1,021,376. Axial-flow fans. C. W. CLARK. Dec. 9, 1964 [Dec. 10, 1963], No. 48814/63. Heading F1C. In a cooling fan for vehicle engines, having two or more fixed blades, the blades are distorted to vary their pitch in accordance with temperature and air reaction. Blades 6, 7, Fig. 1, formed from a flat sheet-metal strip are each provided with a pair of bimetallic elements 8, 9. These elements are arranged to twist the parts at each side of the blade longitudinal axis in opposite directions to increase the pitch with increases in temperature. Additionally, the blade are sufficiently flexible to enable the reaction of air on them to decrease their pitch with increases in fan speed. In an alternative embodiment, Figs. 3 and 4 (not shown), the blades each comprise a rigid arm integral with the hub and extending parallel to a radial line to form the leading edge of the blade, and a flexible bimetallic sheet-metal part riveted to the downstream side of the rigid arm. The arm is twisted at its radially inner end to provide some initial blade pitch.
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