Patent ID: 6972653

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