Torque balanced rotors for helicopters.

Abstract

To provide an anti-torque rotor for a helicopter.SOLUTION: An anti-torque rotor 4 includes: a mast 6 rotatable about a first axis A; a plurality of blades 8 rotatable about respective second axes B; an element 16 being slidable relatively to the mast along the first axis, rotating integrally with the mast, and operatively connected to the blades; a control rod 10 slidable along the first axis; a first ring 30 rotating integrally with the element; a second ring 31 radially internal to the first ring with respect to the first axis; a first bearing 17 with a plurality of first rolling bodies; a third ring 50 sliding along the first axis integrally with the control rod and angularly fixed with respect to the first axis; and a locking element 55 that is arranged in a standard configuration to prevent the relative rotation of the second and third rings, and is movable from the standard configuration to an emergency configuration to render the second ring free to rotate with respect to the third ring when the first bearing is in a failure condition.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority from European Patent Application No. 19182720.3, filed June 26, 2019, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a torque balancing rotor for a helicopter. [Background technology]

[0003] A helicopter is known that basically comprises a fuselage, a main rotor arranged on top of the fuselage and rotatable about an axis of the fuselage, and a torque balancing rotor arranged at the tail end of the fuselage.

[0004] The helicopter also comprises, in known manner, one or more power units, for example turbines, and a transmission unit interposed between the turbines and the main rotor and adapted to transmit motive power from the turbines to the main rotor itself.

[0005] More specifically, the torque balancing rotor further comprises: - a mast rotatable about a first axis; - a hub rotatable about a first axis; a plurality of vanes hinged to the hub and cantilevered away from the hub, each vane extending along a respective second axis transverse to the first axis; Basically, it is equipped with:

[0006] The mast of the torque balance rotor is driven in rotation by a set of gears which are driven by the main transmission unit.

[0007] The vanes of the torque balance rotor rotate integrally with the mast about a first axis and can be selectively tilted about a second axis to vary their respective angles of attack and, consequently, to adjust the thrust exerted by the torque balance rotor.

[0008] To adjust the angle of attack of each blade, the torque balance rotor: - a rod operably connected to a pedal operable by the pilot through a mechanical connection or a fly-by-wire linkage, the rod sliding inside the mast along a first axis but angularly fixed relative to the first axis; - a control element, also known as a "spider", which is integrally rotatable with the mast about a first axis and which is provided with a number of arms connected to each vane in an eccentric position relative to an associated second axis; a rolling bearing mounted in a sliding manner relative to the first axis and interposed between the rod and the control element and configured to transfer an axial load from the rod to the rotatable element; Equipped with.

[0009] More specifically, the rolling bearing further comprises: - a radially outer ring fastened to the control element; a radially inner ring fastened to the control rod; a plurality of rolling elements rolling in respective raceways defined by a radially inner ring and a radially outer ring; Equipped with.

[0010] In normal operating conditions of the bearing, the rolling elements permit rotation of the outer ring relative to the inner ring, and therefore the control element relative to the rod.

[0011] Actuation of the pedal causes the control rod to slide parallel to the first axis, which causes the control element to slide, via the rolling bearing, parallel to the first axis along a given path of travel.

[0012] This sliding causes rotation of the vanes about associated second axes, thereby changing their respective angles of attack by equal amounts associated with a given path of travel.

[0013] From the above, it can be seen that the possible failure of a rolling bearing could cause the torque balanced rotor to become substantially uncontrollable, creating a dangerous situation for the helicopter.

[0014] Specifically, a failure situation may occur when the rolling elements and / or raceways of the inner or outer ring are damaged due to, for example, accidental incorporation of foreign matter into the bearing, loss of lubricating grease, or damage to the rolling element raceways or surfaces.

[0015] In this condition, instead of allowing relative rotation of the control element to the control rod, the rolling bearings will inadequately transmit torsional moments from the outer ring to the inner ring which increase progressively over time.

[0016] This torsional moment is transmitted to the control rod, creating the risk of damaging the control rod.

[0017] A rolling bearing failure condition is usually preceded by an increase in torque acting on the inner ring and an increase in temperature and vibration in the area around the rolling bearing.

[0018] There is a recognized need within the industry to reduce the risk of these failure conditions which would nullify the blade angle of attack adjustments and thereby cause torque balanced rotor thrust and the helicopter's yaw angle to become substantially uncontrollable.

[0019] There is also recognition within the industry of the need to ensure proper control of the torque balanced rotor in the event of a rolling bearing failure.

[0020] Finally, there is a recognized need within the industry to quickly identify incipient rolling bearing failure conditions and to provide clear and rapid instructions to the crew.

[0021] US Patent No. 9,359,073(B) describes a torque balancing rotor for a helicopter according to the preambles of claims 1, 16, 28, 35, 46, 57 and 69.

[0022] More specifically, US Pat. No. 9,359,073(B) describes a torque-balanced rotor that includes a mast, a rod, and first and second bearings arranged in series.

[0023] The first bearing includes a first ring rotatable with the mast and a second ring.

[0024] The second bearing includes a third ring and a fourth ring.

[0025] The third ring of the second bearing and the first ring of the first bearing are connected to each other in a non-rotatable manner.

[0026] Specifically, the first ring and the second ring define first and second raceways, respectively, for the first rolling elements of the first bearing.

[0027] The third ring and the fourth ring define third and fourth raceways, respectively, for the second rolling elements.

[0028] In other words, each of the first, second, third and fourth rings defines a respective first, second, third and fourth raceway. The torque balance rotor also comprises a locking device interposed between the third ring and the fourth ring and adapted to prevent rotation of the third ring relative to the fourth ring. The locking device comprises an element that is destructible in the event of failure of the first bearing and is not destructible in the event of correct operation of the first bearing.

[0029] The solution shown in US Pat. No. 9,359,073(B) is particularly complex as it requires the use of two rolling bearings and a locking device.

[0030] In particular, the solution shown in U.S. Pat. No. 9,359,073(B) requires four rings to define four raceways, with a first bearing and a second bearing spaced axially from each other.

[0031] This makes the solution shown in US Pat. No. 9,359,073(B) particularly cumbersome and unsuitable for easily adapting to the small axial dimensions of a helicopter tail rotor.

[0032] Additionally, both the first bearing and the second bearing include a single ring of spherical rolling elements.

[0033] Due to the low rotational stiffness of the single ring of rolling elements, the frangible element of the locking device can only transmit axial loads parallel to the axis of rotation of the mast.

[0034] The solution shown in US Pat. No. 9,359,073(B) is therefore effective when transmitting substantially only loads parallel to the axis of rotation of the mast.

[0035] Furthermore, the use of a single ring of spherical rolling elements inevitably results in the presence of axial loads which can result in objectionable vibrations and noise.

[0036] Furthermore, because of the single ring of spherical rolling elements, the illustrated bearing is particularly susceptible to the wear damage mechanism of false brinelling, i.e., the development of hollow defects which resemble Brinell pits and are due to wear caused by vibration and wobble at the contact points between the rolling elements and the raceways. [Prior art documents] [Patent documents]

[0037] [Patent Document 1] U.S. Patent No. 9,359,073(B) Summary of the Invention [Problem to be solved by the invention]

[0038] The object of the present invention is to provide a torque-balancing rotor which is able to meet at least one of the above requirements in a simple and inexpensive manner. [Means for solving the problem]

[0039] The aforementioned objects are achieved by the present invention insofar as it relates to a torque balancing rotor as defined in claims 1, 16, 28, 35, 46, 57 and 69.

