Patent Application
20050066833
This invention relates generally to passive restraint systems and more particularly, to a single pin initiator such as for use in actuating a gas generator device employed in such passive restraint systems.
Common types or forms of passive restraint system actuators include airbag inflators and seat belt pretensioners. For example, such a pretensioner in conjunction with a seat belt which is extendable across the vehicle occupant maybe provided to move at least a portion of the seat belt relative to the occupant. For example, one modem seat belt is known as a 3-point restraint because it is secured to the vehicle at three points arranged about the vehicle occupant to provide a diagonal torso section and a horizontal lap portion to hold the vehicle occupant in the seat. The belt is customarily attached to the vehicle by a spring-loaded locking retractor tending to tighten the belt, and by a buckle for quick release of the belt. Seat belt pretensioners are typically sited at the retractor or at the buckle end of the restraining seat belt. Seat belt pretensioners are commonly designed to store energy which, when released, effects the pretensioning operation. Modem pretensioners are typically pyrotechnically operated. Pyrotechnically-operated pretensioners commonly comprise a sealed tube containing a gas generant composition which reacts rapidly to generate gas and rapidly expand to provide the energy to effect the pretensioning operation. For example, such generated gas may be used to drive a piston or the like, such as included or used in a pretensioner, in association with a seat belt or other restraint device. In view of the relatively small amount of gas generated or produced from, in or by such devices, as compared to gas generating inflators typically used in the inflation of inflatable restraint system airbag cushions, such devices are commonly referred to as “micro-gas generators.”
Micro-gas generators are generally composed of a housing which contains an initiation element, or squib, and a high output, gas generating material. Squibs used in such devices typically include a heated bridgewire or other electrothermal transducer to which has been applied a thermally sensitive, very rapid burning, initiation composition. Thus, micro-gas generators are typically very small devices which generally contain components corresponding to those contained in an airbag inflator, including an initiation element, an igniter composition and a high output, gas generating material, but without the same degree of physical separation typically present in airbag inflators.
For example, typical micro-gas generators may include an initiator device or assembly. The initiator device generally includes a housing that contains or stores a supply or charge of a pyrotechnic composition. The initiator device also includes a body such as adapted or suited for the secure positioning and placement of the initiator device in a larger assembly such as a passive restraint system assembly, for example. The initiator device further includes a metal eyelet forming a bore therethrough. A first conductive pin having an outer connection end and an opposed inner terminal end is positioned through the bore and held in place by an insulator. The initiator device also includes a second conductive pin having an outer connection end and an opposed inner terminal end. An initiator transducer, e.g., a bridgewire, couples the first and second conductive pins. The initiator transducer serves to ignite the charge when properly actuated. A cap or cup member surrounds, covers or otherwise encloses the charge contained therewithin and is suitably joined or connected to the eyelet.
Typical passive restraint squibs require multiple parts, such as an initiator header and a separate connector shell. Further, a surface of the header is typically required to be made smooth, such as by grinding, to provide a smooth surface against which the initiation charge can be pressed without breaking the bridgewire or damaging the electrical connection between the bridgewire and the initiator header. Additionally, conventional passive restraint squibs typically require a separately machined feature or component to maintain an initiator pyrotechnic material in proper position relative to the initiator header and the bridgewire.
In view of the above, there is a need and a demand for an improved initiator device for use in combination with a gas generator device of a passive restraint system. In particular, there is a need and a demand for an initiator device that combines the functions of the header of a conventional initiator with the connector shell in an easily fabricated single unit. Additionally, there is a need and a demand for an initiator design that does not require additional processing to provide a smooth header surface capable of withstanding compression forces or pressure to prevent breakage of a bridgewire or other transducer element. Further, there is a need and demand for providing a mechanism for securely positioning or locking the pyrotechnic material into the assembly without pressing into a receiving feature, i.e., a “chargeholder.”
A general object of the invention is to provide an improved passive restraint system assembly.
A general object of the invention is to provide a single pin initiator for use in a gas generator device employed in the passive restraint system assembly.
A more specific objective of the invention is to overcome one or more of the problems described above.
The general object of the invention can be attained, at least in part, through a single pin initiator including a header body forming an eyelet, a header lip surface and a connector shell. An initiator canister is connected to the header body and defines a first storage chamber. A pin is positioned within the eyelet. The pin includes a head portion and a body portion. At least the head portion of the pin extends into the first storage chamber. The initiator also includes a bridgewire which forms or provides electrical communication between the pin and the header body. A supply of initiation pyrotechnic material is disposed on at least a portion of the bridgewire. In accordance with one preferred embodiment, the single pin initiator further includes a supply of initiation charge material contained within the first storage chamber. The supply of initiation pyrotechnic material is in initiation communication with the supply of initiation charge material.
The header body of the present invention serves multiple purposes and/or functions including, but not limited to: functioning as a point of attachment with the bridgewire; forming an eyelet within which an insulating seal can be formed to secure a pin body portion within the eyelet; providing a connector shell for electrical connection to the passive restraint system assembly; and interfacing with the initiator cannister joined or welded to the header body.
