Patent Publication Number: US-2007114311-A1

Title: Stock re-pulper

Description:
BACKGROUND OF THE INVENTION  
      (1) Field of the Invention  
      The present invention relates to a stock re-pulper for re-pulping stock such as paper pulp, collection paper and broke in a paper machine.  
      (2) Description of the Related Art  
       FIGS. 14 and 15  are schematic illustrations of a construction of a conventional stock re-pulper  500 , and  FIG. 16  is a partially enlarged perspective view (partially sectional view) showing an essential part of this stock re-pulper  500 , where broken line arrows indicate flows of stock. The stock re-pulper  500  shown in FIGS.  14  to  16  is for stock disaggregatable in a relatively easy way.  
      As  FIG. 14  shows, this stock re-pulper  500  is equipped with a porous plate  503  at a bottom portion of a tub  501  made to accommodate stock. In addition, a large number of holes are made in this porous plate  503  and a rotor  502  is located at a central portion thereof. Still additionally, six macerating blades  521  are protrusively formed outwardly on the rotor  502 . The structures of the rotor  502  and the porous plate  503  can be changed into various modes according to the degree of difficulty of the stock re-pulping.  
      Furthermore, as shown in  FIG. 15 , a motor  508  is connected to a rotary shaft  506  of the rotor  502  so that the rotor  502  receives power from this motor  508  for rotation and the rotation of the rotor  502  also rotate the macerating blades  521 .  
      More concretely, as shown in  FIG. 16 , the rotor  502  is attached through shims  561  to a flange  502 A fixedly secured to the rotary shaft  506  so that the space between the porous plate  503  and the macerating blades  521  is properly adjustable by increasing/decreasing the number of shims  561  or changing the thickness of the shims  561 .  
      Moreover, the rotation of the macerating blades  521  agitates stock supplied together with water serving as a dilute solution into the tub  501 , thereby conducting rough maceration processing. In general, the ratio of water and stock is set such that the stock has a concentration of approximately 3 to 8% with respect to water.  
      Still furthermore, as shown in  FIG. 14 , on the bottom portion of the tub  501  there are formed turning plates  507  extending radially from the center of the tub  501  and protruding toward the interior of the tub  501 , which turns a circumferential flow of stock, occurring in the interior of the tub  501  due to the rotation of the rotor  502  and the macerating blades  521 , to a longitudinal flow.  
      Thus, the stock is agitated while circulating in a circumferential direction or longitudinal direction in the interior of the tub  501 , thereby undergoing the maceration processing, while the maceration processing is further conducted between the macerating blades  521  which is in rotation and the porous plate  503  which is in a fixed state.  
      In addition, after the rotation of the rotor  502  for a predetermined period of time, a valve (not shown) provided in an output pipe  505  of a chamber  509  positioned on a rear side of the porous plate  503  is opened and, in this state, the stock is dischargeable through the output pipe  505 .  
      That is, in this stock re-pulper  500 , the maceration of the stock is mainly carried out in a manner such that the macerating blades  521  mounted on the rotor  502  and the holes  514  made in the porous plate  503  are in cooperation with each other. A little more detailed description will be given hereinbelow of this point. The stock flows into the gap between the macerating blades  521  and the porous plate  503  due to the rotation of the rotor  502 . Moreover, this stock is lacerated between the lower edges of the macerating blades  521  and the circumferential edges of the holes  514  so as to reduce the size thereof, thereby performing the maceration.  
      Meanwhile,  FIG. 17  is a perspective view (partially sectional view) showing a construction of an essential part of a stock re-pulper  600  to be employed for the maceration of relatively hard-to-dissolve stock.  
      As shown in  FIG. 17 , in this stock re-pulper  600 , a plurality of elongated holes  614  extending radially are made in the porous plate  603  and, on a rear surface (surface opposite to the surface confronting macerating blades  621 ) of the porous plate  603 , a ring-like stationary blade  681  is mounted on an outer-circumferential side relative to the elongated holes  614 .  
      In addition, a flange  602 A of the rotor  602  is made to extend from a center side thereof toward the rear surface of the porous plate  603 , and a ring-like rotary blade  682  is mounted on an outer-circumferential portion thereof so as to confront the aforesaid stationary blade  681 .  
      With the construction of this stock re-pulper  600 , the rotation of the rotor  602  causes the stock flowing in the gap between the macerating blades  621  and the porous plate  603  to be lacerated by the lower edges of the macerating blades  621  and the circumferential edges of the elongated holes  614 , thereby carrying out the maceration processing.  
      Following this, the stock after passing through the elongated holes  614  is macerated more finely between the stationary blade  681  and the rotary blade  682  and then returned through a circulation opening  660 , bored in an outer-circumferential portion of the porous plate  603 , to a tub (not shown).  
      When the maceration processing reaches completion by the rotation of the rotor  602  for a predetermined period of time, a valve (not shown) provided in an output pipe (not shown) of the chamber  609  located on a rear side of the porous plate  603  is opened to discharge the stock which is in a macerated condition.  
      Furthermore,  FIG. 18  is a perspective view (partially sectional view) showing a construction of an essential part of a stock re-pulper  700  to be employed for the maceration of harder-to-dissolve stock than the stock to be macerated by the above-mentioned stock re-pulper  600 .  
      As shown in  FIG. 18 , a plurality of round holes  714  are formed in a porous plate  703 . A flange  702 A of a rotor  702  is formed so as to extend from a central axis side of the rotor  702  toward a rear surface of the porous plate  703 .  
      Moreover, a rotary blade (pump blade)  725  is mounted on an outer-circumferential side of the rotor  702  so as to confront a rear surface (surface opposite to the surface confronting macerating blades  721 ) of the aforesaid porous plate  703 . This pump blade  725  is composed of a ring-like base portion  725 A and a plurality of blade portions  725 B formed at a given interval on an upper surface of the base  725 A.  
      With the construction of this stock re-pulper  700 , the rotation of the rotor  702  enables the stock flowing in the gap between the macerating blades  721  and the porous plate  703  to be lacerated between lower edges of the macerating blades  721  and the circumferential edges of the round holes  714 , thereby conducting the maceration.  
      Following this, the stock after passing through the round holes  714  is macerated more finely between the blade portions  725 B of the pump blade  725  and the round holes  714  and then returned through a circulation opening  760 , formed in an outer-circumferential portion of a chamber  709  located on a rear side of the porous plate  703 , to a tub (not shown).  
      The technique related to the foregoing conventional stock re-pulper shown in FIGS.  14  to  16  is disclosed in Japanese Patent No. 3581686.  
      As described above, the macerating blades  521  and  621  provided in the conventional stock re-pulper  500  shown in FIGS.  14  to  16  and in the conventional stock re-pulper  600  shown in  FIG. 17  have a function to agitate the stock in a tub while lacerating and, in addition, a function to further promote the stock maceration in cooperation with the porous plates  503  and  603 .  
      However, in these stock re-pulpers  500  and  600 , if the agitating capability of each of the macerating blades  521  and  621  is low, then difficulty is encountered in concentrating the stock at a portion (working portion) of each of the porous plates  503  and  603  where the holes  514 ,  614  are formed. This because the stock rises when the macerating blades  521 ,  621  have a low agitation capability.  
