WO2015019039A1

WO2015019039A1 - A ballistic curtain

Info

Publication number: WO2015019039A1
Application number: PCT/GB2014/000305
Authority: WO
Inventors: Robert james CLIFFE
Original assignee: The Secretary Of State For Defence Dstl
Priority date: 2013-08-05
Filing date: 2014-08-04
Publication date: 2015-02-12
Also published as: WO2015019039A8; GB201313971D0; GB201413653D0; GB2520106B; GB2520106A

Abstract

There is provided a ballistic curtain (50) comprising a plurality of flexible protective layers (10, 12, 14, 16) and a support structure. The plurality of flexible protective layers (10, 12, 14, 16) are connected to the support structure around a periphery of the flexible protective layers (10, 12, 14, 16). The ballistic curtain (50) is movable between open and packed configurations. In the open configuration the support structure holds the flexible protective layers (10, 12, 14, 16) spaced apart from one another by free space to allow each flexible protective layer (10, 12, 14, 16) to deform independently from the other flexible protective layers (10, 12, 14, 16), and in the packed configuration the support structure allows the flexible protective layers (10, 12, 14, 16) to collapse together.

Description

A BALLISTIC CURTAIN

Technical Field of the Invention The invention relates to a ballistic curtain, and a related method and use thereof. Background to the Invention

Ballistic curtains are typically used to protect areas from high-speed incoming projectiles, for example from bullets and shrapnel. Applications for ballistic curtains include protecting electrical equipment, protecting areas where personnel are operating, blocking bullets on shooting ranges, etc.

Known ballistic curtains commonly comprise multiple layers of ballistic material that are laminated to one another to block the passage of projectiles. Ballistic materials are materials capable of defending against dense high-speed projectiles such as bullets or shrapnel, and include materials such as Kevlar™, Dyneema™, Ultra-High-Molecular-Weight Polyethylene (UHMWPE). Two of the drawbacks of known ballistic curtains are their size and their weight, which can make them difficult to transport.

It is therefore an object of the invention to provide an improved ballistic curtain. Summary of the Invention

According to an embodiment of the invention, there is provided a ballistic curtain comprising a plurality of flexible protective layers and a support structure. The plurality of flexible protective layers are connected to the support structure around a periphery of the flexible protective layers. The ballistic curtain is movable between open and packed configurations, wherein in the open configuration the support structure holds the flexible protective layers spaced apart from one another by free space to allow each flexible protective layer to deform independently from the other flexible protective layers, and wherein in a packed

configuration the support structure allows the flexible protective layers to collapse together. The use of a plurality of flexible protective layers that are spaced apart from one another by free space means that a projectile impacting a first one of the flexible protective layers will stretch and deform the first flexible protective layer before the first flexible protective layer contacts a second one of the flexible protective layers. The second one of the flexible protective layers is then also able to stretch and deform, further reducing the speed of the projectile. The second flexible protective layer may then contact a third one of the flexible protective layers, if such a third flexible protective layer is present. Each flexible protective layer acts individually to slow the projectile and prevent its penetration through the ballistic curtain as a whole or reduce its potential to cause injury. This spacing apart of flexible protective layers by free space has been found to be more effective at stopping projectiles than simply laminating all of the flexible protective layers together with one another as a single laminate.

Preferably, at least one of the flexible protective layers comprises a plurality of sub-layers. The sub-layers may be detachable, thereby further improving the anti-ballistic performance of the curtain.

In one embodiment, the sub-layers may comprise discrete regions within a single material layer separated by one or more regions of weakened material.

By forming the sub-layers as discrete regions separated by one or more regions that are weaker than (i.e. can be more readily damaged than) the sub-layers, one or more of the sublayers can detach, or partially detach, from the at least one flexible protective layer, thereby- absorbing energy from the projectile (this is described in more detail below). The weakened material regions may be formed, for example, by removing fibres from the weave or fabric. Alternatively, the weakened regions may be formed by perforations, or holes, in the material of the flexible protective layer.

Alternatively, at least one of the flexible protective layers may comprise a plurality of overlapping sub-layers. The plurality of overlapping sub-layers may be laminated together in a laminate to form the flexible protective layer.

At least one of the sub-layers may only extend over less than 75% of the area of the corresponding flexible protective layer. For example, if the area of the flexible protective 9

layer is 4m , then the area of one of the sub-layers forming the flexible protective layer may be less than 3m . More preferably, at least one of the sub-layers may only extend over less than 50%, or even more preferably only extend over less than 25%, of the area of the corresponding flexible protective layer.

