WO1998001021A1

WO1998001021A1 - Soil moisture responder

Info

Publication number: WO1998001021A1
Application number: PCT/AU1997/000435
Authority: WO
Inventors: Clive Lindsay Ragless
Original assignee: Clive Lindsay Ragless
Priority date: 1996-07-09
Filing date: 1997-07-09
Publication date: 1998-01-15
Also published as: TR199900001T2; EP0910238A4; IL127953A0; EP0910238A1

Abstract

A soil moisture responsive system which has a sensor (40) using a moisture swellable material (42) in controlling a flow of water therethrough in response to an amount of water detected and an acuator (47) connected through a conduit to the water flowing through the sensor and arranged to use such supply of water as is provided from the sensor to develop a sufficient pressure to operate a bi-stable device (47) to effect a snap action contol of a valve (51).

Description

SOIL MOISTURE RESPONDER

This invention relates to a soil moisture responder and in particular to an arrangement which can provide for control of water flow in response to an extent of soil moisture.

It is known to use moisture responsive valves using moisture swellable materials to control water supply.

One example among others is Gil et al US 4989628. In this example a body of swellable material is used to operate in conjunction with a snap action device of some complexity by directly acting against it in order to ensure an output so that any actuator by way of a control valve will be turned only either fully on or fully off at any time to assist efficiency of distribution of water.

The problem with the arrangement shown in Gil et al is that the snap action mechanism is complex and implicitly requires a number of separate parts which in turn require a substantial volume within a chamber in order to operate. Further, the snap action device includes relatively moving parts and at least one helical spring all of which are extremely vulnerable in the circumstances in which devices are expected to be used and to operate reliably over a long period of time.

Further, the swellable material acts directly against the complex snap action device. The problem here is that a block of swellable material is used and appears to be needed for the arrangement and this implicitly results in the swellable material needing a substantial time to take up moisture or more specifically time to sufficiently permeate through the material. This will mean that when sufficient water has reached the soil from a watering, nonetheless the swellable material is still having the water level permeate and build up and there is this delay which therefore removes significant advantage from having a water responsive system

Further, such a device as is described by Gil requiring as it does a substantial housing is implicitly relatively expensive.

An object of this invention is to provide a soil moisture responder or components for this which can provide for more effective control of an actuator with the advantage that this allows for better response from the sensor and where a connection between a sensor and the actuator can be simplified over that disclosed by Gil et al or at the least provides the public with a useful alternative.

Accordingly this invention can be said to reside in a soil moisture responsive system including a sensor adapted to act in response to soil moisture levels controlling thereby an actuator, the actuator arranged to convert a change of water flow controlled from the sensor to effect a snap action control of a valve.

In preference the actuator includes a unitary member which is adapted to provide the snap action effect.

In preference the actuator includes a dished spring disk which is adapted to provide the snap action effect.

In preference the actuator is arranged to receive water at pressure from the sensor in response to detected soil moisture and to have this directed against a membrane so that as a result of pressure changes the membrane will effect an opening or closing of a valve with a snap action effect.

In a further preferred form of this invention, there is proposed in respect of a soil moisture responder, a soil moisture sensor which has an element comprised of a material the dimensions of which will change in response to a degree of soil moisture detected in the vicinity, and there are means activated by reason of such change of dimensions so that a flow of water through the sensor will have the rate of flow changed in response to the change of dimension and there is provided water flow control means to provide for a water flow control which includes a valve within a body adapted to locate upon a seat whereby to control a water flow therethrough where the position of the seat is constrained to be in a valve closing position in response to a selected range of water flow from the sensor, and is adapted to be in an open position to allow water flow therethrough when water flow from the sensor is within a different range of water flow.

In preference, there are means controlling the water valve which include a mechanical support comprising a dished spring disk which will have a bulging part which can be caused to move for a substantial distance only (from a concave to convex shape on one side with a snap effect) with a sufficient force which will only be available when water flow from the sensor is within a selected range of flow rate so that there will be an abrupt opening of the valve or an abrupt closing of the valve upon selected flow rates being reached in respect of water flow from the sensor.

