Rotorcraft rotor including a flapping abutment mechanism, and a rotorcraft

Abstract

A rotor for a rotorcraft, the rotor having a plurality of lift assemblies, together with a flapping abutment mechanism for each lift assembly. Each abutment mechanism has a projection secured to a lift assembly with an abutment end provided with an inner face and an outer face, and at least one pivotally-mounted lever extending longitudinally from a flyweight to a hook. The hook is provided with two walls in elevation and a bottom wall forming a periphery that defines the groove, a first wall in elevation having an upper bearing zone for blocking the inner face and a second wall in elevation including a lower bearing zone for blocking the outer face.

Claims

1. A rotor for a rotorcraft, the rotor comprising: a plurality of lift assemblies and a drive system for driving the lift assemblies in rotation about an axis of rotation, the drive system including a hub that is movably solely in rotation about the axis of rotation, each of the plurality of lift assemblies having a retention and mobility member connected to the hub in order to hinge the lift assembly to the hub about three pivot directions, the rotor having an abutment mechanism for each lift assembly in order to limit the upward and downward flapping movement of the lift assembly under predetermined conditions; wherein each abutment mechanism for a lift assembly comprises: an abutment projection secured to the lift assembly, the abutment projection having an abutment end with an inner face facing the drive system and an outer face opposite from the inner face, the abutment end having an asymmetrical configuration providing the inner face with an upper bearing zone and the outer face with a lower bearing zone; at least one lever that is pivotable about a pivot shaft secured to the drive system, the at least one lever extending longitudinally from a flyweight towards a hook that defines a blind groove suitable for longitudinally surrounding the abutment end in an engagement position and for releasing the abutment end in a disengagement position obtained under the effect of centrifugal force, the hook being provided with two walls in elevation extending up from a bottom wall so as to form a J-shaped periphery that defines the groove, a first wall in elevation having an upper bearing zone, which in the engagement position, blocks the upper bearing zone of the inner face as a result of downward flapping movement of the lift assembly, and a second wall in elevation having a lower bearing zone, which in the engagement position, blocks the lower bearing zone of the outer face as a result of upward flapping of the lift assembly, in the engagement position, the upper bearing zone of the first wall and the upper bearing zone of the inner face intersecting in a higher horizontal plane overlying a lower horizontal plane intersecting the lower bearing zone of the second wall and the lower bearing zone of the outer face; and return means acting on the lever tending to position it in the engagement position.

2. A rotor according to claim 1, wherein the pivot shaft extends along an axis of symmetry contained in a horizontal reference plane situated above the lower bearing zone and below the upper bearing zone when the lever is in the engagement position.

3. A rotor according to claim 1, wherein, in the engagement position, the inner face is not parallel to the first wall in elevation, and the outer face is not parallel to the second wall in elevation.

4. A rotor according to claim 1, wherein the first wall in elevation is not parallel to the second wall in elevation, the first wall in elevation coming closer to the second wall in elevation on going away from the bottom wall.

5. A rotor according to claim 1, wherein the pivot shaft extends along an axis of symmetry contained in a horizontal reference plane, the flyweight being offset relative to the horizontal reference plane.

6. A rotor according to claim 1, wherein at least one mechanism includes a redundant lever, comprising two identical levers arranged symmetrically on either side of a plane in which the lift assembly extends, the two levers being movable in pivoting about a common pivot shaft.

7. A rotor according to claim 1, wherein at least one mechanism includes a support carrying the pivot shaft, the support being fastened to the drive system.

8. A rotor according to claim 7, wherein the support is provided with a pad for the at least one lever in order to limit the pivoting of the lever.

9. A rotor according to claim 7, wherein the support is provided with an abutment track facing the inner face comprising a clear low abutment that is active in flight to block the inner face as a result of downward flapping movement reaching a predetermined amplitude.

10. A rotor according to claim 1, wherein the abutment end includes an edge face extending between the inner face and the outer face and facing the bottom wall in the engagement position, the edge face being arcuate in order to allow the pitch of the lift element to be modified.

11. A rotor according to claim 1, wherein the drive system includes the hub together with a rotor mast secured to the hub and a scissors link element, and at least one lever is attached to the drive system.

