Igniter with a locked consolidated powder charge

Abstract

An igniter with a charge sleeve is provided with a through hole having a cylindrical wall, a bridge wire extending at least partially within the through hole, and a consolidated ignition powder charge retained within the through hole of the charge sleeve such that the bridge wire is at least partially embedded in the ignition powder charge. The cylindrical wall comprises at least one of i) a protrusion embedded into consolidated ignition powder charge, ii) a dimple filled with the consolidated ignition powder charge, and iii) at least 2 cylindrical wall sections that are eccentric to each other. The at least one of the protrusion, dimple and 2 cylindrical wall sections positively interlock with the consolidated ignition and output powder charge to prevent the charge both from moving in a radial direction in relation to the bridge wire and from rotating in relation to the bride wire.

Claims

1. An igniter comprising: a charge sleeve comprising a through hole comprising a cylindrical wall; a bridge wire extending at least partially within the through hole; and a consolidated ignition and output powder charge retained within the through hole of the charge sleeve such that the bridge wire is at least partially embedded in the consolidated ignition and output powder charge; wherein the cylindrical wall comprises at least 2 cylindrical wall sections that are eccentric to each other, wherein each of the at least 2 cylindrical wall sections that are eccentric with respect to each other positively interlock with the consolidated ignition and output powder charge to prevent the charge both from moving in a radial direction in relation to the bridge wire and from rotating in relation to the bridge wire.

2. The igniter of claim 1, wherein a step extends between a first cylindrical wall section and a second cylindrical wall section of the at least two cylindrical wall sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a shows a sectional view denoted A-A in FIG. 1b of a first embodiment comprising an output can having a consolidated ignition and output powder charge.

(2) FIG. 1b shows a sectional view denoted B-B in FIG. 1a of the first embodiment shown in FIG. 1a.

(3) FIG. 2a shows a sectional view denoted A-A in FIG. 2b of a second embodiment comprising an output can having a consolidated ignition and output powder charge.

(4) FIG. 2b shows a sectional view denoted B-B in FIG. 2a of the second embodiment shown in FIG. 2a.

(5) FIG. 3a shows a sectional view denoted A-A in FIG. 3b of a third embodiment comprising an output can having a consolidated ignition and output powder charge.

(6) FIG. 3b shows a sectional view denoted B-B in FIG. 3a of the third embodiment shown in FIG. 3a.

(7) FIG. 4a shows a sectional view denoted A-A in FIG. 4b of a first embodiment comprising a charge sleeve having a consolidated ignition powder charge.

(8) FIG. 4b shows a sectional view denoted B-B in FIG. 4a of the first embodiment shown in FIG. 4a.

(9) FIG. 5a shows a sectional view denoted A-A in FIG. 5b of a second embodiment comprising a charge sleeve having a consolidated ignition powder charge.

(10) FIG. 5b shows a sectional view denoted B-B in FIG. 5a of the second embodiment shown in FIG. 5a.

(11) FIG. 6a shows a sectional view denoted A-A in FIG. 6b of a third embodiment comprising a charge sleeve having a consolidated ignition powder charge.

(12) FIG. 6b shows a sectional view denoted B-B in FIG. 6a of the third embodiment shown in FIG. 6a.

DETAILED DESCRIPTION OF THE DRAWINGS

(13) FIGS. 1a and 1b show a first preferred embodiment of the present invention. FIG. 1a is a sectional view along the line A-A as shown in FIG. 1b. FIG. 1b is a sectional view along the line B-B as shown in FIG. 1a. As shown in FIG. 1a, an output can 1 accommodates a header 2 and a consolidated ignition and output powder charge 3. The header 2 comprises an electrode 4, a housing 5, an insulator 6 and a bridge wire 7 that connects and the housing 5 with the electrode 4. The output can 1, the electrode 4, the housing 5 and the bridge wire 7 are made from electrically conductive material. The bridge wire 7 is typically in direct contact with or embedded into the consolidated powder charge 3 or at least in such close proximity that heat generated by the bridge wire 7 can easily be transferred from the bridge wire into the consolidated powder charge 3 for igniting the same.

