Patent Publication Number: US-2020284700-A1

Title: Planar grinder

Description:
CROSS-REFERENCE TO RELATED APPLICATION DATA 
     This application claims the benefit of and priority to Provisional U.S. Patent Application Ser. No. 62/078,628, filed Nov. 12, 2014, the disclosure of which is incorporated therein in its entirety. 
    
    
     BACKGROUND 
     Grinders are in use in many industries. One type of grinder is used to prepare samples of materials such as metals, polymers, ceramics or the like for further examination, such as by microscopic examination. 
     Known grinders include a sample or specimen holder that is configured to rotate relative to a grinding media that is also configured to rotate. In this manner, there are two rotating motions occurring simultaneously. A fluid, such as water, is injected onto the grinding media to lubricate and cool the sample and media and to remove debris, such as grinding debris generated during the grinding process. 
     One known grinder/polisher, disclosed in Shewey, et al, U.S. Pat. No. 8,574,028, includes a head on which a sample holder is mounted for rotation of the sample. The sample is held against a rotating plate or platen in a base of the grinder. The plate or platen has an abrasive surface or an abrasive fluid media is introduces onto the platen to effect the sample preparation. Typically, the abrasive surface on the platen is an abrasive paper or other removable and replaceable media. The disclosure of Shewey, as well, the disclosures of Hart. U.S. Pat. No. 8,465,347 and Hart, U.S. Pat. No. 8,152,603 are commonly assigned with the present application and are incorporated herein by reference. 
     The head of the grinder/polisher of Shewey reciprocates (moves toward and away from the platen) to maintain a predetermined force between the sample and the platen. Reciprocating movement of the head is determined based, in part, on input from a load cell that is operably connected to the specimen holder (via a chuck and drive shaft). 
     When used as a grinder, a grinding wheel is mounted to the platen. In use, the abrasive particles that form the grinding wheel become worn as a result of contact with and grinding of the specimen. As a result, the grinding wheel must be “dressed” or resurfaced to continue to effectively prepare the sample. Dressing is carried out during the grinding operation using an arm that swings over an opposite side of the wheel that has a head mounted to the arm. The arm moves in an arc and contacts the wheel to remove the worn areas and expose fresh surfaces of the abrasive that more efficiently effect the grind. In known automated grinder systems, dressing is carried out on a timed basis, regardless of whether it is needed, or is overdue. 
     In addition, known grinders have a base in which the platen is positioned that has an open top. That is, the areas above the platen, surrounding the specimens on the holder are open to the environs. While this makes access to the wheel and/or platen and specimens readily available, it can also result in splashing and debris being ejected from the grinder during operation. 
     It is also common to, at times, change out wheels to carry out different grinding operations. For example, different materials to be prepared (such as steel and aluminum) may require that different types of grinding wheels (different wheel materials) be used. As such, a wheel for grinding steel may be removed and a wheel for grinding aluminum then installed in the grinder. When the steel grinding wheel is then reinstalled, it may require dressing or redressing to assure that the wheel surface is planar and normal to the specimen due to the orientation of the wheel as it is installed on the platen. Otherwise, the grind may not be flat due to high spots and low spots on the wheel relative to the specimen. This additional dressing to assure a planar surface on the wheel can be time consuming and can result in removing portions of the wheel that are not yet consumed or portions of the wheel that are still effective for grinding. 
     Accordingly, there is a need for an improved grinder. Desirably, such a grinder includes an automated system for dressing the grinding wheel based on need. More desirably, such a grinder includes a cover over the specimen to reduce the amount of splashing and debris ejection, but that permits ready access to the grinding wheel. More desirably still, such a grinder permits removing a grinding wheel and reinstalling that grinding wheel in such a way that the orientation of the wheel is maintained during reinstallation. 
     SUMMARY 
     A sample grinder includes a base having a bowl and a rotating drive plate to operably support a grinding wheel. A head is configured to support a specimen holder and has a first drive for rotational drive of the specimen holder and a second drive for moving the head and the specimen holder toward and away from the rotating plate. The head has a depending sleeve that has an inner outer periphery larger than the specimen holder. 
