Note: Descriptions are shown in the official language in which they were submitted.
~1~5~
~ ~094118394 PCT~4/00317
IMPROVED 8URFACES FOR SPORTING AND OTHER A~ lvlllE8
FIELD OF T~E lNv~..-lON
The present invention relates to improved surfaces for
sporting and other activities, and more particularly to
surfaces suitable for equestrian usage, for ball games, such
as football and golf, and other leisure activities.
BACRGROUND OF THE lNv~L.~lON
The natural surface for most equestrian events,
particularly horse jumping, is grass. This is acceptable for
large areas such as race courses where the usage is low and the
grass therefore has time to recover between race meetings.
Where the surface is used more extensively, for example, in
training areas, grass, particularly in the autumn and winter
period, becomes worn and muddy patches appear. These patches
form dusty hard surfaces in dry conditions, and this may lead
to an unacceptable incidence of leg injuries.
As an alternative to grass a number of artificial surfaces
have been used. A first known surface comprises natural wood
fibre and this when new provides a good surface. It is however
a natural material and therefore deteriorates with age. Thus
it has to be replaced and since it is fairly expensive the
replacement cost is high. A second known surface comprises
finely chopped PVC often from used electrical cable insulation
material. This produces a good surface but if laid deeply the
surface is rather loose and the cost of the material is very
high. A third known surface comprises ashes from power
CONFIRMATION COPY
WO94118394 ~ PCT~4/00317 ~
stations. The ashes provide a surface which drains readily
when newly laid in wet weather but in dry conditions the
surface produces dust and becomes compacted becoming hard
especially after prolonged use. An alternative surface is
silica sand which provides a good surface in wet weather
conditions but in dry weather conditions the sand provides an
extremely difficult surface for both jumping and landing
particularly for an equestrian practise ring. The principal
problem of silica sand is that it lacks cohesion therefore
providing a surface which is described as riding too deep and
loose.
The natural surface for most ball games is also grass.
The damage to the turf and soil structure which is caused by
normal usage is intensive and the scale of damage can exceed
the rate of such recovery. This is particularly pronounced in
areas such as goal mouths and centre circles of football
pitches and on golf tees where the turf can be totally
destroyed and the soil severely compacted. In wet weather this
means mud; in dry weather the surface is hard and bumpy.
As an alternative to grass a number of artificial surfaces
have been used. A first known surface, commonly known as hard
porous, comprises water bound grit/sand/clay mixtures of
differing proportions, normally laid over a drainage layer of
coarser material. This surface provides inadequate cushioning
and is too abrasive. The surface material also becomes
destructured and therefore loses permeability. In dry weather
dust is a problem.
~ WO94/18394 ~ PCT~4/00317
A second known surface comprises a synthetic material
designed to imitate real turf. This may be laid on soil or on
a drainage layer of sand or other material. This synthetic
turf may or may not be infilled by a top dressing of sand.
Such a surface is expensive to install and has insufficient
resilience for falling players. Maintenance and repairs are
difficult and costly.
A third known surface comprises a layer of fibres which
are joined together in a loose pattern, laid in a bed of sand
which in turn may be laid on a drainage layer of other
material. Maintenance and repairs are difficult and costly.
Play characteristics are poor.
A fourth known surface comprises a layer of sand or
granular material bound by bitumastic or similar material.
Such a surface has insufficient resilience, is too abrasive and
is difficult and costly to repair and maintain.
It can be seen from the above that where the wear on a
playing surface is severe, the tendency has been to move away
from grass to synthetic surfaces of various kinds. However,
for many reasons, both aesthetic and practical, it would still
be preferable to employ a grass surface if its wearing
properties could be improved.
In British patent No.2184765B there is described and
claimed an all weather surface for equestrian events which has
proved to be highly successful in practice. The surface
comprises a layer of material, the material comprising a
mixture of sand and elongate synthetic fibres, the fibres being
randomly dispersed as separate individual fibres throughout the
WO94118394 1 ~;S ~? ~ 1 PCT~4/00317~
sand, in which the fibres are in the range of 25 to 75 mm in
length and are of uncrimped form. This is still, however, a
wholly synthetic surface.
