A hydraulic system is provided. The hydraulic system includes a pump, a load sense conduit, a tank conduit, a function workport, and a function control valve. The hydraulic system further includes a function poppet valve arranged between the function workport and the function control valve and having a function poppet vent passage, and a system control valve arranged downstream of the function control valve. The system control valve is biased into a first position where fluid communication between the function poppet vent passage and the tank conduit is prevented and fluid communication between the load sense conduit and the tank conduit is provided. The system control valve is selectively movable to a second position where fluid communication between the function poppet vent passage and the tank conduit is allowed and fluid communication between the load sense conduit and the tank conduit is prevented.

An example valve includes a main stage, a pilot stage, and a solenoid actuator. The main stage includes a sleeve and a piston axially movable within the sleeve. The piston defines a cavity therein. The pilot stage includes a pilot pin received at, and axially movable in, the cavity of the piston, where the piston forms a pilot seat at which the pilot pin is seated when the valve is in a closed state. The solenoid actuator includes a solenoid coil, an armature, and a solenoid spring. The solenoid spring applies a biasing force in a distal direction on the pilot pin to seat the pilot pin at the pilot seat. Energizing the solenoid coil causes the armature to move in a proximal direction, thereby reducing the biasing force that the solenoid spring applies on the pilot pin.

Provided are a control valve, a derricking cylinder and a working method thereof, and an aerial work platform, relating to the field of aerial work. The control valve of the derricking cylinder includes a first balance valve provided on the oil circuit between the first port G and the second port F, and a second balance valve provided on the oil circuit between the third port H and the fourth port E; and a switch valve in series with the first balance valve is further provided on the oil circuit between the first port G and the second port F.

An example valve assembly includes a meter-in valve configured to be fluidly coupled to a first source of pressurized fluid and control fluid flow from the first source of pressurized fluid into a first chamber of an actuator; a counterbalance valve including configured to open and control fluid flow from a second chamber of the actuator to a tank in response to a pilot pressure fluid signal received at a pilot port of the counterbalance valve; and a pressure reducing valve configured to be fluidly coupled to a second source of pressurized fluid and to be fluidly coupled to the pilot port of the counterbalance valve, where the pressure reducing valve is configured to receive pressurized fluid from the second source of pressurized fluid and, when actuated, provide the pilot pressure fluid signal to the pilot port of the counterbalance valve.

The disclosure relates to a hydraulic driving system and a driving method for barring. The driving system comprises: three or more main drive hydraulic cylinders, which are divided into two groups to provide pulling and pushing forces to a driven impeller, each main drive hydraulic cylinder including a cylinder body and a piston rod which divides the cylinder body into a rod cavity and a godless cavity, wherein an oil line for the rod cavity and an oil line for the godless cavity of each main drive hydraulic cylinder are controlled by one control valve module; and a control device, which controls the control valve module according to wind and/or load signals, to simultaneously convert flow directions of hydraulic oil in the oil line for the rod cavity and the oil line for the godless cavity of at least one of the three or more main drive hydraulic cylinders.

The invention provides a hydraulic circuit for feeding an actuator (1) comprising first and second chambers (5, 6), the circuit comprising a slide valve (10) with a slide (16) that is movable between first and second extreme positions (18, 19) on either side of a stable central position (17) so that: in the central position, it connects the chambers (5, 6) of the actuator to a return port; in the first extreme position (18), it connects the first chamber (5) to a feed port and the second chamber to the return port; and in the second extreme position (19), it connects at least the second chamber (6) to the feed port. According to the invention, the hydraulic circuit includes pressure-maintaining means (20) for maintaining pressure in the first chamber of the actuator while the slide is passing through the central position on being moved from the first extreme position to the second extreme position.

A hydraulic system of a work machine includes a first hydraulic device to operate in a first operation mode while pressure of hydraulic oil supplied from a hydraulic pump via a first oil passage is equal to or higher than a first pressure threshold. The hydraulic oil in the first oil passage is to be discharged via a second oil passage. A pilot check valve is provided in the second oil passage and has a pilot port to receive a pilot pressure of the hydraulic oil. The pilot check valve is closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is lower than the fourth pressure threshold. The pilot check valve is opened while the pilot pressure is higher than or equal to the second pressure threshold. The first hydraulic device is an operation control valve.

A hydraulic system (600) and method for reducing boom dynamics of a boom (30), while providing counter-balance valve protection, includes a hydraulic cylinder (110), first and second counter-balance valves (300, 400), and first and second control valves (700, 800). A net load (90) is supported by a first chamber (116, 118) of the hydraulic cylinder, and a second chamber (118, 116) of the hydraulic cylinder may receive fluctuating hydraulic fluid flow from the second control valve to produce a vibratory response (950) that counters environmental vibrations (960) on the boom. The first control valve may apply a holding pressure and thereby hold the first counter-balance valve closed and the second counter-balance valve open.

An excavator includes a hydraulic oil holding circuit that is provided in an oil passage between a bottom-side oil chamber of a boom cylinder and a control valve and is closed when the boom is not lowered, and a controller. The controller releases a closed state of the hydraulic oil holding circuit when the excavator is in a predetermined unstable state, and controls a released state so that an acting velocity in a lowering direction of the boom becomes less than or equal to a predetermined reference.

An implement attachment device, for selectively attaching an implement to a working machine includes a hydraulic cylinder including a cylinder housing with first and second longitudinal ends, a piston in the cylinder housing, and a piston rod fixed to the piston and protruding through the first end of the cylinder housing, an attachment element being connected to a protruding portion of the piston rod, and adapted to engage with a complementary element of the implement, and a hydraulic conduit and valve arrangement connected to the hydraulic cylinder, wherein the conduit and valve arrangement is arranged to selectively allow a communication between a piston side chamber of the hydraulic cylinder and a rod side chamber of the hydraulic cylinder.