FR3101826A1 - PART FOR FIXING SYSTEM AND FIXING SYSTEM INCLUDING THIS PART - Google Patents

Abstract

Part (1) intended to cooperate with a barrel (4) to form a fixing system between two elements (2-3) comprising: - a body (6) comprising a flat base (9) and a cavity (7) for housing the barrel (4); - a retention member comprising several retention tabs (8), extending from the body (6) towards the interior of the cavity (7), comprising a main flexible part (19) forming a spring exerting a restoring force towards a central axis (X) on the distal part (20) of the leg when the latter is spaced from the axis; characterized in that the distal portion (20) of each retention tab (8) forms a blade arranged to bite into a material less hard than the material of the retention tab (8) and a radially inner edge (21) of the blade follows a helix portion winding around the central axis (X) with a given inclination with respect to a plane parallel to the base (9). Figure for abstract: Figure 1

Description

PART FOR FASTENING SYSTEM AND FASTENING SYSTEM COMPRISING THIS PART

Technical field of the invention

The present invention relates to the production of a removable fastening system for assembling elements together, in particular elements at least partially in the form of panels, in particular vehicle body elements, and more particularly a removable part cooperating with a pawn to form such a system.

Technical background

The known fixing devices for fixing an element to a door panel, for example, such as the riveting of a pin or the installation of a star washer ( starlock according to English terminology) on a shaft emerging from the panel, are easy to implement and inexpensive. In particular when the door panel is made of plastic material, it is easy to place the fixing barrels at the desired locations during the manufacture of said panel. During assembly, it suffices to slip a suitable fixing lug of the element to be fixed around the fixing shaft, then to carry out the riveting operation or to apply a star washer.

Unfortunately, in this case, the dismantling of the element from the door panel cannot be carried out easily without damage and or loss of the device, which leads to the scrapping of the complete panel.

In addition, controlling the quality of the riveting is delicate and has an impact on the resistance to side impacts, etc. In the case of repair, the riveting is replaced by a screw which leads to a high cost.

The object of the present invention is to provide a simple and reliable device for fixing elements on shafts emerging from a panel, for example a vehicle door panel, for example automobile, allowing easy disassembly and reassembly and to a low cost. The fixing must guarantee the connection of the element on the panel and guarantee the function in all the stresses of the said panel, for example the opening and closing of the door or the vibrations during the rolling of the vehicle. The disassembly of the fixing device must be carried out without damaging the barrel and thus allow reassembly.

The invention thus relates to a part intended to cooperate with a shaft emerging from a substantially flat surface of a first element to form a fastening system for a second element comprising:

- a body comprising a flat base and a cavity opening through said base, said cavity leaving a cylindrical passage around a central axis perpendicular to said face, so as to accommodate the barrel;

- a retention member comprising several similar retention tabs, at least two, extending from the body towards the interior of the cavity and regularly distributed in azimuth around the central axis, said retention tabs comprising a flexible main part one radially outer end of which is fixed relative to the body and one radially inner end carries a distal part intended to press on the shaft, said main part being inclined radially in the axial direction opposite to the base and forming a spring exerting a restoring force towards the central axis on the distal part when the latter is moved away from the axis.

The part is remarkable in that the distal part of each retention lug forms a blade arranged to bite into a material less hard than the material of the retention lug and that a radially inner edge of the blade follows a portion of helix winding around the central axis with a given inclination with respect to a plane parallel to the base, the characteristics of the helix being the same for all the retaining legs.

The characteristics of the main part of the retaining lugs of the retaining member allow, as for a star washer, to slide a barrel of suitable diameter into the cavity along the axis by the base of the body, then to block a sliding in the opposite direction of the shaft by pressing the distal part against the shaft all the more strongly as a force in this opposite direction is exerted on the shaft. It is thus possible to fix the second element on the first by installing a flat part of the latter around the barrel and then by pressing it towards the surface of the first element by pressing on the part threaded beforehand around the barrel.

In addition, the existence of the blades at the end of the retention lugs and their shape create a groove forming a thread if the part is rotated around the barrel, the material of the barrel being softer than that of the retention lugs. This thread allows the part to be removed by unscrewing it around the barrel. Once removed, the part leaves a thread on the barrel which does not prevent its reuse with the same part, for example to fix a second element which will have needed to be replaced. Indeed, the part can be slid again on the barrel regardless of the position of the blades with respect to the thread grooves. Thus, it is possible to use as the first element, for example, a door panel with fixing shafts coming from the material of the panel without having to scrap the latter when changing a second element which is fixed there.