     A removable cover is disposed over the bowl and rotating drive plate. The cover has an opening having an inner periphery greater than the outer periphery of the sleeve, so that the sleeve traverses through the cover opening when the specimen holder is moved toward the rotating drive plate. 
     The cover has a top that is non-planar and slopes away, toward a front-side corner. The sleeve can be formed from a transparent or semi-transparent material. 
     The cover can include a fluid delivery manifold and a plurality of fluid dispensing nozzles in fluid communication with the fluid delivery manifold. The fluid delivery manifold can be formed as part of the cover and the fluid dispensing nozzles can be mounted to the cover over the fluid delivery manifold. The nozzles can be formed as openings in a plate and the plate mounted to an inside surface of the cover. The openings can be asymmetrically disposed generally along a line of the plate. A fluid delivery conduit in the base is in fluid communication with the fluid delivery manifold. 
     A grinding wheel has a central axis and is mountable to and coaxial with the platen. The grinding wheel mounts to the platen in a single radial orientation only and has one or more mounting elements thereon cooperating with the platen mounting elements to permit mounting the grinding wheel in the single radial orientation only. The grinding wheel is initially mounted to the platen, removed from the platen and remounted to the platen, and when the grinding wheel is remounted to the platen, it can be remounted in only the same radial orientation as initially mounted to the plate. 
     The platen mounting elements and the grinding wheel mounting elements can be, for example, cooperating projections and recesses. The cooperating projections and recesses can be pins and bores. The pins can be positioned on the platen and the bores formed in the grinding wheel. 
     In an embodiment, four pins are positioned on the platen, three of which are symmetrically disposed on the platen and the fourth pin is asymmetrically disposed on the platen relative to the three symmetrically disposed pins. The grinding wheel includes four bores positioned to cooperate with the four pins. 
     The sample grinder can also include a dressing system including an arm and a hardened face for contacting the grinding wheel to dress the grinding wheel. A monitor monitors the current of one or both of the drive plate motor and the head first drive. The sample grinder includes a controller. 
     The monitor monitors the current drawn by one or both of the drive plate motor and the head first drive, and the dressing system is actuated based upon a the current drawn by one or both of the drive plate motor and the head first drive motor falling below a predetermined value. 
     In an embodiment, the controller determines whether a grinder cycle has commenced, and once commenced, the controller initiates a dressing operation. When the controller determines that a dressing operation is in progress, the controller monitors and captures current data points, and when the controller determines that a dressing operation is not in progress, the controller determines the predetermined current value for the drive plate motor and/or the head first drive. 
     These and other features and advantages of the present invention will be readily apparent from the following detailed description, in conjunction with the claims 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The benefits and advantages of the present invention will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying and drawings, wherein: 
         FIG. 1  is a perspective illustration of an embodiment of a planar grinder; 
         FIG. 2  is a perspective schematic illustration of the planar grinder shown with the head in the lower or grinding position; 
         FIG. 3  is a view similar to those of  FIGS. 1-2  with the head withdrawn and rotated away from the base and cover; 
         FIG. 4  is a view similar to  FIG. 3  with the cover removed for ease of viewing the grinding wheel, and showing the dressing arm in an operating position on the grinding wheel; 
         FIG. 5  is a view similar to  FIG. 4  showing the grinding wheel removed for ease of viewing the platen; 
         FIGS. 6 and 7  are partial perspective views of the head height drive assembly and having portions of the head removed for clarity of illustration 
         FIG. 8  is a perspective view of a portion of the specimen (rotational) drive shown with a specimen holder therein and the specimen drive assembly shaft; 
         FIG. 9  is an exploded view of the platen drive and drive assembly; 
         FIGS. 10A-10C  are bottom and sectional views of the base,  FIGS. 10B and 10C  taken along lines  10 B- 10 B and  10 C- 10 C, respectively in  FIG. 10A ; 
         FIG. 11  illustrates the head and sleeve in the upper or retracted position; 
         FIG. 12  is an illustration of the underside of the cover and the fluid manifold inlet and spray nozzles in the cover; 
         FIG. 13  is partial enlarged illustration of the fluid manifold and the fluid spray nozzles; 
         FIG. 14  is a perspective view of the base, with the cover and grinding wheel removed for clear illustration of the platen; 
         FIG. 15  is an illustration of the bottom of the grinding wheel; and 
         FIG. 16  is an example of an operating scheme for the planar grinder. 
