EP4004959A1

EP4004959A1 - Pyrotechnic cut-off device

Info

Publication number: EP4004959A1
Application number: EP20754004.8A
Authority: EP
Inventors: Frédéric MARLIN; Romain LORENZON; Lun BREVET; Philippe Lopez
Original assignee: ArianeGroup SAS
Current assignee: ArianeGroup SAS
Priority date: 2019-07-25
Filing date: 2020-07-21
Publication date: 2022-06-01
Anticipated expiration: 2040-07-21
Also published as: FR3099287A1; US11482391B2; WO2021014088A1; FR3099287B1; EP4004959B1; US20220262587A1

Abstract

The invention relates to a pyrotechnic cut-off device (100) comprising: a pyrotechnic initiator (20), a conductive portion (40) and a movable piston (30), the piston being able to move in a cavity (14) in a movement direction (A) following the activation of the pyrotechnic initiator between a first position allowing the current to flow in the conductive portion and a second position allowing the current to be cut-off, characterised in that the piston (30) defines a first sealing portion (33) having a narrowing cross-section in the movement direction (A), and in that the cavity (14) has a wall defining a second sealing portion (14b), which extends on either side of the conductive portion (40) and which has a narrowing cross-section in the movement direction (A), the first sealing portion (33) being in contact with the second sealing portion (14b) along a contact surface extending on either side of the conductive portion (40) when the piston is in the second position.

Description

Title of the invention: Pyrotechnic cut-off device

Technical area

The present invention relates to the general field of electrical switching devices, and more particularly those of the pyrotechnic actuation type.

Prior art

Pyrotechnic cutoff devices are known comprising a body in which is present a pyrotechnic initiator configured to, when triggered, set in motion a piston provided with a relief in the direction of a conductive bar to be cut. Documents WO 2016/038043 and

WO 2016/038050 show examples of devices of this type.

[0003] Known devices make it possible to obtain satisfactory results when switching off low voltage circuits. However, as the operating voltage increases, the reliability of known cut-off devices decreases and the cut-off time increases.

[0004] There is thus still a need for a pyrotechnic switching device which is more reliable at high voltages while being of simple and economical design.

Disclosure of the invention

[0005] To this end, the invention provides a pyrotechnic switching device

comprising: a pyrotechnic initiator, a conductive portion and a movable piston, the piston being able to move in a cavity in a direction of movement following the actuation of the pyrotechnic initiator between a first current flow position in the portion conductive and a second current cutoff position. The cutting device is characterized in that the piston defines a first sealing portion having a section narrowing in the direction of movement, and in that the cavity has a wall defining a second portion

sealing which extends on either side of the conductive portion and which has a section narrowing in the direction of movement, the first sealing portion being in contact with the second sealing portion according to a contact surface extending on either side of the conductive portion when the piston is in the second position.

[0006] The first sealing portion of the piston and the second sealing portion defined by the wall of the cavity can cooperate in the second position of the piston so as to create a surface seal on either side of the conductive portion , which makes it possible to separate in a sealed manner the two terminals of the device between which the conductive portion extends. Thus, the power cut and the reliability of the device are improved. In addition, the sectional narrowings of the sealing portions allow the piston to fit into the cavity in the manner of a Morse taper or fitting cone, which makes it possible to center the piston in the cavity, to prevent piston to move once it is in the second position and also to maintain this seal.

[0007] When the power is cut off by section of the portion

conductive by the piston, the device according to the invention makes it possible to obtain a characteristic low cut-off time, corresponding to the time between the moment when the conductive portion is cut off from the moment when the current is effectively cut off, which can generally be between 50 ps and 150 ps.

[0008] In an exemplary embodiment, the sections of the piston and of the cavity may be circular or oblong. These rounded cross-sectional shapes improve the seal between the piston and the wall of the cavity.

In an exemplary embodiment, the conductive portion can be broken by impact with the piston during the passage from the first to the second position. In particular, the conductive portion can be broken into three parts, one of which is driven by the piston.

