Abstract
A drilling assembly for percussive drilling includes at least two of a drill bit, a drill rod and a guide adapter. A peripheral surface of the shoulder on the drill rod is at least partially encased in both radial and axial directions inside the mounting sleeve of the drill bit or the mounting sleeve of the guide adapter, and/or the peripheral surface of the shoulder on the guide adapter is at least partially encased in both radial and axial directions inside the mounting sleeve of the drill bit.
Claims
1. A drilling assembly for percussive drilling, comprising: at least two of a drill bit, a drill rod and a guide adapter; the drill rod including a hollow elongate main length section extending axially between a male end and a female end, the male end including a male connecting means and a radially projecting shoulder that axially separates the main length section and the male connecting means, wherein the shoulder includes a peripheral surface having a greater outer diameter (D.sub.1) than an outer diameter of the main length section (D.sub.2), a first annular side surface that abuts the drill bit or guide adapter and a second annular side surface that flares radially from the main length section; the drill bit including a mounting sleeve for connecting to the drill rod to the guide adapter; and the guide adapter including a mounting sleeve for connection to the drill rod and a shoulder having a peripheral surface for connection to the drill bit, wherein the peripheral surface of the shoulder on the drill rod is at least partially encased in both radial and axial directions inside the mounting sleeve of the drill bit or the mounting sleeve of the guide adapter, and/or the peripheral surface of the shoulder on the guide adapter is at least partially encased in both radial and axial directions inside the mounting sleeve of the drill bit.
2. The drilling assembly according to claim 1, wherein at least 20% of a length (L.sub.2) of the peripheral surface of the shoulder is encased inside the mounting sleeve.
3. The drilling assembly according to claim 1, wherein the mounting sleeve on the drill bit or the guide adapter has a connecting section having a first wall thickness at its thinnest point the connecting section being arranged for securing to the male connecting means on the drill rod and an encasing section, having a second wall thickness at its thickest point, for the shoulder of the drill rod to fit inside, wherein the second wall thickness is less than the first wall thickness.
4. The drilling assembly according to claim 3, wherein the second wall thickness is at least 1.5 mm.
5. The drilling assembly according to claim 3, wherein the encasing section has a length (L.sub.1) and the shoulder has a length (L.sub.2), wherein L.sub.1 is at least 20% of L.sub.2.
6. The drilling assembly according to claim 3, wherein the shoulder has an outer diameter (D.sub.1) and the encasing section has an inside diameter (D.sub.3), wherein D.sub.1 is within the range of 80%-100% of D.sub.3.
7. The drilling assembly according to claim 3, wherein a clearance between the peripheral surface of the shoulder and an internal surface of the encasing section is between 0.5-4 mm.
8. The drilling assembly according to claim 3, wherein the peripheral surface of the shoulder and the internal surface of the encasing section are substantially cylindrical.
9. The drilling assembly according to claim 3, wherein the peripheral surface of the shoulder and the internal surface of the encasing section have a conical shape.
10. The drilling assembly according to claim 1, wherein a junction between edges of the peripheral surface and the first annular side surface and a junction between the peripheral surface and the second annular side surface on the shoulder are chamfered.
11. The drilling assembly according to claim 1, wherein the length of the shoulder is between 5-60 mm.
12. The drilling assembly according to claim 1, wherein the male connecting means on the drill rod is a spigot having an externally threaded section and a non-threaded shank positioned axially between the threaded section and the shoulder and wherein the mounting sleeve on the drill bit or the guide adapter is internally threaded.
13. The drilling assembly, according to claim 1, wherein the male connecting means on the drill rod is conical and non-threaded and the mounting sleeve on the drill bit or the guide adapter is internally conical and non-threaded, forming a tapered connection.
14. The drilling assembly according to claim 3, wherein the first annular side surface of the shoulder on the drill rod abuts an annular endmost surface on the connecting section of the mounting sleeve on the drill bit or the guide adapter.
15. The drilling assembly according to claim 3, wherein the drill bit or the guide adapter has an outer diameter (D.sub.4) at its annular rearward end in the section surrounding the encasing section, wherein D.sub.4 is at least 5% greater than the outer diameter (D.sub.1) of the shoulder.
16. A drill bit or guide adapter having a mounting sleeve that has a connecting section, having a first wall thickness at its thinnest point, for securing to the male connecting means on the drill rod and an encasing section, having a second wall thickness at its thickest point, for the shoulder of the drill rod to fit inside, wherein the second wall thickness is less than the first wall thickness.
17. The drilling assembly according to claim 3, wherein the drill bit or the guide adapter has an outer diameter (D.sub.4) at its annular rearward end in the section surrounding the encasing section, and wherein D.sub.4 is at least 3 mm greater than D.sub.1 up to a maximum of the diameter of the drill bit or guide adapter at its largest cross section.
