MASK FOR FIXING SCREWS OF ROTOR DISCS OF A TURBOMACHINE

Abstract

The invention relates to a mask (100) for screws for fixing rotor discs (200, 2001, 2002) of an aircraft turbomachine, this mask (100) having an annular shape around an axis (A0) and comprising a first annular portion (102) capable of covering screw heads (TI204) of an annular row of screws (204, 2041-32) arranged around the axis (A0) and parallel to this axis, the mask (100) further comprises a second annular portion (104) connected to the first annular portion (102) and capable of extending radially inside the screws (204, 2041-32) and threaded rods (TT204) of these screws, said second annular portion (104) comprising an annular edge opposite the first portion (102) and comprising through notches (108) in the radial direction, these notches (108) being distributed around the axis (A0) and being capable of being crossed by a nut tightening tool (300) on said threaded rods. Figure for the abstract: Fig. 2A

Description

Title of the invention: MASK FOR FIXING SCREWS OF ROTOR DISCS OF A TURBOMACHINE Technical field of the invention

[0001] The present invention relates to a mask for fixing rotor discs of an aircraft turbomachine, a set of discs comprising the mask and a method of mounting a turbomachine comprising this set of discs. Technological background

[0002] An aircraft turbomachine comprises at least one rotor, for example a turbine, comprising bladed wheels connected to each other. A wheel comprises a disc carrying blades at its periphery. The rotor discs are fixed coaxially to each other. For this purpose, they comprise annular flanges which are applied axially against each other and which are crossed by fixing screws.

[0003] The discs are generally fixed by stacking the discs coaxially on top of each other so that their axis is oriented vertically. The fixing screws are inserted into holes in the flanges so that their heads are above these flanges. The screws comprise threaded rods which pass through the holes in the flanges and which each receive a nut which is screwed on and is found under the flanges. The flanges are thus axially clamped between the heads of the screws and the nuts.

[0004] Screws generally need to be tightened according to a given tightening pattern. A tightening pattern means a tightening in which each nut, arranged on the shank of each screw, is tightened (or each screw is fixed), following a predefined chronological order so that all screws are correctly fixed.

[0005] This diagram is not always respected by an operator during assembly. Screws may not be correctly fixed which can result in poor plating of the discs, a reduction in the performance of the rotor (and therefore of the turbomachine) or degradation of the turbomachine.

[0006] There is therefore a need to find a solution for complying with the tightening pattern of the rotor disk screws of a turbomachine, which is as simple and effective as possible. Summary of the invention

[0007] A mask is therefore proposed for screws for fixing rotor disks of an aircraft turbomachine, this mask having an annular shape around an axis and comprising at least a first annular portion capable of covering screw heads of an annular row of screws arranged around the axis and parallel to this axis, characterized in that the mask further comprises a second annular portion connected to the first annular portion and capable of extending radially inside the screws and threaded rods of these screws, said second annular portion comprising an annular edge opposite the first portion and comprising through notches in the radial direction, these notches being distributed around the axis and being capable of being crossed by a tool for tightening nuts on said threaded rods.

[0008] During assembly, the operator positions the mask according to a given tightening pattern and must first tighten the nuts accessible via the notches. Since some nuts are not accessible via the notches, they are inaccessible. The operator cannot therefore tighten the nuts in succession, one after the other, and is forced to respect the tightening pattern.

[0009] Thus, the invention makes it possible to improve the fixing of the discs by reducing or limiting the degrees of freedom possible for fixing the screws on the discs. The fixing of the discs is thus facilitated, which has the consequence of avoiding the problems mentioned above.

[0010] The invention can also allow savings in energy and material resources, the fixing of the discs being carried out without damaging surrounding parts, for example, and in a non-limiting manner, the discs or moving rings. Indeed, degradation of one of the parts of the rotor can lead to the manufacture of a new part to replace the damaged part. This can involve an expenditure of energy (electrical, thermal, etc.) and the use of materials for the manufacture of the new part.

[0011] The invention also allows for a saving in time. Indeed, the mask makes it possible to respect a given tightening pattern which by definition makes it possible to ensure that the screws are fixed correctly. Maintenance operations aimed at repairing defects linked to poor tightening, i.e. contrary to the tightening pattern, are thus reduced or avoided.

