WO2001001759A1

WO2001001759A1 - Plant irrigation apparatus and method

Info

Publication number: WO2001001759A1
Application number: PCT/GB2000/002481
Authority: WO
Inventors: Peter Barnes
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-06-30
Filing date: 2000-06-28
Publication date: 2001-01-11
Anticipated expiration: 2001-12-30
Also published as: AU5555100A; GB9915322D0

Abstract

Apparatus for irrigating plants has a reservoir chamber (1) with a substantially rigid wall and a tube (6) connecting the chamber interior to the external environment. The tube has first (11) and second (10) openings, communicating with the interior of the chamber and the external environment respectively. At least part of the tube between the openings is above the level of the first opening. Partially filling the chamber with a liquid, creates a gas tight cavity (12) above the liquid. A change in cavity pressure due to a change in environmental conditions causes either the liquid to be dispensed from the tube or gas from the environment to be drawn into the chamber.

Description

PLANT IRRIGATION APPARATUS AND METHOD

The present invention relates to an apparatus and method for irrigating plants. Most house plants require frequent watering in order to keep them in a healthy condition. For many varieties it is preferable to irrigate the plant frequently with a limited supply of water rather than soaking the soil thoroughly one day and waiting for a much longer period before soaking it again. Frequent irrigation is not always convenient for the plant owner and this can be a particular problem when the owner takes a holiday for example.

In accordance with a first aspect of the present invention we provide apparatus for supplying a liquid from a reservoir in response to changing environmental conditions, the apparatus comprising a chamber, defining a reservoir, having a substantially rigid wall; and a tube connecting the interior of the chamber to the external environment, the tube having a first opening and a second opening, wherein the first opening communicates with the interior of the chamber and the second opening is open to the external environment, and at least part of the tube between the first and second openings is above the level of the first opening, the arrangement being such that when the chamber is partially filled with a liquid to a level above the first opening of the tube, a gas tight cavity is created above the liquid, whereby a change in pressure within the gas tight cavity in response to a change in environmental conditions, causes either the liquid to be dispensed from the tube or gas from the environment to be drawn into the gas tight cavity through the tube.

Partially filling the chamber with a liquid produces a gas tight cavity above the liquid. If the chamber is then subjected to a change in environmental conditions such as an increase in temperature, the temperature of any gas within the cavity will increase accordingly. The gas will therefore expand causing an increase in the pressure within the cavity. A sufficient increase in pressure will cause some of the liquid to be ejected from the chamber through the tube. Conversely, a reduction of the temperature will cause the pressure within the gas tight cavity to drop, allowing gas to be drawn into the chamber through the tube. Even if the second opening of the tube is lower than that of the first opening, the portion of the tube which is higher than the first opening will prevent the simultaneous flow of gas into and liquid out of the chamber. In some cases, the chamber may be formed by first and second subsidiary chambers coupled by a conduit, whereby in use the second chamber contains liquid and the first chamber contains only gas. This is particularly useful if it is inconvenient to locate the chamber as a whole in an area where the environmental conditions change sufficiently. Thus, in the case of a greenhouse application or the like, the first chamber could be situated in an area which is subject to substantial changes in temperature while the second chamber is located closer to the plant to be irrigated.

The second opening could be connected to a conduit to convey liquid to its desired point of use and this conduit could be porous so that the liquid is dispensed throughout the length of the conduit. Typically the liquid will be water but it may contain dissolved or dispersed additives such as commercially available liquid feeds or medicinal treatments which are added to the water to promote the plant's growth or health. In this case a filter may be fitted to the first opening of the tube.

Preferably the second opening of the tube will dispense the liquid into a basin designed to contain the liquid. The basin might comprise one of many known receptacles designed to allow irrigation of plants contained in plant pots. A number of plant pots may be arranged to stand within the basin, the liquid being absorbed into the soil through holes in the base of the pots. Alternatively the liquid can be dispensed directly onto the plant itself, for example dripping either directly on to the foliage or on to the soil.

