Abstract:
A moisture sensitive irrigation control system provides automatic watering of potted plants, lawns, crops, etc. The system utilizes a control valve to effect watering of the soil upon automatic detection of a predetermined level of dryness in a control sample of the soil. The system uses a weight-based method of detecting the amount of moisture in the control sample to regulate the automatic release of a predetermined amount of water into the entire soil for rehydration thereof. As the weight of the control sample increases with the volume of water, the valve is automatically closed to terminate the irrigation process.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a system for performing automatic irrigation of soil containing plants or other vegetation based upon the constant monitoring of the moisture content of the soil. The present invention ensures water conservation, especially when used in large scale applications. 
     For the individual plant owner, the present invention ensures a constant periodic supply of water to multiple potted plants for an extended period of time without the inconvenience and guesswork associated with manual watering of the plants. The irrigation control system of the present invention also provides an aesthetically pleasing display of the plants being watered. Unlike the irrigation systems which employ capillary action (wicks) to effect watering, such as disclosed in U.S. Pat. No. 4,171,593, the present invention may also allow periodic drying out of the roots prior to rehydration if desirable, which thereby ensures the health of the plants. Because the present invention provides watering of the plants from above the soil, harmful salts do not accumulate in the soil as occurs with irrigation systems that employ capillary action, which pulls water up from below. 
     Moisture sensitive irrigation systems are generally known. In particular, my own U.S. Pat. No. 5,020,261 discloses a self-watering planter which activates a watering mechanism when the weight of a liner filled with soil decreases through evaporation of water. However, this self-watering planter is completely self-contained, in that the water supply, liner and moisture detecting mechanisms are all integrally combined within the planter housing. Thus, it is not possible to utilize the self-watering feature with conventional planters or pots, and separate units are required for each plant. 
     Additionally, large area irrigation control systems are disclosed in U.S. Pat. Nos. 2,577,337 and 2,781,228. These control systems are characterized by complex counterweight balancing control and valve mechanisms, and complicated electrical circuitry. Consequently, there exists a need in the art to provide a simpler, more cost-effective irrigation control system which overcomes the disadvantages of the prior art. 
     SUMMARY OF THE INVENTION 
     It is thus an object of the present invention to overcome the problems and limitations of the prior art as discussed above. 
     It is another object of the present invention to provide a system which conserves water during irrigation. 
     It is a further object of the present invention to eliminate the need for periodic manual watering of potted plants by a plant owner. 
     It is a still further object of the present invention to provide an irrigation control system which is aesthetically pleasing and is readily portable. 
     It is a still further object of the present invention to provide a moisture sensitive irrigation control system which effects top-watering of multiple potted plants upon detection of a predetermined level of dryness of the soil in one of the planters (chosen to be the control) based upon the planter&#39;s weight. 
     The objects of the present invention are fulfilled by providing an irrigation control system comprising, in a first preferred embodiment, a base unit with raised platforms for displaying potted plants, a water reservoir located at the top of a water tower, weight determination means (configured as one of the raised platforms) for determining the weight of the control planter, which is indicative of the moisture content of its soil, feeder tubes which extend from the potted plants to the water tower, valve means connecting the feeder tubes to the reservoir for selectively allowing water to be delivered to the potted plants, and control means, responsive to the weight determination means determining a specific weight of the control planter for opening and closing the valve means when the weight of the planter reaches first and second specific values respectively. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: 
     FIG. 1 is a plan view of the base unit of the irrigation control system of one preferred embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of the control platform 30 of FIG. 1; 
     FIG. 3 is a cross-sectional view of the water tower 20 of FIG. 1; 
     FIG. 4 is a schematic view of the electrical circuit used to actuate the solenoid valve 210 of FIG. 3; 
     FIG. 5 is a cross-sectional view of a mechanical valve assembly of a second preferred embodiment of the present invention; 
     FIG. 6 is a cross-sectional view of the water tower of a second preferred embodiment of the present invention; and 
     FIG. 7 is a cross-sectional view of the irrigation control system of a third preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a first preferred embodiment of the present invention wherein a base unit 10 is provided that is generally of rectangular shape having raised platforms 12 and 14 for displaying multiple potted plants. The rear platform 14 is elevated more than the front platform 12 to enhance the appearance of the display. A control platform 30 (on which the control planter is placed) and water tower 20 are also situated on the base unit. 