The use of a sub-layer, preferably a sub-layer having a smaller area than the area of the corresponding flexible protective layer, means that the sub-layer may be able to detach from the corresponding flexible protective layer under the force of a projectile impacting the sublayer, sapping energy from the projectile as it causes the detachment. The use of at least one detachable sub-layer may therefore improve anti-ballistic performance. The detached sublayer may be carried along by the projectile, reducing the speed of the projectile through increased air resistance. Furthermore, the detached sub-layer may help to prevent the projectile from passing through a subsequent flexible protective layer when the detached sublayer impacts the subsequent flexible protective layer together with the projectile. The sub- layer may fully detach, or only partially detach, but in either case will help reduce the speed of the projectile.

The at least one sub-layer may form part of an exterior surface of the flexible protective layer, so that it can more easily detach from the flexible protective layer when the flexible protective layer is impacted by a projectile.

The at least one sub-layer may not be directly connected to the support structure, but instead be held in place by the remainder of the flexible protective layer of which the sub-layer forms part. This may further assist in allowing the at least one sub layer to detach from the flexible protective layer when the flexible protective layer is impacted by a projectile.

In the case of an overlapping sub-layer, the at least one sub-layer may for example be attached to the remainder of the corresponding flexible protective layer by an adhesive, so that some energy of a projectile is taken from the projectile when overcoming the adhesive to detach the sub-layer from the remainder of the corresponding flexible protective layer. In an alternative example the at least one sub-layer may be attached to the remainder of the corresponding flexible protective layer by fibres, or stitching so that some energy of a projectile is taken from the projectile when stretching and breaking the fibres or stitching to detach, or partially detach, the sub-layer from the remainder of the corresponding flexible protective layer.

At least one of the sub-layers, preferably at least one of the overlapping sub-layers, may have a maximum dimension of between 20 and 200mm, and/or an area of between 400 and 40000 mm . Reducing the sub-layer in size beneath those ranges may undesirably reduce the energy expended by the projectile in detaching the sub-layer from the protective layer. Increasing the sub-layer in size above those ranges may undesirably increase the chances of the projectile simply passing right through the sub-layer, rather than expending energy in detaching and displacing the sub-layer from the protective layer.

One of the at least one overlapping sub-layers may be a base layer that extends over the whole area of the flexible protective layer, and other ones of the at least one sub-layers that extend over less than the whole area of the flexible protective layer may be attached to base layer, either attached directly to the base layer or attached via other sub-layers. Where the flexible protective layer comprises a base layer, the ballistic curtain may be arranged such that the sub-layers are positioned towards the rear of the curtain (i.e. on the side opposite the ballistic challenge). This can improve the detachability of the sub-layers by removing the need for the sub-layer to travel through the material of the base layer in order to detach. Furthermore, this may minimise damage to the base layer, thereby improving the ballistic performance of the curtain against further projectiles.

Preferably, the flexible protective layers are formed from materials known for their ballistic qualities in protecting against projectiles, for example Kevlar , Spectra , Dyneema , Aramid,^" UHMWPE fibres, etc, as will be apparent to those skilled in the art. The projectiles may include objects such as stone, sand, grit, metal, glass, ceramic, plastic or composites of various masses, shapes, sizes or velocities.

Each flexible protective layer may be a flexible fibre layer or flexible fibre sheet for protecting against explosively driven projectiles. For example, flexible fibre layers may be formed from textiles of woven or knitted or crocheted fibres, which may be processed to form felt. Advantageously, where the protective layer comprises a base layer, the base layer may be a mesh or a net, preferably a mesh or a net suitable for providing ballistic protection. The use of net and mesh materials provides the advantage of being lower in weight than alternative configurations of the same material. This can enable a lower weight ballistic curtain to be produced. Additionally, the reduced area of contact between the mesh or net and the overlapping sub-layers can improve the ease with which the sub-layers are able to detach. More than one of the flexible protective layers may comprise a plurality of sub-layers. In this case, the position of sub-layers in a longitudinal direction are preferably offset or staggered such that the total area of the ballistic window(s) through which a projectile might pass unhindered or substantially unhindered is minimised. By longitudinal direction is meant the through-direction of the ballistic curtain. Preferably, the ballistic curtain is configured to protect against fragments of at least 0. lg mass impacting the garment at a velocity of at least 150m/s, wherein the fragments are made of made of glass, metal, ceramic, stone, or other material likely to be encountered in an explosive event. The ballistic curtain may be configured to provide protection against standard fragment simulating projectiles (FSP) as specified in STANAG 2910 edition 2.

