TURBOFAN FOR RANGE HOOD, AND RANGE HOOD CONTAINING THE TURBOFAN

摘要

PROBLEM TO BE SOLVED: To mold a blade of a blade section shape according to design by suppressing springback of the blade pressed from sheet metal. SOLUTION: A blade is press-molded from sheet metal into an internally hollow blade section shape with opposite open sides fixed to an upper and a lower plate. The blade is formed after the sheet metal (a) with a rectangular shape with a blade width W dimension at one side in the plan view is subjected to coining work that forms a multitude of juxtaposed straight deformed portions parallel to the side of the blade width W dimension and properly spaced along the sides perpendicular to the side of the blade width W dimension, and that molds the sheet metal (a) into a curved surface of a given curvature in a direction perpendicular to the side of the blade width W dimension. The straight deformed portions interrupt propagation of restoring force generated in band plate portions between the straight deformed portions to suppress the propagation to the overall sheet metal (a).