Piston guide element, rock drill and method

Abstract

A piston guide element for supporting a front end portion of a percussion piston of a rock drill, a rock drill, and a method. The element (20) has a braking recess (16) at its rear end (24). The element further comprises at least one bearing sleeve (29) provided with two axially consecutive plain bearing sections (AS1, As2). Hydraulic fluid is conveyed between the plain bearing sections via a feed system (21).

Description

[Technical field]

[0001] The present invention relates to a piston guide element for a rock drill. The element is intended to provide a bearing for the front part of the percussion piston.

[0002] The present invention further relates to a rock drill and method for supporting a front end portion of a percussion piston. [Background technology]

[0003] The field of the invention is more particularly defined in the preambles of the independent claims.

[0004] In mines and other work sites, different kinds of rock drilling rigs are used. The rock drilling rigs are provided with one or more booms, the rock drill being arranged at the distal end of the boom. The rock drill comprises an impact device provided with an impact piston, supported on the body of the machine by bearing means. In hydraulic impact devices, the front bearing of the piston is subjected to large pressure peaks, in particular when the movement of the piston in the impact direction has to be stopped by a braking recess located in front of the impact device. In order to eliminate pressure peaks harmful to the bearings, different kinds of solutions have already been disclosed. However, the known solutions show some drawbacks. Summary of the Invention

[0005] SUMMARY OF THE PRESENT EMBODIMENT It is an object of the present invention to provide a new and improved piston guide element, a rock drill equipped with such an element, and a method for supporting the front end of a percussion piston.

[0006] The piston guide element according to the invention is characterized by the characteristic features of the first independent device claim.

[0007] The rock drill according to the invention is characterized by the characteristic features of the second independent device claim.

[0008] The method according to the invention is characterized by the characterizing features of the independent method claim.

[0009] The concept of the disclosed solution is that the piston guide element is a sleeve-like part that can be mounted inside the body of the rock drill between the percussion piston and the body. The element comprises a first end facing in the impact direction and a second end facing in the return direction. The second end is provided with a damping recess capable of receiving a collar of the piston. Furthermore, the element comprises at least one separate bearing sleeve mounted inside the body of the element, and is provided with a first axial section and a second axial section. Both sections comprise a plain bearing material. Between the aforementioned axial sections and on the inner surface of the element there is a first groove, the bottom of which comprises at least one radial opening between the bottom of the first groove and the outer surface of the element. The hydraulic fluid can be conveyed between the aforementioned two consecutive plain bearing sections by means of the at least one radial opening and the first groove.

[0010] The advantage of the disclosed solution is that when the hydraulic fluid is led between the two axial bearing sections, the magnitude of the pressure peaks led to the bearing can be reduced. Furthermore, when the hydraulic fluid is conveyed to the bearing at a location other than forming the braking recess, the temperature of the bearing can be reduced. Furthermore, the disclosed structure is simple and easy to manufacture and implement.

[0011] According to one embodiment, the at least one separate bearing sleeve is made of a plain bearing material, which may for example be a suitable metallic bearing material.

[0012] According to one embodiment, a bronze alloy material is used as the above-mentioned plain bearing material, which may be, for example, tin bronze, lead-containing tin bronze, aluminum bronze or manganese bronze.

[0013] According to one embodiment, cast iron is used as the above-mentioned plain bearing material, which may for example be grey cast iron.

[0014] According to one embodiment, the inner surface of at least one bearing sleeve comprises at least one layer made of at least one plain bearing material.

[0015] According to one embodiment, the above-mentioned inner surface of the bearing sleeve or bearing section is coated with a plain bearing material.

[0016] According to one embodiment, the at least one bearing sleeve has a bimetallic configuration with the sleeve being made of steel and having a layer of bronze on its inner surface, whereby intermetallic diffusion occurs between the steel and bronze materials. Potentially, some other metallic materials may also be used to form the bimetallic structure.

[0017] According to one embodiment, the element comprises one single bearing sleeve mounted therein, the bearing sleeve being therefore a homogenous piece and provided with the above-mentioned first and second axial sections for supporting the piston.

[0018] According to one embodiment, the element comprises two separate bearing sleeves mounted successively inside the element. The first bearing sleeve is configured to form the above-mentioned first axial section, and the second bearing sleeve is configured to form the above-mentioned second axial section. The first groove is then located between the first bearing sleeve and the second bearing sleeve. In this way, the mechanism of the bearing sleeve can be adjusted as required.

