GB734888A - An improved helicopter rotor hub - Google Patents

Abstract

734,888. Helicopters. SHORT BROS. & HARLAND, Ltd. April 29, 1954 [April 30, 1953], No. 11959/53. Class 4. A helicopter rotor hub comprises a spider 43 transmitting pitch change to the blades 10, being rockable universally for cyclic pitch change, and movable bodily for collective uniform pitch change, pitch control movements being transmitted to the respective blades through rocking beams 38, the fulcra 39 of which are movable independently of the spider to produce a non- sinusoidal pitch change. The blades 10 are mounted in sleeves 11, and are tied by torsion bars 33 to levers 32 secured to the hub. Each blade root 10 has an arm 35 extending therefrom, connected by link 37 to one end of a rocking beam 38, the other end thereof being linked to one arm 42 of the spider 43. The latter is rotatably mounted on one end of a rod 44 ball jointed at 45 to a tubular member 46 threaded at its lower end 47, so that rotation of drum 48 engaged therewith will move rod 44 axially of the rotor shaft for uniform collective pitch change. Rod 44 may be rocked for cyclic pitch change. The fulcra 39 of beams 38 are carried by levers 40 pivoted in the rotor hub, and bearing with surfaces 51 on cam surfaces 53, 54 formed on one end of a tubular member 56, the other end of which is threaded at 57 and engages a drum 58 rotatable to move axially the cams 53, 54 to rock the levers 40, and effect a collective pitch change. The rotor drive shaft 15 is driven by the planet wheels 18 between a pinion 19 driven from shaft 24, and a fixed ring gear 17. The pilots' controls are shown in Fig. 4, where movement of column 64 fore and aft moves rods 70, 77; 68, 75 and 66, 71 equally and therefore moves the lower end 59 of rod 44 fore and aft: Similarly, lateral rocking o column 64 produces lateral movement of rod 44. Lever 82 operates a cable 78 to rotate drum 48 and vary the collective pitch. A trimming adjustment of collective pitch is provided by rotation of lever 88 to operate drum 58. According to the Provisional Specification the spider may be operated through a swash plate, and the cam surfaces 53, 54 may be of circular cross-section where the cams 51 engage them when the trimming lever 88 is in the datum position, and of oval cross-section elsewhere to give a non- sinusoidal cyclic pitch change.