Abstract:
A tongue for a motor vehicle seat belt restraint system providing high friction restraining belt webbing transfer through the tongue in an impact condition. The tongue incorporates a deformable element which maintains the webbing away from contact with high friction elements in the normal use of the belt system. In a crash condition in which significant tension loads are applied to the belt webbing, the deformable element yields to provide contact between the belt webbing and a high friction surface which restricts the transfer of the webbing from the shoulder belt portion of the webbing to the let belt portion of the webbing which is normally more highly loaded in an impact condition. Several embodiments of deformable elements are described.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a seatbelt motor vehicle occupant restraint system and particularly to a tongue component for such systems. 
       BACKGROUND OF THE INVENTION 
       [0002]    Seatbelt assemblies and systems are in widespread use in motor vehicles. Present systems have certain common elements including seatbelt webbing which extends across the upper and lower torso of the occupant, and a retractor for allowing protraction and retraction of the webbing so that the belt may adapt to different sizes of occupants and be conveniently retracted out of the way when not being used. Seatbelt assemblies further typically include a buckle which releasably attaches to a latch plate or tongue. 
         [0003]    Seatbelt assemblies must be securely affixed to motor vehicle structural elements in order to provide the necessary restraint effect in vehicle impact conditions and further to meet government regulations. Further, seatbelt assemblies must securely retain an occupant within the seat, while also allowing the occupant easy ingress and egress from the vehicle under a variety of conditions and situations. 
         [0004]    Typical seatbelt assemblies include a buckle that is securely mounted to a vehicle structure, such as a seat frame or the floor of the occupant compartment. A tongue (or latch plate) is received by the buckle and is typically attached to the seatbelt webbing. The seatbelt webbing is typically fixed to the vehicle structure at one end, and the opposite end is fixed to a retractor having an internal spool provided to protract and retract the webbing and a lock in impact conditions. 
         [0005]    Manufacturers of seatbelt restraint systems and their OEM customers constantly seek to enhance the restraint performance of such systems, both in response to government regulations and consumer demand. With increasing use of seatbelt active type restraint systems, increasing attention is paid to the restraint performance of these systems in impact conditions. 
         [0006]    It has been shown in the occupant restraint industry to be beneficial to the occupant in a crash to restrain the occupant&#39;s hips as much as possible in order to allow the occupant upper torso to rotate and better utilize the energy management capabilities of the belt system and the frontal impact airbag. One approach to enhance restraint of the hips is to utilize what is known as a crash locking tongue which will lock the belt webbing at the point of transition from the lap to the torso belt sections of the webbing. With a conventional system utilizing a single belt retractor, the tongue (or latch plate) is allowed to slide along the length of the belt webbing enabling it to adapt to different occupant characteristics, seat positions, and other variables. Using a conventional tongue in a frontal impact, the webbing will tend to move from the high load segment (the lap belt portion) to the lower load segment (the torso belt portion). If a crash locking tongue is used in place of a conventional tongue, then the load will not transfer the webbing through the tongue and consequently lower loads are maintained in the torso belt. Although crash locking tongues are used in the industry, but they carry disadvantages in the form of larger size and weight, and higher cost compared to a conventional tongue. This higher weight and cost derive from the fact that there is a specific mechanism inside the tongue that is used to clamp the webbing during a crash. 
         [0007]    Some vehicle applications may not need a crash locking tongue to achieve good occupant response. However, these vehicles may still benefit from a tongue which provides higher friction at the lap-torso belt portion transition, and which limits transfer of webbing during a crash without actually locking the webbing. 
         [0008]    Also available for motor vehicle applications are tongues which provide increased friction reducing webbing transfer at the lap-torso transition. Such tongues typically utilize specific materials and surface finishes and features for a webbing sliding surface which increases friction, especially when tension is applied to the belt webbing. However, such designs typically have the webbing sliding over the gripping surface during normal use of the belt webbing which may lead to belt abrasion and the degradation of performance of the high friction surface over time. 
         [0009]    The present invention is related to a tongue for a belt restraint system that provides higher friction than a standard tongue at the lap-torso transition, but without the locking mechanism of a crash locking tongue and without the above referenced disadvantages. The tongue according to this invention, referred to as a “grip tongue”, will be lighter in weight and more cost effective than a crash locking tongue. 
