Patent ID: 8141639

Claim:
An apparatus for activating a wellbore tool, comprising: an upper section having a housing; a piston element releasably coupled to the housing; a detonator in the housing that applies a force sufficient to release the piston element from the housing when activated; an intermediate section having a first end matable with the upper section and having a bore; an elongated member having a first end coupled to the piston and a second end, the elongated member being at least partially positioned in the bore of the intermediate section; a lower section having a housing matable with a second end of the intermediate section, the housing including at least one opening providing communication between a bore of the housing and an exterior of the housing; and a movable barrier in the lower section that has a first position, wherein the barrier substantially blocks communication between the bore of the intermediate section and the at least one opening, and a second position, wherein the movable barrier does not substantially block communication between the bore of the intermediate section and the at least one opening, wherein the piston element, the elongated member, and the movable barrier are connected and move in unison.