GB2429171A - Artificial turf - Google Patents

Abstract

Artificial turf comprising a backing layer 10, pile representing turf 11, infill particulates 13 and a base layer 14 comprising a sheet of elastically resilient flexible material shaped to provide voids 16, loosely packed with particulates 22. Optionally the base layer may comprise a mesh (fig.4) or plural sheets with voids that are loosely packed with particulates. Preferably the particulates are sand or particulate rubber or a mixture of sand and particulate rubber.

Description

ARTIFICIAL TURF

The present invention relates to novel artificial turf.

Artificial turf has been used to replace natural turf in many sports e.g. American football, soccer, hockey, tennis etc. Of late, the trend in artificial turf is to provide artificial turf comprising a backing sheet provided with rows of synthetic ribbons with a row spacing of at least 1cm, with blades of artificial turf at least 4 cm high and with a compliant inf ill laid on top of the backing sheet which supports the tufts of artificial turf. The infill comprising resilient rubber particles, sand or a mixture of both or separate layers of both. An example of such a product can be found in the British patent application GB232991OA.

Whilst artificial turf having surface infill has been very successful, there is a problem with such artificial turf caused by the fact that the rubber granules and/or the particles of sand become compacted over time. Thus the resilience of the pitch surface varies over time and this is detrimental to the performance of the surface in mimicking natural turf. Also the degree of compliance of the surface which can be provided is limited by the depth of the rubber particulate layer.

The sand/rubber granule-filled artificial turf surfaces are typically laid on an engineered base (e.g.concrete or Tarmacadam) . Not only does such an engineered base give a sound foundation for the artificial turf but an engineered base can be laid flat to a high degree of tolerance so that there are no problems of sloping in the surface of the artificial turf laid on top of the engineered base. Such problems would be present if the artificial turf is laid solely on a bed of particulates. For a start, it would be difficult to get the particulate layer completely flat and then the particulate layer would be subject to movement over time which could lead to dips forming in the playing surface. Not only is this undesirable for the true movement of a ball across the playing surface, but also it is undesirable because the particulate material laid as inf ill in the artificial turf would tend to migrate into any dips.

Therefore, there would be an uneven covering over the

playing field.

The present invention provides artificial turf comprising: a backing; pile secured to the backing representing turf; an inf ill layer of particulates provided on the backing sheet and supporting the pile; and a base layer supporting the backing sheet; characterised in that the base layer comprises a sheet of elastically resilient flexible material shaped to provide voids in which particulates are loosely packed.

The present invention provides artificial turf with a novel base layer interposed between the backing sheet and e.g. an engineered base. The use of a combination of a resilient flexible sheet along with particulate material in the base layer allows the artificial turf laid on the base layer to flex downwardly on the application of pressure and then flex upwardly after the removal of the application of pressure, due to the resilience of the resilient sheet.

This action reduces the compaction of the resilient particles, both in the base layer itself and also in the infill layer of the artificial turf. This is clearly desirable and it improves the long-term performance of the product. Also the base layer gives the artificial turf extra resilience not possible with the use of resilient inf ill materials alone. Furthermore, the base layer reduces the need for the artificial turf to be laid on an engineered base or at least the need for the engineered base to be laid to a high degree of precision; the particulates in the base layer will move to accommodate an uneven surface underneath and provide a levelling effect.

Further embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a crosssection through a first embodiment of artificial turf according to the present invention; Figure 2 is a perspective view of a part of a resilient sheet used in the embodiment of Figure 1; Figure 3 is a cross- section through a second embodiment of artificial turf according to the present invention; Figure 4 is a perspective view of part of a resilient sheet of the embodiment of artificial turf shown in Figure 3; Figure 5 is a cross-section through a third embodiment of artificial turf according to the present invention; Figure 6 is a cross-section through a fourth embodiment of artificial turf according to the present invention; and Figure 7 is a cross-section through a fifth embodiment of artificial turf according to the present invention; Figure 8 is a cross-section through a resilient sheet of the base layer of Figure 7; and Figure 9 is a crosssection through an alternative resilient sheet useable in any of the described embodiments.

