TECHNICAL FIELD

This specification relates to a pyromechanical separation device.

BACKGROUND

Pyromechanical separation devices or pyrotechnical safety switches (PSSs) are for example described in EP 1 447 640 A1 , US 2007/0034491 A1 , and US 2019/0108957 A1. A PSS is a device that utilizes a small pyrotechnical charge in order to either couple or decouple a conductive wire. A PSS is triggered with a control signal having an electric current high enough to cause the PSS’s pyrotechnical charge to explode. The explosion then propels a non-conductive cutting head through the PSS’s conductor, thus breaking a circuit.

US2014061161 A1 discloses a conduction breaking device, which includes a conductive body arranged between a pair of devices in an electric circuit, a gas generator, which is arranged away from the conductive body and generates gas, and a cutting member, which is arranged between the conductive body and the gas generator. The cutting member is moved due to gas from the gas generator to cut the conductive body, divides the conductive body into a first cut piece and a second cut piece, which have cut ends separated from each other, and breaks the conduction between the devices. The conduction breaking device includes an arc-extinguishing chamber. In the arc-extinguishing chamber, the conductive body is cut by the cutting member and an arc occurring between the cut end of the first cut piece and the cut end of the second cut piece is extinguished. A first inner wall in the arc-extinguishing chamber is formed with an uneven portio, which includes recesses and protrusions arranged at constant intervals in the direction extending from the cut end of the first cut piece to the cut end of the second cut piece. A magnet may be applied for applying a magnetic attractive force (Lorentz force: force to be applied to charge particles moving in a magnetic field) toward the uneven portion on an arc outside the arc-extinguishing chamber, and near the uneven portion or on the opposite side of the cut end of the first cut piece across the uneven portion, when an arc occurs between the cut ends, a magnetic attractive force of the magnet acts on the arc. The arc is pulled toward the uneven portion due to the magnetic attractive force. Therefore, the uneven portion is formed at the portion meeting the above condition on an inner wall of the arc-extinguishing chamber, and however, the arc moves along the wall of the uneven portion. The arc moves along the uneven portion, and therefore, the distance (creeping distance) of the arc moving path is longer than when the uneven portion is not provided, and the arc is easily extinguished.

SUMMARY

This specification describes a pyromechanical separation device comprising a housing, an electrical bus bar being at least partly arranged inside the housing, a separation element being arranged inside the housing and having a cutting section, which is arranged above the part of the electrical bus bar being arranged inside the housing and provided for cutting through the electrical busbar, a pyrotechnical element being arranged inside the housing above the separation element such that an ignition of the pyrotechnical element propels the separation element in the direction of the part of the electrical bus bar being arranged inside the housing for cutting through the bus bar with the cutting section, a cooling element comprising metal wool and being arranged in in a predetermined distance to the part of the electrical bus bar, which is arranged inside the housing and provided to be cut through by the cutting section, and a magnet providing a magnetic field such that an electric arc occurring at the cut through electrical bus bar is directed to the cooling element. With directing an electric arc incurred between the cut through bus bar to the cooling element, the electric arc may be quicker extinguishing than without a cooling element. The magnetic field supports the extinguishing of the arc since it may speed up the extinguishing by forcing the arc to the cooling element and may also extending the length of the arc, which may increase its voltage and, thus, help to break and extinguish the arc. The quick extinguishing of electric arcs inside the housing may also help to reduce the pressure inside the housing of the pyromechanical separation device and by this to avoid damages of the housing such as for example a breaking of the housing. Metal wool can be placed for example in a chamber of the housing, which has the predetermined distance to the part of the electrical bus bar, which is arranged inside the housing and provided to be cut through by the cutting section. Metal wool has the advantage that its contact surface with hot gases of the arc is large and can, therefore, efficiently cool the arc and its hot gases, respectively.

The cooling element may comprisesteel wool.

The housing may have a cylindrical shape and the separation element may be shaped as a plunger movably arranged inside the cylindrically shaped housing, wherein one side of the separation element is faced to the pyrotechnical element and the other side of the separation element comprises the cutting section.

