Patent Publication Number: US-2023141185-A1

Title: Grinding apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/JP2021/012036, filed on Mar. 23, 2021, which claims priority to Japanese Patent Application No. 2020-074891, filed on Apr. 20, 2020. The entire disclosures of the above applications are expressly incorporated by reference herein. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to a grinding apparatus that grinds a substance to be ground. 
     Background Art 
     As an apparatus configured to grind a substance to be ground, a powder processing apparatus including a deposition surface for the substance to be ground to deposit on, a processing surface opposed to the deposition surface and curved in a convex shape, and moving unit for relatively moving the deposition surface and the processing surface along the deposition surface has heretofore been proposed (for example, see WO 2004/112964). The deposition surface corresponds to an inner peripheral surface about an axis of a container member in which the substance to be ground is accommodated. In the abovementioned powder processing apparatus, when the deposition surface and the processing surface are relatively moved along the deposition surface, the substance to be ground is pressed toward, and rubbed against, the deposition surface by the processing surface. In other words, the substance to be ground undergoes a compression force and a shear force from the deposition surface and the processing surface. As a result, the substance to be ground is ground by the powder processing apparatus. 
     Aside from the foregoing, there has been a planetary ball mill as a powder processing apparatus using centrifugal force, where a plurality of mill pots arranged around a rotation shaft are rotated and revolved (for example, see Japanese Patent Application Laid-Open Publication No. 2002-143706). 
     According to WO 2004/112964, however, the substance to be ground is unable to be ground at all unless the substance to be ground deposits on the deposition surface. The substance to be ground is unable to be efficiently ground if the substance to be ground is collected to the inner bottom surface of the container member in the depth direction thereof by gravity. Japanese Patent Application Laid-Open Publication No. 2002-143706 discloses a batch type apparatus, which is difficult to be scaled up by upsizing. 
     In view of the foregoing circumstances, an object of the present invention is to provide a grinding apparatus that efficiently improves throughput. 
     SUMMARY 
     A grinding apparatus according to the present invention is a grinding apparatus configured to grind a substance to be ground, the grinding apparatus including: a rotating body configured to include therein a channel extending up to an opening formed in its own outer peripheral surface, the rotating body being configured to be capable of accommodating in the channel the substance to be ground and a grinding medium capable of grinding the substance to be ground; and a grinding container configured to include therein an accommodation space accommodating the rotating body and an opposed surface opposed to the opening of the rotating body, the opposed surface extending annular about a center axis of the rotating body. The grinding medium and the substance to be ground are capable of being moved from the channel to the accommodation space through the opening by rotating the rotating body. 
     In the grinding apparatus according to the present invention, the rotating body has an inlet opening capable of letting in the substance to be ground and the grinding medium, and the channel includes an interval where a channel width decreases outward in a radial direction of the rotating body. 
     The grinding apparatus according to the present invention also includes a moving mechanism configured to move the substance to be ground and the grinding medium separated from the rotating body into the channel of the rotating body again. 
     In the grinding apparatus according to the present invention, the grinding container has a reception opening capable of letting in the substance to be ground and the grinding medium, and a discharge opening capable of discharging the substance to be ground and the grinding medium to outside. The rotating body has an inlet opening that serves as an inlet for the substance to be ground and the grinding medium that have passed through the reception opening. The moving mechanism includes a circulation-path forming pipe that is connected to the grinding container through the discharge opening and the reception opening and forms a circulation path with the grinding container, and an airflow generation unit configured to generate an airflow from the discharge opening toward the reception opening in the circulation-path forming pipe. An opening of the circulation-path forming pipe on a side where the substance to be ground and the grinding medium are discharged is located inside the channel of the rotating body or in front of the inlet opening. 
     The grinding apparatus according to the present invention also includes a removal unit that is located between the opposed surface and the rotating body so as to be opposed to the opposed surface in a radial direction of the rotating body, and a moving unit configured to move the removal unit in a circumferential direction of the opposed surface. The removal unit is moved by the moving unit to come into contact with the substance to be ground deposited on the opposed surface and remove the substance to be ground deposited on the opposed surface. 
