Patent Publication Number: US-2016229371-A1

Title: Vacuum enhanced method and apparatus for sealing one or more sewn seams

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     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. 
     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 
         FIG. 1  shows a typical curtain airbag having a plurality of sewn seams. 
         FIG. 1 a    shows an inflatable mattress with a plurality of sewn seams. 
         FIG. 2  shows typical leak paths relevant to an airbag having a sewn seam. 
         FIG. 3  shows an exemplary, simplified airbag, useful in explaining the benefits of the present invention. 
         FIG. 3 a    shows an exemplary air bag with a center path terminating at end coil, loop, or oval sections. 
         FIG. 4  shows sealant applied to one of the seams of the airbag of  FIG. 3 . 
         FIG. 5  shows a work table useable with the present invention. 
         FIG. 5 a    is a cross-sectional view taken through section  5   a - 5   a  of  FIG. 5 . 
         FIG. 5 b    shows vacuum applied to sealant. 
         FIG. 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. 
         FIG. 7  shows the present invention applied to more than two layers of material. 
         FIG. 8  shows an alternate construction of a work table and in particular the construction of grooves with raised sides. 
         FIG. 8 a    shows the airbag draped about a section of groove with raised sides. 
         FIG. 8 b    shows the template atop the airbag with the raised walls of the groove extending into a cutaway portion of the template. 
         FIG. 8 c    shows a template or guide with portions cut away designed to be placed atop the airbag which has been placed upon the work table.  FIG. 8 d    adds to  FIG. 8 c    a solvent applicator which is pictured about to add solvent to the airbag. 
         FIG. 8 e    shows a quantity of sealant being application to fabric. 
         FIG. 8 f    shows a piece of fabric under vacuum pressure. 
         FIG. 8 g    shows an alternate embodiment of side walls of a groove. 
         FIG. 8 h    shows an alternate sealant applicator. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 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  12   a  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  22   a  is a peripheral seam, another seam  22   b  shows a center path  22   c  terminating at end coil, loop, or oval sections  22   d.    
       FIG. 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  40   a  and  40   b . 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  40   c  and  40   d . 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  40   e . Airbags such as the one illustrated in  FIG. 1  may also include a peripheral sewn seam  22   a  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. 
     Reference is briefly made to  FIG. 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.  FIG. 1 a    is provided to illustrate the present invention can be used on different types of inflatable devices. 
     Reference is now made to  FIGS. 3 and 3   a  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  ( 68   a  in  FIG. 3 a   ) 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  FIG. 3 a    the interior seam  68   a  includes a center path  84   a  terminating at end coil, loop, or oval sections  80   a.    
       FIG. 4  illustrates airbag  60 . In addition,  FIG. 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  FIG. 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  68   a ,  80   a  and  84   a ). 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. 
       FIG. 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  FIG. 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  110  though passages such as  112  and  114 . The width W 1  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  FIG. 3 a    or  3   a , 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. 
     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. 
       FIG. 5 a    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 .  FIG. 5 b    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  FIG. 3 or 3   a  they would look substantially the same.  FIG. 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  FIG. 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. 
     Reference is briefly made to  FIG. 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. 
     Reference is made to  FIGS. 5 and 8 . As previously mentioned  FIG. 5  is a top view of a work table wherein the solid lines show the layout of a plurality of grooves.  FIG. 8  is another cross-sectional view through groove  166  and additionally shows an alternate embodiment with a plurality of raised groove walls  166   a . In  FIG. 8 a    airbag  60  is draped over the plurality of raised walls which include  166   a . 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  FIG. 8 a   , the view would look substantially the same. 
       FIG. 8 c    shows a template or guide  150  which shows a plurality of cutouts  152  and  154 . As shown in  FIG. 8 b   , cutout  152  is sufficiently wide to be placed over each raised wall  166   a  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  166   a . In doing so a seam such as  68 , or other seam, is positioned within the space defined by the opposed raised walls  166   a . 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 .  FIG. 8 d    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  166   a . The other cutout  154  is positioned above sewn seams  66  and  68 . 
     Reference is briefly made to  FIG. 8 e    which shows the quantity of sealant  90  applied between the raised walls  166   a . In  FIG. 8 f    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.  FIG. 8 g    shows an alternate embodiment of the invention in which the raised walls  166   a  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. 
       FIG. 8 h    shows an alternate applicator  170   a  relative to the one shown in  FIG. 8 d   . Here this applicator  170   a  includes a bottle  180  in which is a quantity of sealant  90 . The applicator  170   a  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. 
     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.