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

Abstract

Screw fastening device and flat retaining ring for annular flanged parts and method of fastening with this device. One aspect of the invention relates to an assembled unit (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 fastening device (22) comprising fastening elements (23) whose shanks (6) are housed in the axial passages and pass through both flanges. The fastening device further comprises a flat retaining ring (26), interposed between the flanges, which extends around the shanks of the fastening elements and engages in a peripheral groove (12) of each of said shanks. Another aspect of the invention relates to a method of assembling such a unit. Figure to be published with the abbreviation: Figure 4

Description

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

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

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

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

[0004] In many technological fields, and particularly in the aeronautical field, one frequently encounters parts with annular flanges that must be assembled with each other. These are, for example, parts assembled around and / or with a shaft, and often rotating parts.

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

[0006] Depending on the application, this assembly sometimes has to be done vertically and in a confined 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 out, particularly during tightening.

[0008] A set 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 retaining rings 3, which are, as shown in [Fig.3], open rings 4 with a round section 5 which are individually placed around the stem 6 of each of the screws 2.

[0010] As shown in [Fig. 2], after engaging the screws 2 through the flange 7 of the first part 8, or the adjacent flanges 7, 9 of the first group 10 of parts 8, 11 to be assembled, a retaining ring 3 is placed at the base of the protruding shank 6 of each screw 2, in a circular groove 12 formed for this purpose in the shank 6 of the screws 2. The screws 2 are thus held in position and do not fall out, even when vertically oriented, when they are inserted through the flange 13 of the second part 14 to be assembled or during the tightening of the nuts 15 on the screws 2.

[0011] However, since these retaining rings 3 are very rigid, they must be spread apart using pliers to allow their installation in the groove 12 of the screws 2. It is then impossible to tighten these retaining rings without risking damage to the screws once they are in place. Therefore, a significant amount of play always remains between the retaining rings and the screw on which they are mounted.

[0012] This inherent play in the assembly is particularly problematic later on. Indeed, the circlip 3 does not always remain properly seated in the groove 12 of the screw 2 and can become jammed between the flanges 7, 13 of the parts 8, 14 to be assembled. Subsequently, for example during the balancing phase, it may come loose due to 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 that cannot be eliminated without completely disassembling the entire assembly.

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

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

[0015] There is therefore a need, currently unmet, for a device that is reliable, fast, and easy to implement, which would allow the assembly of annular flanged parts while retaining the fasteners during assembly. Summary of the invention

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

[0017] To this end, a first aspect of the invention teaches an assembly comprising: • A first part and a second part comprising respectively 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 line with each other so as to form a plurality of axial passages through the first flange and the second flange; and • a device for attaching the first part to the second part, comprising a plurality of fastening elements, each having 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 fastening device further includes a flat retaining ring, which is interposed between the first flange and the second flange and which extends around all the rods of the fastening elements, being engaged in the groove of each of said rods.

[0018] The retaining ring allows the entire fastening elements to be held axially 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 assembled, the retaining ring is perfectly held between the two flanges and is not at risk of shifting due to vibrations. Furthermore, the problematic retaining rings have been eliminated. Therefore, there are far fewer parts that could potentially cause problems.

[0020] Furthermore, the fastening device is much quicker to install. Indeed, a single retaining ring replaces a multitude of retaining rings that must be mounted individually. Installation is greatly simplified and its time reduced.

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

[0022] Furthermore, this solution requires only minor modifications to existing parts. Indeed, the fastening elements do not need to be modified compared to those of the previous solution with retaining rings.

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

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

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

[0026] The installation of the retaining ring is thus facilitated, as 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 have 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 defined as a circular hollow area located on the periphery of the face concerned, that is to say at the level of its external portion, this hollow area being open in the direction of the interface between the first and second flange.

[0029] The ring is thus perfectly positioned during the 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 less hard (or softer) material than the material of the first flange and the second flange.

[0031] In this 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 resists pressure less than the other.

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

[0033] Advantageously, the assembly may further comprise at least one third part having a third annular flange, coaxial and disposed against a face of the first flange that is not in contact with the second flange, this third flange being pierced with a plurality of circumferentially arranged through openings placed in line with the through openings of the first flange so as to extend the axial passages. The shanks of the fasteners housed in the axial passages may 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 for assembling an assembly as described above, which comprises the following steps: • Insertion of the rod of the fasteners into the through openings of the first flange, until the groove of these rods emerges from these through openings; • placement of the retaining ring against one face of the first flange intended to be in contact with the second flange and around all the rods of the fixing elements, engaging it in the groove of each of these rods; • Insertion of 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 process makes it possible to assemble the whole in a simple, reliable and quick way.

[0038] Advantageously, in this method, the retaining ring can be put in place by spreading apart the free ends of the retaining ring located on either side of the transverse slot.

