MXPA97009387A - Assembly of air bag filter and mi assembly method - Google Patents

Abstract

An efficient, light weight airbag inflation filter (50) includes a substantially rigid, gas permeable support tube (56) having a plurality of uniform perforations (58). A filtering element (62) formed of a continuous, inorganic ceramic wire or fiber, wound helically around the support tube (56) to form a further layer covering the perforations (58) of the support tube (56). ). An almbre mesh (60), having apertures therethrough smaller than the perforations (58) in the support tube (56) to act as a gas diffusion layer for gases passing through the inglation filter ( 5

Description

ASSEMBLY OF AIR BAG FILTER AND ASSEMBLY METHOD OF THE SAME BACKGROUND OF THE INVENTION This invention relates to the inflatable airbag restraint systems used in vehicles for the protection of the driver and passengers during a collision. More particularly, this invention relates to an airbag inflation filter for use in filtering the particles released during the instantaneous discharge required to inflate vehicle airbags. Inflatable airbags have instantly become more and more common as a means of protection for automobile drivers and passengers in the event that the vehicle encounters a sudden deceleration, such as in a collision. The airbag restricts the movement of an occupant of the vehicle during the collision, and is inflated by a gas generated by the actuation of the gas generating material contained in the inflator of the airbag. The air bag inflates in a shorter period of time (typically 20-80 milliseconds) by the rapid ignition and combustion of gas generating material. The gas generated, which initially at high temperature (for example, 700 ° C- REF: 26212 1200 ° C) and pressure (eg, 2000 PSI), contains metal particles and / or reactive, fine-molten oxides. To avoid damaging the bag or burning the skin or clothing of the passengers of the vehicle, the gas must be filtered to remove the particles before it enters an air pocket. An air bag filter in this way works by cooling the hot gases before that. Reach the airbag, and serves to remove particles and debris generated during ignition, so that they do not enter the airbag and contaminate the vehicle. Suitable filters for removing these particles should be able to withstand relatively high temperatures and have already been described in the prior art. The most common type of filter uses layers of woven or sewn metal mesh screen sheets, sometimes with additional layers of ceramic or sheet metal wool, or ceramic or glass paper, or ceramic or glass cloth. Those materials are wound in layers around the perforated support tube, that structure has been tightly wound with a single thick gauge wire welded on the outer side of the finished part. The airbag inflator filter designs of the prior art are typically assembled by hand and tend to be labor intensive and expensive. These filter materials are generally very heavy and the construction of the filter is complex. Usually, several layers of materials are wound spirally into a unitary structure. Due to this complexity, it is very difficult to maintain the same filtering characteristics from filter to filter and to obtain consistent operation of the filter. This is due not only to the inconsistency of the materials applied in the manufacturing process but also to the fact that spiral winding necessarily forms different depths of filter material around the filter. They often use ceramic papers, which do not have low porosity and high strength. Therefore they must be sandwiched between layers of wire mesh, thereby significantly increasing the weight of the filter. Ceramic paper is also inherently non-uniform .. '.. Examples of such filter types are shown in the following patents: US Patent No. 4,012,211, US Patent No. 5,230,726, US Patent No. 5,268,013, US Patent No. 5,308,370, U.S. Patent No. 5,346,252, U.S. Patent No. 5,087,070, and U.S. Patent No. 5,215,721. Other filter materials include porous metal or ceramic foams usually covered with a thermally and structurally stable material. Examples of such filter materials are found in U.S. Patent No. 5, 372,380 and European Patent Application No. 0640515. The preferred coating technique in those cases is the deposition of chemical vapor, which is extremely expensive. It has also been proposed to filter the inflation gases from the airbag with the material of the airbag itself. References describing this concept are U.S. Patent No. 5,071,161, U.S. Patent No. 4,536,439, U.S. Patent No. 5,104,727, PCT Publication No. WO 94 26,334, and PCT Publication No. WO 94 21, 494. Thus, US Pat. you want to develop a cleaner, lighter, more efficient airbag inflation filter. The efficiency in this respect means not only less expensive and easier to handle and manufacture, but also more efficient in its filtration capacity, (that is, it allows less particles through the filter and into the airbag). An air bag inflation filter is designed to be used only as a filter, it should work effectively when needed.

