Expansion-compensating sealing device

Claim 1

A SEALING DEVICE FOR EFFECTING A SEAL BETWEEN A CYLINDRICAL SURFACE DEFINING AN OPENING IN A MACHINE CASING OF RELATIVELY WEAK METAL AND A CYLINDRICAL SURFACE OF A ROD EXTENDING COAXIALLY THROUGH SAID OPENING AND BEING MOVABLE RELATIVELY TO SAID CASING, SAID DEVICE COMPRISING AN ANNULAR, OUTER SHELL MEMBER OF SHEET METAL OF APPROXIMATELY THE SAME DEGREE OF STRENGTH AND OF APPROXIMATELY THE SAME COEFFICIENT OF THERMAL EXPANSION AS THE METAL OF THE CASING AT SAID OPENING, AND HAVING A CYLINDRICAL PORTION WHICH IS ADAPTED TO FIT TIGHTLY INTO SAID OPENING AND TO EXPAND AND CONTRACT RADIALLY IN RESPONSE TO TEMPERATURE CHANGES TO APPROXIMATELY THE SAME EXTENT AS CONCURRENT EXPANSION AND CONTRACTION OF ADJACENT METAL PORTIONS OF SAID CASING AT SAID OPENING, A SEPARATE, ANNULAR, INNER SHELL MEMBER OF SHEET METAL OF GREATER STRENGTH AND A LOWER COEFFICIENT OF THERMAL EXPANSION THAN SAID OUTER SHELL MEMBER AND HAVING A CYLINDRICAL PORTION EXTENDING CLOSELY WITHIN SAID CYLINDRICAL PORTION OF SAID OUTER SHELL MEMBER TO SUPPORT THE LATTER MEMBER AGAINST DEFORMATION, SAID SHELL MEMBERS HAVING INTER-ABUTTING PORTIONS OPPOSING RELATIVE AXIAL MOVEMENT OF SAID MEMBERS, AND THE DEVICE FURTHER COMPRISING AN ANNULAR SEALING ELEMENT OF FLEXIBLE MATERIAL, FLUID-TIGHTLY SECURED AGAINST THE OUTER ONE OF SAID SHELL MEMBERS AND ADAPTED TO EFFECT A SLIDING SEAL WITH SAID CYLINDRICAL SURFACE OF THE ROD.