SEALING NUT

Abstract

The invention relates to a sealing nut comprising a nut (101) and a deformable sealing ring (130), the nut having an annular body, a base (104) having a chamber (110), a bore (120) formed in the base, the bore comprising an annular bottom wall (124) having a width extending between a first inner radius (r1) and a second inner radius (r1), the sealing ring comprising an annular body and an end face adapted to bear against the bottom wall, the end face having a width extending between an inner radius (r2) and an outer radius (r2). The ratio of the width (l1) of the bottom wall of the bore to the width (l2) of the end face of the ring is between 20% and 45%.<!--endfragment-->

Description

[0001] The present invention generally relates to sealed nuts, and more particularly to nuts comprising a sealing ring.

[0002] Sealed nuts (see for example document EP 2 682 615 A) are used in the aeronautical industry to assemble structural elements through which a screw or similar component comprising an external thread is inserted, said elements requiring a sealed assembly to fluids and vapors.

[0003] When it is necessary to assemble structural elements which work mainly in shear, in traction or in a combination of the two, screws having a smooth, cylindrical or conical barrel part are used, having a length allowing them to completely cross a range of thickness of the elements to be assembled. The length of the barrel makes it possible to assemble thicknesses varying between a minimum thickness (“grip min”) and a maximum thickness (“grip max”), the difference generally being 1.6 mm (1 / 16" inch in system). imperial). The thickness range is called “grip capacity” in English terminology.

[0004] The cylindrical or conical portion of the barrel of the screw used therefore exceeds the length of this range when the screw passes through elements having the minimum thickness that the screw can assemble. In contrast, the cylindrical or conical portion does not protrude when the screw passes through elements having the maximum thickness that the screw can assemble.

[0005] Furthermore, shear screws generally comprise a barrel having an outer diameter greater than the maximum outer diameter of the thread.

[0006] To assemble the structural elements, it is therefore necessary to use in conjunction with a shear or traction screw a nut 10 shown in figure 1 comprising a space 12 made in the support surface 14 intended to come into contact with a surface S of one of the elements to be clamped. This space, created between the bearing surface 14 and the first thread of the nut, is conventionally called a chamber, and can have various shapes and dimensions. In the example given above, the chamber can accommodate up to 1.6 mm of the screw barrel which can protrude from the structure having a minimum thickness.

[0007] In some cases, these nuts must also be waterproof. Such a nut is shown in figure 2 . A deformable sealing ring 16, generally made of Teflon®, is arranged in a bore 18, made in the chamber 12. The ring 16 has an internal diameter greater than the diameter of the tapping and the diameter of the smooth barrel so as not to interfere with the opinion. The ring is mounted in interference in the bore 18 to ensure that it holds in the nut during transport.

[0008] The sealing ring has a conical shape which generally protrudes beyond the bearing surface of the nut. Thus, when the nut is tightened against a structural element, the sealing ring is both axially compressed and radially deformed towards the inside of the chamber and against the barrel and / or the threads of the screw, thus forming a waterproof seal.

[0009] The applicant has noticed that in certain assembly configurations comprising a screw 20 and a sealed nut 10 represented in Figure 3 , the ring 16 did not flow entirely in the chamber 12 but flowed in part 22 between the bearing surface 14 of the nut and the surface S of the element to be tightened. This can occur when the screw is installed in a structure with a minimum thickness and the entire barrel length extending beyond the structure is in the chamber.

[0010] Such creep must be completely prevented, since it seriously compromises the mechanical strength of the screw / nut assembly. Indeed, the presence of a lubricating material between the bearing surface of the nut and the surface of the element to be tightened influences the coefficient of friction between these surfaces. When the coefficient of friction decreases, the tension of the screw increases above the threshold allowable by the screw, which can cause the screw to break.

[0011] The present invention relates to a sealed nut which prevents creep of the sealing ring between the nut and the structure, regardless of the assembly configuration, without reducing the strength, capacity or structural integrity of the assembly or components of the assembly.