     In the grinding apparatus according to the present invention, the moving unit moves the removal unit so that the removal unit revolves about a rotation axis of the rotating body, and a revolving speed of the removal unit revolved by the moving unit is lower than a rotation speed of the rotating body. 
     The grinding apparatus according to the present invention also includes a guide blade that has a surface facing in a direction of rotation of the rotating body and extending in a radial direction of the rotating body and is disposed to be capable of revolving about a rotation axis of the rotating body. Revolution of the guide blade about the rotation axis generates an airflow in the accommodation space. 
     In the grinding apparatus according to the present invention, the opposed surface is formed of ceramics. 
     The grinding apparatus according to the present invention also includes a rotating-body rotating unit configured to rotate the rotating body about an axis parallel to an axis direction of the center axis of the rotating body. 
     In the grinding apparatus according to the present invention, when the rotating body is rotated by the rotating-body rotating unit, the substance to be ground in the channel is moved toward the opposed surface through the opening by a centrifugal force along with the grinding medium and collides with the opposed surface. 
     Advantageous Effects of Invention 
     The grinding apparatus according to the present invention can provide an excellent effect that the substance to be ground can be efficiently ground. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a grinding apparatus according to an embodiment of the present invention. 
         FIG.  2 (A)  is a plan view of a rotating body accommodated in a grinding container of the grinding apparatus according to the embodiment of the present invention.  FIG.  2 (B)  is a cross-sectional view taken along line F-F of  FIG.  2 (A) . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention will be described below with reference to the accompanying drawings. 
     &lt;Overall Configuration&gt; 
     A grinding apparatus  1  according to the embodiment of the present invention will be described with reference to  FIG.  1   . The grinding apparatus  1  grinds a substance to be ground  100 . As shown in  FIG.  1   , the grinding apparatus  1  includes a rotating body  2 , a rotating-body rotating unit  3 , a grinding container  4 , a grinding medium  5 , a circulation mechanism  6 , a removal mechanism  7 , and guide blades  8 . 
     &lt;Rotating Body&gt; 
     As shown in a cross-sectional view of the rotating body  2  taken along an axial direction A of the rotating body  2  (hereinafter, referred to simply as an axial direction A) shown in  FIG.  1   , the rotating body  2  includes tapered channels  20  of frustum shape having an interval where the channel width decreases (tapers off) outward in a radial direction R of the rotating body  2  (hereinafter, referred to simply as a radial direction R) from the center of the rotating body  2 . The tapered channels  20  may have a circular, polygonal, or other sectional shapes. The tapered channels  20  extend both to the right and left from the center along the radial direction R. An inlet opening  21  at which the tapered channels  20  open to outside and that is opposed to a reception opening  47  of the grinding container  4  in the axial direction A is formed in an upper end  20 A of the rotating body  2  in the axial direction A (the end located near a lid unit  41  of the grinding container  4 ). Output openings  22  at which the tapered channels  20  open to outside and that are opposed to an inner wall surface  42  of the grinding container  4  in the radial direction R are formed in an outer peripheral surface  23  constituting outer edge portions (outer edge areas) of the rotating body  2  in the radial direction R. The tapered channels  20  described above accommodate the substance to be ground  100  to be ground by the grinding apparatus  1  and the grinding medium  5 . The substance to be ground  100  and the grinding medium  5  accommodated in the tapered channels  20  enter through the inlet opening  21  and are discharged from the output openings  22 . The rotating body  2  does not open at any location other than the inlet opening  21  or the outlet openings  22 . As shown in  FIG.  1   , the rotating body  2  is attached to a rotating-body driving shaft  30  of the rotating-body rotating unit  3 , and rotates with the rotation of the rotating-body driving shaft  30 . 
