The present invention concerns a barrier comprising a plurality of individual barrier units in a linear arrangement and a relatively rigid energy transfer means. The barrier may be used to resist vehicle ramming attack.

Barriers intended to deal with vehicle collisions are well known in the art. In some applications, such as in military applications, barriers are required to prevent the vehicle from breaking through the barrier i.e. to be resistant to vehicle ramming attack. Otherwise, the vehicle itself or other subsequent vehicles can launch further attacks once the barrier has been breached. Standard testing for such barriers is well known in the art, for example by measuring the resistance of the barrier to an impact of a 15,000 lb truck travelling at 22.35 m/s.

Barriers currently used for this purpose include rows of concrete blocks, with each block connected to the blocks adjacent to it. The concrete is sufficiently heavy that it is resistant to vehicle ramming attack. However, such barriers require water in order to make the concrete, which is not always available.

Various barrier elements are known in the art. For example, WO90/12160 discloses a gabion barrier that can be filled with concrete, wherein a concrete reinforcing rod can pass through the gabion baskets. GB2512336 discloses a gabion barrier comprising a row of gabions and a row of posts and panels supported by the gabions. The posts may be supported by concrete blocks engaged with the fill material. WO01/1 1 146 discloses a barrier system comprising abutting barrier elements and a longitudinally extending guard mounted thereon.

GB2440145 discloses a barrier formed from vehicle tyres arranged to form a tube that are secured together using straps, wires or cord, or by a support frame or a wrap of material such as plastic sheeting or a mesh sleeve. JP2004230697 discloses a row of logs arranged in parallel and surrounded with steel band members which are attached to each of the logs. EP0202552 discloses a space element that can be used to reinforce slopes comprising latticework baskets that may be spaced apart by a rod. l There is also a requirement for barriers to be simple and fast to deploy, as well as being easy to move, if desired. Again, this is particularly important in military applications. The concrete walls known in the art do not fulfil these requirements.

There is therefore a requirement for an easily deployable barrier that has an improved resistance to vehicle ramming attack, specifically a barrier that can absorb almost 1 100 kJ of energy without being compromised.

According to the present invention there is provided a barrier comprising a plurality of individual barrier units in a linear arrangement and a relatively rigid energy transfer means, wherein the energy transfer means comprises at least one continuous member extending along the length of the plurality of individual barrier units that is connected to each individual barrier unit in the plurality, such that when a force is applied to one individual barrier unit in the plurality, the energy transfer means transfers part of the energy associated with the applied force to other individual barrier units in the plurality of individual barrier units.

The force applied to one individual barrier unit in the plurality may be the result of a collision between an object and the barrier unit, wherein the object may be a vehicle. The barrier units may be placed on a surface and the force applied to the individual barrier unit may be perpendicular to the length of the plurality of individual compartments and parallel to said surface.

It is generally understood that two simple idealisations of collisions between two objects are possible, namely elastic and inelastic collisions. As the vehicle and the barrier unit remain in contact after the collision, this interaction may be considered to be an inelastic collision as the kinetic energy associated with the vector of the impact is not conserved.

The absorption of this kinetic energy is determined by the masses involved in the collision. However, it is known that if the weight of the individual barrier units is too great then the barrier tends not to slide along the surface on which it is placed, but instead experiences a punching shear effect localised at the point of impact as the inertial mass of the adjoining cells is too high. This reduces the barrier's ability to resist a vehicle ramming attack.

The energy transfer means in the present invention enhances the connection between the individual barrier units, thereby increasing the effective mass of the system without requiring an increase in mass of the individual barrier units. In other words, by connecting the barrier units with the energy transfer means, it is no longer only the mass of the barrier unit involved in the collision that is relevant but the mass of all of the barrier units in the plurality connected by the energy transfer means. This reduces the kinetic energy that must be absorbed through the work of sliding and increases the sliding resistance, thereby reducing the length of slide required to absorb the kinetic energy. This therefore increases the barrier's ability to resist a vehicle ramming attack.

The arrangement of the present invention means that if a force is applied to an individual barrier unit, such as a vehicle colliding with the barrier unit, the energy transfer means is engaged and acts to pull the other barrier units in the plurality in the direction of the force. The energy transfer means therefore connects the plurality of barrier units such that in combination, the plurality of barrier units and the energy transfer means act as a single energy transfer system. This acts to dissipate the energy involved in the collision, thereby increasing the barrier's resistance to ramming attack.

