Sub-assembly, rock drilling rig, and method of absorbing vibrations in drilling

Abstract

A sub-assembly, rock drilling rig and method of absorbing vibrations in rotary and DTH drilling. The sub-assembly is for transmitting torque and axial forces between a rotating head and a drilling tool. There is an axial floating arrangement for providing an allowed limited axial relative movement between coupling elements of the sub-assembly. The arrangement comprises several axial drive pins for transmitting the torque. First ends of the drive pins are mounted immovably and second ends are mounted with clearances, whereby the drive pins can bend under torsional shocks. Thus, the drive pins serve as torsional dampening elements.

Claims

1. A sub-assembly for a rock drilling unit, wherein the sub-assembly is configured to transmit torque and axial forces between a rotating head and a drilling tool, the sub-assembly comprising: a first coupling element located at a first end of the sub-assembly for coupling the sub-assembly to the rotating head, wherein the first coupling element includes a first cover element provided with a protruding adapter pin and a second cover element located at an axial distance from the first cover element, wherein a housing element having a cylinder-like configuration is arranged between the first cover element and the second cover element for providing a floating space for the axial floating arrangement, and; a second coupling element located at an opposite, second end of the sub-assembly for coupling the sub-assembly to the drilling tool; an axial floating arrangement for providing an allowed limited axial relative movement between the first coupling element and the second coupling element, the axial floating arrangement including a plurality of axial drive pins for transmitting the torque; at least one axial fluid passageway passing centrally through the axial floating arrangement; an axial dampening arrangement having at least one first end cushion element and at least one second end cushion element for dampening axial shocks at extreme axial positions of the axial floating arrangement; and a torsional dampening arrangement for absorbing torsional shocks, wherein the plurality of axial drive pins include first ends mounted immovably and second ends mounted with clearances, whereby the plurality of axial drive pins are configured to be bent in relation to the first ends under torsional shocks and the plurality of axial drive pins serve as torsional dampening elements of the torsional dampening arrangement, wherein the first cover element is provided with a plurality of first blind openings arranged for receiving the first ends of the plurality of axial drive pins, and the second cover element is provided with a plurality of second blind openings arranged for receiving the second ends of the plurality of axial drive pins, whereby the plurality of axial drive pins are mounted between the first and second blind openings, the first blind openings of the first cover element and the first ends of the plurality of axial drive pins having tight fit connections, whereas the second blind openings of the second cover element and the second ends of the plurality of axial drive pins have clearance fit connections.

2. The sub-assembly as claimed in claim 1, wherein the plurality of axial drive pins serve as metallic spring elements.

3. The sub-assembly as claimed in claim 1, wherein the plurality of axial drive pins are made of spring steel.

4. The sub-assembly as claimed in claim 1, wherein the torque is configured to be transmitted between the plurality of axial drive pins and the second coupling element directly by means of the contact surfaces.

5. The sub-assembly as claimed in claim 1, wherein a number of the plurality of axial drive pins is 8-12, the axial pins being spaced evenly around the central fluid passageway.

6. The sub-assembly as claimed in claim 1, wherein the second end portions are provided with cushion rings surrounding the plurality of axial drive pins for assisting dampening.

7. The sub-assembly as claimed in claim 1, wherein the first end cushion element is a ring-shaped top pad and the second end cushion element is a ring-shaped bottom pad, and wherein the top and bottom ring-shaped pads are made of a resilient cushion material.

8. The sub-assembly as claimed in claim 1, wherein the second blind openings of the second cover element are provided with cushion space portions provided with cushion rings made of a resilient material.

9. The sub-assembly as claimed in claim 8, wherein the resilient material is polyurethane.

10. The sub-assembly as claimed in claim 1, wherein a magnitude of the clearances is 1-3 mm.

11. A rock drilling rig for drilling drill holes to a rock surface, the rock drilling rig comprising: a movable carrier; at least one drilling mast; a drilling unit including a feed device for moving the drilling unit on the drilling mast in a drilling direction and a return direction, and a rotating head for rotating a drilling tool around its longitudinal axis; and a sub-assembly as claimed in claim 1, the sub-assembly being coupled between the rotating head and the drilling tool for transmitting axial forces and torque between the rotating head and the drilling tool, and wherein the sub-assembly is configured to allow axial floating between the rotating head and the drilling tool and to absorb axial and torsional shocks.

