Abstract
A down-the-hole drilling assembly activated by fluid under pressure includes a casing having an axially rearward and forward end, a piston arranged movably inside the casing, a plurality of fluid passages for feeding and discharging pressurized fluid into and out of a working chamber for generating reciprocating movement of the piston, a drill bit at the forward end and provided with an anvil facing towards the piston for receiving impacts therefrom and an annular drive sub surrounding at least a portion of a shank and cooperating with the bit to form fluid passages extending length-wise along the shank. The drive sub has a concave arcuate groove extending circumferentially to form a chamber for collecting fluid from the hammer exhaust and redistributing a volume of the collected fluid from channels formed between complimentary splines of the drive sub and splines of the bit to flushing holes arranged in the bit.
Claims
1. A down-the-hole drilling assembly activated by fluid under pressure, said assembly comprising: an elongate casing having an axially rearward end and an axially forward end; a fluid-powered piston arranged movably inside the casing; a top working chamber at a top side of the piston; a bottom working chamber at a bottom side of the piston; a plurality of fluid passages for feeding and discharging pressurized fluid into and out of the working chambers for generating reciprocating movement for the piston; a drill bit connectable to the axially forward end of the casing and provided with an anvil facing towards the piston for receiving impacts of the piston; an annular drive sub surrounding at least a portion of an elongate shank and cooperating with the drill bit to form fluid passages extending length-wise along the shank, wherein the drive sub includes a concave arcuate groove extending circumferentially in the drive sub and forming a chamber arranged for collecting fluid from hammer exhaust flow and redistributing a volume of the collected fluid from channels formed between a plurality of splines of the drive sub and a plurality of splines of the drill bit to flushing holes arranged in the drill bit.
2. The down-the-hole drilling assembly claimed in claim 1, wherein the fluid passage are created between an outer surface of the drill bit and an inner surface of the drive sub for collecting the fluid from the exhaust flow.
3. The down-the-hole drilling assembly claimed in claim 1, wherein the drill bit and the drive sub are configured to be arranged such that the drive sub is positionable to axially overlap and to radially encompass at least a part of the shank of the drill bit.
4. The down-the-hole drilling assembly claimed in claim 1, wherein the drive sub plurality of splines are arranged for engaging with the plurality of complimentary splines on the shank of the drill bit for transferring the torque from the sub to the drill bit.
5. The down-the-hole drilling assembly claimed in claim 1, wherein the drill bit includes a bit head with the elongated shank connected to the head and a head-shank transition area wherein the head connects to the shank in such a way that an angle formed between the head and the shank at the head-shank transition area is greater than 100 degrees.
6. The down-the-hole drilling assembly claimed in claim 5, wherein the angle formed between the head and the shank at the head-shank transition area of the drill bit is greater than 100 degrees and smaller than 160 degrees.
7. The down-the-hole drilling assembly claimed in claim 5, wherein the angle formed between the head and the shank at the head-shank transition area of the drill bit is greater than 110 degrees and smaller than 130 degrees.
8. The down-the-hole drilling assembly claimed in claim 1, wherein an outer surface of the head-shank transition area of the rock drill bit has a recess which is positioned proximally to openings of the flushing holes.
9. The down-the-hole drilling assembly claimed in claim 1, wherein the bit head and the shank of the bit are constructed as a single integrated unit.
10. The down-the-hole drilling assembly claimed in claim 1, wherein an internal bore at a center of the bit is closed at the forward end of the shank and open at the rear end of the shank towards the piston and wherein the internal bore is configured to constitute a part of the bottom working chamber of the assembly.
11. The down-the-hole drilling assembly claimed in claim 1, wherein the drive sub includes a plurality of peripheral projections on its top edge creating radially spaced slots, which extend through a radial thickness of a wall of the drive sub.
12. The down-the-hole drilling assembly claimed in claim 1, wherein the drive sub includes a bottom edge having an angle corresponding to the angle of the bit head transition area, said bottom edge being positionable over the bit head transition area.
