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Title: Method of controlling the relative humidity in a soil environment and apparatus for accomplishing same
Claims: What is claimed is: 1. A method for regulating the flow of water to an environment in order to maintain the relative humidity in said environment at a preselected value which comprises sensing an increase or decrease in said environmental humidity relative to said preselected value by means of osmotic swelling or shrinking of a material capable of swelling no less than about 25 times its dry volume when in equilibrium with water at 100% relative humidity, wherein said swelling or shrinking obstructs or relieves, respectively, the flow of water to said environment thereby maintaining said relative humidity at the preselected value. 2. The method of claim 1 wherein said preselected value is prescribed by the concentration of said material which is water-soluble or a water-swellable slightly cross-linked hydrogel and by its volume at a particular environmental humidity relative to the volume of an enclosure which contains it. 3. The method of claim 2 wherein said enclosure is separated from the environment by a semipermeable membrane which is impermeable to said water-soluble material or water-swellable slightly cross-linked hydrogel but permeable to water and wherein the amount and direction of flow of water passing through said membrane due to osmotic transfer resulting in swelling or shrinking is dependent on the relative humidity of the ambient environment. 4. The method of claim 3 wherein said water-swellable slightly cross-linked hydrogel is capable of swelling to about 25 times its dry volume when in equlibrium with water at 100% relative humidity and wherein said semipermeable membrane has pores up to about 0.2 mm. in diameter. 5. The method of claim 3 wherein said swelling or shrinking of said enclosed volume of water-soluble material or water-swellable slightly cross-linked hydrogel results, respectively, in obstructing or relieving the flow of water, said water provided in a pressurized water-line which communicates hydraulically or mechanically with said enclosed volume through a compliant and water-impermeable conduit. 6. The method of claim 5 wherein said water-impermeable conduit is comprised of silicone rubber. 7. An osmotic relative humidity sensor-regulator valve comprising: a chambered body section; means for attaching the valve body section in a waterline; compressible means in the waterline for opening and closing the waterline; and osmotically-sensitive means contained in said chamber for opening and closing the compressible means in the waterline, and capable of swelling no less than about 25 times its dry volume when in equilibrium with water at 100% relative humidity. 8. The valve of claim 7 wherein the compressible means in the waterline for opening and closing the waterline is a section of a flexible tube with a water-impermeable wall and wherein said osmotically sensitive means comprises a chamber surrounding the flexible tube, a water-soluble or water-swellable material occupying the chamber, and a water-permeable membrane, forming at least part of the outer wall of the chamber, which is impermeable to said water-soluble or water-swellable material. 9. The valve of claim 7 wherein the compressible means in the waterline for opening and closing the waterline is a section of a flexible tube with a water-impermeable wall and wherein said osmotically sensitive means comprises a chamber a portion one wall of which is the flexible tube, a water-permeable fine mesh membrane which is impermeable to a water-swellable slightly cross-linked hydrogel, which membrane forms a second wall of the chamber, a piston in the chamber contactable with the flexible tube, water-swellable slightly cross-linked hydrogel occupying a shallow part of the chamber between said membrane and said piston and relatively rigid means located adjacent the flexible tube on the side opposite the piston forming an outer wall of the chamber, all moving parts enclosed. 10. The valve of claim 9 wherein said piston has a flat upper surface and a conical lower surface tapering to a blunt point free to move axially to press upon said flexible tube and said relatively rigid means located adjacent the flexible tube on the side opposite the piston configured to seat the compressed flexible tube and tapered conical point. 11. The valve of claim 9 wherein said piston has flat upper surface and lower surface configured to seat the compressed flexible tube and a tapered conical point free to move axially upon said flexible tube, and said relatively rigid means located adjacent the flexible tube on the side opposite the piston is a member having a conical upper surface tapering to a blunt point contacting the bottom surface of the flexible tube and threaded to provide an adjustable chamber volume. 12. The valve of claim 7 wherein the compressible means in the waterline for opening and closing the waterline is a flexible water-impermeable diaphragm and wherein said osmotically sensitive means comprises a chamber one side of which is the diaphragm, a water-permeable membrane which is impermeable to a water-soluble or water-swellable material which membrane forms a second side of the chamber, piston in the chamber in contact with the diaphragm, water-soluble or water-swellable material occupying a part of the chamber between said membrane and said piston, and relatively rigid means located adjacent the diaphragm on the side opposite the piston. 13. The valve of claim 12 wherein said piston has a flat upper surface and a conical lower surface tapering to a blunt point and said relatively rigid means located adjacent the diaphragm on the side opposite the piston has an upper surface configured to receive the diaphragm conforming to the shape of conical lower surface of said tapering conical piston forming a valve seat. Other info: Inventors: Ornstein, Leonard (White Plains, NY, US) Application Number: 882789 Filing Date: 1978-03-02 Publication_date: 1980-01-08 Assignee: Primary Class(es): 137/1 47/48.5, 137/78.3, 239/63, 251/4, 251/5 Other Classes: US Patent Ref:
Other Refs:
"Soil-Water Potential: Direct Measurement by a New Technique," Peck, Science, vol. 151, Mar. 18, 1966, pp. 1385-1386. "Viscoelastic Properties of Polymers" Ferry, Univ. of Wisconsin, 2nd Ed. Wiley & Sons, Chapter 17, pp. 519-573, 1970. | |