| 摘要 |
PURPOSE:To prevent projections from being cut at mold release by a structure wherein a vent plug consisting in opening a vent path, which communicates to at least a part of a vent hole, on the other end surface of the vent plug is fitted in a mold so that the opening side end surface of the vent hole is flush with the inner surface of the mold. CONSTITUTION:A vent plug 20 consists in concentrically fitting the larger diametrical part 24 of a cylindrical body 22 into an outer tubular body 21 so that both the respective end surfaces of the bodies 21 and 22 are flush with each other. A vent hole 25, which is open on the top end surface and has an annular section, is formed parallel to the axial direction by a minute gap produced between the inner peripheral surface of the outer tubular body 21 and the outer peripheral surface of the smaller diametral part 23 of the cylindrical body 22 on the top end part side of the vent plug 20, while a vent path 26, which communicates to said vent hole 25, is formed so as to open on the bottom end surface by means of a gap produced between the inner peripheral surface of the outer tubular body and the transverse surface of the larger diametral part 24 of the cylindrical body 22 on the bottom end part side of the vent plug 20.
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