be added in this way and in this position the sealing liquid is added to the end gable of the housing and lubricates the conical surfaces of the rotor and housing that are held in a predetermined minimal play against each other in order to minimize the leakage of high pressure liquid from one pocket to another i e from the high pressure position to the low pressure position as shown in fig1 is the individual pocket of the rotor 10 filled with chip slurry when the pocket is in register with ports p 1 and p 3 which is the low pressure position of the rotor as shown in the figure could a screen member 24 be located in the port p 3 such that the chips are prevented from escaping from the pocket while liquid l lp being drained therefrom when the pocket is filled with chips in the position shown in fig1 the rotor 10 continue the rotation in the direction r and expose the through going pocket for the second and fourth ports p 2 and p 4 respectively in this position the through going pocket is pressurized from the port p 4 with a liquid l hp that expels the chips held in the pocket trough port p 2 and further to the pressurized digester once the pocket is emptied the rotor 10 continues to rotate in the direction r and once again occupies the filling position as shown in fig1 but at this time with inlets and outlets of the through going pocket being switched in a conventional manner is also the inside of the conical surface of the housing equipped with.