A STRONG SELF-DRILLING RIVET WITH AN EJECTABLE DRILL ELEMENT

Abstract

A self-drilling rivet (1) is provided. The self-drilling rivet comprises a bearing collar (3) and an expandable hollow tubular body (2), the body (2) having, at one end, a first cylindrical portion (5) adjacent to the collar (3), and at the other end of the body (2), a second cylindrical portion (6) arranged to receive a drill element (4), and between the cylindrical first and second portions (5, 6), a third portion (7) that is expandable. The third portion (7) of the body (2) and the drill element (4) have respective connection means (11, 15) that are arranged so as to separate the drill element (4) from the body (2) during expansion of the third portion (7) of the body (2).

Claims

1. A self-drilling rivet comprising a bearing collar and an expandable hollow tubular body, said body having, at one end, a first cylindrical portion adjacent to said collar, and at the other end of said body, a second cylindrical portion arranged to receive a drill element, and between said cylindrical first and second portions, a third portion that is expandable, wherein said third portion of said body and said drill element have respective connection means that are arranged so as to separate said drill element from said body during expansion of said third portion of said body.

2. A self-drilling rivet according to claim 1, wherein said hollow tubular body presents a solid axial wall.

3. A self-drilling rivet according to claim 1, wherein said body presents an end wall on said cylindrical second portion.

4. A self-drilling rivet according to claim 1, wherein said cylindrical second portion has an inside thread.

5. A self-drilling rivet according to claim 4, wherein said expandable third portion is arranged to deform radially when said internally-threaded cylindrical second portion is driven in axial translation towards said collar by traction.

6. A self-drilling rivet according to claim 1, wherein said cylindrical second portion is arranged to receive a cylindrical rod extending axially in said body.

7. A self-drilling rivet according to claim 6, wherein said rod has, at one end, a first rod portion that extends in the first portion of the hollow body and that projects beyond said collar outside said body.

8. A self-drilling rivet according to claim 7, wherein said rod has, at its other end, a second rod portion arranged to be received in said second portion of said body, and wherein said second rod portion presents a shoulder for co-operating with a narrowing of section of said second portion of said body so as to be prevented from moving axially in said body.

9. A self-drilling rivet according to claim 8, wherein said expandable third portion of said body is arranged to deform radially when said first rod portion of said rod is driven in axial translation by traction.

10. A self-drilling rivet according to claim 8, wherein said rod has a third rod portion between the first and second rod portions and including a breakable zone, and wherein said third rod portion is arranged so that a fraction of said third rod portion is inserted in said first portion of said body when said third portion of said body is fully expanded radially.

11. A self-drilling rivet according to claim 10, wherein said fraction of said third rod portion is defined by said breakable zone arranged flush with said collar when said third portion of said body is fully expanded radially.

12. A self-drilling rivet according to claim 1, wherein said drill element is in the form of a hollow cylinder for being fitted via a first end on said cylindrical second portion of said body.

13. A self-drilling rivet according to claim 12, wherein said second portion of said body presents flats for preventing said drill element from turning relative to said body when said drill element is fitted on said body.

14. A self-drilling rivet according to claim 12, wherein said drill element presents at a second end a drill tool in the form of a crown saw.

15. A self-drilling rivet according to claim 14, wherein said hollow cylinder of said drill element presents edges projecting towards the inside of said hollow cylinder between said first end and said second end of said drill element in order to block the engagement of said hollow cylinder on said cylindrical second portion of said body.

16. A self-drilling rivet according to claim 12, wherein said drill element presents second connection means for connecting to said body.

17. A self-drilling rivet according to claim 16, wherein said second connection means for connecting said drill element to said body are in the form of flexible tabs extending axially beyond said first end.

18. A self-drilling rivet according to claim 17, wherein said flexible tabs of said drill element have outside surfaces that are abrasive.

19. A self-drilling rivet according to claim 16, wherein said expandable third portion of said body presents first connection means for connecting to said drill element.

20. A self-drilling rivet according to claim 19, wherein said first connection means for connecting said expandable third portion of said body with said drill element is in the form of notches arranged to receive said flexible tabs of said drill element.

21. A self-drilling rivet according to claim 1, wherein said self-drilling rivet is made of rolled and welded sheet metal.

