GB2267552A - Watering device - Google Patents

Abstract

A watering device releases a charge of water when a predetermined amount of water has evaporated from a control measure in a dish or pan 9, 93. Thus, the device can be arranged to release water to plants in accordance with the conditions around the device, in a greenhouse, for example. The pan 9, 93 is connected to a valve closure member 3, 98 by a rod 5, 96. As in Fig. 9, the valve may act as a pilot control for a main valve 114, various forms of which are disclosed. Water may be supplied to the pan 93 and to a reservoir via a float-operated valve 100 connected to a float through an over centre mechanism. <IMAGE>

Description

WATERING DEVICE This invention relates to a watering device for plants, to a liquid reservoir having a liquid release valve therein, and to a float operated valve suitable for use in a liquid reservoir.

Known automatic watering systems, for example for a greenhouse, either rely on complex electronic control systems timing the release of water, or to systems which release water at a very slow continuous rate.

One aspect of the present invention provides a watering device which releases a charge of water when a predetermined amount of water has evaporated from a control measure. Thus, the device can be arranged to release water to plants in accordance with the conditions around the device. In a greenhouse, for example, conditions which result in a high rate of evaporation of moisture from the soil in which the plants are held will give rise to the release of the water from the device more quickly than when the temperature is lower and the rate of evaporation less.

Preferably in accordance with the invention a liquid reservoir has a valve in a lower part thereof, the valve being openable to release liquid from the reservoir, and control means receiving a measure of the liquid and arranged to open the valve when a predetermined portion of, or all of, said measure has evaporated.

Preferably the control means comprises a substantially vertical rod urged downwardly by the weight of said measure to hold the valve closed, and biasing means urging the rod upwardly to cause the valve to open, the force exerted by the biasing means being just less than the force exerted by said measure before evaporation.

The reservoir may be supplied with liquid through a float operated valve from an external supply, opening of the valve being arranged to replenish the measure of liquid in the control means. The float valve arrangement is preferably provided with interlock means to ensure that the valve in the lower part of the reservoir is held open until the float reaches its lowermost position in the reservoir, thereby ensuring that substantially all the liquid in the reservoir is released. Additionally, the float valve is preferably also arranged to prevent the admission of liquid into the reservoir until the float is at or near to its lowermost position in the reservoir. This ensures that the replenishing liquid admitted through the valve does not close the outlet valve before the reservoir has emptied, or immediately escape through the lower valve in the reservoir.

According to another aspect of the invention, a liquid reservoir has a valve in a lower part thereof, the valve comprising an inlet communicating with the interior of the reservoir, an outlet communicating with the exterior of the reservoir, and a closure member for the inlet and outlet, the inlet, outlet and closure member being arranged such that one side of the closure member can simultaneously close the inlet and outlet, and the closure member can move to open the inlet and outlet to allow communication therebetween, the closure member enclosing on its other side a control chamber in fluid communication with a control reservoir, arranged such that, when the control reservoir is full of liquid, the head of liquid in the control chamber is greater than that at the valve inlet, whereby the closure member is caused to close the inlet and outlet, and a pilot valve operable to allow the liquid from the control chamber to flow into the outlet, thereby releasing the closure member and allowing liquid to flow from the inlet to the outlet.

The closure member is preferably provided with biasing means having two stable states, in a first state the biasing means biasing the closure member to close the inlet and outlet, and in the second state the biasing means biasing the closure member away from the inlet and outlet. For example, the closure member may be mounted in a flexible diaphragm arranged to flip the closure member between its two positions. The pilot valve is preferably operable by a vertical rod extending through a pipe linking the control chamber with the control reservoir. The pilot valve may be arranged to close the pipe when it has moved to a position in which the liquid in the control chamber is released to the outlet.

The control of the pilot valve may be by an evaporative control device in which reduction of the weight of a sample of the liquid by evaporation releases the pilot valve.

Alternatively, a lever arrangement may be provided. In the latter case, the amount of movement by, and the force required on, the lever arrangement to release the pilot valve, thereby releasing the main valve, will be very small, and this renders the reservoir useful as a water closet cistern, usable, for example, by disabled people for whom the normal action required to flush a conventional cistern is difficult or impossible. Flushing can also be controlled by very low powered electrical devices, permitting automatic flushing, for example in response to detection of a user.

