Abstract:
An irrigation control valve has two movable members that can independently or in combination block the flow of water in a conduit, or be fully retracted of at some point in-between. A moisture sensitive element is arranged to be placed in contact with the soil and expands or retracts dependent on the moisture within soil adjacent the moisture sensitive element. The moisture sensitive element is connected or coupled to a moisture controlled member. Dependent on the moisture of the soil adjacent the moisture sensitive element, the moisture controlled member is moved further into the conduit with increasing moisture in the soil. The moisture controlled member and an electronically controlled member are located adjacent each other at the conduit. The electronically controlled member determines how far the moisture controlled member needs to move in order to fully block the flow of water in the conduit. An electronic controller is operable to determine the achieved level of moisture in the soil, by means of the electronically controlled actuator and the electronically controlled member.

Description:
FIELD OF THE INVENTION 
   The present invention relates to agricultural and landscape irrigation, and more specifically, an irrigation control valve and system for irrigating plants. 
   BACKGROUND OF THE INVENTION 
   Increasing scarcity and cost of water is driving advances in irrigation. In California and Australia, for example, wine growers are now utilizing techniques such as root deficit irrigation (RDI) and partial root zone drying (PRD). The grapevines are hence irrigated with less water than in conventional viniculture. These techniques not only save water, but can increase the value of the crop by improving crop attributes for which the market will pay a premium. These techniques will reach maximum effectiveness when irrigation can be economically controlled on a plant-by-plant basis. 
   Another advance in irrigation is the deployment of wireless sensor networks to enhance crop management. One of the challenges to this approach is the cost of the network nodes and the energy they require for communication, especially for powering electro-mechanical actuators such as irrigation valves. 
   Thus, there is a need for an automatic irrigation system that controls irrigation of one or more plants according to their actual moisture requirements, but also allowing a remote or environmental dependent adjustment of the desired or achieved moisture level. The valve of the irrigation system should have low requirements for electric energy and a low price. 
   It is an object of the present invention to provide for low cost, individual or small group plant water control that is preferably suited for supporting RDI and PRD techniques. 
   SUMMARY OF THE INVENTION 
   An irrigation control valve has two movable members that can independently or in combination block the flow of water in a conduit, or be fully retracted or at some point in-between. A moisture sensitive element is arranged to be placed in contact with the soil, and expands or retracts dependent on the moisture within soil adjacent the moisture sensitive element. The moisture sensitive element is connected or coupled to a moisture controlled member. Dependent on the moisture of the soil adjacent the moisture sensitive element, the moisture controlled member is moved further into the conduit with increasing moisture in the soil. Analogously, the moisture controlled member is moved further out of the conduit as the soil dries. The second movable member is an electronically controlled member coupled or connected to an electronically controlled actuator. The latter is controlled by an electronic controller. 
   The moisture controlled member and the electronically controlled member are located adjacent each other at the conduit. The electronically controlled member determines the shut-off position of the moisture controlled member, i.e. how far the moisture controlled member needs to move in order to fully block the flow of water in the conduit. The electronic controller is thus operable to determine the achieved level of moisture in the soil, by means of the electronically controlled actuator and the electronically controlled member. 
   It is an advantage of the invention that the electronically controlled member and the electronically controlled actuator need only to move when a desired level of moisture in the soil changes. Since this usually takes place over longer intervals, minimal electric energy for moving the electronically controlled member is required. Changes in the actual moisture content of the soil occurring with higher frequency, dependent on the daytime evaporation, etc., only influence the moisture controlled member which does not require electric energy. 
