A valve unit includes a first piston, which has a first opening and a control chamber. A fluid connection between a first and a second port is closed or, in a position defined by the first piston, is held open in the event that a hose which is connected to the first port bursts. A pilot valve (48) is present, which has a core and a coil, and a fluid flow from the control chamber to the first port can be regulated by an electric current in the coil. The current is regulated by a logic unit which is suitable for receiving signals from at least one sensor, in particular a pressure sensor, an inertia detector and/or position sensor and for regulating the electric current in the coil.

A closed-loop hydraulic circuit associated with a swing mechanism of a machine is controlled to obtain both a pressure control during acceleration and deceleration of the swing mechanism and a velocity control during coasting. In this manner, a system pressure in closed-loop hydraulic circuit is maintained below a maximum allowable pressure during acceleration and deceleration, and the swing mechanism can be rotated at a desired constant speed during coasting. This is achieved by controlling a hydraulic actuator adjusting the displacement of a variable displacement pump in different control modes, depending on a comparison between a desired displacement of the pump and an actual displacement of the same.

An actuating system for a valve which can be used as a control valve. The valve system having an outer housing. a receiving region for a switching spindle of the valve, at least one inductive sensor running in parallel to the receiving region, and at least one substantially circular cylindrical position encorder.

The present invention provides a low-cost detachment determining device capable of determining whether or not an electromagnetic valve-equipped device has been detached. The detachment determining device determines whether or not at least a part of an electromagnetic valve-equipped device included in an industrial machine, such as a construction machine or an industrial vehicle, has been detached from the industrial machine, the electromagnetic valve-equipped device being a hydraulic device equipped with an electromagnetic valve. The detachment determining device includes: an electrical characteristic detecting portion configured to output a detection signal to the electromagnetic valve-equipped device and detect an electrical characteristic of the electromagnetic valve-equipped device based on the detection signal; and a detachment determining portion configured to determine, based on a plurality of electrical characteristics detected at different time points by the electrical characteristic detecting portion, whether or not at least a part of the electromagnetic valve-equipped device has been detached.

Hydraulic workover system having at least two sets of hydraulic cylinders coupled with a single load. A plurality of control valves transitionable between a closed position and an open position, the plurality of control valves having at least one extend control valve disposed between each set of hydraulic cylinders and an extend supply pump, at least one retract control valve disposed between each set of hydraulic cylinders and a retract supply pump, and at least one float control valve disposed between each set of hydraulic cylinders and a float supply pump. A logic control system coupled with the plurality of control valves and configured to transition the plurality of control valves between the closed and open position, thereby controlling flow between the at least two sets of hydraulic cylinders and the extend supply pump, retract supply pump, and float supply pump.

A construction machine that can easily regulate a set maximum flow rate at a time of replacement of an attachment and that can improve an energy conservation performance is provided. A controller selects a corresponding map in response to an attachment designation signal from among maps each of which sets a relationship between an operation signal per type of the attachment and a flow rate of a hydraulic fluid supplied to an actuator, generates a control signal by causing the selected map to refer to the operation signal, and controls a flow control valve of an attachment flow rate regulation valve device in such a manner that a position of the flow control valve is switched over from a neutral position on the basis of the control signal. An unloading valve that maintains a differential pressure across the flow control valve is disposed in the attachment flow rate regulation valve device.

In a construction machine with a hydraulic pilot type hydraulic control device, occurrence of jerking is prevented. A hydraulic excavator 1 having hydraulic pumps 51L and 51R, travel motors 22L and 22R, traveling operating levers 34L and 34R, a pilot pump 54, hydraulic pilot valves 55La, 55Lb, 55Ra, and 55Rb, and directional control valves 53L and 53R includes: changeover switches 35L and 35R which change the operating mode of the traveling operating levers 34L and 34R; pilot pressure adjusting devices 5L and 5R which adjust the pilot pressure applied to the directional control valves 53L and 53R; and pilot pressure sensors 56La, 56Lb, 56Ra, and 56Rb. The pilot pressure adjusting devices apply the pilot pressure at the time when the operating mode of the traveling operating levers 34L and 34R is changed to a control mode, to the directional control valves 53L and 53R.

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.

An actuator control device performs a reception process in which designations of a minimum operation amount and maximum operation amount of an operation unit for driving an actuator, and a maximum driving speed which is the actuator driving speed corresponding to the maximum operation amount are received. It also performs a determination process in which a function representing a characteristic line that links a first point, which corresponds to the minimum operation amount and the driving speed of 0, and a second point, which corresponds to the maximum operation amount and the maximum driving speed, is stored in a storage unit as a drive control characteristic and a drive control process in which, in response to operation of the operation unit, the actuator is driven at a driving speed corresponding to the operation amount specified by the drive control characteristic stored in the storage unit.

Apparatuses, systems and methods are provided for controlling at least one fluid actuated device; e.g., an actuator such as a hydraulic cylinder. A method is provided, for example, involving an actuatable component and an actuation system, which includes an actuation system component and an actuator. During a mode of operation, the actuation system component is fluidly coupled with a first chamber and a second chamber of the actuator using the actuation system. The actuator is operable to move the actuatable component.