In addition, the formation of a thread allows the part to be screwed onto the barrel after having pressed it against the wall of the second element. This increases the pressure exerted between the two elements by the connection system. This has advantages in terms of bond strength, impact resistance and reduced parasitic vibration.

Advantageously, the winding angle of the helix around the axis is small, preferably between 5 degrees and 8 degrees with respect to the plane of the base of the body. This corresponds to a thread allowing to control the degree of screwing and to maintain the part in place on the barrel. Also advantageously, the propeller rotates clockwise looking at the part from the base, which corresponds to the usual screwing direction.

At least two opposing retention tabs are required to enclose the barrel and ensure a grip. Advantageously, three or more retention lugs, regularly distributed, allow natural centering of the barrel between the retention lugs.

Preferably, the blade of the distal part is formed by a thin plate inclined radially towards the base of the body, preferably at an angle at least equal to 5 degrees with a plane parallel to the base of the body.

The inclination of the blade favors the holding of the barrel by the radially internal edge with respect to an extraction force along the axis.

Even more preferably, a thin plate forms the main part of each retention tab and is bent at approximately 90 degrees at its free end to form the distal part.

Advantageously, the radially inner edge of the blade, intended to be in contact with the barrel, is cut by a transverse surface cut in the thickness of the blade, which is inclined towards the base of the body, preferably making a lower angle or equal to 45 degrees with a plane parallel to the base of the body.

The slope of the cross-sectional surface on the radially inner edge of the blade allows the material of the barrel to be notched to form the thread. In addition, the existence of a contact surface on the edge of the blade makes it possible to trace a clean groove forming a thread with good retention surfaces in the axial direction. The less the difference in hardness between the material of the retention legs and that of the barrel, the more it is preferable to increase the inclination with respect to the plane of the base.

Advantageously, internal walls of the body in the cavity form, for each retention lug, an abutment limiting the spacing of the distal part in the radial direction.

Preferably, when the retention tab is in the abutment position against the wall, the blade of the distal part is not inclined in the direction opposite to the base. This avoids accidental reversals when inserting the part around the barrel, which could alter the holding function, or even damage the part.

Preferably, the retention tabs are metallic.

The metal provides both greater hardness than most plastic materials that can be used for panels in a vehicle and good elasticity for the main part of the retaining tab.

Even more preferably, the retention tabs are formed of material with a metal core surrounding the cavity and inserted into the body.

This gives a rigid core to the retention device which ensures good stability of the part around the barrel when the connection is formed.

Advantageously, the body is formed of a plastic material.

This has at least two advantages. On the one hand, plastic dampens vibrations better than, for example, metal; therefore the fixing will not be a source of parasitic vibrations. On the other hand, the manufacture of a plastic part is inexpensive and can be done by molding.

Advantageously, in the case where the retention member comprises a core forming a ring supporting the retention lugs, surfaces of the ring cooperate with the geometry of the body to form means for positioning in rotation of one with respect to the other. 'other. This makes it easier to manufacture by overmolding the body around the retention device and also can make it possible to exert considerable force when screwing the part around the barrel.

Advantageously, the cavity passes through the body. This makes it possible to manufacture a flat, space-saving part that can adapt to barrels of different heights.

Advantageously, the body comprises abutments for positioning the shaft, arranged in the cavity so as to place the latter on the axis, said abutments extending axially around the position of the distal parts of the retention lugs.

Preferably, the body carries on the periphery an annular row of compensation lugs inclined towards the base so as to position their free ends at the level of the plane of the base or below with respect to the body.

In fact the free end of the compensating legs is very slightly below the base. When the base is pressed against the surface of the second element, the free ends of the compensation tabs can move by elasticity of the material to position themselves in the same plane as the base on the surface of the second element. This creates a repulsion force along the axis of the barrel which puts the retention tabs in tension against the barrel, which improves the quality of the connection between the two elements at the level of the fixing system.

Advantageously, the body comprises at least two outer surfaces arranged to provide a grip allowing a torque to be applied around the central axis.

Thus a suitable tool can be used to easily screw or unscrew the part on the barrel.

