Drill pipe end piece, drill pipe assembly and method

Abstract

The invention provides an end piece, a drill pipe assembly and a method. The drill pipe assembly (13) is used for rotary drilling and down-the-hole drilling and comprises a drill pipe (14) provided with end pieces (15, 16) at opposite ends thereof. Shrink fit and welding are performed for the installation of the end pieces. To improve the shrink fit, the contact surfaces (22, 24) between the components are tapered.

Description

Technical Field

[0001] The invention relates to an end piece for a drill pipe of a rotary or down-the-hole drilling rig.

[0002] The invention also relates to a drill pipe assembly and a method of forming a drill pipe assembly for a rock drilling rig.

[0003] The field of the invention is defined more particularly in the preambles of the independent claims. Background Art

[0004] In mines and other workplaces, different types of rock drills are used to drill holes in rock faces. In rotary drilling and down-the-hole drilling (DTH drilling), a drill pipe is connected to a rock drilling machine or unit and is rotated by a rotary device. The drill pipe is an elongated hollow tubular and thin-walled element through which the drilling fluid is pumped down the hole to the drill bit. The drill pipe transmits the rotation and torque from the rotary device to the drill bit, and it also transmits the axial feed force. Usually, the drill pipe is provided with separate end pieces at its opposite ends. The joint between the end pieces and the drill pipe consists of a shrink fit. However, known solutions have shown some drawbacks and in particular relate to crack formation at the joints between the above-mentioned components and overall durability. Summary of the invention

[0005] It is an object of the present invention to provide a new and improved end piece and drill pipe assembly for rotary or down-the-hole drilling, and a method of forming a drill pipe assembly for a rock drilling rig.

[0006] The end piece according to the invention is characterized by the characterizing features of the first independent device claim.

[0007] The drill pipe assembly according to the invention is characterized by the characterizing features of the second independent device claim.

[0008] The method according to the invention is characterized by the characterizing features of the independent method claim.

[0009] The disclosed solution is conceived as a drilling tool intended for use in a rotary or down-the-hole drilling rig, comprising one or more drill pipes. The drill pipe is provided with an end piece. The end piece is an elongated tubular piece and comprises a first end provided with a first coupling means comprising a threaded surface for threaded mounting with other drilling components. An opposite second end is provided with a second coupling means for coupling the end piece to the drill pipe by means of a shrink fit. The second coupling means comprises a first contact surface facing radially outwards, the first contact surface extending a first axial distance from the second end to the first end. Furthermore, the first contact surface for providing the shrink fit has a tapered configuration.

[0010] In other words, the tapered second coupling means is formed on a male formation configured to be received by a female formation formed at the end of the drill pipe.The female portion may also be considered as a spigot with receiving features and provided with a matching tapered surface.

[0011] One advantage of the disclosed solution is that the shrink fit using a tapered shape provides an improved stress distribution between the assembled parts and reduces the risk of cracks in the joints. In this way, a higher load-bearing capacity can be achieved. Furthermore, less interference is required to transmit the forces, and this lower degree of interference means less stress at the joints.

[0012] These tapered surfaces also provide for proper alignment of the end fitting with the drill pipe, thereby facilitating assembly of the components of the present solution.

[0013] Furthermore, due to the tapered outer surface, the drill pipe end can have a greater wall thickness, which also benefits the load-bearing capacity and durability of the solution.

[0014] Another advantage is that the disclosed structure is relatively simple and inexpensive to manufacture. It is relatively easy and quick to precisely manufacture the tapered contact surface using a modern lathe.

[0015] According to one embodiment, the first contact surface forms a truncated cone that can be inserted into a socket formed at the end of the drill pipe. When the contact surface of the truncated cone and the contact surface of the socket overlap due to the insertion, an interference fit between the truncated cone and the socket is formed. In an interference fit or shrink fit, there is a slightly oversized truncated cone (shaft portion) that is assembled into a slightly undersized socket (hole portion). Therefore, the two parts being connected have slightly different sizes, and this difference holds the parts together. Before assembly, the truncated cone (i.e., the inner part) is larger than the socket (i.e., the outer part) to form the required interference fit.

[0016] The end piece and the drill pipe in which the end piece is mounted are intended to be connected between a rotating head and a drill bit of a rock drilling rig. The end piece is part of a drill string and is configured to transmit torque and axial forces between components of the drill string during drilling.

