U.S. patent application number 09/983091 was filed with the patent office on 2003-05-29 for sports surface.
Invention is credited to Fink, Wilbert E..
Application Number | 20030099787 09/983091 |
Document ID | / |
Family ID | 25529789 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030099787 |
Kind Code |
A1 |
Fink, Wilbert E. |
May 29, 2003 |
Sports surface
Abstract
A sports surface is disclosed with upstanding synthetic yarn
tufts which simulate blades of grass. The blades are widely spaced
and supported by an under layer of high denier, knit-deknit yarn
tufts, without the need of particulate in-fill.
Inventors: |
Fink, Wilbert E.;
(Villanova, PA) |
Correspondence
Address: |
Samuel C. Miller, III
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
25529789 |
Appl. No.: |
09/983091 |
Filed: |
October 23, 2001 |
Current U.S.
Class: |
428/17 |
Current CPC
Class: |
D10B 2505/202 20130101;
D02G 3/445 20130101; E01C 13/08 20130101 |
Class at
Publication: |
428/17 |
International
Class: |
A41G 001/00 |
Claims
I claim:
1. A synthetic sports surface comprising: a flexible backing; a
first yarn tufted at spaced intervals in said backing to provide
first yarn segments extending upwardly from said backing suggestive
of blades of grass; and a second yarn tufted in the intervals
between said first yarn, to provide second yarn segments; wherein
the second yarn segments are a texturized yarn having a length
under tension approximately equal to that of the first yarn
segments; wherein the second yarn segments form a layer having a
lower vertical height than the first yarn segments; and wherein the
second yarn segments are sufficiently numerous and of sufficient
dimension to maintain the first yarn segments in an approximately
vertical orientation in use without requiring the provision of a
particulate fill.
2. The synthetic sports surface of claim 1, wherein the second yarn
is a knit-deknit yarn having a kinked form.
3. The synthetic sports surface of claim 2, wherein the second yarn
has a denier of at least 7000.
4. The synthetic sports surface of claim 1, further comprising a
third yarn tufted in the intervals between the first yarn to
provide third yarn segments, which together with the second yarn
segments form the mat which maintains the first yarn segments in an
approximately vertical orientation.
5. The synthetic sports surface of claim 2, wherein the first,
second and third yarns are of different denier.
6. The synthetic sports surface of claim 1, wherein the first yarn
is a twisted fibrillated, polyethylene tape yarn.
7. The synthetic sports surface of claim 1, wherein the first yarn
segments extend upwardly from the backing from 2 to 3 inches.
8. The synthetic sports surface of claim 1, wherein the first yarn
is made from a thermoplastic having a coefficient of friction lower
than unmodified nylon.
9. The synthetic sports surface of claim 8, wherein the first yarn
is made from a nylon modified with an additive for lowering the
coefficient of friction selected from the group comprising silicone
and Teflon.
10. A game playing surface having first upstanding tufts of
polymeric yarn at least one inch in height, tufted at intervals of
at least 1/2 inch and having second, tufts of knit-deknit yarn
located around the upstanding tufts wherein the upstanding tufts
extend upwardly beyond the second tufts and wherein at least about
half of the yarn face weight is contained in the second tufts.
11. A method of making a sports surface comprising: providing a
carpet tufting machine for producing rows of tufts in a backing
with a separation distance G; feeding a first yarn to the tufting
machine for producing first tufts at line separations no less than
twice G to form tufts of vertical length L; feeding a second,
knit-deknit yarn to the tufting machine for producing second tufts
between said first tufts, said second tufts having a length under
tension approximately equal to the height L; and heat treating the
tufted backing to cause the yarn of the second tufts to tend to
return to their knitted shape, thereby forming a supporting base
for maintaining the first tufts in an approximately vertical
orientation.
12. The method of claim 11, wherein at least about half of the yarn
face weight is contained in the second tufts.
13. The method of claim 12, wherein the denier of the yarn of the
second tufts is at least about 7000.
