Abstract:
The force and energy associated with a collision of a land vehicle is absorbed by a multiple stage system which includes a first stage associated with low impact collisions and a second stage that is associated with high impact collisions. The first stage includes a spring system located in the bumpers of the vehicle and the second stage includes springs and fluid shock absorbers and is located beneath the chassis of the vehicle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the general art of land vehicles and to the particular field of collision impact absorption. 
     2. Discussion of the Related Art 
     The death and injury toll associated with automobile collisions in the United States, and around the world, is frightening. Deaths associated with automobile accidents in the United States alone exceeds fifty thousand per year. 
     While automobiles are safer each year and safety is improved with each new model, there is always room for further improvements in the area of automobile safety, especially collision force and energy absorption. 
     Therefore, there is a need for a system for absorbing force and energy associated with a collision of a land vehicle. 
     While many automobiles have special designs for absorbing the force and energy associated with a collision, such as special crumple zones, and the like, these designs generally are directed to protecting the occupants of the vehicle from high impact collisions. Of course, high impact collision protection is important; however, much damage can be done to the vehicle and/or the occupants of the vehicle in low impact collisions as well. Again, many automobiles have systems for protecting the vehicle and/or the occupants from low impact collisions. An example of this type of system is the simple vehicle bumper. However, even when such bumper systems are combined with crumple zones and the like, there is still much room for improvement in the protection of vehicle occupants from the energy and force associated with vehicle collisions. 
     Therefore, there is a need for a system for absorbing force and energy associated with a collision of a land vehicle which includes a plurality of stages. Still further, there is a need for a system for absorbing force and energy associated with a collision of a land vehicle which includes a plurality of stages including a low impact stage and a high impact stage. 
     PRINCIPAL OBJECTS OF THE INVENTION 
     It is a main object of the present invention to provide a system for absorbing force and energy associated with a collision of a land vehicle. 
     It is another object of the present invention to provide a system for absorbing force and energy associated with a collision of a land vehicle which includes a plurality of stages. 
     It is another object of the present invention to provide a system for absorbing force and energy associated with a collision of a land vehicle which includes a first stage associated with low impact collisions. 
     It is another object of the present invention to provide a system for absorbing force and energy associated with a collision of a land vehicle which includes a stage associated with high impact collisions. 
     SUMMARY OF THE INVENTION 
     These, and other, objects are achieved by a system for absorbing force and energy associated with a collision of a land vehicle which comprises a first stage absorbing system which includes a plurality of spring units in a bumper of a land vehicle, each spring unit including a compression spring and a rod, and a one-way mechanism on the rod which permits the rod to move one way against the force of the compression spring and which includes locks that prevent the rod from moving in an opposite direction under force exerted thereon by the compression spring; and a second stage absorbing system which includes a plurality of shafts extending in a length direction of the land vehicle, a stationary mounting bracket fixed to the land vehicle and which slidably accommodates two shafts with the shafts being offset from each other, a movable spring mounting bracket slidably mounted on each shaft, a fixed spring mounting bracket fixedly mounted on each shaft, a first compression spring having one end thereof mounted on the stationary mounting bracket and a second end thereof mounted on the movable mounting bracket on each shaft, a second compression spring having one end thereof mounted on the fixed spring mounting bracket of each shaft and a second end thereof mounted on the movable spring mounting bracket on each shaft, the first compression spring being aligned with the second compression spring on each shaft, a first hydraulic spring unit having one end thereof mounted on the stationary mounting bracket and a second end thereof mounted on the movable mounting bracket on each shaft, a second hydraulic spring unit having one end thereof mounted on the fixed spring mounting bracket on each shaft and a second end thereof mounted on the movable spring mounting bracket on each shaft, and the first compression spring of one shaft mounted on the stationary mounting bracket being aligned with the first hydraulic spring unit of a second shaft mounted on the stationary mounting bracket. 