      For solving such a problem, although it can be considered to employ a method of enhancing the agitation capability of the macerating blades  521 ,  621 , this method naturally requires the enhancement of a driving force with respect to the rotors  502 ,  602  and it is not preferable in light of energy-saving.  
      Moreover, when the concentration of the stock is high with respect to the dilute solution, a large driving torque is required for rotating the rotor  502 ,  602  and, in this case, the further enhancement of the driving torque produces no practical solutions and leads eventually to insufficient maceration processing or prolongation of time needed for the maceration processing.  
      Thus, the conventional stock re-pulpers  500  and  600  do not always produce good maceration effects.  
      In addition, although the conventional stock re-pulper  500  shown in  FIG. 16  is designed to macerate the stock between the macerating blades  521  and the porous plate  503 , the stock in this stock re-pulper  500  flows more strongly in radial directions in comparison with circumferential directions and, hence, the stock is collected toward the outer-circumferential side, which makes it difficult for the stock to flow in the gap between the macerating blades  521  and the porous plate  503 .  
      Still additionally, the conventional stock re-pulper  600  shown in  FIG. 17  is equipped with, in addition to the macerating blades  621  and the porous plate  603 , the stationary blade  681  and the rotary blade  682 , which can provide an advantage in that even the maceration of hard-to-dissolve stock becomes feasible.  
      However, since a portion (working portion) where the stationary blade  681  and the rotary blade  682  confront each other is positioned at an outer-circumferential side remote from the center of rotation of the rotor  602 , there exists a need for the enhancement of the driving torque for rotating the rotor  602 .  
      Yet additionally, in this stock re-pulper  600 , if the stock flowing through the elongated holes  614  into a lower surface of the porous plate  603  is relatively large, this stock cannot enter the gap between the stationary blade  681  and the rotary blade  682 .  
      Accordingly, there is a problem which arises with the stock re-pulper  600  in that the non-macerated stock tends to accumulate on an inner-circumferential side relative to the stationary blade  681  and the rotary blade  682 .  
      On the other hand, since the conventional stock re-pulper  700  shown in  FIG. 18  is equipped with the macerating blades  721  and with the rotary blade (pump blade)  725  on the rear side of the porous plate  703 , there is an advantage in that it is possible to macerate even stock the stock re-pulper  600  shown in  FIG. 17  is hard to macerate.  
      However, in this stock re-pulper  700 , since the stock flowing in the chamber  709  through the round holes  714  made at a portion which is not positioned on the rotation trajectory of the blade portions  725 B of the pump blade  725  returns directly through the circulation opening  760  to the tub without undergoing the maceration processing by the porous plate  703  and the pump blade  725 , the maceration effectiveness is not high. In addition, since the stock undergoing the maceration processing by the blade portions  725 B of the pump blade  725  and the porous plate  703  is also returned through the circulation opening  760  to the tub and again undergoes the maceration processing, the maceration efficiency is not high.  
      Moreover, although it can be considered that the diameters of the porous plate  703  and the pump blade  725  are enlarged or the rotational speed of the pump blade  725  is increased for improving the maceration effectiveness of the porous plate  703  and the pump blade  725 , these methods require larger power for the rotation of the rotor  702 , and they are also undesirable in light of energy-saving.  
     SUMMARY OF THE INVENTION  
      The present invention has been developed with a view to eliminating the above-mentioned problems, and it is therefore an object of the invention to provide a stock re-pulper capable of producing a high maceration efficiency while suppressing the power needed for the maceration processing.  
      For this purpose, in accordance with an aspect of the present invention, there is provided a stock re-pulper for macerating stock put together with a dilute solution into a stock tub, comprising a first porous plate disposed in the stock tub and having first holes formed therein, first macerating blades disposed to confront one surface of the first porous plate and made to be rotated in proximity to a first open area of the first porous plate where the first holes are formed, a pump blade disposed to confront the other surface of the first porous plate in proximity to the first open area and made to be rotated concentrically with respect to the center of rotation of the first macerating blades, a second porous plate disposed in the stock tub and having second holes formed therein, second macerating blades disposed to confront one surface of the second porous plate in proximity to a second open area where the second holes are formed and made to be rotated concentrically with respect to the center of rotation of the first macerating blades, and a drive source for rotating the first macerating blades, the pump blade and the second macerating blades.  
      This construction can rotate the first macerating blades, the pump blade and the second macerating blades through the rotation of the drive source so that the stock put together with the dilute solution into the tub is positively guided between the first macerating blades, which are in rotation, and the first porous plate (to a first working section) and positively guided between the first porous plate and the pump blade which is in rotation (to a second working section) and further guided between the second macerating blades, which are in rotation, and the second porous plate (to a third working section), which can provide a high maceration effectiveness on the stock while suppressing the power needed for the maceration processing.  
      In addition, third macerating blades are provided above the first macerating blades and are made such that a distance from the center of rotation of the first macerating blades to an outer-circumferential end of the third macerating blades is shorter than a distance from the center of rotation of the first macerating blades to an outer-circumferential end of the first macerating blades.  
      Still additionally, fourth macerating blades are provided above the first macerating blades and are made such that a distance from the center of rotation of the first macerating blades to an outer-circumferential end of the fourth macerating blades is shorter than a distance from the center of rotation of the first macerating blades to an outer-circumferential end of the first macerating blades and a height of the fourth macerating blades is lower than a height of the third macerating blades.  
      Yet additionally, the first macerating blades are composed of a plurality of blades, and the third macerating blades and the fourth macerating blades are alternately disposed above the plurality of first macerating blades.  
      This construction enables the stock put together with the dilute solution into the tub to be agitated and macerated in a better condition.  
      Moreover, the second macerating blades have blade portions protruding toward the second porous plate, and the blade portions of the second macerating blades are made such that a gap relative to the second porous plate becomes gradually wider toward a downstream side of the second porous plate.  
      This enables a negative pressure to occur between the blade portions and the second porous plate, which prevents the stock from being getting jammed in the second holes made in the second porous plate.  
      Still moreover, an open area of the second holes is smaller than an open area of the first holes.  
      Thus, since the open area of the second holes is smaller than the open area of the first holes, only the stock undergoing the rough maceration processing to the extent that it can pass through the first holes can reach the second porous plate and, following this, the stock passing through the second holes formed in the second porous plate, i.e., only the stock undergoing the fine maceration processing to the extent that it can pass through the second holes, can be handled as the stock the maceration processing of which has reached completion.  
      Yet moreover, each of the first holes is formed as an elongated hole extending in a substantially radial direction of the first porous plate and the long axis of the elongated hole is inclined in a range from larger than 0 degree to not larger than 20 degrees with respect to the first macerating blades.  
      This enables the first macerating blades which are in rotation to cut through the first holes at a predetermined angle. That is, this enables the first macerating blades and the first holes forming elongated holes to cooperate with each other like two edges of scissors so that the stock can be lacerated by a large force between the first macerating blades and the first holes (at a first working section), thereby enhancing the maceration efficiency.  
      Furthermore, each of the second holes is formed as an elongated hole extending in a substantially radial direction of the second porous plate and the long axis of the elongated hole is inclined in a range from larger than 0 degree to not larger than 20 degrees with respect to the second macerating blades.  