[0017] The outer diameter of the first contact surface has a minimum at the second end and increases towards the second end. In other words, the taper of the frustoconical portion is arranged such that the diameter of the frustoconical portion increases from the second end towards the first end.

[0018] According to one embodiment, the angle of the tapered first contact surface is 0.2° - 12°.The amount of the angle of the tapered contact surface depends on the size of the end piece, and in particular on the diameter of the end piece.

[0019] According to one embodiment, the angle of the tapered first contact surface is 1° - 6°. It has been found in practical tests that this range is particularly suitable for drilling tools with common diameters.

[0020] According to one embodiment, the length of the first axial distance is 75 - 160 mm. In other words, the axial dimension of the tapered male portion at the second end of the end piece complies with the stated range 75 - 160 mm.

[0021] According to one embodiment, the axial length of the tapered first contact surface is defined by a stop surface, which is oriented perpendicularly relative to the longitudinal axis of the end piece. In other words, the frustoconical portion terminates in the stop surface, which is oriented perpendicularly relative to the longitudinal axis of the end piece. Thereby, the stop surface is configured to be arranged against the front end of the drill pipe in the assembly. The stop surface defines the axial length of the tapered first contact surface and the axial length over which the contact surfaces of the frustoconical portion and the contact surfaces of the spigot portion engage with each other.

[0022] According to one embodiment, the second end of the end piece is provided with a radial inner surface, which extends an axial distance from the second end to the first end. The inner surface has a tapered configuration. In other words, the end piece comprises two tapered surfaces at its second end. The taper of the inner surface is of a much greater angle than the taper of the outer surface.

[0023] According to one embodiment, the outer surface of the end piece is provided with at least one discard indicator, which comprises a recess having a predetermined depth. The discard indicator has the advantage of providing a simple, robust and reliable visual indicator for providing information about the degree of wear of the drill pipe assembly. The outer surface of the drill pipe assembly is subject to wear during use and material may loosen on the outer surface, resulting in a reduction in the depth of the discard indicator. Therefore, the operation of the discard indicator is based on the phenomenon that the loosening of the material around the recess causes a reduction in depth and information about the degree of wear is provided to the operator in an intuitive manner. The discard indicator is cheap to manufacture.

[0024] According to one embodiment, the depth of the rejection indicator marking is defined relative to the wall thickness of the drill pipe.

[0025] According to one embodiment, the depth of the waste indicator mark is set to half the dimension of the wall thickness of the drill pipe.

[0026] According to one embodiment, the depth of the waste indicator mark is set to 5% - 70% of the wall thickness of the drill pipe.

[0027] According to one embodiment, the depth of the waste indicator mark is set to 10% - 60% of the wall thickness of the drill pipe.

[0028] According to one embodiment, the depth of the waste indicator mark is set to 30% - 50% of the wall thickness of the drill pipe.

[0029] According to one embodiment, the scrap indicator is located at a maximum axial distance of 150 mm from the weld joint between the end piece and the drill pipe. Thus, the scrap indicator is intended to provide wear data of the weld joint and to indicate when the degree of wear has reached a level where there is a risk that the weld joint is no longer able to transmit axial loads and torques.

[0030] According to one embodiment, the waste indicator comprises at least one notch, groove, blind drilled hole or any other type of recess.

[0031] According to one embodiment, there may be a plurality of discard indicators in the end piece. Alternatively or additionally, one or more discard indicators may be provided on the drill pipe.

[0032] According to one embodiment, there may be multiple waste indicators with different depths to indicate the wear of the drill pipe or drilling component. The waste indicators may form a set of blind holes, grooves or recesses with different depths. The depth of these recesses may increase in predetermined steps and they may clearly indicate the degree of wear of the component being inspected.

[0033] According to one embodiment, the disclosed solution also relates to a drill pipe assembly for rotary or down-the-hole drilling. The drill pipe assembly comprises a drill pipe and two end pieces fixedly mounted to the drill pipe at opposite ends. The end piece comprises a male part with a second coupling device, the second coupling device being provided with an outwardly facing contact surface and being inserted into a socket part at the end of the drill pipe, whereby the end piece is connected to the end of the drill pipe by means of a shrink fit based on the difference in diameter existing between the male part and the socket part. The end piece is described according to the features disclosed in the present document. Therefore, the matching radial contact surfaces between the male part and the socket part have a tapered configuration.

[0034] According to one embodiment, the amount of the shrink fit is 0.1 - 0.8 mm. The amount of interference (the tightness of the fit, or how tight) is controlled by the amount of interference.

