Patent Application
20080248887
This invention relates to play or playground areas and more particularly to a method of constructing a fall-safe, resilient, all-weather play area wherein the thickness and resulting resilience of the play area surface is related to the height of the equipment situated in the play area.
Play areas for children, commonly called “playgrounds”, have traditionally been characterized by dirt or turf play area surfaces. More recently, it has become customary to spread shredded rubber on the play area surface; e.g., under swings, at the end of slides and around and beneath steps which permit children to climb onto elevated decks. The objective is to create a soft surface which cushions a fall onto the surface and, therefore, reduces the risk of injury.
A disadvantage of loosely spread particulate rubber is that it tends to get moved around; e.g., the area at the base of the slide contacted repeatedly by children's feet tends to wear thin until eventually there is little or no particulate rubber in the area. Similar circumstances exist immediately under swings, where repeated dragging of feet tends to move the particulate rubber away. The rubber can, of course, be redistributed by raking, but this requires regular maintenance which is not always provided in municipal or private play areas.
Another approach is described in a published patent application, U.S. 2003/0104157 published Jun. 5, 2003 wherein the inventors Brady and Sutcliffe proposed the use of highly engineered safety tiles with tongue-in-groove interlocking features which permit the tiles to be installed on a uniform subsurface. Because the tiles interlock, they tend to stay in place. The Brady/Sutcliffe tiles are expensive and unnatural in appearance.
According to the present invention, a resilient play area surface is constructed on a pre-existing subsurface which can be bare ground, natural turf, asphalt concrete, or compacted gravel. The surface is constructed through simple steps similar to those used in the casting of concrete to create a seamless resilient play area surface which is engineered to provide a thickness and resulting degree of cushioning resilience which is objectively related to the height of decking or other equipment situated in the play area; i.e., the higher the equipment or decking, the thicker the surface. By virtue of this process, the thickness of the cast surface material is directly and objectively related to the resilience needed to reduce the risk of injury due to falls from the decking or maximum climbable height of other equipment situated in the play area.
In accordance with the invention, a mixture of flowable particulate rubber and a urethane binder is prepared. The height or heights of play equipment such as decks, slides, or other climbable equipment already situated or to be later erected within the play area is determined and from this the thickness of the resilient surface needed to meet an objective safety standard for falls from such height or heights is determined. Using any of a variety of techniques to ensure the proper thickness, the mixture is then spread onto the subsurface, typically within pre-determined boundaries, until the appropriate thickness or thicknesses are reached. The mixture is then allowed to at least partially cure and the partially or fully cured surface is then covered with a synthetic turf. A suitable synthetic turf is a woven polyethylene fabric which is needle-punched and adhesively bonded to a backing material and known in the trade as Astroturf®.
The preferred particulate rubber material is shredded tire casing and the preferred shape is strand-like, approximately ¼ to ½ inch in length by approximate 2-3 mm in thickness. Such material is available, packaged and shipped in 50 pound bags.
Referring to
The surfaces 12 and 14 are installed on graded concrete base 20. Poured, troweled or cast over the concrete surface 20 is a first thickness layer 22 of resilient material made by combining particulate rubber with a urethane binder. That same material is smoothly troweled or cast into the higher level surface 14 having a greater thickness 24 so that the resilience factor of the surface 14 immediately under the slide 18 is greater than that of the surface 12 surrounding the riding animal 16 and the end of the slide 21. It will be appreciated that the fall height from the riding animal 16 and/or from the terminal end 21 of the slide 18 is significantly less than the fall height from the top of the ladder 19 or the upper reaches of the slide 18. Accordingly, the resilience and cushioning effect of the surface 12 can objectively be less than that of the surface 14 while still providing a substantial safety factor as far as the risk of injury from fall is concerned. The lower level surface is bordered by wooden rails 28 and the entire play area is covered over with synthetic turf 26 which is tacked down by fasteners 20 at all edges.
Looking to
A layer of Astroturf 50 is installed over the rubber and urethane layers 46 and 48 in the same fashion as the Astroturf layer 26 is installed on the play area of
Referring now to
Turning now to the description of methodology associated with this invention, the resilient layers consist of shredded rubber mixed with 100% polyurethane binder with no solvents added and meeting all applicable U.S. material safety standards (MSDS). The shredded rubber comes from the sidewalls of tires and is typically ground to a length of approximate ⅜ of an inch by 2-3 mm in thickness. Such materials are commercially available in 50 pound bags.
The rubber and binder is mixed in any convenient vessel such as a cement mixer or tub and spread over the prepared underlayment when the temperature is within the range of 45 degrees to 90 degrees Fahrenheit. Each 50 pound bag of shredded rubber is mixed with about 7-8 pounds of polyurethane binder in an appropriate mixer vessel and conveyed by wheel barrow or the like to the construction area where it is dumped and poured or spread onto the underlayment of concrete asphalt or compacted stone. It can be troweled or spread like concrete using various types of equipment including long handled spreaders. The appropriate thickness can be achieved in a variety of ways including the use of dowels or other bordering elements of appropriate thickness or by installing a height-graded border structure such as that shown at 28 in
Once the first layer is complete it must cure or at least partially cure for approximately 12 hours or overnight. A higher level can be built on top of the first after the first is completely cured. Alternatively, the higher level can be created first and the second level created around it without waiting for the first level to completely cure.
After the rubber/urethane layer is sufficiently cured, a layer of synthetic turf which is either 100% Nylon or 70% polyethylene and 30% Nylon is laid on top if it. A suitable material is the needle punched woven material described above which comes in rolls of 6, 10 or 12 feet in width by 30 feet in length. It can be slit and taped at the various uprights, slide legs, trees and other pre-existing articles. The entire perimeter can be attached to a 2×2 nailer board and tacked similar to the process used to lay carpeting.
The suggested correlation between equipment height or deck height and thickness is as follows:
The resulting structure is one having a natural appearance and a significantly higher degree of safety than bare ground or natural turf and a much lower degree of maintenance than ground or turf on which loose particulate rubber has been spread. The surface is essentially an all-weather surface which can be easily cleared of snow through the use of brooms and which is tolerant to ultraviolet light, rain and freeze/thaw cycles.
