Artificial turf system

Abstract

An artificial turf system comprises a resilient layer, an artificial grass layer comprising a substrate and pile fibers upstanding from the substrate and an infill layer. The infill layer comprises smooth, hard granules having a mean size of between 1.8 mm and 10 mm disposed on the substrate and interspersed between the pile fibers. The smooth, hard granules provide improved characteristics in terms of foot release.

Claims

1. An artificial turf system comprising: an artificial grass layer comprising a substrate and pile fibres upstanding from the substrate; a resilient layer comprising a shock-pad structure beneath the substrate of the artificial grass layer; an infill layer, disposed on the substrate and interspersed between the pile fibres, the infill layer consisting of particles comprising smooth, hard granules having a mean size in a range A of between 2 mm and 4 mm and the infill layer further comprising infill particulates, wherein the granules have a surface hardness in a range B of greater than Shore D 45; wherein the granules are smooth with a surface for which a frictional coefficient is in a range C of less than 0.5, and wherein a range D of at least 50 vol % of the particles are smooth, hard granules falling within the defined size range; and wherein the values within the ranges A, B, C, and D are selected such that a foot release force of the artificial turf system does not exceed 3.5 KN according to a BEAST pre-load translation test.

2. The system according to claim 1, wherein at least 80 vol % of the particles are smooth, hard granules having a mean size of between 2 mm and 4 mm.

3. The system according to claim 1, wherein the granules have a surface hardness of greater than Shore D 48.

4. The system according claim 1, wherein the granules are compostable and biodegradable and comprise a material selected from the group consisting of: PEF, PHA, PLA, PBS, PCL, PBAT, and TPS.

5. An artificial turf system comprising: an artificial grass layer comprising a substrate and pile fibres upstanding from the substrate; a resilient layer comprising a shock-pad structure beneath the substrate of the artificial grass layer; an infill layer, disposed on the substrate and interspersed between the pile fibres, the infill layer consisting of particles comprising smooth, hard granules having a mean size in a range A of between 2 mm and 4 mm and the infill layer further comprising infill particulates, wherein the granules have a surface hardness in a range B of greater than Shore D 45, wherein the granules are smooth with a surface for which a frictional coefficient is C of 0.5, and wherein a range D of at least 50 vol % of the particles are smooth, hard granules falling within the defined size range; and wherein the values within the ranges A, B, and D are selected and value C is such that a foot release force of the artificial turf system does not exceed 3.5 KN according to a BEAST pre-load translation test.

6. The system according claim 1, wherein the granules are of medium to high sphericity and roundness, with sphericity greater than 0.5 and roundness values of greater than 0.5.

7. The system according to claim 1, wherein the granules exhibit an angle of repose of less than 40 degrees.

8. The system according to claim 1, wherein the infill layer has a depth of at least 20 mm.

9. The system according to claim 1, wherein the pile fibres have a length of greater than 50 mm and extend at least 10 mm above the level of the infill.

10. The system according to claim 1, further comprising one or more additional particulate layers disposed on the substrate beneath the infill layer, the additional particulate layers being selected from the group comprising: sand, grit, rubber, cork, wood, elastomer and plastic particulates.

11. An infill material for use in an artificial turf system, the infill material consisting of particles, the particles comprising hard granules having a mean size of between 2 mm and 4 mm and infill particulates, wherein the granules have a surface hardness of greater than Shore D 45 and at least 50 vol % of the particles are hard granules falling within the defined size range, and the granules are compostable and biodegradable and comprise a material selected from the group consisting of: PEF, PHA, PLA, PBS, PCL, PBAT, and TPS.

12. The infill material of claim 11, wherein at least 80 vol % of the particles are hard granules having a mean size of between 2 mm and 4 mm.

13. The infill material of claim 11, wherein the granules have a surface hardness of greater than Shore D 48.

14. The infill material of claim 11, wherein the granules have a frictional coefficient of 0.5.

15. The infill material of claim 11, wherein the granules are of medium to high sphericity and roundness, with sphericity greater than 0.5 and roundness values of greater than 0.5.

