Patent Publication Number: US-2019184598-A1

Title: Extruder, operational method thereof, and method of producing honeycomb green body using said extruder

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims a priority of Japanese Patent Application No. 2017-243181, filed on Dec. 19, 2017, the entire content of which is expressly incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure is generally related to an extruder, an operational method thereof, and a method of producing a honeycomb green body using the extruder. 
     BACKGROUND 
     Japanese Patent Application Laid-open No. 2017-149002 discloses a biaxial extruder used in a process for extrusion-molding of honeycomb green body. US Patent Application Publication No. 2014/0271969 discloses a technique to restrain a pair of screws for suppressing deflections of the screws. U.S. Pat. No. 3,680,994(B) relates to an extruder for foodstuff, and discloses that a downstream end of a screw housed in a barrel chamber is axially supported at an upper position over an outlet passage that extends downward from the barrel chamber. 
     SUMMARY 
     In a case where a downstream end of a screw is axially supported as disclosed in U.S. Pat. No. 3,680,994(B), a bent would be required for a flow path of raw material, resulting in more complicated configuration of an extruder. 
     An extruder according to an aspect of the present disclosure may include: at least one screw that extends along an axial direction, the screw including a downstream end positioned downstream in a conveying direction of raw material that is conveyed along the axial direction in accordance with rotation of the screw; a housing that houses the screw; and at least one axial support that axially supports the downstream end of the screw, the axial support including at least one rectifier plate. 
     In some embodiments, an upstream end of the screw positioned upstream in the conveying direction of the raw material is coupled to a driving mechanism. 
     In some embodiments, the extruder may further include at least one axial portion that extends along the axial direction toward the screw or toward the axial support, an end of the axial portion being fitted to a first receiving portion of the axial support or with a second receiving portion of the downstream end of the screw such that the screw is free to rotate. 
     In some embodiments, the axial portion may be inserted into a bushing and/or a sealing member, and/or the axial portion may be fitted to or held by a bearing. 
     In some embodiments, the first or second receiving portion may receive a bushing to which the axial portion is inserted or a bearing to which the axial portion is coupled. 
     In some embodiments, the axial portion may have a diameter that is smaller than a diameter of a shaft of the screw. 
     In some embodiments, the axial portion may be a portion of at least one coupler that couples the downstream end of the screw and the axial support such that the screw is free to rotate. 
     In some embodiments, the downstream end of the screw is fitted to the rectifier via a coupler such that the screw is free to rotate. 
     In some embodiments, the coupler is non-rotatably fitted to the downstream end of the screw. 
     In some embodiments, the rectifier plate includes a first rectifier plate and/or a second rectifier plate, the first rectifier plate having a through-hole into which an axial portion extending along the axial direction from the screw to the rectifier is inserted, and the second rectifier plate having a first receiving portion that is to receive an end of the axial portion. 
     In some embodiments, the first and second rectifier plates are stacked. 
     In some embodiments, the first and second rectifier plates are attached to a flange of the housing. 
     In some embodiments, the extruder may further include a sealing member that prevents the raw material from flowing into the first receiving portion of the second rectifier plate through the through-hole of the first rectifier plate. 
     In some embodiments, through-channels of the rectifier plate may be arranged in a circle so as to surround the first receiving portion. 
     In some embodiments, a sealing member is attached to the rectifier plate so as to surround one or more through-channels of the rectifier plate. 
     A method of producing a honeycomb body according to an aspect of the present disclosure may be a method of producing a honeycomb body from raw material using an extruder according to one of the above described extruders wherein the extruder further comprises an extrusion die disposed downstream of the axial support in the conveying direction of the raw material. 
     A method of producing a honeycomb body according to an aspect of the present disclosure may be a method of producing a honeycomb body from raw material using an extruder. The extruder may includes: 
     at least one screw that extends along an axial direction, the screw including a downstream end positioned downstream in a conveying direction of raw material that is conveyed along the axial direction in accordance with rotation of the screw; 
     a housing that houses the screw; 
     at least one rectifier plate that axially supports the downstream end of the screw; and 
     an extrusion die disposed downstream of the rectifier plate in the conveying direction of the raw material. 
