WO2006110086A1

WO2006110086A1 - An arrangement of percussive drill components and percussive drill component incorporating a thread joint

Info

Publication number: WO2006110086A1
Application number: PCT/SE2006/000430
Authority: WO
Inventors: Roger Noel
Original assignee: Sandvik Intellectual Property AB
Current assignee: Sandvik Intellectual Property AB
Priority date: 2005-04-14
Filing date: 2006-04-10
Publication date: 2006-10-19
Anticipated expiration: 2007-10-14
Also published as: SE528777C2; SE0500844L

Abstract

The present invention relates to a thread joint, including a male portion and a female portion, for percussive drilling. The thread joint (10) includes a male portion and a female portion for percussive drilling. The threaded joint forms a center flush channel (20) and comprises at least one external thread and at least one internal thread. The external thread is provided on a spigot (12) which has at least one impact surface (16). The internal thread is provided in a socket which has at least one impact surface (18). The at least one impact surface of the spigot (12) and the at least one impact surface of the socket are shaped to lie on an imaginary sphere (35).

Description

MALE AND FEMALE THREADED DRILL COMPONENTS AND ATHREAD JOINT FORMED THEREBY

Background of the invention

The present invention relates to a thread joint, including a male portion and a female portion, for percussive drilling.

A conventional thread joint between two components in a rock drilling equipment for percussive drilling normally uses male and female threads, see for example SE-B-469,602, US-A-4,332,502 and US-B1 -6,767,156. A conventional thread joint has one or two axially facing planar support surfaces which abut one another upon tightening the thread. When the known thread joint is subjected to bending forces during drilling, the thread joint is subjected to bending moments which might lead to fatigue breakage in the treaded portion of the joint. It is usually the male thread that breaks first and thus limits the life span of the joint. Furthermore, bent joints, i.e., joints having non-aligned axes of the male and female portions can result in an uneven impact interface between the male and female portions, leading to increased damage and a less efficient transmission of percussive energy.

Objects of the invention

One object of the present invention is to provide a thread joint of the above-mentioned type, for which a long life span is attained.

Another object of the present invention is to provide a thread joint of the above-mentioned type, wherein the male portion obtains a long life span. Still another object of the present invention is to provide a thread joint of the above-mentioned type, wherein the thread joint always transfers impact waves effectively.

Still another object of the present invention is to provide a female portion for which a long life span is attained.

Brief description of the drawings

Below, preferred embodiments of the invention are described with reference to the enclosed drawings wherein Fig. 1 shows a partly sectioned view of a thread joint according to the invention between two identical drill components. Fig. 2 shows a female portion according to the present invention in a cross-sectional view. Fig. 3 shows a male portion according to the present invention in a side view. Fig. 4 shows an alternative female portion according to the present invention in a cross-section. Fig. 5 shows a cross-sectional view of an alternative embodiment of a thread joint according to the invention between two identical drill components. Fig. 6 shows the alternative embodiment of a female portion according to the present invention in a cross-sectional view.

Detailed description of preferred embodiments of the invention

In accordance with the present invention, the male and female thread portions of a thread joint used in percussion drilling equipment include at least one pair of axially facing surfaces which contact one another to define impact surfaces. These mutually contacting impact surfaces can be disposed within the socket portion of the female portion, and/or at a free end of the female portion. The mutually contacting impact surfaces are not of planar shape; rather each impact surface is part-spherical, i.e., shaped as part of an imaginary sphere. One of the mutually abutting impact surfaces is concave, and the other is convex. The impact surfaces contact each other along a portion of a common imaginary sphere. Therefore, surface or area-type contact (in contrast to line contact or point contact) is maintained between the impact surfaces, even if the respective center lines of the male and female portions become slightly misaligned. As a result, during the transmission of percussive energy, damage to the parts is minimized, and energy transmission efficiency is maximized. With reference to Figs. 1 , 2 and 3, one embodiment of a thread joint 10 according to the present invention preferably comprises two drill components such as drill tubes or drill rods 1OA, 1OB, each including an end with a projecting spigot or male thread portion 12 and an opposite end with a sleeve or female thread portion 13. The spigot has a generally cylindrical external or male thread 14, and the sleeve has a generally cylindrical internal or female thread 15.

Each of the male and female portions of the thread joint will be described below, with reference being made to "inner" and "outer" regions of each. The term "outer" means toward an axially free end of the male or female part of the threaded joint, whereas "inner" means axially remotely from the free end. Thus, with reference to Figure 3 which depicts the male portion (spigot) of a thread joint, the right-hand side of the male portion corresponds to the outer (free) end thereof, whereas the left-hand side corresponds to the inner end thereof. Likewise, with reference to Figure 2, which depicts the female portion (socket) of a thread joint, the left-hand end of the female portion corresponds to the outer (free) end thereof, whereas the right-hand end of the socket corresponds to the inner end thereof.