[0040] For a better understanding of the invention, three preferred embodiments are described hereinafter, using pure water as a non-limiting example, and with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0041] [Figure 1] FIG. 1 is a top view of a helicopter with a torque balance rotor according to a first embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view taken along line II-II of FIG. 1, with some parts omitted for clarity and greatly enlarged in scale. [Diagram 3] FIG. 3 is a greatly enlarged perspective view of some components of the torque balance rotor of FIGS. 1 and 2. [Figure 4] FIG. 4 is a side view of the components of FIG. 3 in a standard configuration. [Diagram 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. 4 in a standard configuration. [Figure 6] FIG. 6 is a side view of the components of FIGS. 3 and 5 in a first emergency configuration. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 6 in a first emergency configuration. [Figure 8] FIG. 8 is a side view of the components of FIGS. 3-7 in a second emergency configuration. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX of FIG. 8 in a second emergency configuration. [Figure 10] FIG. 6 is a cross-sectional view of FIG. 5 with hatched portions for clarity. [Figure 11] FIG. 4 is a cross-sectional view taken along line XI-XI in FIG. [Figure 12] FIG. 2 is a greatly enlarged to scale perspective view of some components of a torque balance rotor according to a second embodiment of the invention in a standard configuration. [Figure 13] FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. [Figure 14] FIG. 13 is a greatly enlarged to scale perspective view of some components of a torque balance rotor according to a third embodiment of the invention in a standard configuration. [Figure 15] FIG. 13 is a perspective view of a third embodiment of a torque balance rotor in one of a first emergency configuration and a second emergency configuration. [Figure 16] FIG. 16 is a cross-sectional view taken along line XVI-XVI in FIG. 14. [Figure 17] FIG. 17 is a cross-sectional view taken along line XVII-XVII in FIG. 15. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] Referring to FIG. 1, reference numeral 1 denotes - Aircraft 2 and one or more turbines 5; - a main rotor 3 arranged on top of the fuselage 2 and rotatable about an axis A; a torque-balanced rotor 4 located at the aft end of the fuselage 2 and rotatable about an axis transverse to the axis A; This standard specifies helicopters that are basically equipped with the following:

[0043] The helicopter 1 also comprises a transmission unit, known per se and not shown, for transmitting motive power from the turbine 5 to the main rotor 3 .

[0044] Furthermore, the transmission unit - a gear train transmitting motive power from the turbine 5 to the main rotor 3; - a shaft 13 which transmits the motive force from the gear train 12 to the torque balance rotor 4; Equipped with.

[0045] In known manner, the main rotor 3 is adapted to provide vectorable thrust that enables the helicopter 1 to take off and fly forward.

[0046] The torque counterbalancing rotor 4 generates thrust that creates a counter torque on the vehicle 2 .

[0047] This counter torque is directed in the opposite direction to the torque exerted by the main rotor 3 .

[0048] It is therefore possible to orient the helicopter 1 according to a desired yaw angle depending on the magnitude of the thrust generated by the torque balance rotor 4, or to vary said yaw angle depending on the maneuver one wishes to perform.

[0049] Referring to FIG. 2 to FIG. 11, the torque balance rotor 4 is - a mast 6 rotatable about an axis A and operatively connected to a shaft 13 in a known manner; a plurality of vanes 8, three in number in the illustrated case, extending in a cantilever manner along respective axes B transverse to the axis A; - a hub 9 externally fastened to a portion of the mast 6 and rotatable together with the mast 6 about an axis A, to which the vanes 8 are hinged; Basically, it is equipped with:

[0050] More specifically, the vanes 8 are - to be rotatable together with the hub 9 and the mast 6 about the axis A, and - tiltable about their respective axes B at the same angle and simultaneously with respect to time, in order to vary their respective angles of attack; It is hinged to hub 9.

[0051] Specifically, the hub 9 includes a plurality of connecting elements 18 projecting radially relative to the axis A for connection to respective vanes 8. Each vane 8 also includes a root 14 disposed radially inwardly relative to the axis A and hinged to an associated connecting element 18 of the hub 9.

[0052] To change the angle of attack as mentioned above, the torque balance rotor 4 is flight controls 15 operable by the pilot, for example pedals (only shown diagrammatically in FIG. 1 ); a control rod 10 sliding parallel to the axis A and operable by a flight control 15 using a mechanical link or a fly-by-wire method; a control element 16 rotatable together with the mast 6 about an axis A and connected to the vane 8 in an eccentric manner with respect to an associated axis B; a bearing 17 interposed between the control rod 10 and the element 16 and sliding together with the control rod 10 parallel to the axis A; It also provides:

[0053] More specifically, the mast 6 is hollow.

[0054] Mast 6 is an axial end 20; a further open axial end opposite end 20, not shown; a main part 22 interposed between the axial end 20 and the further axial end, on which the hub 9 is fitted and adapted to receive a driving force from the shaft 13 (FIG. 1) via the flange 19; It also has the following features (Figure 2).

[0055] The control rod 10 is partially housed inside the mast 6 .

[0056] The control rod 10 is a first axial end (not shown) connected to the shaft 13; a second axial end 24 (FIG. 2), opposite to the first axial end, connected to the bearing 17; a main body 25 passing through the end 20 and the further axial end of the mast 6; It also provides:

[0057] The main body 25 is arranged along the axis A starting at the end 24 as follows: - a section 26 of larger diameter than the end 24, - section 27, which has a diameter greater than section 26; a shoulder 28 interposed radially between the sections 26 and 27; It further comprises:

[0058] The end 24 is disposed outside the mast 6 .

[0059] The first end is operatively coupled to flight control 15 by a linkage (not shown) or by fly-by-wire actuation.

[0060] Element 16 further includes: a tubular body 40 partially housed in the mast 6 and connected thereto in a sliding manner relative to the axis A and partially housing the control rod 10; a flange 42 extending perpendicular to the axis A and fastened to the tubular body 40 at its end opposite the mast 6; a plurality of levers 43 hinged to the flanges 42 about respective axes C transverse to the axis A and hinged to respective vanes 8 in eccentric positions relative to the associated axes B; (Figure 2).

[0061] The flange 42 and bearing 17 are housed on the outside of the mast 6 and surround the control rod 10 .

[0062] The flange 42 is connected to the mast 6 by a single variable length bellows connection 44 which allows sliding movement along the axis A.

[0063] Lever 43 is generally inclined relative to axis A and extends from flange 42 to end 20 .

[0064] Translation of the control rod 10 along the axis A causes translation of the element 16 via the bearing 17 .

[0065] Following the sliding of the elements 16 along axis A, the levers 43 change their inclination relative to axis A at the same mutually identical angle, resulting in a simultaneous rotation of the vanes 8 about their respective axes B at the same mutually equal angles.

[0066] Specifically, the lever 43 is hinged to the root portion 14 of each of the blades 8 .

[0067] The bearing 17 is capable of transmitting axial loads parallel to the axis A in both directions.

[0068] In other words, the bearings 17 are configured such that translation of the control rod 10 in both directions along the axis A causes translation of the element 16 in the same direction.

[0069] In this way, the bearing 17 connects the control rod 10 and the element 16 in an axially integral and angularly movable manner relative to the axis A.

[0070] The bearing 17 further comprises: a radially outer ring 30 rotatable integrally with the element 16; a radially inner ring 31 sliding integrally with the control rod 10; a plurality of rolling elements 32, in the illustrated case a double ring of balls, rolling in respective raceways 33 and 34 defined by respective rings 30 and 31; Equipped with.

[0071] In the illustrated case, ring 30 has, on opposite sides, a pair of shoulders 35 and 36 which project radially towards ring 31 and which respectively define axial abutment surfaces for rolling elements 32. Shoulders 35 and 36 define raceways 33.

[0072] Specifically, the rolling element 32 is interposed between the shoulders 35 and 36 in the axial direction.

[0073] Furthermore, the ring 30 is made of two half rings 41 which in the illustrated case are arranged axially in contact with one another.

[0074] The ring 30 is press fitted onto the tubular body 40 of the element 16 at a radially outer location.

[0075] The ring 31 is provided with shoulders 37 which are interposed axially between the shoulders 35 and 36 and which project radially towards the ring 30. These shoulders 37 are interposed axially between the rolling elements 32 in a plane of radial symmetry of the bearing 17 relative to the axis A.

[0076] Furthermore, the ring 30 is fastened to the tubular body 40 of the element 16 on the opposite side of the flange 42 in a direction that is radial to the axis A.

[0077] The bearing 17 also comprises two annular cages 39 adapted to keep the rolling elements 32 of each ring angularly equidistant from one another.

[0078] Ring 31 is radially inward relative to ring 30 relative to axis A.

[0079] Specifically, raceway 34 is radially inward relative to axis A with respect to raceway 33 .

