Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02095158 2000-07-20
FIELD OF THE INVENTION
This invention relates to synthetic turf
playing surfaces for various sports, and particularly
those sports where spike (or cleat) bearing shoes are
worn.
BACKGROUND OF THE INVENTION
Synthetic turf fields have been in existence
for approximately twenty years. Sand-filled (top-
dressed) synthetic turf fields have been in existence
~o for about fifteen years. On these sand-filled
synthetic turf fields, the use of elastomeric
underpads have been extensively used to add resiliency
for the impact of the player running or falling on the
top surface thereof. However, most of these synthetic
grasses become very hard and compacted at their top
surface, thereby causing these top surfaces to become
very hard for the athletic shoe spikes or cleats to
properly penetrate in order to maintain the necessary
footing for the various sports.
2o Heavy use and the nature of the synthetic
grass-like turfs cause turf compaction, whereby
uncompacting of the surfaces, or at least keeping
these surfaces at a level of compaction that is
acceptable to the various sports, has been virtually
impossible.
Therefore, no prior art athletic synthetic
turf currently exists, in the present inventor's
knowledge, which is of very low manufacturing cost,
which can be maintained at a reasonably high level of
3o resiliency and compaction, whereby the synthetic turf
can be longer lasting so as to thereby provide more
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CA 02095158 2000-07-20
predictable spike or cleat shoe footing over the life
of the surface.
There is also an unmet need for low cost
sand filled and/or sand and resilient materials for
synthetic grass surfacing, that could be economically
installed for municipal and professional applications.
In Canadian Patent No. 1,182,484, issued on
February 12, 1985 to Mod-Sod Sports Surfaces, there is
disclosed a synthetic turf playing surface comprising
~o at least a firm subsurface, a plurality of grass-like
pile fabric elements, upstanding over the firm
subsurface, and particulate material, laying over the
subsurface and interspersed among the grass-like pile
elements. The length of the pile element is limited
to a range between 0.5 to 2 inches; while the
thickness of the particulate material is limited to a
depth of at least half the length of the pile
elements. Such a synthetic turf construction is
claimed to address the needs of players engaging
2o contact sports such as soccer, football, and the like,
on the playing fields. The playing fields for such
sports must generally meet a number of goals, from the
players' perspective:
(a) the soil must remain substantially stable
throughout the duration of the game. This is
important in view of limiting the problems associated
with mud or dust, namely: time-dependent (variable)
load-bearing properties, ambient air clearness, mud-
gathering on the player's skin, and the like. With
3o such outcomes, the performance of the players will
inevitably decrease as the game
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advances, and more to the point, the likelihood of accidental
physical injuries to the players, typically slipping and falling
repeatedly over ground during the game, will undesirably increase;
(b) yet, the stability-enhancing features of the playing field
should not introduce surface abrasiveness, since as a player falls
on such surfaces, upon running or making sharp turns thereon or
sustaining bodily impact from an opponent's party player, he may
involuntarily inflict upon himself severe rug-burns i.e, may scrape
his skin (there is rapid motion over ground of these players);
(c) preferably, the resiliency of the playing surface should not
be too pronounced, to prevent generating a feeling for the players .
of running or walking across a springy or spongy surface.
Other considerations, less critical to the players but
more important to the playing field managers and maintenance crews
thereof, that should also be met, are as follows;
(d) the durability of the playing surface should be high, since
maintenance costs of such playing fields are labour-intensive and
therefore expensive;
(e) the appearance of the artificial turf should remain attractive
throughout the game, so that the psychological interest of the
paying assistance fans should not be compromised for aesthetic
reasons; and
(f) the manufacturing cost and maintenance cost of this artificial
playing surface should be as low as possible.
In the specification of this Canadian patent No
1,182,484, the upstanding grass-like pile elements are defined as
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'each ccnsisting of a multi-filament yarn, made on a machine 3\8
gauge from polypropylene ribbon 5 mils thick, being slit and
twisted to farm a plurality of thin filaments. Each strand of pile
yarn is said to comprise between 20 to 50 or more individual
filaments. The density of the tufts is said to be variable,
depending upon the weight of the pile yarn and the intended use of
the playing surface. It is stated, in a generally incidental
fashion (and not claimed in the claims), that a stitch rate from
about 3 to 8 stitches per inch of grass-like pile elements having
3\8 gauge, 5 mil thick polypropylene ribbon yarns over a playing
field, would be useful. Such a stitch rate ranging between 3 to 8
stitches per inch, means in other words an average spacing between
two successive grass-like pile elements, ranging between 0,125 of
an inch to 0,333 of an inch.