The invention also relates to a system for removably connecting a first mechanical element to a second mechanical element, which are preferably vehicle body elements, comprising a part as described above, a shaft emerging from the first mechanical element, cylindrical with a circular section having a radius adapted to pass between the retention tabs by distancing them from the central axis, made of a material less hard than that of the retention tabs, preferably a plastic material, and a panel of the second element mechanism having an opening configured to be traversed by the barrel while forming an obstacle to the passage of the base of the part when the latter is threaded around the barrel.

The panel of the second element may include a through perforation configured to be traversed by the shaft or a notch allowing the panel to be slid along the first element to position it around the shaft.

Preferably, the shaft is made in one piece with the first element.

Brief description of figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

Figure 1 is a perspective view of a part according to the invention;

Figure 2 is a top view, from the side axially opposite the base, of the part of Figure 1;

Figure 3 is a bottom view, through the base, of the part of Figure 1;

FIG. 4 schematically represents an axial section of a retaining lug of the part of FIG. 1;

FIG. 5 schematically represents a side view of a portion of the retention member of the part of FIG. 1, showing the angle made by the free end of a retention tab with a plane perpendicular to the axis central;

Figure 6 is a perspective view schematically representing the first mechanical element with a barrel, and a perforation of a second element placed opposite for its sliding around the barrel, the part being shown to scale above the two elements;

FIG. 7 is a perspective view schematically showing the second element positioned around the barrel against the first element, and the part facing the barrel by a handling tool;

FIG. 8 is a schematic axial section of the two elements and of the part in position according to FIG. 7;

Figure 9 is a perspective view schematically showing the part slid around the drum and pressed against the surface of the second element by a handling tool, after the step shown in Figure 7;

FIG. 10 is a schematic axial section of the two elements and of the part in position according to FIG. 9;

Figure 11 is a perspective view schematically showing the part slid around the barrel and being unscrewed on the barrel, for disassembly after the step shown in Figure 9;

FIG. 12 is a diagrammatic axial section of the two elements and of the part separated from the second element during the step shown in FIG. 11;

Figure 13 is a perspective view schematically showing the spare part of the barrel and the barrel emerging from the second element after the dismantling operation;

Figure 14 is a schematic axial section of the two elements and the part in position according to Figure 13.

Detailed description of the invention

In the following description, a part 1 according to the invention is used (FIGS. 6 and 7) to implement a removable fixing system between a first mechanical element 2 and a second mechanical element 3, for example respectively a door panel car and a decorative element of the panel, medallion, insert or other vehicle body elements at least partially in the form of panels, that is to say having at least one connecting sub-portion in the form of a panel. The door panel 2 is here made of plastic material and comprises one or more shafts 4, integral with the rest of the panel, while the second element 3 comprises at least one sub-part in the form of a panel with a perforation 5 allowing engage this sub-part around one of the shafts 4 of the first element 2.

Referring to Figures 1 to 3, a part 1 according to a preferred embodiment of the invention comprises a plastic body 6, pierced with a through-cavity 7, and a metal retention member comprising retention lugs 8 extending to inside this cavity 7. The assembly is of revolution around a central axis X.

The plastic body 6 comprises a base 9 inscribed in a plane perpendicular to the axis and limiting the extension of the body of the part 1 in the direction of the central axis X.

In the figures, the central axis X is oriented starting from the base 9 towards the opposite side of the body 6. respectively in the direction that the X axis is pointing or what is in the opposite direction.

The external shapes of the body 6 starting from the base 9 here give it the general shape of a hexagonal nut centered on the axis X. In this example, the body 6 thus comprises six sides 10 perpendicular to the base 9, distributed around the central axis X. These hexagons 10 can cooperate with a tool 11 in the form of a key to rotate the part 1 around the central axis X (FIGS. 7, 9 and 11).

Two substantially triangular compensation lugs 12 extend outwards from each of these sections 10, approximately halfway up the body 6 along the axis X. These retention lugs 12, here of generally triangular shape, are inclined so as to that the bottom of their point forming their free end 13, is located at the level of the plane of the base 9 of the body 6, preferably slightly below this plane. The compensation tabs 12 are integral with the rest of the body 6. Their plastic material gives them a certain flexibility to slightly shift the position of their tip 13 if the base 9 of the body 6 is supported on a surface, so as to exert on part 1 a tension in the opposite direction along the central axis X.