      This enables the second macerating blades which are in rotation to cut through the second holes at a predetermined angle. That is, this enables the second macerating blades and the second holes forming elongated holes to cooperate with each other like two edges of scissors so that the stock can be lacerated by a large force between the second macerating blades and the second holes (at a second working section) thereby enhancing the maceration efficiency.  
      Still furthermore, each of the second holes is formed as a round hole having a generally complete round configuration.  
      This enables the second holes to be bored easily, which improves the production efficiency and contributes to the cost reduction.  
      Yet furthermore, the second porous plate is formed into a cylindrical configuration whose longitudinal central axis coincides with the axis of rotation of the first macerating blades, and the second macerating blades are made to be rotated on the inner-circumferential side of the second porous plate having the cylindrical configuration.  
      This enables a centrifugal force to be applied to the stock, thereby guiding more stock the second porous plate having the cylindrical configuration.  
      In addition, the second macerating blades include the plurality of blade portions and a groove portion is formed between the plurality of blade portions.  
      This can enhance the maceration processing efficiency. A negative pressure occurs in the groove portions made among the blade portions of the second macerating blades, which can prevent the stock from being getting jammed in the second holes made in the second porous plate and blow away the stock, accumulated on the second porous plate without passing through the second holes, through the groove portions to the outer-curmferential side of the second porous plate.  
      Still additionally, each of the first holes is formed to have a hole width in a range from 3 mm to 40 mm, and each of the second holes is formed to have a hole width in a range from 0.15 mm to 16 mm, and the rates of open areas of the first and second porous plates are set at values in a range from 10% to 50%.  
      This can provide a high maceration efficiency while securing the rigidities of the first and second porous plates.  
      Yet additionally, an angle made between an outer edge portion of each of the third and fourth macerating blades and an upper surface portion of the first macerating blades is set at a right angle or an acute angle.  
      This enables an outer edge portion of each of the third and fourth macerating blades to have an pointed configuration, which lacerates the stock in a good condition for achieving the efficient maceration processing.  
      Moreover, the stock re-pulper further comprises an output pipe which is a passage disposed on the other surface side of the second porous plate opposite to the one surface thereof and which is made to discharge the stock, after passing through the second holes from the one surface side of the second porous plate to the other surface side thereof, to the external, and circulation holes made in the first porous plate to be positioned on an outer-circumferential side of the first porous plate with respect to the first open area thereof to make communication between the other surface side of the first porous plate and the interior of the tub.  
      Thus, the stock macerated minutely to the extent that it can pass through the second holes, i.e., only the stock after macerated, can be discharged to the external. In addition, the stock (i.e., semi-macerated stock) macerated to the extent that it can pass through the first holes but non-macerated minutely to the extent that it can pass through the second holes can be returned to the interior of the tub, which enables conducting the maceration processing in a continuous running fashion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a top view illustratively showing the entire construction of a stock re-pulper (stock macerating apparatus) according to an embodiment of the present invention;  
       FIG. 2  is a top view illustratively showing a construction of an essential part of a stock re-pulper according to an embodiment of the present invention;  
       FIG. 3  is a cross-sectional view illustratively showing the entire construction of a stock re-pulper according to an embodiment of the present invention, and is a cross-sectional view taken along arrows III-III of  FIG. 1 ;  
       FIG. 4  is a cross-sectional view illustratively showing a construction of an essential part of a stock re-pulper according to an embodiment of the present invention;  
       FIG. 5  is a plan view illustratively showing a construction of an essential part of a stock re-pulper according to an embodiment of the present invention and showing a portion of a pump blade;  
       FIG. 6  is a plan view illustratively showing a construction of an essential part of a stock re-pulper according to an embodiment of the present invention, and showing second macerating blades;  
       FIG. 7  is a cross-sectional view illustratively showing a construction of an essential part of a stock re-pulper according to an embodiment of the present invention, and is a cross-sectional view taken along arrows VII-VII of  FIG. 4 ;  
       FIG. 8  is a perspective view illustratively showing a construction of an essential part of a stock re-pulper according to an embodiment of the present invention, and mainly showing third macerating blades;  
       FIG. 9  is a perspective view illustratively showing a construction of an essential part of a stock re-pulper according to an embodiment of the present invention, and mainly showing fourth macerating blades;  
       FIG. 10  is a plan view illustratively showing a portion of a first hole-made plate of a stock re-pulper according to an embodiment of the present invention;  
       FIG. 11  is a cross-sectional view illustratively showing an essential part of a stock re-pulper according to a modification of the present invention;  
       FIG. 12  is a cross-sectional view illustratively showing an essential part of a stock re-pulper according to a modification of the present invention;  
       FIG. 13  is a plan view illustratively showing a portion of a first hole-made plate of a stock re-pulper according to a modification of the present invention;  
       FIG. 14  is a top view illustratively showing a construction of a conventional stock re-pulper;  
       FIG. 15  is a cross-sectional view illustratively showing a construction of a conventional stock re-pulper, and is a cross-sectional view taken along arrows XV-XV of  FIG. 14 ;  
       FIG. 16  is a perspective view (partially sectional view) showing a construction of an essential part of a conventional stock re-pulper;  
       FIG. 17  is a perspective view (partially sectional view) showing a construction of an essential part of a conventional stock re-pulper; and  
       FIG. 18  is a perspective view (partially sectional view) showing a construction of an essential part of a conventional stock re-pulper.  
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      First of all, referring to FIGS.  1  to  10 , a description will be given hereinbelow of a stock re-pulper  100  according to an embodiment of the present invention.  
       FIG. 1  is a top view illustratively showing the entire construction of the stock re-pulper  100  according to this embodiment,  FIG. 2  is en enlarged view illustratively showing a central portion thereof,  FIG. 3  is a cross-sectional view taken along arrows III-III of  FIG. 1 ,  FIG. 4  is a cross-sectional view illustratively a construction of an essential part of the stock re-pulper,  FIG. 5  is a plan view illustratively showing a part of a pump blade,  FIG. 6  is a plan view illustratively showing second macerating blades,  FIG. 7  is an illustrative cross-sectional view taken along arrows VII-VII of  FIG. 4 ,  FIGS. 8 and 9  are perspective views illustratively showing a construction of an essential part thereof, and  FIG. 10  is a plan view mainly showing a first hole-made plate (board). In the description, an essential part construction (marked with a reference numeral  100 A) of the stock re-pulper  100  shown in  FIG. 4  will sometimes be referred to hereinafter as an “agitation maceration unit”.  
      As shown in  FIGS. 1 and 3 , this stock re-pulper  100  is equipped with a stock tub  101  having a cylindrical configuration, and this tub  101  is made to accommodate water serving as a dilute solution and stock.  
      In addition, to a bottom portion  101   b  of the tub  101 , there are fixedly secured a first porous plate (first hole-made plate)  131  and a chamber  109 , and to this chamber  109 , there is attached a second porous plate (second hole-made plate)  132 .  
      In the chamber  109 , an output pipe  105  is provided in order to discharge the stock, the maceration processing of which reached completion, to the external and a dilution waterspout  110  is provided to put water into the tub  101 . These output pipe  105  and dilution waterspout  110  are openable and closable through the use of valves (not shown).  
      Still additionally, as shown in  FIG. 4 , a sleeve  109 A, into which a rotary shaft  106  is to be inserted, is formed in a central portion of the chamber  109 . The axis C 102  of the rotary shaft  106  coincides with the central axis of rotation of a rotor  102  to be mentioned later.  