BRIEF DESCRIPTION OF THE INVENTION The present invention is an airbag inflation filter, which includes a substantially rigid gas-permeable support tube, having perforations therethrough, and a filter element formed from a continuous inorganic strand that is helically wound around of the support tube to form one or more layers that cover the perforations through the support tube. The present invention in this way is a simple, lightweight, reproducible air bag inflation filter useful for removing particles from the gas used to inflate an air bag. In use, the particle-laden gas flows through the filter radially from the inside out, and the substantially clean gas flows out of the filter. In a preferred embodiment, the air bag inflation filter includes a gas permeable diffusion layer. The diffusion layer has perforations therethrough smaller than the perforations through the support tube. Preferably, the strand is wound crosswise around the support tube. In preferred embodiments, the strand has a core from which the filaments fiber segments project outward, and opposite cores are wound into successive convolutions at each stage to provide interwoven cores. In one such embodiment, the convolution cores of each layer are spaced apart to provide substantially uniform four-sided openings within which at least one of the projecting filaments or fiber segments intertwine to form particle traps. In addition, the convolution cores of at least one layer are laterally offset from the convolution cores of an adjacent layer to generally divert the flow of radial gas through the filtering element towards tortuous paths therethrough. In another such embodiment, the successive convolutions of each successive layer are radially aligned to provide walls that are spaced apart to define four-sided openings within which at least one of the projecting filaments or fiber segments intertwine to form traps of particles. Preferably, the continuous strand is formed of a textured, heat resistant yarn. The air bag filter inflator assembly is formed from a housing having walls defining a chamber for receiving an air bag inflation filter, wherein the filter has a substantially rigid support tube, permeable to the gases, having perforations therethrough, and a filtering element formed from a continuous inorganic strand that is wound helically around the support tube to form one or more layers that cover the perforations through the support tube. The inflator assembly also has gas generating materials, solids, placed inside the air bag inflation filter support tube, and means for activating the solid gas generating material to generate the inflation gas of the air bag. air of it. The walls of the inflator housing have defined openings therethrough to direct the flow of inflation gas from the air bag out of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic, partial sectional view through an air bag inflator assembly on the passenger side, which includes the inflation filter of the air bag of the present invention. Figure 2 is a sectional view taken along lines 2-2 in Figure 1. Figure 3 is a side elevational view of an airbag inflation filter of the present invention, with the broken layers for purposes of illustration. Figure 4 is an elevational view from one end of the air bag inflation filter of Figure 3. Figures 5, 6 and 7 are perspective views of alternative support tubes for the bag inflation filter. air of the present invention.

Figure 8 shows a portion largely elongated from the surface of the air bag inflation filter of the present invention. Figure 9 is a schematic, partial, magnified sectional view taken laterally along the inflation filter of the present invention. Figure 10 is a portion of the amplified surface of an alternative embodiment of the inflation filter of the present invention. Figure 11 is a sectional view, schematic, partial, magnified 1 taken laterally along the alternative embodiment of the inflation filter of the present invention. Figure 12 is a schematic sectional view of an air bag inflator assembly on the operator's side, which includes an inflation filter of the air bag of the present invention. Figure 13 is a graphical representation of the flow velocity vs. Pressure drop for inflation filters shows and prior art. Figure 14 is a graphic representation of the pressure drop vs. Percent efficiency for inflation filters shows and prior art. Although the previously identified drawings set forth preferred characteristic embodiments, other embodiments of the present invention were also contemplated, as noted in the discussion. The description presents illustrative embodiments of the present invention by way of representation and not limitation. Numerous other modifications and embodiments may be contemplated by those skilled in the art, falling within the scope and spirit of the principles of this invention. The Figures of the drawings have not been scaled since it has been necessary to amplify certain portions for clarity.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention relates to an air bag inflation filter used to filter inflation gases for air bags, to protect the occupants of a vehicle. The filter is designed to withstand the high temperatures and gas pressures encountered in contact with the gas generated in a pyrotechnic air bag inflator assembly of the gas generating material such as the sodium azide wafers. The filter works by cooling the hot gases before they reach the airbag and serves to capture the particles and debris generated during ignition, so that they do not enter the airbag and contaminate the vehicle.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention relates to an airbag inflation filter used to filter the inflation gases for an airbag to protect the occupants of a vehicle. The filter is designed to withstand the high temperature and gas pressures encountered from contact with the gas generated in a pyrotechnic air bag inflator assembly of gas generating material such as sodium azide wafer. The filter works by cooling the hot gases before they reach the airbag and serves to capture the particles and debris generated during ignition so that they do not enter the airbag and contaminate the vehicle. In the description of the present invention and in the claims, the following terms are intended to have the meanings defined below: "filament or inorganic fiber" refers to any filament or fiber based on an inorganic compound that is resistant to high temperatures (e.g. , temperatures greater than about 400 ° C), and has textile qualities (ie, it is suitable for becoming a yarn that can be wound around a support tube, as defined); "fiber segment" refers to the portion of a broken fiber projecting from the core of a strand; "fiber" means a plurality or bundle of filaments of generally parallel fibers; "yarn" means a plurality of individual fiber bundles that have been combined by means such as twisted or tied; "thread" means either a thread or a fiber; "circuit" means winding down the application of the thread on a support tube; and "layer" means a complete cover of the support tube by strands wound in a predefined pattern, with each cover defined by a plurality of circuits. Figure 1 illustrates schematically an air bag inflator assembly for use in a passenger side air bag restraint system. The air bag inflator assembly 20 includes an inflator housing, generally indicated at 22, which has a cylindrical container 24 defining a cavity 26 therein.

