GB2610585A - Bistable liquid level control device - Google Patents

Abstract

A bi-stable liquid level control device comprises a housing 1 having an open bottomed first chamber 2 containing a pivotally installed valved first float arrangement 14 which is used to control a supply liquid. A valved second float arrangement 15 is pivotally mounted on the outside of the housing to vent air from the first chamber. The first chamber has a lower positioned annexed breather 6 which communicates with the upper portion of the first chamber. The first chamber has an extension 12, the top of which is raised up in semi-circular fashion to direct the inbound liquid downwards into the vessel to avoid disturbing the first float arrangement. The first float valve has an extension which is received within the extension of the first chamber, the top of the extension of the first float valve having at least one aperture. The control device may be installed in a shallow vessel containing a potted plant, to provide liquid thereto

Description

BISTABLE LIQUID LEVEL CONTROL DEVICE

Field of Invention

This invention relates to an improved bistable liquid level control device which when connected to a liquid supply hose and placed within the confines of a shallow vessel or tray is useful for controlling the periodic flow of liquid, principally water, to the basal root region of plants in tubs, pots, bags and the like also placed in the shallow vessel.

Most importantly this invention offers a significant advantage over the prior art -described in patent US 5,671,562 FAH and demonstrated commercially as the 'Smart-valve' and as the 'AQUAvalve5'. The improved device can operate repeatably with greater efficiency especially towards the top end of its head pressure operating limit of one metre plus, which is an essential requirement in much of the horticultural sector.

Without modification both the current commercial designs are limited in their application: The original 'Smart-valve' has a liquid supply orifice in the region of 2.5mm bore and this is very readily blocked by mobile debris which is always present in the irrigation water supplied from tanks and via distribution hoses employed for general horticultural use. The commercially available 'Smart-valve' needs to operate with clean water, and this restricts its use to specialist applications within the horticultural sector.

By comparison the commercially available AQUAvalve5' has a 5mm bore liquid supply orifice which is much less susceptible to blocking. However, at the commencement of each refilling of the shallow tray the increased water flow through the device disturbs the buoyancy of the inner float arrangement. The result is that the inner float rarely descends fully and so cannot open the liquid flow valve to its full potential, negating some of the gain offered by the larger 5mm bore liquid supply orifice.

Whilst the AQUAvalve5' is described in this text by way of comparison, it will be understood that the improvements may be incorporated beneficially into both and all similar devices. The current designs feature a housing connected to a liquid supply hose containing an inner float/liquid valve arrangement, an outer float/air valve arrangement and a low-level breather vent.

In general, the current devices are mechanical and compact and principally used to control the supply of irrigation water and nutrients to plants in shallow vessels. Such control devices are used principally by horticulturalists, gardeners and growers of plant species where the liquid level in a shallow vessel needs to range between being almost empty of liquid, i.e., approximate the bottom of the plant tub, to being full of liquid to a predetermined maximum, in bistable manner, for example upwards of 30mm depth of liquid -the liquid being removed from the shallow vessel by the plant or plants, and automatically replenished each time by the liquid level control device when the liquid level in the shallow vessel is reduced to a pre-determined minimum.

It is known to be beneficial in many horticultural applications for plant roots not to be permanently waterlogged but to have periods of relative wetness and periods of relative dryness for aeration and the like. Hence the need for the plant or plants to consume much of the free liquid available in the shallow vessel and in the growing medium, before each re-watering event -allowing for a degree of aeration of the growing medium towards the base of each tub, pot, bag and the like.

Description of Prior Art

Patent: Liquid Level Control Device -US 5,671,562 -FAH, describes a liquid level control device being a combination of a float-assisted liquid flow control valve, a float-assisted air flow control valve in combination with a low-level breather vent. This achieves a bistable effect from two pivoted float arrangements which operate the valves. Where a first float arrangement is housed within an open-bottom chamber and employed to open and close the liquid flow control valve to, for example, fill a shallow vessel with liquid in which it is installed. And where a second float arrangement is located outside the chamber and employed to open and close the air flow control valve on the top of the device, to assist in the build-up of a small air pressure within the chamber during filling to then release the pressure and to then assist in the creation and maintenance of a partial vacuum within same, as the liquid level in the shallow vessel is reduced.

This achieves a delay as the liquid level reduces (being consumed by the plant) between each refilling of the shallow vessel. The maximum liquid level state being, for example, 30mm, and the minimum liquid level state in the region of 5mm depth -in a shallow vessel containing one or more potted plants. And where a low-level breather vent in communication with the chamber is employed, such that as the predetermined lowest liquid level in the shallow vessel is reached, the breather vent is exposed to atmosphere to initiate the process that refills the shallow vessel. Thus, as the liquid level diminishes, there is an opportunity for some aeration of the growing medium as the roots draw the available liquid away.

A commercial example of this patented bistable liquid level control device is revealed on website www.autopot.com.au where the valve is called a 'Smart-valve'. The commercial Smart-valve' adheres faithfully to the text in claim 1 of the FAH granted patent -which has now run its term.

A copy of this type of bistable liquid level control device is also revealed on website www.autopot.co.uk where the device is called an 'AQUAvalve5'.

However, in its practical application -within the cramped confines of a typical commercially available custom shallow vessel -the design is inherently flawed. When the minimum liquid level is reached, and the breather vent is exposed to atmosphere the trapped liquid -held up by the partial vacuum prevailing inside the housing -descends and escapes from underneath the perimeter of the housing. This enables the inner float to drop downwards so opening the liquid supply valve. However, the liquid escaping from the housing requires time' and 'room' to escape from around the perimeter of the housing but as the inner float drops from its buoyed 'upmost sealed' position, new liquid streams in through the liquid supply valve -impacting violently on the rear of the inner float body -replacing some of the liquid that is escaping The effect is to hinder the descent of the inner float so that it only descends partially before the incoming liquid starts to inundate the first chamber and refill the shallow vessel. The liquid supply valve is therefore only partially opened for the duration of each refilling of the shallow vessel, and this is a major disadvantage. Also, the dispersal of the liquid from around the perimeter is slowed as it competes for space with the residual liquid standing in the shallow vessel (approx. Smm depth) within the cramped confines.