There are currently repeated calls to conserve water, and conventional water closet cisterns are frequently adapted by the introduction of a solid body into the cistern to reduce the volume of water used. However, conventional float-operated valves are arranged to admit water as soon as the level drops in the cistern. In the case of a water closet, this means that water is being admitted to the cistern during emptying of the cistern for the flushing action. The volume of water released can therefore be greater than the capacity of the cistern. While the additional water consumed is relatively small in a single flushing operation, the combined additional volumes for, say, a town can be significant.The present invention provides, according to another aspect, a valve which can substantially reduce the additional volume lost by ensuring that the valve does not open until the float reaches its lowermost position, but stays open until the float again reaches its uppermost position. This has the additional advantage of ensuring that the cistern refills as rapidly as possible.

According to this aspect of the invention, a float operated valve comprises a lever whose movement controls the opening and closing of the valve, biasing means connected to the lever and having two stable positions corresponding to the fully open and closed positions of the valve, and a float having an arm arranged to cause the lever to move the valve to its fully open position when the float reaches a predetermined lower level during downward movement thereof, and to cause the lever to move the valve to its closed position when the float reaches a predetermined higher level during upward movement thereof.

Preferably, the biasing means comprises an overcentre spring arrangement, the arm having two spaced stops, one of which engages the lever when the float approaches the lower level, and the other of which engages the lever when the float approaches the upper level. Thus, the lever is flipped quickly from a fully open to a fully closed position when the cistern is full and is opened again only when the cistern is substantially empty. A valve of this aspect of the invention is particularly suitable for use with the reservoirs according to the other aspects of the invention.

Reference is made to the drawings, in which: Figure 1 is a sectional elevation of a watering device according to one embodiment of the invention; Figure 2 is a sectional elevation through a device according to another embodiment of the invention; Figure 3 is a sectional elevation through a liquid reservoir according to yet another embodiment of the invention; Figure 4 is an enlarged sectional elevation through a part of another alternative configuration to that shown in Figures 2 and 3; Figure 5 is a detail partial view of a ball valve arrangement for use with the device shown in Figure 4; Figure 6 is a plan view of part of the device shown in Figure 4, on an enlarged scale; Figure 7 is a sectional elevation through a device according to a fourth embodiment of the invention; Figure 8 is a sectional elevation through a device according to a fifth embodiment of the invention;; Figure 9 is a sectional elevation through a device according to a sixth embodiment of the invention; and Figure 10 is a sectional elevation of a plant watering device of an alternative construction to that shown in Figure 1.

Referring first to Figure 1, the watering device comprises a container 1, suitably formed of a plastics material or of metal, having in the lowermost part thereof an outlet pipe 2 closed within the container by a stopper valve 3. The container 1 has a hinged lid 4 linked from its underside to the stopper valve 3 by a rod 5 which carries at a short distance above the stopper 3 a fixed shoulder 6.

A compression spring 7 extends between the shoulder 6 and the floor 8 of the container 1 around the outlet pipe 2.

The lid 4 is formed with a shallow depression 9 therein and has an outlet pipe 10 extending therethrough. A lip 11 surrounds the lid so that water may be poured onto the lid, some of it collecting in the depression 9 and the rest passing through the pipe 10 into the body of the container 1. Overflow outlets 12 control the maximum height of the water in the container. The force of the spring 7 is such as to be just overcome by the lid 4 when the depression 9 is full of water.

In use, the device is positioned in the same area as the soil, for example, to be watered. The outlet 2 may be connected to the soil to be watered by means of a pipe, or the device can simply be stood on the soil. When sufficient water has evaporated from the depression 9, the spring overcomes the weight of the lid and eases the valve 3 open, thereby releasing the water. It will be appreciated that, when the conditions are very hot and dry, the water will be released from the container more quickly than in cool and moist conditions, thus ensuring that watering takes place when most needed, but not before.

Figure 2 illustrates a larger scale apparatus, which provides watering at intervals over a longer period, instead of a single release of water as in the embodiment of Figure 1. The reservoir 20 is provided with a float operated valve 21 connected to a water supply inlet pipe 22 and discharging water into a control pan 23, when opened. The control pan 23 is mounted above a lid 24 for the reservoir on an arm 25 pivotally mounted on one edge of the reservoir.The arm 25 carries at its free end a slidably adjustable weight 26 and is pivotally linked intermediate to the pivot and the control pan 23 to a control rod 27 at whose other end is mounted a stopper valve 28 which can close an outlet pipe 29 connected to the base of the reservoir 20, and in turn connected to a distribution pipe, or other distribution means providing, for example, a plurality of outlets where needed for watering purposes.

