WO2008004937A1

WO2008004937A1 - An extension joint and rod for percussive extension drillin

Info

Publication number: WO2008004937A1
Application number: PCT/SE2007/000628
Authority: WO
Inventors: Peter Nava
Original assignee: Sandvik Intellectual Property AB
Current assignee: Sandvik Intellectual Property AB
Priority date: 2006-07-04
Filing date: 2007-06-27
Publication date: 2008-01-10
Anticipated expiration: 2009-01-04
Also published as: SE0601450L; SE530193C2

Abstract

The present invention relates to an extension joint for percussive drilling, which joint comprises a male part (1) as well as a female part (10), the male part (1) being intended to be received in the female part (10), the male part (1 ) being pro- vided with an eccentric portion (5) and the female part (10) being provided with a cavity (11). The invention also relates to a rod intended to be included in an extension joint in a drill string for percussive drilling as well as to a method for the manufacture of a part cavity of the cavity in the female part. Characteristic of the extension joint according to the present invention is that a part cavity (14) of the cavity (11) has portions having different radii of curvature (R1. R2).

Description

An extension joint and rod for percussive extension drilling

Technical Field and Background of the Invention

The present invention relates to an extension joint for percussive drilling, which joint comprises a male part as well as a female part, the male part being provided with an eccentric portion and the female part being provided with a cavity. The invention also relates to a rod intended to be included in an extension joint for percussive drilling as well as to a method for the manufacture of a part cavity of the cavity in the female part.

An extension joint for a rock drill bit, preferably of chisel type, is previously known. The extension joint comprises a rod, which has a first cylindrical nose portion, an eccentric portion connecting to the nose portion as well as a second cylindrical portion that connects to the eccentric portion, the second cylindrical portion having a greater diameter than the first cylindrical nose portion.

The drill bit has a female part having a third cylindrical bottom portion, an non-cylindrical engagement portion connecting to the bottom portion, as well as a fourth cylindrical portion having a greater diameter than the third cylindrical portion.

In order to activate the extension joint, the male part and the female part are rotated in relation to each other, the eccentric portion of the male part coming into engagement with the engagement portion of the female part. In that connection, a line contact arises between surfaces that slope in relation to the rotational axis. Based on experience, that type of joint has a tendency to become extremely firmly tightened, which leads to complications upon loosening of the joint.

Objects and Features of the Invention

A primary object of the present invention is to provide an extension joint of the kind defined by way of introduction, wherein the extension joint should transfer rotation in a reliable way, i.e., there should not be any risk of the driving function ceasing.

Another object of the present invention is that the extension joint should be easy to mount and to loosen. Still another object of the present invention is that at least the cavity included in the female part should be simple to manufacture.

At least the primary object of the present invention is realised by means of an extension joint having the features defined in the appended independent claim 1. Preferred embodiments of the invention are defined in the dependent claims.

Brief Description of the Drawings

Below, a preferred embodiment of the invention will be described, reference being made to the accompanying drawings, wherein: Fig. 1 shows a side view of a male part included in the extension joint;

Fig. 2 shows an end view of the male part according to Fig. 1 ;

Fig. 3 shows a perspective view of the male part according to Fig. 1 ;

Fig. 4 shows a side view of a female part included in the extension joint according to the present invention, the cavity in the female part being shown by dashed lines;

Fig. 5 shows an end view from the left in Fig. 4 of the female part according to the present invention; Fig. 6 shows an enlarged detail in Fig. 5, which is indicated by a dashed and dotted line; Fig. 7A shows a longitudinal section along the line VIIA-VIIA through the male part; Fig. 7B shows a longitudinal section along the line VIIA-VIIA through the female part;

Fig. 7C shows a view along the line VIIC-VIIC in Fig. 7B; Fig. 7D shows a section along the line VIID-VIID in Fig. 7B;

Fig. 8A shows a longitudinal section through the extension joint according to the present invention when the male part and the female part are in an initial position;

Fig. 8B shows a section along the line VIIIB— VIIIB in Fig. 8A; Fig. 9A shows a longitudinal section through the extension joint according to the present invention when the male part and the female part are in engagement with each other;

Fig. 9B shows a section along the line IXB-IXB in Fig. 9A; Fig. 10A shows a longitudinal section through the extension joint according to the present invention when the male part and the female part are in an initial position; Fig. 10B shows a section along the line XB-XB in Fig. 10A; Fig. 11A shows a longitudinal section through the extension joint according to the present invention when the male part and the female part are in engagement with each other; and

Fig. 11 B shows a section along the line XIB-XIB in Fig. 11 A;