In Figure 1 there can be seen artificial turf comprising a tufted pile carpet having a backing 10 of UV-stabilised polypropylene with polyester reinforcement, with a typical weight of 215 gr/m2. This backing is coated with carboxylated (SBR) latex and has perforation drainage holes through it of 4 mm diameter. Its water-permeability is 60 litres/min/m2. The pile is tufted onto the backing to a height of approximately 52mm and a weight of approximately 1150 gr/m2 The tufts are laid out in parallel rows and the row spacing is 1.5 cm (approx), with the tufts spaced in each row by roughly 0.8 cm. There are approximately 9,450 stitches per m2. The pile material is polyolefin and the pile is fibrillated and TJV-stabilised. Each tape used to make the pile has a width of 12mm and a thickness of 100 pm.

The inf ill on top of the backing sheet 10 comprises a layer 12 of silica sand of gradation 0.5 - 1.0 mm laid at 37 kg/rn2. On top of this there is a layer 13 of rubber particles of gradation 0.5 - 1.0 mm laid at a weight of 9 kg/m2.

The backing, pile and inf ill described above are known. However, in the prior art the backing 10 would have been laid loosely on an engineered base, e.g. a Tarmacadarn base. Instead, in the present invention a base layer 14 is provided. The base layer comprises three resilient sheets 15, 16, 17 laid one on top of the other. A plan view of part of one of the base layers 15 can be seen in Figure 2.

It can be seen from the Figure that the base layer comprises a plurality of domes, e.g. 18, 19, 20. equally spaced across the surface of the material. The sheet 15 is made of PVC of a resilient, elastic nature.

During the laying of the artificial turf a first layer is laid on an engineered base 21. During the laying, particulate material 22 (either sand or rubber granules or a mixture of both) is laid in a such a way as to partially fill each cup formed by each dome. The particulate material is not compacted tight, because this would prevent the sheet flexing at all. The loosely packed particulate material allows some flexing of the sheet 15 without the sheet totally collapsing under pressure. Once the first sheet 15 and loosely packed particulate material have been laid, then a second sheet 16, identical to sheet 15, is also laid again with loosely packed particulate material in the cups formed by the domes in the material. Once this has been laid then a third layer 17 of material identical to layers 16 and 15 is again laid, once again with particulate material loosely packed in the cups formed by the domes in the sheet. The previously described backing 10 is then laid directly on top of the top sheet 17 and the loosely packed particulate material associated therewith.

In use, the artificial turf provides a playing surface for a game such as soccer. Players will run along the surface and will expect some compliance in the surface along which they are running (the artificial turf provides the same feel as natural turf) . This compliance is provided by the rubber particulate layer 13, to some extent by the sand layer 12 and also by the base layer 14. The base layer 14 adds an extra degree of compliance not present in the prior art. The base layer 14 is important because it is resilient in a way that the rubber granules 13 are not resilient. The rubber granules 13 will each compress and will also move.

However, the rubber granules 13 will not return elastically to exactly the same configuration that they were in before contact with, e.g. a football player's boot. On the other hand, the base layer 14 is constructed so that it will elastically deform upon application of pressure e.g. by a football player's boot and will then recover to its previous dimensions once the pressure is removed. This is achieved by the resilience of the sheets 15, 16 and 17. The recovery of the base layer will cause a movement which will act to lessen compaction of the particulate material between the layers 15, 16 and 17 and will also, to some degree, cause movement of the backing 10 and thereby movement of the sand in the layer 12, again to lessen compaction of the material in the layer 12.

It should also be appreciated that the amount of compliance which can be provided by a layer of rubber granules such as the layer 13 is limited for practical reasons, e.g. by the pile height of the tufts. The use of a base layer such as base layer 14 allows an extra degree of resilience to be added to the artificial turf in total.

A second embodiment of artificial turf according to the present invention is shown in Figure 3. It comprises a backing 30 made of UV stabilised polypropylene with polyester reinforcement with a total weight of 215 g/m2.

