EP1428935A2

EP1428935A2 - Improvements relating to the construction of playing surfaces

Info

Publication number: EP1428935A2
Application number: EP03257849A
Authority: EP
Inventors: David Dury
Original assignee: Nottinghamshire Sports and Safety Systems Ltd
Current assignee: Nottinghamshire Sports and Safety Systems Ltd
Priority date: 2002-12-14
Filing date: 2003-12-13
Publication date: 2004-06-16
Also published as: GB2396117A; GB2396117B; GB0229181D0; EP1428935A3

Abstract

A playing surface for sports or other recreational activities which comprises a water permeable textile envelope (8) containing a layer of mineral particle (9), an upper layer of the textile envelope (8) bearing a resin bound, adherent, subjacent layer of discrete rubber particles (7). A method of preparing a playing surface is also disclosed. <??>To be accompanied, when published, by Figure 2 of the drawings. <IMAGE>

Description

This invention relates to the construction of playing surfaces, in particular games playing surfaces, and the invention has particular, but not exclusive, reference to surfaces for playing outdoor games and sports or other recreational activities, and for children's playgrounds.

It is known to construct artificial sports surfaces over a layer of sand or stone by applying a geotextile and a top layer of artificial turf to simulate natural performance characteristics. The use of particulate materials other than natural aggregates or combinations of both has also been proposed.

Sand as a particulate infill, whilst being very 'natural' has some unpredictability due to moisture or compaction, along with variations in grading of different sands. This variability has proven satisfactory, with careful selection of the sand, for general multi-purpose use, though it is not predictable enough for better quality sports grounds such as for hockey at higher levels.

Stone is more predictable in relation to moisture, but still unpredictable in its potential hardness due to variations in the level of compaction obtained.

Hockey and football playing surfaces require to be shock absorbing to some extent in order to reduce the risk of injuries, and they are tested to be shock absorbing to different degrees. Sand and stone, of initially selected gradings are inherently shock absorbing but with limitations; this property improves when displacement of the particles occurs, but this is not always a satisfactory outcome as the level of the area may be disturbed, and it is known to provide a shock pad layer.

Most conventional shock pad layers have a degree of elasticity. We produce a shock pad layer by introducing loose rubber granules into a fibre shock pad, inside an envelope. This is very effective, but it is costly to construct, as it is done by hand and is labour intensive.

More rubber and larger particles could be used within the envelope rather than in a fibre shock pad. Problems with larger loose rubber crumb are that if it is disturbed, it does not self-level the in same way as sand or finer crumb. The use of finer rubber in greater depths for greater level stability, can result in too much elasticity so that the surface becomes less stable to play on. This can increase the chance of ankles turning over and other twisting injuries.

Further problems arise when screeding a thin layer of rubber particles for forming the playing surface unless they are stabilised by a fibre shock pad. The application of such particles is disturbed by any adverse weather conditions during the laying: even a light breeze makes it difficult to lay an even layer of rubber particles, and the layer could easily be further disturbed by the positioning of any overlying layer such as a layer of artificial turf without the most careful working procedures. Yet further problems arise where the desired size of the rubber particles is not large in relation to interstices between mineral particles of the desired size.

In order to decrease the cost of incorporating a layer of rubber over the sand or stone layer, it would be possible for this rubber layer to be applied by rolling out a rubber mat or applying a layer of rubber tiles. Unfortunately however, the use of such rubber tiles and mats can entail certain disadvantages for use in outdoor playing areas in that the tiles or mats tend to be either rather impervious to water if made thick enough to withstand handling without damage, in which case the playing area may become waterlogged especially after heavy rain, or the tiles or mats can swell due to the absorption of rainwater and this tends to disturb the evenness of the playing surface. Problems also arise in laying such rolls or tiles in such a manner as to achieve consistent joints between successive elements.

It is a principal object of the present invention to avoid or at least reduce the disadvantages referred to.

According to the present invention there is provided a playing surface for sports or other recreational activities which comprises a water permeable textile envelope containing a layer of mineral particles, an upper layer of the textile envelope bearing a resin bound, adherent, subjacent layer of discrete rubber particles.

The invention affords a number of advantages. It is very simple to unroll a rolled textile web and thereby rapidly cover even rather extensive playing areas, for example for forming football or hockey pitches. The invention accordingly affords considerable advantages in reducing the amount of time required to lay a playing surface incorporating a layer of rubber particles adhered to a textile web. Also, the requirement for lengthy employment of highly skilled labour on site when laying the playing surface is reduced. The layer of rubber particles may be applied to the textile web under factory conditions, and accordingly a much greater degree of precision and reproducibility can be obtained than would be possible by applying the rubber particles to form the layer under field conditions. We have also found that it is simpler to form consistent joints between successive textile webs than it is between successive areas of rubber mat.

The invention includes a method of preparing a playing surface for sports or other recreational activities which comprises laying a first water permeable textile layer to ground, applying thereto a layer of mineral particles, and applying an upper water permeable textile layer bearing a resin bound, adherent, subjacent layer of discrete rubber particles over the mineral layer to form, with the first textile layer, an envelope containing the mineral particles.

