GB634529A - Pitch control for aircraft sustaining rotors - Google Patents

Abstract

634,529. Helicopters. AUTOGIRO CO. OF AMERICA. Aug. 8, 1947, No. 21893. Convention date, Aug. 7, 1942. [Class 4] In a rotative winged aircraft controlled by cyclical and collective variation of the blade pitch, the pitch control mechanism includes a substantially irreversible mechanism to prevent aerodynamic loads developed in the blades being transmitted to the control system and the arrangement is such that the blade pitch angle is substantially unaffected by blade flapping. The rotor hub assembly comprises a hub 10 extended into a hub spindle 11 mounted in bearings 12 in a fixed sleeve 13. A gear ring 15 is secured to the lower end of the spindle 11 and meshes with a pinion 16 mounted on a drive shaft 17. Each blade 18 is connected by a root fitting 19 and bearings 21 to a spindle 20 formed with an apertured eye 22 and mounted on a flapping pivot 23 supported by the rotor head 10. The inner end of each root fitting 19 is formed with a worm-wheel segment 25 with which meshes a worm 26 mounted on brackets 27 extended from the apertured eye 22. The end of the worm spindle is provided with a lever 28 connected by a link rod 29 to a rotative swash ring 30 mounted on a bearing 31 on a non-rotative swash member 32 provided with a depending skirt 36. The swash member 32 is spherically seated on a member 33 capable of sliding movement on the sleeve 13 for effecting collective pitch control under the action of a lever 52 and a control rod 51. Cyclical pitch control is effected by rocking the swash member 32, 36 about the member 33 by two controls such as that shown at 37, 40, 43, 44 disposed at right angles to each other. The swash ring 30 is driven from the rotor hub 10 by a scissors linkage 34, 35. The above arrangement produces small variations in blade pitch as a result of blade movements about the flapping axis and in another arrangement (Figs. 4-7, not shown) the axis of the worm is parallel to the axis of the rotor hub so that the control rod 29 (Fig. 1) is positioned coaxially within the hollow pivot pin 23. In a further arrangement (Figs. 8 and 9, not shown), the pitch control mechanism is rendered independent of the blade flapping movements by placing the flapping pivot outboard of the root fitting 19 (Fig. 1). A drag pivot inclined to the axis of the flapping pivot is also included. Specifications 159,224, [Class 114], and 477,349 are referred to.