Cut yarn is then tufted on the backing 30. The yarn 31 is a polyolefin yarn which is fibrillated and UV-stabilised. The tape used to make the pile has a width of 12mm and a thickness of 100 pm. The backing 30 is coated with carboxylated latex and is provided with 4 mm separated perforation holes to give the backing 30 a water- permeability of 60 litres/min/m2. The pile height is approximately 52 mm and the tufts are laid out in parallel rows, with the tufts in each row being separated from each other by 0.8 cm approximately and the rows being separated by 1.5 cm approximately.

On top of the primary backing 10 there is laid inf ill comprising layer 32 of silica sand with a gradation of 0.5 - 1.0 mm and on top of this a layer 33 of rubber particles of a gradation 0. 5 - 1.5 mm. The sand is laid at a rate of approximately 35 kg/rn2 and the rubber granules are laid at a weight of approximately 8 kg/rn2.

The backing 30 is provided with loops 40 much shorter than the pile, the loops 40 serving to retain in place the sand in layer 32.

The artificial turf in Figure 3 is novel in having a base layer 34 which comprises a PVC mesh 35, part of which can be seen in perspective view in Figure 4. The voids defined by the mesh, e.g. 36, are part-filled with particulate material 37, e.g. sand. The voids are not tightly packed with particulate material, but only loosely packed.

In construction of the artificial turf the mesh material 35 is laid upon an engineered base 38, e.g. a Tarmacadam surface. The voids formed by the mesh 35 are then loosely filled with particulate material and then the backing 30 is laid on top of the mesh 35.

During use the artificial turf of Figure 3 will provide a playing surface, e.g. for soccer. The artificial turf has a resilience akin to that of natural turf. The resilience provided by the compliance of the rubber particles in the layer 33 and also by the compliance of the base layer 34.

The mesh 35 in the base layer 34 is resiliently flexible.

The degree of flexing of the mesh 35 is limited by the presence of the particulate material 37, but the particulate material 37 is not tightly packed and so flexing of the mesh is permitted.

When pressure is applied to the mesh 35 by the foot of the soccer player then it will deform and when the pressure is removed after the soccer player moves on, then the mesh recovers. The recovery of the mesh 35 will cause some agitation of the particulate material 37 and also the particulate material 32 and the rubber granules 33. This lessens compaction of the different layers of particulate material.

It will be appreciated that the use of the base layer 34 gives to the artificial turf in total a resilience that could not be achieved by the use of a layer of rubber granules alone.

Figure 5 shows a third embodiment of artificial turf according to the present invention. In this embodiment there is a primary backing sheet 50 of polypropylene which is UV-stabilised with polyester reinforcement. It is coated with carboxylated latex and has perforation holes spaced at 4 mm which give it a water permeability of 60 litres/mm/rn2.

A polyolefin yarn which is fibrillated and UV-stabilised is tufted onto the primary backing 50 to a pile height of approximately 52 mm, with the tufts being arranged in parallel rows, the tufts in each row being spaced by 0.8 cm approximately and the rows of tufts being spaced by 1.5 cm approximately. Tape used to make the pile has a width of 12mm and a thickness of 100 pm.

On the backing 50 is provided inf ill comprising two layers, a layer 53 of silica-sand with a gradation of 0.5 - 1.00 mm and then on top of this a layer 54 of particulate rubber with a gradation of 0.5 - 1.5 mm. The sand is laid with a weight of approximately 35 kg/rn2 and the rubber particles are laid to a weight of approximately 8 kg/rn2.

The backing 50 is provided with loops 55 much shorter than the strands 52 which provide the artificial turf. The loops 55 serve to retain the particulate material 53 in position.

The artificial turf of Figure 5 is novel in construction in having a base layer 56 underneath the backing 50 and supporting the backing 50. The base layer 56 is laid upon an engineered base 57, e.g. a Tarmacadam surface. The base layer 56 comprises a sheet 58 of PVC material of the same undulating shape with domed features as the material 15 shown in Figure 1 and Figure 2. However, the artificial turf in Figure 5 has a base layer 56 which is provided with only a single sheet of PVC material and not a plurality of sheets. The base layer 56 comprises not only - 10 - the resilient PVC layer 58,but also particulate material 59 loosely packed in the cups formed by the domes in the material 58. The particulate material 59 is only loosely packed so that flexing of the sheet 58 is permitted, the loosely packed particulate material 59 limiting the degree of flexing.

