Elliptical design for drill handle adapter

Abstract

A shank adapter to form part of a drilling assembly, the shank adapter comprising: a body extending axially between a first end and a second end; a male plug portion provided at the second end, having an externally threaded section and an unthreaded shank axially located intermediate the body and the threaded section; a radially projecting shoulder axially located intermediate the body and the male plug portion; the shank having a transition section located adjacent the shoulder at the second end, the transition section having an increasing outer diameter in a direction from the plug portion to the shoulder; wherein a cross-sectional shape profile of an outer surface of the transition section in a plane of the longitudinal axis comprises a segment of an ellipse according to the following equation: (Formula (I)) characterized in that: a ratio of the semi-major axis to the semi-minor axis (a:b) is in a range of 2b

Description

Technical Field

[0001] The present invention relates to a rock drilling shank adapter, and particularly, but not exclusively, to a connector of the drill shank adapter configured to minimize stress concentration. Background Technology

[0002] Percussion drilling is used to create long boreholes by connecting multiple elongated drill strings end-to-end with interconnected convex and concave threaded ends. Established technology involves breaking rock by delivering hammer impacts from a rock drill bit mounted at one end of the drill string to the rock at the bottom of the borehole. Typically, the energy required to break the rock is generated by a hydraulically driven piston that contacts the end of the drill string via a drill shank adapter to generate stress (or shock) waves that propagate through the drill string and eventually reach the bedrock surface. The drill shank adapter includes a body with a threaded convex connection at one end for attachment to the drill string, and at the opposite second end, a solid end section on which the impact piston, integrated into the drilling machine, acts. Connected to the solid end section is a set of splines configured for torsion of the drill shank adapter and the drill string, or for enabling rotation of the drill shank adapter and the drill string.

[0003] When the threaded male spigot of a drill shank adapter is connected to the threaded female spigot of the last drill rod, the joint is typically subjected to bending moments during drilling. These bending moments cause fatigue in the connector and can lead to breakage of the threaded portion of the connector. Typically, it is the threaded male spigot that fails, and this spigot determines the lifespan of the connector.

[0004] In particular, the transition between the different diameters of the threaded lug and the main length of the drill shank adapter (or the annular shoulder on the drill shank adapter in the case of a "shoulder contact" connector) provides a potentially high stress concentration area due to bending moment and tensile loads. Typically, at the axial transition between the threaded lug and the main length or shoulder, the outer diameter of the drill shank adapter flares radially outward and has a curved profile with a single radius of curvature large enough to be accommodated between the two aforementioned areas. However, for a typical threaded connector subjected to a tensile stress of 200 MPa, the transition area can reach stress levels of approximately 300 MPa. Therefore, fatigue and potential fracture are highly likely to occur, leading to severe interruptions in drilling operations. Thus, a drill shank adapter design that addresses these problems is needed. Summary of the Invention

[0005] It is an object of the present invention to provide a pin adapter having a male threaded connection portion that is optimized to minimize the possibility of stress concentration at the transition region between the shoulder and the pin on the pin adapter, thereby extending the service life of the pin adapter and minimizing the risk of fatigue and fracture during use. Another specific object is to provide a pin adapter compatible with existing drilling equipment and methods, which comprises an enhanced ability to withstand large bending moments and tensile loads.

[0006] These objects are achieved by specifically configuring the transition region, which is axially positioned at the interface with the end of the main length section or at the annular shoulder at the end of the main length section. The present invention provides a pin adapter for a drill pipe coupling, which exhibits reduced stress concentration at the junction between the male pin and the main length section compared with known designs, wherein said stress concentration is generated by an incident bending moment or tensile load.

[0007] According to a first aspect of the present invention, there is provided a pin adapter for forming part of a drilling assembly, said pin adapter comprising: a body extending axially between a first end and a second end; a male pin portion provided at said second end, having an externally threaded section and an unthreaded shank axially positioned between said body and said threaded section; a radially projecting shoulder axially positioned between said body and said male pin portion; said shank having a transition section positioned adjacent to said shoulder at said second end, said transition section having an outer diameter that increases in a direction from said pin portion to said shoulder; wherein the cross-sectional contour of the outer surface of said transition section in a plane of the longitudinal axis comprises a segment of an ellipse according to the following equation, said ellipse having a semi-major axis (a), a semi-minor axis (b) and an exponential factor n):

[0008]

[0009] characterized in that the ratio of said semi-major axis to said semi-minor axis (a:b) is in the range of 2b < a < 8b.

