GB1308023A - Bladed rotors - Google Patents

Abstract

1308023 Helicoptor rotors UNITED AIRCRAFT CORP 19 May 1970 [17 July 1969] 24038/70 Heading B7W [Also in Divisions E2 F1 and F2] A helicopter rotor has blades 28 attached to a hub 50 by a flapping hinge 61 or a flexible section 150, Fig. 15, for movement relative to the hub, with a spring stack 104, the stiffness of which may be varied in a given plane, fixed across the hinge 61 or flexible section 150. Each blade 28 is mounted in a cuff 70 through bearings 57 to allow pitch changes controlled by horn 98. Cuff 70 is connected to hub 50 through hinge 61 and transmits centrifugal forces between the blade and hub. Spring stack 104 is rotatably mounted in the cuff 70 and in a mount 118 in hub 50 with an arm 140 or 160, Fig. 15, to rotate it to vary its stiffness. The spring stack comprises a stack of metal laminates separated by layers of Teflon (Registered Trade Mark), fastened together by a bolt 112 and mounted at each end in members 120, 130 which allow longitudinal movement of the laminates relative to one another while preventing lateral movement. The cross-section of the spring stack may be square, rectangular, circular, oval or polygonal. In the position shown in Fig. 3, the spring stack has maximum stiffness to flexing about hinge 61 and on rotation through 90 degrees so that the hinge axis 82 is parallel to the planes of the laminates it has minimum stiffness with intermediate stiffness between these positions. The spring stacks in all the blade hub connections may be operated simultanously through a star member (146), Fig. 9 (not shown). Two rotors are mounted at the wing tips of a convertiplane for rotation about the wing spanwise axis so as to operate as an articulated or semi-rigid helicopter rotor or a rigid propellor.