[0035] The amount of shrink fit indicates how much larger the diameter of the shaft portion is relative to the diameter of the bore portion prior to installation. Since the mating contact surfaces of the shaft and bore portions are tapered, the check needs to be done on sections that have the same axial position and will mate in the final shrink fit joint.

[0036] According to one embodiment, the amount of the shrink fit is 0.2 - 0.6 mm. In practical tests it has been found that this range for the shrink fit is particularly suitable for drill pipes and end pieces with common diameters.

[0037] According to one embodiment, the joint between the end piece and the drill pipe is provided with a welded joint for providing additional fastening and ensuring an interference fit.

[0038] According to one embodiment, the disclosed solution is used for rotary drilling without using a percussion device in rock mass fragmentation.

[0039] According to one embodiment, the rock drilling rig is used for down-the-hole drilling (DTH). In DTH drilling, the drill bit end of the rotary drill tool is provided with a percussion device, ie during the drilling process, the percussion device is located at the bottom of the borehole.

[0040] According to one embodiment, the disclosed solution relates to a method of forming a drill pipe assembly for a rock drilling rig. The method comprises: mounting end pieces to opposite ends of a tubular drill pipe; providing a first coupling device with a threaded surface for a first end of the end piece for threaded mounting; providing a truncated cone portion to an opposite second end of the end piece, wherein a radially outer surface of the truncated cone portion forms a first contact surface; forming a spigot portion to both ends of the drill pipe, the spigot portion being used to receive the truncated cone portion and provided with a second contact surface; heating the end of the drill pipe at the spigot portion to expand the diameter of the second contact surface by thermal expansion; pushing the truncated cone portion into the thermally expanded spigot portion; allowing the heated spigot portion to cool and shrink, thereby forming a shrink fit between the first contact surface and the second contact surface; and fixing the mounting portion between the drill pipe and the end piece by welding. The method also comprises providing a tapered shape for the matching first and second connection surfaces.

[0041] The above disclosed embodiments may be combined to form a suitable solution having desired ones of the above mentioned features. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Some embodiments are described in more detail in the accompanying drawings, in which:

[0043] Figure 1 is a schematic diagram of a surface rock drill rig intended for rotary drilling;

[0044] Figure 2 is a schematic diagram of a rock drilling unit suitable for down-the-hole drilling;

[0045] Figure 3 is a schematic diagram of a drill pipe assembly;

[0046] Figure 4 is Figure 3A schematic cross-sectional view of a detail of a joint between a first end piece and a drill pipe in a drill pipe assembly of FIG.

[0047] Figure 5 is Figure 3 A schematic cross-sectional view of a detail of a joint between a second end piece and a drill pipe in a drill pipe assembly of FIG.

[0048] Figure 6 is a partial cross-sectional view showing the joint between the end piece and the drill pipe; and

[0049] Figure 7 is a schematic cross-sectional side view of a connection end of an end piece; and

[0050] Figure 8 is a schematic cross-sectional side view of a connection end of a drill pipe.

[0051] For the sake of clarity, the accompanying drawings show some embodiments of the disclosed solution in a simplified manner. In the accompanying drawings, the same reference numerals represent the same elements. DETAILED DESCRIPTION

[0052] Figure 1 A rock drilling rig 1 intended for ground drilling is shown. The rock drilling rig 1 comprises a movable carrier 2 and at least one drilling tower 3 connected to the carrier 2. The drilling tower 3 is provided with a drilling unit 4 provided with a rotating head 5 supported on the drilling tower 3 and movable in a drilling direction A and a return direction B by means of a feeding device 6. The rotating head 5 is connected to a drilling tool 7 by means of a subassembly 8. For the sake of clarity, the drilling tool 7 is shown in a simplified manner. The drilling tool 7 comprises one or more tubular elongated drill pipe assemblies and a drill bit 9 at its distal end. The rotating head 5 causes the drilling tool 7 to rotate R about its longitudinal axis and the drilling tool 7 is simultaneously fed towards the rock face being drilled. This is known as a rotary drilling method. The drill cuttings are flushed away by feeding a flushing fluid from a flushing system Fs via the drilling tool 7 to the drilled borehole 10, thereby flushing the drill cuttings away from the borehole 10. The drilling unit 4 may be hydraulic, so that it may be connected to a hydraulic system Hs.

