Screw and flat retaining ring fastening device for annular flanged parts and fastening method with this device

Abstract

Screw fixing device and flat retaining ring for parts with annular flange and method of fixing with this device One aspect of the invention relates to an assembled assembly (1), comprising two parts (8, 14) with coaxial annular flanges (7, 13), arranged against each other and circumferentially pierced with through openings (20) forming axial passages (21) through the flanges, and a fixing device (22) comprising fixing elements (23) whose rods (6) are housed in the axial passages and pass through the two flanges. The fixing device further comprises a flat retaining ring (26), interposed between the flanges, which extends around the rods of the fixing elements and engages in a peripheral groove (12) of each of said rods. Another aspect of the invention relates to a method of assembling such an assembly. Figure to be published with the abstract: Figure 4

Description

Title of the invention: Screw fixing device and flat retaining ring for annular flanged parts and fixing method with this device TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to an assembly comprising at least two annular flanged parts assembled against each other by a circumferential series of fixing elements which pass through the two flanges.

[0002] The present invention also relates to a method of assembling such an assembly.

[0003] The invention finds applications in the field of aeronautics and in particular in that of aircraft turbomachines. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0004] In many technological fields and in particular in the field of aeronautics, we frequently encounter parts with annular flanges which must be assembled with each other. These are, for example, parts assembled around a shaft and / or with it and often rotating parts.

[0005] This assembly is generally carried out by a series of fixing elements, for example a series of screws, which are regularly distributed over the entire circumference of the flanges and which axially pass through the juxtaposed assembly of the flanges of the parts to be assembled.

[0006] Depending on the applications, this assembly must sometimes be done vertically and in a restricted environment. This is the case, for example, in aeronautics, during the assembly and disassembly phases of the turbines of certain turbomachines.

[0007] Once engaged through one or more flanges, the fixing screws must then be held in position so as not to fall, particularly during their tightening.

[0008] An assembly 1 according to the prior art has been shown in Figures 1 to 3.

[0009] To retain the fixing screws 2, it is known to use a set of stop rings 3, which are, as shown in [Fig.3], open rings 4 with a round section 5 which are put in place individually around the rod 6 of each of the screws 2.

[0010] As shown in [Fig.2], after having engaged the screws 2 through the flange 7 of the first part 8, or the juxtaposed flanges 7, 9 of the first group 10 of parts 8, 11, to be assembled, a stop ring 3 is placed at the base of the emerging part of the rod 6 of each of the screws 2, in a circular groove 12 provided for this purpose in the rod 6 of the screws 2. The screws 2 are thus held in position and do not fall out, even in the case of vertical orientation, when they are introduced through the flange 13 of the second part 14 to be assembled or while tightening nuts 15 on screws 2.

[0011] However, as these retaining rings 3 are very rigid, they must be spread apart using pliers to allow them to be fitted into the groove 12 of the screws 2. It is then impossible to tighten these retaining rings, without risking damaging the screws, once they are in place. There therefore always remains a significant amount of play between the retaining rings and the screw on which they are fitted.

[0012] This play inherent in the assembly is particularly problematic subsequently. Indeed, the ring 3 does not always remain firmly in place in the groove 12 of the screw 2 and may become stuck between the flanges 7, 13 of the parts 8, 14 to be assembled. Subsequently, for example during the balancing phase, it may become unblocked by vibrations, which completely loosens the screw. In addition to weakening the assembly, this loosening generates a very significant imbalance in the case of rotating parts, as frequently encountered in aeronautics, an imbalance which cannot be eliminated without completely dismantling the assembled assembly.

[0013] In the prior art, it has been desired to get rid of these problematic snap rings, but no satisfactory solution has been proposed so far.

[0014] For example, a tool has been developed to hold the screws during assembly until they are tightened. However, this tool is complex, difficult to use and its installation takes a long time. For example, it takes more than an hour to set up when used for assembling the disc cone module with the shaft of a turbojet.

[0015] There is therefore a need, not yet satisfied, for a device that is reliable, fast and easy to implement, which would make it possible to assemble parts with an annular flange, while retaining the fixing elements during assembly. Summary of the invention

[0016] The invention aims to meet this need by overcoming the drawbacks of prior devices.

