Patent Application
20090312154
This invention relates to enhancements to areas of ground where children play. The invention relates to minimising the risk of bodily damage as a result of impact with the enhanced playground surface, and in particular the invention relates to improvement by resurfacing of existing playground surfaces.
“Playground” describes an area either indoors or outdoors where people; especially but not solely children play; optionally using playground apparatus such as slides and swings. For the purpose of this document the term also covers areas where games or physical exercises are carried out.
Disclaimer: This specification does not, of course, imply that an injury cannot be incurred when a playground surface has been enhanced according to the details given herein.
Some relevant test standards, the contents of which are hereby imported by way of reference, as prescribed by the American Society for Test Methods are:
ASTM F1292-04 “Standard specification for Impact Attenuation of Surfacing Mats within the Use Zone of Playground Equipment”, for establishing minimum standards specifically for playgrounds,
ASTM E303-98 “Standard test method for measuring Surface Frictional Properties using the British Pendulum Tester”, which relates to the effective grip that a person running over a surface would obtain by contact with the surface, and
ASTM F1951-99 “Determination of Accessiblity of Surface Systems Under and Around Playground Equipments”, which establishes minimum characteristics for those factors that determine accessibility.
ASTM F 2479—Guide for Specification, Purchase, Installation and Maintenance of Poured-in-Place Playground Surfacing. which covers information with regard to the design, manufacture, installation, and maintenance of poured-in-place playground surfaces.
The inventors produce modular, mutually edge-attachable and fusible mats made of a resilient material (usually a vinyl material: polyvinyl chloride plus one or more plasticisers) for use on playgrounds, among other applications. When the inventors supply a playground to be installed at an empty area, they usually lay a draining surface made of gravel or the like upon the existing ground or into an excavated, drained depression. The gravel surface is made flat and then a loose mesh of rubber fragments held together with a permeating coating of a latex is laid down, the resilience of which contributes to the final impact properties, and then an array of the modular mats that are described in this application is placed on top, welded together, and attached to the ground at the perimeter. All steps contribute in predictable ways to a final amount of resilience as required by a relevant Standard, or simply by common sense.
There have been a number of instances where a “poured-in-place” playground that was previously made by an alternative process involving the mixing and then distribution of components including resilient materials at the site has required remediation. Perhaps the need is recognised after the surface has sustained surface damage over time and become unsafe, or because the surface has deteriorated, or because the surface is found to not meet the relevant Standards (see above). Sometimes this event arises as a result of a defect in curing. The present invention is intended to provide materials and a method to upgrade such a playground. The inventors understand that the term “poured-in-place” is not a trade mark but is a generic term in the relevant field of activity.
The object of this invention may be stated as to provide an improved surface for a playground, or at least to provide the public with a useful choice. Alternatively, the object is to at least cut down the rate of accidents such as long bone or skull injuries that occur to children in playgrounds; at least those that result from impact with unduly hard surfaces.
In a first broad aspect, the invention provides a remediated playground for children based on an original playground surface having an inadequate capability for absorbtion of impact energy, hence presenting a risk of injury to users; the playground comprising the original playground surface remediated by addition of an overlying surface comprised of a plurality of mutually adherent modular, manufactured tiles made from a resilient composition selected from the range of natural rubber, synthetic rubber and a plastics material; the plastics material including polyvinyl chloride; each tile having when in use an upper surface, a lower surface, and outer edges; the plurality of tiles collectively having a perimeter, the remediated playground surface having acceptable characteristics in terms of absorbtion of impact energy when tested by an approved test method.
Optionally the plasticised polyvinyl chloride composition is a recycled material
In a first related aspect, the invention provides a tile for a remediated playground as previously described in this section wherein the resilient nature of each tile owing in the first instance to its composition is enhanced by inclusion of a plurality of supported voids beneath the upper surface so that upon impact the upper surface is capable of being temporarily deformed into at least one void, having the effect of increasing the acceptable characteristics in terms of absorbtion of impact energy as compared to a tile having no voids; the or each tile having predictable characteristics in relation to absorbtion of impact energy applied to the upper surface.
