Bore hole air hammer

In percussion drilling apparatus:

• a housing structure connectable to a drill string;
• an anvil in the lower portion of said housing structure and operatively connectable to a drill bit;
• a hammer piston reciprocable in said housing structure for intermittently impacting against said anvil, said piston having a central upper chamber therein;
• an inlet tube piloted in said chamber and adapted to receive a fluid medium under pressure from the drill string and direct such fluid medium into said chamber;
• first passage means for directing the fluid medium from said chamber into said housing structure above said piston;
• second passage means for directing the fluid medium from said chamber into said housing structure below said piston;
• coengaging valve means on said tube and piston wall of said chamber opening said first passage means and closing said second passage means upon upward movement of said piston in said housing structure and closing said first passage means and opening said second passage means upon downward movement of said piston in said housing structure;
• means alternately exhausting the fluid medium from the housing structure above and below said piston;
• said piston including means substantially closing the lower portion of said upper chamber;
• said inlet tube having a lower passage opening into said upper chamber above said piston chamber closing means through which the fluid medium is discharged directly into said upper chamber for action against said piston chamber closing means during the entire downward stroke of said piston toward and against said anvil;
• whereby the fluid medium under pressure acts concurrently over substantially the full cross-sectional area of said piston in driving said piston downwardly toward said anvil.

In percussion drilling apparatus:

• a housing structure connectable to a drill string;
• an anvil in the lower portion of said housing structure and operatively connectable to a drill bit;
• a hammer piston reciprocable in said housing structure for intermittently impacting againt said anvil, said piston having a central upper chamber therein;
• an inlet tube piloted in said chamber and adapted to receive a fluid medium under pressure from the drill string and direct such fluid medium into said chamber;
• first passage means for directing the fluid medium from said chamber into said housing structure above said piston;
• second passage means for directing the fluid medium from said chamber into said housing structure below said piston;
• coengaging valve means on said tube and piston wall of said chamber opening said first passage means and closing said second passage means upon upward movement of said piston in said housing structure and closing said first passage means and opening said second passage means upon downward movement of said piston in said housing structure;
• and means for alternately exhausting the fluid medium from the housing structure above and below said piston;
• said exhausting means including a first exhaust passage in the lower portion of said piston, a second exhaust passage in said anvil, an exhaust tube in said anvil passage projecting upwardly into said first exhaust passage, and an exhaust passageway in the inner side wall of the housing structure;
• said piston and housing structure having coengaging valve means for alternately permitting and preventing passage of the exhaust fluid medium from the housing structure above said piston to said exhaust passageway and from the housing structure below said piston to said exhaust passageway.

In percussion drilling apparatus:

• a housing structure connectable to a drill string;
• an anvil in the lower portion of said housing structure and operatively connectable to a drill bit;
• a hammer piston reciprocable in said housing structure for intermittently impacting againt said anvil, said piston having a central upper chamber therein;
• an inlet tube piloted in said chamber and adapted to receive a fluid medium under pressure from the drill string and direct such fluid medium into said chamber;
• first passage means for directing the fluid medium from said chamber into said housing structure above said piston;
• second passage means for directing the fluid medium from said chamber into said housing structure below said piston;
• coengaging valve means on said tube and piston wall of said chamber opening said first passage means and closing said second passage means upon upward movement of said piston in said housing structure and closing said first passage means and opening said second passage means upon downward movement of said piston in said housing structure;
• and means for alternately exhausting the fluid medium from the housing structure above and below said piston;
• said exhausting means including a first exhaust passage in the lower portion of said piston, a second exhaust passage in said anvil, an exhaust tube in said anvil passage projecting upwardly into said first exhaust passage, and an exhaust passageway in the inner side wall of said housing structure;
• said piston and housing structure having coengaging valve means for controlling passage of the exhaust fluid medium alternately from the housing structure above and below said piston to said exhaust passageway in the inner side wall of said housing structure;
• a third exhaust passage in said piston providing communication between said exhaust passageway and said first exhaust passage to enable the exhaust fluid medium flowing from above and below said piston to pass from said exhaust passageway through said third exhaust passage and through said first exhaust passage into said second exhaust passage in said anvil.