| 摘要 |
A downhole tool (34) comprising a housing (60), a mandrel (76) slidably disposed within the housing (60), the mandrel (76) having a fluid passageway (52) extending axially therethrough, a valve (50) disposed within the mandrel (76), the valve (50) having first and second positions to selectively permit and prevent fluid flow through the fluid passageway (52) of the mandrel (76) and first and second pistons (98, 104) slidably disposed between the housing (60) and the mandrel (76), the first and second pistons (98, 104) slidably displacable in opposite directions relative to the housing (60) in response to a differential fluid pressure, the first and second pistons (98, 104) selectively engagable with the mandrel (76) to respectively displace the mandrel (76) in first and second directions, thereby operating the valve (50) between said first and second positions.
|
