Abstract: A check valve comprises an annular housing defining a generally circular opening. A plurality of radially extending arms extend across the circular opening from the centre of the valve housing to respective nodes at the periphery of the valve housing. A plurality of cross arms extend between circumferentially adjacent nodes, thereby dividing the circular opening into a plurality of primary, generally triangular radially inner openings and a plurality of secondary, generally segment shaped radially outer openings. A plurality of primary, generally triangular flapper elements close the primary openings and a plurality of secondary, generally segment shaped flapper elements close the secondary openings. Respective mounting posts are arranged at a respective node and a respective hinge pin is mounted between respective circumferentially adjacent mounting posts.

Abstract: An actuator release mechanism includes an axially moveable member biased in a first axial position by a bias spring and driven to a second axial position by an actuation means such as a solenoid arranged in substantially the same axis as the axially moveable member. The axially moveable member can be a piston.