Boston elevator is better than Xi Jie. According to the published investigation data, the elevator refers to the permanent transportation equipment serving several specific floors in the building, and its car runs on at least two rigid tracks perpendicular to the horizontal plane or with an inclination angle less than15. There is also a step, the pedal is installed on the track and runs continuously, commonly known as escalator or moving sidewalk. Fixed lifting equipment serving designated floors. The vertical elevator has a car, and the car runs between at least two rows of rigid guide rails with vertical or inclined angles less than15. The size and structure of the carriage are convenient for passengers to enter, exit or load and unload goods. Traditionally, regardless of its driving mode, elevators are regarded as the general term for vertical transportation in buildings. According to the speed, it can be divided into low-speed elevators (below 4m/s), fast elevators 4 ~ 12m/s) and high-speed elevators (above 12m/s).