Preferably the basin is designed so that the second opening of the tube is positioned within the basin itself in such a manner that the filling of the basin with the water covers the upper opening. Advantageously, in such an arrangement the liquid is drawn back into the chamber when the pressure in the cavity drops thus reducing the risk of plants standing in water for extended periods.

In some cases the basin itself may be formed to act as a plant pot, the soil and plants being placed directly within the basin. The tube may then be extended such that the second opening is above the soil surface. In the preferred example, the upper wall of the chamber is formed so as to produce a basin on top of the chamber. In this case one or more plant pots can be supported within the basin and the apparatus comprises a base upon which to stand the plant pots. Additionally, the second opening is preferably located at a position higher than the first opening.

Typically, the present invention uses the natural temperature cycling of the environment to drive the liquid supply process. However, the environmental conditions could also be changed artificially, for example in connection with the first aspect of the invention, by placing the chamber in the vicinity of a lamp, domestic radiator or other heating device which can be turned on and off, possibly automatically. The rigidity of the wall could be achieved by using a suitably rigid material or by reinforcing the wall as necessary. In practice, it is to be expected that a small amount of flexing of the wall will take place.

A cover may be provided to at least partially enclose the chamber. This is particularly advantageous when the apparatus is used in adverse weather conditions. The apparatus may also further comprise a radiation reflector to reflect additional radiation onto at least the chamber. Typically such a reflector may be used to increase the heating effect of incident sunlight. In accordance with a second aspect of the present invention we provide a method for irrigating plants by supplying a liquid from a reservoir in response to changing environmental conditions, the method comprising: partially filling the chamber of apparatus according to the first aspect of the present invention with a liquid; and arranging the second opening of the tube to deliver the liquid to an irrigation position.

Some examples of the present invention will now be described with reference to the accompanying drawings in which: -

Figures la and lb are side views, partly in section, of a first example, under two different environmental conditions; Figure 2 is a side view, partly in section, of a second example;

Figure 3 is a side view, partly in section, of the first example, being used to irrigate a potted plant;

Figure 4 is a side view, partly in section, of the first example having a cover and reflector;

Figure 5 is a side view, partly in section, of a third example;

Figure 6a is a cross-section through a fourth example; Figure 6b is a plan of the fourth example; Figures 7a to 7c are side views, partly in section, of the fourth example, being used to irrigate a potted plant under three different environmental conditions; and, Figure 8 is a side view of a fifth example. Figure 1 shows automatic irrigation apparatus according to the first example of the present invention. A chamber 1 is formed from a substantially spherical portion 2 and an elongate neck region 3 producing a shape similar to that of an inverted round-bottomed flask. In a similar manner to such a flask, the neck region 3 ends in an opening 50 allowing the chamber to be filled with a liquid. Any substantially rigid material can be used to construct the chamber as long as it can be suitably formed. Suitable materials for this purpose include plastics, glass, fibre glass or metal. The requirement of substantial rigidity results from the nature of the apparatus. In order for the apparatus to work efficiently it is desirable that the chamber walls do not flex when subject to a difference in pressure between the inside and outside of the chamber. It is also preferable that the chamber walls are good thermal conductors and respond rapidly to external temperature variations. Of course, rigidity could be achieved by suitable reinforcement instead.

The neck 3 fits into a hemispherical base 4 equipped with a port 5 to receive the neck 3 and provide a seal against gas or liquid leakage. A tube 6 is provided within the chamber 1, in this case having the form of an inverted "L" . The tube can be held in its position by any convenient means and can be constructed from a convenient material such as glass, plastic or metal. The tube 6 runs in a substantially vertical manner 7 from within the neck region 3 up into the spherical body 2 of the chamber where it turns through an approximate right angle and passes substantially horizontally through the side of the chamber's spherical body 2. A water and gas tight seal is provided at the position where the tube 6 passes through the chamber wall . The tube 6 extends beyond the periphery of the chamber and close to its external end has a slightly downwardly inclined region 9. The tube 6 has an opening only at either end, the opening 10 outside of the chamber being positioned higher than the opening 11 inside the chamber neck. It is important that the chamber is gas tight at all points above the lower opening 11 of the tube 6. The second example of the present invention having an alternative tube arrangement is shown in Figure 2. Here the tube 6 enters the chamber via the base 4 such that the tube 6 remains generally external to the chamber 1. This provides advantages in that, in cases where the lower point of the chamber is open ended (such as in the example above having an opening 50) and sealed by interaction with the base, the tube may pass through this open end. This prevents the chamber wall from being compromised by passing the tube through it and also conveniently reduces the complexities of sealing and supporting the tube 6 within the chamber.

