A hydraulic system of a construction machine includes: control valves interposed between a main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: an unloading valve including a pilot port; and a second solenoid proportional valve connected to the pilot port of the unloading valve by a secondary pressure line and connected to an auxiliary pump by a primary pressure line. A switching valve including a pilot port connected to the secondary pressure line by a pilot line is interposed between the auxiliary pump and the first solenoid proportional valves.

A hydraulic system of a construction machine includes: control valves interposed between a main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: an unloading valve including a pilot port; and a second solenoid proportional valve connected to the pilot port of the unloading valve by a secondary pressure line and connected to an auxiliary pump by a primary pressure line. A switching valve including a pilot port connected to the secondary pressure line by a pilot line is interposed between the auxiliary pump and the first solenoid proportional valves.

A hydraulic system of a construction machine includes: control valves interposed between a main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: an unloading valve including a pilot port; and a second solenoid proportional valve connected to the pilot port of the unloading valve by a secondary pressure line and connected to an auxiliary pump by a primary pressure line. A switching valve including a pilot port connected to the secondary pressure line by a pilot line is interposed between the auxiliary pump and the first solenoid proportional valves.

A hydraulic system of a construction machine includes: control valves interposed between a main pump and hydraulic actuators; and first solenoid proportional valves connected to pilot ports of the control valves. The hydraulic system further includes: an unloading valve including a pilot port; and a second solenoid proportional valve connected to the pilot port of the unloading valve by a secondary pressure line and connected to an auxiliary pump by a primary pressure line. A switching valve including a pilot port connected to the secondary pressure line by a pilot line is interposed between the auxiliary pump and the first solenoid proportional valves.

Provided is a pneumatic actuator control device including detectors that are disposed in an air supply passage leading from an air supply source to a solenoid valve or in an air exhaust passage leading from the solenoid valve, and that detect the flow volume or the pressure of the air in the air supply passage, or detect the flow volume or the pressure of the air in the air exhaust passage; and an operational state determination unit that, on the basis of data representing a change in the flow volume or the pressure of the air in the air supply passage, or in the flow volume or the pressure of the air in the air exhaust passage, as detected by the detectors, determines the operational state of a pneumatic actuator connected to the solenoid valve.

Provided is a pneumatic actuator control device including detectors that are disposed in an air supply passage leading from an air supply source to a solenoid valve or in an air exhaust passage leading from the solenoid valve, and that detect the flow volume or the pressure of the air in the air supply passage, or detect the flow volume or the pressure of the air in the air exhaust passage; and an operational state determination unit that, on the basis of data representing a change in the flow volume or the pressure of the air in the air supply passage, or in the flow volume or the pressure of the air in the air exhaust passage, as detected by the detectors, determines the operational state of a pneumatic actuator connected to the solenoid valve.

A hydraulic system for a working machine includes a prime mover, a boom cylinder, a control valve, a first hydraulic pump to deliver pilot fluid to switch the control valve, a second hydraulic pump to deliver hydraulic fluid to activate the boom cylinder, a hydraulic controller configured or programmed to control the second hydraulic pump to set a load-sensing (LS) differential pressure, a first pilot fluid passage, a second pilot fluid passage branching off from the first pilot fluid passage and connected to the hydraulic controller, a solenoid valve to change a pilot pressure that is a pressure of the pilot fluid applied to the hydraulic controller, and a pressure compensator to increase the LS differential pressure as a temperature of the hydraulic fluid including the pilot fluid decreases.

A fluid distribution system includes a boost supply providing a fluid flow, and a fluid metering system downstream of the boost supply. The fluid metering system supplies fluid to a downstream device. A main fluid pump supplies at least a portion of the fluid flow to the fluid metering system. A shut-off valve is positioned upstream of a main fluid pump inlet. An actuation system is positioned downstream of the boost supply. The actuation system supplies fluid to one or more hydraulically-operated devices. An actuation pump supplies at least a portion of the fluid flow to the fluid metering system and to the actuation system. A first valve is positioned between the actuation pump and the fluid metering system. The first valve and the shut-off valve are operable to switch between the main fluid pump and the actuation pump as a source of fluid supply to the fluid metering system.

A fluid distribution system includes a boost supply providing a fluid flow, and a fluid metering system downstream of the boost supply. The fluid metering system supplies fluid to a downstream device. A main fluid pump supplies at least a portion of the fluid flow to the fluid metering system. A shut-off valve is positioned upstream of a main fluid pump inlet. An actuation system is positioned downstream of the boost supply. The actuation system supplies fluid to one or more hydraulically-operated devices. An actuation pump supplies at least a portion of the fluid flow to the fluid metering system and to the actuation system. A first valve is positioned between the actuation pump and the fluid metering system. The first valve and the shut-off valve are operable to switch between the main fluid pump and the actuation pump as a source of fluid supply to the fluid metering system.

In a crop harvesting machine there is provided a pair of hydraulic float cylinders for a header relative to a vehicle, where a float pressure to the cylinders is directly controlled by an electronic control supplying a variable control signal to a PPRR valve arrangement to maintain the float pressure at a predetermined value. At the set pressure a predetermined lifting force is provided to the header. A position sensor is used to generate an indication of movement and/or acceleration. The electronic control is arranged, in response to changes in the sensor signal, to temporarily change the control signal to vary the lifting force and thus change the dynamic response of the hydraulic float cylinder. In order to reduce static friction so that the system can react quickly, an arrangement is provided for causing relative reciprocating movement in an alternating wave pattern between the piston and cylinder.