This application is a 371 National Phase of International Patent Application No. PCT/CA2014/000619, filed on Aug. 12, 2014, which claims priority to Canadian Patent Application No. 2,823,643, filed on Aug. 12, 2013, which are incorporated by reference as if fully set forth.
The present disclosure relates to improvements in apparatus for grinding the hard metal inserts or working tips of rock drill bits (percussive or rotary), tunnel boring machine cutters (TEM) and raised bore machine cutters (RBM) and more specifically, but not exclusively, for grinding the cutting teeth or buttons of a rock drill bit or cutter.
In drilling operations the cutting teeth (buttons) on the drill bits or cutters become flattened (worn) after continued use. Regular maintenance of the drill bit or cutter by regrinding (sharpening) the buttons to restore them to substantially their original profile enhances the bit/cutter life, speeds up drilling and reduces drilling costs. Regrinding should be undertaken when the wear of the buttons is optimally one third to a maximum of one-half the button diameter.
Manufacturers have developed a range of different manual and semi-automatic grinding machines including hand held grinders, single arm and double arm self centering grinding machines and grinders designed specifically for mounting on drill rigs, service vehicles or set up in the shop.
These types of machines utilize a grinding machine having a spindle or rotor rotated at high speed. A grinding cup or grinding pin, mounted on the end of the rotor or spindle, grinds the button and typically the face of the bit/cutter surrounding the base of the button to restore the button to substantially its original profile for effective drilling. In addition to the rotation of the grinding cup, these types of grinding machines may include features where the grinding machine is mounted at an angle to the longitudinal axis of the button and the grinding machine is rotated to provide orbital motion with the center of rotation lying in the center of the grinding cup. When grinding the buttons, the centering aspects of the grinding machine tend to center the grinding machine over the highest point on the button.
The conventional grinding machines switch between grinding pressure and balance pressure to achieve the desired effect. In conventional grinding machines, the minimum grinding pressure is equivalent to the weight of the arm or lever section and the components attached to it.
Longstanding problems with these types of grinding machines are vibration and noise due to high rotational speeds, wear, the requirement for large compressors for pneumatic systems and long grinding times per button, in the larger sizes.
U.S. Pat. No. 7,402,093 addressed a number of problems with earlier machines and provided a grinding machine carried on a support system where the grinding cup is rotated at variable speeds preferably from about 2200 to 6000 RPM and the support system is capable of providing a variable feed pressure preferably or optionally up to 350 kilos. In this type of machine there is a need to control the feed pressure with precision.
Accordingly the present disclosure provides embodiments of a grinding apparatus for grinding the hard metal inserts of rock drill bits. The grinding apparatus has a grinding machine carried on a support system and means for holding one or more bits to be ground. The grinding machine is equipped with a grinding cup driven by a motor to rotate about its longitudinal axis. The support system comprises an arm or lever system to control movement of the grinding machine for alignment of the grinding machine with a hard metal insert to be ground, means to provide grinding pressure, means to monitor and control one or more operational functions of the grinding apparatus selected from the group consisting of force, grinding pressure, movement and speed of movement of the grinding machine during alignment with a hard metal insert. The means to monitor and control one or more functions of the grinding apparatus includes one or more load cells to quantify and measure forces being applied during said one or more functions and a programmable control system capable of monitoring and adjusting the one or more functions based on input from the one or more load cells.
In one embodiment the means to provide grinding pressure is a linear actuator pivotally connected to the arm or lever system to produce forces such as feed (grinding) pressure and a load cell to quantify and measure the force being applied during grinding. The combination of control system, linear actuator and load cell allow for feed (grinding) pressure to start from zero. This differs significantly from conventional grinding machines as the minimum feed pressure in conventional grinding machines is equal to the weight of the grinding machine and support system.
Another aspect of the present disclosure relates to embodiments of grinding apparatus wherein means for holding one or more rock drill bits to be ground are provided that include a moveable pressure plate for each aperture and movement of said pressure plate is controlled by a linear actuator.
A further aspect of the present disclosure relates to embodiments of grinding apparatus having a water and waste collection system for recovery of coolant and metal removed from the hard metal inserts during grinding.
Further features of the invention will be described or will become apparent in the course of the following detailed description.
In order that the disclosure may be more clearly understood, the embodiments will now be described in detail by way of example, with reference to the accompanying drawings, in which:
With reference to the
In the embodiment of the grinding apparatus 1 shown in
In the embodiment shown, the arm or lever system 6 for carrying and positioning the grinding machine 2 as noted previously is journaled onto a stand 7 at the rear 8 of the box 9. The arm system 6 consists of a first arm section 11 having one end 12 journaled to the stand 7. The other end 13 of the first arm section 11 is journaled to the backside 14 of a first control box 15. The first arm section 11, in this embodiment, controls the horizontal location of the grinding machine 2 relative to the bit to be reground. To the front side 16 of the first control box 15 is pivotally mounted a second arm section 17. The second arm section 17 consists of a pair of parallel arms 18,19 with one end 20,21 of each arm 18,19 pivotally mounted to the front side 16 of the first control box 15. The other end 22,23 of each arm 18,19 is pivotally connected to the backside 24 of a second control box 25. The second arm section 17 controls the vertical movement of the grinding machine 2 up and down.
