Variable-pitch rotor, specially for a rotary-wing aircraft

Claim 1

A variable pitch rotor, specially for a rotary-wing aircraft, comprising a hub, at least one blade and one elongate connecting member, connecting said blade to said hub, said connecting member comprising a substantially radial bundle of fibres having high mechanical strength, each fibre being agglomerated by a resin and secured to the other fibres by a vulcanized elastomer, so that said connecting member is sufficiently flexible to be deformed, to permit beat and drag movements of the blade and variations in its pitch, at least one rigid tubular sleeve disposed in a spaced and surrounding relationship to said connecting member, the outer end of said sleeve being secured to the root part of the blade, a rigid ring which is secured to the inner end of said sleeve and to which a blade pitch control level is externally articulated, spherical ball and socket joint members inserted between said rigid ring and rigid parts of said hub, and frequency adaptors, each associated with one of said ball and socket joint members, said ball and socket joint members essentially consisting of laminated elastomer, said frequency adaptors essentially comprising plates of elastomer having great rigidity and high hysteresis, said frequency adaptor plates inserted between said spherical ball and socket joint members and said rigid parts of said hub, said ball and socket members essentially comprising laminated elastomer and said frequency adaptor plates respectively incorporated in said ball and socket joint members, said bundles of fibres of said connecting members of at least two blades being parts of a single bundle of fibres having at least one intermediate part incorporated in the rotor hub, the thickness of said hub perpendicular to the rotor plane being slightly greater than the thickness of said connecting members, and the rigid parts of the hub bearing said spherical ball and socket joint members being rigid metal plates, which are secured to the top and bottom surfaces of the hub respectively, and which extend radially in a spaced relationship to both faces of each elongate radial connecting member over a predetermined fraction of the length of said connecting member.