The control pan 23 has an outlet pipe 23a extending through its base so that water exceeding a predetermined level in the pan 23 will overflow through the pipe 23a into the reservoir 20. The control rod 27 has a shoulder member 27a attached to it engageable by the free end of a control arm 27b separately pivoted to the side of the reservoir and so shaped and weighted that the upper end is biased toward the control rod 27 but the lower part is engageable by the float 21a of the float valve when it is at its lowermost position.

In use, the reservoir is filled by the open float valve through the control pan 23 and the overflow pipe 23a.

When the float 21a is at its uppermost position, as shown by the solid lines, the float valve closes. The control pan 23 is full of water to the level determined by the pipe 23a. The position of the weight 26 is adjusted so that it does not quite counterbalance the weight of the pan full of water. In this position, the stopper valve 28 is urged to the position at which it closes the outlet pipe 29.

After a period of time, water evaporates from the control pan 23, reducing its weight and so causing the weight 26 to pivot the pan upwardly, moving the control rod 27 to the upper position illustrated by broken lines. At this position, the control arm 27b becomes engaged under the shoulder 27a, thus holding the stopper valve 28 open. As the water flows out of the pipe 29, the water level in the reservoir drops and with it the float 21a, until it reaches the lower position illustrated by the broken lines. At this position, it strikes the lower part of the control arm 27b, pivoting the top end of the arm outwardly away from the underside of the shoulder 27a.The control rod 27 is then free to move downwardly under the influence of the weight of the control pan 23, which has been filled again as soon as the float valve 21 opens, thus closing the stopper valve 28. The water continues to flow through the pipe 23a into the reservoir until it is again full.

Figure 3 shows an alternative arrangement, in which the control pan 30 is mounted in a rigid support 31 attached to the under side of the lid 32 of the reservoir. The control pan 30 carries a rotatable disc 33 with a eccentric aperture therethrough, by which the level in the pan 30 can be set. A control rod 34 extends downwardly from the underside of the control pan 30 to a float 35, which is in turn connected to a pilot valve 36, which controls an outlet valve 37 in the reservoir, in a manner described hereinafter.

The support 31 is connected to a tube 38 surrounding the float 35 and connected in turn to the pilot valve arrangement 36. The tube 38 communicates at its upper end with a header pan 39, in which is pivotally mounted an open auxiliary float 40 on one end of a lever 41 whose free end rests beneath, but not in contact with, the lower end of the pan 30 when the header pan 39 is full of water. In this position, the weight of the water in the full control pan 30 just overcomes the upward force due to the float 35.

The reservoir is supplied with water from the mains or from a stored supply through a float valve 100 controlled by a lever 101 engaging a valve stem (not shown) in conventional manner. Instead of mounting the float on the lever 101, the end of the lever is pivotally linked to a second lever 102 which has a fork 102a slidably mounted on a fixed pin 103. A compression spring 104 extends between a shoulder 102b on the second lever and a fixed point, so that, in the position indicated by the solid lines in the figure, the lever 101 holds the valve closed under the force of the spring.The float 105 is mounted on a separate arm 106 which carries an upward curved extension 107 mounting two vertically spaced stops 108 and 109, arranged such that, when the float approaches its uppermost level, the lower stop 108 engages the lever 101 and flips it into the upper, closed, position shown in solid lines. As the float 105 approaches its lowermost level during emptying of the reservoir, the upper stop 109 engages the lever 101 and causes it to flip to its alternative stable position, shown in broken lines, at which the valve 100 is fully open.

Thus, the valve does not open until the float reaches, or approaches its lowermost position, thus ensuring that, during discharge of water from the cistern or reservoir mounting the valve, freshly introduced water is not immediately discharged from the reservoir. Additionally, the valve 100 does not close again until the float is at its uppermost position, when it is shut positively under the action of the spring. Thus, during filling of the cistern, maximum inlet water flow is maintained until the cistern is full, ensuring rapid filling. The positive closure action due to the spring ensures that there is no risk of continued trickling of water resulting in overfilling (or overflowing) and consequent wastage.

