Abstract:
A media-agitation type pulverizer of the present invention includes: a guide ring installed to radially divide a lower region of a pulverization chamber into an inner section and an annular outer section. A flow of a mixture of a raw material slurry and pulverizing media is formed as a helicoidal flow comprising a secondary flow flowing through a circulation flow path which has an upward flow path and a downward flow path created, respectively, in the outer section and the inner section of the lower region of the pulverization chamber, with respect to the guide ring. A rotational-flow suppressing device is provided within the pulverization chamber and adapted to strengthen the secondary flow of the helicoidal flow, thereby stabilizing the helicoidal flow. As a result, a media-agitation type pulverizer is provided which is capable of creating a uniformized, stable helicoidal flow in a mixture of pulverizing media and a raw material slurry, without unevenness of a centrifugal force distribution, thereby performing pulverization/dispersion uniformly with satisfactory energy efficiency.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a media-agitation type pulverizer. The media-agitation type pulverizer of the present invention is particularly suitable for use in, but not limited to, mixing a raw material for ink, paint, pigment, ceramics, metal, inorganic material, dielectric material, ferrite, toner, glass, paper coating color or other nanoparticles, with pulverizing/dispersing media in the form of beads, to pulverize or disperse the raw material into fine particles. 
       BACKGROUND ART 
       [0002]    As a media-agitation type pulverizer, there has been known a media-agitation (agitated media) mill proposed in JP 2005-199125 A. 
         [0003]    The media-agitation mill proposed in the JP 2005-199125A comprises a pulverization tank including an end plate closing up an upper end thereof and internally having a pulverization chamber containing pulverizing media, a rotary shaft rotatably provided in the pulverization tank, and an agitating/separating member provided on a portion of the rotary shaft located inside the pulverization chamber and adapted to be rotatable integrally with the rotary shaft. This media-agitation mill is characterized in that an inner wall surface of the pulverization chamber and an outer peripheral surface of the agitating/separating member are formed in shapes conforming to each other, wherein the media-agitation mill further comprises a separation/discharge passage extending from the outer peripheral surface to penetrate through a central portion of the agitating/separating member and then extending from the central portion of the agitating/separating member to penetrate through a central portion of the rotary shaft and communicate with an outside of the pulverization chamber, and a pressure relief hole penetrating between upper and lower surfaces of the agitating/separating member in an axial direction of the rotary shaft to provide communication between upper and lower regions of an inside of the pulverization chamber. 
         [0004]    However, in the media-agitation mill having the above structure, the pulverizing media are liable to be concentrated around a maximum-diameter portion where a centrifugal force is maximized, i.e., to be localized in a specific position, so that a dispersion or pulverization force varies with position, and the variation is large. Thus, there is a problem that a raw material is not uniformly dispersed or pulverized, causing difficulty in obtaining a high-quality product. 
         [0005]    Therefore, the applicant of this application proposed a media-agitation type pulverizer capable of obtaining a high-quality product by a good pulverizing/dispersing action, in JP 2009-103529 (JP 2010-253339A). 
         [0006]    The media-agitation type pulverizer proposed in the JP 2009-103529 comprises: a pulverization container having an upright cylindrical pulverization chamber containing pulverizing media in the form of beads; a raw-material-slurry supply port provided in the pulverization container; an agitating member disposed in a bottom region of the pulverization chamber and having a rotary shaft substantially coaxial with a central axis of the pulverization chamber; and a media separation member provided within the pulverization chamber and above the agitating member. This media-agitation type pulverizer is characterized in that it further comprises a guide ring installed to radially divide a lower region of the pulverization chamber into an inner section and an annular outer section, wherein an upward flow path of a mixture of the pulverizing media and the raw material slurry is created in the outer section of the lower region of the pulverization chamber. 
         [0007]    In the media-agitation type pulverizer proposed in the JP 2009-103529, the guide ring is installed in the pulverization chamber, as mentioned above, whereby a flow of the mixture of the pulverizing media and the raw material slurry can be formed as a combined flow (i.e., helicoidal (spiral or helical) flow) consisting of a flow moving in a circumferential direction of the pulverization chamber (i.e., a primary flow) and a flow capable of regularly repeating a movement cycle of, after moving in a radially outward direction of the pulverization chamber toward an inner wall of the pulverization container, moving upwardly through the upward flow path between the guide ring and the pulverization container, and then moving downwardly from a central region of the pulverization chamber to return to the agitating member, via a space inward of the guide ring (i.e., a secondary flow). Thus, even if a volume ratio of beads to the pulverization chamber is relatively low, localization (uneven distribution) of the pulverization media can be suppressed to some extent to provide enhanced pulverization/dispersion efficiency. 
