| 摘要 |
Which has the following essential elements:
€¢ A drive shaft (1) joined to the rolling drum (23) of a blind (21), joined by means of a first freewheel mechanism (2) with a drive cylinder (4) which has a freeing sector (5).
€¢ A cogged wheel (17) which has protuberances (18) into which fit the relevant extensions (19) of the slats (20) of the blind (21), joined via a second freewheel mechanism (15) with a blocking sector (26).
€¢ A brake cylinder (7) with teeth (27) housing a brake spring (9) whose ends form stops (10), with the blocking sector (25) acting on the stops (10) in the direction to increase the apparent diameter of the brake spring (9) and the freeing sector (5) in the direction to reduce its apparent diameter.
€¢ Various ratchets (28) that can lock against the teeth (27) as a function of the relative position of a transmission crown (6) on which they are articulated with respect to the drive cylinder (4).
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