GB1055165A - Improvements in or relating to engine cooling fans - Google Patents

Abstract

1,055,165. Axial-flow fans; cooling cylinders. DOWTY HYDRAULIC UNITS Ltd. March 25, 1964 [April 11, 1963 (2); Jan. 2, 1964], Nos. 14621/63; 14622/63 and 251/64. Headings F1B and F1C. An engine-driven cooling fan has blades whose pitch is automatically adjusted by centrifugal moments inherent in the blades, against the action of generally radially-directed torsion springs. A belt-driven fan hub 12, Fig. 5, formed by rivetting together two steel pressings 14, 15, has tubular projections on each of which a sheet metal blade 18 is rotatably mounted. The hub parts may be formed by machining and the tubular extensions welded thereto. The blade roots may extend into sockets formed in the hub. Each blade root carries a pin 22 which extends through slots 21 in the associated tubular extension, the slot extremities providing the limits of angular adjustment of the blades. Centrifugal force reduces the pitch of each blade with an increase in speed against the action of a torsion spring, which may be of double-looped form, extending radially alongside or within the blade, Fig. 3 (not shown), and secured to a rivet 26 in the blade and a rivet in the hub. The torsion spring additionally absorbs the radial force exerted on the blade but if this force becomes excessive the pin 22 contacts the sides of its slots 21 and thereby takes up the load. Optional means for adjusting the fine pitch limit comprises a plate 50 provided with a stop 52 for each blade pin 22, the plate 50 being angularly adjustable to a position in which a spring-pressed pin 55 locates one of two or more holes 56, 57. The hole 56 provides a winter setting in which the whole range of blade adjustment is available down to a fine pitch of 17 degrees. The hole 57 provides a summer setting in which the finest pitch is 35 degrees. Alternatively, the pitch limit may be adjusted by cam means. The plate 50 may be arranged to be capable of rotating to a position in which the holes 56, 57 associated with one blade are moved to the vicinity of an adjacent blade and thereby provides settings for the coarse pitch limit thereof. A second plate 50 may be provided for controlling the coarse pitch limit of the blades. In an alternative embodiment, Fig. 4, the blade pitch may be further controlled, particularly at low speeds, by the temperature of the air passing through the fan. Two wax filled thermostats 40 attached to a finned plate 32 receive heat therefrom, and when the air temperature is approximately 10‹ F. higher than the set operating temperature they each extend a plunger 41 which, through a leaf spring 42, causes a plate 36, receiving the blade pins 22 in apertures 38, to be rotated and thereby coarsen the pitch of the blades and increase the speed at which the blades will commence to be adjusted centrifugally.