Note: Descriptions are shown in the official language in which they were submitted.
3iB2
Back-Jround of the Invention
As is well known, the construction of a good quality all
weather grass playing surface and its maintenance for rec-
reational purposes and active sports, such as soccer and foot-
ball, has been a problem of long standing.
One of the more recent attempts at: resolving ~his l~roblc
has resulted in use of an artificial surface. These sur-
faces have recluced the recJular maintel~ ce re~uired but the
eost to repair for wear and tear generally exceeds the cost
oE mai~tenance of a natural grass field. Further, -the play-
ing conditions immediately over a synthetic surface are far
less tolerable than over a grass surface since the synthetic
and its supp~rting surface retain heat. All synthetic sur-
faces have suffered from the inability to provide adequate
drainage. In general, these synthetic surfaces arc no~
completely acceptable to player associations since they have
a higher incident of injury than that e~xerpienced on a goo(l
quality na-tural grass surface.
In general, the factors which must be considered in
designing and maintainin-3 a playing surface include the needs
of the player utilizing the surface, the requirements of the
agrologists in plant growth and maintenclnce and the correct
application of acknowledged engineering principles. The
finished product will experience variable and sometimes un-
predictable environlllental consid~?ra-tions. The total growth
ar.d maintenance s~stem must have a f~exibility built into it
such that the variables may be accommodated.
The selected grass used must be of a type which has good
wear ability characteristics, but also must satis~y the cli-
,~
3~82
matic conditions in the locality wherc it is to be uscd. Once
the selection has been made as to the seed mixture, the plan-t
itself must be established and must be capable of vigorous
growth to provide for rapid self-repair following user
dama~e. ~he grass mus-t be well anchored in i-ts growing med-
ium to minimize tear out by the participant and it should
provide a uniform surEace throughout the applicable season.
It is desirable that the quality of the surface be con-
stant for the entire g~ras~ed area and that tlle surEace be
able to be used extensively even under adverse climatic
conditions. This desire obviously requires the surface be
free from an accumulation of water and Erost an~ that the
watering and fertilization applica-tion do not interrupt use.
Tile ~round conditions should be firm and yet provide a cushion
normal for a well established turf which experience has shown
to minimize player injuries.
It is further desirable that the playing area should be
free from obstructions such as sprinklers or the like and
reasonably level throughout its entirety.
~laintenance pcrsonnel require a m-ininlization of the oper-
ational function needed to maintain the surface while re-
taining a good quality grass condition.
Prior Art
In general, grass surfaces heretofore provided can be
c3enerally classified as the soil turf Eield, the modified
sand field and the mem4rane sand field.
The soil-turf playing surface is a classical method
wherein the qrowillg medium is a natural good quality soil
~''13~
placed over a granular material. Drainage is provided by
providing a crown to th;e surface and suhsurface drains.
Irrigation is applied to -the surface by conventional methods.
Fertilizer is generally applied to the surface through mech-
anical spreading or through sprinkler applied liquid fertilizer.
These soiL-turf fields in general do not stand up to more
than minimal use and require heavy maintenance. In wet
locations, these fields are consistently muddy due to poor
drainage characteristics whereas in dry conditions, ~he grass
shows the affect of tile heat and in general are no-t well
nourished. In hot loc~tions, surface applied irrigation exp-
eriences large evapora~ion losses to atmosphere and a build
up of water borne impu~ities at the surface damages the grass.
Surface compaction cau~ed by the natural rainfall, surface
irrigation and player use generally renders the drainage system
ineffective. The compaction also prevents oxygen from reachillg
the roots and inhibits growth. The surface runoff attempted by
crowning the field is not rapid enough even under minimal rain-
fall. The grass plants are generally surface huggin~ because
of the fact tllat tlle water, nutrients alld oxyc~en required are
all located there. In this weakened state, the grass may be
easily pulled out during normal play, creating bare areas
which are not readily self-repairable and require extensive
resodding. A weakened grass is more susceptible -to clisease
and infestation problems. This method does not lend itself
to soil warming techniques since the melted frost and snow
a~]gravates the lac~ of drainage and turns the surface to mud.
In cold climates, the surface freezes rapidly due to the high
silt content ancl its moisture retaininq characteristics.
,i 3
The inadequ.lc~ vf the soil turf method has led to
developmellt of both the modified sand and the memb~ane sand
methods. In each of these cases, the primary attempt is -to
overcome the drainage and compac~ion problem.
