GB2506570A - A defence system comprising a net layer and a buffer layer - Google Patents

Abstract

A defence system 2 comprising a net layer 4 and a buffer layer 6, wherein the buffer layer 6 is provided in front of the net layer 4. The buffer layer 6 may comprise a layer of foam material. Preferably, the foam material has a density of less than 80kg/rn3. The buffer layer may alternatively comprise a layer of lightweight fabric. A layer of reticulated foam 110 may be placed between the net layer 72 and the rear buffer layer 76, to act as a spacer and maintain a gap between the net layer and the rear buffer layer. The invention is particularly effective against IEDs and shaped charge munitions.

Description

Defence System The present invention relates to defence system which may be utilised to protect a vulnerable target, such as a vehicle, building or other object, from damage caused by a shaped-charge S warhead, such as a rocket propelled grenade (RPG).

Shaped-charge warheads, such as RPGs are capable of penetrating steel and armour and, therefore, pose a particular problem for tanks and armoured personnel carriers (APC) in combat situations. A shaped-charge' warhead consists of a cone-shaped warhead having a quantity of I 0 explosive disposed behind a hollow space. The hollow space is typically lined with a compliant material, such as copper. The tip of the cone-shaped warhead is provided with a piezoelectric initiator which generates a firing pulse when a force is applied. i.e. upon impact. When detonated the energy is concentrated to the centre of the charge and it is sufficient to translon'n the copper into a thin, effectively liquid, shaped-charge jet having a tip speed of up to l2krns' . The extremely high pressures generated cause the target material to yield and l1o plastically, with devastating effect. To be most effective the shaped-charge has to detonate at the correct distance from the target. If it detonates too close to the target the shaped-charge jet will not ha e properl> formed before hitting the surface and the, effect ill be lessened. (oncrsel. it the shaped-charge is detonated too far away from the target suritce the shaped-charge jet ill ha'. c dillused and, again, the effect is lessened.

The fact that shaped-charge warheads must be detonated at apart icular distance ir.'m the target object has been commonly utilised in defence shields., 15'. providing a preliminan shield at a short distance from the actual armour of the vehicle, or other structure, it is rr'.sible It' cause the warhead to detonate at a safe distance from the actual armour. . ith the eflcci thai the charge explodes between the prelirninan shield and the armour. In elkct. the sarlieu3 bec.incs a eonventtonal grenade. rather than a shaped-charge.

Any preliminary shield which causes premature dctoii;ilioii otthe sliapcd-cIiaric.. ill oiler sonic degree oiprotection. The shield itselfnierelv needs to cause delonatiori. ii is not riieaiil to act as additional armour. During World Waril the German arm> filled sheet metal skirtst,r"Schiiirzen" on to many of their tanks to act as a prelirninar> shield. In more recent tiilie it has become common to fit so-called "slat armour" to tanks and other military vehicles, The slat armour comprises a metal frame which is mounted at a distance of approximately 500mm from the vehicle. The frame comprises a plurality of horizontal struts or slats which are spaced apart at a distance selected to prevent penetration by shaped-charge warheads. The slat armour functions as apreliminary shield, causing the premature detonation of shaped-charge warheads or, ifcaught between slats, disabling damage of the shaped-charge. Slat armour has been used by both the British Army, on the Warrior APC and the American Army, on the Stryker APC. One disadvantage of the slat armour is that it is relatively heavy and adds a great deal of weight to the already very heavy vehicle.

An alternative to slat armour is disclosed in US 2007/0180983 Al, which discloses a protection system featuring a flexible packaged net with perimeter weighting housed in a deployment box releasably attached to a vehicle. One deployment subsystem includes an airbag packaged in the deployment box behind the net. A sensor subsystem detects an incoming threat and a fire control IS subsystem is responsive to the sensor subsystem and is configured to activate the deployment to inflate the airbag and deploy the net in the trajectory path of the incoming threat.

It is the object of the present invention to overcome sonic of the disadvantages of the prior an.

or at least to ofkr an alternative system for counteracting the threat posed by RPGs.

According to the present invention there is provided a defence system comprising a net layer and a hulThr layer. wherein the huller layer is provided in front of the net layer.

The huftCr layer is provided to give the defence system additional properties which cannot be attained using a net alone. l'he huller layer and the net layer cover approximately the same surliice area, such that only the buffer layer is visible when the defence system is viewed from the front. A projectile directed towards the defi2nce system will impact with the buffer layer helore impacting with the net layer.

3(1 The delimce system according to the present invention is specifically intended to he used to defend against shaped-charge projectiles such as RPOs. in particular to diniinish the effectiveness, or cause deformation, of the shaped-charges. As described above, the primary damage inflicted by a shaped-charge warhead, such as an RPG, is not caused by the explosion itself but by the shaped-charge jet which is generated. The primary function of the defence system according to the present invention is to deform the nose cone of the shaped-charge, thus preventing the piezoelectric initiator from generating a firing pulse, and therefore preventing the shaped-charge jet from forming. The defence system will typically be deployed at a distance of approximately 500mm from the target object which it is protecting, such that even if the warhead does function, the shaped-charge jet will be partly diffused when it reaches the target object. It is envisaged that the present invention may be fitted to military vehicles, in much the same way as the conventional slat armour. However, the present invention offers significant advantages, particularly in terms of weight reduction. It is also envisaged that a defence system according to the present invention will be easier to repair.

The biiIir layer functions as an environmental shield for the net layer and provides protection against the elements. In an embodiment of the invention the buffer layer may have one or more IS of the hillowing properties: water-repellence: IJV protection: JR shielding; camouflage patterning: non-stick surläce: flame retardance.

In an eniN'diment otihe in%ention the net layer is attached to the buffer layer. This ensures that the detene s stem can be provided as a single unit and also enables the net layer to he deployed iii an open c4'rlditit'n. The tern) "opeil condition as used herein means that the net is extended such thai it is tree from sagging. hut it does not need lobe held under tension. It is important Ibr the operation of the deknee system that the net layer is free from sagging material when deploed. in order ti reduce the likelihood of a direct hit on a net strand.

In an ei1ilKlimei1i ot the invention. (lie butler layer defines a structure which supports the net Ia'er iii an open condition. Ihe net layer may he in contact with the hulkr layer. hut it should lx tree to ino the butler Iaer may conveniently he provided with means for securing it to a structurt or ehieIe to protected. It is envisaged that a plurality' of individual defence systeni seetion' nia lx combined together to tkirm a complete shield for a structure or vehicle. A 31 niodtilar s stein such a' this has the advantage otheing easier to transport and it also facilitates ea.ier repair of ihe system in the event ofa hit, or other incident necessitating repair.

In an embodiment of the invention a backing layer may be provided such that the net layer is sandwiched between the buffer layer and the backing layer. The backing layer maybe in contact with the net layer, but the net should still be free to move. In an embodiment of the invention the backing layer may be spaced apart from the net layer. The backing layer provides further structural support for the net layer and may form part of a housing in conjunction with the buffer layer.

In an embodiment of the invention the buffer layer comprises a layer of foam material. In an embodiment of the invention the foam material isa closed cell foam. In an embodiment of the invention the foam material has a density of less than 100kg/rn3. In an embodiment of the invention the foam material has a density of less than 90kg/ni3. In an embodiment of the invention the foam material has a density of less than 80kg/rn3. In an embodiment of the invention the foam material has a densit, of less than 70kgrn. In an embodiment of the invention the foam material has a density of less than bOkg'm3. In an embodiment of the invention the foani material has a densit of less than SOkgni'. In an embodiment of the invention the foam material has a derisits of less than 45kg rn'. In an embodiment of the invention the foam material has a densits of less than 40kgm. In an embodiment of the invention the foam material has a densits cii less than 35kg rn'. In an embodiment of the invention the foam material has a densils of Less than or equal to 3t)kgnY.

When the buffer layer is h'nned from a loam material, it ma conveniently form a housing which supports the net layer. In an embodiment of the iii.. ention the hacking layer may also be lbrmed from a foam material ith the same or dillerent properlics it' the hijflr layer.

In an embodirneni of the in entitin a deknee sysieni t-t.niprises: a Front Foam butler layer: a rear Iham hufThr layer: ariI a net las er. 1⁄4 herein th net Ia er is supponed iii open condition in an internal cavity detined hs the (rout loani laser and the rear loam hutkr laser. The defence system lbrms a self-contained unit nhieh tna be easils transported and deployed. lhe front and rear foam butler I ayers deti lie a l] lusi ti liieh atia i rita iris the net iii an "oper( condit jot] and prevents it from becoming tangled As discussed aho c. the lt'nt and rear hutlCr layers also provide environmental protection br the net laser as it is not exposed to the elements.

