Patent ID: 8916074

Claim:
A method for making a resin hollow body having an inlet and an outlet including a hollow portion, an outer wall that divides the hollow portion from outside of the resin hollow body, and a partition wall that projects into the hollow portion to separate the hollow portion between a straight passage and a circulation passage that makes air which is introduced from the inlet and flows straight through the straight passage, flow around to divert the air into the outlet, the method comprising: performing a primary-formation process, wherein the performing of the primary-formation process includes: providing a plurality of dies; and injecting molten resin into spaces defined by the plurality of dies to form a plurality of resin components; performing a die-moving process, wherein the performing of the die-moving process includes: holding each of the plurality of resin components in at least one of the plurality of dies; and bringing joining edges of the plurality of resin components close to each other through relative movement of the at least one of the plurality of dies, to make a predetermined arrangement of the plurality of resin components; and performing a secondary-formation process, wherein the performing of the secondary-formation process includes: injecting molten resin into a region where the joining edges of the plurality of resin components are adjacent to each other; and joining together the joining edges to form the outer wall, the partition wall, and the hollow portion, wherein: at least one of the joining edges that constitute the partition wall includes a linear groove along the straight passage and the circulation passage; the performing of the die-moving process further includes bringing the joining edges that constitute the partition wall into contact with each other to define a hollow cavity by the groove, the hollow cavity surrounded with the joining edges; the performing of the secondary-formation process further includes filling the hollow cavity with molten resin to join together the joining edges that constitute the partition wall and to form a secondary molded part along the straight passage and the circulation passage; and an other end portion of the hollow cavity is configured as an outlet for molten resin.