WO2008033078A1

WO2008033078A1 - Arrangement at rock drilling

Info

Publication number: WO2008033078A1
Application number: PCT/SE2007/000798
Authority: WO
Inventors: Jan-Olof Karlsson
Original assignee: Atlas Copco Rock Drills Ab
Priority date: 2006-09-15
Filing date: 2007-09-12
Publication date: 2008-03-20
Also published as: SE0601910L; SE530827C2

Abstract

The present invention relates to a device for the leak-tight or leakage-controlled transfer of a fluid between a first part and a second part, which are arranged to coaxially interact with each other, and, in an operating mode, to be turned and/or rotated in relation to each other, the said first part including a pressure sealing element, which comprises a first sealing surface for interaction with a second sealing surface present on the said second part. The said pressure sealing element is arranged so as to be axially movable relative to a seat in the said first part, and the pressure sealing element is arranged in the seat such that it is pressure balanced, at least in the radial direction, under the action of pressure. The present invention also relates to a rock drilling tool and a rock drilling machine.

Description

Arrangement: at rock drilling Field of the invention

The present invention relates to a device for the leak-tight or leakage-controlled transfer of a fluid for use with parts which are coupled together and are mutually rotatable, according to the preamble of Claim 1. The invention also relates to a rock drilling tool according to the preamble of Claim 14 and to a rock drilling machine according to the preamble of Claim 15.

Background of the invention

When fluid is transferred under pressure between mutually moving parts, such as, for example, in the coupling together of parts which are coaxially rotatable relative to one another, such as in the interaction between a fixed hub and a movable axle, a chuck or a drill string, it is important for the interaction of the parts to be realized in such a way that minimal heat development and minimal wear is generated. These types of transfer devices have many different fields of application, examples of which are the transfer of a pressurized fluid between a hub and a rotary tool chuck or a rotary drill string in a percussion drill. The pressurized fluid can be used, for example, for controlling the clamping/release of a tool in the chuck, for the swivel function in rock drilling equipment, or for feeding the fluid to a drilling apparatus, for example down-the-hole equipment, disposed at the opposite end of the drill string.

A problem with fluid couplings of this type is, however, that the transfer of the pressurized fluid places high demands upon the seal between the mutually rotating parts. This seal can be realized in a number of different ways, wherein a common method is constituted by the use of radial seals. Radial seals have the drawback that they are deformed differently depending on the nature of their load, and generate friction, the size of which is dependent on the magnitude of the load and/or of the action of the pressurized fluid upon the seal. The resulting friction generates, apart from wear, energy losses in the form of heat, which can adversely affect the life of the seals.

An alternative method for sealing the abovementioned type of fluid couplings is sealing by means of axial plane seals. Where axial plane seals are used, it is very important that the plane seal surfaces really are level and parallel with one another. One problem is however that, when pressurized, the surfaces are deformed, so that the sealing gaps are altered, which can generate increased leakage and/or increased wear.

According to the above, there is therefore a need for an improved process for sealing mutually rotatable parts between which a pressurized fluid is arranged to be transferred.

Summary of the invention

It is an object of the present invention to provide a device for the leak-tight transfer of a fluid between a first part and a second part, which device solves the above problems. This and other objects are achieved according to the present invention by a device as defined in Claim 1.

According to the present invention, a device is provided for the leak-tight transfer of a fluid between a first part and a second part, which are arranged so as, in an operating mode, to be turned and/or rotated in relation to one another. The said first part includes a pressure sealing element, which is arranged so as to be axially movable relative to a seat in the said first part and is arranged in the seat such that it is pressure balanced, at least in the radial direction, under the action of pressure. This has the advantage that the pressure sealing element can constantly be prevented from being tilted when pressurized, which means that leakage and friction losses/wear can be considerably reduced.

The pressure sealing element can be configured such that its pressure-affected surfaces in the radially outward facing and radially inward facing directions, under the action of pressure, are subjected to equal and oppositely directed forces. This has the advantage that the said pressure relief can be realized in a simple and effective manner.

Further features and advantages of the present invention will emerge from the following detailed description.

Brief description of the drawings

Fig. 1 shows an exemplary device according to the present invention .

Fig. 2 shows a part of the device in Fig. 1 on an enlarged scale .

Fig. 3 shows an example of a wearing ring for use with the present invention.