   The electronic controller can be controlled from a remote station at which a computer is located. A user can input data containing information about the desired amount of moisture in the ground into the computer, which data are sent to the electronic controller wirelessly by radio frequency transmission or via a wired control network. The information about the desired amount of moisture in the ground can alternatively or additionally be provided by a control program running on the computer and/or on the controller of the irrigation valve, the program using a model based upon plant characteristics and environmental information. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic representation of an irrigation system incorporating an irrigation control valve according to the invention; 
       FIG. 2  is a schematic representation of the members of the valve, wherein the electronically controlled member is in a closing position and the moisture controlled member is in a partially open position; 
       FIG. 3  is a schematic representation of the members of the valve, wherein the electronically controlled member is in an open position and the moisture controlled member is in a closed position; 
       FIG. 4  is a schematic representation of the members of the valve, wherein the electronically controlled member is in a partially open position and the moisture controlled member is in a partially open position, such that the valve is closed; 
       FIG. 5  is a schematic representation of the members of the valve, wherein the electronically controlled member is in a partially open position and the moisture controlled member is in a partially open position, such that the valve is open; 
       FIG. 6  is a sectional side view of an embodiment of the irrigation control valve; 
       FIG. 7  is a sectional view of the irrigation control valve along lines  7 - 7  of  FIG. 6 ; 
       FIG. 8  is a sectional view of the removable cartridge of the irrigation control valve of  FIG. 6 ; and 
       FIG. 9  is a schematic representation of an irrigation system with a plurality of irrigation control valves and a communication node in the field. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In  FIG. 1 , an irrigation control system according to the invention is shown in a schematic manner. The irrigation control system utilizes an irrigation control valve  10  comprising a conduit  12  having an inlet  14  and an outlet  16 . The cross section of conduit  12  can be circular or rectangular or of any other suitable shape. Inlet  14  is connected via an inlet pipe  18  to a supply  20  of water. The supply  20  can be any suited source of water, especially a tank or cistern standing upon the ground or buried therein collecting rainwater or any other water, a lake, a spring or a water-conducting layer in the ground. A pump (not shown) can be provided between the supply  20  and the inlet  14 , if required. The outlet  16  is connected by means of an outlet pipe  22  to a water discharge  24  located in the vicinity of roots  26  of a plant  28 , for example a vine plant. The roots  26  are within soil  30  surrounding them. 
   The irrigation control valve  10  comprises a moisture sensitive element  32  located within the soil  30  adjacent the water discharge  24  and the roots  26 . The moisture sensitive element  32  consists of or incorporates a hydrophilic material, such as a hydrophilic polymer or nylon or wood, which expands as a function of the amount of moisture in the soil  30  surrounding the moisture sensitive element  32 . The more moisture the soil  30  adjacent the moisture sensitive element  32  contains, the larger the latter gets. Analogously, the moisture sensitive element  32  contracts with decreasing moisture of the soil  30  surrounding it. A membrane permeable to water, but impermeable to salt and other chemicals such as fertilizer may be needed to maintain the quality and function of the hydrophilic polymer in areas where irrigation water has high salt content or if irrigation water is used for chemigation. 
   Moisture sensitive element  32  is mechanically coupled to a movable moisture controlled member  34  that penetrates into the conduit  12  between inlet  14  and outlet  16 . The moisture sensitive element  32  controls the position of the moisture controlled member  34  dependent on the moisture of the soil  30  in the vicinity of the moisture sensitive element  32 . In particular, it moves the moisture controlled member  34  further into the conduit  12  the higher the moisture level of the soil  30  is, such that the cross section in the conduit  12  left free by the moisture controlled member  34  increases with decreasing humidity of the soil  30  and vice versa. 
   Irrigation control valve  10  further comprises an electronic controller  36  connected to an electric power source  38  (such as a battery, solar cell, ultracapacitor, fuel cell, or a motion-to-electricity unit, etc.), an electronically controlled actuator  40 , a position sensor  42 , a ratchet arresting actuator  44 , a transceiver  46 , and two environmental sensors  48  and  50 . The electric power source  38  powers the electronic controller  36  and the sensors  42 ,  48  and  50 , as well as the transceiver  46 . Actuators  40  and  44  are powered from the electric power source  38  once activated by the electronic controller  36 . Controller  36  can use a microprocessor or a microcontroller. 
   The electronically controlled actuator  40  is a linear actuator having a linearly moving output  52 . In the embodiment shown in  FIG. 1 , the electronically controlled actuator  40  comprises an electro-active polymer  76  that expands in the presence of an electric field provided by the electronic controller  36  and contracts when the electric field is removed. In another possible embodiment (not shown), the electronically controlled actuator  40  comprises a DC motor or another suitable bidirectional linear or rotational drive receiving a directional signal from the controller  36 . The motor or drive can have a rotating output driving a pinion or worm gear meshing with a toothed bar that is connected to output  52 . Output  52  is mechanically coupled to a movable member  54  by means of a rod  56 . Rod  56  carries a toothed portion  58  having a number of recesses  60  between adjacent teeth  62 . 