It will be understood that the arrangement uses thereby an existing head of water obtainable from the main water supply and therefor the arrangement is able to use some of the energy from this outside source to assist in the control action in the actuator.

This then differs from Gil et al in so far that firstly as the snap action device being used is a dished spring disk this is very cheap to produce and as it does not require separate parts nor separate springs it is implicitly cheaper and simpler than the device shown by Gil et al. Further however its action is substantially assisted by the separate energy supply of a water flow and further the communication from the sensor to the actuator can be through simply the water conduits and therefore can be at an extended distance. This communication is through a connection that is not of course electric with any attendant problems of wires and electrolysis and extra costs.

In preference, water flowing from the sensor is reduced as the soil moisture detection element detects a greater level of soil moisture.

In preference, when the water flows through an activating chamber, an outlet of the activating chamber is restricted so that there will as a result of increase or decrease in flow rate, result in an increase or decrease correspondingly in the chamber which in turn would cause an activating pressure to effect a change of position of the valve in respect of control of the mains water flow.

The problem with this is that water distribution devices very often require a full and adequate supply of water at a pressure sufficient that, for instance, a sprinkler will distribute water to a sufficient area.

If the water supply to a sprinkler has the flow rate only proportionally restricted, then this will have the result that water distribution as such might be compromised. Accordingly, in preference, there is proposed an arrangement such that the activation chamber will have means that will go to effecting a fully on from a fully off position in response to a very small change of water pressure within the activation chamber.

If the main valve is then attached to a portion of an impressed shape, and especially if this is achieved through a loss motion connection, then this will provide the so-called "snap action" effect that is desirable.

In preference a material that has been found to be very effective for use as a moisture responsive material is known by the acronym "Hema" and is a hydrogel of a type used for contact lenses.

The chemical composition of this material is "2-hydroxyethyl 2-methacrylate".

For a better understanding of the invention this will now be described with the assistance of drawings as attached hereto wherein:

FIG 1 is a schematic arrangement including a mains water flow control unit and a soil moisture sensor coupled together in accord with the embodiment;

FIG 2 is a cross sectional view of a soil moisture sensor in accordance with the embodiment;

FIG 3 is a schematic arrangement including a mains water flow control unit and a soil moisture sensor coupled together in accord with a second embodiment;

FIG 4 is a cross sectional view of a soil moisture responder in accordance with a third embodiment;

FIG 4a is a side view of the spring disk in the sensor of the third embodiment;

FIG 4b is a perspective view of the disk of the third embodiment;

FIG 5 is a cross sectional view of a soil moisture responder in accordance with a fourth embodiment; FIG 6 is a cross sectional of the sensor shown in FIG 5 enlarged and shown in one of three alternative positions the first in FIG 6 being shown when the swellable material is dry;

FIG 7 being a cross sectional view of the sensor when the swellable material is at a mid range of wet and dry; and finally

FIG 8 shows the sensor in accord with the fourth embodiment when the swellable material is wet;

FIG 9 is an alternative actuator in accord with a fifth embodiment which could be usefully incorporated as a replacement for the actuator in FIG 5;

FIG 10 is the same view of an actuator as in FIG 9 except that the bi-stable device is an alternate position closing a mains water conduit;

FIG 11 is a sixth embodiment showing a further arrangement for an actuator showing this in an open status; and finally in

FIG 12 this is the same view as in FIG 11 of the same sixth embodiment showing this in a closed status.

Referring in detail to the drawings, and in particular FIGS 1 and 2 there is a soil moisture sensor 1 which is connected at an inlet side to a supply of water at pressure supplied through conduit 2 and at an outlet, a connection to an inlet 3 a mains water flow control 4 through conduit 5.