When the thread joint 10 is to be formed for percussive drilling, the axially facing free end surface or first part-spherical impact surface 16 of the male portion 12 will enter a socket 9 of the female portion through a mouth encompassed by the axially facing free end surface or part-spherical second impact surface 17 of the female portion. In most cases the rods must be rotated relative to each other while initially pushing them together such that the threads can engage each other. Then the rods are further rotated until the free end surface 16 of the rod abuts against a preferably part-spherical bottom impact surface or part-spherical second impact surface 18 of the socket 9, and/or the impact surface 17 abuts against an inner shoulder or first part-spherical impact surface 19 located at an inner end 12B of the spigot 9. The threads 14 and 15 are conventionally designed such that when assembled, abutment therebetween arises only at certain thread flank portions of the respective male and female portions. Contact between curved thread parts or between thread tips and thread bottoms preferably does not occur. In US-A-4,968,068, which patent hereby is incorporated by reference into the present description, a thread joint is shown in which the present invention can be utilized. The female portion 13 constitutes an integral part of the drill rod, preferably by friction welding. Furthermore, the drill rod has a through-going flush channel 20, through which a flush medium, usually air or water, is transported.

Referring to Fig. 3, the generally cylindrical external or male thread 14 includes at least one outer thread end 21 and at least one inner thread end 22 arranged in connection with the associated full profile male thread. As can be seen in Fig. 2, the generally cylindrical internal or female thread 15 includes at least one outer thread end 23 and at least one inner thread end 24 arranged in connection with the associated full profile female thread. Each of the four thread ends 21-24 includes a sharp edge due to clearances developed before threading, i.e. conical clearances 31 , 32 on the spigot 12 and clearances 33, 34 on the sleeve 13.

The male thread 14 and the female thread 15 have a specific mutual relationship as regards length and position to ensure that both thread ends or end areas 23, 24 of the female thread 15 do not contact the male thread 14 once the joint is tightened. By "do not contact" is here meant that the ends 23, 24 are spaced by a distance from the male thread in a tightened joint as described in US-B1 -6,767, 156, which patent hereby is incorporated by reference into the present description as regards the general thread geometries.

The outer and inner ends 12A, 12B of the spigot 12 may include respective outer cylindrical support surfaces 25, 26 which may cooperate with inner cylindrical surfaces 27 and 28, respectively, of the socket 9. The cylindrical surfaces 25-28 are substantially coaxial with the centerline of the joint 10. The outer cylindrical surfaces 25, 26 are preferably radially spaced from the inner cylindrical surfaces 27 and 28, respectively, for avoiding the formation of local welds therewith. The radial gap between the cooperating cylindrical surfaces will be closed at one annular position only when the thread joint becomes unintentionally loose during drilling.

The outer cylindrical surface 25 of the outer end 12A of the spigot 12 connects via a radiussed corner 29 to the convex part-spherical impact surface 16 which lies on an imaginary sphere 35. The impact surface 16 extends within a cone angle β in the range of 5-20° of the imaginary sphere 35, the cone angle having an apex coinciding with the center C of the sphere and lying in the flush channel 20. Thus the cone angle is determined from the center C of the imaginary sphere 35, which center lies on the common center line CL1 , CL2 of the male and female threads. The diameter D of the sphere 35 is greater than the length L1 of the spigot and is in the range of 110 % to 500 % of a male thread major diameter 0M or 110 % to 500 % of a female thread major diameter 0F. The length L1 of the spigot 12 is defined as the distance between the axially forward part of the surface 16 and the axially forward part of the inner shoulder 19, in a direction parallel with the centerline CL. The sphere diameter D is greater than the greatest diameter of the joint 10 in this embodiment.

The cylindrical inner surface 26 of the inner end 12B of the spigot 12 connects via a radiussed corner 36 to the convex part-spherical impact surface 19 which lies on the sphere 35. The impact surface 19 extends within a cone angle α in the range of 5-30° of the imaginary sphere 35, the apex of the cone angle coinciding with the sphere center C and lying in the spigot and the flush channel 20. Thus the cone angles α and β are in the interval range of 5-30°. The inner surface 27 of the inner end 13B of the female portion 13 connects via a radiussed corner 37 to the concave part-spherical impact surface 18 which lies on the imaginary sphere 35. The impact surface 18 extends within the cone angle β in the range of 5-20° of the imaginary sphere 35, the cone angle lying in the socket 9. The cone angle has an apex coinciding with the center C of the sphere 35. The diameter D of the sphere 35 containing the impact surface 18 is greater than the depth L2 of the socket 9. The depth L2 of the socket 9 is defined as the distance between the axially forward part of the surface 18 and the axially rearward part of the impact surface 17, in a direction parallel with the centerline CL.

