inclined oval thread bottom

Abstract

An impact drill component (2) having a longitudinal central axis (14), the impact drill component comprising at least one threaded portion (4); wherein the threaded portion comprises a plurality of thread forms (16); wherein each thread form comprises a crest (6), a root (8), a contact flank (10); a non-contact flank (12); a contact flank transition section (22) extending between the root and the contact flank; and a non-contact flank transition section (24) extending between the root and the non-contact flank; characterized in that at least one of the contact flank transition section and the non-contact flank transition section has a curvature defined by a portion of an ellipse having a semi-major axis (a), a semi-minor axis (b), and an index factor (n) according to the equation: (I) wherein the semi-major axis (a) and the semi-minor axis (b) are non-parallel to the longitudinal central axis, wherein the ratio of the semi-major axis to the semi-minor axis (a:b) is in the range of 10:1 to 1.5:1, and the major axis (a) of the ellipse extends in a generally longitudinal direction.

Description

Technical Field

[0001] This disclosure generally relates to a thread profile for impact drilling, which provides stronger connections, fewer sudden failures, and reduced stress. Background Technology

[0002] Percussion drilling is used to create long boreholes via multiple extended drill strings, which are connected end-to-end by interconnecting external and internal threads. A well-established technique involves breaking rock by hammering impacts transmitted 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.

[0003] Impact drilling components are typically joined together via threaded sections. Generally, a single radius exists in the transition region between the root and surface of the thread. Stress is generated in these abrupt transitions, leading to increased wear and thus reduced component life. Therefore, the problem to be solved is how to reduce the stress generated in threaded connections in order to increase their wear resistance and extend component life. Summary of the Invention

[0004] The object of the present invention is to provide an impact drill bit component having a longitudinal central axis, the impact drill bit component including at least one threaded portion; wherein the threaded portion includes a plurality of thread profiles; wherein each thread profile includes a crest, a root, a contact surface, a non-contact surface, a contact surface transition section extending between the root and the contact surface, and a non-contact surface transition section extending between the root and the non-contact surface; wherein at least one portion of at least one of the contact surface transition section and the non-contact surface transition section has a curvature defined by a portion of an ellipse, the ellipse having a semi-major axis (a), a semi-minor axis (b), and an exponential factor (n) according to the following equation:

[0005] The semi-major axis (a) and the semi-minor axis (b) are not parallel to the longitudinal central axis.

[0006] Advantageously, this allows the maximum possible radius of the ellipse to be positioned in the region of the transition section with the smallest cross-section, located between the tooth root and the tooth surface. Therefore, less steel needs to be removed to form the thread profile without altering the length of the contact and / or non-contact tooth surfaces. By tilting the ellipse, it can be advantageously positioned tangent to both the tooth surface and the tooth root of the thread. This tilting also allows for an increase in the major and minor axis radii of the ellipse, resulting in a smoother transition. Overall, the stress level in the threaded portion is reduced, making it less prone to wear or premature breakage, thus increasing the lifespan of the threaded connection.

[0007] In some example embodiments, both the contact tooth surface transition section and the non-contact tooth surface transition section have a curvature defined by a portion of an ellipse, wherein the semi-major axis (a) and the semi-minor axis (b) are not parallel to the longitudinal central axis. Advantageously, the stress in the thread profile is further reduced.

[0008] In some example embodiments, an angle (γ) exists between the semi-major axis (a) of the elliptical profile of the transition section and the longitudinal central axis, wherein γ is in the range of 1- Between. Advantageously, this range results in the lowest stress level in the said thread profile.

[0009] In some example embodiments, the cross-sectional shape profile of the outer surface of the transition section includes a segment between 5% and 50% of an ellipse. Advantageously, this range results in reduced stress while still being geometrically fitted into the thread profile to enable good contact with corresponding threads from adjacent components.

[0010] In some example embodiments, the ratio (a:b) of the semi-major axis to the semi-minor axis is in the range of 10:1 to 1.5:1. Advantageously, this range results in reduced stress while still being able to geometrically fit into the thread profile to allow for good contact with corresponding threads from adjacent components.

