GB2601465A - Apparatus for breaching a barrier - Google Patents

Abstract

An apparatus for breaching a barrier comprises four blades 1 in a frame 2. A source of energy 4, such as a gunpowder charge or pneumatic source, produces a force which is transmitted along tubes 6 to primary 5 and secondary 3 expansion chambers. The primary expansion chamber 5 contains a first, counterbalance piston (20, figure 3) and the secondary expansion chamber 3 contains a second, drive piston (7, figure 3) attached to a blade 1. The counterbalances may be provided with ballast such as lead shot. The energy source 4 may be a pyrotechnic charge or compressed nitrogen. The blades may be made from steel or titanium and may be coated with bronze. The blades may be serrated (figure 2).

Description

Apparatus for breaching a barrier Background

Gaining access through various barriers is a problem faced by both emergency services and the military. Each has their own requirements and is dependent on the scenario faced. The needs of medical and rescue services are driven by the circumstances they face which will drive the timeframe and other factors such as the (noise levels generated. For the police and military the ability to deny knowledge to others until, at least, the moment that the breach of the barrier is initiated can be essential.

Examples of barriers faced by emergency services and the military include masonry (see US4902601 for an explosive method of cutting dense materials); metal and glass (see DE19961032610 for an explosive method for railway carriage windows). In particular attempts to gain access through laminated glass has been a long term issue on which a significant investment has been made in attempts to find a solution.

Laminated glass is produced by bonding two or more layers of glass together with a plastic interlayer, usually polyvinyl butyral (PVB). The plastic film holds the glass in place when the glass breaks and can also stretch whilst the glass still bonds to it, helping to lessen injuries from flying glass, and making it extremely difficult to penetrate laminated safety glass when compared to normal window pane glass. Laminated glass may well crack but will not shatter and is difficult to cut.

Attempts to gain rapid access through laminated glass using hand and power tools such as hammers, axes, rotary saws and chainsaws have proven inadequate in the required timefranne for police and military requirements and the only effective method so far identified has been the use of explosives.

The use of explosives to break through laminated glass has various drawbacks including the risk of injury due to the explosion itself and its overpressure, especially when used in a confined space, or due to flying glass or other debris. Additionally, the use and handling of explosives is dangerous in its self and requires highly specialist training to achieve safe operation. The time to safely set explosives and the need for the personnel to evacuate the immediate area, in order to avoid the associated risks, also.leads to considerable delays.

In a significant proportion of emergency situations it may also prove, at best, difficult, if not impossible, to warn those on the opposing side of the barrier prior to the use of explosives, drastically increasing the risk to these individuals of sustaining injuries as a result of the blast or associated debris; especially where individuals are injured or incapacitated. In police or military operations it can be impractical or undesirable to to provide warning prior to initiating entry; in alternative situations it can also prove highly beneficial, if not essential, that entry can be achieved stealthily which is largely unachievable when using explosives.

A further disadvantage in the use of explosives to breach the barrier in police and military operations is the built-in delay in effecting entry after breach associated with the time taken to return to the breach from the safe distance to which the personnel have to retire from the explosive charge. The use of explosives in confined spaces also considerably increases the risks to those on both sides of the barrier.

Non-explosive equipment is available on the market that is capable of breaching a wide variety of such barriers. The use of such non-explosive equipment has utility in hazardous areas such as those of explosive or flammable atmospheres however the equipment should ideally be man-portable, self-contained and require little if any ancillary equipment for use. With compressed air type systems weighing in excess of 150Kg their utility for police or military applications in achieving the breach in a stealthy or timely manner are limited.'

Description

To overcome the disadvantage of the flying debris resulting from the unrestrained explosive energy the present invention provides an apparatus that utilises the energy to drive a captive cutter, thus minimising debris on the other side of the barrier. To overcome the further disadvantage of the explosive risk to the operator the present invention provides an apparatus that contains the energy source, and any by products, within the apparatus.

The primary object of the invention is to provide an apparatus for gaining entry through a barrier by the manipulation of the energy dissipation around the system to provide both sufficient energy to breech the barrier and provide a counter-recoil force sufficient to facilitate the operator's use of the apparatus.

A further object of the invention is to provide an intrinsically safe apparatus for io gaining entry through a barrier for use in all locations that it may be required.

Still a further object of the invention is to provide an apparatus for gaining entry through a barrier that is both deployable and operable by a single person without the need for the operator to evacuate the location during the operation of the apparatus; such operation by a person can include holding the apparatus in place during operation.

A yet further object of the invention is to provide an apparatus for gaining entry through a barrier that minimises both the quantity and energy of debris resulting from 20 the breaching of the barrier Accordingly there is provided an apparatus for breaching through a barrier comprising a force producing means, a cutting means interconnected with two or* more piston assemblies each piston assembly comprising a first counterbalance piston and a second drive piston wherein the force firsts acts upon the counterbalance pistons which are oriented such that the direction of motion of the counterbalance is in opposition to that of the cutting means; characterised in that the force produced acts upon the two or more drive pistons simultaneously to accelerate the cutting means towards and through the barrier.

