Rock Breaking Tools

Abstract

1. A rock breaking tool comprising: a tool head (4) supported by a guide means (2) so as to be linearly displaceable relative to the guide means between a retracted position and an extended position, the tool head (4) having a distal end extending from the guide means so as to engage a surface to be fractured when the tool head is in its extended position; drive means (5, 18, 20) configured to drive the tool head towards its retracted position in a first movement and to drive the tool head towards its extended position in a second movement, the drive means comprising a drive part attached to the guide means (5, 20) and a driven part (18) attached to the tool head and engaged by the drive part so as to be linearly displaceable relative to the guide means when the drive part of the drive means is operated; and a controller configured to control the operation of the drive means.

Description

[Technical field]

[0001] The present invention relates to a rock breaking tool, and in particular to an improved design of a rock breaking tool, which may be electrically powered. [Background technology]

[0002] Rock breaking tools are typically used as attachments for excavators when the objective is to break rocks, concrete or any other relatively hard material. Tools for such applications typically have a striking device configured to apply an impact to the tool head and thereby transmit such impact to the material to be broken. The striking device typically has a pneumatically or hydraulically driven striking piston that reciprocates and strikes an impact surface at the top end of the tool head. At the same time that an impact is applied by the striking piston, the tool head is pressed against the material to be broken and the tip of the tool head penetrates the material to be broken under the influence of the striking device.

[0003] Typically, such rock breaking tools are used in an upright position with the tool head extending from the lower end of the tool. The rapid reciprocating motion of the impact device relative to the tool head not only breaks the rock, but also creates substantial vibration forces that are transmitted to the excavator or other work machine to which the rock breaking tool is attached, leading to rapid wear of both the tool and its supporting structure and possible injury to the operator. Such rock breaking tools tend to be heavy because they must withstand the vibration forces generated during use of the tool. Furthermore, the use of pneumatically or hydraulically powered impact devices also requires a supply of pressurized fluid along with associated piping and fittings that are prone to leaks. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE PRESENT EMBODIMENT It is an object of the present invention to provide a rock breaking tool which overcomes the above mentioned problems associated with the prior art. [Means for solving the problem]

[0005] According to the present invention there is provided a rock breaking tool comprising: a tool head supported by a guide means so as to be linearly displaceable relative to the guide means between a retracted position and an extended position, a distal end of the tool head extending from said guide means so as to engage a surface to be fractured when the tool head is in its extended position; drive means configured to drive the tool head towards its retracted position in a first movement and to drive the tool head towards its extended position in a second movement, the drive means comprising a drive part attached to the guide means and a driven part attached to the tool head and engaged by said drive part so as to be linearly displaceable relative to the guide means upon operation of the drive part of the drive means; and a controller configured to control operation of the drive means.

[0006] Preferably, the drive means is electrically powered, more preferably the drive means comprises an electric motor.

[0007] In a preferred embodiment, the driven part of the drive means is decoupled from the drive part of the drive means during said second movement, before the tool head reaches its extended position.

[0008] The guide means may be configured, in use, to extend from a lower end of the guide means when the tool head is in its extended position and arranged such that the tool head is displaceable between its extended and retracted positions along a vertical axis.

[0009] The guide means may be configured to be attached to the arm of an excavator.

[0010] The guide means may comprise a hollow tubular body within which the tool head is axially slidable, the distal end of the tool head extending through a hole in the end of the guide means when in its extended position.

[0011] In one embodiment, the drive means may comprise a first rack mounted on the tool head, said drive portion of the drive means comprising a first motor driven pinion mounted on the guide means to be driven by a drive motor and configured to drivingly engage a first rack of the driven portion upon rotation of the pinion to displace the tool head relative to the guide means. The drive motor may comprise an electric motor operating under control of the controller. The first rack may be positioned on the tool head such that as the tool head approaches its extended position, the first pinion disengages from one end of the first rack, thereby decoupling the drive portion of the drive means from the driven portion of the drive means.

