Abstract:
A method of forming an airbag cushion ( 10, 10 A) has the steps of providing placing the cushion in a vacuum bag ( 20 ) and evacuating the air shrinking the airbag cushion ( 10, 10 A) to a compacted size; conforming the airbag cushion to a predetermined shape; placing the airbag cushion ( 10, 10 A) in a high temperature environment between +50° C. to +140° for a predetermined time to thermally set the fabric material ( 120 ) to maintain the compacted airbag cushion ( 10, 10 A) to the predetermined shape; and releasing the vacuum and removing the thermally set airbag cushion ( 10, 10 A) from the vacuum bag ( 20

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to airbag cushions generally and more specifically a method for manufacturing the airbag into small mini packs. 
       BACKGROUND OF THE INVENTION 
       [0002]    Vehicle compartments are stored with plenty of features and technologies; therefore the space for each individual component is more and more limited. Airbag modules have to become smaller for each new generation of vehicles. One major issue is the volume of the folded cushion pack defines the size of the housing and cover. To receive a small package the cushion has to be packed under high load into a small housing or plastic shell and consequently the cushion pack is applying high reaction loads to its surrounding environment. Soft Pack modules, as they are called, for curtain and seat backs for instance don&#39;t have separate covers that could support this tight packaging. 
         [0003]    In seat mounted airbags, the folded airbag can create unsightly bulges. In curtain airbags mounted in roof rails, the cushion material needs to be hand stuffed into a long narrow channel. Accordingly, the size of the folded material is critical. 
         [0004]    It is an object of the present invention to provide a fully functional airbag pack that occupies less space without sacrificing the inflation volume of the airbag or weakening the strength and overall physical characteristics of the cushion material. These and other advantages are achieved by the invention as described hereinafter. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention relates to a method of forming a mini pack airbag cushion having the steps of providing an airbag cushion made of fabric material; placing the cushion in a vacuum bag and evacuating the air shrinking the airbag cushion to a compacted size; conforming the airbag cushion to a predetermined shape; placing the airbag cushion in a high temperature environment between +50° C. to +140° C. for a predetermined time to thermally set the fabric material to maintain the compacted airbag cushion to the predetermined shape; and releasing the vacuum and removing the thermally set airbag cushion from the vacuum bag, the cushion maintaining the predetermined shape being formed as a mini pack airbag cushion. The predetermined time to thermally set the material is preferably in the range of 20 seconds to 2 hours. Preferably the relaxed folded mini pack airbag cushion retains a size reduction in thickness in the range of 20% to 40% compared to the same cushion folded but not processed using this method. 
         [0006]    The method further can have the steps of providing a shape forming contoured mandrel surface upon which the airbag cushion is positioned, so it can follow the contour during the steps of pulling a vacuum; applying a compression load or force on the evacuated airbag cushion during the step of thermally setting the fabric material and removing the compression force prior to removing the airbag cushion from the vacuum bag; or folding the airbag cushion prior to placing in the vacuum bag. 
         [0007]    The method may further have the steps of inserting an inflator simulator in the cushion to mimic the shape of an inflator; assembling the airbag cushion about a curtain airbag manifold pipe prior to the step of evacuation; or placing the formed mini pack airbag cushion in the airbag module housing. The airbag module can be of a reduced size to form a micro module. The method may further have the step of attaching an inflator after finishing the process. A mini pack airbag cushion can be made by the method. The mini pack airbag cushion can include micro module housing or a module for storing the mini pack airbag cushion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The invention will be described by way of example and with reference to the accompanying drawings in which: 
           [0009]      FIG. 1  is a side view of an exemplary embodiment airbag cushion showing a thickness t 1 . 
           [0010]      FIG. 2  is the airbag cushion of  FIG. 1  placed in a vacuum bag and compressed to a thickness t 2 . 
           [0011]      FIG. 3  is the relaxed cushion after being processed using the inventive method of the present invention showing a relaxed thickness t 3 . 
           [0012]      FIG. 4  is a top view of the airbag cushion treated according to the present inventive method as shown in  FIG. 3 . 
           [0013]      FIG. 5  is a view of an exemplary vacuum forming machine having a mandrel with a contoured predetermined shaped surface. 
           [0014]      FIG. 5A  illustrates how a vacuum membrane using vacuum can be made to envelope a product such as a pair of shoes  404 . 
