Valve cylinder block, impact device and method

Abstract

A valve cylinder block, an impact device of a rock-breaking device, and a method for preventing cavitation in a hydraulic impact device of a rock-breaking device. The valve cylinder block (23) is an elongate member that includes a central opening (32) arranged to impact a piston (19). The valve cylinder block includes two pressure spaces (25, 27) that are located at a certain axial distance from each other and are fluidly connected via an axial fluid passage (28). One of the pressure spaces is a control space (25) within which a sleeve-shaped control valve (26) can be mounted. The control space includes a radial groove (29) whose bottom surface (33) is non-circular and has a lateral opening (30).

Description

Technical Field

[0001] The present invention relates to a valve cylinder block for a hydraulic impact device of a rock-breaking device.

[0002] The present invention also relates to an impact device of a rock-breaking device and a method for preventing cavitation in a hydraulic impact device of a rock-breaking device. Background Art

[0003] The field of the present invention is more specifically defined in the preamble part of the independent claims.

[0004] In mines and other work sites, different types of rock-breaking devices are used to drill holes in rock surfaces and break rocks and other hard materials. Rock-breaking devices are typically hydraulically driven and include a hydraulic impact device having a reciprocating impact piston. The working cycle of the impact piston can be controlled by a sleeve-shaped control valve, which can be pilot-controlled. The control valve can be installed in the control space of the valve cylinder block. Known solutions have shown some disadvantages, which particularly relate to hydraulic cavitation that is harmful to the durability of the components of the impact device. Summary of the Invention

[0005] The object of the present invention is to provide a novel and improved valve cylinder block and impact device, as well as a method for preventing cavitation in a hydraulic impact device of a rock-breaking device.

[0006] The valve cylinder block according to the present invention is characterized by the features of the characterizing part of the first independent device claim.

[0007] The impact device according to the present invention is characterized by the features of the characterizing part of the second independent device claim.

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

[0009] The idea of the present invention is that the valve cylinder body of the hydraulic impact device of the rock-breaking equipment is an elongated member having a central axis. The valve cylinder body includes a central opening extending from the front end to the rear end of the elongated valve cylinder body. The impact piston of the impact device can be installed through the central opening. There are at least two pressure spaces defined by the radial surface of the central opening. The pressure spaces are located at a certain axial distance from each other. A number of axial pressure fluid channels are arranged to connect the said pressure spaces. One of the said pressure spaces is a control pressure space located at the rear end portion of the valve cylinder body. The control pressure space is configured to receive a sleeve-shaped control valve for controlling the working cycle of the impact piston. The control pressure space has an inner radial groove, and the inner radial groove includes a bottom surface which defines the radial extension of the groove relative to the said central opening adjacent to the groove. In addition, the said axial pressure fluid channels pass through the radial groove in the axial direction without being fluidly connected to the groove. The cross-sectional shape of the bottom of the said radial groove is non-rotationally symmetric and includes a plurality of surfaces at several different distances from the central axis. In other words, in the radial groove forming the bottom surface of the radial groove, there is not only one circumference, but there are several different surface configurations defining the bottom or bottom line of the groove.

[0010] The advantage of the disclosed solution is that the size of the radial groove can be increased compared to a simple groove with a circular bottom surface. In addition, the increase in size is possible even though the axial pressure fluid channels define the available space for expanding the groove. In the disclosed solution, the bottom surface is formed by several suitably shaped parts that can bypass the axial pressure fluid channels.

[0011] According to one embodiment, the purpose of forming the disclosed groove is to increase the fluid volume of the groove and thus reduce the possible operating conditions where cavitation may occur.

[0012] According to one embodiment, the rock-breaking equipment is a rock drill.

[0013] According to one embodiment, the rock-breaking equipment can alternatively be a breaker hammer.

[0014] According to one embodiment, the valve cylinder body is a cylinder that can be installed within the base body of the impact device.

[0015] According to one embodiment, the valve cylinder body is a pilot valve cylinder body, in which the sleeve-shaped control valve moves in opposite directions by means of a pilot pressure pulse fed through the said axial pressure fluid channels.

[0016] According to one embodiment, the bottom surface of the radial groove includes a plurality of curved surfaces. In other words, the bottom of the groove has a curved cross-sectional configuration. The advantage of this embodiment is that the bottom surface has a curved shape that is hydrodynamically beneficial and thus does not interfere with the hydraulic flow. The curved shape and surface ensure smooth fluid flow.

[0017] According to one embodiment, the bottom surface only includes a curved shape.

