FR3071657A1 - PYROTECHNIC CUTTING DEVICE - Google Patents

Abstract

The invention relates to a pyrotechnic breaking device (1) comprising a first (41a) and a second (41b) electrical terminals intended to be connected to a first electrical circuit (111) to be cut, and a third (42a) and a fourth (42b) terminals for connection to a second electrical circuit (112) to be cut, the device comprising: a pyrotechnic initiator (20), a chamber (15) in which a first (41) and a second (42) are present conductive portions, and a piston (30) comprising a lower face (33) from which project a first (34) and a second (35) relief respectively located opposite the first and the second conductive portions, the distance (dl) separating the relief of the first conductive portion being less than the distance (d2) separating the relief of the second conductive portion.

Description

Invention background

The present invention relates to the general field of electrical cut-off devices, and more particularly those of the type with pyrotechnic actuation. The invention also relates to an electrical system secured by such a device.

Are known pyrotechnic cutoff devices 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.

Such devices are generally reliable and allow the current in an electrical circuit to be cut off in a short time. Some electrical systems include, for example, a power part and a control part, or more generally two circuits which are electrically independent but which are used in the same system and which must both be cut in the event of failure. In some cases, the two cuts must not be made simultaneously, for example when trying to cut the power circuit first and then the control circuit.

However, the aforementioned known devices do not make it possible to cut off two independent circuits at a predetermined time interval in a reliable and reproducible manner. To do this, it would be necessary, for example, to use two cut-off devices each connected to a circuit and connected to the same control device which would activate the two cut-off devices at a predefined time interval. Such an assembly is bulky, and the cut is not very reproducible when the cuts must be made in a short time interval.

There is therefore a need for such a pyrotechnic breaking device which makes it possible to cut the current in two independent circuits sequentially and which does not have the abovementioned drawbacks.

Subject and summary of the invention

To this end, the present invention proposes, according to a first aspect, a pyrotechnic cut-off device comprising a first and a second electrical terminal intended to be connected to a first electrical circuit to be cut, and a third and a fourth terminal intended to be connected to a second electrical circuit to be cut, the device comprising:

- a pyrotechnic initiator,

a chamber in which are present a first and a second conductive portion, the first conductive portion electrically connecting the first terminal to the second terminal of the breaking device, the second conducting portion electrically connecting the third terminal to the fourth terminal of the breaking device , and

a movable piston delimiting the chamber and comprising a lower face from which protrudes at least one relief facing the first and the second conductive portions, the distance separating the relief from the first conductive portion being less than the distance separating the relief of the second conductive portion.

The pyrotechnic initiator is configured to switch the cut-off device from a first current flow configuration to a second current cut configuration, the piston being set in motion when switching from the first to the second configuration in order to disconnect first the first conductive portion by rupture thereof by impact with the first relief, then the second conductive portion by rupture thereof by impact with the second relief.

The device according to the invention thus makes it possible to cut off the current in two independent circuits, each connected to a conductive portion by the terminals of the device. This device makes it possible to take advantage of the reliability of the pyrotechnic cut-off devices to cut the current in two circuits sequentially with a predefined time interval. It is understood that the two circuits, thanks to the distance difference separating the relief from the conductive portions, will be cut sequentially at a predefined time interval. The predefined time interval 5 is dependent on this distance difference, as well as on the power of the pyrotechnic initiator which gives the piston its speed of movement in the device. The predefined time interval can be simulated, and easily measured by observing the variation in the voltage and / or the electric current at the terminals of the breaking device after triggering of the initiator.

Compared to an assembly comprising several cut-off devices of the prior art, the cut-off device according to the invention has the advantage of being reliable, more compact, and thus easily integrated into an electrical system.

In an exemplary embodiment, the conductive portions are present on a support facing the relief of the piston, said support being provided with a groove in which the relief of the piston is intended to be received when the device is in the second configuration .

In an exemplary embodiment, the piston may include a first relief and a second relief situated respectively opposite the first conductive portion and the second conductive portion, the first relief 25 extending from the underside of the piston on a length different from the length over which the second relief extends from said face.

In this case, the first relief may extend from the lower face 30 of the piston over a length strictly greater than the length over which the second relief extends from said face.

Alternatively, the piston may comprise a single relief having a lower face facing the conductive portions, said face being separated by a constant distance from the lower face of the piston.

In an exemplary embodiment, the conductive portions may be located in the same plane transverse to an axis of movement of the piston in the cut-off device.

In an exemplary embodiment, the first conductive portion can be offset with respect to the second conductive portion along an axis of movement of the piston in the cut-off device.

