BREAKING HAMMER AND METHOD OF SUPPORTING PERCUSSION PISTON

Abstract

A hydraulic breaking hammer and method of supporting a percussion piston is provided. The breaking hammer includes a percussion device provided with a reciprocating piston. The piston is supported on a frame at its end portions by a first piston bearing element and a second piston bearing element. The second piston bearing element includes a collar sealing element facing towards a working collar of the piston. The piston bearing elements are easily mountable and dismountable separate components.

Claims

1. A hydraulic breaking hammer, comprising: a percussion device including a frame and a piston arranged inside the frame and, the percussion device being configured to perform a working cycle including reciprocating longitudinal movement of the piston in an impact direction and a return direction due to pressure of hydraulic fluid fed to first and second working pressure spaces of the percussion device; at least one control device is arranged for controlling feeding and discharging of the hydraulic fluid of at least one of the first and second pressure spaces for executing the working cycle; a working collar of the piston located between the first and second working pressure spaces and wherein an outer surface of the working collar is sealed to surrounding structures so that the first and second working pressure spaces are hydraulically separated; and a first piston bearing and a second piston bearing are located at an axial distance from each other, wherein the first and second piston bearings are configured to provide support for the opposite first and second end portions of the piston, whereby the first working pressure space, the working collar and the second working pressure space are all located between the first and second piston bearings, at least the second piston bearing being a separate sleeve-like element mountable to the frame in one piece, wherein a radial clearance is disposed between the outer surface of working collar and the second piston bearing element and at least one separate collar sealing element being arranged to seal the clearance, and wherein the second piston bearing element includes at least one first sealing housing for the collar sealing element.

2. The breaking hammer as claimed in claim 1, wherein the first sealing housing is located at a tool side end portion of the second bearing element and includes a sealing groove on an inner surface of the second bearing element, the collar sealing element being a slide ring mounted to the sealing groove-.

3. The breaking hammer as claimed in claim 1, wherein the second piston bearing element is provided with a dedicated lubrication channel.

4. The breaking hammer as claimed in claim 1, wherein the second piston bearing element is provided with an end cushion space which is configured to form a closed pressure space together with the working collar when the piston movement in the return direction exceeds a predetermined dead point where the movement of the piston changes between the return and impact direction movements directions.

5. The breaking hammer as claimed in claim 1, wherein the first and second piston bearings are both replaceable and elongated bearing bushings.

6. The breaking hammer as claimed in claim 1, wherein the percussion device includes a direct acting pressure accumulator which is located at a return direction end of the piston and is configured to store pressure energy when the second end of the piston protrudes inside the accumulator during its movement in the return direction, the second piston bearing element is being provided with at least one second sealing housing at its second portion facing towards the pressure accumulator, and wherein the second sealing housing is provided with a gas sealing element facing towards the piston and separating a bearing portion of the second piston bearing element and the pressure accumulator in a fluid tightly tight manner from each other.

7. The breaking hammer as claimed in claim 1, wherein the second working pressure space, which is located at a side of the return direction, is limited only by the piston and the second piston bearing element.

8. The breaking hammer as claimed in claim 1, wherein the first and second piston bearings are both replaceable and elongated bearing bushings and wherein magnitudes of outer diameters of the bushings facing radially to the frame are equal, the frame of the percussion device comprises having a central through opening, at least both end portions of the central through opening having coaxial inner diameters a magnitude of which are equal and match with the magnitudes of the equal outer diameters of the bearing bushings.

9. The breaking hammer as claimed in claim 1, wherein the control device is configured to direct substantially constant hydraulic fluid pressure to the first working pressure space for moving the piston in the return direction and wherein the control device is further configured to feed and discharge hydraulic fluid pressure to and from the second working pressure space and to thereby control reciprocating movement of the piston during the work cycle.

10. A method of supporting a piston of a hydraulic breaking hammer, the method comprising: supporting the piston axially movably relative to a frame of a percussion device of the breaking hammer by means of a first piston bearing and a second piston bearing; sealing working pressure spaces of the percussion device from each other by means of a sealing element which is located at a working collar of the piston; arranging the first piston bearing at an impact direction side end portion of the piston and the second piston bearing at an opposite returning direction side end portion of the piston; using a separate sleeve-like bearing bushing at least for the second piston bearing element; providing the mentioned second piston sealing bushing with a first sealing housing facing towards the piston; mounting a changeable collar sealing element to the first sealing housing; and mounting the second piston bearing bushing together in one piece with the collar sealing element to the frame of the percussion device wherein the second piston bearing element provides bearing and sealing for the piston.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0029] FIG. 1 is a schematic side view of an excavator, which is provided with a breaking hammer.

[0030] FIG. 2 is a schematic and sectional side view of a hydraulically operated percussion device of a breaking hammer.

[0031] FIG. 3 is a schematic and partly sectional side view of a second piston bearing bushing mountable at a reverse direction side end of a percussion device.

[0032] FIG. 4 is a schematic view of the second piston bearing bushing of FIG. 3.

[0033] FIG. 5 is a schematic view of a first piston bearing bushing mountable at a tool side end of a percussion device.

[0034] FIG. 6 is a schematic view of a diagram showing some issues and features relating to the disclosed second piston bearing bushing.

[0035] FIG. 7 is a schematic and sectional side view of a frame of a percussion device.

[0036] 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

[0037] FIG. 1 shows a breaking hammer 1 arranged on a free end of a boom 2 of 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, for example. The breaking hammer 1 includes a percussion device 4 for generating 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. The percussion device 4 is hydraulic, whereby it is connected to a hydraulic system of the working machine 2.