      Yet additionally, in the chamber  109 , a sorting unit  109 F is a space formed between the first porous plate  131  and the second porous plate  132  and on the outer-circumferential side relative to a pump blade  125  and second macerating blades (second macerating blade unit)  122 . The pump blade  125  and the second macerating blades  122  will be mentioned later.  
      Inside the tub  101 , there are formed a turning plate  111 A and a revolution preventing plate  111 B.  
      The turning plate  111 A is formed in a state inclined (obliquely) from a side portion  101   a  of the tub  101  to a bottom portion  101   b  thereof and in a state protruded toward the inside of the tub  101 . The formation of this turning plate  111 A enables turning a flow of stock in a circumferential direction (hereinafter referred to as a “revolving flow”) to a flow thereof in a longitudinal direction (hereinafter referred to as a “longitudinal flow”).  
      The revolution preventing plate  111 B is formed at the side portion  101   a  of the tub  101  so as to extend in a longitudinal direction in a state protruded toward the inside of the tub  101 , thereby preventing the occurrence of a revolving flow.  
      The first porous plate  131  is one ring-like plate having an opening at its central portion and is disposed horizontally and concentrically with respect to the axis C 102  forming an axis of rotation of the rotor  102 . In addition, this first porous plate  131  has a plurality of elongated holes (first holes)  141  and a plurality of circulation openings  160 , which are bored therein.  
      Moreover, as shown in  FIG. 4 , this first porous plate  131  is fixedly secured through bolts  170  to a drum portion  109   b  of the chamber  109  so as to cover the chamber from the above. Still moreover, first macerating blades (first macerating blade unit)  121 , which will be mentioned later, are rotated in proximity to an upper surface (one surface)  131   a  of the first porous plate  131  while a pump blade  152 , mentioned later, is rotated in close vicinity to a lower surface (the other surface)  131   b  of the first porous plate  131 .  
      Still moreover, as shown in  FIG. 10 , the first holes  141  are made to be 11 in number for each segment. In  FIG. 10 , there are exemplified one segment  131 A of the porous plate  131  divided virtually into 16 segments. Yet moreover, in  FIG. 10 , a two-dot chain line depicts a front lower edge  121   b  of each of the first macerating blades  121 , and this first macerating blades  121  are designed to be clockwise rotated around the axis C 102  of the rotor  102  as indicated by an arrow R 121 .  
      Incidentally, in  FIG. 10 , the angle indicated by a reference mark α 121b  is an angle made between a major axis C 141  of the first hole  141 A and the front lower edge  121   b  of each of the first macerating blade  121 . For convenience only,  FIG. 10  shows only an angle made between the major axis C 141A5  of the first hole  141 A 5 , which is fifth in order from the right, and the front lower edge  121   b  of each of the first macerating blades  121 .  
      In the segment  131 A shown in  FIG. 10 , the first hole  141 A 1  formed on the rightmost side is made such that the angle α 121b  made between the major axis C 141A1  of the first hole  141 A 1  and the front lower edge  121   b  of each of the first macerating blades  121  is slightly larger than zero degree (for example, α 121b ≈1°) in a state where the front lower edge  121   b  of each of the first macerating blades  121  crosses the first hole  141 A 1 .  
      On the other hand, the other first holes  141 A 2  to  141 A 11  are made such that their major axes are parallel with the major axis C 141A1  of the aforesaid rightmost first hole  141 A 1 .  
      In addition, in the segment  131 A shown in  FIG. 10 , the angle α 121b  made between the major axis C 141A11  of the first hole  141 A 11 , positioned on the leftmost side, and the front lower edge  121   b  of each of the first macerating blades  121  is approximately 20 degrees.  
      That is, in the segment  131 A, the angle α 121b  is in a range from approximately 1° to approximately 20° and increases gradually from the first hole  141 A 1  formed on the rightmost side toward the first hole  141 A 11  formed on the leftmost side.  
      Owing to such formation of the respective first holes  141 A 1  to  141 A 11 , at the rotation of the first macerating blades  121 , the front lower edge  121   b  of each of the first macerating blades  121  cuts through the respective first holes  141 A 1  to  141 A 11  while intersecting obliquely with them so that the first macerating blades  121  and each of the first holes  141 A 1  to  141 A 11  are in cooperation with each other like two edges of scissors.  
      Moreover, a result of the study by the inventor shows that, as practicable, the hole width of each of the first holes  141 A 1  to  141 A 11  is properly changeable in a range from approximately 3 mm to approximately 40 mm and the hole length of each of the first holes  141 A 1  to  141 A 11  is properly changeable in a range from approximately 3 mm to approximately 25 mm. Still moreover, another result of the study by the inventor shows that, preferably for practical use, the ratio of the opening area of the first holes  141  (i.e., the rate of open area of the first porous plate) to the area where the first holes  141  are physically formable in the first porous plate  131  is approximately 10 to 50%.  
      In this connection, since the stock maceration efficiency further improves as the number of first holes  141  increases, it is desirable that the number of the first holes  141  is as large as possible in the range where the rate of open area of the first porous plate is agreeable.  
      At the center of the first porous plate  131 , the rotor  102  is disposed to be rotatable around the axis C 102  relative to the first porous plate  131 .  
      In addition, this rotor  102  is connected through the rotary shaft  106  and a V belt  107  to a motor (drive source)  108  and, in response to the driving of the motor  108 , the rotor  102  is rotated around the axis C 102 . This motor  108  is provided with a control switch (not shown) so that an operator can on/off-control the motor  108  through the use of this control switch.  
      Still additionally, a sleeve  106   a  of the rotary shaft  106  is supported by a sleeve  109   a  of the chamber  109  through a solution leakage preventing seal  119  to be relatively rotatable.  
      Yet additionally, a rotor sleeve  102 B for supporting a flange  102 A of the rotor  102  is inserted into a tip portion of the rotary shaft  106 , and the rotor  102  and the rotary shaft  106  are fixed through a cover  190 , mounted on a top portion of the rotor  102 , to each other by means of a bolt  191 .  
      As  FIG. 4  shows, the flange  102 A is made to extend from the axis C 102  side of the rotor  102  toward an outer-circumferential side of a lower surface of the first porous plate  131 . Moreover, each of the first macerating blades  121  is fixed by a bolt  140  on the axis C 102  side of the flange  102 A. Incidentally, although in this embodiment the first macerating blades  121  are six in number, the present invention is not limited to this but the number thereof can be properly changed in a range from 3 to 16.  
      Furthermore, a shim  151  is interposed between the first macerating blades  121  and the flange  102 A so that the distance between the first macerating blades  121  and the first porous plate  131  can be properly changed by changing the thickness of this shim  151  or by changing the number of shims  151 . In this connection, a result of the study by the inventor indicates that a high maceration effectiveness is attainable when the distance between the first macerating blades  121  and the first porous plate  131  is set at approximately 0.5 to 5 mm.  
      With reference to  FIG. 2 , a description will be given hereinbelow of a rotating area A 121  of the first macerating blades  121  and a first porous area A 141  of the first porous plate  131 .  