     As shown in the plan view of  FIG.  2 (A) , the rotating body  2  includes a disk portion  200  located at the center and four protrusions  210  protruding radially from an outer rim  201  of the disk portion  200  outward in radial directions R. The protrusions  210  are each formed in a frustum shape and arranged at regular intervals of approximately 90° in the circumferential direction of the disk portion  200 . As shown in the cross-sectional view of  FIG.  2 (B) , in terms of the relationship with the grinding container  4 , the four protrusions  210  protrude toward the inner wall surface  42  of the grinding container  4 , starting at the outer rim  201  of the disk portion  200 . As shown in the plan view of  FIG.  2 (A) , the entire rotating body  2  is thus formed in a substantially ninja-star shape (cross shape). The inlet opening  21  described above is formed in the center of the top side of the disk portion  200 . The outlet openings  22  described above are formed in the ends of the protrusions  210 . The tapered channels  20  are provided inside the disk portion  200  and the protrusions  210 . The tapered channels  20  are therefore also arranged at regular intervals of approximately 90°. 
     Note that a plurality of protrusions  210  and a plurality of tapered channels  20  are located at regular intervals in the circumferential direction of the rotating body  2  or the disk portion  200 . The protrusions  210  and the tapered channels  20  both only need to be at least two in number. 
     The entire rotating body  2  may be configured in a disk-like shape. Even in such a case, tapered channels  20 , an inlet opening  21 , and outlet openings  22  having similar structures to the foregoing are provided inside the rotating body  2 . 
     &lt;Rotating Unit&gt; 
     As shown in  FIG.  1   , the rotating-body rotating unit  3  rotates the rotating body  2 . As employed in the present invention, “rotation” may refer to being rotatable in forward and backward directions or being rotatable in either one of the forward and backward directions. The rotating-body rotating unit  3  includes the rotating-body driving shaft  30  and a rotating body-side shaft driving unit  31 . In the present embodiment, the rotating-body driving shaft  30  is coaxial with a center axis  24  of the rotating body  2 . The rotating-body driving shaft  30  is connected to the rotating body  2 . The rotating body-side shaft driving unit  31  rotates the rotating-body driving shaft  30  about the center axis  24 . When the rotating-body driving shaft  30  is rotated by the rotating body-side shaft driving unit  31 , the rotating body  2  rotates with the center axis  24  as the axis of rotation. An example of the rotating body-side shaft driving unit  31  is a motor. However, this is not restrictive, and other members may be used. If the rotating-body driving shaft  30  is not coaxial with the center axis  24  of the rotating body  2 , the axis of rotation of the rotating body  2  is an axis other than the center axis  24  and parallel to the center axis  24 . Such a configuration is also covered by the present invention. 
     &lt;Grinding Container&gt; 
     The grinding container  4  accommodates the rotating body  2 . As shown in  FIG.  1   , the grinding container  4  includes a container main body unit  40  and the lid unit  41 . In the present embodiment, the container main body unit  40  has a closed-bottomed circular cylindrical shape. However, this is not restrictive, and the container main body unit  40  may have other closed-bottomed cylindrical shape. 
     As shown in  FIG.  1   , the container main body unit  40  has an accommodation space  49  having a size sufficient to accommodate the rotating body  2 . The container main body unit  40  has an upper container opening  44  in the upper end in a depth direction D of the container main body unit  40 , and a lower container opening  45  in the lower end in the depth direction D of the container main body unit  40 . The accommodation space  49  is opened to outside through the upper container opening  44 . The lower container opening  45  is intended for the rotating-body driving shaft  30  to be passed through. The rotating-body driving shaft  30  extends through the lower container opening  45  to near the center of the accommodation space  49  and is connected to the rotating body  2 . 
     As shown in  FIG.  2   , the rotating body  2  is accommodated in the accommodation space  49  of the grinding container  4  so that its own center axis  24  and a center axis  40 C of the container main body unit  40  along the depth direction D are coaxial with each other. Moreover, the outer periphery of the rotating body  2  is surrounded by the inner wall surface  42  of the container main body unit  40 . The inner wall surface  42  has an opposed area opposed to the outlet openings  22  of the rotating body  2  in the radial directions R of the rotating body  2 . The surface constituted by the opposed area will be referred to as an opposed surface  43 . Since the outlet openings  22  rotate with the rotating body  2  about the center axis  24  of the rotating body  2 , the opposed area is an annular area and the opposed surface  43  is an annular surface. 
