ROTOR BLADE WITH A SYSTEM FOR RETENTION AND FOR TAKE-UP OF SEPARATE STRESSES AND ROTOR PROVIDED WITH SUCH BLADES

Abstract

A blade, for a rotor of an aircraft, comprising a hollow cylindrical sleeve, a stop fastened to the cylindrical sleeve, a profiled portion, and an anchoring device, a blade body and a hollow torsion box secured to the profiled portion. The anchoring device and the blade body are positioned inside the cylindrical sleeve. The anchoring device surrounds the stop in order to form a stop for the profiled portion parallel to a longitudinal axis of the blade. The hollow torsion box is secured to the profiled portion, and comprises a bearing zone in contact with an inner wall of the cylindrical sleeve, taking up the bending loads on the blade.

Claims

1. A blade for a rotor, the blade comprising: a hollow cylindrical sleeve extending around a longitudinal axis and provided with an inner wall; a stop fastened to the cylindrical sleeve; a profiled portion; an anchoring device secured to the profiled portion; and a blade body secured to the profiled portion, wherein the blade comprises a hollow torsion box secured to the profiled portion, and comprising a bearing zone in contact with the inner wall of the cylindrical sleeve; the anchoring device is positioned inside the cylindrical sleeve and at least partially surrounds the stop; and the blade body is positioned inside the cylindrical sleeve.

2. The blade according to claim 1, wherein the anchoring device is U-shaped.

3. The blade according to claim 1, wherein the anchoring device comprises unidirectional fibers.

4. The blade according to claim 1, wherein the anchoring device and the blade body are secured to at least one spar of the blade.

5. The blade according to claim 1, wherein the stop comprises a cylindrical part arranged perpendicular to the longitudinal axis and connecting the anchoring device to the cylindrical sleeve and at least one fastening device for fastening the cylindrical part to the cylindrical sleeve.

6. The blade according to claim 1, wherein the stop comprises a hollow bushing secured to the anchoring device and a cylindrical part arranged perpendicular to the longitudinal axis and at least one fastening device for fastening the cylindrical part to the cylindrical sleeve, the anchoring device at least partially surrounding the bushing, the cylindrical part being positioned in the bushing in order to connect the anchoring device to the cylindrical sleeve.

7. The blade according to claim 1, wherein the inner wall of the cylindrical sleeve is cylindrical with a circular base and the bearing zone of the torsion box may comprise, at least partially, a cylindrical shape with a circular base cooperating with the inner wall to form a connection with a degree of freedom to rotate about the longitudinal axis and with a degree of freedom to move in translation along the longitudinal axis.

8. The blade according to claim 1, wherein the torsion box comprises fibers oriented at angles of between ±10° and ±80° in relation to the longitudinal axis.

9. The blade according to claim 1, wherein the blade body comprises at least one flat spot and the cylindrical sleeve comprises at least one planar face cooperating with the flat spot.

10. The blade according to claim 9, wherein the cylindrical sleeve comprises two planar faces and a clevis, the clevis comprising two supports each provided with a planar face, the blade body flanking the anchoring device between the two planar faces.

11. The blade according to claim 1, wherein the blade body bears against the stop along the longitudinal axis.

12. A rotor comprising: a hub; and at least two blades, wherein the at least two blades are according to claim 1, the longitudinal axis of the cylindrical sleeve coinciding with a pitch axis of the blade, the rotor comprising a connection, with a degree of freedom to rotate about the longitudinal axis, between the hub and each cylindrical sleeve.

13. The rotor according to claim 12, wherein the rotor comprises at least one rotational guide device respectively connecting each cylindrical sleeve and the hub.

14. The rotor according to claim 13, wherein the guide device(s) comprise an inner ring, an outer ring and rolling elements, the inner ring being secured to the cylindrical sleeve and the outer ring being secured to the hub, the cylindrical sleeve comprising a first stop device and the hub comprising a second stop device along the longitudinal axis.