The prior art generally fails to provide a single pin initiator having a header body that is easily fabricated or manufactured as a single part. Further, the prior art also generally fails to provide a mechanism for maintaining an initiation pyrotechnic material properly positioned within the initiator and in initiating contact with the bridgewire, without requiring additional machining of parts or components.
The invention further comprehends a single pin initiator having a longitudinal axis and including a header body forming an eyelet, a header lip surface and a connector shell. The initiator includes an initiator canister that is mounted to the header body and forms a first storage chamber, wherein a supply of slurry-loaded initiation charge material can be contained. The initiator also includes a pin positioned within the eyelet along the longitudinal axis of the single pin initiator. The pin includes a body portion and a head portion, with the pin body portion secured within the eyelet by an insulating seal positioned within the eyelet. A bridgewire mounted to the header body forms or provides electrical communication between the pin head portion and the header body. A supply of slurry-loaded initiation pyrotechnic material is disposed on at least a portion of the bridgewire, wherein at least a portion of the supply of slurry-loaded initiation pyrotechnic material is in initiating contact with at least a portion of the supply of slurry-loaded initiation charge material.
The invention still further comprehends a passive restraint system assembly including a single pin initiator assembly having a longitudinal axis. The single pin initiator assembly includes a header body that forms an eyelet, a header lip surface and a connector shell. An initiator canister is mounted to the header body and defines a first storage chamber, wherein a supply of initiation charge material is contained. A pin is positioned within the eyelet along the longitudinal axis, and includes a head portion and a body portion with at least the pin head portion extending into the first storage chamber. The pin body portion is secured within the eyelet by a glass seal. Electrical communication between the pin head portion and the header body is formed by a bridgewire mounted to the header body. A supply of initiation pyrotechnic material is disposed at least in part on at least the bridgewire, and at least a portion of the supply of initiation pyrotechnic material contacts at least a portion of the supply of initiation charge material. A gas generant canister is positioned over the initiator canister and securely connected to the header body. The gas generant canister defines a second storage chamber containing a supply of gas generant material.
Other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawings.
This invention relates generally to passive restraint systems and more particularly, to a single pin initiator such as for use in actuating a gas generator device employed in such a system assembly.
Referring to
In one embodiment of the invention, the supply of initiation charge material 38 includes zirconium and potassium perchlorate made into a slurry-loaded charge containing a strong binder material, such as an acrylic emulsion. In certain preferred embodiments of the invention, the acrylic emulsion may desirably include materials such as hydroxypropylcellulose for enhancing viscosity of the slurry-loaded charge. With the addition of a low level of hydroxypropylcellulose and additional carrier fluid, for example, the slurry-loaded charge is made less dense, such as to facilitate or increase the deformability of the slurry-loaded charge. Further, the thermal conductivity of the slurry-loaded charge may be enhanced with the addition of at least one thermal conductivity enhancer, such as aluminum powder. The thermal conductivity enhancer may desirably compensate for a reduction in conductivity such as due to an inherent lower density of the slurry-loaded charge, compared to conventional pressed materials. The thermal conductivity enhancer maintains a level of “no-fire” resistance to inadvertent firing. The term “slurry” as used herein refers to a free-flowing suspension of fine nonsoluble solid material in a viscous liquid matrix.
As shown in
The generally flat or convex pin head surface 43 provides an area for mechanical connection to or contact with a bridgewire 50. The pin head surface 43 allows for adjustment and control of a length of the bridgewire 50. As shown in
The supply of initiation pyrotechnic material 58 is deposited or disposed on, and preferably bonds to, at least a portion of the bridgewire 50. Thus, the surface 43 of the pin head portion 42 provides a retention mechanism for maintaining at least a portion of the supply of initiation pyrotechnic material 58 properly disposed or deposited onto and adhered to at least a portion of the bridgewire 50. Preferably, but not necessarily, at least a portion of the supply the initiation pyrotechnic material 58 is also at least partially disposed or deposited under the pin head portion 42, and adhered to a portion of the lip end portion 23. By adhering to the pin head portion 42, the lip end portion 23 and/or the glass to metal seal 48, the supply of initiation pyrotechnic material 58 is “locked” in proper position relative to the bridgewire 50, as shown for example in
In one embodiment of the invention, the supply of initiation pyrotechnic material 58 comprises a slurry-loaded initiation pyrotechnic material. Those skilled in the art and guided by the teachings herein provided will appreciate that various slurry-loaded initiation pyrotechnic materials, such as known in the art, can desirably be used in the practice of the invention. Thus, the broader practice of the invention is not necessarily limited to specific or particular such pyrotechnic materials.
As discussed above, the initiator canister 30 is preferably securely connected to the header body 20 to maintain an initiation contact or communication between the supply of initiation pyrotechnic material 58 and the supply of initiation charge material 38. As shown in
Referring to
Preferably, the supply of initiation charge material 238 includes zirconium and potassium perchlorate made into a slurry-loaded charge containing a strong binder material, such as an acrylic emulsion. In certain preferred embodiments of the invention, the acrylic emulsion may desirably include materials such as hydroxypropylcellulose for enhancing viscosity of the slurry-loaded charge. With the addition of a low level of hydroxypropylcellulose and additional carrier fluid, for example, the slurry-loaded charge is made less dense, such as to facilitate or increase the deformability of the slurry-loaded charge. Further, the thermal conductivity of the slurry-loaded charge may be enhanced with the addition of at least one thermal conductivity enhancer, such as aluminum powder.
