Note: Descriptions are shown in the official language in which they were submitted.
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"SYNTHETIC TURF"
This invention is directed toward improved
synthetic grass surfaces. The invention is more
particularly directed toward improved, synthetic grass
sports surfaces. The invention is also directed toward a
method of making an improved synthetic grass sports
surface, and an apparatus for carrying out the method.
This application is a divisional application of
Canadian patent application Serial No. 2,218,314, filed
October 16, 1997.
Synthetic grass sports surfaces are well known.
They are used to replace natural grass surfaces which do
not stand up well to wear and which require a great deal
of maintenance. Also, natural grass surfaces do not grow
well in partly or fully enclosed sports stadiums. The
synthetic grass surfaces stand up to wear much better
than the natural grass surfaces, do not require as much
maintenance, and can be used in closed stadiums. Some
synthetic grass surfaces comprise rows of strips or
ribbons of synthetic material, extending vertically from
a backing mat with particulate material infilled in
between the ribbons on the mat. The ribbons of synthetic
material usually extend a short distance above the layer
of particulate material and represent blades of grass.
The particulate material usually comprises sand, as shown
by way of example in U. S. Patents 3,995,079, 1976, Haas,
Jr. and 4,389,435, 1983, Haas, Jr., but can comprise
other materials or a mixture of sand and other materials,
as shown in U. S. Patent 4,337,283, 1982, Haas, Jr., by
way of example. The particulate material provides
resiliency to the synthetic grass surfaces, and the
surfaces are often laid on a resilient pad to provide
further resiliency to the surfaces.
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The known sand-filled synthetic grass sports
surfaces have some disadvantages. The surfaces usually
become hard after extended use because the sand, between
the rows of ribbons, becomes compacted. Compacting
occurs, in part, because the rows of ribbons are quite
close together, and the sand cannot spread a great deal
laterally during use. Compacting also occurs, in part,
because the close spacing of the ribbon rows traps
debris, worn and torn off the ribbons, in the sand, even
when the particulate material comprises rounded sand
particles. With an increase in compaction, the surface
becomes progressively harder and less resilient. The
performance of the surface is shortened, and it has
lessened playing qualities. The surfaces also become
harder after use because the resilient pads, if used,
slowly collapse under use, becoming denser. Removal and
replacement of the compacted particulate material, or
even loosening of it, is difficult because of the close
spacing of the rows of ribbons. It can require expensive
equipment to remove and replace the compacted particulate
material, or even loosen it, and this adds to the cost of
maintaining the surface.
Another problem with the known synthetic grass
sport surfaces is the problem of drainage. Water flow
through the surfaces has generally been slow. The
ribbons are usually attached to the mat by tufting them
through the mat, and then the bottom of the mat is coated
with a bonding layer to bond the ends of the ribbons to
the mat. The bonding layer is non-porous. To provide
adequate porosity, the coated mat is punctured to provide
holes. However, the particulate material often flows
into these holes, plugging them up and thus reducing the
drainage qualities of the surface. The loss of the
particulate material into and through the holes also
requires that it be replaced on top of the mat, adding to
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the cost of maintaining these surfaces. Compaction of
the surface also inhibits drainage.
The known synthetic surfaces also have
relatively poor playing qualities. When infilled with
rounded sand particles more rounded than angular, because
the rounded particles are thought to compact less and
cause less abrasion, the surface can become too slippery,
particularly when the ribbons are only slightly longer
than the thickness of the layer of particulate material.
Also, the closely spaced fine ribbons, if penetrated, can
tightly grip the cleats and do not tear as easily as
grass, thus making release of the cleats more difficult
and making playing on the surface more difficult and
dangerous than when playing on grass. If a player's
cleats do not release easily, he could injure his leg,
ankle, or knee. It has also been found that if the
athlete's cleat penetrates a seam area, the chances of
the shoe not being released or allowed to pivot is much
greater.
The known synthetic surfaces, with closely
spaced rows of ribbons, also increase the speed of a
rolling ball from the speed with which it rolls on
natural grass. The closely spaced ribbons create an
almost solid, low resistance surface for a rolling ball,
thus adversely affecting the playing qualities of the
surface. If the surfaces are employed with a resilient
base pad, balls bounce more on the surfaces than on
grass, subtly changing the nature of the game. The low
resistance surface also makes it more slippery for tennis
players.
The known surfaces have other disadvantages.