It is clear from the analysis of the specification and
claims of Canadian patent No 1,182,484 that, contrarily to the
density of the grass-like pile elements, which is commented only in
an incidental fashion, the specific length of the grass-like pile
elements, as well as the specific depth and composition of the top-
dressing particulate material interspersed among the pile elements
over the firm supporting subsurface, are the subject of careful and
detailed developments, indicative of their criticality in the mind
of the inventor in this latter patent.
OBJECTS OF THE INVENTION
The gist of the present invention is therefore to provide
a synthetic turf playing surface that addresses the needs of
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players wearing spike (or cleat)-bearing shoes, particularly for
sports such as soccer, football and golf.
An object of the invention is that this synthetic turf
would be capable of being maintained for very long periods of time
at an at least minimal level of resiliency over the whole life of
the synthetic turf.
An object of the invention is that such large fields of
synthetic turf would require only minimal time for full operative
installation, at very low costs, typically at costs of up to 30 to
50 ~ less than the cost for prior art sand-filled synthetic turf
fields.
An important object of the invention is to provide such
a synthetic turf as above-disclosed, wherein the top-dressing would
be sand-filled with resilient material (such as the particulate
material disclosed in the above-captioned Canadian patent No
1,182,484) so as to be appropriate for use in driving golf balls
off driving ranges as well as for use over tee off areas, thereby
simulating real grass without altering the normal down stroke of
golfers that hit on natural grass.
An object of this invention is that such large synthetic
turf playing surfaces could be installed without secondary
backings, except for golf playing fields (where there is needed a
secondary backing to hold the tufts in for tee off grass).
A further object of the invention is that where tuft bind
is important for such large field applications of synthetic turfs,
a tack coat can be applied to the crushed aggregate surface to bind
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the tufts to it, whereby the need for a secondary backing through
an oven is eliminated.
An object of the invention is that such large synthetic
turf fields have a low cost but, because the carpet rolls be sewn
rather than glued, whereby the synthetic turf seams become more
resistant.
An object of the invention is that the granulometry of
the top-dressing of such large synthetic turf playing surfaces can
be larger than other similar, narrow pile interspacing synthetic
turfs, while still providing a very low abrasion surface.
The general object of the invention is that such large
synthetic turf fields with sand-filled resilient particulate
material-filled topdressing, be of a low density of pile elements,
to allow the sports shoe spikes or cleats to easily penetrate the
surface without sustaining appreciable torsional loads which would
be applied by a sudden bodily weight transfer or change in
direction of the player.
An object of the invention is that such sand-filled
synthetic turf fields use regular washed, undried sand, in view of
still lowering the costs.
A corollary object of the invention is to facilitate
picking of ground-standing golf balls.
A further object of the invention is to improve water
drainage of the synthetic turf surface, because of the backing
porosity.
An object of the invention is that low abrasion of the
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CA 02095158 2000-03-30
synthetic turf golf playing surface is achieved for
driving ranges, because of the ability of the widely
interspersed pile elements to yieldingly bend over
upon sustaining the impact of the ball picker
motorized unit's rotary wheels.
SUi~iARY OF THE INVENTION
A construction in accordance with the
present invention comprises a synthetic surface
comprising a flexible backing member, parallel rows of
~o pile fabric extending upwardly from the backing
member, the rows of pile elements being spaced apart
between 0.75 inch and 1.5 inches, and a top dressing
layer of particulate material interspersed among the
pile elements to a substantially uniform depth at
least half the length of the pile elements.
