Abstract:
A seat restraint system whose torso belt inflates upon impact to protect the occupants of a vehicle such as an automobile. The inflating component of the present invention is a braided tube linked to a gas generator and crash sensor. When an impact is detected, the gas generator is ignited, inflating the braided tube. As the braided tube inflates, the diameter of the tube increases significantly and its length decreases significantly, due to the orientation of the fibers comprising the braided tube. The contracting tube pretensions the seat belt system by pulling any slack out of the seat belt systems. The inflated structure restricts the forward motion of an occupant and distributes crash loads over a larger occupant surface area to reduce both primary and secondary injuries. In a side impact the inflated structure restricts occupant motion, distributes crash loads and provides head protection.

Description:
This application claims priority from U.S. provisional patent Application Ser. No. 60/021,052, filed Jul. 2, 1996. 
     BACKGROUND 
     Field of the Invention 
     This invention relates to a system for restraining the body of an occupant in a vehicle to reduce the extent and severity of injuries during a crash. More specifically, the invention relates to a seat belt restraint system which incorporates an inflatable tubular section in the torso section of the belt. The inflatable tubular section is made of a woven or braided tube of continuous high-strength fibers. The restraint system reduces the extent and severity of both primary and secondary injuries to vehicle occupants. 
     Background of the Invention 
     Conventional seat belts are designed to protect the occupants of vehicles such as automobiles, trucks, vans, airplanes and helicopters from primary injuries during an accident. Primary injuries are injuries caused by the initial impact of the occupants against the interior of the vehicle. However, the protection provided by conventional seat belts against primary injuries may sometimes be inadequate. For example, slack in the seat belts may lead to unnecessarily serious primary injuries. In side impacts conventional belts do not provide occupant head protection on the struck side of the vehicle. Moreover, the seat belts themselves may often be responsible for secondary injuries, since the load from the seat belts is distributed only over small areas of the occupant&#39;s body. However, some prior art belts have tried to lessen primary injuries by incorporating an inflating mechanism into the seat belt restraint. 
     For example, U.S. Pat. No. 5,282,648, which is incorporated by reference herein, discloses an inflatable body and head restraint system, wherein inflatable bladders are attached to the shoulder straps of a harness restraint. The bladders are stowed partially underneath and partially on top of harness straps. This configuration provides stability and prevents the bladders from rolling out of position during inflation. During a crash, the bladders inflate to protect the upper body, primarily the head and neck of the occupant. 
     Additionally, U.S. Pat. Nos. 3,948,541 and 3,905,615 to Schulman disclose another inflatable body and head restraint system, wherein a bladder is securely affixed to shoulder straps and a lap belt. The bladder has chin, chest, and pelvic bags. Upon impact, the bladder automatically inflates to cushion the pelvic areas and to prevent forward rotation of the head. However, upon inflation the bladder tends to roll out from its position under the shoulder straps. Also, because the bladders are constricted by the harness, portions of the bladder are subjected to high pressures, which can lead to splitting of the bladder. 
     Simple inflatable body restraints are also disclosed in U.S. Pat. Nos. 3,682,498 and 4,348,037 to W. Rutzki and B. Law et al, respectively. These patents disclose inflatable protective devices that are located in or under the seat harnesses to which they are attached. These inflatable body restraints are subject to roll-out and seam or web splitting problems. 
     In yet another prior art seat belt disclosed in, U.S. Pat. Nos. 3,841,654 and 3,970,329 both to Lewis, a vehicle seat system which comprises a seat belt having an inflatable section is shown. When a collision is detected, the inflatable section is inflated to protect the person wearing the seat belt. 
     The prior art inflatable seat belt structures, such as those identified above, generally use a unitary inflatable section made from a tightly woven material, such as 420 denier nylon, which is conventional air bag material. When deployed, the inflatable section will contract in length somewhat because the inflation pressure causes it to go from a flat, generally 2-dimensional shape to a 3-dimensional cylindrical shape. However, only the of the inflatable section contract as they fill and assume a hemispherical shape. This causes only the ends of the inflatable section to shorten, thus shortening the overall length of the inflatable section. The fibers of the material do not change their orientation: the two sets of fibers in the material remain roughly perpendicular to each other throughout the inflation process. 
     In the case of the typical inflatable seat belt made of conventional air bag material as described above, the maximum theoretical amount that the inflatable structure contracts upon inflation, in an unconstrained condition prior to being loaded by the occupant, is based only on the width of the flat material. If inflation results in a relatively small cylindrical diameter then a relatively small contraction, or shortening, of the length of the seat belt will occur. The calculation for determining the amount of contraction that will occur with conventional air bag material upon inflation and in an unconstrained condition is as follows: 
     
