| 主权项 |
1. A pig launching apparatus comprising:
a frame including a first guide rail with a first pig supporting surface and a second guide rail with a second pig supporting surface, the first guide rail extending substantially parallel to, and spaced apart from, the second guide rail, the first guide rail and the second guide rail configured to support a pig on the first and second pig supporting surfaces; a drop tube at an end of the frame into which the pig is positioned for dropping into a pipeline; a drive system including a pushing finger protruding into the frame, the drive system configured to move through a cycle from a starting position through a forward stroke to move the pushing finger toward the drop tube and a rearward stroke to pull the pushing finger back to the starting position, the forward stroke moving the pushing finger to push the pig axially along the first and second pig supporting surfaces; an extension of the guide rail in the drop tube, the extension of the guide rail being moveable between (i) a support position for supporting the pig in a substantially vertical position in the drop tube and (ii) a release position wherein it can release the pig to drop out of the drop tube; and a lock mechanism for the extension, the lock mechanism configured to alternately lock the extension in the support position and release the extension for movement to the release position, the lock mechanism configured to release the extension when the drive system moves through the rearward stroke. |
