Manufacture of pulp from fibrous substances

Claim 1

METHOD OF PRODUCINT PULP FROM FIBROUS MATERIALS IN A CONTINUOUS DIGESTER BY SUBJECTING THEM TO THE CHEMICAL ACTION OF A LIQUOR AND STEAM, COMPRISING THE STEPS OF CHARGING THE COMMINUTED RAQ MATERIAL INTO THE INLET OF A FIRST CHAMBER, THEREAFTER CLOSING THE INLET AND OUTLET OF SAID FIRST CHAMBER SO AS TO ISOLATE IT, ADMITTING STEAM AND LIQUOR UNDER PRESSURE INTO SAID ISOLATED CHAMBER, CIRCULATING THE LIQUOR THROUGH SAID FIRST CHAMBER IN A SUBSTANTIALLY CLOSED FIRST CIRCUIT SO AS TO IMPREGNATE THE RAW MATERIAL THEREIN, THEN DRAINING SURPLUS LIQUOR FROM WITH A SECOND CHAMBER AND THE SAMME DIGESTER THE FILLING CLOSED, THEN OPENING THE OUTLET OF SAID FIRST ISOLATED CHAMBER, THEN DISCHARGE THE CONTENTS OF SAID FIRST CHAMBER INTO THE PRESSURE ZONE OF THE DIGESTER, REPEATING SAID STEPS WITH A SECOND CHAMBER AND THE SAME DIGESTER, THE FILLING OF THE SECOND CHAMBER WITH SAID RAW MATERIAL BEING TIMED TO OCCUR DURING THE IMPREGNATION OF SAID RAW MATERIAL IN THE FIRST ISOLATED CHAMBER, AND THEREAFTER REPEATING THE CYCLE ALTERNATINGLY WITH THE FIRST AND SECOND CHAMBERS AND WITH THE SAME RELATIVE TIMING, WITH THE LIQUOR CIRCULATING THROUGH SAID SECOND CHAMBER MEANS IN A SECOND SUBSTANTIALLY CLOSED CIRCUIT.