Patent GB-947547-A (GB)
Title: Improvements in rotors for convertible aircraft
IPC: B64C27/46
Filed: 1962-03-19
Abstract: 947,547. Magnus effect rotors on aircraft. L. BOLKOW, [trading as BOLKOW-ENTWICKLUNGEN KOMM.-GES. March 19, 1962 [March 18, 1961], No. 10425/62. Heading B7W. A convertible aircraft has a rotor with flexible arms which provide lift by the Magnus effect, the arms being retractable into the rotor head or aircraft. The arms may be a single piece of flexible material, or as shown in Fig. 2, may each be composed of elements la coupled together so as to rotate about the axis of the arm as a unit, and so that the arm can flex. Either construction of arm may have a central wire taking up tensile stresses, and radiallyextending loops of wire connected to the central wire to act as reinforcement. The arm may have a resilient protective air-tight covering and be connected to an intermittent source of compressed air to provide de-icing. Fig. 6 shows one form of rotor head, in which a fixed gear-case 2 supports a rotary hollow member 3 driven by a prime mover through gears 14, 16. For each rotor arm 1, there is an arm 3a on member 3 which supports a planet bevel gear 11 meshing with a central bevel gear 10 on a tube 20 rotatably mounted within member 3. Member 3 supports a drum 9 having external grooves 9a. Each arm extends through an aperture 9b in the drum and is secured to a planet gear 11 so as to rotate therewith. Each arm also extends through an aperture 34a in a member 34 mounted on a collar 34b which is rotatably mounted on member 3 by bearing 33, and can be braked relatively to the fuselage by a band brake 35. Tube 20 can also be braked relatively to the fuselage by mating friction surfaces 20a, 21a operated by linkage 27. In use, member 3, drum 9, and members 34 all rotate as a unit. Gear 10 is fixed by braking tube 20 by linkage 27. The bevel gears 11 thus rotate about their axes and rotate the arms 1 about their axes, to generate lift by the Magnus effect. To retract the arms, the brake on tube 20 is released, and gear 10 comes to rotate at the same speed as the rotor head, the arms 1 therefore no longer rotating. The brake 35 is then applied, retarding the members 34 with respect to the drum and winding the arms on to the drum grooves 9a. The rotor head may then be retracted into the fuselage, the drive through gears 14, 16 being stopped. The arms are extended by centrifugal force on rotation of the rotor head. Once extended, the arms are set in rotation by braking tube 20 and gear 10. A weight 8 on the end of each arm increases this centrifugal force, and acts as an end plate on the arm. Fig. 7 shows another rotor head, with the same driving arrangement, but in which a drum 40 is provided for winding in each arm, which is attached through a rotary joint 45 to a cable 44 anchored on the drum. Each arm passes through its associated bevel gear 11, and has a coupling member 42 which establishes a positive rotary connection with a socket 11a in the bevel gear when the arm is fully payed out. Each drum 40 is rotatable through worm gearing driven by rotation of the rotor head, Fig. 10 (not shown), or an electric motor, Figs. 11 and 12 (not shown), to wind in the arm, and is declutched from the worm gearing to permit paying out, or the electric motor is reversed. Retraction of the arms may be initiated automatically when sufficient forward speed is attained to enable fixed wings to generate adequate lift.