GB2502285A

GB2502285A - Flow control device

Info

Publication number: GB2502285A
Application number: GB1208946.2A
Authority: GB
Inventors: Michael Edward Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-05-21
Filing date: 2012-05-21
Publication date: 2013-11-27
Also published as: GB201208946D0; WO2013175180A1

Abstract

A flow control device for locating in a vessel to control the level of a liquid comprises a housing 1 defining a primary chamber 5, and a liquid supply aperture 11 at an upper portion. A float 15 is located within the primary chamber 5 and has a through bore 16 therein for flow of liquid. A fluid conduit 13 communicates between the liquid supply aperture 11 and the through bore 16 in the float 15. The fluid conduit 13 comprises a flexible tube which in an extended state has a substantially open through bore when the float 15 is in the down position, and assumes a kinked state with a substantially occluded through bore when the float 15 is in the up position.

Description

FLOW CONTROL DEVICE

Field of Invention

The invention relates to a flow control device to control the flow of a liquid. The invention in particular for example relates to a flow control device to control the level of a liquid such as a water based liquid in a container. This invention in particular relates to a flow control device based on a hi-stable float valve for the timely and expeditious topping up of the liquid level in a container to a predetermined maximum after the liquid level has dropped significantly to reach a minimum height The invention more particularly for example relates to a flow control device to control the supply of a liquid such as a water-based hquid to plants within such a container, and for example to control the supply of a liquid such as a water-based liquid to a medium such as a growing medium for such plants, for agricultural or horticultural purposes. The invention further for example relates to a liquid supply system such as an irrigation system to provide a controlled supply of a liquid such as a water based liquid to a container in particular to control liquid level in bistable manner between a higher level and a lower level and to a method of the same for the supply of liquid to a container in particular at a higher level and a lower level and for example to growing plants therein, and for example for irrigation of a medium such as a growing medium) for example for agricultural or horticultural purposes.

The invention more particularly concerns flow control devices for controlling the supply of irrigation water and the like to shallow vessels such as trays and dishes) containing onc or a number of plants, whether separately contained and/ or in a growing medium or otherwise. Such systems are used principally by horticulturalists, gardeners and growers of plant species both under cover and outdoors) where the bi-stable operation of the valve is desirable. It is known to be desirable in many agricultural or horticultural applications for growers of plant species both under cover and outdoors to provide a watering system that has a degree of hi-stable operation to ensure that plant roots are not permanently waterlogged but have periods of relative wetness and periods of relative dryness for aeration and like purposes for example to ensure that plant roots are not permanently waterlogged. It may be desirable also for the device to have a secondary closure feature which will operate in the event of a failure of the primary valve, so reducing the risk of flooding.

Description of the Prior Art

A known general class of device suitable for providing flow/ liquid level control for such a watering system incorporates a float valve. Many designs of liquid-control float valves are known to facilitate the movement of liquids from a source to both open and enclosed containers and these can be broadly arranged into groups, four of which can be represented by: 1. End Stop Valves for example incorporating float valves under the action of which an orifice may be closed off by a resilient disk, 2. Pinch Valves for example incorporating float valves under the action of which a liquid supply tube can be mechanically pinched to restrict the supply, 3. Kink Valves for example incorporating float valves under the action of which a liquid supply tube can be mechanically kinked to restrict the supply, and 4. Atmospheric Valves, with or without a float, which rely on the breaking of a partial vacuum to release a quantity of liquid.

Examples of such devices are described below.

Automatic Plant Waterer -DE 19808654 -Schiermeir and Kapfer Describes a float valve fittcd through a sidc wall of a water tray. Because this type of valve can operate with a pressurised liquid supply (1 to 4 Bar gauge) i.e., it has a large mechanical advantage, one valve could supply water to many pots in a single large tray. However it can be seen that such a valve needs height in which to operate the float arm which has to be longer than illustrated for the higher supply pressures, as a consequence the flower pots are shown raised up from the base to prevent much of the plant root system from being permanently submerged in water.

Further the orifice, approximately 2 mm in diameter, may easily be blocked by debris, matter, etc. and only has a small liquid level difference between its closed maximum liquid height and a lower liquid height at which it starts to reopen. This valve is best described as a top up' valve and works very well at maintaining the level of liquid in a tank within the limits of a centimetre or so. Without secondary intervention it is not able to reproduce the beneficial drain-out state' described above.

Liquid Level Control Device -US 5,671,562 -Fab Describes a combination float valve and an atmospheric valve, where a first float is employed to close off the supply liquid (conventional float) and a second float is employed in the process of both releasing and creating a partial vacuum -in order to effect a delay between a maximum liquid level state and a beneficial minimum liquid level state thus allowing time for aeration of the root systems being watered.

This device, though proven to be effective even with a pressurised liquid supply of up to 1 Bar gauge, requires a clean liquid supply to operate effectively. For very low pressure operation typically in the range of 0.5 to 2.0 metres water-head (which is a more practical operating range for growers supplying irrigation water from water butts, etc) and to be necessarily compact the valve has a short float arm length and consequently a small sealing orifice in the region of 2 mm in diameter which readily blocks up unless clean water is employed. At the preferred low head pressure and because of the need for compactness each device is only capable of satisfying the watering needs of one or two large plants if it must also provide for the beneficial drying out period during each watering cycle. Consequently it is not realistic to consider scaling up this lever-arm float device to operate with an orifice bore in the region of 6 to 10 millimetres, so as to be able to irrigate many more plants from a single device -AND with water containing all manner of suspended matter.

Additionally experimentation shows us that the potential for this valve to benefit from a maximum partial vacuum condition -to securely effect the desirable delay in refilling -is not properly realised as the liquid level in the vessel or shallow tray has to drop appreciably to lower the second float sufficiently to close-off the air access into the chamber containing the first float, i.e. the partial vacuum is less robust than would be the case given an improved design requiring no movement of a float to effect ftc air valve seal. Further this device does not offer the user any protection against the risk of flooding in the event that the primary float valve seal crumbles or becomes displaced from its seating.

Sap Feeder and Regulator -US 430,968 -E Minor Describes a pinch valve operated by a float and a lever arrangement having a mechanical advantage sufficient to dose off the liquid supply when a predetermined liquid height is reached. In common with the first example, and though not specifically designed for the supply of liquid to shallow trays containing plants, the device opens and closes incrementally at the nip zone and so is readily blocked by debris when this is present in the supply liquid. As a top up valve and given a clean free-flowing liquid the valve is satisfactory and operates effectively within reasonable limits of a centimetre or two. Noteworthy is the fact that the float has a large base area -to generate the primary force necessary to pinch the supply rube -and is shallow in height having its operational alignment controlled by the connecting rod and lever arm arrangement.