8UMMARY OF lNV~:N'llON
We have now discovered an improved all weather grass
surface in which the root zone is stabilised with synthetic
fibres, whilst maintaining a structure with good drainage and
aeration, and an improved sub-base for surfaces for sporting
and for other activities.
According to one aspect of the present invention there is
provided an improved grass surface in which the grass is grown
in a layer of material comprising sand, an organic growth
supporting medium and elongate synthetic fibres, the fibres
being randomly dispersed as separate individual fibres in the
material, and having a fibre length from 5mm to 75mm.
In another aspect the invention provides a method of
forming an improved grass surface, which comprises sowing grass
seed in, or applying turf to, a layer of material comprising
sand, an organic growth supporting medium and elongate
synthetic fibres, the fibres being randomly dispersed as
separate individual fibres in the material, and having a length
from 5mm to 75mm.
In a further aspect, the invention provides a growing
material for a grass surface, which comprises sand, an organic
growth supporting medium and elongate synthetic fibres, the
fibres being randomly dispersed as separate individual fibres
~55~ ~
~ W094l1~94 PCT~4/00317
in the growing material, and having a fibre length from 5mm to
75mm.
In a still further aspect the invention provides a sub-
base for a surface for sporting and/or other activities which
comprises a layer of mater~al comprising a mixture of sand, a
particulate or fibrous organic material comprising vegetable
matter and elongate synthetic fibres, the fibres being randomly
dispersed as separate individual fibres in the mixture and
having a fibre length of from 5mm to 75mm.
DET~TT~F!n DE8CRIPTION OF THE lNV~!iL. lON
The components of the material of the present invention
are sand, an organic medium which may be an organic growth
supporting medium or a particulate or fibrous organic material
lS comprising vegetable matter and elongate synthetic fibres.
Sand, suitable for use in the present invention, may be
silica sand, or a sand bonded with a water activated clay.
Sands bonded with an organic liquid activated clay, which are
sometimes used for equestrian surfaces, are in general not
suitable for use in the present invention.
Silica sand is a sand which is relatively clean, is clay
free, and is a well graded sand produced by a wet
classification method. Sand bonded with water activated clay
is a sand in which the sand particles are coated with a water
activated clay which imparts a degree of cohesive strength to
the sand, the extent of the cohesive strength being dependent
on the relative amounts of clay and water.
WO94/18394 ~ ) PCT~4/00317 ~
Preferably the sand particles have an average diameter in
the range of from 100 to 1000 microns.
The organic growth supporting medium may be any suitable
particulate or fibrous material which can be penetrated by
grass roots, but is preferably soil, peat, or a mixture
thereof.
Where soil is used, this is preferably good quality top
soil (screened and/or sterilised) from an approved source. Top
soil provides a base source of nutrients for the grass and
provides moisture retention characteristics.
The peat is preferably from an approved source and
provides an organic content which acts to retain moisture and
provide a source of root promoting bacterial activity in the
root zone.
The organic growth supporting medium is preferably
supplemented with a soil conditioner such as a seaweed based
soil conditioner, for example, Alginure soil improver, which
contains an organic colloid capable of aggregating soil and
intensifying microbial life as well as providing a supply of
trace elements.
Where the organic medium is a particulate or fibrous
organic material comprising vegetable matter, it may also be,
but need not necessarily be, growth supporting. The
particulate or fibrous organic material can for example be
soil, humus, peat or other similar materials derived from the
partial decomposition of vegetable matter.
The elongate synthetic fibres preferably comprise fibres
of a synthetic polymeric material having good resistance to
~ ~094/1~94 21~ 1 PCT~4/00317
environmental conditions. Fibres of polyolefins such as
polyethylene, polypropylene, polybutene or co-polymers thereof
are suitable, together with polyamides such as nylon,
halogenated polymers such as PVC, and other similar materials.
