| 摘要 |
PURPOSE:To aim at avoiding water hammer and to prevent water from uselessly flowing out after closing of a water valve, by gradually closing the valve after the valve is steppedly driven in the direction in which the flow rate of water is constricted. CONSTITUTION:There is provided a resistance which offers a minimum flow rate Q1 causing a valve 4 to generate no water hammer when it is closed. A resistance 25 for applying a valve closing voltage is connected in parallel with the resistance 24. Further, there is provided a capacitor 26 which starts electrical charge after the closing of the valve, and which lowers the voltage Vs to gradually decrease the flow rate Q1 until the valve is completely closed. With this arrangement, it is possible to prevent water hammer from occurring after closing of the valve, and to prevent water from uselessly flowing out after closing of the valve.
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