The container 24 contains gas generating material, solid, 28, which is in the form shown, in the form of a disc (see Figure 2). As is well known, this can also be provided in other forms, such as granules.

One end of the cylindrical container 24 is closed by means of an integral circular end wall 30. A separate end cap 32 is provided at the opposite end and is secured by a seal in place by suitable means (eg, threaded, welded or bent inward) after all the internal components of the air bag inflator assembly 20 are in place within the housing 22. The end cap 32 has an initiator 34 that extends coaxially and fully sealed to secure a seal gas-tight for the cavity 26. An internal end of the ignition device or ignitor 34 is coupled to the material of the ignition device or ignitor 36 within the cavity 26 for activation thereof. One or more spacers 38 (either inert or formed from gas generating material) can be placed at either end of the cavity 26, as desired, to place the gas generating material 28. One or more alignment bolts 40 are provided, support plates (not shown) or the like on the housing 22 to facilitate mounting in place in a vehicle. The cylindrical container 24 has a plurality of perforations 42 extending through its wall to allow the gases generated by the inflator assembly of the air bag 20 to escape outward to quickly fill and inflate an air pocket toward deployment. A layer of moisture impermeable sheet or gas 44 is mounted on the inner surface of the cylindrical container 24. The sheet 44 thus covers and seals the perforations 42 prior to use of the air bag inflator assembly 22 to inflate a bag of air. The sheet 44 breaks under the increasing pressure developed after the formation of the inflation gases by activation of the gas generating material 28. A tubular air bag inflation filter 50 is deposited within the cavity 26 of the cylindrical container 24, between the inner surface of the container 24 and the gas generating material 28. One or more annular spacers 52 or spacer discs 54 may be provided adjacent the ends of the inflation filter 50 to align and support the same within the housing 22. The filter inflation 50 is positioned to be disposed between the gas generating material 28 and the perforations 42 in the wall of the container 24, so that any gases generated must pass through the inflation filter 50 before being released into an air pocket. A preferred embodiment of the air bag inflation filter 50 of the present invention is illustrated in Figures 3 and 4. The inflation filter 50 has a substantially rigid, gas permeable support tube 56, which has a plurality of perforations. 58 that extend through it. The support tube 56 comprises any material capable of maintaining its resistance at high temperature (e.g., above 500 ° C) such as metals and ceramics. Metals such as steel and stainless steel are preferred. A wire mesh 60 is aligned on the support tube 56 to cover at least all of the perforations 58 therethrough. A filtration element 62 is formed from a continuous inorganic strand that is wound helically crosswise over the wire mesh 60 and the support tube 56 to form one or more layers covering the support tube 56, and that particularly They cover the perforations 58. Preferably, the perforations 58 are generally of uniform size and placement on the support tube 56. The openings in the wire mesh 60, also preferably generally uniform, are smaller in size than the perforations. 58 through the support tube 56. The wire mesh 60 thus serves to diffuse the inflation gases which rapidly pass radially outwardly from the inflation filter 50 through the perforations 58. Alternative tube configurations of support are shown in Figures 5, 6, and 7. Figure 5 illustrates a perforated metal or ceramic support tube 56a, wherein the perforations 58a extend completely from end to end of the support tube 56a, thereby defining the entire support tube 56a as the drilling area. Figure 6 illustrates an expanded metal support tube 56b, wherein the expansion of the metal segments defines the size of the perforations 58b. In an expanded metal tube 56b, the perforations 58b can thus extend end to end of the tube 56. Figure 7 illustrates a perforated or slotted ceramic or metal tube 56c having pre-defined perforations 58c. Again, the perforations extend from end to end on the tube 56c. Regardless of the configuration of the support tube, the perforations in the support tube preferably occupy the range of about -20 to 70 percent of the total area of the tube, and are generally uniformly distributed along the tube and that area of drilling. The perforations can be of any desired geometric shape. Although not shown, it was contemplated that other support tube configurations could be suitable for use in the present invention, such as, for example, a welded or woven screen. In a preferred embodiment of the present invention, the filtration element 62 is formed with an inorganic thread wound in a substantially helical manner around the support tube 56 (see Figure 3). Examples of techniques for winding such inorganic strands around the support tube are found in U.S. Patent No. 5,248,488 to Bloom, et al, which describes a laterally deviated winding method, and U.S. Patent No. 5,248,482 to Bloom, et al. al, which describes a radially aligned winding process. In a lateral deflection winding method, a continuous strand (which preferably has a plurality of continuous filament loops or fiber segments projecting outwardly thereof) is wound in a substantially helical, cross-wound manner around the tube. of support to form a plurality of layers of strands. The successive convolutions of the strand are wound in opposite layers to provide interwoven cores. The cores of successive convolutions of each successive layer are separated to define four side openings, with the filament loops or segments of fiber on the strand projecting towards each of the four lateral openings to provide a particle trap in the inflation gas of the air bag The cores of the strand in at least one layer are laterally offset from the cores of the strand in an adjacent layer to divert the gas towards a tortuous path through the filtration material. Referring to Figures 8 and 9, the construction of the laterally deflected winding for a continuous strand is illustrated. Figure 9 illustrates an eight layer filtration element formed by the helical winding of a strand 70. As noted, the cores of the strand in one layer are laterally offset from the cores of the strands of the adjacent layers. The surface effect of this helical crossover is seen in Figure 8, where the strands 70a, 70b, 70c and 70d are observed for the four outermost layers, together with the interconnected filament curls or fiber segments 75. The process The radially aligned winding also uses a strand having filaments or fiber segments projecting outwardly therefrom, and which are helically wound around the support tube. The successive convolutions of the strand are wound in opposite layers to provide interwoven cores, with the cores of the successive convolutions of each layer aligned radially to provide walls that are spaced apart to define four-sided openings. The strands of filaments or fiber segments of the strand project to each of the four-sided openings to provide a trap for particulate material.

