Method and device for checking the tightening tension of an aeronautical fastening

Abstract

The invention relates to a method for tightening a fastening (30), comprising the following steps: - providing a screw (32) comprising a head (322), a threaded portion (324) and a socket (326); - inserting the screw into a drilled hole (20) and placing a nut (34) on the threaded portion; - engaging an endpiece (76) in the socket, until it makes contact with the bottom; - rotating the nut while locking the endpiece and the screw in rotation; - exciting an ultrasonic transducer (88) arranged on the endpiece; - receiving and processing ultrasonic waves reflected by a front surface of the screw head, in order to calculate a tension in the screw; - stopping the rotation of the nut when said tension equals a predefined threshold.

Description

[0001] DESCRIPTION

[0002] TITLE: METHOD AND DEVICE FOR CONTROLLING THE TIGHTENING TENSION OF AN AERONAUTICAL FIXING

[0003] Technical field of the invention

[0004] The present invention relates to a method for controlling the tightening tension of a fastener and a device enabling this control, in particular for the aeronautical industry.

[0005] Technical background

[0006] It is known in the art that in order to fix two elements together, for example structural elements of an aircraft, these elements comprise aligned holes intended for the mounting of fasteners which ensure the fixing of the elements by tightening them axially against each other.

[0007] In this application, the term "fastener" means an assembly comprising a screw and a nut. In the aeronautical industry, the tightening of the nut on the screw must be carried out to a torque predetermined by calculation during the development of the fastener to guarantee the tightening of the elements and avoid their accidental separation during operation.

[0008] Suitable fasteners for such use are, for example, HI-LOK™ fasteners as described in patent US3138987A or HI-LITE™ screws as described in patent US4326825A. An example of a HI-LITE™ fastener is shown in Figures 1A and 1B.

[0009] The HI-LITE™ fastener comprises a screw 10, having a protruding head 12, a smooth shank 14 and a threaded end 16. The threaded end 16 comprises a hexagonal recess 18. The screw 10 is installed in a bore 20 made in first 22 and second 24 elements until the head 12 bears on a front face 26 of the first element 22. The nut 30 is screwed onto the threaded end 16 emerging from the rear face 28 of the second element, opposite the face 28, the screw being immobilized by a wrench or bit (not shown) inserted into the hexagonal recess 18, until the nut contacts the face 28. The nut comprises a break groove 31 designed to break at a predetermined tightening torque, providing a tension, or preload, in the screw 10 necessary to resist the stresses of shear and traction exerted by the elements 22, 24 on the screw 10.This assembly solution is widely used and is very efficient, but it does not allow you to check, once the nut is installed on the screw, that the installed tension does not vary over time.

[0010] When a conventional nut, without a shear groove, is used, tightening is generally carried out using a torque wrench to the predetermined torque. Even if the torque is well controlled using a wrench, the geometry, surface condition and lubrication tolerances inevitably lead to a large dispersion of the preload actually installed, which can lead to a risk of breakage of the head or threads, or conversely, tightening to a preload lower than the desired preload.

[0011] Direct measurement of tension, i.e. the tensile force applied to the screw and the compression force applied to the elements held in place, is not possible. There are fasteners that include one or more strain gauges, or an ultrasonic transducer, allowing indirect measurement of the screw tension during or after tightening the nut. The gauges or transducers must be positioned on the fastener and powered electrically. This solution therefore requires instrumenting each fastener, which significantly increases its cost. Furthermore, the addition of components increases the weight of the fastener, which limits their use in large quantities on an aircraft since several tens of thousands of fasteners are installed on an aircraft.Furthermore, the resistance of electronic components to temperature variations, environmental conditions, and paint does not allow all fasteners to be instrumented and represents a qualification difficulty. The addition of electrical contacts on the terminals of gauges or transducers cannot be carried out on all fasteners, since these terminals must be accessible.

[0012] Current technology therefore does not allow a fixing to be installed at a predetermined tension in an industrial operating context, and this tension to be checked repeatedly and reliably.

[0013] Summary of the invention

[0014] The present invention aims to overcome these drawbacks and relates to a control method and a centering device allowing its implementation, which are simple and effective.

[0015] The invention thus proposes a method for tightening at least one fastener, comprising a screw and a nut, the screw comprising: a head having a flat front surface; a threaded portion; and a recess, comprising a flat bottom and a non-circular section; and a nut comprising a drive surface; the method comprising the following steps: a) inserting the screw into a bore passing through at least two elements until one end of the threaded portion emerges from the elements, and placing the nut on the emerging end of the threaded portion of the screw; b) engaging an immobilizing tip in the recess, until a front face of the tip contacts the flat bottom of said recess, said immobilizing tip comprising a shape complementary to the non-circular section of said recess; c) rotating the nut on the threaded portion of the screw while locking the immobilizing tip and the screw in rotation;excitation of an ultrasonic transducer disposed on a rear face of the tip, the ultrasonic transducer being capable of generating ultrasonic waves in the tip and the screw when the tip is engaged in the recess of the screw; reception of the ultrasonic waves reflected by the flat front surface of the screw head and processing of the received ultrasonic waves to calculate a voltage in the screw; stopping the rotation of the nut when the calculated voltage in the screw equals a predefined threshold voltage.;

[0016] Thus, thanks to the invention, we ensure that the attachment is installed at the required tension, without the attachment having any transducer or sensor.

[0017] The method according to the invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another:

[0018] - at the stage of engaging the tip in the impression of the screw, the immobilizing tip is engaged with a predetermined pressure on the screw by means of at least one elastic member;

[0019] - the nut is rotated by a sleeve and, after step b) and before step c), a stress is applied to the nut to limit a relative axial movement of the nut with respect to the sleeve, a resultant of said stress axially opposing the pressure imparted to the screw by the immobilizing end piece;

[0020] - a dry couplant is inserted between the front face of the tip and the flat bottom of the impression prior to excitation of the transducer;

[0021] - a liquid or gel couplant is poured into the impression prior to excitation of the transducer.

[0022] The present invention also relates to a tightening device allowing the implementation of a tightening method as described above, of a screw in a bore passing through at least two elements, the screw comprising: a head having a flat front surface; and a threaded portion; one end of said threaded portion comprising an axially arranged imprint, said imprint comprising a flat bottom and a non-circular section; the tightening device comprising: a body; and an immobilizing tip fixed in rotation and axially movable relative to the body, the tip comprising: an anti-rotation interface configured to engage with the non-circular section of the imprint of the screw; a flat front face, configured to contact the flat bottom of the imprint; and an opposite rear face.The tightening device further comprises: a socket movable in rotation relative to the body and configured to drive the nut in rotation; an ultrasonic transmitter, arranged on the rear face of the tip, the ultrasonic transmitter being capable of generating ultrasonic waves in the tip and in the screw when the front face of the tip is in contact with the flat bottom of the screw recess; and an ultrasonic receiver, arranged on the rear face of the tip, the ultrasonic receiver being capable of converting a reflected ultrasonic wave into an electrical signal.

