Method and apparatus for an improved initiator and retainer
An initiator is provided for use with an initiator holder. The initiator comprises a can; at least two electrodes; an explosive charge positioned to be ignited when electrical charge is passed through said electrodes; and a body portion surrounding the electrodes. The body portion may have a first portion with a first cross-sectional area and a second portion having a second cross-sectional area, wherein the second cross-sectional area has a shape different from the first cross-sectional area and wherein the second cross-sectional area is less than 40% of the first cross-sectional area; wherein the second portion is shaped to extend outward from an opening in the holder when the body portion is seated in the holder.
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1. Field of the Invention
This invention relates to initiators and more specifically to creating a robust interface between an initiator body and an initiator holder.
2. Description of Related Art
Initiators or “popcorn” squibs are well-known in the art. They are used in a variety of applications such as but not limited to deploying airbags or pretensioning of seat belts during rapid deceleration of an automobile. These known initiators are designed to conform to certain industry standards for size and shape. Unfortunately, these conventional designs fail to provide a sufficiently robust device that can withstand the rigors of rapid, hot gas expansion and high pressure.
For example, in microgas generators (MGGs) which use initiators, the conventional initiator retainer or holder 10, as seen in
Now, the initiator has an explosive primary charge which may be used to initiate or ignite a secondary charge. The initiator may include a header 20 with a stainless steel body, a piece of glass, and two pins (it is called a glass to metal seal interface). A bridge wire is placed between the centerpin, that is insulated by glass, over to the body. This bridge wire creates an electrical connection between the two pins. When current is sent though the pin, the current heats the bridge wire and causes the initiator to ignite its charge. This explosion in an inflator makes an airbag begin to expand. This explosion in an MGG lights propellant that is housed in another can on top of the initiator and generates a pressure wave that will push a piston that may be used in situations such as (but not limited to) tightening a seat belt. In an airbag application, the initiator will ignite airbag propellant which generates gas and inflates an airbag.
As discussed above, the standard retainer or holder for use with the header has a circular hole as seen in
To determine the robustness of these initiators, there are certain safety and performances tests where there is a fairly high amount of pressure in the test chamber. The only thing that prevents the pressure from exiting through a “rearward” direction as indicated by arrow 30 in
This failure of the interface between the header and the retainer or holder is extremely undesirable due to the potentially lethal chain reaction that could result from high velocity ejection of the header from the holder.
SUMMARY OF THE INVENTIONAccordingly, one object of the present invention is to provide improved header and retainers to withstand the extreme pressures and heat associated with charge detonation.
Another object of the present invention is to provide improved design without significantly increasing manufacturing cost or difficulty.
Yet another object of the present invention is to design the holder to allow a user to visually observe the polarity of the electrode pins during assembly of the initiator into the holder.
A still further object of the present invention is to provide a holder and initiator that is correctly sized for use in MGGs and inflators.
At least some of these objects are achieved by some embodiments of the present invention.
In one aspect of the present invention, an initiator is provided for use with an initiator holder. The initiator comprises a can; at least two electrodes; an explosive charge positioned to be ignited when electrical charge is passed through said electrodes; and a body portion surrounding the electrodes. The body portion may have a first portion with a first cross-sectional area and a second portion having a second cross-sectional area, wherein the second cross-sectional area has a shape different from the first cross-sectional area and wherein the second cross-sectional area is less than 40% of the first cross-sectional area; wherein the second portion is shaped to extend outward from an opening in the holder when the body portion is seated in the holder.
In another embodiment, the present invention comprises an initiator having a can; at least two electrodes; an explosive charge positioned in the can and configured to be ignited when electrical charge is passed through the electrodes; and a body portion surrounding the electrodes, wherein the body portion having a first portion with a first cross-sectional area and a second portion having a second cross-sectional area; a holder configured to engage at least a portion of the body portion, wherein the holder is capable of holding the body portion in a manner sufficient to withstand a backpressure of at least about 200 megapascals pushing the body portion against an inner surface of the holder.
