An actuator device includes two drive units for an actuator output element. The first drive unit has a first piston chamber and a first piston displaceable therein and also first hydraulic means for displacing the piston. The second drive unit has a second piston chamber and a second piston displaceable therein and also second hydraulic or pneumatic means for displacing the piston. The second piston is joined to the actuator output element for conjoint movement therewith and can be coupled to the first piston for thrust, so that the second piston is displaceable in an outward direction by the first piston. The first drive unit is configured for a larger thrust force than the second drive unit, while the second drive unit is designed for a greater stroke speed than the first drive unit.

An electrohydraulic system includes a hydraulic load and at least one closed hydraulic circuit. The hydraulic circuit includes at least one control mechanism, a hydraulic machine, and a closed hydraulic reservoir. The closed hydraulic circuit is filled with degassed hydraulic fluid. A method, in one embodiment, includes filling the electrohydraulic system with degassed hydraulic fluid. In one embodiment, equipment is provided for filling the electrohydraulic system with the degassed hydraulic fluid

An electrohydraulic system includes a hydraulic load and at least one closed hydraulic circuit. The hydraulic circuit includes at least one control mechanism, a hydraulic machine, and a closed hydraulic reservoir. The closed hydraulic circuit is filled with degassed hydraulic fluid. A method, in one embodiment, includes filling the electrohydraulic system with degassed hydraulic fluid. In one embodiment, equipment is provided for filling the electrohydraulic system with the degassed hydraulic fluid

A modular fluid-driven linear actuator comprising an actuator support comprising a first part and a second part configured for relative linear movement, wherein the actuator support is configured to hold a plurality of removable actuator modules in parallel and in respective module-receiving locations defined between the first part and the second part. At least one actuator module is removably installed in the actuator support and held in a respective module-receiving location of the plurality. A first fluid manifold is configured to provide a drive fluid to each actuator module when received in a respective module-receiving location, to act on a piston of the actuator module having a respective piston area to drive the piston in a first direction. A total piston area of the modular actuator is variable by installing and uninstalling actuator modules in the actuator support.

A hydraulic system and a method comprising a linear actuator 23 for generating discrete sum forces, chambers A-D for generating discrete force components, at least two charging circuits 3,4 configured to maintain predetermined pressure levels of hydraulic fluid, independent control interfaces 9-16 configured to open and close connections of the first and second charging circuits to the chambers, and an electronic control unit 50 for controlling the control interfaces. At least two control interfaces are proportional valves which are used as shut-off valves and are independently switchable to the open and closed positions in a controlled manner. Moreover, non-throttled control and secondary control are implemented in the hydraulic system and the method.

A hydraulic system and a method comprising a linear actuator 23 for generating discrete sum forces, chambers A-D for generating discrete force components, at least two charging circuits 3,4 configured to maintain predetermined pressure levels of hydraulic fluid, independent control interfaces 9-16 configured to open and close connections of the first and second charging circuits to the chambers, and an electronic control unit 50 for controlling the control interfaces. At least two control interfaces are proportional valves which are used as shut-off valves and are independently switchable to the open and closed positions in a controlled manner. Moreover, non-throttled control and secondary control are implemented in the hydraulic system and the method.

The invention relates to a hydraulic drive (1) comprising a working cylinder (2) and a travel cylinder (3) which is mechanically connected to the working cylinder (2). The working cylinder (2) and the travel cylinder (3) each comprise an upper and a lower cylinder chamber (21, 22, 31, 32), and all four cylinder chambers (21, 22, 31, 32) of the working and travel cylinder (2, 3) are connected to one another in a suitable manner in a closed pressure circuit (4) which is filled and prestressed with a hydraulic fluid (F). A rotational speed-variable hydraulic machine (5) with a first and second pressure connection (51, 52) is arranged in the pressure circuit (4) in order to conduct the hydraulic fluid (F) between the individual cylinder chambers (21, 22, 31, 32) of the working and travel cylinder (2, 3) during the operation (B) of the hydraulic drive (1). At least one first and second distributing valve (6, 7) are arranged in the pressure circuit (4) such that the respective valve switch positions (61, 62, 71, 72, 73) which are suitable for the different operating phases of the hydraulic drive (1) together with the suitably driven hydraulic machine (5) allow a common movement of the work and travel cylinder (2, 3) in one or the other piston movement direction (R1, R2). For this purpose, preferably only the first and the second distributing valve (6, 7) are arranged in the pressure circuit (4). The hydraulic drive (1) requires a minimum number of components, maintains a low installation complexity, improves the energy efficiency, can be constructed in a compact manner, and can be operated in a sufficiently variable manner.

A system for determining the operability of a valve in active service which provides a user with real time information pertaining to the Safety Margin, the valve torque or thrust, and the percentage of valve MAST that is required for operation. The system employs a combination of an actuator package comprised of a primary actuator, a tandem force module, and a controller operatively connected to the output shaft of the primary actuator, the controller including a processor for calculating the above-described values and providing an output which can be visually, audibly, or electronically observed.

A dual mode thermal actuator (hereafter the actuator) comprises a first cup defining a first chamber filled with thermally-responsive wax and a second cup defining a second chamber filled with thermally-responsive wax. A piston is disposed between the first and second cups. A first guide is received by the first cup. The first guide surrounds the piston and extends axially away from the first cup. A second guide is received by the second cup. The second guide surrounds the piston and extends axially away from the second cup. Expansion of the wax in the first chamber or expansion of the wax in the second chamber causes the actuator to go from a retracted position to an extended position. Expansion of the wax in the first chamber and expansion of the wax in the second chamber also causes the actuator to go from the retracted position to the extended position.

An assembly for hoisting and lowering a drill string of a drilling rig includes a multiple displacement hydraulic cylinder having a blind end, a rod end, and a single piston rod configured for slidable extension and retraction movement within the interior space of the cylinder. The interior space is defined by three chambers, each chamber having a port allowing switchable flow of hydraulic fluid into and out from the cylinder. The assembly also includes a pumping and switching system with hydraulic fluid connections to each port of the cylinder. The pumping and switching system is configured to switch the direction of hydraulic fluid flow through each of the ports of the three chambers, thereby providing the assembly with a plurality of hydraulic fluid flow path combinations. Each flow path combination provides a different speed-to-force ratio for extending or retracting the piston rod, thereby hoisting or lowering the drill string.