| 摘要 |
A swivelling device is provided for picking up or backing off a drive string after it has been stuck in a down hole. The device allows the drive string to move longitudinally and rotate. The device has a shaft rotatably mounted in a housing so that the shaft can freely rotate but can not move radially or axially relative to the housing. A frame support is moveably connected to the housing and has an aperture that is attachable to a support system capable of lifting up the drive string. A pair of biasing mechanisms bias the housing towards the frame support. When a downward force is applied to the shaft by the drive string, the housing can be displaced downwards away from the support frame. Once the downward force ceases, the biasing mechanism moves the housing back towards the support frame. |