[0018] According to one embodiment, the bottom of the groove includes a plurality of surfaces having at least three different radii of curvature R1, R2, R3.

[0019] According to one embodiment, at the radial groove, the axial fluid channels of the valve cylinder block are evenly spaced around the central opening in the cross-section. Then, there are a plurality of intermediate sections between the axial fluid channels. The groove has its minimum radial dimension at the axial fluid channels and its maximum radial dimension at the said intermediate sections.

[0020] According to one embodiment, in addition to the features of the foregoing embodiments, the radial dimension of the groove at the intermediate section is the largest at the middle of the intermediate section and continuously decreases from the middle towards the section having the axial fluid channel, whereby the shape of the bottom bends at the intermediate section.

[0021] According to one embodiment, the shape of the bottom of the groove at the said intermediate section is arched.

[0022] According to one embodiment, the bottom of the groove at the intermediate section can have any other curved shape other than the said arched shape. Then, for example, the radius or curvature can vary continuously or gradually.

[0023] According to one embodiment, the number of axial fluid channels is three. In other words, there are three axial fluid channels spaced apart at an angular interval of 120° relative to each other. At the axial fluid channels are channel sections, and between the channel sections are intermediate sections. There are a total of three channel sections and three intermediate sections.

[0024] According to one embodiment, in some configurations, the axial fluid channels can be unevenly spaced around the central opening.

[0025] According to one embodiment, the number of axial fluid channels can be from 2 to 8.

[0026] According to one embodiment, the groove is made by a milling technique.

[0027] According to one embodiment, the groove is made by a modern CNC lathe using synchronized turning movement and cutting tool movement. Another possibility is to implement a modern computer numerical control turning center.

[0028] According to one embodiment, the bottom of the groove at the intermediate section can be made by a rotating side milling cutter. The bottom of the groove for the intermediate section is fast and inexpensive to manufacture.

[0029] According to one embodiment, the bottom of the groove at the intermediate section can be made by a rotating end mill. Then, the shape of the bottom can be freely designed. A modern CNC machining center can accurately achieve the desired cutting tool path.

[0030] According to one embodiment, the radial groove is located at the front end portion of the control pressure space.

[0031] According to one embodiment, the bottom of the radial groove has at least one transverse fluid passage that provides a fluid connection between the groove and the outer surface of the valve cylinder block. In other words, the groove serves as part of a fluid path intended for conveying a fluid flow.

[0032] According to one embodiment, the axial fluid passages are spaced around the central opening, whereby the cross-section of the valve cylinder block includes fluid passage sections and intermediate sections located between the fluid passage sections. The bottom of the radial groove has a number of transverse fluid passages at each intermediate section. Due to the non-circular shape of the bottom surface of the groove, the nominal thickness of the cylinder wall of the valve cylinder block at the groove can be smaller at the intermediate section compared to the fluid passage sections. In other words, the valve cylinder block can have a varying wall thickness at the cross-section of the groove.

[0033] According to one embodiment, the disclosed solution relates to an impact device of a rock-breaking device. The impact device includes: a main body having a central space; an impact cylinder axially disposed within a rear portion of the central space and including a valve cylinder block; an impact piston passing through the impact cylinder and capable of moving in the impact direction towards the front end of the impact device and in the opposite direction towards the rear end of the impact device; a working pressure space having a hydraulic pressure fluid for moving the impact piston in the opposite direction; a control pressure space located at the rear end of the valve cylinder block and having a sleeve-shaped control valve for controlling the hydraulic pressure acting at the control pressure space and thereby controlling the reciprocating movement of the impact piston; and wherein the valve cylinder block has a pilot pressure space for providing a pressure pulse in response to the movement of the impact piston in the impact direction; and the valve cylinder block further has a number of axial fluid passages for connecting the pilot pressure space and the control pressure space. In addition, the valve cylinder block of the impact device is the valve cylinder block according to the embodiments and features disclosed in the present application.

[0034] According to one embodiment, the disclosed solution relates to a method for preventing cavitation in a hydraulic impact device of a rock-breaking device. The method includes: increasing the volume of a hydraulic space between an inner surface of a control pressure space of the impact device and an outer surface of a sleeve-shaped control valve, the sleeve-shaped control valve being mounted in the control pressure space in a reciprocating motion manner; providing a groove in the inner surface of the control pressure space at a cross-section where a plurality of lateral fluid channels are arranged for feeding hydraulic pressure fluid to and from the control pressure space; and increasing the volume by shaping a bottom of the groove to expand towards an outer surface of the impact device at the lateral fluid channels, whereby a reduced wall thickness exists only at the lateral fluid channels and a shape of a bottom line of the groove deviates from a circle.