Usually the ribbons employed are quite narrow, and they
can curl creating an appearance unlike grass. The narrow
ribbons also abrade easier, creating debris that can
increase compaction of the surface. The close spacing of
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the ribbon rows also causes skin abrasion on players
falling or sliding on the surfaces.
It is the purpose of the present invention to
provide an improved synthetic grass sports surface that
is more resilient, and remains more resilient for a
longer period of time, than known synthetic grass
surfaces .
It is another purpose of the present invention
to provide improved synthetic grass sports surfaces that
have improved drainage properties and improved playing
properties.
It is yet another purpose of the present
invention to provide improved synthetic playing surfaces
that are relatively less expensive to manufacture, to
install, and particularly to maintain.
It is another purpose of the present invention
to provide a method for making one embodiment of the
present invention having improved drainage properties and
a machine for carrying out the method.
In accordance with an embodiment of the present
invention, the improved synthetic grass surface is
constructed to have improved drainage qualities provided
by the manner and pattern in which the ribbons are
attached. In accordance with the present invention, the
rows of ribbons are attached by strips of bonding
material applied to the back of the mat. The strips of
bonding material are spaced apart and leave areas of the
mat uncoated. Since the mat in this embodiment is
porous, the uncoated areas provide for excellent
drainage. Providing a surface with a relatively large
spacing between the rows of ribbons allows strips of
bonding material to be provided with relatively wide
porous areas of mat between them. The invention is also
directed to an apparatus to simply and easily apply the
bonding strips to the backing.
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Improved drainage properties are also obtained
by having at least one of the backing layers, a needle
punched fabric, provided with fuzzy fibers on one or both
surfaces. The fuzzy fibers improve the drainage
qualities of the backing layer, and thus of the surface,
since the fuzzy fiber ends wick away the moisture.
The invention is also particularly directed
toward a synthetic grass surface having a flexible,
porous, backing layer and spaced rows of ribbons,
representing blades of grass, projecting through and
upwardly from the backing layer. Strips of bonding
material on the back of the backing layer overlie the
tufted rows of ribbons, one strip of bonding material
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overlying one row of ribbon, to bond the ribbons to the
backing layer. The rows of bonding material are spaced
apart to provide non-coated areas of backing material to
improve overall drainage.
The invention is also directed toward a method
of manufacturing a synthetic grass surface comprising the
steps of tufting ribbons of synthetic material in spaced-
apart rows in a porous backing member and applying
spaced-apart strips of coating material to the back of
the backing member. Each strip of coating material
covers one row of ribbons to bond the ribbons to the
backing member. The strips of coating material are
spaced apart to leave narrow areas of the backing member
uncovered to promote increased drainage.
The invention is further particularly directed
toward an apparatus for applying coating material to the
back of a backing member tufted from behind with rows of
synthetic ribbons representing grass blades. The
apparatus has a support table for supporting the backing
member for longitudinal movement along the table and a
comb-like device overlying the table and having spaced-
apart fingers positioned to cover areas of the backing
member between the rows of ribbons. Each finger is
located between two adjacent rows of ribbons. Means are
provided for placing coating material on the back of the
backing member across its width as it is moved over the
support table and beneath the device. A doctor blade
adjacent the coating station spreads the coating material
and presses it against the backing member between the
fingers to form strips, each strip covering a row to bond
the rows of ribbons to the backing while leaving the
areas of the backing uncoated.
Having thus generally described the nature of
the invention, reference will now be made to the
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accompanying drawings, showing by way of illustration, a
preferred embodiment thereof, and in which:
Fig. 1 is a cross-section view of a surface of
the present invention;
Fig. 2 is a view similar to Fig. 1, showing the
free ribbon ends in a natural lying down position;
Fig. 3 is a side view of the coating machine;
Fig. 4 is a cross-section view taken along line
4-4 in Fig. 3;
Fig. 5 is a top view of the machine;
Fig. 6 is an enlarged top view of a portion of
the machine shown in Fig. 5;
Fig. 7 is a fragmentary perspective view of the
backing member after it has been coated;
Fig. 8 is an exploded, end view of a seam in
the surface, the seam forming a marking line; and
Fig. 9 is an assembled view of the seam of Fig.
8.
The synthetic grass surface 1 of the present
invention, as shown in Fig. l, has a thin, flexible,
backing member 3 with parallel rows 5 of strips or
ribbons 7 projecting upwardly from the backing member 3.
A relatively thick layer 9 of infilled particulate
material is provided on the backing member 3 supporting
the ribbons 7 in a relatively upright position on the
backing member 3.