In use of the artificial turf of Figure 5 the artificial turf will provide a playing surface, e.g. for soccer.

As with the previous embodiments, the base layer 56 provides a degree of compliance and resilience which is extra to the resilience provided by the resilient particles 54. Also, the fact that the PVC layer 58 will recover to its undeformed shape after applied pressure is removed means that there is movement and redistribution of the particulate material in the layers 53 and 59 and this lessens compaction of the particulate material.

A fourth embodiment of artificial turf according to the present invention is shown in Figure 6. In this figure there is a backing 70 on which a polyolef in UV-stabilised yarn is tufted to provide tufts such as tuft 71. The backing 70 is formed of polypropylene which is UV-stabilised and which has a polyester reinforcement. It is coated with carboxylated latex and is provided with perforation holes at 4mm spacing in order to provide the primary backing sheet 70 with a water permeability of 60 litres/min/m2.

The tufted pile 71 has a height of approximately 52 mm and the tufts are arranged in parallel rows with the tufts - 11 - in each row being separated by approximately 0.8 mm and each row being separated by approximately 1.5 mm.

On the top of the backing 70 there is provided inf ill comprising two layers, a lower layer 72 of silica-sand of gradation 0.5 - 1.00 mm and another layer 73 of rubber particles of gradation 0.5 - 1.5 mm. The silica sand is laid to a weight of approximately 70 kg/m2 and the rubber inf ill is laid to a weight of approximately 8 kg/m2.

The artificial turf of Figure 6 is novel in having a base layer 74 on which the backing 70 is laid. The base layer 74 is itself laid upon an engineered base 75, e.g with a Tarmacadam surface.

The base layer 74 comprises two mesh sheets 76 and 77 of the type previously illustrated in Figure 3, each formed from PVC. The mesh sheet 77 is laid upon the mesh sheet 76 with the sheet 77 deliberately offset from the underlying sheet 76 so that there is not a direct alignment of all of the walls of the mesh sheet 77 with those of the mesh sheet 76.

In assembly of the artificial turf of Figure 6, the mesh sheet 76 is first laid on the engineered base 75 and then the voids in the mesh sheet 76 are loosely filled with particulate material. Then the mesh sheet 77 is laid on top of the mesh sheet 76, with a deliberate offset. The voids in the mesh sheets 77 are then loosely filled with particulate material.

- 12 - In use the artificial turf of Figure 6 provides a playing surface for e.g. the playing of a soccer match.

When a player's boot applies pressure to the artificial turf then it will flex due to the flexibility of the rubber S particles 73 and also due to the additional flexibility of the base layer 74. After removal of pressure, the base layer 74 will recover its original shape due to the resilient nature of the PVC mesh sheets 76 and 77. This will have the effect of lessening compaction of the particulate material provided in the voids of the sheets 76 and 77 and also the particulate material of the layer 72.

The overall compliance and feel of the artificial turf of Figure 6 is improved by the use of the base layer 74.

A fifth embodiment of artificial turf according to the present invention is shown in Figure 7. In this figure there can be seen a backing 90 formed of polypropylene which is tJV stabilised and which has polyester reinforcement. It is coated with carboxylated latex and has 4mm spaced perforation holes. These provide the backing sheet 90 with a water permeability of 60 litres/min/m2.

The backing 90 is tufted with pile formed from polyolef in yarn which is fibrillated and UV stabilised. The tape used for the pile has a width of 5 mm and a thickness of 110 pm. The pile height is approximately 60 mm and the tufts are laid out in rows which are separated by roughly 1.5 mm with the tufts in each row being separated by roughly 0.75 mm.

