Patent Publication Number: US-8986071-B2

Title: Parts carrier assembly for grinding machine

Description:
BACKGROUND 
     Grinding machines are used to flatten surfaces of machine parts. In a known grinding machine, a parts carrier is located between two grinding wheels, i.e., an upper grinding wheel having an upper planer grinding surface and a lower grinding wheel having a lower planer grinding surface. The known parts carrier assembly consists of a fixed outer ring, a driven inner pinion, and toothed planet wheels all located between the upper grinding surface and the lower grinding surface of the respective grinding wheels. The parts to be ground are located in sockets found in the toothed planet wheels. 
     Such a grinding machine provides adequate results; however, loading and unloading of the grinding machine can require a significant amount of time because the plurality of toothed planet wheels that must be loaded into and unloaded from the grinding machine. 
     SUMMARY 
     In view of the foregoing, a parts carrier assembly for a grinding machine is provided. The parts carrier assembly includes an annular parts carrier and a bearing insert. The annular parts carrier includes an upper surface, a lower surface, an inner edge, an outer edge, and a plurality of loading apertures. The loading apertures extend though the parts carrier from the upper surface to the lower surface. The inner edge is configured to engage a driving wheel of the grinding machine. The driving wheel of the grinding machine rotates about a central axis resulting in rotation of the parts carrier about an offset axis, which is offset from the central axis. The loading apertures are configured to receive associated parts to be ground by the grinding machine. The bearing insert includes an inner bearing surface complementary in shape to the outer edge of the parts carrier. The outer surface the parts carrier bears against the inner bearing surface of the bearing insert as the parts carrier rotates about the offset axis. 
     The parts carrier assembly can be provided in combination with the grinding machine. The grinding machine includes an upper grinding wheeling having an upper substantially planar grinding surface, a lower grinding wheel having a lower substantially planar grinding surface, the driving wheel which is axially interposed between the upper grinding wheel and the lower grinding wheel, and an outer fixed ring axially interposed between the upper grinding wheel and the lower grinding wheel. 
     A method for loading parts to be ground into a grinding machine is also provided. The grinding machine is similar to that described in the previous paragraph. The method includes loading a plurality of parts to be ground into respective loading apertures found in an annular parts carrier. The method further includes operatively connecting the parts carrier with the driving wheel such that the parts carrier and the plurality of parts to be ground are axially disposed between the upper grinding wheel and the lower grinding wheel. The method further includes rotating the driving wheel about the central axis resulting in rotation of the parts carrier about an offset axis, which is offset from the central axis. 
     A method for grinding parts is also provided. The method includes loading a plurality of parts that are to be ground into a parts carrier. The method further includes rotating a grinding wheel including a substantially planar grinding surface about a central axis. The grinding surface has an outer diameter od 1 . The method further includes rotating the parts carrier having an outer diameter od 2 , which is greater than od 1 /2, about an offset axis, which is offset from the central axis. The method further includes contacting the grinding surface of the rotating grinding wheel with the parts that have been loaded into the parts carrier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional side view of a grinding machine. 
         FIG. 2  is a cross-sectional view of a parts carrier assembly used to carry parts to be ground by grinding machine shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The description and drawings herein are merely illustrative and are provided so that one of ordinary skill in the art can make and use a grinding machine and a parts carrier assembly described herein. Various modifications and alterations can be made in the structures and steps disclosed without departing from the scope of the invention, which is defined by the appended claims. Various identified components of a grinding machine disclosed herein are merely terms of art that may vary from one manufacturer to another. The terms should not be deemed to limit the invention. The drawings are shown for purposes of illustrating one or more exemplary embodiments and are not for purposes of limiting the appended claims. All references to direction and position, unless otherwise indicated, refer to the orientation of the components illustrated in the drawings and are not to be construed as limiting the appended claims. 
       FIG. 1  schematically depicts a grinding machine  10  that includes an upper grinding wheel  12  and a lower grinding wheel  14 . The upper grinding wheel  12  includes an upper substantially planar grinding surface  16 . The lower grinding wheel  14  includes a lower substantially planar grinding surface  18 . The grinding surfaces  16 ,  18  are used to flatten machine parts that are loaded into a parts carrier assembly  20  located between the grinding surfaces. 