The flexible protective layers may for example be spaced apart from one another by at least 5mm, or at least 10mm. Spacing the flexible protective layers apart from one another by greater than or equal to the deformation depth that is created by a projectile in the flexible protective layer before the flexible protective layer ruptures and allows the projectile through, allows each flexible protective layer to perform to its maximum extent in blocking the projectile. This helps to minimise the weight of the ballistic curtain by extracting maximum performance from each of the flexible protective layers that are present in the ballistic curtain.

There may be between 5 and 25 flexible protective layers depending upon the level of protection that the ballistic curtain is required to provide. The 5 to 25 flexible protective layers may each be spaced apart from one another by between 5 and 50mm. The flexible protective layers are preferably substantially the same shape as one another.

The ballistic curtain comprises a support structure to facilitate holding the protective layers apart from one another in an open configuration for protecting against projectiles, and to enable packing of the ballistic curtain into a packed configuration where it can be more easily stored or transported. This means that although the ballistic curtain may be very thick in the open configuration when many flexible protective layers are implemented spaced apart from one another, the ballistic curtain can be reduced in thickness for convenient transportation in the packed configuration by allowing the flexible protective layers to collapse together to meet one another.

In the open configuration, the support structure may hold the flexible protective layers spaced apart from one another in substantially parallel planes, to make the best use of the space in the depth dimension perpendicular to the parallel planes. The flexible protective layers may be arranged to fully overlap one another in a direction perpendicular to the substantially parallel planes.

In the packed configuration, the flexible protective layers may collapse to meet one another whilst remaining attached to the support structure. Alternatively, the support structure may allow disengagement of the flexible protective layers from the support structure so that the flexible protective layers can collapse to meet one another.

A ballistic curtain is a curtain suitable for blocking explosively driven projectiles such as bullets and/or shrapnel/fragmentation. Even if a particular projectile is large enough and fast moving enough to penetrate through the ballistic curtain, the ballistic curtain may

significantly reduce the kinetic energy of the projectile to help protect a region behind the ballistic curtain.

The support structure may be entirely sufficient to support the ballistic curtain, for example the ballistic curtain may not require any supporting elements in addition to the support structure that is part of the ballistic curtain in order for the ballistic curtain to be deployed to block projectiles in the open configuration.

Advantageously, the support structure may comprise two crosspieces at the periphery of the flexible protective layers, each crosspiece being aligned perpendicular to the flexible protective layers, each flexible protective layer being connected to a respective point along each crosspiece. Accordingly, the crosspiece is used to set the separation distance between the various flexible protective layers. The two crosspieces may be arranged at opposing edges or corners of the flexible protective layers. Each crosspiece may be used as an anchor point for anchoring the flexible protective layers in position wherever the ballistic curtain is deployed. In particular, the support structure of the ballistic curtain may further comprise guy lines for tensioning against the crosspieces to hold the ballistic curtain in position. Alternatively, or additionally, the support structure may comprise support rod(s) for holding the crosspieces in position above the ground. For example the support structure may comprise a support rod for each crosspiece, the support rod for each crosspiece being connected to a tensioning guy line of each crosspiece. Preferably, the flexible protective layers are substantially rectangular, and the two crosspieces are at two respective corners of the flexible protective layers.

Advantageously, the support structure may comprise two stabilising guy lines for each crosspiece, the two stabilising guy lines for each crosspiece being connected to opposing ends of the crosspiece for holding the crosspiece in tension in the open configuration. Then, the stabilising guy lines prevent the flexible protective layers from excessive movement in the depth direction of the flexible protective layers. Accordingly, each crosspiece may be a \ flexible fibre string so that the flexible protective layers can easily collapse towards one another to move into the packed configuration.

The support structure may comprise two support rods for each crosspiece, the two support rods for each crosspiece being connected to opposing ends of the crosspiece, and to a common base member. In the open configuration, the two support rods may be held biased apart from one another, for example by stabilising guy lines, and/or by the base member. The support rods may suspend the flexible protective layers in space by way of the support rods holding up the crosspieces. The base member of the support structure may rest upon the ground in the open configuration.