The outlet valve 37 for the reservoir has a screw threaded outlet pipe42 which passes through a hole in the base of the reservoir and is secured by a large screw threaded collar with sealing washers in a manner conventional for cistern outlets. The outlet pipe 42 has at its upper end an angled passage 43 opening into an annular chamber 44 beneath a closure member 45 held by an annular resilient diaphragm 46. A generally horizontal inlet pipe 47 extends inwardly and upwardly from the body of the reservoir to open centrally of the chamber 44 in such a manner that the closure member 45 closes it off to prevent communication between the inlet pipe 47 and the outlet pipe 42. A conduit 48 leads from the pilot valve 36 to the outlet pipe 42, and is closed off when the valve is held down by the control pan 30.The lower part of the tube 38 communicates with a chamber 49 above the closure member 45 and membrane 46.

In use, with the pilot valve 36 closed and the head of water in the pipe 38 exceeding the head of water in the reservoir, the closure member 45 is held in engagement with mouth of the inlet pipe 47 and therefore closing it off from the outlet pipe 42. As water in the control pan 30 evaporates, the pilot valve 36 is allowed to ease upwardly slightly, in turn allowing water to leak away slowly from the tube 38 to the outlet pipe 42. This gradually drains water from the header pan 39, causing the auxiliary float 40 to drop and the lever 41 to lift the underside of the pan 30, fully opening the pilot valve 36. This closes off the tube 38 from the outlet 42, but more particularly from the chamber 49, which now freely communicates with the outlet.Since the pressure in the chamber 49 is now greatly exceeded by that in the reservoir on the underside of the closure member 45, the closure member lifts, allowing water to flow from the reservoir out through the outlet pipe 42.

As explained hereinbefore, the float valve 100 opens when the float reaches its low water level, admitting water to the control pan 30 and to the tube 38. Excess water overflows from the header pan 39 into the reservoir itself.

At this stage, the float 40 is lifted fully and therefore does not cause the control pan 30 to lift. With the weight of water in the pan 30 again overcoming the lift of the float 35, the pilot valve 36 is caused to close. The head of water in the tube 38, and thus in the chamber 49, quickly exceeds that in the reservoir, and this causes the closure member to move back against the inlet pipe mouth, sealing it off from the outlet pipe 42.

It will be seen that it is not necessary for the control pan 30 to be emptied fully by evaporation to permit the pilot valve 36 to operate. Thus, a very slowly changing evaporating weight can be sensed and go on to open the pilot valve and the outlet valve quickly, producing a large flow of water out of the reservoir. This will enable a distribution header to fill and distribute effectively.

Figures 4, 5 and 6 illustrate an embodiment of the control device usable with the outlet valve for the reservoir shown in Figure 3. The control pan 50 is fixed into the upper lid of the reservoir and contains a control member 51 held by an annular flexible diaphragm 51a. An overflow pipe 52 extends through the control member 51, its upper edge setting the desired height of the water in the control pan 50. By providing the overflow pipe 52 with a screw thread fitting in the control member 51, the height of the water may be adjusted. The control rod 53 extends from the underside of the control member 51 downwardly to the main release valve for the reservoir.A rotatable funnel member 54 may be positioned beneath the overflow pipe 52 to pass water downwardly into the header pipe 55 connected to the outlet valve for the reservoir or may be rotated, as hereinafter described, away from the overflow pipe 52 so that water passing through that pipe passes straight into the reservoir. A helical compression spring 56 extends between the control member 51 and the base of the funnel member 54.

Rotation of the funnel member 54 into and out of position beneath the overflow pipe 52 is controlled by the float valve admitting water to the control pan 50 from a mains supply or from another storage reservoir. The float 60 is mounted on an elongate arm 61 pivotally connected to the body of the valve 62 and having an extension 63 engaging a plunger 64 in the valve when the float is at its uppermost position to close the valve. The extension 63 includes an arcuate slot 65 in which is engaged a pin 66a at the end of a link rod 66, the opposite end of which is shown in enlarged form in Figure 6. Referring again to Figure 5, the upper edge of the funnel member 54 is also provided with a small post 59 around which a slide member 67 (Figure 6) is received.

As the float 60 lifts during filling of the main reservoir, the pin 66a travels along the slot 65 until it reaches the end remote from the valve, when the rod 66 is then pulled.

Further upward movement of the float then causes the funnel member 54 to be pulled by the arm 66 to rotate in a horizontal plane to the position shown in dotted lines in Figure 6.

In this position, the water passing through the overflow pipe 52 will pass straight into the reservoir.

