GB597931A - Improvements in pitch changing mechanisms for screw propellers - Google Patents

Abstract

597,931. Variable-pitch propellers. FORSYTH, A. G., and FAIREY AVIATION CO., Ltd. July 5, 1944, No. 12836. Convention date, Aug. 12, 1943. [Class 114] A variable-pitch propeller control device comprises two geared rings mounted for relative rotation, one, 3, being driven by the propeller shaft, and the other, 5, connected to the propeller blades, these rings engaging coaxial gearwheels 13, 14, which can be selectively coupled together. The gear ratios of the wheels are such that when the wheels 13, 14 are coupled by energizing the electromagnet 19, and engaging teeth 16, 17, the wheel 5 rotates slowly relative to wheel 3, this movement moving the propeller blade for pitch alteration in one direction. A similar unit is provided for pitch movement in the opposite sense. The wheels 3, 5 also operate a similar device electromagnetically controlled for moving limit switches for coarse and fine pitch, and for reverse and feathering movements. In a modified form, extra units are added of increased gear ratio for carrying out reversing and feathering movements. A reversing motor 75 (Fig. 14) is added for auxiliary operation to the fine or feathered position should the engine fail. In another modified form Fig. 16), a unit with epicyclic gearing 99, 101, 103, 106, 107, 108 is controlled by a reversible electric motor 95 for carrying out slow movement for coarse or fine pitch, with additional devices similar to those shown in Fig. 3 for feathering or reversing movements. In a further modified form, the teeth 16, 17 for coupling the gears are replaced by arms 125 (Fig. 18) engaging the edge of the disc 127. In still a further modified form, the electromagnets such as 19 (Fig. 3) or 130 (Fig. 18) are replaced by external electromagnets 145, 146 (Fig. 21) operating the clutch discs 171 through rodding 150, 153, &c. Specification 580,488 is referred to.