| 摘要 |
In one aspect a novel valve, when used with water conveying conduits of water supply or of irrigation systems, will purge them of residual water in the conduits, when the water supply is "cut off", but will close the system when the water supply is on (e.g. there is water pressure above a predetermined threshold, or a "head" occurs). When this valve is closed the system then operates, conventionally, and for irrigation systems to eject water from water dispensing nozzles or spray heads located at or in proximity to the ground surface so that irrigation can take place. With this novel valve, the periodic (or annual) need to purge the irrigation system of residual water to clean out contaminants or to prevent winter freeze-up is avoided, since self-purging of the residual water and of any water suspended solids in the network takes place each time the water pressure in the system is reduced to approximately zero (or to below the said predetermined threshold pressure), as on each occurance of water shut off. A further embodiment contamplates a compound nozzle valve assembly formed as a single structure housing a conventional water dispensing nozzle, and the novel purging valve. Such compound nozzle valve assembly simplifies installation of the irrigation system and of its subsequent operation and maintenance.
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