       SUMMARY 
       [0010]    Embodiments of the present invention provide a tongue with a high friction surface that will contact the webbing only in the event of sufficient occupant loading during a crash. In normal operation of the seatbelt system, the high friction surface will not contact the webbing thus avoiding a webbing abrasion concern mentioned previously during normal belt use. Contact of the webbing to the frictional surface of the tongue is brought about via a variety of described deformable members designed to deflect during high belt load conditions of an accident, permitting engagement between the webbing and the high friction surface, while maintaining the webbing away from engagement during normal use of the belt system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a front diagrammatic view illustrating an occupant utilizing a conventional three-point type single retractor seatbelt system which may incorporate a grip tongue in accordance with the present invention; 
           [0012]      FIGS. 2, 3, and 4  are isometric views of a first embodiment of a grip tongue in accordance with the present invention; 
           [0013]      FIG. 5  is an isometric view of a second embodiment of a grip tongue in accordance with the present invention; 
           [0014]      FIG. 6  is a cross-sectional view through the grip tongue shown in  FIG. 5 ; 
           [0015]      FIG. 7  is an isometric view of a third embodiment of a grip tongue in accordance with the present invention; and 
           [0016]      FIGS. 8A-8E  show various configurations for a high friction surface which may be used for the grip tongue embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    With reference to  FIG. 1 , there is illustrated in phantom lines an occupant  10  seated in a motor vehicle occupant seat  12 . Occupant  10  is shown fastening a three-point belt restraint system  14 . Restraint system  14  typically includes webbing  15  forming lap belt portion  16 , shoulder belt portion  18 , and further including buckle  20 , and tongue (or latch plate)  22 . A seat belt retractor  24  (not shown), is used for engaging an end of the downward extending section  26  of shoulder belt section  18 , and is used for allowing extraction and retraction of the seat belt webbing. Retractor  24  can be mounted in various locations such as on seat  12 , on the floor pan of the vehicle adjacent the side of the seat, or behind a trim panel on a vertical door pillar at the position of guide loop  28 , as shown in  FIG. 1 . Tongue  22  is permitted to slide along the webbing  15 , dividing the webbing between lap belt portion  16  and shoulder belt portion  18 . 
         [0018]    This invention is related to designs of a grip tongue which can be used in the seatbelt restraint system  14  illustrated in  FIG. 1  (or for modified designs of the restraint system), a first embodiment of which is shown in  FIGS. 2-4  and designated by reference number  30 . Grip tongue  30  may be formed of a yoke shaped metal plate structure having extending engagement tab  32  with engagement slot  34  which are adapted to be received by buckle  20  for latching engagement. Body  36  of grip tongue  30  may be formed by over-molding a resin material onto and underlying metal plate substrate  37 . Body  36  forms webbing receiving slot  38  which is bounded at its lateral edges by sides  40  and  42 . Slot  38  receives seatbelt webbing  15  and guides it to slide along and over webbing contact surface  44 . Depending on the use condition of restraint system  14 , webbing  15  may contact surface  44  at a tangent line, away from contact, or may be wrapped around the surface along a webbing wrapped angle, typically up to around 120° when you achieve restraint system  14  is fastened. Webbing contact surface  44  is arcuate in shape and may be a semi cylinder or some other convex shape. 
         [0019]    Tongue webbing contact surface  44  is formed in part by a deformable or movable plate  46  featuring a plurality of apertures  48 . Plate  46  is biased to be maintained in the position illustrated by  FIGS. 2 and 3  during normal use of the restraint system. As illustrated plate  46  exhibits a generally smooth external surface  50  which provides minimal restriction and friction to the relative sliding contact with webbing  15 . Cavity  49  permits movement of plate  46  from the normal position shown in  FIGS. 2 and 3 , to a deflected condition illustrated in  FIG. 4 . Plate  46  may be biased by various means including discrete spring elements such as spring element  47 , such that the plate moves between the positions without changing its shape. Alternatively plate  46  may be formed of a thin preferably metal material which is readily deformed for purposes which will be described. For such a configuration, plate  46  would change its shape by deflecting without the requirement of a discrete spring element. Four either configuration, once deflected plate  46  may rest against bearing surface  52  formed by body  36 . This configuration would bias the element as shown but permit a deflected condition to occur. The side edges of plate  46  are captured by side pockets  54  and  56 . A metal spring element  47  such as formed from flat sheet metal may be positioned in a cavity  49  to bias plate  46 . 
         [0020]    A number of protrusions  58  are formed by tongue body  36  (or by an insert element  51 ) at positions directly underlying apertures  48 . Protrusions  58  are configured such that in a deflected compressed condition of plate  46 , the protrusions extend beyond the outer surface of the plate and will engage with the webbing. This condition is illustrated by  FIG. 4 . The material forming protrusions  58  may be formed of a resin material, for example as an overmold of the tongue body or a metal or another hard surface designed to present high frictional engagement with webbing  15 . During a vehicle frontal impact, tension forces are exerted on lap and shoulder belt portions  16  and  18  which exert force acting on plate  46  in the direction of the arrows shown in  FIG. 2 . These forces urge plate  46  to retract, allowing protrusions  58  to extend through and beyond apertures  48 , in a position to frictionally engage with webbing  15 . 
