Patent GB-848213-A (GB)
Title: An arrangement for a cyclic pitch control of rotors of rotorcraft
Inventor: SCHON RICHARD
IPC: B64C27/54
Filed: 1957-02-20
Abstract: 848,213. Controlling helicopters. VYZKUMNY A ZKUSEBNI LETECKY USTAV. Feb. 20, 1957, No. 5748/57. Class 4. (1). An arrangement for the cyclic pitch control of rotors of rotorcraft comprises a swash-plate having an outer rotatable part and an inner non-rotatable part, which swashplate is tiltable by means of expansible pillars engaging at their upper ends the outer peripheral cage of its non-rotating part, a cam member slidable longitudinally and/or laterally by mechanism connected to the pilot's control lever, having side surfaces each inclined at an angle to the plane of the movement of the cam member, which surfaces are engaged by the lower ends of the pillars, the angle of inclination of the side surfaces of the cam member being less than the angle of friction for the material of the engaged side surfaces and the material of the lower ends of the pillars, and rods connected between the rotatable part of the swash-plate and the pitch controlling arms of the rotor blades, whereby due to the provision of the cam member and the expansible pillars any transmission of the action of forces from the rotor to the pilot's control lever will be prevented. One rotor blade 1.1 only is shown connected by pitch control arm 1.2 and link 3.8 to the rotatable element of a swash-plate 3.7, the centre fixed element of which bears against balls 6.5, each mounted in the upper end of the smaller piston of a two-component jack, the lower, larger piston carrying a further ball 6.1 which rests on one of four inclined faces of a central plate 3.3 having freedom for lateral movement in all directions under the control of levers 3.4 and 3.5 connected respectively by link 3.10 and shaft 3.11 to a pilot's cyclic pitch control arm 3.9. Collective pitch is achieved by the vertical movement of swash-plate 3.7 and its supporting sleeve 3.1, which at its lower end is formed with a control nut 2.1 engaging a thread on the lower end of a tube 1.7 through which the rotor shaft 1.5 passes. The nut 2.1 is rotated by linkage 2.2 and 2.3 connected to the collective pitch control rod 2.4. The rotor head 1.3 is tiltable and is coupled by two levers 1.4, mutually, at right angles (one only shown in Fig. 1) and rods 5. 2 to an auxiliary swash-plate 5.1 mounted on a tube 1.7, the non-rotatable element being connected by rods 5.3 and 5.4, (the latter being shown only in Fig. 2) to levers 4.3 each secured to a torsion box housing 4.4 mounted in a frame 4.2 which is secured by gimbals 4.1 to the sleeve 3.1. The torsion shaft 4.5 enclosed by and anchored at one end to each tube is connected respectively by a lever 4.6 and 4.8 to tie rods 4.7 and 4.10. The rod 4.7 is secured to a lever 3.13 mounted on a shaft 3.11 so that movement of the rotor head is transmitted through a torsion box as a sense of " feel " to the pilot's control-arm 3.9 as the result of lateral cyclic pitch control movements. Longitudinal cyclic pitch " feel " is transmitted to control-arm 3.9 from the other torsion box through lever 4.8 and rod 4.10 which at its other end is connected to lever 3.4. This system incorporates a clutch actuated by a pilotcontrolled Bowden cable 4.9 so that the torsion box can be set to a neutral position for a selected fore and aft trimmed attitude of the aircraft.