22. A self-drilling rivet according to claim 1, wherein said self-drilling rivet is made of die-stamped sheet metal.

Description

BRIEF SUMMARY OF THE DRAWINGS

[0043] The present invention can be better understood and other advantages appear on reading the following description and the accompanying drawings, in which:

[0044] FIG. 1 is a perspective view of a self-drilling rivet in a first embodiment of the invention;

[0045] FIG. 2 is an exploded view of the FIG. 1 self-drilling rivet;

[0046] FIG. 3 is a profile view of the self-drilling rivet in the first embodiment of the invention;

[0047] FIG. 4 is an axial section view of the FIG. 3 self-drilling rivet;

[0048] FIG. 5 is an axial section view of the self-drilling rivet of the first embodiment of the invention with its body expanded radially;

[0049] FIG. 6 is a perspective view of the self-drilling rivet in a second embodiment of the invention;

[0050] FIG. 7 is an exploded view of the FIG. 6 self-drilling rivet;

[0051] FIG. 8 is a profile view of the second embodiment of the self-drilling rivet;

[0052] FIG. 9 is an axial section view of the FIG. 8 self-drilling rivet; and

[0053] FIG. 10 is an axial section view of the self-drilling rivet of the second embodiment of the invention, with its body expanded radially.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0054] FIGS. 1 to 5 show a rivet 1 in a first embodiment of the invention for the purpose of assembling together two elements, specifically two plates (P and P, as shown in FIG. 5). By way of non-limiting example, the plates may be made of fiberglass.

[0055] The rivet 1 comprises a tubular body 2 both with a collar 3 at one end that comes to bear, by way of example, against one of the two plates that are to be assembled together, and also with a zone (described below) at the other end of the body 2 onto which a drill element 4 is engaged as a sliding fit, which element can be seen in isolation in the exploded view of FIG. 2.

[0056] As shown in FIG. 2, the collar 3 extends in a plane perpendicular to an axis AA of the rivet 1.

[0057] The collar 3 may present teeth (not shown) that bite into the surface against which it bears in order to prevent it from rotating about the axis. The collar 3 may also have cutouts around an inlet orifice to the inside of the tubular body 2.

[0058] The tubular body 2 is hollow, being in the form of a drum or a barrel having an axial wall that is solid.

[0059] The body 2 comprises three portions extending along the axis AA: a cylindrical first portion 5 is adjacent to the collar 3, a cylindrical second portion 6 corresponding to the zone for arranging the drill element 4 as an axial sliding fit, and an intermediate third portion 7 between the two cylindrical portions 5 and 6.

[0060] The height of the cylindrical first portion 5 generally corresponds to the thickness of the plates P and P for assembling together.

[0061] In the first embodiment, as can be seen in FIG. 4, the cylindrical second portion 6 may be threaded internally in order to co-operate with the thread of a screw-driver tool that passes through the tubular body 2 via the orifice in the collar 3. In this example, the inside thread is on a tapped die-stamped bushing 8 that is fastened to the second portion 6 beneath a radial narrowing of section that forms a shoulder 20. The bushing 8 is fastened to the body 2 by welding or by crimping.

[0062] The outside surface of the cylindrical second portion 6 may present axially-extending flats 9, there being three flats 9 in this example, in order to facilitate fitting the drill element 4 on the second portion 6 of the rivet body 2 and in order to prevent the drill element 4 from turning relative to the rivet body 2.

[0063] The cylindrical second portion 6 of the rivet body 2 may present an end wall, as shown in FIG. 4.

[0064] In this example, the intermediate third portion 7 of the rivet body 2 is in the form of a die-stamped drum with an annular zone of weakness 10 in a middle transverse plane so that the third portion 7 of the body 2 can expand radially.

[0065] The expandable intermediate third portion 7 of the rivet body 2 presents first connection means 11 for connecting with the drill element 4. In this example, three notches projecting towards the inside of the body 2 are arranged in axial continuity with the flats 9 of the second portion 6 of the rivet body 2.

[0066] The drill element 4 is in the form of a hollow cylinder that can be fitted via a first end 12 onto the cylindrical second portion 6 of the body 2. The cylindrical inside face of the drill element 4 presents edges 13 in the form of plunged bosses that can be seen in FIG. 4 and that project towards the inside of the cylinder so as to prevent the second portion 6 of the rivet body 2 from moving axially when the drill element 4 is fitted on the cylindrical second portion 6 of the body 2.

