The present invention generally relates to the field of pyrotechnic initiators, and more particularly to a pyrotechnic initiator having an internal sleeve retaining a pyrotechnic charge.
Pyrotechnic initiators have many uses in industrial and consumer applications. One important use is in triggering the inflation of airbags in motor vehicles. Significant efforts have been made in the automotive industry to reduce the cost of manufacturing reliable airbag initiators. One advance has been the use of liquids and slurries in loading pyrotechnic charges into the initiators. As shown in U.S. Pat. No. 5,686,691 to Hamilton et al., it is known to load a slurry charge into a conventionally cup-shaped charge can, and to directly affix such a loaded can onto a header assembly so that the charge comes into contact with the header surface and bridgewire. However, this method poses certain drawbacks and difficulties and limits the available range of slurries since the slurry must be amenable to consolidation. It is believed that hitherto a thin-walled, rigid charge sleeve has not been used to facilitate the loading and durable retention of a pyrotechnic charge in place on the header surface within an initiator.
In accordance with the present invention, an initiator includes an internal charge sleeve that is loaded with a pyrotechnic charge such as through slurry loading. The sleeve is closed at its bottom end by the initiator's header assembly, but has an open top end. The charge sleeve beneficially retains the charge on the header of the initiator, either in conjunction with the upper interior surface of the charge can, or through the use of a monolithic charge and a narrowed top end of the sleeve.
Various initiator configurations can be used, or modified appropriately for use, in the present invention. As can be seen from
1
The present description incorporates by reference in full the disclosures of the following co-pending applications that are filed concurrently herewith and assigned to the assignee of the present application: Ser. No. 10/______ , entitled “Initiator with a Slip Plane Between an Ignition Charge and an Output Charge” by Vahan Avetisian et al., (Express Mail No. EU124494039US); Ser. No. 10/______ , entitled “Initiator with a Bridgewire in Contact with Slurry-Loaded Pyrotechnic Charge at a Position of Relatively High Drying Contraction,” by Vahan Avetisian et al., (Express Mail No. EU124494042US); Ser. No. 10/______ , entitled “Axial Spin Method of Distributing Pyrotechnic Charge in an Initiator,” by Marius Rosu, (Express Mail No. EU124494056US); and Ser. No. 10/______, entitled “Initiator with a Bridgewire Configured in an Enhanced Heat-Sinking Relationship,” by Vahan Avetisian, (Express Mail No. EU124494060US). U.S. Pat. No. 5,648,634 to Avory et al. is also incorporated herein by reference.
In the embodiment of
Following that, preferably substantially the entire open area within the sleeve 36 (i.e., the area within the aforementioned upper half or third that remains above the top surface of the header assembly 58) is loaded with a suitable pyrotechnic charge 32. This is preferably done using a slurry loading technique or similar means known in the art. Some examples of relevant slurry-loadable pyrotechnic compositions are described in U.S. Pat. No. 5,686,691 to Hamilton, et al., the disclosure of which is incorporated herein by reference except to the extent that it contradicts anything explicitly set forth here. A suitable slurry for use in forming charge 32 in the present embodiment may include a binder such as Viton-B® preferably at less than five percent by weight, a solvent such as butyl acetate at approximately twenty percent by weight, and the balance preferably being zirconium/potassium perchlorate and any other desired additives.
Alternately, instead of pre-forming the sleeve's narrowed top end 52 prior to loading the charge 32, the upper end 52 of the sleeve 36 can be circumferentially crimped inwardly after (or while) the slurry dries, so that it becomes narrowed and compresses the charge 32.
Optionally, the top of the charge 32 can be pressed downwardly during or after drying of the slurry in order to pack it more tightly and more firmly press it against the bridgewire 38. Although such pressing is preferably done in such a way as to produce a concave top on the charge 32 (as shown in
Although the sleeve 36 is preferably loaded after it is attached to the header assembly as just described, the sleeve 36 could alternately be separately pre-loaded (preferably with a slurry, and preferably upside-down on a flat surface or suitable fixture) with the charge 32 (so as to fill the desired portion of the upper region of the sleeve 36). Then, preferably after substantial or complete drying of the slurry, the header assembly 58 could be slid into the sleeve 36 such that the charge 32 makes intimate contact with the bridgewire 38. This would preferably be done with the sleeve 36 pre-formed with its narrowed top end 52, and with the application of sufficient pressure on the header assembly 58 against the charge 32 so as to increase the degree of contact therebetween.
In any case, when the sleeve with its narrowed top end 52 is in place on the header assembly and the slurry is dried, the charge 32, which is a monolithic solid mass, is physically retained in place on the top surface of the header assembly 58 by the sleeve 36. Specifically, the obstruction of the narrowed top end 52 (which has a smaller inner diameter than the outer diameter of charge 32 below narrowed top end 52), and possibly also the cohesion and/or friction between charge 32 and the walls of sleeve 36, retain charge 32 in intimate contact with bridgewire 38 (or other suitable electrical initiating element). Thus, the process of assembling the pyrotechnic charge 32 to the header assembly 58 in intimate contact with the bridgewire 38 is simplified and yet more reliable.
