Patent ID: 8123995

Claim:
A method of manufacturing a molded product that includes (i) a head portion including an outward-facing surface that faces in a first direction, and an inward-facing surface that faces in a second direction opposite the first direction and (ii) a projection portion including an elastic lip that protrudes in the first direction, the method comprising: placing a first already-formed member, which has a joining surface, in an injection molding mold, the injection molding mold and the joining surface defining a molding cavity when the injection molding mold is closed, the molding cavity having a center point and tapering from the center point to a sharp edge, as viewed in cross section, the molding cavity having a first thickness at the center point, and having a second thickness less than the first thickness at a midpoint between the center point and the sharp edge, the injection molding mold further defining, when closed, a spill cavity that protrudes in a direction that (i) extends from the joining surface of the first already-formed member and (ii) is a direction of separation from the molding cavity, the spill cavity being in communication with the molding cavity at the sharp edge of the molding cavity, the spill cavity being connected to a surface of the molding cavity other than a surface that forms the outward-facing surface of the head portion, all surfaces of the molding cavity that form the outward-facing surface of the head portion being free of connection to any spill cavity; injecting heated and melted liquid molding material into the molding cavity, at least some of initial molding material which has initially reached the joining surface flowing into the spill cavity due to injection pressure of subsequent molding material injected after injection of the initial molding material, and being replaced with the subsequent molding material, which has a temperature higher than that of the initial molding material and a viscosity lower than that of the initial molding material; holding the subsequent molding material pressed against the joining surface of the first already-formed member for a predetermined time, causing pressure and/or heat of the subsequent molding material to act on the joining surface of the already-formed member; and allowing the liquid molding material to harden to form an injection molded portion joined to the joining surface of the first already-formed member, the first already-formed member and the injection molded portion together being a joined molded product.