      Of these, the rotating area A 121  of the first macerating blades  121  is defined as an area surrounded by an outer circle R 121OUT  having a radius from the axis C 102  of the rotor  102  to an outer-circumferential end  121   c  of the first macerating blades  121  at the center of the axis C 102  and an inner circle R 121IN  having a radius from the axis C 102  to an inner-circumferential end  121   d  of the first macerating blades  121  at the center of the axis C 102 .  
      On the other hand, the first porous area A 141  of the first porous plate  131  is defined as an area surrounded by an outer circle R 141OUT  having a radius forming a distance from the axis C 102  to an outer-circumferential end  141   a  of the first holes  141  at the center of the axis C 102  and an inner circle R 141IN  having a radius forming a distance from the axis C 102  to an inner-circumferential end  141   b  of the first holes  141  at the center of the axis C 102 .  
      That is, the rotating area A 121  of the first macerating blades  121  includes the entire first porous area A 141  of the first porous plate  131 .  
      In other words, when the rotor  102  rotates at the center of the axis C 102 , regardless of its angle of rotation, any one of the six first macerating blades  121  intersects with one of the first holes  141  at all times.  
      As  FIG. 1  shows, third macerating blades (third macerating blade unit)  123  and fourth macerating blades (fourth macerating blade unit)  124  are alternately disposed above the six first macerating blades  121 .  
      Of these, the third macerating blades  123  have a triangular pyramid configuration as shown in  FIGS. 1 and 8 , and a distance L 123  from the axis C 102  to an outer edge portion  123   b  of the third macerating blades  123  is set to be shorter than a distance L 121  from the axis C 102  to an outer-circumferential end  121   c  of the first macerating blades  121 .  
      In addition, each of the third macerating blades  123  is formed such that the angle α 123  made between the outer edge portion  123   b  thereof and an upper surface portion  121   d  of each of the first macerating blades  121  becomes a right angle. A result of the study by the inventor shows that, in a case in which the angle α 123  made between the outer edge portion  123   b  of each of the third macerating blades  123  and the upper surface portion  121   d  of each of the first macerating blades  121  is set at a right angle or acute angle, the stock maceration efficiency is improvable.  
      Each of the fourth macerating blades  124  has a triangular pyramid configuration as shown in  FIGS. 1 and 9 , and a distance L 124  from the axis C 102  to an outer edge portion  124   b  thereof is set to be shorter than the distance L 121  from the axis C 102  to the outer-circumferential end  121   c  of the first macerating blades  121 . Moreover, the height h 124  of each of the fourth macerating blades  124  is set to be lower than the height h 123  of each of the third macerating blades  123 .  
      Still additionally, each of the fourth macerating blades  123  is formed such that an angle α 124  made between the outer edge portion  124   b  thereof and the upper surface portion  121   d  of each of the first macerating blades  121  becomes a right angle. In this connection, a result of the study by the inventor shows that, even when the angle α 124  made between the outer edge portion  124   b  of each of the fourth macerating blades  123  and the upper surface portion  121   d  of each of the first macerating blades  121  is set at an acute angle without being set at a right angle, the stock maceration efficiency is also improvable.  
      On an upper surface of the flange  102 A, a ring-like pump blade  125  positioned at the center of the axis C 102  is fixed through the use of bolts  180  so that the first porous plate  131  is interposed between the first macerating blades  121  and the pump blade  125 .  
      Moreover, a shim  152  is interposed between the flange  102 A and the pump blade  125 , and the distance between the first porous plate  131  and the pump blade  125  is adjustable properly by changing the thickness of this shim  152 . According to the study by the inventor, when the distance between the first porous plate  131  and the pump blade  125  is set to be approximately 0.5 to 5 mm, a high maceration effectiveness is obtainable.  
      Incidentally, in addition to producing the stock maceration effectiveness in cooperation with the first porous plate  131 , the pump blade  125  creates an effectiveness to put the stock within the tub  101  through the first porous plate  131  into circulation in a positive manner.  
      As shown in  FIGS. 5 and 7 , this pump blade  125  is made up of a ring-like base portion  125 A and a plurality of blade portions  125 B formed at a given interval on an upper surface of the base portion  125 A.  
      Of these, the base portion  125 A is formed to have a ring-like configuration when viewed from the above and, as shown in  FIG. 5 , the blade portions  125 B are formed radially and linearly on the base portion  125 A at the substantial center of the axis C 102 , and they are arranged at a given interval. For example, these blade portions  125 B can be formed into a circular arc configuration having a relatively large radius.  
      These blade portions  125 B are formed on the base portion  125 A to occupy an area including the first porous area A 141 . In this pump blade  125 , there are made bolt holes  125 C into which the bolts  180  are inserted in order to make a connection between the flange  102 A and the pump blade  125 .  
      As shown in  FIG. 4 , as well as the first porous plate  131 , the second porous plate  132  is a ring-like plate having an opening in its central portion at the center of the axis C 102 , and a plurality of round holes (second holes)  142  (see  FIG. 7 ) each having a generally complete round configuration are made therein.  
      Moreover, this second porous plate  132  is disposed above the output pipe  105  and fixedly secured through bolts  182 ,  182  to seating  109 C and  109 D formed in the interior of the chamber  109 . Still moreover, the second macerating blades  122 , mentioned later, are rotated in a state close to an upper surface (one surface)  132   a  of this second porous plate  132 .  
      According to the study by the inventor, as practicable, preferably, the diameter of each of the second holes  142  is set to be in a range from approximately 0.15 mm to approximately 16 mm and, preferably, the rate of open area of the second porous plate  132  is set to be in a range from approximately 10% to approximately 50%. Moreover, since the maceration efficiency improves in proportion to the number of second holes  142 , it is desirable that the number of second holes  142  becomes larger, provided that the rate of open area is in a preferable range.  
      As shown in  FIG. 4 , the second macerating blades  122  are fixedly secured through bolts  181  to a lower surface of the flange  102 A of the rotor  102 . In this embodiment, the second macerating blades  122  are four in number as shown in  FIG. 6 . Incidentally, it was found that the number of second macerating blades  122  is not limited to four but, as practicable, the number of second macerating blades  122  is properly changeable in a range from 3 to 8 and, more preferably, 3 to 6.  
      In addition, a shim  153  is interposed between the second macerating blades  122  and the flange  102 A, and the distance between the second macerating blades  122  and the second porous plate  132  is properly changeable by changing the thickness of the shim  153  or by changing the number thereof. According to the study by the inventor, when the distance between the second macerating blades  122  and the second porous plate  132  is set to be approximately 0.5 mm to approximately 5 mm, a high maceration effectiveness is attainable.  
      Still additionally, as shown in  FIG. 7 , a front surface  122   a  of each of the second macerating blades  122  is composed of a surface (inclined plane)  122   a1  inclined by an angle α 122a1  with respect to the flange  102 A and a wall surface (upstanding plane)  122   a2  formed so as to make a right angle with respect to the flange  102 A.  
      That is, the formation of the inclined plane  122   a1  is for reducing the flow resistance occurring at the rotation of the second macerating blades  122  and the formation of the upstanding plane  122   a2  is for preventing the reduction of the maceration effectiveness due to the second macerating blades  122 .  
