| 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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