Abstract
A down the hole drilling assembly having a drill tube adapter, an elongate casing, a fluid powered piston, a top working chamber, a bottom working chamber, a top sub and an exhaust system, wherein the exhaust system is moveable with respect to the drill string. The top sub includes an exhaust valve arranged for opening and closing the connection between the at least one exhaust passage and the at least one exhaust port.
Claims
1. A down the hole drilling assembly having a top end arranged for coupling to a drill string and a bottom cutting end, the drilling assembly comprising: a drill tube adapter positioned at the top end of the assembly; an elongate casing; a drill bit at least partially accommodated within the bottom end of the casing; a fluid powered piston arranged moveably inside the casing to shuttle axially back and forth; a top working chamber at a top end side of the piston; a bottom working chamber at a bottom end side of the piston; a top sub including a retaining shoulder, a plurality of splines, at least one exhaust passage engaged with the casing, wherein the at least one exhaust passage is connected to the top chamber via at least one top vent passage; at least one flushing port at the bottom end of the casing and being connected to the at least one bottom vent passage arranged to vent the bottom chamber; and an exhaust system at the top end of the casing including an exhaust cover and at least one exhaust port arranged to vent the top chamber via the at least one exhaust passage, wherein the exhaust system is moveable with respect to the drill string and the top sub includes an exhaust valve arranged for opening and closing the connection between the at least one exhaust passage and the at least one exhaust port.
2. The down the hole drilling assembly according to claim 1, wherein the exhaust valve is positioned such that the connection between the at least one exhaust passage and the at least one exhaust port is open when the drilling assembly is in drilling mode.
3. The down the hole drilling assembly according to claim 1, wherein the exhaust valve is positioned such that the connection between the at least one exhaust passage and the at least one exhaust port is closed when the drilling assembly is in flushing mode.
4. The down the hole drilling assembly according to claim 1, further comprising an engaging feature, such as a spline connection, disposed between the exhaust cover and the top sub that allows the exhaust cover and top sub to slide longitudinally between a first position and a second position.
5. The down the hole drilling machine according to claim 1, further comprising at least one seal located on both sides of the at least one exhaust port.
6. The down the hole drilling machine according to claim 5, wherein the at least one seal comprises a minimum of 3 seals.
7. The down the hole drilling machine according to claim 1, further comprising a damping device positioned between the top sub and the drill tube adapter.
8. The down the hole drilling machine according to claim 1, wherein the top sub has a guidance feature.
9. The down the hole drilling machine, according to claim 1, further comprising a groove in the exhaust cover surrounding the at least one exhaust port.
10. The down the hole drilling machine according to claim 1, wherein the exhaust port is inclined at an angle of ?90? with respect to the longitudinal axis of the drilling assembly that is oriented towards the drill bit.
11. The down the hole drilling machine, according to claim 1, wherein the fluid is fed to and is discharged from the working chambers via a plurality of fluid passages that are formed between the inner surface of the casing and the outer surface of the control sleeve.
12. The down the hole drilling machine, according to claim 1, further comprising a check valve between the top chamber and the exhaust port.
13. A drilling apparatus for percussive rock drilling, the drilling apparatus comprising: a drill string formed from a plurality of end-to-end coupled drill tubes; and a drilling assembly as claimed in claim 1 releasably attached at an axially forward end of the drill string.
Description
BRIEF DESCRIPTION OF THE DRAWING
(1) A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:
(2) FIG. 1: shows a schematic drawing of a rock drilling rig provided with a DTH rock drilling assembly.
(3) FIG. 2: shows a schematic drawing of a DTH drilling assembly at the bottom of a drill hole.
(4) FIG. 3: shows a schematic drawing of a cross section of a DTH drilling assembly when in drilling mode.
(5) FIG. 4: shows a schematic drawing of a cross section of a DTH drilling assembly when in flushing mode.
(6) FIG. 5: shows an enlargement of the top end of the cross section of the DTH drilling assembly when in drilling mode.
(7) FIG. 6: shows an enlargement of the top end of the cross section of the DTH drilling assembly when in flushing mode.
(8) FIG. 7: shows an enlargement of the top end of the cross section of the DTH drilling assembly in drilling mode having a dampening device.
(9) FIG. 8: shows a schematic drawing of the top sub.
(10) FIG. 9: shows a schematic drawing of the exhaust cover.
(11) FIG. 10: shows a schematic drawing of seals surrounding the exhaust port in flushing mode.
(12) FIG. 11: shows a schematic drawing of seals surrounding the exhaust port in drilling mode.
DETAILED DESCRIPTION
(13) FIG. 1 shows a rock drilling rig 1 that comprises a movable carrier 2 provided with a drilling boom 3. The boom 3 is provided with a rock drilling unit 4 comprising a feed beam 5, a feed device 6 and a rotation unit 7. The rotation unit 7 may comprise a gear system and at least one rotating motor. The rotation unit 7 may be supported by a carriage 8 with which it is movably supported to the feed beam 5. The rotation unit 7 may be provided with drill string 9 which may comprise at least one drilling tube 10 connected to each other, and a DTH drilling assembly 11 at an outermost end of the drilling equipment 9. The DTH drilling assembly 11 is located in the drilled bore hole 12 during the drilling.
