Patent ID: 7096577

Claim:
An explosively actuated tool for driving a fastener into substrate said tool comprising: a barrel; a piston displaceable in the barrel on firing of the tool to drive a fastener from a forward end of the barrel into the substrate upon firing of a charge; and a firing mechanism comprising a firing pin, and a rotary sear pivotal between a first position in which the sear entrains the firing pin and a second position in which the sear is released whereby the firing pin is driven towards the charge to thereby fire the charge; wherein the rotary sear is carried by a cocking rod, and the cocking rod and the sear carried thereby is subject to a rotational and axial bias by a spring anchored at one end relative to the cocking rod and at the other end to a mounting, the mounting being rotatable to apply torsional loading to the spring and being lockable to a housing of the cocking rod in an angular orientation in which torsional loading is maintained in the spring.