12. A method of absorbing vibrations in rotary drilling, the method comprising: rotating a drilling tool around its longitudinal axis by means of a rotating device; providing a sub-assembly as claimed in claim 1 between the rotating device and the drilling tool for allowing axial floating movement between the rotating device and the drilling tool and for transmitting axial forces and torque; transmitting the torque by means of a plurality of axial drive pins of the sub-assembly; absorbing axial shocks by means of an axial dampening arrangement of the sub-assembly comprising axial cushion elements; absorbing torsional shocks by means of a torsional dampening arrangement of the sub-assembly; implementing the plurality of axial drive pins as elements of the torsional dampening arrangement; providing the plurality of axial drive pins cantilever type configuration by mounting their first ends immovably and allowing their opposite second ends to move in transverse direction when torsional shocks are subjected to the sub-assembly; and and allowing the plurality of axial drive pins to bend when subjected to the torsional shocks and absorbing torsional vibrations by material properties of the plurality of axial drive pins.

13. The method as claimed in claim 12, further comprising providing the mountings of the second ends of the plurality of axial drive pins with clearances.

14. The method as claimed in claim 12, further comprising providing the mountings of the second end portions of the plurality of axial drive pins with dedicated dampening rings, and supporting the second ends of any axial drive pins having loose mountings with the dampening rings and absorbing vibrations caused by the movements of the free second ends.

15. The sub-assembly as claimed in claim 1, wherein the second coupling element includes an adapter housing arranged for receiving a coupling end of the drilling tool and protruding into an opposite direction relative to the adapter pin, and a stem, which is arranged inside the housing element and arranged to slide axially inside the floating space, and wherein the stem includes a plurality through openings at the plurality of axial drive pins, whereby the plurality of axial drive pins penetrate axially through the stem.

16. The sub-assembly as claimed in claim 1, wherein the first end cushion element is a ring-shaped top pad, the ring-shaped top pad including a central opening for the fluid passageway and a plurality of radial openings for the plurality of axial drive pins located inside the floating space at a side of the first coupling end, and wherein the second end cushion element is a ring-shaped bottom pad, the ring-shaped bottom pad including a central opening for the stem of the second coupling end and a plurality of radial openings for the plurality of axial drive pins and being located inside the floating space at a side of the second coupling end, wherein the top and bottom ring-shaped pads are made of a resilient cushion material.

17. The sub-assembly as claimed in claim 1, wherein the axial fluid passageway is a sleeve-like element having a first end which is mounted immovably to the first coupling element and a second end portion connected slidingly to the second coupling element.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Some embodiments are described in more detail in the accompanying drawings, in which

(2) FIG. 1 is a schematic side view of a surface rock drilling rig intended for rotary drilling,

(3) FIG. 2 is a schematic view of a rock drilling unit suitable for down-the-hole drilling,

(4) FIG. 3 is a schematic and cross-sectional side view of a sub-assembly,

(5) FIG. 4 is a schematic and partly cross-sectional views of the sub-assembly shown in FIG. 3;

(6) FIG. 5 is a schematic and cross-sectional view of a detail of a sub-assembly,

(7) FIG. 6 is a simplified side view showing bending of drive pins of a sub-assembly, and

(8) FIG. 7 is a schematic and exploded view of a sub-assembly and its components.

(9) For the sake of clarity, the figures show some embodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like elements.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

(10) FIG. 1 shows a rock drilling rig 1 intended for surface drilling. The rock drilling rig 1 comprises a movable carrier 2 and at least one drilling mast 3 connected to the carrier 2. The mast 3 is provided with a drilling unit 4 provided with a rotating head 5 supported on the mast 3 and being movable in a drilling direction A and return direction B by means of a feed device 6. The rotating head 5 is connected to a drilling tool 7 by means of a sub-assembly 8. The drilling tool 7 is shown in a simplified manner for clarity reasons. The drilling tool 7 may comprise one or more tubular elongated elements and a drill bit 9 at its distal end. The rotating head 5 rotates R the drilling tool 7 around its longitudinal axis and the drilling tool 7 is simultaneously fed towards a rock surface being drilled. This is known as rotary drilling method. Drilling cuttings are flushed by feeding flushing fluid from a flushing system Fs via the drilling tool 7 to a drill hole 10 being drilled so that the drilling cuttings are flushed away from the drill hole 10. The drilling unit 4 may be hydraulic whereby it may be connected to a hydraulic system Hs.

(11) FIG. 2 discloses another solution which differs from the one shown in FIG. 1 in that there is an impact device 11 mounted between a drill bit 9 and a drilling tool 7. The disclosed solution is intended for a down-the-hole drilling method, known also as DTH-drilling. Also, in this case a sub-assembly 8 is needed between a rotating head 5 and the drilling tool 7. A drilling unit 4 can be mounted movably on a feed beam 12, or in a similar manner as is shown in FIG. 1.

