FARRINGTON ROY (GB)
AHMED TUHIN (GB)
FARRINGTON ROY (GB)
| GB2345008A | 2000-06-28 | |||
| EP0962363A1 | 1999-12-08 |
| 1. | An airbag device comprising an inflatable airbag (12) made of fabric panels with several seams (14,22, 24,25) which is inflated in the event of an accident by a gas provided from a gas generator (16) through a conduit (18), characterized in that said seams are internally sealed for preventing or reducing the gas leakage with a sealing compound that has not been applied prior to deployment and therefore maintains the fabric ability for being folded before deployment. |
| 2. | An airbag device according to claim 1 wherein said seams (14,22, 24, 25) are sealed during the airbag (12) manufacture. |
| 3. | An airbag device according to claim 2 wherein said seams (14,22, 24, 25) are sealed, being the airbag (12) inflated, injecting said sealing compound to the leakage areas. |
| 4. | An airbag device according to claim 2 wherein said seams (14,22, 24, 25) are sealed coating said sealing compound onto the seams and then activating the sealing compound by inflating the airbag (12). |
| 5. | An airbag device according to claim 1 wherein the seams (14,22, 24, 25) are sealed during the airbag inflation. |
| 6. | An airbag device according to claim 1 further comprising a sealing compound reservoir (15) connected to said gas conduit (14) for supplying gas with said sealing compound. |
BACKGROUND Airbags are constructed in one or more chambers that are usually made by sewing fabric panels. The fabric panels are normally coated with silicon to make the fabric airtight. An inflator produces or supplies pressurised inflation gas to the airbag, which may leak through the sewn seams between the panels.
Leakage is a result of both breaking the fabric coating when two separately cut panels are joined and by puncturing the coating membrane by the action of sewing.
The need to inflate airbags for a long period of time in relation to the inflator output has arisen from the use of airbags to protect against both side impact crash events, that can typically last for up to one tenth of a second, and a rollover crash event, that can typically last for several seconds.
Known proposals satisfying that need include several methods of sealing airbags so that they can remain inflated for an extended duration. Seam sealing prevents gas leakage, allowing the inflated airbag to retain its internal pressure.
Some methods of sealing that apply to the general area of a seam have been published.
GB1057444"Thermo-chemical joining of nylon yarns"describes a method to join nylon using a thermochemical fusion process. The bonding solution is an aqueous solution of chloral hydrate.
W09946110"Ultrasonic seam bonding method and apparatus"describes an apparatus and method for joining fabric ultrasonically, particularly for joining separate pieces of layered fabric, by means of a waterproof seam in a single operation. The bond formed is both strong and flexible.
EP0962363"Airbag"describes a method for sealing the airbags to resist leakage through seams by sewing with yarn and bonding by silicone adhesive.
The prior art regarding tyre sealing has been removed from here in order to avoid an objection about the"obviousness"of using tyre sealants for airbag sealing. Should this be included if there are sufficient differences between airbags and tyres defined below.
This invention is intended to provide an improved method of selectively sealing an airbag at the areas of leakage. Sealing is selective both in terms of the position of sealing action and the efficiency of reduced gas leakage.
SUMMARY OF INVENTION It is an object of this invention to provide an airbag device in which the airbag is sealed internally in a way that maintains the flexible and low weight nature of fabric for folding into the necessary package shape. Bag sealing is required to either prevent or reduce the gas leakage rate during inflation.
It is also an object of the present invention to provide an airbag device in which the airbag remains inflated for an extended duration so that occupant protection is maintained during accidents such as a vehicle rollover.
It is also an object of the present invention to provide an airbag device in which the airbag leakage is controlled to produce an optimised venting characteristic. Controlling the rate of leakage from the airbag improves the occupant protection provided by the airbag in response to different types and severity of accident.
To accomplish these and other objects, the airbag according to this invention is internally sealed by the action of a sealing compound that is injected into the airbag and becomes active at the areas of gas leakage from the airbag.
The sealing compound becomes active because of the difference in pressure, temperature, and velocity of gas flow moving from the inside to the outside of a pressurised airbag at the areas of leakage. The movement of gas inside the airbag acts to transport the sealing compound to the areas of leakage.
If the sealing compound is in a liquid state then the flow of air will act to dry or chemically activate the sealing compound to form a seal at the points of leakage.
If the sealing compound is a solid then the flow of air will act to force the compound to fill the leakage holes. It may be necessary to cover the area of the seams to be sewn with a material or catalyst suitable for either attracting or activating the compound at the critical areas of leakage. The sewn yarn may perform the function of activating the compound if appropriately treated before sewing.
The sealing compound may be released into the airbag at the time of inflation during a crash. In this instance the decision to release the sealing compound into the airbag can be used to change the airbag pressure characteristics. An advanced use of the compound to control the quantity released will enable any characteristic of leakage to be utilised as the main mechanism for venting the airbag in a controlled way. A short or long duration of inflation can be selected depending on the protection requirements.
The action of sealing the airbag may also be made during the manufacturing process. After forming the airbag by stitching the material it can be sealed by inflating and injecting the sealing compound inside the inflated airbag. If necessary any excess sealing compound that has not been activated to seal the airbag can be removed by the action of a vacuum to draw the compound from the airbag and produce a minimum volume pack ready for folding into the airbag module. Alternatively the compound may be coated onto the seam area before stitching and then activated to seal any stitching holes after the stitching process by inflating the airbag and creating a flow of leakage
gas to activate the compound. The chemical and physical composition of the inflation gas may be used to activate the sealing compound.
