BLAST ABSORPTION DEVICE

Field of the Invention

The present invention relates to a blast absorption device, particularly, but not exclusively, for use in absorbing blasts associated with car bombs.

Background to the Invention

Car bombs are an increasingly used method of killing and maiming people and causing damage in urban areas. In theatres of conflict such as Iraq and Afghanistan, car bombs are used with increasing frequency against coalition troops.

Vehicle borne explosive devices cause damage through flying shrapnel and the Shockwave of the explosion. The shrapnel can cause harm to personnel and also pose a threat to vehicles in close proximity to the blast. The Shockwave can weaken structures to the point of collapse, possibly increasing the death toll further, and can also cause internal injuries to personnel such as lung haemorrhage or traumatic brain injuries.

Conventional defensive systems, such as barriers, are out-of-date for modern conflict. The systems currently used were designed when the major threat came from conventional opposition forces following a declaration of war. While present barriers stop a vehicle, they allow the blast, consisting of a Shockwave and shrapnel, to wreak damage to surrounding structures. For example, the Jersey barrier is around 35 inches tall and comprises a large concrete block used to control flow of traffic through checkpoints. When a car bomb explodes adjacent to a Jersey barrier, the Shockwave and shrapnel can easily fly over the top of the barrier to cause severe casualties and damage to surrounding structures.

Summary of the Invention

According to a first aspect of the present invention there is provided a blast absorption device for use in a protection system, the blast absorption device comprising: a flexible member adapted to absorb energy from an explosion; and at least one panel member attached to the flexible member, each panel member adapted to prevent shrapnel passing through the blast absorption device.

In one embodiment, the blast absorption device flexible member deflects with the Shockwave dispersing as much of the Shockwave as possible and therefore reducing damage. The panel members primarily absorb the impact of shrapnel, further reducing the damage caused by a car bomb. Together the flexible member and the panels minimise the effect of a car bomb on personnel or structures sheltered by the blast absorption device. The flexible member may be expandable. The action of expanding will absorb energy from the Shockwave.

The flexible member may comprise a high tensile strength material. A high tensile strength material resists shearing forces applied to the flexible material following the impact of the Shockwave. The flexible member may comprise a net. A net is particularly suitable as the structure facilitates expansion and allows visibility therethrough.

The net may comprise a twaron/polyester. Twaron/polyester is a suitably high tensile strength material.

The blast absorption device may permit visibility therethrough. Visibility through the device permits personnel to see incoming danger. The flexible member may permit visibility therethrough. The at least one panel member may comprise a plurality of tiles.

The/each panel member may be attached to a flexible member surface by an adhesive.

The/each panel member may be located on a first surface of the flexible member. In one embodiment, there are a plurality of panel members, at least one panel member being located on each of a first and second flexible member surfaces.

In one embodiment, for each panel member attached to the flexible member first surface there is a panel member attached to the flexible member second surface in a location opposed to the first surface panel member. Such an arrangement sandwiches the flexible member between two panel members. Where the flexible member is sandwiched between two panel members and the flexible member is a net, the panels may be attached to both the net and each other.

The/each panel member may be triangular. It was found that triangular panel members allowed reasonable flexibility of the flexible member whilst providing sufficient coverage of the flexible member to absorb shrapnel.

The/each panel member may comprise at least one line of weakness. In one embodiment the/each panel member is adapted to break at a line of weakness. In the event of a bomb blast, for example, further dissipation of energy of the blast is achieved by providing the panel with lines of weakness at which the panel member is intended to break into a number of smaller panel members.

In one embodiment the lines of weakness divide the panel into a plurality of smaller panel members.

The smaller panel members may be triangular.

At least one panel member may comprise a first material, the first material being good under compression. A material which is good under compression will absorb the impact of shrapnel.

In an embodiment, the first material may be poor under tension.

In this embodiment, at least one panel member may comprise a second material, the second material being good under tension. A material which is good under compression will allow a bullet to pass therethrough.

The second materia! may be poor under compression. Where there are panel members located on each of a first and second flexible member surfaces in an opposed configuration, one panel member may be of the first material and the opposed panel member may be of the second material. Such an arrangement provides "one way protection". In one embodiment, shrapnel coming from one side will hit the first material, which is good under compression, and be stopped. However, a bullet coming from the other side will hit the second material which is poor under compression and pass straight through. This means in the event of a car bomb, shrapnel can be stopped but armed personnel will still be able to shoot through from the other side of the netting.

