A vertical venetian blind including a driving shaft, a plurality of slat travellers each having a driven shaft and a slip coupling for connecting the driving shaft to the driven shaft, and a plurality of slats each connected to a driven shaft. The slip coupling includes a bushing mounted on the driving shaft to rotate with and to slide along the driving shaft, and a worm tightly enclosing the bushing and having a screw thread. The driven shaft includes a worm wheel and two stop cams for contacting ends of the screw thread. The worm can slip with respect to the bushing when the driving shaft rotates and one end of the screw thread contacts one of the cams or the other end of the screw thread contacts the other stop cam.
展开▼
