HOLDING DEVICE FOR A THREADED ELEMENT, IN PARTICULAR FOR A NUT

Description

[0001] The present invention relates to a retaining device for a threaded member, in particular for a nut.

[0002] In certain applications, particularly in aeronautical applications and even more particularly in aircraft engines, fixings must be made by screwing while one of the threaded members, typically a nut, is very difficult to access to prevent it from turning during the screwing rotation. or unscrewing of the other threaded member, for example a screw.

[0003] Nuts are known that can be pre-fixed in the appropriate position for subsequent screwing. But these nuts are often special, non-standard nuts. There is another problem with such nuts: when two parts have to be fixed by several screws, such nuts fixedly positioned on one of the parts prevent any adjustment of dimensional tolerances of this part in relation to the other. Also known are so-called "floating cage nuts", offered for example by Raceparts (UK) Ltd, Unit 3, Rockfort Ind Est, Hithercroft Rd, Wallingford, UK, specially shaped to couple with radial clearance to a body - or cage - that is pre-fixed to one of the parts. Such special nuts pose problems of interchangeability and approval in the most demanding applications, such as aeronautics. A prior art threaded member retainer is described in JP2016109277A.

[0004] An aim of the present invention is thus to propose a retaining device for a threaded member, in particular for a nut, which allows screwing without access to the threaded member, allows tolerances to be taken up and allows, if desired, the use of standard threaded members, in particular standard nuts.

[0005] According to the invention, the retaining device for a threaded member has the technical characteristics of claim 1.

[0006] The intermediate element and the body cooperate to provide radial clearance allowing the threaded member to have freedom of positioning relative to the part during screwing. It is therefore no longer necessary to use a threaded member specially designed to be prevented from rotating while having this freedom of self-positioning. A standard threaded member, in particular approved for the application concerned, can be used.

[0007] In particular, in one embodiment, the coupling opposing relative rotation between the threaded member and the intermediate element is substantially without radial play and / or substantially without rotational play around the axis. Thus, the connecting conformation of the threaded member cooperates effectively with the intermediate element to prevent rotation of the threaded member, in particular during screwing and / or at the end of the screwing and / or during unscrewing. By "substantially without play", it is meant that there may nevertheless be minimal play of the type necessary between a nut and a conventional screwing / unscrewing tool.

[0008] In certain preferred embodiments, the coupling with radial clearance between the intermediate element and the body further has a rotational clearance around the axis. This rotational clearance allows or facilitates the radial displacement permitted by the radial clearance. It is in principle limited to an angular travel just sufficient to allow the free radial displacement permitted by the radial clearance.

[0009] Typically, the complementary conformation carried by the intermediate element is designed to ensure said coupling with a standard nut connection conformation.

[0010] In one embodiment, the complementary conformation is a grooved bore, particularly for mating with an externally grooved screw head or nut of a standard design in certain industries such as the aeronautical industry.

[0011] Preferably the intermediate element is a ring, capable of forming with the threaded member a coupling distributed all around the axis, typically in the manner of a screwing tool. This makes, if desired, the device capable of preventing rotation of the threaded member even if the screwing torque reaches the maximum value that can be supported by the threaded member used.

[0012] In some embodiments, the ring is closed, in the sense that it has a continuity of material all around the axis. In other embodiments, the ring, substantially closed, nevertheless has a slot, for example in an axial plane, allowing an electroerosion machining wire to be introduced into the orifice of the ring, during manufacture, for machining said complementary conformation in the wall of the bore.

[0013] Typically, the ring surrounds the threaded member and is surrounded by at least a portion of the body.

[0014] Preferably, the intermediate element, in particular the ring, is essentially non-deformable, in particular inelastic, in the sense that its functionality does not rely on its deformation, in particular on its elasticity.

[0015] Preferably, the coupling means are formed on a radially outer surface of the ring, which radially outer surface has said radial clearance with a radially inner surface of the body.

[0016] In one version, the coupling means between the intermediate element and the body comprise radial teeth projecting into housings in a cylindrical wall, the teeth typically being carried by the intermediate element. The housings are then, in one embodiment, notches formed in an edge of the cylindrical wall, said edge being turned away from the part. The assembly of the device is thus facilitated and its radial size is reduced.

[0017] In an advantageous embodiment, one face of the housings forms a stop limiting the axial movement of the intermediate element towards the part to be clamped. In particular, this face may be the bottom of the aforementioned notches.

[0018] The device preferably comprises axial retaining means retaining the intermediate element captive in the body. Thus, at least once installed, the body and the intermediate element form an inseparable unit. This inseparability is even obtained before assembly if the aforementioned stop limiting the axial movement of the intermediate element is also used.