(14) FIG. 2 shows that the DTH drilling assembly 11 comprises an impact device (not shown). The DTH assembly 11 is cylindrical in shape and has a central axis 2. The impact device is at the opposite end of the drill string 9 in relation to the rotation unit 7. During drilling, a drill bit 14 is connected directly to the impact device, whereby percussions P generated by the impact device are transmitted to the drill bit 14. The drill bit 14 is at least partially accommodated within the bottom end 44 of the casing 15. The drill string 9 is rotating around its longitudinal axis in direction R by means of the rotation unit 7 shown in FIG. 1 and, at the same, the rotation unit 7 and the drill string 9 connected to it are fed with feed force F in the drilling direction A by means of the feed device 6. Then, the drill bit 14 breaks rock due to the effect of the rotation R, the feed force F and the percussion P. Pressurized fluid is fed from a pressure source PS to the drilling assembly 11 through the drilling tubes 10. The pressurized fluid may be compressed air and the pressure source PS may be a compressor. The pressurized fluid is directed to influence to working surfaces of a percussion piston 19 of the drilling assembly and to cause the piston 19 to move in a reciprocating manner and to strike against impact surface of the drill bit 14.
(15) FIG. 2 indicates a top end 42 or axially rearward end of the drilling assembly 11 and bottom end 44 or axially forward end of the drilling assembly.
(16) FIGS. 3 and 4 show a cross section of the drilling assembly 11 in drilling and flushing modes respectively. In these figures the drilling assembly 11 is shown to have a solid piston 19 design as described in more detail in patent application EP 3 409 878, it should however be understood that the exhaust assembly disclosed herein could be applied to any other type of DTH drilling assembly construction. The drilling assembly 11 comprises an elongate casing 15, which may be a relatively simple sleeve-like frame piece in the form of a substantially hollow cylinder. At a top end 42 of the casing 15 is mounted a top sub (or connection piece) 80 by means of which the drilling assembly 11 can be connected to a drill tube (not shown). The top sub 80 is at least partially accommodated within the top end 42 of the casing 15. The top sub 80 may comprise a threaded connecting surface 23. A drill tube adapter 16 comes above and around the top sub 80 and, the drill tube adapter 16 may also comprise a threated connection surface 17.
(17) The top sub 80 has an inlet port 18 for feeding pressurized fluid to an impact device 13. The drill tube adapter 16 comprises an air passage 34 (central bore in the drill tube adapter 16) that is connected to the air supply passage 26 of the top sub 80. The inlet port 18 may comprise a valve means 18a, which allows feeding of fluid towards the impact device but prevents flow in an opposite direction. FIG. 8 shows a schematic drawing of the top sub 80. At the top end 42 of the top sub 80 is a retaining shoulder 82 which extends axially outwards from the body of the top sub 80 and acts to retain the top sub 80 to an exhaust cover 46. In some embodiments the top sub 80 has a first bearing surface 84 towards the top end of the top sub 80, preferably positioned above the retaining shoulder 82 and a second bearing surface 86 positioned on the opposite side of the retaining shoulder 82 compared to the first bearing surface 84. The bearing surfaces 84, 86 are substantially cylindrical, the first bearing surface 84 has splines machined from the cylindrical surface. When combined the first and second bearing surfaces 84, 86 form a guidance feature which ensures that the exhaust valve remains correctly aligned so that it is able to either fully open or close the connection between the at least one exhaust passage and the at least one exhaust port when switching between drilling and flushing modes respectively. At least one exhaust passage 56 extends longitudinally through the top sub 80. The exhaust passage 56 connects to a top chamber 21 via at least one top vent passage 63 and then continues outwardly to engage with the exhaust cover 46. The top sub 80, moves with respect to the drill string 9, whereas the drill tube adapter 16 and exhaust cover 46 remain in a fixed position with respect to the drill string 9. The top sub 80 has a central bore 26 extending longitudinally through for the air supply to pass through. The top sub 80 further comprises at least one exhaust passage 56 which is located outside of the central bore and a valve 57 located on its periphery towards the exterior of the drilling assembly 11. The top sub 80 is threaded to the piston casing 15.
(18) The piston 19, which is substantially an elongated cylinder extends axially within the casing 15 and is capable of shuffling back and forth longitudinally through the DTH drilling assembly 11. At a bottom end 44 of the piston 19 is an impact surface ISA arranged to strike an impact surface ISB at a top end 42 of a drill bit 14. Optionally, the piston 19 is a solid-core piece, whereby it is without any through channels or openings in axial and transverse directions. At the top end 42 side of the piston 19 is the top working chamber 21 and at the opposite end side is a bottom working chamber 22. Movement of the piston 19 is configured to feed and discharge the working chambers 21, 22 and to thereby cause the piston 19 to move towards an impact direction A and return direction B.
