The invention is a filtering device for the drilled passage in on-off control valves used in aircraft liquid crop spraying systems. The device is mounted within the on-off control valve in the spray boom supply line at the opening of the drilled passage which connects the low pressure area of the suck...http://www.google.com.tw/patents/US5591339?utm_source=gb-gplus-share專利 US5591339 - Self-cleaning filter screen for venturi suck back passage
