| 摘要 |
An apparatus for at least partially closing a throughbore is described. The apparatus comprises an apparatus housing, the apparatus housing defining a throughbore and a plurality of closure elements, each closure element being adapted to move between a retracted position, in which the throughbore is fully open, and a deployed position, in which the throughbore is at least partially closed, at least a portion of the movement of each closure element between the retracted position and the deployed position being rotational. |
