| 摘要 |
1,274,226. Turbines; axial-flow fans; jet propulsion plant; oscillating motors. DOWTY ROTOL Ltd. Nov. 4, 1969 [Nov. 15, 1968], No.54283/68. Headings F1C, F1F, F1J and F1T. Pitch-change mechanism for the blades 10 of a variable pitch rotor, e.g. a ram air turbine or a ducted fan of a gas turbine engine, comprises a hydraulically operated vane type actuator 16 mounted within the rotor hub 13. The actuator 16 is annular comprising an inner part 17 having ten radially outwardly extending vanes 18 and an outer part 20 having ten inwardly extending vanes 21, the vanes 18, 21 defining chambers 23, 24. Both parts 17, 20 are angularly movable with respect to the hub 13 and are respectively provided with rings of bevel gear teeth 26, 27 which mesh with pinions 14 mounted on the blade roots 15. The actuator 16 is controlled by a rotary valve 29 operable by a mechanical input 30, the valve controlling the flow of liquid from a supply pipe 31 to the chambers 23 or 24 to urge the toothed parts 17, 20 in opposite angular directions and thus decrease or increase the pitch of the blades 10. The valve 29 is of the follow-up type so that when a selected blade pitch is reached the valve regains a neutral position. A drain pipe 32 is provided. The actuator 16 may be controlled by a speed responsive governor.
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