| 摘要 |
An accelerator (10) having a tubular housing (14) and a tubular mandrel (12) telescopingly received therein, the accelerator also including first (22) and second (24) pistons between the housing and mandrel, a sealed gas chamber (16) defined between the pistons, the first piston adapted for movement with the mandrel in repsponse to longitudinal movement of the mandrel in a first direction relative to the housing and adapted to resist longtudinal movement in response to movement of the mandrel in a second direction relative to the housing; the second piston adapted for movement with the mandrel in the second longitudinal direction relative to the housing and adapted to resist longitudinal movemen t in response to movement of the mandrel in the first longitudinal direction relative the housing, and whereby the chamber's pressure increases in response to movement of the mandrel in both the first and secon d direction relative to the housing until released by a jar mechanism.
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