Method of fixing at least two turbine disc flanges
The method of using non-circular screw heads guided by a complementary guide element addresses the issue of incorrect angular positioning during turbine disc flange assembly, ensuring secure and cost-effective assembly without altering existing parts.
Patent Information
- Application Number
- FR2022010183
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-10-05
- Publication Date
- 2025-10-10
- Estimated Expiration
- 2042-10-05
AI Technical Summary
The assembly of turbine disc flanges in turbomachines often results in damage due to incorrect angular positioning of screw heads, which can lead to the need for repairs or scrapping of parts, despite precautions taken by operators.
A method involving the use of non-circular screw heads that cooperate with complementary locking surfaces on the flanges, guided by a guide element to ensure correct angular positioning, without requiring structural modifications to existing parts.
Guarantees proper alignment of screw heads during assembly, preventing damage to flange surfaces and allowing for secure fixation without additional tools, thereby reducing scrap and maintenance costs.
Smart Images
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Abstract
Description
Title of the invention: Method for fixing at least two turbine disc flanges Technical field of the invention
[0001] The invention relates to a method for fixing at least two turbine disc flanges, in particular an aircraft turbomachine turbine. State of the prior art
[0002] A turbomachine conventionally comprises, from upstream to downstream in the direction of circulation of the gases within the turbomachine, a fan, a low pressure compressor, a high pressure compressor, a combustion chamber, a high pressure turbine, a low pressure turbine and a gas exhaust nozzle.
[0003] A low-pressure turbine 1 of a prior art turbomachine is illustrated in [Fig. 1]. This extends along an axis X and comprises several stages each comprising a distributor 2 formed of an annular row of fixed blades 3 carried by an external casing 4 of the turbine 1, and a rotor bladed wheel 5 located downstream of the distributor 2.
[0004] The wheels 5 comprise discs 6 from which frustoconical or cylindrical ferrules 6a extend axially, assembled axially to each other by annular flanges 7. The discs 6 also carry radial blades 8. These wheels 5 are connected to a turbine shaft, not shown, by means of a drive cone 9 fixed to the annular flanges 7 of the discs 6.
[0005] The terms axial, radial and circumferential are defined relative to the axis X of the turbomachine, which coincides with the axis of the low pressure turbine 1.
[0006] Each wheel 5 is surrounded externally with a small clearance by a sealing ring 10 made of abradable material.
[0007] The flanges 7 of the different stages are assembled by means of screws 11 and nuts 12.
[0008] As can be better seen in Figures 2 and 3, each flange 7 extends radially and circumferentially from a connection zone 13 with the corresponding ferrule 6a and comprises lobes 14 regularly distributed around the circumference. Each lobe 14 comprises an orifice 15 intended for the passage of a screw 11.
[0009] Each screw 11 has a square-shaped head 11a and a threaded rod 11b passing through the corresponding orifices 15 of the flanges 7.
[0010] A nut 12, screwed onto the threaded rod 11b, makes it possible to axially tighten the two flanges 7 between the nut 12 and the head 11a of the screw 11.
[0011] A recess or shoulder of the flange 7 at the level of the connection zone 13 delimits an annular rotation-locking surface 16 cooperating with one of the edges of the square head 11a of the screw 11 so as to ensure its rotation-locking.
[0012] Thus, during assembly, the rod 11b of each screw 11 is engaged axially from upstream to downstream in the corresponding orifices 15 until the head 11a of the screw 11 is in abutment on a radial bearing surface 7a of the corresponding flange 7 and the rotation of the head 11a of the screw 11 is prevented by the blocking surface 16. In the remainder of the description, the terms upstream and downstream refer to the direction of introduction of the screws 11 into the orifices 15, and not to the direction of flow of the gases within the turbomachine.
[0013] The nut 12 is then screwed onto the rod 11b of the screw 11, no tool then being necessary to keep the head 11a of the screw 11 rotating.
[0014] However, despite all the precautions usually taken by operators during such assembly, it happens that, due to poor angular positioning of the head 11a of the screw 11 around its axis, a part of the head 11a is supported, not on the support surface 7a of the flange 7, but on a radial surface 13a of the connection zone 13 located upstream of the locking surface 16, which can damage this surface 13a. The damage generated must be repaired, or the entire part must be scrapped. Presentation of the invention
[0015] The present document aims to remedy this drawback, in a simple, reliable and inexpensive manner.
