Apparatus for dewatering of fibrous webs in papermaking and similar machines

Claim 1

IN APPARATUS FOR DEWATERING A WEB OF PAPER BEING MANUFACTURED IN A PAPERMAKING MACHINE BY PURGING OF WATER THEREFROM IN LIQUID FORM THE COMBINATION OF AN ENDLESS BELT OF POROUS MATERIAL HAVING GAS- AND WATERPERMEABLE OPENINGS THERETHROUGH, MEANS FOR DRIVING SAID BELT THROUGH AN ENDLESS PATH AT THE LINEAR SPEED AT WHICH A WEB OF PAPER IS BEING MANUFACTURED IN SAID MACHINE, MEANS FOR GUIDING SAID WEB OF PAPER TO POSITION ONE SURFACE THEREOF IN FACE TO FACE CONTACT WITH ONE SURFACE OF SAID ENDLESS BELT FOR MOVEMENT WITH SAID BELT THROUGH A PORTION OF THE PATH OF SAID BELT, A STATIONARY HOUSING HAVING A SUBSTANTIALLY RECTANGULAR OPENING EXTENDING TRANSVERSELY AND LONGITUDINALLY OF SAID PORTION OF THE PATH OF SAID BELT THROUGH WHICH THE INTERIOR OF SAID HOUSING IS IN COMMUNICATION WITH THE OPPOSITE SURFACE OF THE ENTIRE WIDTH AND A LONGITUDINALLY EXTENDING PORTION OF SAID WEB AS SAID WEB MOVES PROGRESSIVELY THROUGH SAID PORTION OF SAID PATH, FIRST SEALING MEANS FOR FORMING SUBSTANTIALLY GAS-TIGHT SEALS OF THE TRANSVERSELY EXTENDING EDGES OF SAID OPENING WITH RESPECT TO SAID OPPOSITE SURFACE OF SAID WEB, SECOND SEALING MEANS FOR FORMING SUBSTANTIALLY GAS-TIGHT SEALS OF THE LONGITUDINALLY EXTENDING EDGES OF SAID OPENING WITH RESPECT TO SAID OPPOSITE SURFACE OF SAID WEB, MEANS FOR SUPPLYING GAS AT SUBSTANTIAL SUPERATMOSPHERIC PRESSURE TO THE INTERIOR OF SAID HOUSING FOR PASSAGE THROUGH THE THICKNESS OF SAID WEB OF PAPER TO DISLODGE WATER FROM SAID WEB AND TO DISCHARGE SAID WATER INTO THE OPENINGS IN SAID BELT, SAID FIRST SEALING MEANS COMPRISING TWO PAIRS OF PRESSURE ROLLS DISPOSED TRANSVERSELY OF THE PATH OF TRAVEL OF SAID ENDLESS BELT AND WEB TO FORM TWO SPACED NIPS THROUGH WHICH SAID BELT AND THE WEB IN CONTACT THEREWITH PASS SUCCESSIVELY UPON ENTERING AND LEAVING SAID PORTION OF PATH OF SAID BELT, AT LEAST THE PAIR OF PRESSURE ROLLS AT THE ENTERING END OF SAID PORTION OF THE PATH OF SAID BELT HAVING PERFORATED CYLINDRICAL OUTER SHELLS, AND MEANS FOR SUPPLYING GAS AT SUBSTANTIAL SUPERATMOSPHERIC PRESSURE THROUGH THE PERFORATIONS IN THE NIP ZONE ONLY OF THE ROLL WHICH IS IN CONTACT WITH SAID OPPOSITE SURFACE OF SAID WEB