   A ratchet  64  connected to the ratchet arresting actuator  44  is suited to be moved between a locking position in which it penetrates into a recess  60  and a released position, as shown in  FIG. 1 , in which it is moved out of the recesses  60  by the arresting actuator  44 . The latter is a linear actuator, and incorporates in a possible embodiment a solenoid (not shown) operable to pull a magnetic core coupled to the ratchet  64  against force of a spring, such that the ratchet  64  gets out of the respective recess  60 . 
   Arresting actuator  44  and electronically controlled actuator only need electric power when the electronically controlled member  54  is moving. The latter can be brought into a rather large numbers of positions between a position leaving conduit  12  entirely open and a closing position in which it closes the conduit  12 . 
   If the electro-active polymer  76  consumes no or sufficiently little power when the field voltage upon the polymer  76  is held constant, one could also dispense with the ratchet  64  and the arresting actuator  44 . The latter are however required if the electronically controlled actuator  40  comprises a DC motor or another suitable bidirectional rotational drive, unless the drive train between the motor and the output  52  is self arresting, by for example using a worm gear meshing with a pinion. 
   Position sensor  42  is in one embodiment of the invention an optical sensor detecting markings on rod  56 . It submits data containing information about the actual position of output  52  and thus of the electronically movable member  54  to electronic controller  36 . In another embodiment, position sensor  42  can use a potentiometer moved by the electronically controlled actuator  40 . If the electronically actuated actuator  40  comprises for example a stepper motor, one could dispense with sensor  42 , since the position of the actuator  40  is known to the controller  36  from the control signals submitted to the actuator  40 . 
   Transceiver  46  is connected to an antenna  66  that can receive electromagnetic waves from an antenna  68  connected to a transceiver  70  which communicates with a computer  72 . Antenna  68 , transceiver  70  and computer  72  are located at a remote location, e.g. at an operator&#39;s office. The communication line between electronic controller  36  and computer  72  via antennae  66  and  68  is preferably bidirectional, such that error messages can be sent from the controller  36  to the computer  72 , for example if the electrically movable member  54  is stuck in its position and cannot be moved by the electronically controlled actuator  40 . The wireless communication link is preferably only requiring low power, such as using a Zigbee or RFID protocol, but one could also use cellular phone or WiMax connections. 
   Sensor  48  senses the temperature of the soil  30  in the vicinity of the plant  26 , while sensor  50  is a sunlight sensor as sunlight has been identified as key to several plant (especially grape) key attributes. Temperature values can be used for calculating growing degree days for the plant  28  as determined by climate, microclimate and weather. Controller  36  is optionally connected to another sensor (not shown) measuring the moisture within the soil  30 , either with a dedicated separate sensor or by measuring the position of the moisture sensitive element  32  or of the moisture controlled member  34  with a position sensor. 
   It should be noted that while in  FIG. 1 , all elements of the irrigation control valve  10  are shown as lying below the soil  30 , however, at least antenna  66  and sensor  50  are usually located above the soil  30 . All or a part of the remaining elements of the irrigation control valve  10 , except for the moisture sensitive element  32  that should at least for its largest part be located within the soil  30 , could however also be located above the soil  30 . Most of the elements of valve  10 , except the antenna  66 , the sensors  48 ,  50  and the moisture sensitive element  32 , are mounted in a preferably sealed housing  78 . 
   Movable electronically controlled member  54  is located immediately downstream the moisture controlled member  34  on the opposite side of conduit  12 . The electronically controlled member  54  and the moisture controlled member  34  are thus entering the conduit  12  from opposite sides and cooperate to open and close the conduit  12  to open and shut off the water flow. This can be achieved by positioning the adjacent faces of the electronically controlled member  54  and the moisture controlled member  34  in a common plane (as shown in  FIGS. 2 to 5 ), or by providing at least one of the electronically controlled member  54  and the moisture controlled member  34  with a projecting sealing element  74  arranged to touch the adjacent face of the other member  34 ,  54  as shown in  FIG. 1 . 