[0017] For this, a first aspect of the invention teaches an assembly comprising: • A first part and a second part respectively comprising a first flange and a second flange, said flanges being annular, coaxial, arranged against each other and pierced with a plurality of through openings arranged circumferentially in the extension of each other so as to form a plurality of axial passages passing through the first flange and the second flange; and • a device for fixing the first part to the second part, comprising a plurality of fixing elements each comprising a rod which is housed in one of the axial passages and passes through the first flange and the second flange and which has a peripheral groove located at the interface between the first flange and the second flange. • The fixing device further comprises a flat retaining ring which is interposed between the first flange and the second flange and which extends around all of the rods of the fixing elements, being engaged in the groove of each of said rods.

[0018] The retaining ring makes it possible to axially hold all of the fixing elements during assembly of the assembly, in a simple and reliable manner and in a manner compatible with a restricted environment.

[0019] This solution is more reliable because, once the assembly is complete, the retaining ring is perfectly held between the two flanges and is not likely to move with vibrations. In addition, the problematic snap rings have been removed. There are therefore far fewer parts likely to cause difficulties.

[0020] In addition, the fixing device is much quicker to install. In fact, a single retaining ring replaces a multitude of retaining rings that have to be mounted individually. Assembly is greatly simplified and its duration reduced.

[0021] The solution of the invention thus makes it possible to simplify the performance of the axial holding function of the fixing elements even in a restricted environment, to make it more reliable by overcoming a recurring problem of poor assembly, while reducing the number of parts to be used and the installation time.

[0022] Furthermore, this solution requires only minimal modifications to existing parts. Indeed, the fixing elements do not need to be modified compared to those of the previous snap ring solution.

[0023] Advantageously, the fixing elements may be screws. In this case, the fixing device may further comprise a plurality of nuts which cooperate with these screws to form bolts.

[0024] Other types of rod fasteners may also be used, such as rivets or studs.

[0025] Advantageously, the retaining ring may be interrupted by a transverse slot, which may for example be oblique relative to a radial direction of the retaining ring.

[0026] The installation of the retaining ring is thus facilitated, because the ring can be opened by spreading its ends located on either side of the slot and more easily engaged around the fixing elements.

[0027] Advantageously, the first flange and / or the second flange may comprise a peripheral recess at the level of its face intended to be in contact respectively with the second flange or the first flange, recess in which the retaining ring may be at least partially housed.

[0028] In this application, a peripheral recess is called a circular hollow zone located on the periphery of the face concerned, that is to say at the level of its external portion, this hollow zone being open in the direction of the interface between the first and the second flange.

[0029] The ring is thus perfectly positioned during assembly of the whole.

[0030] In this case, the thickness of the retaining ring is preferably greater than the height of the step and the retaining ring can advantageously be made of a material that is less hard (or softer) than the material of the first flange and the second flange.

[0031] In the present application, a material will be described as soft if it offers little resistance to pressure. A material that is less hard or softer than another is therefore a material that offers less resistance to pressure than the other.

[0032] Thus, once in place, the retaining ring protrudes outside the recess. During tightening of the fixing means, the retaining ring is then pressed between the first and second flanges and it is crushed and plasticized due to the softer nature of its material. It is thus perfectly blocked between the flanges and vibrations likely to wear the parts are avoided.

[0033] Advantageously, the assembly may further comprise at least one third part comprising a third annular flange, coaxial and arranged against a face of the first flange which is not in contact with the second flange, this third flange being pierced with a plurality of through openings arranged circumferentially and placed in the extension of the through openings of the first flange so as to extend the axial passages. The rods of the fixing elements housed in the axial passages can then also pass through the third flange.

[0034] It is thus possible to assemble more than two circular flanged parts and to obtain an assembly which comprises more than two circular flanged parts assembled against each other.

[0035] A second aspect of the invention relates to a turbomachine comprising an assembly as described above.

[0036] A third aspect of the invention relates to a method of assembling an assembly as described above, which comprises the following steps: • inserting the rod of the fixing elements into the through openings of the first flange, until the groove of these rods emerges from these through openings; • placing the retaining ring against a face of the first flange intended to be in contact with the second flange and around all of the rods of the fixing elements, by engaging it in the groove of each of these rods; • inserting the rod of the fixing elements into the through openings of the second flange and bringing the first flange into contact with the second flange, the retaining ring being interposed between the first flange and the second flange.

[0037] Such a method makes it possible to assemble the whole in a simple, reliable and rapid manner.