     The method may includes: 
     conveying the raw material to the extrusion die based on rotation of the screw of the extruder; 
     cutting a honeycomb green body being continuously extruded from the extrusion die; and 
     firing the honeycomb green body obtained by the cutting. 
     An operational method of an extruder according to an aspect of the present disclosure may includes: 
     rotating at least one screw that extends in an axial direction and is arranged in a housing of the extruder such that raw material is conveyed along the axial direction; 
     axially supporting, by at least one rectifier plate arranged in the housing, a downstream end of the screw positioned downstream in the conveying direction of the raw material; and 
     rectifying, by the at least one rectifier plate, the raw material conveyed downstream in accordance with the rotation of the screw. 
     According to an aspect of the present disclosure, simplification of configuration of extruder may be facilitated. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Hereinafter, non-limiting embodiments of the present disclosure will be discussed with reference to  FIGS. 1 to 11  in which like numerals of reference indicate like parts. A skilled person would be able to combine respective embodiments and/or respective features without requiring excess descriptions, and would appreciate synergistic effects of such combinations. Overlapping descriptions among the embodiments would be basically omitted. Referenced drawings are prepared for the purpose of illustration of invention, and might be simplified for the sake of convenience of illustration. 
         FIG. 1  is a schematic top view of an extruder according to an aspect of the present disclosure. 
         FIG. 2  is a schematic side view of an extruder according to an aspect of the present disclosure. 
         FIG. 3  is a schematic view of a non-limiting arrangement where a downstream end of a screw is axially supported by an axial support. An end of an axial portion extending along an axial direction from a screw side toward a rectifier plate is fitted to a first receiving portion of the rectifier plate. 
         FIG. 4  is a schematic view of a non-limiting arrangement where a downstream end of a screw is axially supported by an axial support. A bushing is received in a first receiving portion of the rectifier plate, and an end of the axial portion is inserted into the bushing. 
         FIG. 5  is a schematic view of a non-limiting arrangement where a downstream end of a screw is axially supported by an axial support. An end of an axial portion extending along an axial direction from a rectifier plate side toward a screw is fitted to a second receiving portion of the downstream end of the screw. 
         FIG. 6  is a schematic view of a non-limiting arrangement where a downstream end of a screw is axially supported by an axial support. A bushing is received in a second receiving portion of the downstream end of the screw, and an end of the axial portion is inserted into the bushing. 
         FIG. 7  is a schematic perspective view of a non-limiting arrangement where a downstream end of a screw is axially supported by an axial support, cross-section being illustrated by hatching of slant lines for the sake of easier understanding. 
         FIG. 8  is a schematic perspective view of a non-limiting arrangement where a downstream end of a screw is axially supported by an axial support, cross-section being illustrated by hatching of slant lines for the sake of easier understanding. 
         FIG. 9  is schematic perspective view of a non-limiting arrangement where a downstream end of a screw is axially supported by an axial support, cross-section being illustrated by hatching of slant lines for the sake of easier understanding. 
         FIG. 10  is schematic perspective view of a reference example where a downstream end of a screw is not axially supported by an axial support, cross-section being illustrated by hatching of slant lines for the sake of easier understanding. 
         FIG. 11  is a schematic view showing a honeycomb green body. 
     
    
    
     DETAILED DESCRIPTION 
     In the following descriptions, respective features described for an extruder and a method of extruding would be understood as individual features independent to other features, additionally to as combination with other features. The respective features would be understood as individual features without requiring combination with other features, but could be understood as combination with other features. Describing all combinations of individual features would be redundant for a skilled person, and thus omitted. The individual features would be identified by a language of “In some cases”. The individual features would be understood as a universal feature that is effective not only to an extruder and a method of extruding illustrated in the drawings for example, but also effective to other various extruders and methods of extruding not particularly described in the present specification. 