12. A rotorcraft, wherein the rotorcraft has a rotor according to claim 1.

13. A rotor for a rotorcraft, the rotor comprising: a plurality of lift assemblies and a drive system for driving the lift assemblies in rotation about an axis of rotation, the drive system including a hub that is movably solely in rotation about the axis of rotation, each of the plurality of lift assemblies hingedly connected to the hub about three pivot directions, the rotor having an abutment mechanism for each lift assembly in order to limit the upward and downward flapping movement of the lift assembly under predetermined conditions; wherein each abutment mechanism for a lift assembly comprises: an abutment projection secured to the lift assembly, the abutment projection having an abutment end with an inner face facing the drive system and an outer face opposite from the inner face, the abutment end having an asymmetrical configuration providing the inner face with an upper bearing zone and the outer face with a lower bearing zone; at least one lever that is pivotable about a pivot shaft secured to the drive system, the at least one lever extending longitudinally from a flyweight towards a hook that defines a blind groove suitable for longitudinally surrounding the abutment end in an engagement position and for releasing the abutment end in a disengagement position obtained under the effect of centrifugal force, the hook being provided with two walls in elevation extending up from a bottom wall so as to form a J-shaped periphery that defines the groove, a first wall in elevation having an upper bearing zone, which in the engagement position, blocks the upper bearing zone of the inner face as a result of downward flapping movement of the lift assembly, and a second wall in elevation having a lower bearing zone, which in the engagement position, blocks the lower bearing zone of the outer face as a result of upward flapping of the lift assembly, in the engagement position, the upper bearing zone of the first wall and the upper bearing zone of the inner face intersecting in a higher horizontal plane overlying a lower horizontal plane intersecting the lower bearing zone of the second wall and the lower bearing zone of the outer face, with the at least one lever being biased to the engagement position.

14. A rotor according to claim 13, wherein the pivot shaft extends along an axis of symmetry contained in a horizontal reference plane situated above the lower bearing zone and below the upper bearing zone when the lever is in the engagement position.

15. A rotor according to claim 13, wherein, in the engagement position, the inner face is not parallel to the first wall in elevation, and the outer face is not parallel to the second wall in elevation.

16. A rotor according to claim 13, wherein the first wall in elevation is not parallel to the second wall in elevation, the first wall in elevation coming closer to the second wall in elevation on going away from the bottom wall.

17. A rotor according to claim 13, wherein the pivot shaft extends along an axis of symmetry contained in a horizontal reference plane, the flyweight being offset relative to the horizontal reference plane.

18. A rotor according to claim 13, wherein at least one mechanism includes a support carrying the pivot shaft, the support being fastened to the drive system.

19. A rotor according to claim 18, wherein the support is provided with a pad for the at least one lever in order to limit the pivoting of the lever.

20. A rotor according to claim 13, wherein the abutment end includes an edge face extending between the inner face and the outer face and facing the bottom wall in the engagement position, the edge face being arcuate in order to allow the pitch of the lift element to be modified.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

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

(2) FIG. 1 is a view of a rotorcraft rotor fitted with a lever of an abutment mechanism in the engagement position;

(3) FIG. 2 is a view of a rotorcraft rotor fitted with a lever of an abutment mechanism in the disengagement position;

(4) FIG. 3 is a view of a lever;

(5) FIG. 4 is a view of a rounded abutment end;

(6) FIG. 5 is a view of an abutment mechanism having a redundant lever and shown in the engagement position;

(7) FIG. 6 is a view of an abutment mechanism having a redundant lever and shown in the disengagement position; and

(8) FIG. 7 is a view of a groove in a lever.

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

DETAILED DESCRIPTION OF THE INVENTION

(10) Three mutually orthogonal directions referenced X, Y, and Z are shown in FIG. 1.

(11) The first direction X is said to be longitudinal.

(12) The second direction Y is said to be transverse.

(13) Finally, the third direction Z is said to be in elevation.

(14) FIG. 1 shows a rotorcraft 1 having a rotor 2. The rotorcraft 1 and the rotor 2 are shown diagrammatically in part in order to avoid overburdening FIG. 1. The rotor 2 may be a rotor for providing the rotorcraft with lift and for providing it with propulsion.

(15) The rotor 2 is provided with a drive system 3 for controlling and setting into rotation a plurality of lift assemblies 10.

(16) The drive system comprises a hub 5 secured to a rotor mast 6 that is rotatable about an axis of rotation AX. The hub 5 possesses at least one plate for carrying a plurality of lift assemblies 10. The hub is thus movable solely in rotation about the axis of rotation. The hub is thus not a hub that is hinged to a mast.

(17) Thus, the hub may be provided with a top plate and with a bottom plate defining in elevation a space that can receive parts of the lift assemblies. Alternatively, the hub may for example comprise a single plate provided with recesses.

(18) Independently of the way in which the hub is embodied, each lift assembly 10 may comprise a lift element 11 and a cuff 12 incorporated with the lift element or fastened to the lift element 11. The cuff constitutes the member serving to fasten the lift element to a retention and mobility member 15 secured to the hub 5.

(19) Such a retention and mobility member 15 gives the lift assembly 10 freedom to perform pitch movements about a first pivot axis D1, lead/lag movement about a second pivot axis D2, and flapping movement about a third pivot axis D3.

(20) This retention and mobility member 15 may be a laminated abutment having a strength member referred to as a first strength member 16 that is fastened to the cuff, a strength member that is referred to as a second strength member 17 that is fastened to the hub, and a laminated member 18 connecting together the first and second strength members 16 and 17.