5The fibres can have a fibre length of from 5 to 75mm,
preferably from 10 to 75mm, most preferably from 20 to 40mm.
The average diameter of the fibres is preferably from 50 to 150
denier, for example about 65 denier.
The fibres are preferably polypropylene fibres commonly
referred to as staple fibre.
Preferably the layer of growing material or the sub-base
is from 25 to 150mm thick, most preferably from 50 to 150mm
thick.
It is highly advisable to add to the layer of growing
material a fertiliser at least prior to seeding or planting and
at regular intervals thereafter. An inorganic fertiliser
comprising a balanced supply of nitrogen, phosphorus and
potassium (N, P and K) may be added to the root zone, and for
example a typical pre-seeding fertiliser (5, 7.5, 5) may be
added to the growing material at the mixing stage or sprayed
or sprinkled onto the surface of the layer of growing material
in situ. The fertiliser should be chosen to provide a balanced
supply of the main nutrients required for healthy turf growth.
The ratio of the components of the material will depend
to some extent on the nature of the components chosen. Where
silica sand is used, this preferably comprises from 50 to 95%
by volume most preferably from 60 to 85% by volume of the total
composition. Where sand bonded with water activated clay is
-
WO94/1~94 PCT~4/00317 ~
used, this preferably comprises from 50 to 95 percent by volume
of the total composition.
For the organic growth supporting medium, where top soil
is used, this preferably comprises from 5 to 50% by volume most
preferably from 5 to 20% by volume of the total growing
material composition, and where peat is used this preferably
comprises from 5 to 25% by volume most preferably from 5 to 15%
by volume of the composition.
For the particulate or fibrous organic material component
of the sub-base, where top soil is used, this preferably
comprises from 5 to 50% by volume most preferably from 5 to 20
by volume of the total material composition, and where peat is
used this preferably comprises from 5 to 25% by volume most
preferably from 5 to 15% by volume of the composition.
Where a seaweed based soil conditioner is used this is
preferably applied in an amount of from 50 to lOOg/m2,
preferably about 75g/m2.
The fertiliser is preferably added in an amount of from
10 to 50kg/20 tonnes of total composition by weight, for
example about 25kg/20 tonnes of total composition by weight,
or applied to the layer in situ at a rate of from 50 to
lOOg/m2, preferably about 75g/2.
The percentage of synthetic fibres in the total material
composition is preferably in the range of 0.1 to 0.9% by
weight, most preferably from 0.25 to 0.5% by weight, for
example about 0.4% by weight. In general the percentage of
fibres is at the higher end of the range when silica sand is
~094/1~94 2 ~ PCT~4100317
used, and the lower end of the range when sand bonded with
water activated clay is used.
The fibres may be coloured to conform to the colour of the
growing material and thereby be substantially invisible in use.
The components of the growing material may be mixed in any
order, or simultaneously, to give a substantially homogeneous
mixture. It is important to distribute the fibres evenly and
randomly throughout the mixture, and it has been found in
practice that it is preferable to pre-mix the sand and the
fibres together to obtain an even random dispersion.
In the preparation of an all weather grass surface
according to the invention, turf and top soil are removed to
the required depth and replaced with a layer of the growing
material. A greater depth of turf and top soil may be removed
particularly if the drainage characteristics are poor and the
lower layer may be replaced with a drainage base comprising
clean crushed rock or gravel of appropriate size laid to an
appropriate thickness in accordance with normal drainage
engineering design rules.
The growing material is prepared by taking a quantity
(usually several tonnes) of sand which is in a fairly moist
condition and mixing into the sand a quantity of polypropylene
fibres of the desired length. The sand is preferably selected
to have an average particle size of from lOo to lOoo microns
with particles of rounded to sub-angular shape and is mixed
with the fibres for example in a high intensity mixer of the
contra rotating type which mixes the fibres homogeneously in
a randomly orientated distribution throughout the sand.
