Low-stress cavity outlet for conical connection of drill bits

Abstract

1. An impact drill bit having a longitudinal axis, comprising a sleeve section and a bit section, wherein the sleeve section has an axial end at an opposite end of the drill bit compared to the bit section, and wherein a generally conical-shaped internal cavity extends from the axial end for receiving a conical-shaped drill rod to form a conical friction connection, the internal cavity having a transition section extending between the axial end of the drill bit and the linear tapered region, the transition section having a first curved region having a first radius TR1, and wherein a tangent line TT to a center point along the first curved transition section is positioned a first distance TD1 from the axial end.

Description

[Technical Field]

[0001] The present invention relates to a rock drill, and more particularly to a rock drill for use in percussive rock drilling, comprising a drill bit having a first conical surface, the drill bit adapted to be connected to a drill rod having a corresponding second conical surface. [Background technology]

[0002] In percussion drilling, the drill bit is connected to the drill rod during drilling by a threaded connection or a conical friction connection. In the case of a conical friction connection, also known as a taper joint, the drill bit has a generally conical cavity and the end of the drill rod to be received in the cavity is generally conical.

[0003] In known designs, the outlet of the conical cavity of the drill bit has the form of a straight line with a chamfer. The problem with this is that high stresses are formed at the exit of the cavity in the drill bit, which stresses increase the risk of the drill bit breaking in that area, resulting in a shorter lifespan of the drill bit. If the drill bit breaks, the impact shock wave force may no longer be transmitted to the rock, but may instead loosen the rigid connection between the drill bit and the drill rod, which may result in the drill bit spinning freely or even becoming dislodged and lost in the drill hole.

[0004] US20070175671A1, GB-658631A, and GB-860768A show conventional cone friction connections known in the prior art.

[0005] Therefore, the problem to be solved is how to reduce the stress in the drill bit in the area of ​​the exit of the conical cavity in order to improve the performance and life of the drill bit. Summary of the Invention

[0006] The object of the present invention is to provide a new and improved design for reducing stresses in a drill bit in the region of the outlet of a conical cavity at a taper joint. This object is achieved by providing an impact drill bit having a longitudinal axis, including a sleeve section and a bit section, the sleeve section having an axial end at an opposite end of the drill bit compared to the bit section, a generally conical-shaped internal cavity extending from the axial end for receiving a conical-shaped drill rod to form a conical frictional connection, the internal cavity having a transition section extending between the axial end of the drill bit and the linear tapered section, the transition section having a first curved region with a first radius TR1, and a tangent line TT1 to a center point along the first curved transition section being positioned a first distance TD1 from the axial end.

[0007] Advantageously, the inclusion of a curved transition section reduces stresses in the area of ​​the exit of the conical cavity of the drill bit, which means that the drill bit is less likely to break and therefore reduces the risk of the frictional connection coming loose, resulting in a longer life for the drill bit and a reduced risk of the bit spinning freely or coming off the drill rod.

[0008] Preferably, the transition section further includes a second curved section having a second radius TR2, and a tangent line TT2 thereof to a center point along the second curved transition section is positioned a second distance TD2 from the axial end, where TD2 > TD1, and TR2 > TR1. Advantageously, the inclusion of two different radii can reduce stresses while maintaining sufficient contact between the conical rod and the conical cavity within the drill bit.

[0009] Preferably, TR1 is between 0.1 and 1.5, which advantageously provides an optimum balance between providing a tight connection between the conical rod and the conical cavity of the drill bit and achieving stress reduction.

[0010] Preferably, TD2 is between 0.5 and 5.0 mm. Advantageously, this reduces stresses in the exit area of ​​the cavity.

[0011] Preferably, TR1 is between 0.1 and 1.0 mm. Advantageously, this provides optimal stress reduction.

[0012] Optionally, the first curved region connects directly to the second curved region.Advantageously, this design has a low level of stress in the region of the exit of the conical cavity of the drill bit.

[0013] Alternatively, the first curved region connects to the second curved region via a first straight section. Advantageously, this design has a low level of stress in the area of ​​the exit of the conical cavity of the drill bit.

[0014] Optionally, the transition section further comprises a third curved region having a third radius TR3, a tangent line TT3 to the center point along the third curved transition section positioned a third distance TD3 from the axial end, TD3 > TD2, and TR3 > TR2. Advantageously, this design has a low level of stress in the region of the exit of the conical cavity of the drill bit.

[0015] Optionally, there is also a curved connecting section between the linear tapered region and the cylindrical region, which advantageously provides further stress reduction in the cavity of the drill bit.

[0016] Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view of a drill bit having a cone-shaped internal cavity. [Figure 2] FIG. 10 is a close-up view of a transition section according to one embodiment, in which the transition section has a single radius. [Figure 3] FIG. 10 is a close-up view of a transition section according to one embodiment, where the transition section has two radii and the first curved transition region and the second curved transition region are directly connected. [Figure 4] FIG. 10 is a close-up view of a transition section according to one embodiment, wherein the transition section has two radii and the first and second curved transition regions of the transition section are connected through an intermediate straight section. [Figure 5] FIG. 10 is an expanded view of a transition section according to one embodiment, where there is also a third curved transition region within the transition section. [Figure 6] FIG. 10 illustrates a transition section according to one embodiment, where there is also a curved connecting section between the linear tapered region and the cylindrical region. [Figure 7] FIG. 1 shows a stress image of the cone region of a prior art drill bit. [Figure 8] FIG. 10 shows a stress image of the cone region of the drill bit of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 1 shows a cross-sectional view of a drill bit 2 including an integrated sleeve section 4 and bit section 6. The sleeve section 4 has a generally conical shape and includes an internal cavity 8 for receiving a conical-shaped drill rod (not shown). The drill bit 2 has a longitudinal axis 30. The cavity 8 opens at an axial end 18 of the drill bit 2 that is farthest from the bit section 6. The cavity 8 has a largest cross-sectional diameter at the axial end 18 of the drill bit 2. The cavity 8 includes a conical region 14 that tapers inwardly from the open axial end 18 to a cup-shaped cylindrical region 16 that terminates the cavity 8 and is positioned adjacent to the bit section 6. The conical region 14 includes a linearly tapered region 26 positioned adjacent to the cylindrical region 16 and a transition section 32 positioned between the axial end 18 of the drill bit 2 and the linearly tapered section 26.