         [0008]    However, the helicoidal flow formed by the media-agitation type pulverizer proposed in the JP 2009-103529 is unstable due to weakness and instability of the secondary flow thereof, so that centrifugal force distribution is likely to become uneven, which causes localization of the pulverization media in the helicoidal flow. Thus, there is a problem of non-uniform pulverization and not-so-satisfactory energy efficiency. 
       PRIOR ART DOCUMENTS 
     Patent Documents 
       [0000]    
       
         Patent Document 1: JP 2005-199125A 
         Patent Document 2: JP 2010-253339A 
       
     
       DISCLOSURE OF THE INVENTION 
     Solution to the Technical Problem 
       [0011]    It is therefore an object of the present invention to provide a media-agitation type pulverizer capable of creating a uniformized, stable helicoidal flow in a mixture of pulverizing media and a raw material slurry, without unevenness of a centrifugal force distribution, thereby performing pulverization/dispersion uniformly with satisfactory energy efficiency. 
         [0012]    The above object is achieved by a media-agitation type pulverizer having the following features set forth in (1) to (17). 
         [0013]    (1) A media-agitation type pulverizer comprising: a pulverization container including an end plate closing up an upper end thereof and having an upright cylindrical pulverization chamber containing pulverizing media in the form of beads; a raw-material-slurry supply port provided in the pulverization container; an agitating member disposed in a bottom region of the pulverization chamber and having a rotary shaft substantially coaxial with a central axis of the pulverization chamber; and a media separation member provided within the pulverization chamber and above the agitating member. The media-agitation type pulverizer is characterized in that it further comprises: a guide ring installed to radially divide a lower region of the pulverization chamber into an inner section and an annular outer section, whereby a flow of a mixture of the raw material slurry and the pulverizing media is formed as a helicoidal flow comprising a combination of a primary flow flowing in a circumferential direction of the pulverization chamber and a secondary flow flowing through a circulation flow path which has an upward flow path and a downward flow path created, respectively, in the outer section and the inner section of the lower region of the pulverization chamber, with respect to the guide ring; and rotational-flow suppressing means provided within the pulverization chamber and adapted to suppress the primary flow while strengthening the secondary flow, thereby stabilizing the helicoidal flow. 
         [0014]    (2) In the media-agitation type pulverizer set forth in (1), the rotational-flow suppressing means is formed by combining a plurality of plate members, and provided inside of the guide ring. 
         [0015]    (3) In the media-agitation type pulverizer set forth in (1) or (2), the media separation member is disposed within a cylindrical-shaped media-separation-member receiving chamber provided in the end plate and having a bottom formed as a downwardly-facing opening opened to the pulverization chamber, wherein the media-separation-member receiving chamber has a diameter greater than a diameter of the media separation member and less than a diameter of the pulverization chamber. 
         [0016]    (4) In the media-agitation type pulverizer set forth in (3), the media-separation-member receiving chamber has a radius greater than a radius of the media separation member by 10 to 30 mm. 
         [0017]    (5) In the media-agitation type pulverizer set forth in any one of (1) to (4), the media separation member comprises: a circular top plate; a circular bottom plate disposed in axially spaced-apart relation to the top plate, and a plurality of blade members disposed between the top plate and the bottom plate at intervals in a circumferential direction thereof. 
         [0018]    (6) In the media-agitation type pulverizer set forth in (5), the media separation member is formed in a multistage structure in which an intermediate plate is provided between the top plate and the bottom plate. 
         [0019]    (7) In the media-agitation type pulverizer set forth in any one of (1) to (6), the guide ring has a structure which is internally formed with an annular space, and supported by a plurality of pipes attached to the pulverization container, in such a manner as to allow liquid to be supplied and discharged to/from the annular space through the pipes. 
         [0020]    (8) In the media-agitation type pulverizer set forth in (7), each of the pipes is disposed to extend downwardly from above the pulverization container and support the guide ring by a lower end thereof. 
         [0021]    (9) The media-agitation type pulverizer set forth in any one of (3) to (8) further comprises media-flow regulation means disposed to surround the downwardly-facing opening of the end plate and adapted to restrict the pulverizing media in the pulverization chamber from flowing into the media-separation-member receiving chamber. 
