Patent GB-265272-A (GB)
Title: Improvements in or relating to flying machines
IPC: B64C27/04
Filed: 1925-10-30
Abstract: 265,272. Baumhauer, A. G. von. Oct. 30, 1925. Screw propellers.-Aircraft of the kind supported by one or more lifting screws, consisting of blades or wings attached at their roots to a central rotating shaft or structure in such a manner as to be free to turn angularly until the moment of centrifugal force is balanced by the moment of the lift, are provided with yielding means for applying a couple to the wings or blades, tending to turn them in the same direction as centrifugal force in order to enable wings or blades which are light in weight to balance considerable lift forces without rising to a great dihedral angle. Alternatively, a couple for preventing the blades from drooping at low speeds is diminished as the speed rises. Fig. 1 shows two blades pivoted to a central shaft 7 and connected by stays 2 to springs 3. A cable 4 supported by a hinged strut 5 interconnects the upper sides of the blades. Fig. 2 shows a modification in which the blades are interconnected by a cable 2 passing under pulleys 8 on the shaft, upper stays 9 being connected through springs 10 to a post 12. Alternatively, the cables 2 may pass under a quadrant pivoted to the shaft concentrically or eccentrically of its curved edge, or they may be connected to a pivoted plate. These quadrants or plates may be movable by the pilot to impart a rolling or pitching movement to the machine. In another modification, projections 14, Fig. 3, on the wings are connected by springs 3 to a ring 15 which rotates about a member 16 adapted to be tilted in any direction about a ball 17 by control rods or wires 18. Springs may be interposed in the control connections, so that movements of the blades will be elastically interconnected. A pair of blades with bracing similar to the upper part of Fig. 1 is described. Fig. 9 shows two blades rigidly connected together at their roots and braced to a depending part 42, which is hinged at 40 to the central shaft. Tilting movements of the blades are controlled by elastic connections 43 to a conical member 45 rotating in fixed ball bearings. When the blades are mechanically driven their leading edges may be braced by, cables 23. Fig. 5, to arms 21 on the propeller shaft, the ends 22 of the arms being in the axes of the blade hinges 19. These hinges may be universal joints so that connections from points 24 to a swashplate, which can be raised or lowered or tilted, the pitch of the blades also may be varied as a whole or cyclically. Fig. 6 shows a modified driving arrangement in which the cables 23 are connected to a transverse strut 21 passing through the axes of the blade hinges 19, the strut 21 being further braced to the top of the propeller shaft and to points 30 on a gear wheel 28. For accelerating rotation when the plane of rotation is at a small angle of incidence and for retarding rotation when this angle is large a windmill comprising hemispherical cups may be mounted on the central structure or upon the wings, these cups being reversible upon their supports. By directing a jet on to these cups or by utilizing the slipstream from the forward propeller, autorotative blades may be started or maintained in rotation. In power-driven apparatus a brake may be used to give the retardation at high angles of incidence.