Shoulder-Protected Drilling Assembly

Abstract

A drilling assembly for percussion drilling, comprising at least two of a drill bit, a drill pipe and a guide adapter; wherein the outer peripheral surface of the shoulder on the drill pipe is at least partially enclosed within the mounting sleeve of the drill bit or the mounting sleeve of the guide adapter in the radial and axial directions; and / or the outer peripheral surface of the shoulder on the guide adapter is at least partially enclosed within the mounting sleeve of the drill bit in the radial and axial directions.

Description

Technical Field

[0001] The present invention relates to an impact drilling assembly and, although not exclusively, particularly relates to a rock bit and / or guide adapter for top hammer drilling. Background Art

[0002] Impact bits are widely used for drilling relatively shallow holes in hard rock and for forming deep boreholes. For the latter application, a drill string is typically used in which a plurality of rods are interconnected to advance the bit and increase the depth of the hole. In "top hammer drilling", a surface machine is operable to transmit a combined impact and rotary drive movement to the upper end of the drill string, and a bit located at the lower end is operable to break up the rock and form the borehole. A guide adapter may be included between the first drill rod and the bit to improve the straightness and quality of the drilled hole.

[0003] The drill rods connectable to adjacent drill rods and the bit or guide adapter may have shoulders. If a guide adapter is included, it will also have shoulders. The shoulders are formed as a radially expanded extension of the main length portion of the drill rod or are formed on the guide adapter to provide increased energy transfer efficiency between the drill rod and the bit or guide adapter or between the guide adapter and the bit. When the hole collapses and cuttings accumulate behind the bit, the shoulders on the first drill string rod connected to the bit or guide adapter and the shoulders on the guide adapter are exposed to high levels of wear. The problem with this is that when the shoulders wear, the strength of the connection will be prematurely reduced. In addition, as the shoulders wear, the contact area between the drill string rod and the bit or guide adapter or between the guide adapter and the bit decreases, and thus the energy transfer between the bit or guide adapter and the rod or between the guide adapter and the bit decreases. If the energy transfer is not efficient, energy will be wasted and the drilling efficiency will be impaired.

[0004] Accordingly, there is a need for a drilling assembly design in which wear on the shoulders of the drill string rods and / or guide adapter is reduced. A known solution is to hard face the outer peripheral edge of the shoulders; however, this significantly increases the additional cost of producing the drill string rods or guide adapter. Accordingly, there is a need for a drilling assembly design in which wear on the shoulders of the drill rods and / or guide adapter is reduced without significantly increasing the additional production cost. Summary of the Invention

[0005] An object of the present invention is to provide a novel and improved impact drilling assembly and apparatus in which the shoulders on the first rod connected to the bit or guide adapter are less prone to wear and / or in which the shoulders on the guide adapter connected to the bit are less prone to wear.

[0006] This object is achieved by providing a drilling assembly for percussion drilling, the drilling assembly comprising at least two of a drill bit, a drill pipe and a guide adapter;

[0007] The drill pipe includes a hollow elongated main length portion extending axially between a male end and a female end; the male end includes male connection means, and a radially protruding shoulder axially separating the main length portion and the male connection means; the shoulder includes an outer peripheral surface, a first annular side surface adjacent to the drill bit or the guide adapter, and a second annular side surface radially diverging from the main length portion, the outer diameter D1 of the outer peripheral surface being greater than the outer diameter D2 of the main length portion;

[0008] The drill bit includes a mounting sleeve for connection to the drill pipe or the guide adapter;

[0009] The guide adapter includes a mounting sleeve for connection to the drill pipe and a shoulder having an outer peripheral surface for connection to the drill bit;

[0010] It is characterized in that: the outer peripheral surface of the shoulder on the drill pipe is at least partially enclosed within the mounting sleeve of the drill bit or the guide adapter in the radial and axial directions;

[0011] And / or

[0012] The outer peripheral surface of the shoulder on the guide adapter is at least partially enclosed within the mounting sleeve of the drill bit in the radial and axial directions.