[0080] In the remainder of this description, the term "failure" of bearing 17 means any effective or incipient emergency condition in which bearing 17 is no longer able to transmit only axial loads from control rod 10 to element 16, i.e., causing axial translation of element 16 in both directions, followed by axial translation of control rod 10 without generating a torsional moment on control rod 10.

[0081] By way of non-limiting example, a first (initial) emergency condition occurs when the rolling elements 32 and / or raceways 33 and 34 are damaged, for example, by a foreign object accidentally entering the bearing 17 or due to loss of lubricating grease.

[0082] In this first emergency situation, the ring 31 of the bearing 17 is subjected to a torsional moment.

[0083] Furthermore, the first emergency condition of the bearing 17 is generally associated with an increase in temperature and vibration levels in the area around the bearing 17 and / or an increase in the torque transmitted to the ring 31.

[0084] A second emergency situation occurs when the rolling elements 32 of the bearing 17 break so that the control rod 10 is able to move axially relative to the element 16 .

[0085] The torque balancing rotor 4 advantageously comprises: a further ring 50 which slides integrally with the control rod 10 along the axis A and is angularly fixed relative to the axis A; a number of rolling elements 51 interposed between the rings 31 and 50 and rolling in respective raceways 52 and 53 of each ring 31 and 50; - locking elements 55 arranged in a standard configuration, which prevent relative rotation of the rings 31 and 50 when the bearing 17 is in its normal operating condition; Equipped with Locking element 55 is movable from a standard configuration to at least a first or second emergency configuration to allow ring 31 to freely rotate relative to ring 50 about axis A when bearing 17 is in a failure condition.

[0086] Specifically, the rings 30, 31, 50 are coaxial and extend about an axis A.

[0087] Even more precisely, ring 50 is radially inward relative to ring 31 with respect to axis A.

[0088] Furthermore, raceway 53 is radially inward relative to raceway 52 relative to axis A.

[0089] Specifically, the ring 31 is formed in one piece and integrally defines the tracks 34,52.

[0090] More specifically, when bearing 17 is in normal operating condition and locking elements 55 are in a standard configuration, ring 30 rotates about axis A and rings 31 and 50 are angularly fixed relative to axis A.

[0091] In this situation, the ring 50 is essentially non-functional.

[0092] Conversely, when bearing 17 is in a failure condition and locking element 55 is in either the first or second emergency configuration, rings 30 and 31 rotate about axis A and ring 50 is angularly fixed relative to axis A. In this condition, the set of rings 30 and 31 and ring 50 form a backup bearing 54 (FIGS. 5, 7, 9 and 10), which allows control of torque balance rotor 4 even in the event of a bearing 17 failure.

[0093] More specifically, the locking element 55 automatically moves, in the event of a failure of the bearing 17, from the standard configuration to the first emergency configuration when the temperature of the bearing 17 exceeds a respective threshold value.

[0094] The locking element 55 automatically moves from the standard configuration to the second emergency configuration in the event of a failure of the bearing 17 when vibrations in the area of ​​the bearing 17 exceed a respective threshold value and / or when the torque transmitted from the ring 30 to the ring 31 exceeds a respective threshold value.

[0095] Backup bearing 54 is capable of transmitting axial loads in both directions parallel to axis A. In other words, backup bearing 54 is configured such that translation of control rod 10 in both directions along axis A continues to cause translation of element 16 in the same direction, even in the event of failure of bearing 17.

[0096] Ring 50 is a radially outer surface 57 inclined with respect to the axis A and provided with two axially opposed shoulders defining the respective raceways 52 and 53; a radially inner surface 58 opposite the surface 57 and press-fitted onto the section 26 of the control rod 10; It also provides:

[0097] The rolling elements 51, in the illustrated case, are tapered rollers with their respective flanks converging towards the axis A. In particular, the tapered rollers are arranged in an X-shape, i.e. with their respective axes converging towards the axis A.

[0098] The backup bearing 54 further comprises two annular cages 59 adapted to keep the rolling elements 51 of each ring evenly angularly spaced from one another.

[0099] Moreover, in the case shown, the ring 50 is made of two half-rings 45 arranged in axial contact with one another.

[0100] The locking element 55 is angularly fixed with respect to the axis A in both the standard configuration and in the first or second emergency configuration.

[0101] When arranged in the standard configuration, the locking element 55 is axially integral with the rings 31 and 50 and the control rod 10 .

[0102] When positioned in the first or second emergency configuration, the locking element 55 can instead slide parallel to the axis A relative to the rings 31 and 50 and the control rod 10 .

[0103] More specifically, the locking element 55 is in the insertion position (FIGS. 4 and 5) which is reached when the locking element 55 is in its standard configuration, and in the withdrawal position (FIGS. 6 to 9), which is reached when the locking element 55 is arranged in the first or second emergency configuration, The rings 31 and 50 are arranged with reference to the axis A.

[0104] A first axial distance between the locking element 55 and the rings 31 and 50 set in the inserted position is smaller than a second axial distance between the locking element 55 and the rings 31 and 50 set in the withdrawn position.

[0105] The locking element 55 is arranged on the axial side of the bearing 17 facing away from the mast 6 .

[0106] More specifically, the locking element 55 extends annularly about the axis A, - a main body 60; a ring 65 spaced axially from the main body 60; a plurality of arms 70 equally spaced apart about axis A and interposed between main body 60 and ring 65; (Figures 3 to 9).

[0107] When the locking element 55 is in the standard configuration (FIGS. 4 and 5), the ring 65 is blocked by an interference at the surface 38 of the ring 31 radially outwardly relative to the axis A; and The arm 70 connects the main body 60 and the ring 65 .

[0108] In this standard configuration, ring 65 prevents rotation of ring 31 due to radial interference between ring 65 and surface 38 .

[0109] In particular, the ring 65 is also blocked by radial interference at the surface 38 with the axially opposite portion of the mast 6 .

[0110] In the illustrated case, ring 65 surrounds and contacts surface 38 .

[0111] 6 and 7, when locking element 55 is in the first emergency configuration, ring 65 is disengaged from surface 38 of ring 31, and therefore ring 31 is free to rotate about axis A together with ring 30 under the torsional moment improperly transmitted by ring 31.

[0112] 8 and 9, when the locking element 55 is in the second emergency configuration, the arm 70 is blocked and no longer connects the main body 60 and the ring 65. Even in this second emergency configuration of the locking element 55, the ring 31 will be free to rotate about the axis A together with the ring 30 under a torsional moment improperly transmitted by the ring 31.

[0113] The locking element 55 is made from a material having a first coefficient of thermal expansion and the ring 50 is made from a material having a second coefficient of thermal expansion that is less than the first coefficient of thermal expansion.

[0114] The first coefficient of thermal expansion is greater than the second coefficient of thermal expansion.

[0115] In the illustrated case, the locking element 55 is made from aluminum and the rings 30, 31 and 50 are made from steel.

[0116] Thus, in the event of a temperature rise in bearing 17 above a threshold due to failure, ring 65 will expand radially beyond surface 38 of ring 50 until it becomes radially separated from ring 50 .

[0117] When the ring 65 is free to move away from the surface 38, the locking elements 55 are disposed in the first emergency configuration.

[0118] Arm 70 is dimensioned to break in torsion when the vibration and / or torsional moment transmitted to ring 31 exceeds a threshold value.

[0119] In this manner, the locking element 55 moves from the standard configuration to the second emergency configuration (FIGS. 8 and 9) when vibrations and / or torsional moments transmitted to the ring 31 exceed a threshold value.

[0120] Further, the arms 70 are equally angularly spaced about the axis A and extend parallel thereto.

[0121] The main body 60 includes: a cylindrical portion 62 from which an arm 70 projects axially in a cantilevered manner; a ring 61 projecting radially in a cantilever manner from the portion 62 in a direction opposite to the axis A and defining the axial end of the main body 60 opposite the ring 65; It also provides:

[0122] In the illustrated case, the diameter of the main body 60 is equal to the diameter of the ring 65 .

[0123] The locking element 55 also comprises a ring 64 which is arranged axially against the annular portion 61 on the side of the bearing 17 and which annularly contacts the main body 60 on the side opposite the axis A.

[0124] Locking element 55 also includes a plurality of appendages 75 that extend axially in a cantilevered manner from main body 60 and are set axially spaced from ring 65 .

