AU782146B2

AU782146B2 - Hydroponic system

Info

Publication number: AU782146B2
Application number: AU97119/01A
Authority: AU
Inventors: Grant Russell Watson
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-12-15
Filing date: 2001-12-06
Publication date: 2005-07-07
Anticipated expiration: 2021-12-06
Also published as: AU9711901A

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

Name of Applicant: Actual Inventor(s): Address for Service: Invention Title: GRANT RUSSELL WATSON GRANT RUSSELL WATSON SANDERCOCK COWIE 69 ROBINSON STREET DANDENONG VIC 3175 HYDROPONIC SYSTEM Details of Associated Provisional Application(s): No(s): Australian Provisional Application No. PR2116 Filed: 15 t h December, 2000.

The following statement is a full description of this invention, including the best method of performing it known to me: 1 2001-12-0,A:A363watUonfiflcwpd.I la- TITLE: HYDROPONIC SYSTEM FIELD OF THE INVENTION The invention relates to a hydroponic system, and is particularly concerned with aeration of a bulk water based hydroponic system which enables improved root growth.

SSandercock Cowie 2001-12-05,A:\62wa t .comp Iete.wpd I -2- BACKGROUND OF THE INVENTION Hydroponic systems have been developed as an alternative to traditional farming. In traditional farming plants are grown in soil in outdoor paddocks, and then harvested, often using large machinery. Such techniques work particularly well for some crops, such as wheat and sugar cane. However, for some crops, these traditional methods rely heavily on the condition of the soil for favourable outcomes in terms of plant growth, and bearing of fruit and the like.

Hydroponic systems are used to grow plants without soil using only nutrient carrying water solutions to feed the plants. In this way, the level of minerals and nutrients can be accurately controlled and adapted specifically for the plant being grown. Ideal conditions ifor a tomato plant, for example, may be very different to those of a strawberry crop.

A variety of systems have been proposed over time, and have been used to varying degrees of success. Early systems focussed on a model where the roots of the plant being grown were completely submerged in nutrient solution. An example of this type of system is disclosed in US Patent No. 2198150. In these systems, the upper portion of the root system was generally held above the waterline, so as to allow some roots exposure 20 to the open air so that the plant would not "drown".

Later systems proposed intermittently submerging the roots in a nutrient solution, between periods of exposure to the open air. An example of such a system is described in US Patent No. 1500211. The alternating submersion in solution and exposure to air allows the benefits of both full availability of nutrients to the plant roots, and also sufficient air availability directly to the roots.

Many modern systems have adopted the NFT (nutrient film technology) approach to hydroponics. In this type of system, a shallow film of nutrient flows along the base of a channel in which plants are situated. It is the intention of these systems that nutrient solution saturates the root system of the plant via wicking or capillary action, and that much of the root system retains access to the surrounding air so that as much air is Copyright. All rights reserved.

0 Sandercock Cowie 2001-12-05.A:.62wnU oncomplewpd.2 -3available to the roots as possible.

A significant difficulty associated with NFT systems is that installation of the systems requires a considerable degree of accuracy, and is therefore more time consuming and difficult. The reason for this is that a constant, but low, gradient must be achieved in order for the film to form effectively along the base of the channel. For example, any bowing of the channel may cause pooling of nutrient solution, resulting in over wetting of the roots, and lack of access of the roots to air. A gradient that is too high may cause the water to flow through the channel too quickly, preventing formation of a proper film, and interfering with the capillary action of the nutrient solution with regard to the roots.

A gradient of around 20mm drop over 1000mm of channel is required.

A further difficulty with NFT systems is that the channel can become clogged with root growth. This has two major drawbacks. Firstly, the matted root growth blocks the normal flow of nutrient solution causing pooling and loss of aeration as the nutrient solution flows along the channel, and also over wetting of the roots. Secondly, the roots themselves are unable to expand and grow freely to their fullest potential, thus restricting plant growth.

Another development in the area of soil less plant culturing is known as aeroponics. In this field, the roots are allowed to hang from the supported base of the plant in an *environment in which the roots are exposed to air and are effectively sprayed with S" nutrient solution. This method overcomes some of the problems associated with earlier systems, however, without support, the roots are not able to expand outwardly, and tend to hang limply vertically downwards. This reduces air access to the roots at the centre of the root bundle, and fresh nutrient spray is only provided to the outside of the root bundle.

Most of these existing systems recognise the importance of both nutrient solution and air to the health of the roots of the plant, and thus the health of the plant itself. Each of these attempts to balance these requirements with varying degrees of success.

