A forklift includes forks, cylinders for causing the forks to perform an ascending/descending operation in accordance with the flow rate of hydraulic oil, a first valve for controlling the flow rate of the hydraulic oil in accordance with an energizing current, a second valve 6 for regulating the flow rate of the hydraulic oil in accordance with cylinder pressure, and a control portion that calculates the flow rate to be regulated by the second valve, on the basis of cylinder pressure detected by a pressure sensor, calculates a current command value for the energizing current, with the flow rate to be controlled by the first valve being set equal to the regulated flow rate, and changes the energizing current in two stages, with the current command value as the upper limit of the energizing current, thereby decelerating the forks in two stages when stopping the ascending/descending operation.

In one aspect, a piston assembly for a fluid-driven actuator may include a piston defining a passage extending between first and second chambers of the actuator. The piston assembly may further include a valve having a valve head and a valve stem. The valve may be positioned within the passage and slidable between an open position and a closed position. The valve stem may extend outward from the passage into the second chamber when the valve is positioned in the closed position. Additionally, the piston assembly may include a spring compressed between the valve head and the piston. The spring may be configured to bias the valve to the closed position. The valve may be configured to move to the open position when a pressure in the second chamber exceeds a pressure threshold or when the valve stem contacts a cylinder of the fluid-driven actuator.

A control device generates an operation signal for controlling a pressure of hydraulic oil on a downstream side of the swing motor in a hydraulic device based on an azimuth direction, a swing speed, and a target stopping azimuth direction of a swing body during braking of a swing motor.

A wheelchair lift with low energy consumption includes a platform assembly to receive a wheelchair. The wheelchair lift includes a hydraulic drive system to move the platform assembly between an entry level position and a ground level position. The wheelchair lift includes a fluid circuit being embodied to transport a hydraulic fluid from a tank using a pump driven by an electric motor to the hydraulic drive system to raise the platform assembly from the ground level position to the entry level position. The fluid circuit is further embodied to transport the hydraulic fluid from the hydraulic drive system via the pump to the tank, when lowering the platform assembly from the entry level position to the ground level position.

A wheelchair lift with low energy consumption includes a platform assembly to receive a wheelchair. The wheelchair lift includes a hydraulic drive system to move the platform assembly between an entry level position and a ground level position. The wheelchair lift includes a fluid circuit being embodied to transport a hydraulic fluid from a tank using a pump driven by an electric motor to the hydraulic drive system to raise the platform assembly from the ground level position to the entry level position. The fluid circuit is further embodied to transport the hydraulic fluid from the hydraulic drive system via the pump to the tank, when lowering the platform assembly from the entry level position to the ground level position.

In some applications, a piston of a hydraulic actuator may move at high speeds, and large undesired forces may be generated if the piston reaches an end-stop of the hydraulic actuator at a high speed. The undesired forces may, for example, cause mechanical damage in the hydraulic actuator. A controller may receive information indicative of the piston reaching a first position at a first threshold distance from the end-stop, and, in response, may modify a signal to a valve assembly controlling flow of hydraulic fluid to and from the hydraulic actuator. Further, the controller may receive information indicative of the piston reaching a second position at a second threshold distance closer to the end-stop of the hydraulic actuator, and, in response, the controller may further modify the signal to the valve assembly so as to apply a force on the piston in a away from the end-stop.

In some applications, a piston of a hydraulic actuator may move at high speeds, and large undesired forces may be generated if the piston reaches an end-stop of the hydraulic actuator at a high speed. The undesired forces may, for example, cause mechanical damage in the hydraulic actuator. A controller may receive information indicative of the piston reaching a first position at a first threshold distance from the end-stop, and, in response, may modify a signal to a valve assembly controlling flow of hydraulic fluid to and from the hydraulic actuator. Further, the controller may receive information indicative of the piston reaching a second position at a second threshold distance closer to the end-stop of the hydraulic actuator, and, in response, the controller may further modify the signal to the valve assembly so as to apply a force on the piston in a away from the end-stop.

In one aspect, a piston assembly for a fluid-driven actuator may include a piston defining a passage extending between first and second chambers of the actuator. The piston assembly may further include a valve having a valve head and a valve stem. The valve may be positioned within the passage and slidable between an open position and a closed position. The valve stem may extend outward from the passage into the second chamber when the valve is positioned in the closed position. Additionally, the piston assembly may include a spring compressed between the valve head and the piston. The spring may be configured to bias the valve to the closed position. The valve may be configured to move to the open position when a pressure in the second chamber exceeds a pressure threshold or when the valve stem contacts a cylinder of the fluid-driven actuator.

A forklift includes forks, cylinders for causing the forks to perform an ascending/descending operation in accordance with the flow rate of hydraulic oil, a first valve for controlling the flow rate of the hydraulic oil in accordance with an energizing current, a second valve 6 for regulating the flow rate of the hydraulic oil in accordance with cylinder pressure, and a control portion that calculates the flow rate to be regulated by the second valve, on the basis of cylinder pressure detected by a pressure sensor, calculates a current command value for the energizing current, with the flow rate to be controlled by the first valve being set equal to the regulated flow rate, and changes the energizing current in two stages, with the current command value as the upper limit of the energizing current, thereby decelerating the forks in two stages when stopping the ascending/descending operation.

A forklift includes forks, cylinders for causing the forks to perform an ascending/descending operation in accordance with the flow rate of hydraulic oil, a first valve for controlling the flow rate of the hydraulic oil in accordance with an energizing current, a second valve 6 for regulating the flow rate of the hydraulic oil in accordance with cylinder pressure, and a control portion that calculates the flow rate to be regulated by the second valve, on the basis of cylinder pressure detected by a pressure sensor, calculates a current command value for the energizing current, with the flow rate to be controlled by the first valve being set equal to the regulated flow rate, and changes the energizing current in two stages, with the current command value as the upper limit of the energizing current, thereby decelerating the forks in two stages when stopping the ascending/descending operation.