WO94/1~94 PCT~4100317 ~
21~51 lo
The random distribution of fibres stabilises the sand
imparting resistance to particle movement under load from
horses hooves etc, thus minimising spreading and hoof
penetration such that a sure footing is obtained. The fibre
length is required to be long enough such that a "crosslinking"
effect is produced thereby preventing the sand from moving
under the pressure of the horses hooves, players feet, or other
users such as wheeled vehicles or implements.
Thus the particle size of the sand and the diameter and
length of the fibres require to be carefully selected within
the preferred ranges to suit the intended use.
Relatively straight fibres need to be used since crimped
fibres are not readily mixed to produce a substantially
"homogeneous" mixture. The length of the fibres is of
particular importance since this provides, in the homogenous
mixture, the crosslinking which is necessary to prevent the
mixture from spreading under the shock loading produced by
horses hooves, players feet, or other users as aforesaid.
Following mixing of the sand and the fibres, this mixture
is further mixed with the organic growth supporting medium and
any soil conditioner and/or fertiliser as appropriate.
Following mixing the growth material is delivered to the
prepared site and laid out to the required depth to give the
desired surface characteristic. The characteristic of the
surface can be altered by the choice of sand particle size and
the percentage of the individual components mixed therewith.
Grass seed is then applied to the layer of growing
material at a rate depending on local conditions, but usually
21~55~
094/1~94 PCT~4100317
11
within the range of 25 to 35 g/m2. In the alternative, the
layer of growing material may be turfed using turf which has
been grown on the same type of sand as used for the growing
material. For this application so-called washed turf is
preferred.
It is found that using the method of the invention, an all
weather grass surface can be prepared which is frce dlaining,
such that even after prolonged periods of heavy rain water will
not stand on the surface. The surface remains relatively dry
and mud free, to provide a firm footing for sporting
activities. In addition, it is found that the surface resists
compaction, and the root zone retains a good structure even
when subjected to heavy wear under wet conditions. This
improves aeration giving the grass ideal growing conditions,
and allows healthy and vigorous root development. The result
is a thicker, more dense cover of grass.
It is found that the preferred grass surfaces of the
invention have greatly improved sheer resistance and stability.
The synthetic fibres act like a mass of relatively
indestructible roots, and provide a rot proof structure to the
root zone. It is believed that the distributed fibres, rather
than the grass roots, take the strain from shocks and pressure
to the system, and prevent the surface from breaking up. Grass
regeneration after winter conditions is very quick because the
roots have remained intact. For the same reason, recovery from
any shallow divotting is very speedy.
The new all weather grass surface is particularly suitable
for sporting areas having high usage, for example equestrian
-
.O94/1~94 ~J ~ 5 ~ 1 PCT~4/00317
12
training areas, the goal mouths and the centre circle of a
football pitch, and golf tees.
In the preparation of a sub-base for a surface for
sporting and other activities the same procedures are adopted
as set out above. The mixture of sand, particulate or fibrous
organic material comprising vegetable matter and elongate
synthetic fibres is laid out on a prepared site to the required
depth as previously described. A so-called "paving" may then
be laid on the thus formed sub-base, which, in the case of for
example a tennis court or a footpath, can be a clay paving.
Other suitable paving materials may of course also be used.
The reader's attention is directed to all papers and
documents which are filed concurrently with this specification
and which are open to public inspection with this
specification, and the contents of all such papers and
documents are incorporated herein by reference.
All the features disclosed in this specification
(including any accompanying claims, abstract and drawings),
and/or all of the steps or any method or process so disclosed,
may be combined in any combination, except combinations where
at least some of such features and/or steps are mutually
exclusive.
Each feature disclosed in this specification (including
any accompanying claims, abstract and drawings), may be
replaced by alternative features serving the same, equivalent
or similar purpose, unless expressly stated otherwise. Thus,
unless expressly stated otherwise, each feature disclosed is
~ 094118394 21~ ~ 5 5 1 PCT~P94/00317
13
one example only of a generic series of equivalent or similar
features.
