Abstract:
The present disclosure relates to grinding apparatus for grinding the hard metal inserts of rock drill bits, said grinding apparatus having said grinding machine equipped with a grinding cup driven by a motor to rotate about its longitudinal axis wherein the support system comprises an arm or lever system to control vertical movement of the grinding machine and means to provide grinding pressure, wherein the means to provide grinding pressure may be a linear actuator and load cell assembly pivotally connected to the arm or lever system.

Description:
BACKGROUND 
       [0001]    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 (REM) and more specifically, but not exclusively, for grinding the cutting teeth or buttons of a rock drill bit or cutter. 
         [0002]    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. 
         [0003]    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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. 
       SUMMARY OF THE INVENTION 
       [0008]    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. 
         [0009]    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. 
         [0010]    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 aperature and movement of said pressure plate is controlled by a linear actuator. 
         [0011]    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. 
         [0012]    Further features of the invention will be described or will become apparent in the course of the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    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: 
           [0014]      FIG. 1  is perspective view from the right side of one embodiment of a grinding apparatus according to the present disclosure having a grinding machine carried for vertical and horizontal adjustment by a support system, and means for holding the bit(s) to be ground and with a schematic illustration of a large down the hole bit (the bit illustration does not show the hard metal inserts or buttons to be ground). 
           [0015]      FIG. 2  is left side view the grinding apparatus of  FIG. 1  with shielding removed around the bit. 
           [0016]      FIG. 3  is perspective view from the right side of the grinding apparatus of  FIG. 1  with the bit table rotated. 
           [0017]      FIG. 4  is rear perspective view from the left side of the grinding apparatus of  FIG. 3   
           [0018]      FIG. 5  is an enlarged perspective view of the water and waste collection system forming part of the grinding apparatus of  FIG. 1 . 
           [0019]      FIG. 6  is frontal view of the grinding apparatus of  FIG. 1  with shielding removed. 
           [0020]      FIG. 7  is a perspective view of the grinding apparatus of  FIG. 1  with the content of the first arm section and control box exposed. 
           [0021]      FIG. 8  is a right side view of the grinding apparatus of  FIG. 7 . 
           [0022]      FIG. 9  is an internal side view of the first box section and second arm section of the support system of  FIG. 1 . 
           [0023]      FIG. 10  is a top view of one embodiment of bit holder for the grinding apparatus of  FIG. 1 . 
           [0024]      FIG. 11  is a bottom view of the bit holder of  FIG. 10  with the aperature closed. 
           [0025]      FIG. 12  is a bottom view of the bit holder of  FIG. 10  with the aperature open. 
           [0026]      FIG. 13  is perspective view from the left side of another embodiment of a grinding apparatus according to the present disclosure suitable for mobile applications and having a grinding machine carried for vertical and horizontal adjustment by a support system, and means for holding the bit(s) to be ground. 
           [0027]      FIG. 14  is a front plan view of part of the support system of the grinding apparatus of  FIG. 13 . 
           [0028]      FIG. 15  a side plan view of part of the support system of the grinding apparatus of  FIG. 13 . 
           [0029]      FIG. 16  is a schematic drawing of a part of a circuit diagram for one embodiment of a control system in accordance with one embodiment of the present disclosure. 
           [0030]      FIG. 17  is a schematic drawing of another part of a circuit diagram for the control system of  FIG. 16 . 
           [0031]      FIG. 18  is a schematic drawing of another part of a circuit diagram for the control system of  FIG. 16 . 
           [0032]      FIG. 19  is an embodiment of a control panel using the circuitry of  FIG. 16  with joysticks. 
           [0033]      FIG. 20  is a schematic drawing of a part of a circuit diagram for another embodiment of a control system in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    With reference to the  FIGS. 1 to 12  one embodiment of a grinding apparatus according to the present disclosure is generally indicated at  1 . The grinding apparatus  1  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 . The grinding machine  2 , means for holding the bits  3  and support system  4  are arranged to permit relative movement between the grinding machine  2  and the bit to be ground to permit alignment of the grinding machine  2  with the longitudinal axis of the buttons on the bit. The grinding apparatus  1  has a control system, part of which is generally indicated at  5 , having a programmable operator control panel  35  capable of directly or indirectly monitoring and adjusting one or more operational parameters. The operational parameters may include feed pressure, grinding cup RPM, grinding time and other parameters as noted herein. 
         [0035]    In the embodiment of the grinding apparatus  1  shown in  FIGS. 1-12 , the grinding machine  2  is carried by support system  4  which includes an arm or lever system  6  journaled on a stand  7  attached to the rear  8  of an open box  9 . The bit holder means  3  consists of a table  10  mounted within the box  9 . 
         [0036]    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. 
         [0037]    Within the first control box  15  ( FIG. 9 ), is means to provide a balance pressure to the portion of the support system that controls the movement of the grinding machine  2  in the direction of the longitudinal axis of the button or bit when not in use and feed (grinding) pressure when in use. In the embodiment shown, the means to provide grinding pressure is an actuator, generally indicated at  26 , pivotally connected to an end  27  of the lower arm  19  of the second arm section  17 . The end  27  of lower arm  19  extends out from the pivot point  28  at which the lower arm  18  is connected to the first control box  15 . In the embodiment illustrated the actuator is an electro-mechanical linear actuator having a screw  38  whose length and speed of travel is controlled by an electric motor  39 . The advantage of using and electro mechanical actuator powered by an electric motor is that it potentially allows for elimination of alternatives such as pneumatic or hydraulic actuators, generally simplifying assembly of grinding apparatus, increasing control and precision of relevant functions, while potentially reducing cost of manufacture. Installation and operation is also simplified as the power source required to operate the grinding apparatus is potentially reduced to electric powered only. 
