Patent GB-701317-A (GB)
Title: A control system for a variable-pitch aircraft propeller driven by a gas-turbine engine
Inventor: SLATTER BRIAN HUDSON
IPC: B64C11/42
Filed: 1950-07-07
Abstract: 701,317. Gas turbine plant. ARMSTRONG SIDDELEY MOTORS, Ltd. May 24, 1951 [July 7, 1950], No. 16997/50. Class 110 (3). [Also in Groups XXIX and XXXIII] In a variable-pitch propeller, driven by a gas turbine, whose pitch change mechanism 21, Fig., 2, is operated by pressure fluid controlled by a' pilot valve 25 movable by a speed governor 39, movement of the engine throttle actuates a valve, which is independent of the governor mechanism, for selectively supplying pressure fluid directly to the pitch change mechanism so that the propeller will quickly absorb any change in the power developed by the engine whilst keeping the engine speed constant. Pressure fluid supplied by a booster pump 27 is distributed by the valve 25 to either the coarse pitch passage 23 or the fine pitch passage 24, the exhaust fluid from the cylinder 20 passing through annular grooves 34, 35 which are connected permanently with outlet passages 33, 53 leading to the pressure side of the engine oil pump. A relief valve 32 is, provided. A throttle lever 93, Fig. 6, is connected through links 95, 97, carried by an arm 98 pivoted on an adjustable fulcrum 99 with a rotary sleeve valve 76 which controls the flow of fluid from a conduit 50, connected with the booster pump, to either of passages 81, 83. The passage 81 communicates through a port 64 with an annular cylinder 62, 63, Fig. 3, containing a combined sliding and rolling piston 66 which is guided on a partition 69. The annular cylinder also communicates through a port 65 and a conduit 48 with the coarse pitch passage 23 whilst the fine pitch passage 24 communicates directly through a conduit 46 with the passage 83 in the sleeve valve. When the throttle is advanced fluid is supplied to the cylinder 62, 63 thereby causing the piston 66 to roll anticlockwise and to displace fluid through port 65 to the coarse pitch passage ; the fine pitch passage is then connected with the outlet passage 53. The liquid displaced by the piston 66 is dependent upon the number of revolutions made by the piston which is in turn dependent upon the angular movement of the sleeve valve. The piston 66 is coupled through a pin 71, shaft 73 and gearing 74 with a valve stem 75 which completes a follow-up movement. The fulcrum 99 is adjusted automatically in accordance with the indicated air speed. A pitot tube in front of the aircraft transmits pressure to a diaphragm 109 loaded by an adjustable spring 113 and having an adjustable linkage 112. The diaphragm is connected to a pilot valve 107 which controls the flow of fluid from the passage 53 to one side of a spring-loaded power piston 103. The latter is connected through a rack and pinion 102, 101 and a lever 100 with the fulcrum 99. Movement of the throttle lever 93 to the " take off " position 118 causes an arm 120 to engage a spring-loaded pilot valve 121 which controls the flow of pressure fluid from the passage 53 through a passage 90 to the lower end of a cylinder 124 thus raising a plunger rod 125 connected through linkage 61, 37, Fig. 2, with the governor spring 59 whose loading is thereby temporarily increased. In another embodiment the sleeve valve 76 and rolling piston 66 are replaced by a parallel piston and valve connected by a floating lever to provide the follow-up movement.