The cylindrical outer surface 28 of the outer end 13A of the female portion 13 connects via a bevel 38 to the concave part-spherical impact surface 17 which lies on the sphere 35. The impact surface 17 extends within the cone angle β of 5-30° of the sphere 35, the cone angle having an apex coinciding with the center C for the sphere 35 and lying in the socket. It should be understood that the pair of mutually-contacting part-spherical impact surfaces may be provided at only one of the inner and outer ends of the spigot and socket.

The thread configuration shown in the drawings is trapezoidal, but it is understood that the invention can be used in connection with all for percussive rock drilling serviceable threads, such as rope threads for example.

The female portion or the male portion may alternatively be integral with a drill component in the form of a rock drill bit instead of being integral with a drill rod or a drill tube. In Fig. 4 there is shown a rock drill bit 1OC for percussive rock drilling with hard metal buttons 30, having a female portion according to the present invention, with the same reference numerals as used above. Alternatively, the male thread 14 could be applied on a spigot of the rock drill bit in lieu of the female portion.

With reference to Fig. 5, an alternative embodiment of a thread joint 10' according to the present invention preferably comprises two drill components such as drill tubes or drill rods 10A', 10B', each including an end with a projecting spigot or male thread portion 12' and an opposite end with a sleeve or female thread portion 13'. The spigot has a generally cylindrical external or male thread 14', and the sleeve has a generally cylindrical internal or female thread 15'. The basic difference from the previously disclosed embodiments is that the common imaginary sphere on which axially spaced impact surfaces 17', 19' and 16', 18' lie, is replaced by two concentric imaginary spheres 35A' and 35B'. The spheres 35A' and 35B' thus have a common center C but are of different size. The outer cylindrical surface 25' of the outer end of the spigot 12' connects to a convex first part-spherical impact surface 16' which lies on an imaginary sphere 35A'. The impact surface 16' extends within a cone angle β' in the range of 20-90° of the imaginary sphere 35A', the cone angle having an apex coinciding with the center C of the sphere and lying in the flush channel 20'. Thus the cone angle is determined from the center C of the imaginary sphere 35A', which center C lies on the common center line CL1 , CL2 of the male and female threads. The diameter DA' of the sphere 35A' is smaller than the length of the spigot and is in the range of 105 % to 300 % of a male thread major diameter 0M' or 105 % to 300 % of a female thread major diameter 0F. The length of the spigot 12' is defined as the distance between the axially forward part of the surface 16' and the axially forward part of the first part-spherical impact surface 19', in a direction parallel with the centerline CL. The sphere 35A' in this embodiment is smaller than the previously described sphere 35. The impact surface 19' extends within a cone angle α' in the range of 5-

30° of an outer concentric imaginary sphere 35B'. The apex of the cone angle a' coincides with the sphere 35B' center C and lies in the spigot and the flush channel 20'. The cone angle α' is in the interval range of 5-30°.

The inner surface of the inner end of the female portion 13' connects to a concave part-spherical impact surface 18' which lies on the imaginary sphere 35A'. The impact surface 18' extends within the cone angle β' in the range of 20-90° of the imaginary sphere 35A', the cone angle lying in the socket. The cone angle has an apex coinciding with the center C of the sphere 35A'. The diameter DA' of the sphere 35A' containing the impact surface 18' is smaller than the depth of the socket. The depth of the socket is defined as the distance between the axially forward part of the part-spherical second impact surface 18' and the axially rearward part of the part-spherical second impact surface 17', in a direction parallel with the centerline CL.

The cylindrical outer surface of the outer end of the female portion 13' connects to a convex part-spherical impact surface 17' which lies on the sphere 35B'. The impact surface 17' extends within the cone angle α' of 5-30° of the sphere 35B'. The cone angle has an apex coinciding with the center C for the sphere 35B' and lying in the socket. Thus the cone angles α' and β' are in the interval range of 5-90°. Thus, the first impact surfaces 16', 19' or said second impact surfaces 17', 18' lie on two imaginary spheres 35A', 35B' having a common center C, and said spheres have different diameters DA', DB'. A first imaginary sphere 35A' coincides with first 16' and second 18' impact surfaces and a second imaginary sphere 35B' coincides with first 19' and second 17' impact surfaces. The diameter DA' of the first sphere 35A' is smaller than the diameter DB' of the second sphere 35B'.