[0019] In one embodiment, the axial retaining means comprise a stop secured to the body, retaining the intermediate element on the side opposite the part to be tightened. The stop is preferably carried by a cap fixed to the body, preferably by crimping. The cap may have a central opening, for example to allow the passage of the free end of a screw screwing into the threaded member when the latter is a nut.

[0020] In another embodiment, the housings are closed at their two axial ends so as to retain the intermediate member in the body against movements in both directions, parallel to the axis.

[0021] Other features and advantages of the invention will emerge from the description below, and / or from the attached drawings, to which: ■ the Figure 1 is an exploded perspective view of the retaining device according to a first embodiment of the invention; ■ the Figure 2 is a view of the device of the Figure 1 in the assembled state; ■ the Figure 3 is an axial sectional view of the body installed on a part, the left half-view also showing the assembly in service; ■ the Figure 4 is a top view, in section, showing the body in the right half-view, assembled with the intermediate element in the left half-view, the upper half of which further shows the nut as a threaded member and the screw screwed into the nut; and ■ the Figure 5 is a perspective view, with tear-away and partial section, of the retaining device according to a second embodiment.

[0022] In the example shown in figures 1 to 4, the retaining device serves to prevent the rotation of a nut 2 around its axis 3, in particular while a screw 4 is being screwed, unscrewed or is in the screwed state in this nut. The screwing has the effect of tightening together several parts, here two parts 6 and 7 against each other in the axial direction between the nut 2 and the head 8 of the screw 4. The part 6 adjacent to the nut is called the “part to be tightened”, it is for example an aircraft engine casing, the other part 7, adjacent to the screw head 8, called for example an “inserted part”, is for example a component to be fixed on the engine casing, typically by several fastening systems each comprising a nut 2, a screw 4 and a retaining device 1. The screw 4 passes through a bore 9 of the part to be tightened 6 and a bore 11 of the inserted part 7.Due to manufacturing tolerances it is not always possible to perfectly align the bores 9 and 11 along the same screwing axis 3, so that if the nut 2 were fixed to the part to be tightened 6, screwing could be impossible. Furthermore, in the more particularly targeted applications the face of the part to be tightened 6 adjacent to the nut 2 is difficult or completely inaccessible. The retaining device 1 has the dual function of preventing the nut 2 from rotating while allowing the nut 2 a certain margin of radial displacement so that the nut 2 can align axially with the screw 4 even if the two bores 9, 11 have a certain misalignment, the diameter of at least one of the bores having a slight oversize, suitable in view of the aforementioned tolerances.

[0023] The nut 2 has on its radially outer periphery a connecting conformation 22 with respect to rotations around the screwing axis 3. In the example shown, the connecting conformation is a standard conformation, more particularly a groove.

[0024] The retaining device 1 comprises a body 12 equipped with means for fixing to the part to be clamped 6. In one embodiment, the fixing means are two ears 13 extending radially outwards from the body 12 itself and intended to be fixed to the part to be clamped 6 by rivets 14 ( Figure 3 ) which are only sketched. The position of the ears 13 around the axis 3 may vary from one embodiment to another depending on the space available on the surface of the part 6. The two ears 13 could, for example, be radially opposite each other.

[0025] In the example shown, the body 12 has the shape of a cylindrical barrel open at its two axial ends, extending in service along the screwing axis 3 or along an axis parallel to the axis 3 but slightly offset laterally relative to the axis 3.

[0026] The body 12 is equipped with an anti-rotation conformation 16 capable of preventing rotation of the threaded member, here the nut 2, relative to the part 6 while allowing radial play between the threaded member 2 and the body 12. In an embodiment where the body 12 has a cylindrical shaft, the anti-rotation conformation is an alternation of crenellations 18 and bosses 20 formed on the edge 17 of the shaft facing away from the part to be tightened 6.

[0027] Instead of a direct interaction between the body 12 and the nut 2, the retaining device further comprises an intermediate element 19 comprising: ■ a conformation 23 complementary to the connecting conformation 22 of the nut 2, capable of producing a coupling opposing a relative rotation between the threaded member (nut 2) and the intermediate element 19, and ■ coupling means 24 capable of producing with the anti-rotation conformation 16 of the body 12 a coupling with radial play opposing a relative rotation between the intermediate element 19 and the body 12.

[0028] Thus, the threaded member (nut 2) is prevented from rotating relative to the body 12 around an axis parallel to or coincident with the axis 3. The body 12 itself being fixed to the part to be tightened 6, the threaded member (nut 2) is prevented from rotating around such an axis relative to the part to be tightened 6. However, thanks to the radial play of the intermediate element 19 relative to the body 12, the threaded member 2 has freedom of radial movement relative to the part to be tightened 6 to self-center itself on the screw 4. The screw is itself positioned by the bores 9 and 11 which, contrary to what is shown schematically, are generally slightly offset laterally relative to each other, in particular due to manufacturing tolerances.

