Improved structure of threaded drilling tool

Abstract

The invention discloses an improved structure of a threaded drilling tool, and aims to provide a threaded drilling tool of which a drilling rod is not easy to break. The drill rod comprises a drill rod body (1) and a drill bit (2), the drill rod body (1) is composed of a rod body (1-1) and an external thread section (1-4) connected with the rod body (1-1) into a whole through a tool withdrawal groove (1-3), and the drill bit (2) is composed of a trouser body (2-3) with an internal thread blind hole (2-2) at one end. The diameter D3 of the tool withdrawal groove (1-3) is smaller than the large diameter D1 of the external thread but larger than the small diameter D2 of the external thread, and the thread ending section of the external thread section (1-4) extends into the tool withdrawal groove (1-3). The opening of the internal thread blind hole (2-2) extends outwards to form a protective skirt sleeve (2-1) with the inner diameter D4 larger than the large diameter D1 of the external thread, the length h of the protective skirt sleeve is larger than the length L2 of the tool withdrawal groove (1-3), and the distance H from the end opening of the protective skirt sleeve (2-1) to the hole bottom of the internal thread blind hole (2-2) is larger than or equal to the sum of the length L1 of the external thread section (1-4) and the length L2 of the tool withdrawal groove (1-3).

Description

Technical Field

[0001] The invention relates to a rock drilling tool, in particular to an improved structure of a threaded drilling tool. Background Art

[0002] Rock drilling tools are usually made of a drill rod connected to a drill bit body through a thread. The drill rod is generally composed of a rod body, a cylindrical transition section, and an external thread section that are fixed together in sequence. The major diameter of the external thread section is equal to the diameter of the cylindrical transition section (see Figure 5 ). The drill bit body is generally composed of a body with an internal thread blind hole at one end. During the operation, the stress conditions of the drill rod and the drill bit body are relatively complex and severe, which can easily cause the drill tool to fail and affect the life of the drill tool. Among them, the fracture of the external thread section of the drill rod is the main form of drill rod failure. After testing and analysis, the main reason for the fracture of the drill rod is that the drill rod will bend around the bending fulcrum under the action of bending moment: If the length of the external thread section of the drill rod is greater than the depth of the blind hole of the drill bit body, the bending fulcrum is likely to occur at the external thread corresponding to the starting end of the internal thread. This is because, on the one hand, the thread groove of the external thread section is deep, which is easy to form stress concentration after heat treatment; on the other hand, the external thread section at the bending fulcrum is exposed to the outside of the drill bit body, which is easily worn by the rock and causes strength reduction. Therefore, the bending stress is superimposed on the thermal stress at the thread groove of the external thread section, which easily causes the external thread section of the drill rod to break at the bending fulcrum.

[0003] If the length of the external thread section of the drill rod is less than the depth of the blind hole of the drill bit body, the bending fulcrum occurs at the external thread end section. Although the external thread end section is hidden in the drill bit body to avoid rock wear, there is also a defect that the thread groove depth of the external thread end section is large, which is easy to form stress concentration after heat treatment; in addition, the large thread groove depth will also cause stress concentration in the thread slow closing section. Therefore, the bending stress is superimposed on the thermal stress at the thread groove of the external thread section and the stress of the slow closing section, which easily causes the drill rod to break at the bending fulcrum (thread end section).

[0004] In order to overcome the above-mentioned defects of the traditional drill rod, a method of replacing the cylindrical transition section with a back cutter groove has been developed. Figure 6 Although it can effectively avoid the defect of stress concentration in the slow threading section, the strength and fatigue life of the groove will be affected because the diameter of the groove is smaller than the minor diameter of the external thread. Summary of the invention

[0005] In view of the above-mentioned defects in the prior art, the present invention aims to provide an improved structure of a threaded drill tool with a simple structure and a drill rod that is not prone to breakage.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: it includes a drill rod and a drill bit, the drill rod is composed of a rod body and an external thread section fixedly connected to the rod body through a backhoe groove, the drill bit is composed of a trouser body with an internal thread blind hole at one end, and the external thread section is adapted to the internal thread blind hole; the diameter D3 of the backhoe groove is smaller than the major diameter D1 of the external thread but larger than the minor diameter D2 of the external thread, and the thread tail section of the external thread section extends into the backhoe groove; the aperture of the internal thread blind hole extends outwardly along the axial direction to form a protective skirt sleeve with an inner diameter D4 larger than the major diameter D1 of the external thread, the length h of the protective skirt sleeve is larger than the length L2 of the backhoe groove, and the distance H from the end of the protective skirt sleeve to the bottom of the internal thread blind hole is larger than or equal to the sum of the length L1 of the external thread section and the length L2 of the backhoe groove.

[0007] Furthermore, the tool withdrawal groove is connected to the rod body through a conical transition section.

[0008] Furthermore, the external thread section is smoothly transitionally connected to the retreat groove via the arc surface.

[0009] Compared with the prior art, the present invention adopts the above structure, and uses the back cutter groove to replace the cylindrical transition section for transition connection between the rod body and the external thread section, so it has the following advantages: 1) The diameter of the back-cut groove is controlled between the major diameter and the minor diameter of the external thread, thereby reducing the depth of the tail thread groove, which not only reduces the concentration of heat treatment stress at the groove and the processing stress of the slow back-cut section, but also overcomes the defect of the drill rod that the back-cut groove strength and fatigue life are reduced due to the reduction of the back-cut groove diameter.

