| 摘要 |
PURPOSE:To enable to make vent holes for escape at desired positions in beads for forming tread grooves by a method wherein vent pieces with vent holes piercing the convexity on the direction of the thickness are made in advance. CONSTITUTION:Portions, at which vent holes are provided, on the bead 2 for forming tread groove 11 (not shown in fig.) are separately manufactured as vent pieces 5, in which vent holes are bored in advance. A cavity impression is formed by a mold and the plaster casting master model 10 (not shown in fig.) of a tire, in the tread grooves of which said vent pieces are fitted. Next, molten metal is poured in the cavity impression on order to obtain a tread ring 1 integrated with the vent pieces. Because the portions having vent holes are separately manufactured and, after that, integrated with the tread ring 1, effective vent holes can be made at any portion in the bead for forming tread groove, where no drillings of vent holes may be possible if the tread ring has been completed. |
