WO1991002455A1

WO1991002455A1 - Valve apparatus

Info

Publication number: WO1991002455A1
Application number: PCT/AU1990/000367
Authority: WO
Inventors: Emil Richard Smith
Original assignee: Emil Richard Smith
Priority date: 1989-08-23
Filing date: 1990-08-22
Publication date: 1991-03-07

Abstract

A valve assembly is provided having a working piston (14) and seal (20) adapted to sealably engage a water flow inlet pipe (21), entering the chamber (10). This side of the piston (14) is in fluid communication with a reservoir (22), disposed above the chamber (10). The reservoir (22) is provided with a siphon tube (23) extending down outside the reservoir (22) via transfer tube (24), the outlet end of which is directed to the perforate or mesh portion (11) of the chamber (10), containing a water swellable polyacrylamide gel (12). The reservoir (22) is supplied by outlet pipe (25) leading from the chamber (10) to the reservoir (22). In dry conditions, the polyacrylamide gel (12) is in its minimum volume configuration and the piston (14) is urged away from the end of the inlet pipe (21), permitting water to enter the chamber (10). The water is forced up to the reservoir (22) via the outlet pipe (25) which then fills. When the reservoir is full, water passes through the siphon tube (23) and the irrigation outlet (28). Water from the siphoned tube (23) passes through transfer tube (24) to the perforate or mesh portion (11) of the chamber (10), hence wetting the polyacrylamide gel (12). The polyacrylamide gel (12) then expands, driving the piston (14) towards the outlet tube (21) against the bias of spring (26). At full expansion of the gel (12), the seal (20) seats against the end of the inlet tube (21) and stops flow to the reservoir.

Description

VALVE APPARATUS This invention relates to valve apparatus. This invention has particular but not exclusiv application to condition-responsive water flow control valv apparatus, and for illustrative purposes reference will be mad to such application. However, it is to be understood that thi invention could be used in other applications, such as an condition-responsive switching.

Control of water flow to plants in agriculture an horticulture is an ongoing concern, particularly in Australi where water is in generally short supply and rains are ofte unreliable. Also, certain plants are sensitive to the amoun of water received, either by getting too much or too little. In the past, individual control of watering has been provide by manual control of supply and/or location of watering points, either by control of time and distribution of valve systems o by physically relocating watering apparatus. The prior ar watering apparatus is generally of two forms. The first i general broadcast methods such as sprinklers. These have th problems of high evaporation factors and difficulty o individual area controls. The pattern distributed by th sprinkling apparatus is not homogeneous in water applied pe unit area, and accordingly such apparatus requires constan relocation if a constant rate of application is to be obtained. Additionally, sprinkler irrigation suffers from th attendant problems of high evaporation losses. For example where the source water is high in mineral and salt content high evaporation rates results in mineralization and/o salination of the soil with loss of productivity. Drip or root watering systems have also been used i certain applications to attempt to negate the problems o broadcast irrigation. However, present drip irrigation system present a constant problem of volume control to individua watering points. Control by aperture size is insufficien because pressure differentials throughout a system create uneven flow rates. Even if flow rates were modified by varyin aperture sizes, this presents problems of blockage of the smal apertures by mineralization and/or particulates as well as th complication of selecting the aperture size. Therefore, for a given drip system the methods of contro have been via manual,timed or electronically activate condition-responsive valve systems for turning the system on o off. The condition-responsive means has generally comprised a expensive electronic sensor determining soil moisture or ai humidity in, for example, a greenhouse and extrapolating th reading to soil condition. The sensor is often used t generate a signal to a soil computer which in turn controls water supply to maintain soil conditions. Such systems ar expensive to install and maintain and suffer from the inheren defects of inaccurate extrapolation and lack of individua watering point control. Timed systems are even les discriminate, as are block-control manually switched systems.

The present invention aims to alleviate the abov disadvantages and to provide valve apparatus and a method o irrigation which will be reliable and efficient in use.

