Drill rod holder

Abstract

Drill rod holder (10) mounted on a support (6) for clamping action towards a drill rod (40), which rod holder (10) is suitable for use in surface and underground drilling equipment, comprising a first jaw (34) arranged to co-operate with a second jaw (36) in clamping action towards the drill rod (40) from opposite sides; a piston-cylinder arrangement (22) in which a piston rod (28) in one end is attached to a first side of the piston (26) and in the other end is arranged to co-operate with the second jaw (36); a medium supply inlet (48) in the cylinder (2) through which a medium pressure is arranged to force the piston from its first side to pull the piston rod (28) into the cylinder (2) and thereby releases the clamping force on the jaws (34, 36) so that the jaws can be separated, wherein the cylinder (2) on the second side of the piston (26) is pre-filled with pressurised gas (46) acting as a gas spring exerting a pushing force on the piston (26) and thereby on the second jaw (36) via the piston rod (28) and in that the second jaw (36) exerts a clamping force on the drill rod (40) when the gas pressure exceeds the medium pressure and that the second jaw (36) is arranged to move away from the first jaw (34) when the medium pressure exceeds the gas pressure.

Dependencies are inferred from the claim text.