14. The method of claim 11, wherein the separation between first
tufts in a row is at least about 1/2 inch.
Description
BACKGROUND
FIELD OF THE INVENTION
[0001] The present invention relates to synthetic sports surfaces
and, in particular, synthetic grass turf with upstanding
grass-blade-like tufts of polymer yarn.
BACKGROUND AND OBJECTS OF THE INVENTION
[0002] Synthetic turf was originally developed in response to a
need for a sports playing surface which could overcome some of the
limitations of natural grass turf. The advent of the covered,
multipurpose stadium was the impetus of the original
development.
[0003] The expectation was that the relatively high cost of
building the facility could be recovered by using the facility not
only for football and baseball but also for many other events
(e.g., circuses, rodeos, professional wrestling, basketball,
soccer, track meets, trade shows and even political conventions).
It was quickly recognized that natural turf could not be
practically grown indoors, particularly if it was to be in use a
high percentage of the time. Natural turf could not be grown with
so little sunlight and required relatively long periods of time
between events to allow the natural turf to recover from the abuse
caused by the events. The solution to this problem was a new type
of carpeting designed for multipurpose use with a particular
emphasis on the two major sports (football and baseball) that were
to be the major users of the facility (but not the only users).
[0004] Once it was understood that a carpet could be used for
football and baseball at the major league level and that the carpet
could be used far more frequently then natural turf, a broader
market rapidly developed. Numerous high school and colleges
installed synthetic turf football fields, particularly in the arid
southwest where the hot, dry climate made it very difficult to grow
grass. Prior to that time the norm for the natural grass fields had
been to start a football or baseball season with the field in the
best condition possible, depending on the weather. The field would
gradually deteriorate as it was used. Many football fields had
little or no grass left in the center of the field long before the
last game of the season was played.
[0005] Traditional synthetic turf products employed a nylon
monofilament fiber or a polypropylene fibrillated film fiber in a
relatively dense, low pile height carpet (pile height less than
about one inch). This form of sport surface, although very durable
and long wearing, has fallen out of favor for use in soccer and
football.
[0006] The traditional low pile height carpet is now being replaced
by sports surfaces made of polyethylene (PE) fibrillated film fiber
with a much greater pile height. These sport surfaces are being
tufted in a more open, higher pile height construction with only
1/3 to 1/2 the face weight of fiber. The PE material has an
inherently more slippery surface, than either the polypropylene or
Nylon fiber that it is replacing, and a lower flexural modulus. The
taller PE fiber does not stand straight up, but leans or lies to
one side. The playing action then takes place on the sides of the
fiber as opposed to the tips of the fiber. Playing on the sides of
the more slippery PE fiber reduces the traction level for football
and reduces the frequency of skin burns in soccer.
[0007] The traditional carpet was designed using generally accepted
principles for long wearing durable carpets. This meant that the
pile height was kept below one inch and that the face yarn content
was generally maximized. This construction reduces the movement
between fibers and also the opportunity for dirt or sand to get in
between the fibers. This prolongs the useful life of the carpet by
reducing the movement of the face fiber. It is possible to extend
the useful life of the carpet by minimizing fiber-to-fiber
abrasion, and also fiber abrasion by even more abrasive dirt and
sand.
[0008] Typically, the new carpet construction, involves higher pile
height (greater than 1 inch, and preferably 2 to 3 inch pile
height). The face weight of fiber is reduced by using a wider gauge
tufting machine (3/8 inch to as wide as 3/4 inch tuft separation)
and the stitch rates are designed to further produce an even more
open construction (3 to 4 stitches/inch). The typical face weight
of fiber is in the 30 to 40 oz per square yard range. The use of a
higher pile height and wide gauge tufting machine produces a carpet
with much less fiber density per square yard than has been used in
the past.
[0009] The new high pile height and open construction approach has
two major purposes. First it produces a face fiber that is similar
to natural grass in pile or turf height, and it is close in
appearance to natural grass in the way it leans over and also in
density of the tufts. Second, the open construction and the high
pile height make possible an entirely new approach to the padding.
The carpet is installed on the field and then in-filled to a depth
of 1/4 to 1 inch with rubber, sand or a combination of these
materials. The in-fill material is then brushed with a coarse brush
or a rotary powered brush (similar to a street cleaning brush)
until the in fill material settles down, and into the tufted carpet
(largely out of view). The in-fill is soft which can give the
finished field a feel under foot similar to good natural turf
sod.
[0010] U.S. Pat. No. 5,958,527 to Pr{overscore (e)}vost (Fieldturf)
discloses a synthetic grass turf assembly including upstanding
synthetic ribbons representing grass blades and an in-fill of
particulate material including sand granules and rubber granules.
The upper portion of the ribbons may extend upwardly from 0.25 to 1
inch above the top surface of the in-fill.
[0011] A product marketed as AstroPlay.TM. Synthetic Turf Systems
by Southwest Recreational Industries, Inc., employs a polyethylene
fiber with a pile height of 2.3 inches and a fiber denier of 7600
or 10,000. A 100% rubber filing is said to prevent grinding and
compaction associated with sand in-fills. A secondary layer of
highly texturized nylon 6.6 fibers is provided at the base of the
taller polyethylene turf fiber matrix. The stated purpose of this
secondary layer is to enmesh the initial layer of rubber filling
and thus stabilize the fill.
[0012] While the above-described surfaces with in-fill can provide
an installed carpet that looks and feels more like natural turf
than the dense tight carpet it is replacing, it is not likely to
wear as well. There is the potential for accelerated wear due to
increased fiber-to-fiber abrasion and fiber to sand/rubber
abrasion. Sand fills may be subject to compaction and
contamination. Rubber fills may migrate and degrade.
[0013] A large source of complaints regarding in-filled carpets are
related to defective installation. One source of difficulties may
arise from the need to mix filler (blending rubber and sand) on
site. The in-fill must then be brushed or raked into the carpet.
(This is often done with a powered rotary brush similar to that
used for street cleaning). The brushing can subject the new sports
surface to some significant abuse during the installation process.
The specifications for the in-fill typically spell out a uniform
depth or weight per square yard. However, it is difficult to
achieve uniformity under field conditions and a wide variation in
the depth and/or weight of the in-fill material may occur. Later as
the carpet is used and subjected to heavy rain and snow the in-fill
distribution may change, e.g., an all-sand in-fill may compact and
becomes increasing harder with age; and a blend of sand and rubber
in-fill may tend to stratify by density (the sand sinks and the
rubber comes to the top). Where most or all the rubber in-fill is
located on top, the rubber has a tendency to be washed out of the
carpet where drainage occurs.
[0014] Accordingly, it is an object of the present invention to
provide a sport surface which reduces the limitations and
difficulties associated with conventional sports surfaces.
[0015] It is another object of the present invention to provide a
sports surface which is durable and stable.
[0016] It is another object of the present invention to provide a
sports surface with cushioning firmness and frictional properties
appropriate to the playing of the sport(s) for which the surface is
installed.
[0017] It is another object of the present invention to provide a
grass-like sports surface which is easily and inexpensively
fabricated and installed.
[0018] It is another object of the present invention to provide an
improved sports surface which can be made on conventional tufting
machines.
[0019] These and other objects and features of the invention will
be apparent from the following description and drawings.
SUMMARY OF INVENTION
[0020] The present invention includes a synthetic sports surface
made of a flexible backing tufted with a novel combination of yarns
of different final lengths and textures. A first yarn is tufted at
spaced intervals in said backing to provide first yarn segments
extending upwardly from the backing suggestive of blades of grass.
At least a second type of yarn is tufted in the intervals between
said first yarn, to provide second yarn segments. The second yarn
segments may be of a conventional texturized yarn having a length
under tension approximately equal to that of the first yarn
segments. In the finished surface the second yarn segments return
to a sinusoidal or kinked form and constitute an under layer having
a lower vertical height than the first yarn segments.