         [0022]    (10) In the media-agitation type pulverizer set forth in (9), the media-flow regulation means is composed of a downwardly-tapered truncated conical-shaped guide member having an internal space, wherein the guide member is adapted to change an upward flow of the mixture of the raw material slurry and the pulverizing media created by an action of the agitating member, to a downward flow. 
         [0023]    (11) The media-agitation type pulverizer set forth in any one of (3) to (10) further comprises at least one protrusion provided on an inner peripheral wall of media-separation-member receiving means, wherein the protrusion has a flow passage extending in a circumferential direction of the guide member to allow the pulverizing media to pass therethrough. 
         [0024]    (12) In the media-agitation type pulverizer set forth in (11), the protrusion is formed in a triangular shape having a base on the inner peripheral wall of the media-separation-member receiving means. 
         [0025]    (13) In the media-agitation type pulverizer set forth in (11) or (12), the flow passage is provided in a base portion of the triangular-shaped protrusion on the media-separation-member receiving means. 
         [0026]    (14) In the media-agitation type pulverizer set forth in any one of (1) to (13), the media separation member comprises: an approximately conical-shaped or truncated conical-shaped member body having a reduced-diameter distal end portion and an enlarged-diameter base portion; a transfer passage for the mixture, provided in the member body of the media separation member to extend from at least one inlet adjacent to the reduced-diameter distal end portion to an annular outlet in the enlarged-diameter base portion along a peripheral wall thereof, wherein the inlet is adapted to act as a mixture suction hole for sucking the mixture to allow it to flow into the transfer passage; a plurality of blade members provided in the transfer passage at positions adjacent to the annular outlet and arranged side-by-side along the annular outlet to perform a pulverizing-media pumping action; and a raw-material-slurry outlet passage branched from the transfer passage at a position upstream of the blade members. 
         [0027]    (15) In the media-agitation type pulverizer set forth in any one of (1) to (13), the media separation member comprises: an approximately conical-shaped or truncated conical-shaped central member; and a generally hollow truncated conical-shaped outer member having an inner periphery located in spaced-apart relation to an outer periphery of the central member, wherein the transfer passage is formed by the space between the outer periphery of the central member and the inner periphery of the outer member. 
         [0028]    (16) In the media-agitation type pulverizer set forth in (15), the outer member of the media separation member has a distal end fixed to a distal end of the central member of the media separation member. 
         [0029]    (17) In the media-agitation type pulverizer set forth in (16), the distal end of the outer member of the media separation member is formed as a circular distal end plate, wherein the mixture suction hole is formed in the circular distal end plate. 
       Effect of the Invention 
       [0030]    As described above, the media-agitation type pulverizer of the present invention is capable of controlling the helicoidal flow of the mixture of the pulverizing media and the raw material slurry to suppress a rotational flow in the circumferential direction of the pulverization chamber (i.e., primary flow) while strengthening the secondary flow (i.e., a circulation flow around the guide ring), thereby stabilizing the helicoidal flow. Thus, it becomes possible to facilitate uniformizing distribution of the pulverizing media in the flow to provide a flow having highly repetitive shear optimal to pulverization/dispersion with satisfactory energy efficiency. 
         [0031]    In some cases, a satisfactory helicoidal flow is formed without employing the rotational-flow suppressing means as in the present invention. However, this is an accidental result in a situation where all conditions such as viscosity of the mixture are met, but a perfect helicoidal flow as in the present invention is not always formed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  is a sectional view illustrating a media-agitation type pulverizer according to one embodiment of the present invention. 
           [0033]      FIG. 2  is a sectional view taken along the line A-A in  FIG. 1 . 
           [0034]      FIG. 3  is a perspective view schematically illustrating rotational-flow suppressing means. 
           [0035]      FIG. 4  is a horizontal sectional view illustrating an internal structure of a media-separation-member receiving chamber. 
           [0036]      FIG. 5  is a sectional view taken along the line B-B in  FIG. 1 . 
           [0037]      FIG. 6  is an enlarged sectional view illustrating an example of a modification of a centrifugal media separation member. 
           [0038]      FIG. 7  is a bottom view of the centrifugal media separation member illustrated in  FIG. 6 . 
           [0039]      FIG. 8  is a horizontal sectional view of the centrifugal media separation member illustrated in  FIG. 6 , taken in the vicinity of a distal end thereof. 