[0029] Preferably, the coupling opposing relative rotation between the threaded member 2 and the intermediate element 19 is substantially without radial play and without rotational play around the axis 1. Thus, the grip between the threaded member 2 and the intermediate element 19 is perfectly consistent with what is provided for the application of the retaining torque to the nut 2 during screwing. The radial play is fully ensured further from the axis, therefore under lower forces, between the intermediate element 19 and the body 12.

[0030] In the example chosen here of a threaded member having a groove as a connecting conformation, the complementary conformation is preferably a grooved bore complementary to the groove of the threaded member (nut 2).

[0031] In particular, but not limited to, in the example above, the intermediate element 19 is preferably a ring. Preferably, the ring surrounds the threaded member (nut 2), and is surrounded by a part of the body 12, in particular when the latter is made in the shape of a barrel as indicated previously.

[0032] When the intermediate element is a ring, the means for coupling the intermediate element 19 with the body 12 may be formed on a radially outer surface 27 of the ring, which radially outer surface has said radial clearance J ( Figure 4 ) with a radially inner surface 26 of the body.

[0033] In certain embodiments such as that shown, the coupling means between the intermediate element 19 and the body 12 comprise radial teeth 28 which project into housings, here the crenellations 18, of a cylindrical wall which therefore in this example belongs to the body 12, the radial teeth being carried here by the intermediate element 19.

[0034] Even when the intermediate element 19 is maximally offset in the body 12, no tooth 28 can disengage from its housing. In the example shown, this is achieved by a radial length of the teeth 28 which is greater than the diametrical clearance 2J (double the radial clearance J).

[0035] Preferably, one face of the housings, here the bottom of the notches 18, forms a stop limiting the axial movement of the intermediate element 19 towards the part to be clamped 6. The axial movement of the intermediate element 19 is more precisely, in the example shown, limited by the support of the teeth 28 against the bottom of the notches 18.

[0036] Preferably, the coupling with radial clearance J between the intermediate element 19 and the body 12 also has a rotational clearance R ( Figure 4 ) on either side of an average relative angular position around the axis 1. This rotational play facilitates the radial displacement of the intermediate element 19 relative to the body 12.

[0037] In the example shown, the grooves of the nut 2 and of the ring 19 are more numerous, in particular twice as numerous, than the teeth 28 and the notches 18.

[0038] The drawings are typically on an enlarged scale, for example on a scale of 2.5. In such a case, a radial clearance of the order of 0.5 mm (therefore 1 mm on the diameter) between the intermediate element 19 and the body 12 is appropriate in certain applications. However, the invention is not limited to particular dimensions.

[0039] Preferably, the device comprises axial retaining means retaining the intermediate element captive in the body. In one example, these means comprise a stop 29 made integral with the body 12, and retaining the intermediate element 19 on the side opposite the part to be clamped 6. The intermediate element 19 has a reduced axial play but sufficient to allow its radial displacement permitted by the radial play discussed previously, relative to the body 12.

[0040] The stop may be carried by a cap 31 fixed to the body. In the example shown, this fixing is achieved by crimping its lower edge 32 behind an oblique shoulder 33 of the body. Figure 1 , the lower edge of the cap is shown in its conical shape after crimping, this edge being cylindrical before crimping.

[0041] The cap 31 typically has a central opening 34, surrounded by a collar forming the stop 29.

[0042] The retaining device can be made from Inconel alloy, for example.

[0043] The embodiment shown in the Figure 5 will only be described for its differences with that of the Figures 1 to 4 and its elements similar to those of the embodiment of the Figures 1 to 4 will be assigned a numerical reference increased by 50.

[0044] The stop 79 is made in one piece with the body 62, and is therefore an integral part of the body 62. For this, in one embodiment, the body 62 and the ring 69 are made jointly by 3D printing, the ring 69 being directly obtained captive in the body 62. In one embodiment, the housings 68 are windows closed axially, on the side opposite the part to be tightened, by the stop 79, instead of being, as in the example of Figures 1 to 4 , slots open on the side opposite the part, then closed by the cap 31, the installation of which requires additional manufacturing operations.

[0045] The ring 69 is axially captive of the body 62 because the teeth 78 are interposed between the stop 79 and the face of the windows which faces this stop.

[0046] The teeth 78, similar to the teeth 28 of the previous embodiment, are engaged in the windows 68 with sufficient freedom of movement to ensure between the ring 69 and the body 62 the radial clearance proposed by the invention. However, still as in the previous embodiment, the teeth are sufficiently long radially so as not to be able to disengage from the windows 68 but in the event of maximum decentering of the ring 69 in the body 62.

[0047] A structure similar to that of the Figure 5 can also be produced using the MIM (Metal Injection Molding) process using metal powder agglomerated by sintering, as offered in particular by the company Alliance MIM, Zi Foulottière, 22 rue de l'Europe, 25410 Saint-Vit, France.