Christmas Tree Feeder -Us 6,260,303 Bi -Sappenfield Describes an End Stop float valve wherein a cylindrical float rises directly upwards within a hollow cylindrical vessel to abut against a liquid supply entry orifice or exposed tube end. This device works effectively with very low liquid-head pressure (e.g. 500 millimetres or less of water head] but the supply liquid must be kept clean so as not to accumulate any debris on the top sealing surface of the float or around the supply orifice against which it engages in order to close off the passage of a liquid. It is evident that in operation all of the working liquid passes over the top of the float and down its side wall before exiting at the base, to the application vessel, i.e., an external reservoir. By installing the valve remote from the application vessel the designer has been able to gain the dimensional height needed for the valve to operate effectively. However of necessity this device is a simple top up valve, and geared to maintaining a desired liquid level in a system within reasonaHe limits of

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for example a few centimetres. Unlike the previous example it is noteworthy that of necessity the float is relatively tall and narrow, dimensions which help to maintain its vertical alignment within the outer tube and facilitate the accuracy of sealing at its uppermost surface, provided that the liquid is clean and that the float has sufficient buoyancy to effect the required seal against the supply orifice.

Water Level Controller -US 2,241,636 -Eliason This device is one method of producing a Kink Valve operated by a float for use in a shallow system, for example an animal drinking trough. And although very effective the action is similar as before, i.e., a top up valve -the valve operates incrementally, i.e., as it starts to un-kink liquid starts to seep though the constrained region of tube, increasing as the un-kinking develops, but this is only effective when a clean supply of liquid is employed, as for example might be the case if connected to a municipal water supply. Although the illustrations cited appear straightforward in practice it will be understood that the resilient tube being almost permanently semi-kinked will fatigue over time, developing a permanent set' and also entrap debris, which then has the opportunity to clump together, if this is present in the supply liquid.

Fluid Level Control Float Valve -US 5,090,443 -Jacobsen Describes a Kink Valve operated by a float which again is described as a top up valve in that from a shut off [closed state), a small fall in the liquid level will incrementally open [partially un-kink) the resilient tube to allow the passage of liquid -to top up the system. Although the illustrations cited appear straightforward in practice it will be understood that the resilient tube being almost permanently semi-kinked will fatigue over time, developing a permanent set' and also entrap debris, which then has the opportunity to clump together, if this is present in the supply liquid.

Further because of the dimensional constraints of the outer float housing, to keep it upright and moving freely in the vertical plane, the bulk of the supply liquid would normally splash around over the top surface of the float The valve could be engineered to avoid this but the design lacks the delay mechanism, referred to earlier, which is sought after by horticulturalists, gardeners and the like and recognised as essential, if plants are not to rot-off in their pots.

Automatic Potted Plant Waterer -US 5,425,198-Coy Describes an atmospheric valve, comprising an open topped vessel filled with water which is skilfully inverted and stood on a surface to be irrigated, whereby the liquid is held within the vessel by atmospheric pressure for as long as the opening in the vessel (downward facing] remains below the water level in the shallow watering tray. As water is consumed by evaporation and by one or more plants the liquid drops to a level approximate with the opening in the vessel so allowing water to gush out in exchange for air entering until the liquid level rises say 10 millimetres above the opening and the exchange is terminated, i.e., until the liquid level drops back to below the opening and to the point where the meniscus is overcome. It is worth noting the simplicity of this device but similar to most of the previous examples this valve is best described as a top up valve and not capable of creating sufficient desirable variation between the wetted up state and the drained out state previously referred to. Further the regular replenishing of this type of waterer' presents a number of practical challenges.

Control Valves and method of Plant Growing using Flow Control -US 5,273,066-Graham etal.

Describes an end stop valve operated by a disk of moisture swelling polymer wherein, in the wetted-up state, a thin resilient membrane is pressed against a solid surface having both water inlet and outlet ports, to close off the flow of irrigation water to plants in containers. It is worth noting that in practice this valve is very quickly rendered useless when turbid water is employed as the water channels are generally less than 2 mm. The patent document illustrates a number of configurations for the valve which on its own is not capable of reproducing the desirable bi-stable effect for the wetting up and partial draining of the plants being irrigated. In a more recent development this valve has been incorporated into a more complex assembly which enables the User to achieve a variable bi-stable watering effect The valve is currently available in the United Kingdom through www.garden-innovations.co.uk.

All of these types of valve have been used in horticultural applications to control the supply of irrigation water to shallow trays within which are commonly placed one or two pots containing plants. These types of valve generally perform as intended when the supply liquid) for example irrigation water, is clean and free from debris such as suspended particles) dissolved compounds and living and dead biological matter e.g., leaf fragments and mosquito larvae (dead and/or alive). However in practice it may often be desirable to supply from a turbid source containing such debris. The debris can accumulate to quickly render the valves inoperable. It is desirable to develop a design of flow control device that works effectively with turbid water containing such debris.

Further) a number of prior art designs work better at supply pressures in the region of 1 Bar gauge (approximating to 14.5 psi, 33.5 ft or 10.2 m of water head) which it will be understood would require a sizable water tower, and/ or pressure reduced feed from the municipal mains water supply commonly rated at 4 Bar gauge to supply only a limited number of plants. In practice it may often be desirable to supply multiple plants from a source with a limited head of pressure such as a water butt. It is desirable to develop a design of flow control device that is capable of passing the volume of liquid needed to periodically restore the liquid level in large shallow trays (such as might for example contain up to ten mature tomato plants) from a low liquid head supply (for example below 3.0 metres and preferably in the range of 0.5 -2.0 metres). Such a supply head for a water-based irrigation liquid may produce a supply pressure of around 0.05 to 0.20 bar gauge. Often it is desirable for this to be followed by a significant) yet not excessive, time delay between the closure of the valve at its uppermost condition and its subsequent reopening and normal course of refilling, to create a beneficial period of aeration of the root systems.

Further it will be appreciated from the prior art archives that where a resilient tube is employed and required to repeatedly kink and un-kink to control the supply of liquid to a vessel or system) a rupture of same at or in the vicinity of the kink zone'

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would result in continuous leakage until the supply either ran out or was turned off upstream -none of the prior art refers to this issue. It may be desirable to develop a design of flow control device that fails closed rather than open to prevent this.

It is desirable to develop a design of flow control device that mitigates some or aH of the above disadvantages and in particular that works effectively with water containing debris and/ or supplied with a relatively low head of pressure.