Referring in detail to the soil moisture sensor, this is comprised of a body 6 having a cavity 7 within which are provided a plurality of elements to provide for a valving action through valve member 8 whereby to control flow of water from conduit 9 through to conduit 5.

Within the cavity 7, there is firstly provided a porous ceramic element 10 which has an outermost face at 11 to provide for its location to be in contact with soil the moisture of which is to be measured.

The ceramic element 10 is held in place by a circlip 12. At an inner end of the ceramic element 10 is a circular sheet at 13 which is comprised of a material which will change its dimensions in accord with the degree of water to which it is exposed.

In this particular case, this is a hydrogel and it has been chosen because its characteristics provide a significant and effective expansion in the presence of a greater moisture content, and it will contract in the presence of a lesser quantity of moisture.

This material 13 is adjacent to an inner face of support 14 of the ceramic element 10 so that it is therefore in continuous intimate contact with an open cellular structure of the ceramic material which in turn is selected so that it will effect a transfer of moisture in accord with the extent of moisture of the soil that it is in contact with, and further such that as the moisture content reduces in the soil, then in turn, this will reflect in the amount of moisture available to the sheet material 13 which in turn then would be expected to reduce in its dimensions.

The sheet material 13 in the shape of a thin disk is retained within a support 14 which is comprised of an impervious material such as an appropriate metal, and the shape of this material includes an annular groove 15 within which the sheet material 13 fits so that with expansion of the material 13, the material is caused then to be confined to apply pressure only transversely to its planar orientation.

The support 14 has a central boss 16 through which a screw 17 passes which applies therefore an adjustable pressure on resilient valve member 8.

This is turn therefore causes an opening or closing of a connection between the peripheral groove 18 which is connected to conduit 5 and the conduit 9.

This then means that in accord with the degree of moisture passing through the ceramic element 10 and into the sheet material 13, there is a control of the valve element 8 and an opening or closing to allow for water passing from conduit 5 through to conduit 9.

In effect then we have a greater flow of water through the sensor 1 which will have the rate of flow of water changed in response to the change of dimension in respect of the material in sheet 13.

By appropriate selection of this material 13 together with its thickness and volume, the sensitivity and speed with which the sensor therefore reacts to soil moisture or changes can be made very effective indeed.

A material that has been found to be very effective for this purpose is known by the acronym "Hema" and is hydrogel of the type used for contact lenses.

The chemical composition of this material is "2-hydroxyethyl 2-methacrylate".

The next question however is what happens in response to this change of water flow.

Accordingly the mains water flow control or actuator 4 includes an activation chamber 19 within which there exists a sheet 20 which extends across the activation chamber so that there is an enclosed area at 21 such that water flowing through conduit 5 through inlet 3 into this area 21 will have a resulting pressure on the shape of the resilient material which will be in response to the rate of flow of water into this area 21 as compared to the rate at which it will exhaust through restriction 22 to an outlet 23.

The shape of the sheet 20 is such that it has on its inner face a convex shape but such that with sufficient pressure in the area 21 , this will be caused to snap to a reverse position so that the inner face is then concave.

This is a well known snap action effect so as to have the result that the centre of this sheet 20 at 24 will lift element 25 which has a certain degree of lost motion but when it reaches a sufficient distance, will directly engage the element 26 which in turn will then lift valve member 27 off a valve seat 28.

This in turn will therefore allow water to reach conduit 29 from a supply into inlet 30.

Some details in connection with the design are the inclusion of a separate chamber 31 which on one side of a flexible membrane 32 has air and on the other is connected in fluid communication with the activation chamber but more particularly the active area of this at 21. This then simply acts to allow for rapid exhaust of a small quantity of water in the event of a snap action of the sheet 20 returning to a closed position in respect of the valve 27 on seat 28.

Otherwise, the activation chamber is vented to atmosphere at 34 and there is included a helical spring 33 which is used to simply assist in biasing the position of the sheet 20 for an initial setting position.

