Abstract:
The present invention relates to grinding apparatus for grinding the hard metal inserts of rock drill bits, said grinding apparatus having a grinding machine carried on an support system that provides a feed pressure for said grinding machine during grinding, said grinding machine equipped with a grinding pin driven by motor to rotate about its longitudinal axis wherein the grinding cup is rotated at variable speeds and the support system provides a variable feed pressure.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention 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 (TBM) 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.  
       BACKGROUND OF THE INVENTION  
       [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. The present invention is particularly applicable to mobile grinding apparatus of the type described in U.S. Pat. No. 5,193,312 and semi-automatic grinding machines as described in U.S. Pat. No. 5,070,654 and in International Application published under WO 02/04169.  
         [0004]     These types of machines utilize a grinding machine having a spindle or rotor rotated at high speed, typically about 12,000 to 22,000 RPM. A grinding cup 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. On buttons where wear is uneven, typically gauge buttons, this may result in regrinding the button off center from its longitudinal axis.  
         [0005]     The conventional grinding machines switch between grinding pressure and balance pressure to achieve the desired effect. This, for example, does not allow for a grinding pressure equal to zero. 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 of six minutes or more.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an object of the present invention to provide grinding apparatus having a grinding machine for rotation of a grinding cup, bit holding means and a support system where the grinding cup is rotated by said grinding machine at controlled variable speeds, preferably from about 2200 to 6000 RPM, and the support system is capable of providing controlled variable feed pressure, preferably or optionally up to 350 kilos. The speed of rotation of the grinding cup and feed pressure may optionally be varied during a grinding cycle of a working tip on a rock drill bit.  
         [0008]     It is a further object of the present invention to provide grinding apparatus with a grinding machine that utilizes an electric motor capable of producing high torque over a range of RPMs, with a relatively compact size and weight.  
         [0009]     It is a further object of the present invention to provide grinding apparatus having a water-cooled motor optionally using the same coolant that is used during grinding by the grinding cup.  
         [0010]     It is a further object of the present invention to provide grinding apparatus having a frequency inverter to optimize the power and/or torque to size ratio in a grinding machine, and to add the flexibility to change the motor performance characteristics as deemed appropriate for optimized grinder performance.  
         [0011]     It is a further object of the present invention to provide grinding apparatus having an electronic programmable control system capable of controlling, monitoring and adjusting all or select operational parameters.  
         [0012]     Accordingly the present invention provides a grinding apparatus for grinding the hard metal inserts of rock drill bits. The hard metal inserts can be on percussive or rotary drill bits, tunnel boring machine cutters or raised bore machine cutters. The grinding apparatus has a grinding machine, bit holding means and a support system. The support system provides a feed pressure for the grinding machine during grinding. The grinding machine is equipped with a grinding cup driven by a motor to rotate the grinding cup about its longitudinal axis at controlled variable speeds, preferably from about 2200 to 6000 RPM. The support system provides a controlled variable feed pressure preferably up to 350 kilos. In one embodiment the support system includes means to limit the distance of travel and/or to limit speed of travel of the grinding machine during grinding.  
         [0013]     Another aspect of the present invention relates to the grinding machine utilizing an electric motor capable of producing high torque over a range of speeds preferably from about 2200 to 6000 RPM, with a relatively compact size and weight. To further optimize the power and/or torque to size ratio, and to add the flexibility to change the motor performance characteristics as deemed appropriate the present invention preferably utilizes a frequency inverter. The electric motor is preferably water-cooled and optionally uses the same coolant that is used during grinding by the grinding cup.  
         [0014]     A further aspect of the present invention relates to grinding apparatus having a control system optionally but preferably including interconnected control modules including an operator input panel and an optionally attached programmable control card module and/or a separate tilt/laser control card module, all of which are connected to a suitably located multi-function input/output card module that acts as a central communications hub for the all the various modules that are part of the control system which as whole is capable of monitoring and adjusting all components and/or sub-systems connected to the control system, including one or more operational parameters selected from the group consisting of feed pressure, grinding cup RPM and grinding time. In another embodiment the programmable control system is capable of monitoring and adjusting one or more additional operational parameters selected from the group consisting of coolant flow to the surface of the hard metal insert, coolant flow to the electric motor, output frequency and/or voltage from the frequency inverter, biased side load, counter balancing pressure, bit positioning, power indexing of bits, angle of the grinding machine, speed of the rotation motor, tilting of the table or other support holding the bit, etc.  
