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FIELD OF THE INVENTION 
   This invention relates to a vehicle barrier system and relates particularly, though not exclusively, to a vehicle barrier system to prevent intrusion through a barrier by an unauthorised vehicle. 
   BACKGROUND OF THE INVENTION 
   Threats from car bombs have become prevalent amongst terrorists throughout the world. Terrorists will ram a gate of an embassy or other selected building with a vehicle. Once entry is gained they detonate their bomb as close to the building as possible to maximise the death and injuries caused by their actions. Gates and doors are necessary to gain access to the building or perimeter fence and provide a weak link for such terrorist attacks. Most gates rely on the weight of the gate and its mounting to a foundation to decelerate such vehicles. These gates do not attempt to absorb the shock and the vehicle may still penetrate a significant distance. The resulting damage is usually significant and will require costly and timely replacement. 
   SUMMARY OF INVENTION 
   It is an object of the present invention to provide a vehicle barrier system that will absorb the impact energy from the moving vehicle and reduce the penetration distance when the vehicle has been stopped. 
   A further object of the invention is to provide a vehicle barrier system that can be readily repaired or replaced once vehicle impact has occurred. 
   In one aspect of the present invention there is provided a vehicle barrier system including a barrier movable between an open position to allow vehicle access therethrough and a closed position which prevents vehicle access therethrough, said barrier being attached to barrier supports at either end of said barrier, said barrier supports being secured to a slide plate which will slide after a predetermined force is applied thereto by vehicle impact with said barrier to absorb the impact energy of said vehicle. 
   Preferably said slide plate is sufficiently long to have a part of said vehicle sitting thereon at impact. Preferably said movement of said slide plate is controllable. Preferably said movement is controllable by one or more of a group selected from a ballast attached directly or indirectly to said slide plate, at least one further slide plate attached to said slide plate, the extension of attachment means attached to said at least one further slide plate and/or said ballast, the extension of attachment means attached to said slide plate and a surface over which said slide plate moves, and the shearing of at least one rivet securing said slide plate to a surface on which said slide plate slides. 
   In a practical embodiment a plurality of rivets protrudes through said at least one slot in said slide plate. Preferably a pair of slots are provided and said slide plate rests on a sliding surface formed by a pair of ground engaging beams aligned with respective slots. Preferably a pair of upright beams are secured to the ground in front of respective barrier supports, said upright beams being secured to said pair of ground engaging beams at one end and pivotally and/or slidably linked to said barrier supports at the other end. 
   In a further aspect of the invention there is provided a vehicle barrier system including a barrier movable between an open position to allow vehicle access therethrough and a closed position which prevents vehicle access therethrough, said barrier being attached to barrier supports at either end of said barrier, said barrier supports being secured to the ground on a ground engaging plate(s), a pair of bridging slide plates on one side of each of said barrier supports attached at one end to a respective said barrier support and at the other end to said ground engaging plate(s), said slide plates joined by at least one rivet, said slide plates movable with respect to one another when said at least one rivet is sheared after a predetermined force is applied from vehicular impact with said barrier to absorb the impact energy of said vehicle. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings, in which: 
       FIG. 1  is a perspective view of a first embodiment of a vehicle barrier system made in accordance with the invention showing the barrier in the closed position; 
       FIG. 2  is the same view as  FIG. 1  in the open position; 
       FIG. 3  is an underneath view of  FIG. 1 ; 
       FIG. 4  is a plan view of  FIG. 1 ; 
       FIG. 5  is a cross-sectional view along and in the direction of arrows  5 - 5  shown in  FIG. 4 ; 
       FIG. 6   a  is similar view to that of  FIG. 5  which includes a part plan view made in accordance with a second embodiment of the invention showing a vehicle moving towards the barrier; 
