| 摘要 |
A sealing apparatus for a downhole tool having a movable member which moves relative to a housing, the sealing apparatus comprising: at least one sealing member having a first position in which the sealing member is spaced from the movable member and a second position in which the sealing member is in contact with the movable member to provide a sealing barrier; and switching means for switching the sealing member between the first and second positions. |
