BACKGROUND OF THE INVENTION

[0001] This invention relates to a grid structure for use in a protective barrier.

[0002] The incorporation of high density mesh panels in a fence leads to the establishment of an effective security barrier. Nonetheless certain applications require the security level to be enhanced. To meet this challenge a respective grid structure which is made from substantially more robust components than those included in the mesh panels can be installed adjacent each panel.

[0003] One type of grid structure which is employed includes a first plurality of parallel and spaced apart members which extend in a first direction and a second plurality of spaced apart and parallel members which extend in a second direction which is at a right angle to the first direction. The two sets of members are then welded to one another at respective points of contact and in this way a rigid assembly is fabricated. Although the end result has a significant security level the fabrication technique which is used in its manufacture calls for a substantial amount of welding. The welding is labour intensive and time consuming and, moreover, expensive.

[0004] A need exists for a grid structure which can be made in a more efficient manner. SUMMARY OF THE INVENTION

[0005] The invention provides a security grid structure comprising a first elongate channel section which includes a first base and first and second opposed side walls, wherein the first side wall is formed with a plurality of spaced apart first apertures, a second elongate channel section which is spaced from and parallel to the first elongate channel section, the second elongate channel section including a second base and third and fourth opposed side walls, wherein each of the third and fourth side walls is formed with a plurality of spaced apart second apertures and wherein the second apertures in the third side wall are in register with respective second apertures in the fourth side wall, a plurality of elongate members which are parallel to and spaced apart from one another, each elongate member respectively including a first end and an opposed second end, wherein a portion of the elongate member at the first end extends through a respective first aperture in the first side wall of the first elongate channel section, and wherein the elongate member extends through a respective pair of registering second apertures in the second channel section and a part of the elongate member is positioned between opposing surfaces of the third and fourth side walls, and at least one elongate element which is positioned between the first and second elongate channel sections and which extends transversely to, and which is secured to, the elongate members.

[0006] The security grid structure may include at least two of the elongate elements referred to. Each elongate element may take on any suitable form but conveniently is a length of flat bar.

[0007] Each elongate element may be formed with a plurality of spaced apart holes, prior to inclusion of the elongate element in the security grid. The elongate element may then be positioned so that each hole in the elongate element is in register with a respective elongate member. This technique facilitates the securing of the elongate element to each elongate member in that, conveniently, the hole provides a means whereby the elongate element can be welded, e.g. puddle-welded, to the elongate member. [0008] Each elongate member may have any appropriate cross section. In a preferred embodiment each elongate member is tubular and is square or rectangular in cross section.

[0009] To enhance the deterrent effect of each tubular member it may contain or be filled with attack-resistant material. In a preferred form of the invention each tubular member is filled with an ultrahard material. The ultrahard material may include a ceramic or similar composition. Preferably the ultrahard material is preformed, under factory conditions, into elongate, slender briquettes, each of a suitable length, which are then pushed into the interiors of the elongate members. A respective end cap may be engaged with the second end of each elongate member to ensure that the ultrahard briquettes are retained inside the elongate member.

[0010] The security grid structure may be one of a number of similar grid structures which are positioned side-by-side and which are interconnected to form a combined grid of an increased width. The combined grid may be positioned alongside a high density mesh panel in the construction of a security barrier.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention is further described by way of example with reference to the accompanying drawings in which : Figure 1 is a view in perspective of a security grid structure according to the invention,

Figures 2A, 2B, 2C and 2D show details of construction, on an enlarged scale, of parts of the grid structure of Figure 1 ,

Figure 3 is a view in elevation of the grid structure of Figure 1 ,

Figure 4 is a side view of the grid structure,

Figures 5A, 5B and 5C show on an enlarged scale details of construction of parts of the grid structure referring to Figures 3 and 4,

Figure 6 illustrates in perspective a grid structure of enlarged width,

Figures 7A, 7B and 7C respectively show on an enlarged scale constructional details of the grid structure in Figure 6,

Figure 8 is a view in elevation of a security panel which includes a security grid according to the invention,

Figures 8A and 8B show on an enlarged scale constructional details of the security panel, and Figures 9 and 10 are end and plan views respectively of the security panel. DESCRIPTION OF PREFERRED EMBODIMENT

[0012] Figures 1 , 3 and 4 are views in perspective, in elevation, and from one end, respectively, of a security grid structure 10 according to the invention. Figures 2A to 2D respectively illustrate on an enlarged scale portions of the grid structure designated in Figure 1 by the letters A to D. Figures 5A, 5B and 5C similarly illustrate on an enlarged scale constructional details of the grid structure in Figures 3 and 4, designated with the letters A, B and C respectively. [0013] The grid structure 10 includes a first upper elongate channel section 12 which has a base 14 and opposed first and second side walls 16 and 18 respectively - see Figure 5A. The side wall 16 is formed with a plurality of spaced apart first apertures 20.

[0014] A second elongate channel section 26 is spaced from and is parallel to the first channel section 12 and is located at a lower end of the grid structure 10. The channel section 26 (see Figure 5C) has a base 30 and opposed side walls 32 and 34. Registering sets of second apertures 36 and 38 are formed at spaced intervals in the side walls 32 and 34.