         Lf-Li=X                                                    (1) 
    
     where: 
     X is the amount of contraction 
     Lf is the length of flat, uninflated, material 
     Li is the length of unconstrained inflated material, 
     and 
     
         Li=Lf-(Df-Di)                                              (2) 
    
     
         Di=2/π(Df)                                              (3) 
    
     
         Lf-Li=Df(1-2/π)                                         (4) 
    
     where: 
     Df is the width (flat diameter) of flat, uninflated, material Di is the diameter of unconstrained inflated material. 
     As seen in equation (4), the length reduction depends solely on the uninflated width (flat diameter) of the material. 
     For example, an inflatable structure having a flat diameter of 20 cm and a flat length of 100 cm has a maximum achievable contraction of 7.3 cm or roughly 7%. This degree of contraction would provide restraint that is only slightly greater, and, thus, only slightly more protective than a conventional seat belt. 
     The construction disclosed in U.S. Pat. No. 3,888,503 to Hamilton comprises an inflatable restraining band having a series of sections, some of which are inflatable to a greater degree than others interconnecting them. In the Hamilton design, contraction occurs upon inflation only at each end of each section, and because the sections are of variable inflatable size, the amount of contraction varies along the structure. By not allowing full expansion of interconnecting portions or sections of the inflatable band more hemispherical &#34;ends&#34; occur thus the overall band is foreshortened to a greater extent than otherwise on expansion, which causes greater tensioning of the band against the occupant restrained. 
     Hamilton provides greater protection than the conventional inflatable seat belt in terms of the provision of greater restraint and hence improves upon a conventional inflatable seat belt. However, the restraint that results from Hamilton&#39;s patent is still significantly less than the restraint provided by the present invention. 
     None of the patents described above provide the important advantage of significant contraction which occurs as a result of both inflation and construction of the woven material used in the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention is a seat restraint system having an inflatable torso section, connected to a gas generator and crash sensor, that shortens greatly as it inflates. The invention is intended to replace conventional automotive seat belts. It can also be used in other types of vehicles and moving structures, such as trucks, vans, airplanes, railroad trains, elevators and helicopters. 
     The inflatable torso section of the seat belt system comprises a braided tube of continuous high-strength fibers, not the conventional material used for air bags. The fibers of the braided tube of the present invention form spirals and change their orientation upon inflation. Prior to inflation, the spirals are stretched-out longitudinally and the tubular restraint has a relatively small diameter. Subsequent to inflation, the spirals are closer together longitudinally and form a relatively large tubular diameter. That is, upon inflation, the braided tube significantly increases its diameter and significantly decreases its length. This contraction occurs because when the tube is inflated, the fibers seek an orientation that allows a lower resultant stress and hence a larger volume within the tube. In order to provide superior gas retention, the braided tube may additionally contain an inner bladder. 
     In the uninflated state, the braided tube assumes a flat woven belt configuration and acts as a conventional seat belt system and holds the occupant in the seat. However, as the braided tube inflates, the decreasing tube length acts as a pretensioning device by drawing any slack out of the seat belt system. The shortened length of the braided tube helps greatly to further restrict subsequent occupant motion. 
     The inflated braided tube additionally provides a much larger restraint surface area for the occupant&#39;s body, which helps to distribute belt load forces. When the inflated braided tube is loaded by the occupant&#39;s body, it flattens slightly. This flattening increases the contact area between the body and the braided tube, thus further reducing the pressure on the occupant. In a side impact the inflated section provides occupant head protection. 
     The inflatable braided tube is connected to a gas generator which is in turn connected to a crash sensor. When the crash sensor detects an impact above a predetermined threshold, it sends a signal to the gas generator. The gas generator is initiated inflating the braided tube. The gas generator can be integrated within the seat back or base for sound damping purposes and/or other practical considerations. 
     The primary function of the present invention is to prevent or reduce the severity of primary and secondary injuries suffered by a vehicle occupant in the event of a crash, by pretensioning the restraint system, further restricting the motion of the occupant&#39;s body, and by distributing the restraint forces over a larger surface area. 
