KR20080038309A - A drill bit assembly for fluid-operated percussion drill tools - Google Patents

Abstract

The invention relates to a drill bit assembly for fluid-operated percussion drill tools comprising a percussion bit (1) having a head portion (3) formed with an axially extending stub shank (32). The stub shank is provided with axially extending splines (36), which are slideably engageable with complementary splines (35) formed on a drive chuck (4). Rotational drive from the chuck (4) may be transmitted to the stub shank (32) by means of the splines. Bit retaining means (6, 7, 41, 42) at the chuck are adapted for engagement with complementary retaining means (37, 51) at a spline portion of the stub shank to retain the stub shank in the drill bit assembly. Engagement means on the chuck (4) are adapted for connecting the chuck (4) to a drive means (5) of the fluid-operated percussion drill tool. The invention also relates to a down-the-hole hammer comprising an external cylindrical outer wear sleeve (5), a sliding piston (8) mounted for reciprocating movement within the outer wear sleeve (5) to strike a percussion bit (1) of a drill bit assembly located at the forward end of the outer wear sleeve (5) wherein the drill bit assembly is an assembly as described above.

Description

Drill bit assembly for fluid actuated impact drill tools {A DRILL BIT ASSEMBLY FOR FLUID-OPERATED PERCUSSION DRILL TOOLS}

The present invention relates to a drill bit assembly for a fluid actuated impact drill tool, and more particularly to a drill bit assembly for use in a down-the-hole hammer.

Some designs of conventional DTH hammers and fluid actuated impact drill tools include an outer cylinder or outer wear sleeve mounted therein with an inner cylinder that engages a backhead assembly. The sliding reciprocating piston interacts with the inner cylinder and the backhead assembly and is actuated by the impact effect on the drill bit held in the chuck on the outer sleeve when compressed air is supplied to the backhead assembly.

In general, the inner cylinder is coaxially mounted inside the outer sleeve. The sliding piston is mounted in a known manner to reciprocate inside the inner cylinder and the outer sleeve to strike a hammer bit mounted for sliding movement in a chuck located at the front end of the outer sleeve. Above the bit is a foot valve.

Applicant's prior patent application WO2004 / 013530 discloses a DTH hammer having an elongated shank portion having an annular striking surface (or anvil) at its upper end for impacting a bit. It is described. The lower end of the bit shank is formed on the outside with a plurality of splines that are spaced about the outer circumference of the bit shank and extend in the axial direction. The chuck is screwed into the bottom of the outer sleeve. The bit is held in the hammer assembly by a bit retaining ring seated over the chuck and interacting with the annular shoulder on the bit. This prevents the bit from deviating from the assembly during operation.

In operation, the bit shank is forced due to the impact action of the hammer and the rotational torque provided by the chuck. This imparts a significant bending moment on top of the bit shank, increasing the risk of breakage of the shank due to cracking. When the drill bit is lost by falling into the drilled hole, the manufacturing cost and the recovery cost are very large. Thus, the fact that several patents have been filed for the means of retaining broken bits in the bit assembly to prevent them from falling into the drilled hole proves that the drill bits of conventional DTH hammers have significant problems. These patents are for example US Pat. No. 5,065,827, US 4,003,442, WO 96/15349, WO 98/05476, WO 03/062585, WO 03/062586.

However, the invention described in these patents solves a problem that occurs after the bit shaft is broken, but does not prevent damage in advance.

Conventional impact drill tools, such as DTH hammers, are bits with long shanks that are expensive to manufacture. The long shank portion is necessary to provide a spline shank of sufficient length to provide sufficient support for the transmission of the rotational torque, and an area on the spline for the retention of the bit. In the conventional hammers, when the bit head or the cutting surface is worn, the shank is in a good state, but since it is made integral with the cutting surface, it is often necessary to discard it. Early wear of the head / cutting surface may occur when perforation is performed in a very abrasive rock or when tungsten carbide coated material is inserted into the cutting head. Most conventional hammers require a foot valve to be provided on the bit. The foot valve is needed as an integrated part of the function of the hammer. That is, when the piston is in the striking position, the bottom lift chamber is sealed by the bore of the piston and the outside of the foot valve. If this is not the case, the piston will not be raised. Foot valves often break and lead to downtime.

It is an object of the present invention to provide a bit mounting system for a DTH hammer, or other fluid operated impact drill tool, which avoids several of the disadvantages of the prior art system described above. It is also an object of the present invention to provide a bit system in which the length of the shank is shorter than conventional drill shanks. It is also an object of the present invention to provide an improved coupling means for the bit assembly.

