JP2000329500A - Squib - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce manufacturing cost while enhancing reliability of environment resistant performance. SOLUTION: The squib 1 comprises a plug 4 inserted into a tubular body 2 in order to seal a firing powder 3 and an electric bridge wire 7, and two electrode pins 5, 6 connected with the electric bridge wire 7 while penetrating the plug 4. The tubular body 2 and the plug 4 are formed of resin. Each electrode pin 5, 6 is composed of a single conductive material and curved 45 in the plug 4. Since the interface between the electrode pins 5, 6 and the plug 4 is lengthened, sealing performance is enhanced. Furthermore, manufacturing cost can be reduced because the electrodes 5, 6 can be formed of a single conductive material 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a squib used for a gas generator for operating a seat belt pretensioner, an airbag, and the like, and a method of manufacturing the squib.

[0002]

2. Description of the Related Art Seat belt pretensioners, airbags, and the like are known as devices for protecting an occupant from an impact generated at the time of an automobile collision. These pretensioners and the like are activated by a large amount of gas introduced from a gas generator to protect occupants. The gas generator includes a squib (igniter), a gas generating agent, and the like, and ignites the squib at the time of collision to ignite and burn the gas generating agent to rapidly generate a large amount of gas.

As an example of a squib used for a gas generator, as shown in FIG.
2 and an embolus 104 that is inserted into the tube 102 and seals the igniter 103 is formed of a plastic resin or the like. Further, the embolus 104 is provided with two electrode pins 105 and 106 penetrating the embolus 104. Each of these electrode pins 105 and 106 has a pin material 109 projecting into the tube 102 and a pin material 1 projecting to the opposite side of the tube 102.
10 is electrically connected (welded). In addition, the pin material 109 in the tube 102 is
Are connected to each other, and the electric bridge line 107 is covered by an ignition ball 108 in contact with the ignition charge 103. This squib
It is mounted on a gas generator and generates heat on the bridge wire 107 by energizing each of the electrode pins 105 and 106, so that the ignition ball 1
08 is ignited, and the ignition charge 103 is subsequently ignited and burned. Then, the flame of the igniting agent 103 is blown out from the conduction hole (not shown) of the tube 102 into the gas generator, and the gas generating agent loaded in the gas generator is ignited and burned. Also, in the squib, the tube 102 and the embolus 104
Is formed of plastic resin or the like in order to reduce the manufacturing cost as compared with the conventional plug 104 or the like formed of glass or ceramics.

[0004]

In a conventional squib,
As shown in FIG. 7, since the electrode pins 105 and 106 are configured to penetrate the embolus 104 linearly, the embolus 104
The plug 104 and each electrode pin 105,
There is a possibility that a gap is formed between the tube 106 and water, air, and the like enter (leak) the tube 102 and come into contact with the ignition agent 103 and the like. In an automobile environment, it is necessary to guarantee the performance for a long period of 15 years. However, in the conventional squib, the ignition powder 103 and the like are deteriorated by intrusion of water and the like,
It is difficult to guarantee its performance. Further, the pressure at the time of ignition may cause the electrode pins 105 and 106 to jump out of the embolus 104.

In the conventional squib, each electrode pin 10
5 and 106 are composed of two pin members 109 and 110, and the pin members 109 and 110 are electrically connected (welded).
It is not possible to reduce the cost more than forming the second or the like with a plastic resin or the like. In recent years, with the spread of pretensioners and airbags, the cost of gas generators has been demanded to be reduced. Accordingly, it is necessary to reduce the cost of squibs.

[0006] The present invention provides a squib capable of increasing reliability with respect to environmental resistance performance and reducing manufacturing costs.
And a method for manufacturing a squib.

[0007]

The squib of the present invention comprises an embolus which is inserted into a tube to seal an explosive and an electric wire, and two electrodes which are respectively connected to the electric wire and penetrate through the embolus. The embolus is formed of a resin, and each electrode is constituted by a single member, and has a structure having a curved shape inside the embolus. Thereby, the interface between the embolus (resin) and each electrode can be lengthened (the contact area can be increased), and the sealing property can be improved. Also, a structure in which the embolus is difficult to deform due to the curved shape of each electrode can be provided.
Further, the curved shape can prevent the electrode pin from jumping out of the embolus due to the pressure at the time of firing. By configuring each electrode with a single member, it is possible to provide an inexpensive squib with a reduced number of parts and manufacturing steps.

