Tool and method for preloading a rolling bearing

Abstract

The invention relates to a tool (100) for preloading a rolling bearing (48), the tool comprising: - a tie rod (104) having an attachment end (104a); - an annular block (106) mounted around the tie rod (104) and capable of being rigidly attached to the tie rod (104), this block (106) comprising: * an annular actuator (114); * a crown (126) attached to the actuator (114) comprising, at a free end, an annular edge (132) that is configured to bear axially on an outer nut (68b) of a screw-nut assembly (68); * a ring (136) that is capable of being rotated about the axis A inside the crown (126) comprising, at a free end, a toothed annular edge (138) that is configured to be coupled to an internal screw (68a) of the assembly (68); and * a system (146) for rotating the ring (136) inside the crown (126).

Description

[0001] DESCRIPTION

[0002] TITLE: TOOLING AND METHOD FOR PRELOADING A ROLLING BEARING

[0003] Technical field of the invention

[0004] The present invention relates to a tool and a method for preloading a rolling bearing, and has in particular an application in the field of aircraft turbomachines and in particular the propulsive propellers of these turbomachines which comprise variable-pitch blades.

[0005] Technical background

[0006] The state of the art includes in particular documents FR-A1 -3 017 163, FRAI -3 080 322, W0-A1 -2022 / 018353, US-B1 -6,415,489, JP-A-2008 240915 and US-A-1 ,579,737.

[0007] An aircraft turbomachine propeller can be shrouded, as is the case with a fan for example, or unshrouded as is the case with an open-rotor type architecture for example.

[0008] A propeller comprises blades that can be variable pitch. The turbomachine then includes a mechanism for modifying the pitch angle of the blades in order to adapt the thrust generated by the propeller according to the different phases of flight.

[0009] The design of a propeller blade involves several disciplines whose objectives are generally antagonistic. It must allow optimal aerodynamic performance (i.e. provide thrust while maximizing efficiency), guarantee mechanical strength of the blade (i.e. withstand the mechanical constraints resulting from static and dynamic loads) while limiting the mass as well as the acoustic signature. In particular, improving the aerodynamic performance of the propeller tends towards an increase in the BPR (By Pass Patio), which results in an increase in its external diameter and therefore in the blade span. However, increasing the BPR goes hand in hand with reducing the FPF (Fan Pressure Patio). Consequently, a pitch change system (variable pitch blade) is generally required for the propeller to be operable over the entire flight envelope.

[0010] There are several technologies for attaching a variable pitch propeller blade and several technologies for controlling the angular pitch of such a propeller blade.

[0011] A propeller generally comprises a hub which carries systems for retaining the blades and for controlling the angular setting of its blades. The hub has a generally annular or polygonal shape around a first axis which is the longitudinal axis of the turbomachine, and comprises orifices distributed around this first axis and in which the roots of the blades and the aforementioned systems are housed.

[0012] Each of these orifices has a substantially radial orientation relative to the first axis and receives bearings for guiding the root of a blade around a second radial axis relative to the first axis, and which is a setting axis of the corresponding blade.

[0013] Each of the propeller blades comprises a blade connected to a root, the root of each blade being mounted in one of the holes in the hub and in the bearings of this hole, and being retained in this hole by a retaining system. Each root is also associated with a system for controlling its angular setting.

[0014] The holes in the hub intended to receive the blade roots are radially transverse so as to allow the mounting of the propeller and in particular the guide bearings according to a particular kinematics.

[0015] According to this kinematics, the root of each blade is engaged in the corresponding orifice of the hub by translation along the setting axis of this blade, radially from the outside to the inside with respect to the first axis. The root of the blade is then connected to the control system which can be housed inside the hub.

[0016] One of the problems with this technology concerns the accessibility of its blade root retention and preloading system. The retention system must ensure a certain preload of the root along the setting axis. The retention system is not easily accessible and generally requires the use of bulky and complex tools for its assembly, which therefore makes the assembly / disassembly process of a blade very complex.

[0017] The Applicant has developed a new technology in which an annular screw-nut assembly is mounted around the blade root and is axially interposed between an axial stop of the blade root, and a rolling bearing mounted around the blade root.

[0018] The screw-nut assembly comprises an internal screw comprising an external thread, and an external nut comprising an internal thread for screwing onto the external thread of the internal screw. The internal screw is configured to be slid around the blade root and to bear axially on the stop, and the external nut is configured to bear axially on the rolling bearing.

[0019] To improve the life of the blade root and the rolling bearing, especially when it is angular contact, it is necessary to install a very high preload force (several tens of tons to avoid detachments). This preload is applied by the screw-nut assembly. To obtain this preload, it would be necessary to be able to install an enormous tightening torque on this assembly (several thousand Nm). However, this would require reinforcing these parts (oversizing them and increasing their mass) and using very bulky tools (such as a torque multiplier) in a very restricted space. In addition, the value of the torque to be installed would be very dependent on the condition of the thread (lubricated or not, difficult to control), and a seized nut would probably be impossible to loosen.

[0020] The invention provides a solution to at least some of these technical problems.

[0021] Summary of the invention

[0022] The invention relates to a tool for preloading a rolling bearing, this preload being intended to be applied along an axis A by an annular screw-nut assembly which is mounted around a member and which is axially interposed between an axial stop carried by this member, and a rolling bearing mounted around this member, the screw-nut assembly comprising an internal screw comprising an external thread, and an external nut comprising an internal thread for screwing onto the external thread of the internal screw, the internal screw being configured to be slid around the member and to bear axially on the stop, and the external nut being configured to bear axially on the rolling bearing, characterized in that it comprises:

[0023] - a tie rod of generally elongated shape along the axis A, this tie rod having a hooking end configured to be hooked to said member,

[0024] - an annular block mounted around the tie rod and capable of being secured to the tie rod, this block comprising:

[0025] * an annular actuator comprising a first part intended to be integral with the tie rod and a second part intended to be movable in translation along the axis A relative to the first part, the actuator being configured to ensure the movement of the second part relative to the first part and the tie rod,

[0026] * a crown intended to extend around the axis A and the tie rod, this crown being fixed to the second part of the actuator and comprising at a free end an annular edge which is configured to come into axial support on the external nut,

[0027] * a ring intended to extend around the axis A and the tie rod and inside the crown, this ring being movable in rotation around the axis A inside the crown and comprising at a free end a toothed annular edge which is configured to be coupled with the internal screw, and

[0028] * a system for driving the ring inside the crown to rotate.