According to a more specific embodiment of
the invention, there is disclosed a playing surface
for field sports games where the players wear cleat-
bearing shoes, said playing surface comprising: a
zo firm, stable subsurface; a pile fabric, having a
flexible backing and normally upstanding grass-like
pile elements, the length of said pile elements being
substantially uniform and lying in the range from
0.375 to 3 inches, wherein said pile elements further
define an interspacing gap between any two successive
said pile elements (preferably pile element rows), a,
whereby: 0.75 inch <_ a < 1.25 inch; and a top-dressing
layer, comprising sand (preferably a mixture of from
24 to 95 volume percent resilient particles and from 5
so to 75 volume percent fine sand) interspersed among the
pile elements and on the backing to a substantially
uniform depth at least half the length of said pile
elements.
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CA 02095158 2000-03-30
Detailed description of said sand and of
said resilient particles will be found in Canadian
Patent No. 1,182,484.
Preferably, said pile elements are arranged
in generally parallel rows. Advantageously, said
parallel rows of pile elements are arranged in an
irregular pattern, chosen from the group comprising:
standard zigzag, modified zigzag, or step over.
DESCRIPTION OF THE INVENTION
~o The present synthetic turf playing surface
uses ordinary sand (and preferably resilient
particulate) to form a resilient, non-abrasive playing
surface .
The present synthetic turf playing surface
boasts the following features:
- low cost surfacing for sports and other
applications;
- quickly installed surfaces;
- surfaces that can be properly maintained at a level
zo of resiliency that is safe for the players;
- surfaces that have much less torsion-inducing
features for footing of the players, because of lower
density of grass-like pile elements per surface unit;
- low-abrasiveness surfaces for golf driving ranges
on which the golf balls fall; and
- that overall this synthetic grass-like turf playing
surface enhances the playing characteristics of
synthetic fields while lowering the installation
costs.
3o According to the invention, the synthetic
turf is produced according to the general teachings
described in Canadian Patent No. 1,182,484. However,
a major difference is in the interspacing between each
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CA 02095158 2000-03-30
two successive pile elements 6, namely: a spacing gap
ranging between 0.75 to 1.25 inch. Also, the grass-
like pile elements or tufts 6 are now arranged in
rows, which may be regular in shape, or even irregular
(for example, according to the standard zigzag, or
modified zigzag, or step
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over pattern). The irregular patterns are interesting in that the
grass-like appearance looks fuller than it would be if the tuft row
shape would be regular. The pile height would be from 3~8 inch to
3 inch in length.
The reasons for the unusually large distance between the
rows of pile elements (or grass-like tufts), for golf tee off
areas, are the following:
- this widely spaced artificial grass needs to be turned in the
direction that the pile elements where tufted, in order to get the
maximum feel far hitting a golf ball off;
- by turning the grass around when installing at the back of
driving ranges (in long sections), the club head engages more
easily the synthetic surface and in a more normal manner; since the
club head hits a continuous row of grass-like tufts as the club
proceeds along its striking path, it is uninterrupted by the
staggering effect of missing rows when hit across the rows of
grass-like pile elements;
- to allow a golf club head to more easily penetrate through the
grass-like synthetic tufts, during the downswing, in order to more
closely simulate the brushing action-Zike feel of natural grass
such as when hitting down on a golf ball on real grass;
- in known prior art systems, the high density of the synthetic
grasses does not allow the same penetration of the golf club head,
because of the intermeshed tuft yarn multifilaments at the surface
of the synthetic grass;
- by widening the distance between the rows of synthetic pile
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elements, the voided area has been increased (for the club to
effectively penetrate the surface) by at least 50% and up to 80
in relation to an average golf club and for previous synthetic
grasses; this is more similar in density to natural grass fields;
since we have removed a large fraction of the grass-like tufts,
there is a proportional reduction in the resistance to the golf
club head from the impact of a club head;
- by widening the distance between the rows of grass-like tufts,
the voided area has been increased and this allows for a golf tee
to be more easily embedded into the resilient topdressing, without
having to bend the normally upstanding synthetic tufts into the
particulate material topdressing; this prevents the topdressing
compaction, which could eventually lead to difficulties in the
embedding a golf tee into the topdressing with normal physical
force.
