| 摘要 |
The fail-safe valve actuator drives an actuator stem (9) between the first and second positions while energizing the spring (5), whereby the holding device prevents backdriving of the nuts (10, 10', 10") after spring (5) has been energized and thus the holding device does not consume electric power in stand-by mode for sustaining the spring (5) in energized state. Hence the fail-safe actuator drives the actuator stem (9) from either of its positions to its other position for reconfiguring a valve between the first and second state without substantially energizing or de-energizing the spring (5). In the case of a power supply failure the device further comprise the release means, which causes the actuator stem (9) to be moved under the influence of de-energization of the spring (5) to one of its extreme positions after power supply fails and thereby to reconfigure the valve to one of its states (closed/open). |
