Pulp refining apparatus

Claim 1

A PULP REFINING APPARATUS COMPRISING, A REFINER HAVING TWO GRINDING MEMBERS ROTATABLE RELATIVELY TO ONE ANOTHER, MEANS FOR INTRODUCING A PRE-CONCENTRATED SUSPENSION BETWEEN THE GRINDING MEMBERS, A PERFORATED TUBE, A ROTATIVE ACRAPER MEMBER WITHIN THE TUBE, SAID TUBE BEING CONNECTED TO THE INLET SIDE OF THE REFINER, A CASING ARRANGED AROUND THE TUBE AND HAVING ITS WALL SPACED FROM THE OUTSIDE OF THE TUBE, SAID CASING COLLECTING FLUID EXPRESSED FROM THE INSIDE OF THE TUBE THROUGH THE PERFORATIONS THEREIN, A PUMP FOR FEEDING THE SUSPENSION UNDER PRESSURE TO THE INTERIOR OF THE TUBE, MEANS AT THE OUTLET END OF THE TUBE AND BETWEEN SAID END AND THE INLET OF THE REFINER, FOR SETTING UP REGULATABLE COUNTER PRESSURE IN THE TUBE, THE CASING HAVING AN OUTLET, AND MEANS OPERATIVE IN THE SAID OUTLET FOR DEVELOPING A COUNTER PRESSURE WITHIN THE CASING AROUND THE PERFORATED TUBE.