FR3139594A1 - Set of self-locking fastening elements and turbomachine rotor assembly equipped with such a set. - Google Patents

Abstract

The present invention relates to a set of several self-locking fastening elements (10) for assembling at least two parts. This game is remarkable in that each fixing element (10) comprises a split annular snap ring (5) and a nut (1) which comprises: a nut head (2) provided with a threaded hole (20 ), a plate (3) for locking the nut (1) in anti-rotation, which extends around said nut head (2) and a plurality of axial locking lugs (4), in that the plate (3) comprises two opposite circumferential locking end faces (35, 36), in that the stop ring (5) is arranged around said lugs (4) and in that each fixing element (10 ) is configured so that when all the elements (10) are mounted circumferentially end to end on one of the parts to be assembled, the two locking faces (35, 36) of each nut (1) are respectively in contact with the one of the two locking faces (35, 36) of a nut (1) circumferentially adjacent, to prevent the rotation of each element (10). Figure for abstract: Fig. 5.

Description

Set of self-locking fasteners and turbomachine rotor assembly equipped with such a set. FIELD OF THE INVENTION

The invention lies in the general field of turbomachines and more particularly that of gas turbine rotors.

The present invention relates more specifically to a set of self-locking fastening elements, these different fastening elements being intended to cooperate to enable at least two parts to be fastened together, preferably parts of a turbomachine and more particularly those of a rotor.

STATE OF THE ART

Among the parts used in a turbomachine that can be assembled, we can cite for example the flanges of a rotor. On the attached, which represents a part of a turbomachine A according to the state of the art, we can see a turbine rotor disk B, provided with an upstream annular connecting flange C, a high-pressure compressor D, provided with a downstream annular connecting flange E and a disk F carrying several annular sealing labyrinths G, these three annular parts extending around a longitudinal axis H of the turbomachine. The upstream annular flange C, the disk F and the downstream annular flange E are assembled using screws J and nuts K, distributed all around the axis H, the screws J passing through holes provided for this purpose on the parts C, F and E.

K nuts are generally crimped and this can damage the parts of the parts that come into contact with these nuts at the level of the support surfaces ensuring anti-rotation (for example here the C flange or the chamfers of the holes that pass through it). However, these parts are made of expensive or fragile materials that should not be damaged.

Furthermore, the rotating K nuts must be stopped while tightening or loosening the J screws, while these nuts are often positioned in areas that are inaccessible or difficult to access with assembly/disassembly tools.

Finally, these nuts are positioned in places exposed to high temperatures of up to 600°C.

The invention therefore aims to propose a set of several self-locking fixing elements, each fixing element of which can be locked both axially and in rotation about its longitudinal axis, without this locking causing damage to the parts to be fixed, in particular for example on the flange of a turbomachine rotor disk, including holes and chamfers.

The invention also aims to provide a set of self-locking fixing elements whose elements are easily assembled and disassembled and which, advantageously, also withstand high temperatures.

For this purpose, the invention relates to a set of several self-locking fixing elements for assembling at least two parts.

According to the invention, each fixing element comprises an annular stop ring and a nut and the nut comprises:
- a nut head which has a tapped hole with longitudinal axis X-X', configured to receive a screw,
- a plate for locking the nut against rotation, this locking plate extending in a circumferential direction perpendicular to the longitudinal axis X-X', on either side of said nut head, and this locking plate comprising a front face and an opposite rear face,
- and a plurality of axial locking tabs,
the axial locking tabs extend axially projecting, around the longitudinal axis X-X' of the tapped hole and from the front face of the locking plate, and
the anti-rotation locking plate further has two circumferential locking end faces opposite to the circumferential direction,
the snap ring is split and configured to be arranged around and in contact with said axial locking tabs and to be centered on the longitudinal axis X-X',
and each self-locking fastener is configured and dimensioned such that when all the self-locking fasteners of the set are mounted circumferentially end-to-end on one of the parts to be assembled, the two circumferential locking end faces of each nut are respectively in contact with one of the two circumferential locking end faces of a circumferentially adjacent nut, to thereby prevent rotation of each self-locking fastener about the longitudinal axis X-X' of the tapped hole of the nut head.

By virtue of these features of the invention, each nut of a self-locking fastener is held axially by means of the locking tabs which cooperate with the retaining ring and is also blocked tangentially and therefore in rotation by its circumferential locking end faces. The nut can thus be positioned and retained on one of the parts to be assembled, before assembly with the other parts, while it is still possible to access the place where the nuts are positioned.