     
    
    
     DETAILED DESCRIPTION 
     While the present device is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification and is not intended to be limited to the specific embodiment illustrated. 
     Referring now to the figures and in particular, to  FIGS. 1-5 , there is shown a bench top planar grinder  10 . The grinder  10  includes, generally, a base  12 , a head  14  and a controller  16  in communication with a control panel  18 . The base  12  includes a casing  20  that encloses a rotating platen  22  and a drive system  24  for the platen  22 . Referring briefly to  FIGS. 9 and 10A-10C , the drive system  24  includes a drive motor  26 . In a present embodiment, the motor  26  is an AC motor operably connected to the platen  22  by a drive belt  28 . 
     The base  12  defines an upper lip  30  that forms the top edge of a bowl  32 . The platen  22  is positioned in the bowl  32 , above the bottom of the bowl, but below the lip  30 . The bowl  32  has a generally D-shaped profile to allow access to the platen  22  for maintenance, removal and the like. A grinding wheel  34  is positioned on the platen  22 . The D-shaped profile of the bowl  32  also allows ready access to the grinding wheel  34  for maintenance, removal and the like. 
     Referring to  FIGS. 4 and 14-15 , the grinding wheel  34  is positioned on and mounted to the platen  22  for rotation with the platen  22 . The grinding wheel  34  and platen  22  are coaxial with one another (that is, share a common axis A) and are configured so that the grinding wheel  34  can be installed on or mounted to the platen  22  in only one orientation. This single orientation mounting configuration assures that when the wheel  34  is removed and reinstalled on the platen  22 , it is reinstalled in the exact same orientation each time. As will be appreciated by those skilled in the art, the ability to reinstall the wheel  34  at the same orientation each time eliminates the need to redress the wheel  34  each time it is installed on the platen  22 . 
     In a present embodiment the single orientation mounting system is provided by a plurality of locating pins  36 A-D, one of which  36 D is asymmetrically located and which are received in cooperating locating bores  38 A-D in the wheel  34 , one of which  38 D is asymmetrically located to receive the asymmetrically located pin  36 D. For example, the wheel  34  can include three pins  36 A-C located 120 degrees from one another spaced an equal distance from a center axis A of the wheel  34  and a fourth pin  36 D located at any location on the wheel  34  (such as in the illustrated embodiment, along a radial line of one of the three pins), and cooperating bores  38 A-D in the platen  22  for receiving the pins. Essentially, the asymmetric fourth pin  36 D provides an interfering mounting arrangement to prevent installing the wheel  34  at any orientation other than the one orientation in which all four pins  36 A-D will be accommodated in their respective, cooperating bores  38 A-D. A single fastener  40 , such as a countersunk threaded bolt can be used to secure the wheel  34  to the platen  22 . 
     There are a number of advantages to such a single-orientation mounting arrangement. For example, as noted above, once a wheel  34  is dressed, it can be removed from the platen  22  and reinstalled without further dressing or redressing, unless it is needed to resurface the wheel  34 . Moreover, the wheel  34  is readily and quickly installed, removed and reinstalled on the platen  22  with, for example, a single fastener  40 . 
     As illustrated in  FIGS. 1-4 and 11 , the grinder  10  includes a cover  42  positioned over the bowl  32 . The cover  42  envelops the bowl  32  (including the wheel  34 ) when in place. The cover  42  includes an opening  44  through which a specimen holder  46  moves to move the specimens into contact with the wheel  34 . A sleeve  48  is positioned on the head  14 , depending therefrom around and over a shaft  50  to which the specimen holder  46  is mounted. The sleeve  48  depends from the head  14  to a position just above the specimen holder  46 . 
