Abstract: An actuator control arrangement comprising: a hydraulic actuator having a housing and a piston rod axially moveable within the housing between a neutral position, a retracted position and an extended position with respect to the housing in response to application of pressure to the piston rod; the arrangement further comprising a check valve moveable between a first position providing a flow path between a pressure source and the actuator, and a second position in which the flow path is closed off; and characterised by a mechanical link between the piston rod and the check valve, actuated in response to the piston rod passing a predetermined retracted position in a negative stroke direction, to set the check valve to the first position.

Abstract: A fluid control valve system for controlling the flow of hydraulic fluid supplied to and discharged out of an actuator having first and second actuator ports, comprising: a valve housing having a pressure sensing chamber for sensing the pressure of the hydraulic fluid introduced therein and a pressure port for introducing a hydraulic fluid; a valve spool axially movably received in the valve housing; valve spool operating means having the valve spool axially moved and including a force motor, a piston rod having the valve spool slidably received thereon and driven by the force motor, and a fixed piston firmly connected with the piston rod; and resiliently urging means for resiliently urging the valve spool along the center axis of the valve housing, the valve spool being urged by the hydraulic pressure of the hydraulic fluid in the pressure sensing chamber and the resiliently urging means to assume operation positions consisting of normal operation positions where the hydraulic pressure of the hydraulic fluid

Abstract: The mechanism has an actuator provided with a piston, a servo control valve which is actuated by electric input and output signals for supplying working fluid to the actuator and exhausting working fluid from the actuator, a slider which closes an oil passage from the servo control valve to the actuator and which temporarily engages with the piston of the actuator via a link mechanism, when a system for transmitting the input and output signals or the servo control valve breaks down, and a centering valve which is constructed in one body with the slider and which stops supply and exhaust of working fluid after the actuator has been returned to its neutral position by supply of working fluid to the actuator when a system for transmitting the input and output signals or the servo control valve breaks down.

Abstract: The invention relates to the control of a hydraulic jack which can be used, for example, for controlling the orientation of the rear wheels of a vehicle with front guiding wheels. In the event of a failure in the supply of fluid under pressure to the chambers (3, 4) of the jack, these chambers are isolated and the piston (2) is maintained in the position which it occupied when the failure occurred, by means of non-return valves (12). However, when certain conditions are satisfied, for example a sufficiently low speed, the electronic control member (20) activates an auxiliary circuit (30 to 39) in order to return the piston to its middle position and allow driving of the conventional kind with the rear wheels in line.

Abstract: A neutral position resetting device for a servo actuator is described, having reset means that is actuated when the control of the servo actuator by actuator valve means becomes inoperative. The reset means ordinarily separated from a spool of the actuator valve means resets the servo actuator to a neutral position by applying a driving force and forcibly moving the spool.

Abstract: The invention relates to a split hopper vessel consisting of two halves, which can swing about a horizontal longitudinal axis between a closed position in which the hold formed by the two halves is closed and an open position in which the two halves are moved apart. The two halves are interconnected by hydraulic cylinders which can perform or assist the opening and/or closing of the vessel. The hydraulic cylinders under the control of non-return valves (10,11,53) which block the closed position and which by a control pressure system can open to allow the opening of the vessel. The flow of liquid from one side of each cylinder to the other side can be shortened, and safety structure ensures that all cylinders operate simultaneously, all non-return valves (10,11) having a pressure-activated switch, which when activated opens the non-return valve G.sub.1 in the line connecting both sides of each cylinder.

Abstract: An actuator system is disclosed which modulates a linear output shaft associated with a working control valve or the like in response to a control signal input. The system includes a feedback control link, a pneumatic positioner, a pneumatically controlled hydraulic valving system and a hydraulic cylinder and piston assembly controlled by the hydraulic valving system. The hydraulic valving system includes a three-position, four-way valve actuated by pneumatic binary output signals from a signal conditioner which is in turn controlled by the positioner. Hydraulic flow to the three-position, four-way valve may also be controlled from the signal conditioner in response to positioner output for most effective actuation of the hydraulic cylinder and piston assembly. Failure modes are also disclosed with the present system. The resulting system exhibits extremely rapid response times and high accuracy with dynamic stability.

Abstract: An electrohydraulic actuator has a power piston which is controlled from movement between the ends of its travel for performing work by servo control valve. When the actuator is not performing work, the power piston is abutted on one side by a pressure positioned centering piston which prevents the movement in one direction. High pressure fluid operates on the other side of the power piston to prevent movement in the other direction so that the power piston is centered in the cylinder and cannot be moved by external forces.