JP2000008760A - Linear boring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill rod for a drill string, which is high in strength with a long service life, and bores as linearly as possible. SOLUTION: A drill rod 12 for a drill string 10 has a thread at each end so as to be connected to an adjacent rod 12 by a sleeve 14. The threads of the sleeve 14 and rod 12 are formed to reduce stress concentration so as to provide the sacrificial wear of the sleeve 14. The thread has a single initial thread provided with a partially circular bottom part. The wear volume of the sleeve 14 is smaller than that of the rod 12, and the outer diameter of the rod 12 is at least twice as large as an internal bore.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill string.

[0002]

BACKGROUND OF THE INVENTION Drill strings are used to transmit rotational and impact forces from the surface of a drilling device to a drill bit. The hole to be drilled is relatively deep, typically 50 feet (127 cm), so the string is made from a series of drill rods connected by a coupling device. Typically, the end of each rod is threaded and the coupling device is an internally threaded sleeve that receives the end of the adjacent rod.

[0003] When a string is used, for example, to blast holes, it is important to drill the holes as linearly as possible to preserve the required pattern of blast holes. The misalignment of the hole while drilling creates a different hole pattern at the bottom of the hole than the surface, which can result in a discrepancy in the result of the blast. Drill string displacement is primarily caused by bending induced by vertical loads caused by string growth and impact forces on the strings. In some cases, this shift can be extreme and can result in a shift of several feet in a 50 foot (127 cm) hole. The effect of this is to increase the cost so that the waste generated by the blast, or "debris pile", may be unevenly sized and require additional secondary destruction to fit the size of the vehicle. is there. This shift is 1.0
Maintaining within% is the drilling industry's goal, but this has not been achieved on a consistent basis.

[0004]

One solution to reduce slippage is to use a tube drilling system. In tube drilling systems, thin walled metal tubes having an outer diameter close to the size of the hole to be drilled are used in an attempt to provide the requisite bending stiffness. However, this thin walled tubing limits the shape of the threads that can be used to connect the tubing, resulting in unsatisfactory rod life.

[0005] An alternative solution is to place the impact hammer inside the hole and prevent the impact shock wave from propagating through the connecting string, thereby avoiding the impact load on the screw thread. is there. However,
This solution tends to be more expensive.

[0006] It is therefore an object of the present invention to obviate or mitigate the above-mentioned disadvantages.

[0007]

In accordance with one aspect of the present invention, a drill string includes a plurality of drill rods for connecting in series, each at one end thereof for connecting to an adjacent rod. Has at least one screw thread formed in the thread. Each drill rod includes a cylindrical body having an outer surface and an inner bore extending between the ends of the rod. Rod diameter is 65m
The ratio of the body diameter to the bore diameter is greater than or equal to m, and is preferably at least 2: 1 and preferably equal to or greater than 3: 1.

[0008] Increasing the outer diameter of the rod increases the bending stiffness of the rod, but maintaining the bore ratio within the aforementioned limits can provide a suitable form of thread.

[0009] Increasing the rod diameter generally results in a larger root area associated with the increased diameter resulting in an increased area of high stress concentration, thus reducing the rod's fatigue life and thus reducing the rod's fatigue life. It has been considered to be detrimental to the life of threads used to mate internally. If the string is rattled and shaken while retracting to help loosen the coupling, the longitudinal load is significantly increased. The rattling noise imposes a sharp reversal of the vertical load on the string, and the induced stress can damage the screw thread, especially the internal screw thread that is heavier and more loaded than other screw threads. obtain.

[0010] Previous attempts have been made to reduce stress concentrations by adapting the unique profile of the thread. US Patent No. 5,05
In US Pat. Nos. 6,611 and 5,060,740, the threads are formed with a partially oval valley bottom, and these patents provide a larger and more effective valley diameter. Thus, the concentration of stress is reduced.
However, in each case, the thread profile is asymmetric and the ellipses used to define the roots of the male and female threads are different in size and shape to maintain adequate wear volume. Have shape. This makes the production of screw threads overly complex. Moreover, the fatigue life is still determined by the highest stress concentration in the threaded structure, whereby a high stress concentration at one valley bottom effectively limits the life of the joint.

