A linear motion actuator is disclosed in which an actuator shaft is held
in a ready position by a latching ring. A spring is attached to the
actuator shaft to exert a biasing force on the actuator shaft biasing it
toward its actuated position. The latching ring receives one end of the
actuator shaft and has locking elements that hold the actuator shaft in
the ready position. A latching ring is rotated to selectively release the
locking element. A shape memory alloy link extends partially around the
latching ring and is secured to the latching ring. The link is shortened
when current is applied to the link causing the link to rotate and
release the locking element.