Patent GB-606420-A (GB)
Title: Improvements in or relating to helicopters
IPC: B64C27/82
Filed: 1945-01-15
Abstract: 606,420. Helicopters. AVERY, H. T. Jan. 15, 1945, No. 1173. Convention date, July 14, 1941. [Class 4] An aircraft having a power-operated sustaining rotor 2 is provided with means for counterbalancing the turning moment exerted upon the craft by the rotor 2 and which means comprise an auxiliary air-screw 21, rotated from rotor 2 and as shown in sectional plan, Fig. 3, mounted within an obliquely-directed tunnel 19 in the fuselage so that the reaction from the discharge of air by the screw supplies a torque to offset the moment produced by the rotor. In the case of a helicopter with a single tiltable rotor, the pitch of the screw 21 is adjusted to zero and the two sets of pivoted vanes 34 are turned so as to enclose the screw in its tunnel by smooth surfaces conforming to the rest of the fuselage surface, a counterbalancing torque for the rotor moment being obtained by means of a rudder 27 and fixed stabilizing surfaces to receive the air stream from the rotor; the rudder post 29 is angled downwardly to the right, the rotor 2 turning in clockwise direction. Automatic adjustment means for the engine throttle setting is provided to keep the rotor torque in balance with the anti-torque effect of the rudder and stabilizing surfaces. When the craft is not in normal forward flight, but is ascending, descending, hovering or advancing very slowly, the antitorque effect of the rudder and stabilizing surfaces may be supplemented by automatic adjustment of the pitch of the auxiliary screw 21. The pivoted vanes 34 may be connected to the pitch-changing means or the vanes may be turned against biassing springs 37 to the open position shown by the air discharge of the screw. In plan, Fig. 4, and elevation, Fig. 5, there is shown a directional unit in the form of a gyroscopic rotor 40 with a gimbal mounting 42 pivoted in a yoke 44, turning upon a vertical shaft 46 and carrying a horizontal arm 48 connected by link 51 to the engine throttle control lever 53. Should the craft turn, owing to lack of balance between the rotor torque and the anti-torque means or to other causes, the link 51 turns lever 53 to alter the rotor torque so as to obtain a relation of the two torques resulting in the return of the craft to the course set by the gyroscope direction. Steering by rudder not being possible in the conditions described, means are provided for altering the direction of the gyroscope, the craft automatically adjusting itself to this changed direction. Turning of the steering-wheel 60, Fig. 4, changes the direction of arm 48 by causing azimuthal precession of the gyroscope through linkage 94, 100 acting upon gimbal ring 42, for which a clamping lever 282, Fig. 7, is provided to keep the gyroscope out of action when the craft has landed; a pivoted lever 285, provided with a catch 287 to keep the clamping lever raised during flight, is lifted up by rod 294 when the wheel 15 meets the ground. The pivoted pawl-and-ratchet gear shown in Figs. 4 and 5, together with the springs, exerts a centring effect upon wheel 60. In Fig. 9 is shown means for controlling the anti-torque effect and hence the engine output. The control lever 180 is pivoted at 185 on link 181, slidably mounted in a fixed sleeve 182 and urged to the left by a spring 184; when lever 180 is pushed leftwardly, cord 186 turns the rudder 27 counterclockwise, , thereby increasing the anti-torque effect and the gyro unit will increase the engine power to balance it. When maximum displacement of the rudder is reached, further leftward pressure on the upper end of lever 180 will. turn it about a pivot on link 187, now stationary by reason of the arrest of cord 186, and force link 181 to the right to actuate the pitch-control of the auxiliary screw 21. Direct control of lever 53 by lever 180 is obtained by means of additional cord 340 passing over pulleys 344 mounted on a link 345, lowered into the position shown when the aircraft lands by means of block 353 carried on the rod 294 used for clamping the gyro shown in Fig. 7; the block turns a lever 350, pivoted at 348 and connected to the top of the pulley-carrying link 345, the lever 350 