[0011] Therefore, there is a need to provide a threaded joint that eliminates or reduces the above disadvantages.

In accordance with another aspect of the present invention, there is provided a screw coupling device for a drill string having a pair of cooperating male and female threaded members. Each member has a respective thread with a pair of opposing flank extending between a crown region and a root region. The valley bottom region has a partial circular generating surface radially spaced from the top region and having side surfaces extending tangentially therewith.

[0013] Preferably, the female threaded member has a tapered outer surface that decreases in diameter toward the distal end of the female member and extends over at least one thread pitch.

Preferably, the tapered portion is 3 ° to 10 °.
And more preferably between 4 ° and 6 °.

One factor related to the life of a screw thread is:
The wear volume, which is the volume of material between adjacent side portions of the thread that can be sacrificed before the side portions cross. This volume can be increased by using a single start thread as the spacing between adjacent sides increases. However, wear is inevitable and can lead to premature replacement of the rod.

In accordance with a further aspect of the present invention, a connection between adjacent parts of a string includes a male threaded member and a female threaded member that fit within each other. Each thread has an oppositely converging side portion longitudinally spaced along the member. The screw thread contacts at least a part of the side part,
Each wear volume between oppositely facing side portions is defined. The wear volume defined on one of the members is greater than the wear volume on the other member.

Preferably, the female threading member is a sleeve, the wear volume of the female threading member being less than the wear volume of the male threading member, whereby replacement of the sleeve is required before replacement of the rod. right.

Preferably, the thread is formed such that the longitudinal dimension of the top of the female thread is smaller than the longitudinal dimension of the top of the male thread, and the increased wear of the male thread is achieved. Provide volume. The female thread is between 80% and 95% of the male member, more preferably 89%.
It is preferred to have a wear volume of between% and 95%, typically 92%.

In accordance with yet another aspect of the present invention, there is provided a threaded connection for a drill string having a pair of cooperating male and female threaded members. Each of the threaded members may be between 7 ° and 10 ° with a pair of opposing side portions extending between the top and bottom regions.
Has a single opening helix thread with a helix angle between °. The valley bottom region is defined by a partial circular generating surface whose side surface extends tangentially. Each side is delimited by a crest that extends generally parallel to the longitudinal axis of the thread. The depth of each screw thread measured in the radial direction is greater than 5 mm, and the side portion of the male screw thread and the side portion of the female screw thread overlap radially more than 3.7 mm.

Preferably, the female threads and the male threads have different axial dimensions at the tops, and more preferably the female top has a smaller axial dimension than the male tops. .

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a drill string 10 includes a number of drill rods 12 connected end to end at a joint 13 by a sleeve. The rod and sleeve may be made of a suitable metal, typically, for example, AHT, as is well known in the art.
-28 or iron, such as what is known as a "Javelin". String 10 is
Striker bar 15 at one end
And a drill bit (not shown) at the other end, and connected to the drill bit 11 at the other end. The string 10 transmits rotational and impact loads from the drilling device to the bit 11 for drilling holes.

As shown more clearly in FIGS. 2 and 6, each drill rod 12 is cylindrical with an outer diameter d and has opposite ends 17, 19 for connection to a sleeve 14. Male threads 16 and 18 are provided. Each end 17, 19 is identical, so only one end is described in detail in connection with FIG. The screw thread 16 is formed on the outer surface and extends from the planar end face 21 to the waist 23. The end face 21 projects axially beyond the screw thread 16 and forms a cylindrical button 25 having a smaller diameter than the screw thread 16. Waist 2
Numeral 3 has a smaller diameter than the screw thread, and is formed to have a uniform radius in a state where the tangential side portions extend to the rod surface and the thread 16. Bore 27 extends inside through the rod 12 has an inner diameter d _2.