     Eight crash tests simulating four equivalent frontal and four equivalent side impacts were conducted to compare the restraining capability of the present invention to a conventional three-point seat belt, and to two air belt systems. The first air belt was inflated to a relative peak inflation pressure of approximately 1 bar, and the second air belt was inflated to a relative peak inflation pressure of approximately 3 bars. The results of these tests are listed in Table 1. As shown by Table 1, the first air belt shows essentially no improvement over the conventional three-point seat belt. The second air belt shows some improvement 20 compared to a conventional three-point seat belt, i.e., head displacement was reduced by six inches in the forward crash simulation and by 2.5 inches in the side impact simulation. Head rotation, a possible indicator of neck injuries, was also reduced. However, the restraint system manufactured according to the present invention, inflated to a peak inflated pressure of approximately 2 bars, produced the greatest improvements in occupant kinematics: head displacement was reduced by 15.5 inches (from 20.5 inches to 5.0 inches) in the forward direction) and by 8 inches (from 23 inches to 15 inches) in the lateral direction. The superior performance of the present invention is due to its ability to reduce its overall length to a greater extent than prior art restraints. 
     Accordingly, it is an object of the present invention to provide a protective seat belt system that inflates on impact to protect the occupant of a vehicle. 
     It is another object of the present invention to provide a protective apparatus that restricts occupant motion during a crash. 
     It is another object of the present invention to provide an inflatable braided tube member that greatly shortens (by at least 10% to 30%) as it inflates to pretension the restraint system. 
     It is another object of the present invention to provide an inflatable braided tube that distributes crash loads over larger occupant surface area, thus minimizing pain and potential injury. 
     It is another object of the present invention to provide an inflatable braided tube that is not subject to roping, roll-out or seam splitting problems. 
     It is another objective of the present invention to provide an inflatable braided tube that pretensions with a force sufficient to counter body loading. 
     These and other objects of the present invention are described in greater detail in the detailed description and the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1a is a schematic diagram of a side view of the present invention in the uninflated configuration. 
     FIG. 1b is a schematic diagram of a side view of the present invention in the inflated configuration. 
     FIG. 1c is a schematic diagram of a front view of the present invention in the inflated configuration installed with respect to the driver-side seat of a typical automobile. 
     FIG. 1d is a schematic diagram of cut-away rear view of the present invention in the uninflated configuration installed with respect to the driver-side seat of a typical automobile. 
     FIG. 1e is a schematic diagram of a cut-away rear view of the present invention in the inflated configuration installed with respect to the driver side seat of a typical automobile. 
     FIG. 2a is a schematic diagram of the braided tube of the present invention in the uninflated state. 
     FIG. 2b is a schematic diagram of the braided tube of the present invention in the inflated state. 
     FIG. 3a is a schematic diagram showing the relative distance of the head displacement and the degree of head rotation during equivalent simulated forward-impact crash tests in which a conventional seat belt, a first air belt inflated to a relative pressure of 1 bar, a second air belt inflated to a relative pressure of 3 bars, and the present invention during the tests summarized in Table 1. 
     FIG. 3b is a schematic diagram showing the relative distance of the head displacement and the degree of head rotation during equivalent simulated side-impact crash tests in which a conventional seat belt, a first air belt inflated to a relative pressure of 1 bar, a second air belt inflated to a relative pressure of 3 bars, and the present invention during the tests summarized in Table 1. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred embodiment of the invention is shown in the uninflated and inflated configurations in FIGS. 1a through 1e installed with respect to a typical driver-side automobile seat 121. A mirror image of the invention would function equally as well on a passenger-side automobile seat. 
