Patent Publication Number: US-2011070022-A1

Title: Apparatus and Method for Deploying a Vehicle Arresting Device

Description:
The present invention relates to the deployment of vehicle arresting devices such as may be used by law enforcement agencies or military forces to safely stop the progress of a target vehicle, for example if stolen or suspected to be engaged in criminal or hostile activity. 
     The invention is more particularly concerned with the deployment of vehicle arresting devices of a kind comprising a flexible substrate of generally rectangular planform intended to lie flat upon the ground when deployed with an array of upwardly-directed spikes attached to the substrate along a leading edge thereof (in the sense of the intended direction of approach of a vehicle to be arrested). The substrate in a device of this kind may be, for example, a panel of silk or other woven material, or it may be in the form of a net. One form of the latter kind of device is known from WO2004/072382, examples of which are marketed by the present applicant under the trade marks “X-Net” and “TruX-Net”. The  modus operandi  of a successful arrest with a device of that kind is as follows. When a vehicle runs over the device the run-over spikes engage in its front tires and the substrate is caused to wrap around the front wheels, the portion of the substrate between those wheels being pulled tight under the vehicle so that the tension in the substrate prevents further rotation of the wheels and the vehicle is brought to a stop. In practice this occurs in a similar distance to an emergency stop as if the vehicle&#39;s brakes had been applied, and has the advantage that it can stop the vehicle without causing serious damage to the vehicle or injury to its occupants. 
     From WO2007/141479 there is known a system for deploying such a vehicle arresting device across a roadway from a folded condition to one side of the roadway, which comprises a winch located on the opposite side of the roadway to wind in a pair of cables attached to the corner regions of one side edge of the device. In practice when using this system it is also necessary to anchor the device to the ground on the side of the roadway from which it unfolds, and we have found that the means of anchorage on this side can be quite critical to the successful deployment of the device. 
     In this respect it is important to the accomplishment of a vehicle arrest that the device is deployed with its spikes in their intended upright orientation. This in turn requires that the leading edge of the device which carries the spikes is presented to the target vehicle in as even and wrinkle-free a condition as possible after deployment. If it is not then at least some of the spikes may be left tilted relative to their intended orientation with the result that they are simply knocked over when encountered by the vehicle&#39;s tyres and fail to penetrate the tyres as required in order for the substrate to be wrapped around the tyres as intended. If, say, the device is anchored to the ground by pegs or the like at or close to its respective side edge we have found that the device becomes very sensitive to variations in the alignment of the two cables to the other edge and is liable to be left in a wrinkled condition after deployment if they are not wound in at equivalent angles and tension to one another. This is undesirable particularly bearing in mind that the circumstances of use of such a system are such that it may have to be set up in position rapidly and without having the time available to ensure geometrical accuracy in the cable runs. 
     The present invention seeks to alleviate this problem and in one aspect accordingly provides, in combination: a vehicle arresting device comprising a flexible substrate of generally rectangular planform intended to lie flat upon the ground when deployed with an array of upwardly-directed spikes attached to the substrate along a leading edge thereof (in the sense of the intended direction of approach of a vehicle to be arrested); means for deploying said device across a vehicle pathway from a folded condition to one side of said pathway comprising respective first flexible tension members attached to the device in the corner regions at one side edge thereof and means for winding in said flexible tension members from a position to the side of said pathway opposite to said one side thereof; and means anchoring said device from said one side of said pathway comprising respective second flexible tension members attached to the device in the corner regions at the side edge thereof opposite to said one side edge and means anchoring said second flexible tension members to the ground at anchor positions spaced from their respective attachments to the device so that said device is permitted a range of movement in the fore and aft direction relative to said pathway during deployment by virtue of freedom of said second flexible tension members to move arcuately about their said anchor positions. 
     In other words by virtue of the form of anchorage for the device at said one side of the vehicle pathway it is free to “float” over a range in the fore and aft direction during deployment and by this means can to some extent self-correct for variations in the alignment and/or tension of the first flexible tension members (cables, ropes or the like) and deploy in an even and wrinkle-free condition notwithstanding such variations in practice. 
     In another aspect the invention resides in a method of deploying across a vehicle pathway, from a folded condition to one side of said pathway, a vehicle arresting device comprising a flexible substrate of generally rectangular planform intended to lie flat upon the ground when deployed with an array of upwardly-directed spikes attached to the substrate along a leading edge thereof (in the sense of the intended direction of approach of a vehicle to be arrested), which method comprises winding in, from a position to the side of said pathway opposite to said one side thereof, respective first flexible tension members which are attached to the device in the corner regions at one side edge thereof, while said device is anchored from said one side of said pathway by means of respective second flexible tension members attached to the device in the corner regions at the side edge thereof opposite to said one side edge and means anchoring said second flexible tension members to the ground at anchor positions spaced from their respective attachments to the device so that said device is permitted a range of movement in the fore and aft direction relative to said pathway during deployment by virtue of freedom of said second flexible tension members to move arcuately about their said anchor positions. 
     Preferably both said first and second flexible tension members extend from said device at divergent oblique angles. It is also preferred that both said first and second flexible tension members are attached to said device through means adapted to fail preferentially under predetermined tension, and where the predetermined tension at which the means for the second flexible tension members fail is higher than that at which the means for the first flexible tension members fail. 
     The invention may also include a winch adapted to wind in both said first flexible tension members simultaneously and wherein, in use, one of said first flexible tension members runs directly from said device to said winch and the other of said first flexible tension members runs from said device to said winch over a pulley to change its direction from that in which it initially extends from said device. 
     In yet a further aspect the invention resides in a vehicle arresting device, a plurality of flexible tension members, winding means and anchoring means all adapted for use in a method as defined above. 
     The substrate of a said vehicle arresting device is preferably in the form of a net. 
    