The condition becomes worse as the liquid supply water head is increased, for example towards 1 metre head height and beyond, i.e., as the projectile force of the inbound liquid increases.

Therefore, during the filling stage both these devices, though more so the 'AQUAvalve5', fail to operate properly especially when the supply liquid head pressure is approaching the maximum design limit, i.e., prior to when the elevated inner first float arrangement is no longer able to keep the liquid supply valve properly sealed, as a consequence of insufficient leverage on the sealing member. In the case of the 'AQUAvalve 5' which has a Smm bore liquid supply orifice the unwanted effect can be observed from as little as 600mm water head. The general horticultural sector is seeking a device to operate reliably at 1 metre of waterhead and preferably up to 1.5 metres of waterhead.

Further, when the prior art devices are plumbed together to operate in an array, for example where one supply hose originating from a tank, supplies liquid to ten or more devices in shallow vessels with plants in tubs or the like, the watering to each device will drift out of sequence giving rise to pressure surges and drops in the supply liquid as adjacent devices open and close whilst a device is filling a shallow vessel, and a surge can be created if the supply tank is refilled too quickly. The occurrence of surges provides additional opportunity for the supply liquid to further penetrate into the first chamber churning the air and water layers, causing the inner first float arrangement to partially lift, throttling the inbound flow of liquid.

It is desirable therefore to improve on the design and operating performance of the current technology to mitigate at least this drawback to reveal an improved bistable liquid level control device where the filling performance of the device can be optimized and make the best possible use of the 'Smm bore' liquid supply orifice opportunity.

Summary of the Invention

It is possible to overcome the aforementioned limitation concerning the current devices principally by changing the internal design so as to redirect the inbound liquid stream to largely prevent it from impacting on and disturbing the inner first float body of the device. This will also facilitate the development of better self-watering systems for potted plants growing in shallow vessels where the shallow vessels replenish fully and quickly each time in many environments, and this is achievable by purely mechanical means.

According to the invention in a first aspect, a bistable liquid level control device adapted to be located in a shallow vessel to control the level of a liquid therein comprises; a housing having a first chamber with a first tunnel-like extension within which is located a liquid flow control valve having a static orifice for the passage of liquid and a movable resilient first sealing member installed in a first float arrangement, pivotally operatively engaged with said housing and moveable between an up position and a down position responsive to a level of liquid in the first chamber, and where said first float arrangement comprises a first float body having a second tunnel-like extension from one side face which extension is loosely housed within said first tunnel-like extension, the second tunnel-like extension having at least one aperture in its ceiling to facilitate the egress of liquid from above same, the first chamber being open at its bottom to allow liquid ingress and egress, such that when said float arrangement is in a down position, when the level of liquid in the shallow vessel is at or below a minimum first predetermined level, the liquid flow control valve is open to allow supply liquid from a source to enter the device, by way of a hose-fed connection, and where said device incorporates internal liquid deflector means to redirect liquid through the apertured second tunnel-like extension and through the opcn bottom of the device into thc shallow vessel without said liquid disturbing the first float body positioned in its downmost position within the first chamber, and where at least a portion of the first tunnel-like extension would be extended upwards so that its ceiling presents a concave deflector surface of generally semi-circular form, capable of redirecting liquid that is projected upwards from the liquid flow control valve, in an arc-like fashion so as to redirect and expel said liquid more immediately downwards through the bottom of the device, and where about an upper region of the housing there is an air flow control valve having a static orifice for the passage of air and a movable resilient second sealing member installed in a second float arrangement external to and pivotally operatively engaged with said housing and moveable between an up position and a down position responsive to a level of liquid in the shallow vessel, such that when the second float arrangement rises, as a consequence of the liquid flow control valve allowing liquid to pass through the valve and into the shallow vessel the liquid level rises towards a maximum second predetermined level lifting the second float arrangement, which action opens the air flow control valve to enable trapped air to escape from the first chamber to atmosphere, allowing liquid to rise inside the first chamber, raising also the first float arrangement and closing the liquid flow control valve to prevent further liquid flow through the device and into the shallow vessel, and where the level of liquid in the shallow vessel and in the first chamber drops to a third predetermined level of liquid as a consequence of liquid being used or being removed, the second float arrangement descends to close the air flow control valve, the first float arrangement descends also but this is not sufficient to reopen the liquid flow control valve, thereafter as the liquid level in the shallow vessel reduces still further a partial vacuum is established and maintained inside the first chamber where the trapped liquid and the first float arrangement are held aloft, and where there is an external lower mounted breather vent annexed from and communicated with the first chamber, such that when the level of liquid in the shallow vessel falls to a fourth predetermined level as a consequence of liquid in the shallow vessel being used or removed, air enters through the said breather vent into the first chamber to overcome the partial vacuum to allow the trapped liquid to flow out of the first chamber into the shallow vessel, to allow also the first float arrangement to drop down and open the liquid flow control valve to commence refilling the shallow vessel with liquid.

Preferably said internal liquid deflector means incorporated into the said first tunnel-like extension would also comprise a generally straight deflector element positioned cross-wise to the supply liquid path, emanating from the underside ceiling of the first tunnellike extension and extending downwards in the direction of the base of the housing, which portion of said deflector element having a width less than the width of the aperture opening in the ceiling of the second tunnel-like extension within which a portion of the said deflector may reside and where said deflector may be separate from or continuous with one end of the aforementioned concave deflector surface. The generally straight deflector surface being especially important when the device is operated at lower waterhead pressures, i.e., where a liquid supply tank maybe almost empty, so that with little head pressure available the inbound supply liquid overtops the inner first float arm and travels in a generally horizontal direction towards the rear of the inner first float, before which it flows down through at least one aperture in the ceiling of the second tunnel-like extension and into the shallow vessel, and where in the case of a higher waterhead pressure, for example from a full tank of supply liquid, the supply liquid -which can be likened to a torrent -is propelled into and deflected by the concave deflector surface and then the generally straight deflector so as to be directed downwards and into the shallow vessel.

