Abstract:
A collision safety structure is provided to decrease the extent of injuries exerted to occupants in vehicle accidents. The collision safety structure utilizes a diagonally positioned beam to guide buckling in a desired direction during impact and acts as an energy absorber in high speed impacts. The diagonally positioned beam directs a counterclockwise motion to the occupant to counteract a clockwise motion which typically occurs in a head on collision. By guiding the buckling effect of the seat and occupant on impact, an occupant is preserved from the crash scene eliminating lower head and thorax accelerations, thus lower perils of injuries in a cost effective and feasible way.

Description:
RELATED CASES 
   This application relates to the following provisional applications: 
   U.S. Provisional Application: 60/761,769, filed Jan. 25, 2006 
   Title: Vehicle Sub Floor Structure 
   Inventor: Elham Sahraei Esfahani 
   U.S. Provisional Application: 60/774,206, filed Feb. 17, 2006 
   Title: Vehicle Sub Floor Structure 
   Inventor: Elham Sahraei Esfahani 

   BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The present invention relates to the field of vehicle body framework structures, and, more specifically, to the field of safety structures for use in vehicle body flooring systems. 
   Motor vehicle traffic has been the leading cause of death for the 1 to 44 year-old age group in the U.S. and about 40% of serious brain injuries are due to traffic related causes. Head on collisions involving vehicles, result in passengers being thrown toward the front of the vehicle at an acceleration rate affected by the substructure of the flooring and undercarriage. Of particular interest is the structure between the front of the vehicle and the structure located under the driver&#39;s seat and the area which extends from one side of the vehicle to the other side in this area. 
   A typical subfloor frame for buses is shown in U.S. Pat. No. 4,773,701 to Messori. This is a common frame for a bus which has I-beams and cross bars. The front area includes a large bumper section and beams which make up the framework for mounting the floors, seats, walls and roof. Other types of buses, which are initially designed for disabled persons, are low-floor buses which reduce the boarding height. The main platform is a single step far from the ground, and its boarding and aligning time is 13-15% less than its competitors. These features have made low-floor buses popular as the airport or regular city service buses. 
   Prior art vehicle flooring and framework systems include crossbars and rails designed to support the passengers but fail to address impact issues. Those issues are generally addressed with bumper and fender designs. There exists a need for a vehicle frame which reduces the risk of serious injury in head on collision. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing disadvantages with prior art subfloors for use in vehicles now present in the prior art, the present invention provides an improved collision safety structure designed to reduce the risk of sever injury to an occupant or driver of the vehicle. 
   It is an object of the present invention to provide a collision safety structure in the subfloor of a vehicle under a seat assembly which will produce a counter clockwise motion to the occupant seat and to counteract the clockwise acceleration produced by the nature of frontal impact. This counteraction decreases the acceleration transmitted to the occupant body and head significantly and prevents the occupant from going through the frontal parts of vehicle like the steering wheel, the dashboard and the front window. 
   It is another object of the present invention to provide a collision safety structure in the subfloor of a vehicle under a seat assembly which will increase the deformation and energy absorption of the structure in the crash and distribute the energy not only in longitudinal direction but across the structure after a head on collision. 
   It is still another object of the present invention to provide a collision safety structure in the subfloor of a vehicle under a seat assembly which will decrease the acceleration transmitted to the occupant during a head on collision. 
   Another object of the present invention to provide a collision safety structure in the subfloor of a vehicle under a seat assembly which will decrease the acceleration transmitted to the occupant after a head on collision. 
   The present invention provides a collision safety structure in the subfloor of a vehicle under a seat assembly which will produce a counter clockwise motion to the occupant seat and to counteract the clockwise acceleration produced by the nature of frontal impact. This counteraction decreases the acceleration transmitted to the occupant body and head significantly and prevents the occupant from going through the frontal parts of vehicle. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a plan skeletal view of the prior art vehicle subfloor and framework. 
       FIG. 2  illustrates an example of cross sectional view of the prior art cab and subfloor. 
       FIG. 3  illustrates a cross sectional skeletal view of a low floor bus with the collision safety structure. 
       FIG. 4  illustrates partial skeletal view of a collision safety structure of the present invention. 
       FIG. 5  illustrates a schematic representation of a frontal collision without the collision safety structure. 
       FIG. 6  illustrates a schematic representation of a frontal end collision of the collision safety structure of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention is directed to a collision safety structure for limiting severe injury to an occupant in the cab portion of a vehicle as a result of head on impact and more specifically to means for guiding the motion of the occupant during impact of a head on collision. The application is based on published document “Reducing Occupant Injury In Frontal Crashes For a Low-Floor City Bus”, IMECE2005-83113, Proceedings of IMECE2005, 2005 ASME International Mechanical Engineering Congress and Exposition, Nov. 5-11, 2005, Orlando, Fla. USA which hereby incorporated by reference and authored by the present inventor. 
