Patent ID: 6749031
Filing Date: 2004-06-15
Classification: E21B

Abstract:
A drilling system having a drilling head (2, 2â€²) fixed to a drill string (3) which comprises an outer pipe (12, 12â€²) and a percussion string (13, 13â€²) inserted therein, wherein the percussion string (13, 13â€²) comprises a plurality of rods (14, 14â€²) which bear against each other with their end faces (19, 20; 19â€², 20â€²), characterised in that the outer pipe (12, 12â€²) is adapted to be deformable along its longitudinal axis and the end faces (19, 20; 19â€², 20â€²) which bear against each other of two of said plurality of rods (14, 14â€²) are so designed that they bear against each other substantially in surface contact upon inclined positioning of the axes of the two of said plurality of rods (14, 14â€²) relative to each other.