We have found that when adopting the present invention, variations in the nature of the underlying surface, for example the layer of mineral particles referred to, have significantly less effect on the playing characteristics of the surface than would otherwise be the case. This can allow greater freedom in the choice of mineral particulate, and can render the surface appropriate for the playing of a wider variety of sports at high or higher levels of playing skill.

The use of a water-permeable envelope is confers particularly important advantages. In addition to the advantage of allowing ready drainage of the playing surface, the adoption of this feature has the further advantage of allowing reconditioning of the playing surface. If the layer of mineral particles, particularly sand or finer particles, is drenched so that it is effectively put into suspension, it may be allowed to drain and rolled, to impart desired playing characteristics.

Preferred embodiments of the invention incorporate optional features which are defined in subordinate claims forming part of this specification.

Preferred embodiments of the invention will now be described by way of example and with reference to the accompanying diagrammatic drawings in which:

Figure 1 is a diagrammatic illustration of an apparatus for forming a resin-bound particulate rubber layer on a textile web;

Figures 2 and 3 are diagrammatic cross sectional views of two embodiments of playing surface in accordance with the invention.

In Figure 1 a textile web 1 is carried by a conveyor 2 beneath an applicator 3 where a fluid layer 4 of rubber particles in a resin binder is applied. The web passes beneath a doctor blade 5 where this fluid layer is levelled and its thickness regulated, and thence beneath an appropriate curing device 6 where the fluid layer is cured to become an adherent resin bound rubber of rubber particles 7.

In Figure 2, an undersheet 8 of a suitable geotextile material is laid down over a prepared area of ground. A layer 9 of sand or other fine particulate mineral is screeded over the undersheet 8, and a textile web 1 bearing an adherent layer 7 of rubber particles is applied to the layer of sand 9 with the rubber layer 7 facing downwards to form an envelope. The undersheet 8 and the textile web 1 may be bonded together at their margins 10. A layer 11 of artificial sports surface such as an artificial turf is then applied.

In the embodiment shown in Figure 3, the layer of sand 9 is replaced by a layer of angular stone 12, and a protective layer 13 of a suitable geotextile material is incorporated into the envelope between the layer of stones 12 and the rubber-containing layer 7.

If the mineral particles are fine, as in Figure 2, so that interstices between them are small in relation to the rubber particles adhered to the upper textile layer 1, then, if the rubber-containing layer should break down during the course of time it is found that the rubber particles tend to remain as a stable layer between that textile web and the mineral layer. The purpose of the protective layer 13 is firstly to delay and breakdown of the rubber containing layer 7, and secondly, to ensure that any rubber particles which become separated remain in a shock-absorbing layer rather than falling through interstices between the stones.

The textile web used for preparing any of the textile layers of the envelope is suitably a non-woven, needle-punched synthetic fibre mat, for example of polyester, polypropylene or polyamide material. A resin binder for any of the textile webs may be chosen to confer appropriate properties, such as a desired stiffness, on the web.

Specific examples of embodiments of the invention have properties given in the following Table 1.

Example	1	2	3	4
Upper textile layer thickness	1-2mm 200-350g/mm²
Rubber particle density (kg/m²)	1.5-2.3	2.0-3.0	0.5-3.0	0.5-1.2
Rubber layer thickness (mm)	4-6	4-8	1-8	1-3
Mineral	Stone	Sand or stone	Sand or Stone stone
Mineral layer thickness (mm)	50-75	50-100	50-100	50-75
Bottom textile layer thickness	1-3mm
Lower textile layer weight (g/m²)	225-300	207-300	207-300	225-300
Protective layer thickness (mm) (if present)	1-2	1-3	1-4	1-4
Protective layer weight (g/m²) (if present)	270-300	270-350	270-400	270-400
Intended use	hockey	Football	Multi-sport	tennis
Construction	Figure 3	Figure 2 or	Figure 2 or	Figure 3

Compositions of particular examples of mineral beds (parts by weight of particles of particular nominal size ranges) for various stone or sand mixtures are shown in the following Table 2.

Claims

A playing surface for sports or other recreational activities which comprises a water permeable textile envelope containing a layer of mineral particles, an upper layer of the textile envelope bearing a resin bound, adherent, subjacent layer of discrete rubber particles.
A playing surface according to claim 1 which is overlain by a layer of artificial turf.
A playing surface according to claim 1 or 2, wherein a water-permeable protective interlayer is provided between the rubber-containing layer and the layer of mineral particles.
A playing surface according to any preceding claim, wherein said mineral particles substantially all have grain sizes below 10mm.
A playing surface according to claim 4 wherein said mineral particles are selected from one or more of:

coarse angular stone (nominal grain sizes between 10mm and 5mm)

fine angular stone (nominal grain sizes between 5mm and 2mm)