[0019] According to one embodiment, at least the inner surfaces of the above-mentioned first and second bearing sleeves comprise different materials relative to each other, in this way the material of the sleeves can be selected as required.

[0020] According to one embodiment, the outer surface comprises a second groove, and said at least one radial opening extends to a bottom of the second groove.

[0021] According to one embodiment, the exterior surface includes at least one third groove extending from the second end to the second groove.

[0022] According to one embodiment, the diameters of the outer surfaces of the elements are equal except for the second groove.

[0023] According to one embodiment, the element comprises two outer portions having different outer dimensions, and at the first end there is a first outer portion having a first outer diameter. At the second end there is a second outer portion having a second outer diameter. The outer diameters are selected to allow for mounting of the element. In other words, the outer surface of the element has a stepped configuration that facilitates mounting of the element.

[0024] According to one embodiment, the outer surface includes at least one third groove extending from the second end to the second groove. The third groove has a helical configuration.

[0025] According to one embodiment, the outer surface includes at least two helically shaped third grooves positioned at equal angular positions relative to each other in a cross section of the element when viewed axially of the element.

[0026] According to one embodiment, the outer surface includes at least one third groove extending from the second end to the second groove. The third groove has an axial configuration.

[0027] According to one embodiment, the outer surface includes at least three axially oriented third grooves positioned at equal angular positions relative to one another when viewing the element axially.

[0028] According to one embodiment, the disclosed solution relates to a rock drill. The rock drill comprises a body and a percussion device comprising a percussion piston movable inside the body for reciprocating movement in an impact direction and a return direction under the influence of a pressurized hydraulic fluid moving back and forth in a working pressure chamber of the percussion device. The machine further comprises a piston guide element for supporting a front end of the percussion piston on the body. The piston guide element comprises at least one plain bearing section and a damping recess for decelerating the percussion piston. Hydraulic fluid is conveyed between the aforementioned plain bearing section and the damping recess. Furthermore, a front end portion of the percussion piston is supported by the piston guide element comprising two successive plain bearing sections. Furthermore, hydraulic fluid is conveyed between the aforementioned two successive plain bearing sections. The piston guide element follows the mechanism disclosed herein.

[0029] According to one embodiment, the above-mentioned part between two consecutive plain bearing sections is connected to an impact pressure system of an impact device.

[0030] According to one embodiment, the impact device comprises a first working pressure chamber at the front end of the impact device, from which hydraulic fluid is conveyed between the two successive plain bearing sections mentioned above.

[0031] According to one embodiment, the part between two successive plain bearing sections is connected to the percussion pressure system via at least one pressure channel formed in the body of the rock drill. Cooler hydraulic oil can then be conveyed to the piston guide element in comparison with the oil in the first working pressure chamber in the front part of the percussion device.

[0032] According to one embodiment, pressurized hydraulic fluid is conveyed from a location other than the braking recess to the portion between two successive plain bearing sections.

[0033] According to one embodiment, the disclosed solution relates to a method for supporting a front end portion of a percussion piston of a rock drill. The method comprises supporting the front end of the percussion piston on the body of the rock drill by a sleeve-like piston guide element with at least one plain bearing section and a damping recess for decelerating the percussion piston. A hydraulic fluid is conveyed between the above-mentioned plain bearing section and the damping recess. The method further comprises providing the piston guide element with at least one bearing sleeve and supporting the percussion piston by two plain bearing sections. A flow of hydraulic fluid is directed between the plain bearing sections.

[0034] According to one embodiment, the piston guide element is cooled by hydraulic fluid conveyed between the two plain bearing sections.

[0035] According to an embodiment, the solution also relates to a rock drilling rig, the rig comprising a mobile carrier and one or more drilling booms movably connected to the carrier and equipped with rock drilling units, the aforementioned rock drilling units comprising a feed beam and a rock drill movably supported on the feed beam, the rock drill and its operation being in accordance with the mechanism disclosed herein.

[0036] According to an embodiment, the disclosed solution can also be implemented in a hydraulic crusher intended for crushing rock materials. The crusher comprises a body and an impact device comprising a percussion piston movable inside the body for reciprocating movement in impact and return directions under the influence of a pressurized hydraulic fluid moving back and forth in a working pressure chamber of the impact device. The machine further comprises a piston guide element for supporting a front end of the percussion piston on the body. The piston guide element comprises at least one plain bearing section and a damping recess for decelerating the percussion piston. The hydraulic fluid is conveyed between the aforementioned plain bearing section and the damping recess. Furthermore, a front end portion of the percussion piston is supported by the piston guide element comprising two successive plain bearing sections. Furthermore, the hydraulic fluid is conveyed between the aforementioned two successive plain bearing sections. The piston guide element follows the mechanism disclosed herein.