In an embodiment of the invention the rear foam buffer layer comprises a back panel and a raised peripheral rim, and thc front foam layer abuts the peripheral rim to define the internal cavity therebetween. In an embodiment of the invention the peripheral rim of the rear foam buffer layer further comprises an outer portion, which abuts the front foam layer, and an irmer portion, which comprises a plurality of protrusions which are received within a mesh of the net to support the net in an open condition. The protrusions are advantageously received in the outermost meshes of the net, around its perimeter.

In an embodiment of the invention the net layer is spaced at least 60mm from the back panel of the rear foam buffer layer. This spacing enables the net to act on a projectile before it hits the back panel of the defence system.

In an embodiment of the invention a spacer material is provided between the net layer and the rear foam buffer layer to maintain the spacing between the net layer and the rear foam huikr layer. In an embodiment of the invention the spacer material is a Ibani spacer layer. In an embodiment of the invention the spacer material is a reticulated tttani Ia>er.

l'he spacer material maintains a gap between the net layer and the rear loam huller la er tInch.

it is believed, is necessary to ensure optimum performance olthe system. the spacer lacr does not interfere with the operation of the system and, it is belieed. plays no part in the intera'tioIi between the system and a projectile. The spacer material also pros ides additional structural support for the system In an embodiment of the invention the density of the front Ibam Liver is locr titan the density of the rear foani huller layer. In an enihodiment of the invention the front t'arn la er has a density of less than 45kg/rn3 and the rear foam buffer layer has a dcnsiI ol' less than Sl)kg tit In an embodiment of the invention the front foam buffer layer and the rear txtm htttlr his ci are the same density. -, 0

In an embodiment of the invention the deFence system is provided ith lixinç Ineatis hr attaching ittoa vehicleorstructuretoheprotected. man embodimentolihe invention the lixing

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means comprises a plurality of fixing members. In an embodiment of the invention the fixing members comprises spring mounted fixings.

In an embodiment of the invention the system further comprises an elasticated cord which engages with the net mesh around the perimeter of the net. In an embodiment of the invention the elasticated cord engages with the fixing means. In an embodiment of the invention the elasticated cord is attached to the net mesh at a plurality of locations around the perimeter of the net. The elasticated cord is provided to retain the shape of the net in the event of a hit from a projectile, e.g. an RPG, and it may be a continuous length of material. If the defence system is hit by a projectile then the net strands will typically break at the point of impact. If this happens the elasticated cord pulls the net back into shape after the hit and renders the defence system better capable of coping with multiple hits.

In addition to providing environmental protection, the foam material can also function to improve I 5 the performance of the defence system when counteracting the threat posed by an RPG. The objective of the defence system is to prevent the piezoelectric initiator from generating a firing pulse which triggers the formation of the shaped-charge jet. In the defence system the net layer is provided to disable an incoming RPG. Ignoring for the moment the role played by the bufIèr layer, the interaction of the nc layer and an RPG will now be described.

In view of the fact that the net strands only occupy a small area of the total area covered by the net layer. i.e. most of the area is the open space. or net mesh, defined by the net strand, the likelihood is that the nose cone ofan incoming RPG will be received in a net mesh. The nose ione is typically made from aluminum and nets will he selected such that the circumference of each net mesh is smaller than the maximum circumference of the nose cone of the commonly used Rl'(is in the particular location in which the defence system is deployed. such that the RPO cannot pass straight through the net. As it approaches the net the tip of the cone enters the net mesh. 1-lowever. since the circumference of the net mesh is smaller than the circumference of the nose cone, the net strands begin to tighten against the nose cone as it passes through. causing the 3(1 net to strangulate the nose cone As mentioned above, the nose cone is hollow and the strangulation causes the nose cone to crumple. which in turn causes the firing mechanism to fail and prevents the shaped-charge jet from forming. Once the nose cone has been strangulated the remainder of the RPG acts on the net mesh and will typically cause the net strands to break.

However, the damage caused by the body of the RPG will only be that of a high speed projectile, which is not comparable to the potential damage caused by a shaped-charge. Tn most cases it will be necessary to repair or replace the net layer after it has been hit. This is also the case in respect * 5 of the currently available slat armour.

* As noted above, the net strands only occupy a small area of the total area covered by the net layer and the likelihood is that the nose cone of an incoming RPG will be received in a net mesh.

However, the possibility exists that an incoming RPG will hit one of the net strands directly. If this happens then it is possible that the force of the impact will be sufficient to trigger the firing mechanism of the RPG and cause the shaped charge to form.

lt'an incoming RP(i does make a direct hit on a net strand then the defence system will still provide some protection as the net layerwill typically be positioned approximately 500mm from IS the structure hich is being princeS. Consequently the elketiveness of the RPG will he reduced as the shaped charge will be formed 500mm from the structure and will have lost sonic ol its torce h the time is impacts with the vehicle or structure being shielded.

*l uming nm to the rotc pIaed h the Iiam material when the defence system is counteracting 2(1 the threat posed hs an RI'( I. As discussed above, the buffer layer is provided in front of the net layer An incoming RP I ill theret're make contact with the buffer layer before being received in a net mesh, or hitting a net strand. It is therei'ore important that the buffer layer does not trigger the firing niecllanisril of the RIXI beibre the net layer had an opportunity to disable it.

When the butler laer is krmed from a Ibarn material the foam preferably has a density of: less than 100kg in: less thaii 90kg ni: less than 80kg/rn:less than 70kg/rn3: less than 60kg/ni3; less than 50kg rn: ie.s than 45kg ni': less than 40kg/ni3; less less than 35kg/ni3: or less than or equal to 30kg iii. denJiuig tin the intcnded use of the defence system Advantageously, the deiisit ol the Ioarii should not be so high as to trigger the firing mechanism of a RPG upon impact. (onsequentl the RI'(i will passthrough the foam buffer and interact with the net layer as described above. In situations where the RPG enters into a net mesh then it wilt be strangulated as described above and the interaction with the hufThr layer will not affect the operation of the defence system, However, the present inventors believe that a foam buffer layer can improve the effectiveness of the defence system in situations where an RPG makes a direct hit on a net strand. As described above, if an RPG impacts directly on a net strand there is a danger that the impact will be sufficient for the piezoelectric initiator to generate a firing pulse. The present inventors believe that a foam buffer layer can help to reduce the likelihood of the piezoelectric initiator generating a firing pulse in situations of direct impact on a net strand.

Without wishing to be bound by theory, it is believed that the foam buffer layer performs a number of functions. As discussed above, the density of the foam is such that it will not trigger piezoelectric inititor when the tip ol'the RPG strikes the foam buffer layer Instead it is believed that a first part of the foam layer e.g. an outer lavcr. becomes enthedded in the nose of the RPG.

This provides the RPG with a soil tip which it is believed will prevent the RPG from cutting the net strands and thereby passing through the deFence system. Secondly, it is believed that the inner layers of foam form an unstable column on the tip of the RP(i which will tumble upon impact with a net strand so that the net strand is displaced sidessa> sand the cone of the RIM] is received in a net mesh. It is believed that the fiam reduce,. the stress intensih transmitted into the nose upon impact and its loss ZIeOLISIIc impedance propeflies reduec the likelihood that the piezoelectric initiator will generate sullicient electrical output to detonate the RPG.

In an embodiment of the invention the thickness of the moans hufler liner is in the range front 5mm to 100mm. In an embodiment of the ins ention the thickrue' of the loam huller layer is in the range from 15mm to 75mm. In an emlxxliment ol' the ins entitiru the thickness of the foam buffer layer is in the range from 2nhrll U' 50mm. In an enibodinient oI'the invention the Ilium is a closed cell loam. It is belies ed that the cells of the I'arui Ilirni microscopic air.eushions which help to minimise the transfCrence ol lorce k' the nose In an enix.dinienl of the invention the Iham has a smooth outer surhice.

In an embodiment of the invention tlie htutkr laser n.ua\ comprise a layer oilightweight fabric (fabric layer). In an embodiment of the ins entitin the lighisseight Fabric is selected from the group consisting of one or more of: a rip-ship ny Ion Ilibric: an acrylic coated nylon; and a

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polyester. The fabric layer covers the net layer and provides environmental protection. One of the potential problems of a net-based system is that they can be difficult to kecp clean in th field and dirt and debris can cause "hard points" to form on the net which can cause an RPG to detonate. The fabric layer shields the net layer from the environment and is easier to clean. The fabric layer advantageously has one or more properties selected from the group consisting of: water repellence; UV shielding; JR shielding; camouflage patterning; non-stick surface; flame retardant.

The strength of the lightweight fabric is selected such that it will allow an RPG to pass through without triggering the fuse. When an RPG hits the fabric layer it will pass through and engage the net layer as described above. Iii an embodiment of the invention the fabric layer has a mass of less than I óOg/ni2. In an embodiment of the invention the fabric layer has a mass of less than I 55gInY. In an embodiment of the invention the fabric layer has a mass of less than I 50g!rn?. In an embodiment of the invention the fabric layer has a mass of less than 145gm'. In an IS embodiment of the invention the fabric layer has a mass of less than 140g'nY.