     As shown in the FIGS. 1a-1e, the seat belt system 110 of the present invention comprises lap belt 102, shoulder or torso belt 103, including an inflatable section 101 comprising a torso portion 101t, buckle assembly 105, anchor 106, anchored inertial reels 117 and 118, gas generator 122, and sensor assembly (not shown). As shown in FIG. 1c, lap belt 102 and torso belt 103 form one continuous strap which passes through the male portion of buckle assembly 105. Lap belt 102 is designed to restrict the forward motion of a seated occupant at the pelvis. The lap belt 102 is connected to anchored inertial reel 117 that pivotally mounts lap belt 102 to the floor or seat structure on the door-side of seat 121 (as shown in FIGS. 1a and 1b). The other end of lap belt 102 loops through the male portion of buckle assembly 105, so that the length of the lap belt 102 can be adjusted to accommodate a wide range of seated occupants. The female portion of buckle assembly 105 is attached to buckle strap 107. Buckle strap 107 is pivotally mounted to an attachment point in the vehicle, such as the base of seat 121, or a floor structure on the side of seat 121 that is furthest from the door, by anchor 106. The female and male portions of buckle assembly 105 fasten together, thus securing seat belt system 110 around the occupant in a manner similar to that used by conventional three point seat belt systems. 
     As shown in FIG. 1d gas generator 122 is preferably mounted inside the seat back to protect it from impacts and to dampen the noise it produces when activated. The gas generator could also be located in the seat base (not shown). Durable tubing 116 provides a fluid path from gas generator 122 to inflatable braided tube 101. 
     As shown in FIG. 1a, inflatable section 101 extends diagonally from the occupant&#39;s hip to behind and above the occupant&#39;s shoulder and is attached to torso belt 103. The upper end of inflatable section 101 loops through a D-ring 108 that is mounted to the seat 121 as shown or to the vehicle (e.g., at the roof rail or at the upper B-pillar area (not shown)). The torso belt 103 then is anchored to the seat 121 or vehicle (not shown) by an inertial retractor 118. As shown in FIG. 1a, torso strap 103 is preferably routed inside the vehicle seat to inertial retractor 118, which is mounted in the lower portion of the seat back. As discussed below with reference to FIG. 1d, gas generator 122 is preferably mounted inside the vehicle seat. Thus, in the configuration shown in FIGS. 1a and 1d, tubing 116 provides direct fluid communication from the gas generator to inflatable section 101 in the torso of the restraint system. Torso strap 103, buckle strap 107, and lap belt 102 are formed from conventional webbing material such as nylon, dacron, or polyester. Alternatively strap 107 could be a steel cable. 
     The key component of the safety belt system 110 is the inflatable braided tube 101. Braided tube 101 is integrated in the torso belt 103. The braided tube 101 is similar to the braided tubes disclosed in U.S. Pat. Nos. 5,322,322 and 5,480,181, which are incorporated by reference herein. Braided tube 101 is shown in detail in FIGS. 2a and 2b. 
     Braided tube 101 is comprised of a braided tube of continuous high-strength fibers. Typical fiber materials include aramid, nylon, dacron, polyamide and polyester fibers. Braided tube 101 is made of continuous fibers that may or may not be impregnated with elastomeric material, such as silicone rubber or urethane. Unlike the conventional air bag material fibers employed in prior art, the fibers of this invention form spirals and change their orientation (included longitudinal angles) upon inflation. Prior to inflation, the spirals are stretched-out longitudinally and the tubular restraint has a relatively small diameter. Subsequent to inflation, the spirals are closer together longitudinally and form a relatively large tubular diameter. That is, upon inflation, the entire braided tube increases its diameter and decreases its length, or contracts. This contraction occurs because as the tube is inflated, the fibers seek an orientation that allows a larger volume within the tube. 
     As shown in FIG. 2a, angle 201 is a longitudinal angle and angle 202 is a circumferential angle. In the uninflated state, shown in FIG. 2a, braided tube 101 is elongated with its woven fibers forming obtuse and acute angles at the fiber crossing points 111. For the sake of convenience and clarity, the angles which are acute in FIG. 2a (which would be bisected by a line parallel to the longitudinal axis of the braided tube) will be termed the longitudinal angles. The angles which are obtuse in FIG. 2a (which would be bisected by a line parallel to the circumference of the braided tube) will be termed the circumferential angles. 
     When the braided tube is in the uninflated state, its fibers are at a longitudinal angle in the range of about 30° to about 70°. In every case, upon inflation, the fibers will seek a preferred maximum longitudinal angle of about 110° when the tube is in an unconstrained state. Typically, the angle after inflation is approximately 100° in an unloaded, or unconstrained, braided tube. Given the range of angle from about 30° to about 70° in an uninflated tube and an angle of about 100° in an unloaded inflated tube, the range of typical length decrease, or contraction, of the inflatable tube is about 21.5% (for the 70° to 100° change) to about 33.5% (for the 30° to 100° change). The percentage of contraction is irrespective of the initial diameter or length. 
     The calculation for determining the amount of contraction that will occur with the present invention upon inflation and in an unconstrained condition is as follows: 
     