In the squib of the present invention, each electrode, a curved shape is formed on the electrode, an embolus is formed by filling with a resin, and the curved shape of each electrode is arranged inside the embolus.
Thereby, the interface with the embolus (resin) can be lengthened (the contact area can be increased), and the sealing property can be improved. Also, a structure in which the embolus is difficult to deform due to the curved shape of each electrode can be provided. Also, after forming each electrode from one conductive material,
By cutting the U-shaped side of the conductive material protruding from the embolus,
Each electrode can be composed of a single member. Therefore, the number of parts,
It is possible to provide an inexpensive squib by reducing the number of manufacturing steps. Further, by simultaneously forming the curved shape at the time of forming the U-shape, it is possible to further reduce the manufacturing cost.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A squib according to an embodiment of the present invention will be described with reference to the drawings.

The squib 1 shown in FIGS. 1 and 2 has a tubular body 2 and an embolus 4 formed of resin. The squib 1 comprises an ignition charge 3, two electrode pins 5 and 6, and an electric wire 7. It is comprised including.

The tube 2 of the squib 1 is formed in a cup shape for accommodating the ignition charge 3. The tubular body 2 has a stepped shape whose diameter is enlarged at the opening 2a side with respect to the cup bottom 2b side. An annular inner groove 14 is formed in the inner periphery of the cup bottom 2b, and the thinned rupture portion 1 is formed in the cup bottom 2b.
Five. Further, the end of the opening 2a of the tube 2 is formed in such a shape that its diameter is tapered from the outer periphery toward the inner periphery.
The tube 2 is made of, for example, PBT (polybutylene terephthalate), PET (polyethylene terephthalate), PA
6 (nylon 6), PA66 (nylon 66), PPS
(Polyphenylene sulfide), PPO (polyphenylene oxide), and other resins containing glass fibers (reinforcing material) and the like.

The igniting agent 3 in the tube 2 has zirconium (Zr), tungsten (W), and potassium perchlorate (KClO ₄ ) as components and uses a fluororubber or nitrocellulose as a binder. It is preferred to use. Further, it is preferable that the igniting agent 3 is in the form of powder or granules in order to increase the contact with the electric bridge wire 7.

The plug 4 of the squib 1 is formed in a stepped shaft shape closely contacting the inner peripheral shape (stepped shape) of the tube 2. The embolus 4 is composed of a shaft 16 and a flange shaft 18 whose diameter is enlarged from the shaft 16, and has a projection 19 formed on the outer periphery of the shaft 16 to be fitted into the inner groove 14 of the tube 2.
The flange shaft 18 has a tapered shape 21 whose diameter decreases toward the opposite side of the shaft body 16. And embolus 4
Is composed of a resin such as PBT, PA6, PA66 or the like containing glass fiber (reinforcing material) or the like.

Each of the electrode pins 5 and 6 of the squib 1 is
And is arranged in parallel along the axis of the embolus 4. Each electrode pin 5, 6 is made of a single conductive material (for example,
SUS stainless steel, iron / nickel alloy, etc.) and is electrically insulated by the resin of the plug 4. Each of the electrode pins 5 and 6 has a shape 45 (hereinafter, referred to as a “curved shape 45”) that curves from the tip of the shaft body 16 in the embolus 4.
And extending. Curved shape 45 of each electrode pin 5, 6
Are formed at an angle of 180 degrees in the circumferential direction of the embolus 4,
At the position of the flange shaft 18 of the embolus 4, it is formed so as to protrude from the outer peripheral side of the flange shaft 18 so as to be separated from each other. Each curved shape 45 is protruded to the vicinity of the outer periphery of the flange shaft 18, and preferably, the curved apex a is located outside the outer periphery of the shaft 16. Thus, the curved shape 45 has a structure in which the interface between each of the electrode pins 5 and 6 and the plug 4 (resin) is long (the contact area is large).

The electric bridge wire 7 of the squib 1 is connected to the tip of each of the electrode pins 5 and 6 on the shaft body 16 so as to extend between the electrode pins 5 and 6. The electric bridge wire 7 generates heat by energizing the electrode pins 5 and 6 to ignite and burn the ignition charge 3.