Preferably, the energy transfer means transfers a majority of the energy associated with the applied force (i.e. over 50% of the energy). Even more preferably, the energy transfer means transfers almost all of the energy associated with the applied force (i.e. over 80% or over 90% of the energy).

The use of numerous barrier units to form the barrier means that the barrier can be deployed quickly and easily. The length of the barrier is variable, depending on the number of barrier units. The plurality of barrier units in the barrier can be of any number and thus the barrier can be of indefinite length. Additionally, the linear arrangement of the barrier units does not have to be a straight linear arrangement. Instead, the units may be positioned to allow the linear barrier to curve or change direction, so as to avoid any obstacles that may be present as the barrier is deployed. Preferably, the plurality includes three or more barrier units. This means that barriers that are sufficiently long for their intended use can be deployed easily and quickly. Additionally, this means that any energy associated with a force applied to a barrier unit can be transferred to a number of other barrier units. For example, if a force is applied to a central barrier unit of the three or more barrier units, the energy associated with the force may be distributed in both directions along the barrier.

The barrier units are the units that create the front of the barrier, the front being one of the elongate surfaces of the linear barrier, perpendicular to the surface on which the barrier is placed (i.e. not the top or bottom of the barrier), to which a force is likely to be applied. This front is preferably continuous, with no space between adjacent barrier units. It is therefore the barrier units themselves that create the obstacle, while the energy transfer means merely connects the units and preferably does not contribute to the obstacle created by the barrier.

By "relatively rigid", it is meant that the energy transfer means is not readily deformed by weak forces, such as those experienced while the barrier is being deployed. However, strong forces, such as those involved in the collision of a vehicle with the barrier, may act to at least partially deform the energy transfer means. This term is therefore intended to cover means such as wires, which may demonstrate some deformation on the application of strong forces, as long as they are not deformed during the deployment of the barrier.

The energy transfer means may comprise a bar, a rod, a wire, a hollow tubing or another elongate member which can extend along the plurality of the individual barrier units, such as that used in motorway crash barriers seen in central reservations (Armco Barriers). Preferably, a bar is used as it experiences less stretching when a force is applied compared to other arrangements, such as wire. The energy transfer means may be flat, for example a flat bar.

The energy transfer means may be made out of a metal, such as steel, alloys or a woven material such as a canvas netting. If steel is used, this is preferably high tensile steel. Rods made from these materials are considered sufficiently rigid to form the energy transfer means of the present invention. The energy transfer means may comprise two or more elongate members, which may be connected to one another at the point at which the energy transfer member is attached to the individual barrier units. By "elongate", it is meant that the continuous means has a length sufficient to extend along the length of the barrier. Preferably, the length of the continuous means is its longest dimension.

By "continuous", it is meant that the energy transfer means acts as a single member to transfer the energy associated with the applied force. The energy transfer means may comprise a continuous rod (or other elongate members), or may comprise two or more rods (or other elongate members) connected together to form a continuous energy transfer means. The two or more elongate members may have different lengths. In this second embodiment, the connection must be sufficiently strong that the energy transfer means acts as a single member to transfer the energy associated with the applied force, so that there is no reduction of energy transfer at the connection. In other words, the elongate member itself must break before the connection between adjacent elongate members does, so no energy is lost at the connection.

The energy transfer means being "connected to each individual barrier unit" requires a connection between the energy transfer means and each barrier unit, which retains the energy transfer means in a position relative to each individual barrier unit in the plurality. The movement of the energy transfer relative to each barrier unit is therefore restricted, due to the connection between the energy transfer means and the barrier unit in question. Preferably, the energy transfer means cannot move relative to each barrier unit.

Preferably, the elongate member is the same either side of the connection, i.e. two identical elongate members are attached by the connection. This helps to increase the energy transfer along the energy transfer means.

The connection between adjacent elongate members may be any suitable connection known in the art, such as a nut or clamp arrangement. If the energy transfer means comprises a hollow metal tube, such as a square hollow metal tube, the connection may comprise an overlapping region of adjacent tubes, wherein the end of one tube fits inside the end of the adjacent tube. Holes may be present in one or more side walls of both ends, which are then aligned when the ends of the tubes overlap. Pins can then be placed into the holes to hold the tubes together.

