Patent ID: 7320768

Claim:
A method of injection molding a combined product composed of a first molded piece having an insertion hole and a second molded piece having adjacent main molded portions and an insertion portion between the adjacent main molded portions that is inserted into the insertion hole, said method comprising the steps of: preparing a (1) first piece mold for molding said first molded piece; (2) one second piece mold for molding one main molded portion that is bigger than an outer diameter of the insertion portion, wherein at least a thin-walled portion is formed between the first piece mold and the second piece mold; (3) another second piece mold for molding another main molded portion that is bigger than the outer diameter of the insertion portion, wherein at least a thin-walled portion is formed between the first piece mold and the another second piece mold; and (4) a pin core for molding the insertion hole of the first molded piece; cutting off the first piece mold, the one second piece mold, and the another second piece mold by inserting the pin core into a portion corresponding to the insertion hole and the insertion portion; filling a first resin in the first piece mold; connecting the one second piece mold and the another second piece mold through a hole formed between them by removing the pin core from the portion corresponding to the insertion hole and the insertion portion; and filling a second resin, in the second piece mold having a mold shrinkage factor that is bigger than the first resin, in the one second mold piece and the another second piece mold.