     The first stage accommodates low force and/or energy collisions while the second stage accommodates high force and/or energy collisions. The lock on the compression springs of the first stage.prevents the springs from releasing the energy stored therein during the energy absorption of the first stage. The second stage uses the energy absorbing capabilities of the first stage and thus is able to accommodate even higher energies. Thus, a vehicle is protected for both low energy impact as well as high energy impact. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1 is a perspective view of a land vehicle which incorporates the crash force and energy absorbing system embodying the present invention. 
     FIG. 2 is a perspective view of a bumper that includes a first stage of the multiple stage crash force and energy absorbing system embodying the present invention. 
     FIG. 3 is a schematic illustrating the second stage of the multiple stage crash force and energy absorbing system embodying the present invention. 
     FIG. 4 is a perspective view of the multiple stage crash force and energy absorbing system embodying the present invention. 
     FIG. 5 is an enlarged top plan view of the area identified as Detail A in FIG.  4 . 
     FIG. 6 is a perspective view of the area identified as Detail B in FIG.  4 . 
     FIG. 7 is an enlarged schematic view of a shock absorber used in the second stage of the multiple stage crash force and energy system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description and the accompanying drawings. 
     Shown in the FIG. 1 is a land vehicle L, such as an automobile, that will incorporate the force and energy absorbing system of the present invention. Land vehicle L includes a front bumper FB and rear bumper RB. A first stage of the system embodying the present invention is incorporated in the bumpers as indicated in FIG. 2, and a second stage of the system of the present invention is located beneath the chassis of the vehicle as indicated in FIG.  4 . The second stage is shown schematically in FIG. 3 where it can be seen that the second stage of the system works in co-operation with the first stage system and has elements that move toward and away from the bumpers during the force and energy absorbing operation. Thus, the first stage includes movement of the bumpers and the second stage includes movement of the elements shown in FIG.  3 . The stages will be discussed in greater detail below. 
     Referring to FIGS. 4-6, it can be understood that the present invention is embodied in a system  10  for absorbing force and energy associated with a collision of a land vehicle. 
     As mentioned above, system  10  includes a first stage force and energy absorbing system  12  which is shown in FIGS. 4 and 5 and includes two bumpers FB and RB on land vehicle L. Each of the bumpers includes a first wall  14  and a second wall  16  spaced apart from the first wall  14  in a length direction  18  of land vehicle L on which the two bumpers are mounted. A gap  20  is defined between the first wall  14  and the second wall  16 , and each of the bumpers extends across a width dimension W of the land vehicle on which they are mounted. Each bumper has a first end  22  located on one side of the land vehicle and a second end  24  located on another side of the land vehicle. Each of the bumpers has a length dimension LB which extends between the first end  22  of the bumper and the second end  24  of the bumper. 
     A plurality of joints, such as joint  25 , are located in the first wall of each of the bumpers. Each joint  25  permits the bumper wall to flex as necessary to absorb force and energy as will be understood from the teaching of this disclosure. Each joint  25  includes a hinge  26  in the first wall  14  of the bumper, a first compression spring  28  located adjacent to the hinge  26  and fixed to the first wall  14  at one end  30  thereof and fixed to the second wall  16  at a second end  32  thereof. A second compression spring  34  is located adjacent to the hinge  26  and is fixed to the first wall  14  at one end  38  thereof and is fixed to the second wall  16  at a second end  40  thereof. Hinge  26  is interposed between the first spring  28  and the second spring  34 . The joints  25  of the plurality of joints are spaced apart from each other in the direction of the length dimension  18  of the bumper, and one joint  25 ′ is located adjacent to the first end  22  of each bumper and a second joint  25 ″ is located adjacent to the second end  24  of each bumper. 
