Patent ID: 9103165
Filing Date: 2015-08-11
Classification: E21B

Abstract:
1. A down-the-hole hammer comprising an external cylindrical outer wear sleeve, a sliding piston mounted for reciprocating movement within the outer wear sleeve, the piston defining a piston bore therethrough and having a piston nose at a forward end thereof to strike a bit strike face of a percussion bit of a drill bit assembly located at the forward end of the outer wear sleeve, wherein the drill bit assembly comprises: a percussion bit having a head portion formed with an axially extending stub shank; axially extending splines on the stub shank slideably engageable with complementary splines formed on a drive chuck whereby rotational drive from the chuck may be transmitted to the stub shank; a bit retaining ring adapted for engagement with a retaining shoulder on the stub shank to retain the stub shank in the drill bit assembly; and engagement means on the chuck adapted for connecting the chuck to a drive means of the fluid-operated percussion drill tool; the bit retaining ring comprises a shoulder for engagement with an upper end of the chuck to hold the retaining ring in place in the assembly; characterised in that the assembly further comprises: