AU2018205207A1 - Down-hole Hammer Drilling Tool with Interchangeable Drill Head - Google Patents

Abstract

In accordance with present invention, there is provided a down-hole hammer drill tool, the drill tool comprising: a backhead assembly; an outer wear sleeve; and an interchangeable drill head assembly for retaining a drill bit, wherein the interchangeable drill head assembly is adapted to accommodate a specific drill bit.

Description

Down-hole Hammer Drilling Tool with Interchangeable Drill Head

TECHNICAL FIELD [0001] The present invention relates to a down-hole hammer drill tool. More specifically, the drill tool of the present invention is adaptable to various drill bits.

BACKGROUND ART [0002] The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0003] A down-hole hammer drill tool typically comprises a backhead assembly and a drill head assembly. The drill head assembly is provided at the working end of the drill tool and retains a drill bit. The drill bit typically comprises a drill bit head defining a cutting face and a shank extending from the drill bit head away from the cutting face. The backhead assembly comprises an air-operated percussive hammer which provides percussive blows to the drill bit. The drill head assembly further comprises a drive sub, where the drill bit is retained in the drive sub. Typically, splines are provided on the shank of the drill bit which cooperate with counterpart splines on the drive sub. In this manner, rotational torque applied to the drive sub is transmitted to the drill bit through the mating splines while allowing reciprocatory movement of the drill bit in response to percussive blows delivered by the percussive hammer.

[0004] Each manufacturer of down-hole hammer products typically develops a unique drill head assembly for their hammer. This means that a customer who purchases a down-hole hammer from a particular manufacturer is limited to buying drill bits that are specifically designed for that hammer, typically from the same manufacturer. This deters consumers from purchasing drill bits from other manufacturers as the cost to change the entire hammer is often prohibitive.

2018205207 13 Jul 2018

SUMMARY OF INVENTION [0005] In accordance with present invention, there is provided a down-hole hammer drill tool, the drill tool comprising:

a backhead assembly;

an outer wear sleeve; and an interchangeable drill head assembly for retaining a drill bit, wherein the interchangeable drill head assembly is adapted to accommodate a specific drill bit.

[0006] As would be understood by a person skilled in the art, drill bit suppliers manufacture drill bits with dimensions suited to their drill tools. This typically excludes the use of third party drill bits as they do not fit within the drill tool. The inventors have determined that the drill tool of the present invention will allow for the use of drill bits from various suppliers to be used in a single drill tool. It is envisaged that there will be multiple drill head assemblies provided for a single drill tool, each suited to a specific drill bit or set of drill bits.

[0007] In one form of the present invention, the drill tool is a reverse circulation downhole hammer drill tool.

[0008] In one form of the present invention, the outer wear sleeve is secured at a rearward end to the backhead assembly. Preferably, the outer wear sleeve is secured to the backhead assembly by way of a threaded connection.

[0009] In one form of the present invention, the outer wear sleeve is secured at a working end to the interchangeable drill head assembly. Preferably, the outer wear sleeve is secured to the interchangeable drill head assembly by way of a threaded connection.

[0010] A discussed above, the interchangeable drill head assembly retains the drill bit. Preferably, the drill bit comprises a drill bit head and a drill bit shank. As would be understood by a person skilled in the art, the drill bit head defines a cutting face. Further, the drill bit shank extends from the drill bit head in the direction away from the

2018205207 13 Jul 2018 cutting face, terminating at a strike face. Preferably, a central hole extends through the drill bit. More preferably, the drill bit shank comprises a bearing support section.

[0011] In one form of the present invention, the interchangeable drill head assembly comprises an inner tube. Preferably, the inner tube comprises an annular body portion which has an inner surface and an outer surface. More preferably, the inner surface defines a central cavity.

[0012] In one form of the present invention, the inner tube is disposed within the centre of the drill tool, concentric with the outer wear sleeve. More preferably, a working end of the inner tube engages with the central hole of the drill bit. Still preferably, a rear end of the inner tube engages with the backhead assembly. In a preferred form of the present invention, the working end and the rear end of the inner tube are of different diameters. It is envisaged that the diameter of the rear end is adapted to engage with backhead assembly, whilst the diameter of the working end is adapted to engage with a specific drill bit.

