AU628300B2 - Synthetic surface playing field - Google Patents

Description

SSIXTY DOLLARS 62830 COMMONWEALTH OF AUSTRALIA FORM PATENTS ACT 1952 COMPLETE SPECIFICATION FOR OFFICE USE: Class Int.Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: *:*..*Priority: .:..'Related Art: *0 S Name of Applicant: KINGSFORD ROSS HEYLEN '**:Address of Applicant: 16 Armson Avenue, Magill, South Australia 5072, Australia **Actual Inventor: Kingsford Ross Heylen 0 0.0..

Address for Service: SHELSTON WATERS, 55 Clarence Street, Sydney Complete Specification for the Invention entitled: "SYNTHETIC SURFACE PLAYING FIELD" The following statement is a full description of this invention, including the best method of performing it known to me:- -1- Complete of PI 5261 dated 5th November, 1987 S003~3 6 03/11/88 0 SHELSTON WATERS PATENT ATTORNEYS CLARENCE STREET. SYDNEY UJU 1_ I This invention relates to a surface on which sports may be played and more particularly to a sports playing surface having a synthetic turf.

In recent years synthetic artificial turf playing surfaces have been used in the construction of tennis courts, playing fields of the kind used for hockey and football, bowling greens and other like playing surfaces.

Artificial turf is typically a carpet-like construction in which fibres, for example of **i0 polypropylene, are tufted or woven to a backing which is o coated with a rubber or polymer latex.

One such artificial turf is sold in Australia under the brand name "SUPERIOR GRASS" and another is sold under the brand name "SUPER GRASSE".

oHitherto it has been recommended that suchlike artificial turf be laid on a road base, or bituminous or concrete base and sand is applied over the artificial turf backing.

Playing surfaces of this construction provide a high So performance surface with reduced maintenance requirement in comparison with traditional natural surfaces. However, the risk of physical injury to players using these surfaces is greater than when playing on traditional natural lawn surfaces.

For example, Nigg et al ("Sports shoes and playing surfaces", Human Kinetics Publishing Inc.) conducted a survey of Tennis players and found that the incidence of pain relating to back, knee and ankle reported by players 2 L varied according to playing surface. Playing surfaces on which injuries were reported were ranked according to percent incidence of injuries as follows:i. Synthetic grillage (greatest incidence of reported pain).

2. Felt carpet on hard base.

3. Concrete or bituminous concrete.

4. Synthetic grass on concrete or bituminous concrete.

Synthetic grass on sand.

6. Natural grass.

7. Sand-Clay (least incidence of reported pain).

In some sports the response of a playing ball or the like on rebound from an artificial turf surface differs significantly from that of natural lawns.

A further problem with synthetic turf constructions is of drainage. It is usually necessary to incline the o playing surface towards a sump drain and the time required for water to drain from the surface is often eeexcessive.

An object of the present invention is to provide a playing surface which is less likely to injure players than artificial playing fields presently in use and which avoids or at least ameliorates some of the above disadvantages of known synthetic turf playing areas while retaining the advantages of synthetic turf.

According to one aspect the present invention consists in a playing surface comprising artificial turf laid over a layer of particulate matter of at least 100mm 0 3

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compacted thickness, the layer being selected to have a Clegg Impact Hammer deceleration of between 100 and 200g. In preferred embodiments the particulate layer is clinker having a particle size distribution including particles of up to about 20mm in dimension.

Surprisingly, it has been found that playing fields constructed in accordance with the invention resemble the energy absorption characteristics of natural surfaces having a lower risk of energy than many presently used .0 surfaces while providing improved drainage and durability 0 0 o• in comparison with natural surfaces.

According to a second aspect the invention consists in a method for construction of a playing field comprising the steps of: preparing a site; spreading a selected particulate matter as a layer over the site to a depth of at least 0 100mm; compacting the particulate matter until a Clegg £0 Impact deceleration of between 100g and 200g is achieved on a layer having a compacted thickness of at least 100mm, and laying an artificial turf over the particulate layer.

The invention will now be more particularly described with reference to examples.

By way of example, a playing field according to the invention may be constructed as follows:- 4

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A playing field site is first prepared by removal of all topsoil, and other unsuitable material, the surface is graded to an appropriate profile for surface drainage. The surface is then treated to prevent regrowth of vegetation, and the upper 150mm of soil is compacted to a minimum dry density ratio of 95% based on standard compaction (AS 1289 Test El.l).

Surface and subsoil drainage and any special measures required to control moisture content of the o.l0 subsoils is then installed.

A layer of selected particulate matter is next spread upon the site and compacted to a compacted depth of at least 100mm and preferably in excess of 150mm. The particulate matter is selected so that the compacted bed or layer, having a depth in excess of 100mm, will have a Clegg Impact Hammer deceleration of between 100g and 200g.

A highly preferred particulate matter for use in the layer is clinker. The clinker should be a hard, durable furnace ash or similar material and is processed to 20 remove all soft or friable materials. It is strongly preferred that the clinker is screened to produce particulate material within the following particle size distribution.

Maximum particle size Passing 9.5mm sieve 70 100% Passing 4.75mm sieve 40 Passing 0.425mm sieve 2 Passing 0.075mm sieve <3% 5 L A sample of 100 150mm depth when compacted at "Standard" energy and optimum moisture content (as defined in Standard Compaction Test AS 1289 SE 1.1) must be between 100 and 200g when tested by the Clegg Impact Hammer Deceleration test. Such material is hereafter referred to as "approved processed clinker".

