Abstract:
A fabric valve is disclosed that is made of a fabric blank folded in a pattern that promotes the flow of fluid in one direction along an axis of the fabric valve but restricts the flow in the opposite direction along the same axis. The fabric valve is easy to construct and is made by a series of folds. The fabric valve may be particularly suitable for use with inflatable safety devices used in vehicles, such as air bags and air curtains, to restrict backflow of gas from a given air bag when pressure, is applied to the bag. A method of making the fabric valve and a system incorporating the fabric valve are also disclosed.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a fabric valve, and more particularly, to a fabric valve for use in air bags or similar vehicular safety devices. 
     2. Background of the Invention 
     Modern passenger vehicles are manufactured with a number of safety features that are designed to minimize passenger injury in accidents. Such features include, for example, rollover bars, uni-body construction, seat belts, and inflatable devices, such as, for example, air bags and air curtains. Inflatable devices generally remain in an inactive compressed condition until an impact or other physical stimulus activates such devices to inflate to protect passengers during an accident. 
     Thus the term “inflatable devices” will be used throughout this disclosure to describe devices that typically are in an inactive compressed state until a trigger activates them to become inflated. Such devices include, but are not limited to, air bags, air curtains, inflatable tubular structures, and air walls. Inflatable devices generally have an inflatable structure in fluid communication with a source of compressed gas or a gas generator, which, upon activation, releases gas into the inflatable structure. 
     Some conventional air bag systems have multiple bags and gas inflatable compartments, thereby allowing for different and typically layered cushion zones to handle soft and hard passenger impacts. Valves may be used between these different cushion zones to control the amount of gas passable between the zones. These valves may be one-way valves that are simple in design, but may not be fully successful in preventing back flow of gas from a high pressure gas cushion zone to a lower pressure gas cushion zone. Thus, there is a need for a device that acts as a one-way valve to restrict the flow of gas to one direction. 
     SUMMARY OF THE INVENTION 
     The present invention is a fabric valve that is made of a fabric blank folded in a pattern that promotes the flow of fluid in one direction along an axis of the fabric valve, but restricts the flow in the opposite direction along the same axis. The valve is manufactured from, for example, a rectangular sheet of fabric. A series of simple folds are used to create a fabric valve that is then attached onto an inlet tube such that gas is only directed in one direction. The fabric valve prevents backflow of gas back through the valve by creating a wall of fabric that seals the valve when a higher pressure is sensed downstream of a moving lip mechanism on the valve. 
     An exemplary fabric valve implementing the present invention includes a fabric blank having a top edge, a left edge, a bottom edge, and a right edge. A Z-fold is created along the right edge thereby resulting in a Z-folded fabric blank. The Z-folded fabric blank is folded in half along a first traverse fold line that is parallel to the top and bottom edges to result in a bi-folded fabric blank. The bi-folded fabric blank is further folded in half along a second traverse fold line that is parallel to the top and bottom edges and the first traverse fold line to result in a quad-folded fabric blank. The fabric valve further has a first line of stitches parallel to the second traverse fold line. The first line of stitches secures a portion of the Z-fold at the second traverse fold line. The fabric valve also has a second line of stitches parallel to the first line of stitches. The second line of stitches secures another portion of the Z-fold at the first traverse fold line, the top edge, and the bottom edge. Fluid is restricted to flow through the quad-folded fabric blank only in a direction from the left edge to the right edge (and not vice-versa). 
     Another exemplary implementation of the present invention is an easy to follow method for making a fabric valve. First, a fabric blank having a top edge, a right edge, a bottom edge, and a left edge is selected. A Z-fold is created along the right edge to result in a Z-folded blank. The Z-folded blank is folded in half along a first traverse line perpendicular to the Z-fold to result in a half-size Z-folded blank. The half-size Z-folded blank is folded in half along a second traverse line perpendicular to the Z-fold to result in a quarter-size Z-folded blank. The quarter-size Z folded blank is secured along the second traverse line from the right edge across a width of the Z-fold. The quarter-size Z folded blank is secured along the first traverse line from the right edge to the left edge. 