Preferably the first tunnel-like extension, close-by its intersection, has at least one offset open bottomed generally vertical hollow shaft likened to an alcove which can facilitate the outpouring of liquid in a downward direction, so that liquid that bypasses the aforementioned deflection means by way of clearances between the tunnel-like extensions and clearances between said deflector means will be redirected into the shaft or shafts to flow out of the bottom of the device, so preventing liquid from reaching and impacting against the rear face of the inner first float body.

Essentially the means for air communication between the breather vent and the first chamber is via an upper positioned aperture of a lesser cross-section than the cross-section of the breather vent, so as to throttle the passage of air entering the first chamber via the breather vent. This is to allow time for the inner float arrangement to descend in a controlled fashion to its lowermost position, and without it bouncing. If the aperture is too large the air rushes in too quickly and the inner float arrangement comes to rest in a partially descended state, i.e., not at rest on the floor of the shallow vessel -which outcome gives rise to throttled refilling of the shallow vessel.

Further it has been shown that a breather vent and communicating aperture may be positioned in a number of places around the housing and that the shape and cross-section of the breather vent aperture may be altered also -where preferably the breather vent and communicating aperture are positioned on the sidewall of the housing approximate the mid-point of the device -the device is then less prone to malfunction caused by angular displacements of the shallow vessel within which it is installed.

Preferably the major components would be plastic injection moulded.

Preferably the liquid flow control valve would have in orifice with a bore in excess of 3mm and very preferably a bore approaching 6mm so as to be able to pass significant mobile debris which might be present in the supply liquid.

Preferably the liquid supply source would be a source at low pressure for example at a liquid head within a range of 0.1 and 1.5 metres (for example at a pressure of around 0.01 to 0.15 bar gauge). The liquid may be water-based irrigation liquid. The supply source may include an elevated water butt for example providing a maximum water head in the region of 1.5 metres.

Preferably the container intended for use with the bistable liquid level control device is a shallow vessel or tray for growing plants, for example a shallow vessel into which one or a number of growing plants may be disposed in tubs, pots, bags or the like. It is an advantage of the present invention that a single device may continue to operate reliably as designed and supply liquid to a shallow vessel with multiple growing plants even where the supply water contains significant mobile debris, and the size of the shallow vessel may extend to a square metre or more in surface area.

Preferably a method of use for said improved bistable liquid level control device comprises disposing the device in a shallow vessel which can be a shallow vessel open to atmosphere and adapted to contain a liquid, the device comprising at least a housing having an open bottomed first chamber containing an inner pivoted first float arrangement and liquid flow control valve, and having an external pivoted second float arrangement and air flow control valve, and a lower-mounted breather vent, and coupling said device to a source of liquid, operating said device such that the following occur successively and repeatedly: From a dry empty state and with both the first and second float arrangements in a downmost position, liquid (water) is supplied to the device from an external source via a supply hose connected to the device, the liquid passes through a short conduit within the device and then issues from an unobscured orifice of the liquid flow control valve, where it is ultimately discharged through the open bottom of the device into the shallow vessel, having one or a number of plants in pots, tubs, bags or the like placed therein. The liquid passes through the device in a predetermined manner so as not to disturb an air pocket present in the device at the commencement of operation -the air pocket being essential to the correct operation of the device. The liquid flowing inside the device from the external source may be observed as a torrent of water and this is controlled by the internal geometry of the device which is unique to the present invention.

The liquid in the shallow vessel rises to a predetermined maximum level at which point the outer second float arrangement becomes buoyant and pivots upwards sufficient to open the top mounted air flow control valve.

This allows air communication between the atmosphere and the first chamber and releases compressed, trapped air from within the device to atmosphere. Up until now the inner first float arrangement has been pivoted downwards, by force of gravity and by air trapped inside the first chamber, ensuring that the liquid flow control valve was kept open during the filling of the shallow vessel.

As air is expelled to atmosphere, liquid from the shallow vessel is forced up inside the first chamber to equalise with the level in the shallow vessel, which action imparts such buoyancy to the inner first float arrangement that it overcomes the force of gravity and pivots towards an uppermost position, closing off the liquid flow control valve to the passage of any further liquid into the shallow vessel.

Thus far, the filling cycle has taken from less than a minute to a number of minutes depending on the size of the shallow vessel. The next stage may take a number of hours, as the liquid in the shallow vessel is consumed by the plants by transpiration and by evaporation to atmosphere.

The plants consume liquid in the shallow vessel sufficient to lower both float arrangements by a small amount. In the case of the first float arrangement the fall is concurrent with a drawing-in of air from the atmosphere through the opened air flow control valve until the fall of the second float arrangement is sufficient to close the air flow control valve. But the reduced liquid level is not sufficient to reopen the liquid flow control valve associated with the inner first float arrangement. For most of the remaining time, the liquid in the shallow vessel continues to be consumed by the plants and the liquid level reduces towards a lower mounted breather vent near the base of the device. During this time, the inner first float arrangement remains buoyed up by the partial vacuum prevailing in both the first chamber and a breather passage connecting the breather vent to the first chamber via a communicating aperture. This condition keeps the liquid flow control valve closed to the passage of any further supply liquid into the shallow vessel.

Eventually the liquid level in the shallow vessel reduces to below the breather vent and the meniscus clinging around the breather vent collapses. Outside air is propelled in through the breather vent and into the first chamber, filling the partial vacuum and enabling both the elevated liquid to descend and the inner first float arrangement to pivot downwards, so opening the liquid flow control valve to the passage of liquid to refill the shallow vessel.

