GB1319193A - Fans - Google Patents

Abstract

1319193 Axial-flow fans FOLKES BELTING CO Ltd 12 Jan 1972 [28 April 1971] 11921/71 Addition to 1272645 Heading F1C In a fan of which at least one blade is capable of moving to change its pitch, a temperaturesensitive element is provided on the fan and arranged to move the blade to increase the pitch abruptly when the ambient temperature exceeds a predetermined value. The motor vehicle cooling fan shown comprises two or more flexible blades 2 of rubber, metal or plastics secured, as by rivets or bolts 3 or adhesive to a rigid central portion 1 of metal or plastics. When the ambient temperature at the fan is below a predetermined value, the blades 2 are free to flex to a reduced pitch under the influence of aerodynamic forces as the fan speed increases. When the predetermined value is reached, a bi-metallic strip 6 which is riveted or bolted to the central portion 1 at 7 abruptly flexes from a configuration in which it is straight longitudinally and curved transversely to a configuration in which it is curved longitudinally and flat transversely. The tip of the strip 6 then presses against the reinforced edge 4 of the adjacent blade 2 to move the blade into a position of high pitch. This abrupt pitch change may occur at different temperatures for different blades. A flat spring may be interposed between the strip 6 and the edge 4 so as to hold the blade at maximum pitch until a predetermined aerodynamic force is reached. An additional bi-metallic piece may be provided with its tip pressing against the edge 4 so as to limit or vary pitch change at temperatures below the predetermined value. Instead of being flexible, the blades may be substantially rigid and attached to the central portion 1 by a hinge or a narrow strip of flexible material, the restraint against movement to a low pitch position being imposed by the above-mentioned spring and/or the narrow strip.