The invention also relates, according to a second aspect, to a secure electrical system comprising at least:

a secure power system comprising at least:

a breaking device such as that described above, • a first electrical circuit connected to the first and second terminals of the breaking device, and a second electrical circuit connected to the third and fourth terminals of the breaking device,

a first electrical device connected to the first circuit of the supply system and intended to be supplied by the latter,

a second electrical device connected to the second circuit of the supply system and intended to be supplied by the latter, and

- a control device configured to activate the pyrotechnic initiator when an anomaly is detected.

The first electrical circuit may be a ... The second electrical circuit may be a ...

The invention also relates to an electrical installation comprising such a secure electrical circuit. Such an installation can be present for example inside a motor vehicle or an electricity generator.

Brief description of the drawings

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate exemplary embodiments thereof without any limiting character. In the figures:

FIGS. 1A and 1B are exploded perspective views of a cut-off device according to an embodiment of the invention,

FIG. 2 shows a cut-off device according to an embodiment of the invention in cross section along a plane perpendicular to an axis connecting the two terminals of the device,

- Figures 3A to 3D show a cut-off device according to an embodiment of the invention at different times after it is triggered in longitudinal section along a plane perpendicular to the cut plane of Figure 2 and containing the axis of movement of the piston ,

FIG. 4 schematically shows an example of a secure electrical system comprising a device according to an embodiment of the invention, and

- Figure 5 shows schematically a cross-sectional view of a cutting device according to another embodiment of the invention.

Detailed description of the invention

Figures IA and IB show two exploded views of a cut-off device 1 according to an embodiment of the invention, and Figure 2 shows a cross-sectional view. The cut-off device 1 illustrated comprises: a body 10, a pyrotechnic initiator 20, a piston 30, a first conductive portion 41, a second conductive portion 42, and a support 50. In the example illustrated, the longitudinal direction L corresponds to the direction in which the conductive portions 41 and 42 extend connecting terminals 44 and 45 of the device 1. The transverse direction T is perpendicular to this direction in the plane of the conductive portions 41 and 42.

The device 1 comprises a first 41a and a second 41b electrical terminals intended to be connected to a first electrical circuit to be cut, and a third 42a and a fourth 42b electrical terminals intended to be connected to a second electrical circuit to be cut. Each conductive portion 41 and 42 here takes the form of a flattened conductive bar or tab. The first conductive portion 41 extends between the first terminal 41a and the second terminal 41b of the breaking device 1 by connecting them electrically. The second conductive portion 42 extends between the third terminal 42a and the fourth terminal 42b of the breaking device 1 by connecting them electrically. An example of assembly comprising these circuits will be described in connection with FIG. 4.

The body 10 here has a generally parallelepiped shape. The body 10 comprises a lateral opening 11 through which the support 50 is intended to be inserted inside the body 10, a generally circular lower opening 12 through which the piston 30 is intended to be inserted inside the body 10, and an upper opening 13 projecting from an upper face of the body 10 through which the initiator 20 is intended to be inserted inside the body 10. The lateral opening 11 extends in the longitudinal direction L inside the body 10 to form a housing in which the support 50 is held in the body 10.

The pyrotechnic initiator 20 comprises two conductive elements 21 configured to initiate a pyrotechnic charge 22 to which they are connected. The pyrotechnic charge 22 is, when it is initiated for example using a current passing through the conductive elements 21, capable of generating a pressurization gas by its combustion. The conductive elements 21 can be connected to a control device C (FIG. 4) configured to actuate the pyrotechnic initiator 20 when an anomaly is detected.

The piston 30 is, in this example, cylindrical in shape and centered on a vertical axis Z. The axis Z here corresponds to the axis of movement of the piston 30. The piston 30 comprises a circumferential groove 31 in which a gasket sealing 32, for example an O-ring, is intended to be housed. The piston 30 can move along the axis Z inside the body 10 between a high position (first position, device in the first configuration), as in FIGS. 2 and 3A, and a low position (second position , device in the second configuration), as in Figure 3D. As long as the pyrotechnic initiator 20 has not been triggered, the piston 30 is held in the high position. Of course, the piston may have a shape different from that illustrated, adapted to the shape of the cavity inside the body.

As illustrated in FIG. 2, the body 10 comprises a first pressurization chamber 14 in communication with an outlet S of the pyrotechnic initiator 20, and a second chamber 15 in which the conductive portions 41 and 42 are present. The piston 30 separates the first chamber 14 from the second chamber 15 hermetically using the seal 32.