   In another possible embodiment, both the electronically controlled member  54  and the moisture controlled member  34  are located within a common plane and enter to conduit  12  from opposite sides, such that they can engage each other within the conduit  12  to close it. In this embodiment, at least one of the electronically controlled member  54  and the moisture controlled member  34  can be connected to its respective actuator  32 ,  40  by means of a resilient means like a spring or a lost motion connection for sake of protecting the respective actuators  32 ,  40  when they abut each other. 
     FIGS. 2 to 5  show different possible positions of the electronically controlled member  54  and the moisture controlled member  34 . In  FIG. 2 , electronically controlled member  54  closes the conduit  12  entirely, while moisture controlled member  34  leaves ⅔ of the conduit  12  open. In  FIG. 3 , electronically controlled member  54  leaves the conduit  12  entirely open, while moisture controlled member  34  closes the conduit  12 . In  FIG. 4 , electronically controlled member  54  leaves a little more than ⅔ of the conduit  12  open, while moisture controlled member  34  closes a little more than ⅔ of the conduit  12 . Hence, in all of  FIGS. 2 to 4 , no water will get from the inlet  14  to the outlet  16 . 
   In  FIG. 5 , electronically controlled member  54  closes about ⅓ of the conduit  12 , while moisture controlled member  34  also closes ⅓ of the conduit  12 . Thus, water will flow from inlet  14  to outlet  16 . In the embodiment of  FIG. 5 , the position of inlet  14  and outlet  16  was exchanged, in order to demonstrate that the relative position of electronically controlled member  54  and moisture controlled member  34  can be arbitrarily selected. 
   It is apparent that electronically controlled member  54  defines the position where moisture controlled member  34  closes the conduit  12  (shut-off position), and thus how much it needs to travel from an position leaving the conduit  12  open to close the conduit  12 , and how much it needs to move from a closing position to open the conduit  12  when the soil  30  is dry. Hence, the achieved moisture level of the soil  30  surrounding the moisture sensitive element  34  is defined by the position of the electronically controlled member  54 . 
   In operation, electronic controller  36  obtains information about a desired level of moisture in the soil  30  at the roots of plant  28  from computer  72  via transceiver  70 , antennae  68 ,  66  and transceiver  46 . This information is combined with data from sensors  48  and  50  to calculate a desired position of the electrically movable member  54 . Controller  36  then activates the arresting actuator  44  to release ratchet  64  from its recess  60  and controls, using the signals from position sensor  42 , and then commands the electronically controlled actuator  40  to move the output  52  into a position corresponding to the desired position of the electronically controlled member  54 . The roots  26  of plant  28  are thus irrigated with a desired amount of water. Once the desired moisture of soil  30  is achieved, moisture sensitive element  32  expands and moves the moisture controlled member  34  into a position in which it (in cooperation with the electrically controlled member  54 ) closes the conduit  12 . 
   A preferred embodiment of the valve  10  is shown in  FIGS. 6 to 8 .  FIG. 6  shows a sectional side view of the valve  10 , while  FIG. 7  represents a horizontal section through the valve  10  along lines  7 - 7  of  FIG. 6 . 
   The housing  78  is cylindrical and has a point  80  at its bottom end for easier insertion into the soil  30 . Within the housing  78 , a removable cartridge  82  is inserted into a central hollow part of housing  78  defined by an inner cylindrical wall  84 . Inlet  14  and outlet  16  are on opposite sides on top of the housing  78 . Between the outer circumference of the housing  78  and the inner wall  84 , four chambers  86 ,  88 ,  90 , and  92  are defined by separating walls  94 . Cartridge  82  supports an easy exchange of the members  34  and  54  and/or of the power source  38  for maintenance purposes. 
   Chamber  86  is connected to inlet  14  and allows the incoming water to get down to the lower part of the cartridge  82  in which the moisture controlled member  34  and the electronically controlled member  54  are located. The inner wall  78  defining chambers  86  and  88  thus ends above point  80  to allow water from chamber  86  to get to the bottom of the cartridge  82  and from the cartridge  82  to chamber  88 . 
   Chamber  88  is located on the opposite side of chamber  86  and allows water to stream upwardly from the moisture controlled member  34  and the electronically controlled member  54  to the outlet  16 . 