(21) Furthermore, the rotor may have a swashplate assembly 7 for controlling the pitch of the lift assembly 10 by means of pitch rods that are not shown.

(22) This swashplate assembly may co-operate with a rotary scissors link 8. This rotary scissors link connects a rotary swashplate 7 of the swashplate assembly 7 to the rotor mast 6 via a scissors link driver 9. Reference may be made to the literature for a more detailed description of these members.

(23) Furthermore, the rotor 2 is provided with an abutment mechanism 20 for each lift assembly in order, at least, to limit the flapping movement of the lift assembly during predetermined stages. In particular, each mechanism is active for the purpose of at least minimizing this flapping movement when the speed of rotation of the rotor is below a threshold speed.

(24) Each abutment mechanism 20 includes an abutment projection 25 secured to a lift assembly 10.

(25) Such a projection may be in the form of a rod, possibly a bent rod, e.g. secured to the cuff of the lift assembly. This rod then extends from the lift assembly towards a free end that is refereed to as the abutment end 30.

(26) The abutment end has an inner face 31 facing the drive system 3 and in particular the rotor mast, and an outer face 32 that is opposite from the inner face 31. The inner face 31 and the outer face 32 need not be parallel to each other.

(27) In addition, the abutment mechanism 20 is provided with at least one lever 35 suitable for blocking the flapping abutment end when the rotor is rotating at a speed of rotation below a threshold speed.

(28) The lever extends longitudinally from a flyweight 40 to a hook 50. More precisely, the lever extends longitudinally in line with the abutment end 30, e.g. along a radius of the rotor.

(29) Consequently, the lever comprises an arm carrying the flyweight 40 at one of its ends, and the hook 50 at its other end. Between these two ends, the lever is crossed by a pivot shaft 60 imparting a degree of freedom to move in pivoting. The pivot shaft 60 extends transversely between ends 61 and 62 along an axis of symmetry 63, this axis of symmetry 63 being contained in a horizontal reference plane 300.

(30) The pivot shaft is secured to the drive system, e.g. via a support 70.

(31) Such a support may then be fastened by way of example to the hub 5 or to the rotor mast 6, or indeed to the scissors link driver 9.

(32) The lever can then pivot about the pivot shaft 60 in a plane in elevation given reference 500, e.g. containing the axis of rotation AX of the rotor and the abutment end 30 of the mechanism 20.

(33) In particular, the flyweight is offset in elevation relative to the horizontal reference plane in order to cause the lever to pivot in a direction represented by arrow F1 under the effect of centrifugal force. Pivoting in this direction is referred to as the disengagement direction for convenience.

(34) Furthermore, the mechanism includes return means 45 exerting a force on the lever in order to impart pivoting represented by arrow F2 in a direction referred to as the engagement direction. This engagement direction is opposite to the above-described disengagement direction.

(35) In addition, the hook 50 has a jaw 51 defining a groove 52 into which the abutment end can penetrate.

(36) For this purpose, and with reference to FIG. 7, the hook 50 presents a J-shaped periphery 56 defining the groove 52. This periphery 56 is embodied by a first wall in elevation 54 and a second wall in elevation 53 projecting up from a bottom wall 55. The first wall in elevation 54 is interposed longitudinally between the second wall in elevation and the axis of rotation AX. In addition, this first wall in elevation 54 projects from the bottom wall 55 over a first height H1 that is greater than a second height H2 of the second wall in elevation 53, thereby giving the periphery a J-shape.

(37) Consequently, the groove 52 is a groove:

(38) that is not obstructed transversely along an axis 602 so as to open to the outside of the hook;

(39) that is obstructed longitudinally along an axis 601 by the first wall in elevation and by the second wall in elevation; and

(40) that is obstructed in elevation along an axis 603 solely at one of its ends by the bottom wall, the other end thus presenting an opening 604 in elevation through which an abutment end can pass.

(41) The axis 601 represents an axis in which the lever extends longitudinally from the flyweight to the hook. The axis 602 represents a transverse axis of the lever extending in the thickness direction of the lever. Finally, the axis 603 represents an axis in elevation of the lever.

(42) Under such circumstances, the groove may be referred to as being blind since it is partially obstructed in elevation.

(43) With reference to FIG. 3, the first wall in elevation 54 includes an upper bearing zone 54 for blocking the inner face 31 as a result of the lift assembly 10 flapping downwards.

(44) Likewise, the second wall in elevation 53 has a lower bearing zone 53 for blocking the outer face 32 as a result of the lift assembly 10 flapping upwards.

(45) Consequently, the upper bearing zone 54 is present in a higher horizontal plane 100 that lies above a lower horizontal plane 200 containing the lower bearing zone 53 when the lever is in a position referred to as its engagement position.