The configuration of the radially aligned winding is illustrated in Figures 10 and 11. In this embodiment, an eight layer filtration element, which has been formed helically wound to a strand 80, is also illustrated. Each strand 80 has its core radially aligned with the core of the strands in the adjacent convolutions. Continuous fiber loops or fiber segments 85 project outward from each strand 80 and intertwine to define traps for particulate material. In addition to the laterally deviated and radially aligned winding techniques discussed above, it was also contemplated that one or more layers of continuous thread be wound by a uniform winding technique. It was further contemplated that the radially aligned and uniform lateral deflected winding techniques may be combined to achieve alternative strand winding patterns for the filtration element of the present invention. Preferably, the thickness of the filtration element of the present invention is from about 1 to about 15 millimeters thick. In a preferred embodiment, the strand is formed from a heat-resistant inorganic yarn wound cross over the support tube having a diameter in the range of about 0.5 to about 5 millimeters. The inorganic yarn is made from individual filaments or inorganic fibers. Such yarns are typically in the range of about 700 to about 8000 or more individual filaments or inorganic fibers (preferably 1400 to 3500 individual fibers or filaments). The individual fibers or filaments typically have a diameter ranging from about 2 microns to about 20 microns (preferably from 6 microns to 12 microns). The inorganic yarn is a two-ply press yarn because such a construction can be textured to provide a superior filtration material when compared to the inorganic yarn which is not twisted from two ends. In this application, suitable inorganic fibers include ceramic fibers such as alumina-silica fibers, zirconia-silica, graphite, alumina-chromia-metal oxide, and preferably alumina-boria-silica (such as NEXTELm 312, 440 or 550 ceramics (commercially available from the Minnesota Mining and Manufacturing Company of St. Paul, Minnesota), high temperature glass fibers such as S-2 glass or E glass (commercially available from O Ens-Corning Toledo, Ohio), continuous fused silica fibers, such as ASTROQUARTZ "* fibers (commercially available from JP Stevens Company of Slater, North Carolina), QUARTZEL01 fused quartz wire (commercially available from Quartz Products Corporation of Louisville, Kentucky) , leached glass fibers, such as REFRASIL fibers "(commercially available from Hitco Materials of Gardena, California), non-vitreous ceramic fibers, such as NICALON fibers" (commercially available from Nippon Carbon from Tokyo, Japan), and continuous alumina-silica fibers, such as NITIVY fibers (commercially available from Nitivy Co., Ltd., of Japan), or combinations thereof. The texturing of the inorganic yarn improves the efficiency of the filter or trap. Preferably, the inorganic yarn is textured so that it is elastic or fluffed, for example, being textured so that the continuous filament loops, individual fiber segments, or a combination thereof extend outward from a core. dense. The inorganic yarn can be textured by techniques known in the art, including, for example, air or metal jet texturing. Air jet texturing is preferred because it generally provides a textured yarn having fewer fiber segments and more filament curls than yarn textured by the mechanical technique. An air jet texturing machine suitable for this purpose is available under the designation mark SIDEWINDER MODEL 17 of Enterprise Machine &; Development Corporation of New Castle, Delaware. Preferably, the textured yarn has a diameter in the range of about 1 mm to about 10 mm. Alternatively, the strand may be formed from a fiber of inorganic material. A non-braided fiber is formed of a plurality of bundles of filaments or fibers of longitudinally aligned segments. Typically, a plurality of fibers are braided together to form a single piece of yarn. However, a fiber by itself contains elements of fiber and filaments and can thus serve as a thread in this case. In addition, because the fiber has not been braided, the lateral pressure (such as that applied during winding under tension) to the fiber causes the filaments and fiber segments to be exposed out of the strand, thereby allowing them to interwoven behind successively superimposed coiled fiber. In a contemplated additional embodiment, a single fiber can be braided and then wound as a strand to define the filter element of the air bag inflation filter of the present invention. The width of the strip (separation between cores of adjacent strands on the same layer), diameter of the strand, winding angle, number of layers, winding tension and winding pattern can vary to obtain the filtration efficiency and drop of pressure desired in an airbag inflation filter of the present invention. Preferably, the strand is wound at an angle of at least 50 degrees and less than 90 degrees to the axis of the support tube. More preferably, the winding angle of the strand is between about 75 degrees and about 85 degrees. In a preferred embodiment, the winding angle of the strand is about 80 degrees. It was contemplated that the coiling angles of the strand of the successive layers may vary. In additional means for controlling the efficiency of the filter element, it is to vary the texturing of the strand layers comprising the filter element. For example, the innermost layers may be less textured (that is, fewer filaments or fiber segments that are projected) than the outer layers. This arrangement allows the particle traps on the inner layers to trap large particles, while the particle traps in the outer layers will capture finer particles. Such variable texturing can be performed on the same strand, or separate layers of different strands (each strand having different texturing) can be wound sequentially onto the support tube. In this way, strands of different level of texture or strands of different composition can be used.