         [0038]    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. 
         [0039]    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. 
         [0040]    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 acruate 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. 
         [0041]    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 . 
         [0042]    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 . 
         [0043]    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. 
         [0044]    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. 
         [0045]    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. 
         [0046]      FIGS. 16-18  illustrate schematically one embodiment of part of a circuit diagram for a control system according to the present disclosure. In  FIG. 16  an input/output card  49  is schematically illustrated with circuit inputs for grinding pressure  61 , the splash guard control  62 , laser drive  63  and milling pressure  64 , In  FIG. 17  an input/output card  65  is schematically illustrated with circuit inputs  66 ,  67  for controlling the joystick and orbital rotation of the grinding machine. IN  FIG. 19  a control panel is illustrated with joysticks  71 , 72 . the joysticks as either an alternative to load cells measuring operator input or as means to achieve two-hand control for when deemed necessary for reasons such as safety, etc. The joysticks may be used to scroll down the menu as well as select various functions. Two-hand control of things like bit holder tilt function may be achieved by requiring that the operator move both joysticks to activate the desired function. The use of a combination of joystick and load cell could also be used to achieve certain controlled functions whenever required. In  FIG. 18  an input/output card  68  is schematically illustrated with circuit inputs for controlling linear actuator with inputs  69  and  70 . 
         [0047]      FIG. 20  illustrates schematically another embodiment of part of a circuit diagram for a control system according to the present disclosure. In  FIG. 20  an input/output card  299  is schematically illustrated with circuit inputs for feed pressure actuator  201 , load cell amplifier/load cell  202 , milling head  104  and joystick controls  206 ,  208  and orbital rotation of the grinding machine. In  FIG. 20 , a load cell amplifier is illustrated. The load cell amplifier optimizes the input to the load cell. The load cell amplifier is optional and can be used to optimize the input to the load cell if desired and can be a separate device or built into the load cell. 
         [0048]    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. 
         [0049]    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  FIG. 4 . The Water and waste collection system includes drawer  41  that can be moved into position below the open box  9 . The excess coolant water and metal removed from the buttons during grinding are collected in drawer  41  permitting the water to potentially be recycled back into the coolant system. 
         [0050]    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  FIG. 8  a linear actuator  60  is shown as controlling the tilting action of table  10 . The bit holder means  3 , in this case table  10 , may be provided with one or more apertures  50  to hold one or more bits to be ground. In the embodiment illustrated table  10  has one aperture  50  (see  FIGS. 10-12 ). When a bit(s) is positioned in an aperture  50  the shank of the bit is placed against the front edges  51 , 52  of aperture  50 . The front edges  51 , 52  may be rubber coated. The bit is held in place against front edges  51 , 52  by pressure plate  53  controlled by a second linear actuator  54  and lever arm assembly  55 . Means are provided to monitor and control the travel of the linear actuator. In the embodiment illustrated the linear actuator  54  is an electro mechanical actuator. By monitoring the amperage used by the electric motor for the actuator  54 , when the amperage spikes the control system  5  can stop the electric motor from advancing the actuator further. The amperage will spike when the pressure plate  53  contacts the shank of the bit when the shank is contacting front edges  51 , 52  of aperature  50 . A shield  56  is attached to and moves with the pressure plate  53  and fully covers the opening between the rear  57  of pressure plate  53  and back  58  of the aperture  50 . The shield  56  prevents accidental pinching of fingers, etc. when the pressure plate  53  is retracted. The linear actuator  54  can be backed off slightly to rotate the bit (to the next button to be ground) within the aperture  50  without full retraction of the linear actuator  54  and pressure plate  53 . The controls for operating the linear actuator  54  may be provided on the sides of box  9 . While the method of holding a bit in the bit holder means is shown as a pressure plate  53  and linear actuator  54  other arrangements are possible and the present invention is not limited to the embodiment is illustrated. 
         [0051]      FIGS. 13 to 15  illustrate another embodiment of a more compact grinding apparatus, according to the present disclosure, optionally suitable for mobile applications. The grinding apparatus is generally indicated at  100 . The grinding apparatus  100  includes a grinding machine  102 , means for holding one or more bits to be ground generally indicated at  103  and a support system generally indicated at  104 . The grinding machine  102 , means for holding the bits  103  and support system  104  are arranged to permit relative movement been the grinding machine  102  and the bit to be ground to permit alignment of the grinding machine  102  with the longitudinal axis of the buttons on the bit. The grinding apparatus  100  has a control system, part of which is generally indicated at  105 , having a programmable operator control panel capable of directly or indirectly monitoring and adjusting one or more operational parameters. The operational parameters of most interest are selected from the group consisting of feed pressure, grinding cup RPM and grinding time. 
         [0052]    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 . 
         [0053]    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. 
         [0054]    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. 
         [0055]    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 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. 
         [0056]    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. 
         [0057]    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. 
         [0058]    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.