US 12,006,771 B2
Down-the-hole hammer drill bit assembly
Olivier Bruandet, Tampere (FI)
Assigned to Sandvik Mining and Construction Oy, Tamper (FI); and Sandvik Mining and Construction Tools AB, Sandviken (SE)
Appl. No. 17/414,787
Filed by SANDVIK MINING AND CONSTRUCTION OY, Tampere (FI); and SANDVIK MINING AND CONSTRUCTION TOOLS AB, Sandviken (SE)
PCT Filed Nov. 27, 2019, PCT No. PCT/EP2019/082653
§ 371(c)(1), (2) Date Jun. 16, 2021,
PCT Pub. No. WO2020/126359, PCT Pub. Date Jun. 25, 2020.
Claims priority of application No. 18212827 (EP), filed on Dec. 17, 2018.
Prior Publication US 2022/0081974 A1, Mar. 17, 2022
Int. Cl. E21B 4/14 (2006.01); E21B 10/38 (2006.01)
CPC E21B 10/38 (2013.01) [E21B 4/14 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A down-the-hole drilling assembly activated by fluid under pressure, said assembly comprising:
a hammer including an elongate casing having an axially rearward end and an axially forward end;
a fluid-powered piston arranged movably inside the casing;
a top working chamber at a top side of the piston;
a bottom working chamber at a bottom side of the piston;
a plurality of fluid passages for feeding and discharging pressurized fluid into and out of the working chambers for generating reciprocating movement for the piston;
a drill bit connectable to the axially forward end of the casing and provided with an anvil facing towards the piston for receiving impacts of the piston; and
an annular drive sub surrounding at least a portion of an elongate shank and cooperating with the drill bit to form fluid passages extending length-wise along the shank, wherein the drive sub includes a concave arcuate groove extending circumferentially in the drive sub forming a chamber, the chamber being connected to channels arranged for collecting fluid from a hammer exhaust flow and redistributing a volume of the collected fluid from the channels to flushing holes arranged in the drill bit, the channels being formed between a plurality of splines of the drive sub and a plurality of splines of the drill bit, wherein the chamber is located on the top side of a head-shank transition area where feed force transmission occurs, wherein the concave arcuate groove forming the chamber has a minimum volume dimension which is constrained by the lesser of a cumulative flow area between the splines or the flow area of the flushing holes in order to permit even redistribution of flow from the hammer.