The use of such a gradual winding angle (preferably about 80 degrees) produces very narrow four-sided openings or diamond patterns in the filter element. This larger angle provides greater stability in this extremely high pressure environment of an airbag inflation filter. Such an inflation filter is only designed to be used once, and the explosion of the gas generating material tends to increase the diameter of the containment members, and therefore decreases its length. The angle of gradual winding of the strand of the filter element acts to counteract this tendency, at least for the filter element, and provides additional stability to the filter element. The use of filtering element formed from inorganic strands helically cross-wound as described above provides an extremely consistent filter, as compared to stratified air bag filters, spirally wound in the prior art. Although such construction is preferred to achieve such consistency, it may be undesirable from a cost point of view. Inorganic strands, such as ceramic threads, are relatively expensive compared to some alternative filtration materials. In this way, it may be desirable to provide layers of inorganic strands wound adjacent to the support tube (where the gas temperatures will be higher) but to provide low temperature and less expensive resistant filter materials as one or more outer layers. As described above (and illustrated in Figures 3 and 4), in a preferred embodiment the filter element includes a layer defined by a metal mesh or screen. It was also contemplated that this metal mesh be removed from the filter element, thus leaving only the support tube and the inorganic strand layers helically wound as the structure of the inflation filter. In addition to one or more diffusion layers of metal mesh or screen, it was also contemplated that one or more layers of other materials could be provided in the formation of the filtration element of the present invention. Such materials include metallic wool (ie, a non-woven mesh), ceramic or glass cloth (which could be woven, sewn or pressed or a combination of glass cloth or ceramic), non-woven glass or ceramic material, or glass or ceramic paper. To provide additional strength, metal wire or high strength organic fiber (e.g. KEVLAR fibers) (commercially available from EI du Pont de Nemours and Company, Inc., of Wilmington, Delaware) can be wound with the inorganic strand layers or on the upper part of the inorganic strand on the support tube (or braided with the inorganic strand before coiling) The inflation filter of the airbag of the present invention is applicable to various inflator constructions. Figures 1-7, the inflation filter is adapted for use in a passenger side air bag filter assembly Figure 12 schematically illustrates an air bag filter assembly construction on the driver's side, which is shown in FIG. typically mounted on the steering wheel of the vehicle, since the steering wheel is closer to the driver than "of the passenger instrument panel, the airbag on the driver's side is smaller, thus requiring a smaller amount of gas-generating material and a smaller filter.In Figure 12, the air bag assembly air 120 includes an inflator housing 122. which is defined by a generally cylindrical basket 124. The basket 124 has an internally coaxially aligned cylindrical container 125 which defines a cavity 126 therein.The gas generating material 128 is coaxially aligned within the the cavity 126, in disc form, as illustrated, in another suitable form. Typically, a prefilter 127 is located between the gas generating material 128 and the inner container 125. One or more spacers 129 can be placed within the cavity 126, relative to the prefilter 127 and the gas generating material 128. The cylindrical basket 124 has an integral circular end wall 130 at one end, and is fixedly mounted to a circular end cap 132 at its other end. The end cap 132 is also sealingly connected to close one end of the inner cylindrical container 125 and its cavity "126. A circular integral end wall 133 closes its other end, the adjacent end wall 130 of the basket * -cilindrica 124. An ignition device or ignitor 134 is coaxially positioned through the end layer 132, and operably coupled to the material of the ignition device or ignitor 136 positioned within the cavity 126. The internal cylindrical container 125 has a plurality of openings radially arranged 135. These openings 135 lead to an annular slag protector 137. The gas created by the gas generating material must pass through the prefilter 127, the openings 135 and the slag guard 137 before finding the inflation filter of The tubular air bag 150 of the present invention This defined flow pattern is illustrated generally by arrows 139 in Figure 12. L Cylindrical basket 124 has a plurality of perforations or apertures radially disposed therein. Again, a sheet (not shown) may be provided to seal the perforations 142 prior to the activation of the gas generating material 128. The inflation filter of the tubular air bag 150 of the present invention is placed in the assembly of inflator 120 adjacent to perforations 142. The overall structure of inflation filter 150 is the same as previously described although the relative dimensions are different. A support tube 156 having perforations 158 therethrough is provided. You can place a ** <; * wire mesh 160 around the support tube 156 to cover at least the perforations 158. Next, an inorganic material filtration element 162 is provided, formed in the same manner as that of the invention as described above, on the wire mesh 160 and support tube assembly 156. Although different in configuration, the operation of tubular air bag inflation filter 150 in inflator assembly 120 functions the same as inflation filter 50 in inflator assembly. The airbag inflation filter of the present invention has numerous advantages over air bag inflation filters of the prior art. The inflation filter of the present invention has a lower thermal capacity than the inflation filters of the prior art. This absorbs less heat from the expanding inflation gases and, therefore, can allow the dedication of more energy charge to the desired inflation air injection. In this way, a smaller inflation load is possible, since the filter does not absorb much inflation energy. The formation of the filtration element of the present invention is done in a computer controlled coiling machine with the inorganic strand being placed very precisely. This process highly. controlled results in a more consistent filter structure and filtration performance than was possible with the prior art. The use of a continuous inorganic yarn as a strand results in a material having high tensile strength and which can be wound to the desired porosity. In this way, it overcomes the problems associated with the low tensile strength ceramic papers contained in the prior art air bag filters. The airbag inflation filter of the present invention requires less manual assembly, fewer components, is easy to manufacture and is lighter in weight than inflation filters of the prior art. Other advantages of the structure of the invention are illustrated in the following examples, which illustrate the preferred embodiments contemplated up to now and the best mode for practicing the invention, but are not intended to limit the same.

