FR3085994A1 - AXIAL RETENTION RING OF BLADES FOR MOBILE WHEEL OF TURBOMACHINE, PREFERABLY FOR AIRCRAFT - Google Patents

Abstract

The invention relates to a ring (16) for axial retention of blades for a mobile wheel (20) of a turbomachine, the mobile wheel comprising: - a disc (21) having grooves (58) for housing blades; - A plurality of blades (18) each comprising a blade (30), and a foot (24) arranged in one of the grooves (58) of the disc (21). According to the invention, the ring comprises at least one holding system (72) configured to hold the ring (16) axially relative to the disc (21), the holding system (72) comprising a locking member (74 ) pivotally mounted on the ring (16) and configured to be moved between an unlocking position, and a locking position in which a locking end (84) of the locking member (74) is intended to cooperate axially with the disc (21).

Description

AXIAL RETENTION RING OF BLADES FOR MOBILE WHEEL OF TURBOMACHINE, PREFERABLY FOR AIRCRAFT

TECHNICAL AREA

The invention relates to the field of mobile blades for a turbomachine, and more generally the mobile turbine wheels equipped with such blades, such as for example the wheels described in document EP 1264 964 A1. It relates more particularly to the axial retention rings of the blades of these moving wheels.

The invention applies to any type of turbomachine, preferably for an aircraft, such as a turbojet or a turboprop.

STATE OF THE PRIOR ART

Movable turbine wheels have been the subject of numerous developments, in particular as regards the means of axial retention of the blades in the grooves situated at the periphery of the turbine disc.

Usually, an axial retention ring is provided, arranged on an upstream and / or downstream side of the turbine disc, in order to form axial stops for the blade roots housed in the grooves of this disc. The axial maintenance of this ring usually requires specific means, for example hooks of complex shapes provided on the blades and on the disc. The mounting of the ring on the disc is sometimes complicated, especially for wheels with restricted access conditions, such as the wheels arranged at the ends of the turbine.

If certain existing solutions are satisfactory, there nevertheless remains a need for improvement aimed at further facilitating the mounting of the ring on the disc of such a movable wheel, while presenting a simplified design.

SUMMARY OF THE INVENTION

S65877AP-P

To respond at least partially to this need, the invention relates to an axial retention ring of blades for a mobile wheel of a turbomachine, the mobile wheel comprising:

- a disc having blade housing grooves;

- A plurality of blades each comprising a blade, and a foot arranged in one of the grooves of the disc.

According to the invention, the ring comprises at least one holding system configured to hold the ring axially with respect to the disc, the holding system comprising a locking member pivotally mounted on the ring and configured to be moved between a position unlocking, and a locking position in which a locking end of the locking member is intended to cooperate axially with the disc.

The subject of the invention is also a mobile wheel of a turbomachine, the mobile wheel comprising:

- A disc comprising blade housing grooves and at least one hook which extends upstream into a disc;

- A plurality of blades each comprising a blade, a foot arranged in one of the grooves of the disc; and

- A ring as presented above, the hook being formed by an annular flange secured to the disc, the flange possibly being scalloped.

The invention also relates to a method of assembling such a movable wheel, comprising the following successive steps:

- Positioning of the ring against the disc, axially opposite the blade roots arranged in the disc housing grooves, with each locking member in the unlocked position; and

- Pivoting of each locking member towards its locking position so that its locking end cooperates axially with the hook of the disc.

S65877AP-P

The invention thus makes it possible to meet the need formulated above, by providing one or more ring holding systems based on a simple design and operation. The manufacture as well as the assembly of the components of the movable wheel are advantageously improved thereby.

The invention preferably provides at least one of the following optional technical characteristics, taken individually or in combination.

The locking member is configured so that in the locking position, its locking end cooperates with a hook carried by the disc, preferably being in axial support against one end of the hook.

The locking member is configured so that in the locking position, an axial abutment portion of the locking end is oriented substantially radially to cooperate with one end of the hook.

The locking end of the locking member comprises a holding portion of the locking member in the locked position, position in which the holding portion is intended to cover the end of the hook radially, being arranged externally by compared to this end. Thus, the hook forms a radial stop for the holding portion, preventing the whole of the locking member from pivoting towards its unlocking position. Alternatively, maintaining the locking member in the locking position could be ensured by elastic return means, such as a spring forcing this member towards the locking position. In this case, the locking end can be simplified by being devoid of the aforementioned holding portion.

The locking end of the locking member has a general U-shape, one of the two branches of the U of which is formed by the holding portion, and the other branch of which is intended to cover the end of the hook radially. being arranged internally relative to this end in the locking position of the locking member, this other branch of the U being extended by a lever forming an integral part of the locking member.

S65877AP-P

The locking member is pivotally mounted along a pivot axis oriented substantially circumferentially with respect to the ring.

The ring comprises a plurality of retention systems distributed circumferentially, preferably regularly.

The holding system comprises a pivoting member coupled to the locking member, the pivoting member comprising pivotally housed ends in recesses provided in the thickness of the ring, these recesses being covered by a closure plate which locally covers a hollowed-out part of the ring in order to reconstitute the thickness thereof, said plate being preferably brazed on the ring or fixed to the latter by electric welding points.

Finally, the invention also relates to a turbomachine, preferably for an aircraft, comprising at least one turbine comprising at least one such moving wheel, the turbine preferably being a low pressure turbine. In addition, the turbomachine is preferably a double body turbomachine.

However, the invention could be applied to a compressor, without departing from the scope of the invention.

Other advantages and characteristics of the invention will appear in the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be made with reference to the accompanying drawings, among which;

- Figure 1 is a schematic view in axial section of a turbofan engine according to the invention;

- Figure 2 shows a perspective view of a movable wheel of the low pressure turbine of the turbojet engine shown in the previous figure, the movable wheel being in the form of a preferred embodiment of the invention;

S65877AP-P

- Figure 3 is an axial half-sectional view of the movable turbine wheel shown in the previous figure;

- Figure 4 shows an exploded perspective view of part of the locking ring fitted to the wheel shown in the previous figure; and

- Figures 5 and 6 show perspective views similar to that of the previous figure, respectively with the locking member of the ring in the unlocked position and in the locked position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring first to Figure 1, there is shown an aircraft turbomachine 1, according to a preferred embodiment of the invention. This is a double-flow, double-body turbojet engine. However, it could be a turbomachine of another type, for example a turboprop, without departing from the scope of the invention.

The turbomachine 1 has a longitudinal central axis 2 around which its various components extend. It comprises, from upstream to downstream in a main direction 5 of gas flow through this turbomachine, a blower 3, a low pressure compressor 4, a high pressure compressor 6, a combustion chamber 11, a high pressure turbine 7 and a low pressure turbine 8.

Conventionally, after passing through the blower, the air is divided into a central primary flow 12a and a secondary flow 12b which surrounds the primary flow. The primary flow 12a flows in a main stream 14a of gas circulation passing through the compressors 4, 6, the combustion chamber 11 and the turbines 7, 8. The secondary flow 12b flows in turn in a secondary stream 14b delimited radially outwards by a motor housing, surrounded by a nacelle 9.

Figures 2 and 3 show one of the movable wheels 20 of the low pressure turbine 8, but this wheel 20 specific to the invention could also apply to the high pressure turbine 7, without departing from the scope of the invention. In known manner, along the axis of a turbine, the movable wheels are arranged alternately with distributors

S65877AP-P (not shown). All the movable wheels of the low pressure turbine 8 can be produced in the manner which will be explained below, or only some of them. Preferably, it is one of the two wheels arranged at the upstream and downstream ends of the turbine, for which accessibility is particularly restricted.

The movable wheel 20 comprises a disc 21, a plurality of vanes 18 carried by the disc 21, and a ring 16 for axial retention of the vanes arranged on the upstream side of the disc 21. It is noted that the ring 16 specific to the The invention is intended to ensure the axial retention of the blades 18 upstream, and that their retention downstream is ensured by another device (not shown). This other device can be a ring similar to the ring 16, just as such a ring 16 specific to the invention could only be provided downstream of the disc 21, to ensure the axial retention of the blades 18 towards the downstream.

The blades 18 are distributed circumferentially around the disc 21. Each of them comprises in a radial direction 23 in relation to the central axis 2, going from the inside to the outside, a blade root 24, a stilt 26, a platform 28 and a blade 30 constituting the aerodynamic part of the blade. The blade root 24 has an outer dovetail shape called "fir" or "bulb", allowing its insertion into a blade housing groove 58 provided at the periphery of the turbine disc 21. The stilt 26 usually has a small thickness in a circumferential direction 32, while the platform 28 extends radially outside of stilt 26.

With its outer surface 29, the platform 28 delimits radially inward the main vein 14a. The platform 28 has two opposite axial ends, each forming a spoiler. It is an upstream spoiler 44 located upstream of the leading edge of the blade 30, and a downstream spoiler 45 located downstream of the trailing edge of this blade.

