Abstract:
A low cost valve and system for automated ebb and flow irrigation utilizes a collapsible sleeve to control fluid flow direction. No external power, moving parts, or floats are needed to operate the valve, resulting in improved reliability, low operating cost, and minimal need for maintenance. The valve operates using feed pressure to close the drain when hydroponic nutrient solution is pumped into the cultivation chamber. The valve drains automatically once the pump is stopped, usually by means of a timer, and the spent hydroponic solution is recovered. The fill/drain cycle is repeated as needed to keep the plants moist, yet not waterlogged.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to valves for controlling the intermittent flooding or flushing of liquids into a vessel, and more particularly to apparatus for controlling the circulation of hydroponic solutions to and from cultivation containers for plants. 
     In hydroponic culture, a common mode of operation is termed “ebb and flow”. In this operation, plants are contained in a culture vessel and the roots are intermittently flooded with a nutrient solution, and then the solution is allowed to drain out. It is important that this “ebb and flow” operation be automated and functions reliably. If the plants roots are not flooded in time, they will dry out resulting in irreparable damage to the plant roots. On the other hand if the hydroponic solution stagnates in the cultivation container, then the roots will rot, again causing irrecoverable damage. In addition to reliable operation, it is essential that the device be low cost and preferably not require a power source. 
     2. Statement of the Prior Art 
     In the prior art, the vast majority of such “ebb and flow” valves use a float mechanism. In these devices, a float assembly moves as the water level rises in the plant cultivation vessel. When the liquid level is at the desired height, the float shuts the feed valve off and liquid drains out of the cultivation container back into the feed reservoir. In most cases a low pressure pump is required to provide the feed solution. The biggest problem with float valves is that they have mechanical moving parts and these parts tend to get clogged by roots and other foreign matter that prevent the float from moving freely. The float valves also have small diameter seats in order to make them compact. These limitations cause float valves to frequently malfunction, leading to catastrophic crop failure. Pinch valves have been used as an alternative, but these require a power source to open and close the valve. This results in increased complexity and cost. While pinch valves are less prone to clogging, the possible failure of the power source reduces overall reliability. Other prior art approaches eliminate a valve altogether by having a bleeder orifice or venturi. These require high pressure pumps in order to generate sufficient flow to the cultivation vessel and also suffer from the problem that the drain orifice is usually very small and easily clogged, leading to stagnant hydroponic solution remaining in contact with the plant roots and possible root rot. 
     SUMMARY OF THE INVENTION 
     These and other objects, advantages, and novel features are provided by embodiments of the present invention, which overcome the foregoing problems. 
     The present invention relates to a flood control valve and to a simple and low cost hydroponic irrigation system employing that valve. The irrigation system is capable of operating unattended for weeks at a time with little or no maintenance. It is useful both for large commercial applications, as well as hobby and home use. A variety of plants for decorative and food use can be grown in the system. A single feed pump can supply a number of plant cultivation vessels, which can be of different sizes and positioned at different elevations. A feed pump is activated by an automatic electric timer at preset intervals. The pump draws the hydroponic nutrient solution from a reservoir and supplies it through pipes to a flood control valve located on each plant cultivation vessel. The flood control valve has an inlet and an outlet connection for the feed stream, and similar inlet and outlet ports for draining the spent nutrient solution out of the cultivation chamber. The streams are introduced into a cavity in the valve, but kept separated by a flexible rubber membrane. The feed and drain streams are oriented in opposite directions with the feed stream allowed to flow up through the valve into the cultivation chamber, and the drain stream allowed to flow downwards by gravity. When feed is not flowing through the valve, the flexible membrane is in a relaxed state and centered in the cavity. This orientation permits fluid to drain downwards out of the valve. However, when the feed pump is turned on it pushes nutrient solution upwards through the valve. The flow results in backpressure in the valve cavity and this backpressure causes the flexible membrane to expand and push towards the drain side of the cavity. This expansion of the membrane effectively blocks off the drain side and no liquid can drain out of the valve. This permits the cultivation chamber to fill up rapidly and without wastage. Once the fill cycle is completed, usually set by a timer, the feed pump turns off, backpressure rapidly decays and the flexible membrane returns to the center of the cavity causing spent liquid to start draining out of the cultivation chamber. This design has essentially no moving parts (apart from the flexing of a rubber membrane) and operates automatically without the need for any power. A positionable overflow tube is provided in the valve and can be moved up and down to set the desired height of the nutrient solution in the cultivation chamber during the flooding phase of the cycle. 
     Accordingly, it is a general object of embodiments of the present invention to provide a flooding control valve with no moving mechanical parts and no requirement for motive power, thereby reducing the likelihood of failure. 
     More specifically, it is an object of embodiments of the present invention to provide a flooding control valve that is inexpensive to manufacture and can be made with commonly available parts. 