    
     
       These and other aspects and features of the present invention will now be more particularly described, by way of example, with reference to the accompanying schematic drawings, in which: 
         FIG. 1  is a plan view of one embodiment of a deployment system for a vehicle arresting device in accordance with the invention; and 
         FIG. 2  is an end view of the vehicle arresting device from  FIG. 1  in its initial folded condition on the ground, to an enlarged scale. 
     
    
    
     With reference to  FIG. 1  there is shown a vehicle arresting device  1  of the kind more fully described and illustrated in WO2004/072382, in a folded condition to one side of a roadway  2  and ready to be deployed in the path of a target vehicle (not shown) approaching in the direction of the arrow A. The device  1  comprises a net  3  of rectangular planform intended to lie flat across the roadway when deployed and equipped with one or more rows of barbed spikes  4  along its leading edge (in the sense of the direction of approach A). It is folded laterally upon itself in concertina fashion as indicated in  FIG. 2  (from which the spikes  4  are omitted for ease of illustration and in which the successive leaves of the folded net are shown spaced from each other in the vertical direction also for ease of illustration). In use, when a vehicle encounters the deployed device  1  (being then in the position notionally illustrated in broken line in  FIG. 1 ) from the direction of arrow A, its front tyres will run over a number of adjacent spikes  4  (being then extending upwardly from the leading edge of the net  3 ) which become lodged in those tyres. The net  3  therefore becomes attached to the front wheels of the vehicle at two locations across its width and continued movement of the vehicle causes the net to wrap around those wheels, the portion of the net between the wheels being pulled tight under the vehicle and around suspension components until its tension prevents further rotation of the wheels, thereby bringing the vehicle to a stop all as described in WO2004/072382. 
     Returning to the pre-deployment condition of the device  1  in  FIG. 1 , a winch  5  is firmly anchored to the ground on the opposite side of the roadway  2  to the folded device  1  and slightly “upstream” from the device  1  in the sense of the arrow A. A pair of cables  6  and  7  extend from the winch  5  across the roadway  2  and are attached to the device  1  in the respective corner regions of the closer side edge of the net  3 , that is to say the edge at the upper left hand side of the folded device as viewed in  FIG. 2 . The cable  6  to the leading edge of the device  1  runs directly across the roadway  2  from the winch  5  in the illustrated embodiment. The cable  7  to the trailing edge of the device  1 , however, firstly runs from the winch  5  approximately parallel to the roadway to a turn pulley  8  on the same side as the winch, and thence across the roadway to the device  1 . The turn pulley  8  is itself firmly anchored to the ground through a pair of straps  9  and located slightly “downstream” from the device  1  in the sense of the arrow A. It follows from this layout of the device  1 , winch  5  and turn pulley  8  that the cables  6  and  7  diverge at oblique angles with respect to the device  1  towards the winch  5 . 
     The winch  5  may be, for example, powered electrically or by means of a spring mechanism. It has a pair of drums, one for each cable  6 , 7 , which can be set to turn independently to allow the cables to be run out to the device  1  and their slack then taken up, and then can be locked together to wind in the cables simultaneously when the device is to be deployed. 
     The cables  6  and  7  are attached to the device  1  through respective “weak links” notionally indicated at  10  and  11 , which may conveniently be in the form of conventional electrical cable ties made of plastics. 
     To avoid a situation in which the vehicle arresting device  1  is not only unfolded but dragged as a whole across the roadway  2  from the side on which it is initially laid when the winch  5  is operated, it is necessary to anchor it to the ground on that side of the roadway through its side edge that is remote from the cables  6  and  7 —that is to say the edge that is at the lower right hand side of the net  3  in the folded condition as viewed in  FIG. 2 . For this purpose a pair of lanyards  12  and  13  are attached to the device in the respective corner regions of that side edge of the net and these lanyards are firmly anchored to the ground at the positions indicated at  14 - 17 . As shown in  FIG. 1 , these lanyards are positioned to diverge at oblique angles with respect to the device and in the opposite direction to the cables  6  and  7 . They may themselves be in the form of cables or ropes but preferably are in the form of lengths of webbing equipped with eyelets for ground anchors at the positions  14 - 17 . These ground anchors (one of which is notionally indicated at  18  for the lanyard  13  in  FIG. 2 ) will be selected according to the prevailing ground conditions where the device  1  is to be deployed but may be in the form of stakes similar to large tent pegs where the ground is relatively soft or heavy-duty masonry nails where the device is to be deployed in an urban environment over concrete or asphalt for example. Eyelets of different sizes suited to the different types of ground anchors available may be provided in the lanyards  12 , 13  at each position  14 - 17 . Similar types of anchors may be selected for the anchorage of the winch  5  and pulley straps  9 . 