   With reference to  FIG. 1 , a prior art framework for a vehicle, such as a passenger bus, is disclosed. The framework  1  includes longitudinal beams  2 , a cab frame  3 , a cab frame substructure  4  and a cab panel  5 . As shown in  FIG. 2 , a typical cab frame substructure  4  includes a series of long beams  6  and cross beams  7  for supporting a floor  8  to which a seat  9  is mounted for the driver or occupant. Other than the beams  6 , most of the parts like the floor are made of sheet metal. The cab panel  5  and the beams  6  absorb most of the impact energy in a head on collision. Unfortunately, in the case of a severe head on collision, the prior art framework and beams under the seat  8  buckle producing a clockwise rotation of the seat throwing the occupant forward at an accelerated rate. Also the nature of the impact produces a clockwise rotation to the cab frame increasing the risk of serious injury. This common type of framework fails to provide protection for the occupant in case of a severe head on collision. 
   The present invention is illustrated in  FIGS. 3 and 4 . A vehicle framework  10  includes a body  11  with sidewalls  12 ,  13 , a front portion  14 , a rear portion  15 , a top portion  16 , a bottom portion  17 , and a cab  18 . The cab  18  is located in the front portion  14  of the vehicle  10 . Structural parts are all rectangular steel beams with different thicknesses and sizes. 
     FIG. 3  further illustrates a skeletal view of framework assembly  20  which includes a substructure  21 , a flooring assembly  22 , a roof assembly  23 , and a cab frame  24 . The substructure  21 , the flooring assembly  22  and the roof assembly  23  generally extend from the front to the rear of the vehicle  10 . The cab frame  24  is incorporated into the substructure  21  as well as the roof assembly  23 . 
   The substructure  21  includes a series of longitudinal steel beams  30  and cross beams  31  which extend from the rear to the front and from side to side inside the substructure  21  and inside the body  11  of the vehicle  10 . These are the major load carrying and energy absorbing members of the substructure. Both beams  30 ,  31  are continuous or can be discontinuous depending on the substructure of the vehicle. The beams provide support for the flooring assembly  22  which supports a floor  33 . While a detailed framework assembly is illustrated in  FIG. 3 , the present invention is applicable to any framework assembly for a vehicle. 
   Turning now to  FIG. 4 , the cab frame  24  includes floor support frame  35  which supports the floor  33  under area  36  for a driver or occupant of the vehicle  10 . Positioned inside the cab frame  24 . On the floor  33  is a seat assembly  40  which includes a seat  41  which is typically mounted to the floor  33  by welding or mechanical fasteners. In some instances, cross beams  31  are mounted in the substructure under the floor  33  in the cab  18 . The substructure  21  under the floor  33  inside the cab assembly  24  includes a subfloor  42  which supports the area under the floor  33  inside the cab assembly. The subfloor  42  extends to the front portion  14  of the vehicle  10  and plays a major role in absorbing impact from any type of collision to the front of the vehicle due to the make up of one or more longitudinal beams  30  and cross beams  31  located inside subfloor  42 . 
   Attached inside the subfloor  42  is a guide means  50  for guiding buckling of the floor under the seat and movement of the occupant during head on impact. The guide means  50  utilizes a diagonally positioned beam  51  located inside the subfloor  42  of the cab assembly  24  to guide the buckling of the floor under seat assembly  40  and movement of the driver of the vehicle during impact from a head on collision. The diagonally positioned beam  51  has a proximal end  52  and a distal end  53 . The distal end  53  is mounted on one or more of the longitudinally extending beams  30  near cross beams  31 . The proximal end  52  is mounted under the seat  41  to the floor  33 . (In addition to this application, the diagonally positioned beams like  51  may extend the width of the framework assembly  11  or may extend widthwise the length of the seat assembly  40  to absorb energy. Alternatively, the diagonally positioned beams like  51  may extend laterally across the subfloor  42  at any distance less than the width of the body  11 ). Of critical importance is location of the proximal end  52  directly under central area  54  of the seat assembly  40 . The guiding means has 2 advantages, first absorb crash energy and reduce acceleration in exchange of increasing deformation, second the special place described produces a counter clockwise motion to the occupant seat and counteracts the clockwise acceleration produced by the nature of a head on collision. 
   The operation and the calculations for the guide means  50  will now be described in detail. Prior art assemblies typically provided the structure as shown in  FIGS. 1 and 2  with a seat  9  is located on the floor  8 . If there is an occupant restrained with a three point belt to the seat located in the vehicle, and the vehicle experiences a frontal crash, impact of such a crash will produce a frontward movement and a clockwise rotation of the occupant relative to its seat. 
