Patent ID: 8544566

Claim:
A fluid-actuated percussive impact tool comprising: (a) a casing extending longitudinally between a first end and a second end; (b) a back head disposed at the first end of the casing for connection to a pressurized fluid source; (c) a distributor disposed in the casing at the first end thereof proximate to the back head; (d) a drill bit extending longitudinally between a first end and a second end, the first end of the drill bit being disposed within the casing proximate the second end of the casing and the second end of the drill bit being disposed outside of the casing proximate the second end of the casing, the drill bit and the casing being longitudinally movable with respect to each other between an extended position wherein the second end of the drill bit is furthest from the casing and a retracted position wherein the second end of the drill bit is directly adjacent the second end of the casing; (e) a chamber within the casing located between the distributor and the drill bit; (f) a bearing extending longitudinally between a first end and a second end and having a bore extending therebetween, the bearing being fixedly disposed within the casing proximate the second end of the casing, at least a portion of the first end of the drill bit being disposed within the bore proximate the second end of the bearing; (g) a piston extending longitudinally between a first end and second end and located in the chamber for reciprocating longitudinal movement, the second end of the piston being configured to selectively enter the bore of the bearing through the first end of the bearing to impact the first end, of the drill bit, at least one groove having a first end and a second end being formed in an exterior surface of the piston proximate the second end of the piston and extending partially along the piston toward the first end thereof, the tool having a sealed position when the drill bit is in the extended position and the second end of the piston contacts the first end of the drill bit, wherein a water seal is formed between an interior surface of the bearing and a portion of the exterior surface of the piston between the first end of the piston and the first end of the at least one groove.