[0023] The device used allows fasteners to be installed at the desired tension uniformly, which ensures increased reliability and repeatability of the tightening tension in the assembly.

[0024] The clamping device according to the invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another:

[0025] - the immobilizing tip comprises a recess comprising a flat bottom, the ultrasound receiver being arranged on said flat bottom;

[0026] - the tip has a density identical or close to the density of the screw;

[0027] - the tip includes a tin deposit on the front face;

[0028] - the clamping device further comprises an immobilizer support, said support comprising: a part fixed relative to the body; and a movable part, capable of sliding axially inside the fixed part; the ultrasound transmitter and receiver and the immobilizer tip being integral with said movable part;

[0029] - the clamping device comprises a compression spring arranged in the immobilizer support, the spring bearing on the one hand on the movable part and on the other hand on the fixed part of the immobilizer support;

[0030] - the nut comprises an axial stop; and the clamping device comprises a counter-stop device cooperating with the axial stop of the nut, the axial stop and the counter-stop device being capable of limiting a relative axial movement between the nut and the clamping device; the axial stop of the nut comprises at least one portion in depression relative to an outer surface of the nut, and the counter-stop device comprises at least one radially movable locking element, said at least one locking element being adapted to be housed in said at least one portion in depression of the nut;

[0031] - the axial stop of the nut comprises at least one portion of groove or at least one cutout;

[0032] - the counter-stop device further comprises: a first collar arranged at a free end of the sleeve, said first collar having at least one notch extending radially in a thickness of the first collar; a ring arranged around the sleeve, said ring being free to rotate around the sleeve and fixed in translation relative to the sleeve, said ring comprising a second collar bearing against the first collar, a radial surface of said second collar being provided with a helical groove; and at least one movable element capable of sliding in the at least one notch of the first collar, a radial surface of the notch being provided with at least one curved groove capable of cooperating with the helical groove of the second collar, an internal peripheral surface of the movable element being capable of cooperating with the depressed portion of the nut;

[0033] - the sleeve comprises at least one radial through bore; the clamping device further comprising a ring arranged around the sleeve; the at least one locking element being movable in the at least one radial bore between a projecting position inside the sleeve, and a retracted position in which the at least one locking element does not hinder the insertion of the nut into the sleeve;

[0034] - the ring has a first internal surface capable of sliding axially along the sleeve, the internal surface comprising a first circumferential groove, the at least one locking element being contained in the first circumferential groove of the ring in the retracted position;

[0035] - the ring has an internal shoulder, the clamping device comprising an elastic element housed in a space between the sleeve and the ring, said spring bearing on the one hand against the internal shoulder of the ring and on the other hand against an external shoulder of the sleeve;

[0036] - the ring is provided with at least one radially flexible tab extending axially, said tab being provided at one end with a protrusion capable of penetrating into the at least one bore of the sleeve;

[0037] - the clamping device further comprises a second ring arranged around the ring, the second ring comprising a tubular portion pierced with at least one slot, each slot being configured to receive at least the protrusion of a tab, the second ring being able to slide axially on the sleeve, and being configured so that an axial movement towards a second end of the sleeve causes a radial displacement towards the outside of each protrusion;

[0038] - the nut comprises at least one stop extending radially outwards, the counter-stop device comprising a ring arranged around the sleeve, said ring comprising at least one counter-stop, said stops and counter-stops being configured so that a relative rotation of the ring with respect to the nut axially opposes said stops and counter-stops.

[0039] Brief description of the figures Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which one will refer to the appended drawings in which:

[0040] [Fig. 1A] Fig. 1A is a side view of a prior art fastener;

[0041] [Fig. 1 B] Fig. 1 A is a side and sectional view of a prior art fastener installed in a structure;

[0042] [Fig. 2] Figure 2 is a side view of a fastener suitable for use in a tightening method according to one embodiment of the invention;

[0043] [Fig. 3] Figure 3 is a schematic sectional view of a clamping device according to one embodiment of the invention and of the fixing of Figure 2, in a first step of a clamping method according to one embodiment of the invention;

[0044] [Fig. 3A] Figure 3A is a longitudinal section of an immobilizing tip according to one embodiment of the invention;

[0045] [Fig. 4] Figure 4 is a view similar to Figure 3 in a second step of said tightening method;

[0046] [Fig. 5] Figure 5 is a view similar to Figures 3 and 4 in a third step of said tightening method; and

[0047] [Fig. 6] Figure 6 is a block diagram illustrating steps of one embodiment of the method of tightening the fastener of Figure 2 using the tightening device of Figures 3, 4 and 5,

[0048] [fig. 7a, 7b, 7c, 7d] figures 7a, 7b, 7c and 7d are isometric views of nuts suitable for use in a tightening method according to one embodiment of the invention,

[0049] [fig. 8a, 8b, 8c] figures 8a, 8b and 8c are partial isometric views of a clamping device according to a first embodiment of the invention,

[0050] [fig. 9a] Figure 9a is a partial isometric view of a socket used in a clamping device according to a second embodiment of the invention,

[0051] [Fig. 9b] Figure 9b is a sectional view of a clamping device according to a second embodiment of the invention, with the socket of Figure 9a and the nut of Figure 7b,

[0052] [fig. 10a] figure 10a is a partial isometric view of a part of a clamping device according to a third embodiment of the invention,

[0053] [fig. 10b] figure 10b is a partial isometric view of a ring used in the clamping device according to the third embodiment of the invention,

[0054] [fig. 10c] Figure 10c is a sectional view of the clamping device according to the third embodiment of the invention, with the nut of Figure 7c, [fig. 1 1 a] Figure 1 1 a is a partial isometric view of a clamping device according to a fourth embodiment of the invention,

[0055] [fig. 1 1 b] figure 11 b is a front view of the clamping device of figure 11 a, with the nut of figure 7d.

[0056] Detailed description of the invention

[0057] In the following description, the method and device for tightening a fastener are used to assemble aircraft structures.

[0058] This example is not, however, limiting, the method and the clamping device being applicable to other types of assembly or application, such as for example fasteners assembling land vehicle structures or wind turbine blades.

[0059] Reference is now made to Figures 3 to 5 which show a clamping device 40 configured to clamp a fastener, according to one embodiment of the invention.

[0060] Said fixing, shown alone in figure 2, comprises a screw 32 and a nut 34. The screw 32 extends along an axis A and comprises a protruding head 322, a threaded portion 324 and a recess 326.

