Provided is a construction machine capable of detecting a stuck-open state of a surplus flow control valve in real time during operation without involving a reduction in the operational speed. The construction machine is equipped with: a surplus flow control valve control section configured to output a closing command to a first surplus flow control valve at the operation start when an operation amount signal of an operation lever device is detected; a pump delivery control section configured to output a delivery flow rate command to an adjustment section of an open circuit pump; an assist valve control section configured to continue to output a closing command from before to an assist valve; a sticking detection determination section configured to compare a pressure signal with a previously set threshold value and determining that the surplus flow control valve is in a stuck-open state when the pressure signal is less than the threshold value and determining that the surplus flow control valve is normal when the pressure signal exceeds the threshold value; and a stop signal generating section configured to input therein a sticking determination signal, output in the case of a stuck-open state a control signal maintaining a closed state of the assist valve to the assist valve control section, and output in the case of a normal state a control signal causing the assist valve to perform an opening operation to the assist valve control section.

A hydraulic system includes a hydraulic actuator to be operated by an operation fluid, a first hydraulic pump to output the operation fluid, a second hydraulic pump to output the operation fluid, a control valve to which the operation fluid outputted from the first hydraulic pump is supplied, the control valve being configured to control the operation fluid that is to be supplied to the hydraulic actuator, a first fluid tube connecting the control valve to the hydraulic actuator, a second fluid tube to which the operation fluid outputted from the second hydraulic pump is supplied, the second fluid tube being connected to the first fluid tube, and a first switching valve disposed on the second fluid tube. The spool includes a communicating fluid passage being configured to supply the operation fluid to the first inner fluid passage, the operation fluid being received by the pressure-receiving port.

A method of controlling hydraulic fluid flow to an implement of a material handling vehicle includes coupling a boom arm to a vehicle frame for rotation about the vehicle frame, rotating a boom arm with respect to the vehicle frame with an actuator, coupling an attachment to the boom arm for rotation with respect to the boom arm, sensing a pressure of fluid in the actuator, communicating the sensed pressure to a control system, determining a baseline pressure of the attachment based upon the sensed pressure of the fluid in the actuator, and limiting fluid flow to the actuator with a control valve in response to the sensed pressure of the fluid in the actuator being above the baseline pressure.

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.

An apparatus for controlling a hydraulic machine, for example a turbine, pump or pump turbine, using variable-speed driven fixed displacement pumps. The apparatus includes a device for carrying out an emergency shut-off that is characterized by low energy consumption and high efficiency while guaranteeing all the operation-relevant and safety-relevant requirements of a hydraulic machine.

A hydraulic system includes a control device to reduce a first movement speed to be lower than a second movement speed, the first movement speed being a speed at which a spool of a first control valve moves from a first supply position to a first stop position under a state where a second control valve is in the second supply position, the second movement speed being a speed at which the spool moves from the first supply position to the first stop position under a state where the second control valve is in the second stop position. The first supply position allows operation fluid to be supplied to a hydraulic actuator. The first stop position prevents the operation fluid from being supplied to the hydraulic actuator. The second stop position prevents the operation fluid from being supplied to a first fluid tube coupling a hydraulic pump to the hydraulic actuator.

Disclosed embodiments include hydraulic systems which provide power to lift, tilt and auxiliary (e.g., implement) functions, including high-flow auxiliary functions, with increased efficiency. Disclosed embodiments incorporate a single variable displacement pump that supplies pressurized fluid to a main control valve (e.g., for lift, tilt, and auxiliary functions) and a bypass circuit. The main control valve supplies fluid to control lift, tilt, and auxiliary flow for implements. The bypass circuit combines flow with the output of the auxiliary section of the main control valve to optionally provide high-flow for selected implements. The single variable displacement pump can then be set to different output flow levels, with the bypass circuit functioning differently under different conditions to optimize hydraulic flow to carryout various tasks under various conditions.

A linear actuator system includes a linear actuator and at least one integrated pump assembly connected to the linear actuator to provide fluid to operate the linear actuator. The integrated pump assembly includes a pump with at least one fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The linear actuator system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover to exclusively adjust at least one of a flow and a pressure in the linear actuator system to an operational set point.

An apparatus for controlling a hydraulic machine, for example a turbine, pump or pump turbine, using variable-speed driven fixed displacement pumps. The apparatus includes a device for carrying out an emergency shut-off that is characterized by low energy consumption and high efficiency while guaranteeing all the operation-relevant and safety-relevant requirements of a hydraulic machine.

A safe hydraulic drive system and process, comprising at least one first cylinder chamber and a second, separate cylinder chamber which are connected to one another via a connecting line to form a fluid-filled hydraulic circuit, and a hydraulic drive for conveying the fluid from one cylinder chamber, via the connecting line, into the other cylinder chamber in which the connecting line is arranged. The connecting line has at least one parallel system, between the hydraulic drive and one of the two cylinder chambers, including at least one first sub-connection with at least one first stop valve and a second sub-connection with a baffle arranged therein. The connecting line, excluding the second sub-connection, has a first flow resistance and the second sub-connection has a second flow resistance due to the baffle arranged therein, which is greater than the first flow resistance for the fluid, wherein the drive system is provided with at least one open first stop valve in normal mode and with a closed first stop valve in safe mode for conveying the fluid, and a suitably high second flow resistance has been selected so that a maximum permissible speed for a piston rod is not exceeded in safe mode, even when an external force acts on the drive system in the direction of movement of the piston rod.