Resin molded product having through-hole, molding method therefor, mold, and needleless syringe using resin molded product

A molding method for a resin molded product in which a resin molded product is molded by injection molding, the resin molded product having a through hole formed therein, the through hole being open in a predetermined end surface, the molding method comprising:

• closing a mold;
• and
• injecting a resin into the mold, wherein
• the mold includes
• a cavity having a space formed therein in which the resin is to be injected, and
• a core inserted into the space by moving relative to the cavity in a predetermined first direction, the core defining a region, into which the resin does not flow, inside the space,
• the core includes a core pin extending in the first direction and defining a shape of the through hole inside the space,
• the cavity includes an end-surface defining surface facing the space and defining a shape of the predetermined end surface of the resin molded product,
• a core-pin receiving hole is formed in the end-surface defining surface, the core-pin receiving hole including a recessed portion and a receiving portion, the recessed portion being open to the space, being recessed in the first direction, and having an inner wall portion formed in the recessed portion, the receiving portion being open to the recessed portion, extending in the first direction, and being configured to receive a distal end of the core pin of the core inserted into the space,
• an opening width of the recessed portion is set to be larger than an opening width of the receiving portion,
• in the closing of the mold, the core is inserted into the space of the cavity by the core moving relative to the cavity in the first direction, and
• in the injecting of the resin, a protruding portion protruding from the predetermined end surface of the resin molded product is formed along an opening edge of the through hole by the recessed portion receiving the resin injected into the space in such a manner that the resin does not reach the receiving portion.

A mold for a resin molded product, the mold being used for molding a resin molded product by injection molding, the resin molded product having a through hole formed therein, the through hole being open in a predetermined end surface, the mold comprising:

• a cavity having a space formed therein in which resin is to be injected;
• and
• a core inserted into the space by moving relative to the cavity in a predetermined first direction, the core defining a region, into which the resin does not flow, inside the space, wherein
• the core includes a core pin extending in the first direction and defining a shape of the through hole inside the space,
• the cavity includes an end-surface defining surface facing the space and defining a shape of the predetermined end surface of the resin molded product,
• a core-pin receiving hole is formed in the end-surface defining surface, the core-pin receiving hole including a recessed portion and a receiving portion, the recessed portion being open to the space and being recessed in the first direction, the receiving portion being open to the recessed portion, extending in the first direction, and being configured to receive a distal end of the core pin of the core inserted into the space,
• an opening width of the recessed portion is set to be larger than an opening width of the receiving portion, and
• a protruding portion protruding from the predetermined end surface of the resin molded product is formed along an opening edge of the through hole by the recessed portion receiving the resin injected into the space in such a manner that the resin does not reach the receiving portion.