     Yet another exemplary implementation of the present invention is an inflatable vehicular safety system that contains a fabric valve that promotes gas flow in one direction but restricts gas flow in the opposite direction. The system includes a first chamber that is adapted to receive gas from a gas generator. The system also includes a fabric valve having a body member and a Z-fold member. The body member includes four layers of a fabric blank and is adapted to receive a portion of the gas from the first chamber and to discharge the portion of gas out of the Z-fold member. The Z-fold member includes  12  layers of the fabric blank. The system also includes a second chamber upon which the fabric valve is attached, wherein the second chamber receives the portion of gas from the first chamber through the fabric valve. When the first chamber experiences a decrease in pressure, the Z-fold member prevents the portion of gas in the second chamber from returning to the first chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram showing an isometric view of an exemplary embodiment of the present invention. 
     FIGS. 2A through 2E are explanatory views for explaining how the fabric valve shown in FIG. 1 may be made. 
     FIGS.  2 AA through  2 DD are side cut views of the fabric valve in FIGS. 2A through 2D, respectively. 
     FIG. 3 is a schematic diagram showing how the fabric valve shown in FIG. 1 may be attached in an inflatable tubular structure. 
     FIG. 4 is an expanded view of area  400  indicated in FIG.  3 . 
     FIG. 5 is a schematic diagram of the fabric valve between two gas chambers in an inflatable vehicular safety system. 
     FIG. 6 is another exemplary embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     An exemplary embodiment of the present invention is a fabric valve for use in conjunction with an air bag or similar vehicular safety device. A typical vehicular safety device for use with the present invention is the Inflatable Tubular Structure (“ITS”) manufactured by Simula, Inc. of Phoenix, Ariz. ITS is fully disclosed in U.S. Pat. Nos. 5,322,322 and 5,480,181 (both issued to Bark et al.), each of which is hereby incorporated herein by reference in its entirety. 
     The present invention may be adapted for use with other vehicular safety devices having two or more air chambers. For example, it may be used in any multi-chambered inflatable device wherein gas passes through the chambers and exists at different pressures in different chambers. A fabric valve according to the present invention would be suitable to restrict backflow between the chambers. 
     An exemplary embodiment of the present invention is a fabric valve that is designed for use in an air bag system in which a single gas generator fills an ITS through an inlet fill tube and also fills a separate curtain-style (i.e., curtain type) air bag. Gas fills the ITS by entering a bladder of the ITS through the fill tube and fabric valve, but is restricted by the fabric valve from flowing back out of the bladder. Typically, an air bag only remains inflated for less than one second, whereas an ITS preferably remains inflated for a longer period. In this system, the curtain-style air bag may leak at a higher rate than the ITS, causing gas to flow out of the ITS and back into the curtain bag. Therefore, a valve that prevents backflow, such as the fabric valve described herein, may be required to increase the inflated time of the ITS in this air bag system. 
     FIG. 1 is a schematic diagram showing an isometric view of an exemplary embodiment of the present invention. Fabric valve  100  is folded in a unique configuration that is most advantageous to an airbag for which the fabric valve is designed. Fabric valve  100  includes one or more substantially planar sheets  110  of a fabric. Fabric valve  100  may comprise multiple layers  121 , which may be multiple separate sheets  110  attached together or a single sheet  110  folded into multiple layers. The exemplary embodiment shown in FIG. 1 is a single sheet folded into multiple layers, but multiple separate sheets attached together by suitable adhering means, such as, for example, thread, adhesive, clips, or the like, also may be used. In the exemplary embodiment shown in FIG. 1, the single sheet  110  is folded to form at least two free ends  120  and a folded end  122 . The fabric valve  100  has an inlet end  125  and an outlet end  126 , a top side  140  and a bottom side  145 . At the outlet end  126 , there may be a multiple fold region having multiple folds  130 . The multiple layers of the fabric valve  100  may be adhered together through adhering means, such as, for example, thread, adhesive, clips, or the like. In the exemplary embodiment shown, a top stitch  150  secures the top side of the fabric valve  100  and bottom stitch  160  secures the bottom side of the fabric valve. Other stitches also may be used. The stitches provide structural stability to the fabric valve by preventing disintegration of the valve at high pressures, and also serve to keep the valve closed when higher pressures are present downstream of the valve, described in more detail below. 