BRIEF DESCRIPTION OF DRAWINGS The features, objects and advantages of the invention will become apparent by reading this description in conjunction with the accompanying FIG. 1 which is a schematic view of an airbag according to this invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS One method of sealing an airbag according to this invention consists of releasing a sealing compound into the airbag at the time of inflation during a crash.
As illustrated in Fig. 1, the airbag device 10 typically comprises an airbag 12 made of fabric panels with the major seam sewn around the perimeter line 14, minor seams 22,24, 25 sewn to create chambers, an inflator 16 for supplying gas through a conduit 18 with a sealing compound to the airbag 12. To this effect, the device includes a sealing compound reservoir 17 and a spray diffuser 19 at the mouth of outlet 19.
The movement of gas (arrows 20) acts to transport the sealing compound 15 to the areas of leakage and finally the compound accumulates at the major panel seams 21, and the chamber seams 22,24, 25, to prevent gas leakage.
A control device (not shown) can be used to select the quantity of sealant compound to be released depending on the nature of the crash, allowing that the airbag leakage characteristics be utilised as the main mechanism for venting the airbag in a controlled way.
Alternatively, the sealing compound may be applied during the manufacturing process. One method consists of inflating the airbag and injecting the sealing compound to the leakage areas via the gas flow after stitching the material. Another method is coating the sealing compound onto the seam area before stitching and then activating the seal of any stitching holes after stitching
by inflating the airbag and creating a flow of leakage gas to activate the compound. The manufacturing methods can be used when the venting that would occur on the vehicle before the sealing compound has been transported and activated by the pressurised gas is not desirable for reasons of airbag performance.
The latter method has been used for a comparative pressure test between a silicon coated thorax airbag and a silicon coated thorax airbag with 'ultraseal'compound applied to the seams.'Ultraseal'is a trade named product of ULTRASEAL INTERNATIONAL INC. used in puncture resistant tyres. The 'ultraseal'compound was applied to the non-silicon coated side of the airbag and the bag inflated inside out so that the sealing compound was inside the airbag by using a pressurised air line. The baseline test also inflated the bag inside out using an airline. The pressure drop over time was recorded when the air line pressure was turned off. Deflation was standardised by applying an approximate 750g mass on top of the airbag.
The equilibrium starting pressure was 50mBar for both test cases.
Test 1 Baseline-Time for pressure drop to 2mBar was 3 seconds Time for full deflation was 20 seconds Test 2'Ultraseal'-Time for pressure drop to 2mBar was 7 seconds Time for full deflation was 55 seconds The deflation time was approximately doubled using the sealing compound.
The preferred sealant compounds are modified tyre sealants depending on the airbag fabric.
Tyre sealants are mainly composed of natural rubber latex, and contain ammonia at a high concentration of about 1.2 wt. % of rubber solid content to suppress solidification of the latex and enhance stability in the liquid state. They are also in Ethylene Glycol form, which are used in antifreeze and cooling/heating systems. The tyre sealant is chemically inert, and will not attack the tire or wheels. The sealing compound is chemically inert and will not attack the airbag fabric, fabric coating or sewn yarn. It contains anti-corrosive agents that protect steel and aluminium wheels and belts against corrosion. Chemical
bonding does not occur between the tyre and sealant, the compound is water dispersible allowing it to be washed out of the tyre with water. Other properties; will not dry out, seals holes of up to 9 mm in road tyres and up to 15 mm in off road commercial situations, is classified as non-toxic and non hazardous. is biodegradable and present no problems in disposal before or after use, will not freeze at temperatures of-40 degrees C and remains effective at temperatures in excess of +90 degrees C, is a permanent repair, is suitable for all types of tyres-on road, off road & commercial, is non-flammable and safe for air transportation. The sealing compound is classified as non-toxic, non-hazardous and presents no problems for disposal before or after use. The compound remains effective over a wide temperature range.
Some tyre sealants proposals known in the art include U. S. 4,216, 812 which describes a puncture sealant containing a lubricant and an amide wax applied as a layer to the interior of a tire; U. S. Patent 4,304, 281 teaches a run- flat tire having a coating on its interior surface of a lubricating material and FR 2727978 which describes the composition of the sealant to be: (a) deionised water; (b) a sealing agent such as particles of rubber and/or cellulose ; (c) a colloidal film forming agent such as aluminium magnesium silicate; (d) a thickening agent such as xanthan; (e) an antigel such as monoethyleneglycol ; (0 an organic solvent allowing expansion of the sealing agent comprising a mixture of toluene and/or xylene and one or more terpenes; and opt. (g) an anti-rusting agent such as Na nitrate; (h) a catalyst such as NaOH ; and (i) a bactericide such as Parmetol (RTM).
Suitable sealant compounds are any of the above-mentioned tyre sealants modified for its application to airbags taking into account the following differences with respect to tyres. FEATURE AIRBAG APPLICATION TYRE APPLICATION Compound Distribution Pressurised gas flow Centrifugal force Compound Activation Drying, chemical Drying of compound reaction, or thermodynamic phase change Leakage Area Multiple holes Single hole Leakage Surface Flexible fabric Elastic solid Hole Formation Tensioned seam Compressed wall Hole Shape Small and shallow Large and deep
A sealed airbag is capable of an extended duration of inflation and this can be used to deliver injury protection to the occupant of a vehicle during a crash event that involves vehicle rollover. The technique of conserving and controlling the energy stored in the airbag gas pressure by means of controlling the gas leakage serves to make airbag systems more adaptive to different types and severities of crash and also occupant conditions.
Although the present invention has been fully described in connection with preferred embodiments, it is evident that modifications may be introduced within the scope thereof, not considering this as limited by these embodiments, but by the contents of the following claims.