[0015] The grid structure 10 includes a plurality of spaced apart and parallel vertically extending elongate members 40 each of which is tubular in cross section and, preferably, of square cross section, with a first upper end 42 and a second lower end 44. The upper end 42 of each elongate member extends through a respective aperture 20 in the first side wall 16 of the upper elongate channel section 12 and preferably abuts an opposing inner surface 46 of the second side wall 18 - refer again to Figure 5A. The elongate member 40 also passes through a registering pair of apertures 36 and 38 of the lower second elongate channel section 26 - see Figures 2C and 5C.

[0016] Two lengths 50 and 52 respectively of flat bar, which are spaced apart from one another and which are parallel to each other and to the first elongate channel section 12 and the second elongate channel section 26, extend across the elongate members 40. As is shown in an insert drawing to Figure 5 each length 50, 52 of flat bar is predrilled with a plurality of holes 54 which are spaced apart from one another by the same distance as the spacing between adjacent vertical elongate members 40. Each length 50, 52 of flat bar overlies and is in contact with vertical side surfaces of the elongate members 40 and, due to the holes 54 which are centrally positioned on each elongate member, the components can easily be fixed together by means of puddle-welds 58 in each of the holes 54.

[0017] To retain the channel sections 12 and 26 in position the sections are lightly welded, e.g. tack-welded, to a number of the elongate members 40. [0018] To enhance the resistance to attack of each elongate member 40 use is made of a number of briquettes 64 (Figure 1 ) which are precast from an ultrahard ceramic, cementitious or other suitable composition and which have a square profile (cross-section) so that each briquette 64 can be inserted into an interior of a tubular elongate member 40. In order to retain the briquettes 64 in position, inside the tubular members 40, use is made of the technique shown in Figure 2D in that a respective end cap 68 is attached, e.g. welded, to the lower end of each elongate member 40 to seal the open lower end thereof.

[0019] The grid structure 10 is heavy even though it has a relatively narrow width 70. An inspection of Figures 1 and 3 shows that, on the left side of the grid structure 10, the channel sections 12 and 26 and the flat bar lengths 50 and 52 project to the left beyond the leftmost elongate member 40A and form short stubs designated 12A, 26A, 50A and 52A respectively. These stubs overlap with a similarly constructed second grid structure 74 and allow the two grid structures 10, 74 to be interconnected in the manner shown in Figure 6 which shows the structure 10 and a coplanar, similar adjacent structure 74. The adjacent stubs of the two coplanar structures overlap and are bolted or welded together. [0020] The resulting composite structure, shown in Figure 6 and designated 76, has a width calculated to fit between two adjacent fence posts (not shown). Fasteners of the kind shown in Figures 7A, 7B and 7C are provided for this purpose. These Figures correspond to the circled portions in Figure 6 which are marked with the letters A, B and C respectively. Reinforcing brackets 78A, 78B and 78C respectively are fixed to ends of the upper channel section 12, the flat bar lengths 50 and 52, and the lower channel section 26.

[0021] Figure 8 shows a barrier panel 90 in elevation. Figure 9 shows the barrier panel from one end and Figure 10 shows the barrier panel from above. The barrier panel is positioned between and secured to two adjacent and spaced fence posts 92 and 94 respectively which, at lower ends, are embedded in concrete plinths 96 and 98. The ground level is designated 100. Razor wire or electrified strands 106 extend between upper ends of the posts above the barrier panel 90. The composite grid structure 76 shown in Figure 6 is bolted to the posts 92, 94 using the respective reinforcing brackets 78A, 78B and 78C on each of the opposing sides of the grid structure. A high density mesh panel 108, positioned alongside the composite grid structure 76, has opposed vertical edges 1 10, 1 12 fixed to the posts 92 and 94 respectively. Flat bar lengths 120, spaced apart and parallel to one another, extend horizontally across the mesh panel. The flat bar lengths are fixed to the posts and are used to secure the mesh panel to the composite grid structure 76 at intervals spaced apart by a distance 126.

[0022] At an upper end, an angle iron length 130 covers an upper edge 132 of the mesh panel 108 and an adjacent upper surface of the upper channel section 12, and secures these components together.

[0023] The barrier panel 90 shown in Figure 8 has formidable security characteristics. A primary benefit of the invention, however, lies in the manner of fabricating the grid structures which are incorporated in the barrier panel. The use of the channel sections 12, 26 with the apertures which are used to locate the vertically extending elongate members 40, eliminates a substantial number of welds. The elongate members 40 cannot be lifted upwardly because they are held captive by means of the upper channel section 12. The elongate members 40 cannot be moved downwardly because they abut the ground. A lower end 134 of the composite grid structure 76 can be embedded in the ground and use can also be made of anti-burrowing mesh 136, embedded in the ground, to restrict the likelihood that an intruder can go below the barrier.

[0024] Through the use of the construction technique described the grid structure 10 is fabricated using about 14 tack-welds and 14 puddle-welds (excluding the welds for the reinforcing brackets). This is to be compared with a total of at least 112 welds which are required using a conventional construction technique as described hereinbefore.

[0025] Prior to erection the grid structure is coated completely with a liquid polymer which is then allowed to set. The polymer hardens and ensures that the grid structure is bonded together and is rattle-proof. The polymer also provides resistance to corrosion.