ROCK BREAKER TOOL

Abstract

A rock-breaking tool comprising a tool head (4) supported by a guide means (2) that can be linearly displaced with respect to the guide means, between a retracted position and an extended position, a distal end of said tool head extending from said guide means to engage a surface to be broken when the tool head is in its extended position;a drive means (5, 18, 20) adapted to drive said tool head to its retracted position in a first operation and to drive the tool head to its extended position in a second operation, wherein said drive means includes a drive portion mounted on said guide means (5, 20) and a driven portion (18) mounted on the tool head and coupled by said drive portion which is linearly movable with respect to the guide means when operating the drive portion of the drive means; and a controller adapted to control the operation of the drive means.

Description

ROCK BREAKER TOOL FIELD OF INVENTION This invention relates to a rock-breaking tool and, in particular, to an improved rock-breaking tool that can be powered by electricity. BACKGROUND OF THE INVENTION Rock-breaking tools are typically used as attachments for excavators when the goal is to break rocks, concrete, or other relatively hard materials. Such tools usually have a percussion mechanism designed to deliver impacts to a tool head, thereby transmitting those impacts to the material being broken. The percussion mechanism typically consists of a pneumatically or hydraulically driven percussion piston that reciprocates and strikes an impact surface at the top of the tool head. As the percussion piston delivers impacts, the tool head presses against the material to be broken, and the tip of the tool head penetrates the material under the influence of the percussion mechanism. Typically, such rock-breaking tools are used in a vertical orientation, with the tool head extending from the lower end of the tool. The rapid reciprocating action of the percussion device against the tool head creates considerable vibratory forces that, in addition to breaking rocks, are transmitted to the excavator or other work machine to which the rock-breaking tool is attached. This leads to rapid wear of both the tool and its support structure, and can even cause injury to the operator. Such rock-breaking tools tend to be heavy due to the need to withstand the vibratory forces generated during use. Furthermore, the use of a pneumatically or hydraulically driven percussion device also requires a pressurized fluid supply with associated piping and fittings that are prone to leaks. An objective of the present invention is to provide a rock-breaking tool that overcomes the aforementioned problems of the prior art. RACann / zznz / E / YiAi SUMMARY OF THE INVENTION According to the present invention, a rock-breaking tool is provided comprising a tool head supported by a guide means that can be linearly displaced with respect to the guide means, between a retracted position and an extended position, a distal end of said tool head extending from said guide means to engage a surface to be broken when the tool head is in its extended position;a drive means adapted for driving said tool head to its retracted position in a first operation and for driving the tool head to its extended position in a second operation, wherein said drive means includes a drive portion mounted on said guide means and a driven portion mounted on the tool head and coupled by said drive portion which can be linearly displaced with respect to the guide means when operating the drive portion of the drive means; and a controller adapted for controlling the operation of the drive means. Preferably, the drive means is electrically powered. More preferably, the drive means includes an electric motor. In a preferred embodiment, the driven part of the drive means is decoupled from the drive part of the drive means during said second operation before the tool head reaches its extended position. The guide means may be adapted to be arranged, in use, so that said tool head extends from a lower end of said guide means when in its extended position, wherein the tool head can be moved between its extended and retracted positions along a vertical axis. The guide device can be adapted to be mounted on an excavator arm. The guide means may comprise a hollow tubular body within which the tool head can be axially slid, the distal end of the tool head extending through a hole at one end of the guide means when in its extended position. In one embodiment, the drive means may comprise a first rack mounted on the tool head, where said drive portion of the drive means RACAnna / zznz / E / GALA comprises a first motor-driven pinion mounted on the guide means to be driven by a drive motor and adapted to engage by drive with the first rack of the driven portion to displace the tool head relative to said guide means by rotation of the pinion. Preferably, said drive motor comprises an electric motor operated by control of said controller. The first rack may be arranged on the tool head such that the first pinion disengages from one end of the first rack when the tool head approaches its extended position, thereby disengaging the drive portion from the driven portion of the drive means. The drive means may further comprise a second rack mounted on the tool head and a second motor-driven pinion mounted on the guide means and adapted to be driven by said drive motor and to engage the second rack by means of a drive, thereby moving said tool head between its extended and retracted positions by rotating the second pinion in a first direction, wherein the second pinion incorporates a clutch adapted to disengage the pinion from the drive motor by rotating the second pinion in a second direction, opposite to said first direction. The first and second pinions may be mounted coaxially on an output shaft of the drive motor, wherein said first and second racks are mounted side by side and parallel to each other on one side of the tool head. In an alternative embodiment, the first pinion may incorporate a clutch controlled by the controller, and this clutch may be adapted to disengage the first pinion from the electric motor before the tool head reaches its extended position. It is anticipated that other drive means may be provided to move the tool head between its retracted and extended positions while disengaging the driven portion of the drive means as the tool head approaches its extended position. Preferably, the distal end of the tool head terminates in a point. The point can be separated from the rest of the tool head to allow for replacement and / or changing of the point. The guide means may include damping means on which the tool head acts when it reaches its extended position. RACann / zznz / E / YiAi BRIEF DESCRIPTION OF THE FIGURES The following describes a tool according to one embodiment of the present invention, by way of example only, with reference to the accompanying figures, in which: Figure 1 is a perspective view of a tool according to an embodiment of the present invention with the tool head in its retracted or raised position; Figure 2 is a cross-sectional view of the tool in Figure 1 with the tool head in its extended position; Figure 3 is a side perspective