Rotorcraft rotor comprising a hub made of composite materials obtained from carbon fiber fabric dusted in a thermoplastic resin

Patent metadata

Field	Value
Publication number	US-2016200433-A1
Application number	US-201614989142-A
Country	US
Kind code	A1
Filing date	Jan 6, 2016
Priority date	Jan 8, 2015
Publication date	Jul 14, 2016
Grant date	—

Abstract

A rotorcraft rotor comprising a hub made up of a monolithic body of composite material obtained by stacking successive layers of carbon fiber fabric dusted with a thermoplastic resin and compressed while hot. The hub is provided with branches on which respective blades are mounted via hinge systems, each including a strength member bearing radially against a corresponding branch. The strength members are individually received in sockets defined on fabrication so that when the rotor is set into rotation at a predefined operating speed, the radial thrust seat for enabling the strength members to bear against the branches present bearing surfaces that are cylindrical, the radial thrust seats then being of shape complementary to a cylindrical bearing surface of the corresponding strength member.

First claim

What is claimed is:

1 . A rotorcraft rotor having a hub made of composite material obtained by stacking successive layers of mineral fiber fabric that are impregnated with a resin, the hub firstly being mounted coaxially around a rotary shaft extending through a bore in the hub, and secondly including a plurality of branches extending radially from the bore, which branches have respective individual blades mounted thereon, the blades being individually mounted to be movable relative to the hub at least for varying pitch; wherein:
the hub is formed essentially by a monolithic body of composite materials obtained by stacking successive layers of carbon fiber fabric dusted with a thermoplastic resin and compressed while hot; the blades are individually mounted to be movable relative to the hub by respective hinge systems, each having a respective assembly strength member for assembling to a respective one of the branches, the strength member bearing radially against the branches while being individually housed at least in part in respective sockets of the monolithic body, extending in its axially-extending direction; and the sockets being deformable under the effect of the rotor being set into rotation, the shape of the sockets is defined on fabrication so as to form a radial thrust seat enabling the strength members to bear against the branches via respective bearing surfaces that become cylindrical under the effect of the rotor being set into rotation at a predefined operating speed, the radial thrust seat having a cylindrical bearing surface extending along a generator line oriented in the axially-extending direction of the hub and being of shape that is complementary to a given cylindrical bearing surface of the strength member.

2 . A rotorcraft rotor according to claim 1 , wherein the profile of each socket in the diametral plane of the hub is generally oblong in shape, defining a respective circular arc providing the surface portion of the socket that forms the radial thrust seat whereby the strength member bears against the branch; and wherein a first radius of the circular arc as defined by fabrication is greater than a second radius that is imparted to the circular arc under the effect of the rotor being set into rotation at the predefined operating speed, the second radius in the operating situation of the rotor defining the radial thrust seat with a cylindrical bearing surface whereby the strength member bears against the branches.

3 . A rotorcraft rotor according to claim 1 , wherein the portions of the surfaces of the sockets that form radial thrust seats for enabling the strength members to bear against the branches are free from any tapers for unmolding the monolithic body.

4 . A rotorcraft rotor according to claim 1 , wherein each strength member has an elastomer/metal laminated body providing multidirectional freedom of movement for the blades on the hub, and the strength members are placed respectively to bear radially against the branches via respective cylindrical bearing surfaces defined by generator lines extending in the axially-extending direction of the hub.

5 . A rotorcraft rotor according to claim 1 , wherein at least one of the axial end faces of the monolithic body is inclined at least in part relative to the plane of rotation of the hub, and the monolithic body is provided with wedges for compensating the slope that results from the inclination of the at least one axial end face of the monolithic body, the wedges providing axial thrust seats on the hub for enabling the strength members to bear against the branches.

6 . A rotorcraft rotor according to claim 5 , wherein the wedges are incorporated in the monolithic body by molding.

7 . A rotorcraft rotor according to claim 6 , wherein the wedges are incorporated more particularly in the monolithic body by overmolding, the wedges being obtained from composite materials incorporating mineral fibers embedded in a thermoplastic resin.

8 . A rotorcraft rotor according to claim 1 , wherein the blades are also mounted to be movable with lead/lag motion relative to the hub, and the peripheral end faces of each of the branches are provided with respective protector members.

9 . A rotorcraft rotor according to claim 8 , wherein the protector member may equally well be formed by a wear part and/or by an abutment member limiting the individual lead/lag stroke of a blade.

10 . A rotorcraft rotor according to claim 8 , wherein each of the protector members is fitted with fastener tabs bearing respectively against the axial end faces of the monolithic body, and being fastened to the peripheral end of the corresponding branch by first fastener members extending through respective first passages provided in the monolithic body in its axially-extending direction.

11 . A rotorcraft rotor according to claim 1 , wherein the monolithic body is of thickness that decreases progressively from an axially-central zone in which at least the bore is provided, towards the outer margin of a peripheral zone of the monolithic body incorporating the branches.

12 . A rotorcraft rotor according to claim 1 , wherein the monolithic body is symmetrical on either side of a diametral plane that is an axial midplane.

13 . A rotorcraft rotor according to claim 1 , wherein the branches project towards the periphery of the monolithic body, and the projecting portions of the branches present a radially-extending dimension lying in the range 0.2 to 0.3 times the outside diameter of the monolithic body, and with reference to a given branch, the distance between the peripheral end of a branch and the radial thrust seat whereby a strength member bears against the branch lies in the range 0.1 to 0.15 times the outside diameter of the monolithic body.

14 . A rotorcraft rotor according to claim 11 , wherein the monolithic body comprises:
the axially-central zone of a constant thickness in which there are provided at least the bore and second passages extending along the axially-extending direction of the hub and distributed in a margin around the bore, the second passages receiving second fastener members for fastening the hub to at least one plate of the rotary shaft placed facing either one of the axial end faces of the hub; and the peripheral zone radially extending the axially-central zone while decreasing progressively in thickness towards its periphery from the thickness of the axially-central zone, the peripheral zone including at least part of each of the sockets for receiving respective strength members and third passages oriented along the axially-extending direction of the hub, the third passages receiving third fastener members fastening the strength members to the hub.

15 . A rotorcraft rotor according to claim 12 , wherein:
the thickness of the monolithic body at its periphery lies in the range 30% to 40% approximately of the thickness of the monolithic body in its axially-central zone; and the outside diameter of the monolithic body lies in the range six to ten times approximately the thickness of the monolithic body in the axially-central zone.

16 . A rotorcraft rotor according to claim 10 , wherein each of the first passages and/or the second passages and/or the third passages may equally well be provided with a respective reinforcing ring.

17 . A rotorcraft rotor according to claim 16 , wherein the reinforcing rings are incorporated in the monolithic body by sealing.

18 . A rotorcraft rotor according to claim 16 , wherein the reinforcing rings are incorporated in the monolithic body by overmo

Assignees

• Airbus Helicopters

Inventors

• Ferrant Matthieu
• Mazet Stephane

Classifications

• B64C27/48

  Root attachment to rotor head · CPC title

• B64C27/39 Primary

  with individually articulated blades, i.e. with flapping or drag hinges · CPC title

• B64C11/02 Primary

  Hub construction · CPC title

• B64C27/32

  Rotors · CPC title

• B64C27/021

  Rotor or rotor head construction (for helicopters B64C27/32) · CPC title