US Patent 12006771 Down-the-hole hammer drill bit assembly

A down-the-hole drilling assembly activated by fluid under pressure includes a casing having an axially rearward and forward end, a piston arranged movably inside the casing, a plurality of fluid passages for feeding and discharging pressurized fluid into and out of a working chamber for generating reciprocating movement of the piston, a drill bit at the forward end and provided with an anvil facing towards the piston for receiving impacts therefrom and an annular drive sub surrounding at least a portion of a shank and cooperating with the bit to form fluid passages extending length-wise along the shank. The drive sub has a concave arcuate groove extending circumferentially to form a chamber for collecting fluid from the hammer exhaust and redistributing a volume of the collected fluid from channels formed between complimentary splines of the drive sub and splines of the bit to flushing holes arranged in the bit.