Expansible mandrel

Claim 1

AN EXPANSIBLE MANDREL FOR USE IN CONNECTION WITH THE MANUFACTURE OF TUBULAR MEMBERS, SAID MANDREL COMPRISING (A) A BASE, (B) AT LEAST THREE SECTORS MOUNTED ON SAID BASE FOR SLIDING RADIAL MOVEMENT BETWEEN A RETRACTED POSITION AND AN EXPANDED POSITION, SAID SECTORS HAVING OUTER PERIPHERIES ADAPTED TO ENGAGE THE INTERIOR SURFACE OF A TUBULAR MEMBER WHEN SAID SECTORS ARE IN EXPANDED POSITION, EACH OF SAID SECTORS HAVING AN ELONGATE BEARING SURFACE THEREON POSITIONED INWARDLY FROM THE PERIPHERY OF SAID SECTORS AND EXTENDING GENERALLY PARALLEL TO SAID BASE, SAID BEARING SURFACE HAVING A LENGTH ENCOMPASSING AT LEAST A MAJOR PORTION OF THE WIDTH OF THE SECTOR TAKEN ALONG A LINE INCLUDING THE BEARING SURFACE. (C) A FORCE TRANSMITTING MEMBER FOR EACH OF SAID SECTORS AND HAVING A WIDTH SUBSTANTIALLY GREATER THAN THE THICKNESS THEREOF AND HAVING FIRST AND SECOND ELONGATE BEARING SURFACES ON OPPOSITE ENDS THEREOF OF LENGTHS CORRESPONDING AT LEAST TO THE WIDTH OF SAID FORCE TRANSMITTING MEMBER ALONG THE CORRESPONDING ENDS THEREOF, SAID FIRST BEARING SURFACE ON EACH OF SAID FORCE TRANSMITTING MEMBERS BEING DISPOSED IN COEXTENSIVE COMPLEMENTARY ENGAGEMENT WITH THE BEARING SURFACE ON THE CORRESPONDING SECTOR AND DEFINING THEREWITH AN AXIS ABOUT WHICH SAID FORCE TRANSMITTING MEMBER IS OSCILLATORY MOVABLE TOWARD AND AWAY FROM SAID BASE, SAID SECOND BEARING SURFACE ON SAID TRANSMITTING MEMBER BEING OF SUFFICIENT RELATIVE LENGTH TO SAID FIRST BEARING SURFACE THEREON AND SAID FIRST BEARING SURFACE AND SAID BEARING SURFACE ON THE CORRESPONDING SECTOR BEING OF SUFFICIENT RELATIVE LENGTH TO THE CHORD LENGTH OF THE PERIPHERY OF THE SECTOR THAT A MAJOR PORTION OF THE SECTOR IS SUBJECTED TO COMPRESSIVE LOAD TO SUBSTANTIALLY OFFSET THE BENDING LOADS THEREON, AND (D) FORCE APPLYING MEANS HAVING ELONGATE BEARING SURFACES COEXTENSIVELY AND COMPLEMENTARILY ENGAGING THE SECOND BEARING SURFACES ON SAID FORCE TRANSMITTING MEMBERS FOR APPLYING FORCE THERETO IN A DIRECTION TO MOVE SAID FORCE TRANSMITTING MEMBERS TOWARD SAID BASE AND TO MOVE SAID SECTORS RADIALLY OUTWARDLY FROM THE RETRACTED POSITION TO THE EXPANDED POSITION.