Preferred features of the method will be appreciated from the general description of the device when deployed to operate automatically in a shallow vessel populated with at least one plant in a tub, pot, bag or the like and the invention achieves this in an admirably simple manner.

Brief Description of the Drawings

Figures 1-6 show the same embodiment of an improved bistable liquid level control device in accordance with the invention in perspective view, opened-out view and in a staggered sectional schematic view in various operational positions, and like numerals are used where applicable. Figures 12-15 show staggered sectional schematic views of the same embodiment at different stages of operation.

Figures 7-9 show a prior art bistable liquid level control device upon which the present invention is modelled. And figures 10 & 11 -tracings from photographs -show an operating comparison of liquid streams between the prior art and the present invention.

Figures 16 &17 illustrate an alternative and first preference position for the breather on the side of the housing which differs from convention.

In the following text: Figure 1 is a general perspective view of the present invention in an assembled state, Figure 2 is an opened-out perspective view of the present invention as illustrated in figure 1, Figure 3 is a staggered sectional schematic view of the present invention, Figure 4 is an underside view of the present invention, Figure 5 is a perspective view of the underside of the housing and the inner float arrangement of the present invention, Figure 6 is an enlarged perspective underside view of the housing showing the deflector elements and side shaft features, of the present invention, Figure 7 is a general perspective view of a prior art bistable liquid level control device in an assembled state, Figure 8 is an opened-out perspective view of the prior art device as illustrated in figure 7, Figure 9 is a staggered sectional schematic view of the prior art device as illustrated in figures 7 and 8, Figure 10 is a tracing of a photograph showing the liquid paths exiting the prior art device when operated with one metre of liquid head pressure, Figure 11 is a tracing of a photograph showing the liquid paths exiting the present invention when operated with one metre of liquid head pressure, Figure 12 is a staggered sectional schematic view of the present invention installed in a shallow vessel which is in a dry starting condition where both float arrangements are downmost, Figure 13 is a staggered sectional schematic view of the present invention installed in a shallow vessel filled with liquid to a predetermined maximum level where both float arrangements are buoyed up, Figure 14 is a staggered sectional schematic view of the present invention installed in a shallow vessel and where the liquid level has reduced marginally, to reseal the top mounted air flow control valve, Figure 15 is a staggered sectional schematic view of the present invention installed in a shallow vessel where liquid has been removed to almost a pre-determined minimum level -both valves remain dosed immediately prior to exposing a breather vent to atmosphere and initiating refilling the shallow vessel, Figure 16 is a general perspective view of the present invention showing a first preference position for the breather passageway and horizontally communicated aperture, Figure 17 is a perspective view of the underside of the housing of the present invention shown in figure 16 showing the breather passageway and the horizontally communicated aperture.

Detailed Description of the Drawings

The invention will now be described by way of example and by comparison only, with reference to figures 1 -6 of the accompanying drawings the embodiment shown is a bistable liquid level control device 0, comprising a housing 1, within which is a first chamber 2 open at its base 3. Atop the first chamber is a generally vertical air orifice 4 to allow air to pass between the first chamber and the atmosphere. The air orifice having a sharp-ringed outward projecting rim to assist with sealing.

Adjoined to the housing at the front face is a vertically aligned breather passageway 5 closed at the top and having a bottommost breather vent 6. High up inside the housing is a horizontally communicating aperture 7 which provides for the passage of air between the uppermost regions of the breather passageway and the first chamber.

For simplicity the figures 3, 9 (prior art), and 12 to 15 are staggered sectional schematic views where the device is generally sectioned longwise along its central axis and has a short, staggered section at the front of the device revealing the details of the offset breather passageway and horizontally communicating aperture.

In plan view the first chamber is hammer shaped and open across the whole of its underside to facilitate liquid flow between the first chamber and a shallow vessel in which is it placed, and wherein plants may be positioned in tubs, pots, bags or the like.

The first chamber is of generally block shape approx. 70mm x 70mm x 40mm high, having also, a narrow extension from its rear face approx. 15mm wide by 20mm high and 40mm long forming a first tunnel-like extension 8 having side walls 9 and an extreme end, end-wall 10. Inside the housing (figure 6) rearward of the intersection between the block shape and the first tunnel-like shape of the first chamber, there is present a cross-wise centrally located, generally vertical downward projecting first deflector surface 11 having clearances on either side with the inside of the tunnel walls 9, the first deflector surface extending approximately halfway towards the bottom of the housing.

Between the first deflector surface and the end wall of the first tunnel-like extension the tunnel is raised up to form a concave semi-circular second deflector surface 12 in the ceiling of the tunnel. The two deflector surfaces are aligned to provide one continuous deflection surface.

The deflection surface being shaped to optimally obstruct and redirect the incoming liquid stream which will overtop the inner workings. Also, close-by the inboard end of the first tunnel-like extension the walls stop abruptly and locally extend outwards forming a pair of opposing open bottomed side shafts 13 likened to alcoves which serve to direct liquid in a downwards direction. The combination of the two deflection surfaces and the two side shafts ensure pre-determined paths, for incoming supply liquid to flow downwards through the device without jeopardising the stability of the inner first float arrangement The device also features an inner first float arrangement 14 to control the flow of inbound supply liquid, and an external second float arrangement 15 to control air flow into and out of the first chamber.

The inner first float arrangement 14 is housed inside the first chamber 2 and the tunnel-like extension 8 and comprises a rectangular first float body 16 which may be hollow and open at the base. When assembled there is a normal clearance all round of approx. 5mm between the outside of the inner first float body and the inside walls of the first chamber.

A tunnel-like first float arm 17 extends from one end of the first float body 16 towards a narrow end wall 10 of the first chamber 2. At the opposing end to the breather passageway 5, the first float arm terminates in a pair of opposing stubby axles 18 extending laterally, between which and locally offset at approx. 90 degrees of angle is housed a resilient first sealing member 19. The first float arrangement is pivotally mounted to the first chamber by way of shaped mating slots 20 in same, and this is free to pivot upwards inside the first chamber and downwards out of the bottom of said chamber. The resilient first sealing member may be in the form of a cylindrical plug of Silicone of 40 Shore A Hardness.