[0125] The appendages 75 define respective axial slots 76 .

[0126] In the illustrated case, the appendage 75 is U-shaped. The appendage 75 also comprises two axial sections 71 cantilevered from the main body 60 and a free connecting section 72 between the arms 71.

[0127] In the illustrated case, the segments 72 of the appendages 75 extend from the respective segments 71 such that they diverge with respect to the axis A and run parallel to the axis A in the opposite direction to the segments 71 .

[0128] The appendages 75 are evenly angularly spaced from one another.

[0129] The appendages 75 and the arms 70 are circumferentially distinct from one another.

[0130] The appendage 75 is axially spaced and distinct from the ring 65 .

[0131] In the illustrated case, the ring 65 is disposed axially between the main body 60 and the rolling elements 32 .

[0132] The torque balance rotor 4 is a ring 80 connected to the ring 50 by a number of axial pins 82, six in the illustrated case, angularly fixed relative to the axis A and spaced apart from one another such that they slide axially together with the ring 50, the bearing 17 and the control rod 10; a ring 85, which is angularly fixed with respect to the axis A and slides axially together with the ring 50, the bearing 17 and the control rod 10; a plurality of radially extending pins 81, in the illustrated case four, engaging with axial play in the respective slots 76, fastened to the ring 80 and arranged in axial abutment with the ring 85; It also has the following features.

[0133] In the illustrated case, portion 62 of main body 60 is radially interposed between rings 80 and 85 .

[0134] 3 to 9, the ring 80 is fastened to the section 26 of the main body 25, which is axially interposed between a nut 29 screwed onto the end 24 of the control rod 10 and a shoulder 28 of the control rod 10.

[0135] When positioned in the first or second emergency configuration (FIGS. 6-9), the locking element 55 can slide along the axis A relative to the rings 85, 80, 31, and 30 and the control rod 10. This occurs due to the engagement of the pins 81 with the respective slots 76 with axial play.

[0136] When the locking element 55 is in the standard configuration (Figures 4 and 5), the pins 81 are positioned axially abutting respective axial ends 77 of corresponding slots 76 located on opposite sides of the bearing 17 (Figure 5).

[0137] Conversely, when positioned in the first or second emergency configuration (Figures 6 to 9), the locking elements 55 can be slid to a withdrawn position in which the pins 81 are positioned against their respective axial ends 78 located on the side of the bearing 17 opposite the ends 77 of the corresponding slots 76 (Figure 7).

[0138] The torque balance rotor 4 also comprises a spring 100 interposed between the ring 50 and the locking element 55 .

[0139] Spring 100 is oriented parallel to axis A and is configured to exert a resilient force on locking element 55 oriented away from bearing 17. This force resiliently preloads locking element 55 towards the extracted position in Figures 6-9.

[0140] This elastic force is opposed by an opposing axial frictional force resulting from the radial interference between ring 65 and surface 38 that is reached in the standard configuration when locking element 55 is in the inserted position (Figures 4 and 5).

[0141] When the locking element 55 is arranged in this first or second emergency configuration, it is pushed axially by the spring 100 from the side opposite the bearing 17 until it reaches the extracted position (FIGS. 6 to 9).

[0142] Reaching this withdrawn position is indicative of a bearing 17 failure condition.

[0143] More precisely, the spring 100 is interposed between a ring 64 integral with the locking element 55 and a ring 85 in abutment against the pin 81 .

[0144] In the illustrated case, the spring 100 is a wave spring.

[0145] Specifically, the spring 100 comprises two annularly extending corrugated elements which cooperate with one another in the axial direction.

[0146] With reference to FIG. 2, the torque balance rotor 4 also comprises a cover element 46 which is fastened to the flange 42 and is consequently rotatable about the axis A with the element 16 .

[0147] Cover 46 is symmetrical about axis A and defines cavity 47 which houses main body 60 , spring 100 , nut 29 , pin 81 , and rings 80 and 85 .

[0148] Preferably, the cover 46 is made from a transparent material and is visible from outside the helicopter 1 .

[0149] The cover 46 is rotatable about the axis A together with the control element 16 .

[0150] The locking element 55 also preferably comprises a colored annular band (not shown in the accompanying drawings).

[0151] This annular band is externally visible through the cover 46 when the locking element 55 is in the withdrawn position so as to provide a quick indication of the fact that the locking element 55 is in the withdrawn position.

[0152] Conversely, this annular band is not visible from the outside through the cover 46 when the locking element 55 is in the inserted position.

[0153] 5, 7 and 9, shoulder 37 of bearing 17 is set radially away from ring 30. As shown in FIG.

[0154] The outer diameter of shoulder 37 is greater than the inner diameter of raceways 33 and 34 .

[0155] Thus, in the event of a failure of the bearing 17 resulting in the destruction of the rolling elements 32 , translation of the control rod 10 towards the raceway 33 will bring the shoulder 37 into abutment against the raceway 33 .

[0156] Similarly, translation of the control rod 10 towards the track 34 causes the shoulder 37 to abut the track 34 .

[0157] The axial contact of shoulder 37 with raceways 33 and 34 allows the set formed by control rod 10 and rings 31 and 50 to slide again together with ring 30 along axis A, thereby preventing loss of controllability of torque-balancing rotor 4.

[0158] Furthermore, the shoulder 37 is set axially away from the cage 39 of the rolling element 32 .

[0159] The bearing 17 also comprises an annular insert 93 axially interposed between the half rings 41 and arranged on the radially outer surface of the ring 30 .

[0160] Backup bearing 54 also includes an annular insert 94 disposed between half rings 45 and on the radially inner surface 58 of ring 50 .

[0161] The operation of the torque balance rotor 4 is described hereinafter starting from the state in which the bearings 17 are functioning properly and the locking elements 55 are arranged in their standard configuration and insertion position (FIGS. 2, 4 and 5).

[0162] In this state, operation of the flight control 15 results in translation of the control rod 10 in a given direction along the axis A.

[0163] This translation results in a joint translation of bearing 17 and element 16 along axis A.

[0164] As a result, the element 16 moves away from (or towards) the vane 8 , changing the inclination of the lever 43 relative to the axis B and increasing (or decreasing) the angle of attack of the vane 8 .

[0165] This movement of lever 43 results in simultaneous rotation of vanes 8 through an equal angle about associated axis B, resulting in adjustment of the angle of attack of vanes 8 .

[0166] Bearing 17 allows rotation of element 16 relative to control rod 10 about axis A.

[0167] More specifically, ring 30 rotates integrally with element 16 about axis A, while rings 31 and 50 remain fixed relative to axis A.

[0168] This occurs because ring 65 is forced against ring 31 with radial interference, preventing rotation of ring 31 and, consequently, ring 50 as well.

[0169] The axial frictional force generated by the interference assembly is greater than the elastic force exerted by the spring 100 on the locking element 55 .

[0170] In this condition, the ring 50, and consequently the backup bearing 54, is essentially non-functional.

[0171] In the event of a failure of the bearing 17 resulting in a rise in temperature in the region of the bearing 17 above the respective threshold value, the radial thermal expansion of the ring 65 will be greater than that of the ring 31 .

[0172] As a result, the locking element 55 moves to a first emergency configuration (FIGS. 6 and 7) in which the ring 65 is set away from the ring 31 .

[0173] Thus, ring 31 can rotate about axis A relative to ring 50 , which instead remains angularly fixed about axis A because it is prevented by control rod 10 .

[0174] In this condition, ring 31 and bearing 17 are substantially non-functional and rotation of element 16 relative to control rod 10 about axis A is permitted by backup bearing 54 .

[0175] In the event of an increase in the torque transmitted from ring 31 to ring 30 and / or a failure of bearing 17 resulting in vibrations in the area of ​​bearing 17 exceeding a threshold value, a torsional fracture of arm 70 is induced.

[0176] This destruction causes the locking element 55 to assume the second emergency configuration (FIGS. 8 and 9).

[0177] Thus, similar to the first emergency configuration, ring 31 can rotate about axis A relative to ring 50, which instead remains angularly fixed about axis A.

[0178] Furthermore, ring 31 and bearing 17 are substantially non-functional, and rotation of element 16 relative to control rod 10 about axis A is permitted by backup bearing 54 .