Each crosspiece may be connected to each of the flexible protective layers by respective control strings, such that the control strings hold the flexible protective layers spaced apart from one another when the crosspiece is pulled in a direction away from the flexible protective layers by guy lines and/or support rods. In particular, the support structure may comprise a tensioning guy line for each crosspiece, the tensioning guy line for each

crosspiece being suitable for pulling the crosspiece away from the flexible protective layers in a direction parallel to the planes of the flexible fibre layers in the open configuration. The presence of the control strings allows the flexible protective layers to collapse towards one another in the packed configuration, even when the crosspieces are rigid rods. The tensioning guy line may be directly connected to the crosspiece, or indirectly connected to the crosspiece, for example via a support rod. Rigid rod crosspieces may be implemented even when control strings are not present, for example a rigid rod could pass through apertures in the flexible protective sheets.

The tensioning guy line for each crosspiece may be connected to the crosspiece at a midpoint along the crosspiece, so that each of the flexible protective layers are pulled with

substantially the same force by the crosspiece. Each crosspiece may pass through a peripheral region of the flexible protective layers, for example by connecting directly to each one of the flexible protective layers rather than connecting via control strings. Advantageously, _teach crosspiece may comprise a first end connected to a first one of the flexible protective layers and a second end connected to a final one of the flexible protective layers: The first one of the flexible protective layers and the final one of the flexible protective layers form opposite faces of the overall ballistic curtain in the open configuration. The support structure may further comprise two scissor rods that are pivotally connected to one another, each scissor rod being connected to the first end of one of the crosspieces and the second end of another of the crosspieces. Accordingly, the ballistic curtain may be moved between open and packed configurations by pivoting the scissor rods about one another.

In another aspect, the invention provides the use of a plurality of spaced apart flexible protective layers as a ballistic curtain, wherein at least one of the flexible protective layers comprises a plurality of detachable sub-layers.

In a further aspect, the invention provides a method of providing ballistic protection, the method comprising the step of providing a plurality of spaced apart flexible protective layers, at least one of the flexible protective layers comprising a plurality of detachable sub-layers.

It will be understood that each feature in one aspect can be applied to any other, aspect of the invention. In particular, device aspects may be applied to use and method aspects, and vice versa. Brief Description of the Drawings

- Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Fig. la shows a schematic perspective diagram of a ballistic curtain according to a first embodiment of the invention, the ballistic curtain being in an open configuration;

Fig. lb shows a schematic perspective diagram of the ballistic curtain of Fig. la in a packed configuration;

Fig. 2a shows a schematic perspective diagram of a ballistic curtain according to a second embodiment of the invention, the ballistic curtain being in an open configuration;

Fig. 2b shows a schematic perspective diagram of the ballistic curtain of Fig. 2a in a packed configuration;

Fig. 3a shows a schematic perspective diagram of a ballistic curtain according to a third embodiment of the invention, the ballistic curtain being in an open configuration;

Fig. 3b shows a schematic perspective diagram of the ballistic curtain of Fig. 3a in a packed configuration;

Fig. 4a shows a schematic perspective diagram of a ballistic curtain according to a fourth embodiment of the invention, the ballistic curtain being in an open configuration;

Fig. 4b shows a schematic perspective diagram of the ballistic curtain of Fig. 4a in a packed configuration; and

' Fig. 5a shows a plan diagram of a flexible protective layer suitable for use in embodiments of the invention, for example in any of the first to fourth embodiments.

' Fig. 5b shows a plan diagram of an alternative flexible protective layer suitable for use in embodiments of the invention, for example in any of the first to fourth embodiments.

Fig. 5c shows a plan diagram of a further alternative flexible protective layer suitable for use in embodiments of the invention, for example in any of the first to fourth embodiments.

Fig. 5d shows a plan diagram of a further alternative flexible protective layer suitable for use in embodiments of the invention, for example in any of the first to fourth embodiments.

The drawings are for illustrative purposes only and are not to scale. Same or similar reference signs denote same or similar features. Detailed Description

A first embodiment of the invention will now be described with reference to the schematic diagrams of Fig. la and lb, which show a ballistic curtain 50 in open and packed

configurations respectively.