The ceiling of the tunnel-like first float arm has apertures 21 (figures 3 8,z 5) to allow liquid to pass therethrough bounded on its sides by walls. The apertures are separated by a crosswise stiffener 21a to provide rigidity to the component. The stiffener also serves as a deflecting surface and conduit (fig 3) by virtue of surface tension effects, and this further prevents streams of the supply liquid from impacting on the rear face of the inner first float body.

A horizontal liquid supply orifice 22 faces into the first chamber from the narrow end wall 10 of the first chamber, having a sharp-ringed projecting rim facing in towards the tunnel. The orifice has a through bore of at least 3mm and preferably 5mm and more and terminates on the outside of the housing where there is present a conventional low pressure hose connection comprising a hollow male threaded spigot and bulb end (not shown), over which is assembled a mating nut 23 to secure a flexible liquid supply hose 24. The hose is resilient and pushed over the bulb end to form a liquid tight connection, afterwhich the nut is gently tightened.

Spaced around the bottom perimeter of the housing are three stubby feet 25 which ensure that liquid can flow underneath the device when it is used in a plain flat-bottomed shallow vessel.

The liquid flow control valve 26 is employed to control the supply liquid and comprises the first float arrangement 14 complete with the resilient first sealing member 19 and the liquid supply orifice 22 protruding inwards from the end wall 10 of the first tunnel-like extension 8 of the first chamber 2.

The operation of the inner first float arrangement 14 is to respond to a level of liquid inside the first chamber 2 which will vary in bistable manner between a relatively drained-out state and a filled state, e.g., 30mm liquid depth. Such that when the inner first float body 16 is in a downmost first position, when the liquid level in the first chamber is at or below a first predetermined level, the liquid supply orifice 22 is open to the flow of liquid into the device from an external source through the liquid supply hose 24. And when the inner first float body is raised up to a second, higher position, when the liquid level in the first chamber is approaching a second and maximum predetermined level, the resilient first sealing member 19 is swung into position to press against the liquid supply orifice and close off the passage of the supply liquid.

The external second float arrangement 15 is slidable for assembly and comprises two float bodies 27 which may be hollow and closed off at their top and at their bottom and attached to a crossbar 28 which straddles the tunnel-like extension 8 of the housing. The crossbar being attached to the extreme end of the second float arm 29 about its mid-point. The second float arrangement extends over the outside of the housing and is pivotally mounted at one end relative to the first chamber 2 such that the two float bodies are able to pivot upwards and downwards. Away from the float bodies the second float arm extends on either side in blade-like fashion terminating in axles 30, which are mated with a through-hole 31 and a slot 32 present in a pair of upright lugs 33 projecting upwards on the top of the housing.

For compactness on the underside of the second float arm 29, close to and equidistant to the axles 30, there is a shallow cylindrical cavity wherein may be installed a resilient second sealing member 34 facing downwards. For clarity a region of the second float arm in and around the shallow cylindrical cavity is sectioned. This local section applies to figures 3 and 12 -15.

Together the second float arrangement 15, the resilient second sealing member 34 and the air orifice 4 constitute an air flow control valve 35 which controls the passage of air into and out of the first chamber of the device by the pivotal movement of the second float arrangement.

PRIOR ART

The device in figures 7-9 shows an 'AQUAvalve5' a copy version of the original Australian 'FAH' Smart-valve' and illustrates the prior art device upon which the present invention is modelled -FAH Patent US 5,671,562.

Figure 7 the prior art, shows a front perspective view of the bistable liquid level control device 00 in a closed assembled form. The housing 501, the second float arrangement 515 having a pair of second float bodies 527, and the second vent 506 near the base of the housing are visible. As is the vertical breather passageway 505 positioned on the front of the device housing. The pivot lugs 533 for the second float arrangement having a mating pivot through-hole 531 and a slot 532 are shown protruding upwards from the top of the housing for comparison. Also shown is one of the stubby forward feet 525.

Figure 8 the prior art, shows a partially opened assembled side view of the three main components of the bistable liquid level control device 00 where the housing 501 has an integral first chamber 502, and an internal pivoted first float arrangement 514 having a first float body 516. Outwith of which, is pivotally attached a second float arrangement 515 and a threaded liquid supply connection mating nut 523. The basal opening 503 across the extent of the first chamber is shown, as is the narrow end wall 510 of the first chamber and the second float arm 529 of the second float arrangement. Also shown is the lower positioned second vent 506 at the bottom of the breather passageway and the tunnel-like first float arm 517.

Figure 9 the prior art, shows a staggered sectional schematic view through the assembly. The housing 501 of the bistable liquid level control device illustrates where both the first 514 and second 515 float arrangements are downmost and where the lower positioned second vent 506 is communicated to the first chamber 502 by way of a vertical breather passageway 505 and a horizontal communication aperture 507. The open underside 503 of the first chamber is shown also, as is the first tunnel-like extension 508 of the housing. The image shows a first vent or air orifice 504 at the top of the first chamber, part of the air flow control valve arrangement 535. Also, the position of the orifice 522 which is a part of the liquid flow control valve arrangement 526. And outboard of the narrow end wall 510 of the housing is shown the mating nut 523 used to secure a hose type liquid supply hose 524.

A mating slot 520 for the first float arrangement and one mating stubby axle 518 is shown also. One pivot lug 533 and its mating slot 532 associated with the second float arrangement 515 is shown along with one of the stubby axles 530. Also shown is the resilient first sealing member 519 and the resilient second sealing member 534 as is the rectangular first float body 516 inside the first chamber and one of the external float bodies 527 and at the rear of the device one of the three stubby feet 525. For clarity a region of the second float arm 529 in and around the cylindrical cavity is sectioned to show the sealing member 534.

