A switching valve includes a sleeve on which a plurality of ports are disposed; a spool that is disposed inside the sleeve to move in an axial direction by a pilot hydraulic pressure to switch between switching lines each serving as a flow channel for hydraulic fluid that is formed by a combination of the ports; a first energizing unit that energizes the spool against the pilot hydraulic pressure; a relief hole that is disposed on the spool to discharge the hydraulic fluid with the pilot hydraulic pressure; a valve body that closes the relief hole; and a second energizing unit that energizes the valve body toward the relief hole of the spool against the pilot hydraulic pressure, and when the pilot hydraulic pressure exceeds a predetermined value, opens the relief hole.

Various embodiments of the present disclosure provide a rotorcraft-assisted system and method for launching and retrieving a fixed-wing aircraft into and from free flight. The launch and retrieval system includes a modular multicopter, a storage and launch system, an anchor system, a flexible capture member, and an aircraft-landing structure. The multicopter is attachable to the fixed-wing aircraft to facilitate launching the fixed-wing aircraft into free, wing-borne flight. The storage and launch system is usable to store the multicopter (when disassembled) and to act as a launch mount for the fixed-wing aircraft by retaining the fixed-wing aircraft in a desired launch orientation. The anchor system is usable with the multicopter, the flexible capture member, and the aircraft-landing structure to retrieve the fixed-wing aircraft from free, wing-borne flight.

A lift device and a method of controlling the lift device are provided. The lift device has an electric motor drivingly coupled to a traction device, and a traction battery. A hydraulic circuit has a pump with a pump motor, and a valve. In response to a voltage being above a threshold voltage while the electric motor is outputting a braking torque and providing electrical power to the battery, flow of the pump is increased and the valve is controlled to reduce a size of the valve opening and increase pressure in the pressure galley thereby reducing electrical power to the traction battery. The flow of the pump and the valve position are therefore controlled in response to a braking power output being greater than a threshold to dissipate braking power output into the hydraulic circuit and charge the traction battery with the remaining braking power output.

Problem to be solved: To provide a hydraulic circuit for the construction machine which enables to use the relief valve of low capacity in the work tool circuit. Solution: The hydraulic circuit 2 for a construction machine has: a hydraulic pump 4 of variable capacity, a work tool 6 operated by hydraulic oil delivered by the hydraulic pump 4, a work tool operating device 10 to output a signal for operating the work tool 6, a control valve 14 allowing the hydraulic pump 4 to supply the hydraulic oil to the work tool 6 based on the signal output from the work tool operating device 10, a tool's relief valve 44 to release the hydraulic oil flowing between the control valve 14 and the work tool 6, a pressure sensor 46 to detect a pressure of hydraulic oil flowing into the work tool 6, and a controller 48 to reduce a delivery rate from the hydraulic pump 4 when the pressure detected by the pressure sensor 46 exceeds a predetermined value.

A hydraulic system for a working machine includes a first electric machine connected to a first hydraulic machine; a second electric machine connected to a second hydraulic machine, an output side of the second hydraulic machine being connected to an input side of the first hydraulic machine; at least one hydraulic consumer hydraulically coupled to an output side of the first hydraulic machine via a supply line and configured to be powered by the first hydraulic machine; and a valve arrangement arranged between the hydraulic consumer and the first and second hydraulic machines, wherein the valve arrangement is configured to control a return flow of hydraulic fluid from the hydraulic consumer to either the input side of the first hydraulic machine or an input side of the second hydraulic machine based on a requested output pressure from the first hydraulic machine.

A hydraulic system for controlling an implement on a work machine may include a hydraulic reservoir, a hydraulic pump in fluid communication with the reservoir, a central valve in fluid communication with the pump and configured for controlling the implement, a pressure relief system arranged in fluid communication with the hydraulic pump and the central valve, and a controller. The controller may be configured for controlling the hydraulic pump, the central valve and the pressure relief system and selecting between operating the hydraulic system at a first pressure and a second pressure based on a factor relating to implement position.

There is provided a relief valve capable of realizing miniaturization, weight reduction, and simplification of structure, and preventing vibration during operation. A relief valve for releasing a pressure by causing a valve body to separate from a valve seat when a pressure exceeding a set value is applied to the valve body, including an urging member that applies an urging force to the valve body to press-contact the valve body with the valve seat, the urging member being locked to a force receiving section fixedly formed in a middle portion in the axial direction of the valve body either integrally with or separately from the valve body and directly applies the urging force to the force receiving section.

A single solenoid-controlled electro-hydraulic liftomatic system is provided. The single solenoid-controlled electro-hydraulic liftomatic system is developed for controlling electrically, automating a hydraulic mechanism used in three-point hitch systems of tractors lifted and lowered by a mechanically controlled hydraulic mechanism. The single solenoid-controlled electro-hydraulic liftomatic system includes an actuator, a hydraulic pump, a safety element, a tank line, a valve body, a hydraulic piston, at least one solenoid valve, a piston spring, a check valve, a time-delay relay, and a button.

A work machine comprises: a work implement; a hydraulic cylinder; a hydraulic pump that supplies the hydraulic oil to the hydraulic cylinder via a hydraulic circuit; a relief valve that can set a relief pressure of the hydraulic circuit to either a first set pressure or a second set pressure higher than the first set pressure; a detection unit that detects at least one of a pressure of the hydraulic oil in the hydraulic circuit and a speed of the work implement; and a relief pressure changing unit that changes a relief pressure of the relief valve from the first set pressure to the second set pressure based on a detection value of at least one of the pressure of the hydraulic oil in the hydraulic circuit and the speed of the work implement when the controlled state of the work implement is the excavation state.

A hydraulic system for a machine includes an implement pump, a valve, and an implement valve subsystem. The implement pump includes a load sensing control, and the valve controls the flow of hydraulic fluid to the implement pump. The implement valve subsystem includes one or more implement control subsystems to control movement of an implement. The valve is an electrohydraulic proportional relief valve and includes a solenoid configured to adjust the pressure of hydraulic fluid delivered to the implement pump proportionally to a current delivered through the solenoid.