[0012] A mask according to the invention may further comprise one or more of the following optional features, in any technically possible combination: - the second portion is formed or constituted by a cylindrical wall; - the first portion is formed or constituted by a cylindrical rim; - the first portion includes holes suitable for receiving screw heads, or an annular cavity capable of receiving screw heads; - the mask is made of plastic or composite material; - the mask is made of soft and / or flexible material; - the mask is made of a single piece; - the mask is sectorized and includes several angular sectors arranged end to end around the axis.

[0013] The present invention also relates to an assembly comprising a mask according to the invention and at least two rotor discs of an aircraft turbomachine, the discs being stacked on top of each other along an axis of revolution which is vertical and which passes through the center of said discs and comprising radially internal annular flanges which are applied axially one on the other and which comprise screw receiving orifices, these screws being parallel to said axis of revolution and each comprising a head located above the flanges and a threaded rod which passes through the orifices of the flanges and which receives a nut intended to be located under the flanges, the mask being positioned on the screws so that its axis is aligned with the axis of revolution, that its first portion covers the screw heads and that its second portion extends radially inside the screws and the threaded rods of these screws.

[0014] A fan casing according to the invention may further comprise at least the following optional characteristic, in any technically possible combination: - the number of notches in the mask is less than the number of screws;

[0015] The present invention also relates to a method of mounting a turbomachine comprising at least one assembly according to the invention.

[0016] The method is characterized in that it comprises at least one step of fixing the discs together by means of a clamping tool, the fixing step comprising at least: - tightening the nuts through the notches of the second portion of the mask using a tightening tool;

[0017] A method according to the invention may further comprise one or more of the following optional features, in any technically possible combination: - the tightening of the nuts is carried out according to a tightening pattern in which each nut is tightened in a predefined chronological order; - the tightening comprises a succession of sub-steps in which: a. positioning the mask in a first position so that each notch of its second portion is radially aligned with the threaded rods of certain screws; b. tightening the nuts on the threaded rods of these screws; c. positioning the mask in a second position so that each notch of its second portion is radially aligned with the threaded rods of other screws; d. tightening the nuts on the threaded rods of these other screws; e. steps b) and c) being repeated if necessary until all the nuts of the screws are tightened. Brief description of the figures

[0018] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: - [Fig. 1 A] is a schematic perspective view of a rotor disc for an aircraft turbomachine; - [Fig.lB] is a partial schematic view of a radial section of a stack of two discs connected together by screws; - [Fig.2A] is a schematic perspective view of a mask according to a first variant of the invention; - [Fig.2B] is a schematic perspective view of a portion of the mask according to the invention; - [Fig.3] is a schematic view in radial section of a mask according to the invention; - [Fig.4] is a schematic perspective view of a mask according to a second variant of the invention; - [Fig.5] is a partial schematic view of a radial section of a set of rotor disks comprising a mask according to the invention; - [Fig.6] is a schematic perspective view of the rotor disc assembly of [Fig.5]; - [Fig.7] is a schematic perspective view of a tightening tool, one end of which passes through a notch in the mask according to the invention, for tightening a nut accessible via this notch; - [Fig.8] is a schematic view of a screw nut tightening diagram, and - [Fig.9] is a schematic view of a method of tightening screw nuts according to the invention. Detailed description of the invention

[0019] By convention, in the description below, the term "axial" qualifies the orientation of structural elements extending in the direction of an axis. This axis corresponds substantially to an axis of rotation or revolution. The term "radial" qualifies an orientation of structural elements extending in a direction perpendicular to the axis of rotation or revolution. The terms "internal", "internal" and "external" are used in reference to a positioning relative to the axis of rotation or revolution. Thus, a structural element extending along the axis of rotation or revolution comprises an inner face facing the longitudinal axis and an outer surface, opposite its inner surface.

[0020] [Fig. 1 A] represents an example of a rotor disc 200 of an aircraft turbomachine.

[0021] The disc 200 comprises an annular body C200 which extends around an axis of revolution A and which comprises at least one radially internal annular flange 206, this flange 206 comprising screw-receiving orifices 202 which are parallel to the axis of revolution A.

[0022] The rotor comprises a stack of discs such as that illustrated in [Fig.lA]. The discs are stacked on top of each other and then fixed together to form the rotor.