With the foregoing and other objects in view, thi invention in one aspect resides broadly in a method o irrigation comprising the steps of:- providing a source of irrigation water; providing distribution means for said water, and providing a plurality of water outlets from said distributio means, wherein a flow of water out of said outlets i controlled by flow control means operable in response to th moisture level of the soil about said outlets. The irrigation water is preferably pressurized and may b pressurized by any suitable means such as by direct tappin from municipal mains, pumping from reservoir or by a gravit feed head.

Preferably, the distribution means comprises a manifold o the like having distribution pipes conveying water to th individual sites of use. The distribution network may take an form consistent with its function and as such may comprise branched, terminated main having single or dendritic branche or alternatively may comprise a ring main extending from th water source.

In one preferred embodiment of the present invention th distribution system comprises flexible polymer tubing adopte to be buried in the ground or laid upon it.

The water outlets may take any form consistent with th requirement that the water be able to flow therethrough t provide irrigation. Accordingly the outlets may comprise plai cut ends of the termini of the distribution network if the cu ends provide the correct flow characteristics, or alternativel the termini of the network comprising the water outlets may b provided with flow controlling apertures, non return valves o the like.

The flow control means may take any form consistent wit the function of controlling the flow of water from the outlet in response to the moisture level of the soil about th outlets. Preferably, the flow control means includes a valv such as a poppet valve, butterfly valve, ball valve, sprin valve, simple gate or the like, consistent with being operabl by means responsive to the moisture level of the ground. Th valve means may operate to interrupt the flow to the outlets b closing of flow at any point of the distribution network However it is preferred that the flow be interrupted by th valve means at each of the outlets of the distribution networ such that control of the water flow from a particular outlet i exercised by flow control means located at or near the outlet. Accordingly, it is preferred that the water flow throug each of the outlets is controlled by its own individual flo control means comprising a valve and valve operating mean which is responsive to the soil moisture content about th particular flow control means. Hereinafter, the expressio "soil moisture content about the outlet" should be taken t mean the soil moisture content within the area serviced by th individual outlet, and as such, the valve operating means ma or may not be located at or immediately about the outlet.

The valve control means may take any form consistent wit the function of controlling the valve in response to a detecte condition of the moisture content of the surrounding soil an as such the valve control means may comprise any known mean capable of this function such as electronic moisture detectin means coupled to electromechanical valve operating means Preferably, the valve control means is of an independently operating type, that is, of a type not reliant on an externa power source such as electricity or on a consuming interna power source such as batteries. It is also preferred that th control means be completely self governing in that no externa control is required. Accordingly, in a further aspect, thi invention resides broadly in flow control apparatus fo controlling the flow of liquid from an outlet including:- valve means; sensing means for determining the amount of liquid about sai outlet, and operating means responsive to said sensing means for operatin said valve means.

Preferably, the flow control apparatus is adapted t control the flow of water such as in irrigation or water leve control applications such as swimming pools.

The valve means may take any form consistent with it function of being able to substantially interrupt the flow o water from the outlet and is preferably selected fro mechanical valves such as poppet valves, butterfly valves o slide valves. In order to minimize the amount of forc required to operate the valve and the amount of sealing abou the moving element of the valve it is preferred that the valv be a poppet valve.

The sensing means may take any form consistent with th function of sensing the amount of water about the outlet an responding accordingly. For example, the sensing means ma sense the amount of water indirectly via measurement o conductivity of the surrounding air or soil, or alternativel may sense the relative humidity of the air about the outlet However, in the interests of simplicity it is preferred tha the sensing means include a substance that exhibits reversibl expansion by hydration in contact with water, together wit means for monitoring any such change.

The substance is preferably a hydratable synthetic polyme gel capable of substantial reversible volume change o hydration. Preferably, the substance is in the form of wate swellable gel beads such that the amount of substance can b accurately metered and to present sufficient surface area t the environment for a useful rate of change of volume Particularly suitable substances are selected from the grou comprising water swellable polyacrylamides in the form of ge beads. Suitable polyacrylamides are those crosslinked to for an insoluble network polymer such that the interstices of th network, in conjunction with the hydrophilic amide groups o the polymer, reversibly absorb water from the surroundin environment.