The cavity 7 has an essentially cylindrical shape with a circular section around the axis. In the example, with reference to FIG. 1, the walls of the body 6 in the cavity comprise a first section 14, connected to the base 9, the section of which is circular, and a second section 15, connected to the face opposite the base 9, which here comprises six radial projections 16 distributed regularly in circumference. The internal radial end of these projections 16 is at a distance R1 from the central axis X, identical for each. Thus, these projections 16 form centering stops for a barrel 4 inserted into the cavity 7 and having substantially the same radius R1.

Furthermore, three notches 17 of semicircular section are cut in the axial direction in the walls of the two wall sections 14 and 15, over the entire extension of the cavity. These notches 17 are related to the presence of the retention member and their function is explained in the description of the latter.

The retention member, which is formed of a metallic material in a preferred embodiment, comprises a ring 18 parallel to the plane of the base 9 of the body 6 which here supports three retention tabs 8 extending into the cavity 7 towards the central axis X.

The ring 18, part of which is visible in Figure 3, is inserted into the plastic body of the part around the cavity 7, at the connection between the first section 14 and the second section 15 of the walls of the body 6 in the cavity 7. The ring 18 surrounds the cavity 7 leaving an annular passage around the central axis X, of radius greater than that R1 of the space between the stops 16. Furthermore, its geometry can be arranged to cooperate with that of the body 6 in order to lock it in rotation around the central axis X with respect to the body.

The ring 18 comprises notches of semi-circular cross-section placed in correspondence with those 17 of the walls of the plastic body 6 in the cavity 7. The presence of these notches corresponds to an ease for the manufacture of the part 1. Indeed, the realization of the body 6 is preferably done by molding the plastic material around the ring 18 of the retention member, previously made of metal. The three circular notches 17 are used to position the retention member on the central pin of the mold during the overmolding of the plastic body 6.

The ring 18, which holds the retention lugs 8, forms a rigid core for the retention member but also for the whole of the part 1. It avoids deformations and makes it possible to resume more intense efforts than the single body plastic in the direction of the X axis.

The retention member here comprises three metal retention tabs 8 integral with the ring 18, which are regularly distributed around the central axis X and which extend inside the cavity 7, at the inside the axial extension of the second section 15 of the walls of the body 6 and circumferentially between the projections 16 forming stops.

Referring to Figures 4 and 5, the retention tabs 8 are here formed by thin plates starting from the radially inner edge of the ring 18. A main part 19 of the retention tab extends in the opposite direction to the base 9 of the body by making an angle α a little greater than 90°, preferably 95 degrees, with the surface of the ring, located in a plane P parallel to the base 9. In other words, the main part 19 goes towards the high by being inclined radially towards the central axis X, by deviating from the walls of the body 6, parallel to the axis X, by a relatively small angle, α - 90 degrees. At the end of this main part 19, the thin plate is bent substantially at 90 degrees towards the X axis, so as to obtain a distal part 20 oriented towards the base 9 of the body by making an angle substantially equal to α-90 degrees with a plane P parallel to base 9.

It will be noted, with reference to FIG. 5, that the fold of the thin plate, between the main part 19 and the distal part 20, is slightly inclined, at an angle β preferably between 5 and 8 degrees, with respect to a plane P parallel to the base 9, following the same direction of rotation around the central axis X for all the retention tabs 8. This means that the distal part 20 is itself inclined by the same angle β in the direction perpendicular to the radial direction in the center of the retaining tab 8.

The free end of the distal part 20 of each retention lug 8 is cut along a cylinder parallel to the central axis X and having a radius substantially equal to the distance R1 from the stops 16. Thus, the free end forms an edge 21 radially inside the distal part which, when positioned substantially at the distance R1 from the central axis X, follows a portion of helix having a radius substantially equal to that of a barrel 4 centered between the stops 16; the helix winding here clockwise looking at part 1 through the base 9. The angle of winding of the helix corresponds to the angle β and is between 5 and 8 degrees with respect to a plane P parallel to the base 9.

Referring to Figure 4, the radially inner edge 21 is cut substantially perpendicular to the flat plate of the distal part 20. It makes an angle substantially equal to α with a plane P parallel to the base 9 to come into contact with the barrel 4. The internal edge 21 is bevelled in the thickness of the thin plate forming the distal part 20 by a transverse surface 22 which makes an angle γ of approximately 130 degrees with the plane of the distal part 20. Thus, this transverse surface 22 is oriented towards the base 9 of the body 6 and makes an angle δ of approximately 45 degrees with a plane P parallel to the base 9. This transverse surface 22 allows the blade formed by the distal part 20 to bite into the material of shaft 4 and notch it to form the grooves when turning part 1 around shaft 4.