In order to use the apparatus it is necessary to partially fill the chamber 1 with water. This is achieved by detaching the chamber 1 from the base 4 and adding water 13 to the chamber using the opening 50 at the end of the neck 3. For the apparatus to function correctly it is necessary for the chamber to be filled to an extent that the level of the water 13 is above the lower end 11 of the tube 6 when the chamber is in its operating position and that an air cavity 12 is created between the water level and the top of the chamber. Hence the chamber should be partially but not fully filled. The neck 3 is then inserted in the port 5 of the base 4 and the apparatus is placed in its correct orientation with the chamber 1 supported by the base 4.

Maximum efficiency of the apparatus is achieved by reducing the internal volume of the tube 6 to a minimum. As the apparatus operates according to the volume change of the air cavity, the volume of the tube 6 is preferably considerably smaller than the typical volume changes of the air cavity caused during operation. A typical example is 1/32 gauge brass tubing. It has also been found that microtubing such as the kind used intravenously in the medical profession is particularly well suited for use as the tube 6. Typically, such microtubing is constructed from a material such as flexible nylon, the tubing may have an internal diameter down to the order of 0.5mm.

The apparatus should then be positioned in a location where natural temperature cycling occurs, for example on a daily basis. A window sill provides a convenient location. As shown in Figure 3, a potted plant 60 requiring irrigation should be positioned such that the second opening 10 of the tube 6 lies above the soil 61 in which the plant is potted. Any water dispensed from the opening 10 then falls on to the soil 61.

As shown in Figure 1, following positioning of the apparatus, the water 13 is held within the chamber 1 with an air cavity 12 above it. Even if the water level is above the external opening 10 of tube 6, the water is prevented from flowing out as this would reduce the pressure of the air in the cavity 12 above the water level. Similarly if the tube 6 is extended such that the external opening 10 is positioned lower than that of the internal opening 11, the apparatus will continue to function correctly as long as part of the tube 6 between the two ends is at a level higher than the internal opening 11. This prevents air from entering the chamber and displacing water in the absence of a difference in the air pressure between the air cavity 12 and the external environment . Referring to Figures la and 3, if the temperature of the apparatus increases, for example during the daytime, the air within the cavity 12 will be heated and will expand. The resultant increase in pressure forces the water through tube 6 where it drips from opening 10 on to the soil 61 of plant 60 (shown in Figure 3) . The downwardly inclined portion 9 of the tube promotes detachment of the water from the tube and prevents it from flowing along the lower exterior of the tube 6 and down the outside of the chamber 1. When the temperature of the environment drops, such as at nighttime, the air in the cavity 12 cools accordingly and contracts as shown in Figure lb. The resultant reduction in pressure draws air 15 into the tube 6 through the opening 10 and down through the tube 6 to the first opening 11, where it bubbles upwards and increases the amount of air in the cavity 12. The air replaces the water that was lost due to the earlier higher temperature. It will be appreciated that the cycling of the temperature in the air cavity 12 causes water to be periodically dispensed from the chamber during high temperature portion of a cycle, to be replaced by air from the outside during the low temperature portion. It will also be appreciated that a temperature increase within the chamber can be produced due to radiant heat from the sun in addition to any increase due to the ambient temperature. This is advantageous in that plants positioned in direct sunlight are likely to require more water and the amount of water dispensed is dependent upon the difference between the maximum and minimum temperatures experienced by the air cavity 12.