(12) FIGS. 3 and 4 disclose a sub-assembly 8 comprising a first coupling element 13 at a first end for coupling the sub-assembly 8 to the rotating head, and a second coupling element 14 at an opposite second end for coupling the sub-assembly 8 to the drilling tool. The sub-assembly is also provided with an axial floating arrangement 15 for providing an allowed limited axial relative movement between the first coupling element 13 and the second coupling element 14. The axial floating arrangement comprises several axial drive pins 16 for transmitting torque between the coupling elements 13, 14. There is an axial fluid passageway 17 passing centrally through the axial floating arrangement 15. The sub-assembly 8 comprises an axial dampening arrangement comprising at least one first end cushion element 18 and at least one second end cushion element 19 for dampening axial shocks at extreme axial positions of the axial floating arrangement 15.

(13) The mentioned drive pins 16 comprise first ends 16a mounted immovably and second ends 16b mounted with clearances 20, which are shown better in FIG. 5. The drive pins 16 are configured to be bent in relation to their first ends 16a under torsional shocks. The drive pins 16 serve as torsional dampening elements.

(14) The first coupling element 13 comprises a first cover element 21 provided with a protruding adapter pin 22 and a second cover element 23 at an axial distance from the first cover element 21. A cylinder shaped housing element 24 is arranged between the first cover element 21 and the second cover 23 element for providing a floating space 25 for the axial floating arrangement 15.

(15) The second coupling element 14 comprises an adapter housing 26 for receiving a coupling end of the drilling tool. The adapter housing 26 protrudes into an opposite direction relative to the adapter pin 22. Further, the second coupling element 14 comprises a stem 27 which is arranged inside the housing element 24 and can slide axially inside the floating space 25.

(16) The first cover element 21 is provided with several first blind openings 28 for receiving the first ends 16a of the drive pins 16. The second cover element 23 is provided several second blind openings 29 for receiving the second ends 16b of the drive pins 16. Thereby, the drive pins 16 are mounted between the first and second blind openings 28, 29. The stem 27 comprises several through openings 30 through which the drive pins 16 penetrate axially.

(17) The ring-shaped top pad 18 is provided with a central opening for the fluid passageway 17 and several radial openings for the drive pins 16, and it is located inside the floating space 25 at a side of the first coupling end 13. The ring-shaped bottom pad 19 is provided with a central opening for the stem part 27 of the second coupling end 14 and has several radial openings for the drive pins 16. The bottom pad 19 is located inside the floating space 25 at a side of the second coupling end 14. The axial fluid passageway 17 is a substantially sleeve-like element a first end of which is mounted immovably to the first connecting element 13 and a second end portion is connected slidingly to the second connecting element 14. The stem 27 can slide axially in relation to the tubular fluid passageway 17 and its sealings 31.

(18) The mentioned first blind openings 28 of the first cover element 21 and the first ends 16a of the drive pins 16 have tight fit connections, whereas the second blind openings 29 of the second cover element 23 and the second ends 16b of the drive pins 16 have clearance fit connections. Further, the second end portions 16b are provided with cushion rings 32 surrounding the drive pins 16 and are thereby configured to assist the dampening.

(19) FIG. 5 discloses the above mentioned clearance 20 and the cushion ring 32 in an enlarged view. The second blind openings 29 of the second cover element 23 are provided with cushion space portions 34 for receiving the cushion rings 32.

(20) FIG. 6 shows in a simplified manner bending 33 of disclosed cantilever supported drive pin 16. When the first cover 22 moves in left direction, the drive pin 16 follows that movement. Movement of the stem 27 is resisted since it is connected to the drilling tool. When sudden high forces occur i.e., the torque shocks exist, then the drive pin 16 bends 33 in a manner typical for a cantilever support, which is fixed at it one end. The cantilever support arrangement requires that the second end 16b of the drive pin 16 can move laterally and this is possible because of the clearance 20. In FIG. 6 there is no separate dampening ring at second end portion 16b of the drive pin 16, but it is possible to implement such dampening ring or any other resilient dampening element, dampening mass, or material therein if needed.

(21) FIG. 7 shows some components of a sub-assembly 8. The structure of the sub-assembly 8 is in accordance with the FIGS. 3 and 4. The drawings and the related description are only intended to illustrate the idea of the invention. In its details, the invention may vary within the scope of the claims.