         [0015]     The benefit of the electronic programmable control system and its various built in capabilities is that the range of RPMs for example is upgradable and/or adjustable to meed future demands. For example, with the configuration of the present invention it would be rpossible to change the overall range of RPMs to 1000 to 11000 RPMs if for example a new grinding cup matrix and/or new overall configuration were developed. Another potential reason that the operating characteristics may need to be modified would be if the material in the button being ground changed. Due to the inherent flexibility of the overall control system and components/modules connected to it the ability for the grinding apparatus to meet future demands is maximized.  
         [0016]     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  
       [0017]     In order that the invention may be more clearly understood, the preferred embodiment thereof will now be described in detail by way of example, with reference to the accompanying photographs, in which:  
         [0018]      FIG. 1  is perspective view from the left side of one embodiment of a grinding apparatus according to the present invention having a grinding machine carried for vertical and horizontal adjustment by a support system, and means for holding the bit(s) to be ground.  
         [0019]      FIG. 2  is perspective view of a percussive drill bit.  
         [0020]      FIG. 3  is a view of the left side of the grinding apparatus of  FIG. 1 .  
         [0021]      FIG. 4  is a top plan view of the grinding apparatus of  FIGS. 1 and 3 .  
         [0022]      FIG. 5  is a front view of the open box and stand and that forms part of the support system of the grinding apparatus of  FIG. 1 .  
         [0023]      FIG. 6  is a left side view of the box and stand of  FIG. 5  showing the controls for tilting the table that is pivotally mounted within the box.  
         [0024]      FIG. 7  is a top view of the box and stand of  FIGS. 5 and 6 .  
         [0025]      FIG. 8  is a top plan view in partial section of the table for holding the bits for pivotally mounting in the box of  FIGS. 5 and 6 .  
         [0026]      FIG. 9  is a side plan view of the support bracket assembly attached to the front of table of  FIG. 8 .  
         [0027]      FIG. 10  is a rear view of the first arm section of the support system of  FIG. 1 .  
         [0028]      FIG. 11  is a bottom view of the first arm section of  FIG. 10 .  
         [0029]      FIG. 12  is a left side view of the first arm section of  FIGS. 10 and 11 .  
         [0030]      FIG. 13  is an internal side view of the first box section and second arm section of the support system of  FIG. 1 .  
         [0031]      FIG. 14  is a left side view in partial cross section of the second box section for the grinding apparatus of  FIG. 1 .  
         [0032]      FIG. 15  is a front view of the second box section of  FIG. 14  and the attached grinding machine.  
         [0033]      FIG. 16  is an enlarged side view partially in cross section of the motor housing for the grinding machine of  FIG. 15 .  
         [0034]      FIG. 17  is a cross section of the motor housing of  FIG. 16 .  
         [0035]      FIG. 18  is a bottom view of the motor housing of  FIGS. 16 and 17 .  
         [0036]      FIG. 19  is an enlarged cross section of the spindle assembly for the grinding machine of  FIG. 15 .  
         [0037]      FIG. 20  is a bottom view of the spindle assembly of  FIG. 19 . 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0038]     With reference to  FIGS. 1, 3  and  4  one embodiment of a grinding apparatus according to the present invention 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 been 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  preferably has a control system having a programmable operator control panel  5  capable of 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. The control system is preferably capable of monitoring and adjusting one or more additional operational parameters selected from the group consisting of coolant flow to the surface of the hard metal insert, coolant flow to the electric motor, output frequency and/or voltage from the frequency inverter, biased side load, counter balancing pressure, bit positioning, power indexing of bits, angle of the grinding machine, speed of the rotation motor, tilting of the table or other support holding the bit, etc.  
