| 摘要 |
<p>An assembly (100) to be positioned on a tubular (200), said assembly comprising a first abutment (101), a second abutment (102), a body (103) to be positioned on said tubular such that said body is free to travel relative to said tubular and is limited by said abutments, characterized in that said body and at least an abutment have a shape (106, 106') such that upon rotation of said tubular, said body is periodically urged to move with an axial component relative to said tubular.</p> |