SSandercock Cowie 2001.12.o0A:362wato.compIceixp.

-4- It is an object of the present invention to overcome or ameliorate one or more of the problems associated with prior art systems, and to provide a new and improved hydroponics system in which nutrient solution and aeration are both able to be provided to the plant roots in sufficient quantities.

SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a tank for use in growing plants hydroponically, the tank including:at least one wall, forming a wall of the tank and holding a hydroponic solution within the tank; and at least one aerating device for issuing air bubbles into hydroponic solution held within the tank; wherein the wall is positioned at an angle to the vertical, and the aerating device is positioned with respect to the wall such that, when in use, a substantial proportion of air bubbles issued from the aerating device are forced against the surface of the wall as they 20 rise.

According to a second aspect of the present invention, there is provided a method of growing plants hydroponically, the method including the steps of:providing a wall at an angle to the vertical in a hydroponic solution filled tank; and causing air bubbles to be issued adjacent to the angled wall of the tank such that they rise through the hydroponic solution whilst being forced against the wall of the tank.

Sandercock Cowie 2001- 2-05,A:U62.aoncompiete.wp&4 PREFERRED ASPECTS OF THE INVENTION Preferably, the action of the bubbles rising against the angled surface of the wall causes circulation of hydroponic solution within the tank. Preferably, when in use, this circulation of hydroponic solution tends to discourage plant roots from floating to the surface of the hydroponic solution.

Preferably, the tank is elongate, with a pair of opposed angled walls forming two of the walls of the tank. Preferably, a pair of opposing end walls and a base are also provided, together with the pair of opposed elongate angled walls, to form the hydroponic system tank.

Preferably, the aeration device is positioned at the base of each sloped wall of the tank.

Preferably, the aeration device is formed at least in part by a perforated tube positioned in the tank and having air supplied to it from an external source of compressed air.

Preferably, the angle of the wall or walls to the vertical is between approximately 5 and Preferably, the angle is between approximately 10° and 20°. Preferably, the angle is around 150.

Preferably, at the upper edge of the angled wall or walls, there is provided a ledge adapted for supporting a plant with respect to the hydroponic tank. Preferably, a plant grown using the hydroponic system will be supported by a substrate. Preferably, the substrate is supported on the ledge. Preferably, the substrate is a rock wool block.

Preferably, there is provided attachment means connected to the angled wall or walls for attaching a cover means to the tank. Preferably, the cover means is able to be used to hold the substrate in place to support the plant. Preferably, the cover means is a flexible sheet, possibly of plastic, connected between two angled walls of the tank, and which is removable to enable removal of the plant and substrate.

(0 Sandercock Cowie 2001.120S.A:U62wauon.compicte.wpd.

-6whereby, when the solution falls below a certain preferred level in the tank, additional water (or solution) is added automatically.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS A preferred embodiment of the invention will now be described with reference to the drawings, in which:- Figure 1 is a cross sectional end elevational view of a hydroponic tank in accordance with a first embodiment of the present invention; Figure 2 is a similar view to Figure 1 of the hydroponic tank of the first embodiment, but i showing a plant in situ as per the proposed use of the hydroponic tank; and 15 Figure 3 is a partial side elevational view of the hydroponic tank of Figure 1.

DETAILED DESCRIPTION WITH RESPECT TO THE DRAWINGS Referring firstly to Figure 1, there is shown (in sectional view) a hydroponic tank °20 having a base 12 and opposing angled side walls 14 forming the major portion of the tank Above the angled side walls 14 are low angle flat portions 16, upper side portions 18 and lip portions 20, collectively referred to as the upper portions 22. End portions (not shown) seal each end of the tank The base 12, angled side walls 14, and upper portions 22 may be formed of a single sheet of appropriate material formed or bent to form the cross-section shown in Figure 1. The material may be, for example, steel, plastic, or acrylic. In a preferred form, the base 12, angled side walls 14, and upper portions 22 may be formed by PVC extrusion.

Perforated tubes 24 are located adjacent to the comers of the base 12 and angled side walls 14. The tubes 24 release air bubbles 26 (shown in Figure 2) into the hydroponic solution 28 in the tank. The air bubbles 26 naturally rise in the direction of arrows A.

Sandercock Cowie 2001-12-OA:362wuaoncampee.wpd.6 The flow of bubbles 26 adjacent to the surface of the angled side walls 14 causes a flow of nearby solution 28, and this in turn causes a downward flow of solution 28 in the centre of the tank. This movement results in circulating flow of hydroponic solution as generally indicated by arrows B.