         [0039]      FIG. 2  illustrates a percussive rock drill bit  10 . The bit  10  has a head portion  11 , and a shank  12 . The head portion  11  has a front face  13  and a peripheral edge  15 . A series of buttons  14  are assembled on the front face  13 . Around the peripheral edge (gauge) are a series of gauge buttons  16 . The buttons  14 , 16  are typically formed as a cylinder from wear resistant hard metals such as tungsten carbide. The buttons  14  are, in this example, mounted with their longitudinal axis  17  perpendicular to the front face  13  of bit  10 . The peripheral edge  15  is beveled and gauge buttons  16  are mounted with their longitudinal axis  18  at an angle. The working tip  19 ,  20  of buttons  14 , 16  is typically provided with a semi-spherical, hemispherical, conical, semi-ballistic or ballistic profile and have a diameter from 6 mm to 26 mm or more depending on the size of the bit  10 . As noted above, the buttons become flattened after continued use. Regular maintenance of the drill bit or cutter by regrinding the buttons to restore them to substantially their original profile enhances the bit/cutter life, speeds up drilling and reduces drilling costs.  
         [0040]     In the embodiment of the grinding apparatus  1  shown in  FIGS. 1, 3  and  4  the grinding machine  2  is carried by support system  4  which includes an arm or lever system  21  journaled on a stand  22  attached to the rear  23  of an open box  24 . The bit holder means  3  consists of a table  25  mounted within the box  24 .  
         [0041]     In order to minimize operator set up and movement of a bit during grinding, means for holding the bits  3  is a table  25  (as shown in  FIGS. 4 and 8 ) preferably mounted within the box  24  at pivot points  26 ,  27  on each side  28 ,  29  of the box  24  (see  FIGS. 1,3  and  4 ) to permit the table  25  to be tilted. The bit holder means  3 , in this case table  25 , is provided with one or more apertures  30  to hold one or more bits to be ground. In the embodiment illustrated table  25  has two apertures  30 . When a bit(s) is positioned in an aperture  30  the shank  12  of bit  10  is placed against the front edges  31 , 32  of aperture  30 . The front edges  31 , 32  are preferably rubber coated. The bit is held in place against front edges  31 , 32  by pressure plate  33  controlled by a locking cylinder  34 . A shield  35  is attached to and moves with the pressure plate  33  and fully covers the opening between the rear  36  of pressure plate  33  and back  37  of the aperture  30 . The shield  35  protects the piston rod of the cylinder  34  and prevents accidental pinching of fingers, etc. when the pressure plate  33  is retracted. The locking cylinder  34  can be depressurized and backed off slightly to rotate the bit (to the next button to be ground) within the aperture  30  without full retraction of the locking cylinder  34  and pressure plate  33  attached to it. The controls  38  for operating the locking cylinder  34  are provided on the sides  28 ,  29  of box  24 . While the method of holding a bit in the bit holder means is shown as a pressure plate  33  and locking cylinder  34  other arrangements are possible and the present invention is not limited to the embodiment is illustrated.  
         [0042]     Large down-the-hole bits to be reground typically have a relatively long shank that fits through the aperture  30 . In order to regrind smaller bits a floor plate  39  that can be slid in and out of position under the aperture  30  is provided. A knob  41  and slot  40  in the table  25  control the location of the floor plate  38 . Adapters (not shown) for holding multiple small sized bits can be inserted into the aperture. Use of the adapters eliminates repetitive set up time for the operator.  
         [0043]     In order to facilitate set up of large bits, the grinding apparatus illustrated (see  FIGS. 8 and 9 ) is provided with a bracket  42  on which the end of a threaded bit and/or shank of the Down the Hole bit or similar can rest. Bracket  42  slides up and down on tube  43  that is attached to the front  44  of table  25 . Tube  43  is aligned with the center of aperture  30 . Knob  45  is tightened to lock bracket  42  at the desired height. Table  25  can be replaced by a table (bit holder) having one aperture for holding even larger bits.  
         [0044]     If the button to be ground is a gauge button, it is typically mounted in the bit at an angle relative to the face of the bit. The grinding machine  2 , in order to properly regrind a worn button, should be aligned with the longitudinal axis of the button. Accordingly to regrind the gauge buttons, in the embodiment shown, the table  25  is tilted to correspond to the angle at which the gauge buttons are mounted in the bit. Alternatively, the grinding apparatus could have, for example, a tilting feature or positioning feature allowing the grinding machine to be aligned with the longitudinal axis of the button, without tilting the bit or button.  
