Pyrotechnic device with plastic housing

Abstract

The invention relates to a pyrotechnic switch, which comprises, a housing formed by a first housing part that is assembled with a second housing part, and at least one pyrotechnic actuator arranged in the housing, wherein at least one out of the first housing part or the second housing part comprises a metal reinforcement and a plastic body overmolded onto the metal reinforcement, wherein the plastic body comprises, a first portion made of a first plastic material, and a second portion made of a second plastic material.

Claims

1. A pyrotechnic switch, the pyrotechnic switch comprising: a housing formed by a first housing part assembled with a second housing part; and at least one pyrotechnic actuator arranged in the housing; wherein at least one of the first housing part or the second housing part comprises a metal reinforcement and a plastic body overmolded onto the metal reinforcement as a liquid plastic material such that the metal reinforcement is embedded within the liquid plastic material of the plastic body, wherein the plastic body comprises: a first portion made of a first plastic material, and a second portion made of a second plastic material.

2. The pyrotechnic switch according to claim 1, comprising a boundary arranged between the first portion and the second portion.

3. The pyrotechnic switch according to claim 1, wherein one of the first portion and the second portion has, at the boundary, at least one contact surface with a continuous periphery, in order to provide continuous contact for a mold for manufacturing the other of the first portion and the second portion.

4. The pyrotechnic switch according to claim 2, wherein the metal reinforcement is overmolded on both sides, and wherein the boundary between the first portion and the second portion, arranged on one side of the metal reinforcement is offset relative to the boundary between the first portion and the second portion, arranged on the other side of the metal reinforcement.

5. The pyrotechnic switch according to claim 1, comprising a movable part, the movable part housed in a guide interface made in one of the first portion and the second portion, and wherein the boundary between the first portion and the second portion is discrete and/or separate from the guide interface.

6. The pyrotechnic switch according to claim 1, wherein the first plastic material is selected from polyphthalamide (PPA), polyoxymethylene (POM), poly(methyl methacrylate) (PMMA).

7. The pyrotechnic switch according to claim 1, wherein the second portion is formed to define connection interface open at an axial end of the pyrotechnic switch and arranged to receive an electrical connector intended to connect the pyrotechnic actuator to a control circuit.

8. The pyrotechnic switch according to claim 1, wherein the second plastic material is selected from polyamide (PA, PA6, PA6-12, PA6-6) and comprises between 10% and 50% by weight of reinforcing fibers.

9. The pyrotechnic switch according to claim 1, wherein the metal reinforcement comprises a plurality of overmolding openings, so as to enable overmolding of the plastic body on both sides of the metal reinforcement, and material continuity of the plastic body through the overmolding openings.

10. The pyrotechnic switch according to claim 1, wherein the metal reinforcement comprises at least one cylindrical portion delimited by a shoulder, wherein the shoulder is free of openings.

11. The pyrotechnic switch according to claim 10, wherein the boundary between the first portion and the second portion is arranged at the shoulder.

12. The pyrotechnic switch according to claim 1, wherein the pyrotechnic actuator is overmolded in the second plastic material.

13. The pyrotechnic switch according to claim 1, wherein the metal reinforcement comprises a terminal shoulder defining a central hole, the pyrotechnic actuator being arranged in the central hole, and wherein the terminal shoulder lacks other recesses.

14. The pyrotechnic switch according to claim 13, comprising rivets, wherein the first housing part is assembled with the second housing part with the rivets, and wherein the metal reinforcement comprises through-holes for the rivets.

15. The pyrotechnic switch according to claim 1 in combination with a motor vehicle.

16. A pyrotechnic switch, the pyrotechnic switch comprising: a housing formed by a first housing part assembled with a second housing part; and at least one pyrotechnic actuator arranged in the housing; wherein at least one of the first housing part or the second housing part comprises a metal reinforcement and a plastic body overmolded onto the metal reinforcement, wherein the plastic body comprises: a first portion made of a first plastic material, and a second portion made of a second plastic material, and wherein a boundary between the first and second portions on a first side of the metal reinforcement is offset relative to the boundary between the first and second portions on a second side of the metal reinforcement, the metal reinforcement overmolded on both the first side and the second side.