           [0040]      FIG. 9  is an enlarged sectional view illustrating another example of the modification of the centrifugal media separation member. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0041]    With reference to the accompanying drawings, the present invention will now be described in connection with a media-agitation type pulverizer according to one embodiment thereof. 
         [0042]      FIG. 1  illustrates a media-agitation type pulverizer  10  according to one embodiment of the present invention. This media-agitation type pulverizer  10  comprises an upright cylindrical pulverization container  12  including an end plate  12   a  closing up an upper end thereof. The pulverization container  12  internally has a columnar pulverization chamber  14 , and which is equipped therein with a raw-material-slurry supply port  16  for introducing a raw material in a slurry form (raw material slurry) into the pulverization chamber  14 . 
         [0043]    An agitating member  22  is rotatably disposed in the center of a bottom region of the pulverization chamber  14  of the pulverization container  12 . The agitating member  22  is composed of an impeller which comprises, for example, a pair of annular plates  22   b ,  22   c  fixed to an outer periphery of a boss  22   a  in vertically spaced-apart relation to each other, and a plurality of blades  22   d  disposed between the plates  22   b  and  22   c.    
         [0044]    A rotary drive shaft  24  serving as an agitating-member driving shaft is fixed to the agitating member  22 . The rotary drive shaft  24  has an upper end attached to the hub  22   a  of the agitating member  22  and extends axially downwardly to penetrate through the pulverization container  12  and a frame  18 . A lower end of the rotary drive shaft  24  is connected to a driving source via a non-illustrated conventional driving mechanism to allow the rotary drive shaft  24  to be rotationally driven in the direction indicated by the arrow in  FIG. 1 . Preferably, the rotary drive shaft  24  has a rotation axis aligned with a central axis of the pulverization chamber  14 . Further, the rotary drive shaft  24  is provided with a shaft seal  25  (e.g., a mechanical seal). 
         [0045]    In place of the above centrifugal impeller, the agitating member  22  may be composed of an oblique-flow impeller. 
         [0046]    As is well known in the field of media-agitation type pulverizers, pulverizing media  30  in the form of beads (which are illustrated in  FIG. 1  in a significantly enlarged manner) are contained in the pulverization container  12 . As the pulverizing media  30 , it is possible to use a type having a diameter of 0.02 to 2 mm. A total volume of the pulverizing media  30  is in the range of 30% to 75% of a volume of the pulverization chamber  14 . In a typical media-agitation type pulverizer, the total volume of the pulverizing media is in the range of 75% to 90% of the volume of the pulverization chamber. Thus, the media-agitation type pulverizer of the present invention is capable of performing soft pulverization/dispersion with less constraining force. 
         [0047]    A centrifugal media separation member  32  is disposed in a top region of the pulverization chamber  14  of the pulverization container  12  and adjacent to the central portion of the pulverization chamber  14 , in opposed and axially spaced-apart relation to the agitating member  22 , and adapted to separate the pulverizing media  30  dispersed in the raw material slurry from the raw material. The media separation member  32  comprises: a boss  32   a  having a tubular boss body formed with an internal space in a lower portion thereof; and a closing plate  32   b  for closing up the lower portion of the boss body. The boss body of the boss  32   a  is provided with a plurality of openings, and the media separation member  32  is adapted to introduce only the raw material slurry into the internal space of the boss body through the openings. While it is preferable that the media separation member  32  is disposed in coaxial relation with the agitating member  22 , the axes thereof may be offset from each other. A hollow rotary drive shaft  34  is fixed to that media separation member  32 . The rotary drive shaft  34  extends upwardly to penetrate through the end plate  12   a , and an upper end of the rotary drive shaft  34  is connected to a driving source via a non-illustrated conventional driving mechanism to allow the rotary drive shaft  34  to be rotationally driven in the direction indicated by the arrow in  FIG. 1 . Further, the rotary drive shaft  34  is provided with a shaft seal  36  (e.g., a mechanical seal). The hollow space of the rotary drive shaft  34  is communicated with the internal space of the media separation member  32  to form a raw-material-slurry exit  38 . As the media separation member, a conventional screen may be used. 
         [0048]    A jacket  40  is provided around an outer periphery of the pulverization container  12  to allow a cooling or heating medium (typically, a cooling medium such as a coolant water) to flow therethrough so as to adjust an internal temperature of the pulverization chamber  14 . This jacket  40  has a coolant water inlet  42  provided in a lower portion thereof to introduce a coolant water therethrough and a coolant water outlet  46  provided in an upper portion thereof to discharge the coolant water therefrom. 
