DOWN HOLE HAMMER HAVING ELEVATED EXHAUST

摘要

A percussive assisted rotary drill includes a top sub for connection with a drill pipe. The drill pipe imparts torque to the drill and also supplies motive fluid to the drill. The drill includes a shank adapter to facilitate affixing a rotary drill bit to the drill. The motive fluid is divided between a bit flow which flows through the bit to clear debris at the bottom of the drill, and an actuator flow, An actuator, which may be in the form of a reciprocating piston, moves within the drill under the influence of the actuator flow to impart cyclical blows to the shank adapter, The blows are transferred to the drill bit through the shank adapter to provide a relatively high frequency low amplitude percussive force on the rotating drill bit to assist in the drilling operation, At least a portion of the actuator flow portion of the motive fluid is exhausted through the top end of the drill. The relative flow rates and volumes of the bit and actuator flows can be adjusted with a check valve in the actuator flow exhaust path.