[0179] When set in the first or second configuration, the locking element 55 is urged by the spring 100 towards the retracted position (FIGS. 6-9).

[0180] This sliding results in movement of the slot 76 relative to the pin 81 and movement of the ring 85 .

[0181] In the withdrawn position, the annular band of the locking element 55 is visible from the exterior of the helicopter 1 and provides a visual guide to the pilot or test technician that the bearing 17 is in an incipient or active failure state.

[0182] In the event of failure of the bearing 17 resulting in destruction of the rolling elements 32, translation of the control rod 10 towards the raceway 33 (34) will cause the shoulder 37 to abut against the raceway (34), maintaining two-way axial contact between the control rod 10 and the bearing 17, thereby ensuring controllability of the torque balanced rotor 4.

[0183] With reference to Figures 12 and 13, reference numeral 4' designates a torque balancing rotor according to a second embodiment of the invention.

[0184] Rotor 4' is similar to rotor 4 and only the differences with rotor 4 are described below, identical or equivalent parts of rotors 4, 4' being marked with the same reference numbers where possible.

[0185] Rotor 4 ′ differs from rotor 4 in that it does not include a shoulder 37 .

[0186] Furthermore, rotor 4' differs from rotor 4 in that a pair of blocking elements 90' is interposed axially between shoulders 35, 36.

[0187] Rotor 4' also differs from rotor 4 in that surface 38' includes a pair of expansions 99' interposed between rolling elements 32 in the axial direction.

[0188] The telescoping portions 99' are axially contiguous and converge symmetrically toward one another on opposite sides of the axis A relative to the remainder of their respective surfaces 38'.

[0189] The extension 99' is planar so as to define an inverted V-shape towards the blocking element 90'.

[0190] The blocking element 90 ′ is fixed to the ring 30 .

[0191] In a normal configuration, the bearing 17 does not allow axial movement between the rings 30,31.

[0192] In this normal configuration, blocking element 90' rotates integrally with ring 30 relative to ring 31.

[0193] Additionally, the blocking elements 90' are spaced apart by respective telescoping portions 99' with respective clearances 108'.

[0194] The difference is that a certain axial movement is permitted between the rings 30, 31 in the event of damage to the raceways 33, 34 of the rolling elements 32, a phenomenon known technically as "spalling."

[0195] In this condition, the blocking elements 90 ′ contact and engage the respective surfaces 99 ′, thereby substantially reducing, or even substantially preventing, wear between the rings 30 , 31 .

[0196] More specifically, the blocking elements 90' are interposed between the rolling elements 32 in the axial direction.

[0197] Each blocking element 90 ′ includes a respective radially inner surface 101 ′ that tapers relative to the axis A.

[0198] Further, each blocking element 90' is bounded by a respective inner surface 101' and a respective radially outer surface 102' diametrically opposed with respect to the axis A.

[0199] The size of surface 101' parallel to the axis is greater than the size of surface 102' parallel to the axis A.

[0200] Each element 90' is further bounded by a respective radial surface 103' extending between and in contact with respective surfaces 101', 102'.

[0201] Each element 90' has - each main body 105' defining a surface 101', 102', 103'; - a respective radial shoulder 106' projecting from the body 105' and bounded by the surfaces 102', 103'; a respective further radial shoulder 107' projecting from the body 105', spaced axially from the respective shoulder 106' and bounding the blocking element 90' on the axially opposite side relative to the respective surface 103'; It also has the following features.

[0202] The radial extent of shoulder 106' relative to axis A is greater than the radial extent of shoulder 107' relative to axis A.

[0203] A shoulder 106' of each blocking element 90' is axially interposed between a respective shoulder 107' and the surface 103'.

[0204] The blocking elements 90', the respective clearances 108' and the respective surfaces 101' are arranged symmetrically with respect to a plane perpendicular to the axis A.

[0205] Specifically, surfaces 103' of each element 90' abut one another in an axial direction parallel to axis A and lie in a plane perpendicular to axis A.

[0206] The surfaces 101' diverge symmetrically from one another starting from their respective surfaces 103' towards the axis A and proceed towards respective shoulders 107'.

[0207] The clearances 108' diverge from one another starting at each surface 103' toward each shoulder 107'.

[0208] Shoulders 106 ′ and 107 ′ contact respective half rings 41 of ring 30 .

[0209] Even more precisely, the shoulders 106' are interposed between the half-rings 41 in the axial direction.

[0210] The shoulder 107 ′ radially abuts against a radially inner surface 109 ′ of each half-ring 41 .

[0211] The operation of rotor 4' differs from that of rotor 4 in that when bearings 17 are operating correctly and locking element 55 is in the standard configuration and insertion position, blocking element 90' rotates together with ring 30 about axis A relative to stationary ring 31 and is spaced from relative expansion portion 99' with relative clearance 108'.

[0212] In this condition, the bearing 17 substantially prevents axial movement between the rings 30,31.

[0213] The difference is that a certain amount of axial movement can be permitted between the rings 30, 31 in the event of failure of the bearing 17 due to damage to the raceways 33, 34 of the rolling elements 32, a phenomenon known technically as "spalling."

[0214] However, in this condition, blocking element 90' resists relative expansion 99' of ring 31, thus preventing this axial movement and the resulting wear, heat generation, and potential damage to rings 30,31.

[0215] Specifically, the axial displacement of the ring 31 is caused by the movement of the control rod 10 by the action of the pilot.

[0216] With reference to Figures 14 to 17, reference numeral 4'' designates a torque balancing rotor according to a third embodiment of the present invention.

[0217] Rotor 4'' is similar to rotor 4 and only the differences to rotor 4 are described below, with identical or equivalent parts of rotors 4, 4'' being marked with the same reference numbers where possible.

[0218] The rotor 4'' differs from the rotor 4 in that the rings 50'', 31'' and the rolling elements 51'' form a bearing 17''.

[0219] The difference is that the rings 31'', 30'' and rolling elements 32'' form a backup bearing 54''.

[0220] In the embodiment shown, the rolling elements 51'' roll in respective raceways 52'', 53'' of respective rings 31'', 50''. Furthermore, the rolling elements 51'' form two axially spaced apart rings of a tapered roller.

[0221] The rolling elements 51'' are axially preloaded in the embodiment shown and are tapered rollers.

[0222] The rolling elements 32'' roll in respective raceways 33'', 34'' of respective rings 30'', 31''. In the embodiment shown, the rolling elements 32'' form two axially spaced rings of a tapered roller.

[0223] The rolling elements 32'' are, in the embodiment shown, axially preloaded and are interposed axially between the rolling elements 51''.

[0224] The radially outer surface 57'' of the ring 50'' includes a pair of telescoping portions 98'' that define respective raceways 53'' and a pair of telescoping portions 99'' axially interposed between the telescoping portions 98''.

[0225] The telescopic portions 99'' are axially continuous and converge symmetrically towards each other on the side of the axis A relative to the remainder of the surface 57''.

[0226] The extension 99'' is planar so as to define an inverted V-shape.

[0227] Ring 31'' also includes: - a central body 120''; a pair of lateral projections 101 ″ axially opposite one another and projecting from opposite axial sides of each of the body 120 ″; Equipped with.

[0228] The body 120'' is bounded by a pair of radially inner surfaces 103'' that converge towards each other on the side of the axis A and face the respective telescopic portions 99''.

[0229] In particular, surface 103'' is radially outward relative to relative expansion portion 99''.

[0230] When the bearing 17'' is operating correctly and the locking elements 55'' are in their normal configuration and insertion position, the surfaces 103'' are separated from the respective expansion portions 99'' of the ring 50'' by respective clearances 108''.

[0231] The surface 103 ″, the clearance 108 ″, and the expansion portion 99 ″ extend symmetrically with respect to a plane perpendicular to the axis A.

[0232] The difference is that a certain amount of axial movement can be permitted between rings 50'', 31'' in the event of failure of bearing 17'' due to damage to the raceways 52'', 53'' of rolling elements 51'', a phenomenon known in the art as "spalling".

[0233] However, in this condition, surface 103'' axially blocks against the relative expansion 99'' of ring 31'', thus preventing this axial movement and the resulting wear, heat generation, and potential damage to rings 50'', 31''.

