| 摘要 |
A downhole tool has a housing, a mandrel, a seat, and a piston. The housing defines a first bore, and the mandrel is movably disposed in the first bore and defines a second bore. The mandrel has first and second mandrel sections or upper and lower cones, and the first mandrel section defines a cross-port communicating the second bore with an annular space between the mandrel and the housing. The seat is disposed in the first bore of the housing between the first and second mandrel sections. The seat is movable to a constricted state in the first bore to catch a dropped ball and is movable to an expanded state in the first bore to pass a dropped ball. The piston is disposed in the annular space and at least temporality supports the seat in its constricted state. |