         [0045]     The means of tilting the table  25  is best shown with reference to  FIG. 6 . An arced slot  46  is provided in the left side  28  of the box  24 . A similar slot is provided in the right side  29  of the box  24  so the means for tilting the table can be mounted on either side of the box. A linear actuator  47  is provided on the left side  28  of the box  24  and the end  48  of the actuator rod  49  is connected to the side  50  of the table  25  through slot  46 . When activated extension of the actuator rod  49  will tilt the table  25  around pivot points  26 , 27 . The operation of the linear actuator  47  in this embodiment is controlled by the control system  5 . A tilt/laser control card  51  receives input from sensor  52  on the position of the actuator rod  49  and transmit this data to the control system  5 . Operation of the control system is explained in more detail later. The tilting of the table  25  can be accomplished by other means, such as hydraulic or pneumatic cylinders, gears etc or controlled manually. The tilting means can be mounted on either side of the box  24  so that two boxes may be mounted side by side, while leaving the tilting means easily accessible  
         [0046]     A splash-guard  53  is provided at the front  54  of the box  24  that can be raised and lowered along a slot on each side of the front edge  55  of the box  24  (see  FIGS. 4 and 5 ). The splash-guard  53  can be set and retained at different heights as desired. Lights  56  are provided in the front corners  57 ,  58  of box  24  to provide light on the bit(s) to be ground.  
         [0047]     In the embodiment shown, the arm or lever system  21  for carrying and positioning the grinding machine  2  as noted previously is journaled onto a stand  22  at the rear  23  of the box  24 . With reference to FIGS.  10  to  15 , the arm system  21  consists of a first arm section  59  having one end  60  journaled to the stand  22 . The other end  61  of the first arm section  59  is journaled to the backside  62  of a first box section  63 . The first arm section  59 , in this embodiment, controls the horizontal location of the grinding machine  2  relative to the bit to be reground. To the front side  64  of the first box section  63  is pivotally mounted a second arm section  65 . The second arm section  65  consists of a pair of parallel arms  66 , 67  with one end  68 , 69  of each arm  66 , 67  pivotally mounted to the front side  64  of the first box section  63 . The other end  70 , 71  of each arm  66 , 67  is pivotally connected to the backside  72  of a second box section  73 . The second arm section  65  controls the vertical movement of the grinding machine  2  up and down.  
         [0048]     Within the first box section  63  ( FIG. 13 ), 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 grinding pressure when in use. In the embodiment shown, the means to provide a balance pressure is a first cylinder  74  pivotally connected to an end  75  of the lower arm  67  of the second arm section  65 . The end  75  of lower arm  67  extends out from the pivot point  76  at which the lower arm  67  is connected to the first box section  63 . The cylinder  74  provides a balance pressure to the second arm section  65  when the grinding machine  2  is not in use.  
         [0049]     The present invention has determined that relatively high feed forces applied during grinding, optionally combined with varying or relatively low spindle rpm&#39;s can optimize grinding of the buttons with reduced vibration, noise and grinding time. High feed forces in self-centering grinding machines could potentially cause the grinding machine  2  to fall off the button with great force. To produce the high feeds safely, a means by which to limit the travel of the feed is required. The need to limit travel may not be limited to feed but in any direction deemed necessary. In the embodiment shown, a brake or lock  77  within the bottom of cylinder  74  is activated on grinding to lock the position of the cylinder  74 . Balance pressure regulator  78  is used by the operator to adjust the balance pressure when not grinding. A filter  79  for the pressure regulator and all other pneumatics is provided. A second short stroke feed cylinder  80  provides the feed pressure during grinding. The maximum stroke is about 10 mm in this embodiment. The first and second cylinders  74 , 80  are provided in an end to end alignment with the second cylinder  80  pivotally connected to the control box  63  at pivot point  81 . When this type of combination is activated, the travel of the grinding machine  2  in the direction of feed is limited to the relatively short stroke of the feed cylinder  80  once the grinding cycle is activated. In the event that the grinding machine  2  falls off the button during a grinding cycle, the chances of any danger to the operator or damage to the grinding machine  2  etc. are minimized. To further minimize any damage to the equipment, grinding cups, bits, and to further minimize any chance of injury to operator, sensors in the above described cylinder combination would detect for example the feed cylinder reaching max stroke and immediately shut the grinding process down automatically. Similar safely systems can be incorporated into any method of achieving controlled feed.  