Each nut does not require crimping to be locked and therefore there is no damage to the parts to be assembled.

Since each nut is self-locking, it is not necessary to use tools to hold it while tightening the screw and the disassembly of the parts can also be done by simply unscrewing the screw that cooperates with the nut and which remains accessible. Each nut is thus easily assembled and disassembled.

According to other advantageous and non-limiting characteristics of the invention, taken alone or in combination:

- each nut comprises at least three axial locking tabs, uniformly distributed around the longitudinal axis X-X’ of the threaded hole of the nut;

- each axial locking tab of a nut comprises an inner face oriented towards the longitudinal axis X-X’ of the tapped hole and an opposite outer face and a groove for receiving a part of the stop ring is formed on the outer face of each axial locking tab;

- said nut locking plate has on its front face, a support rim which projects from this front face and which extends around the longitudinal axis X-X' of the tapped hole;

- the support edge is annular;

- the two circumferential locking end faces are flat, each circumferential locking end face extending in a plane which is parallel to the longitudinal axis X-X' of the tapped hole and distant from it and these planes are convergent;

- the anti-rotation locking plate of the nut comprises at least one material-relieving recess, preferably two, located on either side of the tapped hole;

- the nut head is extended by a tubular part which projects axially around the longitudinal axis X-X’ of the nut head, from the rear face of the anti-rotation locking plate, this tubular part forming a self-brake for the nut.

The invention also relates to a turbomachine rotor assembly comprising at least two rotor parts to be assembled, one of said parts comprising an upstream face and a downstream face and several axial cylindrical bores, arranged around an axis of revolution X1-X'1, each bore comprising internally an annular shoulder, so as to delimit a bore part of smaller diameter, which opens onto said downstream face and a part of larger diameter, which opens onto said upstream face.

According to the invention, said parts to be assembled are assembled with a set of several self-locking fixing elements as mentioned above, each self-locking fixing element of the set being arranged so that the axial locking tabs of the nut are in one of the holes of the part and that the stop ring is placed around the axial locking tabs and inside the part of larger diameter and in that the different self-locking fixing elements of the set are mounted circumferentially end-to-end, so that the two circumferential locking end faces of each nut are respectively in contact with one of the two circumferential locking end faces of a circumferentially adjacent nut.

Finally, the invention relates to a turbomachine comprising a turbomachine rotor assembly as mentioned above.

DESCRIPTION OF FIGURES

Other characteristics, aims and advantages of the invention will emerge from the description which follows, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

represents a longitudinal sectional view of a part of a state-of-the-art turbomachine.

is a longitudinal sectional view of a self-locking fastening element according to a first embodiment of the invention, mounted on a screw, for fixing several flanges together.

is a perspective view of the nut according to the first embodiment of the invention.

is a perspective view of an alternative embodiment of the nut according to the first embodiment of the invention.

is a perspective view of several self-locking fastening elements according to the invention, mounted next to each other, each element comprising a nut and a stop ring.

is a perspective view showing a first step in mounting a nut on a flange.

is a perspective view showing a second step in mounting the nut on a flange.

is a perspective view showing a first step in removing the nut from the flange.

is a perspective view showing a second step in removing the nut from the flange.

is a diagram representing a set of self-locking fixing elements, in accordance with the invention.

is a longitudinal sectional view of a self-locking fastening element whose nut conforms to a second embodiment of the invention.

is a perspective view of a nut according to a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figures 2 and 5, a self-locking fastener 10 can be seen belonging to a set 100 of self-locking fasteners which is only shown in the .

Each fixing element 10 comprises a nut 1 and an annular stop ring 5.

The nut 1 generally comprises a nut head 2, a locking plate 3 for preventing the nut from rotating and axial locking tabs 4. This nut 1 is intended to cooperate with a screw 6.

The nut head 2, the locking plate 3 and the axial locking tabs 4 of the nut 1 are made of a single block. Preferably, the self-locking nut 1 is made of a heat-resistant material, for example Inconel, in particular to withstand high temperatures of around 600°C.

The nut head 2 preferably has a generally cylindrical shape and is provided with a threaded cylindrical orifice 20, with a longitudinal axis X-X', the latter also constituting the longitudinal axis of the nut 1. The dimensions of this orifice 20 and its threading are adapted to the dimensions and the thread of the screw 6 with which this nut 1 is intended to cooperate.

The anti-rotation locking plate 3 extends on either side of the nut head 2 and the tapped hole 20 (left and right on the ), that is to say in a circumferential direction perpendicular to the longitudinal axis X-X' and, preferably, all around this orifice.

Advantageously, the anti-rotation locking plate 3 has substantially the general shape of a rectangular parallelepiped and comprises an opposite front face 31 and a rear face 32, an opposite external longitudinal face 33 and an opposite internal longitudinal face 34 and finally, two circumferential locking end faces 35, 36.

The two circumferential locking end faces 35, 36 (or side faces) have the function of preventing rotation of the nut 1 around its longitudinal axis X-X’, as will be detailed later.

By convention, the front face 31 is that from which the locking tabs 4 extend axially, and the longitudinal faces 33 and 34 are called respectively “external” and “internal”, by reference to their radial position when all the nuts 1 of the set 100 are assembled circumferentially end-to-end (see ) around the central longitudinal axis X1-X'1 of the parts to be assembled.

Preferably, the front face 31 is flat and preferably also, it is perpendicular to the longitudinal axis X-X’.

In the embodiment of the nut head 2 shown in FIGS. 2, 4 and 6 to 9, the nut head is extended by a tubular part 21 which projects axially (around the axis X-X'), from the rear face 32 of the anti-rotation locking plate 3, that is to say in the direction opposite to that of the locking tabs 4.

Preferably, this tubular part 21 can be internally tapped.

Advantageously, this tubular part 21 is slightly ovalized so as to form a self-brake for the nut.

The locking tabs 4 which project from the front face 31 extend axially, that is to say parallel to the axis X-X’ and are separated from each other by notches 40 which are also axial. The locking tabs 4 are distributed around the longitudinal axis X-X’.

Preferably, the nut 1 is provided with at least two locking tabs 4, more preferably at least three and even more preferably, comprises eight tabs 4, as shown in the .

Each leg 4 comprises an inner face 41, facing the longitudinal axis X-X’ and an opposite outer face 42.

Preferably, the dimensions of each leg 4, i.e. its length, width and thickness, as well as the choice of the material constituting the nut 1 are chosen so that each leg 4 has an elasticity which allows it to deform elastically and not plastically. In other words, the legs 4 can bend so that their ends approach the axis X-X' when they are stressed and can then return to their original position parallel to the axis X-X'.

Preferably, each tab 4 comprises on its outer face 42, a groove 43 for receiving part of the circumference of the stop ring 5. This groove 43 is preferably located at the free end 44 of the tab 4.

The snap ring 5 is split (provided with a slot 50), as can be seen in the It is advantageously made from a flexible, deformable material, for example inconel, which resists temperatures of around 600°C.

Preferably, and as it appears better on the , the locking plate 3 comprises on its front face 31, a support rim 311, which projects from this front face 31 and which extends around the longitudinal axis X-X' of the tapped orifice 20. This support rim 311 makes it possible to limit the surface of the nut 1 which comes into contact with the part to be assembled using this nut. The functional surface is thus reduced to its strict necessity.

Preferably, this support rim 311 is annular.

According to an embodiment variant shown in the , the locking plate 3 may have at least one recess 37, for example two, distributed on either side of the axis X-X', which make it possible to achieve a reduction in material and therefore a reduction in the mass of the nut 1. It is thus possible to obtain a mass saving which can reach 60% depending on the size of the recesses 37.

Such a reduction in mass allows both a saving of material in the manufacture of the nut 1 and therefore a saving of resources, as well as a lightening of the turbomachine in which these nuts are used and therefore a reduction in the kerosene consumption of the aircraft equipped with this turbomachine.

The assembly of a self-locking fastening element 10 and a screw 6 will now be described in connection with FIGS. 2, 6, 7 and 10. The nuts 1 of the set 100 of self-locking fastening elements 10 make it possible to assemble at least two parts, or even more, for example three parts as shown in FIG. , these parts preferably being parts of a turbomachine, for example those of a turbomachine rotor assembly.

In addition, the parts to be assembled are annular parts, with a longitudinal central axis X1-X'1, which comprise a series of holes arranged on a circle whose center is located on the axis X1-X'1, said holes being axial (i.e. parallel to the axis X1-X'1). On the , the three assembled parts are for example two annular flanges 7, 8 and a disc 9.

The flange 7 comprises a face 71, called “upstream”, because it faces upstream of the turbomachine relative to the direction of circulation of the gases inside it and an opposite face 72, called “downstream”.

The annular flange 7 comprises several axial cylindrical bores 73, distributed over its circumference. Each bore 73 internally comprises an annular shoulder 74, so as to delimit a smaller diameter bore portion 731, which opens onto the downstream face 72 and a larger diameter portion 732, which opens onto the upstream face 71.

As can be seen on the , the nut 1 is inserted axially into the bore 73 of the flange 7 until its front face 31 (or its support rim 311 if present) comes into contact with the downstream face 72 of the flange 7, its locking lugs 4 penetrate into the smaller diameter part 731 of the bore and the free ends 44 of the lugs 4 (possibly provided with the groove 43) are in the larger diameter part 732 of the bore 73. The direction of assembly of the nut 1 is represented by the arrow i.

The annular stop ring 5 is then introduced on the upstream side of the flange 7, in the part 732 of the bore 73 and around the locking tabs 4, until it is received in the groove 43 if it is present. The slot 50 allows deformation of the ring 5 during introduction. The direction of introduction of the ring 5 is represented by the arrow ii. The ring 5 is clipped onto the tabs 4 of the nut 1 and the nut 1 is thus retained and self-locked axially since the ring 5 is held against the annular shoulder 74.

As previously stated, the nut 1 of a self-locking fastener 10 is intended to be used with the other nuts 1 of the set 100 of self-locking fasteners.

Each nut 1 of the set 100 is configured and dimensioned so that when all the self-locking nuts 1 of a set 100 are mounted circumferentially end-to-end on the part to be assembled, here on the flange 7, the two circumferential locking end faces 35, 36 of each nut 1 are respectively in contact with one of the two circumferential locking end faces 36, respectively 35 of the circumferentially adjacent self-locking nut 1. The number of nuts 1 of a set 100 is adapted accordingly.

So, as we can see on the , when all the nuts of a nut set are in place, none of them can rotate about its central longitudinal axis X-X', since its circumferential locking end faces 35 and 36 are in contact with the circumferential locking end faces of the neighboring nuts, which prevents any rotational movement.

Furthermore, when all the nuts 1 of a set of nuts 100 are mounted circumferentially end-to-end, on one of the parts to be assembled (for example the flange 7), the respective centers of their tapped holes 20 (passing through the axis X-X') are positioned on the same circle M with center C1, this center C1 being positioned on the axis of revolution X1-X'1 of said part, (see ).

Preferably and as best seen in Figures 3, 5 and 10, the two circumferential locking end faces 35, 36 of each nut 1 are flat. As seen in the , each circumferential locking end face 35, 36 then extends in a plane P35, respectively P36, which is parallel to the longitudinal axis X-X' of the nut 1 and distant from it and these planes P35, P36 are convergent, that is to say they are radial with respect to the circle M. In other words, these planes P35, P36 are secant along a straight line which passes through the center C1.

However, the circumferential locking end faces 35, 36 of each nut 1 could also not be flat and have another shape as long as it allows the axial mounting of the nuts 1, as explained previously in connection with the .

As can be seen on the , as a purely illustrative example, such a face 35, 36 may for example be only flat at its external radial end 351, respectively 361 and at its internal radial end 352, respectively 362 and have a hollow 353, 363 in its central part. The contacts between two circumferentially adjacent nuts 1 are then made only on the flat ends 351, 352, 361 and 362.

The disassembly of a fixing element 10 and a screw 6 will now be described in connection with figures 2, 8 and 9.

The screw 6 is unscrewed, the parts 8 and 9 are removed, then the snap ring 5 is removed using a suitable tool which passes through the notches 40 (see arrow iii). The snap ring 5 being split, it can deform and open and the legs 42 fold back towards the axis X-X’ during the passage of the snap ring.

Once the retaining ring 5 is removed, the legs 4 return to their original position and the nut 1 can be extracted from the downstream side of the part 7 (arrow iv).

It can therefore be seen that the nut 1 according to the invention can be fitted and dismantled several times without damaging the part against which it is fixed since it is not crimped.

There illustrates an alternative embodiment of the nut previously described, in which the nut head 2 and the anti-rotation locking plate 3 have the same axial length. In other words, in this case, the nut head 2 does not include a tubular part 21 projecting from the rear face 32 of the plate 3. The nut 2 then bears the reference 1' and it does not have a self-locking device. For the rest, what has been described previously for the structure, assembly and disassembly of the nut 1 applies to the nut 1'.

