Patent ID: 6722424
Filing Date: 2004-04-20
Classification: E21B

Abstract:
A downhole tool hydraulic firing head comprising: a housing connectable into a tubing string and having a bore extending therethrough from its upper end to its lower end; a vent opening extending through a side wall of the housing, the vent opening being open to the bore; a piston in the bore, the piston being drivable by fluid pressure applied though the bore; a firing pin for activating detonation of explosives, the firing pin connected to the piston to move with the piston; a sleeve on the piston and moveable therewith from a position covering the vent opening to a position clear of the vent opening; and a collet including a plurality of collet fingers with collet lugs extending therefrom acting between the sleeve and the housing to engage a shoulder, formed as a part of a ring mounted within the bore, and lock the sleeve into the position where it is clear of the vent opening.