Summary of the Invention

According to the invention in a first aspect, a flow control device adapted to be located in a vessel to control the level of a liquid therein is provided, the flow control device comprising: a housing defining at least a primary chamber open towards a base portion to effect fluid communication in use with liquid in the said vessel and having a liquid supply aperture through an upper portion of the housing and a one way valve aperture letting into an upper portion of the chamber to allow the egress of air from the chamber but to restrict return flow; a float located within the primary chamber such as to rise and fall therein in use at least between a higher or up position and a thwer or down position having a through bore therein for flow of llquid; a fluid conduit fluidly communicating between the liquid supp'y aperture and the through bore in the float so that the said liquid supply aperture, fluid conduit and through bore together constitute a fluid supply path within the chamber from outside and through the upper portion of the housing towards the base portion (and hence to the said vessel in use); wherein the fluid conduit comprises a flexible tube so configured as to describe an cxtcndcd statc with a substantially open through boro whcn the float is in thc down position and to describe a kinked state with a substantially occluded through bore when the float is in the up position; and wherein the housing includes a lower apertured portion providing fluid communication into the primary chamber, the lower apertured portion opening externally approximate with but extending above a base level of the housing.

Thus, ftc float sits in a primary chamber defined by the housing and is able to move at least between a higher or up position and a lower or down position. It defines (although it is not required to fluidly seal between or isolate) an upper portion of the primary chamber and a lower portion of the primary chamber. The housing includes at least one aperture letting into an upper portion of the chamber, for example comprising an aperture in the housing above the top position, having a one way valve to allow the egress of air from the chamber as the float rises, but to restrict its reentry. A further aperture letting into an upper portion of the chamber provides for the inlet of a liquid supply, but is otherwise sealed to outside air. A lower portion of the chamber is open, for example in that the housing is at east partially open at its base, to allow liquid ingress and egress to and from a vessel in which the device is located. In use, the device is located in a vess& with a variaNe liquid level, so as to both contrcil and respond to liquid eve1s in the vessel.

In use, with the liquid level low in the vessel, liquid level is correspondingly low at or below a first predetermined level. In this state the float is pulled down under action of gravity and the flexilMe resilient kinkable tube is pulled straight and fully open [un-kinked). In this state it is not occluded and liquid can pass through the supply aperture in the housing, through the tube, and on through the float through bore into a lower portion of the primary chamber beneath the float and outwards into the vessel. The vessel fills with liquid.

The vessel is open to the atmosphere and liquid level rises accordingly. Increasing accumulation in the vessel will additionally tend to raise the float and to displace air in the primary chamber via the one way valve aperture to the atmosphere. The float rises. As the float moves in use to an up position when the lev& of liquid in the chamber is at or above a second predetermined level the flexible resilient tube will become kinked and closed-off to the passage of further liquid flow downward through the device and into the vessel. The float and flexiHe resilient kinkable tube thus act as a float valve in admirably simple manner, in which the float valve closes once the level of liquid in the chamber is at or above a second predetermined lev&.

The present invention provides a hi-stable delayed-action flow control by means of the lower apertured portion providing fluid communication in use between the chamber and the vessel, which apertured portion opens externally to be in fluid communication with the vessel at a point towards but above a base level of the housing.

As water is lost from the vessel over time for example through evaporation and use by plants growing therein) the liquid level in the vessel starts to drop. The one way check valve is sealed to the inward passage of air and a partial vacuum is created in the uppermost region of the chamber which will maintain the liquid level therein at a level such that the float will not fall to a level to open the first valve by un-kinking the resilient tube.

This may continue until the liquid reaches a lower third predetermined level [which maybe approximate to the first predetermined level) at which point the liquid level in the vessel has fallen to below the level at which the lower apertured portion opens thereinto. The vessel is open to atmosphere. Thus, at this point, the lower apertured portion in fluid communication with the chamber and previously submerged is open to atmosphere. By means of this the partial vacuum is overcome and air is drawn in through the lower apertured portion and upwards into the upper region of the primary chamber above the elevated float, allowing the liquid beneath and round the float to drop down and the float to drop to a down position, in so doing pulling fully open the flexible tube, and allowing the supply liquid to resume flowing downwards through the float to the lower portion of the primary chamber and outwards into the vessel. The cycle is repeated in successive bistable manner. This is known to be desirable to ensure that plant roots are not permanently waterlogged but have periods of relative wetness and periods of relative dryness for aeration and like purposes. Most plants do not grow well if much of their root system is permanently water-logged. In most cases for land based plants, periodic short term draining of the water from their roots allowing air to enter the growing medium is beneficial to the plant. The invention achieves this in admirably simple manner with few moving parts.

The design of the invention means that none of the apertures/ channels defining the flow of liquid from a supply source externally of the housing to a delivery point below the float and hence into the vessel in use need be particularly restricted.

Many prior art designs have necessarily restricted apertures, for example as small as 2 mm in diameter, at some point in the flow channel. Such small bore points in the flow channel may serve as flow restrictions and/ or as a likely site for blockage if the water is turbid. Accordingly, in practice) such designs may be limited to supply with clean water and/ or with water at relatively high pressure) for example 1 bar or more. It can be noted that to produce a pressure of 1 bar gauge at atmospheric pressure at sea level by gravity alone will require a head of water of around tOm.

By contrast, the design of the invention has no such limitation. The valve closure is constituted in the flexible resilient kinkable tube, which may have a tube bore that is relatively large. Similarly, any aperture letting into the housing that connects any external supply tube to this flexible resilient kinkable tube, and through bore in the float, and any downstream supply conduit that may be present to deliver liquid from the through bore to a supply site in the lower portion of the chamber) may be relatively large.

A typical supply tube for supply of liquid from an external source to a device in accordance with the invention may have a bore linear dimension and for example a bore diameter of 3 mm or more and for example 5-10 mm. In accordance with the invention it is possible for there to be no more constricted point in the flow path. All parts of making up the flow path channel may conveniently define, and in the preferred case do define) a through bore at least as large in cross section as the intended external supply tube. Thus for example each may conveniently define, and in the preferred case do define, a through bore with a diameter of 3mm or more and for example 5-10mm or more.

This flow path is defined in particular by the flexible resilient kinkable tube, the aperture letting into the housing that connects any external supply tube to this flexible resilient kinkable tube, the through bore in the float, and any downstream supply conduit that may be present to deliver liquid from the through bore to a supply site in the lower portion of the chamber. Each such component may conveniently have, and in the preferred all do have, a through bore at least as large in cross section as the intended externa' supp'y tube and for example a through bore with a diameter of 3 mm or more and for example 5-10mm or more.