In practice, the degree of moisture to be detected is governed by the setting of the screw 17 on the soil moisture sensor.

Soil moisture sensor can either be located remotely from the mains water controller 4 and connected to this simply by tubes that simply will handle the water pressure or in another case, this sensor arrangement can be integrated into the body of the water control valve.

One of the advantages of the arrangement described is that in the event that the sensor 1 is located remotely from the control valve, and if there is a fracturing of any of the connecting conduits, then at the least, the position of the element 20 will be such as to keep the mains water valve closed and therefore water will not be left to pour out unnecessarily.

There are however a number of variations in respect of the details described which can have advantages in specific cases.

Accordingly in FIG 3 with respect to a second embodiment there is a sensor which includes a hydrophilic material 42 contained between a protecting porous disk 41 and a flexible diaphragm 44 which is positioned a short distance from a valve orifice 45. Water is absorbed through the disk and into the hydrophilic material 42 which expands displacing the diaphragm and reducing the flow of water through the valve orifice 45. The valve orifice 45 is supplied with water from the actuator which, in turn, is supplied from the high pressure water line through a flow restricting device 46. A reduction of flow through the sensor results in an increased pressure within the actuator 47.

The actuator 47 has in this case a purpose of converting gradual change in water flow through the sensor 40 to a snap action independent of a rate of change of flow at the sensor 40. The actuator 47 consists of a housing 48 which contains a dished spring disk 49 which is arranged so that a convex side of the disk will be caused to invert only when a sufficient force is applied. The disk 49 is then adapted by reason of the known characteristics of a dish shape to rapidly invert and there are then means including an actuating rod 50 arranged to close valve 51. The resultant change in flow can then be used to open and close a larger pilot operated diaphragm valve either in the same housing or remotely from this.

In FIG 3, the sensor 40 is arranged so that water at pressure from a high pressure water line 54 defined through housing 67 is fed through conduit 68 through the flow restricting device 46 into chamber 69. The spring disk 49 is biased in the first instance by the actuating rod 50 being pushed into an apex of the dish shape by spring 70.

The actuating rod 50 has at its lower end a valve element 71 which is adapted to sit on valve seat 72 of the valve 51.

This is a pilot valve so that by closing this valve, pressure of water in conduit 73 is no longer equalised so that the effect of spring 74 on diaphragm 75 is such as to then as a result of the balance of pressures close on seat 76.

One of the characteristics of this arrangement is that the pressure in chamber 69 causing the effect on the convex shape or otherwise of the spring disk 49 is subsequent to the restrictor 47 so that the pilot valve 51 will be closed when a higher pressure is attained within the chamber 69 by reason of closure of the bypass through sensor 40 at the valve orifice 45.

In order to clarify the arrangement, there is a conduit 77 feeding into a chamber 78 the opening of which in terms of connection to the conduit 79 is governed by the position of the membrane 44 which in turn is controlled by the extent of expansion or otherwise of this hydrophilic material 42 which is swellable or otherwise in the presence of an appropriate level of moisture.

Conduit 79 exhausts to negligible pressure.

One of the advantages of this arrangement is that there needs only to be a single conduit connection shown at 77 between the actuator 47 and the sensor 40. Referring now to the third embodiment as shown in FIG 4, the sensor 80 cooperates with the actuator 81 by providing control of water being fed from a mains conduit 82 through a conduit 83 which is controlled by reason of pressure of a valve member 84 being pressed against grooves 85 which when the valve member 84 is lifted allows water to pass into the conduit 86 or at least provide water or a combination of water and air so as to flow into the conduit 87 to actuate the actuator 81.

The sensor in accord with the previous descriptions has a thin slice of swellable material 88 which is held within an annular support 89 which is adapted to push through the screw 90 onto the valve 84 thereby to selectively open or close this in response to the degree of swelling of the swellable material 88.