[0061] The imprint 326 is arranged along the axis A and opens onto one end of the threaded portion 324, opposite the head 322. Transversely to the axis A, the imprint 326 has a non-circular section.

[0062] In the embodiment shown, the non-circular section is hexagonal in shape. Alternatively, the non-circular section of the imprint is multi-lobed, for example as described in the applicant's patent FR2967735B1, or of any other non-circular shape making it possible to block the rotation of the screw 32 by inserting a key or a bit of complementary shape.

[0063] Unlike the screw 10 of the prior art, the bottom 328 of the imprint is flat and parallel to the end surface 330 of the head 322. More precisely, the bottom 328 of the imprint and the end surface 330 of the head are perpendicular to the axis A.

[0064] Preferably, the flat bottom 328 is obtained either by machining the bottom of the impression, previously produced by broaching, or by electroerosion, or by adding material to the impression with a conical bottom so as to obtain a flat bottom. Preferably, the addition of material has a density comparable to that of the screw so as not to disperse or diffract or disturb the path of the ultrasonic waves, as will be described later. Preferably, the roughness Ra of the flat bottom 328 is less than 2.

[0065] Apart from the modification relating to the bottom of the impression and the possible addition of a coupling agent, the screw 32 is similar to the screw 10 of the prior art previously described. In particular, the screw 32 is devoid of any tension sensor, flexion sensor, transducer capable of emitting sound waves, ultrasonic waves, or any electrical or electronic component such as batteries, capacitors or antennas.

[0066] The nut 34 comprises external driving surfaces 36, for example six or twelve flat surfaces. A suitable nut is for example described in the applicant's patent EP2350473. The nut 34 is also devoid of any tension sensor, bending sensor, transducer capable of emitting sound or ultrasonic waves, or any electrical or electronic component such as batteries, capacitors or antennas.

[0067] Figures 7, 7b, 7c and 7d respectively show nuts 34a, 34b, 34c and 34d comprising an axial stop capable of cooperating with a counter-stop device of the clamping device, the axial stop and the counter-stop device being capable of limiting a relative axial movement between the nut and the clamping device.

[0068] On the nuts 34a, 34b and 34c, the axial stop is a portion in depression relative to an outer surface of the nut. More particularly, in the embodiments shown, the portion in depression is produced respectively on the nuts 34a, 34b and 34c, by a circumferential groove 37a disposed between the base and the outer drive surfaces 36, a cutout 37b of rectangular shape produced on each edge between two outer drive surfaces 36, and a cutout 37c of triangular shape produced on each edge between two outer drive surfaces 36.

[0069] In a variant not shown, the depression portion is a circumferential groove made on the drive surfaces 36.

[0070] The cutouts 37b and 37c may have other shapes than those shown in Figures 7b and 7c. They may, for example, be portions of circumferential grooves.

[0071] On the nut 34d, the axial stop comprises four projecting portions 37d, extending radially outwards. Said projecting portions are arranged in this example at 90° on the base of the nut. The number of projecting portions 37d is not limited to four: the nut may be provided with one, two, three or more projecting portions, arranged uniformly or non-uniformly around the base. A uniform arrangement has the advantage of being more easily grasped by the clamping device, as will be explained below.

[0072] Regardless of the embodiment chosen to form the axial stop, the axial stop comprises a radially outwardly or inwardly extending surface adapted to interact with at least one radially inwardly or outwardly extending surface of a member of the clamping device adapted to cooperate with the nut, in order to limit axial relative movement of the nut with respect to the clamping device. The axial stop is designed to resist failure in tension and torsion in order to preserve the structural integrity of the nut.

[0073] The clamping device 40 extends along an axis X and comprises a tubular body 42, a sleeve 44 and an immobilizer support 46. The sleeve 44 is rotatable relative to the body 42. In the embodiment shown, the clamping device further comprises a hollow transmission shaft 48, secured to an axial end of the sleeve. The shaft 48 is configured to drive the sleeve 44 in rotation about the axis X.

[0074] In the embodiment shown, the clamping device further comprises ball bearings 50 and roller bearings 52. The ball bearings 50 are arranged radially between the sleeve 44 and the body 42, allowing rotation of the sleeve relative to the body. The roller bearings 52 will be described below.

[0075] The socket 44 is internally hollowed out, the hollowed out portion forming an internal housing extending axially between a first end 54 and an opposite second end 56, both ends being open.

[0076] The housing of the sleeve 44 comprises: a distal portion 60 close to the first end 54, an intermediate portion 64 and a proximal portion 66 close to the second end 56 (FIG. 5). The distal portion 60 has an inner diameter substantially smaller than the inner diameters of the intermediate 64 and proximal 66 portions. The intermediate portion 64 has a diameter substantially smaller than the inner diameter of the proximal portion 66.

[0077] The junction of the distal 60 and intermediate 64 portions forms a first shoulder 68. The junction of the intermediate 64 and proximal 66 portions forms a second shoulder 70 (figure 4).

[0078] The distal portion 60 of the sleeve 44 is configured to receive the nut 34 and drive it in rotation. The internal peripheral wall of the distal portion 60 comprises at least two planar faces 62 intended to engage with at least two planar driving surfaces 36 of the nut 34. Preferably, the sleeve is adapted to the shape of the nut that it must drive, and comprises for example as many planar faces as there are driving surfaces 36 of the nut. An axial dimension Xi of the distal portion 60 is configured to entirely house the nut 34 and a projecting part of the threaded portion 324 of the screw, when the nut is installed on the threaded portion and in contact with the rear surface 28 of the second element 24, as shown in FIG. 5.

[0079] The immobilizer support 46 comprises a fixed part 72 and a movable part 74. The fixed part 72 is fixed relative to the body 42 in rotation and in translation. The movable part is able to slide axially in the fixed part. The fixed part 72 comprises a tubular portion 722 and a crown 724, adjacent along the axis X. The tubular portion 722 is arranged in the hollow shaft 48. The roller bearings 52 are arranged radially between the tubular portion 722 and the shaft 48, allowing the rotation of said shaft relative to the fixed part 72 of the immobilizer support 46.

[0080] The crown 724 has a tubular shape. A first portion of the crown 724 extends into the hollow shaft and a second portion of said crown extends into the proximal portion 66 of the sleeve 44. An external diameter of the crown 724 is less than an internal diameter of the proximal portion 66 of the sleeve 44. A free end of the crown is disposed near the second shoulder 70. The junction between the tubular portion 722 and the crown 724 forms a counterbore 726, such that the internal diameter of the crown is greater than the internal diameter of the tubular portion 722.

