Patent ID: 8602105

Claim:
An actuator device for downhole tools comprising: indexing means for progressively moving a rupturing member; a pressure activated actuating member in fluid communication with a chamber; and a frangible member interposing the indexing means and the chamber, wherein the actuator device is adapted such that, upon a predetermined movement of the rupturing member, the rupturing member ruptures the frangible member to allow high pressure fluid to enter the chamber and activate the actuating member; and wherein the indexing means comprises a counter comprising a piston and return spring, wherein the piston is biased towards the frangible member due to the biasing force of the return spring, wherein each time a pressure is exerted on the piston that exceeds the biasing force of the return spring, the piston is moveable away from the frangible element against the biasing force of the spring, and on release of said pressure, the piston returns towards to the frangible element under spring force, wherein upon each piston return the rupturing member is incrementally moveable towards the frangible element.