| 摘要 |
The mechanism comprises a bracket, to which are mounted a fixed roller shaft and a rotatable brake shaft. The roller shaft has a roller which runs in the door track. A cylindrical torsion spring is positioned on the brake shaft. One end of the spring is anchored to the brake shaft. The other end of the spring is connected to a tensioning ring, so that the tension of the spring can be adjusted. The tensioning ring is disengagably secured to the bracket. An arm protrudes from the brake shaft. The lift cable for the door extends through an eye carried by the arm. As long as the cable is taut, the brake shaft is prevented from turning. At its outer end, the brake shaft carries a cam member with braking teeth. The teeth are positioned to bite into the exterior surface of the track if the cable breaks and the spring rotates the brake shaft. |