[0037] The above disclosed embodiments can be combined to form a suitable solution having the above features as required.

[0038] Some embodiments are explained in more detail in the accompanying drawings. [Brief description of the drawings]

[0039] [Figure 1] FIG. 2 shows a schematic side view of a rock drilling rig for surface drilling, provided with a rock drilling unit equipped with a hydraulic rock drill; [Diagram 2] FIG. 1 is a schematic diagram of a hydraulic rock drill. [Diagram 3] FIG. 1 is a schematic diagram of a hydraulic rock drill. [Figure 4] FIG. 4 is a schematic cross-sectional top view of the rock drill of FIG. 2 and FIG. 3. [Diagram 5] FIG. 5 is a schematic cross-sectional view of a detail of FIG. [Figure 6] FIG. 2 is a schematic diagram of a piston guide element. [Figure 7] FIG. 2 is a schematic diagram of a piston guide element. [Figure 8] FIG. 8 is a schematic end view of the piston guide element of FIGS. 6 and 7; [Figure 9] FIG. 9 is a schematic cross-sectional view of the piston guide element of FIGS. 6 to 8, taken along section BB; [Figure 10] FIG. 2 is a schematic cross-sectional view of the element taken along section CC. [Figure 11] FIG. 2 is a schematic diagram of a piston guide element having a spiral groove on its outer surface. [Figure 12] FIG. 2 is a schematic cross-sectional view of a piston guide element with two axially successive plain bearing elements. [Figure 13] FIG. 2 is a schematic cross-sectional view of a piston guide element comprising a plain bearing material on its inner side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] For clarity, the figures show some embodiments of the disclosed solutions in a simplified manner.In the drawings, like reference numbers indicate like elements.

[0041] FIG. 1 shows a rock drilling rig 1 intended for surface drilling. The rock drilling rig 1 comprises a mobile carrier 2 and at least one drilling boom 3 connected to the carrier 2. At the distal end part of the drilling boom 3 there is a drilling unit 4 provided with a feed beam 5 and a rock drill 6 supported on the feed beam 5. To the drill 6 a drilling tool 7 can be connected. The rock drill 6 can be provided at the front end of the rock drill 6 with a shank adapter for connecting the tool 7. The rock drill 6 comprises an impact device 8 and a rotation device 9. The rock drill 6 can be moved on the feed beam 5 by means of a feed device 10. The rock drill 6 can be provided with a piston guide element according to the mechanism disclosed herein. It is to be mentioned that the disclosed piston guide element can be used in any kind of hydraulic rock drill utilizing the so-called top hammer principle. Furthermore, the disclosed piston guide element can be used in the impact device of a hydraulic demolition hammer.

[0042] Figures 2 to 5 disclose a rock drill 6 comprising a body 11, an impact device 8, a rotation device 9, a flushing housing 35, a shank adapter 12 and a gear housing 13 attached to the front end of the body. The impact device 8 comprises an impact piston 14 in the shank adapter 12 connected to a tool 7 for generating an impact pulse in an impact direction ID. The piston 14 reciprocates in the impact direction ID and in a return direction RD. The shank adapter 12 is located at the front end FE of the drill 6 and an end cover 15 is a distal component located at the rear end RE.

[0043] The front end of the piston 14 strikes an impact surface located at the rear end of the shank adapter 12. If the shank adapter moves forward and the impact surface moves away from the designed impact position, the movement of the piston 14 is slowed down by the damping recess 16 at the end of the impact movement. The damping recess 16 can receive a collar 17 of the piston, which together can form a closed pressure space. The piston 14 is supported in the body 11 by a front bearing 18 and a rear bearing 19, which can both be plain bearings. The front bearing 18 and the damping recess 16 are part of a piston guide element 20, which is an elongated sleeve-like part that surrounds the front of the piston 14. The element 20 comprises two axially consecutive plain bearing parts, between which there is a feed system 21 for the supply of hydraulic fluid from the impact device 14 or from another fluid source. The body 11 can be provided with channels, grooves or other fluid conducting structures to enable the supply. Alternatively or additionally, the outer surface of the element 20 may have fluid conducting grooves or other fluid conducting structures. 2-4 also show pressure accumulators P1-P4 which are part of the hydraulic circuit of the percussion device 8. The percussion device 8 comprises several working pressure spaces for moving the percussion piston under the influence of hydraulic pressure. For clarity only, the most forward working pressure space 22 is shown in FIG. 4. The working pressure space 22 is connected in series during operation to the high pressure system and to the accumulators P1 and P2. The feed system 21 can be connected to the working pressure space 22 via the above-mentioned pressure supply path, whereby a high pressure prevails between the plain bearing parts of the guide 20. Alternatively, the high pressure hydraulic fluid may be supplied from any other location or source. However, the pressure fluid is not led from the damping recess to the feed system 21. The supplied hydraulic fluid can leak through the bearing clearance of the piston, be collected at the front end FE and then be led to the drain line of the hydraulic system.