Additional features to enhance the effectiveness of the apparatus are shown in Figure 4. Here the apparatus is protected from the environment using a cover 51. The cover 51, which is preferably formed as a clear plastic dome, advantageously allows outdoor use of the apparatus whilst protecting it from adverse weather. The cover may be adapted to be large enough to enclose the vegetation being watered. Alternatively the cover 51 may be provided with an aperture through which the end of the tube 9 may pass.

To further enhance the heating effect of sunlight, a reflector 52 may be positioned so as to reflect additional thermal radiation onto the chamber, as shown in Figure 4. The reflective surface may be provided by known materials such as foil or aluminium paint . The surface of the reflector 52 may also be formed in such a manner so as to focus the sunlight, for example using a parabolic surface. Figure 5 shows the third example of the present invention. Here the chamber is formed from two subsidiary chambers 1,70 connected by a conduit 71. The subsidiary chamber 1 contains the water for irrigating the plant 60 whereas the subsidiary chamber 70 contains only air. The chamber 70 is positioned in a location where it will experience a large temperature cycling effect for example in direct sunlight at the top of a greenhouse. The resultant pressure changes within the air contained in the chamber 70 are transmitted via the conduit 71 to the air cavity 12 above the water in the chamber 1. The use of subsidiary chambers and the location of the chamber 1 close to the plant 60 advantageously maximises the volume of water delivered to the plant.

Apparatus according to the fourth example of the present invention is shown in Figures 6a, 6b. In this case a chamber 1 ' is formed in a manner so as to provide a stable base on which to stand a plant pot. The chamber 1' is formed as a single unit, for example a plastic moulding, unlike the previous example and has no separate base. A filling port 20 is provided with a screw on cap 21 to allow the chamber to be partially filled with water. The cap 21 provides a gas tight seal for the chamber. As shown in Figure 6b, the chamber is substantially circular when viewed from above. In the top wall 30 of the chamber 1', a recess is provided forming a circular basin 22. The tube 6' in this case is simply a linear tube mounted substantially vertically and having an opening only at each end. The length of the tube 6 ' is arranged so that the first opening 11' is close to the bottom wall 23 of the chamber 1' and the tube 6' passes through the top wall 30, terminating in an opening 10 ' flush with the base of the basin formed by the outer surface of the top wall 30. The tube 6' is positioned so that the opening 10' is located within the base of the basin adjacent to the circumferential wall 31 of the basin. In principle similar material requirements are necessary for this example as the previous one. Preferably the chamber in this case is constructed from a matt black rigid plastic such as Polypropylene. The apparatus operates in a similar manner to the previous example. The chamber is partially filled with water 32 through the filling port 20 producing an air cavity 33 above the water. Again the chamber must not be totally filled but a minimum amount of water must be added to cover the lower opening 11' of tube 6' during operation. Once the cap 21 is replaced effecting a gas tight seal, the apparatus is positioned in a location where temperature cycling will occur. In this case a plant pot 40 containing a plant 41 is placed directly within the basin 22 as generally indicated in Figure 7. Plant pot 40 contains holes in its base (not shown in the figure) allowing irrigation from beneath by simply standing the pot in a tray of water, as is well known. As indicated in Figure 7a, placing the plant pot 40 in the basin 22 of the chamber 1 ' and positioning the chamber in a location experiencing direct sunlight causes the temperature to rise within the air cavity 33. The increase in pressure drives some of the water 32 up the tube 6 ' and out through the opening 10' to begin filling the basin 22. The initial filling of the basin 22 with water is indicated in Figure 6b by the numeral 34. As the water level in the basin 22 rises, the water 34 covers the opening 10' of the tube 6 ' . Some of the water 32 is absorbed through the holes in the base of the plant pot 40 causing the plant 41 to be irrigated.

Figure 7b indicates a situation when the gas cavity 33 has reached its maximum volume and no more water is dispensed from opening 10'. It is at approximately this time that the basin 22 will contain the largest volume of water 34.

