US Patent 6,557,213 B1, granted May 6, 2003 to William E. Winn of Levelland, Texas, for a closed loop push/pull air system for cotton gins. It uses a hot shelf tower dryer and strategically placed push and pull fans to recirculate conveying air through dryers, cleaners, extractors, collectors and lint cleaners, reducing pollutant emissions. The document has the patent front page, two sheets of schematic drawings (Figs. 1 and 2), the full specification and 12 claims, and a second printed copy from the USPTO web database.