Abstract:
The inboard buckle for a four-way seat is attached to the seat through a variable buckle guide. Attaching the inboard buckle to the seat allows the buckle to move with the seat and obviates the need for a long buckle which introduces undesirable slack into the seat belt system during a crash event. Since the buckle moves with the seat, it remains in a location that is convenient for the occupant and provides the maximum occupant protection. The variable buckle guide is attached to the upper rail supporting the seat, and in a crash event, the variable buckle guide transfers the occupant load on the belt to the upper rail, avoiding distortion of the seat or the height adjusting levers supporting the seat, and thus precludes slack in the belt caused by such distortion.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to a seat belt system and more particularly to an inboard buckle attachment in a seat belt system. 
     BACKGROUND OF THE INVENTION 
     Modern seat belt restraining systems utilize a three-point belt that is anchored on the B-pillar above the occupants shoulder, to the floor next to the B-pillar, and to an inboard buckle positioned next to the seat in a region adjacent to the occupant&#39;s hips. The inboard buckle secures two portions of the seat belt strap to the inboard anchor point, the portion that extends from the B-pillar over the occupant&#39;s outboard shoulder across the chest and to the waist on the inboard side, and the portion that extends from the outboard anchor point on the floor to the waist of the occupant. 
     A two-way seat is one that moves fore and aft, with no up and down position adjustment of the seat possible. An inboard buckle may be attached to a two-way seat without comprising the safety provided by the seat belt since the seat can be securely fastened to the upper rail and the engagement of the upper rail with the lower rail is one which will resist occupant loads on the belt in a crash event. 
     A four-way seat is one that is adjustable fore and aft, and also up and down to accommodate the physical dimensions and comfort of the occupant. Not only does a four-way seat provide additional motion to the seat that has to be accommodated in the design of the seat belt and the inboard buckle, it also introduces another element into the support system for the seat, pairs of levers that are pivoted together to open and close with a folding motion to raise and lower the seat. The pivoted levers are prone to distortion in a crash event and hence result in seat motion. Further, because of the location and design of the pivoted levers, in a crash event, the levers tend to unfold, pitching the seat forward and upward. If the inboard buckle is attached to the seat, this motion of the seat creates slack in the seat belt. 
     SUMMARY OF THE INVENTION 
     A variable buckle guide is provided for the inboard buckle of a seat belt system for a four-way seat. The variable buckle guide permits attachment of the inboard buckle to the seat, so that the buckle mechanism remains positioned for convenient use by the occupant regardless of the position of the seat. In a crash event, the occupant load on the belt is transferred from the inboard buckle to the rails on which the seat is mounted to avoid distortion of the seat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and best mode, appended claims and accompanying drawings in which: 
         FIG. 1  is a side view of the inboard side of a vehicle seat showing the anchoring points for a seat belt restraining system according to the prior art; 
         FIG. 2  is a perspective view showing the lower frame elements of a four-way seat; 
         FIG. 3  is a side view of a seat in a lowered position showing the inboard buckle; 
         FIG. 4  is a detail view partly in section taken along line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is an exploded perspective view of a variable buckle guide; 
         FIG. 6  is a view similar to  FIG. 3  but with the seat in a raised position; 
         FIG. 7  is an enlarged view of the encircled portion  7  of  FIG. 3  showing the motion of a gear in the variable buckle guide when the height of the seat is being adjusted; and 
         FIG. 8  is a view like  FIG. 7  showing the gear in the variable buckle guide in the locked position during a crash event. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows the inboard side of typical seat  10  and a seat belt restraining system  12  used in a modern automobile vehicle. The seat  10  includes a lower cushion  14  and a back cushion  16 . A seat belt strap  18  extends from a spring loaded spool  20  mounted in the B-pillar of the vehicle up through a shoulder guide  22  mounted on the B-pillar. The strap extends from the shoulder guide  22  to an inboard guide  24  and from the inboard guide  24  to a floor mounted anchor point  26  on the outboard side of the seat  10 . The spring-loaded spool  20  may include a pretensioning device to take up slack in the strap  18  in a crash event as is well known in the art. The inboard guide  24  is mounted on the end of a tongue  25  which engages an inboard buckle  28 . The inboard buckle  28  comprises a buckle mechanism  29  that is mounted on one end of an extension strap  30 , the opposite end of which is attached to an inboard anchor  32  on the floor of the vehicle. 
       FIG. 2  is a perspective view showing the lower frame  33  of a modern four-way seat and its attachment to the floor of a vehicle. Four mounting pads  34  for the seat are attached to the floor of the vehicle. Two parallel lower rails  36  running fore and aft are secured to the mounting pads  34 . Two upper rails  38  are slidably mounted to the lower rails  36  and are interlocked with the lower rails to allow sliding motion in the fore and aft directions, but to prohibit up and down or rotary motion relative to the lower rails. The bottom of the seat frame is formed by two side members  40 , a front crossbeam  42 , and a rear cross beam  44 . A seat pan  45 , omitted for clarity in this view, but partially shown in  FIGS. 3 and 6 , spans the width of the seat and is supported by the two side members  40 , and the two cross beams  42 , 44 . The seat pan  45  supports a seat cushion  46  as shown in  FIGS. 3 and 6 . Four pairs of folding links  48  are positioned one each at the four corners of the seat to permit the height of the seat to be adjusted relative to the upper rails. The pairs of folding links each comprise a fixed link  49  that is attached to the upper rail  38  and a lifting link  50  that is pivoted at one end to the fixed link  49  and at the other end to one of the side members  40 . A suitable mechanism is used to raise and lower the seat as well known in the art. An inboard bracket  51  is attached to the upper rail  38 , and moves fore and aft with the seat. The inboard bracket  51  does not move up and down with the seat. An inboard buckle is normally attached to a mounting aperture  52  on the inboard bracket  51 . The upper and lower rails, the frame members for the seat, the lifting levers and the inboard bracket are all fabricated from steel, aluminum, or other metal alloy, as is the common practice in the art. 
       FIG. 3  shows the inboard side of a seat  54  with a variable buckle guide  56  attached to the upper rail  38 . The extension strap  30  of the inboard buckle  28  is attached to the side member of the seat through the variable buckle guide  56  as more fully explained below. The extension strap  30  may be made from metal, or seat belt strap material that is stiffened with a plastic or fiber covering so that the buckle will be extended from the seat toward the occupant. Since the inboard buckle  28  is attached to the seat, the inboard buckle  28  moves fore and aft, and up and down with the seat. The typical length of an inboard buckle that is attached to and moves with the seat is between 150 and 200 mm. This positions the buckle mechanism  29  at about the midpoint of the occupant&#39;s hips for maximum occupant protection in a crash event for all positions of the seat. Attaching the inboard buckle to the seat allows the occupant to comfortably and easily locate the buckle mechanism  29  and clinch the tongue portion  25  of the buckle into the buckle mechanism  29 , regardless of the position of the seat. The variable buckle guide  56  preferably is bolted, welded or otherwise attached to the upper rail  38  and moves fore and aft with the upper rail and with the seat that is attached thereto. The variable buckle guide  56  does not move up and down with the seat when the height of the seat is adjusted by the occupant. 
       FIGS. 4 and 5  show the variable buckle guide  56  and the components used to attach the inboard buckle  28  to the seat. The variable buckle guide  56  comprises a base plate  58  and an upright guide plate  60  with an elongated arcuate slot  62 . A lower convex portion  64  of the arcuate slot  62  is formed with serrations or teeth  66 . The teeth  66  formed in the arcuate slot  62  comprise a first set of teeth. An upper concave side  68  of the arcuate slot is smooth. An elongated plate or bug gear  70  fits inside of the arcuate slot  62  and has serrations or teeth  72  formed along the side of the gear that is opposite the teeth  66  formed in the slot. The teeth  72  formed on the bug gear  70  comprise a second set of teeth. The opposite side  74  of the bug gear is smooth. The dimensions of the bug gear  70  are such that it is able to slide in the arcuate slot  62  with the smooth side  74  of the bug gear in contact with the smooth side  68  of the arcuate slot without the teeth  72  of the bug gear coming into contact with the teeth  66  of the slot. The bug gear is formed with a mounting aperture  78 . 
