GB657689A - Improvements in or relating to rotary wing aircraft - Google Patents

Abstract

657,689. Helicopters. KRAUSS, S. J. May 17, 1949, No. 10880/48. [Class 4] A helicopter comprising two or more blades rotating in the same sense and in a normally substantially horizontal plane in which each blade is permitted a limited amount of flapping movement is characterized in that all of said blades are rotated about a common point by a power driven mechanism which comprises for each blade two elements capable of exerting on the blade mutually dependent forces, the lines of action of which are contained in substantially rectangular planes. The drawing illustrates the mechanism for one blade only, wherein each blade is extended by a crank A which terminates in a sleeve B, a fork G rotatably and slidably mounted on the root end of the blade being pivoted on an axis X to a second fork H fast with a hollow shaft F. A further shaft E, coaxial with the shaft F, carries a stirrup mounting for a crank D inclined in a plane containing the vertical axis Z and the horizontal axis X and slidably mounted within the sleeve B, the crank being angularly adjusted in the aforementioned plane by a control mechanism C. The shafts E and F are driven in the same direction by an engine K through a mechanism J1-J10, contained within the fuselage L. The drive mechanism comprises a bevel gear J1 driven by the engine K and meshing with gears J2 and J10. The gear J10 is fast with another gear J9 which in turn meshes with a pinion J8, the bearings supporting all of these gears being fast with the aircraft structure. A positive drive is provided between the engine K and the shaft E by the gears J1, J10, J9, J8 and a gear J7 fast with the shaft E, rotation of which causes combined flapping and pitch change movement of the blade A if the blade is held fast at any cyclic position, the magnitude of such movement being determined by the angular deflection of the crank D. The gear J2 carries a planet carrier J3 having pinions J4 freely pivoted thereon and engaging one gear J6 fast with the shaft E and another J5 fast with the shaft F. The arrangement of gears is such that under normal conditions of flight when the aerodynamic forces acting on the blade in the vertical and horizontal planes are balanced respectively by the loads exerted on the crank D through the shaft E and on the stirrup H, G through the shaft F, no relative motion takes place between the shafts E and F which rotate in the same direction. Under such conditions, the angular relationship of the crank D and the resolved aerodynamic force exerted on the blade A with a plane containing the axes Z and Y is the same. Should these conditions be disturbed either by external aerodynamic forces acting on the rotor system or by manual adjustment of the control mechanism C relative rotational. movement will take place between the gears J5 and J6 and consequently, between the shafts E and F, to vary the attitude of the blade in the flapping and/or pitch change sense to restore the conditions of equilibrium.