The ballistic curtain 50 comprises four flexible fibre layers 10, 12, 14, and 16 that are each formed from multiple layers of Aramid fibres. The flexible fibre layers 10, 12, 14, and 16 constitute flexible protective layers and all have the same rectangular shape as one another. In the open configuration shown in Fig. la, the flexible fibre layers 10, 12, 14, and 16 are all held in substantially parallel planes by a support structure. The support structure comprises eight control strings 27, two crosspieces 25, two tensioning guy lines 21, two support rods 20, and two base plates 30. The support structure holds the flexible fibre layers 10, 12, 14, and 16 in free space and separated apart from one another by a distance Spl of 10mm.

The two crosspieces 25 are connected to the flexible fibre layers at two respective corners of the flexible fibre layers. Each crosspiece is aligned perpendicular to the flexible fibre layers, and each flexible fibre layer is connected to a respective point along each crosspiece by one of the control strings 27. The two crosspieces 25 are rigid rods.

The two tensioning guy lines 21 are connected to the two crosspieces 25 respectively, each tensioning guy line 21 being connected to the midpoint of the respective crosspiece. The tensioning guy line 21 for each crosspiece pulls the crosspiece in a direction parallel to the planes of the flexible fibre layers, at an inclined angle from the crosspiece to help support the weight of the flexible fibre layers.

Each tensioning guy line 21 is associated with one of the support rods 20, and passes through the support rod 20 and down to ground, where it is held by a ground anchor 22 such as a peg in the ground. The support rod 20 is a rigid rod that supports the weight of the flexible fibre layers under the action of the tensioning guy line 21. Each support rod 20 extends vertically upwards from a respective base plate 30, each base plate 30 being held in the ground by pegs 32. The support structure further comprises two additional crosspieces 40 at the other two corners of the rectangular shaped flexible fibre layers. The additional crosspieces 40 are strings that are aligned perpendicular to the flexible fibre layers and connected to each one of the flexible fibre layers. The additional crosspieces 40 are held in tension by ground anchors 42, and so hold the flexible fibre layers spaced apart from one another. The ground anchors 42 are pegs that are inserted into the ground to retain the additional crosspieces 40.

The ballistic curtain 50 in the open configuration shown in Fig. 1 a protects against explosively driven projectiles such as the projectile PI, by the projectile PI being

progressively slowed as it successively impacts the flexible fibre layers 10, then 12, then 14, then 16.

As shown in Fig. lb, the ballistic curtain 50 may be moved into a packed configuration by un-pegging the ground anchors 22 and 42 and base plates 30, and allowing the flexible fibre sheets to collapse towards one another to meet one another. The flexible fibre sheets may be further packed for storage, for example by folding them together about the fold line Fl and then rolling them up about the support rods 20 and crosspieces 25. Furthermore, the control strings 27 may be configured to detach from the flexible fibre sheets 10, 12, 14, 16 or from the crosspieces 25, to enable packing of all or some of the support structure separately from the flexible fibre sheets.

In a variation to the first embodiment, each tensioning guy line 21 may be directly fixed to the corresponding support rod 20, and a separate guy line may be provided to extend between the support rod 20 and the ground.

,

A second embodiment of the invention will now be described with reference to the schematic diagrams of Fig. 2a and 2b, which show a ballistic curtain 150 in open and packed

configurations respectively. The ballistic curtain 150 comprises four flexible fibre layers 110, 112, 114, and 116 similar to the four flexible fibre layers 10, 12, 14, and 16 of the first embodiment. The ballistic curtain 150 also comprises additional crosspieces 140 and ground anchors 142, similar to the additional crosspieces 40 and ground anchors 42 of the first embodiment. In the second embodiment, the support structure comprises crosspieces 125 which are flexible fibre strings, rather than the rigid rod crosspieces 25 of the first embodiment. Each crosspiece 125 is held in tension by two stabilising guy lines 123 in the open configuration, the two stabilising guy lines being connected to opposite ends of the crosspiece 125.

Each crosspiece 125 is also connected to two support rods 120 at either end of the crosspiece. The two support rods of each crosspiece are both connected to a common (the same) base plate 130 with pegs 132 for holding the base plate in position on the ground. The two support rods of each crosspiece help bear the weight of the four flexible fibre layers that is exerted on the crosspiece.

The crosspieces 125 are directly connected to the flexible fibre layers 110, 112, 114, and 116, by passing through the flexible fibre layers at the corners of the flexible fibre layers. Each flexible fibre layer is connected to each crosspiece 125 at a fixed position along the length of the crosspiece 125, to set the separation distance Spl 1 between the various flexible fibre layers.

Since there are no control lines' similar to the control lines 27 of the first embodiment, the support structure of the second embodiment ma be less liable to tangling than the support structure of the first embodiment when in the packed configuration.

