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a blade-type scarifier, a machine for breaking up friable substances; it is used chiefly in foundries to loosen molding sand. The operating member of an aerator is a rotor with replaceable blades (24 to 32 units) encased in a housing that is open at the bottom and contains a chain screen. Mounted on the top of the housing is a loading funnel and a pipe for connection to exhaust ventilation. The aerator rotor, which turns at a rate of 580 to 640 rpm, is continuously supplied with molding sand through the loading funnel. The rotor blades catch the sand and throw it vigorously against the chain screen. Impact with the chain breaks up large lumps in the sand. The dust thus created is sucked up through the pipe by a fan. The output of an aerator is between 40 and 80 cu m/hr.