| 摘要 |
PROBLEM TO BE SOLVED: To provide a core for molding a concrete which can be simply drawn at the time of molding the concrete and has excellent durability even with a simple constitution. SOLUTION: The core 1 comprises an outer cylindrical member 2 made of an elastic material, a fixed side support member 4 for supporting the member 2 from its inside and a movable side support member 5. In this case, the member 5 is superposed on the member 4 so that a part of the member 2 not supported by the member 5 can be elastically deformed to its inside. Thus, when the member 5 is not superposed on the member 4 at the time of molding a concrete, the member 2 is supported by the member 5 and the member 4, and hence the member 2 can be satisfactorily molded. Meanwhile, at the time of drawing the member 2 after molding, the member 5 is superposed on the member 4, the member 2 is elastically deformed at its inside at the part, and can be smoothly drawn.
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