Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SYNTHETIC TURF GAME SURFACE
TECHNICAL FIELD
This invention relates to an improved synthetic turf surface for grass-type
game playing fields.
BACKGROUND OF INVENTION
Synthetic turf game playing surfaces typically are formed of carpets having
upright piles or strands that are fastened to a base or backing sheet. The
strands
may be formed of thin, flat, narrow strips of suitable plastic material which
may be
gathered into tufts that are fastened to the base sheet. Commonly, the base
sheet
is formed of a woven cloth, made of a suitable plastic fabric, with a
resilient coating
or binder applied to the base sheet for anchoring the strands thereto. The
detailed
construction of such pile carpets varied considerably. However, in general,
they are
made of a weather resistant or outdoor type of construction.
Such carpets are usually laid upon a prepared, flat ground surface to form a
game playing field which is intended to simulate a naturai grass playing field
surface.
For some types of games, a resilient underpad is placed beneath the carpet and
upon
the firm ground support surface to provide a shock absorbing effect. Aiso, in
some
instances, a layer of sand or other particulate material is placed upon the
upper
surface of the carpet base sheet and around the strands. An example of this
type of
construction is shown in U.S. Patent No. 4,389,435 issued June 21, 1983 to
Frederick
T. Haas, Jr. Another example is shown in U.S. Patent No. 4,637,942 issued
January
20, 1987 to Seymour A. Tomarin.
Further, examples of artificial turfs which are formed with the grass-like
carpet
placed upon a resilient underpad are disclosed in U.S. Patent No. 3,551,263
issued
December 29, 1970 to Carter et al., which discloses a polyurethane foam
underpad;
U.S. Patent No. 3,332,828 issued July 25, 1967 to Faria et al., which
discloses a PVC
foam plastic or polyurethane foam plastic underpad; U.S. Patent No. 4,637,942
issued
January 20, 1987 to Seymour A. Tomarin which discloses a rubber-like underpad;
U.S. Patent No. 4,882,208 issued November 21, 1989 to Hans-Urich Brietschidel,
which illustrates a closed cell polyethylene foam underpad; U.S. Patent No.
3,597,297
issued August 3, 1971 to Theodore Buchholz et al., which discloses a
polyurethane
underpad having voids; and U.S. Patent No. 4,505,960 issued March 19, 1985 to
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James W. Leffingwell, which discloses shock absorbing pads made of foamed
polyvinyl chloride, polyethylene, polyurethane, polypropylene, etc.
As these various prior patents demonstrate, there has been a search in the
past for an underpad material and construction which, when combined with a
suitable
synthetic blade forming carpet, provide a game playing surface which very
closely
simulates the feel and action and reaction effect of a natural grass playing
field
surface. The large variety of materials disclosed in the foregoing patents
demonstrate
that such a synthetic turf playing surface had not been found.
The present invention relates to a particular plastic underpad surface
combined with an artificial grass forming carpet which very closely simulates
a natural
grass field which is particularly close in feel and performance to the natural
grass
portions of a typical golf course, as well as being very similar to other
natural grass
surface game playing fields.
SUMMARY OF INVENTION
This invention contemplates combining with a synthetic grass carpet a
particular resilient polypropylene molded underpad which, together with the
synthetic
grass carpet, produces an effect which is strikingly similar to a natural
grass playing
surface formed particularly for golf courses. Thus, this invention
contemplates
utilizing expanded beads of polypropylene of a density of approximately
between
about 1.3 to 2.8 pounds per cubic foot molded into a thick sheet or pad of
open cell
structure with a density of between about 1.5 to 3 pounds per cubic foot. The
combined turf carpet and supporting underpad effect may be enhanced by
treating the
free ends of the synthetic grass blades with a sandblast which splits or
shreds the
blade ends into fine slivers which intertwine and entangle with each other to
form a
dense mat upper surface upon the carpet.
An object of this invention is to provide an artificial turf with a particular
resilient underpad formed of open cell, expanded beads polypropylene plastic
which
produces, as part of the turf surface, an effect which very closely simulates
a natural
grass playing field.
These and other objects and advantages of this invention will become
apparent upon reading the following description, of which the attached
drawings form
a part.
DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic, fragmentary, cross-sectional end view of a synthetic
turf
pile carpet.
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FIG. 2 is a schematic view similar to FIG. 1, showing the carpet positioned
upon a resilient, molded open cell, expanded bead polypropylene underpad.
FIG. 3 is a view, similar to FIG. 2, illustrating the step of sandblasting the
upper end portions of the blade forming strands of the carpet.
FIG. 4 schematically illustrates the artificial turf surface with the dense
mat
formed by the shredded slivers and with a layer of sand deposited by the
sandblasting
step upon the upper surface of the carpet base sheet.
FIG. 5 schematically illustrates a further, optional, step of spraying the
carpet
with a water wash for further severing the slivers on a strand while
additionally
entangling or intertwining adjacent slivers to form the dense mat surface and,
also,
a rotary brush treating the upper surface of the mat.
