Patent Publication Number: US-6991286-B2

Title: Retractor location for seat with integrated restraints for a mobile vehicle

Description:
This patent issued from a non-provisional patent application claiming the priority of provisional patent applications Ser. Nos. 60/548,030, filed Feb. 26, 2004, and 60/548,080, filed Feb. 26, 2004. 

   BACKGROUND 
   Automotive vehicles have had three point seat belt systems that combine a lap belt and an upper torso belt for some time now. The tongue may be swung across the person and engaged with a buckle affixed to the seat thereby positioning one portion of the belt across the lap and another portion of the belt across the upper torso. 
   Designers of school buses face a conundrum in including three point seat belts in buses in that the requirements involved with installing a three-point seat belt may act in conflict with the requirements for passive restraints. The U.S. federal government requirement for passive restraints requires that the rear side of the seat provide an impact barrier in which the seat back bends or deforms when subjected to the force of occupants impacting the rear side in a deceleration event. The National Highway Traffic Safety Administration, DOT (NHTSA), sets the federal requirements for these passive restraints. These are codified as 49 C.F.R. Section 571.222 (FMVSS 222). 
   The code specifies a passive restraint system, and does not require any sort of active restraints such as a two-point passenger restraining lap belt or a three-point passenger restraining lap belt and torso harness combination. The passive restraint requirement effectively provides a compartment in which an unbuckled passenger is constrained during a rapid deceleration of the bus. Although two point belt systems are offered on buses, designers need to consider three-point seat belts where there is a request for them through local, state, or transportation/parental action groups. Three point seat belt designs are also regulated under NHTSA code. These requirements relate to belts that are mounted in such a fashion that they inhibit a belted passengers forward movement. This three-point belt-mounting requirement is codified in 49 C.F.R. Sections 571.209 and 571.210 (FMVSS 209 and FMVSS 210). 
   The design conundrum results from the fact that tests have shown that in a rapid deceleration where the passenger in the front seat is buckled and the passenger in the rear seat is not, the initial action is that the buckled passenger moves forward applying tension on the buckled seat belt and the component the belt is affixed to. This results in a pulling of the fixture component in a forward direction thereby reducing the strength on the rear impact face for the unbuckled passenger behind the seat in question. Following the tension applied on the three-point belt, the rear passenger would be expected to contact the seat back. The reduction in seat back strength due to the pull on the three-point seat belt for FMVSS 210 requirement may reduce the ability of the seat back to meet the FMVSS 222 requirements. Recent school bus seat designs have been developed that involve a movable inner seat for the mounting of the three point seat belts and an immovable seat back portion for the absorption of the rear unbuckled passenger loads. The movable inner seat was inserted into a recess within the immovable seat back. The immovable seat back would be designed to deform in order to comply with FMVSS 222. One of these designs was disclosed in U.S. Pat. Nos. 6,123,388, and 6,485,098. The concept of a seat inserted within a seat was not new to this bus seat. That concept was disclosed in U.S. Pat. No. 4,784,352. One problem with this prior art was the complexity of the mechanism to stop the movable inner seat. 
   SUMMARY 
   The invention involves shifting the location of the seat belt retractor in order to reduce the thickness of the seat especially in the lower regions for a mobile vehicle seat. The seat may be used for a mobile vehicle as a school bus as well as for automotive applications. The seat belt retractors are attached to a portion of the seat structure that allows the webbing to exit the retractor on the front surface of the seat back. The webbing is then allowed to cross over to the rear surface of the seat back as it rises to the turning-loop. The retractor may be located forward of the seat back pivot point on the seat frame in order to allow for the webbing to exit on the front surface of the seat back. 

   
     DRAWINGS 
     Other objects and advantages of the invention will become more apparent upon perusal of the detailed description thereof and upon inspection of the drawings, in which: 
       FIG. 1  is a cutaway view of a vehicle using an embodiment of the seat sub-system made in accordance with this invention. 
       FIG. 2  is a perspective view of the seat sub-system without showing foam padding for use with the vehicle shown in  FIG. 1 . 
       FIG. 3  is a side view of the seat sub-system of  FIG. 2  showing foam padding. 
   