         [0049]    The end plate  12   a  is adapted to be detached to open the pulverization container  12 , so that the pulverization container  12  can be readily subjected to maintenance. 
         [0050]    In the media-agitation type pulverizer of the present invention, the agitating member  22  may be driven at a rotational circumferential speed ranging from 5 to 30 m/s, and the media separation member  32  may be driven at a rotational circumferential speed ranging from 10 to 20 m/s. 
         [0051]    A guide ring  50  is disposed in a lower region of the pulverization chamber  14 . This guide ring  50  comprises: an annular inner-peripheral plate  52 ; an annular outer-peripheral plate  54  disposed in spaced-apart relation to the inner-peripheral plate  52  in a radially outward direction; an annular lower plate  56  forming a bottom wall; and an annular upper plate  58  forming a top wall, and internally has a liquid-tight space. 
         [0052]    The guide ring  50  is installed to radially divide the lower region of the pulverization chamber  14  into an inner section  14   a  and an annular outer section  14   b . The inner section  14   a  of the lower region of the pulverization chamber  14  serves as an upward flow path for a mixture of the pulverizing media and the raw material slurry, and the outer section  14   b  of the lower region of the pulverization chamber  14  serves as an upward flow path for the mixture of the pulverizing media and the raw material slurry. Thus, in the pulverization chamber  14 , a flow of the mixture of the pulverizing media and the raw material slurry is formed as a combined flow (i.e., helicoidal flow) consisting of a flow moving in a circumferential direction of the pulverization chamber (i.e., a primary flow) and a flow capable of regularly repeating a movement cycle of, after moving in the radially outward direction of the pulverization chamber toward an inner wall of the pulverization container, moving upwardly through the upward flow path between the guide ring and the pulverization container, and then moving downwardly from a central region of the pulverization chamber to return to the agitating member, via a space inward of the guide ring (i.e., a secondary flow). As mentioned above, this helicoidal flow has suffered from the problem of instability due to weakness of the secondary flow thereof. 
         [0053]    Further, a rotational-flow suppressing means  92  (see  FIGS. 2 and 3 ) is provided in the inward space of the guide ring  50  to control the helicoidal flow of the mixture of the pulverizing media and the raw material slurry flowing axially downwardly through the inward space within the pulverization chamber  14 , to suppress a rotational flow while strengthening the secondary flow. Preferably, the rotational-flow suppressing means  92  is formed in a cruciform shape by combining a plurality of plate members. The combined flow of the circumferential flow (primary flow) and the axial flow (secondary flow) created, mainly, by actions of the agitating member  22  and the guide ring  50 , is controlled to strengthen the secondary flow by the newly provided rotational-flow suppressing means  92 , thereby providing a stable helicoidal flow. This makes it possible to uniformize distribution of the pulverizing media contained in the combined flow and eliminate unevenness of a centrifugal force distribution to produce vigorous shearing forces between the pulverizing media, thereby further enhancing the function of the pulverizing media. A portion of the agitating member  22  located beneath the rotational-flow suppressing means  92  appears in  FIG. 2 . However, this is only for convenience of illustration, and the portion does not actually appear. 
         [0054]    The guide ring  50  has a structure which is internally formed with an annular space  50   a , as mentioned above, and supported by a plurality of pipes  60   a ,  60   b  (see  FIG. 2 ) attached to the pulverization container, in such a manner as to allow a coolant water to be supplied and discharged to/from the annular space through the pipes  60   a ,  60   b . Therefore, in the present invention, the raw material slurry can also be cooled from inside the pulverization container  12 . 
         [0055]    Preferably, each of the pipes  60   a ,  60   b  is disposed to extend downwardly from above the pulverization container  12  and support the guide ring  50  by a lower end thereof, as illustrated in  FIG. 1 . 
         [0056]    Preferably, the guide ring  50  has a lower end located at a position equal to or higher than an upper end of the agitating member  22 , and an upper end located at a position downwardly spaced apart from a lower end of the media separation member  32  by a predetermined distance, as illustrated in  FIG. 1 . 
         [0057]    Preferably, a distance between an outer peripheral wall of the guide ring  50  and an inner peripheral wall of the pulverization container  12  is in the range of 10 to 50 mm. If the distance is less than the lower limit, movement of the beads will be excessively constrained. On the other hand, if the distance is greater than the upper limit, the freedom of the movement will be excessively increased. 
