Abstract: A ring bit comprises an annular or cylindrical shape. The ring bit is configured to be provided around a pilot bit at a distal end of a drilling tool concentrically with the pilot bit. The ring bit comprises at least one protrusion protruding inwards from a first surface provided inside the ring bit, and at least one ring bit pulling surface, which ring bit pulling surface is formed in the protrusion and formed in relation to a radial direction of the ring bit in a direction of a longitudinal axis of the drilling tool in such a manner that a first length of the protrusion at the first surface in the direction of the longitudinal axis is greater than a second length of the protrusion at a second surface. The second surface is defined by the inner-most surface of the protrusion and the first surface is provided at the base of the protrusion on the pulling surface side of the protrusion.

Abstract: A drill assembly for percussive drilling, includes a drill bit having a downhole portion and an attachment portion having a cylindrical male coupling thread, and a drill string element for transferring impacts from a percussion device to the drill bit and having a female coupling thread for threadedly coupling with the male coupling thread. The drill bit includes a first annular impact surface arranged on an uphole-side end the downhole portion, the first annular impact surface surrounding the attachment portion, and the drill string element includes, at a downhole-side end thereof, a second annular impact surface. The first and second impact surfaces are inclined with respect to a plane perpendicular to the longitudinal direction. A drill bit and drill string element are also disclosed.

Abstract: A drill assembly for percussive drilling, comprising a drill bit and a percussion device. The drill assembly further includes a hollow cylindrical foot valve partially received within a first central flushing channel thereof and extending therefrom in the uphole direction, such that the foot valve is also partially received within a central recess of an impact piston of the percussion device, at least when the impact piston is in a lowermost position of its reciprocation cycle, and such that the foot valve is no longer received within the central recess, at least when the impact piston is in an uppermost position of its reciprocation cycle. The foot valve includes an internal stiffener extending radially inwardly from at least two circumferential positions of an inner surface of the foot valve.

Abstract: A drill assembly for percussive drilling, includes a drill bit having a downhole portion and an attachment portion having a cylindrical male coupling thread, and a drill string element for transferring impacts from a percussion device to the drill bit and having a female coupling thread for threadedly coupling with the male coupling thread. The drill bit includes a first annular impact surface arranged on an uphole-side end the downhole portion, the first annular impact surface surrounding the attachment portion, and the drill string element includes, at a downhole-side end thereof, a second annular impact surface. The first and second impact surfaces are inclined with respect to a plane perpendicular to the longitudinal direction. A drill bit and drill string element are also disclosed.

Abstract: A drill assembly for percussive drilling, comprising a drill bit and a percussion device. The drill assembly further includes a hollow cylindrical foot valve partially received within a first central flushing channel thereof and extending therefrom in the uphole direction, such that the foot valve is also partially received within a central recess of an impact piston of the percussion device, at least when the impact piston is in a lowermost position of its reciprocation cycle, and such that the foot valve is no longer received within the central recess, at least when the impact piston is in an uppermost position of its reciprocation cycle. The foot valve includes an internal stiffener extending radially inwardly from at least two circumferential positions of an inner surface of the foot valve.