FIG. 6 schematically illustrates a single U-shaped strand whose free upper
ends have been shredded into fine slivers by the sandblasting treatment.
FIG. 7 schematically illustrates a fragmentary portion of a golf course where
the golfer may use a Tee.
FLG. 8 is an enlarged, fragmentary, schematic, cross-sectional view showing
a Tee inserted in a slot provided in artificial turf which has a mat formed on
its upper
surface.
FIG. 9 is a view similar to FIG. 8 showing a Tee inserted in a slot formed in
turf which is not formed with upper end slivers and a matted surface.
DETAILED DESCRIPTION
FIG. 1 schematically illustrates a fragment of a synthetic turf pile carpet.
The carpet has numerous, closely spaced, tufts 11 which are formed of U-
shaped,
flat, narrow bent strips or strands 12 that form artificial grass blades. The
turfs are
fastened upon a base or backing sheet 14. This sheet may be made of a woven
cloth
or the like fabric material formed of stable, weather resistant, plastic such
as
polypropylene or nylon fibers or the like. The specific cloth must be flexible
but,
otherwise, may vary as to its composition.
As schematically illustrated in FIG. 1, the tufts are inserted around or
through
the fibers forming the base sheet. A suitable binder layer 1 fi may be applied
to bind
the turfs and base sheet together. The binder may be formed of a polyurethane
adhesive material or some other suitable, outdoor usable adhesive which
remains
resilient or flexible.
The carpet is placed upon a resilient cushion underpad 18. This underpad is
formed of a relatively thick, molded sheet or pad of resilient, open cell,
expanded
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bead polypropylene. The sheet may be approximately between about 1/2 inch to 2
inches in thickness, with a preferred density of approximately 2.36 pounds per
cubic
foot. The density may be varied within the range of between about 1.5 to 3
pounds
per cubic foot. The thickness of the pad, depending upon the particular
results
desired, may also be varied from about 1/4 inch thickness to as much as up to
12
inches thick.
With the carpet positioned upon the resilient cushion underpad 18, the upper
portions of the strands or blades are sprayed with a blast of sand 20 or
similar sand-
like particulate material from a pressurized nozzle 21. This blast of sand
shreds each
of the strand upper end portions into numerous slivers 23 (see FIG. 6). The
slivers
extend laterally and intertwine and entangle together to form a dense mat 24.
The spray nozzle 21 may be moved back and forth from one side to the other
in a scanner-like movement across the upper end portions of the blades formed
by
the strands. The exact pressure of the sand blast spray may be varied.
However,
a preferred blast pressure is in the range of 100 to 120 pounds per square
inch. The
blast may use silica sand of a size range of between about 16 to 40 mesh and,
preferably, in the range of between about 20 to 24 mesh or even more
preferably in
the approximate area of 24 mesh. The sandblasting is conducted at a speed of
movement and for a length of time which is sufficient to shred the strand end
portions
into finely divided slivers. For example, the upper, about one-fifth portions
of the
blades may be shredded into fine slivers that remain attached to their
respective
blades.
The force of the sand blast, depending upon how long, that is, how slowly the
blast is moved across the surface of the carpet, not only shreds the blades,
but also
forces the sprayed sand downwardly between the strands to deposit sand upon
the
surface of the base sheet of the carpet. The sand layer 25 formed thereby may
be
kept upon the base sheet of the carpet where it is maintained in position by
the dense
intertwined or entangled sliver mat formed on the upper ends of the blades.
By way of example, a blade height of approximately 5/8 of an inch above the
surface of the base sheet, which is useful for a golf green surtace may have
its upper
20 to 33 percent of its length shredded into fine slivers. In this example,
strands
which are approximately 1/16 of an inch, i.e. about 0.07 inches, wide and
about 0.002
inches thick, so that they are approximately rectangular in cross-section.
They are
bent in half, to form two blades, and are gathered into tufts of about 9 to 11
strands.
These form about 18 to 22 blades per tuft. The upper about 20 percent portions
of
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each blade may be severed into about four slivers. Thus, each tuft may have as
many as about 70 to 80 slivers whose lower ends remain attached to the blade
body
and whose upper ends extend off into transverse directions to entangle with
the
slivers of adjacent strands. The slivers are about 0.02 inches in width and
about
0.075 to 0.125 inches long.
Following the sandblasting step, the carpet may be further treated with a high
pressure water spray 27 applied by a pressurized nozzle 28. The water spray,
which,
for example, could be at a roughly 100 to 150 pounds per square inch nozzle
pressure, acts like a wash which further separates adjacent slivers that were
shredded, but not fully separated from each other on the same strand, and
simultaneously further twists, bends and entangles the slivers of one strand
with
slivers on its adjacent strand to further densify the mat formed by the
intertwined
slivers. This forms a denser and more uniform mat surface.
The mat surface may be further treated by brushing it with, for example, a
rotary brush 29 applied upon the mat surface to make the mat surface more
uniform.
