Patent GB-1127604-A (GB)
Title: Improved variable-pitch cooling fan
Inventor: LOWE KENNETH STANLEY
IPC: F04D29/36
Filed: 1964-10-19
Abstract: 1,127,604. Axial-flow fans; cooling engine cylinders. KENLOWE ACCESSORIES & CO. Ltd. Oct. 6, 1965. [Oct. 19, 1964; Oct. 20, 1964; April 21, 1965; May 19, 1965; May 31, 1965], Nos. 42545/64; 42636/64; 16685/65; 21111/65; and 22964/65. Headings F1B and F1C. A variable-pitch cooling fan which may be used for cooling an I. C, engine comprises fan blades pivotally supported by radial pins carried by a driven member, and a pitch-controlling member coaxial with the driven member rotatable relative thereto and carrying radial fingers equal in number to the fan blades, the root of each fan blade having a pair of slots arranged at an angle to one another and defining equal angles to the chord of the fan blade, and the two slots being engageable alternatively by the corresponding finger when the fan blades are assembled on the driven member to adapt the position of the fan blades for the motion of air in the desired axial direction for the same direction of rotation. The engine cooling fan shown in Figs. 5 and 6a comprises blades 3 of moulded plastics each secured on a pivot pin 2 by a clip 4, the pivot pins being carried by a hub plate 1. Pins 14 carried by a ring 13 each engage a slot in a blade root. As shown in Fig. 3a, there are two such slots 7 in each blade root, arranged at an angle to one another and defining equal angles to the chord of the blade. The air flow can be in either direction, depending on which of the two slots 7 is engaged by the pin 14. The slots 7 may be curved. The ring 13 is connected by spokes 28 to a hub 27 which is pivotally connected by a rivet 26 to a star-shaped spring 25. The arms 24 of the spring 25 are slidably supported in support arms 23 projecting axially from the hub plate 1. So the fan speed rises, the blades 3 are turned by the aerodynamic or centrifugal forces acting on them towards a position of reduced pitch. This causes axial movement of the ring 13 (an accompanying slight rotation of the ring is allowed by the looseness of the rivet 26) and a consequent flexing of the spring 25 which opposes the movement. The ring 13 may be omitted, Figs. 7 and 8 (not shown), the spring arms (24) then being connected directly to the blades (3), and the spring (25) being connected at its centre to a fixed front plate of the fan hub by means of a pivoted rivet. The spring 25 may be replaced by a wax-type thermostat, so that the pitch is controlled by temperature instead of speed. In another modification, Figs. 9 and 10 (not shown) the spring 25 is omitted and the ring (13) is adjustably fixed to the hub plate (1) so that the blade pitch can be adjusted to a desired value but is fixed during operation of the fan. In further embodiments, Figs. 1, 2 and 4 (not shown), the spring is of spiral form, secured at its centre to the hub plate (1) and connected at its outer end to the ring (13). If the spring is of bi-metallic material, the blade pitch is controlled in accordance with air temperature as well as rotational speed, increasing with temperature and decreasing with speed. It may be arranged that the pitch increases with temperature until a certain speed is reached and thereafter decreases in accordance with speed increase. In another embodiment, wedges running up an inclined place between the hub plate and a front plate are moved outwardly by centrifugal force against the action of a spring as the speed rises, thereby allowing the front plate and the hub plate to approach each other to permit the blades to feather.