Fig. 4 shows an alternative exemplary device according to the present invention.

Fig. 5 shows a further exemplary device according to the present invention.

Detailed description of an exemplary embodiment

In Fig. 1 is shown an example of a device 10 in which the present invention can advantageously be used. The device comprises a first part 11, which is designed to rotate during operation and which can be constituted, for example, by an axle, a hydraulically operated rotary chuck, for example designed to secure some type of rock drilling tool (the fixing of the tool is not shown) . The said first part can also be constituted, as in this case, by a drill string component 11 used in rock drilling, for example down-the-hole drilling. In down-the-hole drilling, a percussion tool (hammer drill) is disposed down in the borehole and is connected to a carrier on the surface by a drill string, which is usually constituted by threaded-together pipes, so-called drill string components, which conduct a pressurized fluid, in the form of, for example, compressed air, down to the drilling hammer. The shown component 11 is constituted by a component fixed to the carrier, wherein drill string components are being gradually introduced between the component 11 and the percussion tool as the drilling progresses.

The shown device 10 also comprises a second part 12, which is arranged coaxially around the drill string component 11 and is used to transfer a pressurized fluid to (or from) the drill string component 11. In the figure, the said second part 12 is constituted by a hub and, during operation, a pressurized fluid is fed from the hub 12 to the drill string component 11 via one or more ducts 13 disposed in the hub 12 and emerging towards the drill string component 11. In the drill string component 11 there are one or more corresponding holes 14 (which, upon rotation, are periodically aligned with the ducts 13), whereby the pressurized fluid can be transferred to the drill string component 11 so as then, via ducts (not shown) disposed in the first part, to be conducted to the desired member, in this case the percussion tool disposed in the borehole .

In the device of the type shown in Fig. 1, the transfer of the pressurized fluid can, according to the above, generate problems. These problems escalate further upon use in exposed environments, such as, for example, in down-the-hole drilling, where, apart from the effect of the mutual rotation of the parts, factors such as shakes, vibrations and kickbacks put stress upon sealing surfaces between the parts 11, 12. As has been mentioned above, radial seals can be used in couplings of this type, but, apart from the previously stated drawbacks, the radial seals will become additionally worn in the event of, for example, the radial kickbacks which usually occur when drilling into granite. As has also been mentioned, axial plane seals also exhibit similar problems. The present invention solves, or at least alleviates, these problems by means of the pressure sealing element 15 shown in Fig. 1.

In the device shown in Fig. 1, the pressure sealing element 15 is used to ensure that no undesirable stresses arise when pressure fluid is transferred from the hub 12 to the drill string component 11 during rotation of the drill string component 11. The pressure sealing element 15 comprises a sealing surface 16, which, during operation, is arranged to run against a corresponding sealing surface 17 disposed on the hub 12. To ensure that pressure fluid is transferred during rotation of the drill string without much wear and with good sealing, it is important that these sealing surfaces are always kept totally parallel. In a conventional device having a pressure sealing element of the type shown in Fig. 1, the pressurized fluid tends, however, to penetrate between the drill string component 11 and the pressure sealing element 15 according to the arrow A, which leads to a tilting tendency of the pressure sealing element 15 (the gap between the pressure sealing element 15 and the drill string component 11 becomes larger at the point B than at the point C) , with the result that the sealing surfaces 16, 17 are no longer kept parallel, with increased wear and/or leakage of pressurized fluid as a consequence . The pressure sealing element 15 according to the invention, on the other hand, ensures that the sealing surfaces are always kept parallel and are held in contact with each other at a suitable pressure.

The pressure sealing element 15 is shown on an enlarged scale in Fig. 2 and is sealed against the drill string component 11 by means of sealing rings 20, 21. During operation, the pressure sealing element 15 rotates with the component 11, so that no, or essentially no, friction losses arise at the sealing rings 20, 21. Furthermore, the pressure sealing element is held in place by being disposed in a seat formed by a seal retainer affixed to the drill string component 25, against which the pressure sealing element 15 is sealed via sealing rings 28, 21. The seal retainer 25 is locked by means of a locking ring 33.