[0010] In an exemplary embodiment, the conductive portion may present to the

at least one zone of weakness to facilitate the breaking of said conductive portion. The fragile zone can for example comprise a plurality of tongues, or even at least one groove.

[0011] In an exemplary embodiment, the first sealing portion can

have a first surface and the second sealing portion can have a second surface, said surfaces each forming an angle of between 1 ° and 10 ° with the direction of movement of the piston. In particular, the angles made by the first surface and the second surface may be different to allow one sealing portion to fit into the other, in order to further improve the sealing.

[0012] In an exemplary embodiment, the hardness of the material forming the first sealing portion and the hardness of the material forming the second sealing portion may be different. The difference in hardness between said materials may be between 50 Shore A and 100 Shore D. This

This feature allows one seal portion to deform relative to the other when the piston moves to the second position, further improving the seal and power cut.

In an exemplary embodiment, in the first position, the piston may have a housing and the device may further comprise a relief which extends from a bottom of the cavity, said relief being housed in the housing when the piston is in the second position. In this configuration, the conductive portion can be cut into three parts, one of which is driven by the piston and then folded against the relief in the housing when the piston is in the second configuration. This configuration further improves the cut by isolating in the housing the folded part of the conductive portion from the remaining parts of the latter.

[0014] The invention is also aimed at a secure electrical installation comprising a switching device such as that presented above and an electrical circuit connected to the conductive portion of said device.

Finally, the invention relates to a vehicle comprising an electrical installation

secure such as that described above. Such a vehicle can for example be an electric motor vehicle.

Brief description of the drawings

[0016] [Fig. 1] Figure 1 is a perspective view of a switching device according to a first embodiment of the invention.

[0017] [Fig. 2] Figure 2 is an exploded view of the device of Figure 1. [0018] [Fig. 3] Figure 3 is a sectional and perspective view of part of the body of the switch-off device of Figure 1.

[0019] [Fig. 4] Figure 4 shows a sectional and perspective view of the piston of the switch-off device of Figure 1.

[0020] [Fig. 5A-5B] Figures 5A and 5B respectively show sectional views of the switch-off device of Figure 1 when the piston is in the first and second positions.

[0021] [Fig. 6] Figure 6 is a sectional and perspective view of part of the body of a switching device according to a second embodiment of the invention.

[0022] [Fig. 7] Figure 7 is a sectional and perspective view of the piston of the

switch-off device according to the second embodiment of the invention.

[0023] [Fig. 8A-8B] Figures 8A and 8B respectively show sectional views of the switching device according to the second embodiment of the invention when the piston is in the first and in the second position.

[0024] [Fig. 9] Figure 9 shows a secure electrical circuit in which is

present a cutting device according to the invention.

Description of embodiments

The switching device 100 according to a first embodiment illustrated in Figures 1 to 5B comprises: a body 10 in two parts 10a and 10b, a pyrotechnic initiator 20, a piston 30, and a conductive portion 40.

The device 100 comprises a first 41 and a second 42 terminals

electrical circuits intended to be connected to an electrical circuit to be cut and which correspond here to two ends of the conductive portion 40. The conductive portion 40 here takes the form of a conductive bar or tab. In an embodiment not illustrated, the device 100 can comprise a plurality of conductive portions. An example of an installation comprising an electrical circuit connected to terminals 41 and 42 will be described in conjunction with Figure 9.

[0027] The body 10 has a generally parallelepipedal shape. The body 10

comprises a part 10a housing the various elements of the device 100 and a cover 10b which closes the body 10 at an upper end. The cover 10b is fixed to part 10a by screws 10c. The part 10a of the body 10 has an upper opening 11 in which the piston 30 can be inserted. The cover 10b has an opening 12 for passing connectors 21 of the pyrotechnic initiator 20. The part 10a of the body 10 has two openings lateral 13 in which the conductive portion 40 can be inserted.

The pyrotechnic initiator 20 comprises a pyrotechnic charge connected to the connectors 21. The pyrotechnic charge is, when it is initiated for example using a current passing through the connectors 21, capable of generating a pressurization gas by its combustion. The conductive elements 21 can be connected to a control device C (Figure 9) configured to actuate the pyrotechnic initiator 20 when an anomaly is detected.

