| 摘要 |
A means which is suitable for preventing rolling shutter doors, rolling grilles and similar systems from falling down provides a second bevel worm wheel which is arranged, independently of the worm wheel effecting the transmission of force, on the rolling-shutter-door shaft and exhibits, distributed over the circumference, cutouts in the thread or in the toothing. Consequently, after the actual worm wheel has been worn out and the bevel worm wheel has responded, it is ensured that the prevention means remains effective and actively prevents an unrolling procedure, regardless of whether this is intentional or unintentional. <IMAGE>
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