Method of making a unitary bowl, waterway, and trap for a toilet

In a method of forming a unitary blow molded bowl, waterway and trap for a gravity-flush toilet which is free of any joints, the steps of:

• (a) downwardly extruding a tubular parison of thermoplastic material, the parison being thinner at the top due to the weight of the parison and due to that portion of the parison being hotter as a result of its being extruded last;
• (b) positioning said tubular parison of thermoplastic material between a pair of blow mold sections, each of said sections including a semibulbous bowl cavity portion and a trap cavity portion extending from said bowl cavity portion, said mold sections including non-identical waterway sections which extend between said trap and bowl cavity portions;
• (c) orienting said blow mold sections such that the trap and waterway sections are near the top of said parison and said bowl cavity portions are near the bottom of said parison;
• (d) closing the blow mold sections on the parison and forming a blowable shape comprising parison portions destined to form the bowl, trap and waterway, by simultaneously (i) enclosing the thicker bottom major part of the parison within the bulbous major part of the blow mold cavity, including the bowl for the final article, (ii) pinching a portion of the parison shut along a tortuous path communicating with the major part of the blow mold cavity amd conforming to the trap, and (iii) pinching another portion of the parison shut along a waterway communicating with the major part of the parison between the trap and the bowl parison portions;
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• (e) introducing blow air under pressure into the interior of the parison and thereby (i) expanding the major part of the parison into a bulbous shape including the bowl and (ii) expanding the pinched-shut parison portions respectively into a tortuous-shaped trap and a waterway;
• (f) removing the blown article from the mold cavity, and trimming excess peripheral plastic material from said blown article to leave ribs of reinforcing material between said waterway and trap and between said waterway and bowl.