摘要 |
A method of controlling fluid flow through a hollow body, uses a ball seat assembly (12) comprising a hollow body (14) defining a bore (16) and a ball seat (18) mounted said bore, the ball seat being moveable relative to the bore between an extended position in which the seat defines a restriction to passage of a ball (20) along the bore, and a retracted position spaced axially along the bore from the extended position and in which position passage of the ball along the bore is permitted. A subsequent reduction in the fluid pressure force acting on the ball seat facilitates movement of the seat from the extended position shown in the upper half of FIG. 1, to the retracted position shown in the lower half of the Figure, to permit passage of the ball through the bore to thereby re-open fluid flow through the bore.
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