16. A method for reducing shoe entrapment forces in an artificial turf system, the method comprising: providing an infill material according to claim 11 and arranging the infill material over a depth of between 10 mm and 40 mm of the artificial turf such that a foot release force of the artificial turf does not exceed 3.5 KN according to a BEAST pre-load translation test.

17. The method according to claim 16, wherein the artificial turf system is a pitch for soccer, American football or rugby.

18. The system according to claim 1, wherein the shock-pad structure comprises bound granules of recycled plastic arranged to allow transport of water.

19. The system according to claim 18, wherein the granules of recycled plastic are bound with polyurethane binder in an amount of 14 wt. % PU binder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The features and advantages of the invention will be appreciated upon reference to the following drawings of a number of exemplary embodiments, in which:

(2) FIG. 1 shows a cross-section through an artificial turf system according to the prior art;

(3) FIG. 2 shows a cross-section through an artificial turf system according to an embodiment of the present invention; and

(4) FIG. 3 shows a schematic view of a BEAST testing apparatus.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Example 1

(5) FIG. 1 shows a cross-section through a conventional artificial turf system 1, comprising a stabilised sub base 2, a substrate 4, pile fibres 6 and an infill 8 formed of elastomeric rubber particles and a sand layer 7. The substrate 4 and pile fibres 6 were the Slidemax60 tufted grass system from Greenfields with DS XWR pile fibres 6. The sand layer 7 was 15 mm and the infill 8 had Shore A hardness 60-65 and a grain size of 0.8 mm-2.5 mm of undefined shape. The turf system 1 of Example 1 was considered to represent the most optimal state of the art artificial turf system presently available for purposes of foot breakaway and sliding performance.

Example 2

(6) FIG. 2 shows a cross-section through an artificial turf system 10 according to an embodiment of the present invention. The turf system 10, comprises a stabilised sub-base 12, a resilient layer 13, substrate 14 having pile fibres 16, a particulate layer 17 and an infill layer 18. According to the example, the resilient layer 13 was an Ecocept 40 mm layer comprising 60% rubber and 40% recycled plastic granules with a 14 wt. % PU binder. The artificial grass layer was a woven carpet MX from Greenfields with 50 mm Trimension fibre having diamond section fibres. The particulate layer 17 was 10 mm sand infill graded 0.2-1.0 mm with a coverage of 15 kg/m2. The infill layer consisted of 25 mm depth of PE granules, having a hardness of 40 Shore D, well rounded with medium sphericity, 3.8 mm average diameter and a coverage of 12.5 kg/m2.

(7) Both of the turf systems of Example 1 and Example 2 were subjected to testing according to the BEAST test protocols as defined in the Kent article.

(8) FIG. 3 shows a schematic view of the BEAST device 50 set up for the purpose of performing the translation test on a turf system 10 according to the invention. The BEAST device 50 comprises an outer frame 52 that stands freely on the turf system 10. Wheels 54 are provided for transporting. An inner frame 56 is mounted for slideable vertical movement within the outer frame 52 and carries a shaft 58 having a studded sole 60 that contacts the turf system 10. The shaft 58 is mounted in the inner frame by sliding bearings 62 for lateral movement under the control of a pneumatic actuator 64. Weights 66 may be applied to the inner frame to apply pressure to the studded sole 60. A load cell 68 measures the force and torque between the shaft 58 and the studded sole 60.

(9) The BEAST device 50 was used to carry out three tests reflecting generic classes of tasks: 1) full power translation test with 285 Kg weight and 11.4 bar pneumatic pressure; 2) half power translation test with 285 Kg weight and 5.5 bar pneumatic pressure; and 3) half power rotation test with 285 Kg weight and 4.0 bar pneumatic pressure applied to rotate the shaft 58. All three tests were performed using a molded American football shoe as the studded sole 60. The test specifications and protocol were as defined in the Kent article.