       FIG. 1  is a schematic top view of an extruder  2 .  FIG. 2  is a schematic side view of an extruder  2 . As would be understood from  FIGS. 1 and 2 , in some cases, the extruder  2  has at least one screw  10  extending along an axial direction AX 1 , and a housing  20  that houses the at least one screw  10 . Rotation of the at least one screw  10  causes a raw material to be conveyed along the axial direction AX 1 . In some cases, the screw  10  is an elongated axial member having a downstream and upstream ends  11 ,  12  in the conveying direction of the raw material. The screw  10  may be referred to as a screw shaft. The raw material being conveyed along the axial direction AX 1  may include the raw material being spirally conveyed along the axial direction AX 1 . 
     In some cases, the screw  10  has a shaft  13  extending along the axial direction AX 1 , and a blade  14  spirally extending along the shaft  13 . Embodiment is envisioned where the shaft  13  is omitted. Slight clearance may be provided between the outer periphery of the blade  14  and the inner wall surface of the housing  20 . Alternatively, the outer periphery of the blade  14  may touch the inner wall surface of the housing  20 , and the outer periphery of the blade  14  may slide on the inner wall surface of the housing  20  in accordance with the rotation of the shaft  13 . 
     Depending on cases, the blade  14  may have different pitches along the axial direction AX 1  of the shaft  13 , and conveying distance of raw material per one rotation of the screw  10  may not be constant along the axial direction AX 1 . Notches recessed radially inward of the shaft  13  may be provided at regular or irregular interval in the blade  14 . In some cases, the raw material may be clay. In some cases, the raw material includes at least ceramic powder, water, and binder. In some cases, the raw material may be a slurry in which ceramic powder, water, and binder are mixed. 
     The extruder  2  may have a plurality of, i.e. a pair of screws  10 .  FIG. 1  shows a case where the extruder  2  has a pair of screws  10 . An embodiment is envisioned where the extruder  2  has only one screw  10  (See  FIG. 9 ). An embodiment is also envisioned where the extruder  2  has three or more screws  10 . As the number of screws increases, an extrusion-pressure of raw material by the extruder  2  may be increased. The housing  20  may be a tubular member extending along the axial direction AX 1  of the screw  10  and/or has an inner wall surface defining a chamber for the screw  10  or a flow passage of raw material, in some cases. The housing  20  can be referred to as a barrel. Both of the screw  10  and the housing  20  may consist of metal. Note that, a hopper  29  for the raw material may be coupled to the housing  20 . The hopper  29  may be disposed upstream in the conveying direction of raw material conveyed by the screw  10 . It is envisioned that two or more hoppers  29  are coupled to the housing  20 . 
     In the present embodiment, the screw  10  has a downstream end  11  positioned downstream in the conveying direction of the raw material that is conveyed along the axial direction AX 1  in accordance with the rotation of the screw  10 , and the downstream end  11  of the screw  10  is axially supported by at least one axial support. In other words, additionally to the screw  10  and the housing  20 , the extruder  2  is provided with at least one axial support that axially supports the downstream end  11  of the screw  10 . Accordingly, an axial deflection or axial swing of the screw  10  would be avoided or suppressed. Note that, in some cases, the upstream end  12  of the screw  10  positioned upstream in the conveying direction of the raw material may be coupled to a driving mechanism, e.g. an output axis of an electric motor  83  or an output axis of a speed reducer  84  described below. 
     Additionally or alternatively to the feature described in the previous paragraph, in some cases, the screw  10  may be straddle-supported by the driving mechanism and the axial support. In other words, the downstream end  11  and the upstream end  12  of the screw  10  are axially supported by the driving mechanism and the axial support, respectively. Axially supporting the upstream end  12  of the screw  10  may be achieved by coupling the upstream end  12  of the screw  10  to the driving mechanism for driving the screw  10 , e.g. an output axis of an electric motor  83  or an output axis of a speed reducer  84  described below. Note that, the downstream and upstream ends  11 ,  12  may alternatively be referred to as first and second ends. 