     The fabric valve  100  is a piece of fabric folded and attached to the end of the ITS fill tube. The fold pattern and stitching on the fabric valve  100  are dependent upon one or more factors. The factors are, for example, the nature of the fabric used, desired strength of valve, and anticipated fluid pressures and temperatures that would be encountered during deployment. For example, higher density stitching would be more desirable for higher strength fabrics. Such a fabric may be constructed of, but is not limited to, the same types of fabrics used in construction of an air bag or air curtain. Thus, a silicone-coated nylon fabric could be used. Heavier fabrics that may be used include a double side silicone-coated nylon. For the heavier fabrics, the stitching is usually denser to preserve the integrity of the fabric valve. The valve material and configuration are dependent upon the gas generator used in the air bag system. The temperature and pressure of the gas determines the fabric weight, coating weight, thread material, and sewing configuration. Multiple fabrics, thread materials, and stitch densities may be used to construct a valve according to each application. 
     Materials that may be needed to construct an exemplary embodiment of the fabric valve  100  include, but are not limited to, fabric, fabric coating, and thread. The fabric may be, for example, nylon, from about 420 denier to about 840 denier. The fabric coating may be applied on a single side or on both sides of the fabric. Such fabric coatings may be, for example, silicone, neoprene, or other such coatings. The thread used to stitch the fabric may be, for example, nylon, polyester, para-aramid (KEVLAR), or other such threads. 
     The seams in the fabric valve  100  may have varying stitch densities. For example, stitch densities of about six stitches per inch to about 20 stitches per inch may be used. One or more needles may be used to sew the seams. For example, a double needle may be used to create two parallel seams. A silicone sealant may be used to seal the threads at the stitch points. Alternatively, an adhesive may be used to promote the seal of the stitches or to adhere the layers of fabric together. 
     The fold geometry may vary from the exemplary embodiment shown in FIG. 1 without departing from the scope and spirit of the present invention. For example, alternative fold geometries may have: different lengths of segments; differing numbers of layers; different location and numbers of transverse folds; different number of folds in series; different lengths of materials on different sides of the folds; and different widths of the folds; or the like, without departing from the scope and spirit of the present invention. 
     The variables described above are tuning parameters, which can be utilized to modify the valve design based upon a desired need. For example, a higher temperature and pressure gas may require a higher denier fabric with heavier coating and a double needle seam with sealant. Based on the operating pressure, the fold geometry (length, number of folds, etc.) may be changed. 
     FIGS. 2A through 2D, and  2 AA through  2 DD, are explanatory views for showing how a fabric valve  200  shown in FIG. 2E may be made. Fabric valve  200  comprises a fabric blank  210 , which may be of a suitable size and material to communicate with a corresponding ITS (not shown). Preferably, the fabric blank  210  has a rectangular shape with a top edge  202 , a bottom edge  204 , a left edge  208 , and a right edge  206 . For example, each of the left  208  and right  206  edges is about 260 mm long, and each of the top  202  and bottom  204  edges is about 140 mm wide. Depending on the number of folds, length of folds, and seam geometry, these dimensions may range from about 60 mm to about 600 mm in width, and from about 200 mm to about 500 mm in length. 
