Cone-spread screw-thread insert

Claim 1

AN EXPANSIBLE INSERT COMPRISING, AS A UNITARY STRUCTURE, A CYLINDRICAL BODY HAVING AN UPPER END PORTION FOR THE ATTACHMENT OF AN EXTRANEOUS MEMBER AND A LOWER PLANE END FACE OPPOSITE SAID END PORTION, AND AN INTEGRAL FRUSTO-CONICAL PLUG HAVING ITS SMALLER END FACE ADJOINING SAID LOWER END FACE OF SAID BODY, SAID BODY HAVING A LOWER PORTION SOLID EXCEPT FOR ONE DIAMETRIC TRANSVERSE THROUGHGOING BORE OF CIRCULAR-SEGMENTAL CROSS-SECTION PROVIDED IN SAID SOLID PORTION AT RIGHT ANGLES TO THE AXIS OF SAID CYLINDRICAL BODY, THE AXIS OF SAID BORE BEING SPACED UPWARDS FROM SAID END FACE LESS THAN THE LENGTH OF A RADIUS OF SAID BORE SO AS TO FORM TWO PARALLEL SUBSTANTIALLY SHARP EDGES OF SAID END FACE, SAID FRUSTO-CONICAL PLUG HAVING A MINOR DIAMETER APPROXIMATELY THE SPACING OF SAID EDGES AND A MAJOR DIAMETER SMALLER THAN THAT OF SAID CYLINDRICAL BODY AND HAVING IN ITS SMALLER END FACE A PARTCYLINDRICAL RECESS FORMING WITH THE MEDIAN PORTION OF SAID BORE A COMPLETE HOLLOW-CYLINDRICAL SURFACE, AND THIN FRANGIBLE WALL PIECES CONNECTING THE SMALLER PLUG END TO SAID EDGES, RESPECTIVELY, SAID PLUG BEING SO DIMENSIONED AS TO EXPAND THE LOWER PORTION OF SAID BODY ADJACENT SAID BORE AND TO BE WHOLLY ENCASED IN SAID ORIGINALLY CIRCULARSEGMENTAL CROSS-SECTION OF SAID BORE WHEN SAID WALL PIECES ARE BROKEN UPON SAID PLUG BEING URGED INTO SAID BORE IN THE DIRECTION OF SAID BODY AXIS.