The present invention relates to improvements in or relating to support mats or panels, especially mats or panels for supporting vehicles and other heavy apparatus, particularly on soft or unstable ground.

Support mats, also referred to as panels, are commonly used for supporting equipment at constructions sites and other locations where the surface is soft, unstable or uneven. A plurality of mats are typically interconnected to cover a large area or to provide a roadway. Such mats are typically moulded from high density plastics materials, such as HDPE. To reduce the mass of the mats, typically they are assembled from two moulded half-shells which are secured together and in which each half-shell is formed with a plurality of cells such that walls of cells in one half-shell align with walls of cells in the other half-shell to form a rigid structure. US 6 511 257 discloses one such mat, in which two rectangular panels are overlaid offset to two adjacent sides to form an upper continuous peripheral extension along two adjacent edges and a lower continuous peripheral extension along the other two adjacent edges. Adjacent mats are then laid with the peripheral extensions overlapping and secured together by fastening devices in the form of pegs.

However, the mats are prone to damage due to the high mass of the vehicles travelling over them or the mass of equipment placed on the mat, or the way in which the vehicles are used. The damage can result in puncture of one of the surfaces of the mat. This can lead to ingress of water and, in some environments, potentially toxic liquids or other materials. The cellular nature of the mat then acts to retain the liquid within the cell, rather than allowing the liquid to drain away. This increases the mass of the mat, making moving of the mat problematic. Additionally, because the liquid cannot drain away this gives rise to health concerns due to residence of noxious liquids within the mat. Even if the liquid is water, such as rainwater or groundwater, it can become a habitat for organisms. As mats of these types are generally intended for temporary use, the issue of transportability of the mat from one location to another is an important consideration.

The present invention seeks to provide a solution to this problem.

Accordingly, in its broadest sense, the present invention provides a support mat comprising upper and lower substantially planar elements providing upper and lower surfaces to the mat, the elements being in a spaced apart relationship having a layer comprising a plurality of cells between the upper and lower planar surfaces. The mat is characterised in having at least one barrier layer between the upper and lower planar elements.

In one embodiment, the barrier layer comprises a film layer.

Preferably, the film layer includes a plurality of closed pockets, each pocket shaped and dimensioned to correspond with the cells of the mat.

In certain embodiments, the closed pockets are each filled with a gas, suitably air.

In an alternative embodiment, the barrier layer comprises a foamed or expanded polymeric material.

Preferably, each cell is filled with the foamed or expanded polymeric material.

In preferred embodiments, the barrier layer comprises a film layer and a foamed or expanded polymeric material. Preferably, the foamed or expanded polymeric material fills each cell.

Preferably, the foamed or expanded polymeric material is a polypropylene, polyethylene, polyurethane or polystyrene polymer.

The above and other aspects of the present invention will now be described in further detail, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of an embodiment of a mat in accordance with the present invention;

Figure 2 is an exploded perspective view of the mat of Figure 1;

Figure 3 is a part perspective view of elements of a second embodiment of a mat in accordance with the present invention;

Figure 4 is a part cross-sectional view of the mat of Figure 3, shown during assembly;

Figure 5 is a part cross-sectional view of the assembled mat of Figure 3;

Figure 6 is a part perspective view showing elements of a third embodiment of a mat in accordance with the present invention;

Figure 7 is a part cross-sectional view of the mat of Figure 6;

Figure 8 is a part perspective view of a fourth embodiment of a mat in accordance with the present invention; and Figure 9 is a part cross-sectional view of the mat of Figure 8.

Referring to Figures 1 and 2, there is shown a mat 10 having a central portion 11 and projecting peripheral overlaps or flanges in upper 12 and lower 13 pairs to allow coupling of a plurality of adjacent mats.

As shown in Figure 2, mat 10 is formed of upper and lower substantially planar mat elements 14, 15. The mat elements 14,15 are secured together by means of screws or bolts (not shown). In alternative constructions, the two elements are held together by adhesive or welding. Lower mat element 15 is formed with a plurality of cells 20 arranged in an array. Each cell is defined by walls 21 extending upwardly from the base of the element 15. Walls 21 extend upwardly to contact the under-surface of the upper mat element such that forces applied to the upper surface of the mat are transferred through the mat to the supporting ground. In the embodiment shown, each cell is rectangular. Other shapes are equally suitable. Hexagonal cells are particularly preferred. Such a mat construction is generally well known in the art.

Each cell is filled with a foamed or expanded polymeric block 22. In accordance with preferred embodiments of the invention, the foam is a closed-cell foam, to prevent flow of material through the foam. Accordingly, in the event of a puncture to the upper surface of mat 10, flow of water or other material into the mat is prevented. The closed-cell foam acts as a seal against the punctured surface.

Suitable foams or expanded polymers include polyurethane, polyethylene, polypropylene and polystyrene. An alternative solution is illustrated in Figures 3 to 5. In this embodiment, upper and lower mat elements 30, 31 are formed as identical mouldings, such that each cell is formed in two cell halves, one half from the upper mat element and one half from the lower mat element. Prevention of material ingress and flow into the mat is achieved in this embodiment by means of a 'bubble wrap'-type sheet 32. Sheet 32 comprises a generally planar film 33 having a plurality of gas-filled pockets 34 projecting from one face thereof. The gas is suitably air, but inert gases may be used.

Each pocket 34 is shaped and dimensioned to correspond with the shape of the cells of the mat such that each pocket 34 of sheet 32 fits into a corresponding cell of the mat element. As is apparent from Figures 4 and 5, both mat elements 30,31 are provided with bubble-wrap type sheets 32, thereby providing a sealing function irrespective of the orientation of the mat.

Figures 6 and 7 show a modification to this embodiment in which each pocket 34 is filled with a polymeric foamed or expanded material 35, suitably polyurethane, polyethylene or polypropylene or expanded polystyrene. This embodiment provides additional strength to the mat between the upper and lower faces, compared with the gas-filled pockets of the embodiment of Figures 3 to 5.

A third embodiment is illustrated in Figure 8 and 9. Each cell 42 of each of the upper and lower mat elements 40,41 is individually filled with a polymeric foamed material or expanded polymeric material 43. A film 44 is applied over the cells. Film 44 is suitably a high density polyethylene film or may be any other suitably resilient film.

Films 33 and 44 act to provide a barrier against ingress of material into the cells of the mat in the event of a surface of the mat being punctured. In the event of a puncture penetrating through the film, the additional foamed polymeric material of the embodiments of Figures 6 to 9 acts as a further barrier to ingress of material.