     In the illustrated embodiment, each grinding surface  16 ,  18  has an outer diameter od 1  and an inner diameter id 1 . Each grinding surface  16 ,  18  includes grinding particles such as cubic-boron-nitride (CBN) particles embedded in each respective grinding wheel  12 ,  14  between the outer diameter od 1  and the inner diameter id 1 . In this embodiment, the CBN particles are suspended in a plastic carrier located at the planar grinding wheel surface  16 ,  18  of each respective wheel  12 ,  14 . Other grinding particles and other carriers for grinding particles may be employed. 
     A first motor  22  operatively connects with a first drive shaft  24  to rotate the upper grinding wheel  12  about a central axis  26 . A second motor  28  operatively connects with a second drive shaft  32  to rotate the lower grinding wheel  14  about the central axis  26 . A third motor  34  can operatively connect with a drive gear shaft  36  to rotate a drive pinion  38  about the central axis  26 . The drive pinion  38  drives the parts carrier assembly  20  in the grinding machine  10  in a manner that will be described in more detail below. During a grinding operation coolant fluid can be fed into the grinding machine  10  through a fluid conduit  42 . 
     The grinding machine  10  also includes a driving wheel  52 , which is configured to be driven by the drive pinion  38 . The driving wheel  52  includes a central opening  54  and a plurality of bolt holes  56  to facilitate attachment of the driving wheel  52  to the drive pinion  38 . In the illustrated embodiment, the driving wheel  52  is a circular gear that rotates about the central axis  26 . With reference to  FIG. 2 , the driving wheel  52  includes an outer circumferential surface  58 , which in the illustrated embodiment includes a plurality of gear teeth, referred to herein as driving wheel gear teeth  62 . 
     The grinding machine  10  further includes an outer ring  64  having an interior circumferential edge  66 . A plurality of outer ring teeth  68  on the interior circumferential edge  66  extend inwardly toward the central axis  26 . The interior circumferential edge  66  of the outer ring  64  is offset from the central axis  26  a radius r 1 . 
     With reference back to  FIG. 1 , the parts carrier assembly  20  is disposed in the grinding machine  10  axially between the upper grinding surface  16  of the upper grinding wheel  12  and the lower grinding surface  18  of the lower grinding wheel  14  during a grinding operation. The parts carrier assembly  20  includes an annular parts carrier  70  and a bearing insert  100 . Parts P (only one part P is depicted in  FIG. 2 ) that are to be ground are loaded into the annular parts carrier  70  and the parts P are contacted by the upper grinding surface  16  of the rotating upper grinding wheel  12  and the lower grinding surface  18  of the rotating lower grinding wheel  14  to flatten the parts. 
     With reference back to  FIG. 1 , the annular parts carrier  70  includes an upper surface  72  disposed generally normal to an offset axis  74 , which will be described below, and a lower surface  76  that is disposed generally normal to the offset axis  74 . An annular parts carrier height is defined between the upper surface  72  and the lower surface  76  measured parallel to the offset axis  74 . The annular parts carrier  70  also includes a plurality of loading apertures  78  extending through the parts carrier from the upper surface  72  to the lower surface  76 . The loading apertures  78  are depicted as circular (see  FIG. 2 ) in the illustrated embodiment; however, the loading apertures can take an alternative configuration based on the size and shape of the parts P that are to be ground by the grinding machine  10 . The thickness (measured parallel to the offset axis  74 ) of the parts P that are to be loaded into the loading apertures  78  should at least be equal to, and preferably slightly greater than, the annular parts carrier height, which allows the parts to contact the upper grinding surface  16  of the upper grinding wheel  12  and the lower grinding surface  18  of the lower grinding wheel  14  during a grinding operation. 
