A hydraulic circuit includes a pump connected to a tank for supplying hydraulic liquid under pressure to a component via a directional control slide valve provided with a feed port connected to an inlet of the component and with a return port connected to an outlet of the component. The hydraulic circuit further includes a pressure limiter connected to the inlet of the component and the tank, and a feed control system for the hydraulic component including a pressure sensor installed upstream of the hydraulic component downstream of the feed port for supplying information about the pressure of the hydraulic liquid and a setpoint pressure. The feed control system further including an actuator for controlling the movement of the directional control slide valve, and a control unit for generating a control signal for the actuator based on information about the pressure measured at the feed port.

A hydraulic drive system raises and lowers an object by supplying and discharging operating oil to and from each of two ports of an actuator and includes a control device, first to third electromagnetic proportional control valves, a hydraulic pump, a control valve, and a lock valve. When a second pilot pressure is output, the control valve causes the operating oil to be discharged from a first port in order to lower the object. The lock valve is disposed so as to be able to prevent the operating oil from being discharged from the first port by closing a path between the first port and the control valve, and only when a third pilot pressure is output, allows the operating oil to be discharged from the first port by opening the path between the first port and the control valve.

A manual override assembly for a hydraulic power source operates to override an actuator of a hydraulic power source. The assembly includes a lever arm and connecting rods. The lever arm pivotally moves relative to a valve body of the hydraulic power source. The lever arm is connected to valve spools via the connecting rods, respectively. Each spool has a bore with an off-set opening for inserting one end of the connecting rod.

A field bus solenoid valve assembly has a sensor for detecting the commencement of an actuation cycle for moving a piston in a cylinder and piston assembly. A position sensor detects an end position of a piston in a cylinder and piston assembly at the end of the actuation cycle. A timer times the elapsed time between the initiation of the actuation cycle of the piston and when the position sensor for detecting an end position detects the piston in its end position at the end of the actuation cycle. A comparator operably connected to a storage device and the sensors for comparing elapsed time from the sensors to a normalized time or profile and a predetermined tolerance boundary in the storage device. An alarm device is actuated if the elapsed time is outside of the set tolerance boundary.

A hydraulic system for controlling bleed down and retraction of a boom within a safety envelope includes a backup battery power supply, and at least a first boom lift hydraulic cylinder configured to raise and lower the boom. The first boom lift hydraulic cylinder includes a solenoid bleed valve electrically connected to the backup battery power supply. The hydraulic system also includes an input device controllable by an operator of the boom. The input device may, for instance, be used by the operator to initiate bleed down and retraction of the boom from an elevated position. To accommodate independent failsafe features of the system, the input device is configured to selectively actuate the solenoid bleed valve using electrical power supplied from the backup battery power supply.

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.

An actuator control arrangement includes a hydraulic actuator having a housing and a piston rod axially moveable within the housing, a stop disposed within the housing to limit the extent of movement of the piston rod into the housing, and a solenoid valve arranged between a pressure source and the actuator. The solenoid valve is switchable between a first mode and a second mode in response to an electric control signal, wherein, in the first mode, the solenoid valve creates a fluid flow path from the pressure source to the actuator so as to locate the stop in its neutral position and in the second mode, the solenoid valve creates a fluid flow path to release pressure from the actuator to permit the stop to move to its retracted position. In the event of electrical failure, the stop will set the actuator to its neutral position.

A control device and method for controlling a disengaging actuator (1) of a tool attachment, the device comprising a three-state switch (2), with a middle neutral position (20), a first end position (21), and a second end position (22), a control unit (3, 3′) having an input corresponding to an activation of the first end position (21), an electro-valve (4) coupled hydraulically to the disengaging actuator (1), having a coil (40), a first control line (41) and a second control line (42) coupled respectively to first and second terminals of the coil (40) of the electro-valve, wherein one of the first and second control lines is coupled to the second end position (22) of the three-state switch and the other of the first and second control lines is coupled to an output of the control unit, such that both control lines have to be activated to allow disengagement.

An arrangement includes a field device with an on/off valve, a pneumatic actuator that moves the on/off valve, when applied with compressed air, into one on/off position and when ventilated into the other on/off position, a magnetic valve that applies compressed air to the actuator during electric actuation and ventilates the actuator during non-actuation and a function monitoring device that detects at least one parameter that refers to the movement of the on/off valve, where the function monitoring device includes a magnetic field sensor detecting changes to a magnetic field, where the magnetic field sensor is arranged in the region of the magnetic valve and generates a signal awakening the function monitoring device to detect the at least one parameter.

An arrangement includes a field device with an on/off valve, a pneumatic actuator that moves the on/off valve, when applied with compressed air, into one on/off position and when ventilated into the other on/off position, a magnetic valve that applies compressed air to the actuator during electric actuation and ventilates the actuator during non-actuation and a function monitoring device that detects at least one parameter that refers to the movement of the on/off valve, where the function monitoring device includes a magnetic field sensor detecting changes to a magnetic field, where the magnetic field sensor is arranged in the region of the magnetic valve and generates a signal awakening the function monitoring device to detect the at least one parameter.