     The first force and energy absorbing system  12  further includes a plurality of energy absorbers, such as energy absorber  41 , on each bumper. The energy absorbers  41  are spaced apart from each other in the direction of the length dimension  18  of each bumper, with one energy absorber  41 ′ located adjacent to the first end  22  of each bumper and a second energy absorber  41 ″ located adjacent to the second end  24  of each bumper. Like the joints  25 , the energy absorbers  41  are identical to each other. Thus, only one energy absorber  41  will be described. Each energy absorber  41  includes a hole  42  defined through the second wall  16  of the bumper associated therewith, a first pivot pin  44  located adjacent to the hole  42  and having one end  46  fixed to the second wall  16  of the bumper associated therewith adjacent to the hole  42  and a second end  48  located in gap  20 . A second pivot pin  50  is located adjacent to the hole  42  and has one end  52  fixed to the second wall  16  of the bumper associated therewith adjacent to the hole  42  and a second end  54  located in gap  20 . Hole  42  is interposed between the first pivot pin  44  and the second pivot pin  50 . 
     Each energy absorber  41  of the first system  12  further includes a cylindrical rod  60  extending through hole  42 . Rod  60  has a first end  62  located adjacent to first wall  14  and a second end  66  located adjacent to second wall  16  of the bumper associated therewith. A head  68  is located on first end  62  of rod  60  and is located to abut first wall  14  during operation of the energy absorber  41 . Rod  60  includes a length dimension  60 L which extends between the first end  62  of the rod  60  and the second end  66  of the rod  60 , and a blind-ended bore  70  is defined along the length dimension  60 L of the rod  60  from the second end  66  of the rod  60  towards the first end  62  of the rod  60 . A first triangular foot  72  is located on the second end  66  of the rod  60 . First triangular foot  72  includes a base  74  on the rod  60 , an apex  76  spaced apart from the rod  60 , and a leg  78  connects the base  74  of the first triangular foot  72  to the apex  76  of the first triangular foot  72 . Leg  78  of the first triangular foot  72  extends radially outward from the rod  60 , and a hypotenuse  80  connects base  74  of the first triangular foot  72  and apex  76  of the first triangular foot  72 . Leg  78  of the first triangular foot  72  is interposed between the hypotenuse  80  of the first triangular foot  72  and second wall  16  of the bumper associated therewith. 
     A second triangular foot  90  is located on the second end  66  of the rod  60 . The second triangular foot  90  is a mirror image of the first triangular foot  72  and includes a base  92  on the rod  60 , an apex  94  spaced apart from the rod  60 , a leg  96  connecting base  92  of the second triangular foot  90  to apex  94  of the second triangular foot  90 . Leg  96  of the second triangular foot  90  extends radially outward from the rod  60  and is diametrically opposed to leg  78  of the first triangular foot  72 . A hypotenuse  98  connects the base  92  of the second triangular foot  90  and the apex  94  of the second triangular foot  90 . Leg  96  of the second triangular foot  90  is interposed between the hypotenuse  98  of the second triangular foot  90  and second wall  16  of the bumper associated therewith. 
     A lever arm  100  is interposed between first triangular foot  72  and second triangular foot  90 . Lever arm  100  includes a head  102  in contact with the base of the first triangular foot and also in contact with the base  92  of the second triangular foot  90 . A body  104  extends from the head  102  of the lever arm  100  in the direction of the length dimension  60 L of the rod  60 . The lever arm  100  is fixed to the triangular feet  72 ,  90  to keep them spaced apart as shown in FIG.  5 . 
     The head  68  is located on the rod and is fixed to the rod  60  for movement therewith. Head  68  is located adjacent to the first wall  14  of the bumper associated therewith. 
     Energy absorber  41  further includes a conical housing  110 . Housing  110  includes a skirt section  112  and an apex section  114 . Apex section  114  includes a hollow cylindrical portion  116  which is fixed to the rod  60  to move therewith. The skirt section  112  of the conical housing  110  contacts second end  48  of the first pivot pin  44  and contacts second end  54  of the second pivot pin  50 . A first compression spring  120  connects a first end  122  of the skirt section  112  of the conical housing  110  to the second wall  16  of the bumper associated therewith and a second compression spring  126  connects the first end  122  of the skirt section  112  of the conical housing  110  to the second wall  16  of the bumper associated therewith. Second compression spring  126  is spaced apart from first compression spring  120 . 