     In some cases, the at least one axial support may include at least one rectifier plate  30 . In other words, the rectifier plate  30  functions as the axial support, i.e. the rectifier plate  30  is used as the axial support. Accordingly, mounting to the extruder  2  a dedicated part for the axial support would possible be avoided, and simplification of configuration of the extruder  2  would be facilitated. The rectifier plate  30  is an example of axial support, and thus descriptions about the rectifier plate  30  would equally apply to the axial support. In light of such a viewpoint, in the present specification, the rectifier plate  30  can be replaced with the axial support so that the meanings of sentences would be understood. For example, a sentence “the extruder  2  has one plate-like rectifier plate  30  that is arranged orthogonal to the axial direction AX 1 ” would be understood to indicate “the extruder  2  has one plate-like axial support that is arranged orthogonal to the axial direction AX 1 ” either. 
     The rectifier plate  30  may be any part that has a functionality of rectifying the flow of raw material. In some cases, the rectifier plate  30  has a flat plate  38  and one or more through-channels  39  that penetrate the flat plate  38 . The raw material being conveyed continuously or intermittently by the one or more screws  10  would be prevented by the flat plate  38  from outflowing downstream, but it can indeed flow downstream through the one or more through-channels  39  arranged in the flat plate  38 . Number, outline shape, and arrangement manner of the through-channels  39  would be various. Note that, other parts such as, e.g. an extrusion die  81  or a mesh  82  described below could be employed as the axial support. 
     In some cases where a pair of screws  10  is employed, an extrusion-period of raw material by one screw  10  and an extrusion-period of raw material by the other screw  10  may be complementary. That is, in a time period during which raw material is extruded by the first screw  10 , raw material is not extruded by the second screw  10 . In a time period during which raw material is extruded by the second screw  10 , raw material is not extruded by the first screw  10 . The rectifier plate  30  is disposed downstream of the screw  10 , and the raw materials alternately conveyed by the pair of screws  10  are transferred into and stored in a pooling space between the screws  10  and the rectifier plate  30 . Certain amount of raw materials are newly alternately conveyed by the pair of screws  10  to the pooling space and, accordingly a part of raw material filled in the pooling space is extruded downward through the through-channels  39  of the rectifier plate  30 . When the respective paired screws  10  rotate continuously, the raw material would be extruded at a constant rate through the through-channels  39  of the rectifier plate  30 . 
     The extruder  2  may have a driving mechanism to rotate the screws  10 . The driving mechanism may be arranged integrally or separately to the housing  20 . The driving mechanism may include an electric motor  83  and a speed reducer  84 , for example. A rotational torque produced by the electric motor  83  is increased by the speed reducer  84  and transmitted to the screw  10 . The electric motor  83  may be a stepping motor, for example. Any kind of speed reducer available in market such as a planetary speed reducer or worm speed reducer can be employed as the speed reducer  84 . 
     Optionally, the extruder  2  may have an extrusion die  81  and/or a mesh  82 . The extrusion die  81  and/or the mesh  82  is disposed downstream of the axial support in the conveying direction of the raw material. The extrusion die  81  may be a molding part for molding the raw material so as to have a honeycombed structure of a honeycomb green body such as illustrated in  FIG. 11 . By passing through the extrusion die  81 , the raw material is molded to form cell-walls of the green honeycombed structure, and the cell-walls define opening cells. Note that, the cells may have various shapes such as rectangular, pentagonal, hexagonal shapes. “Honeycomb or honeycombed structure” includes any lattice shapes that are different from a typical lattice shape of beehive. The mesh  82  is provided to exclude contaminants included in the raw material. In  FIGS. 1 and 2 , the extruder  2  has a housing  25  that is provided downstream of the housing  20  and is integral to or separated from the housing  20 . The extrusion die  81  and mesh  82  are attached to the housing  25 . 
     In some cases, the extruder  2  has an axial support  65  that supports the upstream end  12  side of the screw  10 . The axial support  65  may have one or more through-holes into which the shaft  13  of the screw  10  is inserted. A bushing and/or O-ring may be arranged in the through-hole of the axial support  65  into which the shaft  13  is inserted. 