           [0015]      FIG. 6  shows the folded airbag cushion being placed over the mandrel of the vacuum machine and treated by a vacuum membrane. 
           [0016]      FIG. 7  is a view of an exemplary curtain airbag; the top view showing the airbag cushion prior to being treated by the present invention; the lower view showing the same airbag cushion after being treated using the present invention showing a reduction in the overall thickness of the airbag along its longitudinal length. 
           [0017]      FIG. 8  is a diagrammatic flow chart showing the steps used in the present invention. 
           [0018]      FIG. 9  is an exemplary view of a plurality of cushion airbags placed in vacuum bags and placed into an elevated heating chamber to produce a thermal set according to the method of the present invention. 
           [0019]      FIG. 10  is an exemplary vacuum chamber apparatus to which the airbag when placed in a vacuum bag can be placed in to evacuate the airbag cushion and vacuum bag. 
           [0020]      FIG. 11  is the airbag module showing a typical airbag cushion extending above the surface of the module structure. 
           [0021]      FIG. 11A  is an isometric view of the housing of  FIG. 11 . 
           [0022]      FIG. 12  is an exemplary airbag module shown in a view placed inside a vacuum bag prior to treatment according to the present invention. 
           [0023]      FIG. 13  is a side view wherein the airbag module is shown in a min pack cushion made according to the present invention hidden by the walls of the chamber and is lying below the surface of the walls as opposed to that in  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    With reference to  FIGS. 1-4 , an exemplary airbag cushion  10  is illustrated and the process of the present invention explained. The airbag cushion  10  is folded and as illustrated has a thickness t 1  of approximately 38 mm. This initial cushion thickness is shown at approximately the mid location of the airbag cushion  10 . With reference to  FIG. 2 , a clear generally plastic vacuum bag  20  has been placed around the folded airbag cushion  10  of  FIG. 1  and a vacuum has been pulled or applied and the airbag has been compressed such that it has a compressed cushion thickness t 2  of 16 mm. This compressed thickness t 2  is substantially thinner by a large margin when compared to the initial cushion thickness t 1  of 38 mm. To achieve this thickness, the airbag cushion  10  preferably is placed on a vacuum table  100 , held in position and a vacuum is applied as illustrated in  FIGS. 1 and 2  as well as in  FIGS. 5 and 6 . This vacuum is preferably well below 1 atmosphere and preferably in a range of 1 millibar to 50 millibar. Once positioned, a high temperature of up to 200 degrees C. can be applied for a short time to conform or set the fabric to the mandrel  102 . The airbag shown in  FIG. 1  has already been folded. The airbag  10 , as mentioned, can then be placed in a vacuum bag  20  and a vacuum can be pulled to reduce the thickness of the airbag  10  down to 16 mm. This is preferably achieved by applying not only vacuum, but a pressure on the airbag  10  squeezing it down tightly using flat plates or presses  15  into this very flat and constrained condition. This pressure is also enhanced by atmospheric pressure. Once the airbag  10  is in this condition it can then be placed in a rack  21  with a plurality of other airbags  10  similarly compressed in vacuum bags  20  and placed in an elevated heating chamber  200  as illustrated in  FIG. 9 . In  FIG. 9  the rack  21  is shown partially inside of the chamber  200  with the chamber door  202  open. 
         [0025]    Preferably the heating chamber  200  is set at a temperature of 50 to 140 degrees C. The airbag  10  is then left in the heating chamber for a predetermined amount of time. Depending on the temperature, this time can be as short as 20 seconds or preferably extends to about 2 hours. In a preferred embodiment, the airbag  10  of  FIG. 1  was held in a chamber at an elevated temperature for approximately 1.5 hours at a temperature of approximately 85 degrees C. At this temperature, the airbag  10  when removed is allowed to cool and then is pulled out of the vacuum bag  20 . The vacuum bag  20  can be reusable or it can be disposable. In any event, the airbag cushion  10 , when allowed to cool and pulled from the vacuum bag  20  will retain its shape at a level as illustrated in  FIG. 3  wherein the relaxed cushion thickness t 3 , after being thermally set and evacuated in the vacuum bag  20 , will have a thickness t 3  of approximately 22 mm. 