     It is of note that the nearest lanyard ground anchorage points  14  and  16  to the side edge of the net  3  are spaced an appreciable distance from the points of attachment of the respective lanyard  12 ,  13  to the net. For example with a device  1  having a typical deployed width of 6 m and a typical length of 3 or 5 m the free length of lanyard between the net  3  and the point  14  or  16  may be approximately 2 m. It follows that the device  1  is permitted a range of movement in the fore and aft direction relative to the roadway during deployment (that is to say generally in the sense of arrow B in  FIG. 1 ) by virtue of the freedom of the lanyards  12  and  13  to move arcuately about their anchor points  14  and  16  (that is to say in the sense of arrows C and D in  FIG. 1 ). 
     The lanyards  12  and  13  are attached to the device  1  through respective “weak links” notionally indicated at  19  and  20  and having a greater breaking strain than the links  10  and  11 , which may conveniently be in the form of thinner sewn lengths of the lanyards themselves at their inboard ends. 
     Unfolding and deployment of the device  1  from the position shown in full line in  FIG. 1  to the position shown in broken line in that Figure is accomplished by running the winch  5  to simultaneously wind in the cables  6  and  7 . This may be initiated by any suitable means but in  FIG. 1  is notionally indicated as a footswitch  21  connected to the winch  5  through an electrical cable  22  and which can be actuated by a human operator situated at a safe distance from the arrester when a target vehicle is sighted. The signal from the switch  21  may actuate a power switch in the winch  5  when electrically operated or may actuate a solenoid in the winch  5  to withdraw a lock on the drums when spring operated. 
     In any event operation of the winch  5  winds in the cables  6  and  7  initially to the positions shown for them in broken line in  FIG. 1 . During this movement it will be appreciated that the side edges of the net  3  will be kept under tension as well as its leading and trailing edges by virtue of the divergent disposition of the cables  6 , 7  and lanyards  12 , 13  and this will help to ensure that the device is left in an even and wrinkle-free condition across the roadway with the spikes  4  in their intended upright orientation. In particular the tension in the near side edge (to the cables  6  and  7 ) prevents it from dragging or catching on the ground and causing wrinkles throughout the net. In addition the fore and aft “float” afforded to the device through the lanyards  12  and  13  as described above means that the device is to some extent self-correcting for variations in the alignment and/or tension in the cables  6  and  7  during deployment and also helps to ensure that the device is left in as even and wrinkle-free a condition as possible. By virtue of this freedom of movement it follows that the deployed position of the device  1  may in any practical case actually be displaced somewhat “upstream” or “downstream” from the position indicated in broken line in  FIG. 1 . 
     At this point, when the device  1  has reached across the roadway  2  as far as it can while being constrained by the lanyards  12  and  13 , the weak links  10  and  11  between the cables  6 , 7  and the net  3  will normally break under the tension in the system and the cables can retract fully into the winch. In this respect the tension force to break the links  10 , 11  should be above the resistance to deployment due to the weight of the device  1  but below the tension force to break the links  19 , 20  between the lanyards  12 , 13  and the net which should in turn be below the force to dislodge any of the ground anchors for any of the system components. If for any reason the links  10  or  11  do not break at this point they will be broken during the course of a vehicle arrest as the net  3  wraps around the vehicle&#39;s wheels and is carried along by the vehicle, as will the links  19  and  20  during the arrest. It is desirable that the device  1  detaches in this way from the cables  6 , 7  and lanyards  12 , 13  in the course of an arrest (i) to prevent damage to the winch  5 , (ii) to prevent flying object hazards and (iii) to limit the restraining forces which can be applied by the deployment and anchoring system components to the net in opposition to the engagement of the spikes  4  in the vehicle tyres and thereby avoid the risk of the spikes being pulled from the tyres by those components as the net is carried along by the vehicle. 
     An additional advantage of the spacing of the lanyard anchorage point  14  from the point of attachment of the lanyard  12  to the net as compared to, say, pegging the net down directly at its side edge, is that there is greater opportunity for the net to wrap around the adjacent vehicle tyre before the tension applied from the ground anchorage builds up to the extent to break the weak link  19 . This is because it more readily facilitates lifting of the net as the net wraps around the circumference of the tyre. This further helps to ensure that, once engaged, the spikes  4  will not be dislodged from the tyre as the arrest proceeds.