[0012] More precisely, the sealed nut comprises a nut and a deformable sealing ring, the nut comprising an annular body extending in a direction of an axis of revolution, a base comprising a chamber and a bore made in the base, the bore comprising an annular bottom wall having a width extending between a first inner radius and a second radius. The sealing ring comprises an annular body and an end face capable of resting against the bottom wall, the end face having a width extending between an interior radius and an exterior radius. The sealed nut is such that the ratio of the width of the bottom wall of the bore and the length of the end face of the ring is between 20 and 45%.

[0013] Such a configuration allows the sealing ring to always be guided towards the interior of the chamber, regardless of the configuration of the assembly, without creeping beyond the chamber or out of the bore.

[0014] Furthermore, the nut according to the invention may include one or more of the following characteristics: The sealed nut comprises a chamfer between the bottom wall of the bore and a wall of the chamber of the nut, the chamfer makes an angle with the axis of revolution of between 45° to 60°, the bottom wall and the end face have complementary shapes, the bottom wall and the end face each comprise a portion arranged substantially perpendicular to the axis of revolution, a wall of the bore comprises a groove extending radially to the 'inside the base, and an outer wall of the ring comprises a projection of complementary shape to that of the groove, the ring has an outer radius greater than an inner radius of the bore, the ratio between the outer radius of the ring and the interior radius of the bore is between 1.010 and 1.016, the volume of the ring compared to the available volume of the nut is between 70% and 85%, said available volume being the smallest hollow volume inside of the nut between a bearing surface and a first thread of the nut, at one end of the tapping located on the side of the base, once a screw placed in the nut, when the screw occupies a maximum volume.

[0015] The invention will be better understood on reading the description which follows, in connection with the drawings illustrating by way of example embodiments of the invention. There figure 1 (already described) is a section of a chamber nut of the prior art, La figure 2 (already described) is a section of a sealed nut of the prior art, The Figure 3 (already described) is a partial sectional view of an assembly comprising a screw and a sealed nut of the prior art, The figure 4 is a side view of a sealed nut according to one embodiment of the invention, The Figure 5 is an exploded section of the waterproof nut of the figure 4 , There Figure 6 is a section of a sealed nut according to a second embodiment, The Figure 7 a partial sectional view of an assembly comprising a screw and a sealed nut according to one embodiment of the invention, figure 8 is a section of a sealed nut according to a third embodiment.

[0016] A sealed nut 100, shown in figures 4 and 5 , comprises a nut 101 and a sealing ring 130. The nut 101 extends in the direction of an axis of revolution A of said nut and comprises a key socket 102 and a base 104. The key socket 102 is here a hexagon. The base, with an enlarged external diameter compared to the largest dimension of the hexagon, has a frustoconical upper surface 106 which has six recessed sides relative to this frustoconical surface, like those described in patent application FR 2937386 in name of the plaintiff. Each recessed pan is aligned with a flat surface of the hex key socket.

[0017] There Figure 5shows more precisely that the base 104 comprises a bearing surface 108 opposite the frustoconical surface, and a chamber 110, having a cylindrical wall 112 and an end wall 114 connecting the cylindrical wall 112 and the first thread of the tapping 116 In this example, the end wall 114 is a frustoconical surface.

[0018] The tapping 116 extends on the interior surface of the nut, between the end of the end wall 114 and the upper end 118 of the nut, opposite the bearing surface 108.

[0019] The base 104 also comprises a cylindrical bore 120 made in the chamber 110, opening onto the bearing surface 108, and having a first interior radius R1 greater than the radius of the chamber 110. The bore 120 comprises a cylindrical wall 122 and a flat bottom wall 124. In this example, the bottom wall is substantially perpendicular to the axis A. By substantially we mean that the angle can vary by a few degrees.

[0020] A chamfer 126 connects the bottom wall 124 of the bore 120 to the cylindrical wall 112 of the chamber 110.