The modified sand method uses two classifica-tions of sand
as a growing medium, i.e. a bottom layer Gf natural clear
sand while the top surface is a mixture of sand an~ organics.
Drainage is provided by an underlyin(J grid ~nd irrk~ation and
fertilizers are surface supplied by tllc s.~ e mealls .1; lor
soil turf method.
The modified sand method has essentially uncon-trolled
drainage through the sand layer and therefore the modified
surface zone is essential to avoid drought conditions at
the level of plant growth. Although the addition of organics
lS retain the nutified moisture and oxygen relation in the sur-
face layer for good plant growth, the oryanics also re-tain
water, slow down the drainage rate and result in a soft and
slippery surface. The grass is surface hugging for the same
reasons as the soil turf field. A major problem in this method
is lack of lony term control. The surface zone, although -
selected for pro~er liquid retention charac-teris-tics at the time
of design, is subject to normal decomposition and leeching of
the organics resulting in their loss through the drainage
system. Further, the decomposition of the oryanic material
consumes nitrogen necessary for strong healthy growth. The
eventual replacement of the organics is impossible without
entire replacement of the surface layer, an expense similar to
resodding for the soil-turf field. The effectiveness of soil
warming techniques to remove snow and frost are inhibited by
the lack of the systems ability to continuously replace lost
3~2
moisture caused b~ the cold weather drying effect. The
surface condition results in freezing condi-tions similar -to .
the soil'turf field.
The membrane sand method is the result of efforts to
capitalize on the principles o~ hydroponic growth, which has
proven to be totally successful with a controlled propagation
of plants in a nursery environinent. Althouc3h variations ex,ist,
in c~eneral, the membrane sand method comprises of a natural
sand growing medium which is completel~y isolated by ~n imper-
vious membrane to ~rovide a contained reservoir of w~-ter and
isolate the area. Over the membrane and within -the isolated
area is placed the pipe or conduit system which is -tiec~ into
a drainage discharge system located outside the field area to
allow removal of e~cess water. Over and around the pipes are
placed sand and the regulation of the excess drainage discharge
is provided by some form of weir like action or ~umps or both.
These systems have not been adec~uately designed to properly
handle sub-surface apu:Lied irrigation or fertilizer and gen-
erally those installed use surface sprinkler systems and
fertilizer applic.ltioll ~y Ille.lnS Sillli]..lr LO tl~o soil turE Ul-1C1
modified sand methods. The majority oE installa-tions have
also used a modified surface zone by incLudincJ a layer of
organics. This effect minimizes the capillary action (a
benefit of the membrane) since capillary rise will no-t
readily transfer from the pure sand to the modified sand thus
creating a barrier and necessitating supplementary surface
applied irrigation and fertilizer. Those with perEorated
distribution pipes placed directly on the plastic membrane are
impaired since the standard location of the perforation holes
3:~32
and the normally expected onelnchground settlement after
construction causes some of the pipes -to indent into the
plastic blocking the holes and making them ineffective.
Pumps used to assist in the removal of excess drainage water
S are ineffective when the water table is below the entry par-ts
of the pipes due to loss of vacuum. Installations using
special piping cross joints have shown irregular drainage
capabilities due to restricted flow. Systems using only sand
exhibit poor lateral liquid movement to or from a pipe sys-
tem and require a lar~er head pressure Eor drainage. Vnder
certain conditions, the head requirement resul-ts in a sat-
uration curve within the sand that will intersect the surface
between the pipes and cause surEace puddling. Conversely,
liquid attemptin;J subsurface entry into -the field is restricted
in uniformity of distribution unless sufEicient pressure is
used which could tilen lead to a quick sand condit,ion in the
areas of the initial entry ~oints. None of the systems
e:~hibit positive and responsive control systems.
Although a search has not been made, U. S. Patent Number
3,~61,675 granted to Izatt on August l~, L9G~ is illustrdtive
of the type of systelll de~cribed hereillabove and improved upon
by the presellt inve~n~ion.