[0234] The projections 101'' define respective raceways 34'' on their respective radially outer surfaces and respective raceways 52'' on their respective radially inner surfaces.

[0235] Rotor 4'' differs from rotor 4 in that, when arranged in the standard configuration and insertion position shown in Figures 14 and 16, when bearing 17'' is in its normal operating condition, locking element 55'' prevents relative rotation of rings 30'', 31'' and allows relative rotation between the assembly formed by rings 30'', 31'' and stationary ring 50''.

[0236] In this state, ring 50'' is angularly stationary relative to axis A, while rings 31'', 30'' rotate about axis A.

[0237] In such a situation, rotation between rings 50'' and 30'', 31'' may be lubricated by grease.

[0238] Furthermore, when the locking element 55'' is disposed and set in the extracted position shown in Figures 15 and 17, in either the first or second emergency configuration, it holds the rings 31'', 50'' together about the axis A when the bearing 17'' is in a failure condition, and allows rotation of the ring 30'' about the axis A relative to the stationary assembly formed by the rings 31'', 50''.

[0239] Thus, when bearing 17'' is in a failed condition, ring 30'' rotates about axis A while rings 50'', 31'' are angularly stationary relative to axis A.

[0240] In this condition, the rings 31'', 30'' define a backup bearing 54''.

[0241] The locking element 55 ″ differs from the locking element 55 for rotating together with the spring 100 and the cover 46 about the axis A in unison.

[0242] Specifically, the locking element 55'' is similar to the pin 81, rotates integrally with the cover 46, and includes a plurality of pins 81'' each of which engages with a slot 76'' with axial play similar to the slot 76 which rotates integrally with the cover 46.

[0243] The rotor 4'' is a tank 150 ″ filled with lubricant fluid; - a breakable element 151'' which bounds the tank 150'' on the side of the rings 30'', 31'', 50'', a plurality of punching elements 152'' carried by the locking elements 55''; In order to advantageously provide the rotor 4, The punching element 152'' is spaced apart from the breakable element 151'' when the locking element 55'' is in the insertion position (FIGS. 14 and 16) and punches the breakable element 151'' when the locking element 55'' is in the withdrawal position (FIGS. 15 and 17).

[0244] The breakable element 151'' fluidly isolates the tank 150'' from the rolling body 32'' when the locking element 55'' is in the inserted position (Figures 14 and 16) and fluidly connects the tank 150'' to the rolling body 32'' when the locking element 55'' is in the extracted position (Figures 15 and 17).

[0245] In particular, the tank 150 ″ is defined by the cover 46 and extends annularly about the axis A.

[0246] The breakable element 151 ″ extends parallel to the axis A when the locking element 55 ″ is in the inserted position and closes the tank 150 ″ on the side opposite the cover 46 .

[0247] In the embodiment shown, the breakable element 151'' is a disk-shaped membrane, preferably made from aluminum.

[0248] The punching element 152 ″ projects from the body 60 of the locking element 55 ″ on the axially opposite side to the ring 65 .

[0249] In the illustrated embodiment, the punching elements 152 ″ are angularly spaced about axis A.

[0250] As shown in FIG. 15, the punching element 152'' is shaped as a relative lance with converging sharp tips leading from the body 60 towards the breakable element 151''.

[0251] Preferably, punched element 152'' is radially outward relative to element 65 and defines the radially outer perimeter of element 55''.

[0252] In the illustrated embodiment, the body 60 and punching element 152'' are made from titanium.

[0253] The ring 65 and arms 70 are made from aluminum in the embodiment shown.

[0254] When the locking element 55'' is in the withdrawn position shown in FIG. 17, the rotor 4'' defines a fluid path 170'' from the tank 150'' to the area 160'' surrounding the rolling elements 32''.

[0255] In particular, region 160'' is radially bounded between rings 30'', 31''.

[0256] The region 160'' is bounded axially between the shoulders 35, 36 on the opposite radial side to the axis A and between the projections 101'' on the side of the axis A.

[0257] 17, the fluid path 170'' extends radially around the rotor 4''. Additionally, the path 170'' includes a plurality of through openings 171'' that extend axially through the broken element 152'', the passage 175'' between the rings 65'' and 31'', and the passage 176'' between the rings 31'' and 30''.

[0258] The difference is that when the locking element 55'' is in the withdrawn position shown in FIG. 17, the fluid path 170'' is blocked by the breakable element 151''.

[0259] The rotor 4'' also comprises a labyrinth seal 180'' arranged on the opposite axial side of the rolling body 32'' relative to the breakable element 151'' and adapted to tightly close the fluid path 170'' and to keep the lubricant fluid in continuous contact with the rolling body 32'' when the locking element 55'' is in the withdrawn position.

[0260] In particular, the labyrinth seal 180'' is a seal 181 ″ interposed radially between the rings 50 ″, 31 ″ on the axially opposite side to the element 55 ″; a seal 182'' interposed between the rings 50'', 30'' radially on the axial side opposite the seal 181'' with respect to the rolling element 32'', (Figure 17)

[0261] Specifically, seals 181'', 182'' are shaped as annulus. In the illustrated embodiment, seal 182'' has a larger radial dimension than seal 181''.

[0262] The operation of the rotor 4'' differs from that of the rotor 4 in that the locking element 55'' rotates about the axis A integrally with the cover 46 and the ring 30'' by virtue of the connection between the pins and the respective slots.

[0263] When the locking element 55 ″ is in the insertion position and standard configuration of FIGS. 14 and 16 , the bearing 17 ″ formed by the rings 50 ″, 31 ″ and the rolling elements 51 ″ allows rotation of the element 16 about the axis A relative to the rod 10 .

[0264] More specifically, ring 50'' is stationary about axis A, and rings 31'', 30'' rotate together about axis A. In this state, locking element 55'' is in contact with ring 31'' and is angularly unitary with ring 31''.

[0265] Furthermore, the backup bearing 54'' is essentially non-functional.

[0266] The punching element 152'' is spaced apart from the breakable element 151'', which has not yet been broken.

[0267] Thus, lubricant fluid remains in the tank 150''.

[0268] In the event of a failure of the bearing 17'' resulting in an increase in the temperature of the bearing 17'' exceeding a threshold value or an increase in the torque transmitted from the ring 31'' to the ring 50'' and / or an increase in vibrations in the area of ​​the bearing 17'' exceeding the respective values, the locking element 55'' is displaced into the first or second emergency configuration shown in Figures 15 and 17.

[0269] The spring 100 therefore biases the locking element 55'' into the extracted position shown in FIGS.

[0270] In this state, ring 31 ″ remains angularly stationary and rolling elements 32 ″ allow rotation of ring 30 ″ relative to ring 31 ″ about axis A.

[0271] Furthermore, the punching element 152'' destroys the breakable element 151''. In this way, the lubricant fluid contained in the tank 150'' can flow along the fluid path 170'' from the tank 150'' to the area 160'' to ensure continuous lubrication of the rolling bodies 32''.

[0272] More precisely, the lubricant fluid flows through a passage 171'' through the broken breakable element 151'' and through a passage 172'' between the rings 65, 31''.

[0273] The locking elements 55'', the cover 46 and the rings 31'', 30'', due to centrifugal action, generate a lubricant fluid bath (shown in grey in FIG. 17) in the peripheral area of ​​the rotor 4'' where the rolling elements 32'' are arranged, as shown in FIG.

[0274] The labyrinth seal 180'' is effective in containing the lubricant fluid within the region 160''.

[0275] Regardless of the configuration of the locking element 55'', the normal blocking surface 103'' rotates with the ring 31'' about the axis A relative to the stationary ring 50'' and is spaced from the relative expansion 99'' with a relative clearance 108''.

[0276] In this condition, bearing 17'' substantially prevents axial movement between rings 50'', 31''.

[0277] The difference is that a certain amount of axial movement can be permitted between rings 50'', 31'' in the event of failure of bearing 17'' due to damage to the raceways 53'', 52'' of rolling elements 51'', a phenomenon known in the art as "spalling".