Detailed Description of a Preferred Embodiment of the Invention

The male part 1 according to the present invention shown in Figs. 1-3 comprises a rod-shaped element 3 having a circular-cylindrical basic shape. In Figs. 1-3, the rotational axis C1 of the rod-shaped element 3 is indicated, said rotational axis also constituting the rotational axis C1 of the extension joint as well as defining the axial direction of the extension joint. On the rod-shaped element 3, there is provided a portion 5 being eccentric in relation to the rotational axis C1 and having an extension along a part of the longitudinal direction of the rod-shaped element 3, see Fig. 1 , and along a part of the circumference of the rod-shaped element 3, see Fig. 2. As is seen in Fig. 1 , the connection of the eccentric portion 5 to the rod- shaped element 3 is effected, in the longitudinal direction of the rod-shaped element 3, by means of chamfers 7. In the top part thereof in Figs. 1 and 2, the eccentric portion 5 has the greatest eccentricity thereof, which is indicated by the measure H. There, the chamfers 7 form an angle α with the inner periphery of the rod-shaped element 3, the angle α having a preferred value of approx. 25°.

In the embodiment shown in Figs. 1-3, the extension of the eccentric portion 5, between the chamfers 7, in the longitudinal direction of the rod-shaped element 3, is less than half of the total length of the rod-shaped element 3. This is most clearly seen in Fig. 1. In the area of the free end thereof, the rod-shaped element 3 is provided with a guide portion 9, which defines an impact surface 9A at the free end thereof. In Fig. 2, there is shown how great part of the circumference of the rod- shaped element 3 that is overlapped by the eccentric portion 5. As is seen in Fig. 2, the eccentric portion 5 has full eccentricity H in the top portion thereof in Fig. 2. From there, the eccentricity of the eccentric portion 5 decreases continuously towards both the right and the left, the eccentricity of the eccentric portion 5 vanishing into nothingness on the underside of the rod-shaped element 3. In conclusion, the male part 1 comprises two circular-cylindrical portions of different diameter, the first circular-cylindrical portion consisting of the rod-shaped element 3 and the second circular-cylindrical portion consisting of the eccentric portion 5. The rod-shaped element 3 has a smaller diameter than the eccentric portion 5. The rod-shaped element 3 and the eccentric portion 5 coincide along a line 4, see Fig. 2, running perpendicularly to the paper in Fig. 2. In Figs. 4 and 5, a female part 10 according to the present invention is shown, the female part 10 generally being in the form of a sleeve, i.e., the female part 10 comprising a cavity 11 as well as an opening 12 situated at the free end thereof, which opening is in connection with the cavity 11. The male part 1 is intended to be inserted through the opening 12 in connection with establishing the extension joint according to the present invention.

The cavity 11 formed in the female part 10 comprises two part cavities. Thus, the cavity 11 comprises a bottom cavity 13 having a circular-cylindrical cross- section, said bottom cavity 13 being intended to receive the guide portion 9 of the male part 1. The bottom cavity 13 has an abutment surface 13A, which is intended to co-operate with the impact surface 9A of the male part 1. The bottom cavity 13 is shown by dashed lines in Fig. 4 and by continuous lines in Figs. 5 and 6.

The cavity 11 also comprises an intermediate cavity 14 situated between the bottom cavity 13 and the opening 12. The shape of the cavity 14 will be described closer below.

With reference to Figs. 7A-9B, the mutual co-operation of the male part 1 and of the female part 10 will be described schematically. The shape of the cross sections of the male part 1 and the female part 10 will also be described in connection with certain operations of the manufacture being explained. The male and female parts may be provided at each end of one and the same rod.

In this connection, it should be pointed out that in Figs. 7A-9B, the male part and the female part are shown more schematically than in Figs. 1-6.

In Figs. 7A and 7B, the male part 1 and the female part 10 are shown separated from each other in side view. In Fig. 7C, a view is shown along VIIC-VIIC in Fig. 7B, and in Fig. 7D, a section is shown along VIID-VIID in Fig. 7B.

The intermediate cavity 14 is composed of a number of portions. The intermediate cavity 14 may be manufactured by means of an end-cutting shank-end mill. In the manufacturing of the female part 10, a hole is first drilled, which generates the bottom cavity 13, which has a first centre axis C1 coinciding with the centre axis of the external circular-cylindrical surface of the female part 10. The centre axis C1 also constitutes a rotational axis of the extension joint. Next, the hole 12 is reamed by means of the shank-end mill, said hole 12 having a second centre axis C2 situated below the centre axis C1 in Figs. 7B, 7C and 7D. The distance between C1 and C2 has been designated D1 in Fig. 7D. In an intermediate manufacturing stage, the hole 12 has an extension all the way down to the bottom cavity 13, which is indicated by a dashed line 12' in Fig. 7B.

