A valve assembly is disclosed. The valve assembly includes a valve housing defining a bore, a first valve, and a second valve. The first valve and the second valve are disposed within the bore and each of the first valve and the second valve include a first end and a second end. Further, the first end of the first valve and the first end of the second valve are configured to contact each other. The valve assembly further includes a pilot chamber defined within the bore. The pilot chamber is configured to receive a pilot fluid. Further, a pressure of the pilot fluid inside the pilot chamber is controlled to permit independent movement of the first valve and the second valve within the bore.

The present invention relates to a hydraulic control valve for construction machinery that is used to maintain secondary pilot pressure which is formed proportionally to the switching of a switching device so as to be equal to or below a setting pressure of a pilot pump. The hydraulic control valve of the present invention includes: a port of the pilot pump into which the pilot pressure flows; a tank port to which the pilot pressure is drained; a valve body at which a secondary pilot pressure port that selectively communicates with the port of the pilot pump and the tank port is formed; the switching device that is pivotally mounted on the valve body; a pilot control valve that is linked through pressurization of the switching device and has a spool which forms the secondary pilot pressure proportional to the amount of switching of the switching device by communicating the port of the pilot pump and the secondary pilot pressure port with each other during the switching; a valve spring that elastically supports the spool so as to communicate the secondary pilot pressure port and the tank port with each other; and a check poppet that is disposed in an openable and closable manner at a pilot passage whose inlet side communicates with the secondary pilot pressure port and whose outlet side communicates with the port of the pilot pump.

A pilot relief valve is provided, including: a sleeve, a valve body, a piston, an adjusting member, a support base, a blocking member and an elastic member, all disposed inside the sleeve. The support base includes a head portion and a rod portion, the head portion includes an exhaust channel penetrating the first surface, the rod portion includes an air intake channel communicating with the exhaust channel. The blocking member is disposed on the head portion. As such, the air in the sleeve is discharged through the inside of the support base, and the hydraulic oil fills the sleeve to maintain pressure balance so that the support base and the blocking member will not thrust, the perforation of the valve body and the outlet of the tipping valve remains unblocked, and the pressure of the hydraulic oil is stable when the hydraulic oil enters the hydraulic cylinder.

A pilot relief valve is provided, including: a sleeve, a valve body, a piston, an adjusting member, a support base, a blocking member and an elastic member, all disposed inside the sleeve. The support base includes a head portion and a rod portion, the head portion includes an exhaust channel penetrating the first surface, the rod portion includes an air intake channel communicating with the exhaust channel. The blocking member is disposed on the head portion. As such, the air in the sleeve is discharged through the inside of the support base, and the hydraulic oil fills the sleeve to maintain pressure balance so that the support base and the blocking member will not thrust, the perforation of the valve body and the outlet of the tipping valve remains unblocked, and the pressure of the hydraulic oil is stable when the hydraulic oil enters the hydraulic cylinder.

A hydraulic system for a work machine includes a tank to store an operation fluid, a hydraulic device to be operated by the operation fluid, a control valve to control the hydraulic device, a first fluid tube connecting the hydraulic device and the control valve, the first fluid tube being to supply the operation fluid from the control valve to the hydraulic device, a second fluid tube branching from the first fluid tube and connected to the tank, a switch valve provided to the second fluid tube, the switch valve being to control a flow rate of the operation fluid, and an oil cooler provided to the second fluid tube between the switch valve and the tank.

A main valve throttle (53) of a main valve (43) is configured by a lateral hole (53A) communicating an inlet side flow passage (25) and an outlet side flow passage (27) through the inside of the main valve (43) and a groove portion (53C) communicating the inlet side flow passage (25) and the outlet side flow passage (27) via an outer peripheral portion of the main valve (43). The groove portion (53C) is located such that a hydraulic fluid spurting from the groove portion (53C) changes the direction of a flow of a hydraulic fluid spurting from the lateral hole (53A). In this case, the direction of a flow of a hydraulic fluid F2 spurting from the lateral hole (53A) can be changed to approach the direction parallel to the center axis of the main valve (43) by a hydraulic fluid F1 spurting from the groove portion (53C).

A safety valve arrangement includes a fluid distributor to which a first supply valve, a first pilot valve and a first safety valve are assigned. The first supply valve selectively releases or blocks a first supply channel extending in the fluid distributor between a first supply port and a first working port. The first pilot valve selectively releases or blocks a first pilot channel extending in the fluid distributor between a first pilot air inlet and a first pilot air outlet, and the first safety valve selectively releases or blocks a first safety channel which extends between the first working port and a first safety outlet. A first separation channel, which is permanently open to the environment, is located between the first supply channel and the first pilot channel to ensure a fluid separation between the first supply channel and the first pilot channel.

A valve unit includes a first piston, which has a first opening and a control chamber. A fluid connection between a first and a second port is closed or, in a position defined by the first piston, is held open in the event that a hose which is connected to the first port bursts. A pilot valve (48) is present, which has a core and a coil, and a fluid flow from the control chamber to the first port can be regulated by an electric current in the coil. The current is regulated by a logic unit which is suitable for receiving signals from at least one sensor, in particular a pressure sensor, an inertia detector and/or position sensor and for regulating the electric current in the coil.

The present invention provides an improved high-low hydraulic system for compacting machinery, such as balers, horizontal balers, compactors, transfer station compactors, and the like. The high-low hydraulic system comprises at least one double rotary pump, a plurality of directional control valves, a pilot-operated back pressure reducing valve, a flow control valve, a plurality of one-way valves, and a plurality of pressure switches. The high-low hydraulic system may be regenerative or non-regenerative and provides many advantages over conventional hydraulic systems. Such advantages include greater system efficiency due to a reduced back pressure during the time of the retraction stroke and clever flow sequencing, mitigation of hydraulic shocks at the beginning and end of compaction and retraction strokes, and reduced cycle time of the cylinder during operation due to the concurrent filling of the rod end side during decompression of the blind end side after the compaction stroke. Moreover, the present high-low hydraulic system allows for the cylinder to operate at three or more independent speeds.

A control valve includes a housing formed with first and second supply ports, first and second actuator ports, and a pilot port, and a spool accommodated slidably in the housing, and the spool is configured to allow the first supply port and the pilot port to communicate with each other both at the first communication position and the second communication position.