The characteristics of absorption and desorption of wate may be selected according to the use for which the apparatus to be put. For the purposes of apparatus for control response to soil moisture levels, it has been found that t polyacrylamide beads ALKASOIL AB3 from Allied Colloids exhibi suitable properties.

Preferably, the water swellable substance is contained i a housing such that the swelling of the substance may directed into useful work. The housing may take any fo consistent with the function of containing the substance whils permitting the substance to access the condition to responded to. Preferably, the housing comprises a perforate o permeable portion through which the substance may be exposed t the moisture about the outlet. In irrigation applications, t perforate or permeable portion of the housing may be in contac with or buried in the soil to be monitored, whilst in swimming pool level controlling application, the perforate o permeable portion of the housing may be affixed to the wall the pool or in the filter box at the desired level.

The operating means may take any form consistent with it function of being able to respond to the sensing means i operating the valve. Preferably, the operating means include a moving operating member in contact with the preferred wate swellable substance and adapted to translate the expansion the substance into a movement which may be used to operate t valve. For example, the operating means may include a pisto like operating member within the preferred housin Alternatively, the operating member may take the form of diaphragm disposed in the housing.

The operating member may linked to the valve to opera the valve directly, or may otherwise act upon any desir intermediate operating element such a switch for activating electrically operated valves. Of course, the movement of t operating member may also be used to activate alarm controls the like. For horticultural and/or agricultural use it preferred that the operating member act directly on the val to control the flow of irrigation water in response to chang in the water content condition of the soil. In one embodiment of the present invention, the operati means and valve are combined to form a valve assembly, th valve being incorporated in the housing. In order to contro the rate of response of the apparatus in an irrigatio application where an outlet is to serve an extended area, i may be desirable to include an outlet conduit to convey th water flow to a point away from the valve assembly but withi the area to be serviced.

In a further aspect, this invention resides in a valv assembly for use in controlling water flow from an outlet an including:- a housing having a water permeable portion; a reversibly water swellable substance disposed in sai housing; an operating member in contact with said reversibly wate swellable substance and movable in response thereto, and a valve operable by said operating member, wherein movement o said operating member in response to water swelling and dryin contraction of said reversibly water swellable substanc serving respectively to restrict and allow water flow from sai outlet.

The housing is preferably of cylindrical form fo simplicity of manufacture and may be divided into a perforat portion and an imperforate valve housing portion by the movabl operating member. The perforate portion may be provided b perforating one end portion of a piece of tubular stock, o alternatively the perforate portion may be of a mesh materia assembled to the cylindrical valve portion. Preferably, bot ends of the housing are closed to provide an assembly whic restricts the egress of dirt particles into the valve assembly The perforate portion of the housing is preferably stocke with the preferred polyacrylamide gel beads hereinbefor described.

The movable operating member is preferably a piston o diaphragm disposed at or about the boundary between th perforate and imperforate portions of the housing, it bein particularly preferred that the piston or diaphragm being suc that the portions of the housing are substantially sealed on from the other to prevent loss of beads into the valve spac and to prevent entry of dirt thereto. The movable operatin member is preferably spring biased towards the open or flowin position to counter any tendency to stick in the valve-close position. Alternatively, the movable operating element an valve may be so configured such that the water pressure at th inlet to the valve maintains the flow unless the gel i sufficiently swelled to urge the movable operating member int closing off the valve.

The valve may take any suitable form . as describe hereinbefore. Preferably, the valve comprises an inlet to th imperforate portion, a delivery outlet from the imperforat portion, and sealing means provided on the moving operatin means, the sealing means being adapted to sealingly cooperat with seating means provided on either or both of the inlet o the delivery outlet of the valve. In one embodiment of th present invention, the movable operating member is a piston o a waisted type having an annular space between two surfaces an slidably sealing to the housing, with a transfer por communicating between the inlet side of the piston and th annular space, and the delivery outlet communicating with th annular space for a specified part of the piston travel. Thi arrangement provides for flow control both by the sealing o the inlet by the piston face sealing means at full ge expansion together with closing of the delivery outlet at ful expansion and/or any other selected position of the piston b the wall of the piston covering the delivery outlet. The delivery outlet may be connected to a condui carrying the water some distance away from the gel such tha control of the flow is exercised in response to the wate diffused through the soil from the end of the conduit to th gel, thus avoiding excessive sensitivity of the apparatus an permitting each assembly to service a larger area than would b possible if the water left the delivery outlet directl adjacent to the gel.

