FEILSIKKER FRIGJOERENDE AKTIVERINGSMEKANISME.

摘要

A mechanical actuator for moving a shaft axially has a motor driving a gear assembly giving a mechanical advantage of at least 30:1, preferably 50 to 150:1. The assembly drives an internally screw threaded sleeve on external screw threads of the shaft so that rotation of the sleeve moves the shaft axially. A stop connected to a gear of the gear assembly for the sleeve ensures that it is the shaft that moves. The actuator is suitable for all valves, chokes and control mechanisms for oil or gas production, particularly sub-sea production and the motor is preferably a reversible DC electric motor. The mechanical advantage allows heavily loaded shafts to be moved with low power input. When applied to spring loaded fail-safe valves the stop for the sleeve may be one or more moveable locking dogs actuated by the gear assembly. The gear assembly acts as a differential transmitting torque either to the gear wheel actuating the stop of the gear wheel rotating the sleeve.