US 12,065,907 B2
Drill assembly for percussive drilling
Adam Baker, Wickenby (GB); and Joonas Sokka, Tampere (FI)
Assigned to ROBIT PLC, Lempäälä (FI)
Appl. No. 18/003,940
Filed by ROBIT PLC, Lempäälä (FI)
PCT Filed Jul. 1, 2021, PCT No. PCT/FI2021/050508
§ 371(c)(1), (2) Date Dec. 30, 2022,
PCT Pub. No. WO2022/003253, PCT Pub. Date Jan. 6, 2022.
Claims priority of application No. 20205718 (FI), filed on Jul. 3, 2020.
Prior Publication US 2023/0258043 A1, Aug. 17, 2023
Int. Cl. E21B 4/14 (2006.01); E21B 6/00 (2006.01); E21B 10/36 (2006.01)
CPC E21B 4/14 (2013.01) [E21B 6/00 (2013.01); E21B 10/36 (2013.01)] 16 Claims
OG exemplary drawing
 
1. A drill assembly for percussive drilling, the drill assembly comprising:
a drill bit extending along a longitudinal direction and including:
a distal portion having an end surface equipped with inserts configured for transferring percussive impact to points of contact with a borehole during operation;
a shank portion extending from the distal portion in an uphole direction, the shank portion being equipped with a male coupling configuration and, on a longitudinal uphole end of the shank portion, a first impact surface; and
a first central flushing channel for conducting a flushing fluid flow to an end surface of the distal portion, said central flushing channel extending through at least the shank portion and being open towards the longitudinal uphole end of the shank portion, such that the first impact surface is formed annularly around the first central flushing channel;
a percussion device extending along a longitudinal direction and including:
on a downhole side end thereof, a female coupling configuration for coupling with the male coupling configuration of the drill bit; and
an impact piston arranged within a housing and configured to reciprocate in the longitudinal direction, the impact piston having, on the downhole end of the piston, a central recess and a second impact surface annularly surrounding the central recess for impacting against the first impact surface of the drill bit as the impact piston is reciprocated; and
a hollow cylindrical foot valve attached to the drill bit and partially received within the first central flushing channel and extending therefrom in an uphole direction, such that:
the foot valve is also partially received within the central recess, while the impact piston is in a lowermost position during reciprocation of the impact piston; and
the foot valve is no longer received within the central recess, while the impact piston is in an uppermost position during reciprocation of the impact piston;
wherein the foot valve includes an internal stiffener extending radially inwardly from at least two circumferential positions of an inner surface of the foot valve; and
wherein the internal stiffener is formed as an integral part of the foot valve, as one or more internal walls of the foot valve.