Access of ground water to the soil may be provided b locating the assembly unit in the perforate chamber on or i the soil with or without water-conductive wicks or the like.

The assembly in use may be used to control sprinkler flow drip irrigation flow or may, via an operating link, control a external valve.

Various ancillary control means may be associated with th assembly to enhance control of flow. For example, the deliver outlet may feed into a reservoir vented to the atmosphere an containing a siphon tube between the reservoir and the gel bea containing portion of the housing. As water flows from th apparatus, a small proportion may be diverted to the siphon which fills until the siphon action commences. The contents o the reservoir may then drain with relative rapidity to the ge beads, saturating the beads and causing flow to the reservoi to cease. The parameters of reservoir and siphon capacity ma be selected to provide a desired watering regime. The invention will be further described with reference t the accompanying drawings illustrating preferred embodiments o the present invention, together with the following examples wherein:-

FIGS. 1 to 10, 14 and 15 illustrate alternativ embodiments of flow control apparatus in accordance with th present invention;

FIG. 11 illustrates flow control apparatus installed in multiple device irrigation system in accordance with th present invention; and FIGS. 12 and 13 illustrate irrigation layouts suitable fo use in conjunction with the methods and apparatus of th present invention.

Example 1 is an example illustrating test results of th apparatus in accordance with the present invention.

EXAMPLE 1

In order to determine the best starting level of hydration o the polyacrylamide gel ALKASOIL AB3, six samples were prepare in accordance with Table 1.

TABLE 1 Sample Expanded volume

(x dehydrated volume)

1 ⁴

2 12

3 24 4 48

5 96

6 192 For the amounts of gel envisaged for use, sample provided the most suitable volume change over further immersio over the desired range of time, from immersion to approximatel 40 hours. The selection criteria used was to measure th spring pressure exerted by the expansion of the gel through given cross section, as a function of time of immersion of th gel in water. The test apparatus was a simple cylindrica housing having a mesh base and a closed top, a piston bein disposed for free movement in the cylinder and urged int cotact with the gel contained in the lower portion of th housing by a spring of known characteristics.

These results may be correlated to a linear scale o displacement versus spring pressure in accordance with th following TABLE 2. TABLE 2

Compression (mm) Weight Equivalent (g)

15.5 900

15 780

13 660 8 420

5 300

3 180

1 90

Whilst the plot is not linear and tapers exponentiall from zero time, a line of best fit from 200g spring pressure t

400g spring pressure yields an approximate rate of increase o spring pressure (equiv. ) versus time of 0.005 mm/min whic correlates to a linearized rate of 60 g/mm expansion.

The shrinkage characteristics of the gel are characterize by a plateau from 0 - 12 hours presumed to be caused by th preferential loss of unbound external moisture from the ge system, which does not appreciably lose "network" moistur until this humid microenvironment is dispersed. However thereafter the plunger movement rate is approximately linear a 1mm per 5 hour period.

In the figures generally, there is provided irrigatio apparatus comprising a chamber 10 having a perforate or mes portion 11 and containing a polyacrylamide gel 12. The chambe 10 contains the gel 12 and is closed at one end by end porti 13, and at the other end by a movable member consisti variously of a working piston 14 or a working diaphragm 15.

In the embodiment illustrated in FIG. 1, the worki piston 14 is provided with a seal 20 adapted to sealably enga the end of a water flow inlet pipe 21, entering the chamber 1 on the side of the piston 14 remote from the gel 12. This si of the piston 12 is in fluid communication with a reservoir 2 disposed above the chamber 10. The reservoir 22 is provid with a siphon tube 23, extending from the bottom of t reservoir 22 out through a hole provided in the top thereof an extending down outside the reservoir 22 via transfer tube 24 the outlet end of which is directed to the perforate of mes portion 11 of the chamber 10.