         [0026]    A top view of the flattened and compressed airbag  10  is illustrated in  FIG. 4 . The top is basically unaltered, but the thickness of the airbag cushion  10  is drastically reduced. The airbag cushion  10  once processed through this methodology is able to retain this relaxed cushion thickness t 3  for over 3 months, most likely indefinitely, without any additional physical constraints binding the processed airbag  10 . A reduced size airbag  10  in its pre-inflated state is very valuable. The inventors call this reduced size folded airbag cushion a “mini pack”. The present invention allows the use of relatively large airbag cushions to be compressed or compacted to occupy smaller spaces without sacrificing any protective cushioning of occupants often afforded by inflated larger sized airbag cushions. The mini pack airbag cushion  10  takes on a size that is at least 20 to 40 percent or more, smaller than a normally folded airbag cushion. Being able to provide an airbag cushion of a compacted size is particularly important when the airbag cushion  10  is used in the side or back of a seat in that there is often not sufficient room for a large size airbag cushion, not employing the present invention to be compressed in the seat back. Furthermore, when the prior art airbag cushions are typically placed in this condition, if they are not properly constrained such as by using the present invention to a small size, bulges occur on the seat back that are unsightly and unacceptable. With the mini pack airbag cushions  10 , these side airbag cushions  10  can easily be contained within the seat upholstery so that more seat padding can be provided around the seat cushion for a more comfortable seat and yet still providing side airbag protection. With reference to  FIGS. 5 and 6  the vacuum table  100  can employ a fixture, die or mandrel  102  having a contoured or profiled surface  102   a  such that the airbag  10  when draped over the surface  102   a  of the mandrel  102  can be drawn down tightly over the mandrel  102  once a vacuum membrane if placed over the airbag or material. Once positioned, a high temperature of up to 200 degrees C. can be applied for a short time to conform or set the fabric to the mandrel  102 . When this is accomplished a preset in the cushion can be achieved and a thermal set can be formed into the cushion material directly such that the fabric takes on the contour of the underlying forming fixture, die or mandrel  102 .  FIG. 5A  illustrates how a vacuum membrane  400  of a vacuum machine  402  using vacuum can be made to envelope a product such as a pair of shoes  404  or in the context of the present invention a folded airbag. 
         [0027]    With reference to  FIG. 7 , an exemplary curtain airbag cushion alternative embodiment  10 A is shown. As shown in the upper configuration, the airbag  10 A is shown as a longitudinally extending curtain airbag that has been rolled or wrapped in such a fashion that it has a thickness t 4  in the normal relaxed and unconstrained condition and yet after being treated using the method of the present invention, the curtain airbag  10 A as illustrated in the lower configuration has been compacted dramatically to a thickness t 5  that is substantially smaller than the typical untreated curtain airbag. This is a huge advantage in that a curtain airbag  10 A using the present invention can easily be mounted into a roof rail structure occupying substantially less space than is typically required. 
         [0028]    An important aspect of the invention is that airbag cushions  10 A of the present invention often require inflators  40  to be inserted into a pocket  14  within the airbag cushion  10 A shown in  FIG. 7 . These inflators  40  generally are filled with a propellant and are therefore not suitable to be processed at high elevated temperatures over a period of time, therefore, active propellant filled inflators are not placed with the airbag into the chamber  200  as a safety precaution. To avoid this and still be able to configure the mini pack airbag  10  properly, dummy inflators or simulators of the same size and shape of the inflator  40  are used. The dummy inflators act to permit the airbag cushion to achieve a proper shape or profile. The dummy inflators are replaced by the real inflators  40 . 
         [0029]    Reference is made to  FIG. 8 , a diagrammatic process chart showing the process flow of an exemplary airbag  10 . Prior to step one the airbag is folded and the inflator replaced with a dummy inflator. Also any brackets and wiring harnesses are removed. Then in step two, a vacuum operation is conducted on the bagged cushion. One or more plates can be used to provide an additive compressive pressure or specific package shape and the bag as the vacuum is applied. This vacuum has a negative pressure 7 mbar and is held for example at that for approximately 40 seconds. At step three, the airbag  10  is then stored at a hot temperature within a heating chamber, currently a preferred temperature is approximately 85 degrees C. and a time of approximately 1.5 hours. In step four, the cushion pack is unpacked and removed from the vacuum bag  20 . Preferably, the unpacking can occur when the airbag  10  has cooled. At process step five, the dummy inflator is removed and replaced with a live inflator  40  fixing it in the cushion airbag  10  along with the remaining components of the airbag module which could include a bracket and wiring harness (not illustrated). This last step completes the assembly of the mini pack airbag cushion  10 , which can then be installed in a seat back or curtain rail or other suitable location with no other packaging required. 