The piston 30 has, in this example, a shape of revolution about a Z axis. The Z axis corresponds to the axis of movement of the piston 30. The Z axis is transverse, for example perpendicular, to the direction of passage of the current in the conductive portion 40. The piston 30 comprises a circumferential groove 31 in which a seal 32, for example an O-ring, is intended to be housed. The piston 30 can move in a direction of movement A along the Z axis inside the body 10 between a high position (first position) as in Figure 5A, and a low position (second position) as in Figure 5B. The direction of movement A is oriented from the pyrotechnic initiator 20 towards the conductive portion 40 or towards the second sealing portion 14b (downward in the example illustrated). As long as the pyrotechnic initiator 20 has not been triggered, the piston 30 is in the first position.

The piston 30 comprises a first sealing portion 33, corresponding here to a lower part of the piston, which has a section narrowing in the direction of movement A of the piston 30. The first portion

Sealing 33 corresponds here to one end of the piston 30 facing the conductive portion 40. In this example, the first sealing portion 33 is of frustoconical shape, for example of circular section. The angle a1 formed by the surface of the first sealing portion 33 with the direction of movement of the piston A may be between 1 ° and 10 °. The eagle a1 can be measured in a plane containing the direction of travel A (or the Z axis). Alternatively, the piston could have other sections, for example oblong, or even square. The upper part 34 of the piston where the groove 31 is present is for its part here of cylindrical shape.

The body 10 defines a cavity 14 in which the piston 30 can move and which is crossed by the conductive portion 40. The cavity 14 is here divided into three parts: an upper part 14a where the wall of the cavity 14 is generally cylindrical in shape, a second sealing portion 14b where the wall has a section narrowing in the direction of movement A of the piston 30, and a lower portion 14c where the wall of the cavity is generally cylindrical in shape. The second sealing portion 14b extends the upper part 14a, and the lower part 14c extends the second sealing portion 14b. In this example, the second sealing portion 14b has a frustoconical shape. In this example, the internal diameter D1 of the cavity 14 at the level of the upper part 14a is greater than the internal diameter D2 of the cavity at the level of the lower part 14c, and the internal diameter of the cavity at the level of the second portion d sealing 14b is reduced

progressively between the upper part 14a and the lower part 14c. The second sealing portion 14b extends on either side of the conductive portion 40, that is to say here on either side of the openings 13 which open into the cavity 14. The second portion d The seal 14b has a surface which forms an angle a2 with the direction of movement A of the piston 30 which may be between 1 ° and 10 °. The angle a2 could be measured in a plane containing the direction of movement A (or the Z axis). The angle a1 and the angle a2 may be the same or be slightly different. For example, the angle a1 can be 3 ° and the angle a2 can be 4 °, or various.

The section of the cavity 14 and its dimensions will be adapted to those of the

piston 30 so that the latter can move in order to cut the conductive portion 40, and that the sealing portions 33 and 14b of the piston and of the wall of the cavity can cooperate in the second position, that is to say say to be in contact along a contact surface which extends on either side of the conductive portion 40.

The conductive portion 40 has, in this example, two zones of weakness 43 (Figure 2) which facilitate the cutting of the conductive portion 40 by the piston 30. In this example, each zone of weakness 43 has a plurality of tongues 43a spaced apart from each other which connect each terminal 41 and 42 of the conductive portion 40 to a part 44 which is intended to be separated from the terminals 41 and 42 and driven by the piston. Other types of fragile zones can be envisaged, for example grooves made in the conductive portion 40. In this example, the conductive portion 40 is cut into three parts by the piston 30. The conductive portion 40 has a width L0. As a variant, other cut-off configurations are possible.

When the piston 30 is in the cavity 14, it separates the cavity 14 into a

first pressurization chamber 15 and a second chamber 16 in which the conductive portion 40 is present.

In the examples illustrated, the conductive portion 40 is separate from the body 10a. Alternatively, the conductive portion 40 can be overmolded with the body 10 (here part 10a) so as to improve the seal between the conductive portion 40 and the body 10.

