| 摘要 |
A valve operator (10) which includes a ball screw (28) in constant engagement with the output shaft (24) of an air cylinder for automatic operation of the valve, and which includes a manual drive means (20) engageable with the ball screw (28) in any position thereof. The manual drive means (20) includes a ball nut (30) engaged with the ball screw (28), a clutch output member (34) attached to the ball nut (30), a clutch input member (38) which is rotatable by a handwheel (56) through a worm gear train (49, 52), and a manually actuatable clutch actuating assembly (42) which is operable to engage the clutch input member (38) with the clutch output member (34).
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