      Moreover, a lower surface of each of the second macerating blades  122  is formed as an inclined plane whose height from the flange  102 A decreases toward the downstream side and is formed such that the gap relative to the second porous plate  132  becomes gradually wider toward the downstream side, which generates a negative pressure between the lower surface  122   b  and the second porous plate  132 , thereby preventing the stock from getting jammed in the second holes  142  made in the second porous plate  132 .  
      Furthermore, as  FIG. 4  shows, a radial distance W 122  of the second macerating blades  122  is set to be shorter than a radial distance W 132  of the second porous plate  132 , thereby exhibiting a high maceration effectiveness and reducing the drive torque of the motor  108  needed for the rotation of the rotor  102 .  
      The stock re-pulper  100  according to this embodiment is constructed as described above and an operation of this stock re-pulper  100  produces the following effects and provides various effectiveness.  
      First, the operation of the motor  108  takes place when an operator turns on a control switch (not shown) and the power is transmitted from the motor  108  to the rotary shaft  106  to rotate the rotor  102  so that the first macerating blades  121  and the pump blade  125  are rotated around the axis C 102 .  
      At this time, the first macerating blades  121  are rotated in proximity to the upper surface  131   a  of the first porous plate  131 , and the pump blade  125  is rotated in proximity to the lower surface  131   b  of the first porous plate  131 .  
      In addition, the third macerating blades  123  and the fourth macerating blades  124 , alternately formed, are also rotated around the axis C 102  due to the rotation of the rotor  102  at the upper surfaces  121   d  of the six first macerating blades  121 , thus agitating the stock within the tub  101  in a good condition.  
      Still additionally, with the rotation of the rotor  102  (see an arrow R 121  in  FIG. 7 ) , the front upper edges  121   a  of the first macerating blades  121  and the front upper edges  123   a  of the third macerating blades  123  efficiently lacerate the stock within the tub  101 . In particular, the top portions (outer edge upper ends)  123   c  of the third macerating blades  123  and the top portions (outer edge upper ends)  124   c  of the fourth macerating blades  124  have a pointed configuration, thereby sharply lacerating the stock within the tub  101 .  
      Incidentally, although the rotation of the first macerating blades  121 , the third macerating blades  123  and the fourth macerating blades  124  produces a revolution flow of the stock in the tub  101 , the formation of the turning plate  111 A and the revolution preventing plate  111 B within the tub  101  turns this revolution flow to a longitudinal flow so that the stock circulates in the interior of the tub  101 .  
      On the other hand, with the rotation of the rotor  102 , the pump blade  125  is also rotated around the axis C 102 , thus applying a centrifugal force to the stock. In consequence, the stock existing in the chamber  109  (in more detail, a groove portions G 125  defined between the blade portions  125 B of the pump blade  125 ) is shifted forcibly toward an outer circumference thereof and the pressure in the groove portions G 125  of the pump blade  125  drops. Moreover, the stock within the tub  101  is forcibly introduced through the plurality of first holes  141  of the first porous plate  131  formed above the revolution area of the pump blade  125  into the groove portions G 125  of the pump blade  125  where the pressure drops.  
      In this connection, the function of forcibly putting the stock in the tub  101  into the chamber  109  through the rotation of the pump blade  125  is referred to as a “suction function” and, as shown in  FIG. 7 , the stock sucked through the first holes  141  of the first porous plate  131  into the chamber  109  owing to this suction function is lacerated between the front lower edges  121   b  of the first macerating blades  121  and the upper edges  141   a  of the first holes  141  and, following this, it is further lacerated between the lower edges  141   b  of the first holes  141  and the front upper edges  125 B 1  of the pump blade  125 .  
      In addition, the stock sent to the sorting unit  109 F of the chamber  109  then flows downwardly by the function of force of gravity and tends to flow further downwardly through the plurality of round holes  142  made in the second porous plate  132 .  
      Meanwhile, since the inner diameter of each of the round holes  142  is made to be smaller than the inner diameter of each of the first holes  141  formed in the first porous plate  131 , the stock (hereinafter referred to as “semi-macerated stock”) macerated to the extent that it can pass through the first holes  141  but non-macerated to the extent that it can pass through the second holes  142  collects on the upper surface  132   a  of the second porous plate  132  while only the stock sufficiently macerated into fine sizes passes through the round holes  142  and is discharged as macerated stock through the output pipe  105 .  
      Moreover, a portion of the stock sent out into the sorting unit  109 F of the chamber  109  flows between the second macerating blades  122 , which are in rotation, and the second porous plate  132  to be lacerated between the second macerating blades  122  and the second porous plate  132  and, as a result, the stock having minute sizes passes through the round holes  142  of the second porous plate  132  and is discharged as the macerated stock through the output pipe  105 .  
      Incidentally, in addition to the promotion of the stock maceration, the rotation of the second macerating blades  122  can prevent the stock from being left on the second porous plate  132 . That is, the plurality of round holes formed in the second porous plate  132  have a small diameter and, hence, the stock which cannot pass through the round holes  142  remains on the second porous plate  132 . However, in the stock re-pulper  100  according to this embodiment, the rotation of the second macerating blades  122  around the axis C 102  removes the stock left on the second porous plate  132  and, following this, the centrifugal force delivers this stock to an outer circumferential side in the sorting unit  109 F in the interior of the chamber  109 .  
      In addition, since the radial distance W 122  of the second macerating blades  122  is set to be shorter than the radial distance (see reference mark W 132  in  FIG. 4 ) of the second porous plate  132  as shown in  FIG. 4 , although it is apparently considered that the semi-macerated stock remains on the upper surface  122   a  of the second porous plate  132  in the area through which the second macerating blades  122  pass, in fact such an event does not occur. This because, when the second macerating blades  122  are put into rotation and the left stock gathered by the inclined planes  122   a  formed on the front surfaces of the second macerating blades  122  is then sent to the outer-circumferential side of the sorting unit  109 F of the chamber by the centrifugal force, the semi-macerated stock which has not been gathered directly by the second macerating blades  122  is collectively sent to the outer-circumferential side of the sorting unit  109 F.  
      Incidentally, although it is also acceptable that the radial distance W 122  of the second macerating blades  122  is set to be equal to the radial distance W 132  of the second porous plate  132 , in a case in which the radial distance W 122  of the second macerating blades  122  is set to be shorter than the radial distance W 132  of the second porous plate  132  as employed in this embodiment, the power needed for the rotation of the second macerating blades  122 , i.e., the drive torque required for the motor  108  to rotate the rotor  102 , is reducible and, hence, the structure according to this embodiment is more preferable in light of the energy saving.  
      On the other hand, the semi-macerated stock which cannot pass through the round holes  142  of the second porous plate  132  is again returned through the circulation openings  160 , bored in the outer-circumferential side of the first porous plate  131 , to the tub  101 .  
      That is, although the semi-macerated stock temporarily resides at the sorting unit  109 F of the chamber  109 , the pressure in the sorting unit  109 F occurring due to the rotations of the pump blade  125  and the second macerating blades  122  sends the semi-macerated stock from the sorting unit  109 F through the circulation openings  160  formed in the first porous plate  131  to the interior of the tub  101 .  
      Thus, with the stock re-pulper  100  according to this embodiment, the stock put together with the dilute solution into the tub  101  can be guided actively between the first macerating blades  121 , which is in rotation, and the first porous plate  131  (to a first working section) and it can further be guided actively between the first porous plate  131  and the pump blade  125  which is in rotation (to a second working section) and it can still moreover be guided between the second macerating blades  122 , which are in rotation, and the second porous plate  132  (to a third working section), thereby providing a high maceration effectiveness on the stock while suppressing the required drive torque from the motor  108 .  
