A NET TECHNOLOGICAL FIELD

Embodiment of the present invention relate to a net. In particular, they relate to a net for mitigating or preventing wind lift of at least one membrane covering an outdoor aggregation of matter.

BACKGROUND

Agricultural matter, such as silage for livestock feed, chopped forage or other agricultural products may be aggregated outdoors by ensiling it in pits or stacks on the ground. It may then be compressed and covered with a membrane such as plastic sheeting.

The presence of the plastic sheeting creates an anaerobic environment to allow a lactic acid fermentation which preserves the ensiled matter. It is important for the plastic sheeting to be held in close contact with the ensiled matter during storage to maintain anaerobic conditions. In some circumstances, items such recycled tyres or bags containing sand or gravel are placed on the plastic sheeting to hold it in place.

Use of recycled tyres or bags containing sand or gravel to hold plastic sheeting in place can be inconvenient and unhygienic.

BRIEF SUMMARY

According to various, but not necessarily all, embodiments of the invention there is provided a wind lift mitigation net for mitigating or preventing wind lift of at least one membrane covering an outdoor aggregation of matter, the wind lift mitigation net comprising: a plurality of monofilaments, wherein at least some of the monofilaments each have a cross-sectional shape that comprises at least one vertex. At least some of the monofilaments may each have a cross-sectional shape comprising a plurality of vertices. At least some of the monofilaments may each have a polygonal cross-sectional shape. For example, at least some of the monofilaments each have a triangular, square, stellate or tear drop cross-sectional shape.

The plurality of monofilaments may be made from at least one plastics material. The plastics material(s) may comprise high-density polyethylene (HDPE), a HDPE/LDEP (low density polyethylene) blend, polypropylene, a polyamide and/or polyester. At least some of the monofilaments may each have a width dimension of less than 1 millimetre. Preferably, at least some of the monofilaments have a width dimension of 0.6 millimetres or less. More preferably, at least some of the monofilaments have a width dimension of 0.3 millimetres or less. At least some of the monofilaments may each have a depth dimension of less than 1 millimetre. Preferably, at least some of the monofilaments have a depth dimension of 0.5 millimetres or less. More preferably, at least some of the monofilaments have a depth dimension of 0.3 millimetres or less. The wind lift mitigation net may have an area density in the range 100g/m ² to 600g/m ² . Preferably, the wind lift mitigation net may have an area density in the range 200g/m ² to 400g/m ² . More preferably, the wind lift mitigation net may have an area density in the range 250g/m ² to 350g/m ² . The wind lift mitigation net may be a woven or knitted net comprising a plurality of woven or knitted monofilaments. The plurality of monofilaments may be warp knitted, for example, in accordance with a raschel knit pattern or a tricot knit pattern.

According to various, but not necessarily all, embodiments of the invention there is provided a wind lift mitigation net for mitigating or preventing wind lift of at least one membrane covering an outdoor aggregation of matter, the wind lift mitigation net consisting of: a plurality of monofilaments, each monofilament having a cross-sectional shape that comprises at least one vertex. According to various, but not necessarily all, embodiments of the invention there is provided a wind lift mitigation net for mitigating or preventing wind lift of at least one membrane covering an outdoor aggregation of matter, the wind lift mitigation net comprising: a plurality of monofilaments, wherein at least some of the monofilaments each have at least one substantially planar surface.

According to various, but not necessarily all, embodiments of the invention there is provided a net for mitigating or preventing wind lift of at least one membrane covering an outdoor aggregation of matter, the net comprising: a plurality of monofilaments, wherein at least some of the monofilaments each have a cross-sectional shape that comprises at least one vertex.

According to various, but not necessarily all, embodiments of the invention there is provided a net for mitigating or preventing wind lift of at least one membrane covering an outdoor aggregation of matter, the net comprising: a plurality of monofilaments, wherein at least some of the monofilaments each have at least one substantially planar surface.

According to various, but not necessarily all, embodiments of the invention there is provided a knitted wind lift mitigation net for mitigating or preventing wind lift of at least one membrane covering an outdoor aggregation of matter, the knitted wind lift mitigation net comprising: a plurality of monofilaments made from a plastics material, wherein at least some of the monofilaments each have a polygonal cross-sectional shape; and wherein the wind lift mitigation net has: a bending length of 65 - 80mm; a flexural rigidity of 2000 - 4000μ]ουΙβ3Λτι; a mean roughness depth of 1000 - 2500μηι; a mean peak width of 600 - 1000μηι; and a void volume of 840 - 1050cm ³ /m ² .

According to various, but not necessarily all, embodiments of the invention there is provided a method, comprising: covering an outdoor aggregation of matter with at least one membrane; at least partially covering the at least one membrane with a wind lift mitigation net comprising a plurality of monofilaments, wherein at least some of the monofilaments each have a cross-sectional shape that comprises at least one vertex.

According to various, but not necessarily all, embodiments of the invention there is provided a method, comprising: covering an outdoor aggregation of matter with at least one membrane; at least partially covering the at least one membrane with a wind lift mitigation net comprising a plurality of monofilaments, wherein at least some of the monofilaments each have at least one substantially planar surface. The matter may be agricultural matter, landfill items, salt, sand and/or mineral aggregates.