Referring to FIG. 5, sleeve 14 has a complementary pair of female threads 20, 22 for receiving threaded ends 17, 19 of adjacent rod 12. Female threads 20 and 22 are formed on the inner wall 26 of the tubular body 24 of the sleeve 14. The threads 20, 22 are spaced apart annular recesses 28, 30 which are separated by lands 32 projecting inward into the body 24.
Ends with The outer surface 34 of the body 24 has a central cylindrical portion 36 and, in a preferred embodiment, includes tapered portions 38, 40 formed at opposite ends which decrease in diameter from the central portion 36 to the distal end of the sleeve 14. Have.

The configuration of the screw thread can best be seen in FIGS. These threads are not the same but similar to the male and female threads, and the same reference numbers are used to refer to similar configuration requirements. These threads are up to a single starting thread and each thread 16, 18, 20, and 22
(FIG. 2) has a valley bottom 42 defined by a partial circular generating surface with a linear side surface 44 extending tangentially from the valley bottom 42 at an angle α to the longitudinal axis of the rod 12.
The linear side 44 is truncated by a flat top 46 extending between adjacent sides, which typically has a smooth radius of curvature on the order of 6 mm to join the side 44. Has been taken. When assembled, the top 46 is spaced from the root 42 so that only the male and female threaded linear sides 44 are in contact to transfer the load. Each thread has a wear volume 48 indicated by a dash-dot line, the wear volume being defined as the minimum longitudinal spacing between the other threads and the portion of the side that contacts the opposing side. The portion 44 defines a volume of material that can be defined and removed before the side portions 44 intersect.

In the specific example shown, the outer diameter d ₁ of the rod 12 is 68 mm, and more generally should be greater than 65 mm to reduce the strain resulting from the imposed vertical load. . Bore 27 has an inner diameter of 22 mm and provides a ratio of outer diameter to inner diameter of greater than 3: 1. More generally, this ratio should be greater than 2: 1 to provide the requisite hardness and allow for the formation of the thread 16.

The tapered portions 38 and 40 of the sleeve 14
Each of the threads 16 extends over several pitches, and preferably extends over at least one pitch, typically from 2.5 to 3.5 pitches. The angle of the taper, ie half the cone angle, is selected to distribute the load between the threads. The tapered portions 38, 40 match the longitudinal elasticity of the sleeve 14 closer to the elasticity of the thread 16 and thereby reduce the maximum stress on the thread profile. In one example, a taper of 4.2 ° has been found to be beneficial, more typically between 3 ° and 10 °.
Can be used, preferably 4 °.
A taper in the range of 6 ° to 6 ° is preferable. The angle of the taper described above is the angle of the surface with respect to the longitudinal axis, ie half the included cone angle. Although the taper of the sleeve is selected for optimal stress relief, the taper may be omitted if the coupling device operates satisfactorily.

The selected thread may be in any suitable form, but may be 1.179 inches (about 30 m).
At a pitch of m), a side angle of 35 ° and a helix angle of between 7 ° and 10 °, preferably 8.9 °, have been found to give satisfactory results for a nominal main diameter of 68 mm. .

The main diameter of a male screw thread is 2.660.
A circular root profile of inches (approx. 68 mm) and appropriate radius was used. It has been found that a thread depth from the top to the root of greater than 0.2 inches (5 mm) is satisfactory.

It is shown in FIGS. 3 and 4 that the longitudinal dimension of the crest 46, indicated by l ₁ and l ₂ , differs between male and female threads. The top of the female screw thread 20, 22 (l ₂ ) is shorter than the male screw thread by up to 20% of the top of the male screw thread. The top 46 of the female threads 20, 22 may be between 80% and 100%, typically 89% -95%, preferably 92%, of the top 46 of the male thread 16 (l ₁ ). There can be. The difference in the length of the crest 46 allocates the available wear volume between the sleeve 14 and the rod 12 and causes the wear volume of the sleeve 14 to be less. In this manner, the sleeve requires replacement before the rod, thereby preserving the life of rod 12. Threads with a depth greater than 5 mm (about 0.2 inches), preferably greater than 5.3 mm (ie, 0.21 inches) are selected. The male thread and the female thread preferably overlap 3.8 mm (i.e., 0.15 inch), more preferably 3.8 mm (i.e., 0.15 inch) overlap to provide the requisite wear volume. Preferably they should overlap by more than 4.3 mm (ie 0.17 inches).