A microgas generator may use an initiator and/or a holder as described herein.
In another embodiment, the present invention provides a method of manufacturing an initiator comprising: providing a can, at least two electrodes, and an explosive charge positioned in the can and configured to be ignited when electrical charge is passed through said electrodes; forming a body portion surrounding at least a portion of said electrodes, said body portion having a first portion with a first cross-sectional area and a second portion having a second cross-sectional area, said second cross-sectional area having a shape different from said first cross-sectional area and wherein said second cross-sectional area is less than 40% of said first cross-sectional area; wherein said second portion is shaped to extend outward from an opening in the holder when the body portion is seated in the holder.
A further understanding of the nature and advantages of the invention will become apparent by reference to the remaining portions of the specification and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. It may be noted that, as used in the specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a material” may include mixtures of materials and the like. References cited herein are hereby incorporated by reference in their entirety, except to the extent that they conflict with teaching explicitly set forth in this specification.
In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:
“Optional” or “optionally” means that the subsequently described circumstance may or may not occur, so that the description includes instances where the circumstance occurs and instances where it does not. For example, if a device optionally contains a feature for having a shorting bar, this means that the shorting bar feature may or may not be present, and, thus, the description includes structures wherein a device possesses the shorting bar feature and structures wherein the shorting bar feature is not present.
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While the invention has been described and illustrated with reference to certain particular embodiments thereof, those skilled in the art will appreciate that various adaptations, changes, modifications, substitutions, deletions, or additions of procedures and protocols may be made without departing from the spirit and scope of the invention. For example, with any of the above embodiments, notches or cutouts may be incorporated onto the body or other initiator portions to indicate correct orientation or other indicator. The device may also include protrusions to “key” into notches on the holder, or vice versa. These elements may be found on the body portions or other housing on the initiator or holder. For any of the embodiments above, the device may include a shorting bar connecting the electrodes to prevent accidental detonation. Suitable materials for use in the present invention and shorting bar designs may be found in copending U.S. patent application Ser. No. 10/953,468 (Attorney Docket No. 37073-0010C1). Various embodiments of an improved initiator and holder can withstand up to about 160, 170, 180, 190, 200, 210, 220, 230, 240, and/or 250 megapascal of force resulting from detonation of explosive charge.
The publications discussed or cited herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. All publications mentioned herein are incorporated herein by reference to disclose and describe the structures and/or methods in connection with which the publications are cited.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the invention.
Expected variations or differences in the results are contemplated in accordance with the objects and practices of the present invention. It is intended, therefore, that the invention be defined by the cope of the claims which follow and that such claims be interpreted as broadly as is reasonable.
Claims
1. An initiator for use with an initiator holder, said initiator comprising:
- a can;
- at least two electrodes;
- an explosive charge positioned in the can and configured to be ignited when electrical charge is passed through said electrodes; and
- a body portion surrounding at least a portion of said electrodes, said body portion having a first portion with a first cross-sectional area and a second portion having a second cross-sectional area, said first cross-sectional area measured at the interface with the second portion;
- said second cross-sectional area having a shape different from said first cross-sectional area and wherein said second cross-sectional area is less than 40% of said first cross-sectional area;
- wherein said second portion is shaped to extend outward from an opening in the holder when the body portion is seated in the holder.
2. The device of claim 1 wherein the first cross-sectional area has a circular shape.
3. The device of claim 1 wherein the second cross-sectional area has a race track shape.
4. The device of claim 1 wherein the second cross-sectional area has a shape selected from one of the following: rectangular, race track shape with a cutout, oval, square, triangular, three-legged, rectangular with at least one rounded end, rectangular with a cutout, or combinations of these shapes.