         [0050]     Other potential solutions to achieve the same objective could be used including linear actuators or motorized screw or gear assemblies or any combination thereof potentially also including cylinder(s) optionally with brake(s) to provide controlled movement and/or positioning and/or safety coupled with suitable load sensors and means to adjust the loads as deemed necessary.  
         [0051]     Referring to  FIGS. 14 and 15 , within the second box section  73  is a rotation motor  82 , gear box  83  and gear  84  for providing an orbital rotation to the grinding machine  2 . The grinding machine  2  is attached to the second box section  73  by means of a pair of plates  85 . Each of the plates  85  is provided with an acruate slot  86 . The angle of attachment of the grinding machine  2  relative to the second box section  73  can be adjusted by means of slots  86 . 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.  
         [0052]     A conduit  87 , in the form of an aluminum tube in the embodiment illustrated, at the rear of second box section  73  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  88  of conduit  87  is connected to a flexible conduit  89  that connects to grinding machine  2  through connector  90 .  
         [0053]     A bit holder tilt control  91  is provided on the side of second box section  73 . To set the tilt angle of table  25 , the operator presses and holds the button  92  and then sets the angle of tilt using dial knob  93  on the other side of the second box section  73 . The angle of tilt will be determined by the angle of the gauge or other buttons on the bit being ground. Display  95  on the operator input panel  94  on the front of the second box section  73  will optionally display ‘TILT’ for example while button  92  is pressed and held. A second display  95 A will indicate the preset angle or the angle selected by turning dial knob  93 . Once set, button  92  is released and the tilt angle for table  25  is set. When grinding the gauge buttons, to tilt the table to the preset angle the operator presses button  92 . The operator presses button  92 B to return the table to the horizontal (ie. a tilt angle of zero).  
         [0054]     Operator input panel  94  on the front of the second box section  73  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 +/−buttons  96  are used to scroll through a menu and dial knob  93  used to select values. The control system may be programmed with preset default values. Start button  97  and stop button  98  are provided on panel  94 . Stop button  98  can optionally be used to reach one or more sub-menus. 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. In order to make the operation of the apparatus operator friendly, means are provided to easily align and attach the grinding cup and detach the grinding cup after use. Pressing spindle  15 , brake button  99  will set a brake or lock on the spindle of grinding machine  2  for a short delay period of about 8 seconds to enable the grinding cup to be easily attached. The brake or lock is automatically released at the end of the delay period. Alternately a spring-loaded button can be provided that when depressed will fit into a slot in the rotor and prevent it from rotating. This enables the operator to align the hex drive section of the grinding cup with the drive section of the rotor and then push the grinding cup on. To remove the grinding cup after use the operator presses a lever  100  towards the grinding machine  2 . The lever  100  pivots and the extending arms push the grinding cup away from the drive section of the rotor facilitating removal of the grinding cup from the grinding machine. Alternately a powered lever or cylinder can be provided to press against the grinding cup to remove it.  
         [0055]     A programmable control card is provided within the second box section  73  optionally attached to rear of operator input panel  94 , having a circuit board containing a central processor (ie. microprocessor or microcontroller) for the control system of the grinding apparatus. The control system of the present invention 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 and grinding pressure. The control system is preferably capable of monitoring and adjusting one or more additional operational parameters selected from the group consisting of coolant flow to the surface of the hard metal insert, coolant flow to the electric motor, output frequency and/or voltage from the frequency inverter, biased side load, counter balancing pressure, bit positioning, power indexing of bits, angle of the grinding machine, speed of the rotation motor, tilting of the table or other support holding the bit, etc. 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 or turn the motor off. The microprocessor or microcontroller and control system can also control the flow of coolant to the face of the button during grinding.  
