| 摘要 |
PROBLEM TO BE SOLVED: To provide a gravity casting method where the overheat phenomenon of a plaster mold is prevented, the entanglement of air upon the charging of molten metal into a mold is prevented, and defects in casting of a casting product are improved, to provide a mold for gravity casting therefor, and to provide a mold for a pneumatic tire produced by the mold for gravity casting. SOLUTION: Each branched runner part 5a communicated with a cavity in a product part 8 is formed in the vicinity of a riser part 9 in each runner 5. In the initial stage of the packing of a molten metal W, it is passed from each runner 5 into the side of the surface 1a of a plaster mold 1 and the cavity of the product part 8 through each runner part 7. In the middle stage of the packing of the molten metal W, the molten metal feed path of the molten metal W is changed from each runner part 7 to each branched runner part 5a, and it is packed into the product part 8. Each runner part 7 is provided with a cut-off means 10 where each runner part 7 in the vicinity of the product part 8 is cut off in accordance with the packing amount of the molten metal to be packed into the cavity of the product part 8, and the molten metal passage of the molten metal is changed to the branched runner part 5a on the side of the riser part 7. COPYRIGHT: (C)2008,JPO&INPIT
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