EXAMPLES Six airbag inflation filters of the present invention were constructed, and were referred to herein as sample filters A, B, C, D, E and F. For each sample filter, the support tube constituted a steel support tube. 28 gauge stainless steel (0.4 mm) 1.56 inches (39.8 mm) external diameter and 9.33 inches (237 mm) in length. A central perforated portion was 63 percent open via round perforations of the same size (each perforation was 0.1875 inches (4.76 mm) in diameter of the hole, and no margins were drilled (approximately 0.785 inches "; (19.94 mm) in length). Each end of the support tube A support tube of this type is illustrated in Figure 3. Each of the perforated support tubes was mounted on a computer controlled filament winder.A suitable winder for this purpose is the winder of three-axis filaments, Model W35, available from McClean Anderson, of Schofield, Wis. As mentioned, six air bag inflation filters were formed by winding helically-wound strands > Three different winding protocols were used. different strand, with each protocol used to wind a pair of airbag inflation filters sample.In each pair, a sample filter had only one the perforated support tube, and the other tube a stainless steel wire mesh (open area of 46% - 40/40 mat with a wire diameter of .008 inches (.203 mm)) rolled (one layer) around of the perforated support tube. The first winding protocol used the radially aligned winding process (sample filters A and B), the second winding procedure used the lateral winding winding method (sample filters C and D), and the third winding method used a winding procedure. of lateral deviated winding of multiple angles (filters shows E and F). All sample filters were rolled with NEXTEL "* 312. This material is an inorganic fiber, the NEXTEL 312, Denier of 1800, size 170 was braided in a 2/2 1.5z construction, which was subsequently textured by air jet A SIDEWINDER MODEL 17 air jet texturing machine was used from Enterprise Machine &Development Corporation, New Castle, Delaware, for this purpose.A 52D air jet set was used, with a fixed machine speed of 26.5 / min. , the jet was fixed three quarters of its most closed position and operating under an air pressure of 585 kPa.The winding or winding of all the sample filters was made with a tension of 1000 grams on the wire. 1 shows the parameters and data of winding or winding for the six inflation filters of air bag shows.