[0021] Advantageously, the second yarn segments are sufficiently
numerous and of sufficient dimension and texture so as to maintain
the bases of the first yarn segments in an approximately vertical
orientation without requiring the provision of a particulate
fill.
[0022] In preferred embodiments the second yarn is a conventional
knit-deknit yarn having a kinked form. In more preferred
embodiments, the second yarn has a denier of at least 7000.
[0023] The synthetic sports surface of the present invention may
further include a third yarn tufted in the intervals between the
first and second yarn tufts to provide third yarn segments, which
together with the second yarn segments form an intertwined mat
which maintains the first yarn segments in an approximately
vertical orientation. Third and subsequent yarn segments forming
the intertwined mat may all be knit-deknit textured yarn.
[0024] The first yarn may be a twisted or flat fibrillated,
polyethylene tape. The first yarn segments extend upwardly from the
backing from 1 to 3 inches. In preferred embodiments the first yarn
is made from a thermoplastic having a coefficient of friction lower
than unmodified nylon. The first yarn may be made from a nylon
modified with an additive for lowering the coefficient of friction
selected from the group comprising silicone and Teflon. Various
combinations of yarn types are possible such as first, second and
third yarns of different denier, color, composition and
texture.
[0025] In accordance with the foregoing teachings, a game playing
surface may be provided having first upstanding tufts of polymeric
yarn at least one inch in length and having second tufts of
generally sinusoidally curved yarn located around the upstanding
tufts, the first tufts extending upwardly beyond the second tufts.
At least about half of the yarn face weight may be contained in the
second tufts.
[0026] The present invention also includes a method of making a
sports surface. In accordance with that method, a carpet tufting
machine is used to produce lines of tufts in a backing with a
separation distance S. A first yarn is fed to the tufting machine
for producing first tufts at line separations no less than twice S
to form tufts of vertical length L. A second knit-deknit yarn is
fed to the tufting machine for producing second tufts between the
first tufts, the second tufts having a length under tension
approximately equal to the height L. The tufted backing is then
heat treated to cause the yarn of the second tufts to tend to
return to its knit shape, thereby forming a supporting base for
maintaining the first tufts in an approximately vertical
orientation.
[0027] Using more fiber in place of the more abrasive in-fill and
increasing the fiber density will result in a longer wearing
carpet. Controlling the fiber density and creating more than one
level of yarn within the carpet can adjust the firmness under foot.
Controlling tufting machine gauge, stitch rate and finished pile
height does this. It is also possible to use different combinations
of fiber (different deniers, different colors and polymer type) to
combine the benefits of different fibers within one carpet. The
different fibers can include fibrillated film fiber made from
polyethylene, polypropylene or Nylon resin. The denier of the
tufted yarns can be from 1,850 to 15,000 denier.
[0028] The sports surface construction of a preferred embodiment of
the present invention need not rely on the field installation to
provide in-fill and, thus, would not require that the carpet be
subjected to any rotary brushing. Once installed there is no need
for particulate in-fill. Cushioning is achieved using a dense
combination of multiple pile heights and yarn textures that will
stay in place. The total weight of fiber is inherently much greater
and the life expectancy of the sports surface is improved by
reducing fiber-to-fiber abrasion and fiber to sand/rubber abrasion.
While such a sports surface may be somewhat more expensive
initially due to the greater weight of yarn used, this cost may be
offset by the cost savings associated with simplified installation
and longer life of the sports surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a side elevation of a prior art sports surface
based on FIG. 2 of U.S. Pat. No. 5,958,527;
[0030] FIG. 2 is a side elevation of a prior art sports surface
based on marketing literature;
[0031] FIG. 3 is a stylized side elevation of a two yarn component
embodiment of the present invention;
[0032] FIG. 4 is a stylized side elevation of a three yarn
component embodiment of the present invention;
[0033] FIG. 5 is a illustration of length and shape variations in
knit-deknit yarns;
[0034] FIG. 6 is a side elevation of a four yarn component
embodiment of the present invention employing heavy denier,
knit-deknit yarn for the lower pile height tufts.
