Method of assembly using magnetic crimping

Abstract

A method of assembling a first part (1) with a second part (2) having at least one crimping lip (4), a crimping anvil (3) and a crimping groove (9) designed to accept an edge (10) that is to be crimped belonging to the first part, in which method the edge that is to be crimped is introduced into the crimping groove and magnetic crimping is performed by applying to the crimping lip a magnetic field that is designed to bend the crimping lip over and close the crimping groove onto the edge that is to be crimped, characterized in that the crimping anvil has at least one inclined portion.

Claims

1. A method for assembling, in at least one direction of traction (15), comprising: providing a first part (1) having a crimping edge (10), extending to an end of said first part (1) in said direction of traction (15); providing a second part (2) having: a crimping lip (4), at least partly made up of an electrically conducting material; a crimping stop (3), extending opposite and remote from an inner side of said crimping lip (4); a crimping groove (9), wherein said crimping groove (9) is open in said direction of traction (15) and adapted to receive said crimping edge (10) of said first part (1); wherein: said crimping edge (10) of said first part (1) is introduced into said crimping groove (9) of said second part (2) in said direction of traction (15); then magnetic crimping is carried out by applying a magnetic field variation to said crimping lip (4) that is adapted to fold said crimping lip (4) without winding and to plastically deform said crimping lip (4) towards said crimping stop (3), so as to close said crimping groove (9) onto said crimping edge (10) of said first part (1); wherein: said crimping stop (3) has at least one portion that is inclined relative to said direction of traction (15); said crimping lip (4) is longer than the depth of said crimping groove (9); during magnetic crimping a free end (12) of said crimping lip (4) is folded against an inner face (16), of said second part (2), said inner face (16) being distinct from said crimping stop (3), said crimping edge (10) is deformed between said inner face (16) and said free end (12) of said crimping lip (4), so that said crimping edge (10) has a portion in abutment against said inner face (16), on one side, and in abutment against said free end (12) of said crimping lip (4), on the opposite side.

2. The method as claimed in claim 1, wherein: said first part (1) is a rotationally cylindrical wall about an axis of symmetry parallel to said direction of traction; said second part (2) has said crimping groove (9) and said crimping lip (4) that are rotationally symmetrical about an axis of symmetry parallel to said direction of traction.

3. The method as claimed in claim 2, wherein said first part (1) has said crimping edge of frustoconical shape about an axis of symmetry parallel to said direction of traction (15).

4. The method as claimed in claim 3, wherein said crimping stop (3) has a generally frustoconical surface about an axis of symmetry parallel to said direction of traction (15), with an apex equal to the apex of said frustoconical crimping edge (10) of said first part (1).

5. The method as claimed in claim 1, wherein said inner face (16) comprises at least one flat portion orthogonal to said direction of traction (15), said flat portion receiving said free end of said crimping lip during crimping.

6. The method as claimed in claim 5, wherein an annular stop between said crimping edge (10) and said inner face (16) is orthogonal to said direction of traction (15), and wherein an annular stop between said crimping edge (10) and said free end (12) of said crimping lip (4) is orthogonal to said direction of traction (15).

7. The method as claimed in claim 1, wherein a film (5) is interposed between said crimping edge (10) and said crimping groove (9).

8. The method as claimed in claim 7, wherein said film (5) comprises at least one layer of electrically isolating material.

9. The method as claimed in claim 1, wherein an annular stop between said crimping edge (10) and said inner face (16) is orthogonal to said direction of traction (15), and wherein an annular stop between said crimping edge (10) and said free end (12) of said crimping lip (4) is orthogonal to said direction of traction (15).

10. The method as claimed in claim 1, wherein said crimping stop (3) is oriented in a direction forming an angle different from 90 with said direction of traction (15).

11. The method as claimed in claim 1, wherein said crimping groove (9) has a trapezoidal profile.

12. The method as claimed in claim 1, wherein, during magnetic crimping, a magnetic field generator (8) is disposed opposite of said crimping lip (4), offset in said direction of traction (15) relative to said crimping lip (4), so that at least part of said magnetic field generator is beyond said free end (12) of said crimping lip (4).