[0019] 2 shows an enlarged view of the drill bit 2 in the area of ​​the transition section 32 according to one embodiment of the present invention. In this embodiment, the inner surface 10 of the transition section 32 has a first curved transition section 20 having a first radius TR1, and its tangent line TT1 to a center point along the first curved transition section 20 is positioned a first distance TD1 from the axial end 18 of the drill bit 2.

[0020] FIG. 3 shows an alternative embodiment, enlarged similarly to FIG. 2, in which the inner surface 10 of the transition section 32 includes a first curved transition region 20 having a first radius TR1, a tangent line TT1 to a center point along the first curved transition region 20 positioned a first distance TD1 from the axial end 18 of the drill bit 2, and a second curved transition region 22 having a second radius TR2, a tangent line TT2 to a center point along the second curved transition region 22 positioned a second distance TD2 from the axial end 18 of the drill bit 2. In the present invention, TD2 > TD1 and TR2 > TR1. TR1 is 0.1 to 1.5 mm, preferably 0.1 to 1.0 mm. TR2 is 20 to 300 mm, preferably 35 to 200 mm. TD2 is 0.5 to 5.0 mm, preferably 1.5 to 2.5 mm. In this embodiment, the first curved transition region 20 is directly connected to the second curved transition region 22, which is directly connected to the straight tapered region 26.

[0021] FIG. 4 shows an alternative embodiment similar to FIG. 2 but enlarged, in which the first curved transition region 20 is connected to the second curved transition region 22 via an intermediate straight section 34 .

[0022] FIG. 5 shows an alternative embodiment, similar to FIG. 2 but enlarged, in which the transition section 32 further includes a third curved transition region 24. The third transition region 24 has a third radius TR3, and its tangent TT3 to a center point along the third curved transition section 24 is positioned a third distance TD3 from the axial end 18 of the drill bit 2, where TD3 > TD2. TR3 is different from TR1 and TR2, and preferably TR3 > TR2. Optionally, the transition section 32 can also include four or more curved transition sections, each with a different radius. Each of the curved transition sections can be directly connected to one another or can be connected to one another via an intermediate straight section 34.

[0023] FIG. 6 shows an alternative embodiment in which there is also a curved connecting section 40 between the linear tapered region 26 and the cylindrical region 16 .

[0024] Figure 7 shows the von Mises equivalent stress taken at the conical region 14 of a prior art drill bit where there is no curved transition region. Figure 8 shows the von Mises equivalent stress taken at the conical region 14 for a drill bit of the present invention where there is a transition section with first and second curved transition regions. The model includes one rod and one bit, and is axisymmetric. An axial load of 190 kN is applied to the end of the rod, and the bit face is fully supported. Young's modulus 206 GPa, Poisson's ratio 0.3, and volumetric mass density 7800 kg / m 3 An elastic material of 1000 kJ / cm was used. The model was solved using the implicit method in LS-Dyna R10, and von Mises equivalent stress images were obtained at maximum load, using HyperView 2019 for post-processing. It can be seen that the stress in the exit region of the drill exit area of ​​cavity 8 is reduced for the drill bit of the present invention compared to the prior art drill bit.

Claims

1. A striking drill bit (2) having a longitudinal axis (30) and a sleeve section (4) and a bit section (6), the sleeve section (4) has an axial end (18) at an opposite end of the drill bit (2) compared to the bit section (6), from which extends a generally conical internal cavity (8) for receiving a conical drill rod to form a conical frictional connection; the internal cavity (8) has a transition section (32) extending between the axial end (18) of the drill bit (2) and a linear tapered region (26); The transition section (32) has a first radius (TR １ ) and a tangent (TT1) to a center point along said first curved region (20) is a first distance (TD １ ) and The transition section (32) further has a second curved region (22) having a second radius (TR 2 ), and a tangent (TT 2 ) thereof to a center point along the second curved region (22) is positioned a second distance (TD 2 ) from the axial end (18); TD 2 >TD 1 , and TR 2 >TR 1 ; A striking drill bit (2).

2. TR １ The impact drill bit (2) according to claim 1, wherein is 0.1 to 1.

5.

3. TD ２ The impact drill bit (2) according to claim 1 or 2, wherein the diameter is 0.5 to 5.0 mm.

4. TR １ The impact drill bit (2) according to any one of claims 1 to 3, wherein is 0.1 to 1.0 mm.

5. The impact drill bit (2) according to any one of claims 1 to 4, wherein the first curved region (20) is directly connected to the second curved region (22).

6. The impact drill bit (2) according to any one of claims 1 to 4, wherein the first curved region (20) is connected to the second curved region (22) via a first straight section (34).

7. The transition section (32) has a third radius (TR ３ ) along said third curved region (24), and a tangent (TT) thereof to a center point along said third curved region (24). ３ ) is a third distance (TD) from the axial end (18) ３ ) and TD ３ >TD ２ , and T.R. ３ >TR ２ The impact drill bit (2) according to any one of claims 1 to 6,

8. The impact drill bit (2) according to any one of claims 1 to 7, further comprising a curved connecting section (40) between the linear tapered region (26) and the cylindrical region (16).

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