According to various, but not necessarily all, embodiments of the invention there is provided examples as claimed in the appended claims.

BRIEF DESCRIPTION

For a better understanding of various examples that are useful for understanding the detailed description, reference will now be made by way of example only to the accompanying drawings in which:

figure 1 illustrates monofilaments with tear drop, triangular, square and stellate cross- sections;

figure 2 illustrates a portion of a net comprising a plurality of monofilaments; and figure 3 illustrates a flow chart of a method.

DETAILED DESCRIPTION

As described above, one or more membranes may be used to cover matter, such as agricultural matter, in order to create an anaerobic environment for storage. Embodiments of the invention relate to a net that is used to partially or wholly cover the membrane(s), in order to mitigate or prevent wind lift of the membrane(s).

Figure 1 illustrates a first, second, third and fourth monofilaments/yarns 10, 20, 30, 40 with different, non-circular cross-sections. Each of the monofilaments 10, 20, 30, 40 has a cross-sectional shape comprising at least one vertex. Each of the monofilaments 10, 20, 30, 40 has at least one substantially planar surface.

Each of the monofilaments 10, 20, 30, 40 has a length dimension, a width dimension and a depth dimension. The width dimensions are denoted with a W and the depth dimensions are noted with a D in figure 1. The length dimensions are not shown in figure 1 and extend into and out of the page. In respect of each monofilament 10, 20, 30, 40, the length dimension is perpendicular to the width and depth dimensions. The width dimension is perpendicular to the depth dimension. The length dimension of the monofilament 10, 20, 30, 40 is much greater than the width and depth dimensions. The length dimension of the monofilament 10, 20, 30, 40 from which a net is formed will depend upon the size of the net to be made. It might, for example, be tens or hundreds of metres long. The width dimension might, for example, be less than 1 millimetre. Preferably, the width dimension might be 0.6 millimetres or less. More preferably, the width dimension might be 0.3 millimetres or less.

The depth dimension might, for example, be less than 1 millimetre. Preferably, the depth dimension might be 0.6 millimetres or less. More preferably, the depth dimension might be 0.3 millimetres or less.

The monofilaments 10, 20, 30, 40 might be made from at least one plastics material. The plastics material(s) might comprise high-density polyethylene (HDPE), a HDPE/LDEP (low density polyethylene) blend, polypropylene, a polyamide and/or polyester.

The first monofilament 10 has a substantially tear drop cross-sectional shape. The first monofilament 10 comprises a single vertex 1 1 at the apex of the tear drop shape and comprises two substantially planar surfaces 12, 13.

The second monofilament 20 has a substantially triangular cross-sectional shape. The second monofilament 20 comprises three vertices 21-23 and comprises three substantially planar surfaces 24-26. The triangular cross-sectional shape could be an equilateral triangle, an isosceles triangle or a scalene triangle.

The third monofilament 30 has a substantially square cross-sectional shape. The third monofilament 30 comprises four vertices 31-34 and comprises four substantially planar surfaces 35-38. The fourth monofilament 40 has a substantially stellate (star-shaped) cross-sectional shape. The fourth monofilament 40 comprises eight vertices 41-48 and comprises eight substantially planar surfaces 51-58. Each of the second, third and fourth monofilaments 20, 30, 40 has a polygonal cross- sectional shape and comprises a plurality of vertices.

In alternative embodiments, the monofilaments might have a different shape to those illustrated in figure 1 and described above. The example, they might have a rectangular cross-section or a rhombus-shaped cross-section.

Figure 2 illustrates a portion of a net 100 made from a plurality of monofilaments 10, 20, 30, 40, such as those described above. The net 100 is for mitigating or preventing wind lift of at least one membrane covering an outdoor aggregation of matter, such as agricultural matter, landfill items, salt, sand and/or mineral aggregates.

The net 100 could be a woven net comprising a plurality of woven monofilaments, or a knitted net comprising a plurality of knitted monofilaments. A knitted net might be warp knitted, for example in accordance with a raschel knit pattern or a tricot knit pattern. In the embodiment illustrated in figure 2, the net 100 has been knitted in accordance with a tricot knit pattern.

The width and length of the net 100 will depend upon the specific application. The thickness of the net 100 depends upon the width and depth of the monofilaments used to form the net 100 and how the net 100 is constructed. The net 100 might have a thickness in the range 1 millimetre to 1.5 millimetres. Preferably, the thickness of the net 100 is in the range 0.5 millimetres to 2 millimetres. More preferably, the thickness of the net is 1.2 millimetres to 1.4 millimetres. More preferably still, the thickness of the net is in the range 1.25 millimetres to 1.35 millimetres.

A flow chart of a method is illustrated in figure 3. In block 301 in figure 3, an outdoor aggregation of matter, such as agricultural matter, is covered with at least one membrane. The membrane(s) might comprise one or more plastic sheets. In block 302 in figure 3, the membrane(s) are covered with a net 100 such as that described above.

