The invention includes a carrier, a base disposed to the carrier, a linkage, a first driving part, a telescopic rod set and a bottom plate. The base and the linkage form a four-bar linkage structure, which is matched up with the position changes of the first driving part and the telescopic rod set to respectively control the bottom plate to switch among a horizontal and ground placement position, a horizontal and lifting position, a horizontal and near- working plane position, a tilt and folding position and a top folded position. When in the horizontal and near working plane position, a wheelchair can easily enter or exit the carrier smoothly. The invention has the advantages that the bottom plate can be horizontally placed near the working plane to facilitate the passage of wheelchair, the bottom plate can be controlled by the telescopic rod set to be overturned, and an electric cylinder has a self-locking function to improve safety.本發明係包括一載台，及設於載台之一基座、一連桿組、一第一驅動部、一伸縮桿組及一底板。基座及連桿組構成四連桿結構，配合第一驅動部及伸縮桿組之動作變換，分別控制底板依序在平放置地位置、平放上升位置、平放近工作平面位置、傾斜收合位置及置頂收合位置之間來回變換，尤其在平放近工作平面位置時，可供輪椅順利的進、出載台。故，本案兼具底板平放接近工作平面利於輪椅通行、可利用伸縮桿組控制底板翻轉，及電動缸具有自鎖功能可提高安全等優點。
