Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF CREATING A FALL-SAFE,
SYNTHETIC TURF-COVERED PLAY AREA
[0001] This application claiins priority on US Patent Application No.
11/732,298
filed April 3, 2007, incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to play or playground ai-eas and more
particularly to a
method of constructing a fall-safe, resilient, all-weather play ai-ea wherein
the thickness and
resulting resilience of the play area surface is related to the height of the
equipment situated
in the play area.
BACKGROUND OF THE INVENTION
[0003] Play areas for children, commonly called "playgrounds", have ti-
aditionally
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.
[0004] 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.
[0005] Another approach is described in a published patent application, U.S.
2003/0104157 published June 5, 2003 wherein the inventors Brady and Sutcliffe
proposed
the use of highly engineered safety tiles with tongue-in-groove interlocking
featui-es 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.
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SUMMARY OF THE INVENTION
[0006] According to the present invention, a i-esilient 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 i-esilience 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 pi-ocess, the
thiclaless 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.
[0007] In accordance with the invention, a mixture of flowable particulate
rubber and
a urethane binder is prepared. The height oi- heights of play equipment such
as decks, slides,
or other climbable equipment already situated or to be latei- 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 detei-mined. Using
any of a variety of
techniques to ensure the proper thickness, the mixture is then spread onto the
subsui-face,
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 Ox .
[0008] The preferred particulate i-ubber material is shi-edded tire casing and
the
preferred shape is strand-like, approximately 1/4 to 1/2 inch in length by
approximate 2-3 mm in
thickness. Such material is available, packaged and shipped in 50 pound bags.
BRIEF DESCRIPTION OF THE DRAWING
[0009] Figure l is a perspective view, pai-tly in section, of a playground
area with two
different types of equipment mounted on resilient surfaces of differing
thickness wherein
each thickness is related to the height of the play equipment;
[0010] Figure 2 is a perspective view of an example of a two-height play area
with a
step boundary around the higher height area;
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[0011] Figure 3 is a perspective view of a multi-height play area with a
sinooth
transition along the one edge;
[0012] Figure 4 is a perspective drawing of a play ai-ea similar to the play
area of
Figure 1, but showirig how a multi-tliickness resilient sLu-face can be
achieved thi-ough
strategic ground grading; and
[0013] Figure 5 is a perspective view of a play area with single thickness
resilient
surface and a representative deck structure erected thereon.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
[0014] Referring to Figure 1, there is shown a play area 10 characterized by a
first
level surface 12 and a second higher level sui-face 14. Situated on the
surface 12 is a spring-
loaded riding animal 16. Mounted substantially over the higher level surface
14 is a slide 18 having steps 19 which directly overlie the surface 14 and a
slide end 21 which overlies the
lower level surface 12.
[0015] 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/oi- fi-om 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.
[0016] Looking to Figure 2, a play area is shown to comprise a first lower
level 32
and a raised upper level area 34 bounded by 2 x 4's, railroad ties or other
bordering elements
36. Again, higher play equipment is mounted in the area 34 whereas lower play
equipment is
mounted on the area 32. The rectangular shape for area 34 is arbitrary as it
may assume any
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of a variety of shapes as well as any size necessaiy to accommodate the type
and amount of
equipment desired in a given play area.
[0017] Figure 3 shows anothei- appi-oach to a multi-level play area in which
thelower
less resilient surface 36 surrounds a higher, more resilient surface 38. A
transition area 40 is
smoothly trowelled into the structure to allow children to move easily from
one area to the
other.
[0018] Figure 4 illustrates a playground surface 42 with a flat upper level
that
provides different degrees of resilience by contouring the concrete base 44 so
that the
resulting cured rubber/resin matei-ial has a first level 46 around the i-iding
animal 16 and the
end of the slide 18 whereas the ladder and upper areas of the slide 18 overlie
a thicker
resilient area 48. The two level underlayment 44 is created using two depths i-
elative to a
datum level representing the desired upper level for surface 42. The thickness
of layers 46
and 48 must, therefore, be known in advance; i.e., when the underlayment 44 is
poured.
[0019] 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 Figure 1; i.e., a
border or boundary element 28 is laid in place and the Astroturf is secured to
it by means of
tacks or nails 30.
[0020] Referring now to Figure 5, a play ai-ea 52 is shown to have a deck
structure 54
erected thereon with legs 56. The deck structure 54 is reached by steps 58,
and
accommodates slides 60 and 62. Other conventional equipment well known to
persons
familiar with children's play areas may also be used with deck 54. The
thickness of the
resilient material 64 around and under the deck 54 is chosen to provide a
degree of resilience
objectively related to the height of the deck 54. Synthetic turf 66 is placed
over the resilient
layer 64.
[0021] 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 3/8 of an inch by 2-3 mm in thickness. Such materials are commei-
cially
available in 50 pound bags.
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[0022] 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 Fahi-enheit. 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 ti-oweled
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 appro.priate thickness or by installing a height-
graded boi-der
structure such as that shown at 28 in Figures 1 and 4 and as shown at 36 in
Figure 2.
[0023] Once the first layer is complete it must cure or at least partially cLu-
e for
approximately 12 hours or overnight. A higher level can be built on top of the
fii-st 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.
[0024] 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 woveii material described above which
coines 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
perimetei- can be attached
to a 2 x 2 nailer board and tacked similar to the process used to lay
carpeting.
[0025] The suggested correlation between equipment height or deck height and
thickness is as follows:
For a 4 foot deck or equipment height Resilient material of 1 inch thickness
For a 5 foot deck or equipment height Resilient material of 1'/2 inches
thickness
For a 6 foot deck or equipment height Resilient material of 2 inches thickness
For a 7 foot deck or equipment height Resilient material of 2'/z inches
thickness
For a 8-10 foot deck or equipment height Resilient material of 3 inches
thickness
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[0026] 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 sp,-
ead. The
surface is essentially an all-weather surface which can be easily cleai-ed of
siiow through the
use of brooms and which is tolerant to ultraviolet light, rain and freeze/thaw
cycles.
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