[0039] This facilitates the engagement of the retaining ring around the rods of the fixing elements.

[0040] If the fasteners are screws which cooperate with nuts to form bolts, the process may then include a step of screwing the nuts onto a portion of the shank of the screws which protrudes from the second flange.

[0041] The fastening elements are then locked.

[0042] If the assembly includes at least one third part having a third flange, the third flange may be brought into contact with the first flange beforehand, the through-holes of the third flange being positioned in line with the through-holes of the first flange. The stem of the fasteners is then inserted into the through-holes of the third flange before being inserted into the through-holes of the first flange.

[0043] More than two circular flanged parts can thus 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 illustrative purposes only and are in no way limiting of the invention.

[0046] [Fig.1] is a partial perspective view, cut at the level of a fixing screw, of a fully assembled prior art assembly.

[0047] [Fig.2] is a partial perspective view, cut at the level of a fixing screw, of a part of the assembly of [Fig.1] 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 stop bead 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 complete assembly according to the invention, fully assembled.

[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 part of the first piece of the assembly according to the invention of [Fig.4].

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

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

[0054] In the present application, the "axis" of the annular flanges or the "axis" of the retaining ring is 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 this application with reference to a radial direction such that the internal part of an element is, along a radial direction, closer to the axis than the external part of the same element.

[0058] Figures 4 to 6 show an example of assembly 1 according to the invention.

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

[0060] The first flange 7 includes 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 all along the flange 7.

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

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

[0063] Once the assembly of set 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 line with 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 fastening device 22 comprising a set of fastening elements 23.

[0065] These fastening elements 23 comprise a rod 6 in which a peripheral groove 12 is formed. A peripheral groove is understood to be a groove extending all the way around the rod 6.

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

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

[0068] The groove 12 of the rod 6 is then found at the interface between the first flange 7 and the second flange 13, that is to say in an interface zone 25 which includes 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 near this interface.

[0069] The fastening device 22 also includes a retaining ring 26 which is interposed between the first flange 7 and the second flange 13. It is a flat ring which extends 360° all around the screw ring 2 housed in the axial passages 21.

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

[0071] The retaining ring 26 preferably has 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 with respect to the radial direction of the retaining ring 26.

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

[0074] Other mounting techniques are conceivable, such as 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 returns to its original dimensions and engages in the peripheral grooves 12.

[0075] As shown in [Fig. 6], the first flange 7 may have a peripheral and circular recess 30, allowing at least partial housing 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 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 include such a circular step.

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

[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 includes a series of through openings 31, axially oriented and distributed circumferentially all along the flange 9, which extend the axial passages 21.

[0081] Once the assembly of set 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 shanks 6 of the screws 2 pass through the first flange 7, the second flange 13, and the third flange 9.

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

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

[0084] It includes a first step 34 during which the rod 6 of the fastening elements 23 is inserted into the through openings 18 of the first flange 7, until the groove 12 of these rods is accessible, i.e. until it emerges out of the first flange 7 and arrives in the interface area 25.

[0085] It then includes 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 done 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 fastening 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 fasteners 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 fasteners 23 and the tightening of the assembly 1.

[0089] In an embodiment where the assembly includes a third part 11, the method 33 further includes 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 same procedure is followed.

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

Claims

Demands

1. Assembly (1) comprising: - A first piece (8) and a second piece (14) having respectively 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) through the first flange (7) and the second flange (13); and - a fastening device (22) of the first part (8) to the second part (14), comprising a plurality of fastening elements (23) each having 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 has a peripheral groove (12), located at the interface between the first flange (7) and the second flange (13);- assembly (1) characterized in that the fastening 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 fastening 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 fasteners (23) are screws (2) and in that the fastener 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 with respect to a radial direction of the retaining ring (26).

4. Assembly (1) according to any one of the preceding claims, characterized in that the first flange (7) and / or the second flange (13) has a peripheral recess (30) at the level of its face intended to be in contact respectively with the second bridle or the first bridle, notch (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 any one of the preceding claims, characterized in that it further comprises at least one third piece (11) having a third annular flange (9), coaxial and disposed 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 fastening 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 any one of the preceding claims.

8. Method of assembling (33) an assembly (1) according to any one of the preceding claims, characterized in that it comprises the following steps (34, 35, 37): - insertion of the rod (6) of the fasteners (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); - placement of 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 all the rods (6) of the fasteners (23), by engaging it in the groove (12) of each of these rods (6); - insertion of 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 setting 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 subsequently comprises a step (38) of screwing the nuts (15) onto a portion of the shank (6) of the screws (2) which protrudes from the second flange (13).

11. Assembly method (33) according to any one of claims 8 to 10 of an assembly (1) according to claim 6, characterized in that the third flange (9) is first 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 stem (6) of the fastening 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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