The level of the hydroponic solution is preferably maintained at around the junction of the low angle flat portions 16 and the upper side portions 18, as indicated by level line Turning now to Figure 2, features of Figure 1 are correspondingly marked, and in addition, air bubbles 26, plant leafy growth 32 and roots 34 are shown. The plant is ~supported in a rock wool substrate block 36 through which the leafy growth 32 emerges at the upper surface, and the roots 34 emerge from the lower surface. The block 36 in turn is held in place by flexible plastic sheet 38. Flexible plastic sheet 38 is flexed over V 15 the rock wool block 36 and held in place by opposing lips 20. At the early stages of plant growth, the rock wool block 36 does not really need support, but as the plant grows larger, it increasingly needs additional support provided by the flexed plastic sheet 38 to hold the plant steady.

20 As can be seen in Figure 2, the plant roots 34 are provided with a large volume of S"hydroponic solution 28 to expand into, especially when compared to NFT systems, where :the total volume of the root growth and rock wool block containment is often little more Sthan the volume of the upper portions 22 of the present embodiment.

This construction may give rise to a situation where the roots 34 are caused to float to the surface under the action of the rising bubbles 26, except that the configuration of the tank provides the circulation patterns indicated by arrows B in Figure 1, and this circulation tends to cause the roots 34 not to float to the surface, which would cause clogging and reduce the plants root spread. This enables the roots 34 to be able to spread out in a downwards fashion around the centre of the tank 10 as shown in Figure 2. This is of great advantage to the plant as the more spread out the roots 34 are, the better they are able to absorb nutrients and air from the hydroponic solution 28.

Sandercock Cowie -12OSA:U62w wd,7 Further, the action of the bubbles 26 being forced against the wall 14 by virtue of its angle as they rise to the surface provides an increased level of aeration, and thus oxygenation, of the solution 28, and as discussed above, such aeration and oxygenation of the solution 28 is of significant importance to the health of the plant. As a result of higher levels of oxygenation of the solution in the present invention, it has been found that the plant is able to obtain all its oxygen requirements directly from the solution, and it has not been found necessary to provide additional means for the plant to grow "air breathing" roots above the solution level, as has been found necessary in earlier bulk solution systems.

Figure 3 shows one end of the tank 10 of Figures 1 and 2. Components described above are referred to with the same numerals. End portion 40 seals the end of the tank 10 to hold the hydroponic solution 28 in the tank 10. Another end portion (not shown) is provided at the other end of the tank Perforated hose 24 is connected to an air supply tube 42, which connects to an air pump (not shown). Air supply tube 42 exits the tank 10 above the hydroponic solution level Other devices, such as heater 44 (used to maintain hydroponic solution 28 temperature), and solution level controller (mentioned above, not shown) are also 20 connected to the tank 10 above the hydroponic solution level 30. This reduces the S"possibility of leaks at connecting points.

Plastic cards, acting as mixing vanes 46, are positioned at regular intervals along the tank As a result of the downward motion of the hydroponic solution flow in the centre of the tank 10, as shown by arrows B in Figure 1, and the angle of the mixing vanes 46, a secondary flow pattern is established, as indicated by arrow C. The multiple solution flow patterns as indicated by arrows B and C allow very rapid mixing of solution 28 to ensure homogenous distribution of nutrients throughout the tank The mixing vanes 46 also have an important secondary role, in that they hold the perforated hoses 24 in place as shown in Figures 1 and 2. The air in the perforated hoses 24 applies a substantial force to the perforated hoses 24 urging them upwards in the Copyright. All rights reserved.

SSandercock Cowie 200 -12.05.A:\362waan.tcmplt.wpd.8 -9solution 28. The mixing vanes 46 have been found to be particularly useful in restraining upwards movement of the perforated hoses 24. Other methods of restraining the hoses 24 tended to result in build up of large air bubbles associated with the clips and/or other restraining means, and the rising of so formed air bubbles disrupted the orderly rise of small bubbles 26, and also disturbing the plant roots 34.

Where the tank extends over larger distances in the longitudinal direction, the shape of the tank, and the volume of solution held therein may cause some movement in the structure of the tank which can result in the respective upper portions of the tank moving apart from each other. This problem can be easily addressed by addition of a clip (not shown) holding the two upper portions at a set distance apart.