[0011] In some example embodiments, the exponential factor (n) is in the range of 1.1 ≤ n ≤ 8. Advantageously, this produces a smooth transition section, which leads to an increase in stress reduction.

[0012] In some example embodiments, the major axis (a) of the ellipse extends in a substantially longitudinal direction. Advantageously, this produces a smooth transition section, which leads to an increase in stress reduction.

[0013] In some example embodiments, the root of the thread profile has a straight section inclined relative to the longitudinal central axis of the component. Advantageously, by inclining the root of the thread, the radius of the transition between the root and the contact surface can be increased, which reduces the stress level in the root of the thread without increasing the stress level at the transition between the root and the non-contact surface. By inclining the root of the thread, the cross-sectional area increases, which means there is an increased volume of steel, which reduces the stress level and makes the thread more rigid with respect to the non-contact radius, thus allowing the radius of the non-contact surface to be reduced without increasing the stress in this area. Furthermore, the smaller radius of the non-contact surface facilitates disengagement. Therefore, the total stress level in the thread is reduced, making it less prone to wear and premature breakage, thereby increasing the life of the threaded connection.

[0014] In some example embodiments, the crest and root of the thread profile are arched along the length of the threaded portion. Advantageously, this increases the stiffness of the connection under bending loads. Because the curvature of the arched thread is better aligned with the curvature of the bend, the arched thread distributes the bending load more evenly over its entire length. Furthermore, it reduces engagement and disengagement times. Attached Figure Description

[0015] Specific embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of the drilling components.

[0016] Figure 2 This is a schematic diagram showing the thread profile with an inclined thread bottom.

[0017] Figure 3a This is a schematic diagram showing the thread profile of an inclined elliptical transition section, wherein the ellipse is positioned only in one of the transition sections.

[0018] Figure 3b This is a schematic diagram showing the thread profile of an inclined elliptical transition section, wherein the contact tooth surface transition section, the non-contact tooth surface transition section, and the root of the thread all have curvature defined by a portion of the same ellipse.

[0019] Figure 4 This is a schematic diagram showing the thread profile of γ.

[0020] Figure 5 This is a schematic diagram of a thread profile with an inclined tooth root. Detailed Implementation

[0021] Figure 1A percussion drill bit assembly 2 with a longitudinal central axis 14 is shown, comprising at least one threaded portion 4. Three or more thread profiles are typically present on the threaded portion 4. The threaded portion 4 can be externally threaded or internally threaded. The assembly 2 can have one externally threaded portion; or one internally threaded portion; or two externally threaded portions; or two internally threaded portions; or one externally threaded portion and one internally threaded portion. The threaded portion can have any suitable thread form, such as, but not limited to, trapezoidal. The threaded portion can be single, double, or triple-threaded. The percussion drilling assembly can be, for example, but not limited to, drill pipe, drill shank adapter, drill bit, threaded adapter, or connecting sleeve. The drill bit assembly can be configured for shoulder contact or bottom contact engagement. A single thread profile 16 is considered to be located between the midpoint of one crest 6 and the midpoint of the adjacent crest 6.

[0022] Figure 2 A schematic diagram of the thread profile of threaded portion 4 is shown. Threaded portion 4 includes thread profile 16; wherein thread profile 16 includes a crest 6 (also called the thread top), a root 8 (also called the thread bottom), a contact surface 10; a non-contact surface 12; a contact surface transition section 22 between the root 8 and the contact surface 10; and a non-contact surface transition section 24 between the root 8 and the non-contact surface 12. The crest can have any suitable form, such as flat, curved, straight, or inclined. The root 8 is defined as the section that includes the lowest part of thread profile 16, and they can be straight or curved. If the root is curved, it can have a curvature defined by a single radius, multiple radii, or a portion of an ellipse. Typically, the contact surface 10 and the non-contact surface 12 are straight.

[0023] Figure 3a The thread profile (not drawn to scale) is shown, indicating that at least a portion of at least one of the contact tooth surface transition section 22 and the non-contact tooth surface transition section 24 has a curvature defined by a portion of an ellipse having a semi-major axis (a), a semi-minor axis (b), and an exponential factor (n) according to the following equation:

[0024] The semi-major axis (a) and the semi-minor axis (b) are not parallel to the longitudinal central axis 14.

