An interlocked single function activation valve for hydraulic systems is disclosed. The hydraulic valve prevents unsafe tie-down or safety override situations by requiring the safety mechanism to be reset each time the hydraulic system is used. The hydraulic valve includes an interlock spool that moves to an extension position when the hydraulic system is de-pressurized and then re-pressurized while the control lever is engaged (i.e., tied down). When the interlock spool is in the extension position, it prevents the system from reaching a working pressure, thereby forcing a reset of the control lever before the system can reach working pressure.

A hydraulic lockout lever failure detection system preferably includes a first analog sensor, a second analog sensor, at least one electronic control module (ECU) and a solenoid valve. The voltage output level of the first and second analog sensors is monitored by the ECU. The solenoid valve controls the flow of hydraulic fluid to operate an excavator or other equipment. The operation of the solenoid valve is controlled by the ECU. However, a second ECU may be used to control the operation of the solenoid valve. A hydraulic lockout lever causes the first and second analog sensors to output either a low voltage to indicate a closed position, or to indicate an open position to the ECU. If the first and second analog sensors output a voltage that is above a low set value or above a high set value, a fault is detected.

Systems and methods for determining a pre-charge gas pressure in a gas-charged hydraulic accumulator are disclosed. For example, systems and methods for determining pre-charged gas pressure of a gas-charged hydraulic accumulator included as part of a vehicle are disclosed. Further, the present disclosure provides for determining a pre-charge gas pressure of a gas-charged hydraulic accumulator using a position sensor. The accumulator may form part of a hydraulic system used to move one part of the vehicle relative to another.

The present disclosure relates to a hydraulic valve arrangement comprising a first pilot operated proportional directional control valve having a first valve member that is displaceable in a first and a second axial direction for controlling direction of supply and discharge of hydraulic fluid to and from a hydraulic actuator, a first proportional electro-hydraulic control valve for controlling displacement of the first valve member in the first axial direction, a second proportional electro-hydraulic control valve for controlling displacement of the first valve member in the second axial direction, and a second pilot operated proportional control valve having a second valve member configured to be controlled by the first and second proportional electro-hydraulic control valves via a shuttle valve arrangement. Individual meter-in and meter-out control of the hydraulic actuator is providable by having the second pilot operated proportional control valve configured to operate as a meter-in valve of the hydraulic actuator and the first pilot operated proportional directional control valve configured to operate as a meter-out valve of the hydraulic actuator, or by having the first pilot operated proportional directional control valve configured to operate as a meter-in valve of the hydraulic actuator and the second pilot operated proportional control valve configured to operate as a meter-out valve of the hydraulic actuator. The present disclosure also relates to a vehicle comprising a hydraulic actuator and a hydraulic valve arrangement for controlling the motion of the hydraulic actuator.

A hydraulic machine is provided. A first flow control valve directs fluid from a first fluid supply to a first actuator when the first flow control valve is in a first position. A conflux control valve directs fluid from the first fluid supply to a second flow control valve when the conflux control valve is in a conflux position. The second flow control valve directs fluid from a second fluid supply and the first fluid supply to a second actuator when second flow control valve is in a second position. A bypass path allows the first fluid supply to communicate with the conflux control valve by passing around the first flow control valve.

A fluid pressure control device includes a switching valve, a main pilot passage and a sub pilot passage, the switching valve is configured to be switched to the open position when the working fluid is supplied to the pilot chamber, and to be switched to the throttled position with opening on the downstream side of the switching valve in the neutral passage, and the sub pilot passage is provided with a throttle portion and a check valve in parallel in the throttle portion.

A work machine includes directional control valves 43 and 44 each controlling a direction and a flow rate of a pressurized fluid supplied to each a boom cylinder 32 and a bucket cylinder 36; operation amount sensors 51a, 52a, and 52b detecting operation amounts of operation devices 51 and 52; a variable flow control valve 45 that can restrict the flow rate of the pressurized fluid in a meter-in passage of the directional control valve 44 related to the bucket cylinder 36; and a controller 60 controlling the variable flow control valve on the basis of the detection results by the operation amounts from the operation amount sensors, and the controller changes over an action mode to any one of a normal mode for restricting the flow rate of the pressurized fluid by the variable flow control valve and a responsiveness priority mode for not restricting the flow rate of the pressurized fluid by the variable flow control valve in response to the detection results of the operation amounts of the plurality of operation devices. It is thereby possible to enhance responsiveness in an action that requires responsiveness such as an action in which an operation amount of an operation lever frequently changes in a short period of time and to suppress a decline in work efficiency.

Flow control over a hydraulic pump and flow dividing control of a plurality of directional control valves associated with actuators can stably be exercised even in a case in which differential pressures across the directional control valves are quite low, an abrupt change in a flow rate of the hydraulic fluid supplied to each actuator is prevented and excellent combined operability is realized even in an abrupt change in a demanded flow rate at a time of transition from a combined operation to a sole operation, and realizing excellent combined operability, and a meter-in loss in each directional control valve is reduced to realize high energy efficiency. Demanded flow rates of the directional control valves are calculated from input amounts of operation levers, openings of flow control valves are controlled using the demanded flow rates, a meter-in pressure loss of a predetermined directional control valve is calculated from the demanded flow rates and meter-in opening areas of the directional control valves, and a set pressure of an unloading valve is controlled using a value of the meter-in pressure loss.

A valve arrangement for pressure medium supply of a hydraulic consumer according to the invention, wherein said valve arrangement has two utility ports (A, B) for fluid connection to the consumer, having a first control valve, which has a first intake (24), via which a first intake flow from the first utility port (A) to the consumer (10) is controllable, and having a first return control orifice (26), via which a first return flow (28) from the consumer (10) via the second utility port (B) is controllable simultaneously with the first intake (24), and has a second intake (34), via which a second intake flow from the second utility port (B) to the consumer (10) is controllable, and having a second return control orifice (36), via which a second return flow (38) from the consumer (10) via the first utility port (A) is controllable simultaneously with the second intake (34), and having a second control valve (40) having an intake control orifice (42), which can be used to control the respective intake (24, 34) of the first control valve (20).

A hydraulic drive system includes a swing directional control valve 81 and a third boom directional control valve 82 that are connected to a third hydraulic pump 33. Furthermore, the hydraulic drive system includes: a second auxiliary directional control valve 84 that is connected to the third hydraulic pump 33, and is connectable with a second special hydraulic actuator 64 for driving special attachments; and a first selector valve 96 that is connected to the third hydraulic pump 33 upstream of the second auxiliary directional control valve 84, and is connectable with an additional hydraulic pump 97. The first selector valve 96 switches the hydraulic fluid source of the second special hydraulic actuator 64 connected to the second auxiliary directional control valve 84 at least between the third hydraulic pump 33 and the additional hydraulic pump 97. Operability for combined operation of a special attachment can be improved in the hydraulic drive system equipped in advance with an auxiliary directional control valve that is connectable with an additional hydraulic actuator for driving the special attachment.