Abstract: A downhole tool includes a housing; a first piston arranged within the housing such that it can move axially under the action of fluid flowing through the tool; and an indexer configured to control axial movement of the first piston between a first, second and third axial position. The indexer is configured such that the first piston can be selectively moved into the third position in accordance with a variation of a flow of fluid through the tool. A second piston is movable between a closed position in which fluid flowing through the tool is restricted from communicating with an activation chamber and an open position in which fluid flowing through the tool is permitted to communicate with the activation chamber; wherein the second piston is configured to move between the closed position and the open position in response to the first piston moving to the third axial position.

Abstract: A downhole tool includes a housing; a first piston arranged within the housing such that it can move axially under the action of fluid flowing through the tool; and an indexer configured to control axial movement of the first piston between a first, second and third axial position. The indexer is configured such that the first piston can be selectively moved into the third position in accordance with a variation of a flow of fluid through the tool. A second piston is movable between a closed position in which fluid flowing through the tool is restricted from communicating with an activation chamber and an open position in which fluid flowing through the tool is permitted to communicate with the activation chamber; wherein the second piston is configured to move between the closed position and the open position in response to the first piston moving to the third axial position.