[0278] However, in this condition, surface 103'' of ring 31'' axially blocks against the relative expansion 99'' of ring 50'', thus preventing this axial movement and the resulting wear, heat generation, and potential damage to rings 50'', 31''.

[0279] From an examination of the characteristics of the torque balancing rotors 4, 4', 4'' according to the invention, the advantages which can be achieved thereby become apparent.

[0280] More specifically, locking element 55 prevents relative rotation of rings 31 and 50 in a standard configuration (FIGS. 4 and 5) and allows rotation of ring 31 relative to ring 50 in first and second emergency configurations (FIGS. 6-9) when bearing 17 is in an incipient or active failure.

[0281] In this manner, in the event of an initial or effective failure that would result in even partial seizure of bearing 17, rings 30 and 31 can rotate together relative to ring 50, thereby preserving the ability to adjust the angle of attack of vanes 8 via control rod 10. In other words, in the event of a failure, bearing 17 will not function and backup bearing 54 will automatically function.

[0282] More specifically, in the event of a temperature increase in the region of the bearing 17, the locking element 55 moves from the standard configuration to the first emergency configuration.

[0283] More specifically, by having a larger coefficient of thermal expansion, ring 65 disengages from surface 38 of ring 31, which has a smaller coefficient of thermal expansion.

[0284] If the torque acting on the ring 31 or the vibrations in the area of ​​the bearing 17 exceed a respective threshold value, the locking element 55 moves from the standard configuration to the second emergency configuration.

[0285] More specifically, the arm 70 breaks due to twisting.

[0286] In this manner, rings 31 and 30 rotate relative to ring 50 when the temperature in the region of bearing 17 exceeds a respective threshold value and / or when an inappropriately acting torque on ring 31 or vibrations in the region of bearing 17 exceed a respective threshold value.

[0287] Furthermore, the locking element 55 is placed in the withdrawn position when either the first or second standard configuration is reached.

[0288] In this way, it is possible to recognize an incipient or active condition of failure of the bearing 17 based solely on the axial position of the locking element 55 relative to the control rod 10 .

[0289] The spring 100 elastically preloads the locking element 55 towards the extracted position and favours a rapid reaching of this position.

[0290] When the locking element 55 is in the withdrawn position, the strap is visible through the transparent cover 46 to the crew and / or inspection technicians from outside the helicopter 1, thereby providing a clear and immediate indication that the bearing 17 is in a failed condition.

[0291] Shoulder 37 has a larger outside diameter than raceways 33 and 34 of bearing 17 .

[0292] Thus, in the event of failure of the bearing 17 resulting in destruction of the rolling elements 32, translation of the control rod 10 towards the raceways 33 or 34 will bring the shoulder 37 into abutment with the raceways 33 or 34, preventing loss of controllability of the torque-balanced rotors 4, 4'.

[0293] The rotor 4' (FIGS. 12 and 13) further comprises a pair of blocking elements 90' carried by the ring 30 and provided with respective tapered surfaces 101'.

[0294] Surfaces 101' are spaced from respective expansion portions 99' of ring 31 when bearing 17 is in normal operating conditions.

[0295] The difference is that the surface 101 ′ blocks the blocking element 90 ′ integral with the ring 30 against the respective expansion portion 99 ′ of the ring 31 in the event of failure of the bearing 17 due to damage to the raceways 33 , 34 of the rolling elements 32 .

[0296] In this manner, relative axial movement between the rings 30, 31 is substantially prevented even when the raceways 33, 34 are damaged.

[0297] Thus, wear, heat generation and the resulting risk of damage to the rings 30, 31 are substantially avoided.

[0298] The locking elements 55'' of the rotor 4'' allow relative rotation of ring 31'' with respect to ring 50'' in the standard configuration (Figures 14 and 16) and allow relative rotation of ring 30'' with respect to ring 31'' in the first and second emergency configurations (Figures 15 to 17) when the bearing 17'' is in an incipient or active failure.

[0299] In this way, the locking element 55 ″ of the rotor 4 ″ achieves substantially the same advantages as the locking element 55 of the rotor 4 .

[0300] Furthermore, the locking element 55'' comprises a number of punching elements 152'' which break the breakable element 151'' when the locking element 55'' is set in the withdrawn position and in the event of failure of the bearing 17''.

[0301] In this manner, the lubricant fluid contained in the tank 150'' can flow along the fluid circuit 170'' toward the rolling elements 32'' to ensure proper operation of the rolling elements 32'' of the backup bearing 54''.

[0302] Rotation of the cover 46, the locking element 55'' and the ring 30'' about the axis A propels the lubricant fluid towards the rolling elements 32'', which are arranged radially outside the rolling elements 51'', due to centrifugal action.

[0303] In this way, the centrifugal action generates a lubricant fluid bath in the peripheral area of ​​the rotor 4'' where the rolling elements 32'' and the area 160'' are located.

[0304] The labyrinth seal 180'' is effective in containing the lubricant fluid within the region 160''.

[0305] As with rotor 4', surfaces 103'' of ring 31'' are spaced from respective extensions 99'' of ring 30'' when bearing 17'' is in normal operating conditions.

[0306] The difference is that the surface 103'' provides a block against the respective extension 99'' in the event of failure of the bearing 17'' due to damage to the raceways 52, 53 of the rolling elements 51''.

[0307] In this way, relative axial movement between the rings 50'', 31'' is substantially prevented even when the raceways 52, 53 of the rolling elements 51'' are damaged.

[0308] Thus, wear, heat generation and the resulting risk of damage to the rings 50'', 31'' are substantially avoided.

[0309] The rings 30, 30''; 31, 31''; 50, 50'' of the rotors 4, 4', 4'' are coaxial and extend around a common axis A.

[0310] Even more precisely, the rings 50, 50'' are radially inward relative to the rings 31, 31'', which in turn are radially inward relative to the rings 30, 30''.

[0311] The bearings 17, 17''; 54, 54'' of the rotors 4, 4', 4'' are therefore particularly compact in the radial direction of the axis A compared to the solution shown in US Pat. No. 9,359,073(B) and discussed in the introduction to this description.

[0312] In this way, the raceways 52'', 53'', 33'', 34'' can be mounted coaxially inside the rotors 4, 4'', 4'', with a very limited axial dimension, thus making substantially no need for a redesign of the rotors 4, 4'' different from the solution shown in U.S. Pat. No. 9,359,073(B).

[0313] Furthermore, the orbits 52'', 53'', 33'', 34'' are defined by only three rings 30, 30''; 31, 31''; 50, 50'', instead of the four rings disclosed in U.S. Pat. No. 9,359,073(B).

[0314] By making the rings 30, 30''; 31, 31''; 50, 50'' coaxial, the bearings 17, 17''; 54, 54'' can transmit translational loads along a first direction parallel to the axis A and second and third directions perpendicular to the axis A, and can transmit rotational loads about the second and third directions.

[0315] The difference is that the bearings disclosed in US Pat. No. 9,359,073(B) are effective to transmit only axial loads parallel to the direction of rotation of the mast.

[0316] Furthermore, the bearings 17, 17''; 54, 54'' comprise two rings of rolling elements 32, 32''; 51, 51''.

[0317] In this way the rolling elements 32, 32''; 51, 51'' can be easily axially preloaded and therefore axial play and the resulting vibrations and noise can be strongly suppressed.

[0318] The rolling elements 51, 51'' are tapered rollers. In this way the bearings 17, 17''; 54, 54'' are substantially not exposed to the spurious Brinell damage mechanisms.

[0319] Finally, it is evident that improvements and modifications can be made to the torque balance rotors 4, 4', 4'' described and illustrated herein without departing from the scope defined by the claims.

[0320] Specifically, ring 50 may be disposed radially outward of ring 30 .

[0321] Furthermore, the locking element 55 may comprise a number of radial pins interposed between the ring 65 and the surface 38. These pins are breakable if the torque transmitted from the ring 30 to the ring 31 and / or the vibrations in the area of ​​the bearing 17 exceed a respective threshold value. These pins are also made from a material that has a particularly low torsional resistance above a threshold value.

[0322] Locking element 55 may include a braze between rings 31 and 50 sized to allow rotation between rings 31 and 50 when the torque transmitted from ring 30 or vibrations in the region of bearing 17 exceed respective thresholds. Additionally, the braze is made with a material that allows rotation of ring 31 relative to ring 50 when a temperature threshold is exceeded.