The connection may comprise a hole through the end of the energy transfer means. In this embodiment, the energy transfer means preferably comprises a flat surface, for example is a flat bar. A corresponding hole on the adjacent energy transfer means is aligned with said hole and a locking member is then inserted through both holes. The locking member can be fastened using known fastening means such as nuts and bolts.

The elongate member may be threaded. This can help to connect two or more elongate members together to form an energy transfer means, as well as helping to connect the energy transfer means to the individual barrier units.

The energy transfer means may extend along the front and/or along the back of the plurality of individual barrier units. The front and back are defined as the two elongate surfaces of the linear barrier, perpendicular to the surface on which the barrier is placed (i.e. not the top or bottom of the barrier). In other words, the energy transfer means may extend along one or both of the elongate surfaces of the linear barrier. The front surface is intended to refer to the surface to which a force is to be applied, while the back surface is the surface opposite the front surface.

Preferably, the energy transfer means extends along the front of the plurality of individual barrier units. In another embodiment, the barrier comprises a first energy transfer means extending along the front of the plurality of individual barrier units and a second energy transfer means extending along the back of the plurality of individual barrier units. The first and second energy transfer means may be the same or different in construction.

This further increases the effective mass of the barrier and ensures a more efficient transfer of energy from the individual barrier unit to which the force is applied to the other barrier units in the plurality. The energy transfer means may be present within the barrier units or along the outer face of the barrier. Including the energy transfer means internally in the barrier units means that no surface is provided on the outside of the barrier that may help an individual climb over it.

The energy transfer means may be positioned at a height such that the chassis of a vehicle would not hit the energy transfer means. Preferably, the energy transfer means comprises at least two elongate continuous members and is positioned at a height such that the chassis of a vehicle would impact the barrier between the two elongate members of the energy transfer means, such as between two rods. This would mean that the vehicle may be lifted off the ground on collision with the barrier, thereby reducing the energy that is applied to the barrier by the collision.

The barrier may further comprise connecting means that connect an individual barrier unit in the plurality to at least one adjacent barrier unit. The barrier may comprise a plurality of connecting means, with each connecting means connecting an individual barrier unit to one adjacent barrier unit. In this embodiment, it is the connecting means that maintain the barrier units in position relative to one another and the energy transfer means that acts to transfer part of the energy associated with an applied force to other individual barrier units in the plurality of individual barrier units. Such connecting means may be any known in the art, such as screws, bolts, clamps or any other industry standard component joining mechanism. This further increases the efficiency of the energy transfer from the individual barrier unit to which the force is applied to the other barrier units in the plurality. This also increases the ease with which the barrier may be deployed.

The barrier may be surface mounted, i.e. extend less than four inches into a surface on which it is placed. Surface mounted barriers are easy and fast to deploy when compared to barriers that are integrated with the ground, such as those including posts that extend into the surface on which the barrier is placed. Additionally, such barriers can readily be moved, if desired. The increase in energy transfer of the arrangement of the present invention means that a surface mounted barrier can effectively resist a vehicle ramming attack. The individual barrier units may comprise containers, such as gabions. The containers or gabions may be open-topped or may comprise a lid. Possible structures of suitable gabions are well known in the art and are generally made from wire mesh panels, which form side walls and a base, thereby creating a gabion cage. The gabion may include a higher front panel relative to the back panel, which would make it harder for an individual to overcome the barrier. Suitable barrier arrangements are shown, for example, in WO2008/020247, WO2007/060476 and WO201 1/012879.

In this embodiment, the connecting means (if present) may comprise helical coils wound between the wire mesh of the adjacent barrier units, thereby connecting the two. Such arrangements are cheap and easy to manufacture and are well known in the art.

In this embodiment, the energy transfer means may extend through the holes in the wire mesh of the gabion side walls. This helps to maintain the energy transfer means in the correct position and is cheap and easy to manufacture. Additionally, this means that the energy transfer means is present within the barrier units. As discussed above, this prevents the formation of a surface on the outside of the barrier that may help an individual climb over it.

The energy transfer means may be connected to each individual barrier unit using a nut, a clamp or other fastening means that are known in the art. Additionally, a plate may be positioned between individual barrier units. The energy transfer means can then extend through the plate, which may be made of metal or an alloy. This is particularly beneficial if the individual barrier units comprise side walls, such as are present in gabions. In this case, the plate may be placed between side walls of adjacent individual barrier units and the nut or other fastening means may be attached to the energy transfer means on the opposite side of the side wall, i.e. inside the gabion cage.