       FIG. 6   b  is a similar view to that of  FIG. 6   a  showing the vehicle impacting the barrier; 
       FIG. 6   c  is a similar view to that of  FIG. 6   b  showing the shearing of the first set of rivets; 
       FIG. 6   d  is a similar view to that of  FIG. 6   c  showing the shearing of the second set of rivets; 
       FIG. 6   e  is a similar view to that of  FIG. 6   d  showing the shearing of the third set of rivets; 
       FIG. 7  is a plan view similar to that of the  FIG. 6   e  of a third embodiment made in accordance with the invention; 
       FIG. 8  is a similar view to that of  FIG. 6   e  of a fourth embodiment made in accordance with the invention; 
       FIG. 9   a  is a similar view to that of  FIG. 6   a  of a fifth embodiment made in accordance with the invention with the barrier closed; 
       FIG. 9   b  is a plan view of the vehicle barrier system shown in  FIG. 9   a  with the barrier open; 
       FIG. 10  is a perspective view of a sixth embodiment made in accordance with the invention; 
       FIG. 11  is a perspective view of a seventh embodiment made in accordance with the invention; 
       FIG. 12  is a perspective view of an eighth embodiment made in accordance with the invention showing the barrier lowered; 
       FIG. 13  is a perspective view of the embodiment shown in  FIG. 12  with the barrier raised; 
       FIG. 14  is an end view in the direction of arrows  14 - 14  shown in  FIG. 12 ; 
       FIG. 15  is a side view in the direction of arrows  15 - 15  shown in  FIG. 12 ; 
       FIG. 16  is an exploded partial cross-sectional perspective view of the vehicle barrier system shown in  FIG. 13 ; 
       FIG. 17   a  is a longitudinal cross-sectional view of the vehicle barrier system shown in  FIG. 13  before vehicular impact; 
       FIG. 17   b  is a longitudinal cross-sectional view of the vehicle barrier system shown in  FIG. 13  during vehicular impact; 
       FIG. 18   a  is a perspective view of a ninth embodiment made in accordance with the invention showing the barrier lowered; 
       FIG. 18   b  is a perspective rear view of the embodiment shown in  FIG. 18   a  with the barrier raised; 
       FIG. 19  is a perspective front view of the embodiment shown in  FIG. 18   b  with the barrier raised; 
       FIG. 20  is a longitudinal cross-sectional view of the vehicle barrier system shown in  FIG. 19  with the barrier being manually raised; 
       FIG. 21  is a longitudinal cross-sectional view of the vehicle barrier system shown in  FIG. 19  with the barrier being automatically raised; 
       FIG. 22  is a plan view of a tenth embodiment made in accordance with the invention showing the barrier closed; 
       FIG. 23  is a perspective view of one end of the vehicle barrier systems shown in  FIG. 22 ; and 
       FIG. 24  is a cross-sectional view of the embodiment shown in  FIG. 22  during vehicular impact. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Throughout this specification the same reference numerals have been used to identify similar integers in the various embodiments to reduce repetition of description. In  FIGS. 1 to 5  there is shown a vehicle barrier system  10  which will protect an opening (not shown) in a perimeter fence or building opening. The vehicle barrier system  10  includes a pair of I-beams  12 , 14  mounted parallel with each other. Although I-beams have been described it is clear from embodiments to be discussed later that the I-beams could be replaced by an anchor plate on the ground. I-beams  12 , 14  are typically secured to the ground by concrete supports  15 . I-beams  12 , 14  have respective top flanges  16 , 18  and lower flanges  20 , 22 . A pair of hollow beams  24 , 26  are welded to respective support plates  28 , 30 . Apertures  31  in support plates  28 ,  30  allow support plates  28 , 30  to be bolted to concrete supports  15 . A cross- beam  32  bridges hollow beams  24 , 26 . An electric motor  34  is secured to beam  26  and allows barrier  46  to be raised or lowered. 
   Counterweights  36  balance the weight of barrier  46  and are located within hollow beams  24 , 26 . 
   Pulleys  38  guide a cable  40  on either side of barrier  46  with motor  34  providing movement of cables  40 . Barrier guides  42 , 44  are secured to the sides of hollow beams  24 , 26  and allow sliders  41  coupled to barrier  46  to slide up and down. 
   A pair of barrier supports  48 , 50  are mounted parallel to hollow beams  24 , 26 . The top of barrier supports  48 , 50  are pivotally and slidably linked to beam plates  51  on either side of hollow beams  24 , 26 . Pins  51   c ,  51   d  project through slots respectively to allow movement of barrier supports  48 ,  50 . At the other end of barrier supports  48 , 50  there is attached a slide plate  52 . 