[0013] Advantageously, if the shoulder of the drill pipe is at least partially enclosed within the mounting sleeve of the drill bit or the guide adapter, and / or if the shoulder of the guide adapter is at least partially enclosed within the mounting sleeve of the drill bit, then the shoulder is protected from wear by cuttings. This is beneficial because it reduces the risk of premature failure of the drill pipe and / or the guide adapter. In addition, since the shoulder is no longer subject to wear, the contact area between the shoulder and the mounting sleeve is constant, which means that the energy transfer efficiency between the two components is not reduced, thus maintaining a higher level of drilling efficiency.

[0014] Preferably, at least 20%, more preferably at least 30%, even more preferably at least 50%, even more preferably at least 75%, most preferably at least 90% of the length of the outer peripheral surface of the shoulder is enclosed within the mounting sleeve. If less than 20% of the length of the outer peripheral surface of the shoulder is enclosed, then the level of protection will not be sufficient to obtain the benefit of reducing shoulder wear. By increasing the proportion of the shoulder enclosed within the mounting sleeve, a higher level of wear protection will be obtained.

[0015] Preferably, the mounting sleeve on the drill bit and / or the guide adapter has a connecting portion and an encapsulating portion. The connecting portion has a first wall thickness at its thinnest point and is for fixing to the male connecting device on the drill pipe. The encapsulating portion has a second wall thickness at its thickest point and is for fitting the shoulder of the drill pipe into the encapsulating portion, where the second wall thickness is less than the first wall thickness.

[0016] Advantageously, the internal geometry of the female sleeve on the drill bit or the guide adapter must be able to encapsulate the shoulder to protect it from wear.

[0017] Preferably, the second wall thickness is at least 1.5 mm. If the second wall thickness is less than 1.5 mm, the risk of cracking in this area increases.

[0018] Preferably, the encapsulating portion has a length L1 and the shoulder has a length L2, where L1 is at least 20% of L2, more preferably at least 30%, more preferably at least 50%, even more preferably at least 70%, and most preferably at least 90%.

[0019] Preferably, the shoulder has an outer diameter D1 and the encapsulating portion has an inner diameter D3, where D1 is in the range of 80 - 100% of D3, preferably 95 - 99%.

[0020] If the outer diameter of the shoulder is too large compared to the inner diameter of the encapsulating portion, the fit between the shoulder and the mounting sleeve will be too tight, and this will make it difficult to disconnect the components. If the outer diameter of the shoulder is too small compared to the inner diameter of the encapsulating portion, the wall of the mounting sleeve in the encapsulating portion will become too thin, which increases the risk of cracking in this part.

[0021] Preferably, the gap between the outer peripheral surface of the shoulder and the inner surface of the encapsulating portion is between 0.5 - 4 mm. If the gap is too small, the fit between the shoulder and the mounting sleeve will be too tight, and this will make it difficult to disconnect the components. If the gap is too large, the wall of the mounting sleeve will become too thin, which increases the risk of cracking in this part, and the connection between the two surfaces will not be sufficient to maximize the energy transfer between the two connected components.

[0022] Optionally, the outer peripheral surface of the shoulder and the inner surface of the encapsulating portion are substantially cylindrical. The cylindrical profile can have a uniform diameter along their axial length or can be stepped, such that there are at least two portions at the outer peripheral surface of the shoulder and the inner surface of the encapsulating portion, each portion having a different diameter compared to the other portions, but each portion having a uniform diameter along the axial length of each portion. The profile of the outer peripheral surface of the shoulder is designed to match and fit within the profile of the inner surface of the encapsulating portion.

[0023] Alternatively, the outer peripheral surface of the shoulder and the inner surface of the encapsulating portion have a tapered shape. The profile of the outer peripheral surface of the shoulder is designed to match and fit within the profile of the inner surface of the encapsulating portion.

[0024] Preferably, the junctions between the edge of the outer peripheral surface on the shoulder and the edge of the first annular side surface and between the edge of the outer peripheral surface and the edge of the second annular side surface are chamfered or rounded. Advantageously, this reduces the risk of chipping and cracking in these areas.

[0025] Preferably, the length of the shoulder is between 5 - 60 mm, more preferably between 15 - 25 mm. If the length of the shoulder is too short, the risk of chipping or cracking of the shoulder increases. If the shoulder is too long, unnecessary costs are increased. The most preferred length of the shoulder will depend on the thread size used.

