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A multi-layered surface suitable for a playground, including a top layer of perforated resilient mats is also provided with a bottom shock-absorbing layer having pockets or perforations capable of supporting the growth of grass or other plant material from under the mats. A middle mesh layer helps distributes forces sideways. This invention overcomes the inherent absence of resilience in grassed playgrounds and is compatible with formal tests for impact resistance. The resulting playground environment is more natural in appearance than that of an undressed plastics mat surface.

Harris, Paul (Auckland, NZ)
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Primary Examiner:
Attorney, Agent or Firm:
YOUNG & THOMPSON (209 Madison Street Suite 500, Alexandria, VA, 22314, US)
We claim:

1. An artificial surface for a children's playground wherein the artificial surface is resilient and is further comprised of a plurality of layers; the layers providing for the support of a plurality of living plants namely grass plants; the layers being perforated thereby forming an array of apertures over the surface extending downwards to a lower layer bearing soil; said apertures allowing the plants to grow upwards through the apertures in the mats and above the artificial surface.

2. An artificial surface for a children's playground as claimed in claim 1 wherein the plurality of layers comprises a first, uppermost layer made of a flexible, moulded or cast material in the form of a plurality of cast, laterally joinable modular mats; each mat including a plurality of perforations and an embossed upper surface, a second layer comprising a stiff, perforated sheet or mesh, supported upon a third layer comprising a thick resilient weight-bearing layer including a plurality of cavities; each cavity being capable of holding at least one living plant within a support matrix, so that the living plants can, when in use, grow upwards through the perforations in the mats and above the artificial surface.

3. An artificial surface for a playground as claimed in claim 2, wherein the mats of the first layer are comprised of a plastics composition including polyvinyl chloride, at least one plasticiser, and at least one filler.

4. An artificial surface for a playground as claimed in claim 3, wherein the composition of the first layer further includes a coloring material.

5. An artificial surface for a playground as claimed in claim 3, wherein the first layer is spaced apart from the mesh layer by the provision of a plurality of downwardly projecting pegs forming part of the first layer all of which pegs, when in use, rest upon the middle layer.

6. An artificial surface for a playground as claimed in claim 5, wherein the second (mesh) layer is relatively stiff so that a load applied from the uppermost surface over a small area is at least partially distributed in a sideways direction yet the second layer includes sufficient perforations to allow plant material to grow through the middle layer.

7. An artificial surface for a playground as claimed in claim 6, wherein, when in use, the surface has sufficient impact absorbtion capacity characteristics for use as a children's’ playground (as determined by an appropriate standard test method) and includes structural modifications providing for the germination and growth of grass so that the grass emerges through the artificial surface

8. An artificial surface for a playground as claimed in claim 1, wherein the third layer is water-resistant and water-permeable and is resilient.



This invention relates to artificial surfaces for recreational use; more particularly to surfaces having a predetermined “resilience” characteristic and especially to artificial playground surfaces compatible with the growth of vegetable material especially grass.


Natural playground surfaces are well-known. One of the most common is earth (soil) that may or may not have at least one grass species growing in it. The present invention is particularly concerned with children‘s’ playgrounds, where children run about and interact with playground equipment. Note that some of these sports may from time to time involve hard physical impacts by children with the ground. At times a natural earth (soil) surface may become quite hard and the risk of actual injury becomes high.

There is such a material as “artificial turf”. However sliding contact by (for example) children‘s’ knees almost always results in a form of cutting damage to the skin because the strips of plastics material of which the artificial turf “leaves” are made is capable of cutting skin.

Artificial playground surfaces are becoming common, particularly for unstructured play by children involving swings, slides and similar apparatus. Children can fall off such apparatus, and even when landing from an ordinary slide, a child may sustain injury such as head or neck injury and long bone (femur, tibia, fibula etc) fractures if the surface causes a sudden stop.

Problem to be Solved

Given the aforesaid, it would be useful to somehow combine a grass surface (which has the property of regeneration) with an artificial surface that meets or exceeds the Standards so that at any given time, a player can make impact with the surface yet be relatively unlikely to be injured. The general public is becoming aware of a need to ensure that artificial playground surfaces are as safe as possible. The American Society for Test Methods (ASTM) has published a Standard: Impact attenuation of surface systems under and around playground equipment, no F 1292 2004. It would be desirable to provide a playground surface that meets standards of this type.


The object of this invention may be stated as to provide (in combination) a grass surface with an artificial surface for exercising or play, or at least to provide the public with a useful choice.


In a first broad aspect this invention provides a resilient, play-compatible artificial surface also capable of supporting vegetation; wherein the resilient artificial surface includes a an array of pockets capable of supporting germination and growth of at least one species of plant so that the surface is more natural than a surface lacking controlled vegetation.

