PRE-CHARGED BOLTED ASSEMBLY CONTAINING A PRE-CHARGE RESTORATION MECHANISM AND AIRCRAFT CONTAINING AT LEAST ONE SUCH ASSEMBLY

Abstract

PRELOADED BOLTED ASSEMBLY COMPRISING A PRELOAD RESTORATION MECHANISM AND AIRCRAFT COMPRISING AT LEAST ONE SUCH ASSEMBLY The invention relates to a bolted assembly (1) for fixing a part (2) and comprising a nut (11) and a fixing screw (12) for clamping said part. The assembly (1) further comprises means (13) for restoring a preload which includes: - a preload washer (130) comprising a first half-washer (131) and a second half-washer (132), where said half-washers are assembled together to form said preload washer and where said preload washer is intended to be disposed between said part and said nut or between said part and the fixing head of said fixing screw; and - a locking piece (14) clamping said preload washer (13) to lock the position of the half-washers together.In this way, the bolted assembly of the invention allows the preload level to be restored simply, quickly and reliably. Fig. 2.

Description

Title of the invention: PRE-LOADED BOLTED ASSEMBLY COMPRISING A PRE-LOAD RESTORATION MECHANISM AND AIRCRAFT CONTAINING AT LEAST ONE SUCH ASSEMBLY technical field

[0001] The present invention relates to a preloaded bolted assembly comprising a preload restoration mechanism. The invention also relates to an aircraft comprising at least one such assembly. PREVIOUS STATE OF THE ART

[0002] In an aircraft, it is often necessary for parts (such as structural elements of the fuselage or propulsion system, for example) to be fastened together. Bolted assemblies (i.e., a bolt and nut clamping the parts to be fastened) are known to be used for this purpose. More specifically, and to optimize the fatigue resistance of such a bolted assembly, these assemblies are said to be "preloaded," in that their tension is adjusted to ensure an optimal level of compression between the parts to be joined, thus ensuring their secure fastening.

[0003] However, certain events occurring during the manufacture of the aircraft or during its operation can lead to a decrease in the preload of the bolted assembly, which may impact the fatigue life of the parts to be fastened. For example, spontaneous loosening of the bolted assembly, thinning of the parts to be fastened (particularly when they are made of composite material), or thinning of the sealant during application can cause this decrease in the preload of the bolted assembly.

[0004] When such an event occurs, it may be necessary to restore the preload of the bolted assembly to prevent fatigue problems. However, it is not always possible to restore this preload. Indeed, applying a new tightening torque to the bolted assembly can lead to the entry of an area of ​​the screw or nut with an imperfect thread, resulting in a degradation of the bolt's strength. Furthermore, particularly in an aircraft, access to both sides of the bolted assembly is not always possible, which can prevent tightening or replacement of the bolted assembly.

[0005] It is therefore necessary to find a simple solution that allows the preload of a bolted assembly to be restored. Description of the invention

[0006] An object of the present invention is to provide a bolted assembly which allows the preload level of the bolted assembly to be restored in a simple, quick and reliable manner.

[0007] To this end, a bolted assembly is proposed for securing a part having a bore. The bolted assembly comprises a nut and a fixing screw having a fixing head from which a threaded rod extends. Said threaded rod is intended to be inserted into said bore of said part and screwed into said nut. Said nut and said fixing head are intended to clamp said part.

[0008] According to the present technique, said bolted assembly further comprises means for restoring a preload of said bolted assembly comprising:

[0009] - a preload washer having a main passage into which is threaded said threaded rod, said preload washer comprising a first half-washer and a second half-washer, said half-washers being assembled together to form said preload washer, where said preload washer is intended to be disposed between said part and said nut or between said part and said fixing head of said fixing screw; and

[0010] - a locking piece clamping said preload washer to lock the position of the half-washers relative to each other.

[0011] The bolted assembly of the invention makes it possible to restore the preload level in such a way as to reduce the risk of impacting the fatigue life of the part to be fastened. Indeed, restoring the preload level of the assembly prevents spontaneous loosening of the bolted assembly and compensates for the thinning of the part to be fastened (particularly when it is made of composite material) and / or the thinning of the sealant when it is applied. The invention also makes it possible to avoid tightening a defective bolt or systematically replacing the nut and / or the fastening screw, which limits maintenance operations.