The ballistic curtain 150 in the open configuration shown in Fig. 2a protects against explosively driven projectiles such as the projectile PI 1, by the projectile PI 1 being progressively slowed as it successively impacts the flexible fibre layers 110, then 112, then 114, then 116.

As shown in Fig. 2b, the ballistic curtain 150 may be moved into a packed configuration by un-pegging the ground anchors of the additional crosspieces 140, stabilising guy lines 123, and base plates 130, and allowing the flexible fibre sheets to collapse towards one another to meet one another. The flexible fibre sheets may be further packed for storage, for example by folding them together about the fold line Fl 1 and then rolling them up about the support rods 120. The crosspieces 125 may be configured to detach from the flexible fibre sheets 110, 112, 114, 116 or from the support rods 120, to enable packing of all or some of the support structure separately from the flexible fibre sheets. A third embodiment of the invention will now be described with reference to the schematic diagrams of Fig. 3a and 3b, which show a ballistic curtain 250 in open and packed configurations respectively. The ballistic curtain 250 comprises four flexible fibre layers 210, 212, 214, and 216 similar to the four flexible fibre layers 10, 12, 14, and 16 of the first embodiment. The ballistic curtain 250 also comprises additional crosspieces 240, similar to the additional crosspieces 40 of the first embodiment. In the open configuration shown in Fig. 3 a, the additional crosspieces 240 of the second embodiment are connected to base plates 230 at each end of the additional crosspieces 240. The base plates 230 each have pegs for pegging the base plates 230 to the ground, and each base plate 230 is connected to a support rod 220. The support rods 220 are positioned inside sleeves along opposite sides of the flexible fibre layers 210 and 216.

The support structure of the ballistic curtain 250 also comprises flexible fibre string crosspieces 225 that are connected between the flexible fibre layers 210, 212, 214, and 216, and which set the separation distance Sp21 between each of the flexible fibre layers. Stabilising guy lines 223 are connected to the ends of the crosspieces 225 and or ends of the support rods 120, and are tensioned by pegging them to the ground to hold the ballistic curtain 250 in the open configuration.

The ballistic curtain 250 in the open configuration shown in Fig. 3a protects against explosively driven projectiles such as the projectile P21, by the projectile P21 being progressively slowed as it successively impacts the flexible fibre layers 210, then 212, then 214, then 216.

As shown in Fig. 3b, the ballistic curtain.250 may be moved into a packed configuration by un-pegging the stabilising guy lines 223, and base plates 230, and allowing the flexible fibre sheets to collapse towards one another to meet one another. The flexible fibre sheets may be further packed for storage, for example by folding them together about the fold line F21 and then rolling them up about the support rods 220. Since the support rods 220 are retained in sleeves at sides of the flexible fibre layers 210 and 216, and since the additional crosspieces 240 do not have dedicated ground anchors, the ballistic curtain 250 of the third embodiment may be more easily moved between open and packed configurations than the ballistic curtain 150.

The support rods 220 may be configured to detach from the flexible fibre sheets 210, 212, 214, 216 by drawing them out from the sleeves in which they are held, to enable more compact packing of the flexible fibre sheets 210, 212, 214, 216. A fourth embodiment of the invention will now be described with reference to the schematic diagrams of Fig. 4a and 4b, which show a ballistic curtain 350 in open and packed configurations respectively.

The ballistic curtain 350 comprises four flexible fibre layers 310, 312, 314, and 316 similar to the four flexible fibre layers 10, 12, 14, and 16 of the first embodiment. The ballistic curtain 350 also comprises additional crosspieces 340 between base plates 330, similar to the additional crosspieces 240 between the base plates 230 of the third embodiment.

The ballistic curtain 350 further comprises two flexible fibre crosspieces 325connected between support rods 320, similar to the flexible fibre crosspieces 225 that are connected between the support rods 220 in the third embodiment. The support rods 320 are connected to the base plates 330.

The ballistic curtain 350 differs from the ballistic curtain 250 in that the stabilising guy lines 223 that are used to hold the flexible fibre layers apart from one another in the open configuration, have been replaced by two scissor rods 345. The two scissor rods are pivotally connected to one another by a pivot 346.

Each crosspiece 325 has a first end connected to the flexible fibre layer 310 and a second end connected to the flexible fibre layer 316. The flexible fibre layers 310 and 316 define opposite faces of the ballistic curtain 350.