According to the invention, the piston 30 comprises a lower face 33 from which project a first relief 34 and a second relief 35. The first relief 34 and the second relief 35 are located respectively opposite the first conductive portion 41 and of the second conductive portion 42. The reliefs 34 and 35 generally extend here in the transverse direction T and are joined to one another for greater simplicity of manufacture, they then form a step. In this case, each relief 34 and 35 may have a dimension in the transverse direction T which is greater than the dimension, in this same direction T, of the conductive portion 41 or 42 opposite which it is positioned. Of course, the reliefs 34 and 35 could be separated from each other and have a dimension in the transverse direction T substantially equal to the dimension, in this same direction T, of the corresponding conductive portion opposite which it is positioned. The reliefs 34 and 35 also extend in the direction L and have a non-zero thickness in this direction L.

In the example illustrated here, the conductive portions 41 and 42 are present in the same plane P transverse with respect to the axis Z, for example perpendicular to the axis Z (see FIG. 2). Other configurations are possible as will be described below, in connection with FIG. 5.

When the device is in the first configuration, the first relief 34 is spaced from the first portion 41 by a first distance di (see FIG. 2). When the device is in the first configuration, the second relief 35 is spaced from the second portion 42 by a second distance d ₂ (see FIG. 2). The distances di and d ₂ are, unless otherwise stated, measured along the axis Z of displacement of the piston 30. In the example illustrated here, the first distance di is strictly less than the second distance d ₂ . In this way, when the pyrotechnic initiator 20 is triggered, the piston 30 moves in the direction Z in the direction of the conductive portions 41 and 42, and the first relief 34 comes to cut the first conductive portion 41 before the second relief 35 does cut the second conductive portion 42.

As illustrated in FIGS. 1B and 3A, the first relief 34 extends from the lower face 33 of the piston 30 over a length L1 greater than the length L2 over which the second relief 35 extends from this same face 33. The lengths L1 and L2 are measured transversely with respect to the face 33 or in a direction perpendicular to the face 33, that is to say in the direction given by the axis Z of displacement of the piston 30.

The support 50 takes, in the example illustrated, the form of a drawer on which the conductive portions 41 and 42 are present. In the example illustrated, the support 50 is configured to hold the conductive portions 41 and 42 in position in the device 1, for example by providing corresponding housings therein. The support 50 is here provided with a groove 51 which extends in the transverse direction T in which the reliefs 34 and 35 are intended to be housed after triggering of the pyrotechnic initiator 20 and once the conductive portions 41 and 42 were cut. The groove 51 in the support thus makes it possible to lock the piston 30 in the second position and to ensure a definitive cut-off of the conductive portions 41 and 42.

The different stages of operation of the device 1 will now be described in connection with FIGS. 3A to 3D which show views in longitudinal section thereof, that is to say in a plane containing the direction L and the axis Z. The FIG. 3A represents the device 1 in the first configuration (piston in the first position or high position), that is to say before triggering of the pyrotechnic initiator 20. Following the triggering of the pyrotechnic initiator 20, the chamber 14 is pressurized by the gases from the combustion of the pyrotechnic charge 22, the piston 30 sets in motion towards the conductive portions 41 and 42 in the direction Z until the first relief 34 comes to impact the first conductive portion 41 (FIG. 3B). Then, the first relief 34 breaks or cuts the first conductive portion 41 (FIG. 3C). Finally, the piston 30 still continues its stroke until the second relief 35 comes to impact the second conductive portion 42 and also breaks it. At the end of stroke of the piston 30, in the second position or low position, the reliefs 34 and 35 are housed in the groove 51 of the support 50 (Figure 3D).

FIG. 4 shows an example of a secure electrical system 100 implementing a switching device 1 according to the invention. The secure electrical system comprises a secure supply system 110 comprising a cut-off device 1, a first electrical circuit 111 and a second electrical circuit 112. The first electrical circuit 111 here comprises a first electrical generator G1 connected to the first terminal 41a of the switching device 1. The second electrical circuit 112 here comprises a second electrical generator G2, different from Gl, connected to the third terminal 42a of the switching device 1.

The secure electrical system 100 further comprises a first electrical device Dl connected on the one hand to the generator Gl to be supplied by the latter, and on the other hand to the second terminal 41b of the switching device 1, and a second electrical device D2 connected on the one hand to the second generator G2 to be supplied by the latter and on the other hand to the fourth terminal 42b of the breaking device 1.