[0067] On a second end, the drill element 4 presents a drill tool 14, specifically in the form of a circular crown saw having two stages teeth. The crown saw has an internal bore, and its teeth are distributed circumferentially around the bore so as to reduce dust generation and fiber extraction during drilling. During drilling, drilling residue thus accumulates in the hollow cylinder of the drill element 4.

[0068] Without going beyond the ambit of the invention, the second end of the drill tool 14 could be an endpiece of the drill bit type with a diamond coating (not shown).

[0069] The drill element 4 possesses second connection means 15 for connecting to the rivet body 2, and more particularly to the intermediate third portion 7 of the rivet body 2, e.g. in the form of flexible tabs extending axially beyond the first end 12 of the drill element 4.

[0070] The flexible tabs of the drill element 4 in this example present an outside surface that is abrasive, enabling the quality of drilling to be improved, with ends 16 that slope towards the inside of the drill element 4.

[0071] Prior to use, the drill element 4 of the self-drilling rivet 1 needs to be mounted on the body 2 of the rivet 1. For that purpose, while the drill element 4 is being axially fitted on the body 2 of the rivet 1, the flexible tabs splay apart on coming into contact with the second portion 6, and they slide along the flat 9 of the second portion 6 of the body 2 of the rivet 1. Thereafter, the cylindrical second portion 6 penetrates axially into the hollow cylinder of the drill element 4 until the sloping ends 16 of the flexible tabs are received in the notches of the expandable third portion 7 of the body 2 of the rivet 1. The body 2 of the rivet 1 is prevented from moving axially in the hollow cylinder of the drill element 4 by the edges 13 of the inwardly-projecting plunged bosses of the drill element 4. In the invention, the first and second connection means 11 and 15 need to be selected so as to be capable of withstanding the rotation applied to the rivet 1 during drilling.

[0072] In the invention, the flats 9 on the second portion 6 of the body 2 also serve to prevent the drill element 4 from turning relative to the body 2 of the rivet 1 when the drill element 4 is fitted onto the body 2 of the rivet 1, thus making it possible for rotation exerted by a screw-driver tool on the body 2 of the rivet 1 to be transmitted to the drill element 4.

[0073] The rivet 1 is put into place through the two plates P and P in order to assemble them together by driving the rivet 1 in rotation in the conventional screw-driving direction as a result of the tool acting on the bushing 8, the tool passing through the collar 3 in order to make a hole through the two plates P and P and assemble them together as shown in FIG. 5.

[0074] When the collar 3 comes to bear against the upper plate P for assembling together, the second portion 6 of the body 2 is caused to rise towards the collar 3 by the tool applying traction on the thread of the bushing 8, thereby causing the expandable third portion 7 to deform radially. This radial deformation of the third portion 7 of the body 2 causes the flexible tabs to splay apart so that the ends 16 loose contact with the notches, thereby ejecting the drill element 4 from the body 2 of the rivet 1. This arrangement thus enables the drill element 4, containing the drilling residue, to be ejected simultaneously and axially in automatic manner from the body 2 by means of thrust generated by the deformation of the third portion 7 of the body 2 of the rivet 1.

[0075] When the third portion 7 is fully expanded, as shown in FIG. 5, the third portion 7 of the body 2 forms a bead 17 under the assembled-together plates P and P. The bead 17 provides good tear-out strength and good shear strength. The rivet 1 is then anchored on both sides of the two plates P and P.

[0076] In the invention, the abrasive outside surfaces of the flexible tabs of the drill element 4 serve to sand the inside of the hole in order to eliminate projecting fibers and/or locally delaminated zones.

[0077] In a second embodiment of the invention, instead of having a bushing 8 in the rivet body 2 for co-operating with the screw-driver tool, it is possible to have a rod 18 arranged in the rivet body 2. This variant of the invention is shown in FIGS. 6 to 10.

[0078] Elements that are common to both embodiments are given the same references and are not described in detail again.

[0079] FIGS. 6 and 7 show a rivet 1 of the second embodiment of the invention for assembling together two elements, specifically two plates (P and P, as shown in FIG. 10).

