Means and method of irrigation control

• US 4,040,436 A
• Filed: 08/08/1975
• Issued: 08/09/1977
• Est. Priority Date: 08/08/1975
• Status: Expired due to Term

• Current Assignee: Dave L. Caldwell
• Original Assignee: Dave L. Caldwell
• Inventors: Caldwell, Dave L.
• Primary Examiner(s): Schwadron, Martin P.
• Assistant Examiner(s): Gerard, Richard
• Application Number:
  US05/603,081
• Time in Patent Office: 732 Days
• Field of Search: 137/78, 239/63, 239/64, 47/79
• US Class Current: 137/78.3
• CPC Class Codes: A01G 25/167 Control by humidity of the soil itself or of devices simulating soil or of the atmosphere; Soil humidity sensors
• CPC Class Codes: Y10T 137/189 Soil moisture sensing

Abstract

A means and method of irrigation control wherein a porous sensor is placed in the root zone in moisture transfer relation with the soil, and is supplied with air at a pressure sufficient to cause progressively increasing seepage of air through the sensor as soil moisture is lessened, there being means for detecting the rate of seepage of the air utilized to indicate moisture content of the soil for manually or automatically activating a timer for the irrigation system; the irrigation control further including the use of several sensors placed at different soil levels, as well as a warning sensor adapted to be activated should the soil start to become drier than its normal relatively moist condition.

An embodiment utilizes one or more selected plants with corresponding sensors as a means of detecting sudden weather changes to anticipate changes in ground moisture. A further embodiment utilizes an evaporation measuring means designed to detect incipient change in humidity indicative of sudden weather change.

Claims

1. A means for indicating soil moisture condition, comprising:

a. a sensor having a porous wall adapted when in moisture contact with soil to maintain a moisture content corresponding approximately to the moisture content of the soil;

b. a gas line connected to the sensor;

c. means for maintaining the gas in the gas line and sensor at a pressure to cause an increased seepage of gas through the sensor wall as the water content of the sensor wall and soil is lowered;

d. and means for measuring the seepage rate of the gas through the sensor to indicate the soil moisture condition.

2. An indicating means as defined in claim 1, wherein:

a. the pressure maintaining means produces a preselected positive pressure to cause outward seepage of gas through the sensor.

3. An indicating means as defined in claim 1, wherein:

a. the pressure maintaining means produces a preselected negative pressure to cause inward seepage of air through the sensor.

4. An indicating means as defined in claim 1, wherein:

a. a closed chamber containing a liquid is interposed in the gas line;

b. the gas line is provided with a discharge port disposed below the liquid level and an intake port disposed above the liquid level, whereby the gas bubbles through the liquid;

c. and the measuring means senses and counts the bubbles passing through the liquid.

5. An indicating means as defined in claim 1, wherein:

a. a plurality of sensors and gas tubes are provided;

b. a plurality of interconnected chambers forming a closed system having a common source of liquid partially filling each chamber is provided and a chamber is interposed in each gas line;

c. each gas line includes a discharge port submerged in the liquid in a corresponding chamber and an intake port above the liquid therein;

d. and the measuring means includes a counter sensitive to the gas bubbles passing through the liquid in each chamber.

6. An indicating means as defined in claim 1, wherein:

a. means is provided to cause the gas to bubble through a liquid;

b. and the measuring means is a bubble counter.

7. An indicating means as defined in claim 6, wherein:

a. the liquid is water;

b. means is provided to maintain a supply of water;

c. and means is provided to minimize the water content of the gas passing into the gas tube.

8. An indicating means as defined in claim 6, wherein:

a. the liquid and gas are essentially immiscible.

9. An indicating means as defined in claim 1, wherein:

a. a plurality of indicating means, each including a sensor, gas tube and measuring means is provided, at least one sensor being located in an upper portion of the root zone of the soil surface, at least one sensor being located in an intermediate portion of the root zone and at least one sensor being located in a lower portion of the root zone.

10. A means for controlling an irrigation system having timer and valve means for activating and deactivating an irrigation cycle, comprising:

a. at least one moisture sensor having a porous wall adapted, when in moisture contact with soil to maintain a moisture content within said porous wall corresponding approximately to the moisture content of the soil;

b. a gas supply line connected to the moisture sensor;

c. means for maintaining the gas in the gas supply line and moisture sensor at a pressure to cause seepage of gas through the sensor wall as the water content of the seepage sensor wall and soil is lessened, the porosity of the wall and the gas pressure being such as to reduce seepage of air through the sensor as the soil moisture increases;

d. means for detecting seepage of the gas;

e. and control means responsive to the seepage detecting means for activating the irrigation timer and valve means when the soil moisture has been lessened a predetermined amount.