[0026] Optionally, the male connection device on the drill pipe is a plug head having an external threaded portion and a non-threaded shank axially positioned between the threaded portion and the shoulder, and wherein the mounting sleeve on the drill bit or the guide adapter has an internal thread. This mounting option is preferably used for larger drill bits.

[0027] Optionally, the male connection device on the drill pipe is tapered and non-threaded, and the mounting sleeve on the drill bit or the guide adapter is internally tapered and non-threaded, thereby forming a tapered connection. This type of connection is typically used for smaller drill bits.

[0028] Preferably, the first annular side surface of the shoulder abuts the annular outermost surface on the connection portion of the mounting sleeve on the drill bit or the guide adapter. Advantageously, this will mean that the shoulder is encapsulated within the drill bit or the guide adapter.

[0029] Preferably, the drill bit or the guide adapter has an outer diameter D4 at the annular rear end in that part of it which surrounds the encapsulating portion, where D4 is at least 5% larger than the outer diameter D1 of the shoulder, preferably, D4 is at least 3 mm larger than D1, up to the maximum diameter of the drill bit or the guide adapter at its maximum cross-section. This will provide protection for the shoulder.

[0030] It should be understood that the shoulder can be a shoulder on the drill pipe or a shoulder on the guide adapter, and the mounting sleeve can be on the drill bit or on the guide adapter.

[0031] Another aspect of the present invention relates to a drill bit or a guiding adapter having a mounting sleeve, the mounting sleeve having a connecting portion and an encapsulating portion, the connecting portion having a first wall thickness T1 at its thinnest point and being adapted to be fixed to a male connecting device on a drill pipe, the encapsulating portion having a second wall thickness T2 at its thickest point and being adapted to receive a shoulder of the drill pipe within the encapsulating portion, wherein the second wall thickness T2 is less than the first wall thickness T1. Description of the Drawings

[0032] Figure 1 : A perspective view of an impact drilling assembly is shown, in which a drill pipe is coupled to a drill bit.

[0033] Figure 2 : A perspective view of the male end of a drill pipe is shown.

[0034] Figure 3 : A cross-sectional view of a drill bit known in the prior art is shown.

[0035] Figure 4 : A cross-sectional view of a drill bit known in the prior art coupled to a first drill pipe is shown.

[0036] Figure 5 : A cross-sectional view of a drill bit according to an embodiment of the present invention is shown, in which the mounting sleeve has an internal thread.

[0037] Figure 6 : A cross-sectional view of a drill bit according to an embodiment of the present invention coupled to a first drill pipe is shown, which has a threaded connection and a cylindrical shoulder.

[0038] Figure 7 : A cross-sectional view of a drill bit according to an alternative embodiment of the present invention coupled to a first drill pipe is shown, which has a threaded connection and a conical shoulder.

[0039] Figure 8 : A cross-sectional view of a drill bit according to an alternative embodiment of the present invention coupled to a first drill pipe is shown, which has a tapered conical connection.

[0040] Figure 9 : A perspective view of a drilling assembly is shown, in which the drill pipe is coupled to the drill bit through a guiding adapter.

[0041] Figure 10 : A cross-sectional view of a guiding adapter according to an embodiment of the present invention is shown.

[0042] Figure 11 : A cross-sectional view of a guiding adapter according to an embodiment of the present invention coupled to a first drill pipe is shown. Detailed Description

[0043] Figure 1The percussion drilling assembly 1 is shown, in which a first drill rod 12 is releasably coupled to a drill bit 2 of conventional design. The percussion drilling assembly 1 is particularly used for top hammer drilling. The shock wave generated by a surface piston (not shown) is transmitted from the drill rod 12 to the drill bit 2 through a mating surface. The drill rod 12 includes an axially extending main length portion 14 that is terminated at one end by a male end 16 and at an opposite second end by a female end 18, and has a longitudinal axis 5. The drill rod 12 can be coupled end-to-end with other adjacent drill rods 12 to form a drill string (not shown).