[0012] Advantageously, each half-washer comprises a generally cylindrical lateral surface, a first generally flat surface extending generally perpendicularly to said threaded rod and intended to come into contact with said nut or said head of said fixing screw) or with said part, and a second surface opposite said first surface and not extending parallel to said first surface, said second surface being intended to come into contact with the second surface of the other half-washer.

[0013] According to a particular aspect, said first surface has a surface treatment promoting the sliding of each half-washer relative to said nut or to said head of said fixing screw or to said part.

[0014] According to another particular aspect, each half-washer has a thin side and a thick side. Each half-washer has a slot having an end closed located globally in the center of said half-washer and an open end opening at the thin side of said half-washer, said slots of said half-washers together forming said main passage in which said threaded rod of said fixing screw is inserted.

[0015] According to yet another particular aspect, the slots in the half-washers extend along parallel axes when the half-washers are assembled.

[0016] According to a particular aspect, said locking piece is in the form of a metal ring or a clamping collar.

[0017] The invention further relates to an aircraft comprising at least one part to be fixed and at least one bolted assembly as described above.

[0018] Furthermore, the invention also relates to a method for restoring the preload of a bolted assembly as described above. This method comprises the steps of:

[0019] - insertion of a half-washer between said part and said nut or between said part and said fixing head of said fixing screw until said threaded rod is received in said main passage;

[0020] - insertion of the other half-washer between said half-washer and said nut or between said half-washer and said fixing head until said threaded rod is received in said main passage;

[0021] - installation of the locking piece around said half-washers for lock their positioning relative to each other. Brief description of the drawings

[0022] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which:

[0023] [Fig-1] illustrates an aircraft comprising a plurality of bolted assemblies according to the invention;

[0024] [Fig.2] is a side view showing an example of an assembly implementation according to the invention;

[0025] [Fig.3] is a side view showing another example of the implementation of a assembly according to the invention;

[0026] [Fig.4a] ;

[0027] [Fig.4b] ;

[0028] [Fig.4c] ;

[0029] [Fig.4d] ;

[0030] [Fig.4e];

[0031] [Fig.4f] are side views showing the installation of the means for restoring the preload of the bolted assembly according to the invention;

[0032] [Fig.5a] illustrates an exploded and top view of the means for restoring the preload of the bolted assembly according to the invention;

[0033] [Fig. 5b] illustrates a top view of the means for restoring the preload of the bolted assembly according to the invention after assembly; and

[0034] [Fig.6] schematically illustrates the steps of the process of restoring the preload of a bolted assembly according to the invention.

[0035] DETAILED STATEMENT OF IMPROVEMENTS

[0036] Figs. 1 and 2 show a bolted assembly 1 according to the invention, which is hereafter referred to as the "assembly". The assembly 1 allows a part 2, which has a bore 21, to be fixed. The part 2 can take several forms and can, for example, be made up of one or more elements, such as fuselage plates or fastening elements of a propulsion system, for example.

[0037] The assembly 1 includes a nut 11 and a fixing screw 12. More specifically, the fixing screw 12 has a fixing head 121 from which extends a threaded rod 122 which is intended to be threaded into the bore 21 of the part 2 to be fixed and then screwed into the nut 11.

[0038] The nut 11 and the fixing head 121 are intended to be tightened to clamp the part 2 together and to provide a compressive force defining the preload of the assembly.

[0039] In order to resolve the problems of loss of preload, and thus to restore this preload to a sufficient level, the assembly 1 includes means 13 for restoring the preload of the bolted assembly 1. To do this, the means 13 for restoring the preload include a preload washer 130 which has a main passage 130a in which the threaded rod 122 of the fixing screw 12 is threaded.

[0040] More particularly, the preload washer 13 comprises a first half-washer 131 and a second half-washer 132 which are assembled together to form the preload washer 130. The preload washer 130 is intended to be disposed between the part 2 and the nut 11 (as illustrated in [Fig. 1]) or between the part 2 and the fixing head 121 of the fixing screw 12 (as illustrated in [Fig. 2]). Indeed, depending on the accessibility of the nut 11 or the fixing head 121, the preload washer 130 can be positioned on one side or the other of part 2. The thickness of the preload washer 130 is selected so that it is greater than the assembly clearance that may appear between the bolt and part 2. Thus, the preload washer 130 makes it possible to increase the distance between the fixing head 121 and the nut 11 in order to restore the preload of the assembly 1.