[0021] The bottom wall 124 is an annular surface A1 extending between the first interior radius R1 of the cylindrical wall 122, and a second interior radius r1, defined by the distance between the axis A and the distance at which the chamfer 126 cuts the end wall 124. The annular surface A1 has the value A 1 = R 1 2 − r 1 2 . π

[0022] In two dimensions, the bottom wall 124 has a width L1 defined by the difference in radii (R1-r1).

[0023] The bore 120 is intended to receive a sealing ring 130. A chamfer 128 is made on the emerging periphery of the bore in order to guide the insertion of the ring into the bore.

[0024] The ring 130 is an annular crown with axis of revolution A, comprising an upper end face 132 intended to rest against the bottom wall 124 of the bore 120. Preferably, the upper end face comprises at least one surface of complementary shape to the bottom wall 124 of the nut. In the example illustrated in Figure 3 , the upper end surface 132 is entirely flat and substantially perpendicular to the axis A.

[0025] The sealing ring 130 has a bore 134 whose diameter is equal to twice the interior radius r2 indicated on the Figure 3 , is greater than the diameter of the screw barrel so as not to interfere with the threads and the barrel of the screw onto which the nut will be screwed. The ring may come into contact with the barrel of the screw if a screw of larger diameter called "oversize" is used in a maintenance operation in place of a screw of nominal diameter, but the function of the ring is not to slow down the screw and / or limit the lockability of the nut.

[0026] A lower end face 136 of the sealing ring opposite the upper end face 132 is frustoconical, the wall of the bore 134 being longer in the axial direction A than the outer wall 138 intended to come into contact with the cylindrical wall 122 of the bore.

[0027] The outer radius R2 of the ring 130 is greater than the first inner radius R1 of the bore, so that the ring must be inserted by force into the bore. The interference created allows the ring to be held in the bore, particularly during transport, storage and during nut installation. Preferably, the interference ratio between the outer radius R2 of the ring and the inner radius R1 of the bore is between 1.010 and 1.016. The larger the nominal diameter - diameter measured at the bottom of the threads - of the nut, the less the interference ratio.

[0028] The bearing surface 132 of the ring is also an annular surface A2, extending between the outer radius R2 and the inner radius r2, having the value A 2 = R 2 2 − r 2 2 . π

[0029] In two dimensions, the bearing surface 132 of the ring has a width L2 defined by the difference in radii (R2-r2).

[0030] To avoid any untimely creep of the ring, the ratio between the support widths L1 and L2 must be greater than or equal to 20%, and less than or equal to 45%, i.e.: 20 % ≤ L 1 / L 2 ≤ 45 %

[0031] This relationship defines the contact width ratio between the upper end face 132 of the ring 130 and the bottom wall 124 of the nut 101 in a plane substantially perpendicular to the axis A.

[0032] If the contact width ratio between the ring and the nut is less than 20%, the ring is more likely to creep during its installation in the chamber 110 into the threads of the tapping 116: the creep of the ring during its installation insertion into the nut is not controlled. If material from the ring is in the threads, the coefficient of friction between the threads of the screw and the nut will decrease, the tension in the screw may rise well above the allowable limit, which may cause breakage of the screw.

[0033] If the contact width ratio between the ring and the nut is greater than 45%, then the ring 130 is more likely to creep between the bearing surface 108 of the nut and the surface of the structure when the nut 130 is installed on a screw. There is also a risk of inducing uncontrolled tension in the screw, due to the reduction in the coefficient of friction between the surfaces in contact.

[0034] Table 1 below gives examples by diameter of the relationships between the support widths L1 and L2 of a range of nuts of different diameters tested by the applicant: Table 1 Nominal nut Ø L1 (mm) L2 (mm) Ratio 5 0,22 1,06 21% 6 0,24 1,09 22% 7 0,31 1,10 28% 8 0,35 0,96 36% 10 0,37 1,11 33% 12 0,6 1,48 41% 14 0,63 1,66 38% 16 0,41 1,96 21%

[0035] As described previously, a chamfer 126 connects the bottom wall 124 of the bore 120 to the cylindrical wall 112 of the chamber 110. The chamfer 126 here makes it possible to guide the material towards the chamber 110. It increases the space available in the chamber without removing too much material from the base in order to guarantee the integrity of the base when it works in compression.