[0044] Figure 2 The male end 16 of the drill rod 12 is shown, which includes male connection means 20 (in this case in the form of a plug head 38) and a shoulder 22 that projects radially outward relative to the main length portion 14 and extends over a portion of the axial distance of the main length portion 14. The shoulder 22 includes an outer peripheral surface 24 that extends axially along the length of the shoulder 22, a first annular side surface 26 located at the foremost end of the shoulder 22, and a second annular side surface 28 that extends radially away from the main length portion 14. The first annular side surface 26 abuts the drill bit 2 near the male connection means 20. Alternatively, the first annular side surface is referred to as an annular abutment surface. The main length portion 14 has an outer diameter D2, and the shoulder 22 has a length L2 and an outer diameter D1. The drill rod 12 has an inner bore (not shown) that extends axially through the main length portion 14. Optionally, the bore has a uniform diameter over its entire axial length.

[0045] Preferably, the corners or junctions between the edge of the outer peripheral surface 24 on the shoulder 22 and the edge of the first annular side surface 26 and between the outer peripheral surface 24 and the second annular side surface 26 are chamfered.

[0046] Figure 3 The cross-section of a drill bit 2 known in the prior art is shown, and Figure 5 The cross-section of a drill bit 2 according to an embodiment of the present invention is shown. In both forms, the drill bit 2 includes an axially foremost drill bit head of conventional design, for example including rock-breaking means, most typically a plurality of wear-resistant cutting buttons that project axially forward from the drill bit head (not shown); a plurality of grooves that extend in the axial direction of the drill bit for removing mud and drill cuttings (not shown); and a mounting sleeve 10 that includes an internal cavity 50 that extends axially from the axially rearmost surface 46 for receiving the male connection means 20 of the drill rod 12.

[0047] As Figure 3 shown, in the form known in the prior art shown, the mounting sleeve 10 has a connection portion 30 that is adapted to be coupled to the male connection means 20 of the drill rod 12.

[0048] Figure 4shows a drill bit 2 releasably connected to a drill pipe 12 known in the prior art, such as Figure 3 shown, wherein a first annular side surface 26 of a shoulder 22 of the drill pipe 12 abuts an annular outermost end surface 46 of the drill bit 2, thereby forming a "shoulder contact".

[0049] In a form according to an embodiment of the present invention, as Figure 5 shown, the mounting sleeve 10 is modified such that the mounting sleeve 10 has a connecting portion 30 adapted to be coupled to a male connecting device 20 of the drill pipe 12 and further has an encapsulating portion 32 adapted to receive the shoulder 22 of the drill pipe 12 therein. The connecting portion has a wall thickness T1 at its thinnest point, which is thicker than the wall thickness T2 of the encapsulating portion 32 at its thickest point. Preferably, T1 is at least 10% greater than T2.

[0050] Figure 6 shows a drill bit 2 according to an embodiment of the present invention, whereby, as Figure 5 shown, the modified drill bit 2 is releasably coupled to the drill pipe 12 such that the shoulder 22 of the drill pipe 12 is at least partially encapsulated within the drill bit 2 in the radial and axial directions. In other words, the drill pipe 12 is at least partially enclosed within the drill bit 2 in the radial and axial directions such that the drill pipe 12 is inserted into at least a portion of the drill bit 2. The first annular side surface 26 of the shoulder 22 on the drill pipe 12 now abuts the annular outermost end surface 48 of the connecting portion 30. Preferably, at least 20%, more preferably at least 30%, more preferably at least 50%, even more preferably at least 75%, and most preferably at least 90% of the length L2 of the shoulder 22 is encapsulated or enclosed within the mounting sleeve 10 within the encapsulating portion 32.

[0051] The encapsulating portion 32 has a length L1. Preferably, the length L1 of the encapsulating portion is at least 20%, more preferably at least 30%, more preferably at least 50%, even more preferably at least 75%, and most preferably at least 90% of the shoulder length L2. Preferably, L2 is 15 to 22 mm, more preferably approximately 22 mm.

[0052] The encapsulating portion 32 has an inner diameter D3. Preferably, the outer diameter D1 of the shoulder 22 is in the range of 80 - 100% of D3, more preferably 95 - 99%. The clearance 36 is the radial distance between the outer peripheral surface 24 of the shoulder 22 and the inner surface 34 of the encapsulating portion 32, and the clearance 36 is preferably between 0.5 - 4 mm. The drill bit 2 has an outer diameter D4 at its annular rear end in that part thereof surrounding the encapsulating portion 32. Preferably, D4 is at least 5% greater than D1. Preferably, D4 is at least 3 mm greater than D1 up to the maximum diameter of the drill bit 2 at its maximum cross-section.

