GB639351A - Improvements in or relating to helicopters - Google Patents

Abstract

639,351. Helicopters. GRAY, H. D. March 1, 1948, Nos. 6404, 6405, and 9680. [Class 4] A contra-rotating rotor system for a helicopter comprises an inner shaft driving a concentric outer shaft, with an upper rotor head mounted on the upper end of the inner shaft and a lower rotor head mounted on the upper end of the outer concentric shaft, each rotor blade being connected to its respective head by link mechanism supported on rotary couplings capable of vertical movement on the shafts to effect simultaneous pitch change of all the blades and in which the lower end of the inner shaft is mounted in bearings in a wheel case carried by a housing supporting a ball member and a universal joint which enables the inclination of the rotor shafts and the rotors to be varied. The rotor drive system is mounted on a hollow ball member B which is free to tilt in a housing A attached to the helicopter structure. Mounted on the ball member B is a turret C and a tube E. An inner rotor driveshaft F is connected through a universal bearing R to a driveshaft Q and carries a bevel wheel G supported in a casing D by a bearing K and engaging through planetary bevel wheels H with a further bevel wheel I fixed to an outer rotor shaft J supported in the housing D by a bearing M. The outer shaft J is supported by a further bearing 0 and in turn carries a still further bearing P to provide an upper support for the inner shaft F. The pitch control arm of each upper rotor blade is connected by a link 12 to a disc 11 rotating with, but free to slide axially on, the inner shaft F and connected to a member 9 held between thrust bearings enclosed in a casing 8 attached to a disc 7 coupled by rods 6 to a further disc 4 with which it revolves in a direction opposite to that of the disc 11. Links 5 connect the pitch control arms of the lower rotor blades with the disc 4 which carries, in a depending cage 3, thrust bearings supporting a collar 2 surrounding but spaced from the outer rotor shaft J. Axial movement of the discs 4 and 7 to effect collective pitch control of the rotor blades is achieved by pivoting a stirrup 1 mounted on the collar 2 to an arm 17 which is connected by rods 14, 15 and 16 and arm 13 to the ends of flexible cables 21, 22 mounted within the ball member B and actuated by a pilot-controlled lever (not shown). Attached to the inner surface of the ball member B are two ball-ended fittings S positioned at 90 degrees to one another in the horizontal plane and to which are connected link rods for effecting tilting of the rotor head in any azimuth. In order that the rotor head may be locked in a selected position the housing A accommodates a split band urged into gripping engagement with the ball member B by springs adjusted by screwed caps 37 and released by a cam actuating lever 39 connected by a cable control to a hand lever on the pilot's control column in such a position that it can be gripped to free the rotor head before the control column is moved. U.S.A. Specification 2,037,745 is referred to.