The present invention relates to a hydraulic control system for construction machinery capable of variably adjusting a set pressure of a relief valve, which controls a set pressure of a hydraulic system, according to a value inputted by means of pressure in the hydraulic system or the manipulation of a joystick. The hydraulic control system comprises: a flow control valve installed in a passage between a hydraulic pump and a hydraulic actuator, for controlling the driving of the hydraulic actuator by being switched by a control signal according to the manipulation of the joystick; a main relief valve installed in a passage between an upstream-side discharge passage of the hydraulic pump and a hydraulic tank, for returning a working fluid to the hydraulic tank when a high load exceeding a set pressure occurs in the system; a pressure controlling means for controlling, either continuously or in stages, a set pressure of the main relief valve; a pressure sensing means for sensing a pressure at a discharge side of the hydraulic pump; and a controller for determining the value inputted by the manipulation of the joystick, and a required set pressure for the relief valve according to the system pressure sensed by the pressure sensing means, and then outputting a control signal to the pressure controlling means to enable a set pressure of the relief valve to be variably adjusted to a determined set pressure.

Twin poppet mechanism (100) of a valve positioner (101) with progressively reduced leakage, comprising a poppet valve assembly (150) comprising a swivel assembly (110) and a pair of poppet valve assembly (150), a poppet assembly (320) of the poppet valve assembly (150) has a conical tilting freedom (103) around its axis of assembly (151), in a first stable state, the swivel assembly (110) tilts towards a first side (104A) and a rubbing or a lapping action is caused between the first sealing surface (241) and the outer sealing surface (332), and between an inner sealing surface (352) of the poppet body two (350) and the chamber sealing surface (316) of the guide chamber (301), in a second stable state, the swivel assembly (110) tilts towards a second side (104B) and the lapping action is caused between the second sealing surface (261) and the outer sealing surface (332), and between the inner sealing surface (352) of the poppet body two (350) and the chamber sealing surface (316) of the guide chamber (301).

A solenoid valve apparatus for a brake system for a vehicle, including: a main valve unit; a pilot-control valve unit that is fluidically connected to the main valve unit; and a housing to accommodate at least the main valve unit and the pilot-control valve unit; in which the pilot-control valve unit includes a double solenoid unit and at least one valve device, in which the double solenoid unit is formed such that it can be populated with at least one valve device, and in which the double solenoid unit has at least two accommodating portions for accommodating valve devices and at least two solenoid devices for actuating valve devices. Also described are a related braking system and a related method for mounting a solenoid valve assembly for a braking system for a vehicle.

A proportional valve is provided wherein the valve has an actuating element, a compressed-air connection, a working connection, and an air-removal connection. The valve also has three valve elements arranged one after the other and each can be moved in an axial direction. A first valve element is actuated by the actuating element, a second valve element is actuated by the first valve element, and a third valve element is actuated by the second valve element. In a base position, the valve elements are spaced apart, and, within the valve, a first sealing seat effective between the first valve element and the second valve element and a second sealing seat effective between the third valve element and the housing are arranged such that by varying the position of the first valve element, different switching states can be set.

A solenoid valve apparatus for a brake system for a vehicle, including: a main valve unit; a pilot-control valve unit that is fluidically connected to the main valve unit; and a housing to accommodate at least the main valve unit and the pilot-control valve unit; in which the pilot-control valve unit includes a double solenoid unit and at least one valve device, in which the double solenoid unit is formed such that it can be populated with at least one valve device, and in which the double solenoid unit has at least two accommodating portions for accommodating valve devices and at least two solenoid devices for actuating valve devices. Also described are a related braking system and a related method for mounting a solenoid valve assembly for a braking system for a vehicle.

A valve manifold includes a valve body carrying pairs of laterally spaced piston actuated valves controlled by control modules operative to selectively pressurize and exhaust an outlet port connected to a fluid device and configured in groupings permitting varying valve functionalities.

A proportional valve is provided wherein the valve has an actuating element, a compressed-air connection, a working connection, and an air-removal connection. The valve also has three valve elements arranged one after the other and each can be moved in an axial direction. A first valve element is actuated by the actuating element, a second valve element is actuated by the first valve element, and a third valve element is actuated by the second valve element. In a base position, the valve elements are spaced apart, and, within the valve, a first sealing seat effective between the first valve element and the second valve element and a second sealing seat effective between the third valve element and the housing are arranged such that by varying the position of the first valve element, different switching states can be set.

Arrangements of a flow path to achieve a series circuit, a regeneration circuit and a float/passive regeneration circuit. For example, a valve body having a spool bore, a valve inlet, a plurality of cavities opening into the spool bore and a spool disposed in the spool bore. A first cavity fluidly connected to a tank passage, a second cavity fluidly connected to a first work port, a third cavity fluidly connected to an inlet of another valve, a fourth cavity fluidly connected to a second work port, a fifth cavity fluidly connected to the valve inlet, a sixth cavity fluidly connected to the first work port, a seventh cavity, an eighth cavity fluidly connected to the valve inlet, a ninth cavity fluidly connected to the inlet of the other valve and a tenth cavity fluidly connected to the valve inlet.

A valve manifold includes a valve body carrying pairs of laterally spaced piston actuated valves controlled by control modules operative to selectively pressurize and exhaust an outlet port connected to a fluid device and configured in groupings permitting varying valve functionalities.