The pressure sealing element 15 according to the invention is configured such that its pressure-affected surfaces in the radial direction are subjected to equal and oppositely directed forces, i.e. the combined force against the radially outward facing surfaces of the pressure sealing element is equal to the combined force against its radially inward facing surfaces, producing a pressure sealing element which, when subjected to pressure, is pressure balanced in the radial direction. In one case, the said surfaces can be equal in size in the respective direction, but, as will be appreciated by the person skilled in the art, the pressure will not be pi on all pressure-affected surfaces, but rather, at the sealing rings 20, 21, 28, for example, the pressure will decrease from pi to the ambient pressure pO by means of a pressure gradient (the region between the sealing rings 20, 21 is relieved of pressure, as described in greater detail below) . This means that the size of the surfaces may need to be compensated for this, i.e. if the average pressure in the one direction is lower than the average pressure in the other direction, the lower pressure must be compensated with a larger surface area in order to give the same resultant force.

This has the advantage that the described phenomenon of a larger gap at the point A than at the point B due to the action of pressure will not occur, so that the sealing surfaces 16, 17 will be constantly guaranteed to be kept parallel, whereby undesirable wear and leakage can be significantly reduced.

During operation, the only contact surface between the first part 11 and the hub 12 is constituted, in fact, by the sealing surfaces 16, 17, the pressure sealing element therefore serving to ensure that an axial plane seal is obtained, but without the described drawbacks associated with the prior art. Furthermore, between these surfaces, a wearing ring 34 can advantageously be used, the shape and material of which determines the function, leakage and lubrication of the sealing surfaces. If a fluid in the form of hydraulic liquid is used, the wearing ring is preferably formed from bearing metal. If the pressure fluid is constituted by air, teflon, for example, can instead be used as the material. The wearing ring can further be configured such that it "draws in" hydraulic oil, for example, between the surfaces for lubrication purposes, including on the occasions when there is no transfer of pressurized fluid, for example through the use of a wearing ring configuration according to any one of the configurations 34a, 34b, 34c shown in Fig. 3.

In the shown embodiment, the pressure sealing element 15 has an additional feature. Apart from being radially pressure balanced, it is also axially pressure balanced, which is achieved by pressure balancing the sum of the surfaces 16 and 17 and 23 with the surface 24. This has the advantage that the pressure of the element 15 against the sealing surface 17 can be made wholly independent of applied pressure. In this cfase, in order constantly to ensure that the sealing surface 16 of the pressure sealing element is kept pressed against the sealing surface 17 of the hub, a spring 29, of the cup spring or sinusoidal spring type, can be used, which spring runs in a circular-cylindrical groove 30 recessed or milled in the pressure sealing element 15. Instead of the use of a spring to hold the pressure sealing element against the hub, the pressure sealing element and/or the hub can be wholly or partially formed from a magnetic material, the cohesion being instead obtained by means of magnetism. As will be appreciated, the surfaces 16, 23 and 24 can also, however, be tailored such that a pressurized device always has a certain overpressure to the left in the figure. This requires, however, that the device, in principle, is always pressurized, since the desired contact between the sealing surfaces cannot otherwise be ensured.

As is shown in the figure, the pressure sealing element 15 is further provided with a duct 22, through which pressurized fluid can be transferred from that end 23 of the pressure sealing element which faces the duct 13 to its opposite end 24 in order to provide for the pressurization of desired surfaces and thereby achieve the desired pressure balancing. The duct is shown in its entirety in Fig. 1.

The pressure sealing element 15 further comprises an additional (diagrammatically shown) duct 27 for relieving the pressure in the region between the sealing rings 20, 21. As will be appreciated by the person skilled in the art, ducts of this type can be used to relieve the pressure on chosen surfaces to allow pressure balancing of a chosen geometric form. As will also be appreciated by the person skilled in the art, the shown geometric configuration is purely illustrative and the pressure sealing element 15 can assume a large number of different geometric forms, as long as the criteria for radial pressure balancing are met.

In the embodiment shown in the figure, the sealing device has a two-way symmetrical flow, i.e. two similar pressure sealing elements 15, 35 disposed on the respective side of the duct 13 are used to obtain the desired function. The present invention can, however, likewise be used for a unilaterally flowing solution, for example on an axle end, in which only one pressure sealing element is used for contact against a sealing surface on a part fixedly disposed coaxially with the axle.