   Slide plate  52  rests on the top flanges  16 , 18  of I-beams  12 , 14 . Slots  54 , 56  are provided in slide plate  52  and three pairs of rivets  58 , 60 ;  62 ,  64 ;  66 , 68  are secured to the top flanges  16 , 18  of I-beams  12 , 14 . Attachment beams  70 , 72 ,  74 , 76  are welded to the underside of slide plate  52 . The attachment beams  70  -  76  have attachment points  78  for attachment thereto of links  79 . Links  79  allow pull rods or tension bars  80 , 82  to be connected to ballast  84  by attachment points  86  on ballast  84 . Pull rods or tension bars  80 ,  82  have a Z- shaped configuration and can be straightened when tensioned. Pull rods or tension bars  80 , 82  can have a plurality of bends in them to suit requirements and are not limited to the shape shown in this embodiment. Ballast  84  can be any form of weight, for example, a block of concrete, or a plurality of logs located in a framework as shown in  FIGS. 1 to 5 . Ballast  84  is located in a trough  88  with the base of the trough  90  being inclined. 
   In the preferred embodiment barrier  46  includes horizontal ram plates  92  which at each end are slidingly located on barrier supports  48 , 50  through guide holes  94 . A plurality of vertical spacers  96  are welded between—respective horizontal ram plates  92  to provide a strong anti-penetration gate. 
   The number and position of vertical spacers  96  can be varied to suit requirements. It is preferred that the spacing between horizontal ram plates  92  is closer at a position where vehicle impact would occur. Vertical slats are welded to horizontal ram plates  92 . 
   In the embodiment shown in  FIGS. 6   a  to  6   e  the ballast  84  has been replaced by a second slide plate  100  which is supported by  12 , 14 . 
   The second slide plate  100  is similarly affixed to top flange  18  via rivets  60   a ,  64   a ,  66   a  through slot  56   a  and corresponding rivets (not shown) and slot (not shown) on I-beam  12 .  FIGS. 6   a  to  6   e  provide a sequential illustration of a vehicle  102  attempting to crash through vehicle barrier system  10 . The operation of the barrier system  10  is also applicable to the embodiment shown in Figs. to  5 . 
   In  FIG. 6   a , vehicle  102  is moving with a velocity as indicated by arrows  106  and front wheels  104  will roll over second slide plate  100 . Barrier  46  will be in the closed position as shown in  FIG. 1 . Vehicle  102  will continue to move forward and front wheels  104  will roll over slide plate  52  as shown in phantom lines  108  in  FIG. 5  to make contact with barrier  46 .  FIG. 6   b  shows vehicle  102  having contacted barrier  46  with consequent damage to the vehicle and to vertical slats  98 . The slats  98  will crumple and absorb an amount of impact force. The horizontal ram plates  92  and vertical spacers  96  will also assist in reducing the velocity of vehicle  102 . 
   Slide plate  52  will be held fast at this time by rivets  58 - 68 , which will be assisted by the weight of vehicle  102  upon slide plate  52  to increase the frictional forces needed to move slide plate  52 . 
     FIG. 6   c  shows that rivets  66 , 68  have been sheared at a predetermined force applied thereto. The force is applied to slide plate  52  through the impact load applied to barrier supports  48 , 50  passed from horizontal ram plates  92 . Slide plate  52  will thus move to the left as indicated by the increasing width of gap  110  between slide plate  52 , the straightening of pull rods  80 , 82  and the bowing of barrier supports  48 , 50  as shown by phantom lines  112  in  FIG. 5 . Slide plate  52  will slide along I-beams  12 , 14  to move barrier supports  48 , 50  with it and pivot and move about pins However, hollow beams  24 , 26  will not move as they are fastened to  24 , 26 . The second slide plate  100  will provide resistance to assist in the straightening of pull rods  80 , 82 . 
   Further dissipation of the vehicle impact will occur when rivets  62 , 64  are sheared at a further predetermined force applied thereto as shown in  FIG. 6   d . Gap  110  will widen further and pull rods  80 , 82  will be further straightened.  FIG. 6   e  shows rivets  60  being sheared to further increase the width of gap  110 . Pull rods  80 , 82  have been fully straightened. The weight and speed of vehicle  102  will determine whether all rivets  58 - 68  will be sheared or whether the impact force is dissipated prior to that occurrence. If vehicle  102  is still not stationary, then the same sequence of shearing of rivets  60   a ,  64   a ,  68   a , etc will occur for second slide plate  100 . This sequence will not be described, as it will be obvious to the man skilled in the art based on the previous operational discussion. 
