| 摘要 |
The invention discloses a cushion sub-assembly (10) for connection to a drill string to absorb vibrations in the drill string, the cushion sub-assembly (10) including a main body (12) defining a chamber therein (24), a piston member (28) disposed within the chamber (24) capable of axial movement at least partially within the chamber (24) between a first and second position, at least one axially extending piston rod (42) disposed inside a respective axial bore of the piston member (28), the at least one piston rod (42) preventing relative rotation between the piston member (28) and the main body (12) while permitting axial movement of the piston member (28) between the first and second positions, and a vibration absorbing means (44, 46, 48, 50) at opposite ends of the chamber (24) for engagement by the piston member (28) when in either of the first or second positions for absorbing axial vibrations, the configuration of the at least one piston rod (42) inside the piston member (28), and engagement of the piston member (28) with the vibration absorbing means (44, 46, 48, 50) serving to minimise transmission of axial vibrations between the piston member (28) and the main body (12).
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