         [0056]     When grinding buttons the self-centering aspects of the grinding machine tend to center the grinding machine over the highest point on the button. On buttons where wear is uneven, typically gauge buttons, this may result in regrinding the button off center from its vertical axis. One aspect of the present invention provides means to help align the grinding machine with the longitudinal axis of the button to be ground. In the embodiment shown in FIGS.  10  to  12  the means to help align the grinding machine with the longitudinal axis of the button consists of, a cylinder  101  having one end  102  connected to the stand  22  by means of plate  103  and the other end  104  connected to the bottom  105  of the first arm section  59 . The cylinder  101  provides a side load to grinding machine  2  to help align the grinding machine  2  with the longitudinal axis of the button. The side load biases the grinding machine  2  to grind more on either the outside or the inside of the gauge buttons as required thereby tending to shift the grinding machine  2  over the true center of the button. The means to help align the grinding machine with the longitudinal axis of the button to be ground can alternatively include a locking system to lock the arm in place to prevent movement in a direction normal to the longitudinal axis of the button while permitting movement in the axial direction. Suitable side load can also be provided by means other than by the cylinder such as counterweights, linear actuator(s), etc. A further aspect of this invention is to effectively control the grinding cup staying on the button utilizing delays and variable strength biased side loads. This safely enhances the self-centering feature to whatever level deemed necessary. A benefit of a softer enhanced “self-centering” principle, as described above, is that it results in less dramatic wear and loads on built-in grinding cup profile resulting in enhanced grinding cup characteristics throughout it&#39;s life. Additional benefits include maximized bit life due to unnecessary reduction of outside diameter of bit caused by unnecessary grinding of corresponding areas of the gauge buttons.  
         [0057]     To further assist with the alignment of the bits during grinding, laser line indicators  106  are located on the rear  23  of box  24 . When activated the laser line indicators provide a beam of light through slots  107  that is aligned with the center axis of apertures  30 . When grinding a button, rotation of the bit so the button to be ground is centered on the laser line insures grinding machine  2  will be aligned with the longitudinal axis of the button being ground.  
         [0058]     While typical grinding apparatus are aligned so that the longitudinal axis of the bit is generally vertical during grinding, in the case of very large bits, or in drilling equipment where bits or cutters are mounted in a clustered pattern, grinding may be done with the bit aligned horizontally or some other suitable angle. The present invention is equally applicable to this situation. In this situation the grinding machine may be carried on an arm or lever system and the grinding pressure applied in a horizontal or other suitable direction.  
         [0059]     Controlled feed forces in the present invention of between preferably 0 to 350 kilos and most preferably about 115 KG, optionally with constant and/or controlled variable biased side-loads, require more power and torque from the grinding head motor than in known grinding apparatus. The present invention preferably utilizes a motor capable of producing substantially higher amounts of torque and/or power than previously used, over a range of rpm&#39;s, with a relatively compact size and weight. To further optimize the power and/or torque to size ratio, and to add the flexibility to change the motor performance characteristics as deemed appropriate the present invention preferably utilizes a frequency inverter. In the embodiment shown in  FIG. 10 , the frequency inverter  108  is installed within the first arm section  59 . A frequency inverter allows for the base frequency (i.e. typically 50 or 60 Hz) and/or voltage to be varied up or down to enable optimized power and torque to be drawn from a relatively compact motor. The use of frequency inverters allow for substantially changing the motor size to power ratio (i.e. relatively small motors produce more mean power across the range of suitable RPMs). Also, the RPM can be varied by changing the set frequency and/or voltage. A frequency inverter can also be used as a single phase to three phase power converter.  
         [0060]     Until the compact solid-state frequency inverter (a.k.a. High Frequency Drives), the only way to change the frequency of standard 50 or 60 Hz power supplies was through bulky often fixed frequency electromechanical means, often also utilizing maintenance intensive brush type technology. Motors are designed to produce a certain amount of power and RPM at a given frequency (hence same motor will have different RPMs at 50 and 60 Hz). Changing the frequency allows the present invention to change the RPMs while in many cases maintaining the power. Maintaining power output often applies to both increasing and/or decreasing the motor RPM of many motors above or below its rated frequency/RPM.  
         [0061]     Using a frequency inverter allows the present invention to utilize a relatively compact motor and produce similar power across a range of RPMs. One function of the overall control system is to monitor and control the frequency inverter  108 . Like most other functions on the grinding apparatus, the frequency inverter  108  receives its instructions from the microprocessor or microcontroller on the circuit board (programmable control card module) behind the operator input panel  94 , through input/output (I/O) card  109 . Although the microprocessor or microcontroller in the programmable control card module is the brain, the I/O card module acts as a central communications hub in the overall control system, linking the various systems and modules together. Air vents  110 ,  111  are provided in the first arm section  59 . An electrical noise filter  112  is provided to filter electrical noise in the power supply produced by the frequency inverter. As shown in  FIG. 12 , on the side of the first arm section  59  a power input plug  113 , power output plug  114  for a water pump (not shown), water inlet valve  115  and compressed air inlet valve  116  are provided. Conduit  117  permits the power, water and air lines to go from the first arm section  59  to the first box section  64 . Power and air lines  118 ,  119  go from the first arm section  59  to the controls for the tilting of table  25  and control of the locking cylinders  34  in apertures  30 . Auxiliary air and power connections  120 ,  121  are provided at the front of the control housing on the side  28  of box  24 . Legs  122  and feet  123  permit box  24  to be leveled.  