     A fastener such as a mounting post  76  is used to attach the inboard buckle  28  to the seat. One end of the mounting post  76  is welded or otherwise securely attached to the side member  40  of the seat. The mounting post extends through the arcuate slot  62  in the variable buckle guide  56 . The bug gear  70  is attached to the mounting post  76  by welding or an interference fit, and is positioned in the arcuate slot  62 . A load washer  80  and the extension strap  30  are mounted on the mounting post  76  so that the load washer is between the upright guide plate  60  of the variable buckle guide and the extension strap  30 . A mounting aperture  82  is formed in the end of the extension strap  30  to receive the mounting post  76 . The load washer  80  distributes forces from the extension strap  30  to a large area on the upright guide plate  60 , and helps to prevent inward motion of the extension strap toward the seat or the occupant in a crash event. A small washer  84  and a mechanical fastener  86  such as a pin or a circular clip are used to retain the extension strap  30  and the load washer  80  on the mounting post  76 . The variable buckle guide  56 , the mounting post  76 , the bug gear  70  and the load washer  80  may be fabricated from steel or aluminum or other metal or metal alloy having sufficient strength and wear characteristics to withstand the loads to which they will be subjected. 
       FIG. 6  is a side view of the seat  54  showing the arcuate path taken by the seat as the height of the seat is adjusted up or down using the lifting links  50 . The arcuate slot  62  in the variable buckle guide  56  is the same shape as the path taken by the seat  54  and shown by the arrows  88  as it is adjusted up and down to allow the mounting post  76  and the bug gear  70  to move freely in the arcuate slot  62 . 
       FIG. 7  is a detail view of the variable buckle guide  56  and the bug gear  70  showing the motion of the bug gear along the arrow  90  as the height of the seat is adjusted up and down. The smooth side  74  of the bug gear  70  slides along the smooth concave surface  68  of the arcuate slot  62 , and there is sufficient clearance between the teeth  72  of the bug gear and the teeth  66  of the slot that the teeth do not come into contact with one another. 
       FIG. 8  shows the motion of the bug gear  70  in a crash event. The forces in a crash event bend the mounting post  76  causing the bug gear to skew relative to the arcuate slot  62 , bringing the uppermost teeth  72  on the bug gear into contact with the teeth  66  of the arcuate. The lower smooth surface  74  of the bug gear comes into in contact with the smooth concave side  68  of the slot  62 . This position of the bug gear  70  causes it to bind in the slot  62  and transfers the load on the inboard buckle  28  to the variable buckle guide  56  which is attached to the upper rail  38 . Thus, the load on the inboard buckle  28  is transferred to the upper rail  38 , and is diverted from the side member  40  of the seat. As a result, the seat and the folding links  48  do not receive the occupant load, do not distort, and do not create slack in the seat belt system, allowing the seat belt system to protect the occupant as intended. 
     In operation, the seat and the seat belt are able to be used in the normal way. The seat  54  will move fore and aft, and up and down as required by the occupant. When moving the seat fore and aft, there is no motion of the bug gear  70  in the arcuate slot  62  since the variable buckle guide  56  is attached to the upper rail  38  and moves with the seat. When moving the seat up and down, the bug gear  70  will change position in the arcuate slot  62  as the mounting post  76  moves with the seat without the teeth  72  of the gear engaging the teeth  66  of the slot. The inboard buckle  28  will move with the seat since it is attached to the side member  40  of the seat, and therefore the inboard buckle mechanism  29  maintains a constant position relative to the seat, and will remain convenient to the occupant. Since the inboard buckle moves with the seat, it can be short, between 150 and 200 mm in length, and it remains close to the occupant&#39;s body. 
     In a crash event, occupant loads are transferred from the belt  18  to the inboard buckle  28  and to the mounting post  76 . The force on the inboard buckle  28  is distributed over the upright guide plate  60  of the variable buckle guide by the load washer  80 . The upright guide plate  60  helps to prevent inward motion of the inboard buckle  28  toward the occupant, a potential source of slack in the seat belt  18 . The forces on the bug gear  70  causes it to rotate in the arcuate slot  62 , and causes the upper teeth  72  on the bug gear to lock with the teeth  66  in the arcuate slot. This transfers the load from the inboard buckle  28  to the variable buckle guide  56 , and to the upper track  38  to which the variable buckle guide  56  is attached. As a result, the load from the inboard buckle  28  is not transferred to the side member  40  of the seat, preventing local deformation of the side member and the folding links  48 . This maintains the tightness of the seat belt  18  around the occupant, minimizing injury to the occupant. 
     Having thus described a presently preferred implementation of the invention, various modifications and alterations will occur to those skilled in the art. For example, while the base portion of the variable buckle guide is shown in the illustrated embodiment as being generally perpendicular to the upright portion, arrangements can be used. The base and upright portion may be generally in-line, or at any desired angle relative to each other. Still other modifications and embodiments will be apparent from this disclosure. The scope of the invention is defined by the appended claims.