5. The device of claim 1 wherein the first body portion is made of a material selected from a list consisting of: polybutylene terephthalate, polybutylene naphthalate, high strength polyamide, nylon 6,12, nylon 10,12, nylon 12,12, nylon 66, thermoplastic aromatic polyamides, Amodel™ polyphthalamide, polyether-amides; polyimides, Aurum™ (MTC America); polyether-imides, polyether-ketones (PEK), polyether-ether-ketones (PEEK), polyether-ketone-ether-ketone-ketones (PEKEKK), and high temperature thermoplastic aromatic polyketone polymers, liquid crystal polymers (LCP), Vectra™ A515.
6. The device of claim 1 wherein the second portion is shaped to surround the side portions of at least two of said electrodes.
7. The device of claim 1 wherein the second portion is shaped to prevent rotation of the initiator about its longitudinal axis when placed in the holder.
8. The device of claim 1 wherein body portion has a section with a conical shape, said section having conical surfaces at a 45 degree angle.
9. The device of claim 1 wherein the body portion includes a marker positioned to indicate polarity of the electrodes.
10. The device of claim 1 wherein the body portion has a 1.33 mm height.
11. The device of claim 1 wherein the body portion has a 6.45 mm diameter.
12. The device of claim 1 wherein interface between a surface of the first portion of the initiator and an inner surface of the holder is capable of holding the body portion in a manner sufficient to withstand a backpressure of at least about 200 megapascals pushing the body portion against the inner surface of the holder.
13. The device of claim 1 wherein the holder has a shape capable of holding the body portion in a manner sufficient to withstand a backpressure of at least about 220 megapascals pushing the body portion against an inner surface of the holder.
14. The device of claim 1 wherein the holder is capable of holding the body portion in a manner sufficient to withstand a backpressure of at least about 250 megapascals pushing the body portion against an inner surface of the holder.
15. The device of claim 1 further comprising at least one bridgewire coupling said electrodes together.
16. The device of claim 1 wherein the area of the second portion is less than 10% of the area of the first cross-sectional area when measured at the widest point of the first portion.
17. An initiator for use with a holder, said initiator comprising:
- a can;
- at least two electrically conductive pins;
- an explosive charge configured to be ignited when electrical charge is passed through said pins; and
- a body having a first portion with a circular cross-section relative to a longitudinal axis of the initiator and a second portion having a rectangular cross-section relative to a longitudinal axis of the initiator.
18. The device of claim 17 wherein the rectangular cross-section includes a cutout or notch portion.
19. The device of claim 17 wherein the rectangular cross-section includes at least one rounded end portion.
20. An initiator for use with a holder, said initiator comprising:
- a can;
- a plurality of electrodes;
- an explosive charge configured to be ignited when electrical charge is passed through said electrodes; and
- means for supporting and positioning said plurality of electrodes, wherein at least a portion of said means extends outward from the holder when the means are seated against the holder.
21. An initiator holder comprising:
- a housing with an inner surface and an outer surface, said inner surface having a shape to receive an initiator body having a first portion and a second portion;
- an opening on said housing, said opening sized and shaped to receive the second portion of the initiator body, an area of said opening being less than 40% of an cross-sectional area of the first portion of the body, said first cross-sectional area measured at the interface with the second portion.
22. The device of claim 21 wherein the inner surface conforms to the shape of the initiatory body.
23. The device of claim 21 further comprising:
- said opening having a race-track shape.
24. The device of claim 21 wherein said holder can withstand at least 250 megapascals of pressure when the initiator body is pressed against the holder.
25. The device of claim 21 wherein the opening has area of about 9.34 mm2.
26. A micro gas generator including at least one holder of claim 21.
27. An airbag inflator including at least one holder of claim 21.
Type: Application
Filed: Dec 23, 2004
Publication Date: Jun 29, 2006
Applicant: LIFESPARC, INC. (Hollister, CA)
Inventors: Rick Mavrakis (Alta Loma, CA), Alex Orozco (Hollister, CA)
Application Number: 11/023,304
International Classification: F42B 3/10 (20060101);