Description
BRIEF DESCRIPTION OF THE DRAWING
[0034] FIG. 1: shows a perspective view of a percussive drilling assembly wherein a drill rod is coupled to drill bit.
[0035] FIG. 2: shows a perspective view of the male end of a drill rod.
[0036] FIG. 3: shows a cross section of a drill bit as known in the prior art.
[0037] FIG. 4: shows a cross section of a drill bit coupled to the first drill rod as known in the prior art.
[0038] FIG. 5: shows a cross section of a drill bit according to an embodiment of the present invention wherein the mounting sleeve is internally threaded.
[0039] FIG. 6: shows a cross section of a drill bit coupled to the first drill rod according to an embodiment of the present invention having a threaded connection and a cylindrical shoulder.
[0040] FIG. 7: shows a cross section of a drill bit coupled to the first drill rod according to an alternative embodiment of the present invention having a threaded connection and a conical shoulder.
[0041] FIG. 8: shows a cross section of a drill bit coupled to the first drill rod according to an alternative embodiment of the present invention having a tapered conical connection.
[0042] FIG. 9: shows a perspective view a drilling assembly wherein a drill rod is coupled to a drill bit via a guide adapter.
[0043] FIG. 10: shows a cross section of a guide adapter according to an embodiment of the present invention.
[0044] FIG. 11: shows a cross section of a guide adapter coupled to the first drill rod according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0045] FIG. 1 shows a percussive drilling assembly 1 whereby a first drill rod 12 is releasably coupled to a drill bit 2 of conventional design. The percussive drilling assembly 1 is especially used for top hammer drilling. Shockwaves generated by a surface piston (not shown) are translated through the mated surfaces from the drill rod 12 to the drill bit 2. The drill rod 12 comprises an axially extending main length section 14 that is terminated at one end by a male end 16 and at a second opposite end by a female end 18 having a longitudinal axis 5. The drill rod 12 is capable of being coupled end-to-end with other adjacent drill rods 12 to form a drill string (not shown).
[0046] FIG. 2 shows the male end 16 of the drill rod 12 comprising a male connecting means 20, in this case in the form of a spigot 38 and a shoulder 22 that projects radially outward relative to the main length section 14, that extends over a fraction of the axial distance of the main length section 14. The shoulder 22 comprises a peripheral surface 24 that extends axially along the length of the shoulder 22, a first annular side surface 26 at the forwardmost end of the shoulder 22 that abuts the drill bit 2 adjacent to the male connection means 20, alternatively called an annular abutment surface, and a second annular side surface 28 that flares radially from the main length section 14. The main length section 14, has an outer diameter D.sub.2, the shoulder 22 has a length L.sub.2 and an outer diameter D.sub.1. The drill rod 12 has an internal bore (not shown) that extends axially through the main length section 14, optionally the bore has a uniform diameter over its entire axial length.
[0047] Preferably, the corner or junction between the edges of the peripheral surface 24 and the first annular side surface 26 and between the peripheral surface 24 and the second annular side surface 26 on the shoulder 22 are chamfered.
[0048] FIG. 3 shows the cross section of the drill bit 2 as known in the prior art and FIG. 5 shows the cross section of drill bit 2 according to one embodiment of the present invention. In both versions the drill bit 2 comprises an axially forwardmost drill head of convention design for example comprising a rock crushing means, most typically this is a plurality of wear resistant cutting buttons projecting axially forward from the drill head (not shown); a plurality of grooves extending in the axial direction of the drill bit used for the removal of sludge and drill cuttings (not shown)); and a mounting sleeve 10 that comprises an internal cavity 50 extending axially from the axially rearward endmost surface 46 to receive the male connecting means 20 of the drill rod 12.
[0049] In the version known in the prior art shown, as shown in FIG. 3, the mounting sleeve 10 has a connecting section 30 suitable for coupling to the male connecting means 20 of the drill rod 12.
[0050] FIG. 4 shows the drill bit 2 known in the prior art (as shown in FIG. 3) releasably connected to the drill rod 12 wherein the first annular side surface 26 shoulder 22 of the drill rod 12 abuts the annular endmost surface 46 of the drill bit 2 such that a shoulder contact is formed.
[0051] In the version according to one embodiment of the present invention, as shown in FIG. 5, the mounting sleeve 10 is modified so that it has a connecting section 30 suitable for coupling to the male connecting means 20 of the drill rod 12 and additionally also has an encasing section 32 suitable for the shoulder 22 of the drill rod 12 to fit inside. The connecting section has a wall thickness T.sub.1 at its thinnest point, that is thicker than the wall thickness T.sub.2 of the encasing section 32, at its thickest point. Preferably, T.sub.1 is at least 10% greater than T.sub.2.
