【Summary Description】The elevator refers to the permanent transportation equipment that serves several specific floors in the building, and its car runs on at least two rigid rails perpendicular to the horizontal plane or inclined with the vertical line less than 15 °. There are also step type. The step board is installed on the track for continuous operation, commonly known as escalator or moving sidewalk. Fixed lifting equipment serving the specified floor. The vertical elevator has a car that runs between at least two rows of vertical or rigid rails with a tilt angle of less than 15 °. The size and structure of the lift car are convenient for passengers to access or load and unload goods. It is customary to use elevators as a general term for vertical transportation in buildings, regardless of their driving mode. According to the speed, it can be divided into low-speed elevators (less than 4m/s), fast elevators (4~12m/s) and high-speed elevators (more than 12m/s). Hydraulic elevators began to appear in the middle of the 19th century and are still used in low rise buildings. In 1852, E.G. Otis of the United States developed a safety elevator for wire rope hoisting. In the 1980s, the driving device was further improved, for example, the motor drives the winding drum through worm drive, and the counterweight is used. At the end of the 19th century, friction wheel drive was adopted to greatly increase the lift height of the elevator.