     A first ratchet rack  130  is mounted on the second wall  16  of a bumper associated therewith adjacent to hole  42  and extends in the direction of the length dimension  60 L of rod  60  which extends through hole  42  and extends away from second wall  16  and away from gap  20  defined between the first wall  14  of the bumper associated therewith and the second wall  16  of the bumper associated therewith. First ratchet rack  130  includes a body  132  having a first end  134  mounted on second wall  16  and a second end  136  spaced apart from the first end  134  of the first ratchet rack  130 . A plurality of triangular teeth  140  are located on the first ratchet rack  130  and are spaced apart from each other in the direction of the length dimension  60 L of rod  60 . The triangular teeth  140  are identical with each other and each triangular tooth of the plurality of triangular teeth  140  includes a base  142  on the body  132  of the first ratchet rack  130 , an apex  144  spaced apart from the body  132  of the first ratchet rack  130 , a leg  146  extending from the base  142  of the triangular tooth  140  to the apex  144  of the triangular tooth  140  and a hypotenuse  148  extending from the apex  144  of the triangular tooth  140  to the base  142  of the triangular tooth  140 . Hypotenuse  148  is interposed between leg  146  of the triangular tooth  140  and second wall  16  of the bumper associated therewith. 
     A second ratchet rack  150  is a mirror image of the first ratchet rack  130  and is mounted on second wall  16  of a bumper associated therewith adjacent to hole  42  defined through the second wall  16  of the bumper associated therewith. Rack  150  extends in the direction of the length dimension  60 L of the rod  60  extending through hole  42  and extends away from the second wall  16  of the bumper associated therewith and away from gap  20 . Second ratchet rack  150  is spaced apart from the first ratchet rack  130  with hole  42  interposed between the first ratchet rack  130  and the second ratchet rack  150 . Second ratchet rack  150  includes a body  152  having a first end  154  mounted on the second wall  16  of the bumper associated therewith and a second end  156  spaced apart from the first end  154  of the second ratchet rack  150 . A plurality of triangular teeth  160  are identical to each other and are spaced apart from each other in the direction of the length dimension  60 L of the rod  60  extending through the hole  42 . Each triangular tooth of the plurality of triangular teeth  160  of the second ratchet rack  150  includes a base  162  on the body  152  of the second ratchet rack  150 , an apex  164  spaced apart from the body  152  of the second ratchet rack  150 , a leg  166  extending from the base  162  of the triangular tooth  160  of the second ratchet rack  150  to the apex  164  of the triangular tooth  160  of the second ratchet rack  150  and a hypotenuse  168  which extends from the apex  164  of the triangular tooth  160  of the second ratchet rack  150  to the base  162  of the triangular tooth  160  of the second ratchet rack  150 . Hypotenuse  168  is interposed between leg  166  of the triangular tooth  160  of the second ratchet rack  150  and the second wall  16  of the bumper associated therewith. 
     Rod  60  is movable between a first position with the first wall  14  of the bumper associated therewith being located at a first distance from the second wall  16  of the bumper associated therewith and a second position with the first wall  14  of the bumper associated therewith being located a second distance from the second wall  16  of the bumper associated therewith. The first position is shown in FIG. 5 in solid lines, and the second position is indicated by dotted line S in FIG.  5 . The second distance is smaller than the first distance. 
     The hypotenuse  80 ,  98  of at least one of the triangular feet  72 ,  90  on the rod  60  engages the hypotenuse  148 ,  168  of at least one of the triangular teeth  140 ,  160  of the ratchet racks  130 ,  150  during the movement of the rod  60  from the first position to the second position and the leg  78 ,  96  of at least one of the triangular feet  72 ,  90  on the rod  60  engages the leg  146 ,  166  of at least one of the triangular teeth  140 ,  160  of the ratchet racks  130 ,  150  when the rod  60  moves from the second position toward the first position. 
