Patent ID: 7194947

Claim:
A hydraulic actuating device for moving an object comprising: a reservoir for hydraulic fluid, a pump having at least one pressure port for delivering pressurized hydraulic fluid, a double-acting hydraulic actuator for moving the object, which actuator has an actuator housing with a space inside which a piston is moveable, which piston, in the said space, delimits a first working chamber and a second working chamber, the actuator furthermore having an object-coupling member, which is connected to the piston and is adapted to be coupled to the object, and for each of the first and second working chambers an associated first and second connection respectively for supplying and discharging hydraulic fluid, an throttling assembly which is in communication with the first connection of the hydraulic actuator, which throttling assembly is adapted to provide, for hydraulic fluid passing through the first connection, either an throttling opening or a clear passage opening which is larger than the throttling opening, wherein the throttling assembly comprises a pressure-detection means for detecting a second working chamber hydraulic pressure in the second working chamber, and wherein a predetermined switching pressure is associated with said throttling assembly, and wherein the throttling assembly is designed such that—when pressurized hydraulic fluid is being supplied to the said second working chamber—the throttling assembly provides for hydraulic fluid passing through the clear passage opening if the detected second working chamber hydraulic pressure is above the predetermined switching pressure and provides the throttling opening if the detected second working chamber hydraulic pressure is below the predetermined switching pressure, and wherein the throttling assembly has a housing with a first passage, which is in communication with the first connection, in which a substantially constant throttling opening is provided in the first passage, and in which the throttling assembly furthermore has a bypass passage which forms the clear passage opening and forms a bypass around the throttling opening, a valve coupled to the pressure-detection means being present in the bypass passage for opening the bypass passage if the detected second working chamber hydraulic pressure is above the switching pressure and for closing the bypass if the detected second working chamber hydraulic pressure is below the switching pressure.