[0025] “x” represents the horizontal coordinate point on the ellipse.

[0026] “y” represents the vertical coordinate point on the ellipse.

[0027] “a” represents the semi-major axis, which is half the length of the major axis, where the major axis is the longest diameter of the ellipse passing through the center.

[0028] “b” represents the semi-minor axis, which is half the length of the minor axis. This minor axis is the shortest diameter of the ellipse passing through the center. The minor axis is perpendicular to the major axis.

[0029] “n” is the exponential factor.

[0030] In other words, the semi-major axis and the semi-minor axis are inclined relative to the longitudinal axis 14 of the component. The semi-minor axis and the semi-major axis are also not perpendicular to the longitudinal axis 14 of the component 2.

[0031] In some example embodiments, the contact tooth surface transition section 22 and the non-contact tooth surface transition section 24 both have curvature defined by a portion of an ellipse, wherein the semi-major axis (a) and semi-minor axis (b) are not parallel to the longitudinal central axis (14). The transition sections 22 and 24 may have the same or different elliptical profiles.

[0032] Alternatively, the second segment in transition segments 22, 24 may have alternative curvatures, such as, but not limited to, a radius, a portion of a non-inclined ellipse (i.e., such that the semi-major axis (a) is parallel to the longitudinal axis 14), or any other suitable form of curvature.

[0033] In some example embodiments, at least one of the transition segments 22, 24 has a curvature defined by a portion of an ellipse. In other example embodiments, only a portion of at least one of the transition segments 22, 24 has a curvature defined by a portion of an ellipse, and the transition segments 22, 24 may also have straight segments and / or curved segments with a single radius or multiple radii.

[0034] Figure 3b In some example embodiments, the contact tooth surface transition section 22 and the non-contact tooth surface transition section 24, as well as the tooth base 8, have curvature defined by a portion of the same ellipse, namely an ellipse extending between the contact tooth surface 10 and the non-contact tooth surface 12 (having the same equation).

[0035] Figure 4 This is a schematic diagram of the thread profile (not drawn to scale), showing an angle (γ) between the semi-major axis (a) of the elliptical profile in transition sections 22, 24 and the longitudinal central axis 14. In some example embodiments, γ is at 1- Between. For example, γ in 1- Between, for example, γ in 5- between.

[0036] In some example embodiments, the cross-sectional shape profile of the outer surface of the transition sections 22, 24 includes a segment between 5-50% of an ellipse. For example, a segment between 5-20% of an ellipse. For example, a segment between 5-15% of an ellipse, or a segment between 10-15% of an ellipse. For example, a segment between 30-50% of an ellipse. For example, a segment between 35-45% of an ellipse.

[0037] In some example embodiments, the ratio (a:b) of the semi-major axis to the semi-minor axis is in the range of 15:1 to 1:1. For example, the ratio a:b is in the range of 10:1 to 1.5-1. For example, the a:b ratio is between 15:1 and 5:1. For example, the a:b ratio is between 12:1 and 8:1. For example, the a:b ratio is in the range of 5:1 to 2:1.

[0038] In some example embodiments, the exponential factor (n) is in the range of 1.1–8. For example, n is in the range of 1.5–4. For example, n is in the range of 1.5–2.5. In some example embodiments, n is 2. The value of n determines the shape of the curve; when n=2, this forms a normal ellipse; when n<2, this forms a quasi-ellipse; and when n>2, this forms a superellipse.

[0039] The dimensions of the ellipse, the a:b ratio, the exponential factor n, and a segment of the ellipse can be varied in different ways to achieve similar or identical curvature in transition segments 22 and 24.

[0040] In some example embodiments, the semi-major axis (a) of the ellipse extends in a substantially longitudinal direction. In some example embodiments, the semi-minor axis (b) of the ellipse extends in a substantially radial direction.

