TOOL BUSHING, BREAKING HAMMER AND MOUNTING METHOD

Abstract

A tool bushing of a breaking hammer, a tool bushing arrangement, a breaking hammer and a method of mounting a tool bushing of a breaking hammer are disclosed. The tool bushing is a sleeve-like piece having a multi-shouldered outer surface with three or more successive cylindrical portions. The cylindrical portions have different diameters that match with corresponding surfaces of a bushing housing when the tool bushing is mounted. Diameters of the bushing and the bushing housing are dimensioned so that friction forces are generated when the bushing is assembled.

Claims

1. A tool bushing of a breaking hammer comprising: a sleeve-like piece having an inner periphery, an outer periphery and an axial length, the inner periphery forming a bearing surface arranged to face a breaking tool to be supported, and the outer periphery being arranged to face a bushing housing; a first end having a first outer diameter and a second end having a second outer diameter, wherein the first diameter is greater than the second diameter, the outer periphery of the tool bushing having a multi-shoulder configuration including a plurality of shoulders forming at least three successive cylindrical sections having differing diameters, wherein sizes of the diameters of the shoulders are dimensioned to increase step-by-step towards the first end; and at least one axial alignment groove disposed on the outer periphery and extending from the second end along a limited axial length towards the first end.

2. The tool bushing as claimed in claim 1, wherein the outer periphery is stepped into at least six successive cylindrical sections, the diameters of which are different in size.

3. The tool bushing as claimed in claim 1, wherein a step height of the shoulders is 0.1-1.0 mm, whereby sizes of the diameters of every two successive cylindrical sections differ 0.2-2 mm from each other.

4. The tool bushing as claimed in claim 1, wherein each shoulder has an effective axial shoulder length of 20-60 mm.

5. The tool bushing as claimed in claim 1, wherein the outer surface is provided with at least one transverse locking groove, which is located at a section between the second end and a longitudinal middle point of the tool bushing, the at least one transverse locking groove being arranged to partly receive a transverse locking pin in an installed state.

6. A tool bushing arrangement of a breaking hammer comprising: a breaking tool, which is an elongated piece; a tool bushing in accordance with claim 1, the tool bushing being located around the breaking tool and having at least one cylindrical outer surface; and a bushing housing configured to receive the tool bushing inside at least one cylindrical inner surface, wherein the tool bushing is predominantly retained therein by a friction fitting between the at least one cylindrical outer surface of the tool bushing and the at least one cylindrical inner surface of the bushing housing, the bushing housing having a corresponding multi-shouldered configuration with several successive cylindrical inner surfaces with differing diameters for receiving the several cylindrical outer surfaces of the multi-shouldered tool bushing, and wherein the diameters of the outer cylindrical surfaces of the tool bushing and the diameters of the mating inner cylindrical surfaces of the bushing housing are dimensioned to be without mutual radial clearances.

7. The tool bushing arrangement as claimed in claim 6, wherein between each shoulder of the tool bushing and a respective mating cylindrical inner surface of the bushing housing surrounding the respective shoulder is a light interference fit or interference fit, whereby the friction fitting exists on the diameters of the outer cylindrical surfaces.

8. The tool bushing arrangement as claimed in claim 6, wherein the tool bushing is retained by a press fit having an axial mounting length of 20-60 mm.

9. A breaking hammer, comprising: a percussion device including a frame and an impact element arranged inside the frame; a breaking tool connectable to the percussion device and arranged to protrude from the frame; a tool bushing in accordance with claim 1 located around the breaking tool and having at least one cylindrical outer surface; and a bushing housing, which is located at a tool side end of the frame and being configured to receive the tool bushing inside at least one cylindrical inner surface, wherein the tool bushing is predominantly retained by a friction fitting between the at least one cylindrical outer surface of the tool bushing and the at least one cylindrical inner surface of the bushing housing, the bushing housing having a corresponding multi-shouldered configuration with several successive cylindrical inner surfaces with differing diameters arranged for receiving the cylindrical outer surfaces of the multi-shouldered tool bushing, wherein the diameters of the outer cylindrical surfaces of the tool bushing and the diameters of the mating inner cylindrical surfaces of the bushing housing are dimensioned to be without mutual radial clearances.