     A Z-fold  218  is created along the right edge  206  (see FIGS.  2 B and  2 BB). For example, the Z-fold  218  is located approximately 15 mm from the right edge  206 . This results in a Z-folded fabric blank  230  having a width of about 90 mm, which is about 50 mm narrower than the unfolded fabric blank  210 . The “missing” 50 mm is overlapping within the Z-fold  218 . In other words, a first Z-fold line  212  is located about 75 mm from the left edge  208  to facilitate the fabric blank  210  to be folded downwards along the first Z-fold line  212 . A second Z-fold line  214  is located about 25 mm to the left of the first Z-fold line  212  to facilitate the fabric blank  210  to be folded downward along the second Z-fold line  214 . The remaining 15 mm of the fabric blank closest to the right edge  206  is exposed to the right of the first Z-fold line  212 . As shown in FIGS.  2 B and  2 BB, first Z-fold line  212  is above line  216 . 
     The Z-fold  218  may range in width from about 15 mm to about 75 mm, although the exemplary embodiment is shown having a width of 25 mm. The exposed material to the right of the Z-fold  218  in the figures may range from about 10 mm to about 50 mm in width. 
     Next, the Z-folded fabric blank  230  is folded in half along a first traverse fold line  220  (shown in FIGS.  2 B and  2 BB), that is parallel to the top  202  and bottom  204  edges. The first traverse fold line  220  bisects the Z-folded fabric blank  230  to create an upper half portion  232  and a lower half portion  234 . The upper half portion  232  is folded so that it is located below the bottom half portion  234 , resulting in a bi-folded fabric blank  250  shown in FIGS.  2 C and  2 CC. 
     The bi-folded fabric blank  250  is further folded in half to create a quad-folded blank  270  along a second traverse fold line  222 , as shown in FIGS.  2 C and  2 CC, that is parallel to the top  202  and bottom  204  edges and the first traverse fold line  220 . The second traverse fold line  222  bisects the bi-folded fabric blank  250  to create an upper quarter portion  252  and a lower quarter portion  254 . The upper quarter portion  252  is folded so that it is located below the bottom quarter portion  254 , resulting in a quad-folded fabric blank  270  shown in FIGS.  2 D and  2 DD. 
     Finally, the quad-folded fabric blank  270  may be sewn into place using one or more stitch lines, such as, for example, a first stitch line  242  and a second stitch line  244  to create and secure the fabric valve  200 . The stitch lines  242  and  244  may be of any suitable stitch design, such as, for example, a lock stitch. A single needle, such as, for example, a 140/22 needle, may be used to create the lock stitch. The start and end of the lock stitch may be about two mm from the top and bottom edges of the quad-folded fabric blank  270 . The stitch density may be, for example, about 10 to 12 threads per 25 mm, and may use, for example, IAW FED STD 751A TYPE 301. The stitch lines  242  and  244  may be of suitable geometry to handle internal pressure of the valve. For example, FIG. 6 shows a different stitch line configuration. 
     The fabric valve  200  may be attached in position with respect to an ITS  310 , as shown in FIG.  3 . For example, fabric valve  200  may be attached to the ITS  310  by sewing. The ITS  310  may have a bladder having a stretchable portion  330  that expands as gas enters the ITS  310  through an inlet tube  320  and the fabric valve  200  in direction  350 . Once the gas has entered into the ITS  310  as shown by arrow  350 , the gas is prevented from exiting back out of the inlet tube  320  by the fabric valve  200  which prevents gas backflow. 
     The stitch lines  242  and  244  are attached, for example by sewing, onto the ITS  310 . The inlet tube  320  is inserted within the body member  420  in a hole created by the fabric valve  200 . The inlet tube  320  is inserted into the fabric valve  200  to a depth that would not interfere with the Z-fold member  410 . Specifically, the Z-fold member  410 &#39;s moving lip mechanism (see FIG. 4) is not interfered with by the inlet tube  320 . 
     Referring to FIG. 4, the first stitch line  242  may be from about two mm to about 15 mm, for example, approximately five mm, from the fold line  222 . The length of the first stitch line  242  depends upon the length of the Z-fold  218 , and should extend past line  214 . For example, the first stitch line  242  could be about 50 mm long and slope upward and end at fold line  222 . The first stitch line  242  could range in length from about 25 mm to about 125 mm. 