The disc 21 has a main part 46 of revolution which extends around an axis 2, also corresponding to the axis of rotation of the movable wheel 20 in

S65877AP-P operation. This main part 46 has a recess 48 centered on the axis 2, this recess being delimited by the hub 50 of the disc. This also includes an outer peripheral part 52 of the disc, comprising blade housing grooves 58, of axial or oblique orientation. The disc 21 comprises other elements such as fixing flanges (not shown) allowing its connection to other movable wheels of the turbine, and also at least one annular flange 60 projecting from the outer peripheral part 52 of the disc and which extends upstream. More specifically, the flange 60 is either continuous over 360 °, or scalloped by presenting an alternation of hollows and of protruding parts 60a such as that visible in FIG. 3. In the latter case, the circumferential extent of each protruding part 60a remains preferentially weak, for example reduced to an angular sector of 3 to 15 °. The continuous flange 60, or the projecting parts 60a of the scalloped flange, each take the form of a hook. In the following description, reference will be made to a hook 60a, in relation to the shape of the axial section of this element projecting from the external peripheral part 52.

Indeed, the hook 60a has a base 64 arranged substantially radially, projecting inwards from an upstream edge of an internal surface of the peripheral part 52. This base 64 is extended by a bend 66 of axial straightening downstream. Finally, the hook 60a ends in an end 68 in the form of a tongue oriented substantially axially downstream, while remaining at a distance from the main part 46 of the disc 21. An axial space 62 is provided between the end 68 of the hook and the main part 46 of the disc 21, as well as a radial space 70 is provided between this end 68 and the internal surface of the peripheral part 52 of the disc.

In the preferred case of a scalloped flange, or of several isolated hooks 60a, the latter are provided in a number identical to a number of holding systems fitted to the ring, one of which will be described below. Each hook 60a is then associated with one of the holding systems, these couples being preferably distributed evenly, circumferentially. Their number can be set between one and four.

S65877AP-P

In the locked configuration of the ring 16 as shown in FIGS. 2 and 3, this ring is located radially under the upstream spoiler 44. The radially external part 16a of the ring 16 is arranged in axial support on an upstream face of the outer peripheral portion 52 of the disc 21, so as to axially retain the blades at their feet 24 housed in the grooves 58. In this regard, it is noted that each blade housing groove 58 remains open radially outward to allow Léchasse 26 of dawn to pass, as is known from the prior art.

The radially internal part 16b of the ring 16 has the particularity of carrying the holding systems 72, each configured to retain the ring 16 axially with respect to the disc 21. As will be detailed below, each system of holding 72 is effectively designed to prevent the ring 16 from moving axially upstream, thereby allowing it to be kept in its locked configuration on the disc. These systems 72 have an identical or similar design, and one of them will now be described with reference to FIGS. 4 to 6.

The holding system 72 comprises a locking member 74, as well as a pivoting member 76 coupled to the locking member. The pivoting member 76, in the form of a rod, is integral with the locking member 74 or else it crosses the latter in a pivot connection. Its ends are pivotally housed in recesses 78 provided in the thickness of the radially internal part 16b of the ring 16. These recesses 78 are covered by a closure plate 79, which locally covers a recessed part of the ring for reconstitute the thickness. The plate 79 is brazed on the ring or fixed by electric welding points. It allows the pivoting member 76 to be held in its corresponding recesses 78, between the ring 16 and the closure plate 79.

The pivoting member 76 comprises a pivoting axis 80 oriented substantially circumferentially with respect to the ring 16, that is to say it is locally substantially parallel to the circumferential direction 32 of this ring. Thanks to this pivoting ability, the locking member 74 can be moved relatively

S65877AP-P to the ring 16 between an inactive rest position, called unlocking (see FIG. 5), and an axial retention position, called locking and (see FIGS. 3 and 6). To obtain the displacement of the member 74 between these two positions, its pivoting of the order of 90 ° is required around the axis 80.

The pivoting member 76 cooperates with a lever 82 forming an integral part of the locking member 74, of which it constitutes a base in the general shape of an L. More precisely, this pivoting member 76 cooperates with a thickened end of the lever 82, while an opposite end of this L-shaped lever is extended by a locking end 84 of the member 74.

The locking end 84 has a general U shape, one of the branches 84a of which is thus in line with and aligned with the lever 82. The base 84b of the U forms an axial abutment portion, while the other branch 84c of the U forms a portion for holding the member 74 in its locked position. In the position shown in Figure 3, the base 84b of the U forming the axial abutment portion is arranged axially opposite the end 68 of the hook 60a, the latter then forming a complementary retention member. Still in this same position, the base 84b of the U is arranged in the axial space 62, being oriented substantially radially, and preferably in axial abutment against this end 68 of the hook 60a. The branch 84a of the U, like a large part of the portion of the lever 82 which extends it, covers the end 68 of the hook radially, being arranged radially internally with respect to this end. Conversely, the branch 84c of the U radially covers the end 68 of the hook by being arranged radially outside with respect to the latter, in the radial space 70. This is thanks to the radial cooperation between this branch 84c of the U, and the end 68 of the hook, that the locking member 74 is held in its locking position ensuring the locking of the ring on the disc.

