| 摘要 |
A ball-activated mechanism (10) adapted to be incorporated in a drillstring and to control the activation, and de-activation of a downhole tool (13), said mechanism comprising: a ball seat (15) arranged to receive surface launched activation balls (16) and movable from a first position to initiate activation of the downhole tool (13), and being returnable to the first position to initiate de-activation of the downhole tool (13); an indexable latching device (17, 18, 19); and a linearly displaceable actuator (20) co-operable with the indexable latching device (17, 18, 19) and movable between activati ng and de- activating positions relative to the downhole tool (13), the actuator allowi ng pressure fluid communication to activate the tool (13) when the actuator is in its activati ng position: in which the arrangement of the mechanism (10) is such that; (A) upon launch of a first activation ball (16) to engage the ball seat (15), the ball seat (15) moves from its first position so that the latching device (17, 18, 19) carries out indexing movement to a latched position whereby the actuator (20) moves to its activating position so that the downhole tool (13) can be activated; and (B) upon launch of a second activation ball (16) to engage the ball seat (15), the latching device (17, 18,19) is operative to carry ou t return movement so that the ball seat (15) returns to its first position and the actuator (2 0) moves to its de- activating position thereby to deactivate the downhole tool (13).
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