| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to form a rotating shaft member as the center of rotation of a lid member in such a manner that only a small gap can be always formed accurately and easily in respect to the predetermined inner peripheral edge portion of a concrete pouring hole, to prevent wear or deformation of a portion retaining the rotating shaft member and easily to make the outer peripheral surfaces of the rotating shaft member and the lid member flush with respective surfaces. SOLUTION: A concrete pouring hole 12 formed on the plate surface of a form member 2A with its shape in the tunnel peripheral direction made to a circular arc shape is opened or closed by a lid member 13 oscillated around a rotating shaft member 14 as the center. Among the rotating shaft member 14, the shape of the outer peripheral surface of the main body portion 22 is made to a circular arc shape projected in the axis direction, and, as a whole, a barrel shape is created. A notched portion 23 is formed on the outer peripheral surface of the main body portion 22. When the lid member 13 is fitted to a notched portion 23, the outer peripheral surfaces of the main body portion 22 and the lid member 13 are made flush with each other. The rotating shaft member 34 (34B) is desired to be constituted with two members, a shaft member 35 (45) and a barrel-shaped main body member 36 (46) fitted to the outer periphery in a freely rotating manner in view of the prevention of wear or the like.
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