[0323] The rolling elements 32, 32'' and 51, 51'' may be needle rollers, spherical rollers, self-aligning ball bearings, or plain ball bearings.

[0324] The rolling elements 32, 32'' and 51, 51'' may have an "O" (back-to-back) arrangement instead of an "X" (face-to-face) arrangement. [Explanation of symbols]

[0325] 1. Helicopter 2. Aircraft 3 Main rotor 4, 4', 4'' torque balance rotor 5. Turbine 6 Mast 8 wing plate 9. Hub 10 Control Rod 12 Gear train 13 Shaft 14 Base 15 Flight Control Unit 16 Control Elements 17, 17'' bearing 18 Connected Elements 19 Flange 20 Axial end 22 Main Section 24 Second Axial End 25 Main Body 26, 27 division 28 Shoulder 29 Nut 30, 30'' radial outer ring 31, 31'' radial inner ring 32, 32'' rolling elements 33, 33′′, 34, 34′′ orbital 35, 36 Shoulder 37 Shoulder 38, 38′ Ring surface 39 Circular Cage 40 Tubular body 41 Half Ring 42 Flange 43 Lever 44 Variable length bellows joint 45 Half Ring 46 Cover Elements 47 Cavity 50, 50'' Ring 51, 51'' rolling element 52, 52′′, 53, 53′′ orbital 54, 54'' Backup bearing 55, 55'' Locking element 57, 57'' radially outer surface 58 Radial inner surface 59 Circular Cage 60 Main Body 61 Ring part 62 Cylindrical Part 64, 65 Ring 70 Arm 71 Axial division, arm 72 Free connection category 75 Attachments 76, 76'' Axial slot 77, 78 Axial end 80 Ring 81, 81'' pin 82 Axial Pin 85 Ring 90′ blocking element 93, 94 Annular insert 99′ Telescopic part 99′ Telescopic part, surface 99′′ Telescopic part 100 Spring 101' radially inner surface, tapered surface 101′′ Protrusion 102' radially outer surface 103′ radial surface 103'' Radially inner surface, normal blocking surface 105′ Main body 106′ Radial Shoulder 107′ Radial Shoulder 108′, 108′′ Clearance 109′ inner surface 120′′ Center body 150'' Tank 151'' Destructible elements 152'' punching element 160'' Area surrounding the rolling element 32'' 170'' Fluid path, fluid circuit 171′′ Through opening, passage 172'' Aisle 175'' and 176'' aisles 180'' labyrinth seal 181'' Seal 182'' Seal A, B, C axis

Claims

1. A torque balancing rotor (4) for a helicopter (1), comprising: a mast (6) rotatable about a first axis (A), a plurality of vanes (8) hinged to said mast (6), extending along respective second axes (B) transverse to said first axis (A) and rotatable about said respective second axes (B) to vary their respective angles of attack; an element (16) sliding relative to said mast (6) along said first axis (A) and rotating integrally with said mast (6), said element (16) being operatively connected to said vanes (8) in order to bring about a rotation of said vanes (8) about their respective second axes (B) following a translation of said element (16) along said axis (A); a control rod (10) which slides axially relative to said mast (6) along said first axis (A) and is angularly fixed relative to said first axis (A); a first bearing (17) interposed between said control rod (10) and said element (16) and adapted to slide along said first axis (A) in unison with said control rod (10) relative to said mast (6) and to allow, in correct operating conditions, a relative rotation of said element (16) with respect to said control rod (10) about said first axis (A); and the first bearing (17) further comprises: a first ring (30) rotatable together with said element (16) about said first axis (A); a second ring (31) located radially inside said first ring (30) with respect to said first axis (A) and sliding integrally with said control rod (10) along said first axis (A); a plurality of first rolling elements (32) interposed between said first and second rings (30, 31) and adapted to roll in first raceways (33, 34) of said first and second rings (30, 31), respectively; a third ring (50) sliding integrally with said control rod (10) along said first axis (A) and angularly fixed relative to said first axis (A); a plurality of second rolling elements (51) interposed between said second and third rings (31, 50) and adapted to roll in second raceways (52, 53) of said second and third rings (31, 50), respectively; - locking elements (55) arranged in a standard configuration, which prevent relative rotation of said second and third rings (31, 50) when said first bearing (17) is in its normal operating condition during use; Equipped with the locking element (55) being movable from the standard configuration to at least a first or second emergency configuration, allowing the second ring (31) to freely rotate relative to the third ring (50) about the first axis (A) when the first bearing (17) is in a failed condition during use; The locking element (55) further comprises: a main body (60), a fourth ring (65) which is fastened to said second ring (31) at least when said locking element (55) is placed in said standard configuration during use; at least one connecting arm (70) interposed between said main body (60) and said fourth ring (65) at least when said locking element (55) is arranged in said standard configuration during use; Equipped with when the locking element (55) is arranged in the standard configuration during use, the fourth ring (65) is press-fitted by interference in the second ring (31); At least the fourth ring (65) is made from a material having a first coefficient of thermal expansion greater than a second coefficient of thermal expansion of the second ring (31); 1. A torque balanced rotor comprising: a rotor member having a first bearing and a second bearing, the first bearing being configured to receive a torque from the second ring and a torque balancer;

2. 2. A torque balance rotor according to claim 1, characterized in that the locking element (55) is angularly fixed with respect to the first axis (A) and is slidable along the first axis (A) integrally with the third ring (50) when arranged in the standard configuration during use.

3. 3. A torque balanced rotor according to claim 1 or 2, characterized in that the main body (60) and the fourth ring (65) are separated at least when the locking elements (55) are in a second emergency configuration which is reached when, in use, a torque acting on the second ring (31) exceeds a second threshold value.

4. 4. A torque balanced rotor according to claim 3, characterized in that the connecting arms (70) are breakable when, in use, the torque acting on the second ring (31) and the fourth ring (65) is greater than the second threshold value, so as to place the locking elements (55) in the second emergency configuration.

5. The locking element (55), when in use arranged in the first or second emergency configuration, is oriented parallel to the first axis (A) relative to the third ring (50): an insertion position reached in said standard configuration, in which said locking element (55) is at a first axial distance from said third ring (50); a withdrawal position reached in the first or second emergency configuration, wherein the locking element (55) is at a second axial distance from the third ring (50), the second axial distance being greater than the first axial distance; 5. A torque balance rotor according to claim 1, characterized in that it is slidable between

6. the torque balance rotor comprises elastic means (100) at least indirectly interposed between the third ring (50) and the locking element (55); A torque balance rotor according to claim 5, characterized in that the elastic means (100) elastically preload the locking elements (55) towards the extracted position.

7. The torque balance rotor (4) comprises a cover (46) made of a transparent material and housing at least a portion of the main body (60); A torque balance rotor according to claim 5 or 6, characterized in that the main body (60) comprises a band which is visible through the cover (46) when the locking element (55) is placed in the extracted position.

8. at least one pin (81) at least indirectly connected to said third ring (50) and extending radially towards said first axis (A); at least one axial slot (76) carried by said locking element (55) and axially slidable relative to said pin (81) while allowing said pin (81) to pass radially therethrough at least when said locking element (55) is in said first or second emergency configuration; A torque balancing rotor according to any one of claims 1 to 7, characterized in that it comprises:

9. The locking element (55) further comprises: a plurality of said axial slots (76) angularly spaced apart from one another about said first axis (A) and through which each of said pins (81) passes; a plurality of said linking arms (70) angularly spaced apart from one another about said first axis (A); Equipped with A torque balance rotor according to claim 8, characterized in that said axial slots (76) and said connecting arms (70) are divergent about said first axis (A).

10. 10. A torque balance rotor according to claim 9 when dependent on claim 6 or 7, characterized in that the torque balance rotor (4) comprises a fifth ring (85) arranged in axial contact with the pins (81) and to which elastic means (100) are connected.

11. 11. A torque-balanced rotor according to claim 1, characterized in that the second ring (31) is provided with shoulders (37) interposed axially between the first rolling elements (32) and extending over a greater radial distance from the first axis (A) relative to the second raceways (33, 34).

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