[0044] 6 to 10 disclose a piston guiding element 20 with a first end 23, a second end 24, an outer surface 25 and an inner surface 26. The first end 23 is intended to face the impact direction ID of the percussion piston, while the opposite second end 24 is intended to face the return direction RD of the percussion piston. The second end 24 is provided with a braking recess 16 having a large diameter on the inner surface 26. The braking recess 16 extends from the second end 24 towards the first end 23 by a first axial distance Ad1. The inner surface 26 is provided with a first groove 27 located at a second axial distance Ad2 from the braking recess 16. The element 20 is provided with one or more radial openings 28 between the bottom of the first groove 27 and the outer surface 25. The inner surface 26 comprises a first axial section As1 between the above-mentioned braking recess 16 and the first groove 27 and a second axial section As2 between the first groove 27 and the first end 23. Furthermore, the element 20 comprises a separate bearing sleeve 29 mounted inside the element 20 and provided with the above-mentioned first and second axial sections As1, As2. The first and second axial sections As1, As2 comprise a plain bearing material.

[0045] The outer surface 25 of the element 20 may comprise a second groove 30. The at least one radial opening 28 mentioned above extends to the bottom of the second groove 30. Furthermore, the outer surface 25 comprises one or more third grooves 31 extending from the second end 24 to the second groove 30. Through the grooves 31, hydraulic fluid can flow from the working pressure space 22 shown in FIG. 4 to the guide element 20. The third grooves may be axially oriented and the number of grooves 31 may be one, two, three, four or more. As can be seen in FIG. 7, there may be three grooves 31 equally spaced around the circumference of the element 20.

[0046] In an alternative solution, the guide element 20 may not have the second groove 30. In that case, the third groove 31' may terminate in a radial opening 28', as shown in Fig. 7 by dashed lines.

[0047] FIG. 11 discloses a guide element 20 that corresponds to the one shown in FIGS. 5 to 9, except that the third groove 31 is not axially oriented, but instead has a helical configuration.

[0048] FIG. 12 discloses a guide element 20 with two separate bearing sleeves 29a, 29b mounted consecutively on the inside of the element. The first bearing sleeve 29a is made of a plain bearing material and is configured to form a first axial section As1. The second bearing sleeve 29b is made of a plain bearing material and is configured to form a second axial section As2. The first groove 27 is located between the first bearing sleeve 29a and the second bearing sleeve 29b. As may be noted, the bearing sleeves 29a, 29b may have different axial lengths. Furthermore, the bearing sleeves 29a, 29b may be made of different materials and have other different dimensions. Alternatively, the bearing sleeves 29a, 29b may be similar parts.

[0049] 12 further discloses that hydraulic fluid can be conveyed to the second groove 30 or directly to the opening 28 via a dedicated pressure channel 32. The pressure channel 32 can be formed in the body of the impact device and can be positioned to convey cool hydraulic fluid to the guide 20, thereby lubricating and effectively cooling the bearing.

[0050] 13 discloses a bearing sleeve 29 comprising an outer base sleeve 33, which may be made of steel, and an inner structure 34, which may be a coating layer made of plain bearing material. Alternatively, the structure may have a bi-material construction, combining a steel base 33 with a bearing bronze layer 34.

[0051] The drawings and the associated description are intended only to illustrate the concept of the invention. In its details, the invention may vary within the scope of the claims.

