Regulation 3.2 Revised 2/98 AUSTRALIA Patents Act, 1990 COMPLETE INNOVATION SPECIFICATION NAME OF APPLICANT/S: Ozbreed Pty Limited, (ACN 102 705 500) INVENTOR: LAYT, Todd ADDRESS FOR SERVICE Peter Maxwell and Associates Level 6 60 Pitt Street SYDNEY NSW 2000 INVENTION TITLE: SUBSTRATE FOR PLAYGROUND SURFACES PRIORITY: AU - 2014 903 630 - 11 September 2014 The following statement is a full description of this invention including the best method of performing it known to me: m:\docs\20151015\370643.doc 2 FIELD OF INVENTION The present invention relates to a substrate for playground surfaces and, in particular, to a growing medium for grass in soft fall areas, such as the surfaces of child playgrounds. 5 BACKGROUND ART There is generally a requirement that child playground surfaces provide a soft fall area around playground equipment so that children falling from the equipment are not seriously injured. 10 When selling child playground equipment, manufacturers need to state the minimum critical fall height needed for the equipment. Most child playground equipment needs a critical fall height of two metres or less, and so many child playground surfaces have been designed and built around this requirement to achieve an adequate level of safety for children. However, 15 some child playground equipment needs a fall height of up to 3.5 metres. Turf, which in this specification is defined as a surface or covering of grass and the soil through which it grows, is not generally regarded as being a suitable surface for soft fall areas around child playground equipment because turf, and especially the grass growing through it, may not survive the wear and 20 compaction experienced by playground surfaces and because turf may not adequately absorb the energy of falling bodies impacting on it from normal fall heights in child playgrounds. Rubber based materials are commonly used as a substrate for playground surfaces because of their greater resistance to wear and 25 compaction, and their greater capacity to absorb the impact energy of falling bodies, than turf. 13/08/15 3 Rubber, often sourced from rubber tyres, has been used for many years in a mixture with various types of soil as a substrate for sporting field surfaces upon which grass is growing. The rubber component of that substrate reduces wear and compaction and the impact suffered by players as they fall on the 5 surface. The testing and acceptability of these sporting field surfaces does not relate to the critical fall heights needed for child playground surfaces, but rather relate to specialised sports turf requirements, and are therefore irrelevant to the requirements for child playground surfaces. The substrates used for these sporting field surfaces contain high levels of minerals and sand with varying 10 levels of rubber. Although these substrates are good enough for sporting field surfaces, a greater capacity to absorb the impact energy of falling bodies is needed in the substrate used for child playground surfaces. Plant derived organic materials may be used in combination with, or in place of, minerals and sand to achieve a softer surface, but plant derived 15 organic materials have a tendency to slump over time which would cause them to be compacted and sink in any substrate containing them, thereby changing the surface and impact properties of the substrate from those originally intended. 20 SUMMARY OF THE INVENTION It has now been found by the present inventor that an improved substrate for child playground surfaces can be produced by using certain plant derived organic materials that have been composted for a sufficient period of time so that they will not slump over five years (hereinafter referred to as "well 25 composted plant materials") and are therefore resistant to compaction and sinking when mixed with rubber and any other components in the substrate. 13/08/15 4 According to the present invention, there is provided a substrate for child playground surfaces comprising a mixture of: (a) between about 30% and about 75% of well composted plant materials, 5 (b) between 0% and about 50% of soil, sand or minerals, and (c) between about 20% and about 40% of rubber having a size not in excess of about 7mm. Preferably, the well composted plant materials are selected from the group consisting of coir, pine bark and wood chip. 10 It is preferred that the well composted plant materials have a size of from about 0.01 mm to about 7mm. In a preferred form, the substrate has a depth of between about 100mm and about 300mm. Preferably, the rubber is sourced from recycled tyres, and has a size not 15 in excess of about 4mm. The mixture optionally includes a binder to provide a desired level of solidification. According to another aspect of the invention, there is provided a growing medium for grass in soft fall areas of child playground surfaces, the growing 20 medium comprising a mixture of: (a) between about 30% and about 75% of well composted plant materials, (b) between 0% and about 50% of soil, sand or minerals, and (c) between about 20% and about 40% of rubber having a size not in 25 excess of about 7mm. 13/08/15 5 Preferably, the substrate or growing medium further comprises a drainage and shock absorbing underlay pad which includes holes in which the mixture is located. It is preferred that the mixture is located in the holes of the underlay pad 5 by a process of applying the mixture onto the top of the underlay pad and forcing the mixture into the underlay pad, such as by use of a rake. In a preferred form, the underlay pad is a three dimensional mesh. According to yet another aspect of the invention, there is provided turf comprising grass growing through the growing medium described above. 10 DETAILED DESCRIPTION OF THE INVENTION In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying examples of preferred embodiments of the invention. 15 Example 1 A substrate for use in a soft fall area of a child playground surface, which is also a growing medium for grass in the soft fall area, was made by mixing about 45% of well composted pine bark, about 25% of soil and sand, and about 30% of rubber having a size of between about 1 mm and 4mm (as 20 any larger size may constitute a choking hazard), in a mixing apparatus, such as a cement mixer, or on a hard surface by scooping, churning and mixing with a bucket of a loader machine, such as a skid-steer loader, followed thereafter by a process in which the mixture is collected, optionally stored and transported to the site of use. The rubber used in the mixing is sourced from 25 recycled tyres, and the well composted pine bark has a size of from about 1 mm to about 7mm. 13/08/15 6 The substrate was subsequently tested according to Australian standards and with a depth of 200mm it met the critical fall height of 4 metres, which is much higher than is generally required. Example 2 5 Another example of a substrate or growing medium according to this invention, which is very suited to growing grass therethrough to form a well established turf that can be used as child playground surfaces, utilises a drainage and shock absorbing underlay pad or mat, such as a three dimensional mesh, placed underneath the substrate or growing medium 10 described in Example 1. The underlay pad or mat is made of rubber or other polymer that has holes or is otherwise porous to allow water drainage and to allow the roots and rhizomes of the grass to grow therethrough. When a three dimensional mesh is used as the underlay pad or mat, the mesh has a depth of more than about 20mm, or when a pair of three dimensional mesh is used, one 15 on top of the other, each mesh has a depth of about 10mm or more. In use, the mesh is laid on a prepared site, which is either on plastic sheeting when the turf is to be grown in a turf farm or the like, or on soil that has been compacted and levelled when the turf is to be grown on the site of use, and above the mesh is placed the mixture described in Example 1, which 20 is raked into the holes of the mesh and fills them, and on top of that is placed turf. With watering and allowing about four weeks or so for growth, the roots and rhizomes of the grass will penetrate the mesh and anchor into the ground below. A benefit of using this system is that the depth of the substrate or 25 growing medium described in Example 1 for playground surfaces can be reduced. The total depth of the substrate or growing medium produced in this Example 2 (which includes the underlay pad or mat) is from about 30mm to 13/08/15 7 about 200mm depending on the critical fall height required. It also has the benefit that, if the grass dies, and if the substrate or growing medium described in Example 1 becomes loose and is dispersed and holes appear, the underlay pad or mat will still meet critical fall height requirements and soft fall standards, 5 or the combination of the underlay pad or mat and what remains of the loosened and dispersed substrate or growing medium will still meet critical fall height requirements and soft fall standards. It will be readily apparent to persons skilled in the art that various modifications may be made in details of design and construction of the 10 substrate and the growing medium, and of the steps of the method of making the substrate and the growing medium, without departing from the scope or ambit of the invention. 13/08/15