As disclosed in Japanese Patent Laying-Open No. 2003-206894 (PTD 1), Japanese Patent Laying-Open No. 2011-058449 (PTD 2), Japanese Patent Laying-Open No. 2004-293528 (PTD 3), and Japanese Patent Laying-Open No. 2000-054992 (PTD 4), a propeller fan has been improved for the purpose of improvement in blowing performance, lowering in noise, energy saving, or design for resource saving.
USPTO Backgrounds
USPTO Backgrounds