Fuente: WIPO "rice" 5595. Rice, J. D. March 6. Digesters.-In apparatus for the preparation of paper pulp from wood, chopped wood delivered to a hopper 35 is introduced by shoots into one of two stationary boilers 10 through a man-hole 17. The material is heated by rotating steam-pipes which also stir the material, the central pipe constituting a h o l l o w shaft which is in communication with inlet and outlet ports in the walls of the boiler. When the cooking is finished, the valve 56 is opened, and the material is allowed to flow into a conveyer 11, provided with a double spiral screw, which carries the material from either boiler to a perforated shoot 65. Steam may be supplied to the bottoms of the boilers through pipes 53.