A valve for controlling a flow of a fluid between a source, reservoir, a vent, and pressure-based device. The valve has multiple positions each having a source port fluidly coupleable to the source, reservoir port fluidly coupleable to the reservoir, device port fluidly coupleable to the pressure-based device, and venting port configured to vent the fluid. The multiple positions are separately selectable and include a fill position having a fill conduit fluidly coupling the source port and device port, a recycle position having a recycle conduit fluidly coupling the reservoir port and device port, and a vent position having a vent conduit fluidly coupling the vent port and device port. The fill conduit, recycle conduit, and vent conduit each communicate the fluid only when a corresponding one of the multiple positions is selected, and the multiple positions are configured to prevent selection of more than one at a time.

A system for delivering fluid in a machine is provided. The system includes a pump, a first valve disposed downstream of the pump, a check valve disposed downstream of the first valve, at least one accumulator disposed downstream of the check valve, and an auxiliary system disposed upstream of the check valve. The system further includes a control unit configured to receive a signal indicative of a fluid demand from the auxiliary system. The control unit is also configured to selectively control the first valve in a first position to limit flow of the fluid from the pump to the auxiliary system, and in a second position to allow flow of the fluid from the pump to the auxiliary system based, at least in part, on the received signal. The check valve limits flow of a fluid from the at least one accumulator to the auxiliary system.

An energy regeneration device which can regenerate energy of a working fluid discharged from an actuator while controlling a flow rate of the working fluid, and a work machine including the device. The regeneration device includes a boom cylinder, an inertial fluid container, an oil tank, an accumulator, a low-pressure-side opening/closing device, and a high-pressure-side opening/closing device. A calculation unit calculates an opening area of each of the low-pressure-side opening/closing device and the high-pressure-side opening/closing device in accordance with a desired flow rate of a hydraulic fluid discharged from the boom cylinder. A regeneration control unit adjusts an opening area of each of the low-pressure-side opening/closing device and the high-pressure-side opening/closing device, and selects alternately the low-pressure-side opening/closing device and the high-pressure-side opening/closing device as a destination with which the inertial fluid container communicates, to supply a discharged hydraulic fluid to an accumulator.

To provide a hydraulic control circuit for a construction machine capable of shortening a time duration from the start of an engine until the pressure of a pump oil passage reaches a required pressure. A hydraulic control circuit for a construction machine includes a hydraulic pump that is driven by an engine; a hydraulic actuator that is operated by hydraulic oil discharged from the hydraulic pump; a hydraulic pilot type control valve that controls an amount and a direction of supply of the hydraulic oil to the hydraulic actuator from the hydraulic pump; a pump oil passage that connects the hydraulic pump and a pump port of the hydraulic pilot type control valve; a bypass oil passage that branches from the pump oil passage and extends to a hydraulic oil tank; a bypass valve that is disposed in the bypass oil passage and controls an amount of the hydraulic oil returning to the hydraulic oil tank through the bypass oil passage; and a pilot oil passage that branches from the pump oil passage and extends to a pilot port of the hydraulic pilot type control valve; an electromagnetic proportional pressure reducing valve that is disposed in the pilot oil passage and controls a pressure acting on the pilot port; a controller that controls an operation of the bypass valve and the electromagnetic proportional pressure reducing valve; and an operation implement for outputting an operation signal to the controller in response to an operation applied from an operator. The controller sets the opening area A of the bypass valve to a second opening area A1 in a state where an operation signal is not output from the operation implement after the engine has been started and the pressure of the pump oil passage has reached a required pressure P0, and sets the opening area A of the bypass valve to a second opening area A2 which is smaller than the first opening area A1 during a time duration from the start of the engine until the pressure of the pump oil passage reaches the required pressure P0.

A hydraulic drive unit includes: a pump; a pair of supply-discharge lines; a valve block; a sealed tank; a suction line that leads hydraulic oil in the sealed tank to the pump; a connecting line that connects an air vent port of the pump to the suction line; and a gas-liquid separator that separates air and the hydraulic oil flowing through the connecting line from each other. The pump is disposed upward of the valve block and the sealed tank in a vertical direction.

In a vibration suppression control OFF state, a signal pressure supply control valve stops supplying a first signal pressure, a pressure-regulating valve is in first position where a supply/discharge port connects to a pump port, and an open/close signal pressure is not supplied to an open/close control valve, so an open/close valve is closed. When the OFF state switches to ON state, the signal pressure supply control valve allows supplying the first signal pressure, and the pressure-regulating valve is in second position where the supply/discharge port connects to a tank port, so the pressure of a pressure accumulator decreases. In the ON state, when the pressure of the pressure accumulator is equal to pressure of a pressure chamber, the pressure-regulating valve is in third position where the supply/discharge port is blocked, and the open/close signal pressure is supplied to the open/close control valve, so the open/close valve is opened.

A hydraulic system includes a first fixed displacement pump having a first pump output and a second fixed displacement pump having a second pump output. A first actuator requires a first required flow rate to perform a first function. A second actuator requires a second required flow rate to perform a second function. A combined flow control valve is controllable between a first state connecting fluid communication between the first fixed displacement pump and the tank so that only the second pump output is directed to the second actuator, and a second state disconnecting fluid communication between the first fixed displacement pump and the tank to combine the first pump output and the second pump output such that the combined first pump output and the second pump output is directed to the first actuator.

An adjustable ride control circuit and method that includes a head valve that controls flow between a boom cylinder head intake and an accumulator, and a rod float valve that controls flow between a boom cylinder rod intake and tank, where the rod float valve is electronically adjustable and proportionally controls flow restriction. A controller controls ride control activation, and adjustment of the head and rod float valves. When ride control is activated, the head valve allows flow between the head intake and the accumulator, and the controller automatically adjusts the rod float valve. When ride control is deactivated, the head valve blocks flow between the head intake and the accumulator, and the rod float valve blocks flow between the rod intake and tank. An enable valve can control positioning of the head valve. A flow selector can select manual or automatic adjustment of the rod float valve.

A hydraulic system includes a first supply line connecting a boom control valve and a bottom side of a boom cylinder, a second supply line connecting the boom control valve and a rod side of the boom cylinder, a leveling switch valve having: a first operating position allowing a leveling operation of a working tool; and a first stopping position allowing the leveling operation to stop, a ride controller including: a ride-control switch valve connected to a branched fluid line branched from the first supply line; and an accumulator configured to perform an anti-vibrating operation for suppressing a pressure fluctuation of the boom cylinder, and a drain fluid line to discharge operation fluid in a downstream section extending from the leveling switch valve to the rod side of the boom cylinder in the second supply line when the leveling switch valve is switched to the first stopping position.

Passenger restraint systems are provided. The restraint systems can include: a passenger seat supported by a frame; a restraint bar pivotably attached to the frame; and at least one piston operably engaged between the restraint bar and the frame. Restraint system pistons are provided. The pistons can include: a central chamber housing a piston head and rod; a fluid reservoir in fluid communication with the central chamber; and at least one electromechanical valve operable between an open and a closed position. Methods for restraining a passenger within a seat are also provided.