Patent ID: 7997346

Claim:
A percussion drilling assembly for boring into the earth, the percussion drilling assembly coupled to a lower end of a drill string and comprising: a tubular case having a central axis and a lower end; a driver sub having an upper end threadingly engaged with the lower end of the case; a annular locking member disposed about the driver sub, wherein the annular locking member engages the case and the driver sub, and restricts the rotation of the driver sub relative to the case about the central axis; a hammer bit extending coaxially through the driver sub; and a retainer sleeve having an upper end disposed about a lower end of the driver sub and a lower end extending axially from the lower end of the retainer sleeve along an outer periphery of the hammer bit; wherein the annular locking member is axially positioned between the lower end of the case and the upper end of the retainer sleeve; and wherein the annular locking member engages the retainer sleeve and restricts the rotation of the retainer sleeve relative to the case about the central axis.