In particular because of the absence of a restriction on orifice size, the design of the invention is admirably suited to operation with more turbid water and! or at lower heads of pressure when comparison is made with many prior art designs. It is thus suitable for example for supp'y from a water butt. It is mechanically simple and scaleable. The new invention is an admirable solution to provide the preferred higher irrigation flow rate from the preferred lower water head, and to achieve this reliably even when the feed water is turbid and contaminated. The new invention is an admirable solution to provide the desired bistable effect with drain out between a wetted state and a dried state which is known to be desirable for cultivation of many plants, and to achieve this reliably even when the feed water is turbid and contaminated.

An additional advantage in the arrangement can be seen in that it readily lends itself to adaptation such that the flow path defined between the external supp'y aperture letting into the housing and the through bore in the float may inherently close if the tube is ruptured, for example by means of a secondary dosure mechanism if the float rises to a failsafe position above the up position. For example this may be effected by appropriate juxtaposition of the external supply aperture letting into the housing and the through bore in the float and/ or by provision of suitable spigots and/ or pressure surfaces associated with the external supply aperture letting into the container and/ or the through bore in the float that will tend to close the fluid path between the external supply and the lower portion of the chamber if the float rises to a failsafe position above the up position.

In this way, should a rupture occur in the kink tube wall which would normally result in the supply liquid then being supplied continuously and uncontrollably to the vessel -an undesirable condition -the float would be raised up further and beyond its norma' top operating position to reach this fourth predetermined failsafe operating position (desirably in the region of S -25 mm above the height of the second normal operating position) where the two opposing ends of such hollow spigots and whatever portion of kink tube remains attached are pressed together, sandwiching the kink tube, for as long as the float remains in this elevated state, so forming a viable emergency seal to stem the flow of liquid into the vesseL A device in accordance with the invention includes a housing defining at least a primary chamber in which a float is ocated such as to rise and fall therein in use at least between a higher or up position and a tower or down position. A supp'y conduit arrangement as above described provides for supply of liquid into the chamber and through the float to a delivery point below the float in a lower portion of the chamber. The chamber is open towards a base portion to effect fluid communication in use with a vessel in which the device in accordance with the invention is placed in use and hence enables supply of liquid thereto and level control therein.

To effect this, the housing may comprise an elongate enclosure that is at least partly open at the base and for example compet&y open at the base. An upper portion of the endosure above the float level and typically in use exposed to ambient atmosphere, may be fluid tight save for the said liquid supply aperture and for the said one way valve aperture. The liquid supp'y aperture provides a flow channel for liquid from a suitable source to the housing but is sealed to ambient atmosphere.

The one way valve aperture is adapted to prevent the passage of air from ambient to the upper part of the chamber but to have a minimal opening pressure such as to allow the egress of air from the upper part of the chamber as the float rises in use.

The one way valve aperture is for example provided with a valve means such as a diaphragm va've with a minimal cracking pressure such as to allow the egress of air from the upper part of the chamber as the float rises in use but to prevent the return passage of air back from ambient to the upper part of the chamber.

A lower part of the enclosure above the base may be similarly fluid tight save for the lower apertured portion.

As has been noted, it is established that it may frequently be desirable for the system to effect repeated supply cycles in successive bistable manner as is known to be desirable in horticulture to ensure that plant roots are not permanently waterlogged but have periods of relative wetness and periods of relative dryness for aeration and like purposes. The present invention provides a bi-stable delayed-action flow control in part by means of the lower apertured portion which provides a fluid communication in use between the chamber and the vessel, which apertured portion is configured in some way such as to open externally to be in fluid communication with the vessel at a point towards but above a base level of the housing. This acts as a valve mechanism to overcome the partial vacuum initially created when the liquid level in the vessel starts to drop by allowing air through and thence upwards into the upper region of the primary chamber above the elevated float once liquid in the vessel falls below this lower apertured portion.

Most simply, the lower apertured portion may comprise an arrangement of one or more apertures in an enclosure defining the housing located at a point above the base, and for example let into a side wall of the enclosure above the base, which is such as to be at a suitable height in use as to be sealed by the level of liquid in the vessel when the water level is at its higher level but to be exposed to release the vacuum as above described when the water level falls sufficiently below the level of the one or more apertures for any meniscus effects and the like to be overcome and air from ambient to be drawn into the apertures and upwards into the upper region of the primary chamber.

Such a simple aperture lets ambient atmosphere into the primary chamber directly at a point below the float. It must then pass up past the float to the upper part of the primary chamber. This may no be the most stable arrangement as in practice it is common for floating matter to be present in the form of dead insects, leaf litter and the like, and these may also be drawn in, with the inward rush of air, into ftc clearance between the float and the primary chamber and may obstruct any further movement of the float either up or down.

Accordingly, and to cope with a high incidence of floating matter, the lower apertured portion preferably comprises a flow conduit to fluidly link an outlet in direct fluid communication with the vessel in use at a kvel above the base of the housing but below the float and an inlet in direct fluid communication with the primary chamber at a level above the top position of the float. For example the housing may comprise one or more secondary chambers having a first outlet in direct fluid communication with the vessel in use at a evel above the base of the housing but below the float and a second outlet in direct fluid communication with the primary chamber at a level above the top position of the float. Where there is a low incidence of floating matter, the partitioning wall between the primary chamber and the one or more secondary chambers, may be omitted in major part or entirely, so effectively forming lobed annexes to the primary chamber wherein ingested floating matter has more freedom of movement and is less likely to interfere with the up and down movement of the float.

In this way the fluid path between the outlet into the vessel and the chamber is seakd to ambient atmosphere as before so long as the liquid leve' in the vessel is above the outlet but is open to ambient atmosphere when the liquid level falls below allowing ambient air to break the partial vacuum and supplying the same directly to the upper part of the primary chamber above the float.

Conveniently the housing defines a primary chamber with an &ongate cylindrical or prismatic inner volume in which the float may rise or fall. Conveniently the housing correspondingly has elongate parallel side wall(s). Conveniently, a float comprises a float body extending laterally across a major part of the cross section of the chamber. The float is preferably sized and shaped to sit stably in the primary chamber but is not intended to fluidly isolate the top portion of the chamber above the float and the bottom portion of the chamber below the float Indeed, necessarily in embodiments where liquid and/or air needs to flow within the primary chamber past the float at some point in the cycle, and in any event desirably to limit fouling with debris, flow passages between an inner chamber wall and an outer float wall may be desirable. A float may have a cross-section several mm less than that of the chamber. For example a 3-5mm gap around the float body may be desirable.

Stabilising vanes may extend from an outer float wall of the float body towards an inner chamber wall. The float body may be of any hollow or closed cellular or solid construction or combination of the same that is less dense than the supply liquid and will therefore rise with the llquid evel in the desired manner. For examp'e the float body maybe of a hollow or closed cellular or solid construction or combination of the same with a density substantially less than 1 g/cm3.

In a more complete embodiment the flow control device of the first aspect of the invention may be provided with a suitable liquid supply source to supply liquid to the liquid supply aperture of the flow control device and/ or a suitable vessel into which liquid maybe suppiled in level-controlled manner from the open base portion of the chamber in the manner above described.

Preferably the liquid supply source is a source at low pressure for example at a liquid head of 0.2 to 3.0 m (for example at a pressure of around 0.02 to 0.30 bar gauge). The liquid may be water based irrigation liquid. The supply source may include a water butt for example at a head of 0.2 to 3.0 m [taking account of operational maxima and minima water levels).

The flow control device of the first aspect of the invention in particular for example relates to a flow control device used to control the level of a liquid such as a water based liquid in a vessel.

The flow control device of the first aspect of the invention may comprise a small number of components which may for example be modular and assemblable/ disassemblable for cleaning and maintenance.

In a further aspect of the invention a kit of parts is provided for assembly into a flow control device of the first aspect of the invention. For example such a kit of parts may comprise at least one each of the following: a housing as above described for example defining at least a primary chamber open towards a base portion to effect fluid communication in use with liquid in the said vessel and having a liquid supply aperture through an upper portion of the housing and a one way valve aperture letting into an upper portion of the chamber to allow the egress of air from the chamber but to restrict return flow, and a lower apertured portion providing fluid communication into the chamber, the lower apertured portion opening externally towards but above a base level of the housing, and for example at a level below the float but above the base of the housing; a float as above described for example adapted to be located within the primary chamber such as to rise and fall therein in use at least between a higher or up position and a lower or down position and having a through bore therein for flow of liquid; a fluid conduit fluidly as above described for example comprising a flexible tube attachable between the liquid supply aperture and the through bore in the float so that the said liquid supply aperture, fluid conduit and through bore together constitute a fluid supply path within the chamber from outside and through the upper portion of the housing towards the base portion.

Optionally a flow control device of the first aspect of the invention or a kit of parts for such a flow control device may be provided with a vessel for containing liquid, with which vessel it is intended to use the flow control device to control the level of a liquid therein. The vessel is for example a water tray for the containment of growing plants for horticulture or the like. The flow control device and vessel may conveniently be adapted to connect together for use, for example in that a housing of the former is provided with engagement means to engage upon complementary receiving means in the latter.

The invention in a further aspect comprises a system for the control of the level of a liquid such as a water based liquid in a vessel comprising a flow control device as above described in accordance with the first aspect of the invention disposed within a vessel adapted to contain liquid in use, so that liquid may be supplied in level-controfled manner from the open base portion of the chamber to the vessel in the manner above described.

Preferably the vessel intended for use with the flow control device of the first aspect of the invention or provided with the system of the second aspect of the invention is a container for growing plants, for example a tray into which plural growing plants may be disposed whether in further containers or otherwise, and whether in a suitable growing medium or otherwise. It is an advantage of the invention that a single flow control device may supply a tray with multiple growing plants even where the supply of water is relatively turbid or at relatively low pressure.

The invention in a further aspect comprises a method for the supply of a controlled level of a liquid such as a water based liquid to a vessel and for example to growing plants therein, and for example for irrigation of a medium such as a growing medium therein, for example for agricultural or horticultural purposes.

The invention in this further aspect comprises the use of a flow control device of the first aspect of the invention in such a vessel connected to a suitable supply of a liquid such as a water based liquid or to the use of a system of the second aspect of the invention connected to a suitable supply of a liquid such as a water based liquid.

The invention in particular in this further aspect comprises operating the flow control device as above described to effect successive discrete cycles of supply of liquid to the vessel.

More completely the method comprises: disposing a flow control device of the first aspect of the invention in a vessel adapted to contain a liquid; supplying a liquid to the flow control device; operating the device such that the following occur successively and repeatedly: 1. liquid is supplied to the vessel through the device, the liquid level rises in the chamber, the float rises in the chamber, the tube kinks, and the flow channel therein is restricted; 2. liquid is used from the vessel, the liquid level falls but remains above an outlet of the lower apertured portion, a partial vacuum establishes in the chamber such that the float does not fail sufficiently to open the flow channel therein; 3. further liquid is used from the vessel, the liquid level falls below an oulJet of the lower apertured portion exposing the same to ambient, the partial vacuum is broken such that the float falls sufficiently to open the flow channel therein, and liquid supply resumes.

Preferred features of the method will be appreciated from the genera' description of the device and system herein.

Brief Description of the Drawings

The invention will now be described by way of example only with reference to figures ito 7 of the accompanying drawings in which: figures 1 to 5 show a typical operational cycle of a bistable float valve in accordance with an embodiment of the invention is shown operationaily within a shallow vessel (container], with the system in sectional side &evation, respectiv&y: in figure 1 at a lowermost normal operating position with water in the shallow vessel (container) at a lower operational level; in figure 2 at an uppermost normal operating position with water in the shallow vessel (container] having filled to a higher operational level; in figure 3 as water in the shallow vessel [container] falls from a higher operational level back towards the lower operational level; in figure 4 as water reaches the lower operational level; in figure 5 in an exceptional failsafe condition; figure 6 shows the embodiment in exploded view; figure 7 shows an alternative embodiment of float

Detailed Description of the Drawings

Figures 1 to 6 show the same embodiment of a bistable float valve flow control device in accordance with the invention in sectional side elevation and in exploded side elevation in various operational positions, and like numerals are used where applicable. Figure 7 shows an alternative embodiment of the float.

The flow control device comprises a housing comprising an outer casing 1, that in the embodiment shown, with an internal partition 6 to divide its internal volume into a generally cylindrical primary chamber S [in the region of 90 mm bore] and a secondary side chamber 7. The first chamber houses the tube and float assembly; the second chamber communicates with the first chamber in its upper region by way of an in-moulded aperture; which aperture also penetrates through an upper surface allowing also for communication to the outer atmosphere through a valve enclosure with membrane valve 9.