[0081] The fixed part 72 also comprises an annular surface 728 perpendicular to the axis X, abutting against the needle rollers 52. The fixed part is thus axially locked in the hollow shaft and the sleeve 44, between the second shoulder 70 of the sleeve 44 and the needle rollers 52, with a small axial clearance.

[0082] The movable portion 74 comprises a collar 742 and a skirt 744 extending axially from the collar. The outer diameter of the collar 742 is greater than the outer diameter of the skirt 744.

[0083] The collar 742 is housed in the second part of the crown 724, itself housed in the proximal portion 66 of the sleeve 44. The external diameter of the collar 742 is less than the internal diameter of the crown 724, with sufficient clearance for the movable part 74 to be able to move axially in the crown 724 of the fixed part 72.

[0084] The skirt 744 is able to slide in the intermediate portion 64 of the sleeve, the external diameter of the skirt 744 being less than the internal diameter of the intermediate portion 64.

[0085] The clamping device 40 further comprises an immobilizer tip 76 and an ultrasonic transducer 88, housed within the immobilizer support 46. In the embodiment shown, the clamping device 40 also comprises: a resilient member such as a compression spring 90; and a cable 92.

[0086] The tip 76 comprises a front face 78 and a rear face 80, both being planar and perpendicular to the X axis. The immobilizing tip 76 comprises an anti-rotation interface 82, adapted to engage in the recess 326 of the screw 32, the free end of which is the front face 78. The interface 82 may be a cylinder with a hexagonal base if the recess 326 is hexagonal, or a cylinder with a multi-lobed base if the recess is multi-lobed. Such a tip is for example described in the applicant's patent FR2967735.

[0087] Preferably, the material of the tip 76 is the same or similar to the material of the screw 32. Alternatively, the acoustic impedance - or density - of the tip is the same or close to the acoustic impedance - or density - of the screw.

[0088] Acoustic impedance is the product of the wave speed in the material and the material density. Too great a difference in acoustic impedance can cause some of the waves to be reflected at the interface between the tip and the screw, resulting in signal loss.

[0089] For example, if the screw is made of TA6V titanium alloy, the tip will preferably be made of TA6V titanium alloy, or a similar alpha-beta titanium alloy.

[0090] In the embodiment shown, the interface 82 is connected by a conical portion to a cylindrical portion of enlarged diameter, in which an annular groove 84 is made. This groove is shown with a V-shaped section in the figures, but it can adopt all kinds of shapes.

[0091] The immobilizing tip 76 is fixed to the movable part 74 of the immobilizing support by a pin 86, inserted into a hole in the movable part 74 and housed in the annular groove 84.

[0092] The ultrasonic transducer 88 is an ultrasonic transmitter-receiver, fixed on the rear face 80 of the tip 76. An electrical interface 87 is made for example with a connector of the Microdot, SMA or SMB type. The transducer is connected via the electrical interface by the cable 92 to a power supply (not shown) and operates as a transmitter, converting the electrical energy into mechanical oscillations to produce ultrasound transmitted into the screw 32 via the immobilizing tip 76. The transducer 88 also operates as a receiver, converting a reflected ultrasonic wave into an electrical signal, transmitted via the cable 92 to an analog or digital electronic device such as a processor (not shown), capable of processing the received electrical signal to calculate the tension in the screw. The transducer is for example a piezoelectric sensor, preferably in PZT4 or PZT8.The electronic device can be integrated into the tool, or can be remote.

[0093] In a variant shown in Figure 3A, the immobilizing tip 76A comprises a front face 78A and a recess 85 comprising a flat bottom 80A, perpendicular to the X axis. The ultrasonic transducer 88 is fixed on the flat bottom 80A, inside the recess of the immobilizing tip 76A. The integration of the transducer and the electrical interface 87A inside the tip ensures their protection. Preferably, the transducer and the electrical interface are protected by a cover 85A, for example made of plastic, closing the recess 85. Optionally, the recess can be filled, for example with epoxy conductive resin, to adjust the damping and the bandwidth of the transducer.

[0094] Advantageously, the bottom 80A is arranged as close as possible to the front face 78A to avoid deteriorating the quality of the transmission of the ultrasonic waves, due to the geometry of the tip and / or the thickness of material between the transducer and the front face, the latter being able to resonate and pollute the useful measurement in the screw 32.

[0095] Whether the transducer 88 is fixed on the rear face 80 of the tip 76 or fixed on the bottom 80A of the tip 76A, it is preferable that the immobilizing tip 76 or 76A does not have any surface with a half-angle equal to 45°, to avoid total reflection of the waves towards the transducer 88. The external surfaces having an angle with the X axis can be striated or knurled to destroy the incident wave and limit its reflection in the body of the immobilizing tip 76, 76A.

[0096] It is also preferable that the body of the tip 76, 76A be sized so that the resonance of the tip is distinct from the resonance of the screw 32, in order to be easily discriminated during measurement.

[0097] The assembly formed by the transducer 88 and the immobilizing tip 76, 76A is thus secured to the movable part 74 of the immobilizing support, via the pin 86.

[0098] Preferably, a dry couplant 79 is interposed between the front face 78 of the tip and the bottom 328 of the screw recess, in order to improve the acoustic transmission. The couplant 79 may be, for example, a sheet of tin, silver, copper or an elastomeric coupling material such as Aqualene, developed by the company Innovation Polymers, Canada.

[0099] Preferably, the coupling agent is tin deposited on the front face 78, 78A of the immobilizing tip 76, 76A. Tin is a relatively soft metal which ensures compensation for surface defects of the screw 32. In addition, its acoustic impedance is compatible with inspection on a metallic material and promotes the passage of ultrasound from the transducer 88 to the screw 32.

[0100] The coupling agent has a thickness preferably between 0.0175 mm and 0.6 mm. The sheet or material may be deposited dry or wet, by welding or brazing, or may also be glued, on the front face of the end piece.

[0101] The compression spring 90 is arranged in the crown 724 of the fixed part 72 of the support 46. It bears axially on the one hand on the collar 742 of the movable part 74 of the support 46, and on the other hand on the counterbore 726 of the fixed part 72 of the support. The collar ensures guidance of the assembly formed by the transducer 88 and the immobilizing end piece 76 parallel to the axis of revolution X of the clamping device 40. The guidance thus ensures that the ultrasonic waves are emitted in the axis X of the clamping device.

[0102] The assembly formed by the immobilizing tip 76, 76A and the transducer 88 is thus movable in the axial direction X between a first position, in which the spring is relaxed (Figures 3 and 4), and a second position, in which the spring is compressed (Figure 5) and capable of imparting a predetermined pressure to the immobilizing tip 76, 76A. The assembly formed by the immobilizing tip 76, 76A and the transducer 88 is fixed in rotation relative to the body 42.