The reasons for the unusually large distance between the
rows of synthetic grass-like tufts for large surfaces, such as golf
driving range landing zones, are the following:
to greatly reduce the cost to cover such field to be competitive
with laying sod;
- the ball pickers for golf practice in driving ranges, use a tool
that help them work more efficiently; such tool having many plastic
wheels that squeeze a ground-standing golf ball between them in
order to pick them up; these wheels have the unexpected result of
quickly matting down the grass-like tufts, thereby giving the
entire surface a very green look even though there is a very wide
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gap between the rows of fibres that visually expose the sand.
The large distance between the rows of synthetic tufts
also allows for the use of regular (washed) - but not necessarily
dried - sand, as is the case in existing sand-filled synthetic
grass systems. Using damp or wet sand in standard (prior art)
sand-filled applications is virtually impossible, to properly fill
in the voids between the pile elements, since the sand does not
flow. Tndeed, wet sand clings to the grass-like tufts, and the
result is a very uneven distribution of the tufts as well as uneven
compaction for footing. Since there is substantially more room
between the grass-like tufts, damp sand can fall in between these
rows and add to the necessary weight to hold down the synthetic
surface. The use of regular sand substantially reduces the cost
factor of both the installation and the material cost of the
sanding operation. Less surface brushing is necessary, since
approximately half of the sand will be immediately placed in
between the rows of fibre without any agitation or brushing,
contrarily to what is required with conventional, prior art
systems.
Moreover, the distance between the rows of grass-like
tufts also allows for resurfacing (by changing the topdressing) a
field or area at a later date, when the playing field has become
worn out or overly compacted. Prior art systems of sand-filled
grasses become matted down and the tufts tend to mesh together to
w 25 form a virtually unpenetrable surface that is very hard to add or
remove topdressing to in such applications. Using a power sweeper
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to brush out the topdressing, the surface can be renewed to its new
status, whereby the life of the product is extended. This is
especially important for large field applications, where the
topdressing always has a tendency to time-compact and to become
harder than is necessary, which is to say, to become more dangerous
to the players.
':Raking the topdressing to the required depth for
'particular sports and sport shoes can be effectively done using a
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rake that has teeth interspaced to fit the interspacing pattern of
'~i
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~° 10 s nthetic ile elements
y p (0,75 to 1.25 inch interspacing), where
these rake teeth will easily penetrate between the rows of fibres
'~i.' to loosen up the topdressing if necessary.
The large spacing gap between each successive pair of
synthetic grass rows also allows for the removal of contaminants on
a large field, contaminants brought e.g. from flooding activity. On
standard synthetic grass, the removal of such materials would be
very difficult because of the density of the pile elements. This
y also applies to new golf course or other large applications,
whereby sand from sandstorms, or dust and dirt, could cover an
;:
~ 20 entire surface. This sand and\or dirt would normally contaminate
the existing surface and could not be removed. This new grass
could have the sand removed without any adverse effects.
The spacing of the synthetic tufts also allows us to
install the playing surface without a secondary backing. This
means that the playing surface is water-permeable. It also means
quicker installations at lower costs.
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aecause of the interaction of the shoe spikes or cleats
in various sports, the distance between the rows of fibres allows
the pivoting in any direction without undue resistance from the
density of the tufts of pile fabric. The larger distance between
the rows of segments of mufti-filament yarns (synthetic tufts) also
allows for in situ sewing of the seams with a much larger margin of
error, since there is already a large gap between the rows of tufts
(from 3\4th of an inch to 1.25 inch) . This sewing of the seams
reduces the material cost, and saves valuable time to seam up,
since no adhesive is used as well as no seaming plastic on which
the adhesive is usually spread onto in order to lay the grass into
to seam it up.
Sewing of the seams in this manner also allows for the
immediate stretching of the carpet and the immediate installation
filling of the topdressing, or sand, or resilient materials. There
is no need to wait for the adhesive to set up before stretching the
carpet to remove any wrinkles. If the carpet cannot be sewn or
stretched prior to sand filling, it would be virtually impossible
to adequately and economically remove any wrinkles in the carpet
over a large surface for other sports where players run on this
surface without wrinkles to trip on, if installing without a
secondary backing.
