| 摘要 |
A well jar including a mandrel telescopically disposed within a housing, the mandrel and housing being adapted to be disposed in a pipe string and having spaced apart impact surfaces that can be brought together to deliver a jarring blow, an expansible latch sleeve having gripping engagement with the mandrel, cam means for expanding the latch sleeve to release said gripping engagement, a locking sleeve fixed to the housing and having longitudinally spaced internal locking surfaces slidably engaging companion external surfaces on the latch sleeve to prevent expansion of the latch sleeve, the locking surfaces being disengaged from each other by longitudinal relative movement to enable the cam means to expand the latch sleeve, and means for yieldably resisting such longitudinal relative movement to enable a stretch to be taken in the pipe string before the gripping engagement is released.
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