[0010] Advantageously, this provides a male connection end that exhibits increased stiffness and is more resilient to bending moments and tensile forces. The transition section is configured to eliminate or at least minimize stress concentration in the section where the pin projects axially from the shoulder. If the ratio of the length of the semi-major axis to the semi-minor axis is higher or lower than this value, the stress concentration will increase. Therefore, the risk of fracture is reduced, thereby increasing the service life of the pin adapter. Optionally, the transition section may also include segments wherein the profile is straight and / or of different curved profiles.

[0011] Optionally, the non-threaded shank is axially divided into a straight portion positioned axially closest to the threaded section and a curved transition section positioned axially closest to the side surface. Increasing the distance between the shoulder and the threaded portion can be advantageous. In this case, it will also be beneficial to include the straight section.

[0012] Alternatively, the non-threaded shank only has a curved transition section extending all the way from the side surface to the threaded section. When the non-threaded shank is short, it is advantageous to have only the curved transition section, that is, no straight section, as this helps to keep the stress concentration as low as possible.

[0013] Preferably, the ratio of the semi-major axis to the semi-minor axis (a:b) is in the range of 2.5b < a < 6b. Advantageously, within this narrowed ratio range, the stress concentration at the section where the plug axially protrudes from the shoulder is further reduced, which means the ability to withstand large bending moments and tensile stresses is enhanced.

[0014] Preferably, the semi-minor axis (b) is proportional to the dimension of the threaded section according to the following equation:

[0015]

[0016] wherein Di is the diameter of the threaded section between opposite grooves, and Dy is the diameter of the threaded section between opposite helical crests. Advantageously, the length of the semi-minor axis (b) is as large as possible, because this provides an elliptical shape without sharp ends and thus has the lowest stress concentration. However, if the length of the semi-minor axis (b) is too large, there will actually be no shoulder, so energy cannot be efficiently transferred between the male end and the female end, which will lead to fracture of the female end of the rod.

[0017] Preferably, the exponential factor (n) is in the range of 1≤n≤3. Advantageously, this provides a transition section with an elliptical profile that has the lowest stress concentration.

[0018] Optionally, the vertex of the ellipse is positioned at a tangent tangent to the annular side surface of the shoulder. Alternatively, the vertex undercuts the annular side surface of the shoulder. Different load cases can benefit from different forms of ellipse.

[0019] Optionally, the x-axis of the ellipse is parallel to the longitudinal axis. Alternatively, the x-axis of the ellipse is inclined relative to the longitudinal axis. Different load cases can benefit from different forms of ellipse.

[0020] Optionally, the cross-sectional shape profile of the outer surface of the transition section in the plane of the longitudinal axis comprises a quarter segment of an ellipse. Alternatively, the cross-sectional shape profile of the outer surface of the transition section in the plane of the longitudinal axis comprises a quarter segment larger than an ellipse. Alternatively, the cross-sectional shape profile of the outer surface of the transition section in the plane of the longitudinal axis comprises a quarter segment smaller than an ellipse. Different load conditions may benefit from different forms of ellipses.

[0021] In this specification, references to "curvature" include smooth or gradual changes in surface profiles and multiple consecutive linear increases (or decreases) in diameter, which can be collectively referred to as "curved" shape profiles. For example, the term "curvature" includes relatively small linear step changes, such that the edges or middle regions of each step can be considered to collectively define the curve.

[0022] Preferably, the drill shank adapter includes a shoulder projecting radially from the main length section, wherein the outer diameter of the shoulder is larger than the outer diameter of the main length section and the transition section of the drill shank. This configuration allows for a conventional “shoulder contact” connection between the convex plug and the concave sleeve, while this connection is superior to the alternative “bottom contact” due to the larger diameter and surface area contact between the convex and concave portions.

[0023] Preferably, the side surface of the shoulder that contacts the transition section includes an annular radially outer region aligned substantially perpendicular to the longitudinal axis. Therefore, the curved transition section does not extend along the entire radial length of the annular side surface to provide a flat annular surface that contacts the annular end face of the concave sleeve.

[0024] Optionally, the threaded section includes at least one axially extending helical ridge and groove, wherein the outer diameter of the drill shank axially between the threaded section and the transition section is substantially equal to the outer diameter of the threaded section at both the axial and radial positions corresponding to the ridge of the threaded section. Optionally, the threaded section includes multiple threads formed as double helices or triple helices, etc. Such a configuration can be selected to achieve a desired thread profile with the required mechanical and physical properties.