[0036] The chamfer 126 can have different angles α measured relative to the axis of revolution A depending on the nominal diameter of the nut. Table 2 indicates by nut diameter the preferred angle of chamfer 126. Table 2 Nominal nut Ø angle α (°) 5 60 6 45 7 45 8 45 10 45 12 45 14 45 16 60

[0037] In certain configurations, the chamber 110 can be completely conical: as shown in Figure 6 , the end wall 114 of the chamber and the chamfer 126 are combined in one and the same wall having one and the same angle. In the example of the Figure 6 , the angle α is 60° with the axis of revolution A.

[0038] The applicant carried out several assembly tests, and simulated by finite elements in two dimensions these same assemblies, each comprising a screw whose barrel diameter is at the maximum of the tolerance, a structure having a minimum thickness, a nut whose volume of the chamber is at the minimum of the tolerance, and a ring whose all dimensions are at the maximum of the tolerance.

[0039] In the first assembly of the prior art, represented in Figure 3 , the nut is a nut of the prior art, with a contact width ratio of between 78% and 96%. In a second assembly, represented in Figure 7 , the nut includes a contact width ratio between 20% and 45%. The screws 20 are identical in the two assemblies comprising the same structural thicknesses.

[0040] As indicated previously, in the assembly of the Figure 3 , the material of the ring 16 does not flow entirely in the chamber 12 but flows in part 22 between the bearing surface 14 of the nut and the surface S of the element to be tightened.

[0041] In the assembly of the Figure 7 including the nut of the Figure 5 , no material from the ring has leaked between the nut and the structure, and there is no space between the wall of the chamber and the barrel of the screw. The seal is therefore better, and the risk of exceeding the UTS (“Ultimate Tensile Strength”) of the screw is eliminated.

[0042] Preferably, a volume of the ring 130 constituted by the volume of the material of the ring 130, compared to the available volume of the nut 101, is in a range between 70% and 85%. The available volume considered here is the smallest hollow volume inside the nut 101 between the bearing surface 108 and the first thread of the tapping 116 once the screw placed in the nut, when the screw occupies a volume maximum. By convention, the maximum volume of the screw in the available space is calculated as a height of the chamber 110 between the bearing surface 108 and the first thread of the tapping 116, on the side of said chamber, multiplied by a surface of a section, perpendicular to the axis of revolution A, of the smooth barrel of the screw. Below 70%, the volume of the ring is too low compared to the volume of the chamber, and the nut may no longer be tight. Above 85%, the ring risks creeping beyond the chamber towards the threads or under the base and compromising the integrity of the nut during installation.

[0043] The nut is preferably made of titanium alloy, and the ring is for example made of PTFE (also sold under the Teflon™ brand, from the company Dupont de Nemours), in order to keep the nut light. Of course, the nut and the ring can be made from another material if weight is not a major criterion.

[0044] The key grip comprises in a known manner a braking means, such as an elliptical deformation or a three-point deformation of the tapping, produced on an exterior surface of the nut close to the upper end 118. If the nut is made of alloy of titanium, braking will preferably be carried out according to the process described in patent FR2947597 in the name of the applicant.

[0045] The invention is not limited to the sole example described above. Thus, the nut can include a frustoconical base without hollow relative to the frustoconical upper surface.

[0046] The wall of the bore 120 can be conical, with an angle β of between 2° and 5° and opening from the bearing surface 108 towards the bottom wall 124, between the wall 122 and the axis A of the nut 101, in order to improve the retention of the ring 130 in the bore, particularly at low temperatures ( figure 8 ). The ring 130 itself has the same angle β between 2° and 5°, between the outer wall 138 and the axis A. Beyond an angle of 5°, the ring can no longer be inserted into the 120 conical bore. Below 2°, the angle difference is not sufficient to improve the retention of the ring in relation to a cylindrical wall. The interference ratio between an exterior radius R2 of the ring and a radius R1 of the bore, said rays being positioned at the same axial distance from the bottom wall 124 and the upper end surface 132 respectively, is also between 1.010 and 1.016.