In an embodiment of the invention the net layer is supported at or near at least to adjacent corners, such that the body of the net hangs below. Advantageously the net liner is supjxnied at at least three points, and more preferably four, to ensure that the net remains in an open condition when the vehicle is movingor in windy conditions. Testing has revealed the surprising result that the net does not require to be securely supported in order to be effective. In a typical example.

a RPG will he travelling at velocities up to 300mc'. Withoutwishing to be hound by theory. it is believed that in the time-frame iii which the net acts on the nose cone. the cone will be strangulated before the load has had a chance to be transferred to the perimeter il the net. In tests conducted using slow motion cameras it has been possible to view the interaction beteen the net and the RPG. As mentioned above, the nose cone crumples when the net stranJs tighten around it. I'his renders the fuse inoperable and prevents formation of the shaped-charge jet. The remainder of' the RPG then breaks through the net. It has been shown that at losser projectile velocities (in the region of I5Qms') the RPG may he caught" by the net and catapulted hack.

l-Iowever. in order for this to happen the net must be securely supported by a slrt'n Frame.

Jo an embodiment of the invention the buffer layer comprises a hag-like structure which H surrounds the net layer. The buffer layer provides environniental protection for the net layer. The bag-like structure may conveniently be provided with hook and ioop fastenings along one edge, to provide easy access to the net layer, while at the same time ensuring that it is adequately shielded from the environment.

In anembodiment of the invention the net strands of the net layers comprise plastic fibres. It is preferred that the plastic fibres are synthetic plastic fibres aiid have one or more of the foil owing properties: high tenacity; low elongation; high stzength to weight ratio; low density; and soft finish. As will be discussed in more detail below, it is desirable for the net strands to be thin.

I 1) Consequently, suitable fibres must be high tenacity in order to perform the desired function.

Similarly, the fibres must be made of a relatively low elongation material. If the fibres were made of a high elongation material then they would stretch on impact and may allow the nose cone to pass through and impact with the target. In order to improve handling it is desirable for the textile armour to be as light as possible. I-c

iestin has determined that it is desirable for the fibres to he high strength but with a "soft and Ilufl\" finish. Although the term mofi and flullS" does not describe technical features of the fibres it describes a desirable characteristic of them. In the event that a nose cone of a RPG hits one of' the net strands directly it is preferred that the fibre is deflected and the nose cone continues a net mesh. rather than firing and forming a shaped-charge jet. If the net strand has a bhard finish then the possibility exists that the RPG will fire. It is therefore preferred that the fibres do no! have a "hard" or resilient surface finish.

Although it is desirable for the fibres to have a"sofl" finish, they must also he high tenacity as they need to he capable of strangulating the nose cone of a shaped-charge warhead before they fujI In an embodiment of' the invention the net strands comprise ultra high molecular weight (I%etln lene fibres, such as Dyneema or Spectra®. Alternatively, the net strands may he made from tither high-strength man-made fibres. e.g. para-araniid synthetic fibres, such as Kevlar3& li bud materials, such as ZyloS or \eetran®. or any other suitable material. "p

1 raditiunal nets tend to have knotted intersections where net strands arc knotted in order to form the net mesh. It has been discovered that these knots lhrm so-called "hard" surfaces which may *lO.

cause a RPG to fire if it impacts directly onto the knot. Consequently, if a knotted construction is used then it is preferred that the knot is as small as possible to reduce the likelihood of a direct hit occurring.

In an embodiment of the invention the net layer comprises a knotless mesh construction.

Alternatively, the net may comprise a woven construction. In both of these constructions the intersections between nets strands are much less likely to cause a shaped-charge to fire if a direct hit occurs. It is believed that the particular construction of the net does not play any particular role in disabling the shaped-charge. The only consideration for the net construction is that the intersections are as smafl and "soff' as possible.

As discussed above, the prinran function of the net strands is to strangulate the nose cone of a shaped-charge arhead and prevent it from llring. In ordertoperform this function it is preferred that the net strands are as thin as possible in order to increase the likelihood of the nose cone entering one of the net nieshes. rather than hitting one of the net strands. It is a requirement of the invention that the nd is not tensioned and that it is presented in an open condition. The net shoLild not be allowed to sag lithe net material is permitted to sag then it will tend to hunch up, thus increasing the likelihood ofa;ar)iead hitting the net strands. (onsequently. the netmajeriat should be held in an open etindititirt. although it need not necessarily be taut.

As mentioned aPxc. it is conccuaHe thai lithe tip of the nose cone hit directly onto one of the net strands then this ma' catist the RIX; to fire. However, even ifthis was tohappen the defence svstcni would still pros ide sonic protection as it will nonuallv be located at least 500mm from the target objeei nhich it is shielding t onsequentl the shaped-charged jet will he formed at least 5lHUnni Ironi the target and it' ef1ecti eness ill be decreased.

In an eriihodiriieiit ot the in' ciii i*'r' the net strands oi the net layer have a diameter of less than I Onirii In an enibodiniejit of (lie iii'eiitit'ii the net strands havea diameterof less than 6mm. The onl limit lug tudor to the diatnetet of the net strands is the availability of materials from which to mann licItire thetit. Ideal I' the net strands will have as small a diameter as possible. Using currenti' a'.ailahle material' it i' preferred that thedianietcrofthe net strands is in the range from 3-6mm. As technolog ud andes it is envisaged that it will be possible to utilise net strands

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having a diameter of less than 3mm. The dimensions of the net strands are measured in accordance with BSI Aerospace Series Standard BS6F 101): 1998.

As discussed above, thc object of the textile armour is to disable a shaped-charge warhead, such as a RPG. This is achieved by strangulating the nose cone of the RPG, thus preventing it from firing. A number of different RPGs are currently available and it envisaged that over time more will be developed. The size of the warhead tends to vary between different RPGs. For example, a RPG-7 propels a warhead with a diameter of 90mm and a RPG-18 propels a warhead with a di4meter of 64mm. Although a general form of the textile armour will be capable of disabling 1 0 more than one size of warhead, such as the RPG-7 and the RPG-18. it is preferred that the textile armour is selected to counteract the specific threat. i.e. an RPG-7 specific textile armour.

In an embodiment of the invention the circumference oleach individual mesh section of the net is less than the maximum circumference of the RPG warhead which the net is designed to counteract. It is envisaged that one net could be utilised against more than one type of RI'(p. hut in most conflict situations there will usually be one tvjw of RIM I which is most common. The selection ofa suitable mesh size ensures thai the RP( i cannot pass straight through the net mesh.

Each individual mesh section is defined as the shape delined Ii) the interseetnm tit the net strands. The mesh may he a variety of shapes. such as square. rectangular. triangular, circular.

pentagonal. hexagonal octagonal or any combination of these shapes the circunilerenee of the net mesh is the total distance around the perimeter of the net mesh. For eaniple. in a square net mesh with sides of 45mm the circumference ill be lKflriini.

In at) embodiment ofthe invention the circunifrrenee oleach individual mesh see lion is less than.

orequal to. two-thirdsoftheniaxiniurncircumkrenec ottlie RIMI arlicad. Ihis has been bond to be the optimum mesh size which allows lir a' open a net as possible. hUe ensuring that the net is capable of strangulating the nose colic ot an RN I sarhead It i' belieed that it the eircum firence of the mesh section is greater than t o-thirds oF the m;n i mum circuuBLrcnee of the RPG warhead, then the possibility exists that the arhcad cill pass through the net and impact with the target object. It is also desirable to hate as open a net as possible iii order to minimise the likelihood of the warhead impaetinç t liii the net strand(onseqLIentIy. it has been discovered that the optimum circumference ofeach mesh section is ttti'thirds otthe maximum I? circumference of the nose cone of the RPG which the net is designed to disable.

As discussed above the RPG-7* propels a warhead with a maximum diameter of 90mm. The maximum circumference of such a warhead will be approximately 283mm. Consequently, the optimum circumference of each mesh section in a defence system designed to counteract the RPG-7 would be approximately 188mm. In the case of a square net mesh this would require sides of approximately 47mm. In the case of a square or rectangular net mesh the sides will typically be in the range from 20-100mm.

In order to improve the functionality of the textile armour system it is preferred that the buffer layer is provided with a camouflage colouring. More preferably, the buffer layer is provided with a suitable camouflage garnish to compliment the colouring of the surroundings in which the system will be used. The use of such camouflage is well known.

According to a second aspect of the present invention, there is provided a modular detnce system comprising a plurality of defence systems as described above. In an embodiment of the invention the individual defence system elements are provided with fixing means for attaching them to a vehicle or structure. In an embodiment of the invention the individual defence sstcin elements are provided with means for connecting them with each other. In an embodiment of the invention each defence system element comprises a plurality of fixing means. In an embodiment of the invention the fixing means comprise spring mounted fixing elements.