The different operating steps of the device 100 will now be described in connection with Figures 5A and 5B which show sectional views, respectively when the piston 30 is in the first position and in the second position.

[0037] Figure 5A shows the device 100 before it is triggered. Following the

triggering of the pyrotechnic initiator 20, the chamber 15 is pressurized by the gases resulting from the combustion of the pyrotechnic charge, and the piston 30 moves towards the conductive portion 40 until the first sealing portion 33 of the piston 30 impacts the conductive portion 40. More specifically, the first sealing portion 33 of the piston 30 impacts the part 44 of the conductive portion 40 which then detaches from the parts of the conductive portion 40 connected to the terminals 41 and 42 During the passage of the piston 30, the tabs 43a can be folded back as can be seen on

the enlargement of Figure 5B so as not to impede the stroke of piston 30.

When the piston 30 is in the second position or low position as in Figure 5B, its first sealing portion 33 is in surface contact with the second sealing portion 14b of the cavity 14. In the second position, the piston 30 is interposed between the openings 13. In the second position, the piston 30 is interposed between the terminals 41 and 42 of the switching device. In the second position, the piston 30 is interposed between the fragments of the conductive portion 40 broken. The piston 30 covers, in the second position, the openings 13 which open into the cavity. The contact surface between the piston 30 and the wall of the cavity 14 extends on either side of the initial location of the conductive portion 40 (or, equivalently, on either side of the openings 13 ) so as to create a seal preventing the passage of current between terminals 41 and 42. This contact surface may have a frustoconical shape. In this example, the entire surface of the second sealing portion 14b is in contact with the first sealing portion 33. In this example, the contact surface between the piston 30 and the wall of the cavity 14 surrounds the openings 13. which open into the cavity 14. In this way, the terminals 41 and 42 are sealed from each other. The contact surface between the piston 30 and the wall of the cavity 14 extends around, in particular all around (at 360 ° around), the axis of movement Z of the piston 30. The portion 44 cut from the conductive portion 40 is for its part housed in the lower part 14c of the cavity 14 on a bottom 14d thereof.

The materials of the first sealing portion 33 of the piston 30 and of the part of the body 10 forming the second sealing portion 14b may be identical. As a variant, these materials can advantageously have different hardnesses. The difference in hardness between these materials can be between 50 Shore A and 100 Shore D. Thus, the body 10 or the piston 30 can be deformed during the passage of the piston 30 from the first to the second position which ensures even better contact between the two sealing portions, better sealing and therefore better power cut.

Figures 6 to 8B show views of a switching device 200 according to a second embodiment of the invention. Unless otherwise stated, the identical reference signs between the first and the second embodiment denote identical characteristics. Compared to the device 100, the piston 30 of the device 200 comprises a housing 35 and its cavity 14 has a relief 17. The housing 35 of the piston 30 is present in the sealing portion 33 and opens opposite the conductive portion 40 when the piston 30 is in the first position. In this example, the housing 35 is cylindrical in shape.

The relief 17 extends from a bottom 14d of the cavity 14. In the first position, the relief 17 extends here more precisely between the bottom 14d of the cavity 14 and the conductive portion 40. The relief 17 has a triangular section in a plane containing the conductive portion 40 and the axis of movement A of the piston. The relief 17 extends in a transverse direction T relative to the longitudinal direction L along which the conductive portion 40 extends.

In this example, the conductive portion 40 has grooves as areas of weakness 43, which delimit the part 44 of the conductive portion 40 which will be separated from the terminals 41 and 42 when switching off.

The internal diameter D3 of the housing 35 is greater than the width L0 of the conductive portion 40 so that the housing 35 can accommodate the part 44 after the cut.

The operation of the device 200 is similar to that of the device 100, except that, when the piston 30 is in the second position, the part 44 of the conductive portion 40 which is cut and driven by the piston 30 is bent by the relief 17 in the housing 35. In the second position, the part 44 is located between the relief 17 and the piston 30 in the housing 35, which makes it possible to isolate the part 44 from the terminals 41 and 42, and to further improve the power cut. In particular, with this device 200, the speed of separation of the part 44 from the terminals 41 and 42 is increased, and the separation distance between the part 44 and the terminals 41 and 42 is greater while maintaining a reduced size.

