Patent ID: 7377338

Claim:
A pressure fluid actuated percussion tool comprising: an elongated cylinder housing including opposed ends and a central bore forming a bore wall; a reciprocating piston hammer disposed in said bore and having a first enlarged diameter portion in close fitting relationship with said bore wall of said housing, a first reduced diameter portion adjacent one end of said piston hammer and a second reduced diameter portion extending from said enlarged diameter portion in an opposite direction from said first reduced diameter portion; a first sub connected to said housing at one of said housing ends and a second sub connected to said housing at the other of said housing ends; first and second opposed chambers formed in said housing and delimited in part by said first reduced diameter portion and said second reduced diameter portion, respectively; and an impact blow receiving bit supported on said housing and including an anvil surface operable to receive repeated impact blows from said piston hammer, said bit including a shank part operably in driven engagement with said housing for rotating said bit while receiving impact blows, said bit including a plurality of circumferentially spaced bosses supporting formation cutting inserts thereon, respectively, for removing earth material from a borehole in response to rotation of said tool and deliverance of impact blows to and through said bit.