The female portion or the male portion may alternatively be integral with a drill component in the form of a rock drill bit instead of being integral with a drill rod or a drill tube. In Fig. 6 there is shown a rock drill bit 10C for percussive rock drilling with hard metal buttons 30', having a female portion according to the present invention, with the same reference numerals as used above. Alternatively, the male thread 14' could be applied on a spigot of the rock drill bit in lieu of the female portion. It will be readily apparent that from the foregoing description of the preferred embodiment, during the application of bending forces to the thread joint during a drilling operation, the presence of the part-spherical impact surfaces will enable the thread joint to tolerate a slight bending (inclining) of one thread component relative to other to minimize the occurrence of fatigue breakage. Also, despite any misalignment occurring between the axes of the threaded components as a result of such bending, the part-spherical impact surfaces 16, 19 and 18, 17 respectively, are guaranteed to bear against each other in surface or area contact, in contrast to line contact or point contact. That ensures effective transmission of percussion forces from the percussion drive to the drill bit, which is particularly advantageous at large tube or rod diameters such as more than 60 mm.

In the event that the mutually facing impact surfaces, prior to use thereof in percussion drilling, have not been manufactured with such precise dimension that they lie exactly on a common imaginary sphere, it will be appreciated that after being used in a percussive drilling operation, the resulting wearing-in of the components will cause the impact surfaces to lie on the imaginary common sphere after a brief period.

It will be appreciated that it is only necessary to have a single pair of axial facing surfaces in abutment with one another, i.e., either the surfaces 16, 18 or 16', 18' could be in abutment, or the surfaces 17, 19 or 17' and 19' could be in abutment. Those contacting surfaces would thus constitute impact surfaces and would be configured to lie on the imaginary sphere. If both pairs of surfaces are in abutment, then both pairs would be configured to lie on the imaginary sphere 35 or on the concentric imaginary spheres 35A', 35B', respectively. The principles of the invention can be applied also at a thread joint between a spigot adapter and the drill rod as well as between two drill rods with a loose extension spigot. The thread joint according to the present invention will have a more reliable function and better efficiency than hitherto known thread joints.

Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. An arrangement of percussive drill components interconnected by a thread joint, the drill components (1 OA-1 OC; 10A'-1 OC) forming therein an axial flush channel (20;20')₍ the thread joint (10; 10') comprising a male thread (14; 14') disposed on a spigot (12; 12') of one of the percussive drill components, and a female thread (15;15') disposed in a socket (9;9') of the other percussive drill component and coupled to the male thread, c h a r a c t e r i z e d i n that the spigot (12; 12') includes an axially facing first part-spherical impact surface (16, 19; 16', 19'), and in that the socket (9;9') includes an axially facing part- spherical second impact surface (17, 18; 17', 18') abutting the first impact surface, wherein one of the first and second impact surfaces is concave and the other is convex, the first and second impact surfaces lying on an imaginary sphere (35;35A',35B').

2. The arrangement of percussive drill components according to claim 1 wherein the first impact surface (16; 16') is convex, and the second impact (18; 18') surface is concave.

3. The arrangement of percussion drill components according to claim 1 or 2 wherein the first impact surface (19; 19') is concave, and the second impact surface (17; 17') is convex.

4. The arrangement of percussive drill components according to anyone of claims 1-3 wherein the center (C;C) of the imaginary sphere (35;35A',35B') lies within the socket (9;9').

5. The arrangement of percussive drill components according to anyone of claims 1 -4 wherein the center (C;C) of the imaginary sphere (35;35A',35B') lies on a common center line of the drill components (10A- 10C; 10A'-1 OC).

6. The arrangement of percussive drill components according to anyone of claims 1-5 wherein all first and second impact surfaces (16-19;16'-19') lie on one common imaginary sphere (35).

7. The arrangement of percussive drill components according to anyone of claims 1 -5 wherein said first impact surfaces (16', 19') or said second impact surfaces (17', 18') lie on two imaginary spheres (35A',35B') having a common center (C), said spheres having different diameters (DA', DB').

8. The arrangement of percussive drill components according to claim

7 wherein a first imaginary sphere (35A') coincides with first (16') and second (18') impact surfaces and wherein a second imaginary sphere (35B') coincides with first (19') and second (17') impact surfaces, the diameter (DA') of said first sphere (35A') being smaller than the diameter (DB') of the second sphere (35B').

9. The arrangement of percussive drill components according to anyone of claims 1 -8 wherein the mutually abutting first (16,19;16',19') and second (17,18;17',18') impact surfaces extend within a cone angle (α,β) in a range 5-90 degrees of the imaginary sphere (35;35A',35B'), an apex of the cone angle lying on a common center line (CL) of the thread joint (10; 10').