[0038] The impact pulses are generated in the percussion device 4 by means of a percussion piston, that is moved back and forth in the impact direction A and return direction B 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. The percussion device 4 may be in accordance with the solution disclosed herein.

[0039] FIG. 2 discloses a basic structure of a percussion device 4 of a breaking hammer. The percussion device 4 includes a frame 8 inside which is a percussion piston 9 arranged to be moved in an impact direction A and return direction B. The piston 9 includes a working collar 10 at its middle section. At the impact direction A side of the collar 10 there is a first working pressure space 11 and at a return direction B side there is a second working pressure space 12 inside which pressure of hydraulic fluid is controlled by means of a control device CD. The working pressure spaces 11, 12 are separated from each other by means of a collar sealing element 13. A clearance 14 or annular gap surrounds the working collar 10 and this clearance 14 is sealed by the collar sealing element 13.

[0040] The piston 9 includes a first working pressure surface 15 for moving the piston 9 in the return direction B, and a second working pressure surface 16 for moving the piston 9 in the impact direction A. The control device CD may alternate pressure in the second working pressure space 12 by connecting the second pressure space to a tank T or to a pressure source PS. The control device CD may connect the first working pressure space 11 to the pressure source for the duration of the working cycle. Since effective area of the second working pressure surface 16 is larger than the one of the first working pressure surface 15, the piston moves in the impact direction A when high pressure is fed to the second working pressure space 12. It should be appreciated that the control of the pressure flows, and the effective areas of the working pressure surfaces may also be arranged and dimensioned in other ways.

[0041] The percussion piston 9 is supported to the frame 8 by a first piston bearing 17 and a second piston bearing 18. The first and second piston bearings 17, 18 are separate sleeve-like piston bearing elements 19, 20 which can be mounted axially inside a central through opening 21 of the frame 8. The first piston bearing element 19 provides support for the piston 9 at a lower end portion of the percussion device 4, and the second piston bearing element 20 provides support at the upper end portion. The piston bearing elements 19, 20 or bushings are provided with one or more hydraulic seals 22, 23 for sealing an inner opening diameter of the piston bearings elements 19, 20 to outer diameters of the piston 9. In addition to these seals and a sealing section, the piston bearing elements 19, 20 have bearing portions 24, 25 for providing slide bearing for the opposite end portions of the piston 9. The piston bearing elements 19, 20 may also include end cushion spaces 26, 27 forming closed pressure spaces with the working pressure surfaces 15, 16 if the piston exceeds its normal stroke lengths in the impact direction A and return direction B. As can be seen, the second working pressure space 12 may be defined between the piston 9 and the second piston bearing element 20. The bearing portion 25 of the second bearing element 20 may be provided with a dedicated lubrication channel 28 for providing lubrication from a lubrication source L for the slide bearing surfaces. Both piston bearing elements 19, 20 may comprise dedicated tank channels 29, 30 provided with throttling devices 31 and connected to the tank T.

[0042] The percussion piston 9 includes an impact surface 32 facing towards the impact direction A and configured to strike a tool. A rear surface 33 of the piston 9 is facing towards the return direction B and is configured to move inside a gas space 34 of a direct acting pressure accumulator 35. At an end portion of a sealing section of the second piston element 20 there is a gas sealing element 36 for separating the bearing portion 25 and the gas space 34 fluid tightly from each other.

[0043] The control device CD may be a control valve, control valve assembly, or a set of directly or indirectly controlled valve elements, for example. The control device CD may comprise one or more control elements moving in linear or rotational control path and controlling one or more pressure channels of control pressure channels.

[0044] FIG. 2 further discloses axial mounting directions M1 and M2 of the piston bearing elements 19, 20 inside the through opening 21 of the frame 8.

[0045] FIGS. 3 and 4 disclose a second piston bearing element 20 which is substantially in accordance with the one shown in FIG. 2. FIG. 3 further shows sealing housings 23′ for receiving the hydraulic sealing elements. The sealing housings 23′ may be grooves 23a, 23b. A sealing housing 36′ for the gas sealing element may be a sealing groove 36a. A sealing housing 13′ for receiving the working collar sealing element may be a sealing groove 13a. Further, on outer surfaces of both end portions of the second piston bearing sleeve 20 there may be sealing grooves 37, 38 for receiving outer sealing elements facing towards the longitudinal through opening of the frame. The bushing 20 may have several transverse openings 39 for feeding hydraulic fluid through the sleeve-like construction.

[0046] FIG. 5 discloses a first piston bearing element 19 which is in accordance with the one shown in FIG. 2. Inside the element 19 are sealing housings 22′ for the hydraulic seals and on an outer surface is a sealing groove 40 for an outer sealing element.

[0047] The first and second piston bearing elements 19, 20 can be preassembled by providing them with the sealing elements. Mounting the sealing elements to separate bushings is much easier than mounting them to a complete percussion device structure.

[0048] Features disclosed in FIG. 6 have already been discussed supra.

[0049] FIG. 7 discloses an elongated sleeve-like frame 8 of a percussion device comprising a central opening 21 provided with inner coaxial inner diameters D1, D2 having equal dimension. The dimension of the diameters D1, D2 match with equal outer diameter of a first and second piston elements 19, 20. Thus, bearing bushings 41 and 42 for receiving the bearing bushings 19, 20 have equal diameter. Further, at a middle section of the frame may be a third section 43 configured to receive a lower end portion of the bushing 20. Inner diameter D3 of the third section 43 may also have the same diameters as diameters D1, D2 at the ends. All the diameters D1, D2, D3 are also coaxial. Between accurate sections 41, 42, 43 there may be non-machined sections serving as chambers for pressure connections P. As can be seen, the structure of the frame 8 is relatively simple and easy to manufacture.

[0050] 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.