[0038] Advantageously, in this method, the positioning of the retaining ring can be done by separating the free ends of the retaining ring located on either side of the transverse slot.

[0039] This makes it easier to engage the retaining ring around the rods of the fixing elements.

[0040] If the fixing elements are screws which cooperate with nuts to form bolts, the method may then comprise a step of screwing the nuts onto a portion of the screw shank which protrudes from the second flange.

[0041] The fixing elements are then locked.

[0042] If the assembly comprises at least one third part comprising a third flange, the third flange may be previously brought into contact with the first flange, the through openings of the third flange being placed in the extension of the through openings of the first flange. The rod of the fixing elements is then inserted into the through openings of the third flange before being inserted into the through openings of the first flange.

[0043] In this way, more than two circular flanged parts can be easily and reliably assembled.

[0044] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0045] The figures are presented for information purposes only and in no way limit the invention.

[0046] [Fig.l] is a partial perspective view, cut at the level of a fixing screw, of a fully assembled assembly according to the prior art.

[0047] [Fig.2] is a partial perspective view, cut at the level of a fixing screw, of a part of the assembly of [Fig.l] according to the prior art in which the second part of the assembly has not yet been assembled.

[0048] [Fig.3] is a perspective view of a snap ring according to the prior art.

[0049] [Fig.4] is a partial perspective view, cut at the level of a fixing screw, of an example of a fully assembled assembly according to the invention.

[0050] [Fig.5] is a partial perspective view, cut at the level of a fixing screw, of a part of the assembly according to the invention of [Fig.4], in which the second part of the set has not yet been assembled.

[0051] [Fig.6] is a partial perspective view of a part of the first part of the assembly according to the invention of [Fig.4].

[0052] [Fig.7] schematically illustrates the steps of an example of a method according to the invention. DETAILED DESCRIPTION

[0053] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0054] In the present application, the term "axis" of the annular flanges or "axis" of the retaining ring refers to the axis perpendicular to these annular elements which passes through their center.

[0055] Once assembled, the annular flanges are said to be “coaxial” because they have the same X axis.

[0056] The “axial” direction corresponds to a direction parallel to this X axis and a radial direction is a direction perpendicular to this X axis which intersects this X axis.

[0057] Unless otherwise specified, the adjectives "internal" and "external" are used in the present application with reference to a radial direction such that the internal part of an element is, in a radial direction, closer to the axis than the external part of the same element.

[0058] In Figures 4 to 6, an example of assembly 1 according to the invention is shown.

[0059] This assembly 1 comprises a first part 8 which has a first annular flange 7. In the example shown, it is a cone disc 16 for a turbojet-type turbomachine 17.

[0060] The first flange 7 comprises a series of axially oriented through openings 18, which are distributed circumferentially, that is to say over the entire circumference of the flange 7. These openings 18 are thus arranged in a circle along the entire length of the flange 7.

[0061] The assembly 1 also comprises a second part 14 which has a second annular flange 13. In the example shown, this is a shaft 19 for a turbojet-type turbomachine 17.

[0062] The second flange 13 also comprises a series of axially oriented through openings 20, which are distributed circumferentially along the entire length of the flange 13.

[0063] Once the assembly of the assembly 1 is completed as shown in [Fig.4], the first flange 7 is placed against the second flange 13 and the through openings 18 of the first flange 7 are located in the extension of the through openings 20 of the second flange 13, thus forming a series of axial passages 21 which cross the two flanges 7 and 13.

[0064] The first part 8 and the second part 14 are assembled to each other by a fixing device 22 comprising a set of fixing elements 23.

[0065] These fixing elements 23 comprise a rod 6 in which a peripheral groove 12 is formed. By peripheral groove, we mean a groove extending all the way around the rod 6.

[0066] In the example shown, the fixing elements 23 are screws 2 which have a head 24 and a rod 6.

[0067] When the assembly 1 is assembled, each of the axial passages 21 is preferably occupied by the rod 6 of a fixing element 23 which passes through the first flange 7 and the second flange 13.

[0068] The groove 12 of the rod 6 is then located at the interface between the first flange 7 and the second flange 13, that is to say in an interface zone 25 which comprises the interface between the first flange 7 and the second flange 13 and also extends into the portions of the first flange 7 and the second flange 13 which are located close to this interface.