Access of water to the swellable material 88 is achieved through the porous material 91 which is held by a circlip 92 within a housing 93.

The swellable material in this case is the referred to material namely the hydrogel 2-hydroxyethyl 2-methacrylate.

The sensor 80 therefore controls passage of water through the sensor in accord with the degree of swelling of the swellable material and this is fed into the actuator which includes a body 93 which has within it a chamber 94 which has a dished spring disk 95 which in this embodiment has a circular periphery and has an annular rib 96 pressed to extend fully around the outer periphery and at its inner side has an aperture 97 by which it is bolted onto an actuator rod 98 which is connected with lost motion freedom to rod 99 which has at its bottom, a valve closure 100 which is arranged to close onto valve seat 101 thereby closing effectively passage through the mains conduit 82.

The dished spring disk is comprised of a stainless steel sheet material having a raised central boss at 102 but otherwise being shaped so that it is stretched more extensively within its perimeter rather than the metal at its outer perimeter.

This has the effect of causing a bulging effect which results in the material maintaining a first status as is shown in FIG 4 but if sufficient pressure is applied underneath the disk 95, then it will compress or otherwise deform the metal between its perimeter sides to a stage where it will pass through to an inverted shape and with built up resilient forces being released in this way, this action will be an effective snap action.

Helical spring 103 is used to bias the dished spring 95 into the position shown in FIG 4.

Further however, the disk 95 is held and includes a sealing ring at 104 so that there is defined a chamber at 105 where the disk 95 acts as a variably positionable membrane across the chamber 105.

In order to allow for a rapid return from a bulging position of the disk 95, there is a conduit 106 connecting through to a chamber 107 confined by a resilient membrane 108 which allows thereby some buffering to take up some of the excess water ejected from the chamber 105 when this returns in the event of lower pressure within the conduit 87.

The extent of pressure build up in the chamber 105 is governed by the extent of water flowing through the conduit 87 and the extent to which this is allowed to exit through a restriction 108 to a drain 109 which is of course to atmosphere.

Accordingly, it will be seen that there is provided a sensor so as to provide a control of rate of flow of water and this is directed into an actuator whereby a membrane either directly in the form of a disk providing a snap action effect or indirectly through a membrane acting through to a bi-stable member can effect a rapid opening or closing of either a pilot or mains valve in accordance with the degree of moisture detected at the sensor.

We now refer to a fourth embodiment as described in FIGS 5, 6, 7 and 8.

In this case, there is a sensor 110 and an actuator 111. The actuator in this case is substantially the same as that described in terms of the third embodiment and includes a helical spring 112 biasing a spring disk 113 which acts as a membrane to confine liquid within a chamber 114. The difference however is in this case, that the connection to the chamber 114 is by way of conduit 115 but so that water will be directed either solely or in conjunction with air so as to build up pressure as allowed by reason of the operation of the sensor 110 where draining of water is effected directly from the sensor 110.

Otherwise the disk 113 includes the other features including a conduit 116 allowing for access to a buffering chamber at 117 and a connection comprising a rod 118 controlling a mains water supply 119 through valve 120.

The difference however is in connection with the way the sensor operates in that this includes a body 121 which has a central bore 122 in which a rod 123 is acting against a helical spring 124 so that a valve member 125 can act both against a lower seat in the one case at 126 and in an upper seat in the alternate case at 127.

The three alternate positions as shown in relation to each of the FIGS 6, 7 and 8 and the positions are governed by the extent of the swelling of the swellable material 129 which again is selected to be the hydrogel 2-hydroxyethyl 2- methacrylate where the material itself is constrained between an annular carrier 130 and a porous ceramic material 131 which in itself is confined within the body by a circlip 132.

Pressure from the swelling methacrylate 129 is transferred by screw 133 against the valve member 134 which is held in sealing engagement against a seat 135 through seal 136.