   In the embodiment shown in  FIGS. 1 to 5  the second slide plate  100  is replaced by ballast  84 . The operational sequences will be very similar with the resistance of the ballast  84  engaging when rivets  66 , 68  are sheared. In tests the vehicle barrier system  10  has been effective to prevent a 4000-kg (8800lb.) load from entering barrier  46  at  30  The damaged barrier  46  can be readily replaced as hollow beams  24 , 26  are not damaged and the barrier lifting mechanism is on the hollow beams  24 , 26 . It is a relatively simple procedure to replace barrier  46  as barrier supports  48 , 50  can be re-used. The downtime for an attempted intrusion is substantially reduced without compromising safety. 
     FIG. 7  shows a very similar embodiment to that shown in  FIGS. 6   a  to  6   e  with the addition of a third slide plate  114 . Again third slide plate  114  is coupled to second slide plate  100  by pull rods  80   a  and is fastened to I-beams  12 , 14  by rivets  60   b ,  64   b ,  68   b.    
     FIG. 8  shows a very similar embodiment to that shown in  FIG. 7  with the addition of ballast  84  from the embodiment of  FIGS. 1 to 5 . Ballast  84  is coupled to third slide plate by pull rods  80   b.    
     FIGS. 9   a  and  9   b  illustrate a further embodiment where barrier  46  is replaced by a pivotal ramp  116  which is attached to slide plate  52  through pivot plates  118 . 
   Ramp  116  can pivot between a closed or vertical position as shown in  FIG. 9   a  and a horizontal or open position as shown by phantom lines  120 . The ramp  116  is held in either position by a latching mechanism (s) (not shown) and is biased towards the closed position by springs  122 . There are slide plates  52 , 100 , which are constructed and operate in a similar way to those shown in  FIGS. 6   a  to  6   e.    
   Vehicle  102  can drive over ramp  116  when in the open position as indicated in  FIG. 9   a  but cannot pass when ramp  116  is raised. Ramp  116  can be of any suitable construction to withstand the initial impact by vehicle  102 . This embodiment does not have the hollow beams  24 , 26 . The impact force will be applied to slide plate  52  through the impact load applied to pivot plates  118  rather than barrier supports  48 , 50  passed from ramp  116 . The movement of slide plates  52 , 100  will be the same as that described in  FIGS. 6   a  to  6   e.    
   The embodiment shown in  FIG. 10  shows barrier  46  being replaced by a pair of swinging gates  124 , 126 . Slide plate  52  will again operate in a similar manner to that previously described in relation to  FIGS. 9   a  and  9   b.    
   The embodiment shown in  FIG. 11  is similar to the embodiment shown in  FIG. 10  with swinging gates  124 , 126  replaced by a sliding gate  128 . Slide plate  52  will again operate in a similar manner to that previously described in relation to  FIGS. 9   a  and  9   b.    
   The embodiment shown in  FIGS. 12 to 17   b  is similar to the embodiment shown in  FIGS. 9   a  and  9   b . In this embodiment the I-beams are replaced by an anchor plate  130  which is affixed to the ground. A plurality of holes  132  are formed in the ground and are preferably strengthened using concrete. Locking cylinders  134  are pushed through respective apertures  136  in slide plate  52  and locked in place by pins  138 . The locking cylinders  134  are tamperproof as they are located underneath covers  140  and the end of ramp  116 . A pair of tension bars  82  are secured at respective ends to slide plate  52  and anchor plate  130 . 
   Ramp  116  is pivotally mounted to slide plate  52  through bracing elements  142 . 