[0069] The fixing device 22 also comprises a holding ring 26 which is interposed between the first flange 7 and the second flange 13. This is a flat ring which extends 360°, all around the crown of screws 2 housed in the axial passages 21.

[0070] The internal diameter of this retaining ring 26 is provided so that its internal edge 27 penetrates and engages in each groove 12 of the rods 6, these grooves 12 being located opposite the ring 26 when the fixing elements 23 are in the axial passages 21. The retaining ring 26 thus exerts axial support on the fixing elements 23, which cannot fall even if they are in a vertical position.

[0071] The retaining ring 26 preferably comprises a transverse slot 28 which interrupts its length and thus gives rise to two free ends 29 located on either side of the transverse slot 28.

[0072] The transverse slot 28 is for example oblique relative to the radial direction of the retaining ring 26.

[0073] These free ends 29 can advantageously be grasped and moved apart from each other to facilitate the positioning of the retaining ring 26 around the screws 2.

[0074] Other assembly techniques are conceivable, such as for example a slight stretching of the retaining ring 26, if it has sufficient elasticity, to make it pass around the screws, followed by a release so that it regains its original dimensions and engages in the peripheral grooves 12.

[0075] As shown in [Fig.6], the first flange 7 may include a peripheral and circular recess 30, allowing at least partial accommodation therein the retaining ring 26. This recess 30 is open towards the interface with the second flange 13 and towards the through openings 18.

[0076] Advantageously, this recess 30 can, as shown, be open on its external side in order to facilitate the engagement of the retaining ring 26 in the recess 30. A wall can however be provided there, the recess 30 then taking the form of a circular groove.

[0077] The second flange 13 may also or alternatively comprise such a circular recess.

[0078] The assembly 1 shown in the figures further comprises a third part 11 which comprises a third annular flange 9. This is a labyrinth ring 40 for a turbojet-type turbomachine 17.

[0079] This third part 11 forms with the first part 8, a group of parts 10 to be assembled to the second part 14.

[0080] The third flange 9 is coaxial with the first two flanges 7, 13 and also comprises a series of through openings 31, oriented axially and distributed circumferentially along the entire length of the flange 9, which extend the axial passages 21.

[0081] Once the assembly of the assembly 1 is complete, the third flange 9 is interposed between the heads 24 of the screws 2 and the first flange 7. It is in contact with the face 32 of the first flange 7 which is not in contact with the second flange 13 and is located opposite it. The rods 6 of the screws 2 pass through both the first flange 7, the second flange 13 and the third flange 9.

[0082] Although not shown, the assembly 1 could include other parts with coaxial circular flanges, inserted between the head 24 of the screws 2 and the first flange 7.

[0083] The assembly method 33 of the assembly 1 described above results from its characteristics. It has been schematically represented in [Fig.7].

[0084] It comprises a first step 34 during which the rod 6 of the fixing elements 23 is inserted into the through openings 18 of the first flange 7, until the groove 12 of these rods is accessible, that is to say until it emerges from the first flange 7 and arrives in the interface zone 25.

[0085] It then comprises a second step 35 during which the retaining ring 26 is placed against the face 36 of the first flange 7 intended to be in contact with the second flange 13 and around all the rods 6 of the fixing elements 23, by engaging it in the groove 12 of each of these rods 6.

[0086] When the retaining ring 26 has a slot 28, this second step 35 is carried out by spreading the free ends 29 of the retaining ring to engage it more easily around the rods 6.

[0087] It then comprises a third step 37 during which the rod 6 of the fixing elements 23 in the through openings 20 of the second flange 13 and the first flange 7 is brought into contact with the second flange 13, the retaining ring 23 being interposed between the first flange 7 and the second flange 13.

[0088] This third step 37 can optionally be followed by a fourth step 38, if the fixing elements 23 are screws 2, during which nuts 15 are screwed onto the threaded portion of the rods 6 which protrudes from the second flange 13, thus ensuring the locking of the fixing elements 23 and the tightening of the assembly 1.

[0089] In an embodiment where the assembly comprises a third part 11, the method 33 further comprises a preliminary step 39 during which the third flange 9 of the third part 11 and the first flange 7 of the first part 8 are placed against each other with their through openings 31, 18 in line with each other.

[0090] If the assembly includes other circular flanged parts to be assembled in addition to the third part, the procedure is the same.