(14) The bridge wire 7 is heated by running electrical current through the electrode 4 via the bridge wire 7 into the housing 5 and finally the output can which might be grounded or contacted by a negative electrode. The consolidated powder charge 3 is typically inserted into the output can 1 in form of slurry that is allowed to consolidate. While it is also possible to fill in the powder charge as a dry powder and if need be compact this charge, in the manufacturing process, handling slurry during manufacturing rather than a dry powder charge is preferred for several reasons, most importantly for safety reasons since slurry is safer against inadvertent self-igniting during the manufacturing process and prevents hazardous and dangerous explosive dusts from escaping into the environment. The expression consolidated is to be understood for the purpose of the present patent application as any form of making the powder charge stick to some extent together and form a powder body, either by drying a slurry or by compacting a dry powder or by any other means like a chemical reaction like curing or any physical processing.

(15) After the output powder charge 3 in the form of a slurry has been filled into the output can 1, the header 7 is then inserted into the output can 1 and fixed thereto by beads 8, for instance an adhesive or cured resin or simply by deforming the output can 1 from the outside such that a protrusion extends into respective recesses in the housing 5 of the header 2. The protrusions and recesses can be coined into the output can 1 and housing 5 from the outside.

(16) The output can 1 is easy to manufacture by conventional punching and forming, for instance by a deep drawing process. According to this embodiment, the bottom of the output can 1 comprises several corrugations 9 which are arranged in a star-shaped form and create a number of dimples 10 and protrusions 11. These corrugations can be formed by pressing a male die part also used for the deep drawing action into a female die part forming the bottom 12 of the output can 1.

(17) When filled into the output can 1, the powder charge 3 in form of slurry also fills the corrugations 9 which form the set of dimples 10 and protrusions 11. After the header 2 has been inserted into the output can locking the powder charge 3 in a longitudinal direction into place, the slurry can consolidate so that the then consolidated powder charge locks itself in place as to lateral movement and rotational movement with respect to the output can 1 since the then consolidated powder charge 3 fills the dimples 10 created by the corrugations 9. The consolidated power charge 3 is sandwiched between a front face 13 of the header 2 and the bottom 12 of the output can 1 locking it into place in an axial or longitudinal direction of the igniter, while holding it in radial direction in place by the cylindrical inner wall 14 of the output can 1. In a rotational direction, the corrugations 9 forming the protrusions 11 and the dimples 10 hold the output charge in place, i.e. prevent rotating. However, if under the severe conditions the output charge gets compacted in a radial direction so that an annular gap can form between the output charge 3 and in the cylindrical wall 14 of the output can 1, the dimples 10 and protrusions 11 still hold the output charge in place in a radial direction.

(18) As a result, the output charge 3 is prevented from moving in a radial direction in relation to the bridge wire 7, and also is prevented from rotating in relation to the bridge wire 7 so that any shear forces acting from the output powder charge 3 onto the bridge wire 7 are prevented. This protects the bridge wire against a number of potential reasons for failure like detaching from the electrode 4 or housing 5 of the header, breaking due to excessive shear forces, and most importantly against any fatigue fracture, cracks or detaching due to vibrations.

(19) FIGS. 2a and 2b show a second preferred embodiment of the present invention. FIG. 2a is a sectional view along the line A-A as shown in FIG. 2b. FIG. 2b is a sectional view along the line B-B as shown in FIG. 2a. For the purpose of providing a clearer picture, the consolidated powder charge 3 is only shown by a number of dots in the FIG. 2a but omitted in the FIG. 2b. The same reference numerals as in FIG. 1 are used while not all of the reference numerals as described in connection with FIG. 1 are shown, only those that are specifically discussed in connection with this embodiment are shown in FIG. 2.

(20) A retention sleeve 15 is welded to the front face 13 of the header 2 such that it is eccentric in relation to the electrode 4 and the output can 1. The bottom of the output can 1 can be flat according to this embodiment since the lateral and rotational movement of the consolidated output charge 3 is according to this embodiment prevented by the eccentricity of the retention sleeve 15. In the alternative, the bottom 12 of the output can also be provided with the corrugations 9 as shown in FIG. 1. The retention sleeve 15 can be attached to the front face 13 also by ways other than by welding, for instance by soldering, or gluing or it can be formed integrally with the housing 5 of the header 2. One additional advantage this design has is that it allows filling the retention sleeve 15 with an ignition charge 18 that may differ from the output charge 3. Also, this ignition charge 16 is much smaller and therefore lighter and less vulnerable to be compacted within the retention sleeve by inertial forces and vibrations that may occur in using the igniter in extreme environments.

