When were the first mechanical floor cleaners, which later became vacuum cleaners, invented?

第一台机械地板清洁机，后来变成真空吸尘器的机器是什么时候发明的？

Earlier I asked you: When were the first mechanical floor cleaners invented?

第一台机械地板清洁机是什么时候发明的？

In 2019, The Department of City Planning passed a bill for residential towers requiring mechanical floors higher than 30 feet to count towards the total zoning floor area.

2019 年，城市规划部通过了一项住宅楼法案，要求机械楼层高于 30 英尺才能计入总分区建筑面积。