The flexible, backing member 3 can, as shown,
comprise two backing layers 11, 13. The bottom layer 11
can be a woven or needle punched polypropylene fabric.
The top layer 13 can be also be a woven or needle punched
polypropylene fabric. The plastic strips or ribbons 7
are tufted through the backing member 3 as shown in Fig.
2, passing through both layers.
While the backing member 3 has been shown as
comprising two layers, it can also be formed from one
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layer or more. One or more of the layers in the backing
member 3 can be a needle punched woven fabric to provide
better drainage, the fabric being relatively thick if
used only as a single layer. At least one of the layers
11 in the backing member 3 can be needle punched with
synthetic, fuzzy fibers (flw) 15, as shown in Fig. 2, to
provide means to wick moisture through the layer. The
fuzzy fibers further improve drainage of the surface.
The ribbons 7 are made from suitable synthetic
plastic material which is extruded in a strip that is
relatively wide and thin. The preferred plastic material
is polyethylene which is soft and has good abrasion
resistance. However, polypropylene can also be used in
making the ribbons. The strip can have a width ranging
between one-quarter inch and one inch but is preferably
around one-half inch wide. The thickness of the strip
ranges between 65 microns and 150 microns. The ribbons 7
are cut from the extruded strip and fastened by tufting
in the backing member 3 in parallel rows 5. Between 2 to
8 tufts are formed per inch of row with 4 tufts per inch
being preferable. The strips are mechanically
fibrillated or split to approximately one-eighth of an
inch or more.
The fibrillation, which is done mechanically
during the manufacturing of the strip, provides a ribbon
which resembles a hair net, that is, the resulting fibers
are interconnected.
The spacing of the rows of ribbons is dependent
on the activity to be performed on the field. For
instance, cleats worn on the shoes of athletes for
different sports have a spacing on the average of about
three-quarters of an inch. Football cleats or soccer
cleats may be wider than baseball cleats. The spacing is
in relation to the type of sport to be played on the
field and is a consequence of the spacing of the cleats
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on the shoes of the players. Likewise, in sports such as
horse racing, it is contemplated that much wider spacing
will be required between the rows to accommodate the
wider hooves of the horses. Thus, it is contemplated
that for horse racing, a spacing between the rows of up
to 2-1/4. inches would be necessary with a proportionally
longer ribbon of up to 5 inches.
Relatively wide ribbons, at least one-half inch
wide, are preferred because the wider ribbons do not curl
as easily as narrower ribbons and resist wear and
abrasion better. The wider ribbons 7 also cover more of
the particulate material when they lie over, trapping the
infill material as shown in Fig. 2. At least the free
ends of the ribbons 7, above the particulate material
layer 9, are fibrillated to provide a denser appearing
pile. Once the synthetic grass has been installed and
the infill has been placed, the ends of the ribbons can
be further fibrillated by using a steel brush or other
mechanical fibrillating means.
It is also contemplated to mix the ribbons in
terms of their thickness. For instance, depending on the
type of field required, i.e., a field where the ball will
roll more slowly than others, stiffer and softer ribbons
could be mixed. Stiffer ribbons would tend to have more
memory and, therefore, return the ribbons back to an
upright position, relatively speaking. Examples of such
a mix would be a thick ribbon having a 11,000 denier with
possibly 100 to 120 micron thickness. A softer ribbon
would have from 5,700 denier and an 80 micron thickness.
Any combination of these more rigid and softer ribbons
would be determined by the particular requirements of the
playing field. The ratio of stiff to soft ribbons may be
1:1. These stiff and soft ribbons may be alternating or
part of the same tuft.
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In accordance with the present invention, the
rows 5 of ribbons 7 are spaced apart a distance "A" that
ranges between five-eighths and two and one-quarter
inches apart. The row spacing depends on the end use of
the surface, a smaller spacing being used for a surface
that is used for less physical activity, such as a golf
green for example, and a larger spacing being used where
more physical activity is encountered, such as a race
track for horses, for example.