11. A control means as defined in claim 10, which further comprises:

a. an atmospheric change sensing means including soil adapted to receive a selected plant exposed to atmospheric changes, a second moisture sensor disposed adjacent the surface of the soil contiguous to the plant, means for protecting the second sensor from direct exposure to atmospheric change;

a gas supply line, gas pressure maintaining means, seepage detecting means, control means and a water supply line having a valve for said plant, whereby said second moisture sensor is subject to the changes in water demand unique to said plant as determined by the atmospheric changes to which the plant is exposed.

12. A control means, as defined in claim 10, wherein:

a. the seepage detecting means includes a liquid container interposed in the gas line to cause the gas to bubble in sequence therethrough and means for counting the bubbles to produce signals in proportion to the rate of seepage of gas through the moisture sensor wall.

13. A control means, as defined in claim 10, wherein:

a. the gas pressure maintaining means includes a gas pump, and a closed tank connected to the gas line and having a weighted cover movable with change in gas pressure, and a control means actuated by movement of the cover to turn the gas pump on and off.

14. A control means, as defined in claim 10, wherein:

a. a set of moisture sensors and corresponding sets of gas lines and seepage detecting means are provided, the seepage detecting means including a set of closed tanks, each tank interposed in a corresponding gas line and having an inlet under the liquid level therein and an outlet above the liquid level therein whereby the gas produces bubbles in passing from the inlet to the outlet;

b. and the control means includes a counter for the bubbles passing through the liquid in each tank.

15. A control means, as defined in claim 14, wherein:

a. the set of tanks are connected to a common source of liquid supply including means for maintaining a predetermined level of liquid in each tank.

16. A control means, as defined in claim 15, wherein:

a. the gas is air and the liquid is water.

17. A control means, as defined in claim 15, wherein:

a. the liquid is mercury.

18. A control means, as defined in claim 10 which further comprises:

a. means for detecting incipient adverse change in weather prior to said predetermined lessening of soil moisture.

19. A control means, as defined in claim 18, wherein, the detecting means includes:

a. a pot having porous walls adapted to receive a plant and porous soil therein, a sensor adjacent the surface of the soil and means for supplying water to the pot, the pot being placed in full exposure to atmospheric condition,

b. and means for measuring the rate of evaporation from the soil.

20. A control means as defined in claim 18 wherein, the detecting means includes:

a. an evaporator exposed to atmospheric conditions and having a surface adapted to be covered with water;

b. means for supplying the evaporator with water as the water is evaporated therefrom;

c. and means for measuring the rate of evaporation.

21. A method of irrigation control utilizing a sensor having a porous wall adapted, when in moisture contact with soil, to maintain a moisture content approximately corresponding to the moisture content of the soil, the porous wall being saturated when the moisture in the soil is at saturation, the method characterized by:

a. placing at least one sensor in moisture contact with soil;

b. supplying to the sensor a gas at a pressure to cause increased seepage of the gas through the porous wall as the moisture content of the porous sensor wall and the soil is reduced;

c. and measuring the rate of seepage flow of gas to determine the moisture content of the soil.

22. A method of irrigation control, as defined in claim 21, wherein:

a. the gas is supplied at a preselected positive pressure to cause outward seepage through the porous wall.

23. A method of irrigation control, as defined in claim 22, wherein:

a. the gas is air and is maintained at a preselected negative pressure to cause inward seepage through the porous wall.

24. A method of irrigation control, as defined in claim 21, which is further characterized by:

a. bubbling the gas flowing to the sensor through a liquid; and

measuring the rate of seepage flow by counting the bubbles as produced in the liquid.

25. A method of irrigation control as defined in claim 21 which is further characterized by:

a. utilizing the measurement of the seepage rate to activate or deactivate an irrigation cycle.

26. A method of irrigation control, as defined in claim 21, which is further characterized by:

a. placing one of said sensors adjacent a selected plant and contiguous to the surface of the soil whereby said sensor is responsive to the moisture content of the plant as indicated by the corresponding moisture in the adjacent soil;

b. measuring the seepage through the wall of said sensor to indicate change in the atmospheric conditions affecting said plant;

c. and utilizing such measurement to override the indications produced by the other sensors to effect early activation of the irrigation cycle.

27. A method of irrigation control as defined in claim 21, which is further characterized by:

a. placing a first sensor near the surface of the soil;

b. placing a second sensor within the major root zone;

c. placing a third sensor in the lower region of the major root-zone that normally remains constantly moist;

d. primarily activating or deactivating an irrigation cycle in response to measurements related to the first and second sensors;

e. and producing a warning signal in response to measurements relating to the third sensor.