Brake means at devices for converting a rotary motion into a linear one by means of a threaded spindle (1) and a member (4) arranged in engagement with the threads thereof, and moving along this at the rotation of the spindle (1). The brake means consists of a ring (7) arranged at one end of the spindle and operable in one direction with the spindle (1) as well as a collar (14) arranged at the member (4) coaxially with the ring (7) and projecting from said member (4), the collar (14) coacting telescopically with the ring (7) and the surfaces of collar (14) and ring (7) engaging each other and producing a braking moment sufficient to stop the spindle (1).