~resent Invention
The imporant criteria of tllis improved membrane sand
system is to provi-le and maintain a deep rooted grass surface
which e~hibits vigorous growth and which has a level surface
throughout ~ithout obstructions and which does not suffer
compaction problems. The system is capable of minimizing en-
. ,~_
3~2
.. . .
vironmental problems created by variable climatic conditions
of the various locales in which it is installed includes
effective surface drainage abilities as well as nutrified
liquid replacement to the plants growing zone on a uniform
and continuous demand basis as the plant and climatic conditions
dictate. Soil warming techniques for frost and snow melting
create surface drainage and plant dryin~ out effects and
the system is eapable of handlin~ these factors.
The prime eonsideration of this improved membrane sand
system is to eontrol the water table within the isolated
membrane area and the assurance of uniformity of lateral dis-
tribution of the nutrified liquid reservoir such that the
surface zone moisture con-tent is main-tained. This control and
distribution ensures the proper relationship of nutrified
water and oxygen for the particular sand type and within the
toleranee limits for the plant. Water and nutrients, whether
applied by subsurface means or at the surface, move freely
to the membrane reservoir by the excellent vertical d~ainage
characteristics of the sand. This reservoir in turn feeds
the grass plant by capillary action inherent with the sand.
Excess water occuring during rainfall is discharged out
of the system, conservin~ first any rain water that car, be
retained for irrigation purposes. Irriclation water make-up
is preferably ap~lied throucJh the u-tiliza~ion of a su~surface
pipe grid utilized for both the drainaqe and the irricJation
or may be applied ~y conventional surface means. Fertilizer
is added to the irrigation water using liquid fertilizers
and an injection system or may be surface applied.
It has been well demonstrated that depending upon passage
or time and as a characteristic of a selected sand, -the sand
S'82
absorbs the same amount of liquid whether or not it is applied
at the surface or from ~eneath. It can also be easily
demonstrated that the absorption of the sand is propor-tional to
its depth and the moisture content at any level can be
determined as a function of -the depth of a particular
gradation of sand.
The capillary rise in the sand, in addition to the drain-
age characteristics, is dependent upon the gradation and
makeup of the sand and is controllable by proper selection of
these materials and the establishment of a water table. The
rate of capillary rise is particularly critical in extremely
dry climates and the drainage rate is critical in areas of
heavy rainfall. It is also required tha-t the selection of
the gravel be such that its gradation, in comparison with
lS that of the particular sand, be compatible to ensure that the
sand will penetrate the gravel layer by a depth of approximately
one inch. This penetration places the bot-tom of the sand
layer below the minim~n water table -to allow capillary
action and yet the lateral flow characteristics of the gravel
are not impaired.
It can thus be seen that maintaining a wa-ter table at the
bottom of a natural sand layer permi-ts -the more accurate con~
trol of the moisture content at the growing level. Further
the natural sand surface extends the playing season by its low
moisture retention and thus its ability to hold back freezing
for a slightly longer period and to thaw out more rapidly.
The dormant period of the plant is thus reduced. The
addition of a uniform heat source, combined with the proper seed
selection, may further extend the season by encouraging early
cJrowth and resisting die back caused by cold. The inclusion
3~
of an insulation layer under the membrane will minimize
frost penetration to the sub~rade at times when the heating
system is not in use.
In summary, an accurately controlled, frequently watered,
properly fertilized well drained field provides Eor the best
quality grass playing surface as well as encouraging rapid
regrowth and thus providing maximum utilization. ~lealthy
plants are less susceptible to disease and infestation and a
natural grass surface provides much lower air tempera-tures
immediately over the playin~ surface than the prevailin~ ambient
conditions while providing -the immediate air with an enrich-
ment of oxygen. Only this improved membrane sand method with
automatically operated subsurface drainage and fer~ilization
in combination with irriga-tion, i.e. "fertigation,"
provides these requirements on a continuous demand basis as
determined by the plant and the environment. The grass
itself, in growing, has a deep rooted characteristic as
it reaches down to the water table and thus has better wear
and tear capabilities, since the plant is more firmly
anchored and thus su~fers only leaf dallla~Je durin~l exLollsivc
use which is rapidly replaced by vi~orous re~rowth. q'he
utilization of "fertigation" by subsurface auplication is a
continuous, uniform and steady means which wllen coupled with
the membrane isolated area, carefully selec-ted growing
medium and liquid transfer medium and system coupled with
accurate and responsive control method provides these require-
ments.
It is an object of the present invention to provide a
playing surface support ma-terial and method which maximizes the
utility of a field and minimizes the maintenance require-
3~
ments under the most variable and severe climatic conditions.