The squib 1 is integrated by inserting the embolus 4 into the tube 2 from the electric bridge line 7 side (the shaft 16 side) and fitting the projection 19 into the inner groove 14. Now, the embolus 4 and the tube 2
Means that the tube 2 is in close contact from the cup bottom 2b side to the opening 2a, the sealing property is increased by an increase in the contact area, and the electric bridge 7 and the ignition charge 3 are sealed in a contact pressure state. The squib 1 ignites and burns the ignition charge 3 by causing the electric bridge wire 7 to generate heat by energizing the electrode pins 5 and 6. Then, the rupture portion 15 of the tube 2 is ruptured due to an increase in the internal pressure of the tube 2 due to the combustion of the igniting agent 3, so that the flame of the igniting agent 3 is blown out (inside the gas generator).

As described above, in the squib 1 of the present invention, each of the electrode pins 5, 6 has a structure having a curved shape 45 inside the plug 4 (flange shaft 18). The interface with (resin) can be lengthened (the contact area can be increased). Each of the electrode pins 5, 6 reinforces the plug 4 by a curved shape 45 protruding to the outer peripheral side of the flange shaft body 18, and functions as a structure that is difficult to deform the resin. Therefore, even if the embolus 4 is formed of resin, there is no gap between each of the electrode pins 5 and 6, and water, air, and the like can enter (leak) and deteriorate the ignition agent 3. Disappears. As a result, the reliability with respect to the environmental resistance performance can be improved, and the performance can be guaranteed over a long service life.
Further, when the curved shape 45 is formed on each of the electrode pins 5, 6, it is possible to prevent the electrode pins 5, 6 from jumping out of the embolus 4 due to the internal pressure at the time of firing. And in Squib 1,
By increasing the contact area between the embolus 4 and the tubular body 2 to improve the sealing property, the embolus 4 and each of the electrode pins 5,
6, intrusion (leakage) of water, air, and the like from between the embolus 4 and the tube 2 can be reliably prevented.

Further, by forming each of the electrode pins 5 and 6 with a single conductive material, the number of parts and the number of manufacturing steps (connection steps) can be reduced, and an inexpensive squib 1 can be provided. In addition, Denbashi Line 7
And the ignition charge 3 is brought into contact with each other, and the ignition charge 3 is ignited and burned only by the heat generated by the electric bridge wire 7, so that it is not necessary to cover the electric bridge wire with an ignition ball as in the related art (see FIG. 7). .

Next, a method for manufacturing a squib according to the present invention will be described with reference to FIGS.

One conductive material 40 (for example, SUS stainless steel, iron / nickel alloy, etc.) is prepared, and the conductive material 40 is formed into a U-shape by press molding or the like. Thus, two electrode pins 5 and 6 connected in parallel at the U-shaped side 46 of the conductive material 40 are formed (first step). And the conductive material 40
A curved shape 45 is formed for each of the electrode pins 5 and 6 by press molding or the like. Each curved shape 45 is formed so as to protrude outward away from each other at an angle of 180 degrees in the circumferential direction of the electrode pins 5 and 6 (second step) [FIG.
(A)]. Note that the first step and the second step are performed simultaneously by press forming or the like, so that the electrode pins 5 and 6 and the curved shapes 4 of the electrode pins 5 and 6 are formed on the conductive material 40.
5 may be integrally formed.

Subsequently, the conductive material 40 subjected to press forming or the like is used.
Is mounted in the split molds 41 and 42, and the molds 41 and 42 are filled (injected) with resin to form the embolus 4 (third step) [FIGS. 3 (b) and (c). )reference〕. Each of the molds 41 and 42 has a mold space 43 in which the embolus 4 has a stepped shape (outer peripheral shape), and the electrode pins 5 and 6 are arranged in parallel along the axis of the mold space 43. Also, the curved shape 45 of each of the electrode pins 5 and 6 is
By positioning the embolus 4 in the cavity 44 corresponding to the flange shaft 18, both ends of the conductive material 40 are molded in the mold space 43.
Protrude from inside. In this state, the resin is poured into the mold space 4.
3 to fill the space between the straight portions of the electrode pins 5 and 6, between the curved portions 45 of the electrode pins 5 and 6, and the outside thereof, excluding both end sides of the conductive material 40 [FIG. ,
(C)). As the resin, for example, PBT, PE
T, PA6, PA66, PPS, PPO or the like containing glass fiber (reinforcing material) or the like is used. Then, after the resin filled in the molds 41 and 42 is cured, the conductive material 40 and the resin are peeled off from the molds 41 and 42, thereby taking out the plug 4 in which the electrode pins 5 and 6 are integrated.
Thus, the electrode pins 5 and 6 penetrate the embolus 4 and protrude from both ends, and are integrated with the curved shape 45 inside the flange shaft body 18 (see FIG. 3D). .