[0035] The above-disclosed embodiments can be combined in order to form a suitable solution having desired features among the above features. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Some embodiments are described in more detail in the drawings, in which

[0037] Figure 1 is a schematic side view of a rock drilling unit having a hydraulic rock drill,

[0038] Figure 2 is a schematic side view of an excavator having a hydraulic breaker,

[0039] Figure 3 is a schematic cross-sectional side view of a rock drill including a hydraulic impact device,

[0040] Figure 4 is a schematic cross-sectional side view of a valve cylinder block, and

[0041] Figure 5 is a schematic view of the valve cylinder block cut at a cross-section E-E and shows a bottom shape of the groove. Figure 4 For clarity, the drawings show some embodiments of the disclosed solution in a simplified manner. In the drawings, the same reference numerals denote the same elements.

[0042] DETAILED DESCRIPTION DETAILED DESCRIPTION

[0043] Figure 1Shows a rock drilling unit 1 intended for drilling holes in a rock surface. The rock drilling unit 1 is typically mounted on a boom 2 of a rock drilling equipment. The rock drilling unit 1 has a feed beam 3 and a rock drill 4 supported thereon. A rock drilling tool 5 can be connected to the rock drill 4. The rock drill 4 may include a shank adapter 6 at the front end of the rock drill 4 for connecting the tool 5. At the opposite end of the tool 5 is a drill bit 7. The rock drill 4 includes an impact device 8 for providing an impact pulse to the rock drilling tool 5 to break the rock, and a rotation device 9 for rotating the rock drilling tool 5 about its longitudinal axis R. The rock drill 4 further includes a base body 10 for mounting the impact device 8, the rotation device 9 and possibly other required devices and elements. The rock drill 4 can be moved on the feed beam 3 in a drilling or feed direction A and a return direction B by means of a feed device 11. The rock drill 4 can be hydraulically operated, whereby the impact device 8 and the rotation device 9 are connected to a hydraulic system HS. In addition, the impact device 8 can be an impact device according to the solution disclosed in this document and can therefore include the disclosed valve cylinder block.

[0044] Figure 2 Discloses a hydraulic breaker 12 which is mounted on a boom 13 of an excavator 14 and is connected to the hydraulic system HS of the excavator 14. The breaker 12 includes a hydraulic impact device 8 for generating an impact pulse on a breaking tool 15 which can be connected to the breaker 1. The breaking tool 15 can be moved in an impact direction A and a return direction B during rock breaking. The impact device 8 can be an impact device according to the solution disclosed in this document and can therefore include the disclosed valve cylinder block.

[0045] Figure 3 Discloses a rock drill 4 which includes a body 10, an impact device 8, a rotation device 9, a flushing housing 16, an open space 17 for receiving a shank adapter, and a gear housing 18. The flushing housing 16 and the gear housing 18 are located at the front end Fe of the body 10, while the impact device 8 is located at the rear end Re. The shank adapter can be mounted in the open space 17 and its rear end can be connected to a rotating element at the gear housing 18 such that the shank adapter and the rock drilling tool which can be connected to the shank adapter can be rotated by the rotation device 9. Flushing fluid can be fed via the flushing housing 16 to an axial flushing channel of the shank adapter and further to the rock drilling tool.

[0046] The impact device 8 includes an impact piston 19 which is arranged to move in a reciprocating manner in the impact direction A and in the return direction B. The front end of the impact piston 19 is an impact surface 20 which is configured to impact the shank adapter. The impact device 8 includes an impact cylinder 21 which is axially arranged in the rear part Re2 of the central space 22 of the main body 10. The impact cylinder 21 includes a valve cylinder body 23 through which the impact piston 19 passes. The impact device 8 includes a working pressure space 24 which has hydraulic pressure fluid for moving the impact piston 19 in the opposite direction B. There is a control pressure space 25 at the rear end Re2 of the valve cylinder body 23. The control pressure space 25 has a sleeve-shaped control valve 26 for controlling the hydraulic pressure acting at the control pressure space 25 and thus for controlling the reciprocating movement of the impact piston 19. The pressure in the control valve space 25 causes the impact piston 19 to move in the impact direction because the working pressure area of the impact piston in the impact direction A is larger than the working pressure area at the working pressure space 24 or the impact piston, and affects it in the return direction B. In the working pressure space 24, a continuous high pressure can exist during operation, while in the control pressure space 25, the magnitude of the pressure can be changed by the control valve 26 so that the impact piston 19 performs a reciprocating movement. In addition, the valve cylinder body 23 has a pilot pressure space 27 for providing a pressure pulse in response to the movement of the impact piston 19 in the impact direction A. The valve cylinder body 23 further has a number of axial fluid channels 28 for connecting the pilot pressure space 27 and the control pressure space 25. The pressure pulse generated in the pilot pressure space 27 affects the control surface of the control valve 26 and causes it to change its control position.