[0016] For this purpose, the present document relates to a method for fixing at least two turbine disk flanges, each flange being annular and extending around an axis, each flange comprising a plurality of orifices distributed around the circumference, at least one flange comprising at least one circumferentially extending rotational locking surface, the flanges being fixed to each other by means of axially extending screws inserted through said orifices of the flanges, at least one screw comprising a non-circular head capable of cooperating by shape complementarity with the locking surface of the corresponding flange so as to prevent rotation of the screw around its axis, said head axially bearing on a bearing surface of the corresponding flange, a nut cooperating with the screw so as to clamp the flanges between the screw head and the nut, in which, upon insertion of the screw comprising the non-circular head,said head is guided in position around the axis of the screw by a guide element secured to at least one of the flanges, said guide element comprising at least one guide surface capable of guiding the head so that it is oriented in a manner complementary to the locking surface of the flange.
[0017] In this way, the correct positioning of the screw head is guaranteed when it is put in place and inserted into the holes of the flanges. During such insertion, the screw head can thus be guided by the guide surface of the guide element, so as to correctly orient and match the non-circular head of the screw and the complementary locking surface of the corresponding flange. It is guaranteed that the screw head is properly in axial support on the support surface of the corresponding flange and does not come to bear by mistake on another surface, due to an incorrect angular orientation of the screw head around its axis.
[0018] Once the screw is in position, the complementary non-circular surfaces allow the screw to be locked in rotation and the nut can be screwed onto the screw.
[0019] Furthermore, such a method does not require structural modification of the already existing parts, but simply the addition of the guide element.
[0020] The terms axial, radial and circumferential are defined relative to the axis of the flanges.
[0021] The axis of the screws may be parallel to the axis of the annular flanges.
[0022] The guide surface may comprise at least one face inclined relative to a radial plane.
[0023] Said inclined surface may be flat or curved. It may be formed by a chamfer or a fillet. Said inclined surface may be conical or frustoconical, in whole or in part.
[0024] Said inclined surface may comprise an upstream end and a downstream end, the terms upstream and downstream being defined relative to the direction of insertion of the screw. The upstream end is further from the axis of the screw than the downstream end, so as to progressively guide the screw head to its final position, when inserting the screw into the corresponding holes of the flanges, from upstream to downstream.
[0025] The head of the screw may have a polygonal shape.
[0026] The head of the screw may for example have a square shape.
[0027] The polygonal screw head may have a plurality of straight edges, the surface of guide comprises at least two inclined faces, each face being capable of cooperating with one of the edges of the screw head.
[0028] The guide surface comprises, for example, three inclined faces each forming an angle with the radial plane, distributed around the periphery of the orifices, each face being capable of cooperating with one of the edges of the screw head.
[0029] The locking surface of the flange may be annular.
[0030] Such an annular surface may cooperate with a screw head of polygonal shape. Said locking surface may in particular be cylindrical. In such a case, the areas in contact between the bearing surface and the polygonal head are straight lines, for example two straight lines. Such contact is said to be linear.
[0031] Of course, the radius of implantation of such a support surface is a function of the di dimensions of the screw head and the radius of the corresponding screw holes on the flanges.
[0032] At least two screws may have non-circular heads engaged in corresponding holes in the flanges, the guide element then being able to have several guide surfaces circumferentially offset from one another and each capable of guiding the head of one of said screws.
[0033] The same guide element can thus be used to guide several screws.
[0034] Each guide surface may form a light or a recess allowing the axial passage of the screw head in a correct angular position of the screw around its axis. Said light or recess may be defined by the base and the branches of a U-shaped guide element. Of course, other shapes are also possible, for example a square shape comprising in its center said recess, and surrounded for example by four inclined surfaces, each surface being formed on one of the sides of the square, in the case of a square-shaped screw head.
[0035] The guide element may have a ring portion shape, or a ring shape extending over 360°.
[0036] The different guide surfaces of the guide element may be of identical structures. The non-circular screw heads may also have the same shape, for example the same polygonal shape, in particular square.
[0037] The guide element may be removable.
[0038] The guide element can be held on at least one of the flanges by means of a removable holding element.