[0013] In one form of the present invention, the backhead assembly comprises a percussive piston adapted to impact the drill bit. Preferably, the percussive piston is annular in shape. More preferably, the percussive piston surrounds the inner tube. Still preferably, the percussive piston is driven by a supply of compressed air.

[0014] In one form of the present invention, the percussive piston comprises an annular body portion which has an inner surface and an outer surface. Preferably, the inner surface of the annular body portion defines a central piston cavity. More preferably, the inner tube is disposed through the central piston cavity. To permit the inner tube to be disposed therein, the diameter of the inner surface of the percussive piston is equal to or larger than the diameter of the outer surface of the inner tube. It is envisaged that where the working end and the rear end of the inner tube are of different diameters, the diameter of the inner surface of the percussive piston is preferably equal to or larger than the diameter of the outer surface of the rear end of the inner tube.

[0015] Preferably, the diameter of the outer surface of the inner tube is at least 43 mm.

[0016] Preferably, the percussive piston has a forward strike head. Preferably, the strike head impacts with the strike face of the drill bit.

2018205207 13 Jul 2018 [0017] Preferably, the backhead assembly further comprises a top adapter assembly.

More preferably, the top adapter assembly is adapted to connect the drill tool with a drill string. As would be understood by a person skilled in the art, there are many threads common to the art of drilling. By way of example, such threads include Metzke 4-1/2 and Remet 4-1/2.

[0018] In one form of the present invention, the interchangeable drill head assembly comprises a drive sub. Preferably, the drive sub comprises a first portion and a second portion. More preferably, the first portion and the second portion are integrally formed.

[0019] In one form of the present invention, the first portion defines a central head cavity for receiving the bearing support section of the drill bit. Preferably, the first portion comprises a circumferential wall which has an inner surface and an outer surface. More preferably, the inner surface defines the central head cavity.

[0020] Preferably, the second portion defines a central shank cavity for receiving the drill shank. Preferably, the second portion comprises a circumferential wall which has an inner surface and an outer surface. More preferably, the inner surface defines the central shank cavity. Still preferably, the outer surface of the second portion has an outer threaded section for engagement with the outer sleeve.

[0021] As discussed above, drill bit suppliers manufacture drill bits with dimensions suited to their drill tools. As such, a typical drive sub will only allow for the insertion of a drill bit of specific dimensions. The drill tool of the present invention allows for multiple drill head assemblies, each adapted to a specific drill bit or set of drill bit, to be interchanged. This allows drill bits form different manufacturers to be used in a single drill tool.

[0022] Preferably, the diameter of the outer surface of the second portion is sized to cooperate with an internal surface of the outer sleeve. In this manner, it is envisaged that the diameter of the outer surface of the second portion is constant across all interchangeable drill head assemblies of the drill tool.

[0023] Preferably, the diameter of central shank cavity is sized to cooperate with a drill bit shank. It is envisaged that the diameter of the central shank cavity will be determined by the diameter of the specific drill bit each interchangeable drill head assembly is associated with.

2018205207 13 Jul 2018 [0024] Preferably, the longitudinal length of second portion is sized to cooperate with the length of the drill bit shank. As would be understood by a person skilled in the art, the length of the drill bit shank, varies significantly across the various drill bit manufacturers. By varying the length of the second portion of the drive sub, the interchangeable drill head assembly of the present invention allows for drill bits with different lengths to be used with the drill tool.

[0025] Preferably, the diameter of the outer surface of the first portion is sized to cooperate with the outer sleeve. More preferably, the outer diameter of the first portion is sized to match the outer diameter of the outer sleeve. It is envisaged that the diameter of the outer surface of the first portion is constant across all interchangeable drill head assemblies of the drill tool.

[0026] Preferably, the diameter of the central head cavity is sized to cooperate with the diameter of the bearing support section.

[0027] Preferably, the length of first portion is sized to cooperate with the length of the bearing support section.

[0028] As would be understood by a person skilled in the art, the diameter and length of the bearing support section, varies significantly across the various drill bit manufacturers. By varying the diameter and/ or length of the first portion of the drive sub, the interchangeable drill head assembly of the present invention allows for drill bits with different bearing support sections to be used with the drill tool.