Figure 10 illustrates the liquid flow path problem during filling. It is a tracing of a photograph showing the liquid paths exiting underneath the prior art device when operated with one metre of head pressure. For the photograph the device is shown raised on blocks at either end reproducing the operational geometry. A part of the housing 501 is shown as is the tunnel-like extension 508 of the housing and the inner rectangular first float body 516. The arrow 'A' indicates the inbound supply liquid. The arrow 'B' shows that the clearances around the liquid flow control valve can disperse approximately half of the inbound supply liquid directing it downwards and into the shallow vessel.

The arrow 'C' shows how most of the other half of the liquid flow overtops the tunnel-like first float arm to be propelled directly onto the rear of the rectangular first float body, before exiting the first chamber Arrow 'D' as two liquid streams, side by side, in a downwards direction -spilling over on either side of the tunnel-like first float arm.

At the very commencement of refilling the shallow vessel the inbound liquid streams out of the liquid supply valve in a torrent. Half of it impacts on the rear face of the inner float body which deflects it to bare down on any liquid below it, i.e., this is critical when there is elevated liquid around the elevated first float body that is trying to exit the first chamber.

The result is that in the real-life situation the inner float body does not descend fully to touch the bottom of the shallow vessel, and so the liquid supply valve is never opened to its full extent. The presence of these liquid streams entering the first chamber displaces some of the trapped air. This disturbs the essential air / water relationship in the first chamber as described earlier in the text. It is noteworthy that during the filling stage the first chamber is essentially, and of necessity, a large air pocket! Assembly and Installation of the device of the present invention: With the three major components being readily plastic injection moulded, take the incomplete first float arrangement 14 and press a shallow cylindrical-shaped Silicone resilient first sealing member 19 into position in the cavity as illustrated in figure 3. Snap together the first float arrangement and the housing 1 by way of the stubby axles 18 and the mating slots 20, refer to figures 1, 2 & 3. Ensure that the inner first float arrangement is free to swivel approximately half-way up inside the first chamber 2 before meeting the springy resistance of the sealing member and freely downwards and out of the bottom of the first chamber, i.e., some distance below the bottom perimeter of the housing, figures 2 & 3.

Referring also to figures 4 & 5, insert the resilient second sealing member 34 into the cavity provided for it in the underside of the second float arm 29.

Slide the lateral axle 30 on the second float arrangement 15 into position through the slot 32 and the mating through-hole 31 present in the upright lugs 33 on the top of the housing and swivel the second float arrangement downwards approx. 90 degrees of angle to rest on the top of the air orifice 4 -the loading being sufficient to prevent air communication between the first chamber 2 and the atmosphere via the air orifice, refer to figure 3.

Position the assembled device in a chosen shallow vessel 36 and connect a liquid supply hose, emanating from a suitable liquid source, e.g., a water butt (not shown) to the device using the mating nut 23 to complete the connection. The device is now ready to use. Both the float arrangements will be seen to be in their downmost positions. In the case of the first float arrangement 14, in its downmost position, the associated liquid flow control valve 26 is open to the inbound passage of the supply liquid. And in the case of the second float arrangement 15 in its downmost position the associated air flow control valve 35 is closed to the passage of air.

Figure 11 illustrates how the problem is overcome during filling, as compared with figure 10 (prior art). It is a tracing of a photograph showing the liquid paths exiting the present invention when operated with one metre of head pressure. For the photograph the device is shown raised on blocks at either end reproducing the operational geometry. A part of the housing 1 is shown as is the first tunnel-like extension 8 of the housing and the inner rectangular first float body 16. Also shown is one of the hollow vertical shafts 13.

The arrow 'A' indicates the inbound supply liquid. The arrow 'B' shows that the clearances around the liquid flow control valve can disperse approximately half of the inbound supply liquid directing it downwards and into the shallow vessel.

The arrow 'C' shows how most of the other half of the liquid flow which would overtop the second tunnel-like first float arm is projected upwards by its own momentum where it is forced around a semi-circular path 12 (refer also to fig 3) to then be propelled downwards through the aperture 21 (fig 3) in the ceiling of the second tunnel-like first float arm to then exit, further guided by the deflector surface 11, from the open bottom of the device into the shallow vessel.

Any liquid which bypasses the deflector surface 11 (Fig 3) by way of the sidewall clearances between the two tunnels is deflected sideways by 'fluid logic' to spill over into the hollow vertical shafts 13 where it drops out of the bottom of the device as a part of stream 'D'.

The fluid logic can be seen to operate where, due to surface tension, the fluid clings to and passes along the inside of the sidewalls 9 where at the vertical side shaft positions the sidewalls stop abruptly causing the liquid to swing outwards into the shafts 13 and, where present, liquid also drops through the apertures 21, clinging in its descent to both sides of the crosswise stiffener 21a to join with the main stream 'D' and fall into the shallow vessel.

The position of the liquid stream 'D' confirms that during filling there is no significant penetration of the liquid into the broad region of the first chamber and that both the air pocket and the downmost position of the first float body remain undisturbed.

Figures 12 to 15 illustrate the operation of the present invention installed in a shallow vessel where the device either has enough mass or is secured (not shown) to the shallow vessel to resist floating when the shallow vessel is filled with liquid. It is noteworthy that the commercially available prior art devices operate more effectively when they are raised a short distance (between 3mm and Smm) off the bottom surface of a shallow vessel or that the bottom surface of a shallow vessel has grooves to allow liquid to move freely horizontally.

Therefore, in figures 12 to 15 of the present invention the device is raised off the bottom of a flat-bottomed shallow vessel 36 by localised shallow steps 37 on either side and towards the front of the housing and a localised shallow step 38 of equal height at the rear. A shallow preferably sub-divided platform 39 is also shown upon which is positioned a plant in a tub 40 (a part of which is shown, cross-sectioned). This is representative of current practice and may be viewed either as a flat-bottomed shallow vessel with multiple grooves or as a flat-bottomed shallow vessel with steps, either way the result is the same -the liquid is able to flow freely underneath the device, and this is important.