      Furthermore, since the third macerating blades  123  and the fourth macerating blades  124  are alternately disposed on the plurality of first macerating blades  121 , it is possible to agitate the stock, put together with the dilute solution into the tub  101 , in a better condition, and since the third macerating blades  123  and the fourth macerating blades  124 , which are in rotation, can lacerate the stock in a good condition, the maceration processing efficiency is improvable.  
      Still furthermore, since the third macerating blades  123  and the fourth macerating blades  124  are formed on the first macerating blades  121 , even in a case in which the height of the first macerating blades  121  is set at a low value, a sufficient maceration effectiveness is attainable, and in this case, the required drive torque from the motor  108  for rotating the rotor  102  is suppressible, which contributes to the energy saving.  
      Yet furthermore, since the third macerating blades  123  and the fourth macerating blades  124  can agitate and lacerate the stock sucked from the tub  101  through the first holes  141  into the chamber  109  owing to the suction function stemming from the rotation of the pump blade  125 , the stock maceration efficiency is provable without increasing the rotational speed of the rotor  102 , which can further contribute to the energy saving.  
      Moreover, since the second macerating blades (blade portions)  122  are formed such that the gaps relative to the second porous plate  132  become gradually larger toward the downstream side, the generation of a negative pressure between the blade portions  122  and the second porous plate  132  becomes feasible, which can prevent the stock from getting jammed in the second porous plate  132 .  
      Still moreover, since the second holes  142  are formed to have an open area smaller than the open area of the first holes  141 , only the stock undergoing the rough maceration processing up to the extent that it can pass through the first holes  141  reaches the second porous plate  132  and, following this, only the stock undergoing the fine maceration processing up to the extent that it can pass through the second holes  142  is discharged as the macerated stock through the output pipe  105  to the external.  
      Yet furthermore, since each of the first holes  141  is formed as an elongated hole extending in a generally radial direction of the first porous plate  131  and the longitudinal axis (major axis) C 141  thereof is set to be inclined with respect to the first macerating blades  121  in a range between a value larger than 0 degree and a value not more than 20 degrees, the first macerating blades  121  being in rotation can cut through the first holes  141  in a state of intersecting obliquely. That is, this makes a cooperation between the first macerating blades  121  and the first holes  141  forming elongated holes, like two edges of scissors, which enables the stock to be lacerated by a large force between the first macerating blades  121  and the first holes  141  (at the first working section) thereby enhancing the maceration efficiency.  
      In addition, the formation of the plurality of second macerating blades  122  can enhance the maceration processing efficiency.  
      Still additionally, the formation of each of the groove portions G 122 between the plurality of second macerating blades  122  enables the generation of a negative pressure at the groove portions G 122 , which prevents the stock from being getting jammed in the second holes  142  made in the second porous plate  132 , and the semi-macerated stock deposited on the second porous plate  132  without passing through the second holes  142  can be blown away through the groove portions G 122  toward the outer-circumferential side of the sorting unit  109 F.  
      Yet additionally, the hole width W 141  of each of the first holes  141  is set at a value in a range from 3 mm to 40 mm and the hole width W 142  of each of the second holes  142  is set at a value in a range from 0.15 mm to 16 mm and the rates of open areas of the first and second porous plates  131  and  132  are set at a value in a range from 10% to 50%, which provides a high maceration efficiency while maintaining the required rigidity of each of the first and second porous plates  131  and  132 .  
      Moreover, each of the angles α 123  and α 124  made between the outer edge portions  123   b ,  124   b  of the third and fourth macerating blades  123 ,  124  and the upper surface portions  121 A of the first macerating blades  121  is set at a right angle or acute angle, which enables the outer edge upper end portions  123   b  and  124   b  of the third and fourth macerating blades  123  and  124  to be formed into pointed configurations, thus lacerating the stock in a good condition so as to conduct efficient maceration processing.  
      Still moreover, with respect to the second porous plate  132 , there is provided the output pipe  105  disposed on the lower surfaces  122   b  side of the second macerating blades  122  for discharging the stock (i.e., macerated stock), after passing through the second holes  142 , to the external. The formation of the output pipe  105  enables the macerated stock to be promptly discharged to the external for sending it to the next process.  
      Yet moreover, in the first porous plate  131 , there are provided the circulation openings  160  bored in the outer-circumferential side with respect to the first porous area A 141  for making a communication between the first porous plate  131  and the tub  101 . The formation of the circulation openings  160  enables the stock (i.e., semi-macerated stock), macerated to the extent that it can pass through the first holes  141  but non-macerated to the extent that it can pass through the second holes  142 , to be returned to the tub  101 , which enables the maceration processing in a continuous running fashion.  
      In addition, it is possible to concentrate the stock, returned through the circulation openings  160  into the tub  101 , on the first macerating blades  121 , the third macerating blades  123  and the fourth macerating blades  124 , which can provide a high maceration efficiency even in the case of the implementation of the maceration processing in a continuous running fashion.  
      The present invention is not limited to the above-described embodiment. A description will be given hereinbelow of some modifications thereof.  
      The same components as those in the above-described embodiment are marked with the same reference numerals, and the description will be given with emphasis on the differences from the embodiment. The drawings used for the description of the embodiment will sometimes be put to use.  
       FIG. 11  is a cross-sectional view illustratively showing an essential part of a stock re-pulper  200  producing a modification of the stock re-pulper  100  according to the above-described embodiment.  
      In  FIG. 11 , characteristic components are third macerating blades  223 , second porous plate  232  and second macerating blades  222 . The description of the third macerating blades  223  also applies to that of fourth macerating blades  224  and, therefore, as an example, the description will be given here of only the third macerating blades  223 .  
      A difference of the third macerating blades  223  according to this modification from the third macerating blades  123  (see  FIG. 4 ) according to the above-described embodiment is that a notch portion  223   d  is formed in a portion of an outer edge portion  123   b  of each of the third macerating blades  223 .  
      That is, the formation of the notch portion  223   d  in each of the third macerating blades  223  can reduce its front projective area, which leads to enhancing the stock maceration effectiveness while reducing the required drive torque from the motor  108  for the rotation of the rotor  102 .  
      In addition, a difference of the second porous plate  232  according to this modification from the second porous plate  132  (see  FIG. 4 ) according to the above-described embodiment is that it is formed into a cylindrical configuration in which the axis C 102  is set as its longitudinal central axis and formed such that its upper end portion extends horizontally in an outer-circumferential direction. That is, the second porous plate  232  is composed of a portion (cylindrical wall surface portion)  232 A formed as a wall surface of a cylindrical configuration and a portion (horizontal portion)  232 B extending horizontally.  
      Still additionally, in the second porous plate  232 , the horizontal portion  232 B, together with the first porous plate  131 , is fixedly secured through bolts  170  to a chamber  209 .  
      Yet additionally, a plurality of second holes  241  are bored in each of the cylindrical wall surface portion  232 A and the horizontal portion  232 B. These second holes  241  are formed as generally complete round holes as well as the above-described embodiment.  