The backing 90 is also provided with rows of loops 92, which serve to locate in place for the inf ill material which - 13 - is located on the backing sheet 90. The inf ill material comprises a first layer 93 of silica sand of gradation 0.5 - 1.00 mm and a second layer 103 of EPDM rubber particles of gradation 0.5 - 2.00 mm. The sand is laid to a weight of 38 kg/rn2 approximately and the rubber particles are laid to a weight of 13 kg/rn2 approximately.

The artificial turf of Figure 7 has novelty in that it has a base layer 94 which provides support for the backing 90 and on which the backing 90 is directly laid.

The base layer 94 comprises two sheets 95 and 96 of PVC material, each sheet comprising a plurality of domes, as illustrated previously in relation to Figure 1 and Figure 2.

A cross-section through one of the sheets 95 is shown in Figure 8. In this figure a line 99 represents a plane half way through the total depth of the sheet 98. The sheet will have domes e.g. 100 and 101, which are upwardly-pointing domes lying above the plane 99 and downwardly-pointing domes e.g. 101 which lie below the mid-plane 99. In Figure 1 the upwardly displaced domes of each sheet align with the upwardly displaced domes of the other sheets and similarly the downwardly displaced domes of each sheet align with the downwardly displaced domes of the other sheet. However, in the Figure 7 embodiment the upwardly pointing domes of the sheet 95 are aligned with the downwardly pointing domes of the sheet 96 so that the two sheets 95 and 96 meet where the upwardly displaced domes of the sheet 95 contact downwardly displaced domes of the sheet 96.

In the cups formed by the domes there is provided loosely packed particulate material. The artificial turf of - 14 - Figure 7 will be assembled by laying the lower sheet 95 on an engineered base 102, e.g. a Tarmacadam surface, at the same time infill the cups of the sheet 96 with loosely packed particulate material. Then the sheet 96 is laid on top of the sheet 95, with the downwardly displaced domes of the sheet 96 contacting the upwardly displaced domes of the sheet 95. Again, loosely packed particulate material is provided in the cups of the sheet 96 during the time of laying. The primary backing sheet 90 is then laid on top of the base layer 94.

The base layer 94 will provide to the artificial turf of Figure 7 resilience in addition to the resilience provided by the rubber (EPDM) particles of the layer 103.

The recovery of the sheets 95, 96 to their original shapes after removal of pressure causes movement of the particulates in the base layer 94 and, to some degree, the particulates in the layer 92; this lessens compaction of the particulates.

Figure 9 shows a variant of domed PVC sheet which could be used in the base layers previously described in place of the sheets previously described. The sheet 120 which is illustrated has a planar base layer 121 from which a plurality of domes e.g. 122 extend all in the same direction. When a plurality of sheets are used in a base layer the domes of the sheets can all point in the same direction (e.g. all upwardly) or in opposite directions, i.e. one sheet with domes pointing upwardly and the other with domes pointing downwardly. The domes of the different sheets can be aligned or unaligned.

- 15 - The base layers 14,56,74,94 will typically have a depth in the range of 5 to 10 mm. The lowest PVC sheet (or only PVC sheet) in each base layer can be adhered to the underlying base. Whilst it is preferable to lay the base layer on an engineered base, it is also possible to lay it on a dynamic base (e.g. of crushed stone) . The use of particulate material in the base layers facilitates laying of the turf on a dynamic base since the particulates can move to provide a levelling effect.

Whilst above the particulates in the base layers and in the inf ill have been described as sand, rubber or a mixture of both, one of other particulates is possible.

The PVC layers 15,16,17, 58, 95, 96 could be perforated to allow better drainage through base layers 14, 56, 94.

Alternatively or additionally a drainage pipe or pipes could be provided to extend through the base layers to drain them.

It is possible that the sheet of elastically resilient material could be secured to the backing prior to laying and this would require the sheet to have the form illustrated in Figures 4 and 6 so that the sheet could be laid on a particulate material which would move into the apertures in the sheet. The sheet, backing layer and pile would be supplied in a roll and unrolled on site.

The embodiments of Figures 6 and 7 could be varied by horizontally offsetting the sheets of the base layer relative to each other or turning them in a horizontal plane relative to each other.

- 16 - The embodiments of Figures 6 and 7 could be laid with a method comprising the additional step of adhering each sheet in the backing layer to the other sheets which it touches.