Referring to figure 12, from a dry empty state, open the liquid source supply valve (not shown), liquid is supplied to the shallow vessel 36 through the device 0 and out of the bottom of the housing 1 and into the shallow vessel, i.e., in a first chamber 2 a pivotally-mounted first float arrangement 14 is in a downmost position so keeping the resilient first sealing member 19 some distance away from the liquid supply orifice 22 so that the liquid flow control valve 26 is open, allowing liquid to pass from the source through the device and into the shallow vessel. The second float arrangement 15 is also downmost ensuring that the air flow control valve 35 is closed to the passage of air by the resilient second sealing member 34. This ensures that the air inside the first chamber 2 is trapped and acts as a buffer to resist liquid trying to enter the first chamber from the shallow vessel.

Referring to figure 13 the liquid level in the shallow vessel 36 rises to a maximum predetermined liquid level 500, of, for example, 30mm liquid depth, which by design is sufficient to marginally buoy up the second float arrangement 15. As the figure shows the walls of the first tunnel-like extension of the housing are extended upwards to support a raised generally semi-circular concave ceiling 12 so as to present an inverted concave flow path to liquid which is propelled upwards from the liquid supply valve.

This feature forces upwardly rising liquid to curve around through 180 degrees over a short distance providing the opportunity for a greater part of the liquid to exit the bottom of the housing well short of the broad region of the chamber housing the inner first float body.

The concave form 12 and the deflector element 11 provide continual guidance to the greater part of the liquid overtopping the inner first float arm. With residual liquid which passes along the wall and ceiling clearances between the two tunnel-like extensions being redirected to flow down one or both of the hollow vertical shafts 13 and also through the apertures 21, so that there is no measurable disturbance to the stability of the essential air pocket prevailing in the chamber during the period of filling the shallow vessel -refer to figure 11.

If the air pocket is disturbed by supply liquid entering, then the inner first float arrangement will be lifted, partially throttling the inbound supply liquid flow through the liquid supply valve.

The lifting of the second float arm raises the resilient second sealing member from obscuring the air orifice 4. This allows air, which is slightly compressed to pass from the first chamber 2 to atmosphere.

As the figure 13 shows, with the air now free to escape upwards from the first chamber, some of the liquid from the shallow vessel 36 is forced up inside the first chamber by atmospheric pressure to achieve the same liquid level SOO inside the device as prevails in the shallow vessel i.e., 30mm liquid depth. As this action is taking place the first float arrangement 14 is buoyed upwards to come to rest with the resilient first sealing member 19 pressing firmly against the liquid supply orifice 22, closing off the passage of any further supply liquid through the liquid flow control valve 26 and into the shallow vessel.

For the device to operate reliably it is essential that the passage of the supply liquid through the liquid supply orifice is closed off completely by the resilient seal at a lesser liquid depth than the predetermined maximum of in this example 30mm in the shallow vessel -the resilient seal ensuring leak free engagement over a range of liquid depths in and around 30mm. For example, a lesser liquid depth of 25mm for firmly closing the liquid flow control valve would ensure that the subsequent fractional drop required of both float arrangements from 30mm depth would not compromise the sealing capability of the inner first float arrangement. The liquid depth being measured from the bottom of the stubby feet of the device and not from the shallow vessel bottom unless this is the same measurement.

Referring to figure 14 liquid is used from the shallow vessel by the plants and by evaporation until the liquid level in the shallow vessel falls fractionally from its maximum liquid level to a lesser liquid level 501, i.e., both float arrangements have descended fractionally. The inner first float arrangement descending as the liquid level inside the first chamber descends fractionally drawing some air into the first chamber from the atmosphere through the air orifice. During which time the second float arrangement descends also so that the resilient second sealing member obscures the air orifice isolating the first chamber from the atmosphere external to the device as the figure 14 shows, both valve arrangements are closed to the further passage of liquid and of air.

It is important to note that this reduction in liquid depth of the order of 2mm is within the safety allowance of Smm referred to above, and so is not sufficient to disturb the first float arrangement, i.e., both the liquid in the first chamber and in the breather passageway along with the first float arrangement remain elevated, drawn upwards by a partial vacuum that is created inside the first chamber and breather passageway. This achieves a maximum possible common liquid level inside the first chamber, the breather passageway and in the shallow vessel at the fractionally lower liquid level 501, ensuring that the liquid flow control valve controlling the liquid supply into the shallow vessel remains firmly closed.

Further it is important to note that it is the plant that largely determines the operation of the device. For example, liquid from the shallow vessel may be consumed at a rate equivalent to one drop of water every three to five seconds, so there is an observable period during which the liquid level drops from the maximum of level 500 to the fractionally lower liquid level of 501 drawing air into the first chamber before the topmost air flow control valve closes fully.

As more liquid is used from the shallow vessel the liquid level reduces, with the benefit of surface tension the meniscus 41 clings on enabling the liquid level in the shallow vessel to fall until it is marginally below the lower positioned breather vent 6 at the bottom of the breather passageway 5 refer to figure 15. The surface tension will very soon fail to maintain the meniscus at the interface between the liquid and the bottom of the wall of the breather passageway. The meniscus is more secure elsewhere around the periphery of the device, the periphery being measurably lower than the breather vent.

Figure 15 illustrates this condition just before the meniscus 41 collapses at the lowermost liquid level 502 in the shallow vessel. The first float arrangement is still elevated by the liquid level 501 prevailing inside the first chamber and the breather passageway due to the partial vacuum present. Which state keeps the liquid flow control valve closed to the inward flow of the supply liquid.

Eventually sufficient liquid is removed from the shallow vessel to reduce the liquid level to below the liquid level 502 and the meniscus collapses -but only at the breather vent At this point air is forced, by atmosphere, in through the breather vent 6, up through the breather passageway 5 through the horizontally communicated aperture 7 and into the first chamber 2 filling the partial vacuum. This releases the trapped liquid which now descends into the shallow vessel enabling the first float arrangement to descend also, so that the mechanical status of the device matches that of figure 12, with the addition of some residual liquid remaining in the shallow vessel and around the base of the device.