The valve enclosure has a thin raised moulded-in ring seating and the up-stand side wall [protective shield ring] forming the valve enclosure has a vertical slot on its radial outer region to prevent liquid build up around the valve membrane 9. The valve membrane in the embodiment is a disc approx 13 mm diameter x 0.25 mm thick made from a soft grade of neoprene or silicone rubber [20° Shore A]. In use the disc acts as a one way flapper valve, allowing air to pass out of the casing 1 but not to re-enter under normal conditions of use.

This is only one possible one-way valve arrangement In a possible alternative the membrane disc may comprise a shaped diaphragm or be replaced by a self-sealing tubular balloon valve (not shown], the open diameter tube end of which is pushed over an external hollow spigot (not shown] which projects upwards from the valve seating featured.

While both chambers are open at their base the second chamber 7 has a bottom openingS that finishes approx 5mm above the base height of the first chamber S. The first chamber S has an oblong slot in the central region of its topmost surface to accommodate an adapter 11 that provides a liquid inlet otherwise sealed to ambient. In the embodiment, adjacent to this are two small up-stands which act as stops to limit the rotation of the Adapter oblong on assembly. A closed cell foam washer 12, 32 mm diameter and approx 2 mm thick provides an airtight seal between the large circular flanged surface of the adapter and the underside surface of the top of the outer casing once assembled.

The assembly sits in a vessel 3 for containment of liquid, for example being a horticultural water tray. Around the base of the housing 1 there are four shallow equidistant castellations to allow for the flow of liquid out of the casing and into the vessel. Between the castellations four bayonet type lugs are moulded equidistant around the base of the casing 1 and these are intended to engage with a bayonet bracket Without this or some other engagement) or a counter weight, the assembly may float and capsize as the water level in the vessel rises.

The second chamber acts as a lower aperture to serve a vertical breather vent, breaking the partial vacuum in the manner described above and in more detail below when the liquid in the vessel falls to expose the bottom of the vent to atmosphere.

The first chamber 5 holds the float 15, a shallow hollow plastic moulding, having twelve peripheral splines and open at its base and having a central bore 16 therein.

The float has a large base diameter to get good buoyancy and the twelve splines extending above and below the float body prevent it from keeling over and jamming in use. Above the float a hollow central tubular spigot extension 17 provides a push fit connection for the flexible kink tube 13 to fluidly link a liquid supply via the adapter 11 via a similar spigot to the central bore 16. The tube 13 is a thin wall elastomeric tube which is approx 60 mm long having a bore of 6 mm and a wall thickness of 0.3 mm. This is a comfortable push fit onto the spigot ends of the float and the adapter. A lower central tube 18 which extends to the base of the float is present to disperse the supply liquid evenly from the open base of the outer casing 1 into the vessel 3.

The flow control device of the embodiment is modular and assemblable/ disassemblable, without tools, for cleaning and maintenance. A typical assembly process for use might be as described below.

Referring to figure 6, assemble the kink tube 13 and the float 15 by push fitting one kink tube end over the top mounted hollow spigot of the float to the spigot's full length. The adapter 11 is taken and the remaining free end of the kink tube is push fitted over the hollow spigot which extends out from the adapter's large circular flanged disc, to the spigot's full length.

Stretch the closed cell foam washer 12 over the adapter oblong until it is seated flat, on the inner face of the large circular flanged disc of the adapter.

Lower the float/kink tube/adapter sub-assembly down into the inverted outer casing so that the oblong portion of the adapter passes through the oblong slot in the outer casing.

Holding on to the outer casing let go of the float so that it drops inside the outer casing and from the underside, pull the adapter downwards (to make sure it is fully through the opening] and, gripping the oblong section, turn the adapter 90 degrees anti-clockwise until it stops rotating.

Turn the assembly to the upright position and drop in the membrane valve 9 into the second valve ringed enclosure. Optionally add a pressure weight [not shown] on to the top of the membrane valve. Optionally add a protective cap [not shown) on to the top of the ringed valve enclosure.

The device is now assembled and ready for installation.

Alternatively for the second valve arrangement described above) instead of inserting the membrane insert a balloon valve) fully onto the upright hollow spigot described) on the casing.

For use a vessel 3 comprises a shallow tray fitted with an appropriate bayonet bracket is provided. Install the assembled device by inserting the base with its bayonet lugs through the matching opening in the bayonet bracket and turn clockwise 45 degrees [until it stops).

If such a fixing is not available it will be sensible to fasten the device or weigh it down, for example) at its four lugs to secure it to the base of the vessel -otherwise it may capsize when the water level in the vessel and the device approaches the maximum depth of 20-30 millimetres.

If a liquid Supply Hose is ready for use, push fit the delivery end to its full length over the hollow spigot protruding upwards from the Adapter [which protrudes through the top of the casing of the assembled device).

Turn on the liquid supply upstream of the connection to the device and the vessel will start to fill up to a level of between 20 and 30 millimetres deep before the float rises, kinking the tube 13 shutting off the inward flow of supply liquid.

In figure 1 a starting condition is shown with the float 15 at a lowermost normal operating position with liquid in the vessel at a level 4a corresponding to a lower operadonal level. In this state the float 15 is pulled down under acUon of gravity and the kink tube 13 is pulled straight and fully open (un-kinked). In this state liquid passes freely through the supply aperture in the adapter, through the kink tube, and on through the through-bore into a tower portion of the primary chamber beneath the float and outwards into the vessel 3.

The vess& fills with liquid the float 15 rises in the first chamber 5, and air is forced out through the valve 9.

In figure 2 a filled condition is shown, figure 2, with the float 15 at an uppermost normal operating position with liquid in the vessel 3 and in the chambers S and 7 having filled to a higher operational level 4b. The kink tube 13 has become kinked and closed-off to the passage of further liquid flow downward through the device and into the vessel. The kink tube closes and the device thus acts as a float valve that closes once the level of liquid in the chamber is at this level.

The mechanism for achieving hi-stable delayed-action flow control can be seen with reference to figure 3 in which liquid is at an intermediate level 4c as it falls, in the vessel 3, from a higher operational level back towards the lower operational level.

The valve 9 being normally closed, creates a partial vacuum that prevents the float from falling to a level sufficient to open the flow path by un-kinking the kink tube.

This may continue until the liquid reaches a lower predetermined leve' 4d in Figure 4 at which point the liquid level in the vessel has fallen to b&ow the level at which the aperture 8 is exposed and any meniscus or like effects are overcome. At this point, the second chamber 7 is open to atmosphere, the partial vacuum is overcome and air is drawn in through the aperture B and upwards into the second chamber 7.