The inclination of the transverse surface 22 of the example has been defined for a metal retaining member gripping a plastic barrel 4. The less the difference in hardness between the retention lugs and the barrel, the greater the interest in increasing the inclination of said transverse surface, therefore in reducing the angle δ that it makes with the plane of the base.

With reference to FIG. 1, it can be seen that the distal part 20 of each retention lug 8 is positioned between the axial ends of the second section 15 of the walls of the body 6 in the cavity, between two radial stops 16. The flexibility of the part main 19 of the retention lugs 8 allows the edges 21 of the distal parts 20 to move apart to allow the shaft 4 to pass. On the other hand, the low value, α -90 degrees, of the angle that the main part 19 makes with the axial direction gives a small displacement for the displacement of the distal parts 20, which quickly come into abutment against the walls of the body 6 in the cavity 7 if they are moved away from the central axis X.

The use of part 1 according to the embodiment described for fixing a second element 3 to a first element 2 such as a door panel is carried out for example in the manner described below.

With reference to FIGS. 7 and 8, a panel-type part of the second element 3 with a suitable perforation 5, for example a fixing lug, is placed opposite the shaft 4 of the first element 2 on which it must be fixed and then slid against the wall of the first element 2 by passing the perforation 5 through the shaft 4. Here, the first element 2 of this example is made of plastic material and the fixing shafts that it carries, coming from one material with it, are also made of plastic . The barrel 4 shown in the figures is hollow but it could be full. The fixing part 1 is inserted into a tool 7 cooperating with the outer axial hexagonal faces 10 of the body 6 to hold it around its central axis X, then positioned opposite the shaft 4 emerging from the second element 3. FIG. 8 shows in section that the radially internal edges 21 of the distal parts 20 of the retention lugs 8 fit inside a cylinder defined by the outer walls of the barrel 4, when the central axis X of the part 1 is brought into coincidence with the axis of the barrel 4.

Referring to Figure 9, the part 1 is then pressed against the wall of the second element 3 by inserting the emerging part of the barrel 4 in the cavity 7 of the latter. The tool 7 can be used to print a pressure force along the central axis X, in the direction of the arrow A in figure 9, to tighten the connection between the first 2 and the second 3 element.

It will be noted that, during this operation, the projections 16 of the body forming abutments come into contact with the barrel 4 before the latter comes into contact with the free edges 21 of the retention tabs 8, so as to center the part correctly. 1 on the barrel 4. It will also be noted that the wall of the body 6 in the second section 15 of the cavity 7 limits the radial movement towards the outside of the distal part 20 of each retention lug 8, to avoid tilting towards the exterior of tab 8 when a tensile force is applied to part 1.

Referring to Figure 10, at the end of this step, the main part 19 of the retention tabs 8 has bent to let the barrel 4 pass and pushes the edges 21 against the outer wall of the barrel 4. Furthermore, the forms retention lugs 8 and their connection to the ring 18 causes a movement tending to separate the part 1 from the wall of the second element 3 will push the internal edges 21 of the distal parts 20 inwards and will increase the holding force exerted by the radially inner edges 21. The part 1 is therefore blocked axially in the direction of a separation vis-à-vis the two elements, 2 and 3, which it holds around the barrel 4.

In addition, the compensating lugs 12 of the body 6, represented in FIG. 9, maintain a tension in the direction of the separation. In this way, the device prevents separation of the connection between the two elements due to vibrations during operation of the vehicle which would cause the radially inner edges 21 of the distal parts 20 to slip due to small axial movements of the part 1 along the keg 4.

Referring to Figure 9, it is also possible to increase the tightening of the connection after the axial pressing by performing a screwing of the part 1 on the shaft 4. Indeed, by rotating the part 1 thanks to the tool 7 along arrow B, the distal parts 20 form blades whose edges 21 will bite into the material of the shaft 4 and, thanks to the helical shape of the edges 21, create therein a start of threading which will transform the movement of rotation of the part 1 in an axial movement towards the base of the barrel 4, against the second element 3.