In an alternative embodiment, the/each panel member is a composite. The composite may comprise the first material and a second material, the second material being good under tension but poor under compression. The/each panel member may be substantially transparent. The panel members may be adhered to the net using a methacrylat. Araldite® 2022 is a suitable adhesive. The blast protection device may be collapsible. Being collapsible, for example, being rolled up, permits the product to be compacted for shipping and reduces the space occupied by the device.

According to a second aspect of the present invention there is provided a protection system comprising: a blast absorption device comprising a flexible member adapted to absorb energy from an explosion and at least one panel member attached to the flexible member, each panel member adapted to prevent shrapnel passing through the blast absorption device;

a plurality of blast absorption device supports; and a plurality of attachment devices for attaching the protection system to a base.

In one embodiment, in use, a first support and a second support are a spacing distance apart.

In this embodiment, a dimension of the flexible member may be greater than the spacing distance.

Each support may include a frangible fixing device adapted to pull the flexible member taut between adjacent supports. As the flexible member is longer than the gap between supports, when the flexible member is pulled taut it means there will be some slack material adjacent each support. A taut flexible member facilitates visibility through the blast protection device.

In an embodiment, in the event of an impact, the frangible attachment devices separate, permitting the flexible member to absorb the impact. The slack material can be utilised in absorbing the impact.

The flexible member may be attached to each support by a fixed attachment device adapted to secure the flexible member to the support,

In one embodiment, each support has a D-shaped cross-section. Each support may be deformable. A deformable support will absorb energy from a blast. Once the flexible member is fully expanded the blast energy will be transferred to the supports by the fixed attachments.

In one embodiment, the fixed and frangible attachment devices have a lower ultimate tensile strength than the support. This allows the support to deform without reaching its tensile failure point. The support may be made from a high tensile material. A high tensile steel such as ASTM A747 is suitable.

The support may be corrosion resistant.

In one embodiment, each attachment device is adapted to be connected to a support.

Each attachment device may be adapted to be connected to a base such as a Jersey barrier. The system may be retrofittable to an existing barrier. Being retrofittable permits the system to be useable at temporary events such as sports events.

According to a third aspect of the present invention there is provided a panel member for use in a blast absorption device, the panel member comprising a composite of a first material and a second material wherein the first material comprises good compression properties and poor tension properties and the second material comprises good tension properties but poor compression properties.

In one embodiment the panel member is adapted to resist the impact of a body engaging a surface of the first material but allowing a body engaging surface of the second material to pass through the panel member. Such an arrangement provides "one-way protection" in that shrapnel hitting the first material will not pass through the panel member but a bullet fired from the other side through the second material will pass through the panel member.

It will be understood that non-essential features listed in connection with any of the aspects of the invention may be equally applicable to any other aspect and are not repeated for brevity.

Brief Description of the Drawings

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a protection system incorporating a blast absorption device according to a first embodiment of the present invention;

Figure 2 is an enlarged, plan view of part of the blast absorption device of the system of Figure 1 ;

Figure 3 is an enlarged, perspective view of the four panel members and net of the biast absorption device of Figure 1;

Figure 4 is a perspective view of the support of the system of Figure 1 ;

Figure 5 is an enlarged, perspective view of a clamp of the system of Figure 1;

Figure 6 is a close-up view of part of the system of Figure 1 ;

Figure 7 is a schematic showing the impact of shrapnel on a panel member of the system of Figure 1 ;

Figure 8 is a schematic showing the impact of a bullet on the panel member of Figure 1;

Figures 9 to 11 are schematics showing the attachment in operation of the flexible member to one of the posts of the system of Figure 1 ;

Figure 12 is a pane view of part of a net and panel members arrangement of a protection system according to a second embodiment of the present invention; and Figure 13 is a section through the first and second panel members and part of a net of the protection system of Figure 12.

Detailed Description of the Drawings

An embodiment of the present invention will now be described with reference to Figure 1 which shows a protection system, generally indicated by numeral 10 for protecting people such as soldiers and protecting structures such as vehicles or buildings from the blast of a car bomb.

The protection system 10 comprises a biast absorption device 12, first and second supports 14,16 and first and second clamps 18,20, the first clamp 18 supporting the first support 14 and the second clamp 20 supporting the second support 16. As can be seen from Figure 1 , the clamps 18,20 facilitate the connection of the personnel protection systemiO to a Jersey barrier 22.

Referring now to Figures 2 and 3, plan and perspective views of parts of the blast absorption device 12 of Figure 1 respectively. The blast absorption device 12 comprises a flexible member 24 and a plurality of panel members 26. The flexible member 24 is a twaron polyester net which is a high tensile strength material and which can expand under pressure supplied, for example, by a Shockwave. The panel members 26 are triangular tiles made from an acrylic/polycarbonate composite. The structure of the tiles 26 will be discussed in due course.

