GB1196318A - Improvements in Rotors for Rotorcraft - Google Patents

Abstract

1,196,318. Rotorcraft rotor. BOLKOW G.m.b.H. 8 Nov., 1967 [11 July, 1967], No. 50791/67. Heading B7W. A rigid rotor for a rotorcraft having four blades 9 each rigidly connected to a blade shank sleeve 5 rotatably mounted for pitch change in a bearing sleeve 4 formed on the rotor head 3, each pair of diametrically opposed blades being connected by a laminated torsion bar 10, 18 in the form of a stretched loop, the loop of the bar 10 being in a vertical plane, and the loop of the bar 18 in a horizontal plane and passing through the loop of the bar 8. The laminations may be of steel separated by a low friction layer, e.g. of P.T.F.E. The laminations may comprise either a series of loops side by side (as in bar 18) or a series of concentric loops each encircling the previous one. The torsion bars 10, 18 may be tensioned by disc springs 16, 17, the tension when the rotor is stationary, being adjusted by rotating a nut 14 on a screw 12 which slides without rotating because of a key 13. Cyclic pitch Œ# 2 does not twist the bars 10, 18 as both ends are rotated by the angle, Fig. 3 (not shown). However the collective pitch + # 3 twists the bars by 2# 3 as the ends are both rotated by # 3 but in opposite directions. To minimize the maximum twist of the blades, the bars may be given a present twist of # 1 = ¢# 3 at zero pitch angle, resulting in the bar twist being Œ 2 # 1 = Œ# 3 for the collective pitch range from zero to + # 3 . The insulation of 1,190,259 is acknowledged as prior art.