17. A pyrotechnic switch, the pyrotechnic switch comprising: a housing formed by a first housing part assembled with a second housing part; and at least one pyrotechnic actuator arranged in the housing; wherein at least one of the first housing part or the second housing part comprises a metal reinforcement and a plastic body overmolded onto the metal reinforcement, wherein the plastic body comprises: a first portion made of a first plastic material, and a second portion made of a second plastic material, and wherein the metal reinforcement comprises at least one cylindrical portion delimited by a shoulder, wherein the shoulder is free of openings.

18. The pyrotechnic switch according to claim 17, wherein the boundary between the first portion and the second portion is arranged at the shoulder.

Description

(1) Other features and advantages of the present invention will become more apparent upon reading the following detailed description of an embodiment of the invention which is provided by way of entirely non-limiting example and illustrated by the attached drawings, wherein:

(2) FIG. 1 shows a perspective view of a pyrotechnic device according to the invention;

(3) FIG. 2 shows a sectional view of the pyrotechnic device of FIG. 1;

(4) FIG. 3 shows another sectional view of the device of FIG. 1;

(5) FIG. 4 shows a view of a metal reinforcement of the device of FIG. 1

(6) FIG. 5 shows a section of a part of the housing of the pyrotechnic device of FIG. 1, at a first manufacturing stage;

(7) FIG. 6 shows a section of a part of the housing of the pyrotechnic device of FIG. 1, at a second manufacturing stage;

(8) FIG. 7 shows a manufacturing alternative for the pyrotechnic device of FIG. 1;

(9) FIG. 8 shows a detail of FIG. 6, according to a particular embodiment;

(10) FIG. 9 shows a section of FIG. 8, to show another particular embodiment.

(11) FIG. 1 shows a perspective view of a pyrotechnic device according to the invention, comprising a housing 10 formed by a first housing part 11 and a second housing part 12. An electrical conductor 20 is sandwiched between the first housing part 11 and the second housing part 12.

(12) The lower part of FIG. 1 shows a connection interface 31 of a pyrotechnic actuator 32 which is installed in the housing 10 and shown in FIG. 3.

(13) This FIG. 3 shows the internal structure of the pyrotechnic device, arranged here as a switch provided for breaking the electrical conductor 20 if needed (breaking the vehicle power circuit in the event of an accident, for example).

(14) To this end, the electrical conductor 20 carries an overmolded guide part 21, which forms a bore in which a punch 33 is placed, and which forms, with the second housing part 12, a combustion chamber C facing the pyrotechnic actuator 32 (in this instance an electro-pyrotechnic igniter, but it is possible to envisage an additional pyrotechnic booster if required). In FIG. 3, the punch 33 is in a rest position.

(15) The first housing part 11 comprises, facing the punch 33 and on the other side of the electrical conductor 20, a counter-form 34 which may be considered to be an anvil or a matrix.

(16) When it is necessary to break the electrical conductor 20, the pyrotechnic actuator 32 is ignited, which causes a large rise in pressure in the combustion chamber, such that the punch 33 is pushed toward the top of FIG. 3 in a translational movement from the rest position to a final position in which the electrical conductor 20 has been broken.

(17) Considering that the pyrotechnic device is provided to be able to operate even after several years of service life and that, in operation, pressures of several tens of bars or more are anticipated, sealing means are provided between the first housing part 11, the second housing part 12, the guide part 21, with seals 13 and 14, according to the example shown. A seal 15 is also provided between the punch 33 and the second housing part 12.

(18) It is understood that it is then necessary to guarantee good attachment between the first housing part 11 and the second housing part 12. However, in order to guarantee good electrical insulation, it is also necessary to provide for the housing 10 not to conduct electricity between the electrical conductor 20 and the ground of the vehicle, for example. In order to meet the latter condition, each housing part 11 and 12 has a plastic body C1 or C2. In order to meet the attachment condition, it is provided to rivet the housing parts 11 and 12 together, using rivets 40 which can be seen in FIGS. 1 and 2. Before assembling the housing, in order to guarantee efficient holding of the electrical conductor 20 and leaktightness of the device, the first housing part 11 and the second housing part 12 are not in contact.

