左侧杆402和右侧杆403上外侧的竖直方向均等间距间隔设置有横杆700，且间距设置为30-35cm(本实施例优选30cm)；横杆700的延伸方向为水平方向，且平行于背框520；横杆700的长度设置为15cm-20cm(本实施例优选为15cm)，横杆700外套设有防滑橡胶套(未示出)。
通过上述技术方案，使得检修人员在链式升降装置300出故障时，可踩踏横杆700爬出箱体100，属于应急预案，上述横杆700的间距和长度的优选值均是为了检修人员更好的攀爬。
如附图2和附图5所示，左侧杆402和右侧杆403的互相相对的内侧均设置有限位挡块550，且限位挡块550位于同一水平面。限位挡块550设置于升降台500的竖直方向的上方；且限位挡块550与升降台500在竖直方向存在重合区域；限位挡块550的竖直方向的高度低于驱动电机604和旋转齿轮601的竖直方向的高度。
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通过设置限位挡块550，以限定升降台500可上升的Zui高高度，防止升降台500对驱动组件600产生冲撞。
同时，牵引链条602的长度设置为当所述升降台500上升至Zui高点时所述配重块603仍不与地面接触；防止配重块603触地而干扰升降台500的重力平衡。