Patent ID: 7467674

Claim:
A drill bit for a reverse circulation rock drill, the drill bit having a head with a working face and a shank of reduced diameter as compared with the working face, the drill bit having one or more intake holes in the working face leading to a passage extending up the drill bit shank, the drill bit head having, at a location spaced from the working operative face, a circumferential band or collar providing a cylindrical external surface coaxial with the drill bit, the diameter of said circumferential band or collar being substantially equal to the effective diameter of the working face of the drill bit and not less than the diameter of any other part of the drill bit, the drill bit having a circumferential groove around its exterior, below said circumferential band or collar and having passages for exhaust air discharging into said groove, whereby such air can pass around the front of the drill bit and across said face to exit through said intake holes.