Abstract:
A vehicle seat having a back portion bent or deformed forwardly when impacted from the rear by a passenger. A horizontally movable seat platform is slidably mounted to the seat frame and has lap belts secured thereto. The seat platform is normally held in an aft position by fastening devices which break under forward passenger force applied through the lap belts to the movable platform during a crash. The movable platform includes a plurality of sleeves affixed thereto which are slidably mounted to the main frame of the seat.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of vehicle restraint systems including belts for securing an occupant to a seat. 
     DESCRIPTION OF THE PRIOR ART 
     School bus passenger seats usually do not employ active restraint safety devices, but instead rely on a passive restraint seat design. School bus passenger seats are built to specifications conforming to the safety standards set by the National Highway Traffic Safety Administration, DOT. These are codified as 49 C.F.R. Ch.V, § 571.222, Standard No. 222, and require that the seat back bend or deflect forward when a force is applied to the rear of the seat back. The code further specifies that 4000W inch-pounds of energy must be absorbed within a maximum forward deflection of the seat back of 14 inches and 2800W inch-pounds be absorbed within a maximum rearward deflection of the seat back of 10 inches where W represents the number of seating positions for which the seat is designed. 49 C.F.R., Ch.V, § 571.222, S5.1.3-5.1.4. 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. Children riding the school bus are protected in head-on collisions by the seat back in front of them deflecting forward and absorbing some of their forward momentum. 
     Vehicles with deforming or deflecting seats provide special problems regarding the integration of active restraint seat belt systems. Passive restraint systems are designed to protect a passenger who has been thrown forward by having the impacted seat back deflect upon impact of the thrown passenger and absorb some of their momentum. In a school bus seat combining active and passive restraint systems, both of the restraint systems have to be able to perform their functions and the seat must still conform to the regulations set forth in 49 C.F.R. 
     In order to combine a deforming or deflecting seat with a seatbelt, we have mounted the belt to a portion of the seat which slides forward upon crash and away from the forwardly deforming seat back. Thus, the seat conforms with the aforementioned deflecting requirements but in addition includes a belt for securing the occupant to the seat. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention is a seat mountable in a vehicle including a main frame mountable to the vehicle. The main frame has a seat frame and a back frame connected together. A vehicle seat is movably mounted to the seat frame and has a normal aft position on the seat frame and a forward position on the seat frame. The vehicle seat when occupied is movable from the normal aft position to the forward position only during crash. A lap belt is mounted to the vehicle seat and is movable therewith. The back frame remains generally upright and stationary during crash unless impacted behind by a passenger. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side perspective view of a pair of seats arranged in a row incorporating the present invention. 
     FIG. 2 is a front perspective view of one of the seats of FIG.  1 . 
     FIG. 3 is a side perspective view of one of the seats of FIG. 1 only with a portion of the seat and belt moved to the most forward position during crash. 
     FIG. 4 is an enlarged, fragmentary cross sectional view taken along the line  4 — 4  of FIG.  2  and viewed in the direction of the arrows. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Referring now more particularly to FIG. 1, there is shown a pair of identical bench style seats  20  and  21  typically used in a school bus. Each seat is sized to receive multiple occupants with a separate lap belt provided for each occupant. The seats have a tubular construction with the back of the seat being forwardly deformable or deflectable upon rear impact by a passenger located behind the seat back. The seat portion of the vehicle seat extends generally horizontally and is constructed to slide forward with the lap belts securing the occupants thereto during crash and as the seat back deforms forwardly. 
     Seat  21  will now be described it being understood that an identical description applies to seat  20 . The exact construction of seat  21  may vary; however, in the embodiment shown in FIGS. 2 and 3, the chair includes a main frame  22  forming a back portion  23  and a seat portion  24 . The main frame has a tube  25  including opposite and downwardly extending tubular portions  27  and  28  extending from the top  26  of the chair to the bottom  29  of the back  23 . Tube  25  has a pair of forwardly extending tubular portions  30  and  31  located on the opposite sides of the seat portion of the chair with the opposite ends of portions  30  and  31  joined at location  32  at the center and front end of the seat. 