TABLE 1 The length of the filter element formed on the support tube for each sample filter was approximately 9.27 inches (235.5 mm). After being rolled up, each inflation filter sample was placed in a controlled heating environment to remove the inorganic material (sizing 170) from the yarn. This thermal cleaning process was controlled by raising the temperature of the room temperature to 10 ° C per minute up to 550 ° C, and maintaining that temperature for 30 minutes before d-cooling to room temperature. The six air bag inflation filters shown were tested, as reported below, and compared with two air bag inflation filters of the prior art type, to which reference is made here as PA-filters. 1 and PA-2. Those filters of the prior art were a composition of a sieve, wool and ceramic paper wound on a perforated steel tube. Each had a perforated 28 gauge (0.4 mm) stainless steel tube that had an external diameter of 1.56 inches (39.8 mm). The length of the PA-1 filter tube of the prior art was 9.33 inches (237 mm), and the length of the tube for the PA-2 filter of the prior art was 9.95 inches (252.9 mm). One piece of 29.52 inches (750 mm) length of sieve woven stainless steel, 24 x 24 mesh with a wire diameter of 0.011 inches (0.279 mm), which has a width equal to the length of the tube was wound tightly around the perforated tube. This is wrapped in a thin layer of steel wool that had wires of approximately 0.001 inches (0.279 mm). The steel wool had a width that encompassed approximately the same as the length of the tube, and had a rolled length of approximately 18.11 inches (460 mm). Also wrapped within the screen was a thin layer of ceramic paper, which also had a width approximately equal to the length of the tube, and had a rolled length of approximately 5.98 inches (152 mm). The rolled screen was welded with spot welding to secure the stratified component in place around the perforated tube, and a 0.035 inch (0.889 millimeter) stainless steel wire wound spirally around the outside of the screen and welded with spot welding instead. The outer diameter of both prior art air bag inflation filters terminated was 2.00 inches (51 mpt). Unlike the length of the PA-2 filter, it is believed that the support tubes for those two inflation filters of the prior art are identical to those used to construct the six sample inflation filters. The PA-1 filter of the prior art had a total weight of 483.3 grams, while the inflation filter PA-2 of the prior art had a total weight of 511 grams.

The six airbag inflation filters shown and the airbag inflation filter PA-1 of the prior art described above were tested for flow at ambient conditions. The pressure drop across each filter was recorded, with the direction of flow being from inside the filter out of the filter. Pressure drops measured at various flow rates for the six sample inflation filters and the PA-1 filter of the prior art are listed in Table 2 below.

TABLE 2 TABLE 2 (Continued) The information presented in Table 2 is illustrated? Graphically in the graph of Figure-? 3.1 As noted, all air bag inflation filters of the present invention show lower pressure curves than the air bag inflation filter. PA-1 of the prior art. Inflation efficiencies of air bag inflation filters with particles carried by air, with a size of 0.75 microns at a nominal flow rate of 40 CFM (1.13 mVmin). The particles were of undispersed dioctyl sebacate (DOS). An aerosol generator provided the particles, which were then diluted with filtered compressed air. The number of particles in the flow stream was measured with condensate core counters (CNC), both ueam and downstream of the filter.

The efficiency percentage was then determined from the concentration measurements taken from the ueam and downstream sides of each filter. The percent efficiency was calculated using the following formula: Percent of Efficiency = (1 - concentration downstream / concentration ueam) x 100. The comparative data collected are presented below in Table 3.