Claims (10)

Set (100) of several self-locking fixing elements (10) for the assembly of at least two parts, characterized in that each fixing element (10) comprises an annular stop ring (5) and a nut (1),
in that the nut (1) comprises:
- a nut head (2) which has a tapped hole (20) with a longitudinal axis X-X', configured to receive a screw (6),
- a plate (3) for locking the nut (1) against rotation, this locking plate (3) extending in a circumferential direction perpendicular to the longitudinal axis X-X', on either side of said nut head (2), and this locking plate (3) comprising a front face (31) and an opposite rear face (32),
- and a plurality of axial locking tabs (4),
in that the axial locking tabs (4) extend axially projecting around the longitudinal axis X-X' of the tapped hole (20) and from the front face (31) of the locking plate (3), and
in that the anti-rotation locking plate (3) further has two circumferential locking end faces (35, 36) opposite with respect to the circumferential direction,
in that the stop ring (5) is split and configured to be arranged around and in contact with said axial locking tabs (4) and to be centered on the longitudinal axis X-X',
and in that each self-locking fastener (10) is configured and dimensioned such that when all the self-locking fasteners (10) of the set (100) are mounted circumferentially end-to-end on one of the parts to be assembled, the two circumferential locking end faces (35, 36) of each nut (1) are respectively in contact with one of the two circumferential locking end faces (35, 36) of a circumferentially adjacent nut (1), thereby preventing rotation of each self-locking fastener (10) about the longitudinal axis X-X' of the tapped hole (20) of the nut head (2). Game (100) according to claim 1, characterized in that each nut (1) comprises at least three axial locking tabs (4), uniformly distributed around the longitudinal axis X-X’ of the tapped orifice (20) of the nut (1). Game (100) according to claim 1 or 2, characterized in that each axial locking tab (4) of a nut (1) comprises an inner face (41) oriented towards the longitudinal axis X-X' of the tapped orifice (20) and an opposite outer face (42) and in that a groove (43) for receiving a part of the stop ring (5) is formed on the outer face (42) of each axial locking tab (4). Game (100) according to any one of the preceding claims, characterized in that said locking plate (3) of a nut (1) has on its front face (31), a support rim (311) which projects from this front face (31) and which extends around the longitudinal axis X-X' of the tapped orifice (20). Game (100) according to claim 4, characterized in that the support rim (311) is annular. Game (100) according to any one of the preceding claims, characterized in that the two circumferential locking end faces (35, 36) are flat, each circumferential locking end face (35, 36) extending in a plane (P35, P36) which is parallel to the longitudinal axis X-X' of the tapped orifice (20) and distant from the latter and in that these planes (P35, P36) are convergent. Game (100) according to any one of the preceding claims, characterized in that the anti-rotation locking plate (3) of the nut (1) comprises at least one material-relieving recess (37), preferably two, located on either side of the tapped orifice (20). Game (100) according to any one of the preceding claims, characterized in that the nut head (2) is extended by a tubular part (21) which projects axially around the longitudinal axis X-X' of the nut head (2), from the rear face (32) of the anti-rotation locking plate (3), this tubular part (21) forming a self-brake for the nut (1). Turbomachine rotor assembly comprising at least two rotor parts (7, 8, 9) to be assembled, one of said parts (7) comprising an upstream face (71) and a downstream face (72) and several axial cylindrical bores (73), arranged around an axis of revolution (X1-X'1), each bore (73) internally comprising an annular shoulder (74), so as to delimit a smaller diameter bore part (731), which opens onto said downstream face (72) and a larger diameter part (732), which opens onto said upstream face (71), characterized in that said parts (7, 8, 9) to be assembled are assembled with a set (100) of several self-locking fixing elements (10) according to any one of the preceding claims, each self-locking fixing element (10) of the set (100) being arranged so that the axial locking tabs (4) of the nut (1) are in one of the holes (73) of the part (7) and that the stop ring (5) is placed around the axial locking tabs (4) and inside the part (732) of larger diameter and in that the different self-locking fixing elements (10) of the set (100) are mounted circumferentially end-to-end, so that the two circumferential locking end faces (35, 36) of each nut (1) are respectively in contact with one of the two circumferential locking end faces (36, 35) of a circumferentially adjacent nut (1). A turbomachine comprising a turbomachine rotor assembly according to claim 9.