(19) FIG. 2 shows a section at the rivets 40, to illustrate the assembly. In particular, it is provided to arrange, in the second housing part 12, a metal reinforcement 16 so as to limit the stresses on the plastic body of this second housing part 12.

(20) The rivets 40 are shoulder rivets. That is to say that, before riveting, they have a base 40E and a cylindrical body, so as to be able to be inserted into each housing part 11 and 12 which has a through-opening for the rivets 40. Each rivet 40 is subsequently deformed at the head 40T thereof, in order to finalize the assembly, guarantee leaktightness of the device and prevent any subsequent disassembly. According to this implementation, the heads 40T are embedded under, or flush with, the surface of the second housing part 12.

(21) In practice, during this riveting operation, the base 40E of each rivet 40 is brought to bear against a base tool, and a setting tool (riveting tool) movable according to a particular movement to be at least temporarily inclined relative to the axis of the rivet 40 is brought into contact on the head 40T of the rivet 40 in order to apply a vertical force thereto, so as to crush and expand the head 40T by plastic deformation during the rotational and/or oscillating movement of the setting tool.

(22) The riveting operation leads to deforming the head 40T so as to guarantee an axial stop of the second housing part 12, without thereby deforming the cylindrical part of the rivet 40, in particular at the base 40E.

(23) As can be seen in FIG. 2, the plastic body C2 of the second housing part 12 has a wider through-opening than that of the metal reinforcement 16, such that the rivet 40, at the head 40E, only touches the second housing part 12 via the metal reinforcement 16. As a consequence, no radial force is applied by the rivet 40 to the plastic body C2. Risks of cracks, breakage or damage to the plastic are therefore prevented. In other words, the diameter for the passage of the rivet 40 into the plastic bodies C1 and C2 are greater than the diameter for the passage into the metal reinforcement 16.

(24) This implementation guarantees that the rivet 40 only touches the second housing part 12 via the metal reinforcement 16, and swelling of the diameter of its stem does not lead to the rivet 40 coming into contact with either one of the plastic bodies C1 or C2.

(25) Moreover, as the rivet 40 is not deformed at the base 40E thereof, it is not necessary to provide any metal reinforcement in the first housing part 11 to withstand the riveting operation, according to a preferred and optional implementation. The first housing part is therefore composed only of a plastic body C1 according to this implementation.

(26) FIG. 4 shows an example of a metal reinforcement 16 which comprises holes 16T (which can be seen in FIGS. 4, 5 and 6), to enable continuity of the plastic material of the plastic body C2 of the second housing part 12, in order to facilitate the overmolding operation and obtain a solid plastic body C2.

(27) The metal reinforcement 16 may be made of drawing steel of the type DC04-1.0338 (Re: 210-220 MPa, Rm: 270-350 MPa, A %>38%).

(28) The plastic body C1 of the first housing part 11 may be made of polymer, such as polyamide (PA, PA6.6, PA6.12) or polyoxymethylene (POM), optionally loaded with reinforcing fibers, such as glass fibers, for example in a proportion of 25% to 35% by weight. The rivets 40 may be made of steel, copper, aluminum with a high elongation at break (A %>20%, for example).

(29) Regarding the second housing part 12, it is composed of two plastic materials: a first portion 12a made of first plastic material and a second portion 12B made of second plastic material.

(30) The connection interface 31 is therefore produced in the second portion 12B of the second housing part 12 which is manufactured with the second plastic material, and use may for example be made of polyamide (PA, PA6, PA6-12, PA6-6), and comprises between 10% and 50% by weight of reinforcing fibers, for example made of glass. In particular, polyamide PA6 may be chosen, with 30% glass fibers by weight. As a consequence, it is possible to provide shapes (grooves, recesses) of small dimensions but nonetheless precise, at the connection interface 31, since the second plastic material chosen is easy to inject into molds with complex shapes. Moreover, the second material chosen may also properly withstand the pressures present in the combustion chamber C due to the added reinforcing fibers.

