Low permeability, high strength timing fabric for utilization within airbag inflation modules

#This invention relates generally to specific fabric articles exhibiting very low air and/or gas permeability (even upon application of high inflation pressures) and very high tear strengths. Such a specific fabric also permits the incorporation of discrete openings (through cutting, for example) through which air and/or gas introduced by an airbag inflation canister will travel. Such a specific fabric acts as a barrier to the complete introduction of high pressure inflation gases into an airbag cushion, thereby permitting a more controlled, safer inflation upon the occurrence of a collision event. Thus, the specific inventive fabric permits movement of inflation gas and/or air substantially solely through the incorporated openings within the fabric and not through the interstices between the individual fiber constituents. The inventive fabric also withstands the intense heat generated by the explosion that creates the inflation gases and does not lose any appreciable degree of performance during and after such an inflation event. An inflation module, as well as an entire vehicle restraint system, comprising such a specific timing fabric are also contemplated within this invention.

#All U.S. patents cited herein are hereby fully incorporated by reference.

#Inflatable protective cushions used in passenger vehicles are a component of relatively complex passive restraint systems. The main elements of these systems are: an impact sensing system, an ignition system, a propellant material, an attachment device, a system enclosure, and an inflatable protective cushion. Upon sensing an impact, the propellant is ignited causing an explosive release of gases filing the cushion to a deployed state which can absorb the impact of the forward movement of a body and dissipate its energy by means of rapid venting of the gas. The entire sequence of events occurs within about 30 milliseconds. In the undeployed state, the cushion is stored in or near the steering column, the dashboard, in a door, in the roof line or roof rail, or in the back of a front seat placing the cushion in close proximity to the person or object it is to protect.

#The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several potentially preferred embodiments of the invention and together with the description serve to explain the principles of the invention wherein:

#FIG. 1 is a perspective view schematically illustrating the inventive inflation assembly as incorporated within a non-inflated airbag cushion.

#FIGS. 2A-2D are cross-sectional views of the inflation assembly of FIG. 1 that schematically illustrate the flow of inflation gas through the timing member and into the airbag cushion upon activation of the propellant.

#Reference will now be made in detail to potentially preferred embodiments of the invention, examples of which have been illustrated in the accompanying drawings. It is to be understood that it is in no way intended to limit the invention to such illustrated and described embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the true spirit and scope of the invention as defined by the appended claims and equivalents thereto.

#Turning now to the drawings, wherein like elements are denoted by like reference numerals throughout the various views, in FIG. 1 an inflator 20 is illustrated including an elongated propellant 28. Upon ignition, the propellant 28 combusts and generates inflation gasses (among other combustion products) which then inflate the airbag 24. The inflation gas exits through at least one opening 56 within an inflation manifold 52 which directs the flow of inflation gas toward the desired airbag 24. Prior to reaching that final destination, the inflation gas first enters and inflates the inventive timing member 96 (preferably constructed as in Example 1, above) which in turn directs the flow of inflation gas through at least one of its own preselected openings 100. The propellant 28 may be comprised of any well known composition, such as combustible nitrogen-based formulations (e.g., gun-type propellants comprising hexahydrotrinitrotriazine and/or cyclotrimethylene trinitramine and/or cyclotetramethylen-ethanitramine and/or pentaerythritol tetranitrate, and the like), including binding materials, such as hydroxymethylcellulose, and the like, and other standard propellant components (e.g., ammonium nitrate, strontium nitrate, colorants, polymeric thickeners, and the like).

#The cross-sectional illustrations of FIGS. 2A-2D exhibit one preferred example of utilization of the inventive inflation assembly of FIG. 1 (and more specifically the inventive fabric timing member 52) upon ignition of the propellant 28. In its deactivated state (FIG. 2A), the propellant 28 has not yet been activated and no inflation gasses have been generated. In FIG. 2B, a collision event has occurred that has caused the initiator assembly 32 to ignite the propellant 28, which in turn generated combustion products, including inflation gas which exited the openings 56 within the manifold 52, without rupturing or damaging the manifold 52 itself. The inflation gasses then enter the chamber 102 of the timing member 96 and move radially outward from the outer layer 60 of the manifold 52 through the chamber 102 toward the wall of the timing member 96 and ultimately enter the airbag 24. In FIG. 2C, there is shown a substantially uniform entry of inflation gases about the cross-section of the airbag 24, as well as a substantially uniform entry of inflation gases along the entire length of the airbag 24. Such uniform inflation and filling is provided by means of the predetermined spacing and sizing of the metering openings 100 within the timing member 96. As seen in FIG. 2D, the airbag 24 uniformly receives inflation gasses and is uniformly filled or pressurized throughout its volume by means of the timing member 96 by the means noted above. In accordance with this uniform filling, inflation gases directly from the inflator 20 are filling the entire airbag 24 rather than inflation gases entering the airbag 24 at a limited area such that, in order to complete filling of the airbag 24, inflation gases in the airbag 24 itself are required to move longitudinally within the airbag 24 in order to achieve the desired force or pressure. Such non-uniform filling can result in the vehicle occupant being subjected to a less than desirable force due to the inflatable filling nonuniformly. With reference to FIGS. 3 and 4, one application of the inflator assembly 20 is schematically illustrated. In such an application, the inflator assembly 20 is used with an airbag 24 that is located above one or more vehicle side windows. Such an inflator assembly 20 is commonly termed a side curtain inflator. Such an inflator assembly 20 is particularly characterized by having a substantially greater length, particularly in comparison with driver, passenger, and side impact inflators. As seen in FIGS. 3 and 4, a curtain inflator assembly 20 is substantially elongated and has a length that is at least one-half the length of the airbag 24 and preferably is substantially equal to the length of the inflator assembly 20. Consequently, when the inflator assembly 20 is activated to deploy or inflate the airbag 24 of the curtain inflator module 110, there is a substantially uniform filling of the airbag 24 along its length. The generation and entry of inflation gases to the airbag 24 depend on propagation rate associated with the combustion wave. That is to say, the filling of the airbag 24 along its entire length at substantially the same time is limited by, or dependent upon, the rate at which the elongated propellant 28 is ignited beginning at its end adjacent to the initiator assembly 32 and continuing to its opposite end.