A magnetic check valve includes a cage mountable in a fluid flow duct and supporting a plunger movable between a closed position blocking fluid flow past the valve, and an open position permitting fluid flow past the valve. One of the cage and the plunger includes a magnet, and the other of the cage...http://www.google.es/patents/US7506663?utm_source=gb-gplus-sharePatente US7506663 - Magnetic check valve