[0046] Figure 9 shows schematically an example of a secure electrical installation 300 implementing a switching device 100 or 200 according to the invention.

The secure electrical installation 300 comprises a secure power supply system 310 comprising a switching device 100 or 200 (shown very schematically) and a supply circuit 31 1. The supply circuit 31 1 here comprises an electric generator G connected to the second terminal 42 of the conductive portion 40 of the switching device 100 or 200. The electric generator G can be for example a battery or an alternator.

[0048] The secure power system 310 further comprises a control element C configured to actuate the pyrotechnic initiator 20 when an anomaly is detected. The control element C is connected to the pyrotechnic initiator 20 via the connectors 21. The anomaly in response to which the control element C can trigger the pyrotechnic initiator 20 may be an electrical anomaly, such as an electrical fault. current threshold exceeded in the circuit, or a non-electrical anomaly such as the detection of a shock, for example a sudden deceleration of the control element, a

change in temperature, pressure, etc. If an anomaly is detected, the control element C is able to send an electric current to the pyrotechnic initiator 20 for its triggering in order to cut off the current, as described above.

The secure electrical installation 300 finally comprises an electrical device D here connected to the first terminal 41 of the conductive portion 40 of the switching device 100 or 200 to be powered by the secure power system 310.

[0050] By way of example, a motor vehicle can include a secure electrical installation 300.

Claims

[Claim 1] Pyrotechnic cut-off device (100; 200)

comprising: a pyrotechnic initiator (20), a conductive portion (40) and a movable piston (30), the piston being able to move in a cavity (14) in a direction of movement (A) following the actuation of the pyrotechnic initiator between a first current flow position in the conductive portion and a second current cutoff position, characterized in that the piston (30) defines a first sealing portion (33) having a section narrowing according to the direction of

displacement (A), and in that the cavity (14) has a wall defining a second sealing portion (14b) which extends on either side of the conductive portion (40) and which has a narrowing of section according to the direction of movement (A), the first sealing portion (33) being in contact with the second sealing portion (14b) along a contact surface extending on either side of the conductive portion (40) when the piston is in the second position, the first sealing portion and the second sealing portion cooperating in the second position so as to create a surface seal on either side of the conductive portion, making it possible to sealingly separate the two terminals of the device between which the conductive portion extends.

[Claim 2] Device (100; 200) according to claim 1, in

wherein the sections of the piston (30) and the cavity (14) are circular or oblong in shape.

[Claim 3] Device (100; 200) according to claim 1 or

Claim 2, wherein the conductive portion (40) is ruptured by impact with the piston (30; 30 ’) when moving from the first to the second position.

[Claim 4] A device (100; 200) according to claim 3, in

wherein the conductive portion (40) has at least one region of weakness (43) to facilitate the breaking of said conductive portion.

[Claim 5] Device (100; 200) according to any of

claims 1 to 4, wherein the first sealing portion (33) has a first surface and the second sealing portion (14b) has a second surface, said surfaces each forming an angle (a1, a2) of between 1 ° and 10 ° with the direction of movement (A) of the piston (30).

[Claim 6] Device (100; 200) according to any of

Claims 1 to 5, wherein the hardness of the material forming the first sealing portion (33) and the hardness of the material forming the second sealing portion (14b) are different.

[Claim 7] Device (200) according to any of

claims 1 to 6, wherein in the first position the piston (30) has a housing (35) and the device further comprises a relief (17) which extends from a bottom (14d) of the cavity, said relief being housed in the housing (35) when the piston is in the second position.

[Claim 8] Secure electrical installation (300) comprising a switching device (100; 200) according to any one of claims 1 to 7 and an electrical circuit connected to the conductive portion (40) of said device.

[Claim 9] A vehicle comprising a secure electrical installation (300) according to claim 8.