[0041] The means 13 for restoring the preload of the bolted assembly 1 further include a locking piece 14 which clamps the preload washer 13 in order to lock the position of the half-washers 131, 132 together and thus guarantee the level of preload supplied by the preload washer 130.

[0042] The invention thus makes it possible to restore, that is to say, re-establish, the preload level of the bolted assembly 1 in a simple, quick, and reliable manner. Indeed, it is sufficient to place (in the manner described below with reference to Figs. 4a to 4g and 6) the preload washer 130 between the part 2 to be fixed and the nut 11 or the fixing head 121 of the fixing screw 12, and then to lock the position of the half-washers 131, 132 of the preload washer 130 for the preload of the bolted assembly 1 to be restored.

[0043] Thus, the risks of impacting the fatigue life of the part 2 to be fixed are reduced since the restoration of the preload level of the assembly makes it possible to avoid spontaneous unscrewing of the bolted assembly and to compensate for the thinning of the part to be fixed (especially when it is made of composite material) and / or the thinning of the sealant when it is implemented.

[0044] The invention also makes it possible to avoid tightening a defective bolt or systematically replacing the nut and / or fixing screw, which limits maintenance operations.

[0045] More particularly, and as illustrated in particular in Figs. 4a and 5a, each half-washer 131, 132 has a lateral surface 139a, a first surface 139b and a second surface 139c so that each half-washer 131, 132 preferably has a generally triangular section.

[0046] The lateral surface 139a is generally cylindrical. The first surface 139b, on the other hand, is generally flat and extends generally perpendicularly to the axis of the threaded rod 122. In this example, the first surface 139b extends generally perpendicularly to the lateral surface 139a.

[0047] The first surface 139b is intended to come into contact against the nut 11 or against the fixing head 121 of the fixing screw 12 or against the part 2, depending on whether the preload washer 130 is disposed between the part 2 and the nut 11 or between the part 2 and the fixing head 121.

[0048] The second surface 139c is opposite the first surface 139a and does not extend parallel to the first surface 139a. In other words, the second surface 139c extends at an angle to the first surface 139b. Each half-washer 131, 132 thus appears as a beveled washer. Preferably, the half-washers 131 and 132 are identical and have the same inclination of the second surface 139c relative to the first surface 139b.

[0049] The second surface 139c is intended to come into contact with a second surface 139c of the other half-washer 131, 132 to form the preload washer 130. The second surfaces 139c thus allow the half-washers 131, 132 to move relative to each other, that is to say to slide against each other to allow their placement between the part 2 and the nut 11 or between the part 2 and the fixing head 121.

[0050] The half-washers 131, 132 are therefore assembled together to form the preload washer 130. Each half-washer 131, 132 therefore has bearing surfaces which allow the preload of the bolted assembly 1 to be restored, by increasing the distance between the fixing head 121 and the nut 11.

[0051] Preferably, the first surface 139b has a surface treatment promoting the sliding of each half-washer 131, 132 relative to the nut 11 or relative to the fixing head 121 of the fixing screw 12 or relative to the part 2, depending on the positioning of the preload washer 130 in the assembly 1.

[0052] In this way, the insertion (i.e. the positioning) of the half-washers 131, 132 between the part 2 and the nut 11 or the fixing head 121 is facilitated.

[0053] For example, this surface treatment consists of applying a lubricant adapted to the corrosion and conductivity constraints of the bolted assembly. Preferably, each half-washer 131, 132 has a thin side 138a and a thick side 138b. In this example, the thin side 138a is located on the side of the junction between the first 139b and second 139c surfaces, while the thick side 138b is located on the side of the junction between the lateral surface 139a and the second surface 139c, as illustrated in particular in [Fig. 4a].

[0054] Although not illustrated, it could be envisaged that the first 139b and second 139c surfaces are not directly joined. For example, a straight portion or a portion of any other shape could join the two portions, notably to increase the thickness of the preload washer. The same could apply to the junction between the lateral surface 139a and the second surface 139c.

[0055] As illustrated in Figs. 5a and 5b, each half-washer 131, 132 has a slot 133 (extending here in a generally straight line) having a closed end 134 (having here an arc-shaped form) located generally in the center of the half-washer 131, 132 and an open end 135 opening at the thin side of the half-washer 131, 132. Thus, when the half-washers 131, 132 are assembled together to form the preload washer 130, their respective slots 133 together form the main passage 130a of the preload washer 130 into which the threaded rod 122 of the fixing screw 12 is inserted.