The force producing means has to provide sufficient energy to accelerate the cutting means to the required velocity appropriate for the material of the barrier to be cut. The required velocity has to be achieved in the relatively short distance between the location of the cutting means at rest within the frame and the surface of the barrier to be cut. Some adjustment of this distance is achievable within the construction of the framework and a range of framework sizes will achieve a further flexibility in the ability to create a range of offset distances between the cutting means and the surface of the barrier to be cut. The greater the offset distance of the cutting means from the barrier surface the greater the time available to accelerate the cutting* means to the desired velocity and equally the ability to use lower or slower acting energy sources.

Energy sources include pyrotechnic charges, pneumatics and hydraulics.

to Pyrotechnic charges have the advantage of providing, on initiation, high flow rates of combustion gases; this is determined and can be controlled by the selection of a pyrotechnic with the appropriate burning rate to achieve the desired acceleration of the cutting means. Such pyrotechnics are likely to be propellants, which could include gunpowder, although explosives could be used these will require a more robust construction of the apparatus to accommodate the increase forces generated by these types of pyrotechnics.

Where hydraulics are used as the energy source, as they are typically slower acting in generating the necessary force, their use is better suited to materials that require lower cutting velocities.

Counter-recoil methods are well known in the art for example a piston orientated such that the piston, when activated, moves in the opposing direction of travel to the cutting means and acts as a counterbalance to the force exerted by the cutting means. The counterbalance force is determined by the mass that is accelerated and as such the Mass of the piston can be augmented by the inclusion of additional ballast material in the piston chamber that the piston drives back. This material could be a fluid, such as water or where temperature considerations are an issue glycol, or a solid such as lead shot. If water is used as ballast then the water can be ejected from the apparatus significantly negating any recoil and resulting only in minor wetting around the target. If lead shot or alike is used for ballast this will be contained within the apparatus providing only a minimum amount of recoil.

Activation of the counter-recoil system can be biased such that the counter-recoil system initiates fractionally prior to the activation of the cutting means. The activation of the counter-recoil system in advance has the advantage of forcing the apparatus onto the barrier to be cut just prior to the cutting means engaging with the barrier thus providing additional confidence that the apparatus is suitably located against the face of the barrier.

Although capable of being operated by a person, where larger applications and/or where time/covertness is not a determining factor the apparatus can additionally to include a prop system to enable the apparatus to be held in location during operation. The apparatus can therefore be located and pressed against a vertical surface using a propping element engaged with a connector on the back of the apparatus and supported on a horizontal surface, such as the ground.

The apparatus can also incorporate various methods to retain the piece cut from the target and prevent it falling in through the aperture, such as a mechanical claw or by means of an additional element that affixes by adhesion, or any other known means, *to the surface of the piece to be retained.

As well as laminated glass, the apparatus cap equally be used to breach reinforced fire doors or windows, steel plate or most other surfaces with minor modifications taking into account the strength and thickness of the target surface and the size of the required aperture.

The cutting means should be optimised for the application, taking into consideration the type of material to be breached, the thickness of that material and the size of aperture required. Where the cutting means is a blade consideration should be given to a suitable balance between the strength of the blade material, its weight, the blade angle and the length of the blade. The required velocity of the blade is then determined based on a balance between the energy required to breach the surface and the maximum stress the blade can withstand. Blades can be further refined by the use of serrated edges of which various configurations of teeth forms are available, for example v-form or truncated v-form. Blades can be made from metal, such as steels, including carbon steel, stainless steel, high speed steels, as well as titanium or carbides such as tungsten or ceramics such as zirconia. In addition blades can be coated to achieve additional properties such as bronze coating to eliminate sparks on engagement with the barrier material.

In addition, when attempting to breach some materials, for example laminated glass, the material begins to sag as the blade starts to penetrate and this requires that the blade velocity must also be sufficient to overcome this sagging and continue to cut through the entire thickness, otherwise there is a risk that the blade will merely push the surface away without cutting.

Further, the apparatus can be at least partially constructed from materials with a comparatively high strength to weight ratio, such as carbon fibre or titanium, to provide improved portability and ease of use.

Where use demands the construction of the apparatus can be such that it is intrinsically safe to operate in hazardous environments, such as explosive atmospheres found in petrochemical facilities. Such techniques can include *a captive system for the products of combustion resulting from the use of pyrotechnics.

* A further benefit of such a captive system is that once the combustion products have 20 been allowed to cool the apparatus presents no special danger requiring specialist * disposal. Further techniques, well known in the art, such as spark suppression by means of coating the metallic blades of the cuttings means in bronze can also be utilised.

The invention is now described by way of example and with reference to the accompanying drawings of which: Figure 1 show a simplified diagram of the top view of the example apparatus which would be used to cut a square aperture into a target barrier.

* 30 Figure 2 shows a simplified cross-section diagram of a side view of the example apparatus which would be used to cut a square aperture into a target * barrier.

Figure 3 shows a simplified diagram of the source, a primary expansion, chamber, a secondary expansion chamber and the connecting pipe or tube.