According to a third aspect of the present invention there is provided a net comprising a pluralits of intersecting net strands. wherein at least some of the net strands are braided net strands itli a Ibam core running through them. In an embodiment of the invention the density of the hunt is less than I 00kg/nY. more preferably less than 90kg/rn3 and most preferably less than XOkg ni.

As discussed above, if a shaped-charge projectile, such as an RPG. makes a direct hit on a strand then there is a possibility that the fuse will he triggered and a shaped-charge jet;iIl be formed. Without wishing to he hound by theory. the present inventors believe that the introduction of a foam core into a braided net strand will reduce the overall density of the net strand such that the tip of a shaped-charge will displace the net strand without the fuse bcin triggered. The tip of the shaped-charge projectile will then pass into the net mesh defined by the net strand and the net will act on the shaped-charge as described above.

According to a forth aspect of the present invention there is provided a net comprising a plurality of intersecting net strands, wherein at least some of the nets strands are encapsulated in foam. In an embodiment of the invention the density of the foam is less than 100kg/rn3, more preferably less than 90kg/rn3 and most preferably less than 80kg/rn3.

It is believed that anet strand which is encapsulated in foam will minimise the transference of 1 0 fbrce to the nose of the RPG and reduce the likelihood of the piezoelectric initiator triggering the firing pulse.

:ccoidttig to an aspect ofthe invention there is provided a defence system comprising a net layer and a bufThr layer, as hereinhefore described, wherein the net layer comprises a plurality of inersecling net strands with at least some of the net strands being braided net strands having a toam cure running through them.

t-cording to au aspect of the invention there is provided a defence system comprising a net layer and a huller laser. as hereinbeibre described, wherein the net layer comprises a plurality of itItersecticl: net strands with at least some of the net strands being encapsulated in a foam nia;cr,aI.

I or a better tmderstanding of' the present invention reference will now he made to the iwc..nupaun ing dra%dngs showing solely by waofexample.an embodiment ofihe invention and.

11% %% Iui'h: I i I shoss a perspective view okm embodiment ofa defence system attached to a vehicle; I ik1. 2 sIiti a perspective view ol the defence system of Fig. I removed from the vehicle; -"U I ig. shos a partiall cut away view of the defence system of Fig. 2; Fig. 4 shows a side sectional view of the defence system of Figs. 2 and 3; Fig. 4A shows a side sectional view of an alternative embodiment of the defence system of Figs. 2 and 3; Fig. SA shows a perspective view of a second embodiment of a defence system; Fig. SB shows a close up view of a portion of the defence system of Fig. 5A; lO Fig. ÔA shows a perspective view of a third embodiment of a defence system; Fig. 6B shows a close up view of a portion of the defence system of Fig. 6A; Fig. 7 shows a perspective view of an embodiment oVa defence system: Fig. 8 shows a partiall cut a%a\ vie of the dekncc sstem of Fig. 7: Fig. 9 shows a perspective vie titan enthidiment of a deknce system: Fig. 10 shows a pariiail cut aa' ics of the defence s' stem of Fig. 9: Fig. I OA shows a clo%e up of a Nillion of the detkmce s stem of Jig. tO: Fig. 11 ShOws a sidc c tioiial k ut the detciicc s%stem of Figs. 9 -lOA Fig. 12 shows an exploded ie of an eriihliinent of a defniee system; and Fig. 13 shows a side sectional %iC1⁄4 of an aseriih1et) tkleiiee s stem oh Fig. 12.

Referring firstis to I i I. this slit ar einhodinieut of a delCnee system 2 mounted on a military vehicle.t). 1 he construction ot arioti' embodiments of the defence system 2 will he discussed in more detail siili reference it' I 2-13. the present invention relates to a defence system 2 which may be utilised to protect a vulnerable target 50, such as a vehicle, building or other object, from damage caused by a shaped-charge warhead. su.h as a rocket propelled grenade (RPG).

Shaped-charge warheads, such as RPGs are capable of penetrating steel and armour and, therefore, pose a particular problem for tanks and armoured personnel carriers (APC) in combat situations. In order to limit the damage caused by an impact from a RPG a variety of preliminary shields have been developed which either aim to defuse the RPG, to prevent the shaped-charge from forming, or they aim to detonate the RPG at a safe distance from the target object, to lessen 1 0 the damage cause by the shaped-charge.

The defence system shown in Figs. l-4A comprises a net layer 4. a loam hulkr layer 6 and a foam backing layer 7 and it is mounted onto a vehicle 50 h means of a pluralit> of fiexihk stanchions 8. The flexible stanchions 8 comprise a base 10. a spring mid-eetion 12. which is secured to the base 10. and a support strut 14, which is attached to the spring 12 and the net layer 4 and foam layers 6. 7.

The flexible stanchions 8 arc secured to the vehicle 50 b means ofa plurahil) oIsres (hot shown) which pass through the base 10 of the flexible stanchutins 8 and engage ith a panel of the vehicle 50. Due to the fact that the defence system 2 is relativel light-cight (at lea4 compared to currently available systems). the attachrnern poini's on the chicle SI) dii not need to be structural. l'his increases the flexibility of the defence system 2 a' almost an [iI(1t tin the vehicle 50 can he used. Although screws are used to secure the deGmce system 2 Ii' the ehiUe Soother suitable fixing means may also he used, as will be readiI apparent to the skilled N'lL ihe vehicle 50 may he provided with specific points to engage ith the I1eible tanchions K. t'g.

appropriately sized holes to receive the fixing screws, or the flexible siatichion N ni.n sisiiply he secured to a vehicle 50 by drilling holes at the desired locations.

l'he flexible stanchions 8 support the net layer 4 and foam Ia) ers 6. 7 in a spaced relationship to the vehicle 50. The net layer 4 and foam layers 6, 7 are positioned approximately SliOtiun froni the vehicle 50 in order to effectively counteract the threat ixised h RN is. as ill be discussed iii more detail below.

Only one defence system 2 is shown in Fig. 1, but it is envisaged that a plurality of individual defence system elements 2 could be combined in a modular defence system. The number of defence system elements 2 required will depend on the size of the structure or vehicle which is being protected, but it is envisaged that many defence system elements 2 could be combined to protect large structures. Conversely, it may only require one or two defence system elements 2 to protect the side of a small vehicle. The flexible stanchions 8 are provided slightly in-board from the perimeter of each defence system element 2 in order to allow the edges of each defence system element 2 to abut an adjacent defence system element 2 and avoid any gaps.

Referring now to Figs. 2-4k which illustrate one defence system element 2 in more detail. As discussed in relation to Fig. 1, the defence system 2 comprises a net layer 4, a foam buffer layer 6. a rear backing layer 7 and four flexible stanchions 8, which secure the defence system 2 to a structure or vehicle 50 in use of the defence system 2. The flexible stanchions 8 comprise abase 10. a spring mid-section 12 which is secured to the base 10 and a support strut 14 which is IS attached to the spring 12 and the net layer 4 and foam layers 6. 7. As can best be seen in Figs. 4 and 4,\. the support strut 14 of each flexible stanchion 8 passes through the hacking layer 7 and the front foam layer 6 and secures the net layer 4 and foam layers 6. 7 at a predetermined distance from the chicle 50. The support strut 14 comprises a shoulder 14a. which abuts a rear surface of the hacking layer 7. and a support pin IS. which passes through the backing layer 7 and the front foam layer 6. A nut 17 secures the front foam layer 6 on the support pin IS. The support pins 15 pass through a corner mesh of the net layer 4 and provide support for the net layer 4.

As can be best seen in Figs. 3 -4,\. the net layer 4 is encapsulated between the front foam layer 6 and the hacking layer 7. which is also made of' loam. The t'oani is a closed cell foam with a 2 S density of8() kg/rn'. The 11mm layers 6.7 provide structural support and environmental protection 11w the net layer 4. The front Ibam layer 6 and hacking layer 7 are approximately 35mni thick.

The Iront surUtce ol'the front foam layer 6. i.e. the one which Ilices away from the vehicle 50, is smooth and can he easily cleaned to avoid the build up of debris on it surface. The front foam layer band the foam hacking layer 7 are water repellant. non-slick and they are provided with a camouflage patterning to suit the terrain in which the defence system 2 is intended to be used.

l'he foam layers 6. 7 provide environmental protection for the net layer 4 and also provide UV protection, infra-red (IR) shielding (to disguise the IR signature of the vehicle or structure) and they are flame retardant.

The front foam layer 6 and the backing foam layer 7 are both provided with a small lip 6a, 7a around their perimeter, such that when they come together a cavity 16 is defined between the foam layers 6. 7. The perimeter edge of the net layer 4 is "trapped" between the meeting lips 6a, 7a of the front foam layer 6 and the backing layer 7 at the top of the cavity 16 to hold it securely in place. but it is free to move within the cavity 16. In this embodiment the net 4 hangs down from the top edge I 6a of the cavity 16, but in an alternative embodiment the net 4.may be held around its perimeter by the lips 6a, 7a of the foam layers 6, 7. In any event, the net 4 should be supported in open condition, but it should not bp tensioned. The flexible stanchions 8 provide additional support for the net 4 by engaging with a mesh of the net 4 at each corner of the net 4.