The mounting of the ring 16 on the disc 21 is therefore carried out by carrying out a first step of placing the ring 16 against the disc, and more precisely in abutment against the outer peripheral part 52 of this disc. The ring

S65877AP-P is then located axially opposite the blade roots 24 arranged in the grooves 58. This first step is carried out with the locking members 74 in the unlocked position, like that shown in FIG. 5. A second step consists to rotate each locking member 74 so as to bring it from its unlocking position to its axial locking position shown in Figures 3 and 6. This passage from one position to the other is similar to clipping of the locking member 74 on the hook 60a. During pivoting, the passage of the branch 84c above the end 68 of the hook is allowed by the elasticity of the member, for example by the bending of its lever 82 when this branch 84c comes into contact with a radially internal surface of the end 68 of the hook.

Once the assembly of the locking member 74 has been obtained, in the manner of a clip, the ring 16 equipped with the holding systems 72 is retained axially in the upstream direction by the bases 84b in contact with the ends. hook 68, and in the downstream direction by the outer peripheral part 52 of the disc.

Of course, various modifications can be made by those skilled in the art to the invention which has just been described, only by way of nonlimiting examples, and the scope of which is defined by the appended claims.

Claims (11)

1. Ring (16) for axial retention of blades for a moving wheel (20) of a turbomachine, the moving wheel comprising: - A disc (21) having grooves (58) for housing the blades; - A plurality of blades (18) each comprising a blade (30), and a foot (24) arranged in one of the grooves (58) of the disc (21); the ring (16) being characterized in that it comprises at least one holding system (72) configured to hold the ring (16) axially with respect to the disc (21), the holding system (72) comprising a locking member (74) pivotally mounted on the ring (16) and configured to be moved between an unlocking position, and a locking position in which a locking end (84) of the locking member (74) is intended to cooperate axially with the disc (21). 2. Ring (16) according to claim 1, characterized in that the locking member (74) is configured so that in the locking position, its locking end (84) cooperates with a hook (60a) carried by the disc (21), preferably by being axially supported against one end of the hook. 3. Ring (16) according to claim 2, characterized in that the locking member (74) is configured so that in the locking position, an axial stop portion (84b) of its locking end (84) is oriented substantially radially to cooperate with one end (68) of the hook (60a). 4. Ring (16) according to claim 2 or 3, characterized in that the locking end (84) of the locking member (74) comprises a holding portion (84c) of the locking member (74 ) in the locked position, position in S65877AP-P 12 which the holding portion (84c) is intended to radially cover the end (68) of the hook (60a), being arranged radially outside with respect to this end (68). 5. Ring (16) according to claim 4, characterized in that the locking end (84) of the locking member (74) has a general shape of U of which one of the two branches of the U is formed by the holding portion (84c), and the other branch (84a) of which is intended to radially cover the end (68) of the hook by being arranged radially inside with respect to this end (68) in the locked position of the locking member, this other branch of the U (84a) being extended by a lever (82) forming an integral part of the locking member (74). 6. Ring (16) according to any one of the preceding claims, characterized in that the locking member (74) is pivotally mounted along a pivot axis (80) which extends substantially circumferentially relative to the ring (16). 7. Ring (16) according to any one of the preceding claims, characterized in that it comprises a plurality of holding systems (72) distributed circumferentially, preferably regularly. 8. Ring (16) according to any one of the preceding claims, characterized in that the holding system (72) comprises a pivot member (76) coupled to the locking member (74), the pivot member ( 76) comprising ends which are pivotally housed in recesses (78) provided in the thickness of the ring (16), these recesses (78) being covered by a closure plate (79) which locally covers a recessed part of the ring to reconstitute the thickness, S65877AP-P said plate (79) being preferably brazed on the ring (16) or fixed to the latter by electric welding points. 9. Movable wheel (20) of a turbomachine, the movable wheel comprising: - A disc (21) comprising grooves (58) for housing blades and at least one hook (60a); - A plurality of blades (18) each comprising a blade (30), a foot (24) arranged in one of the grooves (58) of the disc (21); and - A ring (16) according to any one of the preceding claims, the hook (60a) being formed by an annular flange (60) integral with the disc (21), the flange (60) being optionally scalloped. 10. Turbomachine (1) comprising at least one turbine (7, 8) having at least one movable wheel (20) according to claim 9, the turbine preferably being a low pressure turbine. 11. A method of assembling a movable wheel (20) according to claim 9, characterized in that it comprises the following successive stages: - Positioning of the ring (16) against the disc (21), axially opposite the blade roots (24) arranged in the housing grooves (58) of the disc (21), with each locking member ( 74) in the unlocked position; and - Pivoting of each locking member (74) towards its locking position so that its locking end (84) cooperates axially with the hook of the disc (21).