| 摘要 |
An actuator for a plug valve of the type having a body with a central chamber having diametrically opposed inlet and outlet ports and a plug within the chamber having a transverse passage therethrough and an upstanding stem. The plug has a first, upper, valve-open position with its transverse passage in alignment with the inlet and outlet ports of the chamber, and a second, lower valve-closed position wherein its transverse passage is oriented at 90 DEG to the chamber inlet and outlet ports and seal means on the plug are in sealing engagement with the chamber walls about the inlet and outlet ports. The top of the chamber is closed by a bonnet having a packing gland through which the plug stem extends. The actuator comprises a hollow cylindrical yoke, the lower end of which is affixed to the bonnet with the plug stem extending into the yoke. The upper end of the yoke is provided with a bearing cap. A drive nut, having a threaded axial bore and a hand wheel or the equivalent affixed thereto, is rotatively mounted in the bearing cap. A threaded stem is engaged in the drive nut. The lower end of the threaded stem and the upper end of the plug stem are both non-rotatively affixed to a cylindrical coupling within the yoke. One of the yoke and the coupling has diametrically opposed cam slots formed therein. The other of the yoke and coupling supports a cam follower for each cam slot. The cam slots are so configured that upon turning the drive nut in one direction, the plug in its valve-open position will be simultaneously partially lowered and turned 90 DEG and there-after lowered without rotation to its valve-closed and sealed position. Upon turning the drive nut in the opposite direction, the plug will first be lifted vertically without rotation out of sealing relationship with the chamber inlet and outlet ports and thereafter simultaneously lifted and rotated 90 DEG to its valve-open position.
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