| 摘要 |
<p>A ratchet mechanism which uses balls lets the balls fall down radially according to the prior art, for locking between the drum (1) which is fitted to the roller blind tube and the immobilised shaft (2). According to the invention the drum (1) is provided with changed depressions which have protrusions (4', 5', 6') for prevention of this movement. The protrusions partly support the ball which at any given instant is topmost and hence enables a slow rotation.</p> |
