IMPROVEMENTS IN LINEAR ACTUATORS

摘要

An electrically operated actuator for opening and closing a valve is driven by an electric motor (34) which operates a planetary roller screw (23, 26) via a fixed differential drive (32). The screw shaft (23) is coupled to the actuator drive shaft (12) which is in turn connected to the valve stem (13). The actuator holds the valve in its operating position by means of an electrically operated locking mechanism (37), If a power failure occurs, the locking mechanism (37) is de-energised, allowing the valve to return to its safe position under the biasing action of a return spring (17). A set of balanced and adjustable dampers (25) control the rate of closure to prevent damage to the actuator and connected equipment.