[0103] Preferably, the clamping device is adapted to be used with a fastener comprising a nut with an axial stop, for example a nut 34a, 34b, 34c or 34d shown in Figures 7a, 7b, 7c or 7d. In the remainder of the description, each clamping device 40a, 40b, 40c and 40d respectively comprises a counter-stop device 94a, 94b, 94c and 94d cooperating with the axial stop 37a, 37b, 37c, 37d of the nuts, the axial stop and the counter-stop device being capable of limiting a relative axial movement between the nut and the clamping device.

[0104] When the axial stop 37 of a nut comprises a depression portion, such as a groove 37a or a cutout 37b, 37c, the counter-stop device 94 preferably comprises at least one radially movable locking element 114a,b,c, said at least one locking element being adapted to be housed in said at least depression portion of the nut.

[0105] Advantageously, the counter-stop device 94 comprises as many locking elements 114a, b, c as there are depressed portions of the nut.

[0106] Figure 8a shows a clamping device 40a comprising a counter-stop device 94a. The counter-stop device 94a comprises: a first collar 110, a ring 112a and three locking elements 114a, only two of which are shown for reasons of clarity.

[0107] The first collar 110 is arranged at the first end 54a of the sleeve 44a, and in this example, is an integral part of the sleeve 44a. Apart from this collar, the sleeve 44a is identical to the sleeve 44 of the clamping device 40 previously described. The first collar 110 could alternatively be an element added to the sleeve 44. The first collar 110 extends radially outwards, and has three notches 116a extending in the radial direction, in a thickness of the first collar. In the embodiment of FIG. 8a, the three notches are arranged at 120°. Each notch advantageously comprises lateral tabs 118, having a function of retaining and guiding a locking element 114a. The ring 112a is arranged around the sleeve 44a. The ring 112a is free to rotate around the sleeve 44a, and fixed in translation relative to said sleeve.The ring 112a comprises a second collar 120, configured to bear against the first collar 110. A radial surface 122 of said second collar is provided with a helical groove 124, the center of which is at the center of the second collar.

[0108] Each locking element 114a is capable of sliding in the radial direction in each notch 116a of the first collar 110. As shown in FIG. 8c, a radial surface 126 of a locking element 114a, intended to bear against the helical groove 124 of the second collar 120, is provided with a set of curved grooves 128 capable of cooperating with said helical groove. The end portion 130 of a locking element 114a is capable of cooperating with the depression portion 37a of the nut 34a, as shown in FIG. 8b. Preferably, the end portion 130 has a shape complementary to the groove 37a. The end portion 130 and the groove 37a each have a surface extending substantially in a radial plane. The engagement of these surfaces limits the relative axial movement between the nut 34a and the clamping device 40a.

[0109] In a second embodiment of a clamping device 40b, the sleeve 44b shown in Figure 9a is adapted to cooperate with a nut 34b. The sleeve 44b comprises six bores 116b extending radially and passing through the thickness of the distal portion 60b of the sleeve 44b. Each bore 116b is arranged on an edge between two adjacent flat faces 62b of the distal portion 60b. Other arrangements are possible if the depression portions 37b of the nut 34b are arranged differently, or elsewhere. The number of through bores can also vary, depending on the number of depression portions 37b of the nut.

[0110] The counter-stop device 94b, shown in figure 9b, comprises: a ring 112b, movable elements 114b in the form of balls, and an elastic element 132.

[0111] The ring 112b is arranged around the distal portion 60b of the sleeve 44b. The ring 112b has a first internal surface capable of sliding axially on the distal portion 60b of the sleeve, the internal surface comprising a first circumferential groove 134 having a first diameter, and a second circumferential groove 136 having a second diameter, smaller than the first diameter.

[0112] Each ball 114b is movable in each radial bore 116b, between a projecting position inside the sleeve 44b, and a retracted position in which each ball 114b is contained in the second circumferential groove 136 of the ring (figure 9b).

[0113] The elastic element 132 is for example a compression spring. It is arranged around the sleeve 44b and inside the ring 112b. The spring 132 bears on the one hand against an internal shoulder of the ring 112b, and on the other hand against an internal shoulder of the sleeve 44b. When the clamping device is in the free state, that is to say when it is not cooperating with the nut 34b, the spring 132 tends to push the ring away from the sleeve: the first circumferential groove 134 is then arranged opposite the holes 116b so that the balls 114b are contained in the first circumferential groove 134, and do not hinder the insertion or removal of the nut in the sleeve.

[0114] In the position of Figure 9, the spring 134 is in a compressed state, so that each ball 114b is housed in a cutout 37b of the nut. The radially contacting surfaces of each ball with each cutout limit the axial movement of the nut 34b relative to the clamping device 40b.

[0115] It should be noted that the 40b clamping device is adapted to a 34a or 34c nut, the number of balls and their location having to be adapted to the geometry of the nut.

[0116] In a third embodiment of a clamping device 40c, the sleeve 44c shown in Figure 10a is adapted to cooperate with a nut 34b or 34c. The distal portion 60c of the sleeve 44c is provided with six rectangular-shaped holes 116c, each hole passing through the thickness of the distal portion 60c. Each hole 116c is arranged on an edge between two adjacent flat faces 62c of the distal portion 60c.

[0117] The counter-stop device 94c comprises: a ring 112c arranged around the distal portion 60c of the sleeve 44c, the ring 112c being provided at one end close to the first end 54c of the sleeve 44c, with at least one tongue 114c extending axially. Each tongue is radially flexible and is provided at one end with a protrusion 115 capable of penetrating into a bore 116c of the sleeve. Figure 10a shows a retaining position, in which the ring 112c comprises six tongues 114c, the protrusions 115 of which penetrate into the six bores 116c of the sleeve 44c.

[0118] The counter-stop device 94c further comprises a second ring 138 arranged around the ring 112c, shown in FIG. 10b. The second ring 138 comprises a tubular portion 140 pierced with six slots 142, each slot being configured to receive the protrusion 115 and an axial portion of each tab. The second ring 138 is capable of sliding axially on the sleeve 44c. It is configured so that an axial movement towards the second end 56c of the sleeve 44c causes a radial displacement, outwards, of each protrusion 115. The second ring 138 thus makes it possible to lift the tabs 114c and to disengage the nut 34b or 34c from the distal portion 60c of the sleeve 44c. The second ring 138 can for example be actuated manually.

[0119] In the retaining position of figure 10c, the sleeve 44c comprises six through holes 116c, the ring 112c comprises six tabs 114c, the protrusions 115 of which penetrate into: the six holes 116c of the sleeve 44c, the slots 142 of the second ring and the cutouts 37c of the nut 34c.

