Percussion assisted rotary earth bit and method of operating the same

1. A hammer assembly, comprising:

a piston;

a flow control tube which extends through the piston, the flow control tube including a drive guide port and return guide port;

wherein the piston is repeatably moveable relative to the drive guide port and return guide port in response to a fluid flow through the flow control tube; and

an adapter sub with an adapter sub channel in fluid communication with a flow control tube channel of the flow control tube, wherein the adapter sub engages the piston with a force between about one foot-pound per square inch (1 ft-lb/in2) to about five foot-pounds per square inch (5 ft-lb/in2).

2. The assembly of claim 1 , wherein the piston includes a drive piston port and return piston port.

3. The assembly of claim 2 , wherein the drive piston port is not in fluid communication with the drive guide port when the return guide port is in fluid communication with the return piston port.

4. The assembly of claim 2 , wherein the return guide port is not in fluid communication with the return piston port when the drive piston port is in fluid communication with the drive guide port.

5. The assembly of claim 1 , wherein the flow control tube extends through drive and return surfaces of the piston.

6. The assembly of claim 1 , wherein the piston engages the adapter sub in response to the return guide port and return piston port being in fluid communication.

7. The assembly of claim 1 , wherein the flow control tube includes a head portion, and a sleeve portion which extends through drive and return surfaces of the piston.

8. The assembly of claim 7 , wherein the piston is repeatably moveable between positions towards and away from the head portion in response to the flow of the fluid through the flow control tube.

9. The assembly of claim 1 , wherein the force at which the piston engages the adapter sub is adjustable in response to adjusting the fluid flow.

10. The assembly of claim 1 , wherein the rate at which the piston engages the adapter sub is adjustable in response to adjusting the fluid flow.

11. The assembly of claim 1 , wherein the adapter sub engages the piston at a rate in a range between about eleven-hundred (1100) times per minute to about fourteen-hundred (1400) times per minute.

12. The assembly of claim 1 , wherein the fluid flows at a pressure less than about one-hundred pounds per square inch (100 psi).

13. The assembly of claim 1 , wherein the fluid flows at a rate in a range of about one-thousand cubic feet per minute (1,000 cfm) to about 4,000 cubic feet per minute (4,000 cfm).

14. A hammer assembly, comprising:

a piston which includes a drive piston port; and

a flow control tube which extends through the piston, the flow control tube including a drive guide port;

wherein the drive piston port and drive guide port move relative to each other in response to a fluid flow through the flow control tube, the piston includes a return piston port and the flow control tube includes a return guide port, and the fluid flows through the return piston port and return guide port in response to the return piston port and return guide port being in fluid communication with each other; and

an adapter sub, wherein the piston engages the adapter sub in response to the return guide port and return piston port being in fluid communication with each other, wherein the piston engages the adapter sub with a force between about one foot-pound per square inch (1 ft-lb/in2) to about five foot-pounds per square inch (5 ft-lb/in2).

15. The assembly of claim 14 , wherein the fluid flows through the drive piston port and drive guide port in response to the drive piston port and drive guide port being in fluid communication with each other.

16. The assembly of claim 14 , wherein the piston engages the adapter sub at a rate in a range between about eleven-hundred (1100) times per minute to about fourteen-hundred (1400) times per minute.

17. The assembly of claim 14 , wherein the fluid flows at a pressure less than about one-hundred pounds per square inch (100 psi).

18. The assembly of claim 14 , wherein the fluid flows at a rate in a range of about one-thousand cubic feet per minute (1,000 cfm) to about 4,000 cubic feet per minute (4,000 cfm).

19. A hammer assembly, comprising:

a piston which includes a return piston port;

a flow control tube which extends through the piston, the flow control tube including a return guide port;

wherein the return piston port and return guide port move relative to each other in response to a fluid flow through the flow control tube, and the fluid flows through the return piston port and return guide port in response to the return piston port and return guide port being in fluid communication with each other; and

an adapter sub, wherein the piston engages the adapter sub in response to the return guide port and return piston port being in fluid communication with each other, wherein the piston engages the adapter sub with a force between about one pound per square inch (1 lb/in2) to about four pounds per square inch (4 lb/in2).

20. The assembly of claim 19 , wherein the piston includes a drive piston port and the flow control tube includes a drive guide port.

21. The assembly of claim 20 , wherein the fluid flows through the drive piston port and drive guide port in response to the drive piston port and drive guide port being in fluid communication with each other.

22. The system of claim 19 , wherein the piston engages the adapter sub at a rate in a range between about eleven-hundred (1100) times per minute to about fourteen-hundred (1400) times per minute.

23. The system of claim 19 , wherein the fluid flows at a pressure less than about one-hundred pounds per square inch (100 psi).

24. The system of claim 19 , wherein the fluid flows at a rate in a range of about one-thousand cubic feet per minute (1,000 cfm) to about 4,000 cubic feet per minute (4,000 cfm).