The valve material 134 is deformable under the swelling pressure of the swellable material 129 and as such as shown in FIGS 7 and 8, by having a downward displacement of this, this will force the member 123 downwardly with respective closing of the valve 125 against the relevant seat 126.

This relative movement either up or down results in relative closing between a supply of liquid at pressure along conduit 137 which in turn is directed to conduit 115 when the valve member is uppermost, and when the valve member is lowermost, water in the conduit 115 is free to release through to the drain conduit 138 which exits to atmosphere.

One the features of this arrangement is that while some water will be lost each time the sensor cycles through from an opening to a closing and back again to an open position, nonetheless, the amount of water actually lost will be very small indeed.

In the arrangement then it can be seen that there is use of made water at pressure so as effect a build up of pressure over time within the chamber 114 and this then over a substantial area of the chamber defined by the movable disk 114 which acts both as a bi-stable device and a membrane, this can cause this rapid snap action effect.

A further advantage of this arrangement is that while some water is taken from the mains, the amount of water also will be quite small and there is therefore a significantly reduced chance of introduction of debris or residue which can interfere with operation of fine parts within the system.

We now refer to the fifth embodiment as illustrated in FIGS 9 and 10 which show a further form of actuator which can replace the actuator as shown in the fourth embodiment and which can be coupled in the same arrangement and in the third embodiment if a restricter is used.

Accordingly, the actuator 140 is adapted to receive water at pressure dependent upon the extent of moisture detected through conduit 141 and in this case, this water is directed into chamber 142 which is confined by reason of a flexible membrane 143 which is held with relative stiffness at a centre part at 144 and which is allowed by reason of folds around a perimeter shape where this is of circular perimeter shape, at 145.

In this case, the position of the membrane 143 which is now separated from the bi-stable device, is constrained by reason of the bi-stable device 146 which comprises a cylinder 147 which has two surrounding grooves at 148 and 149 and a ball 150 is held under spring tension of spring 151 so as to engage from time to time one or other of the grooves 148 and 149.

The effort and energy needed to push the cylinder 147 from one position to another will of course cause resistance until a certain pressure has been reached at which stage the ball 150 will be pushed by reason of relative alignment of sliding surfaces.

The cylinder position 147 is biased by spring 152. The bottom of rod 153 controls through a lost motion arrangement the position of member 154 which can control the position of valve 155 on seat 156.

The arrangement also includes a buffering chamber at 157 and also a mains water supply at 158.

In FIG 10, there is shown the alternate position.

We now refer to FIGS 11 and 12 illustrating a sixth embodiment which shows an alternative actuator again which is suitable to replace the actuator as shown in the assembly as shown in the fourth embodiment in FIG 5.

It is to be noted throughout that the actuator assemblies can be by slight modification such as including a separate drain, be used with alternate arrangements of sensor.

Now referring in detail to FIGS 11 and 12, this includes a high pressure supply conduit 160 supplying a chamber 161 which is defined by a soft membrane 162 which at its mid area is stiffened by plates 163 on the one side and 164 on the other. The membrane as such operates to confine the pressure released from the sensor and being supplied from a mains pressure supply and operates in the same way to control or open the valve 165 of the mains pressure conduit 166.

The difference here is that the bi-stable arrangement is comprised of an elongate strip of stainless steel that's been shown at 167 which is held in a first bowed shape and which is held in a biased position by reason of spring 168.

A rod 169 passes jointly through the sheet 167 and the membrane 162.

The bi-stable device is therefore in the form of a thin strip of metal held in the bowed shape by reason of being confined at each end that is at 170 in the one case and 171 in the other.

By sufficient pressure then a normally resting status as shown in FIG 12 which is achieved by the pressure of spring 168, can be reversed by a build up of pressure in the chamber 161. A buffer arrangement is also illustrated to allow for rapid change of volume which allows water to be surged into a surge buffer arrangement 173.

As with the other examples of an actuator, a rod 174 is operated through a spring and lost motion to control the position of member 175.