After evaporation of water from the control pan 50, the force of the spring 56 upwardly on the control member 51 overcomes the weight, causing the control rod 53 to be lifted to release a pilot valve, which in turn allows the main valve to open as hereinafter described with reference to Figure 8. As the level of water in the reservoir drops, the float 60 drops with it, opening the float valve 62 to allow water again to flow into the control pan 50 and thence to the reservoir. As the float 60 approaches its lowermost position, the opposite end of the slot 65 engages the pin 66a and the funnel member 54 is again rotated to a position beneath the overflow pipe 52 so that it fills with water which flows down the pipe 55 to the pilot valve as hereinbefore described with reference to Figure 3.

In the embodiment shown in Figure 7, the control pan 70 carries a screw-threaded outlet 71 which sets the water level in the pan by allowing excess water to discharge downwardly beneath the pan. By screwing the outlet 71 up or down, the level may be adjusted. The pan is mounted in a rigid support 72 which is located on the lid 73 of the reservoir. A control rod 74 extends down from the pan 70 to an elongate float 75 having a pilot valve member 76 extending from its lower end to close, in the position shown in the figure, an aperture 77 in a closure member 78. The closure member 78 is held by an annular flexible diaphragm 79 in a valve chamber 80.The space 80a in the chamber above the closure member 78 and diaphragm 79 communicates, around the valve member 76, with the tube 81 enclosing the float 75, while the space 80b below the closure member and diaphragm communicates through annular openings 82 with the interior of the reservoir.

In operation, this embodiment is essentially the same as that shown in Figure 3. Water is admitted via the float valve 100, whose operation is described hereinbefore with reference to Figure 3, to discharge on the pan, from which it overflows to fill the tube 81 and eventually a header pan 83, lifting an auxiliary float 84 therein and allowing the pan 70 to drop to close the closure member against and seal the water outlet 85. Further water overflows from the header pan 83 to fill the reservoir, until the float valve 100 shuts off the water supply.

When sufficient water has evaporated from the control pan 70, it rises to release water from the tube 81 through the aperture 77 into the water outlet 85. As with the embodiment of Figure 3, this lowers the water level in the header pan 83, causing the auxiliary float 84 to drop, thereby lifting the control pan and the float more rapidly, in turn allowing the closure member 78 to lift off the water outlet 85 under the influence of the head of water inside the reservoir. The water in the reservoir is thus allowed to discharge through the outlet 85.

The embodiment of Figure 8 differs from that of Figure 7 only in the design and arrangement of the outlet valve and pilot valve, and only these components will therefore be described. The lower end of the float 75 carries a fluted stem 86 to allow the water in the tube 81 to flow into a pilot chamber 87 from which one passageway 88, closable by a pilot valve 89 on the end of the stem 86, leads to the outlet 85, while another passageway 90 leads to the interior of a flexible valve membrane 91 in the form of a bag or balloon within the valve chamber 92. The valve chamber 92 communicates with the interior of the reservoir and with the outlet 85, which is closable by the membrane 91 when the head of water therein exceeds the surrounding head of water. The membrane 91 may be elastic, for example of a synthetic rubber.

The operation of the valve is generally as described with reference to Figures 3 and 7, except that the lifting of the pan and float lift the pilot valve 89 to close the flow of water from the tube 81 to the pilot chamber 87, and allowing direct communication between the interior of the membrane 91 and the outlet 85 so that the pressure of water in the reservoir forces the membrane to collapse, opening the outlet 85 and allowing the water to escape.

Figure 9 shows an alternative to the arrangement shown in Figure 8. The control pan 93 is in annular form, with excess water overflowing down a central space 94 and through holes 95 into the tube 81. The pan 93 is mounted on a shaft 96 leading to the float 75. The shaft 96 has a collar 97 against which the arm of the auxiliary float 84 bears.

At the lower end of the float 75, a pilot valve 98 is mounted on a shaft 99, and is located in a pilot chamber 110 having an inlet 111 from the tube 81, an outlet 112, normally closed by the pilot valve 98, to the outlet pipe 85, and apertures 113 communicating with the interior of an annular curved collapsible membrane bag 114 which, when inflated with the head of water in the tube 81, seals the outlet pipe 85, and when collapsed allows water from within the reservoir to flow to the outlet pipe 85.

As with the previous embodiment, lifting of the pan 93 lifts the pilot valve 98 to open the outlet 112 and close the inlet 111. This puts the interior of the bag 114 in communication with the outlet pipe 85, and the excess head in the reservoir collapses the bag and releases the water to the outlet pipe 85.