     The sleeve  48  has an inner diameter that is slightly larger than the diameter of the specimen holder  46  and an outer diameter configured to allow the sleeve  48  to move through the cover opening  44  with the specimen holder  46  (the outer diameter of the sleeve  48  is just smaller than the diameter of the cover opening  44 ). In this manner, a gap  52  between the sleeve  48  and the cover opening  44  is sufficiently small so as to reduce or eliminate splashing that may occur. As seen in  FIGS. 3 and 12 , a front corner  54  of the cover  42  slopes downward to permit the head  14  (with the specimen holder  46  mounted thereto) to swing away from the cover  42  and wheel  34  for easy access to the holder  46  and wheel  34 . A seal  56  can be positioned around a lower edge of the cover  42 , where the cover  42  is positioned on the base  12 , to further seal the bowl  32 . The sleeve  48  can be formed from a transparent or semi-transparent material to permit viewing the specimen and wheel  34 . 
     In order to access the wheel  34  and platen  22 , the cover  42  is configured for easy removal from the base  12 . In a present embodiment, the cover  42  includes a slotted opening  58  in a rear of the cover that is positioned over the dressing arm housing  60 . The edges of the slotted opening  58  slide into a recess  62  in the dressing arm housing  60  to secure the cover  42  in place. The cover  42  can include clamps  64  that secure and lock the cover  42  to the base  12  and permit removing and installing the cover  42  without the use of tools. 
     When the cover  42  is in place on the base  12 , an opening  66  in the cover  42  is in communication with a fluid supply conduit  68 . The conduit  68  extends upwardly from the base  12  into the opening  66 . A seal  70  is positioned between the conduit  68  and the opening  66 . A fluid, such as water is provided from a supply, through the base  12  and into the opening  66  in the cover  42 . 
     As noted above, a cooling/lubricating fluid is needed for proper grinder  10  operation. The fluid supply conduit  68 , via a fluid delivery manifold  72  in the cover  42 , supplies the cooling/lubricating fluid to the wheel  34 . In an embodiment, the fluid delivery manifold  72  includes a plurality of openings or nozzles  74  that spray the fluid onto the wheel  34 . The nozzles  74  are positioned to provide a desired spray pattern of fluid onto the wheel  34 . In an embodiment, nine (9) nozzles  74   a - 74   i  are arranged to spray fluid from the manifold  72 , with a first nozzle  74   a  near to the fluid entrance (from the conduit  68 ), a set of five adjacent nozzles  74   b - 74   f  spaced from the first nozzle, a seventh nozzle  74   g  spaced from the set of five nozzles, and a set of two nozzles  74   h ,  74   i  at about the end of the manifold  72 , nearest to the center of the wheel  34 . The nozzles  74  can be formed in a plate  76  that is positioned over and forms part of the manifold  72 . 
     Referring to  FIGS. 1-9  the head  14  supports and rotates the specimens S. The head  14  is mounted to the base  12  by a telescoping support  78 . The head  14  contains two drive systems, one drive system  80  for rotation of the specimen holder  46  (see  FIG. 8 ), and a height drive system  82  for up and down movement of the head  14  (see  FIGS. 6-7 ) to move the specimen holder  46  and the specimens S toward and away from the wheel  34 . The movements, rotational and height, are provided by the separate drive systems  80 ,  82 . 
     Referring to  FIG. 8 , the rotational drive  80  is configured to rotate the specimen holder  46  in either a clockwise or counter clockwise direction. In a present grinder  10 , the drive system  80  is a gear drive, driven by a motor  84 , however, a direct drive, belt drive or the like can also be used. It will be understood that the head  14  is stationary as the specimen holder  46  rotational drive is operating. The drive system  80  includes a can-like housing  86  that has a gear  88  that engages a motor gear  90  to rotate the can-like housing  86 . 
