Patent ID: 8985245
Filing Date: 2015-03-24
Classification: E21B

Abstract:
1. A drill bit assembly for fluid-operated percussion drill tools comprising: 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; bit retaining means adapted for engagement with complementary retaining means 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; wherein the bit retaining means comprises a bit retaining ring, and the complementary retaining means comprises a retaining shoulder on the stub shank, the bit retaining ring arranged to engage the retaining shoulder to retain the stub shank in the drill bit assembly; wherein the bit retaining ring further comprises a shoulder for engagement with an upper end of the chuck, wherein the shoulder is an outward taper arranged to engage with a counterbore in the chuck to hold the bit retaining ring in place in the assembly; and wherein a portion of the bit retaining ring adapted to engage the retaining shoulder to retain the stub shank in the drill bit assembly is disposed within the chuck.