[0025] Optionally, over the entire axial length of the drill shank between the threaded section and the main length section or shoulder, the cross-sectional area of ​​the drill shank is at least equal to the cross-sectional area of ​​the main length section in a plane perpendicular to the longitudinal axis. Optionally, the diameter of the threaded section is slightly smaller than the diameter of the main length section. Therefore, the drill shank is constructed to be robust and durable under bending and tensile loads.

[0026] According to a second aspect of the invention, a drilling assembly is provided, which includes a drill shank adapter as claimed herein. Attached Figure Description

[0027] Specific embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0028] Figure 1 This is an external view of the drill string, which is part of the rock drilling equipment.

[0029] Figure 2 This is according to a specific embodiment of the present invention. Figure 1 An external side view of one end of the drill shank adapter in the area of ​​the convex connector, wherein the unthreaded drill shank is axially divided into a straight section and a curved transition section.

[0030] Figure 3 This is an alternative embodiment of the invention. Figure 1 An external side view of one end of the drill shank adapter in the region of the convex connector, wherein the unthreaded drill shank has only a curved transition section;

[0031] Figure 4 This is an enlarged view of the drill shank portion of a convex connector according to an embodiment of the present invention, wherein the apex of the elliptical profile of the transition section is tangent to the shoulder.

[0032] Figure 5 This is an enlarged view of the drill shank portion of a convex connector according to an alternative embodiment of the present invention, wherein the elliptical profile of the transition section is undercut on the annular side surface of the shoulder.

[0033] Figure 6 This is an enlarged view of the drill shank portion of a convex connector according to an alternative embodiment of the present invention, wherein the elliptical profile of the transition section is inclined.

[0034] Figures 7a to 7g It is a comparison with existing technologies ( Figure 7a ) and different embodiments of the present invention ( Figures 7b to 7g The safety factor image. Detailed Implementation

[0035] Figure 1A drill shank adapter 100 is shown, comprising a body 101 having a front end 103 and a rear end 104 relative to a longitudinal axis. A plurality of axially parallel elongated splines 106 project radially outward from an outer surface 102 in a rear region of the body 101 facing the rear end 104. The splines 106 are configured to engage with corresponding splines of a rotary motor (not shown) to cause the adapter 100 to rotate about an axis 109 during drilling operations. The adapter 100 also includes a flushing hole (or drill hole) 105 axially positioned between the ends 103, 104 and extending radially from the outer surface 102 through the body 101 to an axially extending internal cavity or region within the adapter 100. The drill shank adapter 100 is configured for attachment to an elongated drill string and allows stress waves to be transmitted to a drilling tool (not shown) located in the deepest region of the borehole to apply an impact drilling action. Specifically, the adapter front end 103 can be connected to the rear end of the rearmost extended drill pipe 107, which forms part of the drill string. The rearmost adapter end 104 is configured to be contacted by a hydraulically driven piston 108, which generates stress waves within the adapter 100 and the drill string. The front end 103 includes an annular shoulder 110 from which a convex plug 108 projects axially.

[0036] Figure 2 The diagram shows the plug 108 axially divided into a threaded section 107 at the very end and a threadless drill shank 109 axially located between the threaded section 107 and the shoulder 110. When the convex end of the drill shank adapter is connected to the concave end of the adjacent drill rod, the annular surface 115 at the very end of the axially extended drill rod 107 abuts against the shoulder 110 (as shown). Figure 1 As shown), the annular end face 114 of the convex plug 108 is completely accommodated within the sleeve (not shown) on the rearmost elongated drill rod 107.

[0037] The tubular body 101 includes a cylindrical outer surface 200 that flares radially outward at a shoulder 110 to provide an annular recessed region 201 terminating at a cylindrical surface 202 located at the shoulder 110. The diameter and cross-sectional area of ​​surface 202 in a plane perpendicular to axis 204 are therefore larger than the corresponding diameter or cross-sectional area (in a parallel plane) of the main length surface 200. The shoulder 110, particularly the cylindrical surface 202, terminates on the plug side by an annular side surface 203 aligned perpendicular to axis 204. The plug 108 projectes axially from the radially inward region of surface 203 and is coaxially aligned with the body 101 and the annular shoulder 110. The diameter of the body 101 may be equal to or smaller than the diameter of the protruding plug 108. The body 101 may have a constant or varying diameter along its length.