The net 100 mitigates or prevents wind lift of the membrane(s). Advantageously, this may help to maintain an anaerobic environment for the matter covered by the membrane(s).

The net 100 functions differently from tyres and bags containing sand or gravel which, as mentioned in the background section, are used in prior art methods of mitigating wind lift of a membrane. While tyres and bags containing sand or gravel merely provide weight to hold portions of the membrane down, the net 100 provides a wind diffusing layer between the wind and the membrane, equalising pressure differences and preventing the membrane from being sucked from the surface of the covered matter. Woven nets may provide suitable functionality, but knitted nets have been shown to provide better functionality than woven nets in testing. Knitted nets have a more complex three-dimensional structure which causes them to provide a more effective diffusing layer. Knitted nets are also more flexible than woven nets, enabling them to follow the contours of the membrane(s) more closely. This is also thought to improve performance, keeping the membrane(s) in close contact with the covered matter and preventing aerobic spoilage. In some embodiments, each and every monofilament in the net 100 will have substantially the same cross-section as the others. For example, the net 100 might consist of tear drop cross-section monofilaments 10, triangular cross-section monofilaments 20, square cross-section monofilaments 30 or stellate cross-section 40 monofilaments. In other embodiments, a single net 100 might include different monofilaments with different cross-sections.

The net 100 might be a knitted net, having an area density of 100g/m ² to 600g/m ² . Preferably, the area density might be in the range 200g/m ² to 400g/m ² . More preferably, the area density might be in the range 250g/m ² to 350g/m ² . Advantageously, the net 100 may be easier to transport than other items that are used to hold a membrane in place, such as tyres or bags containing sand or gravel. For example, the net 100 may be lighter.

The flexural rigidity of a knitted net 100 might be in the region of 500 to 6000

2000 to 4000ujoules/m, 2500 to 4000ujoules/m or 2900Mjoules/m to 3800ujoules/m, for example. The bending length of a knitted net 100 might be in the region of 30 millimetres to 140 millimetres, 65 to 80 millimetres, 70 to 80 millimetres or 75 to 80 millimetres. Both the flexural rigidity and the bending length are defined as per ASTM International's D1388-14e1 standard.

A test for determining the bending length and flexural rigidity according to ASTM International's D1388-14e1 standard involves sliding a specimen at a specified rate, along a surface, in a direction parallel to its length dimension until its leading edge projects over an edge of the surface. The length of the overhang is measured when the tip of the specimen is depressed under its own mass to the point where a line joining to the edge of the platform makes a 0.724 rad (41.5° angle) with the horizontal. The bending length and flexural rigidity are determined from the measured length.

The following table provides some example results that were obtained from knitted nets having an area density of 300g/m ² and comprising monofilaments 10, 20, 30, 40 having the same shapes as those illustrated in figure 1.

ou es m It will be appreciated that nets 100 of a different area density from 300g/m ² will exhibit different flexing properties from those quantified in the table.

The following table indicates results of a stability test that was performed using the nets identified in the above table. The test involved positioning each net on a plastic sheet which in turn covered a smooth convex surface. The net was then exposed to a laminar flow of wind of a speed of 10m/s and the length of time that each net remained in place was measured.

''stopped recording after 900 seconds because the net did not move.

It is thought that the diffusing effect provided by the net 100 can be determined by measuring the roughness and the void volume of the net 100.

The mean roughness depth (Rz) of a knitted net 100 might be in the range 1000 - 2500μηι. The mean roughness depth (Rz) is the arithmetic mean value of a plurality of Rzi values. Each Rzi value is the sum of the highest peal and the depth of the lowest profile relative to the mean line.

The mean peak width of a knitted net 100 might be in the range 600 to 1000μηι. The mean peak width is the distance between the peaks in the monofilament.

The void volume of a knitted net 100 might be in the range 840 to 1050 cm ³ /m ² . The void volume is the volume of the void within the structure of the net 100, per m ² . In some examples, the net 100 may be a knitted net comprising a plurality of monofilaments 10, 20, 30, 40 with a cross sectional shape such as that illustrated in figure 1. That net 100 might have some or all of the following properties:

an area density of 200g/m ² to 400g/m ² ;

- a flexural rigidity of 2000 to 4000μ]ουΙβ3Λτι;

a bending length of 65 to 80 millimetres;

mean roughness depth (Rz) in the range 1000 - 2500μηι;

a mean peak width in the range 600-1000μηι; and

a void volume of 840 to 1050 cm ³ /m ² .

The bending length of that net 100 might instead be 70 to 80 millimetres and the area density might instead be 250g/m ² to 350g/m ² .

It will be appreciated that there are other uses for net 100 described above other than the examples described above. For example, the net 100 might be used to mitigate or prevent wind lift of one or more membranes in situations that are different from that described above. For example, the net 100 might have applicability in landfill lining, landfill capping, the covering of salt piles, lagoons or ponds, and/or the covering of an aggregation of matter that is not agricultural matter.

Alternatively, the net 100 might have applicability as a windbreaker, a sunshade and/or a dust suppression layer.

Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example, some or all of the monofilaments might have a cross-sectional shape that is different from those described above and illustrated in the figures. Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon. l/we claim: