Drilling shafts

Claim 1

A SLIP JOINT CONSTRUCTION COMPRISING CONCENTRICALLY RELATED, SEPARABLE, FIRST AND SECOND, TUBULAR, JOINT FORMING MEMBERS, SAID FIRST JOINT FORMING MEMBER INCLUDING SIDE WALL MEANS FORMING AN AXIALLY EXTENDING SOCKET OPENING SIZED TO SNUGLY ACCOMMODATE THE SECOND JOINT FORMING MEMBER, WITH AT LEAST ONE PAIR OF OPPOSED, INWARDLY TAPERING OPENINGS EXTENDING LATERALLY THROUGH SAID SIDE WALL MEANS, AND SAID SECOND JOINT FORMING MEMBER INCLUDING SIDE WALL MEANS FORMING AN AXIALLY EXTENDING INTERIOR PASSAGEWAY, WITH AT LEAST ONE PAIR OF OPPOSED, INWARDLY TAPERING OPENINGS EXTENDING LATERALLY THROUGH SAID SIDE WALL MEANS, AND BEING REGISTERABLE WITH THE INWARDLY TAPERING OPENINGS IN THE SIDE WALL MEANS OF THE FIRST JOINT FORMING MEMBER, WHEN SAID SECOND JOINT FORMING MEMBER IS ENGAGED IN THE SOCKET OPENING OF SAID FIRST JOINT FORMING MEMBER, TO FORM A PAIR OF OPPOSED, INWARDLY TAPERING BORES, AND A TRANSVERSE SUPPORT MEMBER SPANNING THE INTERIOR PASSAGEWAY IN SAID SECOND JOINT FORMING MEMBER, BETWEEN THE TAPERED OPENINGS IN THE SIDE WALL MEANS THEREOF, SAID SUPPORT MEMBER BEING RIGIDLY ATTACHED TO THE SIDE WALL MEANS OF SAID SECOND JOINT FORMING MEMBER, AND HAVING AN OPENING THEREIN THAT IS GENERALLY ALIGNED WITH THE TAPERED OPENINGS; AND COUPLING MEANS COMPRISING A PAIR OF PLUG ELEMENTS HAVING TAPERED OUTBOARD PORTIONS SIZED TO SNUGLY FIT WITHIN THE TAPERED BORES, AND INBOARD PORTION INSERTABLE FROM OPPOSITE DIRECTIONS INTO THE OPENING IN SAID SUPPORT MEMBER, TO BE ENGAGED THEREBY, WITH SAID SUPPORT MEMBER SERVING TO SUBSTANTIALLY PREVENT SIDEWAYS MOVEMENT OF THE INBOARD END PORTIONS OF SAID PLUG ELEMENTS, AND BOLT MEANS DETACHABLY CONNECTABLE TO SAID PLUG ELEMENT FOR PULLING THEM TOGETHER, AND THE TAPERED OUTBOARD PORTIONS THEREOF INTO TIGHT ENGAGEMENT WITH THE SIDE SURFACES OF THE TAPERED BORES.