5, A non-limiting example is embodied in an apparatus comprised of a blade whose weight and angle have been suitably chosen to ensure sufficient energy is transferred to the target, which is accelerated by a force produced using a * pyrotechnic, provided by a gunpowder cartridge, or pneumatic charge, such as could * be provided by compressed nitrogen. On initiation this force is used to accelerate the 10 blade to the required velocity for the chosen application and blade.

A non-limiting example makes use of 4 steel blades with a saw-tooth truncated v-form profile blade whose points are separated by 2 inches. This apparatus is used to cut a square aperture of 0.4225m2 (0.65m x 0.65m) in a sheet of laminated glass up to thick. The blades are accelerated to approximately 55-60ms-1using a gunpowder cartridge consisting of 1600 grains of G20 propellant.

Figure 1 shows a simplified diagram of the top view of the example apparatus which would be used to cut a square aperture into a target barrier. The blades (1) sit within a frame (2) and are coupled at each point at which they meet within a secondary expansion chamber (3). Located at the centre of the frame is the source of the force (4) required to accelerate the blades, which can, for example, be provided by a gunpowder cartridge and an ignition apparatus. The source (4) is connected to each primary expansion chamber (5) by a pipe or tube (6).

Figure 2 shows a simplified cross-section diagram of a side view of the example apparatus which would be used to cut a square aperture into a target barrier. The blade (1) sits within the frame (2) whilst each of the blades ends are formed with or are connected to a piston (7) locategl within the shaft (8) of one of the secondary expansion chambers (3). To cut an aperture will normally require the blades to form a closed shape such that each piston is formed from or connected to the ends of more than one blade and each piston couples the blades where they meet.

Figure 3 shows a simplified diagram of the source (4), a primary expansion chamber (5), a secondary expansion chamber (3) and the connecting pipe or tube (6). The energy source (4), when activated, will provide a gas which will rapidly expand through the pipe or tube (6) into the shaft (9) of the primary expansion chamber (5) where the force of the expanding gas will cause the first piston (10) to move in a direction opposite to the required direction of motion of the blade. The gas subsequently continues to expand through pipe or tube (11) and into the shaft (8) of the secondary expansion chamber (3). This continued expansion within shaft (8) then provides a force to accelerate a second piston (7) which is formed from or to connected to the end of at least one blade, and therefore accelerate the blade towards and through the target barrier (12).

On initiation of the energy source the expanding gas travels through the pipe constructed such that the gas expands into the primary expansion chamber first, which contains a piston oriented such that the force of the gas causes the piston to move in a direction opposing the direction of motion of the blade. The expanding gas continues in the pipe to a secondary expansion chamber where the force provided by the expanding gases is exerted upon a second piston formed from or connected to a cutting blade, accelerating the blade towards the target and in an opposing direction to that of the piston. By expanding into the first expansion chamber before entering the second expansion chamber, the motion of the first piston begins just prior to that of the blade such that its initial momentum directs the apparatus towards the target barrier to be breached. The opposing motion of the first piston, including any additional ballast, and the blade significantly reduces the recoil experienced by the user.

The force produced by the gas is such that the blade is accelerated to the optimum velocity required. If the blade is travelling too quickly it will break, to slowly and the blade will not go through the target. The blade velocity and weight should be balanced to provide sufficient energy. If the blade is too light it must travel faster, and is likely to be weaker. If the blade is heavier it need not travel so fast. The weight of the blade and the force required must also be optimised depending upon the thickness of the target. The maximum length of the blade, and therefore the size of cut, is determined by the stress which the blade can withstand.

Claims (16)

1. Claims 1. An apparatus for breaching through a barrier comprising a force producing means, a cutting means and a counterbalance mounted within a frame wherein the force produced acts upon said cutting means to accelerate the cutting means towards and through the barrier; characterised in that the force firsts acts upon the counterbalance which is oriented such that the direction of motion of the counterbalance is in opposition to that of the cutting means thus minimising the recoil due to the opposing motion of the cutting means.
2. 2. An apparatus as in claim 1 in which the force producing means is pyrotechnic.
3. 3. An apparatus as in claim 1 in which the force producing means is pneumatic.is
4. 4. An apparatus as in claim 2 in which force producing means is a gunpowder cartridge.
5. 5. An apparatus as in claim 3 in which the force producing means is a source of compressed nitrogen.
6. 6. An apparatus as in any preceding claim in which the counterbalance is provided with a ballast material.
7. 7. An apparatus as in claim 6 in which the ballast material is lead shot.
8. 8. An apparatus as in claim 6 in which the ballast material is a liquid.
9. 9. An apparatus as in any preceding claim where the cutting means is a blade.
10. 10. An apparatus as in Claim 9 where the blade has a serrated edge.
11. 11. An apparatus as in Claim 10 where the serrated edge has teeth conforming to a truncated v-form.
12. 12. An apparatus as in any preceding claim where the cutting means is manufactured from steel.
13. 13. An apparatus according to claims 1 -11 where the cutting means is manufactured from titanium.
14. 14. An apparatus as in any preceding claim where the cutting means has a coating applied.lo
15. 15. A cutting means according to Claim 14 where the applied coating is bronze.
16. 16. An apparatus substantially as hereinbefore described and with reference to the accompanying drawings.