         [0062]     At higher feed or grinding pressure, lower grinding cup rpm&#39;s (preferably 2200 to 6000 RPM vs 12,000 to 22,000 RPM in conventional grinders) has been shown to produce a much more stable and productive environment in which the abrasive (diamond matrix) on the grinding surface of the grinding cup can operate. The result is improved cutting performance, substantially improved cutting point regeneration, and improved grinding cup profile retention. In other words the abrasive is able to perform at its peak performance. In addition, the present invention has determined that variable RPM may be necessary to optimize grinding performance and economy for any given feed and/or carbide button size. Smaller buttons appear to require less feed than larger ones. Smaller buttons may also require somewhat higher RPM than larger ones. Either one or a combination of both variable RPM and feed may also be necessary during grinding of any one button for the purpose of initial heavy material removal rates followed by final surface finishing.  
         [0063]     Certain known grinding apparatus, that use a gearbox principle tying orbital rotation of the grinding machine to spindle or grinding cup RPM, do not allow separate controls of orbital rotation speed and grinding head speed. Excessive orbital rotation speed has been shown to be a substantial source of instability during the grinding process. While the RPMs of devices using the gearbox principle can be increased or decreased by using a frequency inverter for example to control the output speed of the drive motor, the relatively high orbital rotation speed would result in a harsh and unstable process. The gear ratio used in this type of known grinding machines is approximately 1:3 (ie. 1 orbital rotation results in 3 output spindle rotation). The present invention optimizes stability and overall optimization of system performance by not tying orbital rotation of the grinding machine to spindle or grinding cup RPM.  
         [0064]     Air-cooled electric motors are currently used in various button bit and/or cutter grinders. Traditionally air-cooled electric motors with sufficient torque and power for the present invention utilizing high feeds are substantially larger than what is feasible for mounting as a grinding head motor on an articulating arm of any type without making the unit too cumbersome.  
         [0065]     Thermal management of air-cooled motors is heavily dependent on the fans capability to force air over the motor, thus cooling it. As the fan speed is lowered, so is its ability to produce sufficient air flow to sufficiently dissipate heat. In addition, the efficiency of the heat exchange taking place is heavily dependent on the ambient temperature. As the ambient temperature increases, the cooling ability of the air is decreased.  
         [0066]     The solution to these problems provided by the present invention has been the development of a water-cooled electric motor that can optionally use the same coolant that is used during grinding by the grinding cup. Since liquid cooling is much more efficient in its ability to dissipate heat, the temperature of the water is not nearly as critical as the temperature of the ambient air in an air-cooled motor. Use of a water-cooled motor allows the grinding apparatus of the present invention to grind over a wide RPM range with no dependency on fans to cool the motor, while drawing substantially higher power and torque. There have been problems reported using air-cooled motors (both electric and hydraulic) in hot place (i.e. desserts, etc.) due specifically to the high ambient temperatures and the challenges associated with that. Water-cooling solves most if not all of these problems.  
         [0067]     The preferred embodiment of a water-cooled electric motor for grinding machine  2  is shown in FIGS.  15  to  20 .  FIG. 15  shows the grinding machine  2  attached to plates  85  below the second box section  73 . The grinding machine  2  is locked in place by levers  124 . The water-cooled electric motor, generally indicated at  125 , has an exterior housing  126  defining a chamber  127  in which the rotor  128  and stator  129  are located. Within the wall of the housing  126  are located a series of longitudinal channels  130  for the cooling water. Ports  131 ,  132  permit water in and water out respectively. A drive coupling  133  at the bottom  134  of housing  126  permits attachment of the spindle assembly  135 . The drive coupling  133  is inserted into the mating drive coupling  140  on spindle assembly  135 . The spindle assembly  135  has an output drive shaft  136  to which a grinding cup can be connected. The spindle assembly  135  is attached to the electric motor housing  126  by bolts  137 . Coolant water for delivery to the grinding cup surface is provided though connection  138 . The electric motor  125  is preferably a three-phase motor and power is connected through connection  90  to connection box  139 . A flexible splash cup  141  is placed around the output drive shaft  136  of spindle assembly  135 . Use of a water cooled motor provides additional advantages. Because the motor housing is sealed entry of dirt and other contaminants into the housing is minimized. In addition without a fan as in air cooled motors the motor runs substantially quieter.  
