| 摘要 |
A flexible fan which automatically reduces its pitch in response to increased rotation speed includes a hub having an axis of rotation and a plurality of blades extending radially outwardly therefrom. Each blade has a leading surface, a root portion joined to the hub, a tip portion, leading and trailing edges, and a relatively stiff leading portion joined to a relatively flexible trailing portion by a relatively narrow hinge zone which extends diagonally across the blade from generally the trailing edge of the root portion to generally the leading edge of the tip portion. A pair of stiffening ribs are provided on the leading surface of the leading blade portion which define a triangle with its base joining the hub and its apex extending toward the tip portion, one rib being adjacent and generally parallel with the hinge zone, and the other rib being spaced from and generally parallel with the leading edge. The trailing edge of each blade includes a first portion which extends outwardly from the hub and a second portion joined to the first portion and extending to the tip portion and defining angles with the first portion and the tip portion, and with the junction of the first and second trailing edge portions lying on a line which extends radially from the axis when the blade is in its high speed, reduced-pitch condition, all portions of the blade lying substantially forward of that line in the direction of the leading edge.
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