One of the scissor rods 345 extends from the first end of a first one of the two crosspieces 325 at the flexible fibre layer 310, to the second end of the second one of the crosspieces 325 at the flexible fibre layer 316. The other of the scissor rods 345 extends from the first end of the second one of the two crosspieces 325 at the flexible fibre layer 310, to the second end of the first one of the crosspieces 325 at the flexible fibre layer 316. Although the scissor rods are shown as being implemented across the top of the ballistic curtain 350, scissor rods could alternatively, or additionally, be implemented at the base of the ballistic curtain 350, or to extend substantially vertically between the crosspieces 325 and the additional crosspieces 340 at either end of the ballistic curtain. As shown in Fig.4a, when the scissor rods 345 are pivoted away from one another, out of common alignment, the scissor rods tension the flexible fibre crosspieces 325 and so hold the flexible fibre layers separated apart from one another in the open configuration. A retaining means such as a locking pin may be provided at the pivot 346 to maintain the scissor rods pivoted apart from one another in the open configuration.

The ballistic curtain 350 in the open configuration shown in Fig. 4a protects against explosively driven projectiles such as the projectile P31, by the projectile P31 being progressively slowed as it successively impacts the flexible fibre layers 310, then 312, then 314, then 316.

As shown in Fig.4b, when the scissor rods 345 are pivoted towards one another into common alignment about the pivot 346, the scissor rods collapse the flexible fibre layers towards one another into the packed configuration. The fourth embodiment has the advantage of not requiring any guy lines to hold the ballistic curtain 350 in the open configuration, although guy lines could be added for extra security if desired.

As a variation to the fourth embodiment, and to help prevent the flexible fibre layers from becoming slack when the scissor rods are pivoted away from one another into the open configuration, each support rod 320 may be connected to the corresponding crosspiece 325 by an elastic line, the elastic line being stretched as the scissor rods are pivoted towards one another to move into the packed configuration. The support rods 320 and/or the scissor rods 345 may be configured to detach from the flexible fibre sheets 310, 312, 314, 316 to enable more compact packing of the flexible fibre sheets 310, 312, 314, 316.

Various types of material will be apparent to those skilled in the art for the fabrication of the various guy/control lines and rods of the above embodiments. For example, the guy/control lines may be strings or ropes created from Aramid UHWMPE fibres, and the rods may be rigid elongate members created from metals/plastics.

Each one of the flexible protective layers (flexible fibre layers) of the first to fourth embodiments may comprise a plurality of overlapping sub-layers. The plan diagram of Fig. 5a shows a flexible protective layer 500 that comprises a plurality of overlapping sub-layers 501 - 510.

The overlapping sub-layer 501 is a base layer that fully extends over the whole area of the flexible protective layer 500, and which connects to a support structure (not shown in Fig.5), for example a support structure as shown in any of Figs, la - 4b. The overlapping sub-layers 502 - 510 each extend over less than 15% of the whole area of the flexible protective layer 500, and are glued directly onto to the base layer 501 with adhesive. Each one of the plurality of overlapping sub-layers 501 - 510 is formed of woven Aramid fibres, although other types of flexible protective materials could alternatively be used. Furthermore, the base layer 501 may be formed differently from the plurality of overlapping sub-layers 502 - 510, for example the base layer 501 may be formed as a mesh or a net for supporting the plurality of overlapping sub- layers 502 - 510.

In a further embodiment, shown in Fig, 5b, a flexible protective layer 500 comprises a plurality of overlapping sub-layers 501-510.

The overlapping sub-layer 512 is a base layer that fully extends over the whole area of the flexible protective layer 500. The base layer 512 is formed of a mesh or a net suitable for providing ballistic protection. The overlapping sub-layers 502 - 510 each extend over less than 15% of the whole area of the flexible protective layer 500, and are attached directly to the base layer 512 with adhesive. In an alternative arrangement (Fig. 5c) the sub-layers may not comprise a base layer. For example, the sub-layers 502-510 may all be the same size as one other and partially overlap one another at regions 511 to form the overall protective flexible layer 500. Sub-layers 502- 510 may be attached to each other at regions 511 by any suitable means, for example by adhesive.

In a .further alternative arrangement (Fig. 5d) the sub-layers are formed as discrete regions 514-522 within a single layer of woven Aramid fibre. Region 523 is a weaker region of the woven Aramid fibre material layer, areas of weakness being deliberately imparted using perforations 513. The perforations are not present in the sub-layers 514-522.