[0047] At the front part Fe2 of the control pressure space 25, the control pressure space 25 has an inner radial groove 29. The bottom of the radial groove 29 has one or more transverse fluid channels 30 which provide a fluid connection between the groove 29 and the pressure port 31. The purpose of the radial groove 29 is to provide an enlarged space at the transverse fluid channels 30 and thus to prevent hydraulic cavitation when the control valve 26 performs control measures.

[0048] Figure 3 The impact device 8 disclosed in can also be used in a rock breaker. Then, there is no rotating device, gear housing, flushing housing and shank adapter. The impact piston can be arranged to impact the impact surface of the breaking tool.

[0049] Figure 4The valve cylinder body 23 of the impact cylinder is disclosed. The valve cylinder body 23 is an elongate member having a central axis Ca and includes a central opening 32 extending from the front end Fe2 to the rear end Re2 of the elongate valve cylinder body 23. The impact piston can be mounted through the central opening 32. There are two pressure spaces 25, 27 which are defined by the radial surface of the central opening 32 and are located at a certain axial distance from each other. A number of axial pressure fluid channels 28 connect the pressure spaces 25, 27. The control pressure space 25 is located at the rear end portion Re2 of the valve cylinder body 23 and is configured to receive a sleeve-shaped control valve. The control pressure space 25 has an inner radial groove 29 which includes a bottom surface 33 that defines the radial extension of the groove 29 relative to the central opening 32 adjacent to the groove 29. The axial pressure fluid channels 28 pass through the radial groove 29 without being fluidly connected to the groove 29. Further, the cross-sectional shape of the bottom of the radial groove 29 is non-rotationally symmetric and includes a plurality of surfaces at a number of different distances from the central axis. However, this cannot be seen in Figure 4 the cross-section, but is shown in Figure 5 . The groove 29 is fluidly connected to the outer surface of the valve cylinder body 23 through one or more transverse fluid channels 30.

[0050] Figure 5 The shape of the bottom surface 33 of the groove 29 is disclosed. It can be seen that the bottom surface 33 includes a number of curved surfaces having different radii R1, R2 and R3. The axial fluid channels 28 are evenly spaced around the central opening 32 in the cross-section at the radial groove 29, whereby there is an intermediate section 34 between the axial fluid channels 28. The groove 29 has its minimum radial dimension at the portion 35 of the axial fluid channel 28 and has its maximum radial dimension at the intermediate section 34. The radial dimension of the groove 29 at the intermediate section continuously decreases from the middle towards the section 35 having the axial fluid channel 28, whereby the shape of the bottom 33 is curved at the intermediate section 34. The number of axial fluid channels 28 can be three, and the shape of the bottom 33 of the groove 29 at the intermediate section 34 can be arcuate. Due to the shape of the bottom 33 of the groove 29, the thickness Wt1 of the cylinder wall of the valve cylinder body 23 at the groove 29 is greater than the thickness Wt2 of the cylinder wall at the intermediate section 34.

[0051] The enlarged volume of the disclosed groove and the shape of the bottom of the groove can also be implemented in a solution having only one axial fluid channel, and further, when there are a number of axial fluid channels unevenly spaced in the open space around the valve cylinder body.

[0052] The drawings and the related description are only intended to illustrate the idea of the present invention. In terms of the details of the present invention, the present invention can vary within the scope of the claims.

Claims

1. A valve cylinder block (23) for a hydraulic impact device (8) of a rock-breaking device (4, 12), wherein the valve cylinder block (23) is an elongate member having a central axis (Ca) and includes: a central opening (32) that extends from a front end (Fe2) to a rear end (Re2) of the valve cylinder block (23), and through which an impact piston (19) can be mounted; at least two pressure spaces (25, 27) defined by a radial surface of the central opening (32) and located at an axial distance from each other; a plurality of axial pressure fluid channels (28) connecting the pressure spaces (25, 27); and wherein one of the pressure spaces (25, 27) is a control pressure space (25) located at the rear end (Re2) of the valve cylinder block (23) and configured to receive a sleeve-shaped control valve (26); and wherein the control pressure space (25) has an inner radial groove (29) that includes a bottom surface (33), and the bottom surface (33) defines a radial extension of the inner radial groove (29) relative to the central opening (32) adjacent to the inner radial groove (29); furthermore, the axial pressure fluid channels (28) pass through the inner radial groove (29) without being fluidly connected to the inner radial groove (29); characterized in that the inner radial groove (29) has a minimum radial dimension at a portion of the axial pressure fluid channels (28) and a maximum radial dimension at an intermediate section (34) located between the axial pressure fluid channels (28), whereby the size of the inner radial groove (29) is increased when compared to a simple groove having a circular bottom surface corresponding to the minimum radial dimension at the portion.