The cutting section may be shaped like a chisel having a longitudinally extending body with a cutting edge, wherein a gap is provided between at least a part of the body and the interior side of the housing for guiding an electric arc occurring at the cut through electrical bus bar. Particularly, the gap may be between about 1 to about 500 micrometers. With such a thin gap, the voltage of the electric arc may become high and build-up quick, which may support a faster extinguishing of the arc.

The magnet may be arranged such that the cooling element is positioned between the part of the electrical bus bar, which is arranged inside the housing and provided to be cut through by the cutting section, and the magnet. Other positions of the magnet are possible, depending on the polarity of the bus bar. The position depends also on the magnetic field of the magnet. The position of the magnet must therefore be selected depending on the polarity of the bus bar, i.e. the direction of flow of the electric current through the busbar, and the magnetic field direction such that an electric arc is directed to the cooling element.

The housing may comprise an upper part, in which the separation element and pyrotechnical element are arranged, and a lower part, in which the cooling element is arranged, wherein the part of the electrical bus bar, which is provided to be cut through by the cutting section, is arranged between the upper part and the lower part. Such a housing is easy to assemble. The magnet may be attached to an end of a yoke, which is attached to the lower part of the housing. This allows to easily replace the magnet and adapt the pyromechanical separation device to different polarities.

Finally, the housing may be configured to be enclosed such that a venting of hot gases incurred by the electric arc within the housing out of the housing is prevented, and at least hindered. Thus, damages of devices, which are located close to the pyromechanical separation device, by hot gases may be avoided.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

Fig. 1 shows a sectional view of an example of pyromechanical separation device; and

Figs. 2A and 2B show a front sectional view in the x-y plane and a side sectional view in the z-y plane of the pyromechanical separation device of Fig. 1 .

DETAILED DESCRIPTION

In the following, functionally similar or identical elements may have the same reference numerals. Absolute values are shown below by way of example only and should not be construed as limiting. Also, the example described in the following may be construed as limiting the claimed subject matter.

Fig. 1 shows a pyromechanical separation device 10. Fig. 1 is a sectional view of the device 10 along two planes perpendicular to each other, namely the x-y plane and the y-z plane as the cartesian coordinate system at the top of Fig. 1 shows. The shown device 10 is provided for conducting DC (direct current).

The pyromechanical separation device 10 comprises a housing having an upper part 12 and a lower part 12’. Both parts 12, 12’ may have a cylindrical shape. Seals 12”” may be provided between both housing parts 12, 12’, for example ring seals, tightening the interior of the housing from the environment. The sealing by the seals 12”” may prevent, and at least hinder hot gases, which may be incurred inside the housing 12, 12’ by an electric arc, to be vented out of the housing 12, 12’.

A bus bar 14 is arranged between both parts 12, 12’ so that a part of the bus bar 14 is arranged inside the housing of the device 10. The bus bar 14 part arranged inside the housing is provided to be cut through and, thus, separating an electric circuit connected via the bus bar 14, for example separating an electric consumer such as an electric motor from an electric source such as a battery.

The upper part 12 houses in its upper end portion 12” a pyrotechnical element 18 and a separation element 16 in the form of a plunger, which is made from an electrically isolating material such as plastic. The pyrotechnical element 18 comprises a pyrotechnical charge (not shown), which can be ignited with an electric current. The separation element 16 comprises at its upper side 16’ a cavity 16’” and at its lower side 16” a cutting section 17 in the form of a chisel having a longitudinally extending body 17’ with a cutting edge 17”. The separation element 16 may comprise at is exterior a circumferential groove for a ring seal 16”” tightening the interior of the upper part 12 from the lower part 12’. The ring seal 16”” may be further designed for facilitating the axial movement of the separation element 16 within the upper part 12 of the housing.

In an unfired state, the separation element 16 is positioned at the upper end portion 12” so that its upper side 16’ abuts the lower side of the upper end portion 12”, and a gas outlet 18 of the pyrotechnical element 18’ may project at least partly into the cavity 16’”.