     As will be described below, the substance to be ground  100  flying out of the outlet openings  22  collides with the opposed surface  43 . The substance to be ground  100  is ground by the impact. In this sense, the opposed surface  43  functions as a collision surface to the substance to be ground  100  flying out of the outlet opening  22 . 
     As shown in  FIG.  1   , the container main body unit  40  has a discharge opening  46 , by which the accommodation space  49  is opened to outside, below the opposed surface  43  in the depth direction D of the container main body unit  40  (inner bottom surface  48  side). The discharge opening  46  is provided to discharge the substance to be ground  100  and the grinding medium  5  out of the grinding container  4 . 
     As shown in  FIG.  1   , the lid unit  41  closes the upper container opening  44  of the container main body unit  40 . In the present embodiment, the lid unit  41  has a disk-like shape. The reception opening  47  for making the accommodation space  49  communicate with outside is formed in the center of the lid unit  41 . 
     All or a part of the grinding container  4  is desirably formed of ceramics, for example. If a part of the grinding container  4  is formed of ceramics, the portion constituting the opposed surface  43 , in particular, of the grinding container  4  is desirably formed of the ceramics. 
     &lt;Grinding Medium&gt; 
     The grinding medium  5  is formed of a material capable of grinding the substance to be ground  100 . For example, the grinding medium  5  can include at least one of the following types of beads: zirconia beads, carbide beads, and steel beads. However, this is not restrictive, and other types of beads may be included. The grinding medium  5  has a size that enables passage through a circulation path to be described below. The grinding medium  5  can thus circulate through the circulation path to be described below. 
     &lt;Circulation Mechanism&gt; 
     The circulation mechanism  6  repeatedly returns the substance to be ground  100  and the grinding medium  5  flying out of the rotating body  2  back into the rotating body  2 . Note that a moving mechanism may be defined as a mechanism including not only the circulation mechanism  6  but also a return mechanism that returns the substance to be ground  100  and the grinding medium  5  flying out of the rotating body  2  back into the tapered channels  20  of the rotating body  2  not repeatedly but under an external operation. In such a case, the circulation mechanism  6  according to the present invention may be replaced with other moving mechanisms. The circulation mechanism  6  according to the present embodiment includes, for example, a circulation path-forming pipe  60  and an airflow generation unit  61 . 
     As shown in  FIG.  1   , the circulation path-forming pipe  60  is connected to the grinding container  4  at the discharge opening  46  and the reception opening  47 , and forms the circulation path with the tapered channels  20  of the rotating body  2  and the grinding container  4 . For example, the circulation-path forming pipe  60  according to the present embodiment starts at the discharge opening  46 , turns in 90° directions three times, passes through the reception opening  47  and the inlet opening  21 , and extends up to in front of an inner bottom surface  28  of the rotating body  2 . As a result, an end opening  63  of the circulation-path forming pipe  60  on one end side is located inside the tapered channels  20 . Note that the circulation-path forming pipe  60  may extend up to in front of the inlet opening  21  (between the reception opening  47  and the inlet opening  21 ) instead of passing through the inlet opening  21 . 
     The airflow generation unit  61  generates an airflow from the discharge opening  46  toward the reception opening  47  in the circulation-path forming pipe  60 . For example, as shown in  FIG.  1   , the airflow generation unit  61  includes a nozzle (hereinafter, referred to as a Coanda nozzle)  610  that amplifies the amount of gas flow using the Coanda effect, and a gas supply unit  611  that supplies an amplifying gas to the Coanda nozzle  610 . 