     Non-limiting arrangements of the axially supported downstream end  11  of the screw  10  will be described with reference to  FIGS. 3-6 . Note that, readily envisioned is that the downstream end  11  of the screw  10  is axially supported by the axial support in a manner other than illustrated in the drawings of the present application. In  FIG. 3 , an end (downstream end) of the axial portion  40  extending along the axial direction AX 1  from the screw  10  side toward the rectifier plate  30  is fitted to a first receiving portion  51  of the rectifier plate  30 . In  FIG. 4 , a bushing  60  is received in the first receiving portion  51  of the rectifier plate  30  and the end (downstream end) of the axial portion  40  is inserted into the bushing  60 . The bushing  60  may be attached to the end (downstream end) of the axial portion  40 . The end (downstream end) of the axial portion  40  to which the bushing  60  is attached may be loosely fitted to the first receiving portion  51 . In  FIG. 5 , an end (upstream end) of the axial portion  40  extending along the axial direction AX 1  from the rectifier plate  30  side toward the screw  10  is fitted to a second receiving portion  52  of the downstream end  11  of the screw  10 . In  FIG. 6 , a bushing  60  is received in the second receiving portion  52  of the downstream end  11  of the screw  10  and the end (upstream end) of the axial portion  40  is inserted into the bushing  60 . 
     The receiving portion such as the first or second receiving portion  51 ,  52  may be an opening with or without a bottom. The first receiving portion  51  in  FIG. 3  is a bottomless opening, and penetrates the axial support. The first receiving portion  51  in  FIG. 4  is an opening with a bottom, and does not penetrate through the axial support. The second receiving portion  52  in  FIGS. 5 and 6  is an opening with a bottom. Depth direction of the first and second receiving portions  51 ,  52  matches the axial direction AX 1  that is equal to the extending direction of the axial portion  40 . In some cases, the receiving portion has a circular inner-wall profile in a plane orthogonal to the axial direction AX 1  of the screw  10 . 
     In some cases, at least one axial portion  40  extends along the axial direction AX 1  toward the screw  10  or toward the axial support, and an end of this axis portion  40  is fitted to a first receiving portion  51  of the axial support or a second receiving portion  52  of the downstream end  11  of the screw  10  such the screw  10  is free to rotate. This fitting may be a loose-fitting, a tight-fitting or any other manners of fittings. In some cases, the axial portion  40  may be a cylinder portion having a circular cross-sectional shape, thus facilitating smooth rotation of the screw  10 . 
     In some cases, one of the screw  10  and the axial support is provided with the axial portion  40 , or the axial portion  40  is coupled to one of the screw  10  and the axial support. In some cases of  FIGS. 3 and 4 , it is the screw  10  that has the above-described axial portion  40 . In some cases of  FIGS. 5 and 6 , it is the axial support (the rectifier plate  30 ) that has the above-described axial portion  40 . As such, manners of axially supporting the downstream end  11  of the screw  10  by the axial support would be various. 
     Preferably, (i) the axial portion  40  is inserted into a bushing  60  and/or a sealing member  70  and/or (ii) the first or second receiving portion  51 ,  52  receives a bushing  60  into which at least one axial portion  40  is inserted. The use of the bushing  60  may improve rotational stability of the screw  10 . A bearing (e.g. a needle bearing) can be employed as an alternative of the bushing  60 . In this case, (i) the axial portion  40  is coupled to the bearing or supported by the bearing and/or (ii) the first or second receiving portion  51 ,  52  receives a bearing that is coupled to the at least one axial portion  40 . Various types of bearing could be used and should not be limited to a particular bearing. As an embodiment where the axial portion  40  is coupled to the bearing, an outer ring of a needle bearing may be fixed to the rectifier plate  30 , and an inner ring of the needle bearing may be fixed to the axial portion  40 . As an embodiment where the axial portion  40  is supported by a bearing, an embodiment is envisioned where needle rotators of a needle bearing touch an outer periphery of the axial portion  40  of the screw  10 . Note that reduced smoothness of rotation of the screw  10  is avoided or suppressed by the employment of the sealing member  70 . The sealing member  70  may be an O-ring. Note that, the bushing  60  is a hollow cylinder and facilitates stable or smooth rotation of the axial portion  40 . The bushing  60  may be a metal hollow cylinder. 
       FIGS. 7-9  are schematic perspective views of non-limiting arrangements where the downstream end  11  of the screw  10  is axially supported by the axial support, cross-section being illustrated by hatching of slant lines for the sake of easier understanding.  FIG. 10  is schematic perspective view of a reference example where the downstream end  11  of the screw  10  is not axially supported by the axial support, cross-section being illustrated by hatching of slant lines for the sake of easier understanding. 