The descent of the first float arrangement opens the liquid flow control valve and the shallow vessel refills with liquid. It is noteworthy that during each refilling the residual liquid present in the shallow vessel is churned up and refreshed.

In this manner the improved liquid level control device provides optimal bistable operation over the liquid level in a shallow vessel containing plants in tubs, pots, bags, and the like, by simple mechanical means -with the periodicity of the process being largely controlled by the plant or plants.

Figure 16 shows a general perspective view of an improved version of the present invention 000 where the first preference position for the breather passageway 55 and horizontally communicated aperture 57 are repositioned to the side of the device at about its mid-point instead of at the front of the device so as to better provide for water dispersal from underneath the device when the device is being used in a confined environment such as in a cramped shallow vessel. In the example the original breather passageway 5 has been retained to provide a mounting to secure the device to a custom shallow vessel -the original horizontally communicated aperture being removed from same.

Figure 17 shows a perspective view of the underside of the housing 51 of the said improved device shown in figure 16 showing the internal features of the first preference breather passageway SS, the horizontally communicated aperture 57 and the repositioned second vent 58. In the example the breather passageway is enlarged as is, in proportion, the new horizontally communicated aperture.

It may be understood that referring here to an improved bistable liquid level control device it will be evident to those skilled in the art that further modifications and variations including scale, materials and relative dimensions are possible without departing from the underlying principles of the invention, and that the liquid referred to might comprise water and compounds such as fertilizer, etc, supplied to the device over a practical range of waterheads, and that all such modifications and variations should be considered within the scope of the present invention.

Claims (3)

1. CLAIMS(\J 15 C\ICD a)C\J 20 A bistable liquid level control device adapted to be located in a shallow vessel to control the level of a liquid therein comprises; a housing having a first chamber with a first tunnel-like extension within which is located a liquid flow control valve having a static orifice for the passage of liquid and a movable resilient first sealing member installed in a first float arrangement, pivotally operatively engaged within said housing and moveable between an up position and a down position responsive to a level of liquid in the first chamber, and where said first float arrangement comprises a first float body having a second tunnel-like extension from one side face which extension is loosely housed within said first tunnel-like extension, the second tunnel-like extension having at least one aperture in its ceiling to facilitate the egress of liquid from above same, the first chamber being open at its bottom to allow liquid ingress and egress, such that when said float arrangement is in a down position, when the level of liquid in the shallow vessel is at or below a minimum first predetermined level, the liquid flow control valve is open to allow supply liquid from a source to enter the device, by way of a hose-fed connection, and where said device incorporates internal liquid deflector means to redirect the inbound liquid stream downwards through the apertured second tunnel-like extension and through the open bottom of the device into the shallow vessel without said liquid flow impacting on and disturbing the first float body, and where at least a portion of the first tunnel-like extension would be extended upwards so that its ceiling presents a concave surface capable of redirecting liquid projected upwards from the liquid flow control valve in a semi-circular fashion, so as to expel said liquid more immediately downwards through the bottom of the device, and where about an upper region of the housing there is an air flow control valve having a static orifice for the passage of air and a movable resilient second sealing member installed in a second float arrangement external to and pivotally operatively C\I 15 ('SiCO a)C\J 20 engaged with said housing and moveable between an up position and a down position responsive to a level of liquid in the shallow vessel, such that when the second float arrangement rises, as a consequence of the liquid flow control valve allowing liquid to pass through the valve and into the shallow vessel the liquid level rises towards a maximum second predetermined level lifting the second float arrangement, which action opens the air flow control valve to enable trapped air to escape from the first chamber to atmosphere, allowing liquid to rise inside the first chamber, raising also the first float arrangement and closing the liquid flow control valve to prevent further liquid flow through the device and into the shallow vessel, and where the level of liquid in the shallow vessel and in the first chamber drops to a third predetermined level of liquid as a consequence of liquid being used or being removed, the second float arrangement descends to close the air flow control valve, the first float arrangement descends also but this is not sufficient to reopen the liquid flow control valve, thereafter as the liquid level in the shallow vessel reduces still further a partial vacuum is established and maintained inside the first chamber where the trapped liquid and the first float arrangement are held aloft, and where there is an external lower mounted breather vent annexed from and communicated with the first chamber, such that when the level of liquid in the shallow vessel falls to a fourth predetermined level as a consequence of liquid in the shallow vessel being used or removed, air enters through the said breather vent into the first chamber to overcome the partial vacuum to allow the trapped liquid to flow out of the first chamber into the shallow vessel, to allow also the first float arrangement to drop down and open the liquid flow control valve to commence refilling the shallow vessel with liquid.
2. 2 A bistable liquid level control device in accordance with claim 1 where the said concave internal liquid deflector means incorporated into the said first tunnel-like extension also comprises a generally straight deflector element positioned crosswise to the supply liquid path, emanating from the underside ceiling of the first tunnel-like extension and extending downwards in the direction of the base of the housing, which portion of said deflector element having a width less than the width of the aperture opening in the ceiling of the second tunnel-like extension within which a portion of the said deflector may reside.
3. 3 A bistable liquid level control device in accordance with claims 1 and 2 where the said first tunnel-like extension has at least one offset open bottomed generally vertical hollow shaft likened to an alcove which can facilitate the outpouring of liquid in a downward direction, so that liquid that bypasses the aforementioned deflection means by way of clearances between the tunnel-like extensions and clearances between said deflector means will be redirected into the shaft or shafts to flow out of the bottom of the device, so preventing the inbound supply liquid from reaching and impacting against the rear face of the inner first float body.C\J 15 C\I 4 A bistable liquid level control device in accordance with claim 1 where the said CID means for air communication between the breather vent and the first chamber is CD via an upper positioned aperture of a lesser cross-section than the cross-section of the breather vent.