[0023] With reference to [Fig.IB], an example of two discs stacked one 2002 on the other 200i along the axis of revolution A is illustrated.

[0024] In operation, the axis of revolution A is generally horizontal. However, for assembly, the discs are positioned so that the axis A is vertical, as illustrated in [Fig.lB] for example.

[0025] The discs 200i, 2002 are fixed together by means of screws. The screws are regularly distributed around the axis of revolution A. [Fig.lB] shows only one of these screws 204. The following description concerns a single screw but applies to all the fixing screws.

[0026] Each screw 204 is parallel to the axis of revolution A and comprises a head TT204 located above the respective flanges 206i, 2062 of the discs 200i and 2002. Each screw 204 also comprises a threaded rod TT204 which passes through the orifices 202 h 2022 of the flanges 2061, 2062 and which receives a nut EC204 located under the flanges 2061, 2062.

[0027] The invention relates to a mask 100 to prevent any movement of the screws when tightening the EC204 nuts and to solve the problems of fixing and plating the discs mentioned above.

[0028] [Fig.2A] illustrates an example of mask 100 according to a first variant of the invention.

[0029] The mask 100 has an annular shape around an axis Ao. The mask comprises at least a first 102 and a second 104 annular portion.

[0030] The first annular portion 102 is capable of covering the screw heads TT204, of an annular row of screws 204 arranged around the axis Ao and parallel to this axis.

[0031] [Fig.2B] illustrates a perspective view of a portion of the mask 100. In normal use, the mask is positioned so that the first portion 102 is at the top and the second portion 104 is at the bottom as illustrated in [Fig.2A]. In [Fig.2B] and for clarity, the mask 100 is inverted so that the first portion 102 is at the bottom and the second portion 104 is at the top.

[0032] The first portion 102 is formed or constituted by a cylindrical rim 112 comprising an internal surface Sint capable of coming to bear on the screw heads TT204.

[0033] The first portion 102 may further comprise orifices 110, located on the internal surface Sint and capable of receiving the screw heads TT204.

[0034] In another variant (not shown), the first portion 102 may be an annular cavity capable of receiving the TT204 screw heads.

[0035] Still with reference to [Fig.2B], the second portion 104 of the mask 100 is connected to the first annular portion 102 and capable of extending radially inside the screws and threaded rods of these screws. This second annular portion 104 is formed or constituted by a cylindrical wall 106 and comprises an annular edge opposite the first portion 102.

[0036] The second portion 104 further comprises through notches 108 in the radial direction. These notches 108 are distributed around the axis Ao and are capable of being passed through by a nut tightening tool on the threaded rods TI204 of screws 204.

[0037] Preferably, the through notches 108 are equidistant, two successive notches being separated by the wall 106. The accessible EC204 nuts are positioned at the level of the notches and the inaccessible EC204 nuts, i.e. not accessible via the notches 108, are masked by the wall 106 of the second annular portion 104 of the mask 100. The wall 106 thus constitutes an obstacle to the tightening of these inaccessible EC204 nuts.

[0038] [Fig. 3] illustrates a radial section of the mask 100. The mask 100 comprises an internal diameter Dint defined by the internal wall of the first 102 or second 104 annular portion.

[0039] The mask further comprises a first external diameter Dlext defined by the external wall of the first portion 102, and a second external diameter D2ext defined by the external wall of the second portion 104, the first external diameter Dlext being greater than the second external diameter D2ext.

[0040] In a first variant illustrated by [Fig.2A] described above, the mask 100 is formed from a single piece.

[0041] In another variant illustrated by [Fig.4], the mask is sectorized and can comprise several angular sectors arranged end to end around the axis Ao. In the example of [Fig.4], the mask 100 comprises two angular sectors 100i, 1002.

[0042] The mask 100 is preferably made of plastic or composite material. Preferably, the mask is soft and / or flexible. For example, and in a non-limiting manner, the mask is made of polyurethane or polypropylene.

[0043] Advantageously, the person skilled in the art will understand that the mask 100 thus described makes it easier to fix the discs according to a tightening pattern, the possible degrees of freedom for tightening the screws on the discs being reduced by the wall 106 which adds a constraint to respect the tightening pattern. Indeed, when mounting the discs, the operator positions the mask according to a given tightening pattern and must, as a priority, tighten the nuts accessible via the notches. The nuts not accessible via the notches are then masked by the wall 106 which serves as an obstacle and thus prevents the operator from tightening the nuts in succession, one after the other.

