PIPE MOLDING APPARATUS WITH AIR FLOAT OF PLASTIC ONTO TAPERED COOLING PLUG

摘要

A pipe molding apparatus for forming double walled plastic pipe comprises an extruder which feeds first and second parisons of flowing plastic material to a moving mold tunnel to make respectively the outer and inner walls of the pipe. The moving mold tunnel includes a cooling plug over which the second parison moves to form the inner pipe wall while the outer wall of the pipe is formed against the interior surface of the mold tunnel. The cooling plug has a forward neck which is tapered inwardly towards the extruder and a cushion of air is provided along the neck to float the inner wall forming parison over the neck onto the main body of the cooling plug.