In a dependent aspect each mat comprising the array of modular playground mats is cast in a mould having an internal shape that causes the inclusion of complementary interlocking shapes around the perimeter of the mat, so that any one mat may be joined along at least one edge to at least one adjoining mat.
Preferably the or each tile has predictable characteristics in relation to absorbtion of impact energy by the upper surface, and has known characteristics in relation to surface friction of the upper surface, so that the characteristics in terms of absorbtion of impact energy of the remediated playground may be predicted.
Preferably also the or each tile has predictable characteristics in relation to friction between the upper surface and an item of footwear.
Preferably the or each tile is secured about the outer edges to adjacent tiles by a process involving welding the tile edges together with heat.
In a related aspect, the invention provides a method for joining interlocking mats, wherein each mat is welded to adjoining mats by means of a heating process that heats and liquefies the perimeters of adjoining mats, so that the adjoining mat perimeters become merged, and upon cooling the adjoining mats are welded together.
In one option, the heating process comprises the controlled application of hot air from a heating device.
In a preferred option, the heating process comprises the passage of a controlled electric current through wires laid into the array of mats along mat perimeter lines during installation, so that the adjoining mat perimeters are at least partially liquefied and become merged and upon cooling the adjoining mats are welded together.
In a second related aspect, the invention provides a perimeter enclosure for a plurality of mutually adherent modular tiles for a remediated playground as previously described in this section; the perimeter enclosure comprising an elongate beams comprised of an upper strip and a parallel lower strip side by side, and a third connecting strip opposite an open side thereby forming a rectangular groove along the length of the beam; the perimeter enclosure being capable of being fastened to a substrate, the groove having a width such that it will closely encompass and restrain an exposed edge of a modular tile, so that the tiles around the edge of the remediated playground cannot inadvertently be lifted above the height of the shared upper surface.
Preferably the open side of the elongate strip (the groove) has sufficient depth to accommodate expansion and contraction of the array of tiles in a horizontal plane, when in use.
In one option, the lower strip extends further from the base in a direction towards the groove than the upper strip, so that, when in use, the lower strip may conveniently be fastened to a substrate.
In another option, the upper strip extends further from the base away from the groove than the lower strip, so that, when in use, the extended upper strip protects the corner between the upper strip and the joining strip from damage.
In a dependent aspect, the upper strip is made with an inherent bias or natural curvature tending, when in use, to force said upper strip down against the tile surface, and said upper strip is terminated at each side with a sloping edge.
In a second broad aspect the invention provides a method for providing a remediated playground as previously described in this section; the method comprising the steps of (a) repairing the original surface so that the surface is flat and has consistent properties at least in terms of impact attenuation; (b) laying an array of prefabricated modular mats on the topmost surface; (c) adhering the mats together by their edges, and (d) affixing the array of mats to the perimeter of the playground by means of the perimeter enclosure.
Preferably the method includes provision of resilient preferred underlying materials as required overall or at particular positions for repair of the original surface before being covered by the array of mats, so that the original surface is made flat and has substantially even characteristics in terms of absorbtion of impact energy.
Preferably the method includes the steps of assessing the existing impact attenuative properties of the original surface, and more preferably assessing the impact attenuative properties of the surface after remediation by means of an accepted Standard test Method, before the remediated playground is accepted for use by children.
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.
A typical application for the present invention takes an existing playground surface which will fail or is likely to fail to meet various criteria including (a) that shock (impact attenuation) behaviour of the surface should pass the minimum standard test, (b) the surface should be complete and unbroken, (c) and the surface should be not slippery and should have a “grip” according to the relevant standard test, currently as previously described in the Background. The invention proceeds to cover that existing playground surface, flattened or built up if necessary, with a factory-made surface comprised of modular mats which are constructed so as to inherently provide the required characteristics. The underlying intention is to at least cut down the rate of accidents such as long bone or skull injuries that occur to children in playgrounds; at least those that result from impact with unduly hard surfaces.