     It is another object of embodiments of the present invention to provide a flooding control valve in which the maximum liquid level can be easily adjusted by raising or lowering an overflow tube. 
     It is still another object of embodiments of the present invention to provide a flooding control valve with no flow restrictors or seats, making it less prone to clogging. 
     It is yet another object of embodiments of the present invention to provide a flooding control valve made entirely of non-metallic parts, thereby eliminating corrosion. 
     It is a further object of embodiments of the present invention to provide a flooding control valve with an unrestricted drain making it less prone to clogging by debris or precipitates. 
     It is still a further object of embodiments of the present invention to provide a flooding control valve that is self-cleaning as each cycle compresses and forces any accumulated debris out of the valve cavity. 
     Further objects and advantages of this invention will become apparent from a consideration of the drawings and ensuing detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present invention will become more apparent from the following description of exemplary embodiments, as illustrated in the accompanying drawings wherein: 
         FIG. 1  is a perspective cutaway view of the hydroponic cultivation system which shows the arrangement of the valve of the present invention and other major components; 
         FIG. 2A  is a sectional view of the control valve according to one embodiment of the present invention; 
         FIG. 2B  is a sectional view of the valve in  FIG. 2  showing the pressurized (flood) position; 
         FIG. 2C  is a sectional view of the valve in  FIG. 2  showing the depressurized (drain) position; 
         FIG. 3A  is a schematic view of the valve and other components of the hydroponic system; and 
         FIG. 3B  is an alternate embodiment where an external pump is used to supply a series of cultivation vessels. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments are discussed in detail below. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. In describing and illustrating the exemplary embodiments, specific terminology is employed for the sake of clarity. However, the embodiments are not intended to be limited to the specific terminology so selected. Persons of ordinary skill in the relevant art will recognize that other components and configurations may be used without departing from the true spirit and scope of the embodiments. It is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. Therefore, the examples and embodiments described herein are non-limiting examples. 
     Referring now to the drawings, wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements, there is shown in  FIG. 1  an embodiment of the flooding control valve and its associated apparatus. A fluid reservoir  30  supplies the hydroponic solution  31 . A pump  32 , which may be located inside the reservoir  30 , draws fluid and pumps it up through the flooding control valve  10  into delivery tubing  34  which is contained inside the plant cultivation vessel  36 . Plants  60  are placed in holes cut into the top of the cultivation vessel. The cultivation vessel is liquid tight except for two openings in the bottom for the flooding control valve  10  and overflow pipe  20 . The top of fluid reservoir  30  has a circular cut-out so that when the cultivation chamber is placed on top of the fluid reservoir, the overflow pipe  20  can discharge directly into the fluid reservoir. The discharge pipe from the feed pump  32  is connected to the flooding control valve  10  through another cutout on top of the fluid reservoir. The delivery tubing  34  has a number of spray heads  40  that are distributed along its length. The delivery tubing  34  is closed on the far end by closure fitting  38 . When pump  32  is turned on, hydroponic fluid is pumped into the delivery tubing  34 . The solution is dispensed into the cultivation vessel  36  through the spray heads  40  which are sized such that delivery tubing remains slightly pressurized (about 0.1 to 1.0 psig). The pressurization causes flooding control valve  10  to shut off flow from the cultivation vessel back into the fluid reservoir. This causes fluid to accumulate in the cultivation vessel  36  until it is at a level sufficient to drain back through overflow tube  20 . In the manner, fluid level in the cultivation vessel cannot exceed a preset level as determined by the height of the adjustable overflow tube  20  inside the cultivation vessel  36 . The pump  32  can then be turned off which causes flooding control valve  10  to open allowing the cultivation vessel to drain back completely into the fluid reservoir  30  thus completing the “ebb and flow” cycle of irrigation. It should be apparent that it is not critical when the pump shuts off as long it is set to remain on for enough time to cause fluid to reach the overflow pipe. Leaving the pump on for extra time will not cause cultivation vessel  36  to overflow because of the overflow tube.  FIGS. 2A through 2C  illustrate the operation of the flooding control valve in greater detail. 
     Referring to  FIG. 2A , flooding control valve  10  consists of two symmetric halves  19  and  21  with a flexible rubber membrane  52  mounted in between. Each half has a cavity  50  positioned on either side of the membrane  52 . The feed half  19  has feed port  90  that introduces the feed stream from the pump  32  into the cavity  50 . Port  91  allows fluid to leave the cavity on the feed side  19  of the valve into delivery tubing  34  which then provides nutrient solution to the plants via spray heads  40  as described earlier. The drain side of the valve has port  92  which allows spent solution to drain into the cavity in drain half  21 . Port  93  allows this fluid to drain out of the valve into fluid reservoir  30 . A cleanable strainer  44  is provided over the drain inlet  92  to prevent debris from entering the valve cavity. A small nozzle  45  is provided on the outlet tubing located on port  91 . When nutrient is pumped into the cultivation chamber  36  via tubing  34  a small jet is forced out of nozzle  45  impinging on strainer  44 . This jet cleans the strainer each time the valve is activated thereby cleaning off any debris that may accumulate on the strainer preventing possible cloggage. 
