Adjusting to the form of the surface of the cushion body which in the seat and the back null surface of the chair which uses the multilayer strange hardness cushion body, and its cushion body which are produced by

摘要

PROBLEM TO BE SOLVED: To provide a sufficient cushioning property and a fit even if overall thickness is reduced, to maintain sufficient strength to support the load of a user, etc., and to keep the boundary between soft and hard parts from being felt by the user. SOLUTION: A liquid of a first hard plastic foam 5 is poured over one end of the upper surface of a female mold 1, and after the liquid of the first plastic foam 5 has slightly foamed, a liquid of a second plastic foam 6 softer than the first plastic foam 5 is injected over almost the center of the upper surface of the female mold; after the liquid of the second plastic foam 6 has slightly foamed, a liquid of a third plastic foam 7 further softer than the second plastic foam 6 is poured over the other end of the upper surface of the female mold 1.