The reservoir 22 is supplied by outlet pipe 25 leadin from the chamber 10 to the reservoir 22.

The piston 14 is biased away from the end of the inle pipe 21 by the action of spring 26.

In use, the chamber 10 is installed with the inlet pipe 2 connected to a subterranean micro-irrigation network not shown The perforate or mesh portion 11 extends through the grou level 27.

When installed in dry conditions, the polyacrylamide ge 12 is in its minimum volume configuration and the piston 14 i urged away from the end of the inlet pipe 21, the end of t inlet pipe 21 clearing the seal 20 and permitting water t enter the chamber 10. The water is forced up to the reservo 22 via the outlet pipe 25 which then fills. When the reservoi fills, water simultaneously passes through the siphoned tube 2 and the irrigation outlet 28. Water through the irrigatio outlet 28 services the agriculture whilst water from t siphoned tube 23 passes through transfer tube 24 to t perforate or mesh portion 11 of the chamber 10, hence wetti the polyacrylamide gel 12.

The polyacrylamide gel 12 then expands, driving the pist 14 towards the outlet tube 21 against the bias of spring 26 At full expansion of the gel 12, the seal 20 seats against t end of the inlet tube 21 and stops flow to the reservoir. T reservoir continues to siphon out until the water level dro to the level of the lower end of the siphon tube 23. The parameters of gel volume, chamber diameter, reservo volume and water pressure may be chosen to provide a regula output from the apparatus. This output will of course b regulated by the soil condition, also by virtue of the fac that the chamber 10 is partially buried beneath the surface o the ground 27.

In the embodiment illustrated in FIG. 2, the reservoir 2 of FIG. 1 has been dispensed with. The embodiment of FIG. 2 however, has a side piston 30, within a side chamber 31 adapted to provide a variable volume for the gel 12 to occupy thereby providing adjustability for the apparatus. The regio of the side chamber 31 on the side of the piston 30 away fro the gel 12 may be provided with an adjustment screw adapted t adjustably limit the travel of the piston 30.

In these figures, when the piston 14 is up and the inle 21 is closed, full pressure will be exerted on the piston 30 The piston 30 will be pushed to the left, hard up against th stop. When the piston 14 drops, the inlet 21 is open. Thi valve is so designed, that by limiting the inflow rate, tha this will cause a reduction of pressure on the inlet tube 2 and on the piston 30. Due to this reduced pressure on pisto 30, spring 26 or other means corresponding to spring 26 a illustrated, will then have enough force to push piston 30 t the right. This causes an increase in the total volum available to the gel and gel flows into this. Piston 14 wil then drop by an amount set by the volume of gel so displaced It will therefore take a set amount of time for the gel 12 t expand and push the piston 14 up and so close off inlet 21 When the piston 14 closes off the inlet 21, full pressure i applied to piston 30 and it moves to the right. Such apparatu thereby provides timed irrigation.

Valves as described above may be used to activat secondary valves switching the main water supply, the secondar valves being operated by various methods, including utilizing drop of water pressure against a piston, or an increase i water pressure against a piston.

In further embodiments, when the gel 12 is in its lo volume state, the piston 14 is urged away from the seal 20 b the spring 26 and water is permitted to flow from the inle piper 12 to an outlet pipe 32 which provides irrigation wate to the earth. As the earth humidity rises, the gel 12 become moistened, thereby expanding to occupy the available volume i the chamber 10 and the side chamber 31, and thence causin advancement of the piston 14 such that the seat 20 contacts th end of the inlet pipe 21 against the bias of spring 26, thereb closing off flow. Gradual reduction of the moisture content o the soil then causes progressive shrinkage of the gel, thereb repeating the cycle.

