Patent GB-631098-A (GB)
Title: Mechanism for controlling helicopters
IPC: B64C27/54
Filed: 1945-07-19
Abstract: 631,098. Helicopters. TRIGGS, W. W. (Bendix Helicopter, Inc.). July 19, 1945, No. 18545. [A Specification was laid open to inspection under Sect. 91 of the Acts, Dec. 28, 1945.] [Class 4] A helicopter having coaxial counter-rotating non-flapping rotors is provided with means for non-cyclically varying the lift and drag of the rotors in like or unlike senses and also with means for cyclically varying the lift and drag of the rotors in selected arcs, the control system for the latter means comprising two rings concentric with the rotor axis and capable of tilting relatively to the axis and one another, the rings engaging cam followers which vary the lift and drag of the rotors and being tilted by a system which provides for simultaneous tilting in the same or opposite senses. In the construction shown, banking, pitching and forward and lateral movement are controlled by the cyclic variation of lift and drag while steering and ascent and descent are controlled by the non-cyclic means. Each blade of the rotors 14, 15 is provided as in Specification 590,514 with a control blade 84, Fig. 1, which can be rocked from a position in the plane of the wing to a position in which it projects from the wing by means of a shaft 85, Fig. 2, moved axially of the wing and parallel to the spar 83, Fig. 4, by means of a suitable complemental spirally threaded portion thereon. The motion of each shaft 85 is controlled by cables 134 connected to shafts 135, 135a, 144, 144a pivoted to levers 136, 136a, forming part of a semicircular yoke 138, 138a, 142 or 142a pivoted to the rotor shaft 22 or 23 by means of pivot pins 111. Each of the upper yokes 142, 142a is maintained parallel to a yoke 141, 141a, pivoted to the shaft 23, by means of ball-ended links 145, 145a. The yokes 141, 141a and the lower yokes 138, 138a carry roller cam followers 140, 140a, 139, 139a engaging cam rings 129, 123 so that as the shafts rotate the yokes 138, 138a, 142, 142a are oscillated and through linkages such as 136, 135, 134 project the blades 84 over part of the circle of rotation of each blade. The cyclical projection of the blades may thus be controlled by varying the inclination of the rings 129, 123. Ring 129 is supported by balls 128 engaging grooves in both the ring and in a spherical portion 127 at the top of the shaft 22 so that the ring rotates with the shaft but may rock relatively to it, and is maintained parallel to a lower ring 116 by means of ball-ended links 131, the ring 116 being connected by ball and socket joints 112a, 113a to arms 112, 113 pivoted to a yoke member 110 pivoted at 11 to the shaft 22. A further ring 119 is supported within the ring 116 by means of a ball bearing 120 and supports the ring 123 by means of front and rear pivots, the latter ring being further supported on the curved outer race 124 of a ball-bearing 125. Lugs 146, 147 on the rings 119, 123 respectively are connected to control means for tilting the rings about the (longitudinal) axis of the front and rear pivots so that the rings may be simultaneously operated in the same or in opposite senses. Tilting in the same sense causes the blades 84 on the rotors 14 and 15 to be projected over superimposed arcs laterally of the helicopter to cause it to bank ; tilting in opposite senses causes the blades to be projected over diametrically opposed lateral arcs to cause the helicopter to pitch and to move forwardly or rearwardly. A forwardly projecting arm 148, Fig. 2, on the ring 119 is connected to control means for tilting the ring systems about a lateral axis so that the blades 84 are projected in superimposed areas forwardly or rearwardly of the rotor shafts to cause the helicopter to pitch. The lugs 146, 147 are connected by links 163, 164, Figs. 2 and 10, to levers 153a, 154a pivoted between a pair of parallel plates and integral with worm sectors 153, 154 engaging a worm 155. The plates are pivoted at 159, 160, Fig. 3, to the casing 68 of the transmission. Thus to tilt the rings 119, 123 in opposite senses the worm 155 is rotated by means of meshing spiral gears 156, 157 operated through a flexible shaft 172 from a hand wheel 173, Fig. 2. To tilt the rings in the same sense the plates and worm 155 are turned about the pins 159, 160 by linkwork connected to the control lever 165, Fig. 2. The rings are tilted fore-and-aft by means of the control lever 165 connected by a linkage 169, 170, 171 with the arm 148. The pitch. of each rotor blade is controlled non- cyclically by the vertical movement of a sleeve 89 or 90, Figs. 3 and 4, inside each rotor shaft and rotating therewith and having inclined slots 87 engaging pins 86, 86<SP>1</SP> in the spars 83. The sleeves 89, 90 are raised and lowered by levers 95, 104, Fig. 6, pivoted to ball races 93. These levers are pivoted to blocks 99, 106 in oppositely threaded screwing engagement with the ends of a rod 102 ; thus axial movement of the rod by means of a bearing ring 181 straddled by a bifurcated lever 179, Fig. 2, pivoted to a bracket on the transmission housing causes like change in pitch of the rotors to control ascent and descent ; rotation of the rod 102 by means of a lever 178 keyed to it and controlled through a link 177, Fig. 2, from the rudder bar 175 cause unlike changes in pitch of the rotors and thus controls the steering. The rotor shafts 22, 23 are driven by means of bevel gearing 36, 66, 67, Fig. 3. Integral with the bevel wheel 36 is a pinion carrier 45 to which a brake may be applied and which forms the planet carrier of an epicyclic gear the annulus 48 of which may be braked or positively locked and the sun wheel 41 of which is connected to the engine propeller shaft 33 through an over-running clutch 40. The engine is cooled by air drawn in through louvres 16 in the body 10, Fig. 1, and through a duct 26 by means of a fan 27, Fig. 2, and discharged through louvres 17 in the rear of the body.