In a first aspect, a drill bit assembly for a fluid actuated impact drill tool provided in accordance with the present invention can be slidably coupled with a complementary spline formed in a drive chuck so that a rotary drive from the chuck can be transmitted. an axially extending spline on a stub shank, bit retaining means provided in the chuck to engage with complementary retaining means at the splined portion of the stub shank to retain the stub shank in the drill bit assembly, and the fluid actuation Coupling means provided on the chuck to couple the chuck to a drive means of an impact impact drill tool.

Preferably, the drive chuck is formed with screw threads adapted to engage complementary screw threads on the lower end of the outer sleeve of the drill tool. The axially extending spline is formed in the outer cylindrical wall of the stub shaft and engages with a complementary spline formed inside the drive chuck.

The bit retaining means comprise at least one, preferably a plurality of holes, and corresponding bit retaining pieces, which penetrate the walls of the drive chuck, so that the bit assembly is assembled when the bit assembly is assembled. A bit retaining piece is received in the hole and engages with the complementary retaining means at the splined portion of the stub shank so that the stub shank is retained in the drill bit assembly.

According to a first embodiment of the invention, the hole is formed as a partially annular slot through the wall of the drive chuck, the bit retaining piece is in the shape of a partial annulus, and the complementary retaining means is an upper end of the stub shank. And the partial annular bit retaining piece is received in the partial annular slot and engages with the lower side of the annular shoulder when the bit assembly is assembled so that the stub shank is retained in the drill bit assembly.

According to another embodiment, the aperture is formed as a substantially circular opening through the aperture of the drive chuck, the bit retaining piece being a ball nose pin, and the complementary retaining means of the stub shank. And a plurality of recesses formed in the upper end, such that when the bit assembly is assembled, the ball nose pin is received in the circular opening and engages with the upper inner wall of the recess so that the stub shank is connected to the drill bit assembly. To be maintained.

In one embodiment, one or more recesses at the top of the stub shank are fully formed in the spline on the stub shank. Preferably, each recess is completely formed in one of the splines on the stub shank.

In another aspect, a DTH hammer provided in accordance with the present invention is a sliding mounted to reciprocate within the outer sleeve to strike an outer cylindrical outer sleeve and an impact bit of a drill bit assembly located at the front end of the outer sleeve. A piston, the drill bit assembly as described above.

The hammer can be a conventional DTH hammer or a reverse circulation DTH hammer.

The drill bit assembly of the present invention has a number of advantages over conventional systems. Since the means for holding the bit inside the chuck has moved to the spline portion of the stub shank, the present invention can shorten the length of the shank. In addition, splined support for the transmission of the rotational torque is provided on both the upper and lower sides of the bit holding means. The complementary retaining means comprise a plurality of recesses, each recess being completely formed in one of the splines on the stub shank, and a spline support for the transmission of rotational torque provided over the length of the spline.

Shorter stub shafts are less expensive to manufacture than bit heads with elongated shafts. The stub shank is less short than the bending force due to its short length and therefore less bending problems that occur in the long shank used in conventional impact drill tools. Likewise, with hand hammers, long nails are much more flexible than short nails. As a result, short shanks are stronger than conventional bit shanks.

Another advantage is that it is much cheaper to replace the worn bit compared to a conventional drill bit assembly with an elongated shaft attached to the bit head. Short stub shanks require substantially less material than conventional elongated bit shanks. In addition, in the assembly of the present invention, the bit need not have a foot valve. In the present invention, the interaction of the piston with the foot valve of the prior art can be replaced by the nose of the piston 8 which seals the bore of the bushing 2. Nevertheless, the use of a foot valve is optional.

1 is a side cross-sectional view of a DTH hammer according to a first embodiment of the present invention, showing that the piston is in a position out of the bottom.

2 is a side cross-sectional view of the DTH hammer according to the first embodiment of the present invention, showing that the piston is in the striking position.

3 is a side cross-sectional view of the DTH hammer according to the first embodiment of the present invention, showing that the piston is in the top dead center position.

4 is an exploded perspective view of the bit coupling system of the present invention.

5 is an enlarged side cross-sectional view of the lower part of FIG. 2.

6 is an exploded perspective view of a second embodiment of the present invention.

7 is an enlarged side view of the lower portion of the DTH hammer according to the second embodiment of the present invention, showing that the piston is in a position out of the bottom.

FIG. 8 is an enlarged cross-sectional view of the lower part of the DTH hammer of FIG. 7, illustrating the piston in the striking position. FIG.

9 is an exploded perspective view of the third embodiment of the present invention.

10 is a side cross-sectional view of the lower portion of the DTH hammer according to the third embodiment of the present invention, showing that the piston is in the striking position.

