Patent ID: 8858374

Claim:
Apparatus for pretensioning a tension-element drive powered by a drive motor having a rotary output shaft, the apparatus comprising: an initiation mechanism that utilizes the torque of the rotary output shaft to pretension the tension-element, the initiation mechanism comprising a sleeve that extends axially over an axially-extending section of the rotary output shaft and is operatively coupled for rotation with the shaft in only one direction, and a mechanical device that selectively blocks any rotation of the sleeve with respect to the rotary output shaft, the mechanical device being selectively mechanically engagable with, and selectively mechanically disengageable from, the sleeve, with the mechanical device blocking any rotation of the sleeve with respect to the rotary output shaft when the mechanical device is mechanically engaged with the sleeve, and wherein the tension element is wound in one sense on said rotary output shaft and in the opposite sense on said sleeve, whereby, when the mechanical device is selectively activated so as to block any rotation of the sleeve with respect to the rotary output shaft, the motor overcomes the previous pretension and rotates the rotary output shaft relative to the sleeve in the direction that increases pretension.