After the embolus 4 is formed, the U-shaped side 46 of the conductive material 40 protruding from the embolus 4 is cut, so that each of the electrode pins 5 and 6 is separated and independent. At this time, the U-shaped side of the conductive material 40 is cut at the tip of the shaft 16 of the embolus 4 to penetrate from the tip of the shaft 16 of the embolus 4 to the opposite side (fourth step) [FIG. 4 (a)].

Subsequently, by connecting (welding) the electric bridge wires 7 to the tips of the electrode pins 5 and 6 on the shaft body 16 side, respectively.
The electric bridge line 7 is laid between the electrode pins 5 and 6 (fifth step) (see FIG. 4B).

After the embolus 4, the electrode pins 5, 6 and the bridge 7 are integrated, a cup-shaped tube 2 is prepared.
The ignition charge 3 is housed inside. The tube 2 is formed at the same time as the formation of the embolus 4 and the electrode pins 5 and 6 or in advance with PBT, PET,
It is formed of a resin such as PA6, PA66, PPS, PPO or the like containing glass fiber (reinforcing material) or the like. The embolus 4 is assembled into the squib 1 by inserting the embolus 4 into the pipe 2 from the railway bridge 7 side (the shaft 16 side) (sixth step) [FIG.
(C)). Thus, the embolus 4 and the tube 2 are in close contact with each other from the cup bottom 2b side of the tube 2 to the opening 2a, and the sealing property is increased due to an increase in the contact area, and the electric bridge wire 7 and the ignition charge 3 are connected. It becomes a structure to seal in a pressure state.

As described above, in the squib manufacturing method of the present invention, each electrode pin 5, 6 has a structure having a curved shape 45 inside the plug 4 (flange shaft 18). 4 (resin) can be extended (the contact area can be increased). Each of the electrode pins 5 and 6 has a curved shape 45 protruding to the outer peripheral side of the flange shaft 18,
The embolus 4 is reinforced and functions as a structure that is difficult to deform the resin. Therefore, even if the embolus 4 is formed of resin, no gap is formed between each of the electrode pins 5 and 6, and there is no possibility that water, air, or the like enters (leaks) and deteriorates the ignition charge 3. . As a result, the reliability with respect to the environmental resistance performance can be improved, and the performance can be guaranteed over a long service life. When the curved shape 45 is formed on each of the electrodes 24 and 25, it is possible to prevent the electrode pins 5 and 6 from jumping out of the embolus 4 due to the internal pressure at the time of firing.

In a first step and a second step, the respective electrode pins 5 and 6 are formed from one conductive material 40. In a fourth step after the third step, a conductive material protruding from the embolus 4 is formed. By cutting the U-shaped side 46 of 40, each electrode pin 5, 6 can be constituted by a single member. Therefore, it is possible to provide an inexpensive squib by reducing the number of parts and the manufacturing process (connection process). Further, the first step and the second step can be performed at the same time, whereby the respective electrode pins 5, 6 and the curved shape 45 of each of the electrode pins 5, 6 are formed at a time, thereby further reducing the manufacturing cost. I can do it.

In the squib and the method of manufacturing the squib according to the present invention, the tube 2 is formed of resin. However, a metal cup-shaped tube or a cup-shaped double structure made of metal and resin is used. What was formed in the tube body can be used. Although the curved shapes 45 of the electrode pins 5 and 6 are shown at an angle of 180 degrees from each other, they may be formed at an arbitrary angle. Can also be formed. Further, instead of the electrode pins 5 and 6, an electrode wire composed of a lead wire may be used, and each electrode wire has a structure having a curved shape 45 in the embolus 4. Furthermore,
An adhesive is applied between the inner circumference of the tubular body 2 and the outer circumference of the embolus 4 to improve the sealing property between the tubular body 2 and the embolus 4, and an O-ring is provided between the inner circumference of the tubular body 2 and the outer circumference of the embolus 4 Alternatively, a structure in which a sealing material such as an annular packing is interposed may be used.