Within the first control box 15 (
In conventional grinding machines use of high feed forces could potentially cause the grinding machine to fall off the button with great force. In the present disclosure to produce the high feeds safely, and control the feed pressure, control system, generally indicated at 5, is provided to monitor and control one or more operational functions of the grinding apparatus including feed or grinding pressure. Other functions monitored and controlled may include forces applied during retention of the bit in the bit holder means, movement of the grinding machine, speed of movement of the grinding machine during alignment with a hard metal insert. In the embodiment illustrated the control system includes one or more load cells to quantify and measure forces being applied during the functions of the grinding apparatus including speed of actuator movement, feed pressure, etc. Where the load cell signals a reduction in force, possibly due to the grinding cup moving off the button being ground, the output signal from the load cell may if desired cause the grinding operation to shut off or the electro mechanical actuator to reverse, in order to prevent or minimize a dangerous situation. Load cells measuring operator input and connected to control system 5 allow for force applied on one or more operator inputs such as on handles etc to be translated to, for example, variable speed of movement of electro mechanical actuators. This allows for a programmable control system 5, that is capable of monitoring and adjusting the functions of the grinding apparatus based on input from one or more load cells. In the embodiment illustrated for monitoring and controlling the feed pressure a load cell 29 is provided between the end 30 of the screw 38 of the linear actuator 26 and the end 27 of lower arm 19. The load cell 29 measures the feed pressure of the grinding machine 2 against the drill bit. An output signal from the load cell 29 is directly or indirectly delivered to the control system 5. The control system 5 controls the movement of the screw 38 of linear actuator 26 through the motor 39 and thereby controls the feed pressure.
To accommodate the fact that the surface of the button to be ground may be worn unevenly, means generally indicated at 42, are provided to enable the grinding machine 2 to move slightly during grinding over the uneven button surface without adjustment by the linear actuator. This facilitates a more even and controlled grinding action and reduces load spikes within the grinding apparatus 1 that includes a grinding machine 2, means for holding one or more bits to be ground generally indicated at 3 and a support system generally indicated at 4. In the embodiment illustrated the end 32 of linear actuator 26 remote from the second arm section 17, is adapted to fit within a hole through block 33 at the point of connection to the first control box 15. A spring 31 around the portion of the linear actuator 26 extending through block 33 is biased against the block 33 by nut 34. The spring 31 may be compressed and decompressed similar to a shock absorber to permit the grinding machine 2 to move slightly over the uneven button surface without adjustment of linear actuator 26. As noted above, it is also possible where the grinding machine moves over and off the button surface during grinding the output signal from the load cell will warn the operator and the machine may automatically shut down or linear actuator reversed as desired.
Within the second control box 25 is a rotation motor, gear box and gear for providing an orbital rotation to the grinding machine 2. The grinding machine 2 is attached to the second control box 25 by means of a pair of plates 43,44. Each of the plates 43,44 is provided with an accurate slot 45. The angle of attachment of the grinding machine 2 relative to the control box 25 can be adjusted by means of slots 45. By having the grinding machine 2 slightly off vertical, nipple formation on the button being reground is minimized and uneven wear on the grinding cup avoided.
A conduit 46 at the rear of control box 25 is used to deliver power, water and/or air feeds to grinding machine 2 without being tangled in the orbital rotation of the grinding machine 2. The remote end of conduit 46 is connected to a flexible conduit 47 that connects to grinding machine 2 through connector 48.
Operator input panel 35 on control box 25 can also be used to set for example button size, grinding time, type of buttons, button wear, percentage of biased side load and feed pressure. The control system may be programmed with preset default values. Start button 36 and stop button 37 are provided on panel 35.
The grinding machine 2 illustrated in the FIGURES utilizes a hex drive system of the type described in U.S. Pat. No. 5,639,273 and U.S. Pat. No. 5,727,994.
A programmable control card is provided within the second control box 25 optionally attached to rear of operator input panel 35, having a circuit board containing the central processor (ie. microprocessor or microcontroller) for the control system of the grinding apparatus. The central processor can be located anywhere deepend suitable for the application and can be suitably interconnected with other sub-processors to monitor various functions as deemed necessary for proper function. The overall control system includes systems and controls that together with a microprocessor or microcontroller can control all aspects of the grinding apparatus including grinding time on each button, rotational speed of the grinding cup, grinding pressure, bit holder tilt function, operating lights and coolant flow. The microprocessor or microcontroller and the control system can be used to provide other functions either manual or automatic. For example, the microprocessor or microcontroller and control system, in the case of an electric motor, can monitor the amperage being used and/or the temperature and if it reaches a preset limit automatically decrease the grinding pressure to prevent motor burn out. The microprocessor or microcontroller and control system can also control the flow of coolant to the face of the button during grinding.
In addition, the control panel software can be configured such that the user could select for example whether long grinding cup life or high material removal rate of the grinding cup is preferred.