As shown in the cross-sectional elevation diagram in
Mats according to the invention are each a modular unit, and for example each mat is 20 inches square. Mats may be delivered already made up in (for example) 2×2 modules at the factory or by a distributor. Mats are generally cast from a polyvinyl chloride (vinyl; PVC) composition including plasticisers, filler, and pigments as is known in the art. By way of a non-limiting example, one composition is: plasticiser 4.4%, fillers 25.1%, stabilisers 1.5%, polyvinyl chloride 66.8%, and pigments 2.1%. The composition of the mats should, when appropriately tested, provide a Shore hardness of about 86 Shore, for a desired balance between durability and desired friction.
A particular structure is favoured although the Example shown here is but one way to provide supported voids beneath a flat (or perhaps sculpted for grip, or perforated) upper surface. A perspective drawing of a portion 100 of the underside of a mat is shown in
There may not be any surrounding grass or soil. For that case,
In this version, the perimeter is finished with a novel elongated plastic edging or extrusion 210 (examples shown in detail as a U-shaped cross-section in
The slight bend that is shown in the upper surface of
In
The remediation process comprises the following steps:
A vinyl composition has been described in particular, since the Applicant's products are at this time based on PVC. The invention extends to rubber compositions, which have the advantage of having less temperature-dependent properties than those of vinyl, by which we mean that a mat tested on a hot day will be substantially more resilient than if tested on a freezing day. The nibber composition may use at least some recycled rubber such as from car tyres, and it may use syiithetic rubber such as “Neoprene”. Other suitable resilient materials may be brought into use in the near future.
A foamed mat (in which the “voids” previously described are bubbles) having an unfoamed top surface could be used in place of the moulded versions described herein. However foam mats tend to be less predictable in terms of their properties at the time of manufacture, and do not allow for perforations. Hence there is no widely distributed drainage facility, which the perforated mats do have. Furthermore there is less sideways strength for use in perimeter bonding.
In the event that the original surface has no effective resilience at all, one solution is to prepare and apply a “pour-in-place” resilient composition over the surface.
Optionally, the existing pour-in-place composition can be removed to a desired depth around fall zones around equipment, and shock pads can be installed beneath the final layer of mats as described previously in this specification.
The same edging could be used in factory floors (for example) using this tiling for its ergonomic features, where tripping somebody up could result in a serious accident. It is by no means limited to outdoors uses.
The performance of the finished surface of a playground after resurfacing according to the invention can be guaranteed to the purchaser, since the properties of the finished surface are under control during manufacture of the modular mats. In contrast, there is a possibly variable composition and mixing and curing of a mixture that had been made up at a site. Each mat may be tested before shipping from the factory.
In situations where the original surface did not have enough “give” or resilience, and therefore exposed users to an increased risk of injury, the finished surface should meet the relevant standards.
Building a more resilient surface on top of an existing surface is usually preferable, in terms of sustainability and conservation of resources, to removing and disposing of the existing surface and replacing the existing surface with another.
An existing playground such as one of the type that is “poured in place” can be repaired and brought up to meet the relevant standard, so that the area is rendered safer for play than it would otherwise have been, without the complications of total removal and replacement of the resilient mass.
Further, those responsible for the playground have some defence against claims of negligence in the less likely, but still possible event of injury; particularly if the remediated playground has been certified by test against an accepted Standard.
In regard to the extrusions, their use is visually appealing and they define the tiled space. Tile edges are protected from impact damage. Tiles can't easily be lifted up around the edges because the edges are restrained and because there is a seal to block the ingress over time of sand or small stones. The extrusions allow some scope for shrinkage of tiles over time, before the edging has to be lifted up and moved.
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.