[0029] The invention thus proposes a tool for preloading a rolling bearing. The particularity of this tool is that it is designed to perform traction and stretching of the member along the axis and that the preload of the rolling bearing is obtained by maintaining this stretching or this elongation by means of the screw-nut assembly. The screw-nut assembly is interposed axially between the bearing and the stop of the member and is therefore supported respectively on the bearing and the stop. The screw-nut assembly comprises a screw and a nut which cooperate together so as to be able to adjust the length of the assembly along the axis A. After stretching of the member, a clearance can be created between the assembly and the stop, and the length of this assembly can be increased to compensate for this clearance. The stretching of the member causes a preload on the rolling bearing.The stretching of the organ is maintained by the screw-nut assembly which therefore allows this preload to be maintained even after the forces necessary for stretching the organ have stopped.

[0030] The tooling according to the invention essentially comprises two parts. Firstly, a tie rod and then an annular block intended to be mounted on the tie rod.

[0031] As its name suggests, the tie rod is designed to apply a tensile force to the component in order to stretch it along the axis. For this purpose, it is attached to the component.

[0032] The block is mounted on the tie rod, for example after attaching the tie rod to the member. The block comprises an actuator which provides the force necessary to stretch the member. For this, a first part of the actuator bears axially on the external nut via the ring, and the second part of the actuator is secured to the tie rod. It is therefore understood that the movement of the parts of the actuator, along the axis A, will cause a movement and in particular a distance of the tie rod from the screw-nut assembly, and an axial stretching of the member. The ring can then be moved in rotation inside the ring to move the internal screw and tighten it against the stop of the member to maintain the preload linked to the stretching of the member.

[0033] The tooling can then be dismantled and used to preload another rolling bearing. The preload obtained by elongation of the component makes it possible to minimize the tightening torques to be applied to the screw-nut assembly, and to avoid the need to oversize and increase the mass of this assembly.

[0034] Furthermore, the tooling according to the invention comprises a limited number of parts and its design gives it a small footprint allowing it to be used in spaces that are difficult to access such as inside an aircraft turbomachine propeller.

[0035] The tooling according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another:

[0036] - the actuator is hydraulic and comprises an annular chamber extending around the axis A and intended to be supplied with fluid, such as oil for example,

[0037] - the tie rod comprises an external thread for screwing a nut configured to bear axially on the block, and in particular on the first part of its actuator,

[0038] - the ring is guided in rotation inside the crown by at least one bearing, for example a rolling bearing, interposed radially between the ring and the crown,

[0039] - the annular edge of the ring comprises at least one axially oriented tooth and preferably an annular row of axially oriented teeth,

[0040] - the annular edge of the crown is also toothed and comprises at least one axially oriented tooth,

[0041] - the tooling further comprises a device for detecting the axial alignment of the tooth or one of the teeth of the crown with the tooth or one of the teeth of the ring,

[0042] - the annular edge of the crown comprises an internal cylindrical centering surface configured to cooperate with a complementary external cylindrical surface of the external nut, - the ring comprises an external annular toothing which is configured to cooperate with said drive system,

[0043] - the drive system includes a worm screw,

[0044] - the worm screw has a general elongated shape along an axis B which is tangent to a circumference centered on the axis A and which is contained in a plane perpendicular to the axis A, this worm screw being carried by the crown and guided in rotation in orifices of the crown, at least one of the axial ends of the worm screw being connected or capable of being connected to a crank, and the worm screw being meshed with the teeth of the ring,

[0045] - the crown comprises at least one light passing through in a radial direction and configured to allow an operator to see the annular edge of the ring from the outside through this light,

[0046] -- the end of the tie rod is configured to be axially engaged in the member and comprises at least one radially external hook or flange configured to cooperate with the member, and for example a series of external hooks configured to cooperate with the member,

[0047] -- the end of the tie rod is configured to be mounted axially on the member and comprises at least one radially internal hook or flange configured to cooperate with the member, and for example a series of internal hooks configured to cooperate with the member,

[0048] -- the tie rod is a single piece or is formed by assembling two or more parts; for example, it is sectorized and comprises two or more sectors arranged around the axis A,

[0049] - the stop is formed by a ring, preferably split or sectored, and mounted in an external annular groove of the member,

[0050] -- the internal screw and the external nut each comprise a series of teeth oriented radially outwards relative to the setting axis;

[0051] -- the rolling bearing is a ball or roller bearing and is for example angular contact,

[0052] -- the member is a root of a propeller blade for an aircraft turbomachine. The present invention also relates to a device comprising: - a member carrying an axial stop and around which a rolling bearing is mounted, as well as an annular screw-nut assembly interposed between the axial stop and the rolling bearing, and

[0053] - a tool as described above, the screw-nut assembly comprising an internal screw comprising an external thread, and an external nut comprising an internal thread for screwing onto the external thread of the internal screw, the internal screw being configured to be slid around the member and to bear axially on the stop, and the external nut being configured to bear axially on the rolling bearing.

[0054] Advantageously, the member is a foot of a variable-pitch blade for an aircraft turbomachine propeller, or the member is a shaft of an aircraft turbomachine.

[0055] Preferably, the stop is formed by a sectored ring mounted in an external annular groove of the member.

[0056] The present invention finally relates to a method for preloading a rolling bearing, by means of a device as described above, characterized in that it comprises the steps of: a) hooking the end of the tie rod to the member, b) mounting the block around the tie rod, so that the annular edge of the crown is in axial support on the external nut, and the annular edge of the ring is coupled with the internal screw, c) immobilizing the first part of the actuator with respect to the tie rod, d) translational movement of the first part of the actuator with respect to its second part, so as to cause axial stretching of the member along the axis and the appearance of axial play between the internal screw and the stop of the member, and e) rotational movement of the ring inside the crown, so as to rotate the internal screw with respect to the external nut and the member, and to take up said axial play,the internal screw being screwed with a previously defined tightening torque, f) deactivating the actuator so that its first part returns to its original position with respect to the second part of the actuator, g) detaching the first part of the actuator with respect to the tie rod, h) dismantling and removing the block with respect to the tie rod, and i) dismantling and removing the tie rod with respect to the member.,

[0057] Advantageously, the method comprises, between steps e) and f), a step of angularly locking the internal screw with the external nut, for example to align teeth of the internal screw with teeth of the external nut, by applying an overtorque to the internal screw. This allows the subsequent mounting of an internal cover which allows rotational locking of the screw-nut assembly. Correct angular locking of the screw-nut assembly can be detected by a suitable detection device integrated into the tooling.