10. A method of mounting a tool bushing of a breaking hammer, the method comprising: providing a tool side lower end of the breaking hammer with a tool bushing, the tool bushing having at least one cylindrical outer surface; arranging the tool bushing inside a bushing housing of the breaking hammer, the bushing housing having at least one cylindrical inner surface; retaining the tool bushing by a friction fitting between the at least one cylindrical inner surface of the tool bushing and the at least one cylindrical outer surface of the bushing housing; providing the tool bushing with at least three successive cylindrical outer surfaces and providing the bushing housing with at least three mating cylindrical inner surfaces; mounting the tool bushing into the bushing housing by using two successive pushing phases, wherein the tool bushing is in a first pushing phase when pushed manually partly inside the bushing housing, and is in a second pushing phase when pushed into a final installation position by a pressing device; extending pushing of the tool bushing in the second pushing phase for an axial mounting length of 20-60 mm; and aligning the tool bushing relative to the bushing housing in the first pushing phase by setting an axial alignment groove of the tool bushing in line with a protruding alignment pin of the bushing housing before initiating the second pushing phase.

11. The method according to claim 10, further comprising the steps of: over dimensioning all cylindrical outer surfaces of the tool bushing relative to the cylindrical inner surfaces of the bushing housing; and forcing the tool bushing into the bushing housing by pressing device and generating a press fit between the cylindrical outer surfaces of the tool bushing and the cylindrical inner surfaces of the bushing housing.

12. The method according to claim 10, further comprising using a portable hydraulic press or jack with a maximum stroke length of 60 mm as the pressing device.

13. The method according to claim 10, further comprising: pulling an already installed tool bushing backwards from the bushing housing for a longitudinal distance magnitude greater than the axial mounting length and without totally retracting the tool bushing from the bushing housing; loosening the tool bushing; turning the loosened tool bushing relative to the central axis of the tool bushing to a different angular position compared to a previous position; and pushing the tool bushing longitudinally back into the bushing housing whereby the tool bushing is secured into a new angular position.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] Some embodiments are described in more detail in the accompanying drawings, in which

[0043] FIG. 1 is a schematic side view of an excavator, which is provided with a breaking hammer.

[0044] FIG. 2 is a schematic and cross-sectional side view of a percussion device of a breaking hammer.

[0045] FIG. 3 is a schematic side view of a lower tool bushing having six successive cylindrical outer sections with differing diameters.

[0046] FIG. 4 is a schematic side view of another lower tool bushing comprising three cylindrical outer sections or shoulders.

[0047] FIG. 5 is a schematic and perspective view of a tool bushing and also shows an axial alignment groove and a transverse locking groove.

[0048] FIG. 6 is a schematic and cross-sectional side view of a lower end portion of the breaking hammer.

[0049] FIG. 7 is a schematic side view of a mounting setting having a hydraulic jack.

[0050] FIG. 8 is a schematic diagram showing steps relating to change or turning measures of the tool bushing.

[0051] 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

[0052] FIG. 1 shows a breaking hammer 1 arranged on a free end of a boom 2 in a working machine 3, such as an excavator. Alternatively, the boom 2 may be arranged on any movable carriage or on a fixed platform of a crushing apparatus. The breaking hammer 1 includes a percussion device 4 arranged to generate impact pulses. The breaking hammer 1 may be pressed by means of the boom 2 against material 5 to be broken and impacts may be simultaneously generated with the percussion device 4 to a tool 6 connected to the breaking hammer 1. The tool 6 transmits the impact pulses to the material 5 to be broken.

[0053] The percussion device 4 may be hydraulic, whereby it may be connected to the hydraulic system of the working machine 2. Alternatively, the percussion device 4 may be electrically or pneumatically powered. The impact pulses may be generated in the percussion device 4 by means of a percussion element, such as a percussion piston, that may be moved back and forth in the impact direction and return direction under the influence of hydraulic fluid. Further, the breaking hammer 1 may have a protective casing 7, inside which the percussion device 4 may be located. At a lower end of the breaking hammer, i.e. at the tool side end, is a lower tool bushing arrangement 8 for bearing the tool 6 to a frame of the breaking hammer. The tool bushing arrangement 8 comprises a tool bushing disclosed in this patent application.

[0054] FIG. 2 discloses a structure of a percussion device 4 of a breaking hammer 1. The breaking hammer includes a lower end A at a tool side end and an upper end B. A percussion device 4 may have a percussion piston 9 arranged to move to and fro relative to a frame 10 of the percussion device 4. An impact surface 11 of the percussion piston 9 is arranged to strike an upper end of a tool (not shown in FIG. 2). The tool is allowed to move in the axial direction P during use. The frame 10 may have an upper frame part 10a and a lower frame part 10b.