(21) FIGS. 3a and 3b show a third preferred embodiment of the present invention. FIG. 3a is a sectional view along the line A-A as shown in FIG. 3b. FIG. 3b is a sectional view along the line B-B as shown in FIG. 3a. For the purpose of providing a clearer picture, the consolidated powder charge 3 is only shown by a number of dots in the FIG. 3a but omitted in the FIG. 3b. The same reference numerals as in FIGS. 1 and 2 are used while not all of the reference numerals as described in connection with FIGS. 1 and 2 are shown, only those that are specifically discussed in connection with this embodiment are shown in FIG. 3.

(22) As a mechanism for preventing rotation of the consolidated powder charge 3, flats 17 are coined to the housing 5 of the header 2. The advantage of this embodiment is the very low manufacturing costs, since coining of these flats can be done in mass production at relatively low costs. In the alternative, these flats can be machined into the housing 5, for instance by milling. Since these flats are in a longitudinal or axial direction of the igniter very close to the bridge wire 7, this mechanism is in the form of the flats 17 preventing rotation and lateral movement of the output charge 3 and is located very close in space to this bridge wire 7 and therefore very effective. Also this embodiment in FIG. 3 allows the variation that the bottom 12 can be structured like in the embodiment shown in FIG. 1, i.e. comprise corrugations forming dimples and protrusions and therefore provide additional safety against any movement of the consolidated powder charge 3.

(23) FIGS. 4-6 show additional applications and implementations of the same inventive idea as described in connection with FIGS. 1-3 above, namelyturning first to FIGS. 4a and 4b-applying a similar mechanism for preventing rotation and lateral movement of a consolidated powder charge 18, here used as an ignition charge 18 contained in a charge sleeve 19. A bridge wire 20 extends from an electrode 21 to a housing 22. The electrode 21 is held in place within the housing 22 by an insulator 23, for instance glass or any other type of appropriate material like ceramics or cured resin. The housing 22 is made from electrically conductive material, preferably metal, and can either be grounded, or connected to a negative electrode 24. The charge sleeve 19 comprises a cylindrical wall 25 that comprises a first cylindrical wall section 26 and a second cylindrical wall section 27. The first cylindrical wall section 26 is slightly larger in diameter than the second cylindrical wall section 27 and is eccentric in relation to the second cylindrical wall section 27. This eccentricity forms effectively a protrusion preventing rotation of the ignition charge 18 within the charge sleeve 19 and therefore protects the bridge wire 20 from damage, as already discussed in detail in relation to FIGS. 1-3.

(24) According to the embodiment shown in FIG. 5, the cylindrical wall 25 comprises three different sections, namely a first section 28 of the largest diameter, a second section 29 comprising in a circumferential direction protrusions 31 and indents 32 which are formed in a step that forms a transition between the first section 28 and a third section 30 having a smaller diameter than the first section 28. As shown in FIG. 5b, the indents 32 are filled with the consolidated ignition charge 18 and therefore form sort of teeth in the ignition charge 18 that interlock with the protrusions 31 of the charge sleeve 19. This interlocking mechanism prevents the consolidated powder charge 18 from rotating in relation to the charge sleeve 19, and therefore prevents a movement of the consolidated powder charge 18 in relation to the bridge wire 20.

(25) In a similar fashion as in the embodiment shown in FIG. 5, also in the embodiments shown in FIG. 6, such interlocking teeth between the consolidated ignition power charge in a second section 34 of the cylindrical wall 25 that has a smaller diameter than a first section 33 of the cylindrical wall 25 are formed. The difference between the embodiments shown in FIGS. 6 and 5 is that the embodiment shown in FIG. 6 comprises only two cylindrical wall sections 33 and 34 and the teeth in the second cylindrical wall section 34 are extending over the entire remaining length of the cylindrical wall 25 which is not occupied by the first cylindrical wall section 33. Also here a step is formed between the first cylindrical wall section 33 and the second cylindrical wall section 34 due to a difference in the internal diameter, but this step is not a continuous annular shoulder in a circumferential direction as the gaps between the teeth extend over the entire length of the second cylindrical wall section 34, thus the annular shoulder is interrupted by the gaps formed between the teeth.

(26) In all three embodiments shown in FIGS. 4-6, a step is provided, preventing an axial or longitudinal motion of the consolidated ignition powder charge, and some kind of protrusion, indent or teeth interlocking with the powder charge for preventing any rotation movement. This holds the consolidated power charge in place in longitudinal direction, but at the same time protects the bridge wire 20 from damage by preventing rotation of the powder charge.

(27) The aforementioned embodiments are only shown and explained for the purpose of illustration. The present invention is not limited to these exemplary embodiments.