[0029] In one form of the present invention, the interchangeable drill head assembly further comprises a bearing bush. Preferably, the bearing bush surrounds the drill shank to provide a more stable alignment of the drill bit during use. More preferably, the inner diameter of the bearing bush is sized to cooperate with the diameter of the drill bit shank. The strike face of the percussive piston is preferably smaller than the diameter of the bearing bush.

[0030] In one form of the present invention, the interchangeable drill head assembly further comprises a retaining ring. Preferably, the retaining ring is adapted to engage the drill bit and retain the drill bit within the drive sub. More preferably, the retaining ring engages with retaining flanges provided on the drill shank. Still preferably, the retaining ring permits reciprocatory movement of the drill bit.

2018205207 13 Jul 2018 [0031] In one form of the present invention, the bit drop of the drill tool is common across each drill head assembly. As would be understood by a person skilled in the art, each drill tool has a specific bit drop. The bit drop determines how far the drill bit can move within the drill head assembly before it rests on the retaining ring. As a result, each drill bit is designed to cooperate with that bit drop. The bit drop is important in stopping the piston from cycling when air is being inserted into the hammer. The inventors have determined that by maintaining a common bit drop across all the drill head assemblies, that the cycling of the piston can be consistently controlled for each different drill bit. Preferably, the one or more of the bearing bush length, the retaining ring length and the drive sub length are adapted to ensure that a constant bit drop is maintained across all interchangeable drill head assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS [0032] Further features of the present invention are more fully described in the following description of several non-limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which:

Figure 1 is a cross section view of the drilling tool in accordance with the present invention;

Figures 2 (a) - (c) are cross section views of drilling tools in accordance with the present invention with different drill head assemblies;

Figure 3 is a cross sectional view of an inner tube;

Figure 4 is cross sectional view of a percussive piston;

Figure 5 is a cross section view of a drive sub;

Figure 6 is an upper perspective view of a convention drill bit; and

Figure 7 is a cross section view of the drilling tool in accordance with the present invention that has been annotated to demonstrate the dimensions used in Examples 1-3.

2018205207 13 Jul 2018

DESCRIPTION OF EMBODIMENTS [0033] Throughout this specification, unless the context requires otherwise, the word comprise or variations such as comprises or comprising, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0034] Referring to Figures 1 and 2, there is shown a drill tool 10 in accordance with the present invention. The drill tool 10 comprises a backhead assembly 12 and an interchangeable drill head assembly 14 which is contained within an outerwear sleeve

16. The interchangeable drill head assembly 14 is adapted to accommodate a specific drill bit 17. The outerwear sleeve 16 is secured at its rearward end 18 to the backhead assembly 12 and at the working end 20 to the interchangeable drill head assembly 14.

[0035] The interchangeable drill head assembly 14 further comprises an inner tube 22 which disposed through the centre of the drill tool 10, concentric with the outer wear sleeve 16. A detailed view of an inner tube 22 is shown in Figure 3. The inner tube 22 comprises comprises an annular body portion 24 which has an inner surface 26 that defines a central cavity 28. The annular body portion 24 further comprises an outer surface 30. The inner tube 22 has a working end 32 that engages with the drill bit 17 and a rear end 34 that engages with the backhead assembly 12. The working end 32 engages with the central hole of the drill bit 17 with a sliding/running fit. The typical clearance is about 0.40 mm. The rear end 34 of the inner tube 22 communicates with a corresponding central throughbore in the backhead assembly 12. The rear end 34 engages with the central throughbore in the backhead assembly 12 with a close clearance fit. The typical clearance is about 0.20 mm. As best seen in Figure 3, the diameters of the outer surface 30 of the working end 32 and the rear end 34 are different. It is envisaged that the outer surface 30 diameter of the rear end 34 is adapted to engage with backhead assembly 12. The outer diameter it determined by the inner diameter of the piston. The engagement is a sliding I running fit and the nominal clearance is 0.30 mm. The outer surface 30 diameter of the working end 32 is adapted to engage with a specific drill bit 17. The outer surface 30 diameter of the working end 32 of the inner tube 22 is sized with a sliding/running fit to match the internal diameter of the drill bit.