     The position of the second stitch line  244  depends upon seam geometry, but should be from about ten mm to about 20 mm, for example, about 12 mm, from the bottom edge  204  within the Z-fold member  410 . The length of the second stitch line  244  depends upon seam geometry and the length of the member  410  and/or  420 . The second stitch line  244  may, for example, extend approximately 75 mm along the bottom edge  204  from the right edge  206 , before sloping upward and crossing lines  326  and  324  and communicating with inlet tube  320 . Within the body member  420 , the location of the second stitch line  244  depends upon valve and seam geometry. For example, the second stitch line  244  may be about 24 mm from the bottom edge, although it could range between about ten mm and about 75 mm. 
     Although the description of FIGS. 2-4 were made with specific dimensions, such dimensions are only exemplary, and are not intended to be limiting. Thus, one having ordinary skill in the art would change the dimensions accordingly to fit a particular geometry of ITS or inlet tube. 
     The fabric valve  200  may be attached onto the inlet tube  320  in one of several ways. For example, as shown in FIG. 4, fabric valve  200  may be secured with the inlet tube  320  through various stitches  324  and  326  that prevent relative movement of the fabric valve  200  with respect to the inlet tube  320 . As shown in FIG. 4, the front edge  322  of the inlet tube  320  stops short of the Z-fold line  214 , thereby eliminating any interference between the inlet tube  320  and the moving lip mechanism of the fabric valve  200 . Clamps, rivets, and other fasteners may be used to secure the fabric valve  200  onto the inlet tube  320 . 
     An exemplary method for making the exemplary embodiment of the present invention described above comprises the following steps. The valve begins as a flat blank of material of appropriate size for the application. A single Z-fold is made and temporarily clipped at one end of the fabric blank. The blank is then folded in half perpendicular to the original Z-fold, and then folded in half again to result in a blank one-quarter the size of the original Z-folded blank. Finally, the valve is sewn closed in a configuration according to its particular application. 
     The valve works by creating a resistance to the backflow of the gas. This resistance is created by a moving lip seal mechanism, which allows unidirectional flow by pinching closed when pressure is applied on the downstream side of the valve. The folding and sewing of the valve material results in a more rigid section in the valve (a lip) which opens with pressure from the upstream side, but closes when downstream pressure exceeds the upstream pressure. 
     As shown in FIG. 5, an inflatable vehicular safety system  500  includes a source of gas  510 , which typically is compressed gas or a gas generator. Upon sensing an impact, a signal triggers the release of gas from the gas source  510  through a gas conduit  520  to a chamber  530 , which may be an inflatable safety device, such as, for example, a curtain style air bag or the like. Another chamber  560  may be in communication with chamber  530 . The second chamber  560  may be, for example, an ITS or another inflatable structure. Gas may enter the second chamber  560  through a fill tube  540 . Attached to the fill tube  540  may be a fabric valve  550 , as described above. During operation, compressed gas may be released from the gas source  510 , thereby flowing to and inflating both chambers  530  and  560 . Gas in chamber  530  may leak out in the direction of arrow  571  to the ambient environment through gas escape point  570 . Thus, gas in chamber  530  remains at a higher than ambient pressure for a relatively short amount of time. For example, a conventional air bag remains inflated for about a second before deflating. However, gas that enters chamber  560  through fill tube  540  is prevented from escaping by fabric valve  550 , as described above. 
     Although the above system and fabric valve have been described with respect to a vehicular safety system, the present invention is not limited to only vehicles, and may be used wherever such an inflatable system may be used. Furthermore, such a fabric valve and system may be used to prevent the back flow of gas in an undesired path. 
     Furthermore, the above valve geometry shown in FIGS. 1-4 is only exemplary and is not intended to be limiting of the present disclosure. For example, the valve shown in FIG. 6 is another exemplary embodiment of the valve and is shown with a slope  610  on one side of the valve body. Other geometries for the valve that substantially perform the same functions of the valve described above also are within the scope of this invention. 
     In describing representative embodiments of the invention, the specification may have presented the method and/or process of the invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the invention. 
     The foregoing disclosure of the embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be obvious to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents.