Patent GB-444395-A (GB)
Title: Improvements in and relating to aircraft sustaining rotors
IPC: B64C27/02
Filed: 1934-09-17
Abstract: 444,395. Aircraft with rotary-wing systems. CIERVA AUTOGIRO CO., Ltd., Bush House, Aldwych, London, and HODGESS, F. L., and BENNETT, J. A. J., Holm Foundry, Cathcart, Glasgow. Sept. 17, 1934, No. 26662. [Class 4] In an aircraft sustaining rotor having an even number of blades symmetrically disposed about the rotor axis, each pair of oppositely disposed blades being mounted on a common " flapping " pivot system whose axis intersects the rotor axis, a blade interconnecting member is provided rotatable with respect to the hub and constituting a load transmitting connection between the root members of the opposite blades one at least of which is rotatable on this member to allow independent flapping of the blades. In one form, Figs. 1 and 3, a rotor axle member 26 is mounted for universal tilting movement on a mast 21 through the intermediary of a star joint member 23 of which the axis of rotation is horizontal and transverse of the aircraft. A hub member 27, 28 is rotatably mounted on axle 26, its lower part 28 enclosing the universal joint mounting of the axle and being flared outwardly at 30 to provide a mounting for starter gear ring 31 and to constitute a brake drum. Two rotor blades are articulated by substantially vertical drag pivots 37 to drag links 35, 36, respectively, so shaped as to embrace the hub member and connected thereto by coaxial flapping pivots spaced diametrically opposite to one another as shown in Fig. 3. Each flapping pivot assembly comprises a housing 38 secured by studs 39 to hub member 28 and carrying a pivot pin 40 on which is rotatably mounted a floating sleeve 41. The inner ends 42, 43 of links 35, 36 are rotatable on sleeve 41, the ends 42 of link 35 being bifurcated and the single ends 43 of link 36 fitting between these bifurcations Needle bearings 44, 45, 46 are used between the pivot pin and floating sleeve and between the latter and the drag links. Bushes 42‹, 43‹ may be inserted in the bored ends of the drag links. The axes of pivot pins 40 and of the intersecting elements of star joint member 23 are coplanar. Tilting of the rotor axle for control purposes is effected by means of tube 49 carried at its upper end by a bracket 48 bolted to star joint member 23 and connected at its lower end to a control lever through means providing that movements of tube 49 in response to control lever movements are opposite in direction. Bracket 48 supports a lever 52 carrying a brake shoe 47 operated by control cable 53 and return spring 54. Engagement of the starter gear pinion with gear ring 31 is effected only on extreme forward tilting of the rotor axle. In a modified form, Fig. 5, the floating member of the flapping pivot assembly is constituted by a hollow pin 55 which is extended axially in the directions beyond the central part forming the inner race of the drag link needle bearings and is supported in roller bearings 56 of which the outer races are mounted directly in the flapping pivot housing 38. The drag links are each formed in the one single and one' bifurcated yoke end and are thus interchangeable. In another form, Figs. 6 and 9, the hub member comprises an upper part 27<x> and a lower part 28<x>, the latter being formed by brackets constituting housings 58 for the flapping pivot assemblies to which driving ring 31 is secured by studs 59. Ring 31 is further supported by brackets 60, Fig. 9, secured by studs 61 to member 28<x>. The rotor support comprises struts 62 and an apex member 63 formed with lateral standards 64 supporting in ball bearings 24 the transverse axis pin 23<x> of universal joint assembly 23. Fore-and-aft axis pin 23‹ supports by bearings 25 the rotor axle member 26 which is extended downwardly below to universal joint to socket into a tube 65 connected to the flying controls, the axis member being apertured at 26‹ for the passage of pin 23<x>. An internal-expanding brake is fitted acting on a brake drum 71 secured by bolts 72 to brackets 60. In a third form, Figs. 11 and 12, the rotor supporting structure consists of a pair of V-struts 73 spaced transversely of the craft, the universal joint assembly being formed as a gimbal ring structure comprising outer and inner rings 74, 75. Outer gimbal ring 74 is supported by struts 73 on transverse coaxial pivots 76 arranged slightly in advance of the axis of the rotor axle. Inner gimbal ring 75 is supported by fore-and-aft pivots 77 and is formed integrally with a hollow central housing 78. Rotor axle 81 is journalled in housing 78 and terminates upwardly in a forked standard 82 bored transversely to receive a hollow floating pin 83 on the outer surface of which the ends of drag links 84, 85 are rotatably mounted, the end of link 84 lying between the jaws of the forked end of link 85. The outer ends of links 84, 85 are formed as bearing housings for outwardly inclined ends of drag pins 87, the latter being formed on the inner ends of goose-necked blade root members 88. Rotor axle 81 carries at its lower end a toothed ring 94 meshing with starter pinion 93 of which the shaft is mounted a housing 90 carried by a bracket secured to part 78. The inner face of ring 94 constitutes the drum of the rotor brake. Web member 79 connecting housing 78 with the inner gimbal ring carries a rotor tilting control arm 96. The latter also serves to support flexible drive 99 of the rotor tachometer. Friction dampers 102, Fig. 14, may be provided for damping oscillations of the rotor blades on the drag pins. In a still further form, Fig. 15, rotor axle member 201 carries hub member 204 by means of bearings 202, 203, a divided flapping pivot assembly being carried by brackets 205 integral with the hub member. A flapping pivot pin 206 carries a pair of taper roller bearings 207 on which is rotatable a sleeve 208. The drag link members are of yoke form each having single ends bored to embrace sleeve 208, the end 209 of one link is rigidly secured to sleeve 208, whilst the end 212 of the other link is rotatably mounted on the sleeve. The rotor axle is mounted by means of a universal pivot assembly of which the axes are in a plane perpendicular to the axis of rotation and containing the axis of the flapping pivot assembly.