[0036] Referring again to Figure 1, the interchangeable drill head assembly 14 retains a drill bit 17. As shown in Figure 6, a conventional drill bit 17 comprises a drill bit head 36

2018205207 13 Jul 2018 which defines a cutting face 38. A drill shank 40 extends from the drill bit head 36 in the direction away from the cutting face 38 and terminates at a strike face 42. The drill shank has a bearing support section 43. A retaining flange 44 is provided on the drill shank 40 adjacent the strike face 42. A number of splines 45 are provided on the drill shank 40. A central hole 46 extends through the drill bit 17 from the strike face 42 to branch holes 48 which open on to the cutting face 38 at collection ports. As discussed above, the working end 32 of the inner tube 22 engages with the drill bit 17. This engagement allows communication between the central hole 46 of the drill bit 17 and the central cavity of the inner tube 22. The branch holes 48 and the central hole 46 provide a path for return air flow through the inner tube 22 as is well known.

[0037] The backhead assembly 12 comprises a percussive piston 50 driven by a supply of compressed air. A more detailed image of the percussive piston 50 is shown in Figure 4. As best seen in Figure 4, the percussive piston 50 comprises an annular body portion 52 which has an inner surface 54 that defines a central cavity 56 and an outer surface 58. The rear end of the inner tube 22 is disposed through the central cavity of the percussive piston 50, such that the percussive piston 50 surrounds the rear end of the inner tube 22. The diameter of the inner surface 54 of the percussive piston 50 must therefore be equal to or larger than the diameter of the outer surface of the inner tube

22. The clearance is that of a sliding I running fit and would have a nominal clearance of 0.30 mm.

[0038] The percussive piston 50 has at its forward working end a striking head 60 which is arranged to impact percussive blows to the strike face 42.

[0039] The backhead assembly 12 further comprises a top adapter 62 assembly adapted to connect the drill tool 10 with a drill string (not shown).

[0040] Located within the wear sleeve at the rearward end is a check valve 64 to control flow into the backhead assembly 12.

[0041] The interchangeable drill head assembly 14 comprises a drive sub 66. A more detailed image of the drive sub 66 is shown in Figure 5. As best seen in Figure 5, the drive sub 66 comprises a first portion 68 and a second portion 70. The first portion 68 and the second portion 70 are integrally formed with one another. The first portion 68 defines a central head cavity 72 for receiving the bearing support section 43 and the second portion 70 defines a central shank cavity 74 for receiving the drill shank 40.

2018205207 13 Jul 2018 [0042] The first portion 68 comprises a circumferential wall which has an inner surface 76 that defines the central head cavity 72 and an outer surface 78. The diameter of the outer surface 78 of the first portion 68 is sized to cooperate with the outer wear sleeve

16. Typically, reverse circulation hammers use a shroud/sleeve over the drive sub to direct the air flow to the face holes of the drill bit and the outer surface 78 is sized to match the internal diameter of the shroud. The diameter of central head cavity 72 is sized to cooperate with the diameter of the bearing support section 43. The length of first portion 68 is sized to cooperate with the length of the bearing support section 43.

[0043] The second portion 70 comprises a circumferential wall which has an inner surface 80 that defines the central shank cavity 74 and an outer surface 82. The circumferential wall supports splines for mating engagement with bit splines 45 provided on the drill bit 17 shank. The outer surface 82 of the second portion 70 has an outer threaded section for engagement with the outer wear sleeve 16. The diameter of the outer surface 82 of the second portion 70 is sized to cooperate with an internal surface 71 of the outer wear sleeve 16. The diameter of central shank cavity 74 is sized to cooperate with the diameter of the drill bit 17 shank. The length of the second portion 70 is sized to cooperate with the length of the drill bit 17 shank.

[0044] The interchangeable drill head assembly 14 further comprises a bearing bush 84 located within the wear sleeve at the forward end. The bearing bush 84 is provided within the outer wear sleeve 16 and is held in position by a shoulder on the inner surface of the outerwear sleeve 16. The drill bit 17 shank passes through the bearing bush 84.

