Variable pressure shaft seal

Claim 1

A VARIABLE PRESSURE SEAL FOR COOPERATION WITH A ROTATABLE SHAFT, COMPRISING: (A) A SLEEVE ADAPTED TO BE FREELY RECEIVABLE ABOUT A ROTATABLE SHAFTS; (B) A PLURALITY OF REMOVABLE, HOLLOW, EXPANDIBLE ANNULAR RINGS CARRIED WITHIN SAID SLEEVE AND SECTION RINGS BETWEEN SAID EXPANDIBLE RINGS PROVIDING SPACER MEANS BETWEEN SAID EXPANDIBLE RINGS; (C) SNAP RING RETAINING MEANS FOR SECURING SAID RINGS INTERIORLY OF SAID SLEEVE AND IN ALIGNMENT FOR SEALING ENGAGEMENT WITH THE EXTERIOR OF THE ROTATABLE SHAFT; (D) PASSAGE MEANS IN SAID RINGS FOR PERMITTING FLUID CIRCULATION THERETHROUGH; (E) OPENING MEANS IN SAID RINGS COMMUNICATING WITH SAID PASSAGE MEANS FOR RECEIVING PRESSURE FLUID THEREIN FOR EXPANDING SAID RINGS RADIALLY INTO SEALING CONTACT WITH THE ROTATABLE SHAFT; AND, (F) SAID RINGS INCLUDING THEREWITH AN EXPANDIBLE SAFETY RING BETWEEN A PAIR OF RINGS HAVING FACING ANNULAR RECESSES FOR RECEIVING EXPANSION OF SAID SAFETY RING.