     For example, the gas supply unit  611  includes a compressor, and supplies compressed air to the Coanda nozzle  610 . As the gas supply unit  611  supplies the compressed air to the Coanda nozzle  610 , the Coanda nozzle  610  amplifies the flow rate of gas per unit time. For example, the Coanda nozzle  610  amplifies the flow rate of gas supplied from the gas supply unit  611  by approximately seven times. The gas amplified in the flow rate per unit time then flows through the circulation-path forming pipe  60  from the discharge opening  46  toward the reception opening  47 . As a result, a clockwise airflow is generated in the circulation path. The substance to be ground  100  and the grinding medium  5  flying out of the rotating body  2  are thereby passed through the circulation-path forming pipe  60  and discharged from the end opening  63 , and supplied into the tapered channels  20  of the rotating body  2  again. 
     To stabilize the function of the Coanda nozzle  610 , an air filter  62  is provided to release the gas. If, for example, secondary air (amplified air) taken into the Coanda nozzle  610  is not released from the air filer  62 , the internal pressure of the circulation path increases and the Coanda effect due to negative pressure suction is not successfully obtained. 
     The circulation mechanism  6  according to the present embodiment can repeatedly circulate the substance to be ground  100  along the circulation path. The substance to be ground  100  can thus be made to collide with the opposed surface  43  repeatedly. 
     &lt;Removal Mechanism&gt; 
     The removal mechanism  7  removes the substance to be ground  100  deposited on the opposed surface  43 . As shown in  FIG.  1   , the removal mechanism  7  includes a removal unit  70 , a removal-side driving shaft  71  coaxial with the rotating-body driving shaft  30 , and a removal-side shaft driving unit  72 . 
     The removal unit  70  is located between the opposed surface  43  and the rotating body  2  so as to be opposed to the opposed surface  43 . For example, in the present embodiment, the removal unit  70  includes two L-shaped plate members as illustrated in  FIG.  1   . The L-shaped plate members are held by the removal-side driving shaft  71 . Here, each L-shaped plate member is oriented so that a portion (radially extending portion  73 A) corresponding to one of the sides of the L shape starts at the removal-side driving shaft  71  and extends in the radial direction R up to near the inner wall surface  42  of the grinding container  4 , and a portion (depthwise extending portion  73 B) corresponding to the other side of the L shape extends substantially in parallel with the depth direction D up to a height opposite to the opposed surface  43 . As shown in  FIG.  2 (A) , the portions (radially extending portions  73 A) corresponding to the one sides of the L shapes of the two L-shaped plate members extend in opposite directions, starting at the removal-side driving shaft  71 . 
     As shown in  FIG.  2 (A) , the removal-side shaft driving unit  72  rotates the removal-side driving shaft  71 , so that the two L-shaped plate members revolve in the circumferential direction of the opposed surface  43 . 
     The rotation speed at which the removal-side shaft driving unit  72  rotates the removal-side driving shaft  71  is desirably such a speed as causes a difference in speed from that of the rotating-body driving shaft  30 . In particular, the rotation speed is desirably lower than that of the rotating-body driving shaft  30 . In other words, the revolving speed of the removal unit  70  is desirably lower than the rotation speed of the rotating body  2 . This can prevent the two L-shaped plate members as much as possible from interfering with the collision of the substance to be ground  100  with the opposed surface  43 . 
     Alternatively, the portions (depthwise extending portions  73 B) corresponding to the other sides of the L shapes of the L-shaped plate members may be regarded as a removal unit  70 . Furthermore, the portions (radially extending portion  73 A) corresponding to one of the one of sides of the L shapes of the L-shaped plate members, the removal-side driving shaft  71 , and the removal-side shaft driving unit  72  may be regarded as a moving unit configured to move the removal unit  70  (depthwise extending portions  73 B) in the circumferential direction of the inner wall surface  42  of the grinding container  4 . 
     &lt;Guide Blades&gt; 
     The guide blades  8  are disposed to be capable of revolving about the rotating-body driving shaft  30 . For example, the guide blades  8  are made of plate members. As shown in  FIG.  1   , the guide blades  8  include flat portions facing in the direction of rotation of the rotating body  2  and extending outward in the radial directions R of the rotating body  2 . The guide blades  8  are connected to the rotating-body driving shaft  30  or the rotating body  2 . 
