Air percussion drilling assembly for directional drilling applications

An air percussion hammer apparatus for directional drilling operations with means for rotating the hammer bit while it reciprocates in a housing independent of an attached drill string, said bit rotating means comprising:

• a cylindrical housing forming a first open up-stream end connectable to a drill string component and a second downstream end, said second end containing said hammer bit,
• a pneumatic feed tube forming a first open end and second substantially closed end, said first end of the feed tube is concentric with and fixed within said housing and positioned toward said first up-stream end of said housing, the second end of the feed tube forms one or more metered openings between said first and second ends of the feed tube,
• a piston body is slidably retained within a first cylindrical sleeve formed by said cylindrical housing, the piston body forms a first open upstream end and a second open downstream end, said first open upstream end is reduced in diameter, inner walls formed by said first open upstream end further concentrically contains said second end of said feed tube, said inner walls of said first open upstream end being slidably engaged with an outside surface formed by said second end of said feed tube, said second downstream end of said piston body engaged with said first cylindrical sleeve forms a hammer striking surface, said piston body further forms at least one axially oriented helical groove in an outside wall formed by said reduced diameter first open upstream end of said piston body and at least a pair of pneumatic communication ports between an outside wall of said piston body positioned between said first open upstream end and said second open downstream end of said piston body and an interior chamber formed by said piston body, one of said ports leads from said interior chamber formed by said piston body to a chamber formed between said outside wall of the first open upstream end of the piston body and said first cylindrical sleeve, the other of said ports leads from an interior chamber formed within the first open upstream end of the piston body through a port formed by said piston body to said first cylindrical sleeve adjacent thereto, one or the other of said ports in said body sequentially registers with said metered openings in said feed tube when said reciprocating piston is moved into alignment therewith during an operating cycle of said apparatus, said second open downstream end of the piston body further forms a longitudinally extended sleeve concentrically therein,
• a hammer bit body is slidably contained within a second sleeve formed by said second end of said cylindrical housing, said hammer bit body further forms an upstream shaft end adapted to be axially slidable within said sleeve formed in said second open downstream end of said piston body, said shaft end of said hammer is rotationally keyed to said piston body by an engagement means such that the hammer bit moves in concert with said piston, said bit body forming a second downstream cutter end, and
• clutch means contained within said housing, said clutch means being positioned adjacent to and interconnected with said at least one helical groove formed in said first reduced diameter open upstream end of said piston body, the clutch means serves to rotate the piston body and the hammer bit body engaged therewith incrementally and in one direction only, each time the piston body oscillates within the cylindrical housing during operation of the air percussion hammer apparatus.