This would prevent the sheets in the backing layers moving horizontally relative to each other (which could otherwise result in the compacting of the particulate material therebetween) . A multi-sheet base layer could be manufactured offsite and delivered in a roll to the site of installation.

The use of hydrophobic granules (or granules coated with a hydrophobic coating) may be preferred to prevent the particulate material coalescing when wet.

Claims (20)

- 17 - CLAI MS

1. Artificial turf comprising:- a backing; pile secured to the backing representing turf; an inf ill layer of particulates provided on the backing sheet and supporting the pile; and a base layer supporting the backing sheet; characterised in that: the base layer comprises a sheet of elastically resilient flexible material shaped to provide voids in which particulates are loosely packed.

2. Artificial turf as claimed in claim 1 wherein the sheet of elastically resilient flexible material is configured with domed features spread across the sheet, the domed features providing cups into which the particulates of the base layer are loosely packed.

3. Artificial turf as claimed in claim 1 wherein the base layer comprises a plurality of elastically resilient flexible sheets each configured with domed features spread across the sheet, the domed features providing cups into which the particulates of the base layer are loosely packed.

4. Artificial turf as claimed in claim 3 wherein each sheet has upwardly directed domes extending upwardly from a midplane of the sheet and downwardly directed domes extending downwardly from the midplane of the sheet.

5. Artificial turf as claimed in claim 4 wherein the sheets in the base layer are aligned so that each upwardly - 18 - pointing dome of each sheet is aligned with an upwardly pointing dome of the other sheet(s) and each downwardly pointing dome of each sheet is aligned with a downwardly pointing dome of the other sheet(s).

6. Artificial turf as claimed in claim 4 wherein the sheets in the base layer are aligned so that the upwardly pointing domes of one sheet are aligned with downwardly pointing domes of another sheet.

7. Artificial turf as claimed in claim 3 wherein each sheet comprises a generally planar base layer and domes extending away from the planar base layer.

8. Artificial turf as claimed in claim 7 wherein the sheets are arranged so that the domes of each sheet extend upwardly from the planar base layer of the sheet.

9. Artificial turf as claimed in claim 7 wherein the sheets re arranges so that the domes of each sheet extend downwardly from the planar base layer of the sheet.

10. Artificial turf as claimed in claim 8 or claim 9 wherein the sheets are arranged so that the domes of each sheet are each aligned with the domes of the other sheets(s)

11. Artificial turf as claimed in claim 7 wherein the sheets are arranged so that domes of one sheet extend downwardly from the planar base layer of the sheet and the domes of another sheet extend upwardly from the planar base layer of the sheet.

- 19 -

12. Artificial turf as claimed in claim 11 wherein the upwardly extending domes of one sheet align with the downwardly extending domes of the other sheet.

13. Artificial turf as claimed in claim 1 wherein the flexible resilient sheet is a mesh sheet and the voids are provided by apertures in the mesh and the particulate material is loosely filled in the apertures.

14. Artificial turf as claimed in claim 1 wherein the base layer comprises a plurality of flexible resilient mesh sheets and the voids are provided by apertures in the mesh sheets and the particulate material is loosely filled in the apertures.

15. Artificial turf as claimed in claim 13 wherein one of the flexible resilient mesh sheets is laid over another flexible resilient mesh sheet with the upper mesh sheet offset from the lower mesh sheet so that there is not an exact alignment of the strands of the two mesh sheets.

16. Artificial turf as claimed in any one of the preceding claims wherein the particulate material of the base layer comprises sand.

17. Artificial turf as claimed in any one of claims 1 to 15 wherein the particulate material of the base layer comprises particulate rubber.

- 20 -

18. Artificial turf as claimed in any one of claims 1 to 15 wherein the particulate material of the base layer comprises a mixture of sand and particulate rubber.

19. Artificial turf as claimed in any one of the preceding claims comprising on top of the backing layer: a layer of sand; and a layer of particulate rubber on top of the layer of sand.

20. Artificial turf substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

580546, AWP,23.9.04