FIG. 11 is a cross-sectional view taken along the line X-X of the DTH hammer of FIG. 10.

12 is a side cross-sectional view of the reverse circulation DTH hammer in accordance with the present invention, showing that the piston is in a position off the bottom.

FIG. 13 is a side cross-sectional view of the reverse circulation DTH hammer of FIG. 12 showing the piston in the striking position.

FIG. 14 is a side cross-sectional view of the reverse circulation DTH hammer in FIG. 12 showing the piston in top dead center position; FIG.

Hereinafter, two embodiments of a DTH hammer having a bit coupling system according to the present invention will be described with reference to the accompanying drawings.

Referring to the drawings, one embodiment of the DTH hammer of the present invention includes an outer cylindrical outer sleeve 5. The inner cylinder 25 is coaxially mounted inside the outer sleeve 5. The sliding piston 8 is mounted to reciprocate in the inner cylinder and the shell sleeve 5 to strike the hammer bit 1 located at the front end of the shell sleeve 5 to exert an impact on the drill bit. Rotational force is transmitted by the chuck 4 from the rotating outer sleeve 5. The outer sleeve is threadedly connected to a drill string which is connected to a rotating motor on a drilling rig on the ground.

4 and 5, the head portion 3 of the bit assembly comprises an impact bit 1 with a tungsten carbide insert 31 in a known manner. The stub shank 32 extending in the axial direction is formed in the bit head part 3. The stub shank 32 is formed with a spline portion including a lower annular shoulder portion 33, an upper annular shoulder portion 37, and an intermediate portion 50. The upper and lower annular shoulder portions 33, 37 have a plurality of axially extending splines 36. The intermediate portion 50 does not have a spline. Rotational torque is applied to the bit head 3 via the chuck 4. The hollow cylindrical chuck 4 has a plurality of axially extending inner sides which are machined on the inner side and engage the spline 36 of the shank 32 to transmit rotational drive to the inner wall and from the chuck 4 to the drill bit. It has a spline 35.

The inner thread is formed in the upper part of the chuck 4. The chuck 4 also has an outer annular shoulder 38 which acts as a stop when the chuck 4 is screwed into the outer sleeve 5 as described below. Above the shoulder 38 a plurality of partially annular slots 7 are cut or machined through the walls of the chuck 4 to receive the partially annular retaining pieces 6. In the assembled bit assembly, the bit retaining piece 6 is engaged with the lower side of the annular shoulder 37 formed at the top of the shank to hold the stub shank to the drill bit assembly. The chuck 4 is screwed into the lower end of the outer sleeve 5, thereby retaining the bit retaining piece 6 in the slot 7. In addition, the chuck 4 is screw-threaded with the sheath sleeve 5 such that rotational torque can be transmitted from the sheath sleeve 5 through the chuck 4 to the bit 1.

The reciprocating piston 8 is mounted for reciprocating motion inside the inner cylinder 25 and the outer sleeve 5 to strike the upper surface of the shoulder 37 to exert an impact on the bit. The spline 35 of the chuck 4 is slidably engaged with the complementary spline 36 of the shank 32 such that the head 3 moves axially with respect to the chuck upon impact.

6 to 8 show another embodiment of the present invention. As mentioned above, the head part 3 of the bit assembly comprises an impact bit 1 with a tungsten carbide insert 31 in a known manner. The stub shank 32 extending in the axial direction is formed in the bit head part 3. The stub shank 32 has a plurality of axially extending splines 36 and a plurality of axially extending recesses or milling 47. An upper inner wall or a shoulder 51 is formed in the recess 47. Rotational torque is applied to the bit head 3 via the chuck 4. The hollow cylindrical chuck 4 has a plurality of axially extending inner sides which are machined on the inner side and engage the spline 36 of the shank 32 to transmit rotational drive to the inner wall and from the chuck 4 to the drill bit. It has a spline 35.

Above the shoulder 38 a plurality of circular openings 42 are cut or machined through the walls of the chuck 4 to receive the ball nose pins 41. In the assembled bit assembly, the ball nose pin 41 is engaged with the upper inner wall or shoulder 51 of the recess or mill 47 formed in the upper end of the shank to hold the stub shank in the drill bit assembly. The chuck 4 is screwed into the lower end of the outer sleeve 5, thereby retaining the ball nose pin 41 in the opening 42. In addition, the chuck 4 is screw-threaded with the sheath sleeve 5 such that rotational torque can be transmitted from the sheath sleeve 5 through the chuck 4 to the bit 1.