15. The rotor according to claim 12, wherein each cylindrical sleeve comprises a lever for controlling the pitch of the blade.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The disclosure and its advantages appear in greater detail in the context of the following description of embodiments given by way of illustration and with reference to the accompanying figures, in which:

[0072] FIG. 1 is a view of a rotor provided with blades for an aircraft;

[0073] FIG. 2 is a view of a blade root of a blade of the rotor;

[0074] FIG. 3 is an exploded view of the blade root;

[0075] FIG. 4 is a longitudinal cross-sectional view of the blade root;

[0076] FIG. 5 is a longitudinal cross-sectional view of the blade root of a blade of another rotor;

[0077] FIG. 6 is a first transverse cross-sectional view of the blade root according to FIG. 5; and

[0078] FIG. 7 is a second transverse cross-sectional view of the blade root according to FIG. 5.

DETAILED DESCRIPTION

[0079] Elements that are present in more than one of the figures are given the same references in each of them.

[0080] A rotor 10 for an aircraft is shown in FIG. 1. This rotor 10 comprises a hub 11, at least two blades 1 and an axis of rotation AXROT of the hub 11. The example of a rotor 10 shown in FIG. 1 comprises six blades 1, although a different number of blades 1 may be used without compromising the implementation of the disclosure. The example of a rotor 10 shown in FIG. 1 is a forward propeller of an aircraft intended to provide at least some of the forward motion the aircraft, which may be a fixed-wing and/or a rotary-wing aircraft. The rotor 11 may also be a lift rotor or an auxiliary anti-torque rotor of a rotary-wing aircraft.

[0081] Each blade 1 comprises a blade root 15, a profiled portion 3 and a free end 32, the profiled portion 3 being formed by a series of aerodynamic profiles. The longitudinal axis AXL of a blade 1 extends in a root direction from the blade root 15, fastened to the hub 11, towards the free end 32 of the blade 1.

[0082] When the rotor 10 rotates about the axis of rotation AXROT, the blades 1 are rotated by the hub 11 about this axis of rotation AXROT so that each blade 1, and more particularly the profiled portion 3 of each blade 1, generates an aerodynamic force. During such rotation of the rotor 10, the longitudinal axis AXL of each blade 1 substantially coincides with a radial direction of the rotating rotor 10 and hub 11. This radial direction extends perpendicular to the axis of rotation AXROT of the hub 11 around this axis of rotation AXROT.

[0083] FIG. 2 shows, in detail, the blade root 15 and the junction with the profiled portion 3. The blade root 15 comprises a stop 7, an anchoring device 5, a blade body 4, a cylindrical sleeve 2 and a torsion box 6.

[0084] The torsion box 6, the anchoring device 5 and the blade body 4 are secured to the profiled portion 3. The torsion box 6, the anchoring device 5 and the blade body 4 may therefore be in continuation of the structure of the profiled portion 3, for example being secured to at least one spar of the blade 1. The torsion box 6, the anchoring device 5 and the blade body 4 may also be fastened to the structure of the profiled portion 3.

[0085] The cylindrical sleeve 2 is hollow and extends around the longitudinal axis AXL. The cylindrical sleeve 2 comprises an inner wall 25.

[0086] The torsion box 6 is hollow and extends around the longitudinal axis AXL. The torsion box 6 is positioned between the axis of rotation of the hub AXROT and the profiled portion 3. The torsion box 6 is positioned at least partially in the cylindrical sleeve 2.

[0087] The anchoring device 5 and the blade body 4 are positioned at least partially in the torsion box 6. The anchoring device 5 and the blade body 4 are also positioned at least partially in the cylindrical sleeve 2.

[0088] Moreover, in order to allow the blade 1 to rotate about a pitch axis that substantially coincides with its longitudinal axis AXL, at least one rotational guide device 13 is arranged between the cylindrical sleeve 2 and the hub 11, and more precisely a bore of the hub 11, in order to form a connection with a degree of freedom to rotate, such as a pivot connection, between the hub 11 and the cylindrical sleeve 2. For example, two guide devices 13, such as ball bearings, are positioned around the cylindrical sleeve 2. A guide device 13 may comprise, for example, an inner ring, an outer ring and rolling elements, namely balls in the example shown. According to another example, one or more angular contact ball bearings may be positioned around the cylindrical sleeve 2.