         [0058]    Preferably, the guide ring  50  has a height which is ⅓ to ⅔ a height of the pulverization chamber. If the height is less than the lower limit, control of a bead flow will become insufficient. On the other hand, if the height is greater than the upper limit, smoothness of the bead flow will be impaired. 
         [0059]    As illustrated in  FIG. 1 , a central portion of the end plate  12   a  is formed as a thick-walled portion  70  increased in thickness as compared with a surrounding portion (having a thickness greater than a height of the media separation member), and provided with a through-hole  72 . The media separation member  32  is rotatably received in the through-hole  72 , as illustrated in  FIG. 1 . In other words, the through-hole  72  serves as a media-separation-member receiving chamber or a media separation chamber, which receives therein the media separation member  32 , and the thick-walled portion  70  serves as media-separation-member receiving means. In order to form the media-separation-member receiving chamber, the entirety of the end plate  12   a  may be formed to have a thickness equal to that of thick-walled portion  70 . However, this is not a realistic way, because it leads to an increase in material cost and weight of the pulverizer. 
         [0060]    Media-flow regulation means  80  is provided on a central region of a lower surface of the end plate  12   a  to restrict the pulverizing/dispersing media  30  in the pulverization chamber  14  from flowing into the media-separation-member receiving chamber. The media-flow regulation means  80  is composed of a downwardly-tapered truncated conical-shaped guide member which has a cylindrical space  82  penetrating therethrough in continuous relation to the through-hole  72 , and an outer peripheral surface serving as a guide surface  84 . This media-flow regulation means  80  also has a function of changing an upward flow of the mixture of the raw material slurry and the bead-form pulverizing media created by an action of the agitating member  22 , to a downward flow along the guide surface  84 , thereby eliminating factors causing instability in the mixture flow. Further, based on the controlled flow of the mixture of the raw material slurry and the pulverizing media, media freely flowing within the pulverization chamber  14  can be regulated as much as possible, so that it becomes possible to reduce a concentration of media around the media separation member  32 , and restrict media from flying toward the media separation member  32 , thereby enhancing a separation capacity of the media separation member. 
         [0061]    Preferably, a rotational-flow suppressing means  90  (see  FIG. 1 ) is provided in an internal space of the media-flow regulation means  80  to prevent turbulence in the mixture flow flowing from the pulverization chamber into the media-separation-member receiving chamber via the internal space. Preferably, the rotational-flow suppressing means  90  is formed in a cruciform shape by combining a plurality of plate members. Based on providing the rotational-flow suppressing means  90 , it becomes possible to strengthen the secondary flow of the helicoidal flow of the mixture within the media-separation-member receiving chamber, thereby stabilizing the helicoidal flow to further enhance the function of the media separation member. 
         [0062]    The media-separation-member receiving means (thick-walled portion  70 ) has an inner peripheral surface  74  provided with at least one, preferably a plurality of flow control protrusions  76  (see  FIG. 5 ). 
         [0063]    As illustrated in  FIG. 5 , the flow control protrusion  76  is formed in an approximately triangular shape having a base on the inner peripheral surface  74 , in horizontal cross-section, and a media flow passage  76   b  is formed in a base portion (a portion adjacent to the base)  76   a  of the flow control protrusion  76 . Preferably, an angle α defined between the inner peripheral surface  74  and one side  76   c  of the triangular flow control protrusion  76  having an inflow port of the media  30  i.e., opposed to the media flow, is set to an acute angle. 
         [0064]    When the angle α is set to an acute angle, the opposed side  76   c  functions to direct the media toward the inner peripheral surface  74  of the media-separation-member receiving means (thick-walled portion  70 ), i.e., in a direction away from the media separation member  32 , which is preferable in view of reducing a concentration of the media around the media separation member  32  to enhance a media separation function of the media separation member  32 . 
         [0065]    In the case where the angle α is set to an acute angle, the media are likely to stagnate in an acute-angled region. In this embodiment, the media flow passage  76   b  circumferentially penetrating through the base portion of the triangular flow control protrusion  76  is provided to allow the media to flow toward a downstream side via the media flow passage  76   b , thereby preventing the media from stagnating in the acute-angled region. 
         [0066]    A formation position of the media flow passage  76   b  may be changed depending on a height position of the flow control protrusion  76 . 
         [0067]    In the above embodiment, the thick-walled portion  70  is provided in the end plate  12 , and the media-separation-member receiving chamber is provided in the thick-walled portion  70 . Alternatively, an inside of the media-flow regulation means  80  may be formed as the media-separation-member receiving chamber. 