Description

(1) Further objects, features and advantages of the invention will become apparent upon reading the following description, which is provided by way of non-limiting example, and with reference to the appended drawings, wherein:

(2) FIG. 1 is a schematic representation of an assembly as a longitudinal section view according to one embodiment according to the invention;

(3) FIG. 2a is a detailed drawing, as shown in FIG. 1, of the assembly zone of a first part and of a second part according to a first embodiment according to the invention, before the step of magnetic crimping;

(4) FIG. 2b is a drawing according to FIG. 2a, after the step of magnetic crimping;

(5) FIG. 3 is a detailed drawing, as shown in FIG. 1, of the assembly zone of a first part and of a second part according to a second embodiment according to the invention, before the step of magnetic crimping;

(6) FIG. 4 is a detailed drawing, as shown in FIG. 1, of the assembly zone of a first part and of a second part according to a third embodiment according to the invention, before the step of magnetic crimping;

(7) FIG. 5 is a detailed drawing, as shown in FIG. 1, of the assembly zone of a first part and of a second part according to a fourth embodiment according to the invention, before the step of magnetic crimping;

(8) FIG. 6 is a detailed drawing, as shown in FIG. 1, of the assembly zone of a first part and of a second part according to a fifth embodiment according to the invention, before the step of magnetic crimping;

(9) FIG. 7 is a detailed drawing showing the assembly zone of a first part and of a second part and the advantageous arrangement of a magnetic field generator relative to the crimping lip.

(10) In the embodiments shown, the first part is a receptacle 1 with a closed contour, more specifically rotationally cylindrical, closed by a base 14 at one of its ends along its axis of symmetry 15 and open at the second of its two ends along its axis of symmetry. The object is to close the open end 10 of this receptacle 1 using a second part, which is a cover 2.

(11) In a method according to the invention, the open end, or crimping edge 10, of the receptacle 1 is introduced into a crimping groove 9 provided in a face, called inner face 16, of the cover 2. The shape and width of the crimping groove 9 are adapted to be able to be introduced into the crimping edge 10 of the receptacle 1. The crimping groove 9 is provided in a solid cover 2.

(12) The cover 2 is also rotationally symmetrical about an axis of symmetry that coincides with the axis of symmetry 15 of the receptacle 1 when the crimping edge 10 of the receptacle 1 is introduced into the crimping groove 9 of the cover 2, as shown in FIG. 1.

(13) The assembly between the receptacle and the cover can be expected to undergo traction forces mainly in a direction parallel to the axis of symmetry 15, in particular when the container obtained by assembling the receptacle 1 and the cover 2 contains a pressurised fluid or a partial vacuum relative to the external pressure.

(14) The crimping groove 9 is provided in the vicinity of the peripheral edge of the cover 2 so that said cover has a crimping lip 4 between the crimping groove 9 and its outer peripheral edge.

(15) The assembly zone A between the receptacle 1 and the cover 2 is magnified and is shown as a cross-section in FIGS. 2a, 2b, 3a, 3b, 4, 5 and 6, which represent various embodiments of the invention.

(16) FIGS. 2a and 2b show a first embodiment according to the invention.

(17) In this embodiment, the crimping lip 4 substantially extends in a direction parallel to the axis of symmetry (along a generating line about said axis of symmetry). The width of the crimping lip is constant between its area of attachment with the rest of the cover and its free end.

(18) The crimping groove 9 has a trapezoidal profile. Indeed, the crimping stop 3 is oblique relative to the axis of symmetry 15. The crimping stop 3 is a frustoconical surface with the same axis of symmetry as that of the cover 2 and with a summit that is on the side of the crimping groove relative to the cover. Therefore, the opening of the crimping groove is wider than the bottom of the crimping groove.

(19) The bottom of the crimping groove 9 has the same diameter as the crimping edge 10 of the receptacle, which is a rotationally cylindrical wall. Furthermore, the width of the bottom of the crimping groove 9 is substantially equal to the thickness of the crimping edge 10 so that, after crimping, no radial space remains between the crimping edge and the sides (crimping stop, on the one hand, and crimping lip, on the other hand) of the crimping groove.

(20) FIG. 2b shows the assembly obtained after a step of magnetic crimping is applied to the assembly of FIG. 2a. The space between the crimping edge 10 and the crimping groove 9 is only provided to better understand the drawing. The faces of the crimping edge 10 and of the crimping groove 9 are actually in contact over their entire surface.

(21) Magnetic crimping is realised by applying a magnetic pulse, i.e. by applying a short and intense magnetic field variation to the crimping lip 4. To this end, as shown in FIG. 1, the assembly zone between the receptacle 1 and the cover 2 is introduced into a coil 8 that surrounds the cover 2, in particular that surrounds the crimping lip 4.

