| 摘要 |
A mold 2 includes a pair of mold halves (upper mold half 4 and lower mold half 6). A spherical cavity is formed by mating upper mold half 4 and lower mold half 6. A large number of pimples 10 are provided on the cavity face of the upper mold half 4 and lower mold half 6. The upper mold half 4 and the lower mold half 6 have flat plane 14, protrusions 16 and recesses 18, respectively. Each protrusion 16 projects from the equator Eq. Each recess 18 is depressed from the equator Eq. The protrusion 16 includes a part of the pimple 10. A central angleαbetween a protrusion (a) and a protrusion (b) adjacent to the protrusion (a) is different from the central angleβbetween the protrusion (a) and a protrusion (c) adjacent to the protrusion (a). The absolute value of a difference (α−β) is equal to or greater than 10°.
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