         [0030]    As mentioned and with reference to  FIG. 9 , the airbags  10  with vacuum bags  20  have been placed onto a rack  21  and then placed inside the elevated heating chamber  200  as illustrated. Prior to being packaged for thermal setting the cushion fabric material has been processed on a vacuum machine  300  as illustrated in  FIG. 10 . To speed the process a double chamber vacuum machine  300  can be used. The vacuum machine  300  provides the ability to place the folded airbag  10  into a vacuum bag  20 , sealed and then a vacuum pulled so the air inside the vacuum bag  20  is completely withdrawn as best as possible to completely pull the airbag  10  into its thinnest possible configuration. In addition to the vacuum, pressure can be applied to the airbag  10  to assist in compressing the airbag  10  to its thinnest possible thickness. As shown in  FIG. 2 , the illustrated airbag  10  achieves a compressed thickness t 2  of approximately 16 mm in the first exemplary embodiment. 
         [0031]    With reference to  FIGS. 11-13 , as an alternative, the entire process can also be conducted using an airbag  10  situated in an airbag module housing  30 . A typical airbag cushion not made with the size reducing method, when normally stowed, projects above the open end or mouth of the airbag module housing  30  as illustrated in  FIG. 11 . When both this airbag  10  and module assembly  30  are pre-assembled and placed in a vacuum bag  20  as illustrated, a vacuum can be pulled sucking the airbag  10  down substantially into a smaller shape and one defined by the housing  30 . When this occurs, the side view of the assembled module after treatment using the above process completely hides the airbag cushion  10  inside the housing  30  such that it does not bulge out of the module housing  30  in any fashion, as illustrated in  FIG. 13 . 
         [0032]    The present method of heat setting the cushion fabric material relaxes any tensioning that the fabric would normally have trying to unfurl or open itself from its folded condition. As shown, airbags with different fabric materials can be treated typically the airbag  10  is a woven fabric of a polyethylene construction or similar polymer or nylon; however, these airbags can also be coated or uncoated. When coated, typically a silicon coating or other material is applied that adds to the memory of the airbag when simply folded. These materials and coatings make the airbag want to occupy more space than is desirable. However, using the present method, compressions in the average of 22 to 27 percent are achieved and once achieved a minor relaxation can occur over time at approximately only 2 to 3 percent overall yielding a substantially thinner airbag cushion  10  compared to untreated airbags. Prior art cushions, when compressed using only vacuum, over time expand back to almost the original size showing a relaxation of about 100 percent. These mini pack airbag cushions  10  are able to maintain this compressed or reduced size configuration indefinitely without any additional external constraints. No external packaging or tie downs are needed to keep the airbag  10  in this reduced size shape due to the fact that the fabric material  12  has been set thermally with the high temperature exposure. A variety of tests were conducted. In a test, a force of 8000 Newtons was applied to the airbag over a time of 1.5 hours at a low temperature of 50 degrees C. Under this condition, the maximum compression was 27 percent and the maximum relaxation was 5 percent. In a second test, a force of 8000 Newtons was applied over a time of 1.5 hours and a temperature of 85 degrees C. A 23 percent maximum compression was achieved and a 4 percent relaxation. In a third test of 8000 Newtons for 1.5 hours at 105 degrees C., a 27 percent maximum compression was achieved with a maximum relaxation of only 3 percent. Interestingly, in a fourth series of tests a force of 3000 Newtons over 1.5 hours at 85 degrees C. achieved a 23 percent compression and a maximum relaxation of 4 percent. Testing, of cushion airbag materials using vacuum only or pressure only resulted in similar compressive capabilities, however the fabric material  12  over time simply relaxes back to the original shape or very close to it. In the present invention, by thermally setting the fabric material  12  into the compressed shape, the airbag cushion  10  has no tendency to relax back to the original shape; the airbag cushion has a permanent memory set at this reduced compressed thickness. The method has been successfully demonstrated for use with coated or uncoated fabric materials  12  and can be used on polyester, nylon and any other suitable airbag cushion material regardless of the denier and weave density of the fabric. This is a great advantage in the mini pack airbag cushion  10  of the present invention. 
         [0033]    Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.