Rotorcraft rotor having a flapping abutment mechanism, and a rotorcraft

Abstract

A rotor carrying a plurality of lift assemblies, each having a retention and mobility member. An abutment mechanism of a lift assembly includes an abutment track arranged on the retention and mobility member and a single cylindrical abutment that is movable in pivoting about a movement axis, said abutment extending over a height in elevation and also over a length and over a width. The length is greater than said width, and said height is greater than said length. A fly-weight is secured to pivot with said abutment, and a return spring exerts a force on said fly-weight.

Claims

1. A rotor for a rotorcraft, the rotor having a hub carrying a plurality of lift assemblies, the hub having at least one plate, each lift assembly having a retention and mobility member connected to the at least one plate of the hub, the rotor having a single abutment mechanism for each lift assembly to limit upward and downward flapping movement of the lift assembly, wherein each abutment mechanism for a lift assembly comprises: an abutment track arranged on a rear face of the retention and mobility member facing an axis of rotation in elevation of the rotor; a single cylindrical abutment hinged to the at least one plate of the hub by hinge means to be movable solely in pivoting about a movement axis between an engagement position in which the flapping movement is limited by shape interference between the cylindrical abutment and the abutment track under at least one predetermined condition, and a disengagement position in which the movement is not limited by the cylindrical abutment, the cylindrical abutment extending over a height in elevation along said movement axis and over a length along a longitudinal axis that is arranged substantially parallel to a span direction of the lift assembly when in the engagement position, and over a width along a transverse axis perpendicular to the movement axis and to the longitudinal axis, the length being greater than the width, the height being greater than the length; a fly-weight constrained to pivot with the cylindrical abutment and laterally offset relative to the longitudinal axis when in the engagement position; and a return spring exerting a force on the abutment mechanism to tend to position the cylindrical abutment in the engagement position.

2. A rotor according to claim 1, wherein the retention and mobility member is a laminated abutment.

3. A rotor according to claim 1, wherein the rear face extends over an elevation distance along an axis parallel to the movement axis, and the elevation distance is less than or equal to the height of the cylindrical abutment.

4. A rotor according to claim 1, wherein the abutment mechanism includes longitudinal clearance between the abutment track and the abutment in the engagement position.

5. A rotor according to claim 1, wherein the rear face represents the abutment track.

6. A rotor according to claim 1, wherein the abutment track includes a removable wear member removably fastened to the rear face.

7. A rotor according to claim 1, wherein the hinge means comprise a tube secured to the cylindrical abutment, the tube being hinged to the at least one plate of the hub.

8. A rotor according to claim 7, wherein the fly-weight is secured to the tube.

9. A rotor according to claim 1, wherein the return spring extends between the fly-weight and the at least one plate of the hub.

10. A rotor according to claim 1, wherein the cylindrical abutment comprises a cylindrical body having a rear portion adjacent to a front portion respectively facing the axis of rotation and the abutment track when in the engagement position, the front portion having a base with a periphery that is rounded in part.

11. A rotor according to claim 10, wherein the front portion has a semicircular base.

12. A rotor according to claim 1, wherein the at least one plate of the hub includes a bottom plate and a top plate, and the cylindrical abutment is arranged between the bottom plate and the top plate.

13. A rotor according to claim 12, wherein the fly-weight is arranged under the bottom plate and/or over the top plate.

14. A rotorcraft, wherein the rotorcraft includes a rotor according to claim 1.

15. A rotor according to claim 1, wherein the movement axis of the cylindrical abutment is parallel to the axis of rotation of the rotor.

16. A rotor for a rotorcraft comprising: a hub having a plate; a lift assembly; a retention and mobility member connecting the lift assembly to the plate of the hub; and a single abutment mechanism comprising: an abutment track arranged on a rear face of the retention and mobility member, the abutment track facing an axis of rotation of the rotor, a single cylindrical abutment element connected to the plate of the hub by a hinge for movement solely in pivoting about a movement axis between an engagement position and a disengagement position, the abutment element extending from an upper distal end to a lower distal end along the movement axis to define a height of the abutment element therebetween, the abutment element extending from a front portion to a rear portion along a longitudinal axis to define a length therebetween, the longitudinal axis being parallel to a span direction of the lift assembly when in the engagement position, and the abutment element extending between two opposed side faces along a transverse axis perpendicular to the movement axis and to the longitudinal axis to define a width therebetween, wherein the length is greater than the width, and the height is greater than the length, a fly-weight connected to and constrained to pivot with the abutment element, the fly-weight being laterally offset relative to the longitudinal axis when in the engagement position, the fly-weight configured to tend to position the abutment element in the disengagement position in response to rotation of the rotor, and a return spring exerting a force on the abutment mechanism to tend to position the abutment element in the engagement position, wherein the front portion of the abutment element is configured to contact the abutment track in the engagement position to limit upward and downward flapping movement of the lift assembly, and wherein the abutment element in the disengagement position is configured to not limit flapping movement of the lift assembly.