-As can be seen from the manner in which the embodiment of the invention operates, there is no need for delicate balancing of the slope of the mounting of the tank, as has been required in a number of prior art systems. Aeration, mixing, and constant provision of water and nutrients to the plant are not contingent on slight variations in the angle of mounting of the tank. Thus, mounting of the tank is easier and less complicated.

The claims, illustrations, photographs and drawings, if any, form part of the disclosure 20 of this specification as does the description, claims, illustrations, photographs and CCo...

drawings of any associated provisional or parent specification or of any priority document, if any, all of which are imported hereinto as part of the record hereof.

Finally it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements or parts without departing from the spirit and ambit of the invention.

Sandercock Cowie 2001-12.OS.A:A62wIon.compicwpd.9

Claims

1. A tank for use in growing plants hydroponically, the tank including:- at least one wall, forming a wall of the tank and holding a hydroponic solution within the tank; and at least one aerating device for issuing air bubbles into the hydroponic solution held within the tank; wherein the wall is positioned at an angle to the vertical, and the aerating device is positioned with respect to the wall such that, when in use, a substantial proportion of air bubbles issued from the aerating device are forced against the surface of the wall as they rise.

2. A tank in accordance with Claim 1, wherein the tank is elongate, with a pair of opposed angled walls forming two of the walls of the tank.

3. A tank in accordance with Claim 2 further including a pair of opposing end walls 20 and a base, wherein the opposing end walls, base, and opposed angled walls together form the hydroponic solution tank.

4. A tank in accordance with any one of the preceding claims, wherein, in use, the action of the bubbles rising against the angled surface of the wall causes circulation of hydroponic solution within the tank.

A tank in accordance with Claim 4, wherein the circulation of hydroponic solution tends to discourage plant roots from floating to the surface of the hydroponic solution.

6. A tank in accordance with any one of the preceding claims, wherein the aerating device is positioned at a lower portion of the or each wall of the tank. Copyright. All rights reserved. (0 Sandercock Cowie 2001-12-05,A:\362wason.comnplctwpd. -11-

7. A tank in accordance with either one of Claims 2 or 3, wherein the aeration device is positioned at the base of each angled wall of the tank.

8. A tank in accordance with any one of the preceding claims, wherein the aeration device is formed at least in part by a perforated tube positioned in the tank and having air supplied to it from an external source of compressed air.

9. A tank in accordance with any one of the preceding claims, wherein the angle of the wall or walls is between approximately 5 and 45 to the vertical.

A tank in accordance with any one of Claims 1 to 8, wherein the angle of the wall or walls is between approximately 10 and 20° to the vertical.

11. A tank in accordance with any one of Claims 1 to 8, wherein the angle of the wall or walls is approximately 15' to the vertical.

12. A tank in accordance with any one of the preceding claims, wherein, at the upper edge of the angled wall or walls, there is provided a ledge adapted for supporting a plant with respect to the hydroponic tank.

13. A tank in accordance with Claim 12, wherein a substrate is provided to support plants grown using the hydroponic system, and that substrate is supported on the ledge.

14. A tank in accordance with Claim 13, wherein the substrate is formed of a rock wool block.

A tank in accordance with any one of the preceding claims, wherein an attachment means is connected to the angled wall or walls for attaching a cover means to the tank.

16. A tank in accordance with Claim 15, wherein the cover means, in use, holds a Copyright. All rights reserved. Sandercock Cowie 2001-12-05.A:\362wa son.completwpd, i -12- plant supporting substrate in place.

17. A tank in accordance with either one of Claims 15 or 16, wherein the cover means is a flexible sheet, connected between two angled walls of the tank.

18. A tank in accordance with Claim 17, wherein the cover means is removable to enable the removal of the plant and substrate.

19. A tank in accordance with any one of the preceding claims, having a hydroponic solution maintenance device which automatically maintains the hydroponic solution at above a predetermined minimum level.

20. A method of growing plants hydroponically, the method including the steps of:- providing a wall at an angle to the vertical in a hydroponic solution filled tank; and causing air bubbles to be issued adjacent to the angled wall of the tank such that they rise through the hydroponic solution whilst being forced against the wall of 20 the tank.

21. A method of growing plants hydroponically in accordance with Claim wherein the method includes the use of a tank in accordance with any one of Claims 1 to 19.

22. A tank for use in growing plants hydroponically as described in the preceding description with reference to the accompanying drawings. Dated this 5 h day of December, 2001. SANDERCOCK COWIE PATENT ATTORNEYS FOR GRANT RUSSELL WATSON Copyright. All rights reserved. 0 Sandercock Cowie 2001-12-05A:362wion.compltewpd,12 m