   The chambers  90  and  92  are penetrable for moisture, such that moisture can travel between the soil  30  and the moisture sensitive element  32 . In the cartridge  82 , the electronic controller  36  is located above the moisture sensitive element  32 , the moisture controlled member  34  and the electronically controlled member  54 . Above the controller, the power source  38  is located, while the sensors  48 ,  50  and the antenna  66  are provided above the power source  38 . 
   The controller  36  could also be connected to a display (not shown). A display requiring only little electrical power is preferred, i.e. the power should only be used in changing the display, not in maintaining it. This may be a simple two state display (on-off) tied to a system attribute or may be alphanumeric display using preferably a cholesteric liquid crystal displays. 
   Controller  36  can comprise a self-localizing means (not shown). The integrated localization engine geo-referencing the controller  36  in the field can be used to help localized harvest containers. Software on the controller can implement a security means to ensure that only authorized control commands are downloaded and considered, and optionally, that software used to generate those commands have come from a valid source (i.e., subscription fee has been paid). 
   It is apparent that an irrigation system is normally not used only for a single plant  28 , but for a plurality of plants standing on a field, in a vineyard, or a garden. In order not to need one irritation valve  10  for only one plant  28 , it would be possible to connect a number of water exhausts  24  to the outlet  16  of one irrigation valve  10  for cost reduction. Alternatively or additionally, a single controller  36  could perform processing for number of electrically controlled members  54 . 
   To implement PRD in a vineyard, or with another crop, one irrigation control valve  10  would be provided for the each of the two halves of the root zone to be managed. The electronically controlled member  54  of the first irrigation control valve  10  could be positioned in an open position to enable a water flow to its half of the roots, while the electronically controlled member  54  of the second irrigation control valve  10  could be positioned in a closed position to shut of the water flow to its half of the roots. At some point of time, the two settings would be exchanged. 
   It would also be possible to use a number of more intelligent irrigation control valves  10  as shown in  FIGS. 1 and 6  to  8  having a number of environmental sensors  48 ,  50  together with a much larger number of irrigation valves  10  with less or without any environmental sensors. Those irrigation valves would receive data from the more intelligent irrigation control valves  10  via transmitters  46  and antennae  66 . This reduced number of environmental sensors  48 ,  50  is possible because some environmental attributes, such as sunshine, will hardly vary much over a field. Others, such as temperature, would vary over several field microclimates. Thus, it would be advisable to provide a rather high number of irrigation control valves  10  with a temperature sensor  48 , but only some of them with a sunlight sensor  50 . Soil moisture may be a localized phenomenon, since the actual variability may be highly correlated with soil type and topography variability. Hence, each irrigation control valve  10  incorporates a moisture sensitive element  32  as shown in the attached drawings. In a simpler embodiment, the controller  36  is neither connected to an environmental sensor  48 ,  50  nor to a transceiver  44 , but it controls the actuator  40  only based upon a signal from a clock  100  dependent on the daytime and date. 
   An irrigation control valve  10  can communicate with computer  72  directly via the transceivers  46 ,  70  and antennae  66 ,  68 , as shown in  FIG. 1 . In another embodiment, as shown in  FIG. 9 , a separate communication node  94  is installed in the field, communicating preferably via a global communications infrastructure such as cellular phone, the internet, etc., with another communication node  96  connected to the computer  72 . The communication node  94  in the field would communicate with the controllers  36  of the irrigation control valves  10  preferably via a short range field communication system using the antennae  66  and transceivers  46  shown in  FIG. 1 . 
   The information exchanged between the irrigation control valves  10  and the communication node  94  installed in the field, or some subset or summary, would be received by the computer  72  that is used as a back office management system. The latter would thus receive information on the sunlight, temperature, position of the electronically controlled member  54  and of the moisture controlled member  34 . The data may be time stamped and geo-referenced as described previously. This data is used to develop a database of past and current field conditions in the computer  72 . The current field conditions and trends, possibly supplemented with field scouting reports, are used with business, weather, and crop models to generate a site-specific irrigation plan. This plan, in the form of instructions to the controllers  36 , is communicated from the computer  72  through the communication nodes  94 ,  96  to the controllers  36  of the irrigation control valves  10 . The controller instructions are addressed to individual controllers  36  and include instructions such as where and when to set the electronically controlled member  54 . With respect to the communication hardware and protocol, reference is made to U.S. application Ser. No. 11/348,918, the contents of which incorporated herein by reference. 
   Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.