[0053] Figure 2 Another solution is disclosed, which is similar to Figure 1 The difference of the solution shown is that a percussion device 11 is installed between the drill bit 9 and the drilling tool 7. The disclosed solution is intended for use in the down-the-hole drilling method, also known as DTH drilling. The drilling unit 4 can be mounted in a movable manner on a feed beam 12 or in a manner such as Figure 1 A similar arrangement as shown is mounted on the feed beam 12. The drilling tool 7 may comprise a drill tube assembly according to the solution disclosed in this document.

[0054] Figure 3 A drill pipe assembly 13 is disclosed, which includes a drill pipe 14 and two end pieces 15, 16 fixedly mounted to the drill pipe 14 at opposite ends. Figure 3 A drill pipe 14 is disclosed in a shortened form. On the upper end of the drill pipe 14, i.e. the drilling unit end, a first end piece 15 is provided, and on the lower end of the drill pipe 14, i.e. the drill head end, a second end piece 16 is provided. The end pieces 15, 16 are mounted to the ends of the drill pipe 14 by arranging their joint ends one inside the other and by means of a shrink fit between their substantially radial contact surfaces. Typically, the mounting is ensured by a welded joint 17. The end pieces 14, 15 may be provided with one or more waste indication marks 18, which may be blind holes, for example. Figure 3 Also shown are blocks 19 and 20 at the joint region, and the detailed structure of the joint is shown in Figure 4 and Figure 5 Shown in.

[0055] Figure 4 and Figure 5 The end piece 15, 16 is disclosed to include a male portion 21 provided with a first contact surface 22 facing outwards and inserted into a socket portion 23 located at the end of the drill pipe 14. The socket portion 23 is provided with a matching contact surface 24. As can be seen, the substantially radial matching contact surface between the male portion 21 and the socket portion 22 has a tapered configuration. Based on the difference in diameter between the male portion 21 and the socket portion 23, the end piece 15, 16 is connected to the end of the drill pipe 14 by means of a shrink fit.

[0056] Figure 4 and Figure 5 It is also disclosed that the end facing the drill pipe 14 is provided with a radial inner surface 25, which extends an axial distance from the second end to the first end and has a tapered configuration. Thus, the end pieces 15, 16 include two tapered surfaces at their ends. The taper of the inner surface 25 is of a much greater angle than the taper of the outer surface.

[0057] The end pieces 15 , 16 are elongated tubular pieces comprising an outer surface 26 and an inner surface 27 .

[0058] Figure 3 It is also disclosed that the end piece 15, 16 comprises a first end 28 provided with first coupling means 29 comprising a threaded surface 29 for threaded mounting with other drilling components. An opposite second end is provided with tapered second coupling means for shrink fit with the end of a drill pipe.

[0059] Figure 6A joint is disclosed between the second end 30 of the end piece 15, 16 and the drill pipe 16. A male portion 21 with an angled contact surface 22 is mounted in a socket portion 23 of the drill pipe 14, which is provided with a matching angled contact surface 24. The angle K of the tapered contact surfaces 22, 24 may amount to 0.2° - 12°.

[0060] Figure 7 An end of an end piece 15, 16 provided with a male portion 21 is disclosed. The male portion 21 forms an axially protruding truncated cone at the end of the end piece 15, 16. A substantially radially outwardly facing contact surface 22 is provided, which extends a first axial distance L from the distal end towards the opposite end. The length of the axial distance L may be 75 - 160 mm. The axial length L of the tapered first contact surface 22 may be defined by a stop surface 31 oriented perpendicularly with respect to the longitudinal axis of the end piece 15, 16. A shaped surface 32 may also be provided for forming a groove for a weld joint together with a correspondingly shaped end surface of the drill pipe.

[0061] Figure 8 The end of the drill pipe 14 is disclosed to be provided with a socket portion 23 for receiving the male portion of the end piece. The length L2 of the socket portion 23 is at least equal to or greater than the length of the male portion, and the socket portion 23 includes a tapered contact surface 24. The distal end of the drill pipe 14 may include a shaped surface 33, which forms part of the welding groove.

[0062] The drawings and the related description are intended only to illustrate the concept of the invention. The invention may vary in its details within the scope of the claims.

[0063] Disclosure of Additional Inventions

[0064] Furthermore, an additional solution which is not an independent claim according to this document is disclosed below:

[0065] A drill component for rotary or down-the-hole drilling, wherein an outer surface of the component is provided with at least one discard indicator, the at least one discard indicator comprising a recess having an initial depth, and a reduction in the initial depth is configured to indicate wear of the component.