To connect the pair of rods 12, the sleeve 14 is threaded at the end 17 onto the thread 16 until the end of the thread borders the side of the land 32. In this position, button 25 overlaps land 32. The end 19 of the next rod 12 is screwed into the sleeve 14 until it abuts the side of the land 32. In this position, the end faces 21 are in contact. When torque is applied to the string 10, the joint 13 is tightened, imposing longitudinal stress on the thread.

When the male screw thread and the female screw thread are mated, the radiused root 42 is separated from the top 46 of the mating screw thread and from the contact area between the side faces 44. Located away. The valley bottom 42 is considered effective because it provides an area of maximum stress concentration spaced from the contact area. The tapered portion of the sleeve 14 also contributes to reducing the maximum stress by matching the elasticity of the sleeve 14 in the longitudinal direction to the stress distribution of the thread.

The string 10 exemplified above has been found to provide significant effectiveness over the effects of using currently widely available thread forming, such as, for example, known as HM51. In particular, the wear volume 48 increases by a factor of 2.9 and 3.5, respectively, and the maximum elongational stress in the critical configuration increases the applied shock load of the joint provided by the available thread and sleeve combination. 10% less than the stress on Finite element analysis is 5 times better than that experienced with HM51 joints.
Even with an impact force as high as 0%, the maximum elongational stress in the critical configuration is still 22 times higher than previously encountered.
% Smaller. Reduction of stress, of course,
This indicates that the life of the joint 10 has been increased.

Thus, providing a tapered sleeve to match the longitudinal resilience to the thread stress distribution provides a reduction in the stress level in critical configurations and provides a top and radius of curvature. The distance to the bottom of the valley ensures that the maximum stress concentration is pulled away from the contact area. Thus, larger radius rods increase hardness and enhance the performance of straight drilling of the rod. The different wear volumes resulting from different length peaks provide preferential wear to one of the parts, which can extend the lip of more expensive parts.

While the joint 13 is shown with the sleeve, it will be appreciated that a female thread or female member can be integrally formed with one end of the rod. However, providing a separate sleeve allows it to be replaced at the end of its useful life without sacrificing all the rods.

[Brief description of the drawings]

FIG. 1 is a front elevation view of a drill string.

FIG. 2 is a cross-sectional view of a joint portion of the string of FIG.

FIG. 3 is an enlarged view of a screw thread at a joint portion in FIG. 2;

FIG. 4 is a view similar to FIG. 3 with parts separated.

FIG. 5 is a sectional view of the sleeve shown in FIG. 2;

FIG. 6 is a sectional view of one end of the rod shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Drill string 11 Drill bit 12 Drill rod 13 Joining part 14 Sleeve 16, 18 Male screw thread 17, 19 Threaded end part 20, 22 Female screw thread 21 End face 23 Waist part 24 Body 25 Button 27 Bore 28, 30 Annular recess 34 Outer surface 38,40 Taper part 42 Valley bottom part 44 Side part 46 Top part 48 Wear volume

 ────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 598085157 2442 South Sheridan Way, Mississauga, Ontario L5J 2M7, Canada F term (reference) 3C069 AA04 BA09 BB01 BC01 CA01 CA07 EA03

Claims (28)

