| 摘要 |
A locking mechanism comprises: a hub movable between a raised and a lowered position and a pair of structures, pivotally mounted to a common bracket. Sector gears engage each other rotate in unison. A locking assembly mounted upon the common bracket moves between a locked position preventing rotation of said structures and a released position allows rotating of said structures. At least two rods are pivotally joined to one of said structures. When the lock button is unlocked, and the hub is lifted, the rods are moved together to be substantially parallel, and when the hub is lowered, the gears rotate and the rods are pushed away from each other until the rods lie substantially in a common plane, enabling, the locking button to be moved to its locked position to prevent movement of the hub from the lowered position.
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