Further embodiments falling within the scope of the appended claims will also be apparent to those skilled in the art. For example, other numbers of flexible fibre layers could be used than the four described in the embodiments.

Claims

1. A ballistic curtain comprising a plurality of flexible protective layers and a support structure, the plurality of flexible protective layers being connected to the support structure around a periphery of the flexible protective layers, wherein the ballistic curtain is movable between open and packed configurations, wherein in the open configuration the support structure holds the flexible protective layers spaced apart from one another by free space to allow each flexible protective layer to deform independently from the other flexible protective layers, and wherein in a packed configuration the support structure allows the flexible protective layers to collapse together.

2. The ballistic curtain of claim 1, wherein at least one of the flexible protective layers comprises a plurality of sub-layers.

3. The ballistic curtain of claim 1 or 2, wherein at least one of the flexible protective layers comprises a plurality of overlapping sub-layers.

4. The ballistic curtain of claim 2, wherein the sub-layers are formed as discrete regions within a single material layer separated by one or more regions of weakened material.

5. The ballistic curtain of any one of claims 2 to 4, wherein at least one of the sub-layers only extends over less than 75% of the area of the corresponding flexible protective layer.

6. The ballistic curtain of any one of claims 2 to 5, wherein more than one of the flexible protective layers comprise a plurality of sub-layers, and wherein the position of sub-layers in a longitudinal direction are offset or staggered to reduce the ballistic window(s) for a projectile.

7. The ballistic curtain of any preceding claim, wherein the Flexible protective layers are formed from at least one of Aramid and UHWMPE fibres.

8. The ballistic curtain of any preceding claim, wherein in the open configuration the support structure holds the flexible protective layers spaced apart from one another in substantially parallel planes.

9. The ballistic curtain of any preceding claim, wherein the support structure comprises two crosspieces at the periphery of the flexible protective layers, each crosspiece being aligned perpendicular to the flexible protective layers, each flexible protective layer being connected to a respective point along each crosspiece.

10. The ballistic curtain of claim 9, wherein in the open configuration, each crosspiece is used as an anchor point for anchoring the flexible protective layers in position, and the support structure of the ballistic curtain further comprises at least one of guy lines and support rods for holding the crosspieces in position.

11. The ballistic curtain of claim 9 or 10, wherein the support structure further comprises a tensioning guy line for each crosspiece, the tensioning guy line for each crosspiece being suitable for pulling the crosspiece away from the flexible protective layers in a direction parallel to the planes of the flexible protective layers in the open configuration.

12. The ballistic curtain of any one of claims 9 to 11, wherein the support structure further comprises two stabilising guy lines for each crosspiece, the two stabilising guy lines for each crosspiece being connected to opposing ends of the crosspiece for holding the crosspiece in tension in the open configuration.

13. The ballistic curtain of claim 12, wherein the support structure comprises two support rods for each crosspiece, the two support rods for each crosspiece being connected to opposing ends of the crosspiece, and to a common base member.

14. The ballistic curtain of any one of claims 9 to 13, wherein each crosspiece is connected to each of the flexible protective layers by respective control strings.

15. The ballistic curtain of any one of claims 9 to 14, wherein each crosspiece passes through a peripheral region of the flexible protective layers.

16. The ballistic curtain of any one of claims 9 to 15, wherein each crosspiece is a rigid rod.

17. The ballistic curtain of any one of claims 9 to 15, wherein each crosspiece is a flexible fibre string.

18. The ballistic curtain of any one of claims 9 to 17, wherein each crosspiece comprises a first end connected to a first one of the flexible protective layers and a second end connected to a final one of the flexible protective layers, and wherein the support structure further comprises two scissor rods that are pivotally connected to one another, each scissor rod being connected to the first end of one of the crosspieces and the second end of another of the crosspieces.

19. The ballistic curtain of any preceding claim, wherein the flexible protective layers in the open configuration are spaced apart from each other by at least 5mm, or by at least

10mm.

20. The use of a plurality of spaced apart flexible protective layers as a ballistic curtain, wherein at least one of the flexible protective layers comprises a plurality of detachable sub- layers.

21. A method of providing ballistic protection, the method comprising the step of providing a plurality of spaced apart flexible protective layers, at least one of the flexible protective layers comprising a plurality of detachable sub-layers.

22. A ballistic curtain, use or method substantially as described herein with reference to the accompanying drawings.