Roller shutter safety device preventing out-of-control descent

摘要

A worm (8), driven by a stepping motor (17), and a cooperating worm wheel (7) - fitted to the axis of the winding shaft (5) for the roller shutter (6) - provide a dynamic restraint force to prevent rapid descent of the shutter.The worm can slide in one direction along its axis (9) under control of the stepping motor until it reaches an end stop (15). The worm (8) is pressed into contact with the latter due to the dynamic restraint force between the worm and the worm wheel as the shutter drops down, to block any further descent. Pref. the stepping motor control (18) has a pair of switches (20,21) operated by displacement of the axis (9) of the worm (8)