[0058] Brief description of the figures

[0059] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

[0060] [Fig.1] Figure 1 is a schematic axial sectional view of a propeller for an aircraft turbomachine,

[0061] [Fig.2] Figure 2 is an enlarged view of a portion of Figure 1 and shows the root of a blade mounted in an orifice of a propeller hub, [Fig.3] Figure 3 is an even enlarged view of a portion of Figure 2 and of the blade root retaining and control systems, [Fig.4] Figure 4 is a view similar to that of Figure 2 and illustrating an alternative embodiment,

[0062] [Fig.5] Figure 5 is a schematic perspective view of a screw-nut assembly and an internal propeller cover,

[0063] [Fig.6] Figure 6 is a view similar to that of Figure 2 and illustrating a first step of a method according to the invention,

[0064] [Fig.7] Figure 7 is a view similar to that of Figure 2 and illustrating a second step of a method according to the invention, [Fig.8] Figure 8 is a view similar to that of Figure 2 and illustrating a third step of a method according to the invention,

[0065] [Fig.9] Figure 9 is a view similar to that of Figure 2 and illustrating a fourth step of a method according to the invention,

[0066] [Fig.10] Figure 10 is a schematic axial sectional view of a preloading tool for a rolling bearing,

[0067] [Fig.11] Figure 11 is a schematic perspective view of the preload tooling,

[0068] [Fig.12] Figure 12 is a partial schematic perspective view of the interior of a propeller, and shows a preloading tool positioned on the root of one of the blades of this propeller, and

[0069] [Fig.13] Figure 13 is a partial schematic view in axial section of an alternative embodiment of a blade root for a propeller.

[0070] Detailed description of the invention

[0071] Figure 1 shows a propeller 10 for an aircraft turbomachine, this propeller 10 being shrouded or unshrouded.

[0072] The propeller 10 comprises a hub 12 and blades 14 carried by this hub 12.

[0073] The hub 12 has a generally annular or polygonal shape and extends around a first axis not shown.

[0074] In Figure 1, one of the blades 14 of the propeller 10 is visible and the hub 12 is seen in axial section, the section plane passing through the first axis of the hub 12.

[0075] The hub 12 comprises orifices 12a distributed around the first axis, each of these orifices 12a having a substantially radial orientation relative to this first axis. Each orifice 12a passes radially through the hub 12, that is to say that each orifice 12a opens respectively radially to the outside and radially to the inside.

[0076] The blades 14 each comprise a blade 16 and a root 18. The roots 18 of the blades 14 are respectively engaged in the orifices 12a of the hub 12. The blade 16 has an aerodynamic profile and comprises a lower surface 16a and an upper surface (not visible) which are connected by an upstream leading edge 16c and by a downstream trailing edge 16d, the terms upstream and downstream referring to the flow of gases around the blade 16 in operation.

[0077] The blade 16 has an upper end which is free, called the apex, and a lower end which is connected to the foot 18.

[0078] The blade 14 can be made of composite material by an injection process called RTM (acronym for Resin Transfer Molding). This process consists of preparing a fiber preform by three-dimensional weaving and then placing this preform in a mold and injecting a polymerizable resin such as an epoxy resin, which will impregnate the preform. After polymerization and hardening of the blade 16, its leading edge 16c is generally reinforced by a metal shield 20 added and fixed, for example by gluing.

[0079] The shield 20 may be made of titanium or titanium alloy, stainless steel, steel, aluminum, nickel, etc. The intrados 16a or even the extrados of the blade 16 may be covered with a polyurethane film 22 for protection against erosion.

[0080] A denotes the axis of elongation of the blade 14 and of the airfoil 16 and in particular the setting axis of the blade 14, that is to say the axis around which the angular position of the blade 14 is adjusted. It is generally also a radial axis which therefore extends along a radius relative to the first axis.

[0081] As best seen in Figure 2, the foot 18 is hollow and includes an internal recess 18a in the example shown. The foot 18 has an elongated and tubular shape, its internal recess 18a being closed on the side of the blade 16 and open on the side opposite the blade 16.

[0082] The recess 18a of the foot 18 makes it possible to reduce its mass, the shape and dimensions of the foot 18 being optimized to ensure good mechanical strength of the blade 14 in operation.

[0083] The foot 18 comprises in its recess 18a internal grooves 24 which are configured to allow coupling of the foot 18 with a system for controlling the timing of the blade around its timing axis A (figures 2 and 3).

[0084] The grooves 24 extend around the axis A. In the example shown, they are located between two internal cylindrical surfaces 26a, 26b of the recess 18a, located respectively radially outside and inside the grooves 24 with respect to the first axis.

[0085] The root 18 of the blade 14 further comprises at its radially internal free end (with respect to the first axis), an annular surface 26c which extends in a plane perpendicular to the axis A.

[0086] The root 18 of the blade 14 comprises one or more stops 28, 30. The or each stop 28, 30 has an annular shape and extends around the axis A and radially outwards relative to this axis A.

[0087] In the example shown, the stop 28 is formed as a projection at a radially external end of the foot 18 with respect to the first axis, substantially at the level of the closed end of the recess 18a.

[0088] The stop 30 is formed as a projection on a middle part of the foot 18 with respect to the first axis, located between the stop 28 and the free end of the foot 18.

[0089] The root 18 of the blade 14 further comprises an annular groove 32 which opens radially outwards and which is here formed in the vicinity of the free end of the root 18.

[0090] Between the stop 28 and the groove 32, and more particularly between the stop 30 and the groove 32, the foot 18 comprises an external cylindrical surface 34a.

[0091] The root 18 of the blade 14 comprises several external cylindrical centering surfaces S1, S2 and S3 in the example shown. The surfaces S1, S2 and S3 have decreasing diameters D1, D2 and D3 and are distributed along the axis A, radially from the outside to the inside with respect to the first axis.