10. The arrangement of percussive drill components according to anyone of claims 1 -9 wherein the mutually contacting first (16; 16') and second (18;18') impact surfaces are disposed at an outer surface of the spigot (12;12') and an inner surface of the socket (9;9'), respectively.

11. The arrangement of percussive drill components according to claim 6 wherein first (16) and second (18) impact surfaces constitute a first pair of impact surfaces, the thread joint further including third (19) and fourth (17) mutually contacting impact surfaces disposed at an inner end (12B) of the spigot (12) and at an outer end (13A) of the socket (9), respectively, wherein all of the first, second, third and fourth impact surfaces lie on the common imaginary sphere (35).

12. The arrangement of percussive drill components according to anyone of claims 1-9 wherein the first and second impact surfaces are disposed at an inner end (12B) of the spigot (12; 12') and at an outer end of the socket (9;9'), respectively.

13. A percussive drill component defining therein a flush channel (20;20') and including a male thread portion at one axial end thereof, the male thread portion comprising an external thread (14; 14') disposed on a spigot (12; 12'), and further including an axially facing impact surface (16, 19; 16', 19') disposed adjacent at least one axial end of the spigot (12; 12'), c h a r a c t e r i z e d i n that the impact surface (16,19;16', 19') lies on an imaginary sphere (35;35A',35B').

14. The drill component according to claim 13 wherein the impact surface (16; 16') is disposed at an outer free end (12A) of the spigot (12; 12'), and further including an additional axially facing impact surface (19; 19') disposed adjacent an inner end (12B) of the spigot and lying on one sphere (35) or on two concentric imaginary spheres (35A',35B').

15. The drill component according to anyone of claims 13-14 wherein the impact surface (16;16') disposed at an outer free end (12A) of the spigot (12; 12') is convex and the additional axially facing impact surface (19; 19') is concave.

16. The drill component according to anyone of claims 13-15 wherein the impact surface (16; 16') lies within a cone angle (β;β') in a range of 5-90° of the imaginary sphere (35;35A',35B'), the apex of the cone angle lying on a center (C;C) line of the male thread portion.

17. The drill component according to anyone of claims 13-16 wherein the center (C]C) of the imaginary sphere (35) or of the concentric imaginary spheres (35A',35B') lies on a center line (CL) of the male thread portion (12,12').

18. The drill component according to anyone of claims 13-17 wherein the center (C;C) of the imaginary sphere (35) or of the concentric imaginary spheres (35A',35B') lies within the spigot (12; 12').

19. The drill component according to anyone of claims 13-18 further including a female thread portion disposed at an axial end thereof opposite the end at which the male thread portion is disposed, the female thread portion comprising an internal thread disposed in a socket (9;9'), and further including an axially facing impact surface (17, 18; 17' 18') disposed adjacent at least one axial end of the socket (9;9'), the impact surface lying on an imaginary sphere (35;35A',35B').

20. A percussive drill component defining therein a flush channel (20;20') and including a female thread portion (13; 13') at one axial end thereof, the female thread portion comprising an internal thread (15; 15') disposed in a socket (9;9') that communicates with the flush channel, and further including an axially facing impact surface (17, 18; 17', 18') disposed adjacent at least one axial end of the socket (9;9'), c h a r a c t e r i z e d i n that the impact surface (17,18;17',18') lies on an imaginary sphere (35;35A',35B').

21. The drill component according to claim 20 wherein the impact surface (17;17') is disposed at an outer free end (13A) of the socket (9;9'), and further including an additional axially facing impact surface (18; 18') disposed adjacent an inner end (13B) of the socket and lying on one imaginary sphere (35) or on two concentric imaginary spheres (35A',35B').

22. The drill component according to anyone of claims 20-21 wherein the center (C;C) of the imaginary sphere (35) or of the concentric imaginary spheres (35A',35B') lies within the spigot (12;12').

23. The drill component according to anyone of claims 20-22 wherein the impact surface (17, 18; 17', 18') lies within a cone angle in a range of 5-90° of the imaginary sphere (35;35A',35B'), an apex of the cone angle lying on a center line (CL2) of the female thread portion.

24. The drill component according to anyone of claims 20-23 wherein the center (C;C) of the imaginary sphere (35) or of the two concentric imaginary spheres (35A',35B') lies on a center line (CL2) of the component.

25. The drill component according to anyone of claims 20-24 wherein the center (C;C) of the imaginary sphere (35) or of the two concentric imaginary spheres (35A',35B') lies within the socket (9;9').