[0052] FIG. 6 shows the drill bit 2 according to an embodiment of the present invention whereby the modified drill bit 2, as shown in FIG. 5, is releasably coupled to the drill rod 12 so that the shoulder 22 of the drill rod 12 is at least partially encased in both the radial and axial directions inside the drill bit 2. In other words, the drill rod 12 is at least partially enclosed inside the drill bit 2 in both radial and axial directions, so that the drill rod 12 is inserted inside at least part of the drill bit 2. The first annular side surface 26 of the shoulder 22 on the drill rod 12 now abuts an annular endmost surface 48 of the connecting section 30. Preferably, at least 20%, more preferably at least 30%, more preferably at least 50%, even more preferably at least 75%, most preferably at least 90% of the length L.sub.2 of the shoulder 22 is encased or enclosed inside the mounting sleeve 10 within the encasing section 32.
[0053] The encasing section 32 has a length L.sub.1. Preferably, the length of the encasing section L.sub.1 is at least 20% of the length of the shoulder L.sub.2, more preferably at least 30%, more preferably at least 50%, even more preferably at least 75%, most preferably at least 90%. Preferably, L.sub.2 is 15 to 22 mm, more preferably about 22 mm.
[0054] The encasing section 32 has an inside diameter D.sub.3. Preferably the outer diameter D.sub.1 of the shoulder 22 is within the range of 80-100% of D.sub.3, more preferably 95-99%. The clearance 36, which is the radial distance between the peripheral surface 24 of the shoulder 22 and an internal surface 34 of the encasing section 32, is preferably between 0.5-4 mm. The drill bit 2 has an outer diameter, D.sub.4 at its annular rearward end, in the section surrounding the encasing section 32. Preferably, D.sub.4 is at least 5% greater than D.sub.1. Preferably, D.sub.4 is at least 3 mm larger than D.sub.1, up to a maximum of the diameter of the drill bit 2 at its largest cross section.
[0055] In one embodiment, the peripheral surface 24 of the shoulder 22 and the internal surface 34 of the encasing section 32 are both substantially cylindrical as shown in FIG. 6. If the shoulder 22 and encasing section 32 are substantially cylindrical they could either have a uniform diameter along there is a stepped profile such that the peripheral surface 24 of the shoulder 22 and the internal surface 34 of the encasing section 32 have at least two sections, each section having a different diameter compared to the other sections, but having a uniform diameter along the axial length of each section.
[0056] FIG. 7 shows an alternative embodiment wherein the peripheral surface 24 of the shoulder 22 and the internal surface 34 of the encasing section 32 have a conical shape, having either straight or curved profile.
[0057] In one embodiment, as shown in FIGS. 2, 5, 6 and 7 the coupling between the drill bit 2 and the drill rod 12 is formed by the threaded connection. In this embodiment the male connecting means 20 on the drill rod 12 is a spigot 38 that projects axially forward from the shoulder 22. The spigot 38 has an externally threaded section 40 and a non-threaded shank 42 positioned axially between the threaded section 40 and the shoulder 22. To couple with this the cavity 50 inside the mounting sleeve 10 on the drill bit 2 is internally threaded 44.
[0058] FIG. 8 shows an alternative embodiment, wherein instead of a threaded coupling, a tapered connection is formed. In this embodiment the male connecting means 20 on the drill rod 12 is conical and non-threaded and mounting sleeve 10 is internally conical and non-threaded, so that the parts are held together by friction.
[0059] Any other suitable connecting means could also be used. Any type of connecting means could be combined with any of the profiles of the shoulder 22.
[0060] FIG. 9 shows can alternatively the drill bit 2 may be connected to the drill rod 12 via a guide adapter 60 having a mounting sleeve 10. FIG. 10 shows that the mounting sleeve 10 is modified in the same way as described hereinabove in relation to the drill bit 2 so that it has a connecting section 30 suitable for coupling to the male connecting means 20 of the drill rod 12 and additionally also has an encasing section 32 suitable for the shoulder 22 of the drill rod 12 to fit inside. FIG. 11 shows the guide adapter 60 according to an embodiment of the present invention whereby the modified guide adapter 60, as shown in FIG. 10, is releasably coupled to the drill rod 12 so that the shoulder 22 of the drill rod 12 is at least partially encased in both the radial and axial directions inside the guide adapter 60. The guide adapter 60 also has a shoulder 22 having a peripheral surface 24 for connection to the drill bit 2. The shoulder 22 on the guide adapter could also be protected from wear by using the drill bit 2 design described hereinabove so that the peripheral surface 24 of the shoulder 22 on the guide adapter 60 is at least partially encased in both radial and axial directions inside the mounting sleeve 10 of the drill bit 2. It should be understood that any of the alternative embodiments described hereinabove above in relation to the drill bit 2 could also be applied to the guide adapter 60.