It is now time to ream the cavity 14 including the part cavities thereof. In that connection, the same end-cutting shank-end mill used to ream the hole 12 is suitably used, which hole, in this stage, accordingly, extends all the way down to the bottom cavity 13. In this connection, it should be pointed out that the end-cutting shank-end mill has a shank connecting to the chip-removing part, which shank has a smaller diameter than the diameter of the chip-removing part. Hence, the end-cutting shank- end mill is in the hole 12, 12', the chip-removing part of the shank-end mill having a maximum axial length that corresponds to the length of the cavity 14. During rotation of the shank-end mill, the rotational axis thereof is brought in a semicircle HC around the centre axis C1 , the rotational axis of the shank-end mill defining the axis C3 after finished machining. The distance between C1 and C3 has been designated D2 in Fig. 7C. Since the rotational axis of the shank-end mill has moved along a semicircle HC, D2 equals D1. Thus, the rotational axis of the shank-end mill has moved 180° during the machining. Thus, by this machining, a cavity 14 has been created that extends radially outside the hole 12 for a part of the circumference that corresponds to an angle of 270°, see the dashed line 15 in Fig. 7C.

In connection with the shank-end mill concluding the machining thereof, an axially extending ridge 16 is created, see Fig. 7D, in the intersection to the portion machined first upon the formation of the cavity. Said ridge 16 is important for the function of the extension joint.

The cavity 14 is composed of three portions 14A, 14B, and 14C. The first portion 14A is circular-cylindrical having the radius of curvature R1. The first portion 14A has an extension along the circumference of 90°, the first portion 14A extending from the ridge 16. The second portion 14B is circular-cylindrical having the radius of curvature R2, wherein the radius R2 > R1 , more precisely, R2 equals R1 + D1. The third portion 14C is circular-cylindrical having the radius of curvature R1. The third portion 14C extends up to the ridge 16, which, accordingly, is situated in the part of the cavity 14 that is situated closest to the rotational axis of the extension joint.

In Fig. 8A, the male part 1 is inserted into the female part 10, this being an initial position in order to provide an extension joint according to the present invention. In said initial position, the eccentric portion 5 is facing the lowest point of the cavity 14 in Figs. 8A and 8B, and the impact surface 9A abuts against the abutment surface 13A.

In Figs. 9A and 9B, there is shown the mutual position assumed by the male part 1 and the female part 10 when the extension joint is established. In order to move from the initial position shown in Fig. 8A to the established position shown in Fig. 9A, the male part 1 and the female part 10 are rotated in relation to each other. In a comparative study between Figs. 8A and 9A, the male part 1 has been rotated around the axis C1 while the female part 10 is stationary, see also Figs. 8B and 9B. Upon rotation of the male part 1 , while the female part 10 is locked against rotation, the eccentric portion 5 will move along the circumference of the intermediate cavity 14 until the position shown in Figs. 9A and 9B has been attained. In that connection, the eccentric portion 5 comes into engagement with the ridge 16, i.e., there is no risk that the eccentric portion 5 of the male part 3 should pass past the ridge 16. In this connection, it should also be pointed out that the circumference of the eccentric portion 5, at least partly, is radially outside the circumference of the hole 12, see, for instance, Fig. 9A, a locking in the axial direction between the male part 1 and the female part 10 being provided.

When percussive drilling is exercised using the extension joint according to the present invention, this takes place by so-called bottom abutment, i.e., the impact energy is transferred by the fact that the impact surface 9a of the guide part 9 is in contact with the abutment surface 13a of the bottom cavity 13.

The alternative embodiment of an extension joint according to the present invention shown in Figs. 10A-11 B principally differs from the embodiment described above in that guide/support members are arranged in the area of the open end of a female part 110. The male part 101 included in the extension joint according to Figs. 10A-

11 B differs from the male part 1 described above in that the male part 101 , in addition to the first eccentric portion 105, is provided with a second eccentric portion 106, which is provided, in the axial direction, on the side of the first eccentric portion 105 that is facing away from the guide part 109 of the male part 101. Generally, the two eccentric portions 105, 106 are facing diametrically opposite direction, see Figs. 10A and 11 A. Thus, the first eccentric portion 105 has an extension downward in Fig. 10A, while the second eccentric portion 106 has an extension upward in Fig. 10A. In the embodiment illustrated, the second eccentric portion 106 has a substantially smaller axial extension than the first eccentric portion 105. The extension joint shown in Figs. 10A-11 B also comprises a female part