     The leg  78  of the first triangular foot  72  and the leg  146  of the triangular tooth  140  of the first ratchet rack  130  both extend in a radial direction with respect to the rod  60 . The leg  96  of the second triangular foot  90  and the leg  166  of the triangular tooth  160  of the second ratchet rack  150  both extend in a radial direction with respect to the rod  60 . 
     A compression spring  170  surrounds rod  60  and has one end  172  seated on head  68  and the other end  174  seated on skirt section  112  of conical section  110  adjacent to cylindrical portion  112  of apex section  114 . 
     As can be understood from the foregoing, if a bumper engages an object, the first wall  14  of the bumper will move toward the second wall  16  of the bumper. This movement will be against the force of spring  170 . However, such movement forces the second end  66  of the rod  60  in a direction away from the second wall  16 . As the rod  60  moves in this direction, the feet  72 ,  90  of the lever arm  100  slide over the teeth  140 ,  160  of the ratchet racks  130 ,  150  because of the relative orientations of the hypotenuses  80 ,  98 ,  148 ,  168  of these elements. However, due to the relative orientations of the legs  78 ,  96 ,  146 ,  166  of these triangular elements  72 ,  90 ,  140 ,  160 , the rod  60  cannot return to its initial position. Hence spring  170  remains compressed and the energy stored in that spring  170  is not returned to the vehicle. 
     The system  10  of the present invention also includes a second stage force and energy absorbing system  200  which is best shown in FIG.  2 . 
     Second stage  200  includes a plurality of shafts  202 ,  204 ,  206  and  208 . Each shaft is fixed at a first end, such as end  210  of shaft  204  to the second wall  16  of one of the two bumpers. Each shaft  202 ,  204 ,  206 ,  208  extends in the length direction  18  of the land vehicle and has a second end, such as second end  212  of shaft  206 , spaced apart from the first end of the shaft. Each shaft has an outer dimension OD and a longitudinal dimension SL. Each shaft is spaced apart from adjacent shafts, and the second end of each shaft is spaced apart from the second ends of adjacent shafts. The shafts are arranged in pairs, with two shafts of each pair being oriented to extend closely adjacent to each other. As can be seen in FIG. 4, shafts  202  and  204  form a first pair and shafts  206  and  208  form a second pair. The longitudinal dimensions of the shafts in each pair are spaced apart from each other in the width dimension of the land vehicle, and the pairs of shafts are spaced apart from each other along the width dimension of the land vehicle. 
     A plurality of mounting brackets are on each shaft. The mounting brackets on each shaft are spaced apart from each other along the longitudinal dimension of the shaft on which the mounting brackets are mounted. One mounting bracket  220  on each shaft is fixedly secured to the shaft. A first T-shaped vehicle mounting bracket  222  is fixedly mounted on the land vehicle and includes holes, such as holes  224  and  226  shown in FIG. 6, which respectively slidably accommodate the shafts  202  and  204  of the first pair of shafts. A second T-shaped vehicle mounting bracket  230  is fixedly mounted on the land vehicle and includes holes, that are sized in the manner just discussed in connection with bracket  222 , to slidably accommodate shafts  206  and  208  of the second pair of shafts. The mounting brackets also include brackets such as bracket  224  on shaft  202  and brackets  226  on shaft  204 , and corresponding brackets on shafts  206  and  208  which slide on the shafts. Thus, for example, brackets  224  on shaft  202  slide toward and away from stationary bracket  220  on shaft  202  while shafts  202  and  204  slide through vehicle mounting bracket  222 . 
     A plurality of second stage compression spring units are associated with each shaft. These units include a first set of second stage compression springs, including compression spring  232 , on first shaft  202 , each second stage compression spring of the first set of second stage compression springs being located between each mounting bracket on the first shaft  202  and an adjacent mounting bracket on the first shaft  202 . The second stage compression springs mounted with respect to the first shaft  202  are oriented to extend along the length dimension of the land vehicle and to have one end mounted on one mounting bracket and another end mounted on an adjacent mounting bracket on the first shaft  202 . 