[0092] The surface S1 of larger diameter D1 is located between the stops 28, 30. The surface S2 of intermediate diameter D2 is located between the stop 30 and the surface 34a.

[0093] The surface S3 of smaller diameter D3 is located between the groove 32 and the free end of the foot 18, and more particularly between the groove 32 and the external thread 34b of the foot 18. The thread 34b has a diameter smaller than that of the surface 34a.

[0094] The stop 28 is located at the radially outer end of the surface S1 relative to the first axis. The stop 30 is located at the radially outer end of the surface S2 relative to the first axis.

[0095] The hub 12 may comprise annular fixing flanges 36 at each of its axial ends, as can be seen in FIG. 2.

[0096] In the example shown, each of the orifices 12a of the hub 12 comprises stops 38, 40, 42, 44.

[0097] The or each stop 38, 40, 42, 44 has an annular shape and extends around the axis A and radially inwards relative to this axis A.

[0098] The stops 38, 40, 42, 44 are respectively arranged one after the other along the setting axis A. There is thus a radially external stop 38, a radially internal stop 44 and two intermediate stops 40, 42.

[0099] Stop 38 has a larger diameter than stop 40, and stop 44 has a larger diameter than stop 42.

[0100] The intermediate stops 40, 42 make it possible to accommodate bearings 46, 48 for guiding the feet 18 of the blades 14.

[0101] The bearings 46, 48 are here two in number and are mounted in the orifice 12a of the hub, being arranged radially one to the outside of the other. Thus, the external bearing 46 designates the bearing located radially to the outside, and the internal bearing 48 designates the bearing located radially to the inside.

[0102] The bearings 46, 48 are mounted inside the orifice 12a, bearing axially (with respect to the axis A) on the intermediate stops 40, 42. The bearings 46, 48 are mounted around the foot 18, and in particular around the surfaces S1 and S2, bearing axially (with respect to the axis A) on the stops 28, 30.

[0103] Advantageously, an intermediate piece is provided between the bearing 48 and the blade root 18, and in particular between the inner ring of the bearing 48 and the surface S2. This is a hoop tightly mounted on the blade root 18 which makes it possible to have a harder material than that (for example titanium) of the root 18 as a bearing surface. Indeed, the inner ring of the bearing 48 cannot have significant hooping on its axis because it is displaced during preloading. Therefore, to avoid a fretting phenomenon (tearing of material which would result in the beginning of a break on the blade root), this hard intermediate piece can be added.

[0104] The external bearing 46 is configured to be engaged in the orifice 12a from the outside of the hub 12, by moving it radially from the outside to the inside, until it comes to bear on the stop 40. The bearing 46 is here a ball bearing with angular contact and it is its external ring which bears on the stop 40.

[0105] The internal bearing 48 is configured to be engaged in the orifice 12a from the inside of the hub, moving it radially from the inside to the outside, until it comes to bear on the stop 42. The bearing 48 is here a ball bearing, and in particular a double row of balls, and with angular contact and it is its external ring which bears on the stop 42.

[0106] As seen in Figures 2 and 3, the root 18 of the blade 14 is configured to be engaged in the orifice 12a by translation along the axis A, radially from the outside to the inside with respect to the first axis, inside the bearings 46, 48, until the stop 28 bears axially (with respect to the axis A) on the bearing 46, and in particular its inner ring, and the stop 30 bears axially (with respect to the axis A) on the bearing 48, and in particular its inner ring. The bearings 46, 48, and in particular their inner rings, are then mounted on the surfaces S1 and S2.

[0107] It is therefore understood that the external bearing 46 has an internal diameter greater than the internal diameter of the internal bearing 48 to allow the mounting of the foot 18 in the orifice 12a, insofar as the bearings 46, 48 are mounted beforehand on the foot 18 in the example shown. The stop 28 of the foot 18 may bear directly (along the axis A) on the external bearing 46 and in particular its internal ring. In the example shown, the stop 28 bears on the external bearing 46 by means of an external annular cover 50 which is mounted around the foot and which at least partially covers the external bearing 46.

[0108] This external cover 50 has its internal periphery which is clamped between the stop 28 and the external bearing 46, and in particular its internal ring. The external periphery of the cover 50 bears in the direction of the axis A on an annular seal 52 interposed between this external periphery of the cover 50 and the hub 12, and in particular the stop 38. This assembly allows rotation of the cover relative to the hub, during rotation of the blade root.

[0109] The stop 30 of the foot 18 may bear directly (along the axis A) on the internal bearing 48 and in particular its internal ring. In the example shown, the stop 30 bears on the internal bearing 48 by means of a shim of adjustable thickness 54.

[0110] An internal annular cover 56 may also be mounted around the foot 18 and at least partially cover the internal bearing 48.

[0111] The inner cover 56 has its outer periphery which bears in the direction of the axis A on an annular seal 58 interposed between this outer periphery of the cover 56 and the hub 12, and in particular the stop 44. This assembly allows rotation of the cover relative to the hub, during rotation of the blade root. The cover 56 has its inner periphery which bears radially relative to the axis A on the root 18, in the vicinity of its free end, either directly or via an annular seal 60, on an external cylindrical surface S3, as illustrated in the drawing.

[0112] In the example shown, the internal cover 56 comprises at least two teeth 62, 64 oriented radially towards the axis A.

[0113] The inner cover 56 may further comprise an inner cylindrical centering surface 56a which is configured to cooperate with a complementary outer cylindrical surface of the inner bearing 48, and for example of the inner ring of this bearing. This surface 56a may be located at the inner periphery of an inner annular web of the cover 56. This web may comprise through-orifices 65 for the passage of fluid and in particular of lubricating oil for the bearings 46, 48 (FIG. 3).

[0114] The foot 18 is retained in the orifice 12a of the hub 12 by a retaining system which essentially comprises a stop formed by a ring 66 and a screw-nut assembly 68. It is this screw-nut assembly 68 which makes it possible to apply a preload to the foot of the blade.

[0115] The ring 66 is mounted around the root 18 of the blade and extends around the axis A. The ring 66 is sectorized and therefore comprises ring sectors arranged circumferentially end to end around the axis A. The number of sectors is not limiting and can be limited to two. The ring 66 then comprises two half-rings.

