| 摘要 |
A downhole tool 100 includes closure seats 116, 176 for seating with a closure, such as a ball. Shear pins or other connectors temporarily limit axial movement of each closure seat which is initially housed within a restricted diameter portion of the central throughbore in the tool body. A piston axially moves in response to fluid pressure to pressurize fluid in a chamber and controllably release fluid through one or more restrictions. The closure seat may be lowered to engage a stop 108, 159, such that the seat may move axially to an enlarged diameter bore portion of the tool, thereby allowing radial expansion of a closure seat to release the ball.
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