Abstract:
A D-ring assembly comprising a D-ring and a load limiting device. The D-ring has a slot therethrough for receiving a seatbelt webbing and for guiding the webbing from the retractor to the torso of a vehicle occupant. The load limiting device functions by absorbing kinetic energy of the vehicle occupant during a crash to control the deceleration forces experienced by the vehicle occupant. The load limiting device has a deforming member partially embedded in a swivel ball. When a predetermined amount of force is applied on the D-ring assembly, the swivel ball rotates causing the deforming member to create a channel in the load-limiting device.

Description:
FIELD OF THE INVENTION  
     The present invention relates to an energy absorbing device for a restraint system and more particularly relates to a load limiter incorporated with seatbelt guide.  
     BACKGROUND OF THE INVENTION  
     Three point seat belt systems are well known in the art. They normally comprise a releasable buckle and connecting tongue adjustably attached to a continuous webbing. One end of the webbing is anchored to the vehicle&#39;s frame or seat adjacent to the floor, and the other end of the webbing is connected to a retractor through a web guide attached to the vehicle&#39;s side pillar proximate the shoulder height of a seated occupant. The portion of the webbing between the connecting tongue and the vehicle frame is normally referred to as the lap portion of the webbing and the portion of the continuous webbing between the connecting tongue and the web guide is referred to as the shoulder portion.  
     A conventional D-ring also referred to in the art as a web guide or a turning loop includes a metal support plate with a circular mounting opening and a slit through which the shoulder belt is slidingly received. A threaded bolt serves as the mounting member, which is secured to a threaded nut, which functions as a cooperating mounting member. The threaded nut can be part of a vertically adjustable height adjusting mechanism, or alternatively, the nut can be welded to a support pillar (B, C, or D) or to a part of a seat frame.  
     The seatbelt webbing is wound around the spool of the seatbelt retractor. The seatbelt webbing has a biasing force in the retraction direction, and this biasing force needs to be overcome to protract the seatbelt webbing from the seatbelt retractor. The biasing force on the seatbelt webbing is great  enough to coil the continuous seatbelt webbing around the spool when the connecting tongue is disengaged from the releasable buckle, but the biasing force does not prevent a vehicle occupant from shifting position or leaning forward during seatbelt use. However, at the onset of a vehicle crash, the retractor locks and prevents further belt payout to restrain the occupant during the crash. The vehicle occupant is traveling at the same speed as the vehicle and during the crash both the vehicle and the vehicle occupant experience deceleration forces. In order to minimize vehicle occupant injury during a crash, the goal is to minimize the deceleration forces applied to the vehicle occupant. Thus, by lowering the level of vehicle occupant deceleration during a crash, the risk of injury is lowered.  
     A load limiting device is well known in the art for absorbing the kinetic energy of the vehicle occupant to control the deceleration of the vehicle occupant during a crash. The load limiting device is designed to absorb the kinetic energy of the occupant in a controlled manner and thereby minimize the deceleration forces in a predetermined manner as the occupant loads the belt during the collision. Such force dissipation allows controlled deceleration of the occupant during the collision.  
     The load limiter or energy absorbing mechanism is commonly associated with the retractor portion of the three point seat belt system. For example, a torsion bar installed in the center bore of the spool is well known in the art, which absorbs energy by twisting during a crash. However, there is a desire to identify alternative locations within the three point seatbelt system for a load limiter that is not associated with the retractor.   
     SUMMARY OF THE INVENTION  
     The D-ring assembly according to the present invention comprises a D-ring and a load limiting device. The load limiting device has a swivel member mounted in a socket. The swivel member is restricted from rotating by the presence of a deforming member. The deforming member is partially embedded in the surface of the swivel ball of the swivel member.  
     An aspect of the present invention is that the deforming member is made from a material that is harder than the socket. The deforming member is fixed to the swivel ball. Upon an application of force above a predetermined amount, the swivel ball rotates thereby creating a channel in the socket, and this deforming process absorbs kinetic energy of the occupant.  