     As shown in FIG. 2, the control platform 30 sits atop a base plate 40. The base plate is supported by compression springs 50 that are maintained in an upright position by a number of posts 60 that pass through holes in the periphery of the base plate 40. Washers 70 are placed on the posts between the springs and the base plate. The posts are threaded into receptacles 80 mounted in the base unit 10. The posts 60 are threaded so that they can be rotated in order to fine tune the compression on the springs. Washers 90 are also provided in varying thicknesses to be placed on the posts in order to make gross adjustments in the spring compression. 
     A normally closed micro-switch 100 is mounted on the base unit 10. A movable column 110 is used to operate the micro-switch. The upper end of the column passes through a bearing 42 in the center of the base plate 40 and is secured to the base plate 40 by a threaded cap 120. First and second ring magnets 130 are mounted on a cylindrical base 140 and surround the column. The column 110 passes through a bearing 142 located in the center of the base 140. First and second steel washers 150 are attached to the column 110 above and below the respective magnets by an attachment mechanism such as a threaded groove. However, it is to be noted that other modes of attaching the washers to the column can equivalently be used. A cover 160 for the base 140 also has a bearing 162 located in its center through which the column 110 passes. A washer 170 rests on a shoulder of the column beneath the base plate 40. The thickness of the washer 170 determines the amount of water delivered during irrigation, as explained below. The weight determination and control mechanisms are enclosed within a hollow cylinder 180. 
     With reference to FIG. 3, a water reservoir 190 sits atop the water tower 20 at a height producing sufficient water pressure to irrigate the potted plants. The water reservoir has a cover 192 with a small hole 193 in its center to equalize pressure. Flexible tubing 200 connects the water reservoir to a normally closed solenoid valve 210. The flexible tubing also connects the solenoid valve to flexible feeder tubes 220, which are placed in each of the potted plants. The feeder tubes are passed through openings 230 in the water tower and plugged into holes (not shown) in the segment of flexible tubing 200 connecting the solenoid valve to the openings 230. An external on-off switch 240 is located near the base of the water tower. 
     FIG. 4 illustrates schematically the electrical circuit that is part of the control means used to actuate the solenoid valve. The electrical circuit consists of power supply feed lines 250, an external on-off switch 240, a normally closed micro-switch 100, and a normally closed solenoid valve 210. 
     As mentioned earlier during the discussion of FIG. 2, the amount of compression on the springs 50 can be adjusted by either varying the thickness of the washers 90 or by rotating the posts 60 in the threaded receptacles 80, or both. This adjustability ensures proper operation of the irrigation control system regardless of the initial weight of the potted plant (chosen to be the control), or the subsequent weight of the potted plant resulting from growth. 
     DESCRIPTION OF OPERATION 
     The irrigation control system operates as follows: As evaporation occurs, the weight of the potted plants decrease. The decreased weight of the control planter mounted on control platform 30 causes the springs 50 to produce an upward force on the base plate 40 that is translated to the column 110 through the cap 120. Evaporation continues until a first predetermined weight (level of dryness) is reached, at which point the attractive force between the upper ring magnet 130 and upper steel washer 150 is overcome, the column is forced upward, the micro-switch 100 is closed by releasing the switch contact normally pressed inward by column 110, the solenoid valve 210 is opened, and irrigation is initiated. 
     As the potted plants are irrigated, their weights increase. The increased weight of the control planter produces a downward force on the base plate 40 that is translated to the column 110 through the washer 170. Irrigation proceeds until a second predetermined weight (level of wetness) is reached, at which point the attractive force between the lower ring magnet 130 and lower steel washer 150 is overcome, the column is forced downward, the micro-switch 100 is opened, the solenoid valve 210 is closed, and irrigation is terminated. The volume of water that is delivered to the control planter can be adjusted by varying the thickness of the washer 170 thereby changing the distance that the base plate 40 must travel before the base plate contacts the washer 170 thereby exerting downward force on the column 110. The volume of water delivered to the other potted plants can be adjusted by varying the number, diameter, or length of the feeder tubes 220. 
     FIGS. 5 and 6 are illustrative of a second preferred embodiment of the present invention in which the electrical circuit in FIG. 4 is substituted by a mechanical assembly. The mechanical valve assembly shown in FIG. 5 is used to replace both the micro-switch 100 as well as the solenoid valve 210. A manual shut-off valve 205 illustrated in FIG. 6 is used to replace the on-off switch 240. The remaining elements similar to the first embodiment are denoted by like reference numerals and their description is thus omitted. 