         [0068]     To control all of the above functions the grinding apparatus is provided with a control system having an operator input panel  94  directly connected to an electronic programmable control card module capable of issuing the necessary commands to, for example, the I/O card module  109  etc. is preferably used. The control system utilizes a circuit board (programmable control card module) behind the operator input panel  94  on the second box section  73  for input and processing of operator input. The programmable control card module and its circuit board is in communication with the I/O card module  109  which connects to all main systems, of which two key areas preferably include frequency inverter function and tilt/laser control card module  51  that monitors and controls the tilting of table  25  and the frequency output and/or voltage of frequency inverter  108 . Such a control system can be used to continuously monitor all or select operational parameters, and if deemed necessary, for example continuously adjust the feed pressure if the motor current (i.e. Amps) rises above a set maximum, increase coolant flow if motor temp gets too high, etc. Utilizing software, microprocessor or microcontroller controlled grinding can influence the grinder behaviour characteristics. The software can in addition to providing operational parameters also deal with laser controlled shut off, sleep mode for the apparatus, error reporting, service reminders, forced replacement of worn parts, components, or modules as deemed necessary for proper operation or to control access for maximized performance. It can also be used to substantially modify grinder behaviour by a simple re-programming or replacement of the microchip, microcontroller or processor. It could be made possible for the operator to update the programming or replacement of chip (and thus the grinders behaviour) right on site which ensures maximum grinder availability to the user. This would allow flexibility in terms of future grinder upgrades. For example, a new grinding cup with a new matrix formulation may require the grinder to behave differently. By simply changing the software program used by the grinder, the behaviour characteristics and any other key variables can be adjusted as required. This would ensure that user would receive customized/optimized performance from the grinder. While the location of the control system components has been illustrated in the preferred embodiment the present invention is not restricted to the location and arrangement of the control system components.  
         [0069]     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.  
         [0070]     The present invention also preferably utilizes a “soft start” where grinding/feed pressure and grinding cup RPM are increased progressively either continuously or in steps to enhance the self-centering feature to whatever level deemed necessary. A benefit of a softer enhanced “self-centering” principle, as described above, is that it results in less dramatic wear and loads on built-in grinding cup profile resulting in enhanced grinding cup characteristics throughout it&#39;s life.  
         [0071]     Once the grinder is properly connected to the power source, compressed air source, and water source, the grinding apparatus is ready to grind. An initial operating sequence for a new set of bits, starting off by grinding the face buttons, with bit holder in down (horizontal) position could for example be as follows: a) load bit(s) into bit holder and secure using locking cylinders in bit holder or appropriate bit holder accessories b) determine size and profile of buttons on bit(s) to be ground c) lock the output spindle of the grinding apparatus by pressing the spindle break button on the operator input panel followed by inserting the correct size and profile of grinding cup into chuck of the grinder while the spindle break is active d) Input estimated grinding time into primary menu on the operator control panel using adjusting knob e) Scroll to next menu on the operator input panel and select button size and optionally profile, etc using the adjusting knob f) Scroll to additional menus if necessary to input any other relevant data such as bias side load settings, button wear, etc using control knob when needed for each menu g) Place the grinder with grinding cup on top of button to be sharpened h) Press start and monitor the grinder to ensure proper function.  
         [0072]     Grinding gauge buttons would be performed in the same manner as above after the following steps: a) angle of the gauge buttons is set by pressing and holding down the bit holder tilt up button while turning the adjusting knob until desired angle is displayed on the operator input panel b) release the bit holder tilt up button and the bit holder will tilt to the selected preset angle.  
         [0073]     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 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.  
         [0074]     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.  
         [0075]     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.