[0053] In one embodiment, the outer peripheral surface 24 of the shoulder 22 and the inner surface 34 of the encapsulation portion 32 are both substantially cylindrical, as Figure 6 shown. If the shoulder 22 and the encapsulation portion 32 are substantially cylindrical, they may either have a uniform diameter or they may be of a stepped profile such that the outer peripheral surface 24 of the shoulder 22 and the inner surface 34 of the encapsulation portion 32 have at least two portions, each portion having a different diameter compared to the other portions, but each portion having a uniform diameter along the axial length of each portion.

[0054] Figure 7 An alternative embodiment is shown where the outer peripheral surface 24 of the shoulder 22 and the inner surface 34 of the encapsulation portion 32 have a conical shape and thus have a straight or curved profile.

[0055] In one embodiment, as Figure 2 , Figure 5 , Figure 6 and Figure 7 shown, the connection between the drill bit 2 and the drill pipe 12 is formed by a threaded connection. In this embodiment, the male connection device 20 on the drill pipe 12 is a plug portion 38 that projects axially forward from the shoulder 22. The plug portion 38 has an external threaded portion 40 and a non-threaded shank portion 42 that is axially positioned between the threaded portion 40 and the shoulder 22. To mate with this connection, the cavity 50 within the mounting sleeve 10 on the drill bit 2 has an internal thread 44.

[0056] Figure 8 An alternative embodiment is shown where a tapered connection is formed instead of a threaded connection. In this embodiment, the male connection device 20 on the drill pipe 12 is conical and non-threaded, and the mounting sleeve 10 is internally conical and non-threaded such that these components are held together by friction.

[0057] Any other suitable connection means may also be used. Any type of connection means may be combined with any profile of the shoulder 22.

[0058] Alternatively, Figure 9 shown, the drill bit 2 may be connected to the drill pipe 12 by a guide adapter 60 having a mounting sleeve 10. Figure 10 shown, the mounting sleeve 10 is modified in the same manner as described above for the drill bit 2 such that the mounting sleeve 10 has a connection portion 30 adapted to mate with the male connection device 20 of the drill pipe 12 and also has an encapsulation portion 32 adapted to receive the shoulder 22 of the drill pipe 12 therein. Figure 11 A guide adapter 60 according to an embodiment of the present invention is shown, whereby, as Figure 10The modified guide adapter 60 shown is releasably coupled to the drill pipe 12 such that the shoulder 22 of the drill pipe 12 is at least partially encapsulated within the guide adapter 60 in the radial and axial directions. The guide adapter 60 also has a shoulder 22' which has an outer peripheral surface 24' and is for connection to the drill bit 2. The shoulder 22' on the guide adapter can also be protected against wear by using the design of the drill bit 2 described above such that the outer peripheral surface 24' of the shoulder 22' on the guide adapter 60 is at least partially encapsulated within the mounting sleeve 10 of the drill bit 2 in the radial and axial directions. It should be understood that any alternative embodiments described above with respect to the drill bit 2 can also be applied to the guide adapter 60.