The relatively wide spacing between the rows of
ribbons has several advantages. The wide spacing reduces
the tendency of the surface to compact. If the tendency
to compact is reduced, drainage of the surface is
improved. The wide spacing also reduces the amount of
material required for the ribbons. The wide spacing
further enhances the playing qualities of the surface. A
player playing on the surface is able to obtain better
traction because the player's cleats are better able to
dig into the particulate material between the ribbon
rows. At the same time, the cleats release better
because there is more room between the rows to move the
particulate material during release. The wide spacing
also makes it easier to loosen, clean, and even replace
the particulate material. There is room between the rows
to insert an air wand into the material to gently loosen
it and raise it up slightly. The loosened, raised
material can be collected, cleaned of dirt and debris,
and returned onto the backing member. The life of the
surface is extended and thus replacement costs are
reduced. The wide spacing also makes it easier to sew
adjacent surface sections together without creating bulky
seams since more space is provided for the seam.
The length of the ribbons is also an important
feature of the invention. The length "L" of the ribbons
7, that is, the distance from the backing member 3 to
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their free ends 7, is at least twice the spacing "A"
between the rows 5 of ribbons and preferably between
three and six times the spacing "A" . The length "L" of
the ribbons ranges between three-quarters of an inch and
five inches, with the shorter ribbons being used with the
surface having the smaller row spacing and the larger
ribbons being used with the larger row spacing. The
relatively longer ribbons, as compared with those used in
the prior art, allow for the use of a thicker infill
layer 9, thus providing a more resilient surface without
requiring an underpad. The expense of an underpad and
the cost involved in installing it is thus eliminated. A
thicker infill layer 9 promotes better drainage by
creating a higher level of water, thereby creating a
higher pressure head from water on the top of the
surface. The longer ribbons can also provide more free
ribbon above the infill even if the infill is thicker,
the free ribbon providing more protection from the sand
and other particulate material for players falling on the
surface and minimizing abrasion. The ribbons can project
anywhere from one-quarter inch to one inch above the
infill. The thickness of the infill layer can range
between one and four inches depending on the end use of
the surface. The layer generally has a thickness "T" of
about two-thirds the length "L" of the ribbons.
The layer 9 of particulate material preferably
comprises a mixture of a hard sand, such as silica, and
cryogenically ground crumb rubber. Cryogenically ground
crumb rubber is preferred because the particles are
rounder, minimizing abrasion and also lessening
compaction. The less angular rubber particles also wet
easier thereby aiding drainage. Further, the particles
are also less likely to float away if the surface is
flooded since microscopic air bubbles are not as readily
adhered to the rounded particles. The particles can
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range in size between four mesh and seventy mesh, but
preferably are between fifteen and thirty mesh for sports
where abrasion of the players contacting the surface is a
factor and between four and thirty mesh where abrasion is
not a factor. The silica sand could be replaced by
graded small rocks, hard and heavy granulated plastics,
or other hard sand. The cryogenically ground crumb
rubber could be replaced by other resilient materials,
such as cork, styrene, epdm rubber, neoprene, or other
similar materials, if the particulate shape equates the
shape of cryogenically ground rubber. In some cases,
some or all of the resilient material could be replaced
by other materials which perform specific roles. An
example would be using perlite to replace the resilient
material so as to reduce compaction and possibly absorb
moisture. '
The mix of sand and resilient material can vary
depending on the end use of the surface. More rubber is
used if the surface requires more resiliency. In
relatively thick surfaces the layer 9 of particulate
material can be divided in sub-layers with the lower sub
layer 17 adjacent the backing member 3, as shown in Fig.
2, having smaller particles and the upper sub-layer 19
having larger particles to initiate good drainage. The
particles in the lower sub-layer 17 could be mainly sand
with a mesh size of about forty to seventy mesh. The
upper sub-layer 19 would comprise larger particles of
sand combined with the rubber particles. Using mainly,
or only, sand in the lower layer reduces the cost of the
surface.
The surface 1 is manufactured by attaching the
ribbons 7 by tufting them through the backing member 3 in
rows 5 that are spaced between five-eighths and two and
one-half inches apart, there being 2 to 8 ribbons per
inch in each row. Once the ribbons 7 are tufted in
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place, the backing member 3 can be coated on its back
side to adhere the ribbons to the backing member. The
entire backing member can be coated.
