Liquid hammer drill
A liquid hammer drill comprising: a housing; a drill bit at a leading end of said housing wherein said drill bit includes a trailing end and a leading end that defines a cutting portion; a piston member located inside said housing and having a trailing end, a leading end and an intermediate portion therebetween, said piston member being capable of movement between a first position and a second position at which it impacts the trailing end of the drill bit; a liquid circuit for delivering a liquid to the piston member to cause the piston member to oscillate between its first and second positions and transfer the liquid outside the housing via a liquid outlet; a sealing member for isolating the trailing end of the drill bit from the liquid circuit wherein, in use, the piston member impacts the trailing end of the drill bit in a liquid free environment.
1. A liquid hammer drill configured for insertion into a cutter head of a tunnel boring machine comprising:
(a) a housing;
(b) a drill bit disposed at a leading end of the housing the drill bit including a trailing end and a leading end, the leading end defining a cutting portion;
(c) a piston member located inside the housing and having a trailing end and a leading end, the piston member configured to move between a first position and a second position, such that in the second position the leading end of the piston impacts the trailing end of the drill bit; wherein the trailing end of the drill bit defines a strike face for the piston member and the strike face comprises at least one liquid relief groove;
(d) a closed liquid circuit for delivering a liquid to the piston member within the housing to cause the piston member to oscillate between the first and second positions; and a sealing member for isolating the trailing end of the drill bit from the closed liquid circuit, such that the piston member impacts the trailing end of the drill bit in a liquid free environment.
2. The liquid hammer drill according to claim 1 , wherein the ratio of the length of the liquid hammer drill to its width is less than 6, 5.5, 5, 4.5, 4, 3.5, 3, 2.5 or 2.
3. The liquid hammer drill according to claim 1 , wherein the liquid is any one of water, salt water, petroleum and liquefied gas.
4. The liquid hammer drill according to claim 1 , wherein the drill bit has a reach of about 50, 60, 70, 80 or 90 mm.
5. The liquid hammer drill according to claim 1 , wherein the drill bit comprises at least one aperture to allow for expulsion of any fluid from inside the housing of the drill.
6. The liquid hammer drill according to claim 1 , wherein the piston member comprises a main body that narrows toward the leading end.
7. The liquid hammer drill according to claim 1 , the piston further comprising an intermediate portion between the leading end and the trailing end, wherein the intermediate portion of the piston member defines a shoulder.
8. The liquid hammer drill according to claim 1 , wherein the body of the piston member defines a cavity therein for receiving the liquid of the closed liquid circuit to move the piston member between the first and second positions.
9. The liquid hammer drill according to claim 1 , wherein the piston member has a travel distance between the first and second positions or stroke of about 20, 25, 30 or 35 mm.
10. The liquid hammer drill according to claim 1 , wherein the closed liquid circuit does not exhaust liquid via the drill bit.
11. The liquid hammer drill according to preceding claim 1 , wherein the closed liquid circuit comprises an inlet into the housing and an outlet from the housing to circulate the liquid of the closed liquid circuit within the housing to drive the piston.
12. The liquid hammer drill according to claim 1 , wherein the sealing member is located towards the leading end of the piston member.
13. The liquid hammer drill according to claim 1 , wherein the sealing member is located between the leading end of the piston member and the housing.
14. The liquid hammer drill according to claim 1 , wherein the sealing member is configured to prevent liquid in the closed liquid circuit from contacting the trailing end of the drill bit, to thereby maintain the liquid free environment.
15. The liquid hammer drill according to claim 1 , wherein the drill bit has a square shaped cross-section and the cutting portion located at the leading end of the drill bit is square.
16. The liquid hammer drill according to claim 1 , wherein the cutting portion supports a plurality of buttons.
17. The liquid hammer drill according to claim 1 , wherein a distance between the trailing end and the leading end of the drill bit is between 50-100 mm.