[0055] At the lower end of the lower frame part 10b of the breaking hammer 1 is a bushing housing 12 configured to receive a sleeve-like lower tool bushing 13. The tool is also supported by means of an upper tool bushing 14, which is mounted in place when the lower frame 10b is detached. The tool is configured to pass through the lower and upper tool bushings 13, 14, which both serve as bearing and support elements for the tool. However, the lower tool bushing 13 is subjected to greater mechanical forces and wear than the upper tool bushing 14, thus the lower tool bushing needs to be serviced and changed more often. Since the bushing housing 12 of the lower tool bushing 13 opens towards the lower end A of the breaking hammer 1, the bushing 13 can be dismounted without dismantling the basic structure of the frame 10.

[0056] FIG. 3 shows, in an enhanced manner, a lower tool bushing 13 with an outer periphery 14 including six cylindrical sections C1-C6 with differing diameters D1-D6. The nominal outer diameter of the bushing depends on the size and capacity of the breaking hammer and may typically be between 150-250 mm. An inner periphery 15 of the bushing serves as a bearing surface against a breaking tool. As can be noted, a first cylindrical section C1 at a first end 16 or lower end of the bushing has the greatest diameter D1 and the opposite second end 17 or upper end has the smallest diameter D6. Thus, the outer surface of the bushing 13 is multi-stepped or multi-shouldered. Step height SH between adjacent shoulders may be 0.1-1.0 mm, for example. Further, each of the cylindrical sections C1-C6 or shoulders has an effective axial shoulder length L, which may be 20-60 mm.

[0057] In FIGS. 2 and 3, the lower tool bushing 13 has an extension portion 18 with an axial length, which may be multiplied relative to the effective axial shoulder length L, and which may protrude from the bushing housing 1, as shown in FIG. 2.

[0058] FIG. 4 shows in an enhanced manner a three-stepped tool bushing 13. The basic features of the bushing 13 of FIG. 4 correspond to the bushing 13 of FIG. 3 except that the first cylindrical section C1 is without any extension portion 18.

[0059] FIG. 5 illustrates a tool bushing 13, the basic structure of which is in accordance with the one shown in FIG. 3. However, in FIG. 5 axial alignment groove 19 and a transverse locking groove 20 are shown. The number of alignment grooves 19 and locking grooves 20 may be two or more so that the bushing 13 has two or more alternative angular positions relative to central axis 21 of the bushing 13. Thus, the bushing 13 is turnable 90, for example, as indicated by arrow 22. Further, on the outer periphery of the bushing 13 may be a lubricating groove 23 and several lubricating holes 24 passing through wall of the bushing 13.

[0060] FIG. 6 discloses in a simplified manner a lower end A of the breaking hammer. A tool bushing 13 is mounted inside a bushing housing 12. Mating surfaces of the bushing 13 and the bushing housing 12 are provided with multi-shouldered formations as described herein. For clarity reasons the surfaces are shown without the stepped structure. At a second end portion 17 of the bushing 13 there is one or more alignment grooves 19 arranged to receive protruding alignment pins 25, such as screws. Fastening of the bushing 13 is based on friction mounting, but there may be a second fastening system, namely a transverse locking pin 26 arrangement.

[0061] Between tool 6 and the bushing 13 is a tool seal 27, which is a sealing ring arranged partly inside a sealing groove formed on inner periphery of the bushing 13 at the first end portion 16 of the bushing 13. FIG. 6 further discloses that a lubricating agent may be conveyed through a conduct 28 to a lubricating groove 23 wherefrom the lubricating agent may pass through lubricating holes 24 to a gap between the tool 6 and the bushing 13. An outer edge of the second end of the bushing 13 has a chamfer 29 for alignment purposes.

[0062] FIG. 7 illustrates the mounting of a four-stepped lower tool bushing 13 by means of a pressing device 30, which may be a hydraulic jack having a piston 31 with a maximum stroke length defining a maximum mounting length ML. The bushing 13 has four cylinder sections C1-C4 and each of them has an axial length AL, which is equal or shorter than the maximum mounting length ML.

[0063] FIG. 8 illustrates the steps of a maintenance process of a tool bushing as described above.

[0064] Although the present embodiment(s) has been described in relation to particular aspects thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present embodiment(s) be limited not by the specific disclosure herein, but only by the appended claims.