110, which principally differs from the female part 10 described above in that the female part 110 is provided with a recess 117 adjacent to an opening 112 of the female part 110. The recess 117 is situated outside the opening 112, i.e., on the opposite side of the opening 112 in comparison with a part cavity 114 included in the female part 110. The design of the part cavity 114 may, in principle, be identical to the design of the part cavity 14 described above, and therefore, in that respect, reference is made to Fig. 7D and the text associated therewith. The recess 117 allows the second eccentric portion 106 to move from the position according to Fig. 10B to the position according to Fig. 11 B, said position change taking place by mutual rotation of the male part 101 and the female part 110.

By studying Fig. 11A, it is realized that the second eccentric portion 106 of the male part 101 , by the co-operation thereof with the female part 110, provides an increased stabilization of the extension joint according to the present invention. In this connection, it should also be pointed out that in the active position of the extension joint, the circumference of the first eccentric portion 105 is, at least partly, radially outside the circumference of the hole 112, see Fig. 11 A, a locking in the axial direction between the male part 101 and the female part 110 being provided.

In the embodiment of the invention described above, it is a matter of an extension joint between two rods included in a drill string for percussive drilling.

However, within the scope of the present invention, it is possible to conceive that the extension joint according to the present invention also can be used between a drill rod and a drill bit for percussive drilling.

The disclosures in Swedish patent application No. 0601450-0, from which this application claims priority, are incorporated herein by reference.

The invention is in no way limited to the above-described embodiment but can be freely varied within the limits of the appended claims.

Claims

1. An extension joint for percussive drilling, which joint comprises a male part (1 ; 101) as well as a female part (10; 110), the male part (1 ; 101) being intended to be received in the female part (10; 110), the male part (1 ; 101) being provided with an eccentric portion (5; 105) and the female part (10; 110) being provided with a cavity (11 ; 111), c h a r a c t e r i z e d in that a part cavity (14; 114) of the cavity (11 ; 111) has portions having different radii of curvature (R1 , R2).

2. The extension joint according to claim 1 , wherein the part cavity (14; 114) is provided with an axially extending ridge (16; 116).

3. The extension joint according to claim 2, wherein the ridge (16; 116) is situated in the area of the portion of the part cavity (14; 114) that is situated closest to the rotational axis (C1) of the extension joint.

4. The extension joint according to any one of the preceding claims, wherein the part cavity (14; 114) comprises two portions (14A, 14C) having a first radius of curvature (R1), that said portions have an extension in the circumferential direction of 90°, that the part cavity (14; 114) comprises a portion having a second radius of curvature (R2), that said portion has an extension in the circumferential direction of 180°, and that the first radius of curvature (R1) is smaller than the second radius of curvature (R2).

5. The extension joint according to any one of the preceding claims, c h a r a c t e r i z e d in that the cavity (11 ; 111) comprises a bottom cavity (13; 113), which has a smaller diameter than the rest of the cavity (11 ; 111).

6. The extension joint according to any one of the preceding claims, wherein the male part (101) has an additional eccentric portion (106), that said additional eccentric portion (106) is situated adjacent to the open end of the female part (110), and that the female part (110) has members (117) intended to co-operate with the additional eccentric portion (106) upon mutual rotation of the male part (101) and the female part (110).

7. The extension joint according to claim 6, wherein the eccentric portions (105, 106) have a respective extension towards diametrically different directions.

8. A rod intended to be used for percussive extension drilling, the rod comprising a male part (1 ; 101 ) as well as a female part (10; 110), the male part (1 ; 101 ) being provided with an eccentric portion (5; 105) and the female part (10; 110) being provided with a cavity (11; 111), characterized in that a part cavity (14; 114) of the cavity (11; 111) has portions having different radii of curvature (R1 , R2).

9. The rod according to claim 8, wherein the part cavity (14; 114) is provided with an axially extending ridge (16; 116).

10. The rod according to claim 9, wherein the ridge (16; 116) is situated in the area of the portion of the part cavity (14) that is situated closest to the rotational axis (C1) of the extension joint.

11. A method for the manufacture of a part cavity of a cavity in a female part included in an extension joint for percussive drilling, a hole (12) being provided eccentrically in respect of the rotational axis (C1) of the female part, characterized in that the hole (12) is reamed by means of a shank-end mill, and that the shank-end mill, during simultaneous rotation of the same, is brought to move half a revolution around the rotational axis (C1).