The barrier units may comprise further components, in addition to the gabion or other container. For example, one or more supports may be connected to the gabion or other container, which may extend higher than the height of the gabion or other container. The support may comprise a post, which may be vertical and may further comprise a base portion. The support may act as a brace. A fence panel may be attached to said support at the front of the barrier unit, which may increase the height of the front of the barrier unit. The energy transfer means may be connected to the support. The connection may comprise a nut, a clamp or another fastening means. The barrier unit may comprise one or more gabions or other containers that are connected together.

The gabions may be lined, optionally with a geotextile material. The gabions may be double-lined. A fill material can then be used to fill the gabion to increase the mass of the individual barrier units. Fill materials such as a well graded sand or rock can be used. This means that fill materials that are readily available at the site of deployment can be used, such as desert fill.

Additionally or alternatively, the gabions may include a flexible bag within the gabion cage. This bag may be at least partially filled with a fill material either before or after it is placed within the gabion. The fill materials may be as described above.

Preferably, the flexible bag is a fluted bag. Fluted bags include a member within the bag that internally connects one wall to an adjacent wall. This helps the bag to maintain its shape once filled, as square bags without these members expand towards a circular configuration when filled. In contrast, the members hold the walls in the desired configuration, so that they are easier to place within the gabion cage.

Preferably, the flexible bag or the lining material comprises a lid. This acts to prevent the fill material from escaping the bag or liner when a force is applied to the barrier unit, thereby maintaining the weight of the barrier.

The flexible bag may be positioned towards the rear of the gabion cage. As discussed above, the rear of the gabion is the elongate side of the linear barrier opposite that to which the force is to be applied.

The barrier may further comprise an additional plurality of individual barrier units in a linear arrangement, extending parallel to the first plurality and in contact therewith. Preferably, the second plurality of individual barrier units extends along the rear of the first plurality. The barrier units in the second plurality may be the same as or different to those in the first plurality. This arrangement allows energy to be transferred from the barrier unit to which the force is applied to the second plurality of individual barrier units as well as the first, thereby further improving the resistance of the barrier to vehicle ramming attack. The second plurality of barrier units also reduces the risk of the first plurality of barrier units rolling backwards upon impact, which can reduce the efficiency of the energy transfer and can result in the barrier being breached.

In one embodiment, the second plurality of individual barrier units is staggered compared to the first plurality of individual units, such that the connections between adjacent individual barrier units within each plurality do not fall at the same points along the length of the barrier. This further improves the strength of the barrier, thereby improving the resistance of the barrier to vehicle ramming attack.

The second plurality of individual barrier units may be connected to the first plurality of individual barrier units. Such connection means may be any means known in the art and may be the same means as is used to connect adjacent individual barrier units within the first and/or second plurality of individual barrier units, as discussed above.

The second plurality of individual barrier units may comprise gabions, which may include a bag, as discussed above in relation to the first plurality of individual barrier units. In this case, the bag may be positioned towards the front of the gabion cage. As discussed above, the front of the barrier is the elongate side of the linear barrier closest that to which the force is to be applied.

In the embodiment in which the barrier comprises two adjacent and parallel linear arrangements of pluralities of gabions, the gabions in both pluralities may include a bag. In this case, the bags may be positioned in the gabion cage towards the side of each plurality of gabions adjacent to the other plurality of gabions.

One or more individual barrier unit may also comprise a friction increasing means on its base. The base is the side of the barrier unit in contact with the surface on which the barrier is deployed. This barrier unit may be part of the first plurality of individual barrier units and/or the second plurality of individual barrier units (if present). The friction increasing means extends from the base of the individual barrier unit towards a surface on which the barrier is placed. The friction increasing means can therefore interact with a surface on which the barrier is placed. This increases the friction between the barrier and the surface, thereby helping to transfer the energy associated with the force applied to an individual barrier unit away from the individual barrier unit to which it is applied.

Preferably, the friction increasing means is present on all of the individual barrier units in the barrier. The friction increasing means may be any means that extends from the base of the individual barrier unit. The friction increasing means may comprise bolts that extend from the base of the barrier unit. In the case where the barrier unit is a wire mesh gabion, the bolts may extend through a plate, which may be a flat bar plate, on the inside of the gabion cage and then through the holes in the wire mesh. The bolts (or any other friction increasing means) may be held in place by the weight of the fill material placed within the gabion cage, or may be attached to the base of the barrier unit.

