Background And Summary Of The Invention

[0001 ] The present invention relates to a method and related apparatus to reduce or completely negate gas flow through a sewn seam and a manufactured article made by said method.

[0002] More specifically the invention comprises: an improved method of sealing a sewn seam on an airbag or other inflatable device and apparatus to accomplish this method, the method comprising the steps of: a) creating a sewn seam with the use of thread to join multiple panels of material, the seam extending from a first exposed surface of one of the panels of material to an opposite exposed surface of a last panel of material;

b) applying a seam sealant to an exposed portion of the seam on the first exposed surface;

c) locally applying a pressure differential to the opposite exposed surface proximate a portion of the seam on this surface to urge the seam sealant to migrate along the thread from the first exposed surface to regions between the panels to the opposite exposed surface; and

d) removing the pressure differential.

Brief Description of the Drawings

[0003] Figure 1 shows a typical curtain airbag having a plurality of sewn seams.

[0004] Figure 1 a shows an inflatable mattress with a plurality of sewn seams.

[0005] Figure 2 shows typical leak paths relevant to an airbag having a sewn seam. [0006] Figure 3 shows an exemplary, simplified airbag, useful in explaining the benefits of the present invention.

[0007] Figure 3a shows an exemplary air bag with a center path terminating at end coil, loop, or oval sections.

[0008] Figure 4 shows sealant applied to one of the seams of the airbag of figure 3.

[0009] Figure 5 shows a work table useable with the present invention.

[0010] Figure 5a is a cross-sectional view taken through section 5a-5a of figure 5.

[001 1 ] Figure 5b shows vacuum applied to sealant.

[0012] Figure 6 shows the migration of seam sealant after the application of vacuum, the two sewn together layers of material are moved apart for the purpose of illustration.

[0013] Figure 7 shows the present invention applied to more than two layers of material.

[0014] Figure 8 shows an alternate construction of a work table and in particular the construction of grooves with raised sides.

[0015] Figure 8a shows the airbag draped about a section of groove with raised sides.

[0016] Figure 8b shows the template atop the airbag with the raised walls of the groove extending into a cutaway portion of the template.

[0017] Figure 8c shows a template or guide with portions cut away designed to be placed atop the airbag which has been placed upon the work table.

[0018] Figure 8d adds to figure 8c a solvent applicator which is pictured about to add solvent to the airbag.

[0019] Figure 8e shows a quantity of sealant being application to fabric.

[0020] Figure 8f shows a piece of fabric under vacuum pressure.

[0021 ] Figure 8g shows an alternate embodiment of side walls of a groove.

[0022] Figure 8h shows an alternate sealant applicator. Detailed Description of the Drawings

[0023] Figure 1 shows a somewhat conventional sewn-together curtain airbag 10. The airbag comprises a central inflatable region 12 formed by sewing two panels of material 14 and 16 together. Airbag 10 further includes a non-inflatable linking panel 18, which is used to connect one side of the airbag to an anchor point such as a vehicle pillar and additionally includes another non-inflatable linking panel 20 to connect the other side of the airbag to another vehicle pillar. The inflatable region 12 is subdivided into a plurality of inflatable regions 12a by selectively creating sewn seams 22 to join panels 14 and 16 together. Some of the sewn seams 22 are configured to create non-inflatable regions 30 within the airbag 10. The airbag 10 is configured to include at least one or more inlets 32 through which inflation gas can be provided from an inflator to inflate the airbag. One of the seams 22a is a peripheral seam, another seam 22b shows a center path 22c terminating at end coil, loop, or oval sections 22d.

[0024] Figure 2 shows the location of the leak paths in a sewn-together airbag. When the airbag is pressurized inflation gas can leak out of the material forming the inflatable region 12 as illustrated by arrows 40a and 40b. In practice these leak paths through the airbag material can be eliminated or reduced by coating the woven airbag material with a known sealant such as silicon. Also, such leak paths can also be reduced using uncoated woven material using thin denier thread and by increasing the weave density of the thread. Sewn-together airbags are known to have leak paths through the needle holes created in the joining together of the panels; these paths are shown by arrows 40c and 40d. Further, as the airbag is inflated the sewn seam 22 is stressed creating another leak path between the panels of material and across the thread forming this sewn seam. This additional leak path is shown by arrow 40e. Airbags such as the one illustrated in figure 1 may also include a peripheral sewn seam 22a extending along some or all sides of the airbag which of course creates a variety of leak paths through each needle hole. The present invention shows proven methodology to reduce and/or eliminate each of the above leak paths.

[0025] Reference is briefly made to figure 1 a which illustrates an inflatable mattress 50 which has a structure similar to that of the sewn- together airbag. For example, mattress 50 includes one or more inflatable regions 52 filled with air or some other gas. These inflatable regions can be formed by sewn-together seems 54 which will exhibit leak paths. Figure 1 a is provided to illustrate the present invention can be used on different types of inflatable devices.

[0026] Reference is now made to figure 3 and 3a which represents an exemplary airbag 60 useful in explaining the present method and related apparatus. Airbag 60, as with airbag 10, is formed by sewing together opposing panels of material 62 and 64. These panels of material can be formed as separate pieces of material or these panels can be formed by folding over a large piece of material into, for example, two halves wherein each half forms one of the panels. Airbag 60 includes a peripheral seam 66 and an interior seam 68 (68a in fig 3a) which separates inflatable regions 70 into subregions 72 and 74. The interior seam 68 by way of example comprises oval sew seams 80 and 82 joined by a rectangular section 84. These various seams 80, 82 and 84 create noninflatable regions 90 and 92. Airbag 60 also includes a neck region or area 32 similar to airbag 10. In figure 3a the interior seam 68a includes a center path 84a terminating at end coil, loop, or oval sections 80a.

[0027] Figure 4 illustrates airbag 60. In addition, figure 4 shows a band of sealant material 90 has been applied to the peripheral seam 66. In the preferred embodiment, the sealant material 90 when it is applied to the airbag material is in a semi-liquid condition with a specified viscosity or within viscous range of 50 to 200,000 cP (0.05 Pa.s to 200 Pa.s) (as tested under ASTM D1084). This viscosity can range up 2 million cP if circumstances allow for it. The viscosity range will vary with parameters such as seam thread characteristics, needle and needle hole size, application temperature and humidity, the width W of the sealant material 90 is shown by the distance between phantom lines 92 and 94. The thread seam in each of the one or more rows has 12 to 20 stitches per inch (4.7 stitches per cm to 8.0 stitches per cm), preferably, the number of stitches is 14 to 18 per inch (5.5 to 7.0 stitches per cm). The threads can be coated with a coating compatible to bond with the seam coating material. The seam thread has a denier in the range of 92 to 202 preferably about 138. Furthermore, it is understood that the weave of the cloth material should be in an equivalent range commonly used in any curtain airbag. Typically, these airbag industry fabrics range from 210 denier all the way up to, but not exclusive to 840 denier. For example, a typical exemplary seam would use a minimum of 25 grams/meter of coating material. The width W of the sealant 90 may be just sufficient to cover the seam thread and needle holes to a much larger width in the range of about 6 to 8 mm. It should be appreciated figure 4 only shows the sealant 90 applied to seam 66; subsequently, the sealant is applied to each of the seams 68 and its subparts 80, 82 and 84 (and 68a, 80a and 84a). As will be seen from the discussion below, subsequent to application of sealant to the seam vacuum is applied drawing the seam sealant through the seam from one panel to the other panel or panels. When the sealant is cured the gas flow through the seam is reduced or eliminated.

[0028] Figure 5 shows a work table 100 for use with the present invention. The table includes a top or material receiving surface 102 upon which the airbag to be processed can be laid and help in place. The airbag is not shown in figure 5. Formed on the top surface 102 is a plurality of grooves or channels such as 166, 168. The relative location of each groove corresponds to the placement of each seam on the airbag 60. Each groove is communicated to a vacuum source 1 10 though passages such as 1 12 and 1 14. The width W1 of the grooves 166, and 168 is sufficiently wide to span the underside of the sewn seam and to permit the sealant to be drawn through the layers of material to the lowest exposed surface of material. In practice the width of the grooves can be in the range of about 6-10 mm. The work table 100 includes a means for securing the airbag 60 to the surface 102 of the table 100. For example, this means may include clamps diagrammatically shown as 104 which grab upon the selvage edges of the bag. Alternately this means may include a plurality of pins 106 which enter into a like number of holes 108, see figure 3a or 3a, also located in the selvage edges of the bag. Other securing means or mechanisms can be used with the present invention. As can be appreciated the sealant 90 can be applied to the bag 60 prior to the bag being secured to the table or alternatively the bag 60 can be secured to the table 100 and then the sealant applied to the bag.