What we have now shown of course is that by using a supply of water using water pressure, this can be used to assist to build up a significant switching or distortion pressure.

The result of this is that any bi-stable device again as has been shown, can be significantly simplified and further, because the effect can be achieved even though a swellable material is of very small volume, nonetheless the results can be achieved quite quickly because of the use of the water supply at pressure driven into a chamber defined by a movable membrane.

As will now be seen, any reference to words such as a spring disk, are intended to be read in the broadest sense and should not be considered to be confined simply to a member of even circular periphery but can as we have shown in one instance here, comprise a thin elongate strip.

For instance, while a particular material has been referred to to provide for moisture detection and provide a dimensional change in response to this, and it is believed the material selected has significant advantages of its own, it is known that other materials can provide effects which can be usefully used.

The value of using a snap action effect will be understood when applied to a situation where sprinklers are being used to water ground for which this application is appropriate, but the operation of those sprinklers is not effective if there is only a partial supply of pressure for supply of the mains water. By achieving this snap action in an effective way, then it can be assured that there is this ability to ensure that irrigation devices particularly where they depend for the water pressure to effect distribution and range of spread, this is therefore achievable in a device of this type which does not use and does not depend on electrical activation or does it need the expense of providing electrical power controls or power supply or does it require any of the maintenance difficulties that will be applicable to many of the electrical powered installations.

Claims

1. A soil moisture responsive system including a sensor adapted to act in response to soil moisture levels controlling thereby an actuator, the actuator arranged to convert a change of water flow controlled from the sensor to effect a snap action control of a valve.

2. A soil moisture responsive system as in the preceding claim further characterised in that the actuator includes a unitary member which is adapted to provide the snap action effect.

3. A soil moisture responsive system as in the preceding claim further characterised in that the actuator includes a dished spring disk which is adapted to provide the snap action effect.

4. A soil moisture responsive system as in the preceding claim further characterised in that the actuator is arranged to receive water at pressure from the sensor in response to detected soil moisture and to have this directed against a membrane so that as a result of change of pressure the membrane will effect an opening or closing of a valve with a snap action effect.

5. A soil moisture responsive system including a soil moisture sensor which has an element comprised of a material the dimensions of which will change in response to a degree of soil moisture detected in the vicinity, and means activatable by reason of such change of dimensions of the material so that a flow of water through the sensor will have the rate of flow changed in response to the change of dimension and there is provided water flow control means to provide for a water flow control which includes a valve within a body adapted to locate upon a seat whereby to control a water flow therethrough where the position of the seat is constrained to be in a valve closing position in response to a selected range of water flow from the sensor, and is adapted to be in an open position to allow water flow therethrough when water flow from the sensor is within a different range of water flow.

6. A soil moisture responsive system as in the immediately preceding claim further characterised in that there are means controlling the water valve which include a mechanical support comprising a dished spring disk which will have a concave part which can be caused to move for a substantial distance only from a concave to convex shape on one side with a snap effect with a sufficient force which will only be available when water flow from the sensor is within a selected range of flow rate so that there will be an abrupt opening of the valve or an abrupt closing of the valve upon selected flow rates being reached in respect of water flow from the sensor.

7. A soil moisture responsive system as in any one of the preceding claims further characterised in that the system is adapted such that a rate of water flowing from the sensor will be reduced as the soil moisture detection element detects a greater level of soil moisture.

8. A soil moisture responsive system as in any one of the preceding claims further characterised in that the system is adapted such that when water flows through an activating chamber, an outlet of the activating chamber is restricted so that there will, due to an increase or decrease in flow rate, be an increase or decrease in pressure correspondingly in the chamber which is in part defined by a membrane which will be distorted in response to change of pressure and cause an activating pressure to effect a change of position of the valve in respect of control of the water valve.