[0116] Alternatively, the ring could be continuous and not be sectorized. It could then include a slot to allow elastic deformation of the ring by spreading its longitudinal ends apart.

[0117] The ring 66 is configured to be engaged in the groove 32 of the foot 18. It is understood that it is the sectorization of the ring 66 which allows it to be mounted in the groove 32. The ring 66 comprises an internal periphery housed in the groove 32 and an external periphery intended to remain outside the groove 32 to form an axial stop (with respect to the axis A).

[0118] The screw-nut assembly 68 comprises an internal screw 68a and an external nut 68b. The internal screw 68a has an external thread 68a1 and an internal cylindrical surface 68a2. This internal cylindrical surface 68a2 is intended to cooperate by sliding with the surface 34a of the foot during the mounting and positioning of the assembly 68 on the foot.

[0119] The external nut 68b has an internal thread 68b1 for screwing onto the external thread 68a1 of the internal screw 68a.

[0120] The positioning (by simple sliding) of the internal screw 68a on the foot 18 allows it to be moved axially (with respect to the axis A) on the foot 18 and to be positioned along the axis A. The screw 68a is able to bear in the direction of the axis A on the ring 66 on the side opposite the blade 16.

[0121] Screwing / unscrewing the external nut 68b allows it to be moved axially (with respect to the axis A) on the internal screw 68a and to be positioned along the axis A. The external nut 68b is able to bear in the direction of the axis A on the internal bearing 48, and in particular on its internal ring, on the side of the blade 16.

[0122] The double support of the screw-nut assembly 68, respectively on the ring 66 and the bearing 48, and the screwing of the external nut 68b onto the internal screw 68a, make it possible to apply a certain preload to the root 18 of the blade by the retaining system.

[0123] In the example shown in Figures 2 and 3, the internal screw 68a comprises an annular rim 70 which is located on the side opposite the blade 16 and which extends around the external periphery of the ring 66 to prevent the ring 66 from accidentally coming out of the groove 32.

[0124] The screw 68a and the nut 68b each comprise a series of teeth 72, 74 oriented radially outwards relative to the axis A and configured to cooperate with the teeth 62, 64 of the internal cover 56 in order to immobilize the assembly 68 in rotation around the axis A.

[0125] The series of teeth 74 of the external nut 68b is located on the side of the blade 16 and is configured to cooperate with the tooth 64 of the cover 56. The series of teeth 72 of the internal screw 68a is located on the side opposite the blade 16 and is configured to cooperate with the tooth 62 of the cover 56.

[0126] In the example shown, the series of teeth 72 has an external diameter smaller than that of the series of teeth 74.

[0127] The propeller 10 further comprises a system 76 for controlling the pitch of the blade 14, which is associated with the root 18 of this blade. The propeller 10 therefore comprises as many control systems 76 as there are blades 14 of this propeller.

[0128] Each control system 76 comprises an eccentric 78 of which a sleeve 80 is engaged by translation along the axis A inside the recess 18a of the foot 18, radially from the inside to the outside with respect to the first axis.

[0129] The socket 80 has external grooves 82 configured to be engaged in the internal grooves 24 of the foot 18.

[0130] The sleeve 80 further comprises external cylindrical centering surfaces 80a, 80b cooperating with the surfaces 26a, 26b of the recess 18a when the sleeve 80 is inserted into the recess 18a. These surfaces 80a, 80b are located on either side of the grooves 82 along the axis A.

[0131] In the example shown, the sleeve 80 also comprises an external annular rim 84 (figure 3).

[0132] A threaded ring 86 is screwed onto the thread 34b of the foot, at its free end, and comprises an internal annular rim 86a which bears in the direction of the axis A on the external rim 84 of the sleeve 80, and in the direction of the blade 16 to retain the sleeve 80 in the recess 18a of the foot 18.

[0133] The threaded ring 86 bears in the direction of the axis A on the internal periphery of the internal cover 56, directly or by means of an adjustment shim 88. This shim 88 of adjustable thickness makes it possible to control the compression of the dynamic seal 58 by compensating for the tolerances of the parts forming the stack between its two sealing faces.

[0134] The threaded ring 86 may comprise a series of teeth 90 extending radially outwardly with respect to the axis A, to allow the ring 86 to be engaged with a tool for screwing and unscrewing the ring.

[0135] The embodiment variant of Figure 4 differs from the previous embodiment in that the internal bearing 48 with a double row of bearings is replaced by an internal bearing 48 with a single row of bearings. This makes it possible to reduce the length of the bearing 48, along the axis A, and therefore to reduce the axial size of the assembly along this axis. The recess 18a of the foot 18 also has a different cross-sectional shape.

[0136] Figure 5 shows the assembly 68 with its series of teeth 72, 74. They also show the teeth 62, 64 of the cover 56. The tooth 62 is here axially aligned with the tooth 64. Alternatively, the cover 56 could comprise two teeth 62 and two teeth 64, the teeth 62, 64 being for example diametrically opposed with respect to the axis A.

[0137] In yet another variant not shown, the bearings could be angular contact rolling bearings such as tapered roller bearings.

[0138] According to the invention, the rolling bearings 46, 48 must be preloaded to optimize their service life and that of the blade root 18. This preloading is carried out along the axis A by means of a tool 100 developed within the framework of the present invention.

[0139] The tool 100 can be used to preload the rolling bearings 46, 48 mounted on a member, this member being for example a blade root 18 as in the example described above, or a turbomachine shaft. These examples are not limiting.

[0140] To facilitate the description and understanding of the invention, the tooling 100 is described in the foregoing in relation to rolling bearings 46, 48 on a blade root 18.

[0141] Figure 6 therefore illustrates a blade root 18 as described above and differs from Figures 2 and 4 in particular in that the cover 56, the control system 76, and the threaded ring 86 have been removed.

[0142] The screw-nut assembly 68 is therefore accessible from the inside and the internal recess 18a of the foot 18 is also accessible from the inside.

[0143] At its lower free end, the foot 18 comprises an internal annular groove 102 in the example shown.

[0144] The tool 100 according to the invention is shown alone in Figures 10 and 11. Figures 7 to 9 illustrate steps of a preloading method according to the invention.