[0120] In a fourth embodiment shown in Figure 11a, the clamping device 40d is adapted to cooperate with a nut 34d. The clamping device 40d comprises a sleeve 44d comprising a distal portion 60d identical to the distal portion 60 of the sleeve 44, and an intermediate portion 64d provided with two holes 152. Each hole 152 receives a pin 154 extending radially outwards, projecting from the surface of the sleeve 44d. In this example, the holes, and consequently the pins, are arranged at 180° around the circumference of the sleeve 44d.

[0121] The counter-stop device 94d comprises a ring 112d disposed around the distal 60d and intermediate 64d portions of the sleeve 44d. The ring 112d is tubular in shape, one end of which close to the first end 54d of the sleeve 44d has radially inwardly extending slots 156. Preferably, the ring 112d has as many slots 156 as the nut 34d has protruding portions 37d. As shown in FIG. 11b, the slots have shapes and sizes suitable for interfacing with the protruding portions 37d of the nut.

[0122] The ring 1 12d further comprises: two slots 116d and two grooves 158 interfacing with the pins 154. Each slot extends circumferentially over a ring portion 112d disposed around an intermediate portion 64d of the sleeve 44d. Each slot extends between a first end 160 and a second end 162. In the position of FIG. 1 1 a, each pin 152 is disposed against one end 160 of a slot 1 16d. Each slot 116d is designed to allow the ring 112d to pivot on the pins 152, between the two ends 160, 162.

[0123] Each groove 158 extends axially on an inner surface of the ring, up to an end portion 164 orthogonally intersecting the first end 160 of a lumen 116d. The size and shape of each groove are designed to allow the ring 112d to slide axially on the pins 154 when mounting the ring 112d on the sleeve 44d.

[0124] A method of tightening the fastener 32, 34, 34a, 34b, 34c, 34d in two elements 22, 24 by means of the devices 40, 40a, 40b, 40c and 40d will now be described. This method makes it possible to tighten the fastener while controlling the tightening tension induced in the screw by tightening the nut on the screw and the two elements.

[0125] We now refer to Figure 6 showing the steps of the method 100 for tightening a fastener, implemented by means of a tightening device 40 described previously.

[0126] During a step 101, the screw 32 is inserted into the bore 20 of the elements 22, 24 previously described, until one end of the threaded portion 324 emerges from the element 24. The nut 34, 34a, 34b, 34c or 34d is placed on said end of the threaded portion 324, engaging a few threads, as visible in FIG. 3.

[0127] Then, during a step 102, the tightening device 40, 40a, 40b, 40c and 40d is brought closer to the fastener so that the immobilizing tip 76, 76A engages in the recess 326 of the screw 32. The movement of the device 40, 40a, 40b, 40c and 40d is continued until the front face 78, 78A of the tip contacts the flat bottom 328 of the recess, and the distal portion 60, 60a, 60b, 60c or 60d of the socket contacts the driving surfaces 36 of the nut, as visible in FIG. 4.

[0128] In this position, the axis X of the clamping device coincides with the axis A of the fastener; and the front 78, rear 80 flat faces or the bottom 80A of the end piece 76, 76A, the flat bottom 328 of the imprint and the face 330 of the head end of the screw are parallel to each other and perpendicular to the coincident axes of revolution X and A. The collar 742 is moved axially, away from the shoulder 70, due to the engagement between the screw and the immobilizer.

[0129] The front face 78, 78A of the tip is held in contact against the flat bottom 328 of the impression with a pressure predetermined by the stiffness of the spring 90.

[0130] Due to the engagement of the anti-rotation surfaces of the tip and the screw, the assembly formed by the ultrasonic transducer 88, the immobilizing tip 76, 76A and the screw 32 is fixed in rotation. After this step, if the nut comprises an axial stop and the tightening device comprises a counter-stop device, as described above, an optional stress step 109 is applied to the nut 34a, 34b, 34c and 34d to limit a relative axial movement of the nut with respect to the sleeve 44, a resultant of said stress axially opposing the pressure imparted to the screw by the immobilizing tip 76, 76A.

[0131] When the tightening method 100 is implemented on a fastener comprising a nut 34a by means of a tightening device 40a provided with a counter-stop device 94a, the ring 112a is then rotated around the sleeve. Due to the engagement of the curved grooves 128 of each movable element 114a with the helical groove 124 of the second collar 120, each movable element 114a moves radially inward, until the internal peripheral surface 130 of each movable element enters the circumferential groove 37a of the nut 34a. The thread of the nut 34 being engaged with the thread of the screw 32, the engagement of the end portion 130 of the movable element in the groove 37a of the nut axially opposes the pressure imparted to the screw by the immobilizing end piece 76.

[0132] When the tightening method 100 is implemented on a fastener comprising a nut 34b by means of a tightening device 40b provided with a counter-stop device 94b, the ring 112b is pulled axially towards the second end of the sleeve 44b so that the balls are contained in the first circumferential groove 134 without hindering the insertion of the nut into the sleeve 44d. The ring 112b is then released, and pushed back towards the first end 54b of the sleeve. The balls are then forced to take place in the second circumferential groove 136, in the radial bores 116b of the sleeve 44b and the cutouts 34b of the nut. The nut 34b is thus captive in the tightening device 40b.

[0133] When the tightening method 100 is implemented on a fastener comprising a nut 34c by means of a tightening device 40c provided with a counter-stop device 94c, the insertion of the nut 34c into the sleeve 44c pushes radially outwards the protrusions 115 of the flexible tabs 112c, which automatically return into the holes 116c of the sleeve 44c and the cutouts 37c of the nut once the nut is inserted into the distal portion 60c of the sleeve 44c. The nut 34c is thus captive in the tightening device 40c.

[0134] When the tightening method 100 is implemented on a fastener comprising a nut 34d by means of a tightening device 40d provided with a counter-stop device 94d, the nut 34d is inserted into the distal portion 60d of the sleeve 44d until the projecting portions 37 of the nut are contained in a housing 166 comprised between the slots 156 of the ring 112d and the end 54d of the distal portion 60d of the sleeve 44d. The ring 112d is pivoted around the sleeve 44d so as to axially oppose the slots 156 of the sleeve 44d and the projecting portions 37d of the nut 34d. During this rotational movement, the slots 116d pivot so that each pin 154 comes into abutment against the second end 162 of each slot 116d. Any untimely rotational movement between the sleeve 44d and the ring 112d is thus blocked, ensuring the engagement of the slots 56 of the sleeve with the projecting portions 37 of the nut.

