Fluid handling – Ambient condition change responsive – For controlling soil irrigation
Patent
1991-02-08
1993-12-28
Chambers, A. Michael
Fluid handling
Ambient condition change responsive
For controlling soil irrigation
251 611, 47 485, A01G 2502
Patent
active
052730662
DESCRIPTION:
BRIEF SUMMARY
This invention relates to control valves, more particularly to moisture sensitive control valves, for control of fluid flow and to methods of plant growing using control of fluid flow and to an apparatus for use therein.
Valves which utilise a moisture sensitive material to control flow between an inlet and an outlet of the valve are known. The moisture sensitive material absorbs moisture and swells and this swelling is used to close the valve. Drying of the moisture sensitive material causes it to contract and this contraction in turn is used to open the valve. These valves are particularly (but not exclusively) useful for plant growing systems in which water for the plants needs to be accurately controlled, so that the plants do not become too dry due to lack of water or suffer from overwatering. In such an implementation, the valve is positioned in the vicinity of the plants and operates to control the feed of water to the plants.
In U.S. Specification 3426539, a moisture sensitive valve using redwood bark as moisture sensitive material is described. This material is connected to movable jaws which compress a flexible water-carrying tube passing between them. Water flow is controlled by the degree of compression of the tube. As the bark dries out, it contracts moving the jaws apart and releasing the compression on the tube.
British Patent Specification 201786A describes an irrigation valve device of pinch cock or diaphragm type using a swellable member to control response to moisture content.
British Patent Specification 1006801 discloses the use of vegetables fibres to compress a flexible tube directly. The fibres are held together by a ring, and, as they swell, the tube is compressed to restrict the water flow. As the fibres dry out, the pressure on the tube is released allowing water to flow more freely therethrough.
German Offenlegungsschrift 2513600 and 2325980 both disclose the use of a resilient water impermeable membrane to seal the outlet of the valve.
In Offenlegungsschrift 2325980, the impermeable membrane is deflected by a moisture absorbing material to compress a resilient porous material situated over the outlet. As the moisture absorbing material expands, it acts to deflect the membrane compressing the porous material to seal off the outlet. As the moisture absorbing material dries out, the resilience of the porous material and the membrane moves them away from the outlet allowing water to flow through the porous material to the outlet.
In Offenlegungsschrift 2513600, the water impermeable membrane is operated by pressure in the system. In this case, water flows from the inlet to the outlet on one side of a water impermeable membrane deflecting it due to the system pressure. The moisture absorbing material is connected to a valve on the side of the membrane remote from the inlet and outlet, and as the moisture absorbing material expands, the valve is closed allowing pressure to be built up on this side of the membrane until it reaches a value which forces the membrane against the outlet to seal off the water flow. As the moisture absorbing material contracts, the valve is re-opened reducing the pressure on that side of the membrane to allow the system pressure to deflect the membrane and allow water to flow from the inlet to the outlet.
U.S. Pat. No. 3,204,872 discloses a diaphragm valve which is operated by moisture sensitive material in the form of a strip of wood which, as it expands, deflects a resilient diaphragm and holds it against the valve inlet blocking off the water supply. As the wood dries out, the diaphragm is no longer held against the inlet and returns to its original shape allowing water to flow freely.
U.S. Pat. No. 4,696,319 describes moisture-activated apparatus for controlling the flow of water. Expansion on absorption and contraction on desorption of water by a water-swellable material is used cause the valve stem of the valve to move between closed and open positions.
French Specification 2345894 discloses a diaphragm valve in which a resilient diaphragm is held ove
REFERENCES:
patent: 4095458 (1978-06-01), Wild
patent: 4182357 (1980-01-01), Ornstein
patent: 4648555 (1987-03-01), Gumbmann, Jr.
patent: 4696319 (1987-09-01), Gant
Graham Neil B.
Ross Donald S.
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