(22) More specifically, as shown in FIG. 7, a coil 8 is radially disposed about the crimping lip 4, opposite said lip but without touching said lip

(23) The crimping lip 4 has a mid-plane 19 located between the bottom of the groove 3 and the free end 12 of the crimping lip.

(24) The coil has a plane of symmetry 17 that is disposed beyond the mid-plane 19 of the lip 4 so that the lower edge 18 of the coil is axially disposed (along the axis of symmetry 15) beyond, at a distance d, the free end 12 of the crimping lip.

(25) During crimping, the crimping lip 4 is radially driven inwards towards the crimping stop. The Laplace force experienced by the crimping lip is sufficient for it to gain sufficient kinetic energy to be able to drive the crimping edge 10 of the receptacle until it makes contact with the crimping stop 3, radially deforming the receptacle 1.

(26) FIG. 2b shows the particularly advantageous assembly obtained by a method according to the invention. The crimping edge 10 is clamped between the crimping lip and the crimping stop.

(27) The frustoconical crimping stop 3 is in surface contact with the crimping edge 10, so as to be able to withstand a traction force in a direction parallel to the axis of symmetry 15 that tends to axially bring together the receptacle 1 and the cover 2. In the same way, the crimping lip 4 is in contact along a frustoconical shaped surface with the crimping edge 10, so as to be able to withstand a traction force in a direction parallel to the axis of symmetry 15 that tends to axially separate the receptacle 1 from the cover 2. These frustoconical shaped contact surfaces allow the assembly to withstand much greater axial forces than with straight crimping, in which only the friction forces between the crimping edge and the crimping groove allow the receptacle and the cover to remain assembled.

(28) After magnetic crimping, the receptacle 1 has deformations 11 in the vicinity of the crimping edge 10, in particular the receptacle has a groove just below the cover 2. After crimping, the cover 2 has a frustoconical shaped peripheral surface.

(29) The magnetic crimping of such an assembly allows the crimping operation to be carried out in one attempt and in a uniform manner around the entire assembly zone between the receptacle and the cover. Therefore, such crimping is particularly reliable. Such a method for crimping is also particularly quick, allowing a high rate of production of assemblies according to the invention. Such a method for crimping according to the invention also can be quickly adapted to other shapes of first and second parts as it does not require the design, production and assembly of a new crimping tool for each new cover shape.

(30) Furthermore, by virtue of magnetic crimping, the second part, in particular the crimping lip, does not have crimping marks resulting from tooling impacting the metal. Advantageously, the crimping lip is free from crimping marks. Therefore, such a method allows assemblies to be obtained with remarkable surface aesthetics.

(31) Furthermore, in the groove formed in the vicinity of the crimping edge of the first part, the passage of a crimping tool is difficult and even impossible to implement. Indeed, this groove is generally narrow and mechanical crimping involves the passage of tooling, which would involve simultaneously impacting the first part, thus degrading its external appearance. However, magnetic crimping does not impose any geometric constraint and can be perfectly implemented in the examples shown. It is therefore essential for magnetic crimping to be selected when implementing a method according to the invention.

(32) Furthermore, as claimed in the invention, the crimping lip 4 is longer than the depth of the crimping groove 9 so that its free end 12 is beyond the edge of the crimping groove, i.e. beyond the inner face 16 of the cover 2. For example, this is shown in FIG. 2a using a profile view in a longitudinal section through a plane comprising the axis of symmetry of the receptacle 1.

(33) Therefore, when magnetically crimping the cover onto the receptacle, the crimping edge 10 is partly clamped between the frustoconical crimping stop and the crimping lip, but it is also partly clamped between the inner face 16 and the free end 12 of the crimping lip 4. Indeed, as the free end 12 of the crimping lip 4 is not opposite the crimping stop, it continued its course under the effect of the magnetic pulse until it is folded against the inner face 16 of the cover.

(34) Again, the magnetic crimping technique is particularly advantageous as it allows the crimping lip to be crimped in one attempt, which would not have been the case with mechanical crimping. Magnetic crimping also ensures that the receptacle is not impacted at any time by a mechanical part other than the crimping lip.