The apparatus illustrated in FIG. 3 is similar to tha illustrated in FIG. 2 except that the side piston 30 of FIG. is replaced by side diaphragm 33, piston 14 is substituted b diaphragm 15 and the seal 20 is dispensed with.

The apparatus illustrated in FIGS. 4 and 5 are directed t apparatus for use at higher water supply pressures. In thes embodiments the chamber 10 is provided with a co-axial chambe extension 34 and the piston 14 is unitary with the pisto extension 35 and second stage piston 36. In the embodimen illustrated in FIG. 4, the second stage piston 36 is provide with seal 20, spring 26 as before, whereas the embodimen illustrated in FIG. 5 is provided with a diaphragm 15, also as previously illustrated. In these embodiments, the large working area of the piston 14, permits the gel to exert greater closing pressure on the inlet pipe 21, thereby closin off the high pressure supply when gel saturation is reached.

The embodiment of FIG. 6 is a variation of the apparatus illustrated in FIGS. 4 and 5, wherein the piston 36 is provide with a compression portion 40 adapted to compress and thereb close a collapsible tube 41, disposed between and providin fluid communication between the inlet pip 21 and the outle pipe 32. The embodiment illustrated in FIG. 7 is a variation of th apparatus of FIGS. 5 and 6, in that the piston extension 35 takes the form of a hollow, tubular member, having a transfe passage 42 provided therein. The transfer passage 42 having a inlet 43 and an outlet 44. The transfer passage is sealed b o-rings 45 and packing gland 46.

In use, movement of the piston 14 makes and breaks flui communication between the inlet pipe 21 and the outlet pipe 3 by moving the inlet 43 to the transfer passage 42 and outlet 4 to the transfer passage 42 into and out of registration wit the 0-rings 45. The embodiment illustrated in FIG. 8 is similar to tha illustrated in FIG. 2 with the exception that in this case, t piston 14 acts directly on collapsible tube 41 disposed betwee the inlet 21 and the outlet 32 via compression portion 40 This embodiment again is suitable for use in low-pressu micro-irrigation. Typing of the gel in this embodiment i provided by a feeder tube 47 branched off from the outlet 32.

The apparatus of FIGS. 9 and 10, illustrates hydrauli control of main flow through the apparatus. In thes embodiments, the chamber 10 is substantially configured as i FIG. 2. However, instead of the inlet 21 and outlet 32 bein connected via the chamber 10, in this case, the seat 20 on t piston 14 is adapted to close only a side branch 50 of t inlet 21. Water flow through the side branch 50 when the ge 12 permits flow, is directed through service pipe 51 to second chamber 52, containing a sealing diaphragm 53 and piston 54. The piston 54 is provided with a piston extensio

55 and a seal 56 adapted to close a flow aperture 57 dispose to close fluid communication between the inlet 21 and t outlet 32 as they enter and leave the chamber 52 respectivel

In use, when the gel 12 is dehydrated, inlet pressur water is supplied by the inlet 21 and the side branch 50 to th chamber 10 and thence to the service pipe 51 to the workin side of diaphragm 53 which then urges the piston 54 to advanc the extension 55 and thereby unseat the sealing member 56 fro the transfer passage 57. Flow then passes through the inlet 2 to the outlet 32 via the chamber 52. Concurrently, wit passage of water through the inlet 21 to the outlet 32, wate passes through the feeder tube 47, thereby wetting the gel 12 The gel 12 then expands to close the side branch 50 by sealin of the end thereof against the seal 20, thereby causing reduction in pressure on the working side of the diaphragm 54 allowing the piston 54 to retract and for the sealing porti

56 to close the aperture 57, thereby preventing flow throu the apparatus. The inlet supply pressure bearing on the membe

56, ensures that flow is stopped when the gel is saturated.