         [0068]    In other words, the media-agitation type pulverizer may comprise media-separation-member receiving means provided with a media-separation-member receiving chamber receiving therein the media separation member and disposed on the lower surface of the end plate, wherein an outer peripheral surface of the media-separation-member receiving means is formed as media-flow regulation means adapted to restrict the pulverizing/dispersing media in the pulverization chamber from flowing into the media-separation-member receiving chamber. 
         [0069]    In this case, the media-separation-member receiving means is composed of a downwardly-tapered truncated conical-shaped member having the cylindrical internal space, and disposed in a central region of the lower surface of the end plate, wherein an outer peripheral surface of the truncated conical-shaped member is formed to serve as a guide member adapted to change an upward flow of the mixture of the raw material slurry and the bead-form pulverizing/dispersing media created by the action of the agitating member, to a downward flow. 
         [0070]    In this modification, at least one protrusion is provided on an inner peripheral wall of the above media-separation-member receiving means, and a flow passage is provided in the protrusion to extend in a circumferential direction of the guide member to allow the bead-form pulverizing/dispersing media to pass therethrough so as to create an outward flow of the media, as with the above embodiment. 
         [0071]    During operation of the above media-agitation type pulverizer, the agitating member  22  is rotationally driven, while introducing the raw material slurry containing target particles as a raw material to be pulverized, into the pulverization chamber  14  through the raw-material-slurry supply port  16 . The slurry introduced into the pulverization chamber  14  is moved downwardly toward the agitating member  22 , with a rotational flow of the mixture of the slurry and the media  30  which has already been formed in the pulverization chamber  14 , and then agitated and mixed with the mixture by the agitating member  22 . In this process, the flow of the mixture of the raw material slurry and the pulverizing/dispersing media is controlled to strengthen the secondary flow by the rotational-flow suppressing means  92 , and thereby formed as a stable helicoidal flow. Subsequently, the slurry and the media  30  are moved radially outwardly to the inner wall of the pulverization container  12 . Then, the mixture of the slurry and the media  30  subjected to agitation and mixing is formed as a flow f moving upward through the upward flow path between the inner wall of the pulverization chamber  14  and the guide ring  50 . When the flow moves fully upwardly, it is changed to the aforementioned downward flow. 
         [0072]    Concurrently, in the media-separation-member receiving chamber, a rotational movement is given to the raw material slurry and the media by the media separation member  32 . According to the rotational movement, the media having a relatively large mass are urged radially outwardly and separated from the slurry. In this process, a part of the target particles still having a relatively large particle size due to insufficient pulverization exhibit the same behavior as that of the media. On the other hand, the slurry containing particles sufficiently pulverized and reduced in mass are introduced into the internal space of the media separation member  32 , and discharged to the outside of the media-agitation type pulverizer via the raw-material exit  38  inside the rotary drive shaft  34 . Based on the above configuration, in the regulated flow, target particles as a raw material are subjected to good pulverization and dispersion by means of contact with the freely-moving pulverizing media, so that a high-quality product is obtained. In addition, based on the above functions, the media-agitation type pulverizer of the present invention can achieve pulverization providing a sufficiently narrow particle size distribution width. Furthermore, the media-agitation type pulverizer of the present invention requires a less amount of pulverizing media. 
         [0073]    In the media-agitation type pulverizer of the present invention, the agitating member  22  is sufficiently spaced apart from the media separation member  32 , so that a risk of interference with the media separation member  32  is extremely low. 
         [0074]    The media-agitation type pulverizer of the present invention may employ a centrifugal media separation member  132  as illustrated in  FIGS. 6 ,  7  and  8 . This centrifugal media separation member  132  comprises an approximately conical-shaped or truncated conical-shaped member body  134  having a reduced-diameter distal end portion  134   a  and an enlarged-diameter base portion  134   b . A lower end of a drive shaft  130  is fixed to a center of the enlarged-diameter base portion  134   b  to allow the media separation member  132  to be rotated according to rotation of the drive shaft  130 . A transfer passage  135  for the mixture is provided in the member body  134  to extend from at least one inlet  135   a  adjacent to the reduced-diameter distal end portion  134   a  to an annular outlet  135   b  in the enlarged-diameter base portion  134   b  along a peripheral wall thereof. The inlet  135   a  is adapted to act as a mixture suction hole for sucking the mixture to allow it to flow into the transfer passage  135 . A plurality of blade members  137  are provided in the transfer passage  135  at positions adjacent to the annular outlet  135   b  and arranged side-by-side along the annular outlet to perform a media pumping action. Further, a raw-material-slurry outlet passage  139  is branched from the transfer passage  135  at a position upstream of the blade members  137 . 