The plant watering device illustrated in Figure 10 comprises a container 120, of any desired size having an outlet 121 in the bottom thereof communicating with a hollow spike 122 attached to the underside of the container 120.

The spike 122 has at its lower end a plurality of outlet holes 123. The outlet 121 from the container is closed by a valve 124 at the lower end of a rod 125 whose upper end supports a shallow control pan 126 which also serves as a cover for the container. The rod 125 has a hollow portion 127 which passes through the pan by an amount which determines the depth of water in the pan. The hollow portion 127 opens sideways into the container, so that water poured on to the pan 126 fills it to the predetermined depth and then runs through the hollow portion 127 and into the container. Holes 128 in the sides of the container control the level in it and indicate when it is full. The rod 125 has a collar 129 around it with a helical compression spring 130 extending between the collar 129 and the bottom of the container, the spring 130 exerting an upward force which almost counterbalances the weight of the pan when full of water.

When sufficient water has evaporated from the pan, the spring 130 raises the valve 124, allowing water to escape from the container into the ground via the spike 122.

Claims (17)

1. A watering device which releases a charge of water when a predetermined amount of water has evaporated from a control measure.

2. A liquid reservoir having a valve in a lower part thereof, the valve being openable to release liquid from the reservoir, and control means receiving a measure of the liquid and arranged to open the valve when a predetermined portion of, or all of, said measure has evaporated.

3. A reservoir according to Claim 2, wherein the control means comprises a substantially vertical rod urged downwardly by the weight of said measure to hold the valve closed, and biasing means urging the rod upwardly to cause the valve to open, the force exerted by the biasing means being just less than the force exerted by said measure before evaporation.

4. A reservoir according to Claim 2 or 3, supplied with liquid through a float operated valve from an external supply, opening of the valve being arranged to replenish the measure of liquid in the control means.

5. A reservoir according to Claim 4, wherein the float valve arrangement is preferably provided with interlock means to ensure that the valve in the lower part of the reservoir is held open until the float reaches its lowermost position in the reservoir, thereby ensuring that substantially all the liquid in the reservoir is released.

6. A reservoir according to Claim 5, wherein the float valve is also arranged to prevent the admission of liquid into the reservoir until the float is at or near to its lowermost position in the reservoir.

7. A liquid reservoir having a valve in a lower part thereof, the valve comprising an inlet communicating with the interior of the reservoir, an outlet communicating with the exterior of the reservoir, and a closure member for the inlet and outlet, the inlet, outlet and closure member being arranged such that one side of the closure member can simultaneously close the inlet and outlet, and the closure member can move to open the inlet and outlet to allow communication therebetween, the closure member enclosing on its other side a control chamber in fluid communication with a control reservoir, arranged such that, when the control reservoir is full of liquid, the head of liquid in the control chamber is greater than that at the valve inlet, whereby the closure member is caused to close the inlet and outlet, and a pilot valve operable to allow the liquid from the control chamber to flow into the outlet, thereby releasing the closure member and allowing liquid to flow from the inlet to the outlet.

8. A reservoir according to Claim 7, wherein the closure member is preferably provided with biasing means having two stable states, in a first state the biasing means biasing the closure member to close the inlet and outlet, and in the second state the biasing means biasing the closure member away from the inlet and outlet.

9. A reservoir according to Claim 8, wherein the closure member is mounted in a flexible diaphragm arranged to flip the closure member between its two positions.

10. A reservoir according to Claim 8 or 9, wherein the pilot valve is operable by a vertical rod extending through a pipe linking the control chamber with the control reservoir.

11. A reservoir according to Claim 10, wherein the pilot valve is arranged to close the pipe when it has moved to a position in which the liquid in the control chamber is released to the outlet.

12. A reservoir according to any of Claims 7 to 11, wherein control of the pilot valve is by an evaporative control device in which reduction of the weight of a sample of the liquid by evaporation releases the pilot valve.

13. A reservoir according to any of Claims 7 to 11, wherein control of the pilot valve is by a lever arrangement.

14. A float operated valve comprising a lever whose movement controls the opening and closing of the valve, biasing means connected to the lever and having two stable positions corresponding to the fully open and closed positions of the valve, and a float having an arm arranged to cause the lever to move the valve to its fully open position when the float reaches a predetermined lower level during downward movement thereof, and to cause the lever to move the valve to its closed position when the float reaches a predetermined higher level during upward movement thereof.