The foam layers 6. 7 are bonded together using a suitable adhesive, but any suitable means for connecting to iian layers 6. 7 could he utilised.

Jig. 4.\ shins art alternative version of the system 2 illustrated in Fig. 4. in which a cavity 9 is provided behind the net 4. Ihe system 2 is substantially identical to the system of Fig. 4 and the same numbering ha' been used. In the system of Fig. 4A the lip 7a around the perimeter of the hacking Ii'ani laser 7 is slightI larger than in Fig. 4. This ensures that when the net4 is trapped 21) heu%een the meeting edges ot the lips ha. 7a a cavity 9 is defined behind the net 4. The lip 7a cxtend N)mrii front the main bod oithe hacking form layer 7 such that the net 4 is held away front the main kJ of the hacLing titam layer 7 by approximately this distance. It is believed that this distance is sullieiettt to allot the net 4 to act on a projectile before it impacts with the main til the hacking li am la er 7

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1 he net laei 4 t-t'lllprises a plurality of net strands 18 made from DyneemaQ' SK75 (nlanuLictured h'. l)c\l lhneenta l4.V.) which are ftnmcd with knotless intersections, as is well ii in the art 1 he net strands I X ha e a diameter of approximately 5mm and a strength of approxiunatel l4k\. arid thes define a plurality ol regular net meshes 19. 11w circumference of tO the net me,.he. 19 is approxiruatel\ equal to two thirds of the circumference of the nose cone of the RI'(I hich the de6.mce system 2 is designed to counteract. For example. the RPG-7 propels a sarhead itli a ritaxiniutli diameterof9Omm. The maximum cjrcumferenccofsuch awarhead.

will be approximately 283mm. Consequently, the circumference of each mesh section 19 in a defence system 2 designed to counteract the RJ'G-7 would be approximately 188mm. Jnthe ease of a square net mesh this would require sides of approximately 47mm.

The illustrated embodiment of the invention comprises a net layer 4 with net strands 18 having a diameter of approximately 5mm. The properties of the net layer 4 can be varied by using net strands 18 of differing diameters. For example. Dyneema® SK75 with a diameter of 5.5mm has a strength of approximately I 7.2kN and Dyneema® SK75 with a diameter of 6mm has a strength of approximately 23.lkN. Similarly, it is envisaged that net strands 18 having a smaller diameter 1 0 could also be used in a defence system 2 according to the present invention. An optimum embodiment of the net layer 4 would have net strands 18 with the smallest possible diameter and it is envisaged that new materials will he developed in the future which will make net strands 18 with a diameter of less than 3mm easil achievable. -The operation ofthedefencc svsteni 2 will riots he discussed in nmre detail. The primal) function of the defence system 2 isn disable the nose cone of a RN Ito prevent the piezoelectric initiator in the nose from generating a firing pulse which ssill trigger the formation of a shaped-charge.

This is achieved by strangulating the nose cone ol the RN I. I' basic situations are envisaged when a RPG hits a defence ssslem 2 as illustrated in 1-igs l-4:\. Die most common scenario is that the RPG hits the front foam layer hand passes through and the nose is received in one of the net meshes 19. The density of the front tiiam laser ( is S.. cteJ such that it will not trigger the firing mechanism ofthc RP(i. In thiscase the hiani pla' no function in disabling the RPG. Since the circumference ofihe net mesh 19 is smaller than the ircumkrence ot'the nose cone, the net strands 18 begin to tighten against the nose cone as it passes through. causing the net layer 4 to strangulate the nose cone. As mentioned aIksc. the nose cotie is hollo and the strangulation cattses the nose cone to crumple. %shieh in turn causes Ilit' tiring mechanism to fitil and prevents the shaped-charge jet front f'rining ( )nce hit' T1OS' colic ha' be'ii si rangulated the remainder ot' the RPG acts on the net nwsh 39 and s ill tvpicalh cause one sir n're of the net strands IS to -break. However, the damage caLised h the bod ol ilK Rl'u ssill oul) he that of a high speed projectile. which is not comparable to tile çsitcntial dain;tge s hich ould be caused by a shaped-charge. In most cases it will b.. necessan to repair or replace the net layer 4 and foam layers 6, 7 after the defence system 2 ha' been hit. ji)

The second scenario envisaged is that the RPG hits the front foam layer 6 and again passes through, but this time the path of the RPG is directly towards a net strand 1 8 of th.. net layer 4.

In prior art systems if a RPG hits a net strand 18 then it is possible that the force of the impact would be sufficient to trigger the firing mechanism of the RPG and cause a shaped charge to form. In a defence system 2 according to the present invention the addition of the front foam layer 6 serves to reduce the likelihood of sufficient force being transferred to the piezoelectric initiator in the nose of the RPG to trigger detonation.

As noted above, the density of the foam is such that when the RPG hits the front foam laycr 6 it will pass straight thiough. In addition, the density of the foam is such that it will not trigger the piezoelectric initiator when the tip of the RPG strikes the front foam layer 6. Instead, without wishing to be bound by theory. it is believed that a first pan of the foam layer 6 e.g. an outer layer. becomes embedded in the nose of the RPG. This provides the RPG with a soft tip which it is believed will prevent the RPG from cutting the net strands IS and thereby passing through IS the defence system 2. Secondly. it is believed that the inner layers of loam fbrrn an unstable column on the tip of the RPG which will tumble upon impact with a net strand 18 so thai the net strand IS is displaced sideways and the cone of the RPG is received in a net mesh 19. Ii is believed that the foam reduces the stress intensity transmitted into the nose upon impact and its low acoustic impedance properties reduces the likelihood that the pieloelectriL initiator siil generate sufficient electrical output to detonate the RPG.

Turning now to Figs. SA and 5B which show an alternative embodiment of a debnce system 20.

The defence system 20 comprises a net 22 which is formed from a pluralit of intersecting net strands 24.26 and a plurality of knotless intersections 25. as is known in the an. the nets strands 24. 26 are braided net strands and they have a foam core 28 running through then. Ihe net strands 24.26 are formcd from Dyneema® SK75 and the foam core 28 is a clo.ed ccli haiti t ith a density ol8Okg/m'.

The defence svstetii 20 is provided with a buffer layer 27 in the form of a la'.er olrip-stt'p inloii Ilibric. The huller layer 27 illustrated in Fig. 5A is partially cutaway to slio the net Ia) ci 22 below. hut in use it will cover the net layer 22 completely to provide en irtinniental protection for the net Layer 22. The rip-stop nylon has a mass of l4Og/m2. The rip-stop nylon can be easily wiped clean and it also provides the defence system 20 with the following useful properties; water repellence; UV shielding; JR shielding; camouflage patterning; non-stick surface; flame retardant properties.

The defence system 20 can be mounted onto a vehIcle or structure by means of four flexible stanchions 30 which are positioned at the corners of the net 22. The flexible stanchions 30 are of the same construction as the flexible stanchions 8 of Figs. 1 -4A and comprise a base 32, a spring mid-section 34 which is secured to the base 32 and a strut support 36 which is attached to the spring 34 and the net 22. The flexible stanchions 30 hold the net 22 in an open condition, i.e. the net 22 does not sag, but the net 22 is not held under tension. The strut supports 36 pass through a corner mesh of the net layer 22 and provide support for the net layer 22 to ensure the net layer 22 is held in an open condition even when the vehicle is moving or when conditions are windy'.

The flexible stanehions 30 can he secured to a vehicle or structure by means of a plurality of screws which pass through the base of the flexible stanchions 30 and engage with the vehicle or slructure Although screws are used to secure the defence system other suitable fixing means nia also he used, as will he readily apparent to the skilled person. The vehicle or structure may be provided with specitic points to engage with the fixings members. e.g. appropriately sized 2(J holes to receive the fixing screws, or the fixing members may simply he secured to a vehicle or structure by drilling holes at the desired locations. Due to the fact that the defence system 20 is relatively light-teight (at least compared to currently available systems). the attachment points on the vehicle or structure do not need to he structural. This increases the flexibility of the dekuce ssstem 20 as almost any point on the vehicle or structure can he used.

S

[he flexible stanchions 30 support the net 22 in a spaced relationship to the vehicle or structure.

In use, the net 22 will he positioned approximately 500mm from the vehicle or structure in order to et'Ieetively counteract the threat posed by RPGs. as will be discussed in more detail below.

3(1 It is envisaged that a plurality of individual defence system elements 20 could he combined in a modular defimce system. The number of defence system elements 20 required will depend on the size of the structure or vehicle which is being protected, but it is envisaged that many defence system elements 20 could be combined to protect large structures. Conversely, it may only require one or two defence system elements 20 to protect the side of a small vehicle.