17. A rotor according to claim 16, wherein the movement axis of the abutment element is parallel with the axis of rotation of the rotor.

18. A rotor according to claim 16, wherein the front portion of the abutment element has a rounded periphery.

19. A rotor according to claim 16, wherein the plate of the hub is an upper plate; wherein the hub has a lower plate, the retention and mobility member connecting the lift assembly to the lower plate of the hub, and the single abutment element connected to the upper plate of the hub by the hinge; and wherein the abutment element is positioned between the upper and lower plates.

20. A rotor according to claim 16, wherein the abutment element is positioned between the retention and mobility member and the axis of rotation of the rotor.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the following description of embodiments given by way of illustration and with reference to the accompanying figures, in which:

(2) FIG. 1 is a view of a rotor having a two-plate hub provided with a mechanism of the invention;

(3) FIG. 2 is a diagram showing a rotor having a one-plate hub provided with a mechanism of the invention;

(4) FIG. 3 is an exploded view of such a mechanism;

(5) FIG. 4 is a section view of an abutment; and

(6) FIGS. 5 and 6 are views explaining the operation of the mechanism.

(7) Elements present in more than one of the figures are given the same references in each of them.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIG. 1 shows a rotorcraft 1 having a rotor 2. The rotorcraft 1 and the rotor 2 are shown in part only, in order to avoid overburdening FIG. 1.

(9) The rotor 2 is provided with a hub 5 secured to a rotor mast 3 that is rotatable about an axis of rotation AX1. The hub 5 possesses at least one plate for carrying a plurality of lift assemblies 10.

(10) The embodiment of FIG. 1 presents a hub having a top plate 6 and a bottom plate 7 defining in elevation a space suitable for receiving the lift assemblies 10 in part.

(11) The embodiment of FIG. 2 shows a hub having a plate 8 provided with recesses 9 capable of receiving the lift assemblies 10 in part.

(12) Independently of the embodiment, and with reference to FIG. 1, each lift assembly 10 may comprise a lift element 11 and a cuff 12 incorporated in the lift element or fastened to the lift element 11. The cuff constitutes the member enabling the lift element to be fastened to a retention and mobility member 15 secured to the hub 5.

(13) Such a retention and mobility member 15 may comprise a laminated abutment 19. The retention and mobility member 15 may then for example be provided with an “outer” strength member 16 and an “inner” strength member 17 fastened to at least one plate of the hub, and a laminated member 18 connecting the outer strength member 16 to the inner strength member 17. The outer strength member 16 then possesses a “rear” face facing towards the axis of rotation AX1 and a “front” face that is fastened to the laminated member 18.

(14) Such a retention and mobility member enables a lift element to be hinged about an axis for flapping movement, an axis for pitch movement, and an axis for lead/lag movement, for example.

(15) Furthermore, the rotor 2 is provided with a mechanism 20 for each lift assembly in order at least to limit the flapping movement of the lift assembly during predetermined stages. In particular, the mechanism is active for limiting this flapping movement below a threshold speed of rotation of the rotor. Consequently, for each blade, the rotor 2 has a single mechanism 20.

(16) An abutment mechanism 20 thus includes an abutment track 25 arranged on the rear face 16′ of the retention and mobility member 15.

(17) In the embodiment of FIG. 1, this rear face 16′ represents the abutment track. The rear face may possibly be covered in a protective deposit.

(18) In the embodiment of FIG. 3, the mechanism comprises a wear member 26, e.g. a sheet. This wear member is then fastened reversibly to the retention and mobility member in order to cover the rear face 16′.

(19) With reference to FIG. 1, a mechanism 20 also includes a single abutment 30 for interfering by shape interference with the abutment track 25 in order at least to limit flapping of the lift assembly.

(20) This single abutment 30 is also movable in pivoting about a movement axis AX2 in order to be retractable. In a position referred to for convenience as the “engagement” position, the abutment 30 can block any flapping movement by abutting against the abutment track 25. Consequently, for each blade, the rotor 2 has a single mechanism 20, with this single mechanism 20 having a single abutment 30 for limiting the upward and downward flapping movement of the lift assembly under predetermined conditions.

(21) Conversely, the abutment 30 may be turned so as to be put into a position referred to for convenience as the “disengaged” position. In the disengaged position, the abutment is no longer in a position to block any flapping movement because it is spaced apart from the abutment track 25.

(22) Furthermore, the mechanism includes a fly-weight 45 for controlling pivoting of the abutment 30. As a function of the speed of rotation of the rotor, centrifugal force acts on the fly-weight, thereby causing the abutment 30 to turn.

(23) In addition, the mechanism includes a return spring 50 extending between the fly-weight 45 and the hub 5. The return spring tends to position the fly-weight and the abutment in the engagement position.

(24) FIG. 3 is an exploded view of the mechanism 20.

(25) The abutment 30 is an abutment that is cylindrical. The term “cylindrical” is used of an abutment to indicate that it has the shape of a cylinder, namely a volume obtained by sweeping a generator line around the periphery of a base.

