Cementing of well pipe in stages

Claim 1

APPARATUS FOR USE IN STAGE CEMENTING OF WELL PIPE IN A BOREHOLE COMPRISING A HOLLOW BODY MEMBER CONNECTED IN SAID WELL PIPE AND IN FLUID COMMUNICATION THEREWITH AND HAVING AN OFFSET MANDREL MOUNTED THEREON; SAID MANDREL HAVING A FLUID PASSAGEWAY THERETHROUGH TERMINATING IN A LATERAL PASSAGE OPENING INTO SAID HOLLOW BODY MEMBER; A SLEEVE VALVE SLIDABLE IN SAID BODY MEMBER BETWEEN ONE POSITION WHICH OPENS FLUID COMMUNICATION BETWEEN THE INTERIOR OF SAID BODY MEMBER AND SAID MANDREL PASSAGEWAY AND ANOTHER POSITION WHICH CLOSES OFF FLUID COMMUNICATION BETWEEN THE INTERIOR OF SAID BODY MEMBER AND SAID MANDREL PASSAGEWAY; A CHECK VALVE POSITIONED IN SAID MANDREL PASSAGEWAY FOR PERMITTING FLOW OF FLUID WHEN SAID SLEEVE VALVE IS IN SAID ONE POSITION FROM THE INTERIOR OF SAID BODY MEMBER THROUGH SAID PASSAGEWAY BUT PREVENTING FLOW OF FLUID TO THE INTERIOR OF SAID BODY MEMBER THROUGH SAID PASSAGEWAY; A FLUID PRESSURE RELEASABLE PLUG POSITIONED IN SAID PASSAGEWAY FURTHER FROM SAID SLEEVE VALVE THAN CHECK VALVE AND ADAPTED TO PREVENT FLOW OF FLUID THROUGH SAID PASSAGEWAY; AND MEANS FOR LOCKING SAID SLEEVE VALVE IN ITS OTHER CLOSED POSITION.