Low-stress cavity 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 conically-shaped drill rod to form a conical friction connection, the cavity having a conical region proximate the axial end and a cylindrical region proximate the bit section, and wherein there is a connection section joining the conical region to the cylindrical region, the conical region having a linear tapered region having a starting point adjacent the connection region, and the connection section has a first curved connection section having a first radius CR1, and a tangent CT1 to a center point along the first curved connection section is positioned a first distance CD1 from the tapered region starting point.

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 means of a threaded connection or a conical friction connection. In the case of a conical friction connection, also known as a tapered joint, the drill bit has a generally conical cavity terminating in a cup-shaped cylindrical area, and the end of the drill rod to be received in the cavity is generally conical.

[0003] In known designs, the conical section of the cavity connects directly to the cylindrical region. The problem with this sharp connection is that high stresses are located inside the drill bit, which increases the risk of drill bit breakage in the region, 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 cavity of the drill bit. Summary of the Invention

[0006] The present invention provides 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 conically-shaped drill rod to form a conical frictional connection, the cavity having a conical region proximate the axial end and a cylindrical region proximate the bit section, a connection section joining the conical region to the cylindrical region, the conical region having a linear tapered region having a starting point adjacent the connection region, the connection section having a first curved connection region having a first radius CR1, and a tangent CT1 to a center point along the first curved connection region positioned a first distance CD1 from the start of the tapered region.

[0007] Advantageously, the inclusion of a curved transition section reduces stresses in the conical cavity of the drill bit, which means 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] Optionally, the connection section further has a second curved connection region having a second radius CR2, and a tangent CT2 thereof to a center point along the second curved connection region is positioned a second distance CD2 from the tapered region start point, and<CD1、およびCR2> Advantageously, the inclusion of two different radii can reduce stress while maintaining sufficient contact between the conical rod and the conical cavity within the drill bit.

[0009] Preferably, CR1 is between 1 and 160 mm, more preferably between 5 and 120 mm. Advantageously, this 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] Optionally, the first curved connection region connects directly to the second curved connection region.Advantageously, this design has a low level of stress in the region of the exit of the conical cavity of the drill bit.

[0011] Alternatively, the first curved region connects to the second curved region via an intermediate 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.

[0012] Optionally, the connection section further comprises a third curved connection region having a third radius CR3, a tangent CT3 thereof to a center point along the third curved connection section being positioned a third distance CD3 from the tapered region start point, and<CD2、およびCR3> CR2. Advantageously, this design has a low level of stress in the area of ​​the exit of the conical cavity of the drill bit.

[0013] Optionally, there is also a curved transition section positioned between the axial end of the drill bit and the linear tapered region of the conical region.

[0014] 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]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a drill bit having a cone-shaped internal cavity. [Figure 2] FIG. 10 is an enlarged view of a cross section of a connection section according to one embodiment, in which the connection section has a single radius. [Figure 3]10 is an enlarged view of a cross section of a connection section according to one embodiment, in which the connection section has two radii and the first curved connection region and the second curved connection region are directly connected. [Figure 4] 10 is a cross-sectional view of a connection section according to one embodiment, wherein the connection section has two radii and the first curved connection region and the second curved connection region of the connection section are connected via an intermediate straight section. [Figure 5] 10 is an enlarged view of a cross section of a connection section according to one embodiment, in which there is also a third curved connection region within the connection section. [Figure 6] FIG. 10 is a cross-sectional view of a connection section according to one embodiment, further comprising a curved transition 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

[0016] 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 along a linear tapered region 26 to a cup-shaped cylindrical region 16 that terminates the cavity 8 and is positioned adjacent the bit section 6. A connecting section 40 joins the conical region 14 to the cylindrical region 16. The tapered region 26 has a tapered region beginning 48 adjacent the connecting section 40.

[0017] 2 shows an enlarged view of the drill bit 2 in the area of ​​the connection section 40 according to one embodiment of the present invention. In this embodiment, the inner surface 10 of the connection section 40 has a first curved connection region 42 with a first radius CR1, and its tangent CT1 to a center point along the first curved connection region 42 is positioned a first distance CD1 from the tapered region start point 48.

