Patent 6,368,227 "Method of swinging on a swing" http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=%276,368,227%27.WKU.&OS=PN/6,368,227&RS=PN/6,368,227 Robbie