[0056] Furthermore, the slots 133 allow the insertion of the half-washers 131, 132 between the part 2 and the nut 11 or the fixing head 121. Indeed, thanks to this slot 133, the The half-washer 131, 132 can be moved without obstruction towards the threaded rod 122 of the fixing screw. The movement is achieved by translating the half-washer 131, 132 until the threaded rod 122 is received in the closed end 134 of the slot 133.

[0057] Preferably, and particularly when the half-washers are identical, the slots 134 of the half-washers 131, 132 extend along parallel axes when the half-washers 131, 132 are assembled. This facilitates the insertion and positioning of the half-washers 131 and 132 around the threaded rod 122 and relative to each other.

[0058] The locking piece 14 is in the form of a metal ring or a clamp. It is designed to at least partially surround the preload washer so as to maintain, i.e., to lock, the position of the half-washers 131 and 132 relative to each other. The locking piece 14 therefore also ensures that the preload supplied by the preload washer 130 is maintained and holds the position of the latter around the threaded rod 122 (in other words, between the part 2 and the nut 11 or the fixing head 121).

[0059] The invention also relates to a method 90 for restoring the preload of a bolted assembly 1 illustrated in Figs. 4a, 4f and 6.

[0060] As schematically illustrated in [Fig. 6], process 90 comprises the steps of:

[0061] - insertion 91 of a half-washer 131, 132 between part 2 and nut 11 or between the part 2 and the fixing head 121 of the fixing screw 12 until the threaded rod 122 is received in the main passage 130a of the preload washer 130;

[0062] - insertion 92 of the other half-washer 131, 132 between the half-washer 131, 132 and the nut 11 or between the half-washer 131, 132 and the fixing head 122 until the threaded rod 122 is received in the main passage 130a of the preload washer 130;

[0063] - installation 93 of the locking piece 14 around the half-washers 131, 132 to lock their positioning relative to each other.

[0064] Figs 4a to 4f illustrate the implementation of the means 13 for restoring the preload between the part 2 and the nut 11. It is clearly understood that the process described in detail below is implemented in a corresponding manner when the means 13 for restoring the preload are implemented between the part 2 and the fixing head 121.

[0065] Figs. 4a and 4b illustrate step 91 of inserting a first half-washer 131 between part 2 and nut 11. In [Fig. 4a], the first surface 139a of the first half-washer 131 is intended to be in contact with part 2, and the thin side 138a is located near nut 11. The first half-washer 131 is then moved in translation towards the threaded rod 122 of the fixing screw 12. To do this, the first half-washer 131 is pushed towards the threaded rod 122 with the threaded rod 122 which is received in the slot 133 until the threaded rod 122 is received in the main passage 130a (i.e. up to the closed end 134 of the slot 133 of the first half-washer 131). During this movement of the first half-washer 131, the second surface 139c will be in contact with the nut 11. As the first half-washer 131 advances, and thanks to the inclination of the second surface 139c, the nut 11 will be moved away from the part 2. We then notice, due to the shape of the first half-washer 131, that a free space is created between the nut 11 and the part 2 at the thin side 138a of the first half-washer 131.

[0066] The Figs. Figures 4c and 4d illustrate step 92 of inserting the second half-washer 132 between part 2 and nut 11. In [Fig. 4c], the first surface 139a of the second half-washer 132 is brought into contact with nut 11 and the thin side 138a is located near the threaded rod 122. The second half-washer 132 is inserted into the free space created by the insertion of the first half-washer 131. The second half-washer 132 is then moved translationally towards the threaded rod 122 of the fixing screw 12 until the threaded rod 122 is received in the main passage 130a (i.e. to the closed end 134 of the slot 133 of the second half-washer 132). To do this, the second half-washer 132 is pushed into the free space in the direction of the threaded rod 122 with the threaded rod 122 which is received in the slot 133.During this movement of the second half-washer 132, the second surface 139c of the second half-washer 132 is in contact against the second surface 139c of the first half-washer 131, while the first surface 139b of the second half-washer 132 is intended to come into contact with the nut 11.

[0067] Figs 4e and 4f illustrate step 93 of setting up the locking piece 14 around the half-washers 131 and 132. In [Fig.4e], the locking piece 14 is positioned around the preload washer 130 so that the lateral surfaces 139a of the half-washers 131 and 132 are clamped by the locking piece 14 (and in particular that the lateral surfaces 139a are in contact against an inner surface of the locking piece 14 which in this example is in the form of a ring).