     As would be understood from  FIGS. 7-9 , in some cases, the above-described axial portion  40  is a portion of at least one coupler  55  that couples the downstream end  11  of the screw  10  and the axial support (rectifier plate  30 ) such that the screw  10  is free to rotate. In some cases, the downstream end  11  of at least one screw  10  and at least one rectifier plate  30  are coupled via the coupler  55  such that at least one screw  10  is free to rotate. More appropriate or easier coupling of the downstream end  11  of the screw  10  and the axial support (rectifier plate  30 ) may be facilitated by the use of the coupler  55 . 
     In some cases, the coupler  55  is rotatably attached to at least one of the screw  10  and the axial support (rectifier plate  30 ) and, accordingly, the rotation of the screw  10  is allowed. In some cases, the coupler  55  is non-rotatably mated with the downstream end  11  of at least one screw  10 . The coupler  55  and the screw  10  may be firmly coupled by welding or adhesive. The coupler  55  may consist of metal or alloy which is different from and, for example, which is harder or softer than the shaft  13  of the screw  10  and/or the blade  14 . In some cases, the axial portion  40  has a diameter R 40  that is less than a shaft diameter R 13  of the screw  10 . The flow of raw material conveyed downward by the rotation of the screw  10  is prevented or suppressed from being impeded by the axial portion  40 . 
     The rectifier plate  30  includes a first rectifier plate  31  having a through-hole  33  into which the axial portion  40  extending along the axial direction AX 1  toward the screw  10  or toward the rectifier plate  30  is inserted, and/or a second rectifier plate  32  having a first receiving portion  51  that receives an end (downstream end) of the axial portion  40 . The through-channel  39  of the first rectifier plate  31  is in communication with the through-channel  39  of the second rectifier plate  32  and, for example they are co-axially arranged. When a sealing member is arranged in the through-hole  33  and a bushing  60  is arranged in the first receiving portion  51 , the raw material is prevented from flowing into the first receiving portion  51  of the second rectifier plate  32  through the through-hole  33  of the first rectifier plate  31 . In some cases, the extruder  2  has a sealing member  70  that prevents the raw material from flowing into the first receiving portion  51  of the second rectifier plate  32  through the through-hole  33  of the first rectifier plate  31 . O-ring or other sealing members may be used for sealing member  70 . 
     A sealing member  75  may be attached to the rectifier plate  30  so as to surround one or more through-channels  39  of the rectifier plate  30 . The sealing member  75  may be an O-ring or a linear sealing member that is laid in a circle. The sealing member  75  may be laid in a circular groove formed in a surface of the rectifier plate  30 . The sealing member  75  avoids or suppresses a leakage of raw material. 
     The above-described first and second rectifier plates  31 ,  32  are stacked, thus facilitating easier assembling. The first and second rectifier plates  31 ,  32  are attached to a flange  26  of the housing  20 , thus facilitating easier assembling. The flange  26  of the housing  20  is a protruding portion from the inner wall surface of the housing  20  to the screw  10 , i.e. radially inwardly of the housing  20 . In some cases, the rectifier plate  30  is fixed to the flange  26  of the housing  20  through mechanical fit. In  FIGS. 7-9 , the flange  26  has a projection projected along the axial direction AX 1 . This projection of the flange  26  is inserted through the through-hole of the first rectifier plate  31  and fitted to a recess of the second rectifier plate  32 . An embodiment is envisioned where a projection is provided on the second rectifier plate  32 , and the projection is inserted through the through-hole of the first rectifier plate  31  and fitted to a recess of the flange  26 . 
     In a case of  FIG. 7 , the rectifier plate  30  is provided with one through-channel  39 , but should not be limited to this. The rectifier plate  30  may be provided with a plurality of through-channels  39  as shown in  FIGS. 8 and 9 . The through-channels  39  of the rectifier plate  30  are arranged in a circle so as to surround the first receiving portion  51 . The number of circular arrangements may be one or more.  FIG. 8  shows 3 circular arrangements of through-channels  39 .  FIG. 9  shows one circular arrangement of through-channels  39 . 