15. A valve according to Claim 14, wherein the biasing means comprises an overcentre spring arrangement, the arm having two spaced stops, one of which engages the lever when the float approaches the lower level, and the other of which engages the lever when the float approaches the upper level.

16. A watering device, substantially as described with reference to, or as shown in, the drawings.

17. A float operated valve, substantially as described with reference to, or as shown in, Figure 3 of the drawings.

17. A liquid reservoir, substantially as described with reference to, or as shown in, the drawings.

18. A float operated valve, substantially as described with reference to, or as shown in, Figure 3 of the drawings.

Amendments to the claims have been filed as follows

1. A liquid reservoir having a valve in a lower part thereof, the valve being openable to release liquid from the reservoir, and control means comprising a pan receiving a measure of the liquid and arranged such that the weight of the pan and the measure holds the valve closed until a predetermined portion of, or all of, said measure has evaporated.

2. A reservoir according to Claim 1, wherein the control means comprises a substantially vertical rod urged downwardly by the weight of the pan and the measure to hold the valve closed, and biasing means urging the rod upwardly to cause the valve to open, the force exerted by the biasing means being just less than the force exerted by said measure before evaporation.

3. A reservoir according to Claim 1 or 2, supplied with liquid through a float operated valve from an external supply, opening of the valve being arranged to replenish the measure of liquid in the control means.

4. A reservoir according to Claim 3, wherein the float valve arrangement is preferably provided with interlock means to ensure that the valve in the lower part of the reservoir is held open until the float reaches its lowermost position in the reservoir, thereby ensuring that substantially all the liquid in the reservoir is released.

5. A reservoir according to Claim 4, wherein the float valve is also arranged to prevent the admission of liquid into the reservoir until the float is at or near to its lowermost position in the reservoir.

6. A liquid reservoir having a valve in a lower part thereof, the valve comprising an inlet communicating with the interior of the reservoir, an outlet communicating with the exterior of the reservoir, and a closure member for the inlet and outlet, the inlet, outlet and closure member being arranged such that one side of the closure member can simultaneously close the inlet and outlet, and the closure member can move to open the inlet and outlet to allow communication therebetween, the closure member enclosing on its other side a control chamber in fluid communication with a control reservoir, arranged such that, when the control reservoir is full of liquid, the head of liquid in the control chamber is greater than that at the valve inlet, whereby the closure member is caused to close the inlet and outlet, and a pilot valve operable to allow the liquid from the control chamber to flow into the outlet, thereby releasing the closure member and allowing liquid to flow from the inlet to the outlet.

7. A reservoir according to Claim 6, wherein the closure member is preferably provided with biasing means having two stable states, in a first state the biasing means biasing the closure member to close the inlet and outlet, and in the second state the biasing means biasing the closure member away from the inlet and outlet.

8. A reservoir according to Claim 7, wherein the closure member is mounted in a flexible diaphragm arranged to flip the closure member between its two positions.

9. A reservoir according to Claim 7 or 8, wherein the pilot valve is operable by a vertical rod extending through a pipe linking the control chamber with the control reservoir.

10. A reservoir according to Claim 9, wherein the pilot valve is arranged to close the pipe when it has moved to a position in which the liquid in the control chamber is released to the outlet.

11. A reservoir according to any of Claims 6 to 10, wherein control of the pilot valve is by an evaporative control device in which reduction of the weight of a sample of the liquid by evaporation releases the pilot valve.

12. A reservoir according to any of Claims 6 to 10, wherein control of the pilot valve is by a lever arrangement.

13. A float operated valve comprising a lever whose movement controls the opening and closing of the valve, biasing means connected to the lever and having two stable positions corresponding to the fully open and closed positions of the valve, and a float having an arm arranged to cause the lever to move the valve to its fully open position when the float reaches a predetermined lower level during downward movement thereof, and to cause the lever to move the valve to its closed position when the float reaches a predetermined higher level during upward movement thereof.

14. A valve according to Claim 13, wherein the biasing means comprises an overcentre spring arrangement, the arm having two spaced stops, one of which engages the lever when the float approaches the lower level, and the other of which engages the lever when the float approaches the upper level.

15. A watering device, substantially as described with reference to, or as shown in, the drawings.

16. A liquid reservoir, substantially as described with reference to, or as shown in, the drawings.