[0145] The tool 100 essentially comprises two parts, namely a tie rod 104 and an annular block 106 mounted around the tie rod 104 and capable of being secured to the tie rod 104. The tie rod 104 has a generally elongated shape along the axis A and has a hooking end 104a configured to be hooked to the member and in particular to the blade root 18.

[0146] It can be seen in the example shown that the tie rod has a generally tubular shape and that its end 104a is engaged in the free end of the blade root 18 and cooperates with the groove 102 of this end.

[0147] The tie rod 104 comprises for example at least one external hook 108 configured to be engaged in the groove 102, and for example a series of external hooks 108 configured to be engaged in the groove 102. Alternatively, the tie rod 104 could for example comprise an external annular hooking rim intended to be engaged in the groove 102.

[0148] The tie rod 104 may be a single piece or be formed by assembling two or more parts, depending for example on the method of attachment of the tie rod 104 to the blade root 18. The tie rod 104 is for example sectorized and comprises two or more sectors arranged around the axis A. This is particularly the case when it comprises an external annular attachment rim. Alternatively, it is formed from a single piece and is engaged by dog-engaging in the blade root 18. This is for example the case when the external hooks 108 of the tie rod are complementary to internal hooks (not shown) of the free end of the blade root 18.

[0149] The tie rod 104 further comprises an external thread 110 for screwing a nut 112. In the example shown, this thread 110 is located at one end of the tie rod 104 opposite its attachment end 104a.

[0150] Figure 7 illustrates a first step a) of the method according to the invention in which the end of the tie rod 104 is attached to the member and therefore in particular to the blade root 18.

[0151] Figure 13 shows an alternative embodiment of the blade root 18 in which the internal annular groove is replaced by an external annular groove 102'. It is therefore understood that the tie rod 104 will be engaged around the root 18 to cooperate with this groove 102'. The annular block 106 will now be described with reference to Figures 10 and 11.

[0152] The block 106 comprises an annular actuator 114, a crown 126, a ring 136 and a system 146 for driving the ring in rotation inside the crown 116.

[0153] The actuator 114 extends around the axis A and the tie rod 104 and has a generally annular shape. It comprises a first part 114a intended to be secured to the tie rod 104 and a second part 114b intended to be movable in translation along the axis A relative to the first part 114a.

[0154] In the example shown, the parts 114a, 114b define between them an annular chamber 116 which is intended to be supplied with fluid, and for example with oil, with a view to activating the actuator 114 which is therefore here of the hydraulic type.

[0155] The first part 114a has a general U-shape in axial section and comprises two cylindrical walls, respectively internal 118a and external 118b, which extend around each other. These cylindrical walls 118a, 118b are connected together by a radial wall 118c whose internal periphery is connected to a ring 120 fitted in a fitted manner on the tie rod 104.

[0156] The nut 112 is intended to bear axially on the part 114a and in particular its ring 120 to immobilize it axially on the tie rod 104. The part 114a can also be immobilized in rotation around the axis A with respect to the tie rod 104, for example by complementarity of shapes of the ring 120 with the tie rod 104.

[0157] The second part 114b has a general U-shape in axial section and comprises two cylindrical walls, respectively internal 122a and external 122b, which extend around each other. These cylindrical walls 122a, 122b are connected together by a radial wall 122c whose external periphery is connected to an external annular flange 124. In the example shown, the internal wall 122a is interposed radially between the tie rod 104 and the internal wall 118a, and the external wall 122b extends radially outside the external wall 118b.

[0158] The aforementioned chamber 116 is delimited axially between the walls 118c and 122c, and radially between the walls 118a, 118b, 122a, 122b.

[0159] The supply of oil to the chamber 116 causes an increase in the pressure in this chamber and the displacement of the parts 114a, 114b, one with respect to the other along the axis A. If one positions oneself in the reference frame of the tie rod 104, the part 114a remains fixed and the part 114b moves. If one positions oneself in the reference frame of the blade root 18, the part 114b remains fixed and the part 114a moves with the tie rod 104.

[0160] Chamber 116 can be connected to a hand pump operated by the operator, and to a pressure gauge.

[0161] The crown 126 of the block 106 is intended to extend around the axis A and the tie rod 104. It is fixed to the part 114b of the actuator 14.

[0162] In the example shown, the crown 126 has a generally cylindrical shape and comprises at a first axial end an annular flange 128 which is applied and fixed to the flange 124. The fixing is ensured by bolts 130 or the like, which preferably extend parallel to the axis A.

[0163] On the side opposite the actuator 14, the crown 126 comprises a free end which has an annular edge 132 configured to come into axial support on the aforementioned external nut 68b. This edge 132 comprises a radial support surface 132a and an internal cylindrical guide surface 132b.

[0164] This edge 132 preferably comprises at least one tooth 134 which extends axially from the bearing surface 132a. Advantageously, several teeth 134, preferably regularly distributed around the axis A, extend axially from the bearing surface 132a of the edge 132.

[0165] The tooth or teeth 134 are intended to cooperate with the teeth 74 of the nut 68b in order to secure the crown 126 in rotation with respect to the nut 68b. The internal cylindrical surface 132b of the crown 126 is intended to cooperate with the complementary external cylindrical surface 68b1 of the external nut 68b (figure 6).

[0166] The ring 126 may further comprise at least one light 135 extending radially therethrough and configured to allow an operator to see the ring 136 from the outside through this light 135.

[0167] The ring 136 is intended to extend around the axis A and the tie rod 104 and inside the crown 126.

[0168] This ring 136 is movable in rotation around the axis A inside the crown 126. The ring 136 comprises at a free end located on the side of the free end of the crown 126 a toothed annular edge 138 which is configured to be coupled with the aforementioned internal screw 68a.

[0169] The edge 138 comprises at least one tooth 140 which is axially oriented. Advantageously, several teeth 140, preferably regularly distributed around the axis A, extend axially from the edge 138.

[0170] The tooth(s) 140 are intended to cooperate with the teeth 72 of the internal screw 68a in order to secure the ring 136 in rotation with respect to the internal screw 68a.

[0171] In the example shown, the ring 136 is guided in rotation inside the crown 126 by at least one bearing 142, for example a rolling bearing, interposed radially between the ring 136 and the crown 126. The bearings 142 are here two in number and are arranged side by side.