FIG. 5 shows a modification of the squib. FIG.
The squib 31 in which the tube 2 and the embolus 4 are formed in a straight shape (a shape having no step) with respect to the squib 1 in FIGS. 1 and 2, and has the same reference numerals as those in FIGS. 1 and 2. Indicates the same member. In this squib 31, FIG.
It is possible to obtain the same effect as the squib 1 of FIG.

Next, a gas generator G using the squib 1 of the present invention will be described. The gas generator G of FIG.
The squib 1 includes a holder 52 for mounting the squib 1, a gas generating agent 61, and a metal cup body 62.

The holder 52 of the gas generator G comprises a holder main body 53 and a caulking projection 54 projecting from the holder main body 53. The holder 52 has a stepped mounting hole 55 which is opened at the end of the caulking projection 54 and has a diameter reduced in two steps toward the holder body 53. The mounting hole 55 communicates with a storage hole 56 opened at the end of the holder main body 53 (the side opposite to the caulking projection 54). A gas generating agent 61 that generates gas by combustion is loaded in the cup body 62. At the bottom 62b of the cup body 62, a gas release hole 62a for releasing gas generated by combustion of the gas generating agent 61 to the outside (seat belt pretensioner) is formed. The gas discharge holes 62a are closed by a thin plate 63 made of aluminum or the like.

The squib 1 is connected to the opening 2 of the tube 2.
The tube 2 is inserted into the mounting hole 55 from the side a, and the end of the opening 2 a of the tubular body 2 is partially brought into contact with the first step portion 59 on the opening side of the mounting hole 55, whereby the tube 2 is mounted in the holder 52. In this state, the squib 1 is such that the opening 2 a side of the tube 2 is located in the mounting hole 55, and the end (tapered shape) of the opening 2 a of the tube 2 and the tapered shape 21 of the plug 4 are on the second step 58. A certain seal ring 5
It is touched by 7. Each of the electrode pins 5 and 6 protrudes into the storage hole 56.

Subsequently, the stepped portion 12 of the tube 2 is caulked by bending the tip of the caulking projection 54 inward (toward the squib 1). At this time, it is preferable that the length of the caulking projection 54 be adjusted to caulk the portion of the stepped portion 12 of the tube 2 outside the flange shaft 18 of the embolus 4. With such a structure, the caulking force can be applied to the opening 2a side of the tubular body 2, and the effect of bending the embolus 4 can be reduced. In addition, each electrode pin 5, 6
Due to the curved shape 45, the bending of the embolus 4 due to caulking is reduced. Therefore, the resin of the plug 4 does not peel off from the electrode pins 5 and 6 to form a gap, and it is possible to eliminate intrusion (leakage) of water, air, or the like. Embolus 4
By caulking, the contact pressure state between the electric bridge wire 7 and the ignition charge 3 can be sufficiently ensured.

Then, the holder 52 is inserted into the cup body 62 from the squib 1 side, so that the gas generator G is assembled. The opening side of the cup body 62 is fitted into the outside of the caulking projection 54 of the holder 52 and caulked by the holder body 53.

The gas generator G ignites and burns the igniting charge 3 by the heat generated by the electric bridge wire 7 when the electrode pins 5 and 6 of the squib 1 are energized, and generates the gas generating agent 61 by the flame from the squib 1. Ignition combustion generates a large amount of gas. Subsequently, a large amount of gas generated in the cup body 62 is dissipated by the burst plate 6 broken by the increase in the internal pressure of the cup body 62.
3. It is guided to the seat belt pretensioner through the gas discharge holes 62a. Thus, the seatbelt pretensioner is activated by the high-pressure gas to fasten the seatbelt.

As described above, when the squib 1 having excellent environmental resistance and low cost is used for the gas generator G, the performance of the gas generator G itself can be guaranteed, and the manufacturing cost can be reduced. or,
Since the curved shape 45 of each of the electrode pins 5 and 6 protrudes so as to intersect with the caulking force of the caulking projection 54, it is possible to suppress the deflection of the embolus 4 even when employing a structure in which the squib 1 is caulked to the holder 52. Thus, it is possible to make it difficult to form a gap between each of the electrode pins 5, 6 and the embolus 4.

The squib of the present invention can also be applied to a gas generator that deploys and inflates an airbag due to an automobile collision. This gas generator is for driver's seat,
There is a passenger seat or a side collision type, and an airbag is inflated and deployed by gas generated by burning a gas generating agent. The squib 1 is mounted in a housing (cylindrical body) of the gas generator. In the housing, a gas generating agent, a filter, and the like are arranged, and the squib 1 burns the gas generating agent via a transfer agent or directly by the flame, thereby generating a large amount of gas for inflating and deploying the airbag.

[0037]

In the squib of the present invention, each electrode is constituted by a single member, and has a structure having a curved shape inside the embolus. Therefore, the interface between each electrode and the embolus is long. Contact area). In addition, each electrode reinforces the embolus 4 by a curved shape, and functions as a structure that is difficult to deform the resin. Therefore, even if the embolus is formed of resin, there is no gap between each electrode,
Water and air do not enter (leak) and degrade the igniting charge. As a result, the reliability with respect to the environmental resistance performance can be improved, and the performance can be guaranteed over a long service life. Further, when each electrode is formed to have a curved shape, it is possible to prevent each electrode pin from jumping out of the embolus due to the internal pressure at the time of firing, and to provide a highly safe squib. Furthermore, by forming each electrode with a single conductive material, the number of components and the manufacturing process (connection process) are reduced, and an inexpensive squib can be provided.

In the squib of the present invention, each electrode and a curved shape are formed on the electrode, and an embolus is formed by filling with a resin.
Since the curved shape of each electrode is arranged inside the embolus, the interface between the embolus (resin) and each electrode is long (the contact area is large).
And sealability can be improved. Also, a structure in which the embolus is difficult to deform due to the curved shape of each electrode can be provided. Therefore, even if the embolus is formed of resin, no gap is formed between each electrode, and no deterioration of the igniting agent due to intrusion (leak) of water, air, or the like is prevented. As a result, the reliability with respect to the environmental resistance performance can be improved, and the performance can be guaranteed over a long service life. Further, after each electrode is formed from one conductive material, the U-shaped side of the conductive material protruding from the embolus is cut, so that each electrode can be constituted by a single member. Therefore, it is possible to provide an inexpensive squib by reducing the number of parts and the number of manufacturing steps. And U
By forming a curved shape at the same time when forming a character,
The manufacturing cost can be further reduced.

[Brief description of the drawings]

FIG. 1 is an assembly view showing a squib.

FIG. 2 is an exploded view showing a squib.

FIG. 3 is a diagram showing a method for manufacturing a squib.

FIG. 4 is a diagram showing a method for manufacturing a squib.

FIG. 5 is an assembly view showing a modification of the squib.

FIG. 6 is a diagram showing a specific example in which a squib is applied to a gas generator.

FIG. 7 is a view showing a conventional squib.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Squib 2 Tubular body 3 Igniter 4 Embolus 5 Electrode pin 6 Electrode pin 7 Electric bridge 31 Squib 40 Conductive material 45 Curved shape 46 U-shaped side

Claims (3)

[Claims] An ignition charge (3) inserted into a tube (2).
And an embolus (4) for sealing the electric bridge line (7), and two electrodes (5, 6) connected to the electric bridge line (7) and penetrating through the embolus (4), respectively. The embolus (4) is formed of resin, and each of the electrodes (5, 6) is formed of a single member, and has a shape (45) that curves inside the embolus (4). Squib 2. A method in which one conductive material (40) is formed into a U-shape to form two parallel electrodes (5, 6), and excluding both ends of the U-shaped conductive material (40). The curved shape (4) of each electrode (5, 6) between each electrode (5, 6)
5) Filling the gap and the outer periphery thereof with resin to form an embolus (4), and then cutting the U-shaped side (46) of the conductive material (40) projecting from the embolus (4). 2. The squib according to claim 1, wherein said electrodes (5, 6) are independent of each other. 3. The squib according to claim 2, wherein said curved shape (45) is formed simultaneously with said U-shaped formation.