     A first set of hydraulic spring units  240 , such as spring unit  250 , are mounted with respect to the first shaft  202 . Each hydraulic spring unit  250  of the first set of hydraulic spring units  240  is mounted between each mounting bracket on the first shaft  202  and is located adjacent to each second stage compression spring on the first shaft  202 . The hydraulic spring units  250  are all identical to the unit shown in FIG.  7 . Each of the hydraulic spring units  250  of the first set of units  240  mounted with respect to shaft  202  includes a cylinder  252  mounted on one mounting bracket on the first shaft  202 , fluid  254  in the cylinder  252 , and a seal  256  slidably mounted in the cylinder  252 . The seal  256  has two one-way valves  258  and  260  so fluid  254  in the cylinder  252  can move from one chamber to the other in a manner common to such elements. A ram  262  has a first end  264  thereof connected to the seal  256  of the hydraulic spring unit  250  for movement therewith and a second end  266  fixed to a mounting bracket on the first shaft  202  and which is associated therewith. The hydraulic springs  250  of the first set of hydraulic springs  240  are oriented parallel to the second stage compression springs of the first set of second stage compression springs to operate in parallel therewith. 
     A second set of second stage compression springs  270  is mounted with respect to the second shaft  204 . Each second stage compression spring of the second set of second stage compression springs  270  is located between each mounting bracket  220  on second shaft  204  and an adjacent mounting bracket on the second shaft  204 . The second stage compression springs  270  mounted with respect to the second shaft  204  are oriented to extend along the length dimension of the land vehicle and to have one end  272  mounted on one mounting bracket  220  and another end  274  mounted on an adjacent mounting bracket  220  on the second shaft  204 . 
     A second set  280  of hydraulic spring units is mounted with respect to the second shaft  204 . The hydraulic spring units on the second, third and fourth shafts  204 ,  206 ,  208  are all identical to the hydraulic spring units  250  shown in FIG.  7  and are identical to the hydraulic spring units  250  mounted with respect to first shaft  202 . Thus, while each of the hydraulic spring units  250  will be described in detail in the interest of completeness, no further reference numbers in regard thereto will be attached to the respective units in the interest of clarity of the Figures. Each hydraulic spring unit of the second set of hydraulic spring units is mounted between each mounting bracket on the second shaft  204  and is located adjacent to each second stage compression spring on the second shaft  204 . Each hydraulic spring unit of the second set of hydraulic spring units includes a cylinder mounted on one mounting bracket on the second shaft  204 , fluid in the cylinder of the hydraulic spring of the second set of hydraulic spring units, and a seal slidably mounted in the cylinder of the hydraulic spring of the second set of hydraulic spring units. The seal of each of the hydraulic spring units of the second set of hydraulic spring units has two one-way valves and a ram having a first end thereof connected to the seal of the hydraulic spring unit of the second set of hydraulic spring units for movement therewith and a second end fixed to a mounting bracket on the second shaft  204  and which is associated therewith. The hydraulic springs of the second set of hydraulic springs are oriented parallel to the second stage compression springs of the second set of second stage compression springs to operate in parallel therewith. 
     A third set  290  of second stage compression springs are located on third shaft  206 , each second stage compression spring of the third set of third stage compression springs is located between each mounting bracket on the third shaft  206  and an adjacent mounting bracket on the third shaft  206 . The second stage compression springs on the third shaft  206  are oriented to extend along the length dimension of the land vehicle and to have one end mounted on one mounting bracket and another end mounted on an adjacent mounting bracket on the third shaft  206 . 