9 to 11 show another embodiment of the present invention. In this embodiment, the stub shank 32 comprises a spline 36 in which a plurality of axially extending splines 36 and a plurality of axially extending recesses or milling 47 are formed. Each recess 47 is entirely formed in each spline 36 on the stub shank 32. In the embodiment shown in Figures 9-11, each spline 36 has one recess 47 formed therein. However, in alternative embodiments, not all splines are recessed. As described above with reference to FIGS. 6-8, a ball nose pin 41 is used to hold the stub shank to the drill bit assembly.

In an embodiment of the present invention having a nominal 4 inch hammer that drills holes larger than 10 cm in size, the stub shank 32 has a length of 90 mm to 140 mm, preferably 130 mm. In contrast, the elongated shanks of conventional DTH hammers of similar perforation size generally have a length of 200 mm to 260 mm. According to the present invention, the length of the shank 32 can be shortened to about 30% to 50% of the shaft length of a conventional DTH hammer.

The hammer cycle is as shown in FIGS. 1-3 and 7 and 8. 1 and 7 show that the hammer is in an off-bottom position. The piston 8 is flushed with exhaust air through a bore 9 and a bore 10 of the bit 1 to a face flushing hole 11. 2, 5 and 8 show that the hammer is in the striking position. Bushing 2 is provided to the drill assembly in position in the foot valve to interact with the piston nose 20. Compressed air is supplied to the pressure chamber 12 below the chamber 13 through the piston groove 14 and the outer sleeve undercut 15. This air is surrounded by the piston nose 20 micro bushing 2. At the same time, the upper chamber 16 is opened to be discharged through the bores 9, 10, 11. As a result, the piston 8 is pulled up. 3 shows that the piston 8 is at top dead center. Since the piston nose 20 is not in contact with the bushing 2, the lift chamber 12 is opened to discharge through the bushing 2 and the bores 10, 11. The upper chamber 16 is supplied with compressed air through the port 19 and the channel 17. The chamber 16 is sealed by a distributor probe 18. As a result, the piston is forcedly lowered to hit the beat and the cycle is repeated.

The apparatus of the present invention has the advantage of facilitating the assembly of parts of a drill bit system. The parts can be assembled by sliding the spline 36 of the stub shank 32 into engagement with the spline 35 of the chuck 40 from above and allowing the shank to fit inside the chuck 4.

To simplify the description, the drill bit assembly of the present invention has been described in connection with a conventional DTH hammer. However, the present invention is equally applicable to the reverse-circulation DTH hammer as described below with reference to FIGS. 12 to 14.

In a recirculation system, rock cuts and debris are forced up to the ground surface through the hollow tube or sample tube of the drill itself from the bottom of the hole by the action of pressurized recirculation puncture fluid. The puncturing fluid is circulated below the annular space inside the drill string. The advantage of the recirculation technique is that the rock form is continuously sampled as the perforation progresses and representative samples can be retrieved and monitored from the ground surface as the sample is quickly retrieved from the bottom of the hole.

The reverse circulation DTH hammer of the present invention includes an outer cylindrical shell sleeve 105. The inner cylinder 125 is coaxially mounted in the outer sleeve 105. The sliding piston 108 is mounted for reciprocating motion in the inner cylinder and jacket sleeve 105 to strike the hammer bit 101 located at the front end of the jacket sleeve 105 to impact the drill bit. . The inner diameter of the sheath sleeve 105 is of a size such that an annular gap 170 can be provided between the sheath sleeve 105 and the inner cylinder 105.

According to the invention, the drill bit 101 is formed with a stub shank 132 extending in the axial direction. The stub shank 132 is formed with a spline portion provided with a plurality of axially extending splines 136. The hollow cylindrical chuck 104 has a plurality of axially extending inner sides that are machined on the inner side and engage the spline 136 of the shank 132 to transmit rotational drive to the inner wall and from the chuck 104 to the drill bit. A spline 135 is provided. Splines 135 and 136 are sized to provide a plurality of fluid passages 171 around drill bit 101. The bit 101 may be held at the chuck 104 using any of the devices described above in connection with a conventional hammer, ie a partially annular retaining piece or ball nose pin.

FIG. 13 shows that the hammer is in the striking position, where the piston nose 120 is in contact with the drill bit 101. At the start of the ascending or returning stroke of the piston 108, the chamber 116 is in direct communication with the passage 171 through an annular gap around the central sample tube 178 to allow any compressed air to exit. When compressed air is supplied from the annular gap 170 through the inner cylinder port 179, the annular gap 180, the piston groove 173, and the outer sleeve undercut 174, the chamber 176 is pressurized to form a piston 108. The lift force is applied to). As a result, the piston 108 is raised.