Claims

1. A drilling assembly (1) for percussion drilling, comprising at least two of a drill bit (2), a drill rod (12) and a guide adapter (60); The drill rod (12) includes a hollow elongate main length portion (14) that extends axially between a male end (16) and a female end (18); the male end (16) includes a male connection device (20) and a radially protruding shoulder (22) that axially separates the main length portion (14) from the male connection device (20); the shoulder (22) includes an outer peripheral surface (24), a first annular side surface (26) adjacent to the drill bit (2) or the guide adapter (60), and a second annular side surface (28) that radially diverges from the main length portion (14), and an outer diameter (D1) of the outer peripheral surface (24) is greater than an outer diameter (D2) of the main length portion; The drill bit (2) includes a mounting sleeve (10) for connection to the drill rod (12) or to the guide adapter (60); The guide adapter (60) includes a mounting sleeve (10) for connection to the drill rod (12) and a shoulder (22') having an outer peripheral surface (24') for connection to the drill bit (2); Characterized in that: The outer peripheral surface (24) of the shoulder (22) on the drill rod (12) is at least partially enclosed in the mounting sleeve (10) of the drill bit (2) or the mounting sleeve (10) of the guide adapter (60) in the radial and axial directions; and / or The outer peripheral surface (24') of the shoulder (22') on the guide adapter (60) is at least partially enclosed in the mounting sleeve (10) of the drill bit (2) in the radial and axial directions, wherein the mounting sleeve (10) on the drill bit (2) or the guide adapter (60) has a connecting portion (30) and an enclosing portion (32), the connecting portion (30) has a first wall thickness (T1) at its thinnest point, and the connecting portion (30) is for fixing to the male connection device (20) on the drill rod (12), the enclosing portion (32) has a second wall thickness (T2) at its thickest point, and the enclosing portion (32) is for fitting the shoulder (22) of the drill rod (12) therein, wherein the second wall thickness (T2) is less than the first wall thickness (T1), wherein the outer peripheral surfaces (24, 24') of the shoulders (22, 22') and the inner surface (34) of the enclosing portion (32) are substantially cylindrical, and wherein the first annular side surface (26) of the shoulder (22) on the drill rod (12) abuts the annular outermost surface (48) on the connecting portion (30) of the mounting sleeve (10) of the drill bit (2) or the guide adapter (60).

2. The drilling assembly (1) according to claim 1, wherein at least 20% of the length (L2) of the outer peripheral surface (24, 24') of the shoulder (22, 22') is enclosed within the mounting sleeve (10).

3. The drilling assembly (1) according to claim 1, wherein the second wall thickness (T2) is at least 1.5 mm.

4. The drilling assembly (1) according to any one of claims 1 to 3, wherein the enclosed portion (32) has a length (L1) and the shoulder (22, 22') has a length (L2), and wherein the length of the enclosed portion is at least 20% of the length of the shoulder.

5. The drilling assembly (1) according to any one of claims 1 to 3, wherein the shoulder (22, 22') has an outer diameter (D1) and the enclosed portion (32) has an inner diameter (D3), and wherein the outer diameter of the shoulder is in the range of 80 - 100% of the inner diameter of the enclosed portion.

6. The drilling assembly (1) according to any one of claims 1 to 3, wherein the gap (36) between the outer peripheral surface (24, 24') of the shoulder (22, 22') and the inner surface (34) of the enclosed portion (32) is between 0.5 - 4 mm.

7. The drilling assembly (1) according to any one of claims 1 - 3, wherein the junctions between the edges of the outer peripheral surface (24, 24') on the shoulder (22, 22') and the edge of the first annular side surface (26) and between the outer peripheral surface (24, 24') and the second annular side surface (28) are chamfered.

8. The drilling assembly (1) according to any one of claims 1 - 3, wherein the length (L2) of the shoulder (22, 22') is between 5 - 60 mm.

9. The drilling assembly (1) according to any one of claims 1 - 3, wherein the male connecting device (20) on the drill pipe (12) is a plug head (38), the plug head (38) has an external thread portion (40) and a threadless shank portion (42) axially positioned between the thread portion (40) and the shoulder (22), and wherein the mounting sleeve (10, 10') on the drill bit (2) or the guide adapter (60) has an internal thread (44).

10. The drilling assembly (1) according to any one of claims 1 - 3, wherein the male connecting device (20) on the drill pipe (12) is conical and threadless, and the mounting sleeve (10) on the drill bit (2) or the guide adapter (60) is internally conical and threadless, thereby forming a tapered connection.

11. The drilling assembly (1) according to any one of claims 1 to 3, wherein the drill bit (2) or the guide adapter (60) has a first outer diameter (D4) at its annular rear end in that part thereof which surrounds the encapsulation portion (32), and wherein the first outer diameter is at least 5% larger than the outer diameter (D1) of the shoulder (22, 22') up to the maximum diameter of the drill bit (2) or the guide adapter (60) at its maximum cross-section.

12. The drilling assembly (1) according to claim 11, wherein the first outer diameter is at least 3 mm larger than the outer diameter of the shoulder.

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