     Another aspect of the present invention is that the deforming member is made from a material that is harder than the swivel ball. The deforming member is fixed to the socket. Upon an application of force above a predetermined amount, the swivel ball rotates thereby creating a channel in the swivel ball, and this deforming process absorbs kinetic energy of the vehicle occupant.  
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  shows a perspective view of a D-ring assembly.  
         FIG. 2  shows an exploded view of a D-ring assembly.  
         FIG. 3  shows a perspective view of a socket of the D-ring assembly.  
         FIG. 4  shows the socket from  FIG. 3  with a channel formed thereon from the hardened ball.   
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     The D-ring assembly  10  of the present invention has a load-limiting device  40  incorporated therein, which dissipates forces applied to the seat belt webbing, and allows controlled movement of an occupant during a vehicle collision. The load limiter of the present invention may be used in any of the 3 point seat belts in a vehicle. Three point seat belts are commonly utilized for vehicle occupants occupying front seats of a vehicle compartment and are becoming more common for vehicle occupants occupying rear seats.  
     Referring to  FIG. 1 , the D-ring assembly  10  includes a D-ring  11  and a load-limiting device  40 . The D-ring  11  has a slot  14  therethrough for receiving the seatbelt webbing. The continuous seatbelt webbing is anchored to the vehicle floor on one end and the other end is connected to a seatbelt retractor. The seatbelt webbing passes through the slot  14  of the D-ring  11 , which is located proximate to the vehicle occupant&#39;s shoulder. The primary function of the D-ring  11  is to guide the continuous webbing from the retractor to the torso area of a vehicle occupant. The slot  14  is U-shaped whereby the center portion  12  is slightly longer than the width of the seat belt webbing. The purpose of the end portions  13  of the slot  14  is to prevent the seat belt webbing from “bunching” during use.  
     With reference to  FIG. 2 , above the slot  14  of the D-ring  11  is an aperture  15  for receiving a first fastening means  20  for the D-ring assembly  10 . Examples of suitable fastening means include rivets, nuts and bolts, screws, and the like. The first fastening means  20  for the D-ring assembly  10  rotationally attaches the D-ring  11  to the swivel member  21 . In accordance with the present invention, the D-ring  11  is free to rotate back and forth around the first fastening  means  20 , which affords comfort to a vehicle occupant during use of the seat belt.  
     The load limiter device in accordance with the present invention is an intermediate member of the D-ring assembly  10  disposed between the D-ring  11  and the mounting threaded bolt  34  for fastening the D-ring assembly  10  to a structural support member of a vehicle such as the B-pillar. The components of the load limiter device include the swivel member  21 , the deforming member  35 , the socket cover  24 , and the socket  30 . The swivel member  21  can best be seen from  FIG. 2  and comprises a connecting member  22  extending from a swivel ball  23 . The connecting member  22  is a curvilinear member that interfaces with the D-ring  11 . The swivel ball  23  has essentially a circular shape and has a small recess for the placement of a deforming member  35 , preferably a small, hardened ball. The deforming member  35  of the present invention is illustrated in  FIG. 2  as a ball, but it is contemplated that other shaped deforming members may be employed such as square, rectangle, cone, diamond, and the like. The hardened ball is fixed to the recess via an adhesive whereby a portion of the hardened ball extends beyond the surface of the swivel ball  23 .  
     The swivel ball  23  is mounted in a socket  30  and the deforming member  35  impedes rotation of the swivel ball  23 . The socket  30  is bowl shaped that receives about half of the swivel ball  23 . The socket  30  has a plurality of socket attachment arms  31  radiating from the top of the socket  30 . The socket cover  24  is a physical part that is responsible for rotatably securing the swivel ball  23  to the socket  30 , whereby the socket cover  24  has an equivalent number of socket cover attachment arms  25  as the socket attachment arms  31 . The socket cover attachment arms  25  have first holes  26  therethrough, whereby there is one hole for each attachment arm, and the socket attachment arms  31  have second holes  32  therethrough, whereby there is one hole for each attachment arm. The diameter of the first holes  26  corresponds to the diameter of the  second holes  32  and during assembly of the D-ring assembly  10 , the first holes  26  are aligned with the second holes  32  so that a second fastening means  33  can secure the socket cover  24  to the socket  30 . Examples of fastening means include rivets, bolts and nuts, screws, and the like.  
