| 摘要 |
A valve actuator has an electric driving motor for driving an output shaft through reduction gearing and a manual operator for driving the output shaft manually. A drive transfer device for transferring the drive from the electric motor to the manual operating means incorporates an electric switch which is operated by the initial movement of a manual operator of the drive transfer device to cause the motor if rotating to be brought to a stop. Continued movement of the manual operator causes the drive transfer device to transfer the drive to the output shaft from the electric motor to the manual operator. The drive transfer device advantageously includes a clutch between the motor shaft and a worm shaft forming part of the reduction gear. The driven clutch member may form an integral part of a unit which is slidable as a sleeve along the worm shaft but is keyed for rotation to the worm shaft, the unit also having a pinion for meshing with a drive gear forming part of the hand drive. |