[0041] Figure 5 This is a schematic diagram of a thread profile (not drawn to scale), showing that in some example embodiments, the root 8 of thread profile 16 has a straight section inclined relative to the longitudinal central axis 14. In other words, the root 8 of thread profile 16 is not parallel to the longitudinal central axis 14. In some example embodiments, there is an angle (α) between the longitudinal axis 14 and the root 8. In some example embodiments, α is between 0.1 and... Between. For example, α is between 1 and... Between. For example, α is between 2- Between. The contact tooth surface transition section 22 has a first axial innermost end 18, and the non-contact tooth surface transition section 24 has a second axial innermost end 20; a first length (L1) is measured between the first axial innermost end 18 and the longitudinal central axis 14; a second length L2 is measured between the second axial innermost end 20 and the longitudinal central axis 14. In some example embodiments, within the same thread profile 16, L2 > L1. The axial innermost ends 18 and 20 are considered to be the positions where the curvature of the transition sections 22 and 24 ends and the starting point of the tooth root 8 begins.

[0042] In some example embodiments, the crest 6 and root 8 of the thread profile 16 are arched along the length of the threaded portion 4. Further details of the arched thread profile are described in EP 3536894.

[0043] References to "an embodiment," "embodiment," "example embodiment," etc., in the specification indicate that the described embodiment may include a specific feature or a specific combination of features (e.g., one or more components, elements, integrals, structures, operations, and / or steps), but each embodiment may not necessarily include a specific feature or a specific combination of features. Such phrases do not necessarily refer to the same embodiment. Furthermore, when a specific feature or a specific combination of features is described in connection with an embodiment, it is assumed that implementing such a feature or a specific combination of features in combination with other embodiments is within the knowledge of those skilled in the art, whether or not it is explicitly described.

Claims

1. An impact drill bit assembly (2) having a longitudinal central axis (14), the impact drill bit assembly (2) comprising at least one threaded portion (4); in, The threaded portion (4) includes multiple thread profiles (16); Each thread profile (16) includes a crest (6), a root (8), a contact surface (10), and a non-contact surface (12); There is a contact tooth surface transition section (22) extending between the tooth base (8) and the contact tooth surface (10) and a non-contact tooth surface transition section (24) extending between the tooth base (8) and the non-contact tooth surface (12); Its features are: At least one portion of at least one of the contact tooth surface transition section (22) and the non-contact tooth surface transition section (24) has a curvature defined by a portion of an ellipse, the ellipse having a semi-major axis (a), a semi-minor axis (b), and an exponential factor (n) according to the following equation: The semi-major axis (a) and the semi-minor axis (b) are not parallel to the longitudinal central axis (14), and the ratio (a:b) of the semi-major axis to the semi-minor axis is in the range of 10:1 to 1.5:1, and the major axis (a) of the ellipse extends in a substantially longitudinal direction.

2. The component (2) according to any one of the preceding claims, wherein, Both the contact tooth surface transition section (22) and the non-contact tooth surface transition section (24) have curvature defined by a portion of an ellipse, wherein the semi-major axis (a) and the semi-minor axis (b) are not parallel to the longitudinal central axis (14).

3. The component (2) according to any one of the preceding claims, wherein, The angle (γ) between the semi-major axis (a) of the elliptical profile of the transition sections (22, 24) and the longitudinal central axis (14) is at 1- between.

4. The component (2) according to any one of the preceding claims, wherein, The cross-sectional shape profile of the outer surface of the transition sections (22, 24) includes a segment between 5% and 50% of an ellipse.

5. Component (2) according to any one of the preceding claims, wherein, The ratio (a:b) of the semi-major axis to the semi-minor axis is in the range of 5:1 to 2:

1.

6. Component (2) according to any one of the preceding claims, wherein, The exponential factor (n) is in the range of 1.1 ≤ n ≤ 8.

7. The component (2) according to any one of the preceding claims, wherein, The contact tooth surface transition section (22), the non-contact tooth surface transition section (24), and the tooth base (8) have curvatures defined by a portion of the same ellipse.

8. Component (2) according to any one of claims 1-6, wherein, The root (8) of each thread profile (16) has a straight section that is inclined relative to the longitudinal central axis (14).

9. The component (2) according to any one of the preceding claims, wherein, The crest (6) and root (8) of the thread profile (16) are arched in an arc shape along the length of the thread portion (4).

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