Preferably the artificial surface for a children's playground wherein the artificial surface is resilient and is comprised of a plurality of layers; the artificial surface including means for the husbandry or support of a plurality of living plants; the layers being perforated thereby forming apertures extending downwards from an uppermost or first surface and to a lower layer bearing soil; said apertures allowing the plants to grow upwards through the apertures in the mats and above the artificial surface.

Preferably the living plants are comprised of at least one species of plant including a type of grass (Order: Graminale—the grasses, sedges and rushes); and more particularly the at least one species is selected from Family Poaceae: the grasses.

In a related aspect, the resilient artificial surface includes a plurality of layers, including (from the top) a sculpted, perforate, resilient surface comprised of repeating units called “mats” each including a border carrying interlocking means about all sides (for locking into adjacent mats), an upper or first surface including a plurality of relatively large perforations, and a plurality of supporting legs each of which supports an adjacent portion of the surface above a lower layer, then a middle or second force-distributing layer comprised of a relatively rigid mesh having a plurality of holes, that lies over a third or lower relatively thick shock pad layer, made of a resilient fibrous substance, including pockets or perforations approximately aligned with the relatively large perforations of the mats.

Preferably the third layer is water-permeable and water-resistant, since it will often be wet.

Optionally the second layer may be replaced by a layer of geotechnical cloth which is perforated in places aligned with the cavities of the third or shock pad layer.

Optionally; depending on the local weather patterns, the type of soil underlying an area to be covered, and the configuration of the land, the third or shock pad layer may be laid upon a substrate or layer capable of providing adequate drainage, such as a layer of gravel or a combination of soil including drainage tiles or pipes.

When in use, the perforations/cavities of the third or shock pad layer are filled with soil and grass seeds, from which grass will or does grow upwards and eventually though the perforations of the mats above.

In a second broad aspect the invention provides a method of using the plurality of layers, comprising preparing a substrate, laying the shock pad layer (which may be provided as a roll) optionally on the substrate, at least partially filling each of the perforations/cavities in the shock pad layer with a growth-compatible matrix and then of adding a mixture of matrix and grass seeds into each perforation; then laying the mesh (which may be provided as a roll) on top, and then laying a plurality of mats on top of the mesh, locking the sides of the mats to each other by one or more means including interdigitating lugs, welding or gluing, fixing the periphery of the array of mats to a bordering object, and then of watering the resulting playground surface from time to time so that the grass will germinate and grow and emerge through the apertures in the mats.

The periphery of the array of mats may be fixed using concealed plastics pins or spikes or by other means, including burying the outer mats under soil.

In a related aspect the grass may be mowed, fertilised and watered from time to time, since contact wear by human activity will vary from place to place.

In a further related aspect new seed may be distributed over the surface from time to time, in order to sow new grass. For example, extremely cold or dry weather conditions may have killed the grass.

Preferred Embodiment

The description of the invention to be provided herein is given purely by way of example and is not to be taken in any way as limiting the scope or extent of the invention.

Throughout this specification unless the text requires otherwise, the word “comprise” and variations such as “comprising” or “comprises” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.


FIG. 1: is an “exploded” diagram showing a section through a portion of a resilient playground surface before grass growth has commenced.

FIG. 2: is an “exploded” diagram showing a section through a portion of a resilient playground surface after the grass has grown and has been mown.

FIG. 3: is a top view of part of a preferred artificial mat, including the apertures.

FIG. 4: is an elevation cross-sectional diagram of part of a preferred artificial mat in plan view, along the line A-A in FIG. 3.

FIG. 5: is a diagram of part of a preferred mesh in plan view.

FIG. 6: is a plan view of part of a preferred shock mat material.

Note that FIGS. 3-6 are approximately to scale.


The American Society for Test Methods (ASTM) has published a Standard Test Method for impact attenuation of surface systems under and around playground equipment: F 1292 2004. According to the invention to be described in this specification, it is now possible to fabricate a playground surface that meets or exceeds the Standards, and which includes real grass.

The natural appearance of the artificial surface of this invention relies in part on the inherent capability of grass leaves to grow throughout their length, not just at a growing tip as is the case for most other plants. Hence damage to the protruding tips of the grass plants does not prevent further growth. This characteristic may have evolved during grazing pressure from animals, because those types of plants that lose their growing tips will not survive grazing. Grass (the Family Poaceae: the grasses) as a botanical class evolved relatively recently. In this application this property allows the grass beneath the surface to keep on growing despite damage from time to time at the protruding tip. The term “grass” includes all those species and strains that are already used as “turf” in playgrounds, but is not limited to those species and strains. It may be found that tougher leaves are required and this requirement may apply more particularly in areas that experience higher wear.