[0172] The ring 126 further comprises an external annular toothing 144 which is configured to cooperate with the drive system 146.

[0173] In the example shown, the drive system 146 comprises a worm screw 148.

[0174] The worm screw 148 has a general shape elongated along an axis B which is tangent to a circumference centered on the axis A and which is contained in a plane perpendicular to the axis A.

[0175] This worm screw 148 is carried by the crown 126 and guided in rotation in orifices 149 of the crown 126. At least one of the axial ends 148a of the worm screw 148 may have a generally hexagonal shape as visible in figure 11, and be intended to be connected or capable of being connected to a crank (not shown) which can be directly actuated by an operator for example.

[0176] The worm screw 148 is meshed with the aforementioned toothing 144 of the ring 136.

[0177] The tool 100, and in particular the block 106, further comprises a device 150 for detecting the axial alignment of the tooth 134 of the crown 126 with one of the teeth 140 of the ring 136. It may for example be an optical, mechanical or magnetic device 150 which comprises a first element carried by the part 114b and a second element carried by the ring 136. The axial alignment between these elements is detected by the device 150 and corresponds to an alignment of the aforementioned teeth 134, 140 for example. Figures 8 and 9 illustrate other steps of the method according to the invention.

[0178] Figure 8 illustrates a step b) of mounting the block 106 around the tie rod 104, so that the annular edge 132 of the crown 126 is in axial support on the teeth 74 of the external nut 68b, and that the annular edge 138 of the ring 136 is coupled with the internal screw 68a.

[0179] The through-light 135 of the crown 126 is configured to allow an operator to see the annular edge 138 of the ring 136 from the outside through this light. The operator can thus verify that the ring 136 is properly coupled with the internal screw 68a.

[0180] Figure 9 illustrates a step c) of immobilizing the block 106 and the first part 114a of the actuator 114 with respect to the tie rod 104. For this, the nut 112 is screwed onto the thread 110 of the tie rod 104 and bears axially against the block 106 and in particular the ring 120 of the part 114a of the actuator 114, the block 106 then being clamped axially between the nut 112 and the external nut 68b.

[0181] The method according to the invention comprises other steps of: d) translational movement of the first part 114a of the actuator 114 with respect to its second part 114b, so as to cause an axial stretching of the member and therefore of the foot 18 along the axis A, and the appearance of an axial clearance J between the internal screw 68a and the stop formed by the ring 66 (figure 9), and e) rotational movement of the ring 136 inside the crown 126, so as to rotationally move the internal screw 68a with respect to the external nut 68b and the member 18 and therefore of the foot 18, and to take up this clearance J, with application of a first tightening torque to the internal screw previously defined, f) deactivating the actuator 114 so that its first part 114a returns to its original position with respect to the second part 114b, g) detachment of the first part 114a of the actuator 114 from the tie rod 104, h) disassembly and removal of the block 106 from the tie rod 104,and i) disassembly and removal of the tie rod 104 from the member and therefore from the foot 18. With regard to step d), it causes a stretching of the foot and the appearance of a preload in the axial direction on the bearing 48, that is to say an axial force on the bearing 48. This preload is preferably several tons and may be greater than the preload ultimately desired for the bearing to take into account the loss of load linked to the elimination of the stretching force on the member.,

[0182] The axial play can correspond to the length of the foot stretch and is for example a few millimeters or tenths of a millimeter.

[0183] This play is taken up during the following step e) which consists of rotating the ring 136 inside the crown 126. The internal screw 68a being coupled to the ring 136, it is understood that the rotation of the ring 136 will cause the rotation of the screw 68a since the crown 126 and the nut 68b are coupled and immobile in rotation.

[0184] The rotation of the ring 136 is done in the direction of screwing or unscrewing the nut 68a so that the latter takes up and cancels the play J.

[0185] We continue with the sequence of aligning the teeth 72, 74 of the screw / nut assembly 68. For this, an overtorque in a previously defined range is applied to the internal screw 68a and the alignment of the teeth 72, 74 is detected by the device 150 integrated into the tooling, in order to allow the subsequent assembly of the internal cover 56 which will act as a brake for the screw / nut assembly 68.

[0186] It is then understood that the screw-nut assembly 68 is then intended to maintain and apply the preload previously obtained thanks to the stretching of the blade root 18.

[0187] It is then sufficient to deactivate the actuator 114 and to dismantle the tool 100 during steps d) to g).

[0188] The method according to the invention fits naturally into the method of mounting the propeller 10.

[0189] The method of mounting the propeller 10 comprises: a) mounting the bearings 46, 48 in the orifice 12a of the hub 12; as mentioned above, the bearing 48 is engaged from the inside of the hub 12 in the orifice 12a, and the bearing 46 is engaged from the outside of the hub in the orifice 12a. b) inserting the root 18 of the blade 14 into the orifice 12a, from the outside towards the inside, until in particular the stop 28 of the root 18 bears on the external bearing 46 or the external cover 50 previously mounted.c) mounting the screw-nut assembly 68 on the foot 18, between the stop 28 and the groove 32, by simple displacement on the surface 34a, d) mounting the sectored ring 68 in the groove 32 of the foot 18, forming the stop, e) positioning or unscrewing the screw-nut assembly 68, and in particular the internal screw 68a, so that the internal screw 68a bears on the sectored ring 66 forming the stop, f) screwing the external nut 68b onto the internal screw 68a so that the external nut 68b bears on the internal bearing 48.

[0190] These steps are carried out before the precharging method according to the invention.

[0191] The precharging method according to the invention can be followed by the following steps:

[0192] - a step g) of mounting the internal cover 56, - ​​a step h) of mounting the control system 76,

[0193] - a step i) of mounting the threaded ring 86.

[0194] Figure 12 shows the dimensions and the bulk of the tool 100 according to the invention. It can be seen that this tool 100 is relatively small in size and can be used directly inside a turbomachine propeller. The mounting of the tool 100 on a blade root 18 is in fact possible despite the proximity of the blade roots to each other. After preloading a rolling bearing of one of the blade roots, the tool 100 can be dismantled to preload the rolling bearing of another blade root of the propeller.