The water jet and the brushing may be performed successively or at the same
time
as schematically illustrated in FIG. 5.
Significantly, the force of the sandblasting is sufficiently absorbed through
the
resilient cushioning pad beneath the carpet to prevent the strands from
becoming
crushed or permanently deformed or compacted by such force. That is, the
strands
remain or return to their upright positions after their upper ends are sand
blasted.
The upright positions are maintained, in part, by the deposited sand layer 25.
Similarly, the strands and the mat 24 hold the sand layer 25 in place.
The sand layer filling may be kept in place and the matted carpet may be
rolled and transported to the site where it is to be spread and used with the
sand
layer. This permits the sand blast treatment to be performed either on the
site of the
game playing field or at any work site or factory area where the application
of the
sand, water and brushing treatments may be more conveniently performed. Thus,
the
treated carpet may be unrolled and installed at the game surface site when
desired
and the sand layer will remain in place and additional sand at the use site
for a sand
filling may not be needed.
As mentioned, the particular pile carpet construction may be varied. However,
an example of a useful carpet for a golf green comprises synthetic grass of
approximately 7,600 deniers, an approximate density of 42 ounces per square
yard,
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and a fiber height of approximately 5/8 inch combined with an underpad of 1/2
inch
to 2 inches in thickness.
Similarly, an example of a fairway portion of a golf course may be in the
range
of approximately 7,600 deniers synthetic grass, an approximate density of 42
to 55
ounces per square yard, with a fiber height of about 5/8 to 2 inches with an
underpad
of at least about one inch thick.
Still another example of the synthetic grass would be a weaving standard in
the range of 3,600 to 10,000 deniers, with 13 to 22 stitches per 3 inches,
3/16 gage
and a density of about 34 to 65 ounces per square yard of material.
The raw beaded polypropylene material is commercially available and can be
molded into underpads of the desired density. By way of example, expanded
polypropylene beads are available from BASF under the trade name of NEOPOLEN
P, which is a trademark of BASF. This material is available at densities of
1.3, 1.9
and 2.8 pounds per cubic foot and is referenced by BASF by its trademark
EPERAN
PP, types PP45, PP30 and LBS 20. When the beads are molded in appropriate slab
molding equipment at times and pressures known to those skilled in the art,
the
resulting pad, produced in the desired thickness, can be made in a density
ranging
from 1.5 to 3 pounds per cubic foot. The molded slab or sheet will have an
open c211
construction. The specific density selected may be varied for specific sport
activities.
For example, a density that has been found satisfactory for a golf green is in
the
range of approximately 2.36 pounds per cubic foot.
The particular technique useful for the sandblast treatment involves
sandblasting under pressure using commercially available sandblast equipment.
A
pressure in the range of 100 to 120 pounds per square inch is preferred but
the
pressure may be varied somewhat, such as a low of about 80 pounds per square
inch. By moving the spray nozzle in back and forth movements across the
surface
of the carpet, the projected spray is sequentially concentrated upon small
portions of
the carpet. The angle of the projected spray may vary but a preferred angle,
which
appears to be effective in a minimum of time, is an angle of about 70 to 80
degrees
relative to the plane of the carpet. The distance of the nozzle from the
strands may
vary, with the equipment operator selecting the optimum distance by visually
observing the shredding action of the spray. An example of the distance may be
in
the range of about 4 to 5 feet, depending upon the speed of movement of the
nozzle
across the carpet.
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The resulting synthetic turf is particularly useful for golf courses, such as
the
green portions, approach portions, Tee-off portions and fairway. The turf
surface also
may be used for tennis courts, football or soccer as well as for other sports
which
utilize grass surfaces. Examples of these are grass hockey, croquet, grass
bowling,
children playground, baseball, and the like. The surface of the artificial
turf produced
by the method herein, closely simulates the feel and action or rebound
produced by
a natural grass surfaced playing field. The completed, matted surface very
closely
simulates the natural grass surtaces required for golf courses and the similar
playing
fields. This turf may also be useful upon a rooftop or patio or deck surface
where the
turf will provide an insulated, waterproof covering.
As illustrated in FIGS. 7 and 9, the turf may be used on golf courses in Tee-
off
places, that is, at locations where the golfer uses a Tee to support the ball
for a drive.
!n those locations, a number of slits 30 may be made in the turf carpet base
sheet
and underpad to receive a manually inserted standard Tee. The slits 30 may be
of
a size to closely receive a Tee 31. To assist the golfer in locating a
particular slit, a
colored mark 32 may be applied, as by a suitable ink or paint mark, on the
surface
of the turf. FIG. 7 shows the turf with the sliver forming mat and FIG. 8
shows the turf
mold without the surface mat. In either case the slots can be used to receive
the
golfer's Tee.
This invention may be further developed within the scope of the following
claims. Accordingly, it is desired that the foregoing description be read as
being
merely illustrative of an operative embodiment of this invention and not in a
strictly
limiting sense.