[0012] The drive means may further comprise a second rack mounted to the tool head and a second motor driven pinion mounted to the guide means and configured to be driven by the drive motor upon rotation of the second pinion in a first direction to drivingly engage the second rack to displace the tool head between its extended and retracted positions, the second pinion incorporating a clutch configured to decouple the pinion from the drive motor upon rotation of the second pinion in a second direction opposite to the first direction. The first and second pinions may be mounted coaxially on an output shaft of the drive motor, the first and second racks being mounted side by side and parallel to one another on one side of the tool head.

[0013] In the alternative, the first pinion may incorporate a clutch under control of said controller, whereby said clutch may be configured to disengage the first pinion from the electric motor before the tool head reaches its extended position. It is envisaged that other types of drive means may be provided for moving the tool head between its retracted and extended positions while decoupling a driven portion of the drive means from a drive portion as the tool head approaches its extended position.

[0014] Preferably, the distal end of the tool head terminates in a tip, which may be separable from the remainder of the tool head to allow replacement and / or exchange of the tip.

[0015] The guiding means may include shock absorbing means acted upon by the tool head when it reaches its extended position.

[0016] A tool according to an embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of a tool according to an embodiment of the present invention with the tool head in a retracted or raised position; [Diagram 2] FIG. 2 is a longitudinal cross-sectional view of the tool of FIG. 1 with the tool head in its extended position. [Diagram 3] FIG. 2 is a perspective cross-sectional view of the tool of FIG. 1; [Figure 4] FIG. 2 is a perspective view of the tool of FIG. 1 with the tool head removed. [Diagram 5] FIG. 2 is a detailed view of the lower end of the guide tube of the tool of FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] As shown in the drawings, a tool for crushing rock or other relatively hard material according to the present invention comprises an elongated hollow guide tube 2 in which a tool head 4, driven by a drive means (more preferably an electric drive means such as an electric motor 5), is coaxially mounted so as to be slidably movable along the length of the guide tube 2 between a raised or retracted position shown in FIG. 1 and an extended position shown in FIG. 2.

[0019] In the illustrated embodiment, the guide tube 2 is configured to be mounted to the distal end of the excavator arm and supported in a substantially vertical orientation via a suitable coupling, however, it is envisaged that the tool may be configured to be mounted to any other type of support arrangement or device or may comprise part of a particular rock breaking vehicle or apparatus.

[0020] The tool head 4 comprises a body portion 6 slidably mounted within the guide tube 2 and an elongated tool member 8 of the tool head 4 extending from a lower end of the body portion 6 and terminating in a rock breaking tip 10. When the tool head 4 is in its extended position, the elongated tool member 8 of the tool head 4 extends from the lower end of the guide tube 2 and through an opening 12 in an end cap 14 of the guide tube 2. In a preferred embodiment, at least the tip 10 of the tool member 8 is removable from the remainder of the tool head 4 to facilitate replacement of the tip 10 when worn or to accommodate the material to be crushed.

[0021] The guide tube 2 may comprise a hollow post of square cross section, and a body portion 6 of the tool head 4 is slidably mounted within the guide tube 2. The body portion 6 of the tool head 4 is supported and guided for axial movement within the guide tube 2 via rollers 16 mounted on the side walls of the guide tube 2, allowing the tool head 4 to slide freely within the guide tube 2 between its retracted and extended positions. The rollers 16 may be spring biased against the inner walls of the guide tube 2.

[0022] In the embodiment shown in the drawings, as will be explained in more detail below, the driven part of the drive means comprises a first toothed rack 18 mounted on at least one side of the body portion 6 of the tool head 4, and the drive part of the drive means comprises a first pinion 20 mounted on the output shaft of the electric motor 5 mounted on the guide tube 2, such that the first pinion 20 is in driving engagement with the first toothed rack 18 and the first pinion 20 is fixed to the output shaft of the electric motor 5, such that the motor 5, under the control of the controller, is configured to rotate the first pinion 20 and thereby axially displace and rapidly accelerate the tool head 4 within the guide tube 2 from its retracted position towards its extended position.

