| 摘要 |
<p>The frame (1) has a blocking unit including a ratchet pivotally mounted on a first flange (121) of the blocking unit. The ratchet cooperates with a notch of a second flange (122) to block the frame in a plane parallel to a ground at intermediate height between a bottom position and a top position. The ratchet is configured such that force impressed by a user and/or by springs (R1, R2) of upper posts (20, 21) moved relative to lower posts (10-12) is sufficient to unlock the frame and to bring the frame from an intermediate position to the bottom or top position.</p> |