     As the guide blades  8  revolve about the rotating-body driving shaft  30 , the flat portions agitate the air to generate an airflow in the accommodation space  49 . As a result, the airflow moves the substance to be ground  100  in the accommodation space  49  and guides the substance to be ground  100  to the discharge opening  46 . 
     &lt;Operation of Grinding Apparatus&gt; 
     An operation of the grinding apparatus  1  will be described with reference to  FIG.  1   . For example, the substance to be ground  100  and the grinding medium  5  are initially placed into the tapered channels  20  of the rotating body  2  through the reception opening  47  of the grinding container  4  or through the upper container opening  44  of the container main body unit  40  with the lid  41  removed. When the rotating body  2  is then rotated by the rotating-body rotating unit  3 , the substance to be ground  100  and the grinding medium  5  are moved outward in the radial directions R of the rotating body  2  through the tapered channels  20  by centrifugal force, and fly outward out of the outlet openings  22 . In the present embodiment, the tapered channels  20  taper off outward in the radial directions R of the rotating body  2 . The rotating body  2 , when rotated, can thus function like a centrifugal pump to move the substance to be ground  100  and the grinding medium  5  outward in the radial directions R along the tapered channels  20  at high speed. 
     In the process of the substance to be ground  100  moving through the tapered channels  20 , the substance to be ground  100  undergoes a friction force and a shear force from the grinding medium  5  and the tapered channels  20 , and is thereby ground. The substance to be ground  100  and the grinding medium  5  flying out of the outlet openings  22  then collide with the opposed surface  43 . The substance to be ground  100  is further ground by the impact of the collision. In the present embodiment, the substance to be ground  100  is thus ground not only by the impact force from the collision with the opposed surface  43  but also by the friction force and shear force from the grinding medium  5  moving together. The grinding apparatus  1  according to the present embodiment can thus grind the substance to be ground  100  more efficiently in a shorter time than heretofore. 
     As shown in  FIG.  1   , the substance to be ground  100  adheres to and deposits on the opposed surface  43 . The removal unit  70  (L-shaped plate members) revolving comes into contact with the deposit, i.e., deposited substance to be ground  100 A and causes the deposited substance to be ground  100 A to crumble and fall on the inner bottom surface  48  of the container main body unit  40 . 
     Meanwhile, the airflow generation unit  61  generates the airflow to circulate through the circulation path. As shown in  FIG.  1   , the airflow moves the substance to be ground  100  and the grinding medium  5  fallen on the inner bottom surface  48  of the container main body unit  40  to the circulation-path forming pipe  60  through the discharge opening  46 . The substance to be ground  100  and the grinding medium  5  then pass through the circulation-path forming pipe  60 , the reception opening  47 , and the inlet opening  21 , and are discharged into the tapered channels  20  of the rotating body  2  again. The substance to be ground  100  discharged into the tapered channels  20  is moved outward in the radial directions R by a centrifugal force again along with the grinding medium  5 , collides with the opposed surface  43 , and undergoes the impact of the collision again and is further ground. The substance to be ground  100  is ground finer and finer by the repetition of such operations. Finally, a (not-shown) changeover valve is operated to switch the passage of the substance to be ground  100  to a (not-shown) collection pipe branching off from the circulation path (for example, circulation-path forming pipe  60 ). As a result, the finely ground substance to be ground  100  flows into the (not-shown) collection pipe and collected through a discharge opening of the (not-shown) collection pipe. 
     The grinding apparatus  1  according to the present invention can apply an impact force, a compression force, a shear force, and the like to the substance to be ground  100  by the foregoing operation. The use of the grinding apparatus  1  according to the present invention is thus useful in applying a treatment using a mechanochemical phenomenon to the substance to be ground  100 . It will be understood that the grinding apparatus  1  according to the present invention is also useful for treatments other than that using a mechanochemical phenomenon. 
     The grinding apparatus  1  of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.