Pipe molding apparatus with air assist of plastic onto 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. An air assist is provided internally of and helps to move the inner parison onto the cooling plug.