Flexible drill pipe

Claim 1

A flexible drill pipe for operating around the radius of bend of a curved hole or deflecting tool and the flexible drill pipe comprises, a closed pitch cylindrical spiral coil of wire rod, a female tool joint rigidly secured to one end portion of said rod, a male tool joint rigidly secured to the opposite end portion of said rod, a plurality of tube sections positioned end to end in contact within said coil or wire rod and having complete circumferential contact with said rod, said tube sections extending the full length of said coil of wire rod and contacting said tool joints at each end of said rod, flexible structure formed by said tube sections supports said coil or wire rod under high torsion loads and keeps said coil of wire rod from collapsing, all said tube sections constructed the same permitting an even distribution of flexing moments over the length of said coil of wire rod, said tube sections each having an axial length not more than twice the diameter of said rod and not less than the diameter of said rod for support and maximum flexibility of said coil of wire rod, ends of said tube sections being blunt so the length around the inside radius of bend of the said structure formed by said tube sections will not be reduced when bent or flexed, a thin wall hose extending through said tube sections and secured to said joints at its opposite ends to permit drilling fluids to be pumped through said drill pipe.