The upward movement continues until the piston nose 120 has released contact with the bushing 102. 14 shows the piston 108 at top dead center. The pressurized fluid in chamber 176 is now discharged through annular passage 171 to groove 175 and through passage 177 of bit head 103. Most of the discharged fluid enters the puncturing space and is flushed through the return bores 111, 110, 109 to the surface recovery device. The chamber 116 is supplied with compressed air through the port 179, the annular gap 180, and the groove 117. The annular gap 172 is also surrounded by an enlarged diameter 181 on the piston 108 and the sample tube 178. As a result, the piston is forcibly lowered to hit the beat and the cycle is repeated.

As used herein, the terms “comprise / include” and “having / comprising” are used to specify features, steps, or parts of the invention, but one or more other features, steps, parts, and the like It does not exclude the presence or addition of groups.

As described above, it is apparent that various changes and modifications can be made within the spirit and scope of the novelty of the present invention. It is to be understood that this specification is intended to illustrate the invention by way of example and not to limit it to specific embodiments. It is intended that the specification cover all modifications that come within the scope of the claims.

The technical features are set forth in the claims together with the reference numerals, which are for the purpose of increasing the clarity of the claims, and thus these reference numerals have no effect of limiting the scope of each element.

Claims (11)

In a drill bit assembly for a fluid operated impact drill tool, An impact bit (1) having a head portion (3) on which a stub shank (32) extending in the axial direction is formed, A plurality of axially extending portions on the stub shank 32, which can be slidably coupled with the complementary splines 35 formed in the drive chuck 4, to which a rotational drive from the chuck 4 can be transmitted. Spline (36), Bit retaining means (6, 7, 41, 42) provided on the chuck to engage with complementary retaining means (37, 51) at the spline portion of the stub shank to retain the stub shank in the drill bit assembly, and Coupling means provided on the chuck 4 to connect the chuck 4 to a drive means 5 of the fluid actuated impact drill tool. Including, a drill bit assembly. The method of claim 1, The drive chuck 4 is formed with screw threads adapted to engage complementary screw threads on the lower end of the outer sleeve 5 of the drill tool, the axially extending spline 36 being the stub shank. A drill bit assembly, formed on an outer cylindrical wall of the 32 and coupled with a complementary spline (35) formed inside of the drive chuck (4). The method according to claim 1 or 2, The bit retaining means comprises at least one, preferably a plurality of holes (7, 42) and a plurality of corresponding bit retaining pieces (6, 41) penetrating the walls of the drive chuck (4). The bit retaining pieces 6, 41 are received in the holes 7, 42 when the bit assembly is assembled and the complementary retaining means 37, 51 at the spline of the stub shank. And the stub shank is retained in the drill bit assembly in combination with the drill bit assembly. The method of claim 3, The hole is formed as a partially annular slot 7 penetrating the wall of the drive chuck, the bit retaining piece 6 is in the shape of a partial annulus and the complementary retaining means comprises an annular shoulder 37 When the bit assembly is assembled, the partially annular bit retaining piece 6 is received in the partially annular slot 7 and engages with the lower side of the annular shoulder 37 so that the stub shank is connected to the drill bit. Drill bit assembly, retained in the assembly. The method of claim 3, The hole is formed as a substantially circular opening 42 penetrating the hole of the drive chuck, the bit retaining piece being a ball nose pin 41 and the complementary retaining means of the stub shank. Including a plurality of recesses 47 formed in the upper end, the ball nose pin 41 is accommodated in the circular opening 42 when the bit assembly is assembled and the upper inner wall of the recess 47 In combination with (51) such that the stub shank is retained in the drill bit assembly. The method of claim 5, One or more recesses (47) of the plurality of recesses (47) at the top of the stub shank are fully formed in the spline (36) on the stub shank (32). The method of claim 6, Each recess in the upper end of the stub shank is completely formed in one of the splines (36) of the plurality of splines (36) on the stub shank (32). A sliding piston mounted to reciprocate in the outer sleeve 5 to strike the outer cylindrical outer sleeve 5 and the impact bit 1 of the drill bit assembly located at the front end of the outer sleeve 5. 8), wherein the drill bit assembly is a drill bit assembly according to any one of claims 1 to 7, Down-the-hole hammer. The method of claim 8, Wherein said hammer is a reverse circulation DTH hammer. Drill bit assembly for a fluid actuated impact drill tool substantially as described herein and / or as shown in FIGS. 1-5, 6-8, or 9-11. DTH hammers substantially as described herein and / or as shown in FIGS. 1-3, or 12-14.

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