A hydraulic system according to an embodiment of the present invention comprises: a main hydraulic pump for discharging a hydraulic fluid; a plurality of driving apparatuses operating by receiving the hydraulic fluid; a parallel flow path through which the hydraulic fluid discharged by the main hydraulic pump flows; a plurality of control spools respectively connected to the parallel flow path in parallel to control the supply of hydraulic fluid to the plurality of driving apparatuses; and a plurality of electronic proportional decompression valves for adjusting a pilot pressure, applied to the respective control spools to be proportional to a current signal which has been input, wherein, if the plurality of control spools do not operate, the hydraulic fluid discharged by the main hydraulic pump is drained into an oil tank via the parallel flow path without passing through the plurality of control spools.

A hydraulic actuator control system includes a secondary manifold that is configured to direct a meter-in flow received from a main directional valve to the actuator and to direct a meter-out flow of fluid received from the actuator directly to a tank without the return flow travelling back through the main directional valve. The hydraulic actuator control system has a separate return flow connection that permits the use of a load-holding valve (such as, e.g., counterbalance valves, motion control valves, pilot-operated check valves, or zero-leakage logic elements) flanged on the machine's actuator (such as, e.g., a linear cylinder, a rotary cylinder, or a hydraulic motor) to create a directional control valve without directing the return flow through the main directional control valve.

A hydraulic system is disclosed for use with a machine. The hydraulic system may have a closed-loop, meterless hydraulic circuit with a first pump fluidly connected to a first actuator. The hydraulic system may also have a closed-loop, metered hydraulic circuit with a second pump fluidly connected to a second actuator. The hydraulic system may further have a combiner valve configured to selectively direct fluid from the closed-loop metered hydraulic circuit to the closed-loop meterless hydraulic circuit.

An assembly for machine leveling including a plurality of hydraulic cylinders having upper ends adapted for supporting the machine's base, a lower end, a shaft, and a port opening the cylinder; branch conduits having cylinder ends and pump ends, each branch conduit connecting to one of the ports; first shutoff valves connected to the branch conduits for alternatively permitting and resisting fluid flow within the branch conduits; a manifold conduit connected to the branch conduits; a hydraulic pump connected to the manifold conduit and adapted for raising hydraulic pressure within the manifold conduit to a shaft extending pressure; and an electrically modulated variable pressure relief valve connected to the manifold conduit and adapted for raising and lowering the hydraulic pressure.

A mobile hydraulic working machine includes an upper structure, a lower structure, a boom assembly with an arm, an attachment connected to the arm and a hydraulic system to move the boom assembly and the attachment. The hydraulic system includes at least one hydraulic pump and a valve block to regulate flow through at least one hydraulic line connecting a hydraulic consumer to the at least one hydraulic pump in order to actuate the hydraulic consumer. The at least one hydraulic line includes an emergency stop valve operable to close the hydraulic line in an emergency and located in the hydraulic line in a region of the boom assembly and/or in the upper structure on a flow side of the valve block remote from the at least one hydraulic pump.

A fixed displacement hydraulic pump match flow demand control system that includes a spool valve, a plurality of fixed displacement pumps and a control valve is provided. The spool valve includes a spool. The spool is configured to shuttle within a chamber of a housing based at least in part on a pressure difference between a first end and the second end of the chamber. A fluid flow from each fixed displacement pump of the plurality of fixed displacement pumps is in fluid communication with an associated input port to the spool valve. At least one output port of the spool valve is in fluid communication with a hydraulically operated device and at least one of another output port is in fluid communication with a return. The control valve is configured to adjust the location of the spool in the chamber to regulate fluid flow to the hydraulically operated device.