[0091] Then, during step 34, the rod 6 of the fixing elements 23 is inserted both into the through openings 31 of the third flange 9 (and possibly into those of the other circular flange parts to be assembled) and into the through openings 18 of the first flange 7, until the groove 12 of the rods 6 emerges from the first flange 7 and arrives in the interface zone 25.

Claims

Claims

1. Assembly (1) comprising: - A first part (8) and a second part (14) respectively comprising a first flange (7) and a second flange (13), said flanges (7, 13) being annular, coaxial, arranged against each other and pierced with a plurality of through openings (18, 20) arranged circumferentially in the extension of each other so as to form a plurality of axial passages (21) passing through the first flange (7) and the second flange (13); and - a device (22) for fixing the first part (8) to the second part (14), comprising a plurality of fixing elements (23) each comprising a rod (6) which is housed in one of the axial passages (21) and passes through the first flange (7) and the second flange (13), and which comprises a peripheral groove (12), located at the interface between the first flange (7) and the second flange (13);- assembly (1) characterized in that the fixing device (22) further comprises a flat retaining ring (26), which is interposed between the first flange (7) and the second flange (13) and which extends around all the rods (6) of the fixing elements (23), being engaged in the groove (12) of each of said rods (6).;

2. Assembly (1) according to claim 1, characterized in that the fixing elements (23) are screws (2) and in that the fixing device (22) further comprises a plurality of nuts (15) which cooperate with said screws (2) to form bolts.

3. Assembly (1) according to claim 1 or 2, characterized in that the retaining ring (26) is interrupted by a transverse slot (28), preferably oblique relative to a radial direction of the retaining ring (26).

4. Assembly (1) according to one of the preceding claims, characterized in that the first flange (7) and / or the second flange (13) comprises a peripheral recess (30) at the level of its face intended to be in contact respectively with the second flange or the first flange, recess (30) in which the retaining ring (26) is at least partially housed.

5. Assembly (1) according to the preceding claim, characterized in that the thickness of the retaining ring (26) is greater than the height of the step (30) and in that the retaining ring (26) is made of a material less hard than the material of the first flange (7) and the second flange (13).

6. Assembly (1) according to one of the preceding claims, characterized in that it further comprises at least one third part (11) comprising a third annular flange (9), coaxial and arranged against a face (32) of the first flange (7) which is not in contact with the second flange (13), this third flange (9) being pierced with a plurality of through openings (31) arranged circumferentially and placed in the extension of the through openings (18) of the first flange (7) so as to extend the axial passages (21); and in that the rods (6) of the fixing elements (23) housed in the axial passages (21) also pass through the third flange (9).

7. Turbomachine (17) characterized in that it comprises an assembly (1) according to one of the preceding claims.

8. Method of assembling (33) an assembly (1) according to one of the preceding claims, characterized in that it comprises the following steps (34, 35, 37): - inserting the rod (6) of the fixing elements (23) into the through openings (18) of the first flange (7), until the groove (12) of these rods (6) emerges from these through openings (18); - placing the retaining ring (26) against a face (36) of the first flange (7) intended to be in contact with the second flange (13) and around the set of rods (6) of the fixing elements (23), by engaging it in the groove (12) of each of these rods (6); - inserting the rod (6) of the fixing elements (23) into the through openings (20) of the second flange (13) and bringing the first flange (7) into contact with the second flange (13), the retaining ring (26) being interposed between the first flange (7) and the second flange (13).

9. Assembly method (33) according to the preceding claim of an assembly (1) according to claim 3, characterized in that the positioning of the retaining ring (26) is done by separating the free ends (29) of the retaining ring (26) located on either side of the transverse slot (28).

10. Assembly method (33) according to claim 8 or 9 of an assembly (1) according to claim 2, characterized in that it then comprises a step (38) of screwing the nuts (15) onto a portion of the rod (6) of the screws (2) which protrudes from the second flange (13).

11. Assembly method (33) according to one of claims 8 to 10 of an assembly (1) according to claim 6, characterized in that the third flange (9) is previously brought into contact with the first flange (7), the through openings (31) of the third flange (9) being placed in the extension of the through openings (18) of the first flange (7), and in that the rod (6) of the fixing elements (23) is inserted into the through openings (31) of the third flange (9) before being inserted into the through openings (18) of the first flange (7).

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