Abstract: A displacement control device (1) is adapted to move a member (23) relative to a body (7). The displacement control device includes a drive means (2, 3) and an emergency actuator(8) arranged mechanically in series with the member. The actuator includes a housing (16) and a spring (14) arranged to act between the housing and the member. The improvement comprises: the actuator including a toggle linkage (9) acting between the housing and the spring, the toggle linkage having two pivotally-connected links (10, 11) that are adapted to be selectively moved between a collapsed position at which the links are arranged at an acute included angle, and an extended position at which the links are arranged at an obtuse included angle slightly less than 180°. The toggle linkage is arranged such that the spring will be more greatly compressed when the links are in the extended position than when the links are in the collapsed position.

Abstract: A displacement control device (1) is adapted to move a member (23) relative to a body (7). The displacement control device includes a drive means (2, 3) and an emergency actuator (8) arranged mechanically in series with the member. The actuator includes a housing (16) and a spring (14) arranged to act between the housing and the member. The improvement comprises: the actuator including a toggle linkage (9) acting between the housing and the spring, the toggle linkage having two pivotally-connected links (10, 11) that are adapted to be selectively moved between a collapsed position at which the links are arranged at an acute included angle, and an extended position at which the links are arranged at an obtuse included angle slightly less than 180°. The toggle linkage is arranged such that the spring will be more greatly compressed when the links are in the extended position than when the links are in the compressed position.