(31) Furthermore, the first portion 12A of the second housing part 12 which is manufactured with the first plastic material may be intended to be exposed, during operation of the switch, to an environment in which an electric arc is formed. According to such a scenario, a part of the first plastic material is arranged to be removed by ablation, and the first plastic material is selected from polyphthalamide (PPA), polyoxymethylene (POM), poly(methyl methacrylate) (PMMA).

(32) FIG. 5 shows the second housing part 12 after a first injection molding operation during which the first portion 12A was injection-molded with the first plastic material.

(33) FIG. 6 shows the second housing part 12 after a second injection molding operation during which the second portion 12B was injection-molded with the second plastic material.

(34) FIG. 5 also shows that the first plastic material is molded up to a shoulder of the metal reinforcement 16, with an offset of a boundary F between the two sides of the metal reinforcement 16. Indeed, a lower boundary Fi (on the lower side of the metal reinforcement 16 in FIG. 5) has a smaller inner diameter than an upper boundary Fs, on the other side. The structure provides several advantages. Indeed, the shoulder of the metal reinforcement 16 is free of holes, and in combination with the offsetting of the boundary, this makes it possible to obtain good stiffness of the second housing part 12, and low deformations. This limits the risks of breakage, delamination, and cracking.

(35) It is also possible to mention that the manufacturing mold for the second injection molding operation of the second plastic material may come to bear against the surfaces 12As and/or 12Ai of the first plastic material, at the boundary F, which also simplifies manufacturing.

(36) Moreover, FIG. 8 shows more particularly the detail A illustrated in FIG. 6, corresponding to a particular implementation of the interface between the first and the second portion 12A, 12B, respectively. Indeed, to prevent any exposure of the metal reinforcement 16 to the outside, it may be advantageous to provide a covering for the materials, for example at the lower boundary Fi. Indeed, FIG. 8 shows a return Re of the second plastic material, below the first plastic material, which prevents the metal reinforcement 16 from being uncovered, even in the event of differential expansion of the plastic materials. In order to further improve the mechanical strength between these two portions, it may be advantageous to also provide nesting of the materials. The nesting and the covering may or may not be combined, depending on requirements.

(37) Furthermore, FIG. 9 shows a section in the plane I-I of FIG. 8, to show a particular implementation of nesting of the materials. Indeed, FIG. 9 shows that the two plastic materials are nested one in the other, with undercuts at the lower boundary Fi. In FIG. 9, the complementary shapes have a cylindrical toothed contour or section, but it is possible to provide rectilinear dovetail shapes, for example. This implementation increases the strength of the boundary or interface between the two materials and further limits the risks of material separation or delamination. In the event that nesting of the materials is provided without the covering, the complementary shapes may be visible if they are arranged throughout the thickness of the plastic materials.

(38) Regarding the metal reinforcement 16, the latter comprises holes 16T which can be seen in FIGS. 4, 5 and 7, which comprise holes 16T1 and 16T2, each dedicated to enabling continuity of the first plastic material and the second plastic material, respectively. Finally, the metal reinforcement 16 comprises, in the lower part thereof shown in FIG. 6, a shoulder 16E with a through-hole 16P for the pyrotechnic actuator 32 (which can be seen in FIG. 3 and not in FIG. 6, for the sake of clarity). The shoulder 16E is free of holes or recesses other than the through-hole 16P, so as to have adequate resistance to the forces and stresses present in this area during operation, due in particular to the pressures in the combustion chamber C.

(39) FIG. 7 shows a manufacturing alternative, according to which the second plastic material is injected first. However, the boundary F always comprises an offset (Fs, Fi) between the two sides of the metal reinforcement 16, and contact surfaces 12Bs, 12Bi with a continuous perimeter to provide leaktight contact on the manufacturing mold for the subsequent overmolding operation.

(40) It will be understood that different modifications and/or improvements which are obvious for the person skilled in the art may be made to the different embodiments of the invention described in this present description without departing from the scope of the invention.