(46) For example, the horizontal reference plane 300 containing the axis of symmetry 63 of the pivot shaft 60 is situated above the lower horizontal plane 200 and below the higher horizontal plane 100 in this engagement position.

(47) With reference to FIG. 1, when the rotor is driven in rotation about the axis of rotation AX at a speed greater than a threshold, the lever is positioned by the return means 45 in the engagement position.

(48) In this position, the abutment end 30 is arranged in the groove 52 of the hook. The inner face 31 of the abutment end then faces the first wall in elevation 54 and the outer face 32 of the abutment end then faces the second wall in elevation 53. In the absence of flapping, clearance may separate the inner face 31 from the first wall in elevation 54, and other clearance may separate the outer face 32 from the second wall in elevation 53.

(49) If the lift assembly tends to flap downwards as represented by arrow F3, the inner face comes into collision against the upper bearing zone 54.

(50) If the force exerted by the abutment end on the lever tends to cause the lever to pivot, the lower bearing zone 53 in turn enters into collision with the outer face of the abutment end. Pivoting of the lever is thus prevented.

(51) Consequently, the mechanism may be referred to as self-blocking, and it guarantees that downward flapping movement of the lift element is stopped.

(52) Likewise, if the lift assembly tends to flap upwards as represented by arrow F4, the outer face 32 enters into collision with the lower bearing zone 53.

(53) If the force exerted by the abutment end on the lever tends to cause the lever to pivot, then the upper bearing zone 54 in turn enters into collision with the inner face of the abutment end. Pivoting of the lever is thus stopped, thereby making it possible to avoid the abutment end disengaging from the groove of the hook.

(54) Consequently, in the engagement position POS1 as shown in FIG. 1, the mechanism constrains the freedom of movement in flapping of the lift assembly both upwards and downwards, ignoring clearance.

(55) In order to optimize the operation of the mechanism, the inner face 31 of the abutment end need not be parallel to the first wall in elevation 54 when in the engagement position POS1. Likewise, the outer face 32 need not be parallel to the second wall in elevation 53 when in the engagement position POS1.

(56) In addition, first wall in elevation 54 is preferably not parallel to the second wall in elevation 53, the first wall in elevation 54 coming closer to the second wall in elevation 53 on going away from the bottom wall 55. The groove is thus in the shape of a cylinder on a base that is substantially trapezoidal.

(57) Furthermore, and with reference to FIG. 4, the abutment end 30 includes an edge face 33 that extends longitudinally in the direction of an arrow 700 from the inner face 31 to the outer face 32. This edge face 33 then faces the bottom wall 55 in the engagement position POS1, as shown in FIG. 4.

(58) Consequently, this edge face 33 may be arcuate in order to allow the pitch of the lift element 10 to be modified. Modifying pitch causes the abutment end to pivot as represented by double-headed arrow F5. FIG. 5 shows clearly that the arcuate shape of the edge face 33 does not impede this pivoting pitch movement of the lift assembly.

(59) Consequently, when the rotor is set into rotation about the axis of rotation AX at a speed that is below a threshold, the mechanism 20 blocks movements of the lift assembly that correspond to flapping, but does not block its pitch movements.

(60) With reference to FIG. 2, when the rotor is set into rotation about the axis rotation AX at a speed that is greater than a threshold, centrifugal force FC causes the lever 35 to pivot towards a disengagement position POS2.

(61) In this position the abutment end 30 is no longer engaged in the hook.

(62) It should be observed that the support 70 may include a removable abutment track 72. This abutment track may serve to avoid excessive large-amplitude downward flapping movement in flight by interfering with the abutment end 30. The abutment track may be removable in order to be replaced if it becomes worn.

(63) FIGS. 5 and 6 show an abutment mechanism that is provided for safety reasons with a redundant lever.

(64) Thus, the mechanism has two identical levers 35 arranged symmetrically on either side of a plane 400 in which the lift assembly 10 extends, both performing the same function. The two levers 35 are movable in pivoting about the same pivot shaft 60.

(65) Consequently, the mechanism may have a single rod passing through a plate in elevation of the support 70, with the levers being hinged on either side of the support about the rod.

(66) In another variant, the pivot shaft may have two rods on the same axis extending on either side of the support.

(67) Independently of the number of levers, the mechanism may include one pad 71 per lever 35 in order to limit the pivoting of the lever 35 under the effect of centrifugal force. A given pad may co-operate by interference with a first segment of the lever extending between the pivot axis and the hook, and it may also co-operate by interference with a second segment of the lever extending between the pivot axis and the flyweight.

(68) In FIG. 5, the first segment may come into abutment against the pad in the engagement position POS1. Conversely, the second segment may be in abutment against the pad in the disengagement position POS2.

(69) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several embodiments are described above, 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.