Einrichtung zur Verhinderung der Zurückströmung von verunreinigtem Wasser in Wasserversorgungsanlagen

摘要

1,006,566. Water supply systems. D. G. GRISWOLD, F. K. WYCKOFF, M. M. CHARD and W. S. GRAU. March 29, 1962 [June 26, 1961], No. 12156/62. Heading E1X. [Also in Division F2] A water back flow preventive device comprises an inlet 6, Fig. 3, for connection to the supply main and an outlet 10 to the point of use, the device being provided with two check valves 1 and 2. A zone Z between the two check valves can be connected to atmosphere through a valve 12 which comprises a valve closure member 84 which is connected by a stem 78 to two diaphragms 110, 117 which form walls of chambers 132, 131, the chambers on the opposite sides of the diaphragms being connected to atmosphere by passages 104, 137. The chamber 131 is connected by a passage 13 to the inlet of the check valve 1, the pressure in this chamber acting on the diaphragm 117 to close the valve 12. The chamber 132 is connected by a passage 14 to the zone Z at the inlet of the second valve 2 and the pressure in this chamber acts on diaphragm 110 which, in conjunction with a spring 130, tends to open the valve 12. In operation under normal flow condition the valves 1 and 2 are open and the valve 12 is closed due to the pressure differential across the valve 1, the pressure at the inlet of valve 1 being sufficient to hold the valve 12 closed. If the supply pressure drops or fails the check valves close and the valve 12 opens to drain the zone Z. Further the valve 12 will also drain any leakage back past the second check valve to prevent syphoning. The spring 130 is preferably calibrated or adjusted such that the valve 12 will open when the pressure differential across the valve 1 falls below 2 p.s.i. The seat of valve 12 is shaped to prevent any tendency of the flow through the valve to close this valve. Alternative angles of slope of the seating member are given in the specification. Each check valve comprises a hinged closure member 26, Fig. 5, cooperating with a bevelled seat of about 5 degrees. The closure member is pivoted at 38 and is connected by a toggle lever mechanism, comprising links 34, 45, to the valve housing. The links 34, 45 are pivoted at 48, the pivot being loaded by a spring 54 tending to straighten the links. The link 45 is preferably 4 times as long as the link 34. The loading of the spring of check valve 2 is preferably slightly less than that of check valve 1.