The invention will hereinafter be described primarily with reference to playing fields in which approved processed clinker is a substrate but it will be .10 understood that other materials, for example SCORIA, can go be used provided that a Clegg deceleration within the range of 100g to 200g in a compacted bed thickness in excess of 100mm can be obtained therefrom.

After site preparation, the approved processed clinker is spread on the prepared site and compacted to a minimum dry density ratio of 98% based on "standard" compaction (AS 1289 test El.l), so that a minimum compacted thickness of 100mm and preferably at least 150mm is achieved.

1 !0 Surface gradients should be no flatter than 1% to facilitate surface runoff. Surface irregularities should be no greater than 5mm under a 3 meter straight edge.

Artificial "Turf" is then laid on the prepared base in the same manner as it would be applied over a concrete or road base. Prior to and during the laying of the artificial turf all necessary steps must be taken to ensure the prepared clinker base is not disturbed. Sand is applied over the artificial turf in the usual manner.

6 -i Desirably, the sand particles range between 600 microns and imm in diameter and are obtained by sieving raw drift sand. Use of such sand enables a satisfactory standard to be produced for lawn bowls.

Any suitable artificial turf may be used in practice of the invention. In the preferred embodiment "SUPERIOR GRASS" available from King Heylen Courts in South Australia and having a 7600 denier fibre of 19mm tuft length is used.

'o0 Playing fields prepared according to the invention have an energy absorbing characteristic (measured by impact hammer deceleration) of between 100 and 200g.

This compares favourably with natural grass on a cricket pitch or at a hockey field goal mouth which is in excess of 200g. Measurements made on artificial turf laid on asphalt in domestic tennis courts have been in excess of 250g while measurements on artificial turf laid on concrete or bituminous bases exceed 300g. Artificial turf laid on a rubber base and natural grass tennis 20 courts were measured as having an impact deceleration of 100g or less but those surfaces suffer from drainage and/or maintenance problems. In each case measurement was made on a synthetic turf which was sanded in the usual manner. The impact hammer used in the tests weighed 4.6 Kgs., falling from 150mm. The contact area was 50mm in diameter.

In playing surfaces according to the invention, optionally drainage pipes may be laid in or below the -7 clinker layer to facilitate drainage.

The structure enables the surface to drain vertically through the turf backing and particulate layer which in turn permits the prepared site to be, or to include reactive clays since the moisture content of the clay can readily be controlled between predetermined limits by controlled watering. That avoids an uneven surface from developing due to moisture content variation in the reactive clay. Vertical drainage also permits a 0**S :J0 truly level flat surface to be provided for games such as S* bowls.

The present invention enables the provision of synthetic playing fields which more closely resemble the energy absorption characteristics of natural surfaces and result in a lower incidence of muscle and joint fatigue or injury than prior art while maintaining the advantages of reproducability, appearance, satisfactory drainage and o low maintenance cost of synthetic turf.

Playing surfaces according to the invention may be 0* SO constructed in any desired size or shape and are suitable for use for tennis, hockey, athletics, soccer, football, croquet, bowls and cricket but are not limited to use for those activities. To an extent which will be apparent to those skilled in the art from the teachings hereof, embodiments may be modified without departing from the scope of the invention.

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Claims (15)

1. A playing surface comprising artificial turf laid over a layer of particulate matter of at least 100mm compacted thickness, the layer being selected to have a Clegg Impact Hammer deceleration of between 100g and 200g.

2. A playing surface according to Claim 1 wherein the particulate matter comprises clinker.

3. A playing surface according to Claim 1 or 2 wherein the particulate matter is selected so that at least passes a 9.5mm sieve.

4. A playing surface according to any one of the preceding claims wherein the particulate matter is 00. clinker selected so that at least 40% passes a 4.75mm sieve. A playing surface according to any one of the preceding claims wherein the particulate matter is clinker selected so that less than 3% passes a 0.075mm sieve. o

6. A playing surface according to Claim 1 or Claim 2 wherein the particulate matter is substantially "approved processed clinker" as herein described.

7. A playing surface according to any one of the preceding claims wherein the layer is in excess of 150mm compacted thickness.

8. A tennis court having a playing surface according to any one of the preceding claims.

9. A playing field for hockey, soccer, football, athletics or bowls having a playing surface according to 9 IMF any one of claims 1 to 7. A playing surface according to Claim 1 and substantially as herein described.

11. A method for construction of a playing surface comprising the steps of:- preparing a site, spreading a selected particulate matter as a layer over the site to a depth of in excess of 100mm, es e a* compacting the particulate matter until a Clegg Hammer deceleration of between 100g and 200g is .achieved in a layer having a compacted thickness of at least 100mm, and laying an artificial turf over the particulate layer.

12. A method according to Claim 11 wherein the selected particulate matter comprises clinker.

13. A method according to Claim 12 wherein the clinker is selected so that at least 70% passes a 9.5mm sieve.

14. A method according to Claim 13 wherein the clinker is selected so that at least 40% passes a 4.75mm sieve. A method according to claim 12 wherein the clinker is of a particle size such that less than 3% passes a 0.075mm sieve.

16. A method according to any one of claims 11 to wherein the particulate layer is compacted to a minimum dry density ratio of 98% based on standard compaction according to Australian Standard 1289 Test El.1.

17. A method according to any one of claims 11 to wherein the upper 150mm of soil of the prepared site is compacted to a minimum dry density ratio of 95% based on standard compaction according to Australian Standard AS 1289 Test E1.l.

18. A method according to Claim 11 substantially as herein described. DATED this 1st Day of July 1992 KINGSFORD ROSS HEYLEN Attorney: IAN T. ERNST Fellow Institute of Patent Attorneys of Australia of SHELSTON WATERS 11