The secure electrical system 100 further comprises a control device C configured to actuate the pyrotechnic initiator 20 when an anomaly is detected. The control device C is connected to the pyrotechnic initiator 20 via the conductors 21. In the example illustrated, the control device C is connected to the first circuit 111 and to the second circuit 112 to detect the passing of a current threshold. Of course, the anomaly can be of another type, and in particular be a non-electrical anomaly such as the detection of a shock, a change in temperature, etc. If an anomaly is detected, the control device C is able to send an electrical signal to the pyrotechnic initiator 20 for its triggering in order to cut the current in the first circuit 111, then in the second circuit 112, by breaking sequential of the first conductive portion 41 and the second conductive portion 42.

We have just described a device 1 in which the piston 30 comprises two reliefs 34 and 35 which project from a lower face 33 of the piston 30 over a different length. It is not, however, outside the scope of the invention when this is not the case.

As such, Figure 5 shows a sectional view transverse to the direction L, a variant of the switching device in the first configuration. Unless otherwise stated, identical reference signs in different figures denote the same characteristics. According to this variant, the cut-off device 1 ′ comprises piston 30 provided with a single protruding relief 34 ′, the relief 34 ′ having a lower face 36 facing the conductive portions 41 and 42, said face 36 being separated from a constant distance L3 from the underside 33 of the piston (shown in dotted lines in this figure). In this embodiment, the first conductive portion 41 is present in a first plane PI transverse to the direction Z, and the second conductive portion 42 is present in a second plane P2 transverse to the direction Z and offset with respect to the plane PI along this axis Z. The support 50 can be configured to raise the first conductive portion 41 relative to the second conductive portion 42. Thus, in this variant of FIG. 5, the first distance di separating the first portion 41 from the relief 36 'is always strictly less than the second distance d ₂ separating the relief 35 'from the second conductive portion. The operation of the cut-off device is identical to that described above.

Claims (8)

1. Pyrotechnic breaking device (1; 19 comprising a first (41a) and a second (41b) electrical terminals intended to be connected to a first electrical circuit (111) to be cut, and a third (42a) and a fourth (42b ) terminals intended to be connected to a second electrical circuit (112) to be cut, the device comprising: - a pyrotechnic initiator (20), - a chamber (15) in which are present a first (41) and a second (42) conductive portions, the first conductive portion electrically connecting the first terminal to the second terminal of the breaking device, the second conductive portion electrically connecting the third terminal at the fourth terminal of the breaking device, and - a movable piston (30) delimiting the chamber and comprising a lower face (33) from which projects at least one relief (34, 35; 34 ') opposite the first and second conductive portions, the distance (dl) separating the relief from the first conductive portion being less than the distance (d2) separating the relief from the second conductive portion, the pyrotechnic initiator being configured to pass the cut-off device from a first current flow configuration to a second configuration for cutting the current, the piston being set in motion when switching from the first to the second configuration in order to disconnect the first conductive portion first by breaking it by impact with the relief, then the second conductive portion by breaking thereof by impact with the relief. 2. Device (1) according to claim 1, wherein the piston comprises a first relief (34) and a second relief (35) located respectively opposite the first conductive portion (41) and the second conductive portion (42) , the first relief extending from the lower face (33) of the piston over a length (L1) different from the length (L2) over which the second relief extends from said face. 3. Device (1) according to claim 2, wherein the first relief extends from the underside (33) of the piston over a length (L1) strictly greater than the length (L2) over which the second relief from said face. 4. Device (1 ') according to claim 1, wherein the piston comprises a single relief (34') having a lower face (33) facing the conductive portions, said face being separated by a constant distance from the lower face (33) of the piston. 5. Device (1) according to any one of claims 1 to 3, wherein the conductive portions (41, 42) are located in the same transverse plane (P) to an axis (Z) of displacement of the piston (30) in the cut-off device. 6. Device (1 ') according to any one of claims 1 to 4, in which the first conductive portion (41) is offset with respect to the second conductive portion (42) along an axis (Z) of displacement of the piston ( 30) in the cut-off device. 7. Secure electrical system (100) comprising at least: a secure supply system (110) comprising at least: a cut-off device (1) according to any one of claims 1 to 6, a first electrical circuit (111) connected to the first (41a) and second (41b) terminals of the cut-off device, and a second electrical circuit (112) connected to the third (42a) and fourth (42b) terminals of the breaking device, - a first electrical device (Dl) connected to the first circuit of the supply system and intended to be supplied by the latter, a second electrical device (D2) connected to the second circuit of the supply system and intended to be supplied by the latter, and - a control device (C) configured to activate the pyrotechnic initiator (20) when an anomaly is detected. 8. Electrical installation comprising a secure electrical system according to claim 7.