     Referring to  FIGS. 6-7 , the height drive  82  is a precision drive to precisely position the specimen holder  46  and the specimens S relative to the wheel  34 . The height drive  82  is fixedly mounted in the head  14 . The present grinder  10  uses a servomotor that is operably connected by a timing belt  92  to a pulley  94  (driven by the belt  92 ). A lead screw  96  is mounted to the pulley  94  for rotation with the pulley  94 . The lead screw  96  is mounted to a fixed (relative to the base  12  and the support  78 ) threaded receiving element  98  so that rotation of the lead screw  96  moves the head  14  up and down to move the specimen holder  46  toward and away from the wheel  34 . 
     A further enhancement to the grinder  10  is an automated dressing system  100 . As noted above, dressing is carried out to resurface or recondition the wheel  34  as the wheel  34  becomes worn, that is when the peaks on the abrasive are worn and the valleys between the peaks become filled with the specimen material (referred to as wheel loading). The dressing system  100  includes a head  102  mounted to an arm  104  that moves in an arc and contacts the wheel  34  to remove the loaded area (e.g., the worn and dulled areas or abrasive) and expose fresh surfaces of abrasive that more efficiently effect the grind. Dressing is carried out during the grinding operation by moving the arm  104  to swing over an opposite side of the wheel  34  from the location at which the grinding operation is carried out. 
     The dressing system head  102  has a hardened face  106  that contacts and removes the worn or dulled areas of the wheel  34 . One hardened face is a sacrificial diamond dressing face  106 . In the operation of known grinding systems, dressing is carried out at preset times, regardless of whether dressing is actually required or dressing is overdue. In the former instance, it will be appreciated that dressing too often removes portions of the wheel surface that are still effective for grinding. In the latter, overdue dressing can result in too much time spent grinding a sample or failure to properly grind. Moreover, the required dressing period is a function of many variables, such as specimen material, wheel composition, wheel speed, sample holder speed and the like. 
     In an embodiment of the present grinder  10 , dressing is carried out based upon measured operating conditions and comparing those operating conditions to a preset value. One such way in which to dress the wheel  34  based on operating conditions is to measure the resistance between the specimen S and the grinding wheel  34  and to dress the grinding wheel  34  when the resistance drops below a certain preset value. 
     The resistance can be monitored in a variety of ways. In one embodiment, resistance is related to the amount of power required to operate either the platen motor  26  or the head motor  84  (the two concurrently rotating elements). The power is related to the current drawn by the motors  26 ,  84 . So, in application, one way in which to measure the resistance is to monitor the current drawn by with the platen motor  26  or the head motor  84 . When the current drops below a certain predetermined level, it is indicative of lowered resistance and dressing will automatically commence. 
     A flow chart of the automated dressing operation  1000  is illustrated in  FIG. 16 . At step  1002 , the grinder cycle commences and at step  1004 , a dressing operation is initiated. At step  1006 , the controller monitors whether a dressing operation is in progress. 
     If a dressing operation is in progress, then at step  1008 , the (electrical) current data points (work load on the motor) are captured and stored in the controller and the operation returns to between steps  1004  and  1006 . 
     If a dressing operation is not in progress, then at step  1010 , the controller determines the optimal current trigger point to initiate the next dressing operation. The controller monitors whether the current load has reached a load trigger point at step  1012 . And, if the trigger point has been reached, the controller initiates a dressing operation at step  1004 . If the trigger point has not been reached, the controller continues to monitor whether the current load reaches the load trigger point at step  1012 . 
     In this manner, the dressing operation is initiated only when needed based on actual operating data (data as captured through monitoring the current load on the platen or the head motor), rather than on an arbitrary, time-based measurement. This feature provides an optimal work load with a minimized cycle time. 
     All patents referred to herein, are hereby incorporated herein by reference, whether or not specifically done so within the text of this disclosure. 
     In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. 
     From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present disclosure. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover all such modifications as fall within the scope of the invention.