(35) The assembly obtained by such an embodiment is particularly advantageous as it allows the resistance to relative traction forces between the receptacle 1 and the cover 2 to be increased. Indeed, the crimping edge 10 has a plurality of deformations 11 and has annular stops with the inner face 16 of the cover 2, on the one hand, and with the inner side of the free end 12 of the crimping lip 4, on the other hand. Thus, these stops are substantially orthogonal to the axis of symmetry and therefore to the direction of traction along which a pressurised gas or a partial vacuum would tend to axially separate or axially approach the cover 2 from/to the receptacle 1.

(36) FIG. 3 shows a second embodiment compatible with the first embodiment, before crimping.

(37) In this embodiment, an additional step is added to the method before introducing the crimping edge 10 into the crimping groove 9. During this step, a flexible film 5 is interposed between the crimping edge 10 and the crimping groove 9 (or between the receptacle 1 and the cover 2, more generally).

(38) Advantageously, this film 5 fully extends into the crimping groove 9 and along the entire length of the crimping lip, so that the assembly obtained between the receptacle and the cover does not have any zone that is in direct contact between the receptacle and the cover.

(39) Such a film 5 improves the seal that is obtained when magnetically crimping between the crimping edge 10 and the crimping groove 9. Indeed, the film 5 is compressed between the crimping edge and the crimping groove after crimping, so that it provides a perfect seal by filling any void or surface defect that can remain between the crimping edge and the crimping groove.

(40) Such a film 5 is advantageously selected so that it is electrically isolating. Therefore, it allows oxidation-reduction reactions to be avoided between the receptacle and the cover when they are made up of distinct metallic materials.

(41) Such a film 5 is selected, for example, from an elastomer that is approximately 0.2 to 0.3 mm thick.

(42) FIG. 4 shows a third embodiment that is compatible with the first and second embodiments, before crimping.

(43) In this embodiment, a moulded part 6 is mounted on the crimping edge 10 before it is introduced into the crimping groove 9.

(44) Such a moulded part also improves the seal of the assembly and electrically isolates the receptacle from the cover.

(45) This moulded part 6 advantageously replaces the film 5 disclosed in the preceding embodiment. However, there is nothing preventing the combined assembly of a moulded part 6 on the crimping edge 10 and a film 5 interposed between the moulded part 6 and the crimping groove 9.

(46) For example, the moulded part is selected from a flexible thermoplastic, for example from EPDM (Ethylene Propylene Diene Monomer). The moulded part can be produced in various ways: for example, it can be manufactured using a standard mould, then mounted onto the crimping edge or it can even be moulded directly onto the crimping edge by overmoulding, by encapsulation or by coating on the crimping edge 10.

(47) FIG. 5 shows a fourth embodiment that is compatible with the first, second and third embodiments, before crimping.

(48) In this embodiment, the crimping stop has a slot for the assembly of a seal 7.

(49) Such a seal 7 improves the impermeability obtained when magnetically crimping between the crimping edge 10 and the crimping groove 9. Indeed, the seal 7 is compressed between the crimping edge and the crimping stop after crimping.

(50) This seal 7 advantageously replaces the film 5 and/or the moulded part 6 disclosed in the preceding embodiments. However, there is nothing preventing the combined assembly of a seal 7, in a slot machined in the crimping stop, with a moulded part 6 on the crimping edge 10 and/or a film 5 interposed between the moulded part 6 and the crimping groove 9.

(51) Such a seal 7 is an elastomer, for example a fluoroelastomer made of VITON, for example.

(52) FIG. 6 shows a fifth embodiment compatible with the third and fourth embodiments, before crimping.

(53) In this embodiment, the receptacle is rotationally cylindrical, but the crimping edge 10 is frustoconical. More specifically, the crimping edge has a frustoconical shape flaring out of the open end of the receptacle. Furthermore, the crimping edge is frustoconical with an apex (of the cone on which it is located) that is substantially equal to that of the crimping stop.

(54) Therefore, when the crimping edge 10 is introduced into the crimping groove 9, it is in direct contact with the crimping stop 3. During the step of magnetic crimping, the crimping edge, and especially the receptacle, is not deformed; only the crimping lip 4 is deformed. Indeed, the crimping lip is folded over the crimping edge but, with the crimping edge 10 already being in abutment against the crimping stop 3, its upper portion is neither driven nor deformed by the impact of the crimping lip (with the exception of a possible light compression towards the thickness of the crimping edge); only a portion of the crimping edge, that is impacted by the free end of the crimping lip, is deformed beneath the inner face 16.