[0045] The interchangeable drill head assembly 14 further comprises a retaining ring 86. The retaining ring 86 is adapted to be engaged by the retaining flange 44 on the drill bit 17 for retaining the drill bit 17 within the drive sub 66 while permitting reciprocatory movement of the drill bit 17.

[0046] As described above, the dimensions of drill bits 17 varies significantly across the various drill bit manufacturers. The interchangeable drill head assembly 14 of the present invention allows for drill bits 17 with different dimensions to be used with the drill tool 10. This is achieved by varying the dimensions of the various components of the interchangeable drill head assembly 14. This is best seen in Figure 2, where in each of Figures (a) to (c), the interchangeable drill head assembly 14 has been adapted to accommodate a different drill bit 17. In each instance, the length and internal diameter

2018205207 13 Jul 2018 of the drive sub 66 is varied to accommodate the drill bits 17 , whilst the outer diameters remain constant. Advantageously, this allows the same rear assembly and outer wear sleeve 16 of the drill tool 10 of the present invention to be used for multiple drill bits 17.

[0047] In use, compressed air enters the backhead assembly 12 and flows through apertures and opening past the check valve and into an air chamber. The air then moves down the first air passage into the chamber where it acts on the base of the percussive piston 50 and causes the percussive piston 50 to move to a lifted position. As the percussive piston 50 travels to its lifted position it moves past the shoulder to cut off passage from air chamber. The expanding air in chamber pushes the percussive piston 50 further until the base of the percussive piston 50 passes the shoulder in the cylinder. This allows air in chamber to exhaust through air vents to the atmosphere via the bore of the inner tube 22, carrying cuttings with it. The percussive piston 50 continues to move under its own inertia until shoulder on the percussive piston 50 passes shoulder in the backhead allowing the compressed air in chamber to flow into chamber formed between the cylinder and percussive piston 50 to act on surface of the percussive piston 50. Air pressure on surface and surface of the percussive piston 50 causes the percussive piston 50 to travel downwards at high speed such that the operating head strikes the strike surface of the drill bit 17. The slots align then with the grooves and air exhausts from passage through the vents to the atmosphere via the inner tube 22 again carrying cuttings with it. Hereafter, the air passage opens again and the cycle begins once more.

[0048] As would be understood by a person skilled in the art, each drill tool has a specific bit drop. The bit drop determines how far the drill bit can move within the drill head assembly before it rests on the retaining ring. The bit drop is important in stopping the piston from cycling when air is being inserted into the hammer. This is commonly referred to in the art as the Off bottom’ or ‘blow mode’. This has been identified by the inventors as one of the difficulties faced with using non-OEM drill bits. The difference in the bit drop prevents the cycling of the piston to be controlled. The inventors have determined that by maintaining a common bit drop across all the drill head assemblies, that the cycling of the piston can be consistently controlled for each different drill bit. The bit drop is maintained by altering one or more of the bearing bush length, the retaining ring length and the drive sub length. The dimensions of these components will be determined by the particular dimensions of the drill bit to be retained.

2018205207 13 Jul 2018 [0049] As would be understood by a person skilled in the art, another one of the problems faced with attempting to adapt third party drill bits to conventional down-hole hammer drills is the mismatch of the diameter and thickness of percussive piston with the strike face of the drill bit. The inventors have determined that provided that there are parallel strike planes, the uncommon diameters do not effect the operation of the drill tool.

Example 1

A series of drill head assemblies were fabricated to accommodate three drill bits supplied by various manufacturers. The drill bits were:

The RE545 drill bit manufactured by Sandvik and Schramm Australia;

The RE052 bit manufactured by Sandvik;

The MR120 bit manufactured by Mincon Group PLC;

The RE547 bit manufactured by Sandvik;

The RE054 bit manufactured by Sandvik; and

The AD670 bit manufactured by Schramm Australia.

With reference to Figure 7, the dimensions of the various components of each drill head assembly are shown in Table 1.