[0038] According to the specific embodiment, the threaded section 107 includes a pair of helical coils 209 extending axially from the drill shank 109 to the plug end 114. Specifically, a pair of helical ridges 207 and grooves 208 extend axially along the section 107. The unthreaded drill shank 109 can be axially divided into a straight section 205 positioned axially closest to the threaded section 107 and a curved transition section 206 positioned axially closest to the side surface 203. The outer surface of the straight section 205 is substantially parallel to the axis 204, while the outer surface of the transition section 206 is radially tapered outward from the threaded section 107 to abut against the annular side surface 203. The combined axial length of the straight section 205 and the transition section 206 can be equal to, greater than, or less than the axial length of the shoulder surface 202, but less than the axial length of the threaded section 107. Therefore, the diameter or cross-sectional area of ​​the straight section 205 is smaller than the diameter or cross-sectional area of ​​the transition section 206. Furthermore, the diameter or cross-sectional area of ​​the straight portion 205 is approximately equal to the diameter or cross-sectional area of ​​the threaded section 107 at the axial and radial positions corresponding to the outermost radial portion of the tooth crest 207.

[0039] Figure 3 As shown, alternatively, the unthreaded drill shank 109 may only have a curved transition section 206 extending from the side surface 203 all the way to the threaded section 107. In other words, the straight length section 205 may be absent.

[0040] refer to Figure 2 and Figure 3 The transition section 206 can be considered as the transition area between the plug 108 and the annular shoulder 110. For example... Figure 2 and Figure 3 As shown, the diameter and cross-sectional area of ​​the transition section 206 increase from the threaded section 107 to the shoulder 110, such that the outer surface profile of the transition section 206 in the plane along the axis 204 is curved according to a gradual curvature having a profile corresponding to a quarter segment of the circumference of the ellipse 214, or slightly larger or slightly smaller than a quarter segment of the ellipse 214. The ellipse 214 has a semi-major axis (x) and a semi-minor axis (y). Preferably, there is no abrupt change from a first radius to a second radius along the length of the transition section 206, but rather the radius changes continuously and gradually along the length of the transition section 206. Optionally, the transition section 206 may also include segments in which the shape profile is straight and / or has a different curved profile, which may be located at either end of the elliptical profile or as an interruption along the elliptical profile.

[0041] When n = 2, the equation of the ellipse is defined by the Lamé curve:

[0042]

[0043] in:

[0044] x is the coordinate on the x-axis;

[0045] y is the coordinate on the y-axis;

[0046] a is the semi-major axis (x);

[0047] b is the semi-minor axis (y);

[0048] n determines the shape of the curve. n=2 defines a general ellipse. n<2 defines a hypoellipse and n>2 defines a hyperellipse.

[0049] The elliptical contour 214 is shown in Figure 4 an enlarged view of the transition section 206.

[0050] In the present invention, the ratio of the major axis to the minor axis (a:b) is within the range of 2b<a<8b, preferably 2b<a<6b, more preferably 2.5b<a<6b, even more preferably 2.5b<a<5.75b.

[0051] Preferably, the semi-minor axis (b) is as large as possible. More preferably, the semi-minor axis (b) is proportional to the diameter of the threaded section 107 of the convex plug portion 108 according to the following equation:

[0052]

[0053] wherein (as shown in Figure 4 ):

[0054] Di = diameter of the threaded section 107 between opposite grooves 208;

[0055] Dy = diameter of the threaded section 107 between opposite spiral ridges 207.

[0056] Preferably, the exponent factor n is within the range of 1≤n≤3, preferably 1.8≤n≤2.2, and most preferably 2.

[0057] The equation for the elliptical contour of the transition section 206 can be measured using a contour measuring machine. The contour measuring machine drags a stylus across the surface of the transition section 206, then the device attempts to fit different geometric shapes, and outputs the equation of the measured shape contour.

[0058] At each end of the semi-major axis (x) is the vertex 215 of the ellipse 214, and at each end of the semi-minor axis (y) is the co-vertex 216 of the ellipse 214. Optionally, the vertex 215 of the ellipse is positioned on a tangent line tangent to the annular side surface 203 of the shoulder 110, as shown in Figure 4 .

[0059] Figure 5An alternative design is shown in which the vertex 215 of the ellipse 214 undercuts the annular side surface 203 of the shoulder 110.

[0060] Alternatively, the x-axis of ellipse 214 is parallel to the longitudinal axis 204, as shown below. Figure 4 As shown.

[0061] Figure 6 An alternative is shown in which the x-axis of ellipse 214 is tilted relative to the longitudinal axis 204.

[0062] It should be understood that, as stated above, any combination of the positions of vertex 215 can be combined with any orientation of the x-axis relative to the longitudinal axis 204.