[0080] The rivet 1 has a hollow tubular body 2 in the form of a drum with a solid axial wall, the first, second, and third cylindrical portions 5, 6, and 7 extending along the axis AA, the collar 3, and the zone onto which the drill element 4 is engaged as a sliding fit, which drill element can be seen in isolation in exploded FIG. 7.

[0081] In the second embodiment, the rivet 1 has a rod 18, which in this example is generally cylindrical as can be seen in isolated manner in FIG. 7.

[0082] The rod 18 for inserting in the body 2 of the rivet 1 comprises three portions extending along the axis AA: a first portion 19 of the rod 18 for inserting into the first portion 5 of the body 2 of the rivet 1 has a length so that it also projects beyond the collar 3 outside the body 2 of the rivet 1; a second portion 21 of the rod 18 for being received in the second portion 6 of the body 2 of the rivet 1; and a third portion 22 between the first and second portions 19 and 21 of the rod 18, which third portion 22 is received in the third portion 7 of the body 2 of the rivet 1.

[0083] The portion of the first portion 19 of the rod 18 that projects relative to the rivet body 2 is used for driving the rivet 1 in rotation in the conventional screw-driving direction, by means of the tool acting on this portion extending outside the body 2, and it also serves to apply axial traction.

[0084] The second portion 21 of the rod 18 in this example is bullet-shaped with a shoulder 23 that co-operates with the narrowing of section 20 in the second portion 6 of the body 2 forming the shoulder for preventing the rod 18 from moving axially in the body 2 of the rivet 1. Second flats (not shown) of the body 2 formed on the inside surface of the second portion 6 of the rivet body 2 co-operate with the second portion 21 of the rod 18 to prevent the rod 18 turning relative to the body 2 of the rivet 1. Thus, the body 2 and the rod 18 are constrained to rotate together about the axis.

[0085] The third portion 22 of the rod 18 in this example presents a zone of narrowing that corresponds to a zone 24 that is breakable under the effect of appropriate axial traction. The drill element 4 is fitted onto the cylindrical second portion 6 of the body 2 of the rivet 1 in the same manner as described above.

[0086] In the second embodiment, the rivet 1 is put into place in the two plates P and P in order to assemble them together by driving the rivet 1 in rotation in the conventional screw- driving direction by using the tool acting on the rod 18, thereby making a hole through the two plates P, P and assembling them together as shown in FIG. 10.

[0087] As above, when the collar 3 comes to bear against the top plate P of the plates for assembling together, the second portion 6 of the body 2 is raised towards the collar 3 by the tool applying traction on the rod 18, thereby radially deforming the expandable third portion 7 and thus releasing the drill element 4 from the body 2 of the rivet 1 by automatic ejection.

[0088] When the third portion 7 is fully expanded, as shown in FIG. 10, in addition to the presence of the bead 17 under the assembled-together plates P and P, tear-out strength and shear strength are reinforced by the presence of a fraction of the third portion 22 of the rod 18 in the first portion 5 of the body 2 of the rivet 1. The breakable zone 24 is arranged so that after the elements P and P have been assembled together, the rod 18 breaks in the breakable zone 24 so that the fraction of the rod 18 that remains inside the body 2 of the rivet 1 does not extend out from the body 2 of the rivet 1, with the fraction of the rod 18 that remains inside the body 2 of the rivet 1 coming flush with the collar 3.

[0089] In this second embodiment, when the rivet 1 is anchored against both sides of the two plates P and P, the fraction of the rod 18 that remains inside the body 2 of the rivet 1 serves to fill all of the expanded hollow body, thereby mechanically reinforcing the rivet and also sealing the assembly.

[0090] In the invention, the rivet 1, 1 may be made of rolled and welded sheet metal, or out of die-stamped sheet metal.

[0091] The drill element 4 can thus be made out of rolled sheet metal with clinching by means of a dovetail, on welding, or crimping, or else it can be made out of die-stamped sheet metal.

[0092] The rivet 1, 1 may also be made entirely by molding a plastics material or by injecting a plastics material so as to enable it to be fabricated at low cost and used for assembling together two car floor mats or a floor mat and a plate, for example.

[0093] Without being limiting, the rivet 1 could also be used for fastening wiring tunnels, for positioning heavy or lightweight fastening systems, or indeed for internal fastening in cars with metal or composite bodywork.

[0094] The rivet 1 could also be fabricated by additive manufacturing in a 3D printer, for example if only a short run is to be fabricated.