Puddle level control for twin drum dryers

Claim 1

IN A FOOD DRIVER OF THE TYPE HAVING A PAIR OF ADJACENT PARALLEL ROTATABLE DRUMS AND A PAIR OF END WALLS DEFINING A RESERVOIR BETWEEN THE END WALLS AND THE TOP OF THE DRUMS, A PUDDLE LEVEL CONTROL COMPRISING: A FEED SLURRY SUPPLY CONDUIT FOR DEPOSITING A SLURRY PUDDLE IN SAID RESERVOIR, A SECOND CONDUIT EXTERIORLY OF SAID RESERVOIR IN LIQUID COMMUNICATION WITH THE LOWER PART OF SAID RESERVOIR THROUGH ONE OF SAID END WALLS, MEANS FOR UNIDIRECTIONALLY FLOWING A PURGING LIQUID THROUGH SAID SECOND CONDUIT AT A CONSTANT RATE INTO SAID RESERVOIR, SAID RATE BEING SUFFICIENT TO PREVENT BACK UP OF SLURRY INTO SAID SECOND CONDUIT FROM THE RESERVOIR A DIFFERENTIAL PRESSURE CELL CONNECTED IN PURGING LIQUID COMMUNICATION TO SAID SECOND CONDIT OPERABLE TO SENSE PRESSURE CHANGES IN THE SECOND CONDUIT CAUSED BY A CHANGE IN THE LEVE OF THE SLURRY IN SAID RESERVOIR, A SOURCE OF CONSTANT AIR PRESSURE CONNECTED TO SAID DIFFERENTIAL PRESSURE CELL, SAID DIFFERENMTIAL PRESSURE CELL BEING OPERATIVE TO PROVIDE AN OUTPUT SIGNAL HAVING A MAGNITUDE PROPORTIONAL TO THE DIFFERENCE BETWEEN THE PRESSURE IN SAID SECOND CONDUIT AND THE PRESSURE REFERENCE OF SAID CONSTANT AIR PRESSURE SOURCE, VALVE MEANS IN SAID FEED SLURRY SUPPLY CONDUIT, AND MEANS RESPONSIVE TO SAID OUTPUT SIGNAL OPERABLE TO MOVE SAID VALVE MEANS TOWARDS OPEN POSITION AT OUTPUT SIGNALS GENERATED BY A LOWERING OF THE SLURRY LEVEL IN SAID RESERVOIR.