13. The down-the-hole drilling assembly claimed in claim 1, wherein the drill bit is a reverse-circulation drill bit having the drilling cuttings flowing upstream and passing through a center of the drill bit, said drill bit including the shank attached to the head of the bit, said shank being at least partially surrounded by the annular drive sub having an arcuate concave groove extending circumferentially in the drive sub, which creates the chamber for accumulating the volume from the hammer exhaust.
14. The down-the-hole drilling assembly claimed in claim 13 wherein the reverse circulation drill bit includes a bit head having a plurality of flushing holes positioned between the center and a periphery of the bit head extending from the forward face of the bit to the bit head-shank transition area creating passages for the fluid from the exhaust of the hammer.
15. The down-the-hole drilling assembly claimed in claim 13 wherein the reverse circulation drill bit includes a bit head, wherein the flushing holes comprise a plurality of radially spaced flushing holes positioned at a periphery of the bit head extending from the forward face of the bit to the bit head-shank transition area and creating passages for the fluid from the exhaust of the hammer.
Description
BRIEF DESCRIPTION OF FIGURES
[0028] Some embodiments of the invention will be explained in greater detail with reference to the accompanying drawings in which:
[0029] FIG. 1 shows schematically a rock drilling rig provided with a DTH rock drilling machine;
[0030] FIG. 2 shows schematically a DTH drilling machine at the bottom of a drill hole;
[0031] FIG. 3 shows a perspective view of a known rock drill bit assembly with the drive sub covering a portion of the shank;
[0032] FIG. 4 shows a vertical cross section of a hammer according to a specific implementation of the present disclosure;
[0033] FIG. 5a shows a side view of the drill bit of FIG. 4. FIG. 5b shows a vertical cross sectional view of the drill bit with drive sub covering the shank portion of FIG. 5a.
[0034] FIGS. 5c, 5d and 5e show the cross sectional views taken from different cross sections of FIG. 5a, D-D, E-E, F-F, respectively;
[0035] FIG. 6a is a partial cut-away perspective view of the drill bit assembly of FIG. 4, and FIG. 6b is a cut-away view of the drive sub highlighting the concave groove;
[0036] FIG. 7a is a perspective view of an example of an RC bit assembly according to a further specific implementation, and FIGS. 7b, 7c and 7d show the cross sectional views taken from different cross sections of FIG. 7a, D-D, E-E, F-F, respectively;
[0037] FIG. 7e is a vertical cross-section of the RC bit assembly of FIG. 7a;
[0038] FIG. 8a is a perspective view of an example of RC bit assembly according to a further specific implementation, and FIGS. 8b, 8c and 8d show the cross sectional views taken from different cross sections of FIG. 8a, D-D, E-E, F-F, respectively;
[0039] FIG. 8e is a vertical cross-section of the RC bit assembly of FIG. 8a.
DETAILED DESCRIPTION OF FIGURES
[0040] The present disclosure will now be described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
[0041] 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 one or more rotating motors. The rotation unit 7 may be supported to a carriage 8 with which it is movably supported to the feed beam 5. The rotation unit 7 may be provided with drilling equipment 9 which may comprise one or more drilling tubes 10 connected to each other, and a DTH drilling machine 11 at an outermost end of the drilling equipment 9. The DTH drilling machine or hammer 11 is located in the drilled bore hole 12 during the drilling.
[0042] FIG. 2 shows that the hammer 11 comprises an impact device or a piston 13 (shown in FIG. 4). The piston 13 is at the opposite end of the drilling equipment 9 in relation to the rotation unit 7. During drilling, a drill bit 14 is connected directly to the piston 13, whereby percussions P generated by the piston 13 are transmitted to the drill bit 14. The drilling equipment 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 drilling equipment 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 machine 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 the piston 13 and to cause the piston 13 to move in a reciprocating manner and to strike against impact surface or anvil 26 of the drill bit 14. After being utilized in working cycle of the hammer 11, pressurized air is allowed to discharge form the hammer 11 and to thereby provide flushing for the drill bit 14. Further, the discharged air pushes drilled rock material out of the drill hole 12 in an annular space between the drill hole and the drilling equipment 9. Alternatively, the drilling cuttings are removed from a drilling face inside a central inner tube passing through the impact device. This method is called reverse circulation drilling. FIG. 2 indicates by an arrow TE an upper end or top end or the axially rearward of the hammer 11 and by an arrow BE a lower end or bottom end or the axially forward end of the hammer 11.
[0043] Referring to FIG. 3, a standard drill bit 14 can be seen. Drill bit head 20 comprises of a plurality of peripheral sludge grooves 39 which are recessed radially into an annular outer wall 38 of the bit head 20. Foot valve 34 can also be observed in the FIG. 3. Foot valve is used to control the air cycle of the hammer and, the venting and closing of the bottom working chamber 28.
[0044] Referring to FIG. 4, the vertical cross-section of the hammer 11 is shown, 29 being the longitudinal axis of the hammer 11. The hammer 11 comprises a casing 15 with an axially rearward end 15a and an axially forward end 15b. Within the casing 15 is mounted a conventional free piston 13 which is arranged to be moved in a reciprocating manner during its work cycle. A top sub 16 is at least partially accommodated within the rearward end 15a of the casing 15. Also mounted, is a connection piece 31 by means of which the hammer 11 is connected to the drilling tube 10. The connection piece 31 may comprise threaded connecting surface 30. In connection with the connection piece 31, is an inlet port 32 for feeding pressurized fluid to the piston. The inlet port 32 may comprise valves which allow the feeding of the fluid towards the piston but prevent the flow of the fluid in the opposite direction. At the axially rearward end of the piston is a top working chamber 27 and at the axially forward end of the piston is the bottom working chamber 28. A distributor cylinder 33 extends axially within the casing 15 against the inner face 45 of the casing 15 and defines an axially extending internal chamber which includes the top working chamber 27 and the bottom working chamber 28. Piston 13 is capable of reciprocating axially to shuttle within the chamber regions 27 and 28. Also visible in the FIG. 4, are fluid passages 52 for feeding and discharging pressurized fluid into and out of the working chambers 27, 28 for generating reciprocating movement for the piston 13. The drill bit 14 is positioned at the axially forward end of the hammer 11. The bit 14 comprises a rearward face 26 which represents the anvil on which the piston 13 impacts to cause the bit 14 to move forward. It also comprises a bit head 20 and a shank 17 with a central internal bore 19 which is closed at the forward end. Flushing holes 24 extend axially rearward from the forward face 22 of the bit. Inserts or buttons 23 are provided on the forward face 22 of the bit for cutting the drilling surface. A drive sub 18 surrounds at least a part of the shank 17 extending axially from the rearward face of the bit 26 to the bit head-shank transition area. Bit retaining ring 37 is also visible in the FIG. 4.
[0045] Referring to FIG. 5a, the projected view of the drill bit 14 surrounded by the drive sub 18 is shown. Cross-sections have been taken from three different points on the drill bit 14, one being near the top end or the axially rearward end of the drive sub 18 (D-D), one near the bottom end or the axially forward end of the drive sub 18 (F-F) and one in the middle of the drive sub 18 (E-E). Cross section D-D is shown in FIG. 5c where the splines 42 on the bit can be seen engaging with the corresponding splines 43 on the drive sub 18 forming channels 48. The exhaust fluid from the hammer flows through the channels 48 which are formed between the splines 42 and 43.
[0046] Referring to FIG. 5d, cross section E-E shows the chamber 21 which is formed due to the arcuate concave groove in the drive sub 18. The upstream exhaust from the hammer flows from the splines 42, 43 and then enters the flushing holes 24. But since the number of holes and splines is different, a volume of the fluid gets accumulated in the chamber 21 before making the transition in the numbers of the fluid paths, from splines to the holes. Cross section F-F in FIG. 5e shows the bit head 20 and the flushing holes 24 from which the exhaust fluid enters the bit 14.