     When the hydroponic solution is pumped into the flooding control valve  10  through port  90 , fluid accumulates inside cavity  50  which starts to pressurize as the only possible discharge is through the small orifice sprayers  40 . The rise in pressure forces the flexible membrane  52  against the drain side of the valve cavity as this side is not pressurized. The membrane  52  seals against the cavity shutting off drain flow from port  92  to  93  as shown in  FIG. 2B . With the drain now closed, solution accumulates in cultivation vessel  36  until the pump  32  is shut off. When the pump is switched off, the pressure in the valve cavity dissipates and it collapses back to its natural flat profile as shown in  FIG. 2C . This is turn permits fluid to flow through port  92  and past the gap between the relaxed membrane and the cavity wall out through port  93  causing fluid to completely drain out of cultivation vessel  36 . The overall operation can be readily visualized by reference to  FIG. 3A  which is a schematic of the system using a submersible pump. This is the simplest configuration. A submersible pump  32  in placed inside the fluid reservoir  30 . The discharge from pump  32  is connected to polymeric tube  11  which in turn is connected to feed inlet port  90  located on the underside of the flooding control valve assembly  10 . Distribution tube  34  is connected to the feed outlet port  91 . In operation pump  32  is switched on and hydroponic solution  31  from reservoir  30  is sprayed into cultivation chamber  36 . Fluid is prevented from draining out of cultivation vessel  36  by feed pressure in the flooding control valve  10  as described earlier. Adjustable overflow tube  20  directs excess solution from vessel  36  back into reservoir  30 . Once the flooding is complete, pump  32  is switched off and all the fluid inside vessel drains out through the now depressurized flooding control valve  10  back into reservoir  30 . 
     In a preferred embodiment, delivery tubing  34  may be made from semi-rigid commercial PVC drip irrigation tubing and commercial drip spray heads  40  were pierced into it at 1 foot intervals. Cultivation vessel  36  may be made from 5 inch cross section square fence posts with glued end caps. Pump  32  may comprise a low cost submersible fountain pump and the fluid reservoir may comprise a plastic tote box. A household lamp timer  98  was used to control the system. This design approach and choice of construction materials may result in a cost of less than about $200 for an entire hydroponic cultivation system capable of supplying the needs of a small family. Plant growth and yields also exceeded that of commercial hydroponic units. 
     Multiple plant cultivation vessels can be connected to a single feed pump and reservoir. It is just a simple matter of connecting the flooding control valves in parallel using inexpensive flexible tubing. 
     Referring to  FIG. 3A , the “ebb and flow” cycles may be controlled by a simple timer  98 , or it may be triggered by a sensor  97  that monitors the moisture content of culture media around the plant roots. This sensor would then start the “ebb and flow” cycle on demand when the moisture content drops below a preset limit. This method reduces hydroponic fluid consumption. This moisture sensor can also be used to trigger an alarm  99  to alert the operator in the event a pump or system malfunction is causing the plant roots to dry out. With this early detection alarm it should be possible to correct the situation before the plants are damaged beyond recovery. In a preferred embodiment, a VG400 moisture sensor (manufactured by Vegetronix of Sandy, Utah, USA) may be used to monitor and control moisture content. This sensor provides an analog voltage proportional to moisture content and can easily be coupled to an electronic controller. Either control system allows for unattended operation except for occasional recharging of the fluid reservoir with fresh hydroponic solution. 
     Unlike devices and systems according to the prior art, the system disclosed in the present invention does not drain through the feed pump, so the feed pump can be placed in any orientation, even above the cultivation vessels. This feature of the present invention allows any pump, including positive displacement pumps to be used. This also provides the ability to pump only from a fresh hydroponic fluid reservoir and collect spent fluid in another independent reservoir, thereby not contaminating the feed solution. 
       FIG. 3B  depicts an alternative embodiment where a non-submersible feed pump  32  is located outside the fluid reservoir  30 . The advantage is that non-submersible pumps are cheaper, more reliable, and easier to service than submersible ones. The pump discharge may be piped to any number of cultivation vessels  36 , each equipped with its own flooding control valve  10 . A small sump  80  must be provided on each cultivation vessel to receive the overflow, and drain back spent solution from each cultivation vessel. This fluid can then be directed back to the fluid reservoir by gravity. No power source or mechanical float of any kind is required at any of the cultivation vessels. It is only important that the cultivation vessel and sumps be positioned at a higher elevation than the fluid reservoir, which may be placed in a basement or simply a buried drum. 
     It should be understood that the foregoing description is only illustrative of embodiments of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the spirit of the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.