     A pair of left legs  33  and  34  and a pair of right legs  35  and  36  extend downwardly from the frame and are secured to the vehicle floor. The top ends of legs  33  and  34  are joined to a horizontally extending tubular portion  37 , in turn, secured to tubular portion  30  of tube  25 . Likewise, the top ends of legs  35  and  36  are joined to the opposite end portions of a horizontally extending tubular portion secured to tubular portion  31 . 
     A diagonal brace  38  has a bottom end fixed to the bottom portion of leg  34  and a top end  39  secured to downwardly extending portion  27  of tube  25 . A similar diagonal brace  40  has a bottom end fixed to the bottom portion of leg  36  and the top end secured to portion  28  of tube  25 . 
     A web  41  is secured to the top  26  and portions  27  and  28  of tube  25  forming the seat back portion of the seat. The entire seat back portion is enclosed within suitable upholstery. 
     The seat portion of the vehicle seat includes, in addition to portions  30  and  31  of tube  25 , a cross member  41  (FIG. 3) having opposite ends joined to diagonal braces  38  and  40  or portions  30  and  31  of tube  25 . A pair of stationary members  42  and  43  have first ends fixed to cross member  41  and opposite ends fixed to the opposite end portions  44  and  45  of tube  25 . 
     Movable frame  46  is slidably mounted to stationary members  42  and  43 . Frame  46  includes side tubular portions  48  and  49  having front-end portions joined to cross member  50  and aft end portions joined to cross member  51 . Two interior tubular members  52  and  53  extend between and are joined to cross members  50  and  51 . Fixedly mounted to and depending from tubular portions  52  and  53  are respectively sleeves  54  and  55  through which respectively stationary members  43  and  42  extend. Sleeves  54  and  55  are freely slidable upon members  43  and  42  allowing movable frame  46  to slide from the rearward or aft position depicted in FIG. 2 to the most forward position depicted FIG.  3 . 
     In the embodiment of the seat depicted in FIG. 2, the seat is sufficiently wide to hold three occupants. Thus, three lap belts have their proximal ends attached to cross member  51  with the distal ends having mating tongue and buckle combinations. For example, belts  61  and  63  have their proximal ends  62  secured to member  51  with the outer or distal ends having respectively a buckle and mating tongue. Thus, the lap belts move with the occupant as the movable frame  46  slides from the aft position of FIG. 2 to the forward position of FIG.  3 . 
     Sleeves  54  and  55  are slidably mounted to tubes  43  and  42  but include fastening means for securing the sleeves and movable platform in the most aft position as depicted in FIG.  2 . The fastening means may include conventional fasteners, such as, rivets or shear pins. In the embodiment depicted in FIG. 4, rivet  60  has a shank extending through the adjacent side walls of sleeve  55  and tube  42  with the opposite headed ends of the rivet being positioned within tube  42  and external to sleeve  55 . Sleeve  55  and platform  46  are normally held in the aft position by rivet  60 . Upon crash, forward force may be applied by the occupant to the lap belts urging movable frame  46  forwardly while the main frame of the seat remains fixed to the vehicle floor. Upon application of sufficient force, rivet  60  shears allowing the movable frame  46  with occupant to move to the most forward position as depicted in FIG.  3 . Simultaneously, a passenger sitting on seat  20  behind seat  21  may impact on back frame  22  bending the frame forwardly to be in accordance with the aforementioned regulations. A similar rivet secures sleeve  54  to tube  43  and is shearable in the same fashion as rivet  60 . 
     A suitable upholstery material is provided on movable frame  46  and seat frame  24 . Further, a planar member, such as a wooden sheet may be attached to movable frame  46  and positioned immediately therebeneath to provide a smooth surface to slide atop portions  44  and  45  of tube  25 . 
     Many advantages of the present invention are provided over the prior art. For example, the seats designed in accordance with the aforementioned federal regulations provide a protective envelope in the event of a crash with the occupant striking the cushion back surface of the seat in front of the occupant. By the addition of the seat belts and the movable seat frame, the occupants on the movable frame are further restrained. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.