It is also possible, of course, for the axle (or equivalent) to be fixed, whilst a coaxially outer part is arranged to rotate about the inner part. Above, a device has also been shown in which the sealing element is arranged to rotate with the rotary part. However, it is also possible, of course, for the sealing element (and seal retainer) to be applied to the non-rotary part and hence to be stationary.

In Fig. 4, an alternative exemplary embodiment of a device according to the present invention is shown, which works according to the same principle as has been shown above, but which instead has a spherically shaped gap seal.

Like the device 10 shown in Fig. 1, the device 40 comprises a second part 42, which is designed to rotate during operation and which can be used for the same applications as have been described above.

The device 40 also therefore comprises a first part 41, which is arranged coaxially around the part 42 and which is used to transfer a pressurized fluid to (or from) the part 42 according to the above. As will be appreciated, the part 42 can instead be fixedly disposed and the part 41 can rotate.

In the device shown in Fig. 4, radial pressure balancing can be achieved according to that which will be described below, whilst, at the same time, the spherical sealing surface 43 enables the parts 41 and 42 to move relative to each other about a centre point 44, which means that the device can at least partially absorb, for example, radial kickbacks to which a tool connected to the part 42 can be exposed. The radial pressure relief is obtained in such a way that, along the spherical surface 43, a pressure gradient from Pl to ambient pressure PO is obtained, which balances the pressure Pl acting upon the pressure sealing element 15 in Fig. 1 corresponding to the top sides of the pressure sealing elements 45a, 45b in the figure, in which the pressure acts up to the sealing rings 46, 47. By configuring those areas of the respective surfaces in which, as will be appreciated and is indicated in the figure, the radial combined pressure area of the elements 45a, 45b in towards the centre is less than that area of the spherical surface which interacts with the part 42, typically in the order of magnitude of 40-60% of the latter area, since the pressure acting on average upon the spherical surface in the radial direction, if the effect of the radius is disregarded, is (Pl-PO) /2. In general, the distance Ll and the diameter d2 are used as design parameters in the calculation of a geometry resulting in the desired pressure relief. As is shown in the figure, cup springs 48, 49 are used to hold the elements 45a, 45b in place against the spherical surface in the pressureless state. In addition, pins 50, 51 are used to lock the elements 45a, 45b to the part 41 and hence prevent the elements from rotating with the part 42. A lock part 52 is used to make it easier for parts to be put together during assembly. In this embodiment too, therefore, it is possible to ensure that no undesirable stresses are generated in the course of the pressure fluid transfer between the parts 41, 42. The pressure balancing further means that a very low- friction sealing surface is obtained.

In Fig. 5, a further example is shown of a device 60 according to the present invention, which also works according to the above principle.

Like the device 40 shown in Fig. 4, the device 60 comprises a second part consisting of the elements 61 and 62, and a first part 69, in which at least one or other of the parts is designed to rotate relative to the other during operation. In Fig. 5 also, radial pressure balancing is achieved, whilst, at the same time, a spherical sealing surface 63 enables the elements 61 and 62 to move relative to the first part, according to the above, via elements 65a, 65b. In this case, the pressure sealing elements 45a, 45b in Fig. 4 are corresponded to by the elements 65a, 65b, wherein the pressure gradient from Pl to ambient pressure PO, which pressure gradient is generated along the spherical surface 63, is balanced by the pressure Pl acting upon the bottom side of the elements 65a, 65b, wherein the distance Ll governs the size of the counterpressure area boasting the pressure Pl. The seal 66 corresponds to the seal 28 in Fig. 2. Through appropriate adjustment of the distance Ll, the diameter d2 and the radius R in relation to Pl and PO, pressure balancing can be obtained. Also shown in the figure is a balancing ring 64, which balances the pressure sealing elements. As is shown in the figure, a spring 67 can also be used to force apart the pressure sealing elements. This forcing apart can also be managed, however, by the pressure Pl.

The device shown in Fig. 5 comprises a further feature. A nut 68 can be used to enable the pressure sealing elements to be adjusted somewhat in the axial direction on the part 69. By tightening the nut somewhat so that the elements come somewhat closer together, a play will be generated along the spherical sealing surface. The desired leakage for lubrication/cooling can be set by adjusting the play, whilst, at the same time, pressure balancing is maintained.

In the above description, the direction for the transfer of a fluid between a first part and a second part has been shown as essentially wholly radial. In an alternative embodiment, this direction comprises not only a radial component, but both a radial component and an axial component, i.e. a direction which is not perpendicular to the axis of the device in the longitudinal direction. In another alternative embodiment, the direction comprises just an axial component.