DETAILED DESCRIPTION OF THE DRAWINGS
[0035] FIGS. 1 and 2 illustrate various prior art sports surfaces
using in-fill techniques.
[0036] FIG. 1 is a side elevation of a prior art synthetic grass
turf assembly as depicted in FIG. 2 of U.S. Pat. No. 5,958,527. The
grass turf assembly 10 includes a flexible open weave backing 12
and upstanding synthetic ribbons 14, which are tufted in
spaced-apart rows. An in-fill layer 16 is disposed between the
ribbons. The in-fill is made up of sand granules 18 and resilient
rubber granules 20, arranged in layers of different sand-rubber
proportions.
[0037] FIG. 2 is a side elevation of a prior art turf system
(AstroPlay.TM.) as depicted in marketing literature for the
product. The turf system product 20 includes a fiber glass backing
32 and polyethylene fibers 34. A 100% particulate rubber in-fill 36
is used. Texturized nylon fibers 38 are said to stabilize the
fill.
[0038] In contrast to the above, in the present invention a dense
layer of yarn tufts, rather than a particular in-fill, maintains
the tall, grass-blade-like yarn segments in a generally vertical
orientation through a significant portion of the length of such
segments. In preferred embodiments, the dense layer of yarn tufts
is formed from yarn made in accordance with the teachings of
application Ser. No. 09/392,260 to Auguste et al., filed Sep. 9,
1999 entitled "KNIT-DEKNIT YARN AND METHOD AND APPARATUS FOR MAKING
SAME", the contents of which are hereby incorporated by reference
in their entirety.
[0039] The sports surface of the present invention can be made on
conventional carpet tufting machinery. The general tuft arrangement
will now be discussed with reference to the side elevations of
FIGS. 3 and 4 which have been simplified to illustrate the tufting
procedure. The sports surface 100 includes a suitable flexible
backing such as the open weave flexible backing 102 of a weight
sufficient to withstand forces encountered when the surface is in
use and to maintain the sports surface in contact with, for
example, an adhesive coated playing field substrate surface. A
first yarn 104 is tufted at spaced intervals in the backing and
provides generally upwardly extending segments suggestive of blades
of grass. A second yarn 106 (and in the case of the product of FIG.
4, a third yarn 108) provides yarn segments in supporting layer 110
below the tops of the first yarn segments. In preferred
embodiments, the second yarn segments 106 (and third yarn segments
108) are made of a heavy denier knit-deknit yarn and have a length
under tension approximately equal to the length L of the first yarn
segments. The second (and third) yarn segments form a layer having
a vertical height less than L. The second (and third) yarn segments
are sufficiently numerous and of sufficient bulk to maintain the
first yarn segments in an approximately vertical orientation in the
layer without requiring the addition of particulate fill. (Note
that the necessary density is more accurately depicted in FIG. 6).
Upper portions of the first yarn segments may lay over as shown in
the Figures.
[0040] The machines in general use for tufting carpet are capable
of tufting carpet at one pile height. They are adjustable to a
specific pile height, but once set, all thread lines are cut at the
same pile height (cut pile carpet). The present invention overcomes
this tufting machine limitation by threading the tufting machine
with conventional straight yarn in thread line A (FIGS. 3 and 4),
and with knit-deknit textured yarn in thread line B (and C in the
case of FIG. 4). The tufting machine then tufts all thread lines to
the same height by holding all the yarns under tension as the
stitch is made and then cutting the yarn to form the cut pile tuft.
Once the sports surface is coated with either a latex or
polyurethane coating and the carpet is heated to cure the backing
material, the knit-deknit yarn tufts will pull down into their
preset textured patterns. The making, properties and use of such
knit-deknit yarns are described in detail in the above-mentioned
U.S. patent application Ser. No. 09/392,260.