[0048] Of course, the invention is not limited to the example described and shown. A nut with a standard connection conformation could be a nut other than a grooved nut, for example a hexagon nut, in which case the intermediate element could have a hexagon socket or a twelve-sided socket as a complementary conformation. The cap could be replaced by crimping a deformable part of the body, or by an elastic stop ring, such as a circlip, inserted into the bore of the body. If a cap is used, it could be fixed not by crimping, but for example by welding, in particular by spots, or by shrink fitting. The body such as 12 could be crimped or snapped onto the part such as 6, in which case the ears such as 13 would not necessarily be present.

Claims

1. - Retaining device for a threaded member, in particular for a nut (2), for retaining said threaded member while it undergoes an operation of screwing or unscrewing along a screw axis, or while it is in the screwed-home state, the threaded member (2) comprising a linking shape with respect to the rotations about the axis and supported at least indirectly on a part (6) to be tightened by screwing action, the device comprising a body (12, 62) intended to be fastened to the part (6) and equipped with an anti-rotation shape (16) capable of preventing the rotation of the threaded member (2) with respect to the part (6) while allowing radial clearance (J) between the threaded member (2) and the body (12, 62), wherein the device also comprises an intermediate element (19, 69) comprising: - a shape (23) complementary to the linking shape (22), capable of producing a coupling opposing a relative rotation between the threaded member (2) and the intermediate element (19, 69), and characterized in that the intermediate element also comprises: - coupling means (24, 28, 78) capable of producing, with the anti-rotation shape (16) of the body (12, 62) a coupling with radial clearance opposing a relative rotation between the intermediate element (19, 69) and the body (12, 62), the radial clearance allowing the threaded member (2) to have freedom of positioning with respect to the part (6) during screwing.

2. - Retaining device according to claim 1, characterized in that the coupling opposing a relative rotation between the threaded member (2) and the intermediate element (19, 69) is substantially without radial clearance.

3. - Retaining device according to claim 1 or 2, characterized in that the coupling opposing a relative rotation between the threaded member (2) and the intermediate element (19, 69) is substantially without rotational clearance about the axis (3).

4. - Retaining device according to any one of claims 1 to 3, characterized in that the coupling with radial clearance (J) also has rotational clearance (R) about the axis (3).

5. - Retaining device according to any one of claims 1 to 4, characterized in that the complementary shape (23) is designed to ensure said coupling with a linking shape (22) of a standard nut (2).

6. - Retaining device according to one of claims 1 to 5, characterized in that the complementary shape (23) is a splined bore.

7. - Retaining device according to any one of claims 1 to 6, characterized in that the intermediate element (19, 69) is a ring, in particular a ring substantially closed about the axis (3).

8. - Retaining device according to claim 7, characterized in that the ring (19, 69) surrounds the threaded member (2) and is surrounded by at least a part of the body (12, 62).

9. - Retaining device according to claim 7 or 8, characterized in that the coupling means (24, 28, 78) are formed on a radially outer surface (27) of the ring (19, 69), said radially outer surface having said radial clearance (J) with a radially inner surface (26) of the body (12, 62).

10. - Retaining device according to any one of claims 1 to 9, characterized in that the coupling means comprise radial teeth (28, 78) projecting into recesses (18, 68) in a cylindrical wall.

11. - Retaining device according to claim 10, characterized in that the teeth (28, 78) belong to the intermediate element (19, 69).

12. - Retaining device according to claim 11, characterized in that the recesses are notches (18) formed in an edge of the cylindrical wall, said edge being turned away from the part (6).

13. - Retaining device according to any one of claims 10 to 12, characterized in that a face of the recesses (18) forms a stop limiting the axial movement of the intermediate element (19) towards the part to be tightened (6).

14. - Retaining device according to claim 11, characterized in that the recesses (78) are closed at the two axial ends thereof so as to retain the intermediate element (69) in the body (62) against movements in both directions, axially.

15. - Retaining device according to any one of claims 1 to 13, characterized in that it comprises axial retaining means (29, 79) retaining the intermediate element (19, 69) captive in the body (12, 62).

16. - Retaining device according to claim 15, characterized in that the axial retaining means comprise a stop (29, 79) firmly fixed to the body (12, 62), retaining the intermediate element (19, 69) on the opposite side to the part to be tightened (6).

17. - Retaining device according to claim 15, characterized in that the stop (29) is borne by a cap (31) fastened to the body (12), preferably by crimping.

18. - Retaining device according to claim 16, characterized in that the cap (31) comprises a central opening (34).

19. - Retaining device according to one of claims 1 to 17, characterized in that the intermediate element (19, 69) is essentially not capable of deformation, in particular is inelastic.