Preferably, however, in one embodiment of this
invention, using a porous backing member, only portions
of the backing member are coated to provide better
drainage and to reduce costs. In accordance with this
embodiment, the backing member 3, after the ribbons 7
have tufted in place, is passed, upside down, through any
standard carpet coating machine. The coating machine 31,
as shown schematically in Figs. 3, 4, 5 and 6, has a
support plate 33 to support the tufted backing member 3
of the surface 1 as it is being passed through the
machine. Means, not shown, are provided for moving the
member 3 across the support plate 33 from one side to the
other, as shown by the arrow 34 in Fig. 3. As the member
3 moves across the support plate 33, it passes under a
comb-like device 35 having an array of parallel fingers
37 which rest on top of the bottom of the backing member
3, against the support plate 33. The fingers 37 are
adjustable as to the spacing between them, and are
adjusted to place one finger between each pair of
adjacent rows 5 of ribbon on the backing member 3. A
doctor blade 39 is located above the fingers 37 nearer
the front of the fingers 37 than their back. Applicator
means 40 are provided for applying coating material "M"
onto the comb-like device 35, across its width, just in
front of the doctor blade 39. As the member 3 is moved
to the right, as shown in Fig. 3, under the device 35,
the coating material "M" is carried with it to the doctor
blade 39 where it is spread and laid down against the
narrow areas 41 of the backing member 3 that are not
covered by the fingers 37. These areas 41 contain the
ribbon rows 5, and the ribbon ends in these rows are
covered with the coating material "M" to adhere the
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ribbons 7 to the backing member 3. The fingers 37
prevent coating material "M" from covering the narrow
areas 43 of the backing member 3 adjacent the ribbon rows
5. As the member 3 moves away from under the fingers 37,
the back of the member 3, as shown in Fig. 7, has strips
45 of coating material "M" covering the ribbon rows 5,
but adjacent areas 43 of backing member 3 are uncovered,
because of the fingers, to provide a very porous surface
which easily drains. The coating applied by the coating
machine is much less in quantity than that required to
coat the entire backing member, and thus additional
savings in material are provided making the surface less
expensive.
While one form of applying the coating in
strips on the rows of ribbons has been described, the
coating could be applied by other means. For example, a
series of nozzles could apply thin lines of coatings onto
the rows of ribbons and a doctor blade could flatten the
lines of coating onto the back of the mat while leaving
relative wide, elongated areas of the backing member
uncoated and thus capable of fast drainage. Coating
rolls of different diameters could also be used to apply
the coating.
In accordance with another embodiment of the
invention, lines for marking out a playing area can be
formed in the surface by joining the adjacent edges of
surface sections with a specific seam. As shown in Fig.
8, a seam band 51 is placed under the adjoining but
spaced-apart edges 53, 55 of adjacent surface sections
57, 59 respectively to be joined. The seam band 51 has
rows 61 of tufted ribbons 63 in its central section 65
but no ribbons on its wide side sections 67, 69. The
central section 65 is located between the edges 53, 55 of
the surface sections 57, 59, and the tufted ribbons 63 in
the central section 65 can have a different colour and/or
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a different height from the ribbons 7' in the surface
sections 57, 59 to form a line 71 for marking a playing
field. The wide side sections 67, 69 of the seam band 51
can be needle punched to form fuzzy fabric. Adhesive "A"
is applied on top of the wide side sections 67, 69 to
adhere the overlapping surface sections 57, 59 to it.
The fuzzy fabric enhances the joining of the seam band 51
to the surface sections 57, 59 by the adhesive. The seam
band 51 can be coated on its back with coating material
"M" just under the central section 65 but preferably
under the side sections 67, 69 as well. This prevents
the adhesive "A" used in the seam from bleeding through
the band 51 and perhaps adhering onto the substrate.
When the band 51 has been attached to the surface
sections 57, 59, as shown in Fig. 9, seaming them
together, the ribbons 63, because of their different
appearance from the ribbons 7' in the surface sections
57, 59, define a playing line 71.
In another embodiment of the invention, the
surface could be employed with long ribbons, at least
four and one-half inches in length, and the particulate
layer could be as thick as the ribbons are long. This
surface could be used as a growing surface. The
particulate material could employ materials that enhance
crop growing, such as material that retains moisture for
the plants, and material that allows for strong plant
root development. The enhancement materials can form one
or more sub-layers in the particulate layer. In some
cases, the enhancement materials may have a specific
gravity less than water, and having this material in
bottom sub-layers under the top layer ensures that it
stays in place and is not carried by water. The surface
would be particularly useful in areas that are arid.
Irrigation pipes could be laid right in the layer of
particulate material. The porosity of the backing layer
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could be designed to retain moisture in the material to
promote plant growth. The ribbons would minimize the
amount of particulate material that might be blown away
in windy areas.
A sports field using a high pile of ribbon, a
thick layer of particulate material including
cryogenically ground rubber, could be utilized to support
the planting of natural grass with the roots of the grass
extending in the particulate material.