Please note that the elevation sections—diagrams FIGS. 1 and 2 are “exploded” diagrams in which layers 101, 102 and 103 are separated for purpose of clarity. The layers are normally in contact with each other and with the ground or other substrate (120) below.

The artificial surface (100) which is the basis of this invention is shown in FIGS. 1 to 6. It is comprised of a plurality of layers, the topmost of which is a sculpted, perforate surface (112) made of repeating units herein called “mats” each including a peripheral border 113 (in FIG. 3) that is provided with interlocking (interdigitating) means about all sides for locking into adjacent mats. Suitable interlocking means are for example pegs and sockets, and other joining devices and the use of gluing or welding, separately or together. Such joining means are not shown, being known to those skilled in the relevant arts. The upper surface of each mat 101A includes a plurality of relatively large perforations 107 (for example the size of each perforation is about 1 inch square, with rounded corners), and a plurality of hollow supporting legs 105 having central apertures 106 each of which supports an adjacent portion of the surface above a separate, lower layer. Some of the legs may be only half-cylinders (as referred along the cylinder axis) in order to be more flexible. In one practical embodiment, the legs are connected to each other by under-surface “beams” 114 moulded from the composition used to make the mats. FIG. 4, a section taken along the line A-A in FIG. 3, shows the heights of the beams. The top surface of the mats layer is preferably provided with extra grip or frictional areas that grip against the soles of children's footwear, such as by means of small, slightly raised (typically 0.5 inch) sharp-edged shapes such as the squares 112 best shown in FIG. 3. The total thickness of the mats layer is—as shown by indicator 101—typically about one inch. The mat structure includes (a) an upper surface 101A which is typically 0.2 inch thick, which includes integral strengthening beams 114 of about 0.16 inch thickness that are formed beneath the upper surface where they form connections between one supporting leg and any adjacent supporting leg. The strengthening beams surround apertures 107 which in one example (see FIG. 3) are about 1 inch square spaced apart from each other by about 0.8 inches. Four supporting legs 105 at 2.2 inch centre spacing surround each aperture. Each leg extends 1 inch down from the upper surface, has a diameter of 0.65 inches and an internal aperture 106 of 0.3 inches diameter. Since the legs are hollow, they can support the underside of the mat at about 0.7 inches above the layer below, hence creating a space, while having more inherent resilience than a solid rod in case of direct impact.

The resilience that is required of the playground surface arises from:

    • a) flexibility of the mat material itself, leading to deflection on impact of the material around the legs;
    • b) presence of voids such as apertures 106 and 107;
    • c) the height of the space beneath the mat surface;
    • d) compressibility or “bendability” of the legs 105, some of which may be only half-round;
    • e) stiffness of the screen-like layer 103; and
    • f) compressibility of the underlying shock pad layer 104.

All of these characteristics may be determined at the time of manufacture, taking environmental temperatures and ageing and like parameters into account, so as to satisfy the standards that may be imposed by the relevant authorities or by common sense. According to this invention, the impact properties are relatively independent of the quality of an installer's work. At the tile of preparing this specification the inventors do not expect the plant material to contribute much to the impact test properties of the entire surface, but will wait to see what the properties will be over time.

Flexibility of the material itself is provided by a combination of detailed structural configuration, and selection of suitable materials. The mats are preferably made of a plastics material by casting into a mould, and a composition including polyvinyl chloride plus suitable plasticisers and other additives (as is known to those skilled in the relevant art) is currently the preferred plastics material. Rubber, and synthetic rubber are optional compositions. Alloys or mixtures of those materials, or other options also exist or may be developed. As is well known in the art, colouring matter and/or weathering resistance-promoting materials are examples of additives to the composition of the mats.

The underlying layer (102) see FIG. 5, on which the mats are placed preferably comprises a relatively rigid, tough sieve or mesh-like sheet comprised in this Example of an array of about 0.32 inch holes (102A) separated on average by about 0.12 inch of 0.05 inch thick solid polypropylene material. FIG. 5, from a photograph, serves to show the relative proportions of holes to material. This relatively rigid mesh (commonly called “oyster mesh”) helps to distribute any load applied from the mats above in a sideways direction so that the underlying layer 103 is not broken down or ruptured and so that the playground characteristics remain consistent. The relatively smaller holes of the mesh help to exclude larger foreign bodies from the layer below yet allow growth of the plant material from below. The shock pad layer 103 comprises a relatively thick (in one example; about 1.4 inches thick) layer, made of a resilient fibrous substance including an array of cavities or perforations 108 of about 0.8 inch diameter at about 2 inch spacing, that is preferably placed in approximate alignment with the relatively large perforations of the mats 107. Preferably these cavities are partially open to the surface below, so that soil and other materials placed within tends to remain, but plant roots can travel down into the substrate 120. Even if the perforations of and above the shock pad layer are not aligned, the inherent phototrophic nature of grass growth confers the growing tips with an ability to seek out nearby apertures 107 and grow up through them, as shown in FIG. 2. One example material used for the shock pad layer 103, (see FIG. 6, which is derived from a photograph) comprises a randomly oriented, loose array of adherent rubber shavings which altogether occupy about 40% of the volume of the shock pad (the spaces being filled with air—or water when in use) that are adhered together by a glue such as a vinyl-based material. The deformability of the shock pad layer has not been measured, but a strong squeeze by a thumb approximately halves the thickness of the shock pad layer. The cavities or perforations 108 may be made at the time of manufacture of the shock pads, or may be cut afterwards.

