A hydraulic system of a working machine includes a hydraulic pump to output a hydraulic fluid, at least one proportional valve to deliver the hydraulic fluid to a supply target, a valve body including the proportional valve, a heat-up fluid passage in the valve body and into which the hydraulic fluid flows, a switching valve switchable between an open position in which the hydraulic fluid passing through the heat-up fluid passage is supplied to a hydraulic device and a closed position in which the hydraulic fluid is not supplied thereto and the hydraulic fluid from the hydraulic device is to be returned, a controller to operate the switching and proportional valves, and a return circuit through which the hydraulic fluid flowing into the heat-up fluid passage is returned as a result of at least one of the switching and proportional valves being operated by the controller.

A work machine includes a frame, a traction system supporting the frame, an implement system supported by the frame, and a hydraulic system. The hydraulic system includes a hydraulic oil tank, a control circuit, an oil cooler, and a cooler bypass valve assembly. The cooler bypass valve assembly is connected to the control circuit by a control circuit return line, and includes an unloading valve configured to allow hydraulic oil to flow from the control circuit return line to the hydraulic oil tank if a pressure of hydraulic oil in the control circuit return line exceeds a first threshold, a backpressure valve configured to allow hydraulic oil to flow from the return line to the oil cooler through an oil cooler inlet line if a pressure of hydraulic in the oil control circuit return line exceeds a second threshold, and an orifice configured to limit the flow of hydraulic oil through the backpressure valve.

A control system includes a variable displacement hydraulic pump, the pump having an inlet for receiving fluid, an outlet for discharging fluid under pressure, and a pump displacement input, a hydraulic motor having an inlet and an outlet, a fluid circuit including a supply conduit for conducting fluid discharged by the pump to the motor and a return conduit for returning fluid discharged by the motor to the pump, a pump displacement control cooperating with the pump displacement input in order to vary a displacement of the pump, a control circuit in communication with the pump displacement control for controlling the pump output such that the motor is driven at a constant rotational speed, and a system controller in communication with the control circuit and a remote location to transmit and receive information to and from the remote location.

The self-contained energy efficient hydraulic actuator system of the present invention includes a hydraulic cylinder, a servo motor that is configured to produce rated torque from zero RPM to maximum rated RPM with rotor speed/position feedback to a servo motor, a pump, and a solenoid valve that enables the hydraulic cylinder to maintain its position without the motor running. The system has the ability to hold a load in place without motor operation via the use of the solenoid valve, and therefore saves energy and extends the motor lifetime by minimizing the motor running time.

It is an object of the present invention to provide a construction machine having a good engine starting property in a low temperature environment. The construction machine of the present invention includes: an electric pump having a delivery port connected to a line part of a pilot line, the line part connecting a pilot pump with a pilot control valve; a motor that drives the electric pump; and a temperature sensor that measures a temperature of a hydraulic working fluid delivered from the pilot pump. A controller starts driving of the motor in the case where a key switch is operated from a key OFF state to a key ON state and where the temperature of the hydraulic working fluid measured by the temperature sensor is lower than a predetermined temperature.

This disclosure relates to a hydraulic system for a hydro-mechanical machine comprising a rotary mechanism and a boom cylinder The hydraulic system includes a primary accumulator configured to receive and store high-pressure fluid in response to starting and stopping of the rotary mechanism. A control system configured to enable passage of the high-pressure fluid stored in the primary accumulator to a rotary control valve configured to control the rotary mechanism, and a boom control valve configured to control the boom cylinder through the hydraulic supply circuit, based on a predefined pressure threshold associated with the primary accumulator. A secondary accumulator coupled to the primary accumulator and the control system via the hydraulic supply circuit is configured to store surplus high-pressure fluid provided by the primary accumulator through the hydraulic supply circuit.

A preselection valve is for a hydraulic valve assembly with a switching element, a pressure input line, a first pressure output line and a first load pressure line with a load pressure inlet and output. The switching element is switchable from neutral to a first switching position. The pressure input line is connected to the first pressure output line in the first position. The preselection valve has a second and third load pressure line and a load pressure increasing device. The second load pressure line branches off the pressure input line upstream of the switching element. The load pressure increasing device is connected to the third load pressure line, which connects the pressure increasing device to the first load pressure line. The second load pressure line is connected to the pressure increasing device in the first switching position and the second load pressure line is blocked in the neutral position.

To reduce an increase in the electric power consumption of an electric motor according to the state of an electric power source at the start of driving of an actuator, and make it possible to use devices in an appropriate state in an electrically driven hydraulic construction machine including a driving system that drives a hydraulic pump by using the electric motor. For this purpose, a controller 50 sets a target relief pressure of a relief valve 3 to a normal relief pressure Pn (first relief pressure) when an operation lever device 44 is not being operated and a storage amount SOC(t) of a battery 62 (the state quantity of an electric power source) is equal to or larger than a threshold S1, and sets the target relief pressure to a reduced relief pressure Pr(t) (second relief pressure) lower than the normal relief pressure Pn (first relief pressure) when the operation lever device 44 is not being operated, and the storage amount SOC(t) of the battery 62 (the state quantity of the electric power source) is smaller than the threshold S1.

Disclosed are a slit valve apparatus and a method for controlling a slit valve. The slit valve apparatus includes a slit valve assembly and a servo-control system in communication with the slit valve assembly. The slit valve assembly includes at least one gate able to transition between an open position and a closed position, at least one pneumatic actuator, at least one proportional pneumatic valve including a plurality of controllers, and a continuous position sensor. The servo-control system includes a centralized controller that generates a control signal and adjusts the movement of the at least one gate based on the position trajectory for the gate, a linear position measurement of the gate from the continuous position sensor, and fluid pressure/flow measurements from the plurality of controllers.

A preselection valve is for a hydraulic valve assembly with a switching element, a pressure input line, a first pressure output line and a first load pressure line with a load pressure inlet and output. The switching element is switchable from neutral to a first switching position. The pressure input line is connected to the first pressure output line in the first position. The preselection valve has a second and third load pressure line and a load pressure increasing device. The second load pressure line branches off the pressure input line upstream of the switching element. The load pressure increasing device is connected to the third load pressure line, which connects the pressure increasing device to the first load pressure line. The second load pressure line is connected to the pressure increasing device in the first switching position and the second load pressure line is blocked in the neutral position.