| 摘要 |
<p>A ram-type well blowout preventer is claimed of which the, or each ram is controlled by a piston having a threaded piston rod engaging a lock nut carrying a corotatable first ratchet ring engaging a second ratchet ring which permits the nut to be rotated by the piston rod as the piston is advanced to shift the associated ram to its closed position but which is restrained against rotation in response to the pressure of the fluid used to advance the ram to prevent reverse rotation of the nut and hence undesired retraction of the piston. Ram(s) can be locked at a number of different positions to compensate for wear of its sealing element without need to pressurize separate control lines as in prior blowout preventers.</p> |