[0044] Similarly, those skilled in the art will understand that the mask 100 can be used for fixing the discs without damaging the surrounding parts due to its flexibility. and / or flexibility.

[0045] Furthermore, the mask 100 also allows for a time saving. Indeed, the mask makes it possible to ensure that the tightening pattern of the nuts is respected when fixing or mounting the discs. This makes it possible to ensure that the nuts are correctly tightened and to avoid maintenance operations aimed at repairing defects linked to poor tightening, i.e. contrary to the tightening pattern.

[0046] The invention also relates to a set of rotor discs 200i, 2002.

[0047] [Fig.5] represents a partial section of a set of rotor discs according to the invention. The assembly comprises a mask 100 and at least two rotor discs 200i, 2002 of an aircraft turbomachine.

[0048] The discs 200i, 2002 are stacked on top of each other along an axis of revolution A which is vertical and which passes through the center of the two discs 200i, 2002. Each disc 200i, 2002 comprises radially internal annular flanges 206i, 2062 which are applied axially one on the other and which comprise orifices 202 for receiving screws 204.

[0049] The screws 204 are parallel to the axis of revolution A and each comprise a head TT204 located above the flanges 206i, 2062 and a threaded rod TI204 which passes through the orifices of the flanges 206i, 2062 and which receives a nut EC204 intended to be located under the flanges 2061, 2062.

[0050] The mask 100 is positioned on the screws 204 so that its axis A0 (not shown) is aligned with the axis of revolution A, that its first portion 102 covers the screw heads TT204 and that its second portion 104 extends radially inside the screws 204 and the threaded rods TI204 of these screws 204.

[0051] At least a minimum clearance Jo may be provided between the axial ends of the mask and the discs 200i, 2002 so as to facilitate its positioning on the screws 204 or its movement.

[0052] [Fig.6] shows a perspective view of a set of rotor discs 200i, 2002 described above and an enlargement of a portion of this set.

[0053] The second portion 104 extends radially inside the flanges 206i, 2062 and just inside their inner peripheral edges connected by a screw 204b3. The wall 106 between the notches 108 has a height which covers the flanges 206i, 2062 as can also be seen in [Fig.5] for example. This height may be greater than or equal to that of the notches 108 (see for example [Fig.2B] or 5).

[0054] In this illustrative example, only the nut of screw 2042 is accessible via notch 108 and can therefore be tightened. Wall 106 of mask 100 prevents an operator from tightening screw 204i or 2043 before screw 2042.

[0055] Preferably, the number of notches 108 of the mask 100 is less than the number of screws 204, 204i_3.

[0056]

[0057]

[0058]

[0059]

[0060] The invention also relates to a method of mounting a turbomachine comprising at least the disk assembly described above. The method comprises at least one step of fixing the discs 2001, 2002 together by means of a clamping tool 300 as illustrated for example in [Fig.7]. The fixing step comprises at least one step of tightening 500 of the nuts EC204 through the notches 108 of the second portion 104 of the mask 100 by means of the tightening tool 300 according to a tightening pattern 302 as illustrated for example, and in a non-limiting manner, in [Fig.8]. In this example the tightening pattern is of the “cross tightening” type. Still referring to [Fig.8], each flange has 32 holes. There are also 32 screws 204. However, the chronological order of tightening the EC204 nuts of the screws is predefined and the screws are not fixed in sequence. This tightening pattern ensures that the nuts are tightened effectively and prevents poor plating of the discs, for example. With reference to [Fig.9], the tightening step 500 comprises a series of sub-steps a), b), c), d) and e) comprising at least: a. positioning the mask 100 in a first position so that each notch 108 of its second portion 104 is radially aligned with the threaded rods of certain screws 204b ..., 2048 according to the tightening diagram 302, for example and in a non-limiting manner, shown in [Fig.8]; b. tightening the nuts on the threaded rods of these screws 204b ..., 2048. In the example of [Fig.8], the mask 100 comprises 8 notches 108. This implies that a first series of 8 screws is fixed; c. positioning the mask in a second position so that each notch 108 of its second portion 104 is radially aligned with the threaded rods of other screws 204l)32. The mask is moved in rotation, for example and in a non-limiting manner in the clockwise direction SR as illustrated in [Fig.8], so that each notch 108 is again opposite a screw according to the tightening pattern 302. For example, and in a non-limiting manner, if a notch positioned at location 1 is moved after rotation to location 10, then the notch initially located at location 5 will be located at location 13 after rotation; d. tightening the nuts on the threaded rods of these other screws (2049_32); e. steps b) and c) being repeated if necessary until all nuts EC204 of screws 204b ... 20432 are tightened according to tightening pattern 302.