The cooling of the apparatus is indicated in Figure 7c where some of the water has already been removed from the basin 22 due to absorption into the pot 40 or by evaporation. However, some water 34 may still remain in the basin 22. As the temperature within the cavity 33 reduces, the reduction in pressure causes much of the remaining water 34 to be drawn back into the main reservoir of water 32 within the chamber, through the opening 10' in tube 6' . This process occurs prior to any air being drawn into the chamber because the opening 10 ' is positioned in the base of the basin 22 and therefore below the water level of water 34. As some water has been removed from the system, air is required to fill the cavity 33 to replace the lost water 32. The air is drawn into the tube 6' through the opening 10' when the opening becomes exposed to the air, that is following the removal of the water 34 from the basin 22. In a similar manner to the previous example, the air is drawn down the tube 6 ' and out through the opening 11', to bubble up through the water 32 into the air cavity 33. Advantageously the action of drawing water 34 back into the chamber 1 ' , conserves unused water thereby requiring the chamber to be refilled less often. An additional advantage is that the withdrawal of water 34 prevents the pot 40 from standing in a layer of water for extended periods causing the soil to become saturated. It will be recognised that saturation of the soil in plant pots is often undesirable as this can promote poor plant health and rotting of the plant's roots.

Apparatus according to the fifth example of the present invention is shown in Figure 8. This example has a deeper basin 22 in comparison with the second example. Here the basin walls 31 act as a plant pot and the basin itself is filled with soil 61 and planted with plants 60. In this example, the tube 6' is located centrally within the chamber and is extended to deliver liquid from the reservoir 32 to the surface of the soil. Therefore, with this particular configuration, water will generally not be drawn back into the reservoir (except that contained within the tube 6') when the pressure within the air cavity 33 reduces. The extension of the tube 6' above the soil surface provides an advantage in that the second opening is less likely to become obstructed with soil.

Claims

1. Apparatus for irrigating plants by supplying a liquid from a reservoir in response to changing environmental conditions, the apparatus comprising a chamber (1) , defining a reservoir, having a substantially rigid wall; and a tube (6) connecting the interior of the chamber to the external environment, the tube having a first opening

(11) and a second opening (10) , wherein the first opening

(11) communicates with the interior of the chamber and the second opening (10) is open to the external environment, and at least part of the tube (6) between the first and second openings is above the level of the first opening

(11) , the arrangement being such that when the chamber is partially filled with a liquid to a level above the first opening of the tube, a gas tight cavity (12) is created above the liquid, whereby a change in pressure within the gas tight cavity (12) in response to a change in environmental conditions, causes either the liquid to be dispensed from the tube (6) or gas from the environment to be drawn into the gas tight cavity through the tube (6) .

2. Apparatus according to claim 1, wherein the chamber is formed by first (70) and second (1) subsidiary chambers coupled by a conduit (71) , whereby in use the second subsidiary chamber (1) contains liquid and the first subsidiary chamber (70) contains only gas.

3. Apparatus according to claim 1 or claim 2, further comprising a basin (22) wherein liquid dispensed from the second opening (10) is contained within the basin.

4. Apparatus according to claim 2 or claim 3, wherein the second opening (10) is positioned within the basin (22) such that as the basin fills with liquid the second opening is covered by the liquid.

5. Apparatus according to claim 3 or claim 4, wherein the basin is formed from the top wall (30) of the chamber.

6. Apparatus according to any of claims 3 to 5 , wherein the basin (22) is shaped so as to support a plant pot.

7. Apparatus according to any of claims 3 to 6 , wherein the basin (22) is shaped so as to act as a plant pot.

8. Apparatus according to any of the preceding claims, wherein the second opening (10) is located at a position higher than the first opening (11) .

9. Apparatus according to any of the preceding claims, further comprising a cover (51) , adapted to at least partially enclose at least the chamber (1) .

10. Apparatus according to any of the preceding claims, further comprising a radiation reflector (52) adapted to reflect radiation towards at least the chamber (1) .

11. A method for irrigating plants by supplying a liquid from a reservoir in response to changing environmental conditions, the method comprising; partially filling the chamber (1) of apparatus according to any of the preceding claims with a liquid; and arranging the second opening (10) of the tube to deliver the liquid to an irrigation position.

12. A method according to claim 11, wherein the liquid is water.

13. A method according to claim 11 or claim 12, wherein the gas is air.