Additionally or alternatively, the friction increasing means may comprise a metal grid with one or more angled surface, such as an expanded sheet metal. The angled surfaces extend from the base of the barrier unit and may dig into the surface on which the barrier is placed when a force is applied.

The friction increasing means may be positioned towards the rear of the barrier. This may allow the front of the barrier to lift up as a force, such as a vehicle ramming attack, is applied to the barrier.

According to a second aspect of the present invention, there is provided the use of the barrier discussed above to resist vehicle ramming attacks. A trench may be created in front of the barrier in order to decrease and disrupt the amount of energy with which a vehicle can collide with the barrier. This therefore increases the resistance of the barrier arrangement to vehicle ramming attacks.

According to a third aspect of the present invention, there is provided a method of deploying a barrier comprising the steps of deploying a plurality of individual barrier units in a linear arrangement to form a barrier and connecting the plurality of individual barrier units with a relatively rigid energy transfer means, wherein the energy transfer means comprises at least one continuous member extending along the length of the plurality of individual barrier units that is connected to each individual barrier unit in the plurality.

This method is quick and easy and provides a barrier with an increased resistance to vehicle ramming attack, as when a force is applied to one individual barrier unit in the plurality, the energy transfer means transfers part of the energy associated with the applied force to other individual barrier units in the plurality of individual barrier units.

According to a fourth aspect of the present invention, there is provided a kit comprising a plurality of barrier units that can be positioned in a linear arrangement having a length, as well as a relatively rigid energy transfer means wherein the energy transfer means comprises at least one continuous member that can extend along the length of the plurality of individual barrier units and that can be connected to each individual barrier unit in the plurality such that when a force is applied to one individual barrier unit in the plurality, the energy transfer means transfers part of the energy associated with the applied force to other individual barrier units in the plurality of individual barrier units.

The energy transfer means may comprise two or more rods (or other elongate members) connected together to form a continuous energy transfer means. The two or more elongate members may have different lengths. This allows the connection between the elongate members to be positioned away from the connection between adjacent barrier units.

The invention will now be more particularly described with reference to the figures, in which:

Figure 1 illustrates a first embodiment of a barrier according to the present invention;

Figure 2 illustrates an enlarged view of the energy transfer means of the barrier of Figure 1 ; Figure 3 illustrates the way in which the energy transfer means of the barrier of Figure

1 is connected to the individual barrier units;

Figure 4 illustrates a friction increasing means according to the present invention;

Figure 5 illustrates a second embodiment of a barrier according to the present invention;

Figure 6 illustrates an alternative embodiment of an energy transfer means that can be used in the present invention; and

Figure 7 illustrates an alternative embodiment of an energy transfer means that can be used in the present invention.

Figure 1 illustrates a barrier 1 comprising a plurality of individual barrier units 2, connected by an energy transfer means 3. The barrier units 2 comprise wire mesh gabions in which the front panel 2a is of a greater height than the rear panel 2b. Inside the barrier units 2 is a flexible bag 4 that is filled with a fill material 5. Each barrier unit

2 is connected to an adjacent barrier unit 2 using helical coils (not shown), which are wound through the holes in the wire mesh.

The energy transfer means 3 comprises two threaded metal rods 3a which extend the length of the barrier 1 , inside the barrier units 2. This ensures that no surface is provided on the surface of the barrier 1 that would help an individual climb the barrier. The front of the barrier 1 is the elongate side that comprises the taller front panels 2a, as this is the side at which the force is to be applied. The energy transfer means 3 therefore extends along the front of the barrier 1 .

The energy transfer means 3 is connected to each individual barrier unit 2 at the interface between adjacent barrier units 2 using a metal plate 6 and nuts 7. The metal plate 6 is placed between the side walls of adjacent barrier units 2 and the energy transfer means 3 extends through the metal plate 6. Nuts 7 are attached to the energy transfer means 3 on the inside of each barrier unit 2 (at the inside of the gabion cage), thereby attaching the energy transfer means 3 to the individual barrier units 2.

Figure 2 illustrates an enlarged view of the energy transfer means 3 of the barrier 1 shown in Figure 1 . As shown in Figure 2, the energy transfer means 3 extends through the holes in the wire mesh of the barrier units 2. At the end of the barrier 1 a, a metal plate 6 is attached to the barrier unit 2, through which the energy transfer means is threaded. Nuts 7 are attached to the energy transfer means 3 at the outside of the barrier unit 2, so as to keep the energy transfer means 3 in position.

