Extensible couplings for well pipes

Claim 1

IN MARINE DRILLING FROM A FLOATING VESSEL, (A) A ROTARY DRILL PIPE STRING HAVING ITS UPPER END CONNECTED TO THE VESSEL, (B) A DRILL BIT CARRIED BY THE LOWER END OF SAID DRILL PIPE STRING FOR DRILLING IN SUBNATANT LAND, AND (C) AN EXTENSIBLE COUPLING MOUNTED BETWEEN SECTIONS OF SAID PIPE STRING TO ACCOMMODATE VERTICAL MOVEMENTS OF THE VESSEL RELATIVE TO THE LAND WHILE MAINTAINING SAID DRILLING BIT IN ROTARY DRILLING CONTACT WITH SAID LAND, SAID COUPLING COMPRISING: (D) TELESCOPICALLY ENGAGED INNER AND OUTER TUBULAR MEMBERS, (E) SPLINE MEANS FORMING A NON-ROTATING LONGITUDINALLY SLIDABLE CONNECTION BETWEEN SAID MEMBERS, AND INCLUDING MEANS LIMITING RELATIVE LONGITUDINAL MOVEMENT OF THE MEMBERS, (F) LONGITUDINALLY SPACED SEAL MEANS ARRANGED BETWEEN SAID MEMBERS ON OPPOSITE SIDES OF SAID SPLINE MEANS TO DEFINE A FLUID-CONFINING CHAMBER THEREBETWEEN, (G) A BODY OF HYDRAULIC FLUID CONFINED WITHIN SAID CHAMBER, (H) ONE OF SAID SEAL MEANS COMPRISING AN ANNULAR PISTON LONGITUDINALLY SLIDABLY DISPOSED BETWEEN SAID MEMBERS, (I) AN ADDITIONAL SEAL MEANS ARRANGED BETWEEN SAID MEMBERS IN SPACED RELATION TO SAID PISTON, AND (J) PORT MEANS IN SAID OUTER MEMBER PROVIDING FLUID COMMUNICATION BETWEEN THE EXTERIOR THEREOF AND THE INTERIOR THEREOF BETWEEN SAID PISTON AND SAID ADDITIONAL SEAL MEANS.