[0041] Conventional tufting machines are characterized by a machine
gauge, i.e. a fixed distance between adjacent needles or tufts in a
row. Table I lists some typical gauges. For standard carpet, there
are preferred ranges of yarn denier which can be tufted at each
gauge. These ranges are also listed in Table I.
1TABLE I Tufting Machine Gauge (distance between needles and/or
tufts in a row in inches) Fraction 1/8 {fraction (3/16)} 1/4
{fraction (5/16)} 3/8 {fraction (7/16)} 1/2 {fraction (9/16)} 5/8
{fraction (11/16)} 3/4 Decimal 0.1250 0.1875 0.2500 0.3125 0.3750
0.4375 0.5000 0.56 0.63 0.69 0.75 Denier Low 1000 1850 1850 3000
4500 5700 7600 7600 7600 7600 7600 Range High 5700 8000 8000 10000
10000 10000 10000 10000 10000 15000 15000
[0042] It will be understood that various combinations of yarn
tufts and tuft spacings can be obtained by feeding the appropriate
yarn types to selected ones of the tufting needles of a
conventional tufting machine. For example, two types of yarn A and
B can be interspersed on a 1/4" gauge machine by feeding grass
blade or straight shag yarn to every other needle and feeding
knit-deknit yarn to the remaining needles. As shown in FIG. 3, the
spacing between adjacent A and B tufts is G (1/4 inch in this
example) and the spacing between adjacent A tufts is twice G (1/2
inch in this example). Where three yarn types A, B and C are used,
the resulting product may be as depicted in FIG. 4. Again, assuming
that the gauge is 1/4 inch, the spacing between adjacent A shag or
blade tufts is now three times G (3/4 inch in this example).
[0043] In a similar fashion, for example, the spacing and amount of
stabilizing second yarn tufts B can be doubled relative to the shag
or blade yarn tufts A by appropriate selection of yarn feeds to the
tufting machine needles. To continue with this example, in a 1/8"
gauge machine, A tufts can be placed at 3/4- intervals. Two B tufts
could be evenly spaced between the A tufts, i.e. at 1/4" and 1/2"
needle locations. The other needles need not be used, or could be
used to tuft a third yarn type C in the spaces between the A and B
yarn segments.
[0044] As shown in Table I, a range of yarn deniers may be used,
the range depending on tuft separation. The ranges in denier are
from 1,000 to 15,000 and above. The face fiber in the thread rows
can vary to include polyethylene, Nylon and polypropylene. The
Nylon and polypropylene yarns, if used, may need to be modified to
lower the coefficient of friction, thus making the yarn more
slippery than typical unmodified Nylon or polypropylene fibers.
Various advantages and properties can be achieved by combining
different types of fibers. For example:
[0045] 1. Nylon fiber is inherently the most resilient of these
fibers it resists compacting under heavy use better than the other
fibers. Nylon has the best general reputation for overall quality
among these fibers. A disadvantage is that it has the highest cost
of these three fibers.
[0046] 2. Polypropylene fiber is the lowest cost of these fibers
and has a long tradition of successful use in sports surfaces. Its
disadvantages are similar to Nylon in that it is more abrasive
(less slippery) than polyethylene fiber.
[0047] 3. Polyethylene fiber is the least abrasive (most slippery)
of these fibers and intermediate in cost. Its durability in sports
surfaces is still somewhat in question as it has been in use less
than one half as long as Nylon or polypropylene in sports surfaces
and even less than that in open construction with sand and rubber
in-filling.
