Patent GB-745664-A (GB)
Title: Improvements in and relating to anemo-electric power plants
IPC: F03D7/02
Filed: 1953-03-17
Abstract: 745,664. Wind motors. DE HAVILLAND PROPELLERS, Ltd., and PERDUE, R. J. March 12, 1954 [March 17, 1953], No. 7394/53. Class 110(3) [Also in Group XXIX] A wind motor having a propeller with adjustable pitch blades operated by fluid pressure, mounted on a supporting structure has means responsive to changes in the axial thrust exerted on the propeller by the wind which controls a valve system regulating the supply of fluid to the pitch changing means. The invention is described with reference to a wind motor of the type in which the blades are hollow and are arranged to suck air through a turbine supplying the useful power. The propeller boss 1 is attached to a hollow shaft 2 mounted by bearings 4, 5 in a supporting structure 3. Two annular series of cylinders 7, 9 are formed in blocks 8, 10 secured to the structure 3. Each cylinder 7 has a piston 11 with a piston rod 12 and each cylinder 9 a piston 13 and a piston rod 14. The piston rods 12, 14 engage recesses 15, 16 formed in opposite sides of a thrust block 17. The thrust block has a flange 18 located between thrust bearings 19, 20 retained on the shaft 2 by a lock-nut 6. Rotational movement of the thrust block 17 is prevented by a key 21. The forward end of each of the cylinders 7 is blanked off and provided with a fluid supply orifice 23 and the wall of each cylinder is provided, adjacent its end, with a bleed orifice 24. The forward ends of the cylinders are connected to each other by slots 25 and one of the slots has a tapping by means of which the pressure may be communicated to a servomotor varying the pitch angle of the blades. The rear ends of the cylinders 9 are blanked off and provided with an orifice 27. These ends are connected by slots 28. The axial thrust of the wind on the propeller blades is transmitted to the pistons 11 by the piston rods 12 and the pistons move and start to close the orfices 24. This causes the pressure in the chambers at the head of the pistons to rise until this pressure balances the thrust on the propeller blades. To compensate for the axial thrust on the propeller boss due to the depression inside it a capsule responsive to pressure drop across the boss is used to control the pressure of fluid supplied to the orfice 27. The servo-valve, Fig. 6, controlling the supply of fluid to the pitch changing means comprises a central control piston 40 and a control sleeve 43 which regulate the supply of fluid from the chamber 49 to either of the chambers 48, 50 and from either of these chambers to the drain recesses 61, 63. The control piston 40 is connected to a piston 57 which is subiect to fluid pressure whenever the speed of the propeller rises above a predetermined value. This moves the piston 40 to the left and thus increases the pitch angle of the blades and consequently decreases the speed of the propeller. The sleeve 43 is controlled by a piston 52 in a cylinder 51 which is subject to the pressure in one of the slots 25. On increase of this pressure due to an increase in axial thrust on the propeller the piston 52 moves against the action of the springs 53 and causes fluid to be supplied to the pitch changing means to increase the pitch and so reduce the axial thrust on the blades due to the wind.