Pyrotechnical igniter

Abstract

An electro-pyrotechnical igniter includes a metal case, a cap and a plastic overmolding. The metal case contains pyrotechnical material and includes at least one vent on a side wall thereof. The cap is made from electrically insulating material and covers the metal case at least at the at least one vent. The plastic overmolding covers at least one end of the cap. The metal case includes at least one shoulder arranged between the side vent and a zone of the metal case across from the end of the cap covered by the overmolding.

Claims

1. An electro-pyrotechnical igniter comprising: a metal case containing pyrotechnical material, the metal case including a first end having a first external diameter and a second end having a second external diameter, the first external diameter being smaller than the second external diameter, the first end including at least one vent on a side wall thereof; a cap made from electrically insulating material and having an open end and a closed end, the cap covering the first end of the metal case and at least an axial portion of the second end of the case, the cap covering the at least one vent; and a plastic overmolding radially covering the open end of the cap, wherein the metal case includes a shoulder arranged between the first end of the case and the second end of the case, and wherein a first outer surface of the first end of the metal case including the at least one vent on the side wall thereof is substantially parallel to a second outer surface of the second end of the metal case.

2. The electro-pyrotechnical igniter according to claim 1, wherein a first circumscribed diameter of the metal case at the end of the cap is larger than a second circumscribed diameter of the metal case at the at least one vent.

3. The electro-pyrotechnical igniter according to claim 1, wherein the case includes a first circumscribed diameter at the closed end that is smaller than a second circumscribed diameter of the metal case at the open end.

4. The electro-pyrotechnical igniter according to claim 1, wherein the metal case includes a bottom.

5. The electro-pyrotechnical igniter according to claim 1, wherein the metal case is welded on a hermetic crossing.

6. The electro-pyrotechnical igniter according to claim 1, wherein the cap has a first tolerance with the metal case at a zone where the at least one vent is installed, a second tolerance with the metal case at the end of the cap covered by the overmolding, second tolerance being smaller than the first tolerance.

7. The electro-pyrotechnical igniter according to claim 6, wherein the first tolerance is in a range from 0.15 mm to 0.35 mm.

8. The electro-pyrotechnical igniter of claim 1, in combination with a motor vehicle safety device.

9. The motor vehicle safety device of claim 8, in combination with a motor vehicle.

10. The electro-pyrotechnical igniter of claim 1, wherein the cap is radially spaced from the first outer surface of the case.

11. The electro-pyrotechnical igniter of claim 1, wherein a first tolerance is radially between the cap and the first portion and a second tolerance is radially between the cap and the second portion, the first tolerance is greater than the second tolerance.

12. An electro-pyrotechnical igniter comprising: a metal case containing pyrotechnical material, the metal case including a first end having a first outer surface with a first diameter and a second end having a second outer surface with a second diameter, the first diameter being smaller than the second diameter, the first end having the first diameter including at least one vent on a side wall thereof; a cap made from electrically insulating material and having an open end and a closed end, the cap covering the first end of the metal case and at least an axial portion of the second end of the case, the cap covering the at least one vent; and a plastic overmolding radially covering the open end of the cap, wherein a first tolerance is radially between the cap and the first portion and a second tolerance is radially between the cap and the second portion, the first tolerance is greater than the second tolerance.

13. The electro-pyrotechnical igniter of claim 12, wherein a first outer surface of the first end of the metal case including the at least one vent on the side wall thereof is substantially parallel to a second outer surface of the second end of the metal case.

14. The electro-pyrotechnical igniter of claim 12, wherein the first tolerance is in a range from 0.15 mm to 0.35 mm.

15. The electro-pyrotechnical igniter of claim 12, wherein the cap is radially spaced from the first outer surface of the case.

Description

DETAILED DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the present invention will appear more clearly upon reading the following detailed description of one embodiment of the invention, provided solely as a non-limiting example and illustrated by the appended drawings, in which:

(2) FIG. 1 shows a sectional view of a metal case for an igniter according to the present invention;

(3) FIG. 2 shows a sectional view of an igniter according to the invention, comprising the metal case of FIG. 1.

(4) FIG. 1 shows an igniter case 10 with a generally cylindrical shape with a side wall 11 that has an open end 15, and a closed end with a bottom 12.

