GB709673A - Improvements in or relating to helicopter rotors - Google Patents

Abstract

709,673. Helicopters. UNITED AIRCRAFT CORPORATION. April 18, 1952 [Aug. 18, 1951], No. 9790/52. Class 4 A helicopter rotor comprises a drag hinge pivoted to a hub and having a depending projection, a blade having a root portion pivoted to said drag hinge for flapping movements and having a depending portion terminating adjacent said projection and centrifugally operated locking means movable bodily with said blade as the latter moves about said drag hinge for effecting a locking connection between said projection and said depending portion and preventing upward flapping of said blade when the latter is stationary or is rotating below a predetermined speed. The rotor drive shaft 22 carries spaced plates 32, 34 between which are pivoted drag pivots 54 each carrying a flapping arm 52 to which the blade root 40 is attached for pitch changing movements. Each member 54 carries a depending arm 90 having pivoted thereto at 86 a spring loaded element of a toggle mechanism 30, the other element being formed by a pair of spaced arms 68 pivoted to the spring loaded element at 74 and to the flapping arm 52 at 72. The toggle is biased by springs 105 into an over-centre position in which a stop face on the upper end of the spring loaded member engages a mating face on the arm 90 so that the blade is restrained from upward flapping movements. When the speed of the rotor rises above a predetermined minimum centrifugal force causes the toggle to overcome the action of the springs 105 and swing outwardly so that the blades are free to flap upwardly. U.S.A. Specifications. 2,405,777 and 2,614,640 are referred to.