Still a further object of the present invention is toprovide a system for establishing and maintaininy a grass
play surface comprising the steps of: (1) grading the sub-
grade at the site of the proposed surface, (2) placing a fluid
..
impermeable membrane adjacent the graded surface with or with-
out inclusion of an insulation layer, (3) providing a means
of central supply and removal of fluid at the appropriate
location in the graded surface, (4) providing a layer of
horizontal flow gravel on top of the membrane, ~5) placing
a lateral liquid distribution system throughout the desired
area on top of the gravel layer, (6) providing a layer of sand
with appropriate permeability, capillary and porosity character-
istics and having a substantially level upper surface without
obstructions into which the grass will be planted, t7) pro-
vide a means exterior to the field to direct excess drainage
water from the field to the site storm system, (8) providing
a responsive control system to control the liquid level within
the confines of the membrane beneath the grass, ~9) provide
an adequate feltiliz~r injection ancl waL~r make-up sys~elll to
sustain optimum ~rowth and replace transpired and evaporated
water, (10) provide a drain line -to remove all liquid from -the
contained reservoir, (11) when required, installation of a
soil warming system to melt snow and remove frost, (12) when
required, to provide a means -to sense the nutrified condition
or the contained liquid.
Still another object of the present invention is to
provide a membrane sand type grassed sports surface including
automatic means to provide irrigation as needed, provide
fertilizer on a predetermined schedule, and to withdraw
~3
_~ _
liquid from the field in the event that the level within
the membrane exceeds the ma~imum desirable for optimal
utilization of the field while maintaining the quality and
quantity of nutrified liquid to stimulate healthy growth.
It is another object of the present invention to provide
a grass playing field which includes a growing medium having
predictable capillary action overly:ing a liquid containing
material having horizontal flow characteristics assuring
uniformity of distribution under low infeed pressure require-
ments in which are placed conduits for the addition of water
and fertilizer to the liquid reservoir.
A stil] further objec-t of the present invention is to
provide a grass supporting medium wherein the upper layer pro-
vided a firm noncompacing surface with predictable pe~leability
permitting ready drainage and an underlying surface permitting
lateral fluid movement such that a minimum head is required
to effect the drain~lge.
Still another object of the present invention is to provide
a means located within the field beneath the grass sports
surfa~e for dctermillin(l the l~vel of liquid within tllC? (JraSS
supporting medium interconnected with a means exterior of the
field to provide ready and convenient information as to the
liquid level.
It is ano-ther object of the present invention to pro-
vide a means and mechanism to sense the system's water level
and masnetically transmit this in-to low voltage electrical
signals and relays these to a programmable control panel which,
in turn, operates, using a low voltage power supply, the
irrigation infeed and drainage outflow valves. The system
utilizes available irri~ation water pressure to function the
_,~ _
main valves throucJh small solenoid valves located on the
bleed lines from the irrigation line. 'I'his met!lod thereby
minimizes any electrical hazard.
It is another object of the present invention to pro-
vide a means and mechanism when electrical energy is notavailable to use float operated devices activated by the
systems water table and coupled to -the irrigation bleed line
valves to transmit the irriqation pressure into a Eorce to
open or close the irrigation and drainage valve.
A further object of the present invention is to provide a
means and mechanism for extending the usable seasoll for a
playing field through the use of underground hea-ters and pro-
tective sub-grade insulation layer combined with a sys~em
which accommodates the cJenerated drainage requirements while
simultaneously providing a continuous source of liquid to
avoid the drying effect normally associated wi-th artificial
heating devices.
Yet a further object of the present invention is to
provi~e a grass field which may have a chemical inbalance
corrected withou~ resort~ J to a restLu(,t:urinc~ or replaeemen~.
A drain and irricJa~ion system is provided such that all
chemicals or the like may be easily washed by means of purging
from the grass supporting medium ef~ecting a neutral condition.
It is also the object of the drain to allow removal of all
liquid from the entire system when necesC;ary.
Brief Description of the Drawings
Figure 1 is a plan view of a typical field layout
utilizing the present invention.
~3~1L82
:Figure 2 is a sectional view taken alony the line~ 2-2
of Figure 1.
Figure 3 is a plan view of the preferred control room.
Figure 4 is an elevational view of the water supply header
as seen alony lines 4-4 of Figure 3.
Figure 5 is a plan view of a valve station.