As will be appreciated, the above detailed description constitutes merely exemplary embodiments of the present invention and everything which has been described throughout this description or has been shown in the appended drawings should be construed as illustrative and not regarded as restrictive .

Claims

1. Device (10; 40; 60) for the leak-tight or leakage- controlled transfer of a fluid between a first part (11; 42; 61, 62) and a second part (12; 41; 65a, 65b), which are arranged so as to coaxially interact with each other, and, in an operating mode, to be turned and/or rotated in relation to each other, the said first part (11; 42; 61, 62) including a pressure sealing element (15; 45a, 45b; 65a, 65b) , which comprises a first sealing surface (16) for interaction with a second sealing surface (17) present on the said second part (12; 41; 65a, 65b), characterized

- in that the said pressure sealing element (15; 45a, 45b; 65a, 65b) is arranged so as to be axially movable relative to a seat in the said first part (11; 42; 61, 62) , and

- in that the pressure sealing element (15; 45a, 45b; 65a, 65b) is arranged in the seat such that it is pressure balanced, at least in the radial direction, under the action of pressure.

2. Device according to Claim 1, characterized in that the said fluid is constituted by a pressurized fluid.

3. Device according to Claim 1 or 2, characterized in that the direction for the transfer of the said fluid between the said first part and the said second part is arranged to contain at least one radial component.

4. Device according to any one of Claims 1-3, characterized in that the pressure sealing element (15; 45a, 45b; 65a, 65b) is configured such that its pressure-affected surfaces in the radially outward facing and radially inward facing directions, under the action of pressure, are subjected to equal and oppositely directed forces, which pressure balancing prevents deforming forces.

5. Device according to any one of Claims 1-4, characterized in that the pressure sealing element (15; 45a, 45b; 65a, 65b) is configured such that its pressure-affected surfaces in the axial direction, under the action of pressure, are subjected to substantially equal and oppositely directed forces, whereby pressure balancing in the axial direction is obtained.

6. Device according to any one of Claims 1-5, characterized in that the said pressure sealing element (15; 45a, 45b; 65a, 65b) and/or the said seat comprise (s) a groove or recess for the reception of a spring, the said spring being arranged to act on the pressure sealing element (15; 45a, 45b; 65a, 65b) in such a way that the said first sealing surface is pressed against the said second sealing surface.

7. Device according to any one of Claims 1-6, characterized in that the said pressure sealing element (15; 45a, 45b; 65a, 65b) and/or the said second part (12; 41; 65a, 65b) is/are wholly or partially formed from a magnetic material, a cohesion of the said sealing surfaces being obtained by means of magnetism.

8. Device according to any one of Claims 1-7, characterized in that a wearing ring is disposed between the said first (16) and second sealing surface (17), the configuration of the said wearing ring determining the leak-tightness and the lubricating film flow.

9. Device according to any one of Claims 1-8, characterized in that the said first part (11; 42; 61, 62) is arranged to be rotated.

10. Device according to any one of Claims 1-9, characterized in that the said second part (12; 41; 65a, 65b) is arranged to be rotated.

11. Device according to any one of Claims 1-10, characterized in that the pressure sealing element (15; 45a, 45b; 65a, 65b) is further provided with a through-duct, through which fluid can be transferred from an end facing towards the fluid transfer to an end facing away from the fluid transfer in order to facilitate the pressurization of the desired surfaces and thereby achieve the desired pressure balancing.

12. Device according to any one of Claims 1-11, characterized in that it comprises two sealing elements, symmetrically arranged about a point for fluid transfer between the said first part (11; 42; 61, 62) and the said second part (12; 41; 65a, 65b) .

13. Device according to any one of Claims 1-12, characterized in that the said first part (11; 42; 61, 62) is constituted by any one item from the group: axle, drill string component, tool chuck, percussion drill, rock drilling apparatus.

14. Device according to any one of Claims 1-13, characterized in that the said sealing element comprises a spherical sealing surface.

15. Rock drilling tool, characterized in that it comprises a device (10; 40; 60) according to any one of Claims 1-14.

16. Rock drilling machine, characterized in that it comprises a device (10; 40; 60) according to any one of Claims 1- 14.