2. The valve cylinder block according to claim 1, characterized in that the bottom surface (33) of the inner radial groove (29) includes a plurality of curved surfaces.

3. The valve cylinder block according to claim 1 or 2, characterized in that: the number of the axial pressure fluid channels (28) is three.

4. The valve cylinder block according to any one of claims 1-2, characterized in that: the inner radial groove (29) is made by a milling technique.

5. The valve cylinder block according to any one of claims 1 to 2, characterized in that the inner radial groove (29) is located at a front end portion (Re2) of the control pressure space (25).

6. The valve cylinder block according to any one of claims 1-2, characterized in that the bottom surface (33) of the inner radial groove (29) has at least one lateral fluid channel (30) that provides a fluid connection between the inner radial groove (29) and an outer surface of the valve cylinder block (23).

7. The valve cylinder block according to any one of claims 1 to 2, characterized in that The axial pressure fluid passage (28) is spaced around the central opening (32), whereby a cross-section of the valve cylinder body (23) includes a plurality of fluid passage sections (35) and intermediate sections (34) therebetween; The bottom surface (33) of the inner radial groove (29) has a plurality of transverse fluid passages (30) at each intermediate section (34); and Compared with the fluid passage sections (35), the thickness (Wt1, Wt2) of the cylinder wall of the valve cylinder body (23) at the inner radial groove (29) is smaller at the intermediate sections (34).

8. An impact device (8) of a rock-breaking device (4, 12), comprising: A main body (10) having a central space; An impact cylinder (21) axially arranged in a rear portion of the central space and including a valve cylinder body (23); An impact piston (19) passing through the impact cylinder (21) and capable of moving in an impact direction (A) towards the front end (Fe) of the impact device (8) and in an opposite direction (B) towards the rear end (Re) of the impact device (8); A working pressure space (24) having hydraulic pressure fluid for moving the impact piston (19) in the opposite direction (B); A control pressure space (25) located at the rear end (Re2) of the valve cylinder body (23) and having a sleeve-shaped control valve (26) for controlling the hydraulic pressure acting on the control pressure space (25) and thereby controlling the reciprocating movement of the impact piston (19); And wherein the valve cylinder body (23) has a pilot pressure space (27) for providing a pressure pulse in response to the movement of the impact piston (19) in the impact direction (A); And wherein the valve cylinder body (23) further has a plurality of axial pressure fluid passages (28) for connecting the pilot pressure space (27) and the control pressure space (25); Characterized in that The valve cylinder body (23) of the impact device (8) is the valve cylinder body (23) according to any one of claims 1-7.

9. A method for preventing cavitation in a hydraulic impact device (8) of a rock-breaking equipment (4, 12); Among them, The hydraulic impact device (8) is the impact device (8) according to claim 8, and the method includes: Increasing the volume of the hydraulic space between the inner surface of the control pressure space (25) of the impact device (8) and the outer surface of the sleeve-shaped control valve (26) installed in the control pressure space (25) in a reciprocating manner; And an inner radial groove (29) is provided in the inner surface of the control pressure space (25) at a cross-section where a number of transverse fluid channels (30) are arranged, the transverse fluid channels (30) providing a fluid connection between the inner radial groove (29) and the outer surface of the valve cylinder block (23) and being used for feeding hydraulic pressure fluid to and from the control pressure space (25); Characterized in that it comprises, By shaping the bottom surface (33) of the inner radial groove (29) to expand towards the outer surface of the impact device (8) at the transverse fluid channels (30) to increase the volume, such that the inner radial groove (29) has a minimum radial dimension at a portion of the axial pressure fluid channel (28) and a maximum radial dimension at an intermediate section (34) located between the axial pressure fluid channels (28), whereby the shape of the bottom line of the inner radial groove (29) deviates from a circle, and whereby the size of the inner radial groove (29) is increased as compared to a simple groove having a circular bottom surface corresponding to the minimum radial dimension at the portion.

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