Figure 3 illustrates the connection between the energy transfer means 3 and the individual barrier units 2 in more detail. The metal plate 6 is positioned between the adjacent individual barrier units 2, with the energy transfer means 3 extending through holes therein. The metal plate 6 is therefore outside the barrier units 2. Nuts 7 are attached to the energy transfer means 3 on the inside of the barrier units 2. The nuts 7 hold the energy transfer means 3 in position relative to the barrier units 2 and the metal plate 6, thereby connecting the energy transfer means 3 to both barrier units 2.

Figure 4 illustrates an embodiment of the friction increasing means of the present invention, which can be used in combination with the barrier shown in Figure 1. Friction increasing means 8 comprises a metal plate 9 and bolts 10. The bolts 10 extend through holes in the metal plate 9. The friction increasing means 8, when used in combination with the barrier shown in Figure 1 is placed inside the gabion cage of the barrier units, with the protruding end of the bolts facing downwards. These protruding ends extend through the wire mesh of the base of the gabion cage. The flexible bag and the fill material are then placed over the metal plate 9 and the heads of the bolts 10. This keeps the bolts 10 and the metal plate 9 in position, thereby ensuring that the bolts 10 can interact with a surface on which the barrier is placed when a force is applied to the barrier. This increases the coefficient of friction between the barrier and the surface on which it is placed, thereby increasing its resistance to vehicle ramming attacks.

Figure 5 illustrates a second embodiment of the present invention. Barrier 1 1 is shown, which comprises a first plurality of individual barrier units 12, connected by an energy transfer means (not shown). The barrier units 12 comprise wire mesh gabions in which the front panel 12a is of a larger height than the rear panel 12b. Inside the barrier units 12 is a flexible bag 14 that is filled with a fill material 15. Each barrier unit 12 is connected to an adjacent barrier unit 12 using helical coils (not shown), which are wound through the holes in the wire mesh.

The energy transfer means (not shown) comprises a threaded metal rod which extends the length of the barrier 1 1 , as in Figure 1. The front of the barrier 1 1 is the elongate side that comprises the taller front panels 12a, as this is the side at which the force is to be applied. The energy transfer means therefore extends along the front of the barrier 1 1 .

The energy transfer means (not shown) is connected to each individual barrier unit 12 at the interface between adjacent barrier units 12 using a metal plate 16. This metal plate 16 is placed between the side walls of adjacent barrier units 12 and the energy transfer means extends through the metal plate 16. Nuts 17 are attached to the energy transfer means on the inside of each barrier unit 12, thereby attaching the energy transfer means to the individual barrier units 12.

Barrier 1 1 further comprises a second plurality of individual barrier units 18. This second plurality extends along the rear of the barrier 1 1 (i.e. the side opposite that along which the energy transfer means extends and to which the force is to be applied). The second plurality of individual barrier units 18 are similar in construction to the first plurality of individual barrier units 12, except that the front panel 18a is the same height as the rear panel 18b.

The second plurality of individual barrier units 18 is staggered in relation to the first plurality of individual barrier units 12, such that the connections between adjacent individual barrier units (12c, 18c) within each plurality (12, 18) do not fall at the same points along the length of the barrier 1 1 .

Figure 6 illustrates energy transfer means 21 which comprises square hollow metal tubes 22. One end of each tube 22 has a narrower portion 23, which fits inside the end 24 of the adjacent tube 22. Both ends of the tube 22 comprise holes 25. When connecting the tubes 22, the narrow portion 23 of one tube 22 is inserted through plate 26, which may be positioned in between the gabion units if the energy transfer means 21 is used in combination with the barriers shown in Figures 1 or 5. The narrow portion 23 of the tube 22 is then inserted into the end 24 of an adjacent tube 22, so that holes 25 on each of the tubes 22 align with one another. Pins 27 can then be inserted into holes 25 to hold the tubes 22 in position.

Figure 7 illustrates energy transfer means 31 , which comprises flat bars 32. Both ends of each flat bar 32 comprise a hole 35. When connecting the flat bars 32, the ends of the flat bars 32 overlap such that the holes 35 are aligned. A locking member 37 can then be inserted through the holes 35 and held in position using fastening means 38.