Figure 6 is an elevational view of a valve statioll.
Fiyure 7 is an elevational view oE the electrically
sensed level control unit.
Figure 8 is a flow diac~ram for an automated syst.em.
Figure 9 is an elevational view of an alternate mechanically
sensed level control unit.
Fiyure 10 is a sectional view of an alternate construction
when heating and sub-grade insulation is incLuded.
Detailed Description of the Drawings
As seen in Figure 1, the fieLd generally designated as 2
is divided into three essentially equal sections 4, ~ and 8
and deLined interllally ~y a division al(~ J lines ~2. :I:t is
to be understood that the size and shape of the field as well
as external conditions such as clima-tic fac-to.rs and dec3ree of
use will determille the num~er and shape of t.he sections. Each
section has a slope in the sub-grade designated in diagonal
lines 3 to a low point at approximately the center of the
section where the water level detector 42 will be located as
explained hereinafter. l~ithin each section of the field there
will e~ist a field section main 10, 12 and 14 interconnectilly
with the'required number of horizontal field distribution
piping headers 16, 18 and 20. A plurality of perforated field
~,}~ ~ '
13~2
distribution pipes 22 form a substan~ially equall~ spaced
grid work throuc3hout the field assuring rea!ionably equal
distribution and/or saturation.
Each of the sloping field sec-tion mains 10, 12 and 14 are
connected to a valve station 24, 26, 28 located below grade out-
side the playing area and are interc:onnected by means of an
irrigation feed system 30 which is interconnected with and
controlled from the control room 32 which in turn is connected
to the water supply 34~ These field distribution pipes 22
and the headers 16, 18 and 20 as well as the mains 10, 12
and 14 may also be used to discharge excess water by means
of the drainage system 36, 38 and 40 which lead to an off
site storm system. It is to be no-ted that -the water level
detector 42 and its interconnected tube 44 (one for each sec-
tion) likewise is interconnected with the valve station and with
a storm drain after passiny through the water level sensing unit
110. Also seen in this view is the low voltage electricaL
control system designated generally as 46 from the control
room to each one of the valve stations.
Referring llOW to E`igure 2 which, as noted abovc, is a
vertical sectional view ta}~en along lines 2-2 of Figure 1
it can be seen that the field inclu-les a subgrade S0 whicll
slopes within edch section towards its center and the water
level detector 42 which can also act a~ a drainage me~ns. At
midpoint Or each section is located the trellch 52 to accolMIodate
the piping exitinc3 for each section and includes sand bedding
54 supporting the field section maln 10. The water -t:able
le~fel tube 44 is also placed within trench 52 which is ter-
minated a-t the center of the section with a vertical perforated
~0 tube designated as the water level detector 42. The remainder
_~_
of the trench is filled with onsite m~terial 5h and a men~rane
58 is placed over the sub-grade and sealed at the conduit
entry points thus establishing an enclosed dish-like area for
the irrigation and grass support pur.poses. As the -trench
exits the perimeter of the system a 5 foot long plug using
impervious materials is inserted in the trench to ensure a
positive seal to the trench itself.
As noted above, the entire Eield is broken into fie1d
sections. The field sections are defined by a perimeter
berm 60, which extends around the entire periphery of the
field, and upwardly extending section divisions 62 extendincJ
across the field and across which the ~embrane 58 is ~olded.
The subgrade 50, AS noted above, is sloped toward the center
of each section but the gravel layer 61 which lies thereupo
and supports a perforated field distribution pipincJ 22 as
well as the piping headers 20 has a horizontal or level upper
surface. It is to be noted that tllis surface in general will
define the minimum water level through the weir action of the
perforations in the event of automatic control shutdown. The
gravel layer witllllori~oll~al flow cll.lL~ ris~ics ass~lles evc
.. ..
distribution of water or fertilizer.
The perforations of the field distribution piping are
placed downwards on top of the gravel and the pipes are then
covered with a filter cloth wrapping 66. This cloth is standard
to earth work projects and prevents the fines loss from the
sand from entering the piping system. The pipe is not
entirely wrapped but is covered with the filter cloth which is
tilen tucked on each side of the pipe with the edges pro-
jectiny outward ~y three or so inches. 'I'his method of wrapping
~5
_~_
8;Z
is essential since wrapping the pipe on its entire circumference
could lead to clogging through salted ou-t fertilizer particles
being trapped in the filter material 66. The method employed
allows the holes to remain uncovered whi]e the sand is pre-
S vented from entering the pipe without first passing throughthe gravel 64. This is not possible because of -the particular
selection of the gravel gradation. Tlle sand layer 68 is then
placed, overlying the gravel and the distribution piplncJ.