[0029] The sealant 90 can be applied to the bag by any appropriate method. For example the sealant can be applied using a tube such as a caulking tube, or by spaying, or by using a roller or specially formed applicator or other means.

[0030] Figure 5a shows a section of seam 66 covered by the sealant 90 with the airbag 60 placed and secured upon table 100 and seam 68 positioned above groove 166. Upon activation of vacuum source V, sealant 90 is drawn through the layers of fabric, through the needle holes 200.

Figure 5b shows the vacuum applied to the airbag above the groove and sealant causing the airbag to be drawn into the groove. While the section line mentioned above was taken through the peripheral seam 66, had that cross-section been take through any of the seams in figures 3 or 3a they would look substantially the same. Figure 6 shows the sealant drawn through to the lower exposed surface of the sewn-together layers of fabric. The level of vacuum will vary with the size of the needle holes 200, see figure 7, and with the viscosity of the sealant 90, and whether the bag is sealed or unsealed. A good estimate is the vacuum level required is in a range of 2.5 cm (1 inch) to 35 cm (14 inches) of Mercury

[0031 ] Reference is briefly made to figure 7 in which the sealing process is applied to four (4) layers of material. In this figure the sealant 90 is initially applied to the top or first exposed layer of material and is drawn through to the last or opposite or remote exterior surface of material. [0032] Reference is made to figures 5 and 8. As previously mentioned figure 5 is a top view of a work table wherein the solid lines show the layout of a plurality of grooves. Figure 8 is another cross-sectional view through groove 166 and additionally shows an alternate embodiment with a plurality of raised groove walls 166a. In figure 8a airbag 60 is draped over the plurality of raised walls which include 166a. As needed the airbag will be secured to the edges of the work table using appropriate clamps, tie downs, pins etc. If any of the seams discussed above were draped upon the raised walls of figure 8a, the view would look substantially the same.

[0033] Figure 8c shows a template or guide 150 which shows a plurality of cutouts 152 and 154. As shown in figure 8b, cutout 152 is sufficiently wide to be placed over each raised wall 166a and by its weight, or by vacuum force which pulls the template 160 down or by a pushing force which also pushes template 150 down which causes a portion of the airbag material to closely adhere to the exterior of the raised wall 166a. In doing so a seam such as 68, or other seam, is positioned within the space defined by the opposed raised walls 166a. In this manner sealant 90 can be applied to a relatively narrow swath or width of airbag material about the seams such as seam 68. Figure 8d shows a sealant applicator 170 positioned just above seam 68 prior to the introduction of sealant 90 that defined the width of the airbag material between the elevated walls 166a. The other cutout 154 is positioned above sewn seams 66 and 68.

[0034] Reference is briefly made to figure 8e which shows the quantity of sealant 90 applied between the raised walls 166a. In figure 8f the vacuum source V has been activated drawing the sealant 90 from the first or top exposed surface through to the lower or opposite exposed surface of the airbag material. As previously mentioned one of the benefits of utilizing a groove with raised walls 166 as well as the other raised walls is that it enables the application of sealant upon the airbag material located between the respective raised walls. Figure 8g shows an alternate embodiment of the invention in which the raised walls 166a as well as the other raised walls are directed inward. If using this construction, the spacing between the tops of the walls is narrower, thereby enabling the application sealant to a smaller surface area than illustrated.

[0035] Figure 8h shows an alternate applicator 170a relative to the one shown in figure 8d. Here this applicator 170a includes a bottle 180 in which is a quantity of sealant 90. The applicator 170a includes sloped walls 182 and 182 which apply a downward force on the airbag material forces it against the raised walls 166 and creates a pocket 186 for a small quantity of sealant 92 to be applied to the seam 68. Sealant enters the pocket 196 through a small passage 188. The bottle 180 can be pressurized or the sealant can leave the bottle under the force of gravity. Thereafter, vacuum is applied in the manner as mentioned above.

[0036] Many changes and modifications in the above-described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, that scope is intended to be limited only by the scope of the appended claims.