The basic operation of the net 22 in strangulating a RPG is the same as that discussed above in relation to the net portion of the defence system illustrated in Figs. 1-4A. However, as noted above, there is a potential problem if a RPG impacts directly onto a net strand 24, 26. Without wishing to be bound by theory. it is believed that the foam core 28 in the net 22 of Figs. SA and SB minimjses the transference of force to the nose of the RPG and enables the net strand 24, 26 to be pushed to one side without the piezoelectric initiator trigger detonation of the RPG.

Turning now to Figs. o.k and 613 which show an alternative embodiment of a defence system 40.

The defence system 40 comprises a net 42 which is formed from a plurality of intersecting net strands 44.46 and a pluralit of knotless intersections 45. as is known in the art. The nets strands 44. 46 are braided net strands formed from Dyneema® SK7S. Each net strand 44. 46 is encapsulated in a layer of tarii 48. The liarn is a closed cell foam with a density of 80kg/rn3.

The deknce system 4(1 is prin ided dth a huller layer 47 in the form olà layer ofrip-stop nylon Ilibric. the huller lacr 47 illustrated in Fig. O.k is partially cutaway to show the net layer 42 belot. hut in use it siil cmer the nd laser 22 completely to provide environmental protection 2(1 for the nd layer 22. Ihe rip-stop in Ion ha' a mass of l4Og/rn. ihe rip-stop nylon can be easily ipcd clean and ii also pros ide'. the defence ss1em 40 with the following useful properties: water repellence: t V shicldin: lR shielding: canioullage patterning: non-stick surface: flame retardant properties.

11w deftncc ssteuit 40 can he mounted onto a vehicle or structure by means lour flexible tanehitms 51) %%hich arc jb'.ititnwd at the ct'riiers of the net 42. 1he flexible stanehions 50 are i'I tile savie construcliori;i' the flexible staiiciiions 8 of Figs. l-4A and comprise a base 52, a spring mid-see lion 54 hieh is secured to the base 52 and a strut SUpport 56 which is attached It' the spring 54 and the net 42 the flexible starichions 50 hold the net 42 in an open condition.

i.e. the net 4 does not sag. hut the net 42 is not held under tension. The strut supports 56 pass tiirouzh a corner mesh of the net laser 42 and provide support for the net layer 42 to ensure the net laeu 42 is held in an open condition even when the vehicle is movingor when conditionsare 1) windy.

The flexible stanchions 50 can be secured to a vehicle or structure by means of a plurality of screws which pass through the base of the flexible stanchions 50 and engage with the vehicle or structure. Although screws are used to secure the defence system other suitable fixing means may also be used, as will be readily apparent to the skilled person. The vehicle or structure may be provided with specific points to engage with the fixings members, e.g. appropriately sized holes to receive the fixing screws, or the fixing members may simply be secured to a vehicle or structure by drilling holes at the desired locations. Due to the fact that the defence system 40 is relatively light-weight (at least compared to currently available systems). the attachment points on the vehicle or structure do not need to he structural. This increases the flexibility of the defence system 40 as almost any point on the vehicle or structure can he used.

The flexible stanchions 50 support the net 42 in a spaced relationship to the chick or structure.

In use, the net 42 will be positioned approximatet 500mm from the vehicle or structure in order to effectively counteract the threat posed h RP(i.. as will be discussed in more delail below.

It is envisaged that a plurality of individual delence system elements 40 could he conihtned in a modular defence system. The number ot delenee svsleni elements 40 required will depend on the size ofthe structure or vehicle which is hein protected. hut it is en' isaed that nians defence system elements 40 could be combined to protect large structures (oincrscls. it ma only require one or two defence system elements 4t)to protect the stdc of a small ehiclc.

The basic operation of the net 42 in strangulating a Rl'(t is the same a' that discussed above in relation to the net portion of the defence sssteni illustrated in Ji I-tA and 5.\ and 514.

However, as noted above, there is a potential problem ifa RNi inipacts dircctl onto a net strand 44.46. Without wishing to be bound hs tlwtr. it is bcliecd that the kani cover 4K ot'ligs. bA and 613 niinimises the transiCrence of' Ijirce to the misc of the R l i and enables the net strands 44. 46 to he pushed to one side without the piL'/oelectric mit iattir trigerin detonation of the RPG.

Figs. 7 and 8 show a further embodiment of a delCuce s stem (.t according to the present invention. The defence system 60 is broadly similar to the defence system 2 shown in Figs. I -4A.

but in place of a front foam layer 6 and a backing layer 7 the net layer 62 in the defence system is provided with a buffer layer 64 in the form of a layer of lightweight rip-stop nylon. The buffer layer 64 encapsulates the net layer 62 and provides environmental protection for the net layer. The rip-stop nylon has a mass of I 4Okg/m2 which ensures that an RPG will pass through the buffer layer without sufficient force being transmitted to the nose to cause the piezoelectric initiator to trigger detonation of the RPG. The rip-stop nylon buffer layer 64 can be easily wiped clean and it also provides the defence system 60 with the following useful properties: water repellence; IJV shielding; JR shielding; camouflage patterning; non-stick surface; flame retardant properties.

The defence system 60 comprises a plurality of flexible stanchions 66 which are used to mount the system 60 onto a vehicle or structure. The flexible stanchions 66 are the same as the flexible stanchions 8 described in relation to the embodiment Of the invention described in Figs. I 4A.

The flexible stanchions support the net 62 in an open, non-tensioned condition. It is also envisaged that there maybe a weak line of stitching along the top edge of the buffer Liver hich attached the net to the hufiër layer to support it in an open. non-tensioned condition A line of weak stitching may also be employed in the defence systems 20,40 shown in Figs. 5: and (A.

2(1 In an alternative embodiment of the invention a defence system 60 as described with reference to Figs. 7 and K may be provided with a spacer layer of reticulated foam between the net Ia' ci 62 and the rear of the huIThr layer 64. The spacer layer serves to maintain a gap heteeT1 the net layer 62 and the rear oithe butler layer 64 and also serves to provide structural supN)rt to the system 60. The reticulated foam adds rigidity to the system 60. but does not interfere sith the operation of the system 60. The use of a spacer layer of reticulated foam is described iii more detail with reference to Figs. 12 and 13 and this description is generally applicable in the present case.

ftc operation of the defence system 60 is broadly the same as other net based defence s>ten.s.

Ii is believed that the huller layer 64 only provides environmental protection lhrthe net a) ci and that it does not play a part in counteracting the RPG.

Figs. 9-11 show a further embodiment of a defence system 70. The defence system 70 is broadly similar to the defence system 2 shown in Figs. 1-4A. The defence system 70 comprises a net layer 72, front axd rear foam buffer layers 74, 76 and four flexible stanchions 78, which can be used to secure the defence system 70 to a structure or vehicle. The flexible stanchions 78 are the same as those illustrated in Figs. 1-4A and comprise a base 80, a spring mid-section 82, which is secured to the base 80, and a support strut 84. The means of attachment between the stanchions 78 and the front and rear foam buffer layers 74, 76 is slightly different to that illustrated in respect of the systems shown in Figs. 1-8. The different means of attachment are shown by way of example only and the skilled person will appreciate that both means of attachment can be used on any of the systems described in this application. The means of attachment in the system 70 are in the form of 3-part bushes 94 which will be discussed in more detail below.

As can best be seen in Fig. II. the 3-part bushes 94 comprise a central cylindrical portion 95 hich is provided with an annular projection 96 towards one end. The central cylindrical portion IS 95 passes through the rear foam butkr layer 76 and the annular projection 96 rests on a lip 86, which extends around the perimeter of the rear foam buffer layer 76. as described in more detail helo. A front plug 97 then passes through the front foam huller layer 74 and engages in an intcrkrence lit within the central cylindrical portion 95 to secure the front foam buffer layer 74 to 11w rear fozni butler layer 76. A rear plug 98 passes through the back of the rear foam huller laser 76 and engages in an interference itt with the central cylindrical portion 95. The support strut S4 of the stanchion 78 then engages with the rear plug 98 to enable the system 70 to be deplo'.ed.

I he front and rear foani layers 74.76 form a housing which encapsulates the net 72. The defence 2S ssteni 7v is light-weight and easy to handle. The delCnce system 70 may he part ofa modular sIem chich could be used to protect a vehicle, structure or other vulnerable target. It can he replaced iii the field more easily that some currently available systenis. The net 72 is housed inside the foam layers 74. 76 arid has a degree of freedom to move. The foam layers 74, 76 pros ide environmental protection for the net layer 72. as well as performing a functioti in the event ota direct hit on a net strand, as described in relation to the defence system 2 shown in I igs. I -4A.