(55) Such an embodiment is particularly advantageous when the receptacle material is not very malleable. Indeed, if the receptacle 1 material is too hard, there is a risk that the crimping will be imperfect as the crimping lip 4 would not have enough kinetic energy to deform the crimping edge until it is clamped between the crimping lip and the crimping stop.

(56) Similarly, such an embodiment is particularly advantageous when the receptacle 1 material is fragile and when there is a risk of the crimping edge breaking instead of being deformed during crimping.

(57) Similarly, the crimping lip 4 is advantageously made from a plastically deformable material so that it does not break under the effect of the magnetic pulse imposed by a magnetic crimping coil 8.

(58) According to the document, OPERATING DESCRIPTION FOR A MACHINE FOR WELDING, FORMING, CUTTING OR ASSEMBLING USING MAGNETIC PULSES, Gaille et al, Doc. IX-513-01, Swiss Welding Institute (SWI), skin thickness is determined by the formula:

(59) $=\sqrt{\frac{2}{}}\left[m\right]$ where is the pulse of the imposed magnetic field; is the electrical conductivity of the crimping lip; is the absolute magnetic permeability of the crimping lip, with =.sub.0 .sub.r, with .sub.0 being the magnetic permeability of the vacuum and .sub.r being the relative magnetic permeability of the crimping lip.

(60) According to the same document, the pressure p(t) experienced by the crimping lip over time is therefore determined by the formula:

(61) $p\left(t\right)=\frac{B^2\left(t\right)}{2}\left[\mathrm{Pa}=N\text{/}{m}^2\right]$ where B(t) is the intensity of the imposed magnetic field.

(62) Therefore, a second part is selected, the crimping lip of which has features that are suitable for efficient and reliable magnetic crimping. In particular, the electrical conductivity and the magnetic permeability of the crimping lip are selected.

(63) By way of example, a receptacle as shown in the first embodiments according to the invention is made of aluminium (and therefore so is the crimping edge) and the cover is made of copper (and therefore so is the crimping lip). In the final embodiment, the receptacle is made of steel.

(64) The receptacle wall (and therefore the crimping edge) is approximately 1 mm thick and the crimping lip is approximately 1 mm thick. The diameter of the receptacle, and therefore of the crimping groove, is approximately 30 mm in this particular embodiment, and is more than 30 mm in other embodiments. However, there is nothing preventing the implementation of a method according to the invention on a receptacle with a diameter of less than 30 mm.

(65) Furthermore, the apex of the crimping stop is approximately 30 to 45.

(66) The magnetic pulse generated for the step of magnetic crimping implements approximately 3 kJ of energy for approximately 15 microseconds. The coil 8 is disposed offset along the axis of symmetry 15 so that the distance d between the free end 12 of the crimping lip and the lower edge of the coil 8 is of the order of 3 mm, this particularly ensures that the free end of the crimping lip is effectively folded against the inner face during magnetic crimping. The distance between portions opposite the crimping lip 4 and the coil 8 is of the order of 1 mm.

(67) Therefore, a container obtained by magnetically crimping such a cover onto a receptacle withstands pressure differences of more than 9 bar between the inside and the outside, i.e. pressures of at least 10 bar inside the container.

(68) The invention can be the object of various other variants of embodiments that are not shown.

(69) For example, the invention allows assemblies to be created with a second part on a first hollow part with a distinct cylinder profile, for example a triangular, parallelepiped, pentagonal, hexagonal, octagonal or any type of profile. Magnetic crimping is particularly advantageous as it allows the reliable crimping of any type of shape in one attempt and without requiring tooling changes.

(70) The invention also allows the end-to-end crimping of two tubes, for example.

(71) The crimping stop can have other shapes so that the crimping groove is not necessarily of trapezoidal profile, as long as it allows contact coverage to be obtained that is inclined relative to a direction of traction between the crimping edge and the crimping stop and between the crimping edge and the crimping lip.

(72) Various types of materials can be selected for the cover, and even more can be selected for the receptacle, which is not necessarily electrically conducting.

(73) Furthermore, there is nothing preventing the second part from actually being made up of at least two parts: for example, a plug having crimping stops on its periphery and a closure, into which the plug is introduced, with the shape of said closure being adapted to form a crimping lip opposite the periphery of the plug. Therefore, for example, said plug can be truncated and said closure can be cylindrical and closed at an end that is intended to come into contact with the larger of the two faces of the plug.