Spring force actuators

A spring force actuator comprising a housing, an output member movable axially in said housing, said housing having an end wall, a spring captive between said member and said end wall, said spring being operable to apply an output force to said output member, a threaded wind-off element coaxial with the housing and extending through said end wall for engagement with the output member to apply an opposing force to the spring to relieve the output member of said output force, a nut having a polygonal cross section threadedly engaging said wind-off element, means carried on said end wall defining a recess through which the wind-off element extends, said recess defining an opening accessible from the exterior of the housing, said nut being received in said recess through said opening, said recess having a polygonal cross section compatible with the cross section of said nut to prevent rotation of the nut relative to the housing when the nut is received within the recess, and retaining means cooperating with the nut and the recess to prevent axial movement of the nut relative to the housing.