Claims

1. A piston guide element (20) for supporting a front end portion (FE) of a reciprocating percussion piston (14) of a rock drill (6), comprising: the element (20) being a sleeve-like part that can be fitted inside the body (11) of the rock drill (6) between the percussion piston (14) and the body (11); The element (20) has a first end (23), a second end (24), an outer surface (25), and an inner surface (26); said first end (23) is intended to face the impact direction (ID) of said percussion piston (14); the opposite second end (24) of the element (20), intended to face the return direction (RD) of the percussion piston (14), is provided with a damping recess (16) having an increased diameter on its inner surface (26), said damping recess (16) extending a first axial distance (Ad1) from said second end (24) towards said first end (23); the inner surface (26) of the element (20) comprises a first groove (27) located at a second axial distance (Ad2) from the braking recess (16); said element (20) being provided with at least one radial opening (28) between the bottom of said first groove (27) and said outer surface (25); said inner surface (26) comprising a first axial section (As1) between said braking recess (16) and said first groove (27) and a second axial section (As2) between said first groove (27) and said first end (23); said element (20) comprises at least one separate bearing sleeve (29) mounted inside said element (20) and provided with said first axial section (As1) and said second axial section (As2); It is characterized by: An element, wherein at least the first axial section (As1) and the second axial section (As2) comprise a plain bearing material.

2. The bearing sleeve (29) mounted inside the element (20) is a single piece and is provided with the first axial section (As1) and the second axial section (As2). The element of claim 1 , characterized in that

3. said at least one separate bearing sleeve (29) being made of a plain bearing material; 3. An element according to claim 1 or 2, characterized in that

4. the inner surface of said at least one bearing sleeve (29) comprises at least one layer (34) made of at least one plain bearing material; Element according to any one of claims 1 to 3, characterized in that

5. said element (20) comprises two separate bearing sleeves (29a, 29b) mounted successively inside said element (20); a first bearing sleeve (29a) configured to define said first axial section (As1); a second bearing sleeve (29b) configured to define said second axial section (As2); The first groove (27) is located between the first bearing sleeve (29a) and the second bearing sleeve (29b). Element according to any one of claims 1, 3 or 4, characterized in that

6. The outer surface (25) is provided with a second groove (30), and the at least one radial opening (28) extends to a bottom of the second groove (30). Element according to any one of claims 1 to 5, characterized in that

7. the outer surface (25) includes at least one third groove (31) extending from the second end (24) to the second groove (30); 7. The element of claim 6, characterized in that

8. the outer surface (25) includes at least one third groove (31') extending from the second end (24) to at least one radial opening (28'); Element according to any one of claims 1 to 5, characterized in that

9. the at least one third groove (31, 31') has a helical configuration; 9. An element according to claim 7 or 8, characterized in that

10. the at least one third groove (31, 31') has an axial configuration; 9. An element according to claim 7 or 8, characterized in that

11. an outer diameter in the second axial section (As2) between the second groove (30) and the first end (23) is greater than an outer diameter in the first axial section (As1) between the braking recess (16) and the second groove (30), whereby the outer surface (25) of the element (20) has a stepped configuration; 7. The element of claim 6, characterized in that

12. A rock drill (6), A main body (11); an impact device (8) comprising a percussion piston (14) movable within said body (11) for reciprocating movement in an impact direction (ID) and a return direction (RD) under the influence of a pressurized hydraulic fluid moving to and fro within an operating pressure chamber of said impact device (8); a piston guide element (20) for supporting the front end of the percussion piston (14) in the body (11); said piston guide element (20) comprising at least one plain bearing section and a damping recess (16) for decelerating said percussion piston (14); A hydraulic fluid is conveyed between the plain bearing section and the braking recess (16), the front end portion of the percussion piston (14) is supported by the piston guide element (20) which comprises two successive plain bearing sections (As1, As2); Hydraulic fluid is conveyed between the two successive plain bearing sections (As1, As2); The piston guide element (20) is as claimed in any one of claims 1 to 11. A rock drill (6).

13. the part between two successive plain bearing sections (As1, As2) is connected to the impact pressure system of the impact device (8); The rock drill according to claim 12, characterized in that

14. A method for supporting a front end portion of a percussion piston (14) of a rock drill (6), comprising: supporting the front end of the percussion piston (14) in the body (11) of the rock drill (6) by a sleeve-like piston guide element (20) comprising at least one plain bearing section and a braking recess (16) for decelerating the percussion piston (14); conveying hydraulic fluid between said plain bearing section and said braking recess (16); Including, Providing said piston guide element (20) with at least one bearing sleeve (29); supporting said percussion piston (14) by two plain bearing sections (As1, As2) and directing the flow of said hydraulic fluid between said two plain bearing sections (As1, As2); A method comprising:

15. cooling said piston guide element (20) by means of said hydraulic fluid conveyed between said two plain bearing sections (As1, As2); The method according to claim 14, characterized in that

Images