An ignition of the pyrotechnical element 18’ incurred by an electric current injected into a connector (not shown) of the pyrotechnical element 18 causes an explosion of the pyrotechnical charge contained in the pyrotechnical element 18 and the generation of a gas with a high pressure within the pyrotechnical element 18’. The gas may pass off the pyrotechnical element 18 via a gas outlet 18’ of the pyrotechnical element 18 into the cavity 16”’ of the separation element 16. Due to the high pressure of the gas, the separation element 16 is propelled downwards to the part of the bus bar 14, which is arranged inside the housing parts 12 and 12’ between them. The propelling separation element 16 cuts with the cutting edge 17” through the bus bar 14 separating it into two separate pieces. This fired state with the bus bar 14 cut through into two separate pieces is shown in Fig. 1 .

Depending on the current conducted by the bus bar 14 and the electric voltage on the bus bar 14, an electric arc or arc discharge may be generated between the two pieces of the cut through bus bar 14. The generation of the electric arc may generate a pressure inside the housing 12, 12’. This pressure may increase the pressure already created by the explosion of the pyrotechnical charge and, thus, the total pressure inside the housing 12, 12’. To avoid a damage of the housing by the internally generated high pressure, a measure for cooling the electric arc may be provided, in order to extinguish the arc. This measure will be now described in detail.

A small or thin gap 17’” is provided between the interior of the lower part 12’ of the housing and the longitudinally extending body 17’ of the cutting section 17. “Small” or “thin” means such a dimension that an electric arc generated between the two pieces of the cut through bus bar 14 may be guided into and by the gap in a downward direction into the lower part 12’ of the housing and is not blocked by the cutting section. In other words, the gap 17’” is a channel allowing an electric arc to propagate into the lower part 12’, particularly passing along the cutting section 17.

In a lower end portion 12’” of the lower part 12’ of the housing, a cooling element in the form of metal wool 20 is arranged in in a predetermined distance to the part of the electrical bus bar 14, which is arranged inside the housing 12, 12’ and provided to be cut through by the cutting section 17. The metal wool 20 can cool down the temperature of the electric arc so that it extinguishes and the pressure inside the housing 12, 12’ decreases.

The predetermined distance is selected such that the length of the electric arc directed to the metal wool 20 supports an increase of the arc’s electric voltage, which may in addition to the cooling by the metal wool 20 support extinguishing the electric arc.

A magnet 22 is also arranged at the bottom of the lower part 12’, which abuts the lower end section 12’”. The magnet 22 is arranged outside the lower part 12’ of the housing and hold by a yoke 24, at one end of which the magnet 22 is attached to. The yoke 24 itself is attached to the lower part 12’ of the housing, particularly to its exterior.

The magnet 22, which may be a permanent magnet, e.g. made of SiMCo, or an electromagnet, provides a magnet field, which is selected to direct the electric arc to the metal wool 20. The magnetic field is particularly selected to be adapted to the polarity of the electric current conducted by the bus bar 14, but also to certain other parameters such as for example the amperage. Particularly, the direction and/or strength of the magnetic field of the magnet 22 may be selected depending on the polarity and/or amperage on the bus bar 14. If the amperage is relatively low, a high magnetic field strength may be required to direct an electric arc into the metal wool 20, while a high amperage on the bus bar 14 may require a lower magnetic field strength. Similarly, the direction of the magnetic field may be selected depending on the polarity of the DC flowing through the bus bar 14.

The magnet 22 can be for example a replaceable part in order to adapt the separation device 10 to specific requirements. For example, if the pyromechanical separation device 10 is applied in an electric circuit with high amperage, a permanent magnet 22 may be selected and used in the device 10, which provides a magnetic field strength high enough to direct an incurred electric arc after cutting through the bus bar 14 into the metal wool 20 and to cool the arc down to a temperature where it may extinguish and the pressure caused by the arc may be decreased.

The magnet 22 may be also implemented by an electromagnet, which may be respectively powered depending on the required magnetic field strength and direction.

Fig. 2A shows a front sectional view in the x-y plane of the pyromechanical separation device 10 of Fig. 1 , and Fig. 2B a side sectional view in the z-y plane.