         [0075]    The enlarged-diameter base portion  134   b  of the member body  134  is internally formed with a treated-raw-material-slurry collecting space  139  which is an approximately disk-shaped space, and the raw-material-slurry outlet passage  139   a  and a raw-material-slurry exit  131  are communicated with the treated-raw-material-slurry collecting space  139 . 
         [0076]    The member body  134  of the media separation member comprises an approximately conical-shaped or truncated conical-shaped central member  140 , and a generally hollow truncated conical-shaped outer member  141  (see  FIG. 8 ) having an inner periphery located in spaced-apart relation to an outer periphery of the central member  140 . The transfer passage  135  is formed by the space between the outer periphery of the central member and the inner periphery of the outer member. 
         [0077]    Preferably, the member body  134  is configured such that the outer member  141  has a distal end fixed to a distal end of the central member  140 . 
         [0078]    Specifically, the distal end of the outer member  141  is formed as a circular distal end plate  141   a  as illustrated in  FIGS. 6 and 7 , and the mixture suction hole (inlet  135   a ) is formed in the circular distal end plate  141   a.    
         [0079]    During the operation, the media are partially introduced into the media-separation-member receiving chamber. However, such media are separated from a treated-raw-material slurry and returned to the pulverization chamber again, by the media separation member  132  rotated within the media-separation-member receiving chamber, in the following manner. 
         [0080]    Upon rotation of the media separation member  132 , the blade members  137  provided in a region of the transfer passage  135  on the side of the enlarged-diameter base portion  134   b  of the member body  134  performs a pumping action. Primarily based on this pumping action, the slurry and others in the transfer passage  135  are ejected outside the transfer passage  135  through the outlet  135   b . In conjunction with the ejection, a suction force is generated at the inlet  135   a  so that a flow of the slurry and others from the inlet  135   a  is created, and a rotational movement is given to the flow. According to the rotational movement, the relatively large and heavy media are urged radially outwardly and separated from the slurry. In this process, a part of the target particles still having a relatively large particle size due to insufficient pulverization exhibit the same behavior as that of the media. On the other hand, the slurry containing particles sufficiently pulverized and reduced in size and weight are discharged to the outside of the media-agitation type pulverizer via the raw-material-slurry outlet passage  139 , the treated-raw-material-slurry collecting space  140  and the raw-material-slurry exit  131 . 
         [0081]    The media separation member has the above structure, so that it becomes possible to stabilize a flow of media-containing raw material slurry inside and around the media separation member to form a non-turbulent flow field, thereby performing satisfactory media separation. 
         [0082]    The media separation member illustrated in  FIG. 6  and so forth has been described based on a structure configured to rotate the entire media separation member, i.e., a structure configured to rotate the central member together with the outer member. Alternatively, the media separation member may be configured such that only the central member is rotated, while fixing the outer member, as illustrated in  FIG. 9 . 
       EXPLANATION OF CODES 
       [0000]    
       
         
           
               10 : media-agitation type pulverizer 
               12 : pulverization container 
               14 : pulverization chamber 
               16 : raw-material-slurry supply port 
               18 : frame 
               22 : agitating member 
               24 : rotary drive shaft 
               25 : shaft seal 
               30 : pulverizing media 
               32 : media separation member 
               32   a : hub 
               32   b : closing plate 
               34 : hollow rotary drive shaft 
               36 : shaft seal 
               38 : raw-material-slurry outlet 
               40 : jacket 
               40   a : coolant inlet 
               40   b : coolant outlet 
               50 : guide ring 
               52 : annular inner-peripheral plate 
               54 : annular outer-peripheral plate 
               56 : annular lower plate 
               58 : annular upper plate 
               60   a : pipe 
               60   b : pipe 
               70 : thick-walled portion (media-separation-member receiving means) 
               72 : through-hole (media-separation-member receiving chamber) 
               74 : inner periphery of media-separation-member receiving means (thick-walled portion  70 ) 
               76 : protrusion 
               80 : media-flow regulation means 
               82 : cylindrical space 
               84 : guide surface 
               90 : flow straightening means 
               92 : rotational-flow suppressing means