Variations of the above described principles including increased feeds/grinding pressure, lower grinding cup RPM, water cooled motor, using frequency inverters, biased side loads, counter balancing and position fixing, that can optionally be used to allow for grinding at angles other than vertical, are within the scope of the present invention. Combinations of variations of the above described principle of increased feeds/grinding pressure, lower grinding cup RPM, water cooled motor, using frequency inverters, biased side loads, counter balancing and position fixing can be used to substantially eliminate the need for tilting/pivoting the bit when switching between grinding of face buttons and gauge buttons. Some of the above principles could also be applied to for example pneumatically and/or hydraulically powered motors. In addition on existing air-cooled motors, spindle speed can be varied using a gear box arrangement between the motor output and the spindle drive input to reduce spindle RPM, optionally variable, up to 45% or more.
During grinding a coolant, typically water, is sprayed onto the button being ground. The grinding apparatus shown may include a water and waste collection system generally indicated at 40 in
In the embodiment illustrated the means for holding the bits 3 is a table 10 mounted within the box 9 at pivot points on each side of the box 9 to permit the table 10 to be tilted. In
In the embodiment of the grinding apparatus 100 shown the grinding machine 102 is carried by support system 104 which includes an arm or lever system 106 attached to the frame 107.
In the embodiment shown, the arm or lever system 106 for carrying and positioning the grinding machine 102 as noted previously is attached to the frame 107. The arm system 106 consists of a pair of parallel arms 108,109 with one end 110,111 of each arm 108,109 pivotally mounted to the frame 107. The other end 112,113 of each arm 108,109 is pivotally connected to the backside 114 of a control box 115. The arm system 106 controls the vertical movement of the grinding machine 102 up and down.
Within the frame 107, is means to provide a balance pressure to the portion of the support system that controls the movement of the grinding machine 102 in the direction of the longitudinal axis of the button or bit when not in use and grinding pressure when in use. In the embodiment shown, the means to provide grinding pressure is an actuator, generally indicated at 116 pivotally connected to the arm 108. In the embodiment illustrated the actuator is a electro-mechanical linear actuator having a screw whose length and speed of travel is controlled by an electric motor.
As noted high feed forces in conventional self-centering grinding machines could potentially cause the grinding machine to fall off the button with great force. To produce the high feeds safely, and control the feed pressure, means, generally indicated at 120, is provided to monitor and control the feed pressure. In the embodiment illustrated the means to monitor the feed pressure is a load cell 117 provided between the end 118 of the linear actuator 117 and the point of connection 119 to the arm 109. The load cell 117 measures the feed pressure of the grinding machine 102 against the drill bit. A signal from the load cell 117 is delivered to the control system 105. The control system 105 controls the movement of the screw 121 of the linear actuator 116 through the motor 122 and thereby controls the feed pressure. The combination of control system, linear actuator and load cell also allow for feed (grinding) pressure to start from zero. This differs significantly from conventional grinding machines as the minimum feed pressure in conventional grinding machines is equal to the weight of the grinding machine and support system. Where the load cell signals an abrupt reduction in load, possibly due to the grinding cup moving off the button being ground, the control system may be programmed to shut down the grinding operation or other procedure to minimize danger to the operator.
To accommodate the fact that the surface of the button to be ground may be worn unevenly, means generally indicated at 123, are provided to enable the grinding machine 102 to move slightly during grinding over the uneven button surface without adjustment by the linear actuator. In the embodiment illustrated the means to enable the grinding cup to move slightly is provided by the design of the arms 108, 109 to provide some give or flex.
Having illustrated and described a preferred embodiment of the invention and certain possible modifications thereto, it should be apparent to those of ordinary skill in the art that the invention permits of further modification in arrangement and detail and is not restricted to the specific semi-automatic grinding apparatus illustrated.
It will be appreciated that the above description related to the preferred embodiment by way of example only. Many variations on the invention will be obvious to those knowledgeable in the field, and such obvious variations are within the scope of the invention as described and claimed, whether or not expressly described.
Number | Date | Country | Kind |
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2823643 | Aug 2013 | CA | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CA2014/000619 | 8/12/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2015/021531 | 2/19/2015 | WO | A |
Number | Name | Date | Kind |
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5070654 | Manqvist | Dec 1991 | A |
5193312 | Gudmundsson | Mar 1993 | A |
5639273 | Sjolander | Jun 1997 | A |
7402093 | Sjolander | Jul 2008 | B2 |
20040014406 | Sjolander | Jan 2004 | A1 |
20070004320 | Lindgren | Jan 2007 | A1 |
Number | Date | Country |
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0356663 | Mar 1990 | EP |
Entry |
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International Search Report and Written Opinion mailed in corresponding International Patent Application No. PCT/CA2014/000619 dated Nov. 17, 2014, consisting of 8 pp. |
International Preliminary Report on Patentability completed in corresponding International Patent Application No. PCT/CA2014/000619 dated Nov. 13, 2015, consisting of 10. |
Number | Date | Country | |
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20160184962 A1 | Jun 2016 | US |