[0010] 2) Since the depth of the finishing thread groove is reduced, the stress concentration at the intersection of the back-cut groove and the external thread will also be reduced accordingly.

[0011] 3) A protective skirt is added at the opening of the internal thread blind hole, so that the external thread tail section and the back cutter groove are hidden therein, thereby preventing the external thread tail section and the back cutter groove from being impacted and worn by rocks, thereby extending the life of the drill rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural schematic diagram of the drill rod of the present invention; Figure 2 yes Figure 1 The enlarged view at position I in FIG. Figure 3 It is a structural schematic diagram of the drill bit of the present invention; Figure 4 It is a structural schematic diagram of the drill tool of the present invention; Figure 5 It is a schematic diagram of the structure of a traditional drill rod; Figure 6 It is a structural schematic diagram of an existing drill rod.

[0013] In the figure: drill rod 1, rod body 1-1, conical transition section 1-2, cutter groove 1-3, external thread section 1-4, cylindrical transition section 1-5; Drill bit 2, protective skirt 2-1, internal thread blind hole 2-2, trouser body 2-3. DETAILED DESCRIPTION

[0014] The present invention will be further described below with reference to the specific embodiments of the accompanying drawings: like Figures 1 to 4 As shown, the drill rod 1 is composed of a rod body 1-1, an external thread section 1-4 fixedly connected to the rod body through a back cutter groove 1-3, and a drill head 2 is composed of a trouser body 2-3 having an internal thread blind hole 2-2 at one end. The drill rod 1 is connected to the internal thread blind hole 2-2 of the drill head 2 through the external thread section 1-4 to form a rock drilling tool.

[0015] In the above structure, the diameter D3 of the undercut groove 1-3 is smaller than the major diameter D1 of the external thread, but larger than the minor diameter D2 of the external thread (i.e., D1>D3>D2), and the thread end section of the external thread section 1-4 extends into the undercut groove 1-3. The opening of the internal thread blind hole 2-2 extends outwardly along the axial direction to form a protective skirt 2-1 with an inner diameter D4 larger than the major diameter D1 of the external thread (i.e., D4>D3), and the length h of the protective skirt is larger than the length L2 of the undercut groove 1-3, and the distance H from the port of the protective skirt 2-1 to the bottom of the internal thread blind hole 2-2 is larger than or equal to the sum of the length L1 of the external thread section 1-4 and the length L2 of the undercut groove 1-3 (i.e., H≥L1+L2).

[0016] In order to reduce the stress between the undercut groove 1-3 and the rod body 1-1, the undercut groove 1-3 is connected to the rod body 1-1 through a conical transition section 1-2.

[0017] In order to reduce the stress between the external thread segment 1-4 and the undercut groove 1-3, the external thread segment 1-4 is smoothly transitionally connected to the undercut groove 1-3 via an arc surface (not shown in the figure).

[0018] from Figure 5 It can be seen that the diameter D3 of the cylindrical transition section 1-5 of the conventional drill rod is equal to the major diameter D1 of the external thread section 1-4. Although the strength and fatigue life of the cylindrical transition section 1-5 are good, the thread groove of the end section of the external thread section 1-4 is deep, so on the one hand, the stress formed by heat treatment is more concentrated, and on the other hand, the length of the end section of the external thread is also correspondingly longer (in order to reduce the processing stress, a slow tool closing method is adopted), which increases the processing difficulty.

[0019] from Figure 6It can be seen that the diameter D3 of the undercut groove 1-3 of the existing drill rod is smaller than the minor diameter D2 of the external thread section 1-4 (i.e., D3<D2). Therefore, at the intersection of the undercut groove 1-3 and the external thread section 1-4, due to the deeper thread groove depth, there is a greater thermal stress and processing stress; at the same time, due to the smaller D3, the strength and fatigue life of the undercut groove will also be reduced accordingly.

Claims

1. An improved structure of a threaded drill tool, comprising a drill rod (1) and a drill head (2), wherein the drill rod (1) is composed of a rod body (1-1), an external thread section (1-4) fixedly connected to the rod body via a back cut groove (1-3), and the drill head (2) is composed of a trouser body (2-3) having an internal thread blind hole (2-2) at one end, and the external thread section (1-4) is adapted to the internal thread blind hole (2-2); the characteristics are as follows: The diameter D3 of the tool retreat groove (1-3) is smaller than the major diameter D1 of the external thread but larger than the minor diameter D2 of the external thread, and the thread tail section of the external thread section (1-4) extends into the tool retreat groove (1-3); The opening of the internal thread blind hole (2-2) extends outwardly along the axial direction to form a protective skirt (2-1) having an inner diameter D4 greater than the major diameter D1 of the external thread, the length h of the protective skirt being greater than the length L2 of the tool retreat groove (1-3), and the distance H from the end of the protective skirt (2-1) to the bottom of the internal thread blind hole (2-2) being greater than or equal to the sum of the length L1 of the external thread section (1-4) and the length L2 of the tool retreat groove (1-3).

2. The improved structure of the threaded drill tool according to claim 1, characterized in that: The tool withdrawal groove (1-3) is connected to the rod body (1-1) via a conical transition section (1-2).

3. The improved structure of the threaded drill tool according to claim 1, characterized in that: The external thread section (1-4) is smoothly transitionally connected to the tool retreat groove (1-3) via an arc surface.

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