   Upon severe head on collision, the frontal impact is strong enough to make the beam under the driver&#39;s seat buckle. Provided that cross section height of the beam is less than its width, the structure under the driver&#39;s seat  8  would buckle downward. If the beam under the driver&#39;s seat buckles downward, the seat and accordingly the driver on the seat  9  experience another clockwise rotation. This clockwise rotation in addition to initial rotation due to nature of frontal crash produces a severe rotation of the occupant toward frontal parts of the vehicle. 
   In accordance with the construction of the present invention, a guide means  50  in the form of a diagonal beam  51  beside a cross beam  31  is positioned under seat assembly  40  as described above. The guide means  50  provides a structure to produce the desired motion for the occupant seat  41  and makes the occupant move away from the crash scene by guiding the direction of buckling upward. The placement of centrally positioning the proximal end  52  of the diagonally positioned beam  51  under the seat  41  and the placement of the distal end  53  of the diagonally positioned beam  51  are critical to produce the desired mode of buckling. 
   Placement of diagonal beam  51  under the driver seat  41  cause the seat and driver to buckle upward as shown in  FIG. 6 , the seat  41  and accordingly the occupant experience a counter clockwise rotation due to the location of the diagonally positioned beam. This counter clockwise rotation encounters the initial rotation due to nature of frontal crashes and prevents the occupant from moving toward the frontal parts of the vehicle such as the front windows and the dashboard. While the application shown in the drawings depicts a bus, the collision safety structure of the present invention is applicable to SUVs, vans, trucks and train subfloor structures, and even passenger cars. 
   Location of the diagonal beam has two advantages. First, the diagonally positioned beam  51  increase the deformation and energy absorption of the structure in the crash and distribute the energy not only in longitudinal direction but across the structure. With more energy absorption, this structure will decrease the acceleration transmitted to the occupant. The second advantage of this invention is related to the place it is used, under the driver seat, and guiding the buckling of the beam in the way that produces a counter clockwise motion to the occupant seat and to counteract the clockwise acceleration produced by the nature of frontal impact. This counteraction decreases the acceleration transmitted to the occupant body and head significantly and prevents the occupant from going through the frontal parts of vehicle like the steering wheel, the dashboard and the front window. While a diagonal beam  51  is shown in the drawings, the guiding means could be a series of one or more diagonally positioned beams or a diagonally positioned plate made of steel. 
   These two effects of such a structure are examined in finite element models in the publication “Reducing Occupant Injury in Frontal Crashes for a Low-Floor City Bus”, IMECE2005-83113, Proceedings of IMECE2005, 2005 ASME International Mechanical Engineering Congress and Exposition, Nov. 5-11, 2005, Orlando, Fla. USA which hereby incorporated by reference and authored by the present inventor.  FIGS. 5 and 6  illustrate the time and effect of frontal impact with and without the collision safety structure installed in the subfloor.  FIG. 5  illustrates a three point restrained occupant in a frontal crash. The results of the impact gives the occupant two clockwise rotations as illustrated in the schematic. Using a diagonally positioned beam, as illustrated in the schematic in  FIG. 6 , the buckling is guided upward in a way that the seat is rotated counterclockwise. This motion counteracts the clockwise rotation of the occupant and therefore, reduces the overall acceleration of the occupant and therefore the risk of injury.  FIGS. 5 and 6  illustrate function of the invented structure in finite element model of a bus. The model includes the bus, a hybrid III dummy as its occupant restrained with a three point belt to its seat, and the complete model is positioned in frontal crash situation according to FMVSS 208 test. Results for the initial model with out this invention and the modified model including the invention are compared, simulated in a frontal crash of 30 mph according to FMVSS 208. As illustrated, each model discloses the results of the vehicles as they meet in a head on collision. All specifications of these two models are the same except than the invente collision safety structure is used in the second model. Results show that the second model has much more deformations than the first model and reduction in acceleration caused by the diagonal beam. This reduction in acceleration is the first advantage of using the invented structure. 
   The second advantage of using this invention is the upward buckling of the seat assembly. The results disclose how the diagonal beam is changing shape of buckling and guiding the buckling of beam under driver seat to second mode of buckling and the beam has buckled in the way that produces a counter clockwise rotation for the occupant seat. Accelerations of head and thorax are substantially reduced and severe injury is diminished. This is an example of using this invention in frontal position and for a bus, but this invention can be used for other directions as well and for other kinds of vehicles. With use of different lengths for the diagonal beam and attaching the point in different places produces different modes of buckling and creates different kinds of motions. The overall structure may be used for rear end or side crashes as well by applying the structure in the desired direction and configuration. Also it is not limited to motor vehicle crashes, anywhere else it could be used to control crash effects. This is very hard to produce any kind of utility to act in a fraction of second as in crashes. This invention is advantageous in crash scenarios because it controls buckling which is an immediate and impulsive phenomenon, and the nature of this phenomenon is capable of encountering nature of crashes.