[0023] An upper end of the first toothed track 18 terminates at a position spaced from an upper end of the body portion 6 of the tool head 4 such that the first pinion 20 disengages from the first toothed rack 18 as the tool head 4 approaches its extended position, thereby decoupling the tool head 4 from the drive means before the tool head 4 reaches its extended position, such that the tool head 4 is decoupled from the drive means before the tip 10 of the tool member 8 impacts with the surface of the rock to be crushed. Preferably, the first toothed rack 20 and the first pinion 18 are arranged such that the first pinion 18 disengages from the first toothed rack 20 when the tip 10 of the tool member 8 passes through the opening in the end cap 14 of the guide tube 2.

[0024] A second toothed rack 22 is mounted on said at least one side of the body portion 6 of the tool head 4 in parallel alignment with the first toothed rack 18, and a second pinion 24 is engaged with the first pinion 24 such that the second pinion 24 is in driving engagement with the second toothed rack 22. 18 4 and 5. The rotor 1 is attached to the output shaft of the motor 5 so as to be coaxially aligned with the rotor 1.

[0025] The second toothed rack extends substantially the entire length of the tool head 4 and the second pinion 24 remains engaged with the second toothed rack 22 throughout the entire range of movement of the tool head 4 between the retracted and extended positions.

[0026] The second pinion 24 is preferably attached to the motor output shaft via a one-way coupling, such as a sprag or cam clutch, and is configured to transmit rotational motion in only one direction between the motor output shaft and the second pinion 24, particularly when the motor 5 operates to raise or retract the tool head 4 within the guide tube 2 between its extended and retracted positions.

[0027] Other types of drive means for driving the tool head 4 between its retracted and extended positions are envisioned, such as a chain and wheel, a toothed belt and wheel, a recirculating ball screw, or any other linear drive. Additionally, the drive means may comprise non-mechanical drives, such as a magnetic rail motor (multiple coil pole pieces in the form of a linear motor) or a solenoid. All of these technologies may be considered for scaling the technology for larger or smaller impact energies.

[0028] As best seen in FIG. 5, a shock absorbing bumper 26 is attached to the lower end of the guide tube 2 to absorb any shock between the tool head 4 and the end cap 14 of the guide tube 2 if the tool head 4 reaches its fully extended position before the tool member 8 strikes the surface to be fractured, thereby avoiding damage to the tool.

[0029] In a first stage of operation, the controller operates the electric motor 5 to drive the second pinion 24 along the second rack 22, thereby raising the tool head 4 above the guide tube 2 until it is in its fully retracted or raised position adjacent the upper end of the guide tube 2.

[0030] In a second stage, the controller operates the electric motor 5 to drive the first pinion 18 along the first rack 20 (the second pinion 22 rotates freely on the output shaft of the motor 5 due to the one-way coupling between the second pinion 22 and the output shaft), thereby rapidly accelerating the tool head 4 towards its extended position.

[0031] During said second phase of operation, the tool head 4 continues to be accelerated in a downward direction until a point is reached where the first pinion 20 disengages from the upper end of the first rack 18, thereby decoupling the tool head 4 from the drive means. The tool head 4 continues to move on its downward trajectory towards its extended position due to inertia and under the influence of gravity, until the tip 10 of the tool member 8 impacts the surface to be fractured.

[0032] When the tool head 4 reaches its fully extended position, the body portion 6 of the tool head 4 engages the end cap 14 and the shock absorbing bumper 26 at the lower end of the guide tube 2 prevents damage to the tool due to a collision between the tool head 4 and the end cap 14 of the guide tube 2.

[0033] The cycle then repeats.

[0034] The controller may comprise a microprocessor programmed to precisely control the operation of the electric motor to precisely control the movement of the tool head, thereby optimizing the rock breaking action of the tool head while minimizing the transmission of vibrations and shocks to the components of the tool and its supporting structure, and allowing the weight and size of the rock breaking tool to be significantly reduced compared to prior art devices. The use of electrical power to operate the drive means avoids the problems associated with the use of pneumatic or hydraulic drives and allows the rock breaking tool to be used in a wide variety of different applications.