      Moreover, as a difference from the second macerating blades  122  (see  FIG. 4 ) according to the above-described embodiment, each of the second macerating blades  222  extending vertically is fixed to an outer-circumferential end portion of the flange  102 A and is rotated inside the cylindrical second porous plate  232  and in proximity to an inner surface of the cylindrical second porous plate  232 .  
      Still moreover, inside the cylindrical second porous plate  232  and under the second macerating blades  222 , a circulation pipe  261  is provided which makes a communication between the tub  101  and the interior of the chamber  209 . Yet moreover, an output pipe  205  is located on an outer-circumferential side of the chamber  209  to discharge, to the external, the stock after passing through the second holes  241 .  
      Furthermore, in the construction shown in  FIG. 11 , in accordance with the rotation of the rotor  102 , the stock in the tub  101  is agitated by the first macerating blades  121 , the third macerating blades  123  and the fourth macerating blades  124  and is macerated between the first macerating blades  121  and the first porous plate  131 . Following this, the stock reaches the lower surface of the first porous plate  131  through the first holes  141 , where the stock is lacerated between the first porous plate  131  and the pump blade  125  so that the maceration further advances, and it is delivered to the outer-circumferential side of the pump blade  125 .  
      Thereafter, this stock flows into the gap between the second macerating blades  222  and the second porous plate  232  to be lacerated therebetween, thereby further conducting the maceration processing to further break the stock up.  
      Still furthermore, the stock undergoing the maceration processing so that its sizes become smaller than the hole diameters of the second holes  241  formed in the second porous plate  232  is discharged through the output pipe  205  to the external after passing through the second holes  241 . On the other hand, the stock having sizes larger than the hole diameters of the second holes  241  is returned through the circulation openings  160  to the tub  101  or is returned to the tub  101  through the circulation pipe  261  disposed inside the cylindrical second porous plate  232  and under the second macerating blades  222 .  
      As described above, with the stock re-pulper  200  according to the modification shown in  FIG. 11 , a centrifugal force can be applied to the stock undergoing the maceration processing between the second macerating blades  222  and the second porous plate  232  so that more stock is guided directly to the cylindrical second porous plate  232 . This can improve the maceration efficiency considerably.  
       FIG. 12  is a cross-sectional view illustratively showing an essential part of a stock re-pulper  300  producing a further modification of the stock re-pulper  100  according to the above-described embodiment. In  FIG. 12 , the first macerating blades  121 , the third macerating blades  123 , the first porous plate  131 , the base portion  125 A and blade portions  125 B of the pump blade  125 , the flange  102 A and the second porous plate  132  are the same as those described with reference to  FIG. 7  and other illustrations, and the description thereof will be omitted for brevity.  
      That is, in the stock re-pulper  100  according to the modification shown in  FIG. 12 , a characteristic component is a second macerating blade  322 . This second macerating blade  322  is made up of a ring-like base portion  322 A and a plurality of blade portions  322 B formed at a given interval on a lower surface of the base portion  322 A.  
      Of these, the base portion  322 A is formed into a ring-like configuration when viewed from the above, while the blade portions  322 B are formed radially and linearly at the substantial center of the axis C 102  on the lower surface of the base portion  322 A and arranged at a given interval. For example, these blade portions  322 B can be formed into a circular arc configuration having a relatively large radius. Moreover, a groove portion(s) G 322  is defined between the plurality of blade portions  322 B and  322 B.  
      This construction enables considerably increasing the number of second macerating blades  322 , which improves the maceration efficiency and efficiently blows away the semi-macerated stock accumulated on the upper surface of the second porous plate  132 .  
      For a further understanding of the present invention, a description will be given hereinbelow of modifications other than the constructions shown in FIGS.  1  to  12  as an embodiment and modifications thereof.  
      For example, although in the above description of the embodiment 11 elongated holes  141  are formed in one segment  131 A of the first porous plate  131 , the present invention is not limited to this number of elongated holes  141 , but the number of elongated holes  141  can properly be increased/decreased according to amount or kind of stock to be macerated.  
      In addition, although in the above description of the embodiment the first porous plate  131  is one ring-like plate, the present invention is not limited to this structure, but it is also appropriate that the first porous plate  131  is divided according to segment and, when fixed to the chamber  109 , the divided sections are formed into a ring-like configuration at the center of the axis C 102 .  
      Still additionally, although in the above description of the embodiment all the elongated holes  141 A 1  to  141 A 11  are formed as one elongated hole, the present invention is not limited to this. That is, it is also acceptable that, as shown in  FIG. 13 , the respective elongated holes  141 A 1  to  141 A 8  (see  FIG. 10 ) are divided into two: outer-circumferential side elongated holes  141 A 1-1  to  141 A 8-1  and inner-circumferential side elongated holes  141 A 1-2  to  141 A 8-2 . This can enhance the rigidity of the first porous plate  131 .  
      Yet additionally, although in the above description of the embodiment each of the first holes  141  is formed as an elongated hole, the present invention is not limited to this. However, as mentioned in detail with reference to  FIG. 10 , when the first holes  141  are made as elongated holes, there is a merit in that the so-called scissors effects are obtainable.  
      Moreover, although in the above description of the embodiment each of the second holes  142  is formed as a round hole, the present invention is not limited to this. For example, it is also appropriate that the second hole  142  is formed as an elongated hole extending in a substantially radial direction of the second porous plate  132  and the long axis (longitudinal axis) thereof is inclined in a range from larger than 0 degree to not larger than 20 degrees with respect to the second macerating blades  122 .  
      This enables the second macerating blades  122  which are in rotation to intersect obliquely with the second holes  142  and, in other words, makes the second macerating blades  122  and the second holes  142 , which are elongated holes, cooperate with each other like two edges of scissors, so the stock can be lacerated by large force between the second macerating blades  122  and the second holes  142  (second working section) which improves the maceration efficiency.  
      Furthermore, although the edge portions of the first to fourth macerating blades  121 ,  122 ,  123  and  124  and the pump blade  125  are gradually worn away, as the countermeasures against this abrasion, it is also appropriate that a replacement blade made of a material having a high abrasion resistance is mounted on a front surface of each of these blades  121 ,  122 ,  123  and  124 .  
      The blade dispositions of the first to fourth macerating blades  121 ,  122 ,  123  and  124  and the pump blade  125  and the disposition intervals (pitches) and configurations thereof are not limited to those mentioned above, but various changes and modifications are possible.  
      Still furthermore, although in the above description of the embodiment the stock re-pulper  100  is equipped with the agitation and maceration unit  100 A (see  FIG. 4 ) on a bottom portion of the open type tub  101 , the present invention is also applicable to a stock re-pulper equipped with a hermetically sealed type tub or a stock re-pulper in which the agitation and maceration unit  100 A is provided on a side surface of the tub  101 .  
      Yet furthermore, although in the above description of the embodiment the third macerating blades  123 ,  223  are fixedly secured onto the first macerating blades  121  and the fourth macerating blades  124 ,  224  are fixedly secured thereonto, the present invention is not limited to this structure. For example, it is also acceptable that the third macerating blades  123 ,  223  are disposed above the first macerating blades  121  to be rotatable separately from the first macerating blades  121 , or that the fourth macerating blades  124 ,  224  are made to be rotatable separately from the first macerating blades  121 .