[0195] Typically, the tooling has a maximum external diameter between 100 and 300mm.

Claims

CLAIMS 1. Tooling (100) for preloading a rolling bearing (48), this preload being intended to be applied along an axis A by an annular screw-nut assembly (68) which is mounted around a member and which is axially interposed between an axial stop carried by this member, and a rolling bearing (48) mounted around this member, the screw-nut assembly (68) comprising an internal screw (68a) comprising an external thread (68a1), and an external nut (68b) comprising an internal thread (68b1) for screwing onto the external thread (68a1) of the internal screw (68a), the internal screw (68a) being configured to be slid around the member and to bear axially on the stop, and the external nut (68b) being configured to bear axially on the rolling bearing (48), characterized in that it comprises: - a tie rod (104) of generally elongated shape along the axis A, this tie rod (104) having a hooking end (104a) configured to be hooked to said member, - an annular block (106) mounted around the tie rod (104) and capable of being secured to the tie rod (104), this block (106) comprising: * an annular actuator (114) comprising a first part (114a) intended to be integral with the tie rod (104) and a second part (114b) intended to be movable in translation along the axis A with respect to the first part (114a), the actuator (114) being configured to ensure the movement of the second part (114b) with respect to the first part (114a) and the tie rod (104), * a crown (126) intended to extend around the axis A and the tie rod (104), this crown (126) being fixed to the second part (114b) of the actuator (114) and comprising at a free end an annular edge (132) which is configured to come into axial support on the external nut (68b), * a ring (136) intended to extend around the axis A and the tie rod (104) and inside the crown (126), this ring (136) being movable in rotation around the axis A inside the crown (126) and comprising at one free end a toothed annular edge (138) which is configured to be coupled with the internal screw (68a), and * a system (146) for driving the ring (136) in rotation inside the crown (126).

2. Tooling (100) according to claim 1, in which the actuator (114) is hydraulic and comprises an annular chamber (116) extending around the axis A and intended to be supplied with fluid, such as oil for example.

3. Tooling (100) according to claim 1 or 2, in which the tie rod (104) comprises an external thread (110) for screwing a nut (112) configured to bear axially on the block (106), and in particular on the first part (114a) of its actuator (114).

4. Tool (100) according to one of the preceding claims, in which the ring (136) is guided in rotation inside the crown (126) by at least one bearing (142), for example a rolling bearing, interposed radially between the ring (136) and the crown (126).

5. Tool (100) according to one of the preceding claims, wherein the annular edge (138) of the ring (136) comprises at least one axially oriented tooth (140) and preferably an annular row of axially oriented teeth (140).

6. Tool (100) according to one of the preceding claims, in which the annular edge (132) of the crown (126) is also toothed and comprises at least one axially oriented tooth (134).

7. Tooling (100) according to the preceding claim, in which it further comprises a device (150) for detecting the axial alignment of the tooth or one of the teeth (134) of the crown (126) with the tooth or one of the teeth (140) of the ring (136).

8. Tooling (100) according to one of the preceding claims, in which the annular edge (132) of the crown (126) comprises an internal cylindrical centering surface (132b) configured to cooperate with a complementary external cylindrical surface (68b1) of the external nut (68b).

9. Tooling (100) according to one of the preceding claims, wherein the ring (136) comprises an external annular toothing (144) which is configured to cooperate with said drive system (146).

10. Tooling (100) according to one of the preceding claims, in which the drive system (146) comprises a worm screw (148).

11. Tooling (100) according to all of claims 9 and 10, in which the worm screw (148) has a generally elongated shape along an axis B which is tangent to a circumference centered on the axis A and which is contained in a plane perpendicular to the axis A, this worm screw (148) being carried by the crown (126) and guided in rotation in orifices (149) of the crown (126), at least one of the axial ends of the worm screw (148) being connected or capable of being connected to a crank, and the worm screw (148) being meshed with the teeth (144) of the ring (136).

12. Tool (100) according to one of the preceding claims, in which the crown (126) comprises at least one light (135) passing through in the radial direction and configured to allow an operator to see the annular edge (138) of the ring (136) from the outside through this light (135).

13. Device comprising: - a member carrying an axial stop and around which is mounted a rolling bearing (48), as well as an annular screw-nut assembly (68) interposed between the axial stop and the rolling bearing (48), and - a tool (100) according to one of the preceding claims, the screw-nut assembly comprising an internal screw (68a) comprising an external thread (68a1), and an external nut (68b) comprising an internal thread (68b1) for screwing onto the external thread (68a1) of the internal screw (68a), the internal screw (68a) being configured to be slid around the member and to bear axially on the stop, and the external nut (68b) being configured to bear axially on the rolling bearing (48).

14. Device according to claim 13, in which the member is a root (18) of a variable-pitch blade (14) for a propeller (10) of an aircraft turbomachine, or the member is a shaft of an aircraft turbomachine.

15. A method of preloading a rolling bearing, by means of a device according to claim 13 or 14, characterized in that it comprises the steps of: a) hooking the end (104a) of the tie rod (104) to the member, b) mounting the block (106) around the tie rod (104, so that the annular edge (132) of the crown (126) is in axial support on the external nut (68b), and the annular edge (138) of the ring (136) is coupled with the internal screw (68a), c) immobilizing the first part (114a) of the actuator (114) with respect to the tie rod (104), d) translational movement of the first part (114a) of the actuator (114) with respect to its second part (114b), so as to cause an axial stretching of the member along the axis and the appearance of an axial clearance (J) between the internal screw (68a) and the stop of the member, and e) rotational movement of the ring (136) inside the crown (126),so as to rotate the internal screw (68a) with respect to the external nut (68b) and the member, and to take up said axial play (J), with a previously defined tightening torque, f) deactivating the actuator (114) so ​​that its first part (114a) returns to its original position with respect to the second part (114b) of the actuator (114), g) detaching the first part (114a) of the actuator (114) with respect to the tie rod (104), h) dismantling and removing the block (106) with respect to the tie rod (104), and i) dismantling and removing the tie rod (104) with respect to the member., 16. Method according to claim 15, comprising, between steps e) and f), a step of angular wedging of the internal screw with the external nut, by example to align teeth of the internal screw with teeth of the external nut, by applying an overtorque to the internal screw.

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