GB580923A - Improvements in or relating to variable pitch propellers - Google Patents

Abstract

580,923. Variable-pitch propellers. FAIREY AVIATION CO., Ltd. Oct. 27, 1943, No. 17721. Convention date, Feb. 25. [Class 114] [Also in Group XXIX] A self-contained unit for mounting on the propeller drive shaft 12 of an aircraft engine 11 comprises a governor 42 driven by the engine and controlling clutches for selectively connecting the propeller drive shaft with gearing connected with the pitch changing mechanism 22 to actuate the latter in either direction. The governor may actuate a tubular valve 49 which controls hydraulically actuated clutches 50, 51 for said gearing, the hydraulic fluid being forced to said clutches by a pump 167 driven by the engine. The gearing includes a ring 43 geared to drive a wheel 27 which is geared to the worm-wheels 22, and a gear-wheel 37 which drives a shaft 41 carrying the clutches 50, 51 and driving the governor 42 through bevel gears. Actuation of one of the clutches will cause a bevel-wheel 52 or 53 to rotate a gearwheel 46 or 47 and rotate the ring 43 in one direction or the other to vary the pitch of the blades 23. The ring 43 also drives a shaft 59 carrying cams 60, 61, 62 engaging spring-urged valves 63, 64, 65 (63 and 65 are not shown). If the speed is such as to require fine pitch, the valve 49 allows the pressure fluid to pass into conduits F, F<1>, the former being blocked by the valve 63 in its closed position, and the latter leading to a cylinder containing a spring- urged member 69 which closes the clutch 51. This changes the blades to their fine pitch position, and at the same time bevel-wheel 53 rotates the cams until cam 60 releases the valve 63 and the movement is stopped. A similar action changes the pitch to a coarse position. The operation of the governor 42 may be over-ridden by a lever 66 which may also be used for changing the pitch to a feathering position. For this purpose, the valve 49 is moved to its coarse pitch position, and the cam 61 and valve 64 rendered temporarily ineffective by means of a cable (not shown) so that the changing movement continues until stopped by the feathering cam 62 opening the valve 65. Should the engine stop, the blades may be moved to the feathering position by the auxiliary electric system shown in Fig. 9, wherein an electric motor 74 is connected'by a clutch 75 and bevel-wheels to a shaft 78 geared to the bevel wheel 52, the circuit including a solenoid 80, a cock-pit switch-81, and a switch 82 operated by a cam 82<1> for cutting out the motor 74 when the feathering position is reached. In modifications: (i) the shaft 41 is vertical and directly drives the governor ; (ii) an additional cam and two additional switches are provided whereby the pitch is also changeable to a reverse or braking position ; (iii) the invention is applicable to contra-rotating propellers on coaxial shafts ; and (iv) magnetic instead of hydraulic clutches are employed. Specifications 491,041, 564,221, 568,749, 580,488 and 580,745 are referred to.