     A third set  292  of hydraulic spring units is mounted with respect to third shaft  206 . Each hydraulic spring unit of the third set of hydraulic spring units is mounted between each mounting bracket on the third shaft  206  and is located adjacent to each second stage compression spring on the third shaft  206 . Each hydraulic spring unit of the third set of hydraulic spring units includes a cylinder mounted on one mounting bracket on the third shaft  206 , fluid in the cylinder of the hydraulic spring of the third set of hydraulic spring units, and a seal slidably mounted in the cylinder of the hydraulic spring of the third set of hydraulic spring units. The seal having two one-way valves, and a ram having a first end thereof connected to the seal of the hydraulic spring unit of the third set of hydraulic spring units for movement therewith and a second end fixed to a mounting bracket on the third shaft  206  and which is associated therewith. The hydraulic springs of the third set of hydraulic springs being oriented parallel to the second stage compression springs of the third set of second stage compression springs to operate in parallel therewith. 
     A fourth set  300  of second stage compression springs are located on fourth shaft  208 . Each second stage compression spring of the fourth set of second stage compression springs being located between a mounting bracket on fourth shaft  208  and an adjacent mounting bracket on the fourth shaft  208 . The second stage compression springs on the fourth shaft  208  are oriented to extend along the length dimension of the land vehicle and to have one end mounted on one mounting bracket and another end mounted on an adjacent mounting bracket on the fourth shaft  208 . 
     A fourth set  302  of hydraulic spring units is mounted with respect to the fourth shaft  208 . Each hydraulic spring unit of the fourth set of hydraulic spring units is mounted between one mounting bracket on the fourth shaft  208  and an adjacent mounting bracket on the fourth shaft  208  and is located adjacent to each second stage compression spring on the fourth shaft  208 . Each hydraulic spring unit of the fourth set of hydraulic spring units including a cylinder mounted on one mounting bracket on the fourth shaft  208 , hydraulic fluid in the cylinder of the hydraulic spring of the fourth set of hydraulic spring units, and a seal slidably mounted in the cylinder of the hydraulic spring of the fourth set of hydraulic spring units. The seal has two one-way valves. A ram has a first end thereof connected to the seal of the hydraulic spring unit of the fourth set of hydraulic spring units for movement therewith and a second end fixed to a mounting bracket on the fourth shaft  208  and which is associated therewith. The hydraulic springs of the fourth set of hydraulic springs are oriented parallel to the second stage compression springs of the fourth set of second stage compression springs to operate in parallel therewith. 
     A second end  310  of first shaft  202  is slidably accommodated in first vehicle mounting bracket  222  and is in abutting contact with a cylinder of the second set of hydraulic spring units and which is mounted on the first vehicle mounting bracket. The first shaft  202  is aligned with the ram of a cylinder of the second set of hydraulic springs which is mounted of the first vehicle mounting bracket. Second shaft  204  is aligned with the ram of a cylinder of the first set of hydraulic cylinders mounted on the first vehicle mounting bracket. Second shaft  204  is slidably accommodated in the first vehicle mounting bracket for movement in directions  320  and  322  while first shaft  202  is slidably mounted for movement in directions  322  and  324 . 
     A second end  326  of third shaft  206  is slidably accommodated in second vehicle mounting bracket  230  and is in abutting contact with a cylinder of the fourth set of hydraulic springs and which is mounted on the second mounting bracket. The third shaft  206  is aligned with the ram of a cylinder of the fourth set of hydraulic springs which is mounted on the second vehicle mounting bracket and the fourth shaft  208  is aligned with the ram of the cylinder of the third set of hydraulic cylinders mounted on the second vehicle mounting bracket. Fourth shaft  208  is slidably accommodated in the second vehicle mounting bracket. Thus, as can be seen in FIG. 4, third shaft  206  moves in directions  330  and  332  and fourth shaft  208  moves in directions  332  and  334 . 
     As can be understood from the foregoing, movement of the shafts will be controlled by the compression springs and the hydraulic springs. Thus, energy and force associated with a collision of the land vehicle will be absorbed by the compression springs and the hydraulic springs of the second stage system. 
     It is understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangements of parts described and shown.