(26) With reference to FIG. 4, the cylindrical abutment may be subdivided into a rear cylindrical portion 31 adjacent to a front cylindrical portion 32. In the engagement position shown diagrammatically in FIG. 3, the rear portion faces the axis of rotation AX1 while the front portion 32 faces the retention and mobility member 15.

(27) The base of the rear portion 31 may be rectangular, or it may match the shape of a surface of the hub, for example.

(28) The base of the front portion may possess a rounded periphery, e.g. being semicircular.

(29) With reference to FIG. 3, the cylindrical abutment extends in elevation along the movement axis AX2 over a height 41. This movement axis may for example be parallel to the axis of rotation AX1 of the rotor.

(30) Furthermore, the cylindrical abutment extends lengthwise along a longitudinal axis AX3 over a length 42. This longitudinal axis AX3 may for example be orthogonal to the movement axis AX2, regardless of the position of the abutment 30. In contrast, the longitudinal axis AX2 may optionally be orthogonal to the axis of rotation and/or parallel to the axis in which the lift assembly extends spanwise when the abutment 30 is in the engagement position POS1 as shown in FIG. 3.

(31) The cylindrical abutment extends widthwise along a transverse axis AX4 over a width 43. This transverse axis AX4 is for example orthogonal to the movement axis AX2 and to the longitudinal axis, regardless of the position of the abutment. In contrast, the transverse axis AX4 is optionally orthogonal to the axis of rotation and/or parallel to a span axis of the lift assembly when the abutment 30 is in the disengagement position.

(32) Under such circumstances, the height 41 of the abutment 30 is greater than its length 42, which length 42 is greater than its width 43.

(33) Furthermore, the rear face 16′ extends over a distance 44 in elevation along an axis parallel to the movement axis AX2, with this distance 44 in elevation being less than or equal to the height 41 of the abutment.

(34) The mechanism then has hinge means 35 in order to enable the abutment to pivot relative to the hub.

(35) The hinge means may comprise a tube 36 hinged directly or indirectly to at least one of the plates of the hub. The tube 36 possibly passes right through the abutment 30, e.g. through its rear portion 31.

(36) The tube 36 may also carry the fly-weight 45. The fly-weight is offset laterally relative to the abutment 30.

(37) The fly-weight may thus comprise a heavy element 46 connected to the tube 36 by a rod 47. The term “heavy element” designates a member of mass that is much greater than that of the other members of the fly-weight.

(38) By way of example, the rod 47 extends parallel to the transverse axis AX4, and thus orthogonally to the movement axis AX2. In the engagement position, the fly-weight thus extends at an angle of 90° relative to the lift assembly, and is substantially parallel with the lift assembly in the disengagement position.

(39) The return spring may then be connected for example to the rod 47 of the fly-weight and also to a plate of the hub.

(40) In FIG. 1, the tube is fastened by conventional members to both plates of the hub, these members giving the tube a degree of freedom to move in pivoting about the movement axis AX2.

(41) The abutment is then arranged between the top plate 6 and the bottom plate 7. In contrast, the fly-weight may for example be positioned beneath the bottom plate 7.

(42) In FIG. 2, the abutment is arranged in a recess 9 in a hub having a single plate 8. By way of example, the tube 36 is connected to the plate 8 by two arms 200 extending on opposite sides of the plate 8. One of the arms is thus situated above the plate 8 while the other arm is situated under the plate 8.

(43) FIGS. 5 and 6 show the operation of the abutment. Although this operation is shown with a hub that has two plates, the operation that is described applies equally well to a hub having only one plate.

(44) With reference to FIG. 5, the abutment is in the engagement position POS1 when the hub is not rotating. A small amount of clearance 100 might possibly lie between the front portion 32 of the abutment and the abutment track 25. It can be understood that flapping movement of the lift assembly relative to the flapping axis AX5, as represented by double-headed arrow F1, is then not possible.

(45) When the rotor is set in rotation, centrifugal force acts on the fly-weight 45 in the direction of arrow F2 and causes the fly-weight to turn in the direction represented by arrow F3.

(46) The fly-weight and the abutment then turn about the movement axis AX2. The clearance 100 then increases given the particular shape of the abutment 30.

(47) As from a threshold, the fly-weight 45 is directed along a radius of the rotor, i.e. substantially along an axis along which the lift assembly extends. Turning of the abutment is then complete. The abutment 30 is then in the disengagement position POS2, in which the clearance 100 is maximized.

(48) This clearance 100 serves to guarantee that there is no interference between the abutment and the retention and mobility member by maintaining some minimum amount of clearance even during flapping of the lift assembly.

(49) When the rotor is stopped, a return to the engagement position is made possible by the return spring 50.

(50) Furthermore, it should be observed that for maintenance actions, the fly-weight enables action to be taken manually on the abutment 30 in order to release movements of the blade.

(51) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several embodiments are described, it will readily be understood that it is not conceivable to identify exhaustively all possible embodiments. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.