Subsequently, the resulting initiator subassembly (including the header assembly 58 and the sleeve 36 loaded with the pyrotechnic charge 32) is pressed into and hermetically sealed and attached to the charge can 42 (which preferably may also be 304L stainless steel having a wall thickness of ten thousandths of an inch), such as with a through-weld 24. To complete the initiator 56, a suitable insulator cup 40 (which preferably may be nylon having a wall thickness of ten thousandths of an inch) and insulating body 26 (which may preferably be nylon insert-molded onto the initiator subassembly) may be provided as is well known in the art.
It is noted that the intermediary containment provided by the sleeve 36 may also help insulate the charge 32 within the initiator 56 from external physical stresses such as vibrations, particularly if all (as shown in
Turning to
It is also noted that although the foregoing description of the embodiments of
Next,
In this embodiment, the sleeve 36b can be placed on top of the header assembly 30 as depicted so that the bottom of the sleeve meets the outer circumferential edge of the header assembly 30, and then loaded with charge (or less preferably the sleeve 36b can be loaded prior to placing it on the header assembly 30). Then, the charge can 42 is placed over the loaded sleeve 36b, and pressed downwardly thereover. As it is pressed downwardly, the friction of the interference fit between the charge can 42 and the sleeve 36b and/or the closed top end of the can 42 cause the sleeve 36b to slide downwardly until it hits shoulder 46. The can 42 is preferably pressed onto the header assembly 30 so as to exert a consolidation force downwardly on the charge, preferably of 5000 psi. It is noted that an appropriate length for the sleeve 36b is dictated largely by the distance from shoulder 46 to the top surface of the header assembly 30, and the anticipated length of compression of the charge that will occur when the consolidation force is applied. The can 42 is then attached to the header assembly 30 such as by a circumferential through-weld to the eyelet 44, or a through-weld (not shown) going through both the can 42 and sleeve 36b to the eyelet 44. The shoulder 46 may be omitted if both the can and sleeve are welded to the eyelet 44.
Next,
To the extent that it is difficult in a particular configuration to attain a charge mound that is sufficiently raised above the top of the sleeve, the alternate deformable straight sleeve embodiment depicted in
It is also noted that in suitable embodiments of the invention, methods of loading such as those taught in assignee's co-pending application Ser. No. 10/______, entitled “Axial Spin Method of Distributing Pyrotechnic Charge in an Initiator,” by Marius Rosu, (Express Mail No. EU124494056US) may be used. Also, the bridgewire 38 may preferably be in close contact with the glass 50, and/or may be flattened, as is taught in assignee's co-pending application Ser. No. 10/______, entitled “Initiator with a Bridgewire Configured in an Enhanced Heat-Sinking Relationship,” by Vahan Avetisian, (Express Mail No. EU124494060US). The bridgewire 38 may also preferably be in contact with the adjacent charge at a position of the charge that was subject to a relatively high degree of contraction during the slurry drying process, so as to minimize the presence of voids in the charge at that position, as taught in assignee's co-pending application Ser. No. 10/______ , entitled “Initiator with a Bridgewire in Contact with Slurry-Loaded Pyrotechnic Charge at a Position of Relatively Low Void Formation,” by Vahan Avetisian et al., (Express Mail No. EU124494042US). Finally, a flat slip plane may be provided so as to minimize the physical and environmental stresses affecting the charge near the bridgewire 38, as taught in assignee's co-pending application Ser. No. 10/______, entitled “Initiator with a Slip Plane Between an Ignition Charge and an Output Charge” by Vahan Avetisian et al., (Express Mail No. EU124494039US).
A preferred embodiment of a pyrotechnic initiator having a charge sleeve that facilitates the loading and durable retention of a pyrotechnic charge in place on the header surface within an initiator, has thus been disclosed. It will be apparent, however, that various changes may be made in the form, construction, and arrangement of the parts without departing from the spirit and scope of the invention, the form hereinbefore described being merely a preferred or exemplary embodiment thereof. Therefore, the invention is not to be restricted or limited except in accordance with the following claims.
This application is a continuation-in-part of U.S. application Ser. No. 09/733,755 by Avetisian et al., which was filed on Dec. 8, 2000 and entitled “Pyrotechnic Initiator with a Narrowed Sleeve Retaining a Pyrotechnic Charge and Methods of Making Same,” and which is incorporated herein by reference except to the extent that it contradicts anything explicitly set forth here.
Number | Date | Country | |
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Parent | 10188003 | Jul 2002 | US |
Child | 10903660 | Jul 2004 | US |
Number | Date | Country | |
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Parent | 09733755 | Dec 2000 | US |
Child | 10188003 | Jul 2002 | US |