Referring to Figure 11, during disassembly, the tool 7 is inserted around the part 1 and it is rotated around the axis X in the opposite direction relative to the assembly, along the arrow C. The radially internal edges 21 since the distal parts 20 of the retention lugs 8 are tensioned against the wall of the shaft 4, they are embedded therein. For the same reasons as before, they create a thread 23 on the shaft 4. In this case the thread 23 is created in the opposite direction to the base of the shaft 4 and the rotational movement causes the part 1 to move apart vis- opposite the second element 3, as shown in figure 12.

At the end of the operation, as shown in Figures 13 and 14, part 1 is completely disengaged from barrel 4 and a thread 23 has been created on barrel 4 up to its free end. It is then possible to remove the second element 3 from the barrel 4 of the first element 2.

If we then want to fix another second element on the first element, we can take the same part 1 on the same shaft 4. As can be seen in Figure 13, the shaft 4 of the first element 3 now has a thread 23 but that does not prevent its reuse. Indeed, in this case, part 1 is positioned opposite shaft 4 and pressed against element 3 to tension the connection independently of the position of thread 23.

The example of use presented for the invention is not limiting. It is also possible to use it to fix second elements on a first element whose barrels would be metallic, for example a car hood. It is then necessary to take a part in which the metal forming the retention device is harder than that of the barrel.

The invention also relates to a variant embodiment with a mono-material part, made of a material having a sufficiently high hardness compared to the barrel to ensure the locking of the retention tabs and disassembly by unscrewing.

Claims (10)

Part (1) intended to cooperate with a barrel (4) emerging from a substantially flat surface of a first element (2) to form a system for fixing a second element (3) comprising:
- a body (6) comprising a flat base (9) and a cavity (7) emerging through said base (9), said cavity (7) leaving a cylindrical passage around a central axis (X) perpendicular to said face (9), so as to accommodate the shaft (4);
- a retention member comprising several similar retention tabs (8), at least two, extending from the body (6) towards the interior of the cavity (7) and regularly distributed in azimuth around the central axis ( X), said retention lugs (8) comprising a flexible main part (19) of which a radially outer end is fixed relative to the body (6) and a radially inner end carries a distal part (20) intended to press on the barrel (4), said main part (19) being inclined radially in the axial direction opposite to the base (9) and forming a spring exerting a restoring force towards the central axis (X) on the distal part (20) when this last is separated from the axis;
characterized in that the distal part (20) of each retention tab (8) forms a blade arranged to bite into a material less hard than the material of the retention tab (8) and that a radially internal edge (21) of the blade follows a portion of helix winding around the central axis (X) with a given inclination with respect to a plane (P) parallel to the base (9), the characteristics of the helix being the same for all retention tabs (8). Part (1) according to claim 1, in which the blade of the distal part (20) is formed by a thin plate inclined radially towards the base (9) of the body (6), preferably at an angle at least equal to 5 degrees with a plane (P) parallel to the base of the body. Part (1) according to one of the preceding claims, in which the radially inner edge (21) of the blade, intended to be in contact with the barrel (4), is cut by a transverse surface (22) cut in the thickness of the blade, which is inclined towards the base (9) of the body (6) preferably making an angle less than or equal to 45 degrees with a plane (P) parallel to the base of the body. Part (1) according to one of the preceding claims, in which the retaining lugs (8) are metallic. Part (1) according to the preceding claim, in which the retaining lugs (8) are made of material with a metal core (18) surrounding the cavity (7) and inserted into the body (6). Part (1) according to one of the preceding claims, in which the body (6) is made of plastic material. Part (1) according to one of the preceding claims, in which the cavity (7) passes through the body (6). Part (1) according to one of the preceding claims, in which the body (6) carries on the periphery an annular row of compensation lugs (12) inclined towards the base (9) so as to position their free ends (13) at the level with the base plane (9) or below with respect to the body (6). Part (1) according to one of the preceding claims, in which the body (6) comprises at least two outer surfaces (10) arranged to provide a grip allowing a torque to be applied around the central axis (X). System for detachably connecting a first mechanical element (2) to a second mechanical element (3), which are preferably vehicle body elements, comprising a part (1) according to one of the preceding claims, a shaft ( 4) emerging from the first mechanical element (2), cylindrical with a circular section having a radius adapted to pass between the retention tabs (8) by moving them away from the central axis (X), made of a material less hard than that of the retention lugs (8), preferably a plastic material, and a panel of the second mechanical element (3) having an opening (5) configured to be traversed by the barrel (4) while forming an obstacle to the passage of the base (9) of the part (1) when the latter is threaded around the barrel.