[0068] The locking piece 14 is then moved in translation in the direction of the piece 2 to lock the position of the half-washers 131 and 132 relative to each other.

[0069] It is clearly understood that in the case where the locking piece 14 is in the form of a hose clamp, the hose clamp can be put in place around the half-washers 131 and 132 (in contact against the lateral surfaces 139a) and then the clamp is tightened so as to lock the position of the half-washers 131 and 132 relative to each other.

[0070] Figure 1 represents an aircraft A comprising at least one part 2 to be fixed and to less a bolted assembly 1 according to the invention. The use of such assemblies 1 in an aircraft advantageously facilitates the restoration of the preload of a bolted assembly in a simple, quick, and reliable manner. Furthermore, since workspaces are generally cramped and / or difficult to access in aircraft, the invention eliminates the need for systematic replacement of the nut and / or fastening bolt, thus simplifying maintenance operations.

Claims

Claims

1. Bolted assembly (1) intended to fix a part (2) having a bore (21), said bolted assembly (1) comprising a nut (11) and a fixing screw (12) having a fixing head (121) from which a threaded rod (122) extends, said threaded rod (122) being intended to be threaded into said bore (21) of said part (2) and to be screwed to said nut (11), said nut (11) and said fixing head (121) being intended to grip said part (2), characterized in that said bolted assembly (1) further comprises means (13) for restoring a preload of said bolted assembly (1) comprising: - a preload washer (130) having a main passage (130a) into which said threaded rod (122) is threaded, said preload washer (13) comprising a first half-washer (131) and a second half-washer (132), said half-washers (131,132) being assembled together to form said preload washer (130), wherein said preload washer (130) is intended to be arranged between said part (2) and said nut (11) or between said part (2) and said fixing head (121) of said fixing screw (12); and - a locking part (14) enclosing said preload washer (13) to lock the position of the half-washers (131, 132) between them.,

2. Bolted assembly (1) according to claim 1, characterized in that each half-washer (131, 132) comprises a generally cylindrical lateral surface (139a), a first generally flat surface (139b) extending generally perpendicular to said threaded rod (122) and intended to come into contact with said nut (11) or to said head (121) of said fixing screw (12) or to said part (2), and a second surface (139c) opposite said first surface (139a) and not extending parallel to said first surface (139a), said second surface (139c) being intended to come into contact with the second surface (139c) of the other half-washer (131, 132).

3. Bolted assembly (1) according to claim 2, characterized in that said first surface (139b) comprises a surface treatment promoting the sliding of each half-washer (131, 132) relative to said nut (11) or to said head (121) of said fixing screw (12) or to said part (2).

4. Bolted assembly (1) according to any one of claims 1 to 3, characterized in that each half-washer (131, 132) has a thin side (138a) and a thick side (138b), in that each half-washer (131, 132) comprises a slot (133) having a closed end (134) located generally in the center of said half-washer (131, 132) and an open end (135) opening at the thin side (138a) of said half-washer (131, 132), said slots (133) of said half-washers (131, 132) together forming said main passage (130a) into which said threaded rod (122) of said fixing screw (12) is threaded.

5. Bolted assembly (1) according to claim 4, characterized in that the slots (134) of the half-washers (131, 132) extend along parallel axes when the half-washers (131, 132) are assembled.

6. Bolted assembly (1) according to any one of claims 1 to 5, characterized in that said locking part (14) is in the form of a metal ring or a clamping collar.

7. Aircraft (A) comprising at least one part (2) to be fixed and at least one bolted assembly (1) according to any one of claims 1 to 6.

8. Method (90) for restoring the preload of a bolted assembly (1) according to any one of claims 1 to 6, characterized in that it comprises the steps of: - inserting (91) a half-washer (131, 132) between said part (2) and said nut (11) or between said part (2) and said fixing head (121) of said fixing screw (12) until said threaded rod (122) is received in said main passage (130a); - inserting (92) the other half-washer (131, 132) between said half-washer (131, 132) and said nut (11) or between said half-washer (131, 132) and said fixing head (121) until said threaded rod (122) is received in said main passage (130a); placing (93) the locking part (14) around said half-washers (131, 132) to lock their positioning relative to each other.

Images