(19) At the top end 42 of the drilling assembly 11 is an exhaust system 58 which comprises an exhaust cover 46 and at least one exhaust port 55. The exhaust cover 46 is engaged with the drill tube adapter 16 by a threaded connection. A retaining ring 25 is positioned between the exhaust cover 46 and the tube adapter 16 (shown on FIG. 6) to limit the axial movement of the top sub 80. The at least one exhaust port 55 extends radially through the exhaust cover 46. The at least one exhaust port 55 is open to the exterior of the drilling assembly 11. The exhaust cover 46 and the top sub 80 are connected in a way so that that are able to slide together and apart longitudinally using an engaging feature, for example this could be done by means of a plurality of splines 88 positioned on the top sub 80. This means that torque can be transmitted from the exhaust cover 46 to the top sub 80 from the spline connection (not shown on drawing) or alternative engaging system whilst axial movement is limited.
(20) The bottom chamber 22 is exhausted from the bottom end 44 of the drilling assembly through at least one flushing port 59 to remove cuttings from the drill bit face. The bottom chamber 22 is connected to the at least one flushing port 59 via at least one bottom vent passage 64. The top chamber 21 is fluidly connected to at least one top vent passage 63, which fluidly connects to the at least one exhaust passage 56 and then the top chamber 21 is exhausted through the at least one exhaust port 55 positioned in the exhaust cover 46.
(21) The at least one exhaust port 55 is able to open and close when switched between drilling mode and flushing mode. When the drilling assembly 11 is switched from drilling mode to flushing mode, the exhaust system 58 is moved forward relative to the drill string 9. The opening and closing of the at least one exhaust port 55 is enabled by the presence of at least one exhaust valve 57 positioned on the top sub 80. When the drilling assembly 11 is in drilling mode the exhaust system 58 is located next to the drill string 9 and so the exhaust valve 57 is positioned so that the exhaust ports 55 are open, in other words the at least one exhaust port is in fluid connection with the at least one exhaust passage 56. When the drilling assembly 11 is in flushing mode the exhaust system 58 is positioned forward of the drill string 9 and therefore the at least one exhaust valve 57 is positioned so that the at least one exhaust port 55 is closed. By closing the at least one exhaust port 55 when the drilling assembly 11 is in flushing mode all the air is directed through the drill bit which improves the effectiveness of the hole cleaning and prevents contamination of the hammer. The at least one exhaust ports 55 in the exhaust cover 46 are opened and closed to the exterior of the drilling assembly 11 by the at least one exhaust valve 57.
(22) FIG. 5 shows an enlargement of the top end 42 of the drilling assembly 11 when in drilling mode. In drilling mode, the at least one exhaust valve 57 is positioned so that the at least one exhaust passage 56 and the at least one exhaust port 55 are connected and so the pressurized fluid is exhausted to the exterior.
(23) FIG. 6 shows an enlargement of the top end 42 of the drilling assembly 11 when in flushing mode. In flushing mode, the at least one exhaust valve 57 is positioned so that the at least one exhaust port 55 is blocked off from the at least one exhaust passage 56. This means that all the flushing air is directed through the drill bit.
(24) FIG. 7 shows that optionally, a damping device 27 may be added between the top sub 80 and the drill tube adapter 16. The damping device 27 or element must be suitable for absorbing shock and vibration caused from the drilling operation and could for example be made from an elastic material such as polyurethane or rubber.
(25) FIGS. 10 and 11 show an enlargement of the interface between the exhaust cover 46 and the top sub 80 in flushing and drilling modes respectively wherein at least one seal 81,83,85 is positioned on both sides of the at least one exhaust port 55. Preferably the seals are scraper/washer seal type seals. In the example shown in FIGS. 9 and 10, three seals 81, 83, 85 are used. As shown in FIG. 10, when in flushing mode and the exhaust port 55 is closed the first seal 81 and the second seal 83 block off the sides of the exhaust port 55 and the second seal 83 and third seal 85 block off the sides of the exhaust passage 56 to prevent contamination from dirt and debris entering the drilling assembly 11. As shown in FIG. 11, when in drilling mode and the at least one exhaust port 55 is open, the first seal 81 and the second seal 83 block off the sides of the exhaust port 55 and exhaust passage 56 and in this position the third seal 85 is redundant.
(26) FIG. 9 shows the exhaust cover 46. Optionally, there is a groove 90 or indention in the exhaust cover surrounding the exit of the exhaust port 55. Preferably, the groove 90 extends beyond both sides of the exhaust port 55 and has a curved radius. Optionally, the angle of the exhaust port 55 is inclined at an angle of ?90? with respect to the longitudinal axis 2 of the drilling assembly 11 that is oriented towards the drill bit 14.
(27) Optionally, there is a check valve 65 between the top chamber 21 and the at least one exhaust port 55. Preferably, the check valve 65 is made from a deformable rubber or with a spring.
