GB754033A - Rotor and stabilising mechanism, especially for helicopters - Google Patents

Abstract

754,033. Helicopters. SOC. NATIONALE DE CONSTRUCTIONS AERONAUTIQUES DU SUD-OUEST. June 3, 1954 [June 11, 1953], No. 16467/54. Class 4. A helicopter rotor system comprises a freely tiltable rotative hub supporting, through diametrically opposite articulated connections spaced from the hub axis, the roots of two variable pitch blades also connected to the hub by members adapted to supply, between the blades and hub, a restoring force about the longitudinal axis of the blades increasing with increase in blade pitch, the hub also supporting two balance weights symmetrically disposed on a hub diameter perpendicular to the longitudinal axis of the blades, and a device directly connected to horns on the blades for cyclic pitch control. In Fig. 2, two blades 2A and 2B are connected to the hub 3 by rods 10A, 10B with articulated ends 11, and by members 12 which may consist of a laminated bundle of springs, and may extend through the hub from blade to blade. The hub also supports two masses 8 on arms 9. A control-rod 5 extending through the hub swivellingly supports at 14 a crows-foot 6 universally pivoted at 13 to two arms 7A and 7B rigidly attached to rods 10A and 10B for pitch control, raising or lowering rod 5 giving a collective pitch change, and tilting rod 5 giving a cyclic change. In operation, a cyclic pitch adjustment of the blades gives rise to unequal couples exerted on the hub by members 12, and the hub tilts progressively under the inertia oe masses 8. When a disturbance displaces the tip path plane, the blades affect the hub so that the diameter ab thereof describes a planparallel to the new tip path plane, but the gyrof scopic inertia of masses 8 constrains the diameter gh to remain in its former plane, and the hub rotates. A force is thus transmitted back to the blades, and crows-foot 6 to tilt the control member 5 to a new position to retain the same cyclic pitch setting despite disturbance of the tip path plane. The blades may be driven by jet propulsion units mounted thereon, or from an engine in the fuselage. The hub and pylon construction is shown in Fig. 3, wherein the pylon 1a bears a universal joint 21 mounting the hub and a thrust bearing 22 for transmitting lift, and contains a sliding universal joint 35 for control member 5. An extension 25 of the hub has spherical flanges 29, 25a co-operating with flanges 30 on the pylon and 26a on a chamber 26 surrounding the pylon, to seal this chamber. Flexible pipes 32 extend from the chamber to the blades, and the chamber is fed from a duct 28 with gas under pressure. The arms 9, Fig. 2, may bear small aerofoil elements, to which the masses 8 may be pivoted about vertical axes to accommodate quickening and slowing of the rotational speed of the hub.