Since sewing the seam and stretching same is possible,
the added benefit is that the selvedge of the grass lays flat under
the synthetic grass, producing a very level seam that can be
immediately top-dressed without needing to trim excess material
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off.
The present synthetic grass would be particularly useful
to, without being limited to, playing fields for soccer and
football matches. Soccer player shoes typically have ground-
s engaging, cylindrical spikes, with a flat discoid free end face.
These shoe spikes having an average diameter ranging between 0,35
to 0,5 inch;, while two successive spikes are spaced by a distance
ranging between 0,75 inch to 1,5 inch.
It is therefore understood that the average diameter of
a soccer or football shoe spike or cleat ranges between
approximately 0,35 inch to 0,5 inch, while the spacing gap between
two such spikes or cleats from a given shoe would range between
0,75 to 1,5 inch. We will recall that the allegedly useful spacing
gap between two successive grass-like pile elements mentioned in
Canadian patent No 1,182, 484 was said to range between 0, 125 to
0,333 inch. Clearly, these numbers indicate that the diameter of
a spike or cleat from a conventional soccer or golf shoe (0,35 to
0,5 inch), will be on average greater than the average spacing gap
(0,125 to 0,333 inch) called for in Canadian patent 1,182,484
between two successive grass-like upstanding pile elements. This
therefore means that, each time such a spike or cleat engages
between two successive pile elements, these successive pile
elements will be subjected to a transversely acting load, i.e. they
will be temporarily forced apart from one another. As this spike
or cleat engages - under the weight load of the walking player -
into the particulate material top-dressing, and sinks toward the
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woven fabric backing - to which is sewn the upstanding pile
elements (segments of mufti-filament yarns), the bottom (root)
portion of these filament yarns will in turn be subjected to a
laterally-outwardly acting shearing force, which will in effect
tend to produce a pile element uprooting force. Such an uprooting
force will eventually produce the undesirable result of tending to
release the upstanding filament yarns from the woven fabric
backing. This uprooting force will be substantially magnified (it
will further bias these upstanding filament yarns into a
translational motion) if the ground-standing player engages into a
pronounced, half-turn pivotal rotation around one foot, as when a
soccer player engages into the so-called back-flip kick (in which
the soccer player pivotally rotates on the ground half a turn on
one upstanding leg, before tilting his whole body spacedly over
ground around a horizontal axis, to bring the foot of his other leg
over his body to strike at an incoming aerial soccer ball exactly
at the time the ball reaches the player, which no doubt requires an
exacting timing which could be hampered by any resistance from the
ground surface pile elements).
Since in the present invention, the spacing gap range
between two successive upstanding filament yarns is always greater
than even the largest diameter of spike or cleat of soccer or golf
shoes, then it follows that the filament yarns should not be
subjected to an uprooting-biasing spreading apart force; therefore,
the durability of the present synthetic turf should be increased. w
It is the present inventor's position that an unexpected,
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particularly advantageous outcome results from selecting an
interspacing gap (which could be as large as 0,75 to 1.50 inch, but
preferably ranging between 0,75 to 1,25 inch, and most preferably
being limited to a range between 0,75 to 1,00 inch) between two
successive rows of turf pile elements according to the present
invention, being greater than the average diameter (0,125 to 0,333
inch) of a sporting shoe spike or cleat, while remaining smaller
than the average distance (including the two successive spikes or
~r;
cleats' diameters) spanned between two successive spikes or cleats
~~'~'! 10 (which could be as large as from 1 to 2.167 inch, but usually
within 1.25 - 1.5 to 2.167 inch range) from a given sporting shoe.
Indeed, it is highly desirable that a shoe spike or cleat diameter
be smaller than the interspacing gap between any two successive
turf pile elements (to prevent pile element unrooting), while at
the same time providing that the distance spanned by two successive
spikes or cleats on such a shoe be greater than said pile element
interspacing gap (to ensure that each said interspacing gap form a
single channel for providing free sliding displacement of a single
spike or cleat through the particulate material topdressing).
It is understood that, when we refer hereinabove to a
s~ playing surface, such a playing surface is for field sports such as
soccer, football, golf, and other such sports. When we refer to a
spike bearing shoe, it is also meant to extend to a cleat-bearing
i
shoe.
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