         Lf-Li=X                                                    (5) 
    
     where: 
     X is the amount of contraction 
     Lf is the length of flat, uninflated, material, and 
     Li is the length of unconstrained inflated material 
     and 
     
         Li/Lf=cos (θi/2)/cos (θf/2)                    (6) 
    
     
         Lf-Li=Lf(1-cos (θi/2)/cos (θf/2))              (7) 
    
     where: 
     θf is the longitudinal angle prior to inflation 
     θi is the longitudinal angle after inflation. 
     Merely by way of example, an embodiment of the present invention having an uninflatable flat length of 100 cm and a flat diameter of 20 cm and constructed with fibers that cross each other at a 36° angle would decrease in length, or contract, to 67 cm or by approximately 33% upon inflation in an unconstrained condition. (The calculation assumes that the angle of the fibers in an unconstrained inflated braided tube will be 100°.) 
     As stated above, the invention contracts as a result of both inflation and construction. Therefore, it will typically contract about 21.5% to about 33.5% as a result of the change in orientation of the fibers (construction) plus an additional percent (Lf-Li=Df(1-2/π)) as a result of the geometrical change from a flat belt to a cylindrical belt with hemispherical ends. 
     The fibers in the braided tube form clockwise and counterclockwise spirals both prior to inflation and subsequent to inflation. Prior to inflation, the spirals are stretched-out longitudinally, and have a relatively small diameter. Subsequent to inflation, the spirals are closer together longitudinally, and have a relatively large diameter. This occurs because, as the tube is inflated, the tube fibers seek an orientation that allows a larger volume within the tube, and results in lower resultant stress, with fibers aligned to roughly parallel to the orientation of the resultant stress. 
     FIG. 2b shows that as it inflates, braided tube 101 shortens in length, while its diameter increases. The braid fibers ultimately seek an orientation in which the longitudinal angles increase substantially as the tube diameter increases. As the tube diameter increases, the tube length decreases. If the tube were unconstrained and the longitudinal angles of the tube were in the range of about 30° to about 70°, the typical range for unconstrained decrease of the tube length is about 20% to about 39%, preferably about 21.5% to about 33.5%, and most preferably about 33.5%. 
     The fibers in the uninflated braided tube typically have a longitudinal angle in the range of about 30° to about 70°. Upon inflation the longitudinal angle between the fibers will reach approximately 100°. The preferred maximum longitudinal inflation angle of the fibers is approximately 110°. 
     FIG. 1a shows seat belt system 110 of the present invention in the uninflated state in which braided tube 101 assumes a flat woven belt configuration and the system acts as part of a conventional 3-point restraint. The uninflated braided tube forms a high-strength belt that has the same width (approximately 2 inches) as the conventional webbing material of lap belt 102 and torso belt 103. 
     As best shown in FIG. 1d, when a collision occurs, the crash sensor sends a signal to the initiator in gas generator 122. The initiator then ignites the gas generator 122, thus producing a gas that passes through durable tubing 116 and inflates braided tube 101. As gas flows into the chamber of braided tube 101, the internal pressure causes the tube diameter to increase and the tube length to decrease. However, the seat belt system 110 is constrained on the outboard side by the first inertial reel 117 and on the inboard side by anchor 106, and behind the shoulder by the second (shoulder or torso belt) inertial reel 118. Inertial reels 118 lock up during impact, preventing payout of the belt. Thus as braided tube 101 contracts, it pulls any slack out of seat belt system 110. The occupant is thus provided with a pretensioned seat belt, which restricts the forward motion of the occupant and reduces primary injuries. 