(5) On the side wall 11, several vents 13 are formed by weak lines where the thickness of the side wall is greatly reduced and defines favored opening zones when the pressure inside the metal case 10 increases.

(6) Lastly, a shoulder 14 of the side wall 11 is provided between the open end 15 and the vents 13. Consequently, the side wall 11 has two coaxial cylinder portions (separated by the shoulder 14), and on the small-diameter cylinder, close to the bottom, vents 13 are formed. Cylinder refers to a shape that has a base line, traveled by parallel generatrices. The small diameter may have a diameter of 12.4 mm, while the large one may have a diameter of 12.6 mm.

(7) One may also say that the diameter of the case 10 between the open end 15 and the shoulder 14 is larger than the diameter of the case 10 at the vents, and in particular that the circumscribed diameter of the case 10 between the open end 15 and the shoulder 14 is larger than the circumscribed diameter of the case 10 at the vents.

(8) FIG. 2 in turn shows an electro-pyrotechnical igniter that comprises the metal case 10. The latter may be fastened on a hermetic crossing 40 of the glass-metal type. The electro-pyrotechnical igniter comprises a loading tube 50 that may define a loading well, and the metal case 10 contains one or several pyrotechnical materials, not shown.

(9) The hermetic crossing 40 primarily serves to electrically insulate two connecting pins 61 and 62 of a connecting interface 60 from one another, to force an ignition current to pass through a resistive bridge arranged between the connecting pins 61 and 62.

(10) The pin 61 is directly connected to a metal part of the hermetic crossing and any metal element of the igniter, such as the metal case 10, must be electrically insulated to avoid any risk of untimely ignition. To that end, the metal case 10 is covered by a plastic cap 20, for example, and by a plastic overmolding 30 that covers the rest of the metal case 10, as well as an end of the cap 20.

(11) During the overmolding operation, it is important to prevent infiltrations or injections of liquid plastic between the metal case 10 and the cap 20 and/or the molding tool itself, to avoid blockages of the electro-pyrotechnical igniter in the mold, and appearance rejects or dimensional rejects. It is therefore important to have a good fit between the metal case 10 and the cap 20, at the end of the cap 20.

(12) However, due to the manufacturing operation of the vents 13, this operation often deforms the metal case 10. In order to limit the influence of this or these deformations, the invention provides the shoulder 14, to have a diameter of the metal case 10 at the overmolding zone of the cap larger than the diameter of the zone where the vents 13 are installed. Thus, the deformations do not influence the large diameter, and it is possible to provide a precise adjustment of the cap 20 on the metal case 10, with a small tolerance to limit the infiltrations of plastic between the cap 20 and the metal case 10, or the manufacturing mold.

(13) Furthermore, this embodiment makes it possible to provide a first tolerance J1 between the cap 20 and the metal case 10 at the zone where the vents 13 are installed and a second tolerance J2 between the cap 20 and the metal case 10 at the fastening zone, the second tolerance being positive or nil, and smaller than the first tolerance.

(14) For example, it is possible to provide a second tolerance with a nil radius J2 or even a slightly gripped mounting of the cap 20 on the large diameter of the metal case 10, where the end of the cap 20 is positioned. In this case, the negative tolerance can be comprised between 0 and 0.1 mm at the radius (it therefore involves gripping). At the vents 13, it is for example possible to provide a first tolerance with the radius J1 comprised between 0.10 mm and 0.40 mm, or comprised between 0.15 mm and 0.35 mm. This makes it possible to mount the cap 20 on the metal case 10 without risk of interference, even if the latter is slightly deformed at the vents 13.

(15) With this embodiment, during the mounting of the cap 20 on the metal case 10, the first tolerance J1 allows an easy passage, and the second tolerance J2 guarantees that the cap 20 will deform little or not at all during the overmolding operation, with a good adjustment between the metal case 10, the cap 20 and the manufacturing mold, which reduces the risk of infiltration or rising of liquid plastic.

(16) It will be understood that various changes and/or improvements can be made to the various embodiments of the invention described in the present description without going beyond the scope of the invention defined by the appended claims. In particular, it is provided to mount the cap on the metal case with nil or very slightly negative tolerance J2.