[0063] The profile of the transition section 206 provides a convex connection end that exhibits enhanced stiffness and is more resilient to bending moments and tensile forces compared to conventional connectors. Furthermore, the transition section 206 is configured to eliminate or at least minimize stress concentration at the section where the plug 108 axially protrudes from the shoulder 110.

[0064] Figures 7a to 7g Table 1 shows the safety factor images captured using the Dang van standard, with rotational bending as the load case for different transition segments of profile 206:

[0065]

[0066] Table 1: Description of the transition section contours used in the safety factor image.

[0067] As the Dang van metric value decreases, the risk of failure increases. Therefore, a darker color indicates a higher risk of failure. This can be achieved through comparison. Figure 7a (Prior art) and Figures 7b to 7g (Embodiments of the present invention) As can be seen, the risk of failure has been reduced for the outline of the present invention. The stress image was captured using implicit analysis in LS-Dyna, and the Dang van standard was extracted using nCode software. Table 1 also shows the safety factor measured from the device; a higher safety factor is better and indicates lower stress. The results in Table 1 show that all samples of the present invention have a higher safety factor compared to prior art versions.

Claims

1. A shank adapter for forming part of a drilling assembly, said shank adapter (100) comprising: a main body (101) extending axially between a first end (105) and a second end (106); a male plug portion (108) provided at said second end (106), having an externally threaded section (107) and a non-threaded shank (109) axially positioned between said main body (101) and said threaded section (107); a radially protruding shoulder (110) axially positioned between said main body (101) and said male plug portion (108); said shank (109) has a transition section (206) positioned adjacent to said shoulder (110) at said second end (106), said transition section (206) having an outer diameter that increases in a direction from said plug portion (108) to said shoulder (110); wherein the cross-sectional shape profile of the outer surface of said transition section (206) in the plane of a longitudinal axis (204) comprises a segment of an ellipse (214) according to the following equation, said ellipse (214) having a semi-major axis a, a semi-minor axis b and an exponential factor n: wherein is the coordinate on the x-axis; y is the coordinate on the y-axis; characterized in that: the ratio of the semi-major axis to the semi-minor axis a:b is within the range of 2b < a < 8b, wherein said semi-minor axis b is proportional to the dimension of said threaded section (107) according to the following equation: wherein, Di is the diameter of said threaded section (107) between opposing grooves (208), and Dy is the diameter of said threaded section (107) between opposing helical ridges (207).

2. The drill handle adapter (100) of claim 1, wherein, said non-threaded shank (109) is axially divided into a straight portion (205) positioned axially closest to the threaded section (107) and a curved transition section (206) positioned axially closest to the side surface (203).

3. The drill handle adapter (100) of claim 1, wherein, said non-threaded shank (109) only has the curved transition section (206) extending continuously from the side surface (203) to said threaded section (107).

4. The drill handle adapter (100) according to any one of claims 1-3, wherein, the ratio of the semi-major axis to the semi-minor axis a:b is within the range of 2.5b < a < 6b.

5. The drill shank adapter (100) according to any one of claims 1-3, wherein, the exponential factor n is within the range of 1≤n≤3.

6. The drill shank adapter (100) according to any one of claims 1-3, wherein, the vertex (215) of said ellipse (214) is positioned at a tangent line tangent to the annular side surface (203) of said shoulder (110).

7. The drill shank adapter (100) according to any one of claims 1-3, wherein, the vertex (215) of said ellipse (214) undercuts the annular side surface (203) of said shoulder (110).

8. The drill shank adapter (100) according to any one of claims 1-3, wherein, the x-axis of said ellipse (214) is parallel to said longitudinal axis (204).

9. The drill shank adapter (100) according to any one of claims 1-3, wherein, the x-axis of said ellipse (214) is inclined relative to said longitudinal axis (204).

10. The drill shank adapter (100) according to any one of claims 1-3, wherein, the cross-sectional shape profile of said outer surface of said transition section (206) in the plane of said longitudinal axis (204) comprises a quarter segment of the ellipse (214).

11. The drill shank adapter (100) according to any one of claims 1-3, wherein, the cross-sectional shape profile of said outer surface of said transition section (206) in the plane of said longitudinal axis (204) comprises more than a quarter segment of the ellipse (214).

12. The drill shank adapter (100) according to any one of claims 1-3, wherein, The cross-sectional shape profile of the outer surface of the transition section (206) in the plane of the longitudinal axis (204) includes a quarter segment smaller than an ellipse (214).

13. A drilling assembly comprising a drill shank adapter (100) according to any one of claims 1-12.

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