The grass 70 is planted at the top oE the sand layer at the
field elevation which is level throughout. The root
structure will generally extend vertically downwardl~ to reach
the established water table and not bunching toward the pipes.
As seen in Figure 3, the preferred embodiment of the con-
trol room is shown. For ease of cleaning, the control room
includes a floor drain 80 at the intersection of the various
portions of the sloping floor 82. Mounted about the perimeter
of the room is fertilizer storage 84 and control panel 86,
the required breaker panel and disconnec-t devices 88. Mounted
upon the floor of the control room is the fertilizer holding
tank 90 which ha~ ounted adjacenL thereto the fertLIizer in-
jection pump 92 Eor selectively injectiny the fertiliæer into
the irrigation feed 30 as explained in cJrea-ter detail with
respect to Figure 4.
Referring now to Figure 4, which is a sectional view taken
along lines 4-4 of Figure 3, it is seen that the water suppl~
34 is located beneath grade, is elevated into the water supply
header which includes a wash down hose connection 94, back
flow preventer set 96, a strainer and clean out 106, a pressure
regulator 98, a test pressure gauge connection 108, a fert-
ilizer injection valve 100 and a pump pur~e fe~d connection
102, in addition to manual isolating shutoEf valves 104.
In Figure 5, a plan view oE a valve station, there can be
- seen that the water level tube 44 extends into the water level
sensing unit 110, as described in greater detail hereinafter,
and is connected by means of a conduit to the automatic field
drain valve 112 which can, as the name implies, be used to
remove all liquid from the fiel.d as may be required for purging.
Just befor~ the automatic field drain valve 112 is a vertical
water level sight tube 111 complete with a colored ~loat
and transparent casing to allow for visual inspection of the
water table level within the field section. Also extending
into the valve station is the field sec~ion mai.n lO which at
its termination has located an automatic draina~e valve 128
which, when open, allows excess water to discharge to the
site storm system. The liquid make-up supply -to the field
section main 10 is through the irri~ation feed 36 whi.ch ..
includes an irrigation feed line drain 116. Also to be noted
in view is a bleed line 118 for pressure assisting the auto-
matic valves.
Lookin-l now at Fi~ure 6, which -is a sect:ional view tak~
along lines 6-6 of Figure 5, it can be seen that the valve
station lies below the field elevation and as noted in
Figure 1, is outside the playing bounda:ries and further, out-
side the boundaries of the controlled Eield. The valve station
includes a closing cap 120 and is surrounded by means of a ri~id
side 122 and a Eloor 124. ~s seen in thi S view, the water
level tube 44 e.~ends outwardly generally toward the Eield and
within the manhole chamber it terminates with the automatic
drain valve 112 which is immediately preceded by the water
level sight tube 111. The field section main 10 as seen in
p
this view, lies immediately in front oL the water level tube
44 and terminates with the automatic discharge valve 128.
Further to be seen in this view, is the irrigation supply to the
section mains 10 following the irrigation feed line drain 116,
shown in Fiyure 5, is a strainer and clean out 119, bleed line
shut-of 118, automatic irrigation supply valve 126, a balancing
valve 127 and a test pressure gage connection 12~. rl'he dis-
charge to the storm system is designated 3f~.
The water level sensinc~ unit for use in -the totally
automatic system is seen in Figure 7 and as seen, this also
lies beneath the field elevation and is covered by a removable
cap 130 which covers a vertically placed PCV pipe 13:'. A
plurality of reed switches 134 are mounted and sealed in a
vertical member 135. A buoyant toroidal shaped float 136 having
permanent magnets 137 imbedded therein closes the reed switches
134 by magnetic flux which o~ens and closes the LV=low voltage
electrical switches in the terminal base 138 which relays
a signal to the main control panel which in turn actuates
valves to add or remove liquid from the field. The liquid level
within the wa~er level sensing Ullit iS clirectly re.ponsive to the
level within the field. This unit in conjunction with the
water level detector 42 and the interconn~cting conduit 44 form
a U-tube. Tube 44, lying at the lowest por-tion of the section
may be used as a drain for purging the field by opening the
automatic field drain valve 112 shown in Figure 5 and located
within the valve station. Further to ~e seen in this view, is
the connection with the low voltage electrical control system 46
and the conductivit~ sensor 139 for relaying the condition of
the nutrified liquid.
