Patents Assigned to Rotational Molding Technologies, Inc.
  • Patent number: 6713009
    Abstract: A rotomolded plastic wall and ladder structure (10, 50, or 58)), which may be an article such as a window well (10) or a manhole (50 or 58), includes a thermoplastic wall (12), a ladder (16) whose rungs (18) each include an elongated metallic core (20) and a thermoplastic sleeve (22). Mold apparatus (70) includes a thermoplastic rotomold (72), an elongated hollow metallic core (20) having a heating passage (74) therein, and means for flowing hot air through the heating passage (74). The method includes disposing the hollow metallic core in a mold, placing a quantity of a thermoplastic inside a mold, heating the mold, rotating the heated mold, flowing heated air through the hollow metallic core, and bonding a layer of the thermoplastic onto the hollow metallic core.
    Type: Grant
    Filed: September 5, 2001
    Date of Patent: March 30, 2004
    Assignee: Rotational Molding Technologies, Inc.
    Inventor: Carl W. Van Gilst