The invention is installed by a method of placing each of the plurality of layers over an area of ground which is to receive the artificial playground. This area may even be an old playground surface that requires upgrading. Optionally, depending on the local weather patterns, the type of soil underlying an area to be covered, and the configuration of the land, the shock pad layer may be supported upon a substrate layer 104 capable of providing drainage, such as a levelled layer of gravel or a combination of soil or sand that may include drainage tiles or pipes 111. It is likely that the roots (202) of the grass plants will in time invade the soil in layer 104, or enter the soil beneath.

Then, the shock pad material (typically supplied in a roll) is placed on the substrate so as to cover the substrate surface and each of the perforations 108 in the shock pad is at least partially filled with a growth-compatible soil 109 (including fertiliser as required) and then a mixture of soil (or other matrix known in the horticultural arts, such as a water-absorbent jelly) and grass seeds (110) is added on top, into each perforation. In FIG. 1, only one of the perforations 108 is shown with the added mixture of seeds and soil. This process may be sped up using an array of funnels pressed into a metal sheet (for example); the inter-funnel spacing matching the spacing of the array of perforations 108. Then the oyster mesh 102 is laid on top, and finally a plurality of mats 101 are placed on top of the oyster mesh and locked together by their sides using one or more means (such as interlocking processes, glue, or welding. The periphery of the array of mats (A) is fixed to the ground by methods such as pinning with stakes (such as a provided type of concealed plastic stakes, burying the edge under soil, or fixing the mats overall edge to a perimeter wall, so that the top surface does not creep over time or come loose and present a hazard. Finally, the resulting playground surface is watered according to standard turf management practice so that the grass 110 will germinate and grow and in time its leaves 201 will emerge through the apertures 105, 106 in the mats. Meanwhile the roots 202 will emerge below the shock pad material

The impact properties of the surface should be tested at the time of installation by an approved standard method, in order to demonstrate that the desired amount of resilience is present.

From time to time the grass leaves 201 may be mowed, fertilised and watered so as to provide a controlled height 200, just as for any other turf. Contact wear by human activity will vary from place to place such as at the ends of slides or under swings. It is possible that over time the space beneath the mats and above the mesh will become filled with foreign matter so that the resilience properties of the surface are altered. The mats layer 101 could be pulled up for cleaning a few times during the working life of the surface, or a form of vacuum cleaning or water hosing may be used. The apertures 108 may be seeded or re-seeded from above, through the mat apertures.


Preferably the at least one species of plant is a type of grass (Order: Graminale—more particularly the grasses, sedges and rushes). Some pockets may instead be filled with clover or a grass/clover mixture, in order to fix nitrogen and provide a self-fertilising function. More than one kind of grass seed may be planted, so that a combination of quick (re)growth and a durable surface is provided.

The layers may be supplied separately or together, as is convenient.

The mats may be pre-connected into larger rectangles or into rolled strips.

The soil and the grass may be locally sourced.

The invention may be further developed for use in grounds where team sports such as football are played and a controlled set of impact properties are required.


The playground surface looks more natural at least from a horizontal aspect because of the presence of many tufts of grass growing up through the holes.

The surface will be less likely to injure users than the commonly used alternatives (such as an ordinary lawn, with grass growing from soil, or artificial turf), because it includes a designed component of resilience: the layer of mats in co-operation with the shock pad layer below. More particularly, the incidence of such injuries as head and long bone injuries should be reduced.

The lawn surface will regenerate more quickly after damage than a plain grass/soil lawn, since some of the length of each of the leaves of the grass is always protected from damage as a result of being under the plane of the layer of mats.

The surface may be designed in order to meet certain national or international standards, which may be an at least partial defence against personal injury law suits.

Finally, it will be understood that the scope of this invention as described by way of example and/or illustrated herein is not limited to the specified embodiments. Where in the foregoing description, reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are included as if individually set forth. Those of skill will appreciate that various modifications, additions, known equivalents, and substitutions are possible without departing from the scope and spirit of the invention as set forth in the following claims.