[0039] The holding element may have a general U-shape comprising a base extending axially on either side of which an upstream branch and a downstream branch extend radially, bearing axially upstream on the guide element and downstream on the downstream flange.
[0040] The holding element may also have a general shape of a clamp pressing the guide element onto the upstream flange, said clamp comprising an upstream end and a downstream end bearing respectively on the guide element and on the downstream flange.
[0041] The guide element may comprise means for axially stopping the screw in translation, capable of axially holding the screw in position after insertion of said screw into said orifices.
[0042] The aforementioned stopping means may comprise an oblong element, for example a sheet metal or a blade, capable of forming an axial support for the screw head in the event of downstream movement of said screw, said oblong element extending in a radial plane and being removably mounted on the guide element.
[0043] Said oblong element can be mounted in at least one groove or groove of the guide element. The oblong element can also be a pin.
[0044] Thus, the corresponding screw can be engaged in the holes of the corresponding flanges, from upstream to downstream, until the screw head is in contact with the bearing face of the upstream flange. The oblong stop element can then be mounted on the guide element so as to prevent the screw from being withdrawn before the nut is screwed onto said screw.
[0045] Each flange may extend radially and have a radial upstream surface and a radial downstream surface.
[0046] Each flange may have lobes, each orifice being formed at one of the lobes.
[0047] Each turbine disc may comprise a cylindrical or frustoconical shell, the flange extending from an axial end of said shell.
[0048] The connection zone between the ferrule and the flange may comprise an annular radial surface offset axially upstream, relative to the bearing surface of the flange. The rotational locking surface of the flange may extend axially between said radial surface of the connection zone and the bearing surface of the flange.
[0049] The guide element may comprise a first radial surface or upstream radial surface, bearing on the bearing surface of the flange and an annular surface, for example in the shape of an arc of a circle or a portion of a cylinder, bearing on the locking surface of complementary shape. The guide element may comprise a second radial surface, or downstream radial surface, offset downstream relative to the first radial surface, extending opposite said radial surface offset from the connecting zone.
[0050] Said offset radial surface of the connecting zone can be completely covered near the head by the guide element to avoid any risk of contact between the head and said offset radial surface in the event of incorrect angular positioning of the screw.
[0051] The guide element may further comprise a radially external chamfer making it possible to adapt to a rounded shape of the connection zone.
[0052] The rotational locking surface may be located radially outside the orifices.
[0053] Each screw may have a head and a threaded shank, the threaded shank being inserted into the corresponding holes in the flanges.
[0054] Each disk may be a turbine disk of a turbomachine, for example of an aircraft turbojet or turboprop. The aircraft may be an airplane or a rotary-wing aircraft. Brief description of the figures
[0055] [Fig-1] is a half axial sectional view of a low pressure turbine of the art prior,
[0056] [Fig.2] is a perspective view, in detail, illustrating the attachment of flanges of the art prior,
[0057] [Fig.3] is a perspective view, in detail, of a flange and a screw of the art prior,
[0058] [Fig.4] is a view corresponding to [Fig.3], illustrating one embodiment according to this document,
[0059] [Fig.5] is a side view of the area illustrated in [Fig.4],
[0060] [Fig.6] is a perspective view of the guide element of Figures 4 and 5,
[0061] [Fig.7] is a perspective view of the guide element of Figures 4 and 5,
[0062] [Fig.8] is a perspective view, in detail, illustrating the fixing of flanges according to a another embodiment of this document,
[0063] [Fig.9] is a view corresponding to [Fig.8], illustrating yet another form of production of this document,
[0064] [Fig. 10] is a perspective view, in detail, illustrating the fixing of flanges according to a another embodiment of this document,
[0065] [Fig. 11] is a perspective view of a guide element according to another form of realization,
[0066] [Fig. 12] is a perspective view of a guide element according to another form of realization. Detailed description of the invention
[0067] Figures 4 to 8 illustrate the fixing of two flanges 7 of low pressure turbine discs of a turbomachine according to a first embodiment of the present document.
[0068] As previously, each flange 7 extends radially and circumferentially from a connection zone 13 with the corresponding ferrule 6a and comprises lobes 14 regularly distributed around the circumference. Each lobe 14 comprises an orifice 15 intended for the passage of a screw 11.
[0069] Each screw 11 has a square-shaped head 11a and a threaded rod 11b passing through the corresponding orifices 15 of the flanges 7.