As can best be seen in Figs. 10 and I OA, an elasticated nylon cord 92 is wound through the net mesh at the periphery of the net 72 and around the 3-part bushes 94. The elasticated cord 92 is a continuous length of material, and it is provided to retain the shape of the net 72 in the event of a hit from a projectile. e.g. an RPG. If the defence system 70 is hit by a projectile then the net strands will typically break at the point of impact. If this happens the elasticated cord 92 pulls the net 72 back into shape afier the hit and renders the defence system 70 better capable of coping with multiple hits. Although the elasticated cord 92 is only shown in respect of the embodiment of the invention shown in Figs. 9-11 ii is clear that it could also be incorporated into the other embodiments of the invention disclosed in Figs. 1-8 and 12-13. A plurality of clips (not shown) connect the elasticated cord 92 to the net 72 and are provided around the periphery of the net 72.

These clips serve to retain the integrity of a major portion of the elasticated cord 92 in the event that it is subiect to a direct hit. In this ease the clasticated cord 92 may break in a region between two clips. hut it will remain taut along the remainder of' its length. Typically at least four clips are provided, located inboard from the corner, hut ii will he clear to the skilled person that more or less clips could also he used.

The front Liver of fliam 74 is construeled from a flexible tiiarn with a density of 30 kg/nY. The surface of the front lawr 74 is snuxitli. that it can be easily wiped clean to prevent the build up of debris. ftc rear I'am laer 7 i constn,cted from a closed cell rigid foam with a density of 30kg/rn Ihe front loam laser 74 and 11w rear kiani layer 76 are water repellant. non-stick and they are pros ided sith a camouflage pallerning to suit the terrain in which the defence system is intended to be used. Ihe fliarit la'.ers 74. 76 provide environmental protection for the net layer 72 and ako provide IV protection. uutra-red (1k p shielding (to disguise the IR signature of the vehicle or structure) and tlic are Ilanie retardant. In an alternative embodiment, the defence sssIcrl2 2. 7(1 can lx' pri ided n itli a camouflage cover (not shown) which is a replaceable hag-like structure %%hich surr.tind tIle sstem 2, 70 and can he changed to suit the surroundings. 1 he camouflage co ci nhI% lx' nude from a rip-stop nylon material similar to that used in respect tilihe sstems 21P. 4(1 (ii) slniii in lis. 5:\K. Ihe openings ofthe camouflage cover mas eorienienh)s be secured in h'1'k and ioop ltsIenings. e.g. Velcro®, or by any other

suitable mean'.

The rear Iiani las er 76 is pro' ided c itli a hack panel 85 and a raised lip 86 around its perimeter, which extends outwardly with respect to the back panel 85. A plurality of cylindrical protrusions 88 are provided on the lip 86 extending in a direction away from the back panel 85. The protrusions 88 are sized such that they may engage with a mesh of the net 72 when the defence system 70 is assembled. The protrusions 88 serve to hold the net 72 loosely in place, along with the 3-part bushes which each engage with a portion of the net mesh in the corner of the net 72.

The lip 86 has an outer edge 86a which extends to the same height as the protrusions 88 and upon which the front foam layer 74 sits when the system 70 is assembled. The rear foam layer 76 is formed from a single piece of foam, with the back panel 85, lip 86, outer edge 86a and protrusions 88 being machined out of the foam. The foam layers 74. 76 are bonded together using a suitable adhesive, but any suitable means for connecting two foam layers 74, 76 could be utilised.

The lip 86 has a height of 60mm, measured in a direction away from the hack patiet 85. such that when the net 72 rests on the lip 86 a void 99 is created behind the net 72. The void Q9 can best be seen in Fig. II. This gives the net a degree of freedom of movement and permits the net 72 to hang freely within the system 70 and act on a projectile in a natural manner. It is envisaged that a larger void 99 could be provided in the defence system 70. hut for operatioTwi I1exihitit it is preferred that the void 99 is not too large.

The net layer 72 comprises a plurality of net strands made from l)yneernak Sk 7 manutactured by OSM Dyneema BY.) which are formed with knotless intcrscetitns. a' is scll knosn in the art. The net strands have a diameter of approximateI 5mm and a strength of approximately l4kN. and they define a plurality of regular net meshes. 11w circumkrence ottiw net meshes is approxiniately equal to two thirds of the circumference of the nose cone of the KI'( i hich the defence system 70 is designed to counteract. For example. the RP(-7 propels a arhead ith a maximum diameter of 90mm. The maximum circumftreiice ot such a arhe;,d t ill he approximately 283mm. Consequently, the circumftrenee of each mesh section in a detence system 70 designed to counteract the RPG-7 would be apprt'imateh I NSmiii In the ca's square net mesh this would require sides ofapproxiniatel' 47mm The system 70 functions in the same general manner as the system 2 ot):ig I -t\ and the operation will not he described again.

Figs. 12 and 13 show a fUrther embodiment of a defence system 100. The defence system 100 of Figs. 12 and 13 is substantially the same as the system 70 shown in Figs. 9-11 and the same numbering will be used for like parts.

Fig. 12 is shown as an exploded view to aid understanding of the construction of the system 100 and to highlight the differenàes between the system 100 and the system 70 of Figs. 9-11. The defence system 100 includes a layer of reticulated foam 110 between the net layer 72 and the rear foam buffer layer 76. The reticulated foam layer 110 is a rigid foam and has a plurality of holes 1 0 120 machined out of it to help reduce the total weight of the system 100. The reticulated foam has a density of 35kg/rn3 prior to profiling and approximately 13kg/rn3 after the holes 120 have been machined.

As can best be seen in Fig. 13. the reticulated foam layer 110 acts as a spacer to maintain the gap IS of 60mm between the net layer 72 and the rear foam buffer layer 76. The reticulated foam layer sits in the void 99 between the net layer 72 and the rear foam buffer layer 76 and is in contact with both. The reticulated foam ITO also provides structural support to the system 100, which is particularly important to maintain the integrity of the system 100 in the extreme temperatures to which it is envisaged that the system 100 will he exposed.

Without wishing lobe bound by theory, it is believed that the reticulated foam layer 110 does not play any part in the detonation of a shaped-charge projectile. The operation of the system 100 is believed to he identical to that of the system 70 illustrated in Figs. 9-Il. The layer of reticulated foam could also he incorporated into the system 2 shown in Fig. 4A: Although the present invention has been described with reference to thç embodiments shown in Figs. 1-13. it will he clear to the person skilled in the art that alternative embodiments of the invention could he devised within the scope of the claims.

Claims (9)