[0135] Due to the engagement of the axial stop of the nut and the counter-stop device, the front face 78, 78A of the end piece is held in contact against the flat bottom 328 of the imprint with a constant pressure, predetermined by the stiffness of the spring 90. The advantage of maintaining a constant pressure is to ensure that the signals are transmitted and received without weakening or loss during the advancement of the nut on the thread of the screw, during the rotational driving of the nut 34a, 34b, 34c or 34d by the sleeve 44a, 44b, 44c or 44d.

[0136] Then, during a step 103, the sleeve 44 is rotated along the X axis relative to the body 42. The screw being locked in rotation relative to the body by means of the immobilizing tip 76, the nut 34, 34a, 34b, 34c is screwed onto the threaded portion 324 of the screw. During a step 104, simultaneous with step 103, US ultrasounds are emitted by the transducer 88 through the immobilizing tip 76 and the screw 32 (figure 5). The immobilizing tip 76 thus ensures the propagation of the waves transmitted by the transducer towards the fixing via the bottom 328 of the flat imprint.

[0137] The US ultrasound propagates in the screw, reflects on the end surface 330 of the screw head and returns to the transducer 88 in the form of an echo. The transducer 88 transforms the received acoustic energy into electrical energy, and transmits this energy in the form of an electrical signal to a remote electronic device via the cable 92.

[0138] During a step 105, the external electronic device processes the received electrical signal in order to determine a voltage in the screw.

[0139] According to one embodiment, the tension in the screw 32 is determined from the strain of the screw and the Young's modulus via Hooke's law. The strain of the screw is obtained from measurements of the time of a round trip of a wave, and compared to a pre-recorded strain value corresponding to a predefined threshold tension. The Young's modulus E is a constant associated with the material of the screw 32.

[0140] Alternatively, the voltage in the screw 32 is determined from the measurement of the variation in the impedance of the screw, via the measurement of the resonant frequency which depends on the stress in the screw.

[0141] Alternatively, other methods for calculating bolt tension can be used, such as one of the methods described in the publication "Review of Bolted Connection Monitoring" by Tao Wand et al., available at the URL http: / / dx.doi.Org / 10.1 155 / 2013 / 871213.

[0142] Then, during a step 106, the electronic device emits a signal, or displays an indication that the induced voltage is equal to the predefined threshold voltage, so that an operator installing the fastener stops tightening the nut. Alternatively, the electronic device is configured to control the tightening process and stop it as soon as the calculated voltage value equals the predefined threshold voltage, without human intervention.

[0143] The predefined threshold voltage may be the voltage predetermined by calculation when designing the fastener, or a voltage slightly lower than this value in order to take into account the calculation time of the electronic device and the time required to display the stop instruction, times during which the nut is rotated by the tightening device.

[0144] Then, the clamping device 40 is disengaged from the screw 32 and the nut 34, 34a, 34b, 34c, 34d and can be used to install another fastener. To disengage the nut 34a from the clamping device 40a, the ring 112a is then rotated about the sleeve in the opposite direction. Each movable element 114a moves radially outward, disengaging itself from the circumferential groove 37a of the nut 34a.

[0145] To disengage the nut 34b from the clamping device 40b, the ring 112b is pulled axially towards the second end of the sleeve 44b so that the balls are contained in the first circumferential groove 134, and allow the removal of the sleeve 44d.

[0146] To disengage the nut 34c from the clamping device 40c, the second ring 138 is pulled axially toward the second end of the sleeve 44c to lift the protrusions 115 from the cutouts 37d of the nut.

[0147] To disengage the nut 34d from the clamping device 40d, the ring 112d is pivoted in the opposite direction so that each pin 154 is in abutment with one end 160 of each slot 116d.

[0148] Optional steps can be added to the previously described steps to improve control of the clamping tension. These steps are shown in broken lines in Figure 6.

[0149] Thus, during an optional step 107, inserted between steps 101 and 102, a dry couplant can be interposed between the front face of the tip and the flat bottom 328 of the impression of the screw 32 so as to cover the flat bottom 328 of the impression. This couplant can be useful for ensuring better transmission of the waves in the screw 32.

[0150] Alternatively, this couplant may be a liquid couplant, such as water, or a gel couplant, poured into the impression.

[0151] In an optional step 108, after step 106, the calculated tension value and the reference of the fastener may be recorded in an external database. This recording may be necessary to verify the tension installed in the fastener over time.

[0152] The tightening method described above has the advantage of installing a recessed fastener without additional delay compared to a prior art fastener, while reliably and repeatably controlling the tension in the screw.

[0153] The device implemented also allows for productivity gains. Indeed, the device according to the invention allows for greater precision during control and / or measurements, and therefore eliminates additional verification steps in the event of doubt about the reliability of a measurement.

[0154] The tension in the screw may be measured over time using the previously described tightening device by disengaging the socket 44, since the installed tension of the measured fastener has been recorded in a database, during the additional step 108.

Claims

CLAIMS 1. A method of tightening a fastener (30) comprising a screw (32) and a nut (34, 34a, 34b, 34c, 34d); the screw comprising: a head (322) having a flat front surface (330); and a threaded portion (324), one end of said threaded portion comprising an axially arranged recess (326), said recess comprising a flat bottom (328) and a non-circular section; the nut (34, 34a, 34b, 34c, 34d) comprising a drive surface (36); characterized in that the method comprises the following steps: a. Insertion (101) of the screw into a bore (20) passing through at least two elements (22, 24) until the end of the threaded portion emerges from the elements, and placement of the nut (34, 34a, 34b, 34c, 34d) on the emerging end of the threaded portion of the screw; b.Engagement (102) of an immobilizing tip (76, 76A) in the impression, until a front face (78, 78A) of the tip contacts the flat bottom (328) of said impression, said immobilizing tip comprising a shape complementary to the non-circular section of said impression; c. Rotating (103) the nut on the threaded portion of the screw while locking in rotation the immobilizing tip and the screw; d. Excitation (104) of an ultrasonic transducer (88) arranged on a rear face (80) of the tip, the ultrasonic transducer being capable of generating ultrasonic waves in the tip (76, 76A) and the screw (32) when the tip is engaged in the impression of the screw; e. Receiving (105) ultrasonic waves reflected from the flat front surface of the screw head and processing the received ultrasonic waves to calculate a tension in the screw; f. Stopping (106) rotation of the nut when the calculated tension in the screw equals a predefined threshold tension.

2. Tightening method according to claim 1, in which, in the step of engaging the tip in the impression of the screw, the immobilizing tip (76, 76A) is engaged with a predetermined pressure on the screw (32) by means of at least one elastic member (90).

3. Tightening method according to claim 2, in which the rotation of the nut is carried out by a sleeve (44a, 44b, 44c, 44d) and in that, after step b) and before step c), a stress is applied to the nut to limit a relative axial movement of the nut (34a, 34b, 34c, 34d) relative to the sleeve (44a, 44b, 44c, 44d), a resultant of said stress axially opposing the pressure imparted to the screw by the immobilizing end piece (76).