[0070] A nut 12 makes it possible to axially tighten the two flanges 7 between the nut 12 and the head 11a of the screw 11.
[0071] A recess or shoulder of the flange 7 at the level of the connection zone 13 delimits an annular rotation-locking surface 16 cooperating with one of the edges of the square head 11a of the screw 11 so as to ensure its rotation-locking.
[0072] Thus, during assembly, the rod 11b of each screw 11 is axially engaged upstream to downstream (from left to right in [Fig.5]) in the corresponding orifices 15 until the head 11a of the screw 11 is in abutment on a radial bearing surface 7a of the corresponding flange 7 and the rotation of the head 11a of the screw 11 is prevented by the blocking surface 16. It is recalled that the terms upstream and downstream refer to the direction of introduction of the screws 11 into the orifices 15, and not to the direction of flow of the gases within the turbomachine.
[0073] The nut 12 is then screwed onto the rod 11b of the screw 11, no tool then being necessary to keep the head 11a of the screw 11 rotating.
[0074] In order to prevent incorrect angular positioning of the head 11a of the screw 11 around its axis, the present document proposes mounting a guide element 17 on the flanges 7, intended to guide the head 11a of the screw 11 during insertion of the screw 11 into the orifices 15 until it rests on the corresponding bearing surface 7a.
[0075] The guide element 17 has a general U-shape, and comprises a shoulder 18 cooperating with the shoulder of the connecting zone 13 of the flange 7. In other words, the guide element 17 comprises a first radial surface 19 or upstream radial surface, bearing on the bearing surface 7a of the flange 7 and an annular surface 20, in an arc of a circle, bearing on the rotational locking surface 16. The guide element 17 comprises a second radial surface 21, or downstream radial surface, offset downstream relative to the first radial surface 19, extending opposite the radial surface 13a of the connecting zone 13. The guide element 17 further comprises a radially external chamfer 22 making it possible to adapt to the rounded shape of the connecting zone 13. Another chamfer 23 is located at the connection between the surfaces 19 and 20.
[0076] The guide element 17 comprises a base 24 on either side of which two branches 25 extend. The base 24 and the branches 25 each comprise a flat inclined face 26, in the manner of a chamfer. The inclined faces 26 together define a guide surface for the head 11a of the screw 11. The upstream ends 27 of the inclined faces 26 are further from the axis of the screw 11 than the downstream ends 28 of the inclined faces 26.
[0077] During assembly, in the event of incorrect angular positioning of the head 11a of the screw 11 around the axis of the screw 11, said head 11a is angularly reset to the correct position by contact with the inclined faces, until a desired angular position is reached as illustrated in Figures 1 and 5.
[0078] This avoids any unwanted contact between the head 11a and the radial surface 13a of the connecting zone 13, said radial surface 13a being completely covered in the vicinity of the head 11a by the guide element 17.
[0079] When fixing the flanges 7 together, each screw 11 is inserted into the corresponding holes 15 of the flanges 7. During such insertion, the head 11a of the screw 11 is guided by the guide surface 26 of the guide element 17, so as to correctly orient and place the head 11a of the screw 11 axially opposite the complementary locking surface 16 of the upstream flange 7. It is guaranteed that the head 11a of the screw 11 is indeed in axial support on the support surface 7a of the upstream flange 7 and does not come to bear by mistake on another surface, in particular on the radial surface 13a of the connection zone 13, due to an incorrect angular orientation of the head 11a of the screw 11 around its axis.
[0080] Once the screw 11 is in position, the square shape of the head 11a of the screw 11 and its cooperation with the locking surface 16, ensure that the screw 11 is locked in rotation and the nut 12 can then be screwed onto the screw 11.
[0081] As illustrated in [Fig.8], the guide element 17 can be held in position on the flanges 7 by means of a removable holding element 27. The holding element 27 can have a general U shape comprising a base 27a extending axially and on either side of which upstream and downstream branches 27b extend radially, bearing axially upstream on the guide element 17 and downstream on the downstream flange 7, respectively.
[0082] Thus, the guide element 17 can be mounted before insertion of the screw 11 into the orifices 15, held in position using the guide element 27 during insertion of the screw 11 and during tightening of the nut 12, then removed after tightening of the nut 12 on the screw 11.