[0089] The cylindrical sleeve 2 may also comprise a first stop device 27 forming a stop parallel to the longitudinal axis AXL for an inner ring of a guide device 13. A first stop device 27 is, for example, a shoulder integrated into the cylindrical sleeve 2.

[0090] The bore of the hub 11 may also comprise a second stop device forming a stop parallel to the longitudinal axis AXL for an outer ring of a guide device 13. This second stop device may comprise a shoulder integrated into the bore of the hub 11 and/or be formed by one or more inserts.

[0091] The cylindrical sleeve 2 may further comprise a pitch lever 22, which is eccentric in relation to the longitudinal axis AXL, for controlling the pitch variation of the blade 1.

[0092] The anchoring device 5 is therefore positioned inside the cylindrical sleeve 2 and at least partially surrounds the stop 7 fastened to the cylindrical sleeve 2, so that the assembly formed by the stop 7 and the anchoring device 5 creates a longitudinal stop for the blade 1, in a direction parallel to the longitudinal axis AXL, and for the blade root 15, towards the free end 32 of the blade 1. This longitudinal stop prevents the blade 1 from moving under the effect of the centrifugal force applied to the blade 1 during rotation of the rotor 10 about the axis of rotation AXROT.

[0093] An example of a connection between the stop 7 and the anchoring device 5 is shown as an exploded view in FIG. 3. The anchoring device 5 surrounds the stop 7 over 180 degrees (180°) in order to create the longitudinal stop. The stop 7 comprises a cylindrical part 72 arranged perpendicular to the longitudinal axis AXL and the anchoring device 5 comprises a U-shaped end 51 in order to ensure form-fitting contact with the cylindrical part 72 and, therefore, good take-up of the stresses generated by the centrifugal force applied to the blade 1 during rotation of the rotor 10. The anchoring device 5 also comprises two arms 52,53 connecting the U-shaped end 51 to the profiled portion 3. The blade body 4 is positioned between the arms 52,53 and bears against each arm 52,53 in order to limit the deformations of the arms 52,53.

[0094] The cylindrical part 72 of the stop 7 is, for example, fastened between two supports of a clevis 26 of the cylindrical sleeve 2, each support of the clevis 26 comprising an aperture 29. The stop 7 may comprise at least one removable fastening device 73, such as a screw 73, for example, in order to fasten the cylindrical part 72 to each support of the clevis 26, the cylindrical part 72 comprising a tapped hole at each of its ends. A washer 74 may be interposed between a support and a fastening device 73.

[0095] The stop 7 may also comprise, according to the example shown in FIG. 4, a hollow cylindrical bushing 71, a cylindrical part 72 and at least one removable fastening device 73. The bushing 71 and the cylindrical part 72 are arranged perpendicular to the longitudinal axis AXL. The bushing 71 is secured to the anchoring device 5 comprising a U-shaped end 51 in order to ensure form-fitting contact with the bushing 71 so as to take up the stresses generated by the centrifugal force applied to the blade 1 during rotation of the rotor 10. The anchoring device 5 also comprises two arms 52,53 connecting the U-shaped end 51 to the profiled portion 3.

[0096] The cylindrical part 72 is positioned in the bushing 71 and is fastened between two supports of the clevis 26 of the cylindrical sleeve 2, each support of the clevis 26 comprising an aperture 29. The stop 7 then comprises two removable fastening devices, such as two nuts 73, for example, in order to fasten the cylindrical part 72 to each support of the clevis 26, the cylindrical part 72 comprising a threaded rod at each of its ends. A washer 74 may be interposed between a support and a fastening device 73.

