Abstract: A compact aneroid actuated explosive initiator for releasing a parachute upon descent to a predetermined altitude includes a firing pin releasably restrained by a rotatable sear that is urged toward release position. Cocking is achieved by compressing a driving spring without moving the firing pin, but concomitantly releasing a first restraint upon release of the sear. A second restraint upon release of the sear is provided by trigger levers under control of an aneroid barometer whereby the sear can be released and the firing pin driven by the firing spring only after cocking has been accomplished and a selected barometric condition exists.

Abstract: An explosive initiator for a parachute rip cord release includes a hammer and firing spring mounted at one end of a cartridge chamber and an aneroid device and trigger mechanism mounted at its other end. A slidable sear extends along the cartridge chamber, connected at one end to the hammer and having a cam connection with the trigger mechanism at its other end. The normally uncocked hammer is manually cocked to slide the sear and thereby move the trigger mechanism into an operative position under control of the aneroid device. As ambient pressure decreases below a predetermined value, the aneroid device releases the trigger mechanism to thereby release its restraint upon motion of the sear and allow the spring to drive the hammer and detonate a cartridge in the chamber. Cartridge detonation drives an actuator piston that is connected to the parachute rip cord release.