[0083] As illustrated in [Fig.9], the holding element 27' may also have a general shape of a clamp pressing the guide element 17 onto the upstream flange 7, said clamp comprising upstream and downstream ends 27a' bearing respectively on the guide element 17 and on the downstream flange 7, said clamp 27' being able to be actuated so as to bring said upstream and downstream ends 27a' closer to or further apart from each other so as to be able to press and hold the guide element 17 onto the flanges 7 or so as to release it.
[0084] As illustrated in [Fig. 10], the guide element 17 may comprise axial translational stop means 28 of the screw 11 capable of axially holding the screw 11 in position after insertion of said screw 11 into said orifices 15.
[0085] Said stopping means may comprise an oblong element, for example a sheet metal or a blade 28, capable of forming an axial support for the head 11a of the screw 11 in the event of downstream movement of said screw 11, said oblong element 28 extending in a radial plane and being removably mounted on the guide element 17. Said oblong element 28 is for example mounted in a groove 29 of the guide element 17.
[0086] Thus, the corresponding screw 11 can be engaged in the orifices 15 of the corresponding flanges 7, from upstream to downstream, until the head 11a of the screw 11 is in contact with the bearing surface 7a of the upstream flange 7. The stop element 28 can then be mounted on the guide element 17 so as to prevent the screw 11 from being removed before screwing the nut 12 onto said screw 11.
[0087] [Fig. 11] illustrates the case of a multiple guide element 17, i.e. capable of guiding several screws 11, here four screws 11, and comprising for this purpose four guide surfaces each formed from the three inclined faces 26 of the aforementioned type.
[0088] The same guide element 17 can thus be used to guide several screws 11.
[0089] [Fig. 12] illustrates the case of an annular guide element 17 comprising as many guide surfaces as there are screws 11 intended for assembling the flanges 7. Such a ring can be in one piece or formed from several angular segments.
Claims
Claims
1. Method for fixing at least two flanges (7) of turbine disks, each flange (7) being annular and extending around an axis (X), each flange (7) comprising a plurality of orifices (15) distributed around the circumference, at least one flange (7) comprising at least one circumferentially extending rotational locking surface (16), the flanges (7) being fixed to each other by means of axially extending screws (11) inserted through said orifices (15) of the flanges (7), at least one screw (11) comprising a head (11a) of non-circular shape capable of cooperating by shape complementarity with the locking surface (16) of the corresponding flange (7) so as to prevent rotation of the screw (11) around its axis, said head (11a) axially bearing on a bearing surface (7a) of the corresponding flange (7),a nut (12) cooperating with the screw (11) so as to clamp the flanges (7) between the head (11a) of the screw (11) and the nut (12), characterized in that, when inserting the screw (11) comprising the non-circular head (11a), said head (11a) is guided into position around the axis of the screw (11) by a guide element (17) secured to at least one of the flanges (7), said guide element (17) comprising at least one guide surface (26) capable of guiding the head (11a) so that it is oriented in a manner complementary to the locking surface (16) of the flange (7).,
2. Method according to the preceding claim, in which the guide surface (26) comprises at least one face (26) inclined relative to a radial plane.
3. Method according to one of the preceding claims, in which the head (11a) of the screw (11) has a polygonal shape.
4. Method according to the preceding claim, in which the head (11a) of the polygonal screw (11) comprises a plurality of straight edges, the guide surface (26) comprises at least two inclined faces (26), each face (26) being capable of cooperating with one of the edges of the head (11a) of the screw (H).
5. Method according to one of the preceding claims, in which the locking surface (16) of the flange (7) is annular.
6. Method according to one of the preceding claims, in which at least two screws (11) having non-circular heads (11a) are engaged in corresponding orifices (15) of the flanges (7), the element
7.
8.
9. guide (17) comprising several guide surfaces (26) offset circumferentially from one another and each capable of guiding the head (11a) of one of said screws (11). Method according to one of the preceding claims, in which the guide element (17) is removable. Method according to the preceding claim, in which the guide element (17) is held on at least one of the flanges (7) by means of a removable holding element (27). Method according to one of the preceding claims, in which the guide element (17) comprises means for axially stopping the translation (28) of the screw (11) capable of axially holding the screw (11) in position after insertion of said screw (11) into said orifices (15).