RESIN PISTON FOR MASTER CYLINDER

摘要

PROBLEM TO BE SOLVED: To prevent such a phenomenon that a valve mechanism becomes non-functional by the hooking of the stem of the valve mechanism with the burr formed to the communication hole of a resin piston for a master cylinder during an injection molding process. SOLUTION: An upper mold 11 and a lower mold 12 are combined, and a recessed part molding core 13 and a core 14 are combined with the combined upper and lower molds 11 and 12 at respective predetermined positions. A through-hole molding core 15 is constituted by joining the cores respectively integrally provided to the upper and lower molds 11 and 12 on the extension line of the center axis of the recessed part molding core 13, and a through-hole 33 is molded by the through-hole molding core 15. The recessed part 31 provided with the valve mechanism 41 and the communication hole 32 communicating with the recessed part 31 and the through-hole 33 are molded by the recessed part molding core 13. The through-hole molding core 15 has an insertion hole 16, and the leading end of the recessed part molding core 13 is inserted in the insertion hole 16.