Cementing well pipe in stages

Claim 1

APPARATUS FOR USE IN STAGE CEMENTING OF WELL PIPE IN A BOREHOLE COMPRISING: A MANDREL ADAPTED TO BE CONNECTED IN SAID WELL PIPE AND PROVIDED WITH AT LEAST TWO LATERALLY SPACED-APART CIRCUIT PORTS; FLUID PRESSURE RELEASABLE PLUG MEANS INITIALLY SECURED IN EACH PORT; A SLIDABLE SLEEVE VALVE LONGITUDINALLY MOVABLE WITHIN SAID MANDREL AND PROVIDED WITH AT LEAST TWO OPENINGS, EACH OF WHICH IS LARGER THAN EACH OF SAID PORTS; SEALING MEANS ARRANGED BETWEEN SAID SLEEVE VALVE AND SAID MANDREL ABOVE AND BELOW SAID PORTS AND SAID OPENINGS WHEN SAID PORTS AND SAID OPENINGS ARE ALIGNED; SAID OPENINGS AND SAID PORTS BEING ALIGNED WHEN SAID SLEEVE VALVE IS IN A LOWER POSITION TO FLUIDLY COMMUNICATE THE INTERIOR OF SAID SLEEVE AND SAID PORTS, SAID SLEEVE WHEN IN AN UPPER POSITION BEING ADAPTED TO CLOSE OFF FLUID COMMUNICATION BETWEEN THE INTERIOR OF SAID SLEEVE VALVE AND SAID PORT; AND STOP MEANS ON SAID MANDREL ADAPTED TO LIMIT FURTHER DOWNWARD MOVEMENT OF SAID SLEEVE VALVE WITHIN SAID MANDREL WHEN SAID SLEEVE VALVE IS IN ITS LOWER POSITION; AND MEANS FOR LOCKING SAID SLEEVE VALVE IN ITS UPPER CLOSED POSITION.