[0035] The invention is not limited to the embodiments described herein, which can be amended or modified without departing from the scope of the invention as defined by the appended claims.

Claims

1. A tool for crushing rocks, said tool comprising: a tool head (4) supported by the guide means (2) so as to be linearly displaceable relative to the guide means (2) between a retracted position and an extended position, a distal end (10) of the tool head (4) extending from the guide means (2) for engaging a surface to be fractured when the tool head (4) is in its extended position; a drive means configured to drive the tool head (4) towards its retracted position in a first movement and to drive the tool head (4) towards its extended position in a second movement, the drive means comprising a drive part attached to the guiding means and a driven part attached to the tool head and engaged by the drive part so as to be linearly displaceable relative to the guiding means upon movement of the drive part of the drive means, the drive means being motorized, the driven part of the drive means being decoupled from the drive part of the drive means during the second movement as the tool head (4) approaches its extended position; a controller configured to control operation of said drive means; A tool that is equipped with:

2. 2. A tool as claimed in claim 1, wherein the guide means (2) is configured such that, in use, when the tool head (4) is in its extended position, the guide means (2) extends from a lower end thereof, the tool head being arranged to be displaceable between its extended and retracted positions along a vertical axis.

3. The tool of claim 2 , wherein the guide means is configured to be attached to an arm of an excavator.

4. The tool according to any one of claims 1 to 3, wherein the guide means (2) comprises a hollow tubular body within which the tool head (4) is axially slidable, the distal end (10) of the tool head (4) extending through a hole (12) in the end (14) of the guide means (2) when in its extended position.

5. The tool according to any one of claims 1 to 4, wherein the drive means comprises a first rack (18) attached to the tool head (4), and the drive part of the drive means comprises a first motor driven pinion (20) attached to the guiding means (2) to be driven by an electric drive motor (5), the first motor driven pinion (20) being configured to drivingly engage with a first rack (18) of the driven part upon rotation of the first motor driven pinion (20) to displace the tool head (4) relative to the guiding means.

6. 6. The tool of claim 5, wherein the first rack (18) is positioned on the tool head (4) such that as the tool head (4) approaches its extended position, the first motor drive pinion (20) disengages from one end of the first rack (18), thereby decoupling a driving portion of the drive means from a driven portion of the drive means.

7. 7. The tool according to claim 5 or 6, wherein the drive means further comprises a second rack (22) mounted on the tool head (4) and a second motor driven pinion (24) mounted on the guiding means (2), the second motor driven pinion (24) configured to be driven by the electric drive motor (5) upon rotation of the second motor driven pinion (24) in a first direction and in driving engagement with the second rack (22) to displace the tool head (4) between its extended and retracted positions, the second motor driven pinion (24) incorporating a clutch configured to decouple the second motor driven pinion (24) from the electric drive motor (5) upon rotation of the second motor driven pinion (24) in a second direction opposite to the first direction.

8. 8. The tool of claim 7, wherein the first motor drive pinion (18) and the second motor drive pinion (24) are coaxially mounted on an output shaft of the electric drive motor (5), and the first rack (20) and the second rack (22) are mounted side by side and parallel to each other on one side of the tool head (4).

9. A tool as described in claim 5, wherein the first motor drive pinion (18) incorporates a clutch under the control of the controller, whereby the clutch is configured to decouple the first motor drive pinion (18) from the electric drive motor (5) before the tool head reaches its extended position.

10. A tool according to any one of the preceding claims, wherein the distal end of the tool head (4) terminates in a tip (10).

11. The tool of claim 10, wherein the tip (10) is separable from the remainder of the tool head (4) to allow replacement and / or exchange of the tip (10).

12. Tool according to any one of the preceding claims, wherein the guiding means (2) comprise shock absorbing means (26) acted upon by the tool head (4) when the tool head (4) reaches its extended position.

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