The apparatus illustrated in FIG. 10 is the same as th illustrated in FIG. 9, except that a sealed piston is utilise with o-ring 58 replacing diaphragm 53. FIG. 11 illustrates the installation of apparatus i accordance with the present invention using a supply line 60 t provide operating pressure independently of the supply lin constituting the inlets 21 and the outlets 32 of severa apparatus connected in series. In this case, the control sid provided by line 50 is connected to each of the apparatus i parallel to provide a constant working pressure for th apparatus. By contrast, the flow through the supply line is i series. FIGS. 12 and 13 illustrate suitable layout for micro irrigation apparatus in accordance with the present inventio and in particular suitable for use for the apparatus of FIG 11. In these figures, a control pressure line is illustrate at 60 and the main supply line illustrated at 61. Pressur valve 62 control water flow through the control line an distribution notes are illustrated at 63, located on branche 64 of the main line 61. Due to the presence of the pressur valve 62, in this embodiment, the valves will open sequentiall and close sequentially should this be desired. In the embodiment illustrated in FIG. 14, there i provided a valve comprising a chamber 10 and a mesh chamber 1 enclosing a gel 12. A piston 14 is provided in the chamber 1 which piston 14 constrains and is moved by expansion of the ge 12 in the chamber 10. A piston extension 85 is provided on th face of the piston 14 away from the gel, the piston extensio 85 being provided with a piston face 86, adapted to conform t the bore of a secondary chamber 87, co-axial with the chambe 10. The piston face 86 is adapted to seal via seal 88 to th end of inlet tube 21, the seal 88 being biased away from th end of the inlet tube 21 by the action of spring 26.

In use, when the piston seal 88 is fully pushed up agains the inlet tube 21, by the pressure of the expanded gel agains the face of the piston 14, water cannot flow. The water in th inlet tube will apply a force proportional to the cross sectional area of the inlet tube, against the piston seal 88 When the gel 12 shrinks, and the inlet valve opens, wate enters the chamber 87 and escapes via the small exit tube 89 This will cause pressure to build up in the chamber 87. Sinc the area upon which the pressure is now acting is the area o the piston face 86, the force exerted by the inlet wate pressure against the gel 12 via the piston 14 is no considerably larger and accordingly will take more force on th part of the gel 12 to close the- valve.

The mesh portion 11 of the chamber 10 is in thi embodiment made to have some elasticity, allowing the piston t drop a set amount. As water is distributed from the valve t the environment of the gel, the gel will expand to exceed th limit of elasticity in the mesh portion 11 and to thereafte exert sufficient pressure against the piston 14 to urge th seal 88 against the end of the inlet tube 21, against th spring 26, and thereby cause flow to cease.

In the embodiment illustrated in FIG. 15, there i illustrated a typical flow control valve 90 capable of bein controlled by control of a minor flow diverted from the majo flow to a remote sensing means (not shown) in accordance wit the present invention. In the figure, the valve 90 includes a inlet pipe 91 and a delivery pipe 92 entering and exitin respectively from a housing 93. The inlet pipe 91 is provide with an upstand portion 94 within the housing 93. The housin 93 is divided by a diaphragm 95 including a central button 9 provided with a sealing disc 97 adapted to sealingly engage th upstand portion 94. The button is guided in its movement by guide pin 100 cooperating with a guide aperture 101 provided i the button 96. A spring 102 urges the sealing disc 97 int sealing contact with the end of the upstand portion 94. conduit 103 conveys water filling the upper chamber 104 of th housing 93 to a polyacrylamide-operated shut off valve (no shown) .

In use water passing through the inlet 91 to the deliver 92 is permitted to leak in part past the button 96 to the uppe chamber 104, whereupon the leaked water may be conveyed dow the conduit 103 to the shut off valve. When the gel i saturated and the shut off valve operates, the pressure in th chamber 104 increases until the pressure on both sided of th diaphragm 95 are equal, whereby the pressure of the spring 10 seals the end of the upstand portion 94 against the sealin disc 97.

It will of course be realised that while the above ha been given by way of illustrative example of this invention all such and other modifications and variations thereto a would be apparent to persons skilled in the art are deemed t fall within the broad scope and ambit of this invention a defined in the following Claims-.

Claims

1. A method of irrigation comprising the steps of:- providing a source of irrigation water; providing distribution means for said water, and providing a plurality of water outlets from said distributio means, wherein a flow of water out of said outlets i controlled by flow control means operable in response to th moisture level of the soil about said outlets.