[0047] A surface other than the chamfer 126 may be adopted to connect the end wall 124 of the bore and the cylindrical wall 112 of the chamber, such as for example a radiated or multi-radiated surface.

[0048] Likewise, the bottom wall of the chamber may be conical, or may comprise from the cylindrical wall of the bore a conical portion then a portion perpendicular to the axis of revolution A. In these cases, the end face of the ring which is in contact with the bottom wall will be respectively conical, or will include a conical portion complementary to that of the bottom wall, and a portion perpendicular to the axis of revolution. The measurements of the widths L1 and L2 can either be carried out in the angular direction, or projected onto a direction substantially perpendicular to the axis of revolution. The two surfaces having the same angle with respect to the axis of revolution, the ratio of the two projected widths will be equal to the ratio of the widths measured in the angular direction.

[0049] In another variant, the bore may comprise a groove extending radially inside the wall 122 of the bore - whether the wall is cylindrical or conical -, with a radius greater than the radius R1 of the bore. The ring may comprise a projection extending radially outside the wall 138, of shapes and dimensions complementary to that of the groove, that is to say allowing the engagement of said projection in said groove. The groove / protrusion assembly improves the retention of the ring in the nut. In this case, the additional dimensions of the grooves and projections are not taken into account for the measurements of the lengths L1 and L2. The grooves and projections may be circular, or extend only partially over the periphery of the bore and the ring.

Claims

1. Sealing nut (100) comprising a nut (101) and a deformable sealing ring (130), the nut comprising an annular body extending in a direction of an axis of revolution (A), a base (104) comprising a chamber (110) and a bore (120) made in said base, with the bore (120) comprising an annular bottom wall (124) having a width extending between a first inner radius (R1) and a second inner radius (rl), with the sealing ring (130) comprising an annular body and an upper end face (132) able to rest against the bottom wall (124) of the bore, said upper end face having a width extending between an inner radius (r2) and an outer radius (R2), characterised in that the ratio of the width (L1) of the bottom wall (124) of the bore and the width (L2) of the upper end face (132) of the ring is between 20% and 45%.

2. Sealing nut according to claim 1, wherein the nut (100) comprises a chamfer (126) between the bottom wall (124) of the bore and a wall of the chamber (110) of said nut.

3. Sealing nut according to claim 2, wherein the chamfer (126) forms an angle (α) with the axis of revolution (A) between 45° à 60°.

4. Sealing nut according to one of claims 1 to 3, such that the bottom wall (124) of the bore and the upper end face (132) of the ring have complementary shapes.

5. Sealing nut according to claim 4, such that the bottom wall (124) and the upper end face (132) each comprise a portion arranged substantially perpendicular to the axis of revolution (A).

6. Sealing nut according to one of claims 1 to 5, such that the ring (130) has an outer radius (R2) greater than a first inner radius (R1) of the bore.

7. Sealing nut according to claim 6 such that a ratio between the outer radius (R2) of the ring and the first inner radius (R1) of the bore is between 1.010 and 1.016.

8. Sealing nut according to one of claims 1 to 7, such that a wall (122) of the bore (120) comprises a groove extending radially inside the base (104), and an outer wall (138) of the ring (130) comprises a protrusion with a shape complementary to that of said groove.

9. Sealing nut according to one of claims 1 to 8, such that a volume of the ring (130) is between 70% and 85% of an available volume of the nut (101), said available volume being the smallest hollow volume inside the nut between a bearing surface (108) and a first thread of said nut, at an end of a threading (116) located on the side of the base (104), once the screw is placed in the nut, when the screw occupies a maximum volume.