     The annular parts carrier  70  engages with the driving wheel  52 . The annular parts carrier  70  includes an inner edge  82  that includes a plurality of teeth, referred to herein as parts carrier teeth  84 . The parts carrier teeth  84  on the inner edge  82  of the annular parts carrier  70  engage the driving wheel gear teeth  62  on the outer circumferential surface  58  of the driving wheel  52 . In the embodiment depicted in  FIG. 2 , the parts carrier teeth  84  engage the driving wheel gear teeth  62  near a 12 o&#39;clock position on the annular parts carrier  70  and the driving wheel  52  (per the orientation shown in  FIG. 2 ). Rotation of the driving wheel  52  about the central axis  26  results in rotation of the annular parts carrier  70  about the offset axis  74 , which is offset from and parallel to the central axis  26 . As seen in  FIG. 1 , the central axis  26  is offset from the offset axis  74  a distance d. 
     As illustrated in  FIG. 2 , the annular parts carrier  70  surrounds the driving wheel  52 . The annular parts carrier  70  and the driving wheel  52 , which is a circular gear, define a crescent-shaped void  86  between the inner edge  82  of the annular parts carrier  70  and the outer circumferential surface  58  of the driving wheel  52 . The annular parts carrier  70  further includes an outer edge  88 , which acts as a bearing surface acting against the bearing insert  100 . The outer edge  88  of the annular parts carrier  70  is offset from the offset axis  74  a radius r 2 . The radius r 1  of the interior circumferential surface  66  of the outer ring  64  is substantially equal to r 2  (the radius to the outer edge  88  of annular parts carrier  70 )+distance d, which is the distance that the central axis  26  is offset from the offset axis  74 . 
     The parts carrier assembly  20  further includes the bearing insert  100 . The bearing insert  100  is substantially crescent-shaped when viewed normal to the central axis  26 . The bearing insert  100  can be made from an ultra high weight polyethylene material. The bearing insert  100  includes an inner substantially circular bearing surface  102  and an outer substantially circular surface  104 . The inner substantially circular bearing surface  102  of the bearing insert  100  is complementary in shape to and bears against the outer edge  88  of the annular parts carrier  70  as the annular parts carrier rotates about the offset axis  74 . The inner bearing surface  102  of the bearing insert  100  follows the radius r 2  with respect to the offset axis  74  and the outer substantially circular surface  104  follows the radius r 1  with respect to the central axis  26 . Since the central axis  26  is offset from the offset axis  74  and because of the configuration of the outer ring  64 , the inner bearing surface  102  does not make up a complete circle. As shown in  FIG. 2 , the bearing insert  100  is positioned between the annular parts carrier  70  and the outer ring  64 . The inner diameter 2r 1  of the outer ring, is substantially equal to the outer diameter od 1  of the planar grinding surfaces  16 ,  18  of the respective grinding wheels  12 ,  14 . 
     The outer substantially circular surface  104  of the bearing insert  100  includes a plurality of bearing insert teeth  106 . The outer substantially circular surface  104  of the bearing insert  100  engages with the outer ring  64  to fix the bearing insert  100  with respect to the outer ring  64 . The bearing insert teeth  106  engage with the outer ring teeth  66 . Although the bearing insert  100  is described as having the outer substantially circular surface  104 , the outer surface  104  is non-circular and is configured to engage the fixed, non-rotating, outer ring  64  of the grinding machine  10  to preclude rotation of the bearing insert  100  with respect to the outer ring. 
     During a grinding operation, the grinding wheels  12 ,  14  are rotated about the central axis  26 . Also during the grinding operation, when the grinding wheels  12 ,  14  rotate about the central axis  26 , the annular parts carrier  70  rotates about the offset axis  74 , which is offset from the central axis  26 . While the annular parts carrier  70  rotates, the rotating grinding wheels  16 ,  18  are in contact with the parts P loaded into the respective loading apertures  78  of the rotating annular parts carrier  70 . As mentioned above, each grinding wheel surface  16 ,  18  has an outer diameter od 1 . The annular parts carrier  70  has an outer diameter od 2  (or 2r 2 ), which is greater than od 1 /2. 
     The outer diameter od 1  of the grinding surfaces  16 ,  18  of the respective grinding wheels  12 ,  14  is substantially equal to the diameter of the interior circumferential surface  104  of the outer ring  64  (od 1 =2r 1 ). An outermost edge of the annular parts carrier  70  (shown as the 6 o&#39;clock position in  FIG. 2 ) nearly comes into contact with the interior circumferential surface  104  of the outer ring  64 . As such, rotation of the annular parts carrier  70  results in movement of a respective part (among the plurality of parts that are to be ground by the grinding machine  10 ) from adjacent the inner diameter id 1  of the upper grinding surface  16  or the lower grinding surface  18  to adjacent the outer diameter od 1  of the upper grinding surface or the lower grinding surface. 
