An assembly for controlling displacement.

摘要

A displacement control assembly includes a rotatable lead screw 24 longitudinally extending within a tubular column 16. A nut 22 is threaded to the screw 24 for relative axial displacement of the screw and nut, for example, to adjust the height of a chair seat or similar fixture. A resilient brake structure 38,46 is carried by either the nut or the screw for resiliently biased, alternative locking and unlocking of the nut and screw in order selectively to prevent and allow relative rotation and relative axial displacement of the screw and nut. The lock allows the screw 24 and nut 22 to co-rotate without relative axial displacement so that the chair seat can be swivelled without altering the desired height. The assembly can be designed with the parameters correlated so that the chair seat can be lowered at uniform speed independently of the weight of the seat occupant.