[0047] As is clear from FIG. 5b, the drive sub 18 extends axially from the narrow upper end 17a of the shank to the bit head-shank transition area 40. The arcuate recess in the form of a concave groove in the drive sub 18 forms a chamber 21 which accumulates volume of pressurized fluid coming from the exhaust of the hammer 11 during the drilling operation. The drill bit 14 has an obtuse angle in the bit head-shank transition area 40, shown as a on FIG. 5b. The angle is preferably between 100 and 160 degrees. More preferably, the angle may be between 110 and 130 degrees. Recess 25 in the bit head-shank transition area 40 near the flushing holes 24, is provided to reduce the stress generated in the bit head-shank transition area 40 during the drilling operation.
[0048] Referring to FIG. 6a, a partial cut-away view of the drive sub 18 surrounding the shank 17 of the drill bit 14 can be observed. FIGS. 6b shows the partially cut-away drive sub 18 alone without the drill bit 14. Drive sub 18 is provided with a plurality of peripheral projections 41 which create radially spaced slots 46 which enable the upstream flow of the pressurized fluid from the hammer exhaust to be evenly distributed between the bit splines 42 and the splines 43 on the drive sub while maintaining lubrication between the splines 42 and 43. The slots 46 extend through the radial thickness or the wall of the drive sub 18. The drill bit 14 is provided with concave arcuate recesses 25 in the bit head-shank transition area 40 to help with reducing the stress that is generated in this area during the drilling operation.
[0049] Complimentary splines 42 (on the drill bit 14) and 43 (on the drive sub 18) are also shown in the FIG. 6a. Referring to FIG. 6b, the bottom edge 44 of the drive sub 18 has an angle corresponding to the bit head-shank transition angle of the drill bit 14 such that the bottom edge 44 of the drive sub 18 is mated against the bit head transition area 40. This angled construction of the bottom edge 44 of the drive sub 18 provides a conical surface which facilitates accurate positioning of the drill bit 14 relating to the drive sub 18 and an increased contact area which in turn reduces the surface pressure or stress in the bit head-shank transition area 40.
[0050] The different aspects of the disclosure are also applicable to reverse circulation hammers and the bits used therein. Referring to FIG. 7a, a projected view of a reverse circulation drill bit is shown. Cross sections at three points in the drill bit 14 have been depicted in FIGS. 7b, 7c and 7d. The bit shown in FIGS. 7a-7e is provided with a central internal bore 19 through which the pressurized fluid along with cuttings or drilled material flows upstream. Also provided in the RC bit 14 are flushing holes 24, drive sub 18 with concave groove forming chamber 21, shank 17 and bit head 20 with buttons 23 on the forward face 22. Referring to FIG. 7b, the drive sub 18 is seen surrounding the shank 17 of the bit 14 in the cross-section D-D. The flushing holes 24 and the splines 42 are visible in cross section E-E in FIG. 7c. The chamber 21 collects the upstream exhaust of pressurized fluid from channels 48 formed between the splines 42 and 43 and redistributes it to the flushing holes 24. Cross section F-F taken from the bit head 20 shows the passageways from flushing holes 24 and the central internal bore 19 as seen in FIG. 7d.
[0051] Referring to FIG. 7e, a vertical cross-section of the drill bit 14 used for reverse circulation hammer is shown. The bit 14 has a longitudinal axis 29, bit head 20, shank 17, buttons 23, forward face 22 and rearward face 26. Also provided in the bit 14, is a drive sub 18 surrounding a portion of the shank 17 and extending up to the bit head-shank transition area 40. An internal central bore 19 extends through the length of the bit 14 and is used for the upward passage of the pressurized fluid and the drilled material during the drilling operation. The bit head 20 is provided with a plurality of flushing holes 24 which are positioned between the centre and the periphery of the bit head 20.
[0052] Similarly, FIGS. 8a-8e depict a reverse circulation drill bit 14 in which the flushing holes 24 are positioned at the periphery of the bit head 20.
