Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
2000-11-16
2003-03-11
Larkin, Daniel S. (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
Reexamination Certificate
active
06530264
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to detection systems and methods and, more particularly, to systems and methods for the detection of leaks from devices adapted to contain a pressurized fluid at a relatively high internal pressure, such as certain inflator devices used in the inflation of inflatable articles, such as an inflatable vehicle occupant restraint airbag cushions used in inflatable restraint systems.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an “airbag cushion,” that is inflated or otherwise expanded with gas when the vehicle encounters sudden deceleration, such as in the event of a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins to be inflated, in a matter of no more than a few milliseconds, with gas produced or supplied by a device commonly referred to as an “inflator.”
The term “compressed gas inflator” is commonly used to refer to various inflator devices which contain a selected quantity of compressed gas. For example, one particular type of compressed gas inflator, commonly referred to as a “stored gas inflator,” simply contains a quantity of a stored compressed gas which is selectively released to inflate an associated airbag cushion. A second type of compressed gas inflator, commonly referred to as a “hybrid inflator,” typically supplies or provides inflation gas as a result of a combination of stored compressed gas with combustion products such as result from the combustion of a gas generating material, e.g., a pyrotechnic.
In the past, stored gas inflators have generally been at a disadvantage, as compared to pyrotechnic inflators, in terms of size, weight, and/or cost. Such disadvantages have been especially significant in view of the general design direction of inflatable restraint systems toward relatively small, lightweight, and economical modern vehicle components and assemblies. In particular, the need in compressed gas inflators to store a gas at relatively high pressures typically results in the need for such an inflator device to include a pressure vessel having relatively thick walls. As a result, such vessels tend to be more bulky, heavy, and costly than otherwise desired for modern vehicle components.
Commonly assigned Smith et al., U.S. Pat. No. 5,470,104, issued Nov. 28, 1995; Rink, U.S. Pat. No. 5,494,312, issued Feb. 27, 1996; and Rink et al., U.S. Pat. No. 5,531,473, issued Jul. 2, 1996 disclose and relate to a recently developed type of inflator device, sometimes called a “fluid fueled inflator.” Such inflator devices typically utilize a fuel material in the form of a fluid, e.g., in the form of a gas, liquid, finely divided solid, or one or more combinations thereof, in the formation of an inflation gas for an airbag cushion. In one form of fluid fueled inflator, such a fluid fuel material is burned to produce gas which contacts a quantity of stored pressurized gas to produce inflation gas for use in inflating a respective inflatable device.
While such types of inflator devices can successfully overcome, at least in part, some of the problems associated with the above-identified prior types of inflator devices, there has been a continuing need and demand for further improved apparatus and techniques for inflating an inflatable device, such as an airbag cushion.
In at least partial response thereto, further efforts have led to the development of an apparatus for and methods of gas generation which at least in part rely on the decomposition or dissociation of a selected gas source material for gas generation. In particular, such developmental efforts have resulted in the development of an inflator device which is at least in part the subject of the above-identified patents: Rink, U.S. Pat. No. 5,669,629 and Rink et al., U.S. Pat. No. 5,884,938, as well as Rink et al., U.S. Pat. No. 5,941,562. In at least one form of such recently developed inflator device, inflation gas is produced or formed, at least in part, via the decomposition or dissociation of a selected gas source material, such as in the form of a compressed gas and such as via the input of heat from an associated heat source supply or device. Nitrous oxide is a gas source material disclosed for use in accordance with one or more of these patents. As disclosed, such an apparatus for and method of gas generation can be helpful in one or more of the following respects: reduction or minimization of concerns regarding the handling of content materials; production of relatively low temperature, nonharmful inflation gases; reduction or minimization of size and space requirements and avoidance or minimization of the risks or dangers of the gas producing or forming materials undergoing degradation (thermal or otherwise) over time as the inflator awaits activation.
In general, inflators have specific performance and operational requirements which necessitate that the inflators, or at least particular components thereof, be checked for the occurrence or presence of undesired leaks. For example, compressed gas inflators, such as described above, commonly require the presence therein of at least a certain specified quantity of the particular compressed material in order for the inflator to be capable of properly performing in the manner for which is was designed. In such inflators, it is generally desired that the amount(s) of stored compressed material(s) be maintained in the inflator within at least certain prescribed tolerances in order to ensure proper operation of the inflator. While proper inflator operation can be variously defined, ultimately, an inflator and the associated airbag cushion need provide adequate vehicle occupant protection over an extended period of time (typically fifteen years or more) after original construction and installation in a vehicle. Further, beyond the simple functioning of the inflator and deployment of the associated airbag, such inflatable restraint systems typically need to deploy the associated airbag cushion in a proper and particularly desired manner.
Various methods are available and have been used to determine the leak rate of compressed gas inflators. In practice, a typical or usual leak detection method involves the use of helium as a tracer gas included in the particular stored gas contents. In such a method, a certain fraction of the composition of the stored gas which escapes from the inflator consists of helium. (The exact fraction of helium detected as a result of a particular leak may be equal, less than, or greater than the corresponding loading conditions of the originally stored compressed gas. The physics associated with these various situations, however, is beyond the scope of the present discussion. In general, however, these different situations are typically dependent on certain, particular factors, such as the magnitude of the leak, the total pressure within the storage vessel, as well as the initial gas composition, for example.)
The leak rate of helium from a pressure vessel is normally detected using a mass spectrometer system. For such specific practice, mass spectrometers are normally designed to detect the presence of helium in the gases constituting the sample. The utilization of helium in leak tracing is advantageous in several respects: a) First, since the presence of helium is rather rare in the atmosphere, background helium (or residual helium in the environment such as the environment surrounding the detection apparatus) is normally very low. As a result, the possibility of the mass spectrometer being falsely influenced and possibly producing a spurious signal is significantly reduced or minimized; b) Second, the mass spectrometer signals for certain different molecular species can be nearly the same. Consequently, the mass spectrometer signal produced or resulting from the presence or occurrence of one molecular species may interfere or mask the mass spectrometer signal produced or resulting from the presence or occurrence
Green David J.
Neff George R.
Neff Jimmie K.
Pierotti L. John
Rink Karl K.
Autoliv ASP Inc.
Larkin Daniel S.
Pauley Petersen Kinne & Erickson
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