     With reference to FIG. 5, the valve assembly consists of a valve body 212 having horizontal inlet and outlet ports with an interior vertical passage near the center of the valve body allowing communication therebetween. The movable valve stem 110 has one end inserted into the interior passage of the valve body 212 and includes an O-ring 214 at a terminal end thereof. A tapered groove 216 is provided near the center of the interior passage which keeps the O-ring from being damaged by the sharp edges created by the intersection of the outlet port with the interior passage. The taper further facilitates the movement of the O-ring from the illustrated open position to a closed position in which the O-ring is located below the outlet port by reducing the friction between the passage and the O-ring. 
     As illustrated in FIG. 6, the water tower 20 contains a manual shut-off valve 205 replacing the on-off switch. Flexible tubing 200 connects the water reservoir 190 to the manual shut-off valve 205. The flexible tubing also connects the shut-off valve 205 to the inlet port of the valve body 212 shown in FIG. 5, as well as connecting the outlet port of the valve body to the flexible feeder tubes 220 in the water tower 20. The feeder tubes are placed in each of the potted plants. The feeder tubes are passed through openings 230 near the base of the water tower and plugged into holes in the flexible tubing 200. 
     FIG. 7 illustrates a third preferred embodiment of the present invention wherein a cylindrical housing unit 2 is provided for installation in the ground. A cover 4 which has a grate 5 in its center is mounted on the top of the housing unit. A number of bearings 6 are located near the top interior of the housing unit. Holes 8 are provided in the bottom of the housing unit for drainage. A liner 12, into which a control sample of soil and vegetation is placed, is removably inserted into the center of the housing unit. Drainage holes 14 are provided in the bottom of the liner to allow water drainage of the soil. 
     As shown in FIG. 7, the liner 12 sits atop a base plate 40. The base plate is supported by compression springs 50 that are maintained in an upright position by a number of posts 60 that pass through holes in the periphery of the base plate. Washers 70 are placed on the posts between the springs and the base plate. The posts are threaded into receptacles 80 located in a base unit 85. The posts are threaded so that they can be rotated in order to fine tune the compression on the springs. Washers 90 are also provided in varying thicknesses to be placed on the posts in order to make large adjustments in the spring compression. 
     Referring again to FIG. 7, a normally closed micro-switch 100 is mounted on the base unit 85. A movable column 110 is used to operate the micro-switch. The upper end of the column passes through a bearing 42 in the center of the base plate 40 and is secured to the base plate by a threaded cap 120. First and second ring magnets 130 are mounted on a base 140 and surround the column. The column passes through a bearing 142 located in the center of the base. First and second steel washers 150 are attached to the column above and below the respective magnets by an attachment mechanism such as a threaded groove. However, it is to be noted that other modes of attaching the washers to the column can equivalently be used. A cover 160 for the base also has a bearing 162 located in its center through which the column passes. A washer 170 rests on a shoulder of the column beneath the base plate. 
     The irrigation control system shown in FIG. 7 is placed in the ground in a uniformly irrigated area. The control system operates a remotely located solenoid valve (not shown) that controls the irrigation process for the area by selectively controlling the supply of water from a water source such as a water tower or water main. The soil and vegetation placed in the liner 12 are the same as the surrounding soil and vegetation, and thus the moisture content of the soil in the liner is a sample representation of the moisture content of the surrounding soil. 
     The irrigation control system of the third embodiment operates as follows: As evaporation occurs, the weight of the liner 12 decreases. The decreased weight of the liner causes the springs 50 to produce an upward force on the base plate 40 that is translated to the column 110 through the cap 120. Evaporation continues until a first predetermined weight (level of dryness) is reached, at which point the attractive force between the upper ring magnet 130 and upper steel washer 150 is overcome, the column is forced upward, the micro-switch 100 is closed, a solenoid valve is opened, and irrigation is initiated. 
     As the soil is irrigated, its weight increases. The increased weight of the liner 12 produces a downward force on the base plate 40 that is translated to the column 110 through the washer 170. Irrigation proceeds until a second predetermined weight (level of wetness) is reached, at which point the attractive force between the lower ring magnet 130 and lower steel washer 150 is overcome, the column is forced downward, the micro-switch 100 is opened, a solenoid valve is closed, and irrigation is terminated. The volume of water that is delivered during irrigation can be adjusted by varying the thickness of the washer 170 thereby changing the amount of travel that the base plate must make before exerting force on the column. 
     It should be noted that the mechanical valve assembly of FIG. 5 may also be substituted for the microswitch-solenoid valve mechanism of the embodiment of FIG. 7. 
     The invention having been thus described, it will be obvious to those skilled in the art that the same may be varied in many ways without departing from the spirit of the invention. Any and all such modifications are intended to be included within the scope of the following claims.