2. A method of irrigation according to Claim 1, wherein eac of said outlets is provided with said flow control means.

3. A method of irrigation according to Claim 2, wherein th distribution means comprises flexible polymer tubing adapted t be buried in the ground or laid upon it.

4. A method of irrigation according to Claim 3, wherein th flow control means includes a valve operable by valve contro means responsive to the moisture level of the soil about sai outlet.

5. A method of irrigation according to Claim 4, wherein sai valve control means is of a type not reliant on an externa power source or on a consuming internal power source, an wherein said valve control means is self governing

6. Flow control apparatus for controlling the flow of liqui from an outlet including:- valve means; sensing means for determining the amount of liquid about sai outlet, and valve operating means responsive to said sensing means.

7. Flow control apparatus according to Claim 6, wherein sai valve means is a mechanical valve.

8. Flow control apparatus according to Claim 7, wherein sai means includes an expandible substance that exhibits reversibl expansion by hydration in contact with water and mean responsive to said reversible expansion.

9. Flow control apparatus according to Claim 8, wherein said expandible substance is a hydratable synthetic polymer gel capable of substantial reversible volume change on hydration.

10. Flow control apparatus according to Claim 9, wherein said hydratable synthetic polymer gel comprises beads of a water swellable polyacrylamide.

11. Flow control apparatus according to Claim 10, wherein said expandible substance is contained in a housing comprising a perforate or permeable portion through which the expandible substance may be exposed to the moisture about the outlet.

12. Flow control apparatus according to Claim 11, wherein said valve operating means includes a moving valve operating member in contact with said expandible substance and adapted to translate the expansion and contraction of said expandible substance into a movement which may be used to operate the valve.

13. Flow control apparatus according to Claim 12, wherein said valve operating member comprises a piston or diaphragm disposed in said housing.

14. Flow control apparatus according to Claim 12, wherein said valve is disposed within said housing, and wherein said outlet is provided with an outlet conduit to convey the flow to a point away from the housing.

15. A valve assembly for use in controlling water flow from an outlet and including:- a housing having a water permeable portion; a reversibly water swellable substance disposed in said housing; a movable operating member in contact with said reversibly water swellable substance and movable in response thereto, and a valve operable by said operating member, wherein movement of said operating member in response to water swelling and drying contraction of said reversibly water swellable substance serve respectively to restrict and allow water flow from said outlet

16. A valve assembly according to Claim 15, wherein sai housing comprises a water impermeable valve housing portion the water permeable portion and the water impermeable valv housing portion being substantially divided by the movabl operating member.

17. A valve assembly according to Claim 16, wherein sai reversibly water swellable substance comprises polyacrylamid gel beads.

18. A valve assembly according to Claim 17, wherein sai movable operating member is a piston or diaphragm disposed a or about the boundary between the permeable and impermeabl portions of the housing, said piston or diaphragm being suc that the respective portions of the housing are substantiall sealed one from the other.

19. A valve assembly according to Claim 18, wherein said valv comprises an inlet to said housing, a delivery outlet from sai housing, and sealing means provided on the movable operatin means, said sealing means being adapted to sealingly cooperat with seating means provided on either or both of the inlet o the delivery outlet.

20. A valve assembly according to Claim 19, wherein sai delivery outlet is provided with an outlet conduit fo conveying the water some distance away from the housing.

21. A valve assembly according to Claim 20, wherein sai movable operating member is a piston having a waist defining a annular space between two cylindrical piston surfaces an slidably sealing to the housing, said piston including transfer port providing fluid communication between said inle and said annular space, and said delivery outlet being locate on said housing such that the delivery outlet is in flui communication with said annular space for a selected part o the travel of said piston. 22. A method of irrigation substantially as hereinbefor defined with reference to the accompanying drawings.

22. A flow control apparatus substantially as hereinbefor defined with reference to the accompanying drawings.

22. A valve assembly substantially as hereinbefore define with reference to the accompanying drawings.