   Bracing elements  142  are notched to grip the vehicle at impact and provide deformation of the vehicle to reduce the speed of the vehicle. A back plate  144  is also pivotally mounted to slide plate  52  and provides additional support to ramp  116  under impact. Again bracing elements  146  are provided to strengthen the back plate  144 . Bracing elements  146  protrude slots  148  in ramp  116  and are coupled to pin  150  which is guided within track  152  on bracing elements  142 . When non-operational, the vehicle barrier system in  FIGS. 12 to 17   b  is folded into the position shown in  FIG. 12 . A vehicle may be easily driven over the vehicle barrier system and it will act basically as a speed hump. The operational position is shown in  FIGS. 13 and 17   a  with ramp  116  in the raised position. Any unauthorised vehicle will travel in the direction of the arrow shown in  FIG. 17   a  and ride over covers  140  and hit ram ramp  116 . The impacting of the vehicle is shown in  FIG. 17   b  and is similar in operation to that of  FIGS. 9   a  and  9   b  with slide plate  52  moving along anchor plate  130  and severing in turn the rivets  60 , 64 ,  66  and straightening of tension bars  80 , 82 . The embodiment shown in  FIGS. 18   a  to  21  is very similar to the embodiment shown in  FIGS. 12 to 17   b . In this embodiment a handle  154  is locatable in a tube  156  and has one end located in boss  158  on slide plate  52 . The handle  154  will allow a manual movement of ramp  116  into its raised position as shown in  FIG. 20 . By locating the handle in tube  156 , additional strength will be provided to the ramp  116  on impact. Gas struts  160  will also assist in the raising of ramp  116 . An example of a remote activated raising of ramp  116  is also shown in this embodiment. A pair of springs  162  are held in a tensioned condition as shown in  FIGS. 19 and 20 . The springs  162  are held by pin  164  coupled to an explosive device  166 . When explosive device is detonated electronically by switch  168 , pin  164  will be released and the tensioned force contained within springs  162  will immediately raise ramp  116  as shown in  FIG. 21 . The explosive device  166  can be substituted by any other suitable activation means, for example, solenoid, etc. The impact operation of this embodiment will be the same as the embodiment of  FIGS. 12 to 17   b.    
   The embodiment shown in  FIGS. 22 to 24  differs from the previous embodiments by the different positions of the slide plate and tension bars. This embodiment shows a boom gate  170  which is pivotally mounted to support  172 . 
   Boom gate  170  can be raised manually by handle  174  or electrically through a gear  176  coupled to a gear driven motor means (not shown). A latch  178  is attached at the other end of boom gate  170  and can be locked in position by solenoid  180 . A further support  182  is provided and both supports  172 , 182  are attached to ground anchor plates  184 , 186  which are secured to the ground. 
   Tension bar  80  is secured to ground anchor plate  184  by brackets  188  and pin  190  whilst tension bar  82  is similarly secured by brackets  192  and pin  194 . The other ends of tension bars  80 , 82  are again secured to supports  172 , 182  by brackets  196 , 200  and pins  198 ,  202 . The method of attachment can be varied to suit requirements, for example, direct welding or other means. A pair of fixed plates  204  are also welded to anchor plates  184 , 186  at an angle thereto. Slide plates  206  are attached to both supports  172 , 182 . Respective slots  208  in fixed plates  204  allow slide plates  206  to be held thereagainst by rivets 
     FIG. 24  shows the operation of the vehicle barrier system of  FIGS. 22 to 24 . 
   When the vehicle  102  impacts with boom gate  170  the supports  172 ,  182  will be bent backwards which will cause extension of tension bars  80 , 82 . Further bending of supports  172 , 182  will cause the sequential shearing of rivets  210  in a similar manner to the previously described embodiments. 
   From the above description of the various embodiments it is evident to the man skilled in the art may make changes to the construction of the vehicle barrier system  10 . Depending on construction constraints slide plate  52  need not be coupled to a further slide plate or ballast. The construction of barrier  46  can be of any suitable type that can withstand a heavy impact. The number and types of slide plates can vary. Similarly, the numbers of rivets can be varied from 1 to any number deemed applicable. The shearing strength of the rivets can be varied or be the same. The preferred embodiments have been described with reference to their use as a gate but the construction is also applicable to doors of buildings. 
   The invention will be understood to embrace many further modifications as will be readily apparent to persons skilled in the art and which will be deemed to reside within the broad scope and ambit of the invention, there having been set forth herein only the broad nature of the invention and certain specific embodiments by way of example.

Summary:
The invention discloses a vehicle barrier system ( 10 ) including a barrier ( 46 ) movable between an open position to allow vehicle access therethrough and a closed position which prevents vehicle access therethrough. Barrier ( 46 ) is attached to barrier supports ( 48, 50 ) at either end of barrier ( 46 ) with barrier supports ( 48, 50 ) being secured to a ground engaging slide plate ( 52 ). The ground engaging slide plate ( 52 ) will slide after a predetermined force is applied thereto by vehicle ( 102 ) impact with barrier ( 46 ) to absorb the impact energy of vehicle ( 102 ).