DIMENSION	RE545	RE052	MR120	RE547	RE054	AD670
A	87.6	91.4	92.4	93.8	94.4	96.9
B	46.7	43.1	43.8	46.7	46.9	48.75
C	80	85	85	89	89	89.8
D	74	80.6	83	80.8	81.5	82.3
E	114	124.3	118.5	120.6	124.4	123.25
F	84.5	93.3	98.3	93.9	95.4	95.85

Table 1: Dimensions of Drill Head Assembly

Example 2 [0050] A series of drilling tests were undertaken at a site 100 km east of Kalgoorlie, Western Australia using the drill tool of the present invention, with a drill head assembly

2018205207 13 Jul 2018 adapted to retain a drill bit suited for a RE052 drill bit. The dimensions of the drill head assembly are those of the RE052 assembly of Example 1 .The following observations were made:

• Hammer drilled and sampled with satisfactory results.

• Holding 500psi with rig air. Holding 1,000psi when boosted.

• Piston beats per minute 2,400bpm @ 1,000psi.

• Drilled 292m during the test.

[0051] Following the initial test, further drilling tests were undertaken at the site, to determine the expected meterage out of the drill tool. The hammer has drilled approximately 4,000m and has drilled and sampled with satisfactory results.

Example 3 [0052] A series of drilling tests were undertaken in Leonora, Western Australia using the drill tool of the present invention, with a drill head assembly adapted to retain a drill bit suited for a MR120 drill bit. The dimensions of the drill head assembly are those of the MR120 assembly of Example 1. The following observations were made:

• Hammer drilled and sampled with satisfactory results.

• Holding 61 Opsi with rig air.

• Drilled 560m during the test.

Claims (22)

1. A down-hole hammer drill tool, the drill tool comprising:

a backhead assembly;

an outer wear sleeve; and an interchangeable drill head assembly for retaining a drill bit, wherein the interchangeable drill head assembly is adapted to accommodate a specific drill bit.

2. A drill tool according to claim 1, wherein the drill tool is a reverse circulation downhole hammer drill tool.

3. A drill tool according to claim 1 or 2, wherein the outer wear sleeve is secured at a rearward end to the backhead assembly.

4. A drill tool according to any one of the preceding claims, wherein the outer wear sleeve is secured at a working end to the interchangeable drill head assembly.

5. A drill tool according to any one of the preceding claims, wherein the interchangeable drill head assembly comprises an inner tube.

6. A drill tool according to claim 5, wherein the inner tube comprises an annular body portion which has an inner surface and an outer surface.

7. A drill tool according to claim 6, wherein the inner surface defines a central cavity.

8. A drill tool according to any one of claims 5 to 7, wherein the inner tube is disposed within the centre of the drill tool.

9. A drill tool according to any one of claims 5 to 8, wherein a working end of the inner tube engages with a central hole of a drill bit.

2018205207 13 Jul 2018

10. A drill tool according to any one of claims 5 to 9, wherein a rear end of the inner tube engages with the backhead assembly.

11. A drill tool according to any one of the preceding claims, wherein the backhead assembly comprises a percussive piston adapted to impact the drill bit.

12. A drill tool according to claim 11, wherein the percussive piston has a forward strike head.

13. A drill tool according to any one of the preceding claims, wherein the interchangeable drill head assembly comprises a drive sub.

14. A drill tool according to claim 13, wherein the drive sub comprises a first portion and a second portion.

15. A drill tool according to claim 14, wherein the first portion and the second portion are integrally formed.

16. A drill tool according to claim 14 or 15, wherein the first portion comprises a circumferential wall which has an inner surface that defines a central head cavity and an outer surface.

17. A drill tool according to claim 16, wherein the central head cavity is adapted to receive a bearing support section.

18. A drill tool according to any one of claim 14 to 17, wherein the wherein the second portion comprises a circumferential wall which has an inner surface that defines a central shank cavity and an outer surface.

19. A drill tool according to claim 18, wherein the central shank cavity is adapted to receive a drill bit shank.

20. A drill tool according to claim 18 or 19, wherein the diameter of the outer surface of the second portion is sized to cooperate with an internal surface of the outer sleeve.

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21 .A drill tool according to any one of the preceding claims, wherein the interchangeable drill head assembly further comprises a bearing bush.

22. A drill tool according to any one of the preceding claims, wherein the interchangeable drill head assembly further comprises a retaining ring.