This paper analyzes some symmetry phenomena of escalator when it encounters obstacles on the way up and down by using the rotational symmetry method,and puts forward the equivalence of escalator when it encounters vertical obstacles on the way down and horizontal obstacles on the way up in terms of safety risk,as well as the inversion symmetry of both.It puts forward that the vertical obstacles which can be encountered in the descending direction of escalator should also be equipped with safety protection baffle.
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