view of the tool in Figure 1; Figure 4 is a perspective view of the tool in Figure 1 with the tool head removed; and Figure 5 is a close-up view of the lower end of the guide tube of the tool in Figure 1. DETAILED DESCRIPTION OF THE FIGURES As illustrated in the figures, a tool for breaking rocks or any other relatively hard material according to the present invention comprises an elongated hollow guide tube 2 having coaxially mounted a tool head 4 driven by a drive means, more preferably an electric drive means, such as an electric motor 5, which can be slidably moved along the guide tube 2 between a raised or retracted position, shown in Figure 1, and a lower or extended position, shown in Figure 2. In the embodiment shown, the guide tube 2 is adapted for mounting on the distal end of an excavator arm, which is supported in a substantially vertical orientation via a suitable coupling. However, it is envisaged that the tool can be adapted for mounting on any other type of support arrangement or device, or may form part of a vehicle or device specifically designed for rock breaking. RACann / zznz / E / YiAi The tool head 4 comprises a body portion 6 slidably mounted within the guide tube 2 and an elongated tool element 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 element 8 of the tool head 4 extends from a lower end of the guide tube 2 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 element 8 can be separated from the rest of the tool head 4 to facilitate replacement of the tip 10 when it becomes worn or when the tip 10 is changed to suit the material to be broken. The guide tube 2 may comprise a hollow column with a square cross-section, wherein the 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 by 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-loaded against the inner walls of the guide tube 2. In the embodiment shown in the figures, a driven portion 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, a drive portion of the drive means comprising a first pinion 20 mounted on an output shaft of an electric motor 5 mounted in the guide tube 2, such that the first pinion 20 is driven to the first toothed rack 18, wherein the first pinion 20 is fixed to the output shaft of the electric motor 5, the motor 5 being adapted to operate, under the control of a controller, 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 to its extended position, as will be described in more detail below. An upper end of the first toothed rack 18 terminates in a position separate from the upper end of the body part 6 of the tool head 4 such that the first pinion 20 disengages from the first toothed rack 18 when the tool head 4 approaches its extended position, thereby disengaging the tool head 4 from the drive means when the tool head 4 before the tool head 4 RACANN / zznz / E / GALA reaches its extended position, so that the tool head 4 disengages from the drive means before the tip 10 of the tool element 8 impacts the surface of the rock to be broken. Preferably, the first toothed rack 20 and the first pinion 18 are arranged so that the first pinion 18 disengages from the first toothed rack 20 when the tip 10 of the tool element 8 passes through the opening in the end cap 14 of the guide tube 2. A second toothed rack 22 is mounted on at least one side of the body part 6 of the tool head 4, parallel and adjacent to the first toothed rack 18, where a second pinion 24 is mounted on the motor output shaft 5, coaxially and along the first pinion 24, so that the second pinion 24 is driven and coupled with the second toothed rack 22. The second toothed rack extends considerably along the entire length of the tool head 4 so that the second pinion 24 remains engaged with the second toothed rack 22 throughout the entire range of motion of the tool head 4 between its retracted and extended positions. The second pinion 24 is preferably mounted on the motor output shaft via a one-way coupling, such as a cam or wedge clutch, adapted to transmit rotary motion between the motor output shaft and the second pinion 24 in one direction only, specifically when the motor 5 is operating to raise or retract the tool head 4 within the guide tube 2 between its extended and retracted positions. Other drive systems are considered for moving the tool head 4 between its retracted and extended positions, such as a chain and wheel, toothed belt and wheel, recirculating ball screw, or any other linear drive. Additionally, the drive systems could include non-mechanical drives, such as a magnetic rail motor (a multiplicity of pole pieces of coils in the form of a linear motor) or a solenoid. All these technologies can be considered for scaling up to different impact energies. As best shown in Figure 5, the shock absorbers 26 can be mounted on a lower end of the guide tube 2 to absorb any impact between the tool head 4 and the end cap 14 of the guide tube 2 in case the tool head 4 reaches its AACAnn / zznz / E / YiAi fully extended position before tool element 8 strikes the surface to be broken, thus avoiding damage to the tool. 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 up the guide tube 2 until the tool head 4 is in the fully retracted or raised position, adjacent to an upper end of the guide tube 2. In a second stage, the controller operates the electric motor 5 to drive the first pinion 18 along the first rack 20 (where the second pinion 22 is free to rotate about the output shaft of the motor 5 due to the one-way coupling between the second pinion 22 and the output shaft), thus rapidly accelerating the tool head 4 towards its extended position. During this second stage of operation, the tool head 4 continues to be accelerated downwards until it reaches a point where the first pinion 20 disengages from the upper end of the first rack 18, thus disengaging the tool head 4 from the drive mechanism. The tool head 4 continues its downward trajectory, due to inertia and gravity, towards its extended position until the tip 10 of the tool element 8 impacts a surface that will break. If the tool head 4 reaches its fully extended position, the body part 6 of the tool head 4 engages with the end cap 14 and the shock absorbers 26 provided at the lower end of the guide tube 2 prevent the tool from being damaged due to the impact of the tool head 4 with the end cap 14 of the guide tube 2. Then the cycle repeats. The controller may comprise a microprocessor programmed to precisely control the operation of the electric motor, thereby precisely controlling the movement of the tool head. This optimizes the rock-breaking action of the tool head while minimizing vibration and the transmission of impact forces to the tool components and its support structure. This allows the weight and size of the rock-breaking tool to be significantly reduced compared to prior art devices. Using electrical power to operate the drive system avoids the problems associated with pneumatic or hydraulic drives and allows the tool to operate efficiently. RACann / zznz / E / YiAi for breaking rocks is used in a wide variety of different applications. The invention is not limited to the modality described herein, but may be amended or modified without departing from the scope of the present invention as defined in the appended claims.

