| 摘要 |
A trolley comprising a pair of vertical bars, a pair of linking bars, and a wheel assembly operable by the linking bars to pivotally move between an extended and a retracted positions. A movable block slidable on the vertical bars is connected with the linking bars. A positioning plate is fixedly mounted on the movable block and a sliding movement of the movable block relative to the vertical bars is controlled by a biasing unit in cooperation with the positioning plate. A respective compression spring is additionally provided on the vertical bars to facilitate the sliding movement of the movable block when the movable block is released to move.
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