| 摘要 |
A valve actuator unit is adapted to be removably mounted in a fixed operating relation with respect to the housing of a valve unit having a rotatable valve element by the utilization of an angle-shaped mounting bracket that is adapted to fit over a pair of bolts or studs of the valve housing that are used to maintain it in an assembled relation. The actuator has a rotatable bottom part that is adapted to be secured on the stem of the valve in place of its ordinary manual operating means or handle, and without disturbing its operating mechanism. Turning a handle of the actuator unit to move the valve to an open or closed position builds up spring tension which is employed to provide a smooth spring-actuated return movement. The actuator utilizes a helical return spring within its housing. Convolutions of the spring are positioned about a bearing sleeve and, in such a manner, that they do not interfere with each other when the spring is, in effect, wound-up or tensioned between a stationary housing upper end wall of the actuator and a lower disc-like rotative end wall. The actuator has a simple and quick type of mounting and may be used to smoothly move a valve element or ball against the torque of the spring, either to an open or a closed position, as may be desired. Also, the actuator unit may be utilized for a fail-safe type of operation by, for example, using a fusible link between stationary and movable parts, such that under a melting temperature, the tensioned spring will move the valve element automatically to either a closed or open position, as may be desired.
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