Patent ID: 7673708

Claim:
A ball-activated mechanism adapted to be incorporated in a drillstring and to control the activation, and de-activation of an under reamer, said mechanism comprising: a ball seat arranged to receive surface launched activation balls and movable from a first position to initiate activation of the under reamer, and being returnable to the first position to initiate de-activation of the under reamer; an indexable latching device comprising an upper clutch, a lower clutch, and an intermediate clutch indexable between different latched conditions with respect to the upper and lower clutches; and a linearly displaceable actuator comprising a mandrel coupled with the intermediate clutch for movement therewith, the linearly displaceable actuator co-operable with the indexable latching device and movable between activating and de-activating positions relative to the under reamer, the actuator allowing pressure fluid communication to activate the under reamer when the actuator is in its activating position, wherein the mandrel is provided with a communication port which can be moved to and from fluid communication with actuator pistons in the under reamer and in which the actuator pistons are displaceable in directions towards and away from the axis of the under reamer, and are pressed away from the axis by fluid pressure to urge the reamer cutters away from the axis when fluid pressure is pumped to the mechanism: in which the arrangement of the mechanism is such that; (A) upon launch of a first activation ball to engage the ball seat, the ball seat moves from its first position so that the latching device carries out indexing movement to a latched position whereby the actuator moves to its activating position so that the under reamer can be activated; and (B) upon launch of a second activation ball to engage the ball seat, the latching device is operative to carry out return movement so that the ball seat returns to its first position and the actuator moves to its de-activating position thereby to deactivate the under reamer.