\~
~~~
~ 3~
As seen in Figure 8, the flow diacJram is generally divided
into two sections (A) which is generally within the valve
station and (B) which is generally within -the control room.
As seen in this view, the water enters the control rooms by means
of conduit 34, passes through the back flow preventer 36,
pressure regulator 98, and then for purging of the pump, an
auxillary line is fed to tl~e fer-ti:Li:~er injection ~ump 92 with
the main line proceeding after the injection valve 100 directly
to the valve station via conduit 38. I'ertilizer from the
holding tank 90 is automatically directed to tlle fertilizer pUM
92 and then through line 38 to the valve stations. Also
seen in this view, is a means to purge the pump to the sewer or
to dump the storage tank. Within a typical valve station the
water passes through the irrigation supply ~alve 126, the balance
valve 127, and then to the field section main 10. The feed-
back demonstrating a need for water is generated by the water
level tube 44 and the water level sensing unit 110. Further
to be seen in this view, the electrical supply passes through
the power panel 88, the master irrigation control 86, and is
fed to the various valving, pumps and watcr level sensing uni-ts
necessary to perform the functions as described hereinabove.
It is to be remembered that all power except for the pump is
low voltage.
A preferred control for a system when electrical power
is not available is shown in Figure ~. This installation
provides for a mechanically automated system ermployincJ a
completely controlled method for subs-lrface drainage and
irrigatlon. -l~ith this system, control room is not required and
is replaced with a water supply header and an automatic
fertilizer application is not contemplated and thus is not included.
"
~ 3~
The control utili~es mechanically functioning float
activators 152 linked by parallel linkage 154 to flo~ts 156
all mounted within a manhole 158. A water level tube 44
continues through the control manhole and terminates as for
the automatic system in the valve station wi'th a water level
sight tube 111 and manual drain valve 162. The float
activators utilize the water pressure from the irrigation
line through bleed lines 164, 166 and 168 to open and close
the pressure operated,irrigation and draina~e discharcJe valves.
Figure 10 illustrates, for full disclosure, and alt~r-
nate embodiment of the extreme ri~ht end portion of Fi~ure 2.
Heating ~ables and a sub-grade insulation barrier included as
well as a modified periphery of the field. As can be seen, the
insulation layer 200 is placed directly under the membrane over
the entire field area. At the perimeter this insulation is
carried vertically downwards to a location at least 6 inches
below the contemplated frost penetration for the locale. The
e~terior perimeter is trenched 202 to accommodate the insulation
and a standard type perimeter drainage system 2()4. The drain'age
pipe 20~ is bedded on sand 206 and the entire excavation is
~ck~ d to will~ (, illCll~?S of tllo surr.lc~ wiLII I L~ r~ iri ill(J
select granular fill 208 to ensure elimination of frost
heave problems. Tlle surface of the b~ckfilled trer)c'lis graded
.. . .
with 6 inches o- top soil 210 to support grassing. Referrin~;
to the detail within the membrane isolated area, i,t can be
seen that the heating cable system 212 is locatecl over the
gravel layer and under -the sand layer. The COIl trols -Eor the
soil warming system include ground temperature sensor 214 and
relay signals back to the main panel in the celltral room to
ensure gradual heat elevation and reduction controls using
~?~D
--,;2~--
3~8~
solid state devices such that the grass root system is not
subjected to the~mal shock. The tleatil-CJ system when combined
with the sub-grade insulation may be used intermittently
or continuously throughout the winter as user requirements
and economics demand.
Although the completely automatic system has been
described in detail, it is to be under.Ytood Lhat many of
the operations may be handled manually in any one of
several combinations. In extremely colcl climates, Lhc
installation may be enhanced through the use of an inslJlated~
membrane or heaters, if necessary as pointed out above.
If necessary, the insulation may be used to isolate and keep
dry a portion oE the subsoil to prevent frost heaving and
the subsequent misalignment of the critical elements.
Thus as can be seen, the present system provides a
unique method for establishing and maintaining grass plav
fields with superior lonc~ term results and lower overall
maintenance and upkeep.