being made in two parts connected by spring 349 to allow extra movement of block 353 to occur on landing without overstraining the cord 340. An alternative form of-automatic torque-balancing mechanism shown in Figs. 10, 12 and 13 includes hydraulic means for applying pressure to the gyroscope gimbal ring 42 to produce precession for steering the aircraft. The fork 44, integral with shaft 164 turning freely in a fixed journal 165, carries bearings for the gimbal pivots 45, one of these having fixed to it an arm bearing a vane 116, Fig. 10, movable in a tubular member 119 shaped to a circle concentric with the pivot pin 45 and filled with hydraulic liquid by means of which the vane is caused to swing the gimbal ring when steering-wheel 60 is turned to move the sliding valve member 141 to supply pressure liquid on either side of the vane; means utilizing the consequent precession of the gyro rotor is shown in plan, Fig. 13. The gyroscope is contained in a spherical casing 169 from which a pump driven by the rotor 2 exhausts the air admitted from outside through a tube 162 and jet 161 to drive the gyro rotor, and vertically narrow ports 311, 312 provided in the casing 169 are differentially opened and closed by curved plates 314, carried by fork 44 and closely fitting the casing, as the fork turns in precession. The ports 311, 312 communicate by flexible pipes with a cylinder 304 in which a piston 302 works to move rod 301 to actuate the engine throttle lever either directly or by incorporation in a system such as is shown in Fig. 14. Bleed holes 305, 306 admit air into the cylinder 304 on each side of the piston 302 and the difference in pressure on the two sides produced by the differential action of plates 314 on the ports 311, 312 moves the rod 301; in order to avoid an overbalancing adjustment, the iod 301 adjusts gyro casing 169 through a small turn by an attached lever 317 linked to an arm 322 integral with the casing, the linkage being made capable of transmitting a force without yielding appreciably in a short time, but capable of yielding slowly to a continuing pressure exerted by a spring centring system for casing 169. The linkage shown comprises a hydraulic cylinder with a small leak through its piston. The' control mechanism of Fig. 14 operated by pedal 190 for control during landing, take-off or hovering includes the automatically-controlled rod 301 of Fig. 13, servomotor means for setting anti-torque rudder 27, and other servomotor means for controlling the pitch of the auxiliary screw 21. Depression of pedal 190 moves the lever 192, carrying it away from fixed frame 194, and thus rotates the connected lever 197 about a pivot 200 connecting it to a horizontal link 199 connected at 208 to a lever 202, placed on a fixed pivot 201 and positioned by a stud 251 on the end of rod 301; unless rod 301 is moved by changes in the heading, the link 199 is fixed, thus fixing the pivot 200. Lever 197 turns vertical lever 206, which is pivotally mounted on one end of the piston-rod 222 of a power cylinder 219 and thus moves the piston-rod 211 of cylinder 215 controlling cylinder 219 for operating rudder 27 to increase the anti-torque and to turn cam 242 to move throttle lever 53 by links connected to pivoted lever 257. When rudder 27 has reached its position of maximum torque, the piston of cylinder 219 is stopped from further movement and increased pedal depression will advance the piston-rod of cylinder 215 to cause its end 261 to turn a pivoted rod 262 to move, through servomotor means, a rod 181 for altering the pitch control of the auxiliary screw 21 for supplying further anti-torque. The rotor head and tilting means are shown in Fig. 15. The head of the powerdriven shaft 10 has a universal joint 417 including ring 418, connected by pins 421 to ring 422 on the shaft 10 and to intermediate drive shaft 419 keyed to outer support housing 407, which is supported on a part-spherical bearing ring 404; a lower part-spherical bearing ring 412 concentric with ring 404 is also provided. Lever 414 secured to the lower part of the outer housing is operated through a link 425 to tilt the rotor about the centre 405 of the bearing rings. U.S.A. Specifications 1,993,701 and 2,220,109 are referred to.