     Further, the male portion of the buckle assembly 105 can be located on the lap belt 102 using rip-stitching or a locating snap or button. When a collision occurs and upon inflation, the locating attachment between lap belt 102 and buckle 105 releases, allowing the lap portion to pull tight, thereby further restricting the motion of the occupant and preventing the occupant from sliding under the lap belt (i.e., submarining). 
     Braided tube 101 is not stowed under any belt member. This design allows the tube to inflate evenly without experiencing roll-out problems. Seam splitting problems common to inflating bladders are also avoided because braided tube 101 is a seamless structure. 
     When fully inflated, braided tube 101 has a diameter of approximately 4 to 5 inches and a relative internal pressure of approximately 1 to 4 bars (2 to 5 bars absolute pressure). Due to increased friction, as the area of contact of inflated braided tube 101 with the occupant increases, inflated braided tube 101 helps to further restrict occupant motion. Unlike conventional 3-point seat belt systems, the present invention additionally helps lessen or prevent secondary belt-inflicted injuries by providing a substantially larger restraint surface area for the occupant&#39;s body, which helps to distribute belt load forces. 
     Additionally, the present invention provides side impact crash protection from head injury by restricting head movement, preventing the occupant&#39;s head from striking the window, the side of the vehicle, or any intruding objects. 
     FIGS. 3a and 3b illustrate the results of simulated crash tests. These figures demonstrate that the present invention is more effective in limiting forward and side head displacement in frontal and side impacts, respectively, than are conventional prior art three-point seat belts and air belts fabricated from conventional materials. 
     The gas generator 122 used in the invention is preferably similar to those currently used in automotive side-impact as opposed to frontal air bags. This is due to the relatively smaller volume and faster filling requirements of side-impact air bags as opposed to frontal air bags. Gas generators invention must inflate braided tube 101 to a relative pressure of approximately 1.5 bars (2.5 bars absolute) within 10 to 15 milliseconds. 
     The foregoing disclosure of embodiments of the present 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. For example, one obvious use of the invention is in the rear seat of automobiles. In this application the torso belt retractor could mount to the rear package shelf, C-pillar area or other structural member. The gas generator could also mount to the rear package shelf or even in the trunk of the vehicle. Of course, these components could also be mounted to the seat back structure as in the front seat application. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents. 
     
                       TABLE I______________________________________OCCUPANT RESTRAINT TEST RESULTS                              Present    3 pt  Air Belt 1                    Air Belt 2                              Invention______________________________________FRONTAL IMPACTDisplacement      20.5    18.0      14.5    5.0(inches)Rotation,  110     61        42      28(degrees)HIC        129     406       194     99C .sub.R, (g&#39;s)      32      51        27      26Torso belt, (lbs)      1,466   790       618     500Lap belt (lbs)      1,534   1,294     1,193   554Pressure (psi)      NA      16.0      45.4    33.4LATERAL IMPACTDisplacement      23.0    24.0      20.5    15.3(inches)Rotation   86      74        15      50(degrees)HIC        121     126       73      NDC .sub.R, (g&#39;s)      53      20        ND      35Torso belt (lbs)      709     421       410     417Lap belt (lbs)      595     693       700     383Pressure (psi)      NA      17.3      40.6    31.3______________________________________