As shown in
The generally flat or convex pin head surface 243 provides an area for mechanical connection to or contact with a bridgewire 250. The pin head surface 243 allows for adjustment and control of a length of the bridgewire 250. As shown in
The supply of initiation pyrotechnic material 258 is deposited or disposed on, and preferably bonds to, at least a portion of the bridgewire 250. Thus, the surface 243 of the pin head portion 242 provides a retention mechanism for maintaining at least a portion of the supply of initiation pyrotechnic material 258 properly disposed or deposited onto and adhered to at least a portion of the bridgewire 250. Preferably, but not necessarily, at least a portion of the supply the initiation pyrotechnic material 258 is also at least partially disposed or deposited under the pin head portion 242, and adhered to a portion of the lip end portion 223. By adhering to the pin head portion 242, the lip end portion 223 and/or the glass to metal seal 248, the supply of initiation pyrotechnic material 258 is “locked” in proper position relative to the bridgewire 250, as shown for example in
In one embodiment of the invention, the supply of initiation pyrotechnic material 258 comprises a slurry-loaded initiation pyrotechnic material. Those skilled in the art and guided by the teachings herein provided will appreciate that various slurry-loaded initiation pyrotechnic materials, such as known in the art, can desirably be used in the practice of the invention. Thus, the broader practice of the invention is not necessarily limited to specific or particular such pyrotechnic materials.
As discussed above, the initiator canister 230 is preferably securely connected to the header body 220 to maintain an initiation contact or communication between the supply of initiation pyrotechnic material 258 and the supply of initiation charge material 238. As shown in
A further advantage of the invention is the elimination of “microwelding,” which plagues conventional designs. Microwelding is electrical discharge welding of the bridgewire to the header in the “setback” area of the header, the space between the bridgewire weld and the glass seal material on a flush bridged unit where the pyrotechnic material is pressed against the header. The electrical discharge occurs when an electrostatic discharge (“ESD”) test is conducted on the unit. The effect of microwelding is to lower the resistance of the bridgewire, which causes the unit to violate the performance specifications after ESD testing. This phenomenon does not occur to a significant extent in units of the present invention because the bridgewire is arched up from the weld, and is not in casual contact with the header for any appreciable distance.
Referring to
As shown in
The initiator header body 20 is positionable or mountable relative to a housing 70 and is operatively connected to at least one sensor (not shown) for use in a vehicle. Preferably, the housing 70 forms a bore 72 within which the initiator header body 20 is positioned. The housing 70 provides electrical insulation between the single pin initiator assembly 10 and other components or parts of the passive restraint system assembly 100. The housing 70 may include a variety of compositions including plastic-like compositions that are well-suited for electrical insulation and injection molding. In one embodiment of the invention, the housing 70 is formed or manufactured using a nylon material.
As shown in
The single pin initiator 10 is in signal receiving communication with one or more sensors (not shown) such as known in the art and such as effective to send a signal to the single pin initiator 10 to effect the desired actuation thereof. The single pin initiator 10 is in reaction-initiating communication with the supply of gas generant material 64 such that actuation of the single pin initiator 10 results or otherwise produces reaction of at least a portion of the supply of gas generant material 64. Such reaction will result in the combustion of at least a portion of the supply of gas generant material 64 to produce a product gas. The product gas passes into the associate passive restraint system.
Referring to
Although described herein in the context of a micro-gas generator, it will be appreciated by those skilled in the art and guided by the teachings herein provided, that the single pin initiator 10 of the present invention can be appropriately incorporated into other restraint system applications, as may be desired.
Thus, the invention provides a single pin initiator for use in a gas generator device that includes a header body that is easily fabricated or manufactured as a single part. Additionally, the single pin initiator of the present invention includes or forms a pin having a head portion that forms a generally smooth surface to which a bridgewire is connected. The bridgewire provides electrical communication between the pin head portion and the header body. The generally flat smooth surface formed by the pin head portion provides an area for connection of the bridgewire. Since the initiation charge is not pressed or compacted in this design, there is no tendency to breaking of the bridgewire on an uneven surface. This design approach thereby prevents the breaking of the bridgewire and/or damage to the bridgewire-header body connection (by comparison to current practice), and allows for control of a bridgewire length, both through controlling the pin head diameter and by controlling the amount of “setback,” or radial distance from the inner edge of the bridgewire attachment to the lip end portion of the header. Further, the pin partially positioned within an eyelet formed by the header body forms a pin head portion that provides a retention mechanism for maintaining an initiation pyrotechnic material properly positioned within the single pin initiator and in initiating contact with the bridgewire, without the need for additional machined features or components.
The invention illustratively disclosed herein suitably may be practiced in the absence of any element, part, step, component, or ingredient which is not specifically disclosed herein.
While in the foregoing detailed description this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.