Claims

Claims

1. Mask (100) for screws for fixing rotor discs (200, 200i, 2002) of an aircraft turbomachine, this mask (100) having an annular shape around an axis (Ao) and comprising a first annular portion (102) capable of covering screw heads (TI204) of an annular row of screws (204, 204b32) arranged around the axis (Ao) and parallel to this axis, characterized in that the mask (100) further comprises a second annular portion (104) connected to the first annular portion (102) and capable of extending radially inside the screws (204, 204b32) and threaded rods (TT204) of these screws (204, 204b32), said second annular portion (104) comprising an edge annular opposite the first portion (102) and comprising through notches (108) in the radial direction, these notches (108) being distributed around the axis (Ao) and being capable of being crossed by a nut tightening tool (300) on said threaded rods (TI204).

2. The mask (100) of claim 1, wherein the second portion (104) is formed or constituted by a cylindrical wall (106).

3. A mask (100) according to claim 1 or 2, wherein the first portion (102) is formed or constituted by a cylindrical rim (112).

4. Mask (100) according to one of the preceding claims, in which the first portion (102) comprises orifices (110) capable of receiving the screw heads (TT204), or an annular cavity capable of receiving the screw heads (TT204).

5. Mask (100) according to one of the preceding claims, in which it is made of plastic or composite material.

6. Mask (100) according to one of the preceding claims, in which it is made of soft and / or flexible material.

7. Mask (100) according to one of the preceding claims, in which it is formed in a single piece.

8. Mask according to one of claims 1 to 6, in which it is sectorized and comprises several angular sectors arranged end to end around the axis (Ao).

9. Assembly comprising a mask (100) according to one of the preceding claims and at least two rotor discs (200b 2002) of an aircraft turbomachine, the discs (200b 2002) being stacked on top of each other along an axis of revolution (A) which is vertical and which passes through the center of said discs (200i, 2002) and comprising radially internal annular flanges (206, 206i, 2062) which are applied axially to one another and which comprise orifices (202) for receiving screws (204, 204^), these screws (204, 204, î2) being parallel to said axis of revolution (A) and each comprising a head (TT204) located above the flanges (206, 206i, 2062) and a threaded rod which passes through the orifices of the flanges and which receives a nut (EC204) intended to be located under the flanges (206i, 2062), the mask (100) being positioned on the screws (204, 204132) so that its axis (Ao) is aligned with the axis of revolution (A), that its first portion (102) covers the screw heads (TT204) and that its second portion (104) extends radially inside the screws (204, 204132) and the threaded rods (TI204) of these screws (204, 204b32).

10. Assembly according to the preceding claim, in which the number of notches (108) of the mask (100) is less than the number of screws (204, 204i_32).

11. Method for mounting a turbomachine comprising at least one assembly according to one of claims 9 and 10, the method comprising at least one step of fixing the discs (200i, 2002) together by means of a tightening tool (300), the fixing step comprising at least: - tightening (500) the nuts (EC204) through the notches of the second portion (104) of the mask by means of a tightening tool.

12. Method according to the preceding claim, in which the tightening (500) of the nuts (EC204) is carried out according to a tightening pattern (302) in which each nut (EC204) is tightened in accordance with a predefined chronological order.

13. Method according to claim 11 or 12, wherein the tightening (500) comprises a succession of sub-steps in which: a) positioning the mask in a first position so that each notch (108) of its second portion (104) is aligned radially with the threaded rods of certain screws (204b8); b) tightening the nuts on the threaded rods of these screws (204b8); c) positioning the mask in a second position so that each notch (108) of its second portion (104) is aligned ra- dially with the threaded rods of other screws (2049_32); d) tightening the nuts on the threaded rods of these other screws (2049_32); e) steps b) and c) being repeated if necessary until all the nuts of the screws (204b32) are tightened.

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