To prevent the generation of a gate mark on the outer surface of a product comprising a boxed-shaped body and to efficiently cool the molding material in a cavity.
In a valve gate type mold assembly, the inner surface of a product 1 is formed by a fixed mold 31 provided with a gate 58 and a valve device 81 for opening and closing the gate 58 and the outer surface of the product 1 is formed by a movable mold 32. A core bush 46 is embedded in the fixed mold 31 and the valve device 81 is incorporated in the core bush 46. The core bush 46 is divided to be constituted of an outer periphery bush member 47 and an inner periphery bush member 48 and cooling passages 62 and 63 are formed between the bush members 47 and 48. Especially, both bush members 47 and 48 are joined by diffusion welding at the part on the side of the cavity 33. By this constitution, the cooling passage 62 is allowed to approach the cavity 33.
MURAYAMA FUJIO
HIGUCHI YOSHINORI
HORIKAWA YOSHIHIRO
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