[0048] As noted above, the typical machine available for sports
carpet tufting is capable of cutting only one pile height. In
accordance with a preferred embodiment of the present invention,
different apparent pile heights are achieved using the currently
available tufting machines by cutting all thread lines at the same
pile height in the tufting machine. The yarn is kept under tension
in a stretched out configuration while the cutting is done. When
the cutting is complete the tension is relieved. The straight
non-textured yarn will remain at its full vertical height while the
knit-deknit, heat textured yarn will relax and tend to return to
its textured configuration and a lower vertical height. This effect
is illustrated by example in FIG. 5. The yarn length of the stitch
determines the full vertical height of the non-textured yarn. The
final vertical height of the textured yarn will be determined by
the degree of kinking of the yarn and subsequent heat treatment. In
knit-deknit yarn the yarn has a configuration generally sinusoidal
in shape. This shape is approximately characterizable by an
amplitude A (wave height) and a wavelength .lambda. as explained in
the above-mentioned Auguste et al. patent application. In FIG. 5
segment lengths of 4.lambda. of each of three types of yarn are
shown. As noted in the Figure the pile or vertical height of each
segment is different for each yarn type. By appropriate selection
of .lambda. and A, various vertical heights can be achieved with
yarn segments having the same overall length to create a supporting
layer for the taller blade or shag segments.
[0049] Table II provides some examples of finished pile height for
a three yarn type sports surface such as that shown in FIG. 4:
2 TABLE II Number of Wavelengths Final Pile Height (.lambda.s) per
Segment A Tuft Long(L) = X N/A B Tuft Medium(M) = 50 to 90% of X 2
to 5 C Tuft Short(S) = 10 to 50% of X 4 to 8
[0050] In preferred embodiments of the present invention, the
height X is greater than 1 inch and preferably less than about 3
inches. In more preferred embodiments the height X is from 1.5 inch
to 2.5 inch. The selection of X is dictated to some extent on the
use environment for which the sport surface is designed. Thus, for
example, if the surface is to be used for equestrian activities a
height X of greater than 3 inches might be preferable, whereas the
preferable height X for a miniature golf putting green would be
considerably less.
[0051] An illustration of preferred polymer types and pile heights
are set out in Table III below. In this Table it is assumed that
reduction in frictional force is desirable in the sport(s) for
which the surface is used and/or is desirable to increase the
durability of the sports surface.
3TABLE III Yarn Modified PILE HEIGHT Type Unmodified A B C D PE
Unmodified L M or S M or S M or S PE Modified L M or S M or S M or
S NYLON Unmodified M or S M or S M or S NYLON Modified L M or S M
or S M or S PP Unmodified M or S M or S M or S PP Modified L M or S
M or S M or S
[0052] FIG. 6 is an example of a preferred embodiment of the sports
surface of the present invention. It assumes a machine gauge, G, of
1/4 inch. The yarn is a fibrillated twisted polyethylene yarn of
8000 D. The pile height of L.sub.A of the A yarn is 2 inches. Tufts
of yarn A are separated in the row by a distance of 4.times.G (1"
in the example). The A yarn segments 200 may be twisted or flat.
The A segments are supported in a generally vertical orientation
and cushioning is provided by three other yarn types B, C and D.
The B yarn 202 is an 8000 D knit-deknit polyethylene yarn with a
final pile height of 1.5 inches. The B yarn provides apparent bulk
to the A yarn segments and reduces friction as the A and B yarns
move relative to one another. The C and D yarns are each 8000 D
knit-deknit nylon yarns for improved wear. The amplitude and
.lambda. values of these yarns are selected so that the C and D
yarn segments (204 and 206 respectively) have lower pile heights
(L.sub.C and L.sub.D) than the B yarn segments in the finished
sports surface.
[0053] As shown in FIG. 6, the supporting layer is a dense
intertwined mat of yarn segments B, C and D. In the example given
about 75 % of the face weight of the yarn in the sports surface is
contained in the yarns B, C and D and only about 25 % is contained
in the upstanding segments made of yarn A. In preferred embodiments
an equal or greater yarn weight is contained in the supporting
layer than in the shag or blade yarn segments (A).
[0054] While the invention has been described with reference to
certain examples and preferred embodiments, these should be
regarded as illustrative rather than restrictive. The subject
matter regarded by the inventor as his invention is set forth in
the following claims.
* * * * *