   DESCRIPTION OF INVENTION 
   A motor vehicle  101  includes a passenger carrying body  102 . The vehicle  101  may be a school bus. The body  102  includes a mounting floor  103  for the mounting and placement of passenger seating. The vehicle  101  shown in  FIG. 1  has a series of passenger seats  119   a ,  119   b ,  119   c , and  119   d  installed on the mounting floor  103  of the vehicle body  102  arranged from the front of the vehicle to the back. A rearward passenger  201  may sit in seat  119   c  and a frontward passenger  202  may sit in seat  119   b  in front of rearward passenger  201 . One passenger seat with integrated passenger restraints  119  made in accordance with the invention has a movable front frame  132  that a seat occupant rests his or her back against normally. The front frame  132  is mounted to a seat frame  120  as shown in  FIG. 2 . The front frame  132  is the mounting point for the upper portion of a three-point seat belt  142 . The seat frame  120  is mountable to the bus body  102  mounting surface  103 . The seat frame  120  contains a rear frame  131  to protect a passenger of rearward seat from moving out of his safety zone in a forward direction in the event of a rapid deceleration. This is shown in  FIG. 1  that shows a rapid deceleration condition. The passenger  202  in seat  119   b  is buckled to the seat. The passenger  201  in the rearward seat  119   c  is not buckled. The passenger  201  is contained within the area between the rear frame of seat  119   b  and the front of seat  119   c.    
   The vehicle may have a two-piece seat capable of complying with the federal requirements with reduced complexity. The front frame  132  is movable relative to the seat frame  120 . In the embodiment shown in  FIG. 3 , the front frame  132  is rotatable about the seat frame  120  about a shaft or pivoting mechanism  133  that is at least partially engaged to the seat frame  120 . The movable frame  132  is not shown in  FIG. 2 . The movable front frame  132  normally roughly parallel and in contact with the immovable rear frame  131 . The movable front frame  132  may move forward due to the pull of a passenger held in a seat with belt  142 . The force of the passenger on the belt  142  may pull the movable seat back  132  forward. The movement of the movable or front seat back  132  away from the rear frame  131  leaves the rear frame  131  intact to absorb the force from an unbelted passenger in the seat behind seat  119   b.    
   The rear frame  131  is comprised of three main components: a rear or back frame seat structure  150 ; an energy absorbing back pan  160 ; and variable thickness foam  170 . The rear frame seat structure  150  may be one integral piece of tubing bent or formed. The back pan  160  may be steel, however, in any case it will be of a flexible material allowing for energy absorption. The back pan  160  is engaged to the rear frame structure  150  on three of its four edges. There is a back pan lower edge  164  that is free moving or unengaged to the rear frame structure  150 . The fact that the back pan  160  is only rigidly mounted on 3 edges allows for the lower edge  164  of the back pan  160  to flex in the fore-aft direction. The lower edge  164  of the back pan  160  may be unformed or not folded over or hemmed to allow for enhanced energy absorbing flexibility in the event of impact upon the rearward side of the rear frame  131  by an unbuckled passenger sitting in a seat behind seat  119 . See  FIG. 2 . 
   The back pan  160  may be covered by foam  170  as shown in  FIG. 3 . The foam  170  includes a rear upper foam zone  171  and a rear lower or knee impact zone  172 . The knee impact zone  172  has a foam thickness B while the upper foam zone has a foam thickness A. Foam thickness A is greater than foam thickness B due to the lower back pan  160  flexibility. In one embodiment, the ratio of foam thickness A to B is three to one (3:1). The foam thickness B of the knee impact zone  172  may be as thin as one half inch (0.5″). 
   The three to one ratio of the lower to upper portion for the foam is important in achieving seat thinness. When seat spacing is measured at the h-point or cushion level, the knee protection zone is thinner than conventional seats and allows for a greater number of seats to be placed into a school bus. Utilizing a flexible steel back pan  160  combined with foam  170  in the proper ratios to absorb energy in the knee protection zone through the upper portion achieves the invention. 
   The invention involves shifting the location of a seat belt retractor  141  engaged to the seat frame  120  in order to reduce the thickness of the seat especially in the lower regions for a mobile vehicle seat. The seat  119  may be used for a mobile vehicle as a school bus as well as for automotive applications. The seat belt retractors  141  are attached to a portion of the seat structure that allows the webbing  140  to exit the retractor  141  on a front surface  136  of the movable front frame  132 . The webbing  140  is then allowed to cross over to the rear surface  137  of the front frame  132  as it rises to a turning-loop  138 . This cross over by the seat belt webbing  140  from the front surface  136  to the rear surface  137  of the front frame  132  may be through a front frame web slot  139  cut to allow passage of the webbing without either impeding webbing  140  movement or front frame  132  integrity. This is accomplished by providing the front frame slot  139  in a rectangular shape larger than the cutaway cross-section of the webbing  140 . The retractor  141  may be located forward of the seat back pivot point  133  on the seat frame  120  in order to allow for the webbing  140  to exit on the front surface  136  of the front frame seat back  132  as shown in  FIG. 3 . See  FIGS. 2 and 3  for illustration of this paragraph. The location of the retractor  141  allows the foam  170  to be thinner at the knee impact zone  172 . 
   As described above, the seat belt retractor and seat system of this invention and vehicle made with the seat system provide a number of advantages, some of which have been described above and others of which are inherent in the invention. Also modifications may be proposed to the seat belt retractor and seat system and vehicle made with the seat system of this invention without departing from the teachings herein.