Fluid-tightness device for the passage of a rotating shaft through a wall

Claim 1

A DEVICE FOR ENSURING FLUID-TIGHTNESS BETWEEN TWO GAS-CONTAINING ZONES SEPARATED BY A WALL THROUGH WHICH PASSES A ROTATING SHAFT MEMBER, THE SAID DEVICE COMPRISING ESSENTIALLY, A STATOR MEMBER RIGIDLY FIXED TO THE SAID WALL IN A TOTALLY FLUID-TIGHT MANNER AND FORMING A SLEEVE SURROUNDING THE SAID ROTATING SHAFT WITH A SMALL CLEARANCE, ONE OF SAID MEMBERS HAVING AN ANNULAR GROOVE FORMED IN A SURFACE THEREOF TO PROVIDE AN ANNULAR CHAMBER BETWEEN SAID MEMBERS, TWO HELICAL THREADS FORMED IN SAID ONE MEMBER AND BEING SPIRALED RESPECTIVELY IN OPPOSITE DIRECTIONS AWAY FROM THE ENDS OF THE CHAMBER TO THE ENDS OF THE STATOR THROUGH WHICH THE SHAFT EMERGES, THE DIRECTIONS OF THE THREADS BEING SO RELATED TO THE DIRECTION OF ROTATION OF THE SHAFT AND THE CONTIGUOUS SURFACES OF SAID MEMBERS BEING SO FITTED THAT THE CHAMBER IS EVACUATED UPON ROTATION OF THE SHAFT, SAID THREADS HAVING A DEPTH WHICH DECREASES PROGRESSIVELY TOWARDS SAID ENDS, A SEALING MEMBER SURROUNDING THE SHAFT EXTERIORLY OF THE STATOR AND MOVABLE TO SEAL THE GAP BETWEEN THE SHAFT AND STATOR