4. Method according to one of the preceding claims, in which a dry couplant is interposed between the front face (78, 78A) of the tip and the flat bottom (328) of the impression prior to the excitation of the transducer (88).

5. Method according to one of the preceding claims, in which a liquid or gel couplant is poured into the impression (326) prior to the excitation of the transducer (88).

6. Clamping device (40, 40a, 40b, 40c, 40d) configured for implementing a tightening method according to one of claims 1 to 5, of a screw and a nut (34a, 34b, 34c, 34d) in a bore (20) passing through at least two elements (22, 24); the screw comprising: a head (322) having a flat front surface (330); and a threaded portion (324); one end of said threaded portion comprising an axially arranged imprint (326), said imprint comprising a flat bottom (328) and a non-circular section; the clamping device comprising: - a body (42); - an immobilizing tip (76, 76A) fixed in rotation and axially movable relative to the body (42), the tip comprising: an anti-rotation interface (82) configured to engage with the non-circular section of the imprint (326) of the screw; a flat front face (78), configured to contact the flat bottom (328) of the imprint; and an opposite rear face (80, 80A); - a socket (44, 44a, 44b, 44c, 44d) movable in rotation relative to the body (42) and configured to drive the nut (34, 34a, 34b, 34c, 34d) in rotation; - an ultrasonic transmitter (88), arranged on the rear face (80, 80A) of the tip, the ultrasonic transmitter (88) being capable of generating ultrasonic waves in the tip (76, 76A) and in the screw (32) when the front face (78, 78A) of the tip is in contact with the flat bottom (328) of the imprint (326) of the screw; and - an ultrasonic receiver (88), arranged on the rear face (80, 80A) of the tip, the ultrasonic receiver being capable of converting a reflected ultrasonic wave into an electrical signal.

7. Clamping device (40, 40a, 40b, 40c, 40d) according to claim 6, wherein the immobilizing tip (76A) comprises a recess (85) having a flat bottom (80A), the ultrasound receiver (88) being arranged on said flat bottom (80A).

8. Clamping device (40) according to claim 6 or 7, in which the tip (76, 76A) has a density identical or close to a density of the screw (32).

9. Clamping device (40) according to one of claims 6 to 8, in which the end piece (76, 76A) comprises a tin deposit (79) on the front face (78, 78A).

10. Clamping device (40, 40a, 40b, 40c, 40d) according to claim 6, further comprising an immobilizer support (46), said support comprising: a fixed part (72) relative to the body; and a movable part (74), capable of sliding axially inside the fixed part; the ultrasound transmitter and receiver and the immobilizer tip (76, 76A) being integral with said movable part (74).

11. Clamping device (40, 40a, 40b, 40c, 40d) according to claim 10, comprising a compression spring (90) arranged in the immobilizer support (46), the spring bearing on the one hand on the movable part (74) and on the other hand on the fixed part (72) of the immobilizer support.

12. Clamping device (40a, 40b, 40c, 40d) according to one of claims 6 to 11, wherein: the nut (34a, 34b, 34c, 34d) comprises an axial stop; and the clamping device comprises a counter-stop device (94a, 94b, 94c, 94d) cooperating with the axial stop of the nut, the axial stop and the counter-stop device being capable of limiting a relative axial movement between the nut and the clamping device.

13. Clamping device (40a) according to claim 12, wherein the axial stop of the nut comprises at least one portion in depression (37a, 37b, 37c) relative to an outer surface of the nut, and the counter-stop device comprises at least one radially movable locking element (114a, 114b, 114c), said at least one locking element being adapted to be housed in said at least portion in depression of the nut.

14. Clamping device (40a, 40b, 40c) according to claim 13, wherein the axial stop of the nut comprises at least one groove portion (37a) or at least one cutout (37b, 37c).

15. Clamping device (40a) according to claim 12 or 13, wherein the counter-stop device further comprises: a. a first collar (110) arranged at a free end of the sleeve (44a), said first collar having at least one notch (116a) extending radially in a thickness of the first collar; b. a ring (112a) arranged around the sleeve, said ring being free to rotate around the sleeve and fixed in translation relative to the sleeve, said ring comprising a second collar (120) bearing against the first collar, a radial surface of said second collar being provided with a helical groove (124); and c.at least one movable element (114a) capable of sliding in the at least one notch of the first collar, a radial surface (126) of the notch being provided with at least one curved groove (128) capable of cooperating with the helical groove (124) of the second collar, an internal peripheral surface (130) of the movable element being capable of cooperating with the depression portion (37a) of the nut.

16. A clamping device (40b, 40c) according to claim 12 or 13, wherein the sleeve comprises at least one radial bore (116b, 116c) therethrough; the clamping device further comprising a ring (112b, 112c) disposed around the sleeve; the at least one locking element (114b, 114c) being movable in the at least one radial bore between a projecting position inside the sleeve (44b, 44c), and a retracted position in which the at least one locking element (114b, 114c) does not hinder insertion of the nut into the sleeve.

17. Clamping device (40b) according to claim 16, wherein the ring (1 12b) has a first internal surface capable of sliding axially along the sleeve, the internal surface comprising a first circumferential groove (134), the at least one locking element (1 14b) being contained in the first circumferential groove (134) of the ring in the retracted position.

18. A clamping device (40b) according to claim 16 or 17, wherein the ring (112b) has an internal shoulder, the clamping device comprising a elastic element (132) housed in a space between the sleeve (44b) and the ring, said spring bearing on the one hand against the internal shoulder of the ring and on the other hand against an external shoulder of the sleeve.

19. Clamping device (40c) according to claim 16, wherein the ring (1 12c) is provided with at least one radially flexible tab (1 14c) extending axially, said tab being provided at one end with a protrusion (115) capable of penetrating into the at least one bore (1 16c) of the sleeve.

20. Clamping device (40) according to claim 19, further comprising a second ring (138) arranged around the ring (112c), the second ring comprising a tubular portion (140) pierced with at least one lumen (142), each lumen being configured to receive at least the protrusion (115) of a tab, the second ring being able to slide axially on the sleeve (44c), and being configured so that an axial movement towards a second end (56c) of the sleeve (44c) causes a radial displacement towards the outside of each protrusion (115).

21. Clamping device (40) according to one of claims 6 to 11, wherein the nut (34d) comprises at least one stop (37d) extending radially outwards, the counter-stop device comprising a ring (112d) arranged around the sleeve (44d), said ring comprising at least one counter-stop (150), said stops (37d) and counter-stops (150) being configured so that a relative rotation of the ring (112d) with respect to the nut (34d) axially opposes said stops and counter-stops.

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