[0018] 3 shows an alternative embodiment in which the inner surface 10 of the connection section 40 has a first curved connection region 42 having a first radius CR1, the tangent CT1 to a center point along the first curved connection region 42 being positioned a first distance CD1 from the tapered region start point 48, and a second curved connection region 44 having a second radius CR2, the tangent CT2 to a center point along the second curved connection region 44 being positioned a second distance CD2 from the tapered region start point 48.<CD1、およびCR2> CR1, in other words, the curved connection section with the smaller radius is adjacent to the cylindrical region 16. CR1 is between 1 and 160 mm, preferably between 5 and 120 mm. CR2 is >1 and 160 mm, preferably between 5 and 120 mm. In this embodiment, the first curved connection region 42 is directly connected to the second curved connection region 44, which is directly connected to the straight tapered region 26.

[0019] FIG. 4 shows an alternative embodiment in which a first curved connection region 42 is connected to a second curved connection region 44 via an intermediate straight section 34 .

[0020] FIG. 5 shows an alternative embodiment, where the connection section 40 further includes a third curved connection region 46. The third curved connection region 46 has a third radius CR3, and its tangent CT3 with respect to the center point along the first curved connection region 46 is positioned at a third distance CD3 from the taper region start point 48, and CD3 < CD2. Different from CR1 and CR2, CR3 is preferably CR3 > CR2. Optionally, the connection section 40 can also include four or more curved connection sections each having a different radius. Each of the curved connection sections can be directly connected to each other or can be connected to each other via an intermediate straight section 34.

[0021] FIG. 6 shows an alternative embodiment, where there is further a curved transition section 32 positioned between the axial end 18 of the drill bit 2 and the straight taper region 26.

[0022] FIG. 7 shows the von Mises equivalent stress taken in the conical region 14 of a prior art drill bit without a curved connection region. FIG. 8 shows the von Mises equivalent stress taken in the conical region 14 for the drill bit of the present invention with a first curved connection region. 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. An elastic material with a Young's modulus of 206 GPa, a Poisson's ratio of 0.3, and a bulk mass density of 7800 kg / m 3 The model was solved using the implicit solver of LS-Dyna R10, an image of the von Mises equivalent stress was obtained at the maximum load, and HyperView 2019 was used for post-processing. It can be seen that the stress in the cavity 8 of the drill bit 2 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 conical region (14) closest to the axial end (18) and a cylindrical region (16) closest to the bit section (6); There is a connection section (40) joining the conical region (14) to the cylindrical region (16); the conical region (14) has a linear tapered region (26) having a starting point (48) adjacent the connecting section (40); The connection section (40) has a first radius (CR １ ) and its tangent (CT) to a center point along said first curved connection region (42). １ ) is the first distance (CD) from the tapered region start point (48) １ ), said connection section (40) further comprising a second curved connection region (44) having a second radius (CR 2 ), the tangent (CT 2 ) of which is positioned at a second distance (CD 2 ) from said tapered region start point (48); CD 2 <CD 1 and CR 2 >CR 1 ; A striking drill bit (2).

2. CR １ The impact drill bit (2) according to claim 1, wherein is 1 to 160 mm.

3. CR １ The impact drill bit (2) according to any one of claims 1 to 2, wherein the length is 5 to 120 mm.

4. The impact drill bit (2) according to any one of claims 1 to 3, wherein the first curved connecting region (42) directly connects to the second curved connecting region (44).

5. The impact drill bit (2) according to any one of claims 1 to 3, wherein the first curved connection region (42) connects to the second curved connection region (44) via an intermediate straight section (34).

6. The connection section (40) has a third radius (CR ３ ) along said third curved connection region (46), and a tangent (CT) thereof to a center point along said third curved connection region (46). ３ ) is a third distance (CD) from the tapered region start point (48). ３ ) and CD ３ <CD ２ , and C.R. ３ >CR ２ The impact drill bit (2) according to any one of claims 1 to 5,

7. The impact drill bit (2) according to any one of claims 1 to 6, further comprising a curved transition section (32) positioned between the axial end (18) of the drill bit (2) and the linear tapered region (26) of the conical region (14).

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