As can be seen most clearly from Figure 3, the net 24 is sandwiched between a net first surface tile 26a and a net second surface tile 26b. The tiles 26a and 26b are adhered together, and to the net, by an methacrylate adhesive such as Araldite® 2022.

The gap between the tiles, as indicated by letter "X" on Figure 2 is 30 mm.

This gap X is sufficiently large to allow the flexible material 24 to flex and to permit the blast absorption device 12 to be rolled up for storage and is small enough to ensure the majority of the shrapnel impacting the blast absorption device 12 impacts the panel members 26 rather than the net 24.

Figure 4 shows a support 14,16. The support 14,16 shown is of circular cross-section however any suitable cross-section can be used. As can be seen from

Figure 4 the support 14,16 comprises a bend 30. In the event of a blast, the energy of the blast will act on the support 14,16 against the bend 30, thereby dissipating some of the energy.

Figure 5 shows a perspective view of a clamp 18,20 which incorporates an aperture 42 for receiving an end of the post 14,16. As can be most clearly seen from Figure 6, the aperture 32 has got a contoured edge to facilitate sliding the post 14,16 into the clamp 18,20. As can also be seen from Figure 6, the clamp 18,20 includes lifting eyes 34 to which a handle or the like can be attached for carrying the clamps 18,20.

The composite panel members 26 will now be described with reference to Figures 7 and 8. As can be seen from Figures 7 and 8, the panel member 26 comprises a first layer 40 of acrylic. Acrylic is good in compression but poor in tension. The second layer 42 is a polycarbonate which is poor under compression but good in tension. When the blast absorption device 12 is erected, the acrylic layer 40 of each tile 26 faces outwards and the polycarbonate layer 42 faces inwards, towards the personnel or object to be protected. The mechanical properties mean that, as shown in Figure 7, when a piece of shrapnel 44 hits the acrylic side 40, the acrylic goes into compression (in which it is strongest) and the polycarbonate 42 goes into tension (in which it is strongest), thereby resisting the progression of the shrapnel 44 through the panel member 26.

Referring to Figure 8, when a bullet 46 is fired at the panel member 26 the result is different as the bullet 46 impacts the polycarbonate layer 42, the polycarbonate goes into compression (in which it is weakest) and the acrylic layer 40 goes into tension (in which it is weakest). This permits the bullet 46 to pass through the panel member 26. The acrylic polycarbonate composite is substantially transparent permitting a user to see through the blast absorption device 12.

The connection of the flexible member 24 to the first post 14 will now be described with reference to Figures 9 to 11. As can be seen from Figure 9, the netting 24 is attached to the post 14 by frangible attachment devices 50 in the form of cable ties. The netting 24 is also attached to the post 14 by fixed attachment device 52 in the form of a karabiner. As can be seen from Figure 9, the netting is attached in such away that a net portion 54 extending between posts 14,16 is pulled tight and a further portion of netting 56 is gathered adjacent the post 14. When an explosion occurs, and the Shockwave and shrapnel hit the netting 24, the force applied to the net 24 severs the frangible attachment devices 50 (as shown in Figure 10) with the result that the net 24 deflects and stretches in response to the Shockwave and shrapnel.

As shown in Figure 11 the net 24 is retained in engagement with the post 14 by the karabiner 52 however the ultimate tensile strength karabiner 52 is selected so that it is less than the ultimate tensile strength of the post 14 so that the karabiner 52 will sever and release the net 24 before the post 14 breaks. The post 14 is, however, adapted to deform to absorb more of the explosion.

Reference is now made to Figures 12 and 13, plan and section views of part of a net 124 and panel member 126 arrangement of a protection system 110 according to a second embodiment of the present invention. The system 110 is similar to the system 10 of Figures 1 to 11, the primary difference being the structure of the panel members 126. The panel members 126a, 126b are sheets divided into triangular portions 190 by lines of weakness 192a,192b. In the event of an explosion, the energy of the explosion (indicated by the arrow 194, Figure 13) causes the panel members 126 to break at the lines of weakness 192, thereby dissipating some of the energy of the explosion. Modifications and improvements to the above described embodiment can be envisioned without departing from the scope of the invention. For example, although the panel members are described as being composites, it could be that the panel members 26a (Figure 3) on the external surface are of one material and the panel members 26b on the internal surface of the net 24 are of the other material.