[0066] The drill tool component may be a drill pipe, an end piece of a drill pipe, or any other component that can be connected between the rotary unit and the drill bit.

[0067] Thus, the disclosed drill component may or may not include a tapered contact surface.

Claims

1. An end piece (15, 16) for a drill pipe (14) for a rotary or down-the-hole drilling rig; in, The end pieces (15, 16) are elongated tubular pieces, and the end pieces include: an outer surface (26) and an inner surface (27); a first end (28) provided with a first coupling device (29) including a threaded surface for threaded mounting with other drilling components; an opposite second end (30) provided with second coupling means for coupling the end piece (15, 16) to the drill pipe (14) by means of a shrink fit; and wherein the second coupling means comprises a first contact surface (22) facing radially outwardly, the first contact surface extending a first axial distance (L) from the second end (30) to the first end (28); Features: The first contact surface (22) has a tapered configuration.

2. The end piece according to claim 1, characterized in that: The angle (K) of the tapered first contact surface (22) is 0.2°-12°.

3. The end piece according to claim 1 or 2, characterized in that: The angle (K) of the tapered first contact surface (22) is 1°-6°.

4. An end piece according to any one of the preceding claims 1 to 3, characterized in that: The length of the first axial distance (L) is 75 - 160 mm.

5. An end piece according to any one of the preceding claims 1 to 4, characterized in that: The axial length (L) of the tapered first contact surface (22) is defined by a stop surface (31) which is oriented perpendicularly relative to the longitudinal axis of the end piece (15, 16).

6. The end piece according to any one of claims 1 to 5, characterized in that: A radially inner surface (25) is also provided at the second end (30) of the end piece (15, 16), the radially inner surface extending an axial distance from the second end (30) to the first end (28) and having a tapered configuration.

7. An end piece according to any one of the preceding claims 1 to 6, characterized in that: The outer surface (26) of the end piece (15, 16) is provided with at least one waste indication mark (18), wherein the waste indication mark comprises a recess having a predetermined depth.

8. A drill pipe assembly (13) for rotary or down-the-hole drilling; Furthermore, the drill pipe assembly (13) comprises a drill pipe (14) and two end pieces (15, 16), wherein the two end pieces are fixedly mounted to opposite ends of the drill pipe (14); The end piece (15, 16) comprises a male part (21) with a second coupling device, which is provided with a first contact surface (22) facing outwards and is inserted into a socket part (23) at the end of the drill pipe (14), so that the end piece (15, 16) is connected to the end of the drill pipe (14) by means of a shrink fit based on the difference in diameter between the male part (21) and the socket part (23); Features: The end piece (15, 16) is according to any one of the preceding claims 1 - 7; Furthermore, the matching radial contact surfaces (22, 24) between the male portion (21) and the socket portion (23) have a tapered configuration.

9. The drill pipe assembly according to claim 8, characterized in that: The amount of the shrink fit is 0.1 - 0.8 mm.

10. The drill pipe assembly according to claim 8 or 9, characterized in that: The amount of the shrink fit is 0.2 - 0.6 mm.

11. A drill pipe assembly according to any one of the preceding claims 8 - 10, characterised in that: A weld joint (17) is provided between the end pieces (15, 16) and the drill pipe (14) for providing additional fastening.

12. A method of forming a drill pipe assembly (13) for a rock drilling rig (1), in, The method comprises: Installing end pieces (15, 16) to opposite ends of a tubular drill pipe (14); providing a first coupling means (29) comprising a threaded surface for threaded mounting at a first end (28) of the end piece; providing an opposite second end (30) of the end piece with a frustoconical portion, wherein a radially outer surface of the frustoconical portion forms a first contact surface (22); forming a socket portion (23) at both ends of the drill pipe (14), the socket portion being used to receive the truncated cone portion and provided with a second contact surface (24); heating the end of the drill pipe (14) at the socket portion (23) to expand the diameter of the second contact surface (24) by means of thermal expansion; Pushing the truncated cone portion into the socket portion (23) after thermal expansion; allowing the heated socket portion (23) to cool and shrink, thereby forming a shrink fit between the first contact surface (22) and the second contact surface (24); and Fixing the mounting portion between the drill pipe (14) and the end pieces (15, 16) by welding (17); Features: The invention comprises providing a tapered shape for the first connecting surface (22) and the second connecting surface (24) that are matched.

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