9. A soil moisture responsive system as in any one of the preceding claims further characterised in that there is included a sheet of flexible or resilient material having impressed therein a concave or convex shape which defines and acts as a confining membrane of a part of the activation chamber and such that upon an increase in pressure, the impressed shape can be caused to change from concave to convex in one case or convex to concave in the other with resultant snap action effect.

10. A soil moisture responder as in any one of the preceding claims further characterised in that this includes a sheet of flexible or resilient material which has impressed therein a concave or convex shape which defines parts of the activation chamber and such that upon an increase in pressure, the impressed shape can be caused to change from concave to convex in one case or convex to concave in the other.

11. A soil moisture responder as in any one of the preceding claims further characterised in that the sensor is located at a distance from the actuator which includes a main valve controlling a water supply to a water distribution arrangement.

12. A soil moisture responder including a soil moisture sensor including a water responsive material which will expand and contract in response to a degree of moisture level, and valve means adapted to control a flow of water through the sensor controlled by the extent of changed dimension water responsive material and a water flow control valve adapted to control a mains water flow therethrough in response to an extent of water flow a different range of water flow.

13. A soil moisture responder as in claim 11 further characterised in that there are means controlling the mains water valve which include a mechanical support which will be caused to move for a substantial distance only when water flow from the sensor is within a selected range of flow rate so that there will be an abrupt opening of the valve or an abrupt closing of the valve upon selected flow rates being reached in respect of water flow from the sensor.

14. A soil moisture responder which has two parts, a first being a soil moisture sensor and a second being a main water controller actuator, the soil moisture sensor being arranged to control flow rate of water therethrough in response to an extent of moisture detected, the main water controller including a valve to control a mains water passage, the valve position being controlled by control means connected by a conduit extending between the two parts and adapted to carry water in response to the controlled flow rate so that the rate of water flow through the detector will effect a change in position of the valve to thereby control mains water passage through the controller.

15. A soil moisture responder which has two parts, a first being a soil moisture detector, and a second being a main water controller, the soil moisture detector arranged to control flow rate of water therethrough in response to an extent of moisture detected, the main water controller including a valve to control a mains water passage, the valve position being controlled by control means which includes an activation chamber connected by a conduit extending between the two parts and arranged to be filled with water which will have a pressure which will change in response to changes in the rate of water flow through the detector to thereby effect a change in position of a concave or convex disk to thereby effect control of the valve thereby.

16. A soil moisture responder as in any one of the preceding claims further characterised in that the material is a hydrogel.

17. A soil moisture responder as in any one of the preceding claims further characterised in that the swellable material is 2-hydroxyethyl 2- methacrylate.

18. An actuator for a soil moisture responder of a type as characterised in any one of the preceding claims wherein the actuator is comprised of a chamber adapted to be connected to a supply of water from a sensor in response to a degree of water detected, the chamber being defined by at least one membrane that can be distended with increasing pressure of water and being bi-stable to effect a snap action of an opening or closing of a valve.

19. A sensor for a soil moisture responder of a type as characterised in any one of the preceding claims wherein the sensor is comprised of a moisture responsive material held within a body and such that in response to a degree of swelling of the material there is effected a control of a degree of opening of a valve whereby to control a flow of water which can be used to control an actuator.

20. A soil moisture responder as in any one of the preceding claims further characterised in that the arrangement is such that the actuator will be arranged to effect a fail safe mode in the event of failure of a supply flow of water from the sensor.

21. In combination a plurality of soil responders as characterised in any one of the preceding claims 1 through 17 connected to a common main water supply wherein each of the sensors is implicitly adapted to open or close and associated actuator at a time different from the other actuators.

22. A soil moisture responder substantially as described in the specification with reference to any one of the embodiments and as illustrated by the accompanying drawings.

23. A sensor substantially as described in the specification with reference to and as illustrated by any one or more of the accompanying drawings.

24. An actuator substantially as described in the specification with reference to and as illustrated by any one or more of the accompanying drawings.