very coarse sand (nominal grain sizes between 2mm and 1mm)

coarse sand (nominal grain sizes between 1mm and 0.5mm)

medium sand (nominal grain sizes between 0.5mm and 0.25mm)

fine sand (nominal grain sizes between 0.25mm and 0.125mm)

very fine sand (nominal grain sizes between 0.125mm and 0.050mm)

coarse silt (nominal grain sizes between 0.050mm and 0.020mm)

fine silt (nominal grain sizes between 0.020mm and 0.002mm)

clay (nominal grain sizes below 0.002mm).
A playing surface according to claim 5, wherein said layer of mineral particles substantially consists of at least two of: coarse angular stone, fine angular stone, very coarse sand, coarse sand, medium sand, fine sand, coarse silt, fine silt, clay.
A playing surface according to any preceding claim, wherein at least one textile layer is formed as a resin bonded non-woven mat of synthetic fibre.
A playing surface according to any preceding claim, wherein at least one textile layer is formed from a substantially non-degradable polymeric fibre such as polyester, polypropylene or polyamide.
A playing surface according to any preceding claim, wherein said envelope has at least one textile layer having a fibre density of between 150 and 500 g/m².
A playing surface according to claim 9, wherein said envelope has an upper textile layer having a fibre density of between 150 and 400 g/m².
A playing surface according to claim 9 or 10, wherein said envelope has a lower textile layer having a fibre density of between 150 and 350 g/m².
A playing surface according to any of claims 9 to 11 as dependent on claim 3, wherein said protective layer has a fibre density of between 250 and 400 g/m².
A playing surface according to any preceding claim, wherein the layer of mineral particles has a thickness between 40 and 150mm.
A playing surface according to any preceding claim, wherein the layer of rubber particles has a thickness between 1 and 15mm.
A playing surface according to any preceding claim, wherein the rubber particles in said layer have a density of between 0.4 and 4.0 kg/m².
A method of preparing a playing surface for sports or other recreational activities which comprises laying a first water permeable textile layer to ground, applying thereto a layer of mineral particles, and applying an upper water permeable textile layer bearing a resin bound, adherent, subjacent layer of discrete rubber particles over the mineral layer to form, with the first textile layer, an envelope containing the mineral particles.
A method of preparing a playing surface according to claim 16 wherein a layer of artificial turf is laid over the upper textile layer of said envelope.
A method of preparing a playing surface according to claim 16 or 17, wherein a water-permeable protective interlayer is provided between the rubber-containing layer and the layer of mineral particles.
A method of preparing a playing surface according to any of claims 16 to 18, wherein said mineral particles substantially all have grain sizes below 10mm.
A method of preparing a playing surface according to claim 19 wherein said mineral particles are selected from one or more of:

coarse angular stone (nominal grain sizes between 10mm and 5mm)

fine angular stone (nominal grain sizes between 5mm and 2mm) very coarse sand (nominal grain sizes between 2mm and 1mm)

coarse sand (nominal grain sizes between 1mm and 0.5mm)

medium sand (nominal grain sizes between 0.5mm and 0.25mm)

fine sand (nominal grain sizes between 0.25mm and 0.125mm)

very fine sand (nominal grain sizes between 0.125mm and 0.050mm)

coarse silt (nominal grain sizes between 0.050mm and 0.020mm)

fine silt (nominal grain sizes between 0.020mm and 0.002mm)

clay (nominal grain sizes below 0.002mm).
A method of preparing a playing surface according to claim 20, wherein said layer of mineral particles is formed using at least two of: coarse angular stone, fine angular stone, very coarse sand, coarse sand, medium sand, fine sand, coarse silt, fine silt, clay.
A method of preparing a playing surface according to any of claims 16 to 22, wherein at least one textile layer is formed as a resin bonded non-woven mat of synthetic fibre.
A method of preparing a playing surface according to any of claims 16 to 22, wherein at least one textile layer is formed from a substantially non-degradable polymeric fibre such as polyester, polypropylene or polyamide.
A method of preparing a playing surface according to any preceding claim, wherein said envelope has at least one textile layer having a fibre density of between 150 and 500 g/m².
A method of preparing a playing surface according to claim 24, wherein said envelope has an upper textile layer having a fibre density of between 150 and 400 g/m².
A method of preparing a playing surface according to claim 24 or 25, wherein said envelope has a lower textile layer having a fibre density of between 150 and 350 g/m².
A method of preparing a playing surface according to any of claims 24 to 26 as dependent on claim its, wherein said protective layer has a fibre density of between 250 and 400 g/m².
A method of preparing a playing surface according to any of claims 16 to 27, wherein the layer of mineral particles is applied to a thickness between 40 and 150mm.
A method of preparing a playing surface according to any of claims 16 to 28, wherein the layer of rubber particles is formed with a thickness between 1 and 15mm.
A method of preparing a playing surface according to any of claims 16 to 29, wherein the rubber particles in said layer are applied to a density of between 0.4 and 4.0 kg/m².