The second chamber 7 communicates with the first chamber S in its upper region by way of an in-moulded aperture so that air is thereby drawn into the first chamber above the float. This breaks the partial vacuum in the first chamber allowing the float to fall and the cycle to be repeated in successive bistable manner producing in use the desired periods of relative wetness and periods of relative dryness at any growing medium/plant roots for aeration and like purposes.

It will be appreciated that the second chamber is optional. A similar effect could be achieved by having an aperture directly into the first chamber opening for example at a level approx 5 mm above the base height of the first chamber. However such an arrangement would require air to pass via the float assembly to the space above the float and such an arrangement, where repeat accuracy is sought, may be less reproducible. The second chamber provides a convenient means to let air directly into the space above the float, avoiding passing between the splines of the float Figure 5 shows a case of tube failure. The kink tube 13 is for example ruptured. The float 15 rises to a failsafe position above the uppermost normal position, as the higher liquid level 4e is reached, where the spigots and bent over obstructing ruptured tube wall will be forced together sufficiently to close the flow from the external supply to the vessel.

Figure 6 shows an exploded view of the above embodiment.

As has been noted, the device does not have the restriction on orifice size common in much of the prior art. It is admirably suited to operation with more turbid water and/ or at lower heads of pressure when comparison is made with many prior art designs. It is thus suitable for example for supply from a water butt. It is mechanically simple and scaleable.

It offers the potential to mitigate at least the following four shortcomings of even the most recent prior art delayed-action valve designs, namely: 1. The prior art designs need clean feed water to operate efficiently and without maintenance, principally because of their small feed water orifices (often less than 2 mm diameter] necessary because of their inherent physical design and space constraints during operation.

2. Due to the restrictions on orifice size the prior art designs are not practicably able to pass the preferred larger volumes of liquid supplied from the preferred lower pressure supply of up to 3.0 metres and preferably in the range of 0.5 to 2 metres of water head (0.05 to 0.20 bar gauge)) in the time available per cycle -even if this water were clean -to irrigate for example mature tomato plants per device compared to the 1 or 2 plant capacity of some comparable prior art devices. The present invention works admirably with a supply at low pressure) for example below mains pressure (which can be of the order of4 bar gauge) and below the output pressure of mains pressure reducers or elevated water tower systems [with say 10 m head to produce a pressure of around 1 bar gauge). The invention is able to pass the required large volumes of liquid from a significantly lower liquid head for example below 3.0 metres and preferably in the range of 0.5 to 2 metres of water head (i.e. from a working pressure in the range 0.05 to 0.20 bar].

3. Prior art designs based on a resilient tube may flood in the event of failure of the resilient tube by a rupture of same.

4. In many prior art designs it is not practical to ensure that any inlet orifice and/or minimum bore within a flow channel in the device is at least equal to and preferably larger than that of the supply tubing. Thus it is not practical to eliminate potential blockage/ flow restriction points within the flow channel. In accordance with the inherent design of the invention any point in the flow channel in the device may be at least equal to and without departing from the basic design, made preferably larger than that of the supply tubing -so minimising if not eliminating blockages altogether.

Existing designs of valve with smaller feed water orifices cannot generally have their feed water orifices increased in diameter to increase their flow rates at the now sought after low operating pressures of up to 3.0 metres water head and preferably in the range of U.S -2.0 metres water head) without each device becoming impractically larger and more complicated. Therefore, a more complete redesign is needed to provide the preferred higher irrigation flow rate from the preferred lower water head having regard also for the time required for the drain down period before the commencement of each refilling.

The new configuration of delay valve in accordance with the invention is an admirable solution to provide the preferred higher irrigation flow rate from the preferred lower water head) and to achieve this reliably even when the feed water is turbid and contaminated with all manner of things, and which will continue to operate to at least throttle, if not to close off the supply of liquid to the vessel completely, at least once in the event of a rupture of the internal resilient supply tube.

The new configuration of delay valve in accordance with the invention is for example suited for operation as a bi-stable delayed-action valve that is able to operate in the vertical plane over the preferred shallow liquid height range of 5 -30 millimetres, having within its housing a guided squat wide-based float, above which is attached a thin-walled resilient supply tube with a bore (acting as an orifice) in the region of 3 to 10 millimetres in diameter and capable of kinking and un-kinking with the rising and lowering of the float over this range, and for the feed water supply to pass through the float to the underneath, so avoiding the accumulation of deposits on the top of the float, and for a normally-seated, self-seated low pressure one-way valve (check valve having a minimal cracking pressure) to be positioned in the upper region of the valve housing to vent air above the float to atmosphere during the filling part of the cycle, and having also an independent vent to atmosphere open near the base of the valve housing communicating with the upper region of the float chamber as a means for releasing a partial vacuum, above an ascended float when the water level external to the valve housing falls to a predetermined level of 5 millimetres or so, thus enabling the float to drop most positively and un-kink the supply tube, to start the refilling part of the watering cycle.

The mass of the float as it drops contributes to effectively pulling out the kink in the resilient tube ensuring that the whole of the cross-section of the bore is available for the through passage of feed water. This may overcome significant drawbacks

revealed in the prior art.

Further in the event that the kinkable supply tube ruptures though fatigue or some other activity, the device will continue to operate at least to throttle the liquid supply to the vessel, if not to close it off altogether, and avoid the risk of over-brimming the vessel or flooding the immediate area.

Indeed it is not unrealistic to suppose that in this state of partial breakdown the invention might still be used repeatedly and effectively until such time as the kink tube valve can be replaced. The increased liquid level in the vessel will be readily observable by anyone familiar with the device and because it is envisaged that in many cases the invention will be used indoors, in glasshouses and in poly tunnels, cold frames, etc which act as barriers to UV -the casing could be manufactured from a transparent grade of polypropylene with the kink tube, for visibility, extruded in a bright colour such as red.

In the alternative embodiment shown in figure 7 the upper portion of the float 25 can be modified to incorporate a recessed area 29 in the generally central area surrounded by a raised peripheral body radially partitioned with one or more slots 26 down to a level approximate with the central area, so as to deliberately collect a body of liquid over the float towards the completion of the liquid filling stage. In use the following benefit would be achieved.

Starting from a drained out condition, liquid would pass through the device so raising the liquid level in the vessel and the device.

After which the rising level inside the device would pass up the side of the float and inundate the recessed central area of the float by way of the recessed radial slots.

With the liquid level continuing to rise the now semi-buoyant float would eventually lift up (approx 10 mm) and kink the kink tube -shutting off the inward flow of liquid.

After some time has passed the level of liquid in the vessel would drop back down to the lower breather vent at the base of the second chamber (or an equivalent breather vent at the base of the first chamber). The water and the float held by the partial vacuum would then suddenly drop down) releasing all of the trapped liquid -including that which was on top of the float But before being drained away via the radial slots) the additional weight (mass) of the liquid would first make the float descend more determinedly) and by association the de-kinking would be even more robust than was the case for the first float.

Basically in this arrangement the float is being used as a float in its ascendency and as a more positive drop weight in its decendency -after which it sheds the liquid load via the slots as the refilling stage commences.

Further the accumulation of suspended material including fine sediments on the top of the float would be less than with the prior art as most of this would be carried out by inertia and by gravity along the main flow paths emanating from the base of the device and into the vessel.

Claims

CLAIMS1. A flow control device adapted to be located in a vessel to control the level of a liquid therein is provided, comprising: a housing defining at least a primary chamber open towards a base portion to effect fluid communication in use with liquid in the said vess& and having a liquid supply aperture through an upper portion of the housing and a one way valve aperture letting into an upper portion of the chamber to aliow the egress of air from the chamber but to restrict return flow; a float ocated within the primary chamber such as to rise and fall therein in use at least between a higher or up position and a lower or down position having a through bore therein for flow of liquid; a fluid conduit fluidly communicating between the liquid supp'y aperture and the through bore in the float so that the said liquid supply aperture, fluid conduit and through bore together constitute a fluid supply path within the chamber from outside and through the upper portion of the housing towards the base portion; wherein the fluid conduit comprises a flexiNe tube so configured as to describe an extended state with a substantially open through bore when the float is in the down position and to describe a kinked state with a substantially occluded through bore when the float is in the up position; and wherein the housing includes a lower apertured portion providing fluid communication into the primary chamber) the lower apertured portion opening externally approximate with but extending above a base level of the housing.
2. A flow contr& device in accordance with daim 1 wherein the housing includes at east one aperture ktting into an upper portion of the chamber comprising an aperture in the housing above the top position, having a one way valve to allow the egress of air from the chamber as the float rises, but to restrict its reentry.
3. A flow control device in accordance with claim 1 or claim 2 wherein the lower portion of the chamber is open in that the housing is at least partially open at its base.
4. A flow control device in accordance with any preceding daim wherein a flow path through the device defined by at least the flexible resilient kinkalMe tube, the aperture letting into the housing) the through bore in the float) and any downstream supply conduit that may be present to deliver liquid from the through bore to a supply site in the lower portion of the chamber, has a through bore at least equa' to the bore of the external inbound supp'y conduit.
5. A flow control device in accordance with claim 4 wherein the flow path through the device has a through bore of 3-10 mm.
6. A flow control device in accordance with any preceding claim wherein a flow path defined between the external supply aperture letting into the housing and the through bore in the float may be adapted inherently to dose if the tube is ruptured by means of a secondary closure mechanism if the float rises to a failsafe position above the up position.
7. A flow control device in accordance with claim 6 wherein the secondary closure mechanism is effected by appropriate juxtaposition of the external supply aperture letting into the housing and the through bore in the float and/ or by provision of suitable spigots and/ or pressure surfaces associated with the external supply aperture letting into the container and! or the through bore in the float that will tend to dose the fluid path between the external supply and the lower portion of the chamber if the float rises to a failsafe position above the up position.
B. A flow control device in accordance with any preceding claim wherein the one way valve aperture is adapted in use to prevent the passage of air from ambient to the upper part of the chamber but to have a minimal opening pressure such as to allow the egress of air from the upper part of the chamber as the float rises.
9. A flow control device in accordance with claim 8 wherein the one way valve is a diaphragm valve with a minimal cracking pressure.
10. A flow control device in accordance with any preceding claim wherein the lower apertured portion comprises an arrangement of one or more apertures in an enclosure defining the housing located at a point above the base) and for example let into a side wall of the enclosure above the base) which is such as to be at a suitable height in use as to be sealed by the level of liquid in the vessel when the water level is at its higher level but to be exposed when the water level falls.
11. A flow control device in accordance with any preceding claim wherein the lower apertured portion comprises a flow conduit to fluidly link an outlet in direct fluid communication with the vessel in use at a level above the base of the housing but below the float and an inlet in direct fluid communication with the primary chamber at a level above the top position of the float
12. A flow control device in accordance with claim 11 wherein the housing comprises one or more secondary chambers having a first outlet in direct fluid communication with the vessel in use at a level above the base of the housing but below the float and a second outlet in direct fluid communication with the primary chamber at a level above the top position of the float.
13. A flow control device in accordance with any preceding claim provided with a liquid supply source to supply liquid to the liquid supply aperture of the flow control device and a vessel into which liquid may be supplied in level-controlled manner from the open base portion of the chamber.
14. A flow control device in accordance with claim 13 wherein the liquid supply source is a source at a pressure of around 0.02 to 0.30 bar gauge.
15. A kit of parts is provided for assembly into a flow control device of any preceding claim comprising at least one each of the following: a housing as above described for example defining at east a primary chamber open towards a base portion to effect fluid communication in use with liquid in the said vess& and having a Uquid supply aperture through an upper portion of the housing and a one way va've aperture ktting into an upper portion of the chamber to allow the egress of air from the chamber but to restrict return flow, and a lower apertured portion providing fluid communication into the chamber, the lower apertured portion opening externally towards but above a base evel of the housing, and for example at a level below the float but above the base of the housing; a float as above described for example adapted to be located within the primary chamber such as to rise and fall therein in use at least between a higher or up position and a lower or down position and having a through bore therein for flow of liquid; a fluid conduit comprising a flexible tube attachable between the liquid supply aperture and the through bore in the float so that the said liquid supply aperture, fluid conduit and through bore together constitute a fluid supply path within the chamber from outside and through the upper portion of the housing towards the base portion.
16. A system for the contro' of the leve' of a liquid such as a water based liquid in a vessel comprising a flow control device in accordance with one of claims 1 to 12 disposed within a vessel adapted to contain liquid in use, so that liquid may be supplied in level-controlled manner from the open base portion of the chamber to the vessel in the manner above described.
17. A method for the supply of a controlled level of a liquid such as a water based liquid to a vessel and for example to growing plants therein, and for example for irrigation of a medium such as a growing medium therein, for example for agricultural or horticukura purposes comprising the use of a flow control device in accordance with one of daims 1 to 12 in such a vessel connected to a suitable supp'y of a liquid such as a water based liquid or to the use of a system of the second aspect of the invention connected to a suitable supply of a liquid such as a water based liquid.