1. Claims 1. A defence system comprising a net layer and a buffer layer, wherein the buffer layer is provided in front of the net layer.
2. 2. A defence system according to claim 1, wherein the buffer layer has one or more properties selected from the group comprising: UV protection; water resistance; JR shielding; camouflage patterning; non-stick surface; flame retardanee.
3. 3. A defence system according to claim 1 or claim 2, wherein the net layer is attached to the butThr layer.
4. 4. A deknce system according to claim 3. wherein the buffer layer supports the net in an ojcri condition.
5. 5. A detcnce system according to an\ preceding claim, further comprising a rear buflèr kiwi. nhcrcin the net is sandwiched between a front buffer layer and the rear buffer layer.o A detciicc svteni according to an preceding claim, wherein the huller layer comprises a laner nt a loam material.7. A defence stein according In claim 6. wherein the Ibam material has a density of less than 300kg rn: or less than 90kgm: or less than 80kg/rn3: or less than 6Okg'nY; or less than 4 5kç ni ut kss than or equal to 3(1kg/rn3.S A defiiicc svsteIll according to claim 6 orclaim 7. wherein the foam material is a closed cell lin 9. A detcncc s\ stern according to any one ol' claims 6-8. wherein the foam material has a silk iii outer sttrttee.1(1. A deli.mcc system according to any one of claims 6-9 comprising: a front foam buffer layer: a rear foam buffer layer: and a net layer, wherein the net layer is supported in open condition in an internal cavity defined by the front foam buffer layer and the rear foam buffer layer.II. A defence system according to claim 1 0. wherein the rear foam buffer layer comprises a back panel and a raised peripheral rim, and wherein the front foam buffer layer abuts the peripheral rim to define the internal cavity therehetween.12. A defence system according to claim I I. wherein the peripheral rim of the rear foam buffer layer further comprises an outer portion, which abuts the front foam buffer layer, and an inner portion, which comprises a plurality of protrusions which are received within a mesh of the net to support the net in an open condition.13. A defence svsteni according to claim II or claim fl. wherein the net layer is spaced at least 60mm from the hack panel of she rear fiuni huller la er.14. A defence system according to an' one of claim. LU-Il. wherein a spacer material is provided between the net liner and thc rear iam boiler laser to maintain the spacing between the net layer and the rear fliarll huller laser.15. A defence system according 54' claim 14. hcrcan the spacer material isa foam spacer layer.16. A defence sssIen according I'' claim 15. %sIicrei;I the spacer material is a reticulated loam layer.1 7. A defence svstenl according to am one ot claims I 0-I 6. wherein the density ol the Irorit foam hulir layer is loer thaii file dcIHit% of tile rear foam bul'kr laer.IS. A defence system according to an one olelaims lU-lb. wherein the densityofthefront foam buffer layer is the same as the density of the rear foam buffer layer.19. A defence system according to any one of claims 10-18, wherein the defence system is provided with fixing means for attaching it to a vehicle or structure to be protected.20. A defence system according to claim 19, wherein the fixing means comprises a plurality of fixing members.21. A defence system according to claim 19 or claim 20, wherein the fixing members comprise spring mounted fixings.22. A defence system according to any one of claims 10-2!. wherein the system further comprises an elasticated cord which engages with the net mesh around the perimeter of the net.23. A defence system according to claim 22. wherein the elasticated cord engages nub fixing means for securing the defence system to a vehicle structure.24. A defence system according to claim 22 or claim 23. wherein the elasticated cord it attached to the net mesh at a plurality of locations around the perinwtcr of the net.25. A defence systemaccordingtoanyoneofclaims 1-5.wherein the huller la>erct'mpriscs a layer of Lightweight fabric.26. A defence system according to claim 25. wherein the Iighteighi fabric is a rip-stop nylon fabric.27. A defence system according to claim 25 or claim 26. wherein the lightseight tabric has a mass of less than 1 bOg/nY: or less than I 55g/m: or less than I S()g in: or less 1km 1 4Sg in; or less than I 40g/nY..28. A defence syscm according to any one of claims 25-27. nhcrcin the hutld Ia' er comprises a bag-like structure which surrounds the net layer.29. A defence system according to any preceding claim, wherein the net layer comprises net strands formed from plastic fibres.30. A defence system according to claim 29, wherein the plastic fibres have one or more of the following properties: high tenacity; low elongation; high strength to weight ratio; low density; and soft finish.31. A defence system according to claim 29 or claim 30, wherein the net strands comprise ultra high molecular weight polyethylene.32. A defence system according to any preceding claim, wherein the net layer comprises a knotted construction.33. A defence system according to any one ofclaims 1-31, wherein the net layer comprises a knotless construction.34. A defence system according to any one of claims 1-31. wherein the net layer comprises a woven construction.35. A deI.mce sy'slem according to ans preceding claim, wherein the net strands in the net layer have a diameter of less than 10mm; or less than 6mm: or in the region from 3-6mm; or less than 3mm.A deflnce system according to any preceding claim, wherein the circumference ofeach individual mesh section of the net layer is less than the maximum circumference of the nose cone of the shaped charge arhead which the deknee system is designed to disable.37. A delènce system according to claim 3O. wherein the circumference of each individual mesh section is less than, or equal to. two-thirds of the maximum circumference of the nose cone of the shaped charge warhead.38. A defence system according to any preceding claim, wherein the defence system is provided with fixing means for attaching it to a vehicle or structure to be protected.39. A defence system according to claim 38, wherein the fixing means comprises a plurality of fixing members.40. A defence system according to claim 39, wherein the fixing members comprise spring mounted fixings.41. A modular defence system comprising a plurality of defence systems according to any preceding claim.42. A modular defence system according to claim 41, wherein the individual defence elements are provided with means 11w attaching then) to each other.-43. A defCiiee ss!eni suhstaritiall as hereinhefore described with reference to the aceornpan ing Jra ing. nflCT Amendments to the claims have been filed as follows Claims 1. A defence system comprising a net layer and a buffer layer, wherein the buffer layer is provided in front of the net layer, and wherein the buffer layer comprises a layer of a foam material.2. A defence systQm according to claim 1, wherein the buffer layer has one or more properties selected from the group comprising: UV protection; water resistance; IR shielding; camouflage patterning; non-stick surface; flame retardance.3. A defence system according to claim 1 or claim 2, wherein the net layer is attached to the buffer layer.4. A defence system according to claim 3, wherein the buffer layer supports the net in an open conditidn, 5. A defence system according to any preceding claim, further comprising a rear buffer layer, wherein the net is sandwiched between a front buffer layer and the rear buffer layer.
6. 6. A defence system according to any preceding claim, wherein the foam material has a density of less than lOOkg/m3; or less than 90kg/rn3; or less than 80kg/rn3; or less than 60kg/rn3; or less than 45kg/rn3; or les than or equal to3Okg/m3.
7. 7. A defence system according to any preceding claim, wherein the foam material is a closed cell foam.
8. 8. A defence system according to any preceding claim, wherein the foam material has a smooth outer surface.
9. 9. A defence system according to any preceding claim comprising: a front foam buffer layer; a rear foam buffer layer; and a net layer, wherein the net layer is supported in open condition in an internal cavity defined by the front foarii buffer layer and the rear foam buffer layer.C10. A defence system according to claim 9, wherein the rear foam buffer layer comprises a back panel and a raised peripheral rim, and wherein the front foam buffer layer abuts the peripheral rim to define the internal cavity therebetween.11. A defence system according to claim 10, wherein the peripheral rim of the rear foam buffer layer further comprises an outer portion, which abuts the front foam buffer layer, and an inner portion, which comprises a plurality of protrusions which are received within a mesh of the net to support the net in an open condition.12. A defence system according to claim 10 or claim 11, wherein the net layer is spaced at least 60mm from the back panel of the rear foam buffer layer.13. A defence system according to any one oi claims 9-12, wherein a spacer material is provided between the net layer and the rear foam buffer layer to maintain the spacing between the net layer and the rear foam buffer layer.14. A defence system according to claim 13, wherein the spacer material is a foam spacer layer.15. A defence system according to claim 14, wherein the spacer material is a reticulated foam layer.16. A defence system according to any one of claims 9-15, wherein the density of the front foam buffer layer is lower than the density of the rear foam buffer layer.17. A defence system according to any one of claims 9-15, wherein the density of the front foam buffer layer is the same as the density of the rear foam buffer layer.18. A defence system according to any one of claims 10-17, wherein the defence system is provided with fixing means for attaching it to a vehicle or structure * to be protected.19. A defence system according to claim 18, wherein the fixing means comprises a plurality of fixing members.20. A defence system according to claim 18 or claim 19, wherein the fixing members comprise spring mounted fixings. * 21-A defence system according to any one of claims 9-20, wherein the system further comprises an elasticated cord which engages with the net mesh around the perimeter of the net.22-A defence system according to claim 21, wherein the elasticated cord engages with fixing means for securing the defence system to a vehicle structure.23-A defence system according to claim 21 or claim 22, wherein the elasticated cord is attached to the net mesh at a plurality of locations arcund the perimeter of the net.24. A defence system according to any preceding claim, wherein the buffer layer additionally comprises a layer of lightweight fabric.25-A defence system according to claim 24, wherein the lightweight fabric is a rip-stop nylon fabric.26-A defence system according to claim 24 or claim 25, wherein the lightweight fabric has a mass of less than 160g/m2; or less than 155g1m2; or less than 150g/m2; or less than 145g/m2; or less than 140g/m2..27-A defence system according to any one of claims 24-26, wherein the buffer layer comprises a bag-like structure which surrounds the net layer.26-A defence system according to any preceding claim, wherein the net layer comprises net strands formed from plastic fibres.29-A defence system according to claim 28, wherein the plastic fibres have one or more of the following properties: high tenacity; low elongation; high strength to weight ratio; low density; and soft finish.30. A defence system according to claim 28 or claim 29, wherein the net strands comprise ultra high molecular weight polyethylene.31. A defence system according to any preceding claim, wherein the net layer comprises a knotted construction.32. A defence system according to any one of claims 1-30, wherein the net layer comprises a knotless construction.33. A defence system according to any one of claims 1-30, wherein the net layer comprises a woven construction.34. A defence system according to any preceding claim, wherein the net strands in the net layer have a diameter of less than 10mm; or less than 6mm; or in the region from 3-6mm; or less than 3mm.35. A defence system according to any preceding claim, wherein the circumference of each individual mesh section of the net layer is less than the maximum circumference of the nose cone of the shaped charge warhead which the defence system is designed to disable.36. A defence system according to claim 35, wherein the circumference of each individual mesh section is less than, or equal to, two-thirds of the maximum circumference of the nose cone of the shaped charge warhead.37. A defence system according to any preceding claim, wherein the defence system is provided with fixing means for attaching it to a vehicle or structure tb be protected.38. A defence system according to claim 37, wherein the fixing means comprises a plurality of fixing members.39. A defence system according to claim 38, wherein the fixing members comprise spring mounted fixings.40. A modular defence system comprising a plurality of defence systems according to any preceding claim.41. A modular defence system according to claim 40, wherein the individual defence elements are provided with means for attaching them to each other.42. A defence system substantially as hereinbefore described with reference to* I. -Lthe accompanying drawings.