[Claims] 1. A drill rod connected in series to provide a drill string, the drill rod having a thread formed at at least one end for connection to an adjacent rod, and a cylindrical shape having an outer surface. Having a body and an inner bore extending between opposite ends of the rod, wherein the outer surface of the rod is greater than or equal to 65 mm in diameter and at least twice as large as the bore Said drill rod having a diameter of: 2. The drill rod of claim 1, wherein the diameter of the outer surface is equal to or greater than at least three times the diameter of the bore. 3. The drill rod of claim 2, wherein a thread is provided at each end of the rod. 4. The screw thread has a pair of side portions extending between a top region and a root region radially spaced from the top region, wherein the root region is tangential to the side portions. The drill rod according to claim 1, wherein the drill rod has a partial circular generating surface extending in a direction. 5. The drill rod according to claim 4, wherein the thread has a helical angle between 7 ° and 10 °. 6. The drill rod according to claim 4, wherein a radial spacing between the valley region and the top region is greater than 5 mm. 7. A threaded connection for connecting adjacent parts of a drill string, the connection comprising a male threaded member and a female threaded member, each of said members having a top region and a threaded member. A respective thread with a pair of opposing side portions extending between the crest region and a root region radially spaced therefrom, wherein the root region extends tangentially therewith. Said threaded coupling device having a partially circular generating surface. 8. The threaded connection of claim 7, wherein the female threaded member has a tapered outer surface that decreases in diameter toward a distal end of the member. 9. The tapered outer surface extends at least over a pitch of the thread.
4. The threaded coupling device according to claim 1. 10. The threaded coupling device according to claim 9, wherein the tapered outer surface extends between 2.5 and 3.5 pitches of the thread. 11. The threaded coupling device according to claim 8, wherein said tapered outer surface has a half angle between 3 ° and 10 °. 12. The threaded coupling device according to claim 11, wherein said tapered outer surface has a half angle between 4 ° and 6 °. 13. The threaded coupling device according to claim 7, wherein one root region of said threaded member is radially spaced from a top region of said other threaded member. 14. The threaded coupling device according to claim 13, wherein a top of one of said threaded members has a greater axial dimension than a top of the other of said threaded members. 15. The top of the male threaded member,
15. The threaded coupling device of claim 14, wherein the threaded coupling device has an axial dimension greater than the top of the female threaded member. 16. The female threaded member having an apex having an axial dimension greater than 80% of an axial dimension of the male threaded member apex.
4. The threaded coupling device according to claim 1. 17. The threaded connection of claim 16, wherein the female threaded member has an axial dimension between 89% and 95% of an axial dimension of the crest of the male member. 18. A threaded coupling for connecting adjacent parts of a drill string, the coupling including a male threaded member and a female threaded member, each of which connects the members. Each thread formed therein, and each thread has an opposing convergent side portion longitudinally spaced along the member. And
The screw thread contacts at least a portion of the side portion to define a wear volume between the opposing side portions, wherein the wear volume defined on one of the members is greater than the other wear volume on the screw thread. The threaded coupling device is also large. 19. The threaded coupling device according to claim 18, wherein said female threaded member is a sleeve and has a smaller wear volume than said male threaded member. 20. The threaded coupling device of claim 19, wherein the female threaded member has a wear volume between 80% and 95% of a wear volume of the male member. 21. The threaded coupling device of claim 20, wherein the female threaded member has a wear volume between 89% and 95% of a wear volume of the male member. 22. The side portion extends between a root portion and a top portion, and the top portion of one screw thread of the member has a diameter from a root portion of the other thread portion of the member. 20. The threaded coupling device of claim 19, wherein the threaded coupling device is directionally spaced. 23. The threaded coupling device according to claim 22, wherein the crest extends substantially parallel to a longitudinal axis of the screw thread. 24. The threaded coupling device according to claim 24, wherein the valley bottom is defined by a partial circular generating surface, and the side portions extend tangentially therewith. 25. A threaded connection for a drill string having a male threaded member and a female threaded member, each said member having a helical angle between 7 ° and 10 °. Starting screw threads, each of which has a pair of opposing side portions, wherein the side portions are:
Extending between a crest extending substantially parallel to a longitudinal axis of the screw thread and a valley region defined by a partial circular generating surface with the side portion extending tangentially therewith; The top and root regions of each screw thread are radially spaced apart by more than 5 mm, and the screw thread is 3.7 m
The threaded coupling device wherein the threaded coupling device overlaps radially at a distance greater than m. 26. The threaded coupling device of claim 25, wherein an axial extent of the crest of the female threaded member is different from an axial extent of the crest of the male threaded member. 27. The threaded coupling device according to claim 26, wherein an axial dimension of the top of the female member is smaller than an axial dimension of the male member. 28. A generating surface of the side portion is linear,
26. The threaded coupling device according to claim 25, wherein the threaded coupling device is equally inclined with respect to a radial plane.