     The driving wheel  52  has an outer diameter od 3  that is substantially equal to the inner diameter id 1 . The difference in the diameter of the driving wheel  52  and the diameter of the annular parts carrier  70 , along with the axes  26 ,  74  being offset, results in the crescent-shaped gap  86  between the inner circumferential edge  82  of the annular parts carrier  70  and the outer circumferential surface  58  of the driving wheel  52 . Particles removed from the parts that are being ground can fall into this crescent-shaped gap  86  and then be removed via the conduit  42  providing cleaning fluid into the grinding machine  10 . 
     A method for loading parts to be ground into a grinding machine, such as the grinding machine  10  shown in  FIG. 1 , will now be described. As mentioned above, the grinding machine  10  includes an upper grinding wheel  12  having an upper substantially planar grinding surface  16 , a lower grinding wheel  14  having a lower substantially planar grinding surface  18 , the driving wheel  56  axially interposed between the upper grinding wheel  12  and the lower grinding wheel  14 , and the outer fixed ring  64  axially interposed between the upper grinding wheel  12  and the lower grinding wheel  14 . The upper grinding wheel  12 , the lower grinding wheel  14 , and the driving wheel  56  each rotate about the central axis  26 . The method further includes loading a plurality of parts P to be ground into the respective loading apertures  78  found in the annular parts carrier  70 . The method further includes operatively connecting the parts carrier  70  with the driving wheel  56  such that the parts carrier and the plurality of parts P to be ground are axially disposed between the upper grinding wheel  12  and the lower grinding wheel  14 . The method further includes rotating the driving wheel  56  about the central axis  26  resulting in rotation of the parts carrier  70  about the offset axis  74 , which is offset from the central axis  26 . The method can further include positioning the bearing insert  100  between the parts carrier  70  and the outer fixed ring  64 . The method can further include fixing the bearing insert  100  to the outer fixed ring  64  to inhibit rotation of the bearing insert with respect to the outer fixed ring. 
     A method for grinding parts will be described with reference to the grinding machine  10  shown in  FIG. 1 ; however, the method can be used with other grinding machines. The method includes loading a plurality of parts P that are to be ground into the annular parts carrier  70  that surrounds the central axis  26 . The method further includes rotating a grinding wheel (the upper grinding wheel  12  or the lower grinding wheel  14 ) including a substantially planar grinding surface  16 ,  18  about the central axis  26 . Each grinding surface  16 ,  18  has an od 1 . The method further includes rotating the parts carrier  70  having an od 2 , which is greater than od 1 /2, about the offset axis  74 , which is offset from the central axis  26 . The method further includes contacting the grinding surface  16 ,  18  of the rotating grinding wheel  12 ,  14  with the parts P that have been loaded into the annular parts carrier  70 . Rotating the annular parts carrier  70  can further include rotating the parts carrier with the driving wheel  56  rotating about the central axis  26  and having the outer diameter od 3  substantially equal to the id 1 . The method further includes providing the crescent-shaped gap  86  between the inner edge  82  of the parts carrier  70  and an outer circumferential surface  58  of the driving wheel  52 . The method can further include positioning the bearing insert  100  between the parts carrier  70  and the outer ring  64 . As mentioned above, the inner diameter of the outer ring  64  is substantially equal to od 1 . As mentioned above, the bearing insert  100  and the outer ring  64  are fixed together and do not rotate. 
     A parts carrier assembly for a grinding machine, the parts carrier assembly in combination with the grinding machine, a method for loading parts to be ground into a grinding machine, and a method for grinding parts have been described above with particularity. Modifications and alterations will occur to those upon reading and understanding the preceding detailed description. The invention, however, is not limited to only the embodiments described above. Instead, the invention is broadly defined by the appended claims and the equivalents thereof. 
     It will be appreciated that various of the above-disclosed and other features and functions, or alternatives or varieties thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.