TABLE 3 Figure 14 shows that the efficiency results of air bag inflation filters of the present invention at a pressure drop of 22 inches of water (5.5 kPa) to 32 inches of water (8.0 kPa) are higher than the efficiency results of the airbag inflation filters PA-1 and PA-2 of the prior art. The efficiency results of the airbag inflation filter of the prior art are lower with a higher pressure drop of 50+ inches of water (12.5 + kPa). The test equipment in this case was only able to produce data up to 50 inches of water. Other means to correlate physical differences in air bag filters is the light measurement test. This measures the amount of light transmitted through the filter medium of the airbag inflation filter. A TES-36 Spherical Transmission Evaluation System manufactured by Hoffman Engineering of Stamford, Connecticut, was used to determine the light transmittance. The results of those comparative tests are listed in Table 4 below. Air sample inflation filters allowed a measurable amount of light to pass through while air bag inflation filters of "the prior art did not transmit any measurable light.

TABLE 4 Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention. For example, the perforations in the support tube may not be uniform, either varying in size or pattern of perforation in a selected form to define the flow of gas through the filtration element and into the air bag. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for, the manufacture of the objects to which it refers. Having described the invention as above, property is claimed as contained in the following:

Claims (14)

REVINDICACI0NE3

1. An airbag inflation filter, characterized in that it comprises: a substantially rigid tube having permeable perforations-: a. gases through it; and a filtering element formed of a continuous inorganic strand that is wound helically around a support tube to form one or more layers covering the perforations through the support tube, each convolution of the strand extending at an angle at less a layer of 75 ° to 85 ° to the axis of the support tube.

2. An inflation filter of air bag, according to claim 1, characterized in that each convolution of the strand in at least one layer extends at an angle of about 80 degrees to the axis of the support tube.

3. The inflation filter of air bag according to claim 1, characterized in that it has a diffusion layer adjacent to the perforations through the support tube, the diffusion layer is formed of a metal mesh having perforations permeable to the gases through it smaller than the perforations through the support tube.

4. The inflation filter of air bag according to claim 3, characterized in that the diffusion layer is deposited between the support tube and the filtering element.

5. The airbag inflation filter according to claim 1, characterized in that the strand is helically transverse wrapped around the support tube.

6. The airbag inflation filter according to claim 1, characterized in that the strand has a core from which the filaments or fiber segments project outwardly, and in which the successive convolutions are wound in an opposite manner in each layer to provide interwoven cores.

7. The inflation filter of air bag according to claim 6, characterized in that the filtering element has at least two layers and the amount of fiber or filaments that project is smaller in a first layer near the support tube than in a second layer more separated from it.

8. The inflation filter of air bag according to claim 1, characterized in that the perforations are aligned in a perforated area of the support tube, and wherein the perforations occupy the range of approximately 20 to approximately 70 percent of the perforated area of the support tube.

9. The inflation filter of air bag according to claim 1, characterized in that the filtering element has an annular thickness of approximately 1 to 15 mm.

10. The inflation filter of air bag according to claim 1, characterized in that it also comprises one or more layers of material around the support tube, selected from the group consisting of metal mesh, metal wool, ceramic cloth or glass , ceramic or glass nonwoven fabric, ceramic or glass paper, helically wound high strength organic fibers and helically wound metal wires, and combinations thereof.

11. The inflation filter of air bag according to claim 1, characterized in that the filtering element has at least two layers and wherein the convolutions of the two support layers are wound at different angles in relation to the axis of the support tube .

12. The airbag inflation filter according to claim 1, characterized in that the filtering element is formed from a continuous inorganic strand that is wound helically around the support tube to form a plurality of layers covering the perforations at through the support tube, each. ", Convolution of the strand in a particular layer extends to" a **; tr ' a winding angle in relation to the axis of the pipe, of support, the convolutions of an outer layer have a winding angle smaller than the convolutions of a previously rolled inner layer, the inner layer has a winding angle of convolution of about 80 degrees and the outer layer has a convolution winding angle of about 50 degrees.

13. The inflation filter of air bag according to claim 12, characterized in that the filtering element has a second internal layer previously wound of the outer layer, with the convolutions of the second inner layer, having a winding angle greater than the convolutions of the outer layer.

14. An "air bag inflator" assembly, characterized in that it comprises: a housing having walls defining a chamber for receiving an air bag inflation filter according to claim 1 therein; gas generating material, solid , placed inside the air bag inflation filter support tube, and means for activating the gas generating material, solid to generate the inflation gas of the air bag thereof, wherein the walls have defined openings a- through to direct the flow of inflation gas from the airbag out of the housing.