Patent ID: 9534444
Date: 2017-01-03
CPC Classifications: E21B

Claim:
1. A down-the-hole hammer drill bit assembly comprising: a drill bit having a forward cutting end, a rearward anvil end and an internal passageway extending along a longitudinal axis of the assembly from the anvil end towards the cutting end; a foot valve seated partially within the passageway to extend axially from the anvil end; and complementary abutment regions provided respectively at a radially inward facing surface of the passageway and at a radially outward facing surface of the foot valve, the abutment regions being configured to abut one another and axially lock the foot valve to the drill bit, the abutment regions including a plurality of radially projecting lugs spaced apart in a circumferential direction around the axis and a plurality of radially extending shoulders spaced apart in a circumferential direction around the axis, a circumferential separation distance between the shoulders at least equal to or greater than a circumferential length of the lugs to allow the lugs to pass axially between the shoulders without substantially deforming the foot valve radially, an axially rearward end of each lug being tapered radially to provide an abutment contact surface and an axially forward end of each shoulder is tapered radially to provide an abutment contact surface, wherein a radial length of the lugs and shoulders is configured such that when the lugs are positioned axially beyond the shoulders the abutment contact surfaces of the lugs and shoulders mate together to overlap radially within the passageway to provide friction fit regions that axially lock and inhibit independent rotation of the foot valve at the drill bit.