A valve has a housing which has at least two fluid openings, through which fluid can flow, and a further opening, at least one valve seat which is assigned to one of the fluid openings, and at least one closure member which is adjustable to release and/or close the at least one valve seat, the at least one valve seat which adjoins a cavity through which fluid can flow being formed on a housing part. The valve includes a sensor device which closes the opening in a fluid-tight manner and can acquire data about the fluid is arranged in the further opening. A valve island is furthermore described.

A hydraulic system may include a reservoir of hydraulic fluid, a hydraulic pump, a directional control valve, a hydraulic work loop, a bypass valve, and a hydraulic motor, as well as a plurality of hydraulic conduits interconnecting such components. When excessive hydraulic backpressures are encountered, the system may employ one or more bypass valves and one or more bypass conduits to automatically, and in an on-demand manner, return some or all of the hydraulic fluid from the hydraulic motor to the hydraulic reservoir without the hydraulic fluid passing through flow constrictions causing the excessive hydraulic backpressures.

A hydraulic control apparatus includes an output-side oil passage into which oil from a first oil passage and oil from a second oil passage flow, and a pressure regulating check valve regulating a hydraulic pressure in the second oil passage. The pressure regulating check valve includes first and second elastic portions housed in a spool hole between a valve body and a bottom of the spool hole. A natural length of the second elastic portion is shorter than a distance between the valve body and the bottom when the valve body closes an inflow hole. The second elastic portion applies an elastic force to the valve body in a state in which the valve body opens the inflow hole.

A pilot type switching valve includes: a housing bore formed in a valve body, the housing bore having an opening end; a spool slidably housed in the housing bore, the spool being configured to allow or block a flow of the working fluid to a first relief valve; a pilot chamber to which pilot pressure biasing the spool in the valve opening direction is guided; and a spring configured to bias the spool in the valve closing direction. The spool has a bottom surface on which the pilot pressure acts in such a manner that the spool is biased in the valve opening direction, and the area of the bottom surface is smaller than the sectional area of the housing bore.

A counter pressure valve arrangement for controlling a pressure level of a hydraulic fluid in a return line from a hydraulic actuator arrangement. The counter pressure valve arrangement comprises a counter pressure valve having: a moveable valve member; a counter pressure regulating port configured for being connected to the hydraulic actuator arrangement via the return line; a tank port configured for being connected to a tank or low pressure reservoir for storing low pressure hydraulic fluid; and a pump port configured for being connected to a source of pressurised hydraulic fluid. A first position of the valve member effects fluid communication between the pump port and the counter pressure regulating port for supplying pressurised hydraulic fluid to the return line (4), and a second position of the valve member effects fluid communication between the counter pressure regulating port and the tank port for discharging hydraulic fluid from the return line to the tank.

A counter pressure valve arrangement for controlling a pressure level of a hydraulic fluid in a return line from a hydraulic actuator arrangement. The counter pressure valve arrangement comprises a counter pressure valve having: a moveable valve member; a counter pressure regulating port configured for being connected to the hydraulic actuator arrangement via the return line; a tank port configured for being connected to a tank or low pressure reservoir for storing low pressure hydraulic fluid; and a pump port configured for being connected to a source of pressurised hydraulic fluid. A first position of the valve member effects fluid communication between the pump port and the counter pressure regulating port for supplying pressurised hydraulic fluid to the return line, and a second position of the valve member effects fluid communication between the counter pressure regulating port and the tank port for discharging hydraulic fluid from the return line to the tank.

A fluid power system includes an electro-hydraulic variable displacement fluid pump driving fluid at a first displacement value. The system further includes a directional control valve, a sensor, and a controller. The directional control valve includes a valve member movable between a neutral position and at least one actuated position. The directional control valve diverts at least some fluid to an actuator while the valve member is in an actuated position, and the directional control valve exhausts fluid at an exhaust pressure through an outlet port to the fluid reservoir while the valve member is in the neutral position. The sensor measures a difference between the exhaust pressure and a nominal pressure and generates a signal based on the measured difference. The controller generates a flow command at least partially based on the pressure signal to modify the operation of the pump to drive fluid at a second displacement value.

To reduce the cost by reducing the number of parts and simplify the control of regeneration in the hydraulic actuator even though the meter-in control and the meter-out control can be performed separately while the supply and the discharge of hydraulic fluid is controlled. A meter-in valve that controls supply flow from a hydraulic pump into a hydraulic cylinder is provided, and meter-out switching valve that switches the direction of supply and discharge of the hydraulic oil into the hydraulic cylinder and controls the discharge flow from the hydraulic cylinder to the oil tank is installed on the down stream side of the meter-in valve, and further, a regeneration control valve is installed on the down stream side of the meter-out switching valve.

A quick coupler circuit for attaching and detaching an attachment to a quick coupler includes a coupler cylinder, an actuator, a first hydraulic pump, a boosting valve, a coupler changeover valve, and a changeover switch. The boosting valve switches to a boosting position and the coupler changeover valve switches to a lock-side position when the changeover switch switches to a lock position. When the changeover switch switches to a hold position, the boosting valve switches to a non-boosting position and the coupler changeover valve switches to the lock-side position. When the changeover switch switches to an unlock position, the boosting valve switches to the boosting position and the coupler changeover valve switches to an unlock-side position.

A hydraulic control circuit includes a first pressure regulating valve for regulating a pump discharge pressure, a second pressure regulating valve for adjusting a pilot pressure to a torque converter pressure, and a first oil passage that connects an output port of the first pressure regulating valve and a torque-converter input-side oil passage, the second pressure regulating valve having an input port connected to the first oil passage through a second oil passage, a drive port connected to the first oil passage through a third oil passage, a spool axially displaced according to a drive pressure inputted into the drive port for regulating the torque converter pressure, and an output port. A throttle is provided between the connection section of the first and third oil passages and the connection section of the first and second oil passages, for adjusting the torque converter pressure to an appropriate pressure.