         [0021]    When tongue  30  is used in its normal manner, i.e. donning and wearing the belt without crash forces exerted on webbing  15  during normal use of the belt system, the action of spring  47  and plate  46  keep the webbing from contacting the friction surface protrusions  58 . The webbing may contact one or both outboard side surfaces  40  and  42 , or the opposing inside surface of slot  38 . However, during loading of the webbing in a crash event, plate  46  is deflected, providing the high friction engagement caused by exposure of protrusions  58  which reduces the amount of webbing transferred to lap portion  16  as described previously. 
         [0022]    The high friction surface of grip tongue  30  provided by protrusions  58  can be produced in a variety of ways. This surface can be formed of a polymer based material with varied patterns to provide a high frictional contact surface for the webbing. The high friction surface can also be metallic, such as aluminum or a zinc based casting. The surface will need to have sufficient edge geometry to provide friction to webbing  15  to perform as intended, but at the same time, not provide excess friction that will result in damage of the webbing to the point where minimum tensile properties are not fulfilled. 
         [0023]    Now with reference to  FIG. 5 , a second embodiment of a tongue in accordance with this invention which is generally designated by reference number  60 . Features of tongue  60  which are identical to those previously described are designated with the same reference numbers, and a duplicative description is not provided. Tongue  60  differs from the prior embodiment in that a single spring element  62  is provided at near the center of slot  38  rather than fully extending across the full width of the slot (as does plate  46 ) will. Spring  62  forms webbing contact surface  64  which cooperates with webbing contact surfaces  66  at the outboard edges of slot  38 . For this embodiment a series of protrusions  68  are visually evident but are not operative until a high tensile loading is applied to webbing  15 , in a manner which will be described below. 
         [0024]    Spring  62  operates in a manner similar to that of plate  46  and is shown in its normal condition but can be deflected in a manner to permit direct contact between webbing  15  and a series of protrusions  68  provided in recessed cavity  70 . In a condition of impact loading on webbing  15 , spring  62  is deflected and depressed toward protrusions  68  and the increased tension causes the webbing to move into direct contact with the protrusions. A deflected configuration of spring  62  for tongue  60  is illustrated in the cross-sectional view of  FIG. 6 . That view shows spring element  62  being deflected in the direction of the arrows during a belt loading situation, allowing webbing  15  to contact and frictionally engage with protrusions  68 . Spring  62  can be urged toward its normal condition by its own bending flexibility (for example by cantilever support of it at one end) or a discrete spring element (not shown) may be employed. It is noted that in a restraint condition webbing  15  will not make contact with protrusions  68  since the lateral edges of the webbing will continue to bear against surfaces  66 . However, sufficient engagement between webbing  15  and protrusions  68  will occur to provide the desired high friction interaction. 
         [0025]    Since protrusions  68  do not normally make contact with the belt, webbing abrasion of the webbing or of protrusions  68  does not occur during normal belt usage. One benefit of this approach is that protrusions  68  can be formed having a very aggressive nature in terms of engagement with the webbing, since abrasion during normal use will not be an issue. Various configurations for protrusions  68  may be provided. In this embodiment protrusions  68  are provided in the form of “chevron” shaped elongated slanted teeth. Later in this description, a number of alternative configurations for protrusions  68  are described which may be used for tongue  60  (as well as the next described embodiment). 
         [0026]    A third embodiment of grip tongue  74  is provided with reference to  FIG. 7 . Tongue  74  is similar to tongue  60  except that the single spring element  62  is replaced by a pair of separated round wire spring elements  76 . Spring elements  76  are biased to in a manner similar to spring  62  to hold webbing  15  away from contact with protrusions  68  while permitting engagement with the friction surface formed by protrusions  68  in crash conditions. A pair of slots  78  is provided to allow spring elements  76  to recess in response to belt loading. Protrusions  68  for this embodiment have a shape similar to that described for grip tongue  60 . 
         [0027]      FIGS. 8A-8E  illustrate various friction surface geometries for grip tongues in accordance with the present invention. These configurations can be formed of various materials such as a resin or metal materials.  FIG. 8A  shows a wave like configuration for the protrusions  68   a.    FIG. 8B  illustrates the slanted “chevron” configuration for protrusions  68   b  described previously except here the individual elements are offset such that their upper and lower ends are displaced alternately such that their upper and lower edges are not mutually aligned.  FIG. 8C  illustrates shorter chevron shaped protrusions  68   c  formed in a pair (or more) of rows of protrusions oriented in opposing directions.  FIG. 8D  illustrates protrusions  68   d  which may have a teardrop like or another shape departed from a generally rectangular root configuration.  FIG. 8E  shows protrusions  68   e  is similar to protrusions  68   c  with the protrusions having sharp corner edges. 
         [0028]    Grip tongues  30 ,  60 , and  74  provide numerous embodiments over prior art designs. The main features and advantages of these designs are: lighter weight compared to a crash locking tongue, lower cost due to fewer components compared to locking tongues, and improved occupant restraint performance compared to standard tongues. 
         [0029]    While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.