Claims

1. A rock-breaking tool comprising a tool head supported by a guide means that is linearly movable with respect to the guide means between a retracted position and an extended position, a distal end of said tool head extending from said guide means to engage a surface to be broken when the tool head is in its extended position; a drive means adapted to drive said tool head to its retracted position in a first operation and to drive the tool head to its extended position in a second operation, wherein said drive means includes a drive portion mounted on said guide means and a driven portion mounted on the tool head and engaged by said drive portion that is linearly movable with respect to the guide means when the drive portion of the drive means is operated;and an adapted controller to control the operation of the drive system.

2. A tool as claimed in claim 1, wherein said drive means is powered by electricity.

3. A tool as claimed in claim 1 or claim 2, wherein the driven part of the drive means is disengaged from the drive part of the drive means during said second operation before the tool head reaches its extended position.

4. A tool as claimed in any of the preceding claims, wherein the guide means is adapted to be arranged, in use, so that said tool head extends from a lower end of said guide means when in its extended position, wherein the tool head can be moved between its extended and retracted positions along a vertical axis.

5. A tool as claimed in claim 4, wherein the guide means is adapted to be mounted on an arm of an excavator.

6. A tool as claimed in any of the preceding claims, wherein said guide means comprises a hollow tubular body within which said tool head can be axially slid, said distal end of the tool head extending through a hole in one end of the guide means when in its extended position.

7. A tool as claimed in any of the preceding claims, wherein the drive means comprises a first rack mounted on the tool head, wherein said drive portion of the drive means comprises a first motor-driven pinion mounted on the guide means to be driven by a drive motor and adapted to engage by drive with the first rack of the driven portion to displace the tool head relative to said guide means by rotating the pinion.

8. A tool as claimed in claim 7, wherein said drive motor comprises an electric motor that controls said controller.

9. A tool as claimed in claim 7 or claim 8, wherein the first rack can be arranged in the tool head such that the first pinion disengages from one end of the first rack when the tool head approaches its extended position, thereby disengaging the drive portion of the drive means from the driven portion of the drive means.

10. A tool as claimed in any of claims 7 to 9, wherein said drive means further comprises a second rack mounted on the tool head and a second motor-driven pinion mounted on the guide means and adapted to be driven by said drive motor and to engage the second rack by means of moving said tool head between its extended and retracted positions by rotating the second pinion in a first direction, wherein the second pinion incorporates a clutch adapted to disengage the pinion from the drive motor by rotating the second pinion in a second direction, opposite to said first direction.

11. A tool as claimed in claim 10, wherein said first and second pinion are mounted coaxially on an output shaft of the drive motor, wherein said first and second rack are mounted side by side and parallel to each other on one side of the tool head.

12. A tool as claimed in any of the preceding claims, wherein said distal end of the tool head terminates in a point.

13. A tool as claimed in claim 12, wherein said tip can be separated from the rest of the tool head to allow replacement and / or changing of the tip.

14. A tool as claimed in any of the preceding claims, wherein said guide means includes damping means on which the tool head acts when it reaches its extended position.