     The socket cover  24  is a hollow, circular ring with a radius gradient. The part of the socket cover  24  having the largest radius has a radius smaller than the maximum radius for the swivel ball  23 . This radius differential allows the socket cover  24  to slide over a portion of the swivel ball  23  without being able to slide over the entire swivel ball  23 . For assembly purposes, the socket cover  24  is inserted around the connecting member  22  and the socket cover attachment arms are connected to the socket attachment arms  31 .  
     With reference to  FIG. 3 , the socket  30  has a dimple  41  for receiving the deforming member  35 , preferably the hardened ball. The preferred embodiment for the present invention has only one deforming member, but one of ordinary skill in the art appreciates that the present invention may have multiple deforming, members. The dimple  41  in the socket  30  has the substantially the same dimensions as the recess in the swivel ball  23 . The purpose of the dimple  41  in the socket  30  is to facilitate the initial deforming of the socket  30  during a situation when a predetermined amount of force on the D-ring  11  is reached.  
     Integrated into the socket  30  is a mounting threaded bolt  34  as seen in  FIG. 1 . The threaded bolt  34  is utilized to attach the D-ring assembly  10  to a support structure of a vehicle such as a B-pillar or a C-pillar. It is contemplated that the threaded bolt  34  does not have to be integrated with the socket  30 , but instead the threaded bolt  34  may be a separate physical component for the D-ring assembly  10 .   
     The present invention functions by absorbing kinetic energy from a vehicle occupant during a vehicle crash. Before a crash, the swivel ball remains in a first position. The swivel ball  23  is prevented from rotating about the socket  30  due to the presence of the hardened ball. During a vehicle crash, the vehicle occupant applies force to the seat belt webbing and the load limiter device of the present invention dissipates this force in a controlled manner via a deformation process, and the swivel ball  23  moves from a first position to a second position. The second position is the position where the swivel ball  23  rests after the vehicle occupant ceases to decelerate. Since there is not a pre-existing channel in the socket  30 , the deforming member  35  creates a channel or a groove, which is illustrated in  FIG. 4 . The hardened ball needs to be tightly secured to the recess in the swivel ball  23  to prevent the hardened ball from coming loose from the swivel ball  23  during the deforming process. Furthermore, the hardened ball needs to be harder than the socket  30  so the hardened ball is able to deform the socket  30  without being deformed. There is no predetermined path for the channel in the socket  30 , and the direction of the channel will be dependent upon the characteristics of the crash and the size and weight of the occupant. If the D-ring does not have an adjustable height option, the height of the occupant will directly impact the orientation of the D-ring, thus affecting the path for the channel. Also, the severity of the crash along with the mass of the occupant will affect the length of the channel. The D-ring assembly  10  has a stop feature, which will prevent the D-ring from continuing to move in the direction of the front of the vehicle. The D-ring will be “stopped” when the connecting member  22  of the swivel member  21  is in a position where it contacts the socket cover  24 , and at this point, the swivel ball  23  will no longer be able to rotate.  
     As discussed herein, the hardened ball is fixed to the recess in the swivel ball  23 , and the socket  30  is capable of being deformed. Alternatively, the hardened ball may be fixed to the dimple  41  in the socket  30 , whereby the hardened ball creates a channel or groove in the swivel ball  23 .   
     There are certain features of the load limiting device  40  that allow the performance of the load limiting device  40  to be selectively designed or tuned for a particular occupant restraint. Those features include the size and shape of the deforming member and the type of material selected for the socket  30 .  
     Many changes and modifications in the above-described embodiments of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, that scope is intended to be limited only by the scope of the appended claims.