces form a valve opening opened at varying widths when the valve piston is moved in the valve cylinder because of a changing control pressure, and the working pressure can be finely adjusted corresponding to the valve opening width depending on the control pressure.

The present disclosure relates to a hydraulic system including a variable displacement hydraulic motor for lifting and lowering a load. The hydraulic motor has a high operating speed and a low operating speed. The system also includes an actuator for controlling whether the hydraulic motor is operating at the high or low speed, and a pressure sensor for sensing when a system pressure corresponding to the hydraulic motor exceeds a threshold pressure value. The system further includes a speed control system that controls the actuator such that the hydraulic motor is prevented from operating at the first operating speed when the system pressure exceeds the threshold pressure value.

The present disclosure relates to a hydraulic system including a variable displacement hydraulic motor for lifting and lowering a load. The hydraulic motor has a high operating speed and a low operating speed. The system also includes an actuator for controlling whether the hydraulic motor is operating at the high or low speed, and a pressure sensor for sensing when a system pressure corresponding to the hydraulic motor exceeds a threshold pressure value. The system further includes a speed control system that controls the actuator such that the hydraulic motor is prevented from operating at the first operating speed when the system pressure exceeds the threshold pressure value.

A hydraulic drive device includes a pump, a hydraulic machine, and a tank. The hydraulic machine is connected fluidically to first and second fluid lines, which are configured to be connected fluidically to the tank or the pump via an adjustable main valve. The device further includes a first valve with a continuously adjustable first orifice. Pressure fluid is configured to be conducted out of the second fluid line via the first orifice and into the tank. The first valve is acted upon in the closing direction of the first orifice by a first spring and acted upon in the opposite direction by the pressure at a control point. The control point is connected fluidically to the tank via a first throttle device, connected via a second throttle device to the first fluid line, and connected to the first fluid line via a third throttle device and a second valve.

A hydraulic drive device includes a pump, a hydraulic machine, and a tank. The hydraulic machine is connected fluidically to first and second fluid lines, which are configured to be connected fluidically to the tank or the pump via an adjustable main valve. The device further includes a first valve with a continuously adjustable first orifice. Pressure fluid is configured to be conducted out of the second fluid line via the first orifice and into the tank. The first valve is acted upon in the closing direction of the first orifice by a first spring and acted upon in the opposite direction by the pressure at a control point. The control point is connected fluidically to the tank via a first throttle device, connected via a second throttle device to the first fluid line, and connected to the first fluid line via a third throttle device and a second valve.

A method and a system for recovering and utilizing crane operating energy and a crane includes converting by a first hydraulic power means hydraulic energy generated by a hydraulic actuator into mechanical energy of a transmission shaft; driving, by the transmission shaft, a second hydraulic power means to rotate so as to convert the mechanical energy of the transmission shaft into mechanical energy of the second hydraulic power means; filling, by the second hydraulic power means, pressurized oil into an accumulator so as to convert the mechanical energy of the second hydraulic power means into hydraulic energy for storage.

A hoist system including an air balancer having an air supply and an air exhaust, a lifting device, and a hoist control pendant to control supply and exhaust of pressurized air to and from the air balancer, respectively, the hoist control pendant configured to control vertical movement of the lifting device. The air exhaust from the air balancer includes a first exhaust flow path through a first exhaust opening and a second exhaust flow path through a second exhaust opening, the first exhaust flow path having a first length and the second exhaust flow path having a second length, the second length being shorter than the first length.

A hoist system including an air balancer having an air supply and an air exhaust, a lifting device, and a hoist control pendant to control supply and exhaust of pressurized air to and from the air balancer, respectively, the hoist control pendant configured to control vertical movement of the lifting device. The air exhaust from the air balancer includes a first exhaust flow path through a first exhaust opening and a second exhaust flow path through a second exhaust opening, the first exhaust flow path having a first length and the second exhaust flow path having a second length, the second length being shorter than the first length.

A main winch system of a rotary drilling rig includes a main action loop, a pilot control loop, and a feedback control loop. The main action loop includes an engine, a hydraulic pump, a main control valve, a balance valve, a main winch motor, and an oil tank. The pilot control loop includes a pilot handle, a solenoid valve I, a pressure relay, and the main control valve in the main action loop. The feedback control loop includes a solenoid valve II and the hydraulic pump and the main control valve in the main action loop. In response to a lifting action of the pilot handle for the main winch, under the control of a button, the solenoid valve II is energized continuously, and the solenoid valve I is energized and de-energized according to a given rule.