| 摘要 |
A roll stabilised unit comprises a tool housing ( 30 ) rotatably mounted within a tool collar ( 28 ), the tool housing ( 30 ) having rotatably mounted thereon a first impeller ( 36 ), a variable torque transmission arrangement ( 38 ) being provided to allow the torque transmitted from the first impeller ( 36 ) to the housing ( 30 ) to be controlled, and a second impeller ( 40 ) fixed relative to the housing ( 30 ) so as to be rotatable with the housing ( 30 ).
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