[0097] The blade body 4 and the anchoring device 5 are positioned inside the cylindrical sleeve 2 and the torsion box 6 as shown in FIG. 4. The torsion box 6 comprises a bearing zone 9 in contact with the inner wall 25 of the cylindrical sleeve 2.

[0098] This bearing zone 9, which is in contact with the inner wall 25 of the cylindrical sleeve 2, advantageously takes up the bending forces experienced by the blade 1 resulting from the aerodynamic forces experienced by the blade 1 during rotation of the rotor 10.

[0099] According to the example shown in FIG. 4, the bearing zone 9 of the torsion box 6 comprises a single cylindrical bearing surface around the longitudinal axis AXL and covering, along the longitudinal axis AXL, a length greater than the diameter of the inner wall 25, so as to form a “long centering” connection between the cylindrical sleeve 2 and the torsion box 6.

[0100] According to another example shown in FIG. 5, the bearing zone 9 of the torsion box 6 comprises two cylindrical bearing surfaces positioned along the longitudinal axis AXL.

[0101] Moreover, the blade body 4 may bear against the stop 7, and in particular against the bushing 71, in the example shown, along the longitudinal axis AXL.

[0102] FIG. 6 shows a cross-sectional view of the example of FIG. 5 perpendicular to the longitudinal axis AXL at a bearing surface of the bearing zone 9. The inner wall 25 of the cylindrical sleeve 2 may be cylindrical with a circular base and the bearing zone 9 may comprise, at least partially, a cylindrical shape with a circular base, as shown in FIG. 6, in order to form a connection with a degree of freedom to rotate about the longitudinal axis AXL and with a degree of freedom to move in translation along the longitudinal axis AXL, such as a sliding pivot connection, between the cylindrical sleeve 2 and the torsion box 6.

[0103] The anchoring device 5 and the blade body 4 are positioned at least partially in the torsion box 6, according to the example of FIG. 6, and in contact with an inner surface of the torsion box 6.

[0104] FIG. 7 shows a cross-sectional view of the example of FIG. 5 perpendicular to the longitudinal axis AXL and passing through an axis of the stop 7, in particular an axis of the bushing 71 and of the cylindrical part 72. According to this example, the blade body 4 comprises at least one flat spot 41 and specifically two flat spots 41 that are diametrically opposite in relation to the longitudinal axis AXL. Each support of the clevis 26 then comprises at least one planar face 61 cooperating respectively with one flat spot 41, and specifically two planar faces 61. These two planar faces 61 are thus in contact respectively with the two flat spots 41 so as to help take up the torsional stress generated by the aerodynamic forces experienced by the blade 1 during rotation of the rotor 11.

[0105] Other complementary shapes may be used for the blade body 4 and the cylindrical sleeve 2 in order to help take up this torsional stress. The blade body 4 and an internal shape of the cylindrical sleeve 2 may, for example, be parallelepiped or ovoid.

[0106] The stop 7, the anchoring device 5, the blade body 4, the cylindrical sleeve 2 and the torsion box 6 therefore separately take up the various stresses generated and experienced by the blade 1 during rotation of the rotor 11. The stop 7, the anchoring device 5, the blade body 4, the cylindrical sleeve 2 and the torsion box 6 may therefore form a system for retention and for take-up of separate stresses of the blade 1.

[0107] The stop 7, the anchoring device 5, the blade body 4, the cylindrical sleeve 2 and the torsion box 6 may therefore be advantageously optimized in terms of their dimensions, their weight and their mechanical strength, without compromising the operation and the mechanical resistance to stress and fatigue of the rotor 11 as a whole.

[0108] In the absence of such complementary shapes for the blade body 4 and the cylindrical sleeve 2, the torsional stresses generated by the aerodynamic forces experienced by the blade 1 during rotation of the rotor may be taken up by the stop 7 in connection with the cylindrical sleeve 2.

[0109] Naturally, the present disclosure is subject to numerous variations as regards its implementation. Although several embodiments are described above, it should readily be understood that it is not conceivable to identify exhaustively all the 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 disclosure.