(10) Test 1Full Power Translation Test

(11) The horizontal displacement and horizontal force against time were measured for the turf systems of Example 1 and Example 2 and compared with reference to standard values for natural turf. At full power translation with a lateral force of 11.4 bar pneumatic pressure, the system of Example 2 showed a displacement of the shaft of >200 mm after around 0.1 seconds. The maximum force encountered was 3 kN and the studded sole 60 moved freely through the infill. This is considered to be a full free release, at least equal to natural turf performance. The artificial turf system 1 of Example 1 with elastomeric infill granules achieved a maximum displacement of 40 mm and exhibited peak forces of 5 kN. The studded sole 60 was still holding at this value and this may be considered as an undesirable result. In the case of Example 1, the player would experience too much force on his foot, which could lead to severe injuries.

(12) Test 2Half Power Translation Test

(13) The horizontal displacement and horizontal force against time were again measured for the turf systems of Example 1 and Example 2 and compared with reference to standard values for natural turf. At half power translation, with a lateral force of 5.5 bar pneumatic pressure, the system of Example 2 after under 0.1 seconds showed a maximum displacement of the shaft of >28 mm. The maximum force encountered was around 2.5 kN. The artificial turf system 1 of Example 1 with elastomeric infill granules achieved a maximum displacement of around 17 mm within the same time period and exhibited peak forces of between 2.5 and 3.0 kN. At half power it can be seen that both turf systems of Example 1 and Example 2 hold to a similar level of horizontal force. The test foot holds its position (In this context Hold position means that the horizontal displacement is lower than 40 mm). This is a desirable characteristic, referred to as grip. If at half power translation the foot were to be released, the grip would be too low.

(14) Test 3Half Power Rotation Test

(15) The rotational displacement and torque were measured against time for the turf systems of Examples 1 and 2 and compared to reference values for natural turf. At half power rotation, with a force of 4.0 bar pneumatic pressure applied via a pulley to rotate the shaft 58, the system of Example 2 after around 0.15 seconds showed a maximum rotation of 130 degrees. The maximum torque encountered was less than 80 N.Math.m. The artificial turf system 1 of Example 1 with elastomeric infill granules achieved a maximum displacement of just 10 degrees and exhibited peak forces of over 100 N.Math.m. These values for Example 1 at half power rotation correspond closely to those for natural turf. At half power rotation the artificial turf system 10 according to the invention of Example 2 far exceeds the best values attained both for natural turf or for the existing turf system 1 of Example 1. The test foot easily releases its position and can rotate freely. This is a desirable characteristic in reducing sports injuries. Since the values for rotation measured at half power already indicated adequate breakaway and displacement, no further rotation tests at full power were carried out for the turf system according to the invention.

(16) Further Tests

(17) In addition to the above mentioned BEAST protocol tests, additional investigation was carried out on the turf system 10 of Example 2 tested according to the FIFA** performance protocol (see FIFA Quality Concept January 2012). The results indicated the following values:

(18) Shock absorption: 68%

(19) Vertical Deformation: 9 mm

(20) Vertical Ball bounce: 75 cm

(21) Rotational friction: 30 Nm

(22) Ball roll: 6 m

(23) In addition to the disclosed example described in relation to FIG. 2, the skilled person will understand that many other configurations may be considered, which will equally fall within the scope of the present claims. In particular, according to one artificial turf system, the elastomeric infill layer may be just partly replaced by the smooth, hard infill granules as defined above. In particular, the top 10 mm of infill layer could be replaced by the smooth, hard granules.
Some typical artificial turf systems may include:

(24) TABLE-US-00001 Example 3 Example 4 Shock pad or e-layer No Yes Turf system Turfted 60-70 mm Tufted 40-60 mm Sand infill layer 5-20 mm 5-20 mm Elastomeric infill 5-20 mm 5-20 mm Smooth hard infill 10-20 mm 10-20 mm

(25) Many further modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.