     In the cases of  FIGS. 1-8 , a pair of screws is provided, but should not be limited to this. One screw  10  may be provided as shown in  FIG. 9 . In  FIG. 9 , a portion of hollow-cylindrical bushing  60  arranged in the first receiving portion  51  is illustrated. 
     As to operation of the extruder  2 , a switch of the electric motor  83  is firstly turned ON and the screw  10  starts to rotate. Next, raw material is fed continuously into the housing  20  through the hopper  29 . The rotation of the screw  10  conveys the raw material along the axial direction AX 1  of the screw  10 . The raw material conveyed by the screw  10  flows into and is stored in a pooling space between the screw  10  and the rectifier plate  30 . A part of the raw material filled in this space is extruded downward via the through-channels  39  of the rectifier plate  30 . A space between the rectifier plate  30  and the mesh  82  would be filled by the raw material extruded downward via the through-channels  39  of the rectifier plate  30 . A space between the mesh  82  and the extrusion die  81  would be filled by the raw material which has passed the mesh  82 . The raw material is continuously fed into the housing  20  and the screw  10  is continuously rotated. The raw material would be molded to be a honeycombed-like by the extrusion die  81 , and a honeycomb molded body, i.e. honeycomb green body would be continuously extruded from the extruder  2 . In the next step, the honeycomb green body continuously extruded from the extrusion die  81  would be cut. In the next step, the cut honeycomb green body would be dried and then fired. 
     Analysis by the present inventors has revealed that a cantilevered screw  10  may possibly suffer an axial deflection or axial swing, depending onto a raw material, e.g. its composition or viscosity, to be fed into the housing  20  of the extruder  2 . This axial deflection or axial swing of the screw may accompany a contact between the screw (particularly its downstream end (The downstream end is a free end)) and the housing, thus causing wear of the screw and/or the housing and possibly shortening the lifetime (exchanging cycle) of the screw and/or the housing. Additionally or alternatively, this axial deflection or axial swing of the screw may destabilize extrusion-speed of raw material by the extruder. For example, the extent of axial deflection or axial swing may be increased as the wear of the inner wall of the housing progresses, and an amount of extruded raw material may be destabilized. In the present disclosure, the downstream end  11  of at least one screw  10  is axially supported by at least one axial support, and a technical problem of axial deflection/swing of screw would be avoided or suppressed accordingly. 
     When the extruder is used to produce a ceramic honeycomb green body, there are cases where thicknesses of cell-walls  91 ,  92  defining cells  93  in the honeycomb green body  90  are demanded to be thinner (See  FIG. 11 ). In some cases, the thicknesses of the cell-walls  91 ,  92  are 0.05 to 0.30 mm. If the thicknesses of the cell-walls  91 ,  92  are reduced in accordance with that demand, there may be cases where it is more difficult to secure the shapes of the cell-walls  91 ,  92  as intended. For example, during or after the step of firing, pin-holes or cracks may be formed in the cell-walls  91 ,  92 . In light of such an aspect, one may consider to reduce an amount of ingredient to be volatilized during firing e.g. an amount of binder, and to feed to the extruder a raw material with increased viscosity. However, in this case, greater torque would be required for rotating the screw and an extent of axial deflection/swing of the screw would be greater, resulting in one or more above-described unfavorable outcomes. In the present disclosure, the downstream end  11  of at least one screw  10  is axially supported by at least one axial support, allowing the use of raw material prepared for thinner thickness cell-walls. 
     In an example of  FIG. 10 , the downstream end  11  of the screw  10  may touch the flange  26  due to the axial deflection/swing of the screw  10 . Chipping of the screw  10  or the flange  26  may be caused, and a running cost of the extruder  2  may be increased, resulting in increased cost of honeycomb bodies or making it impossible to use a raw material prepared for thinner thickness cell-walls. 
     The honeycomb green body illustrated in  FIG. 11  is produced by using the extruder  2  which further comprises an extrusion die  81  disposed downstream of the axial support in the conveying direction of the raw material, additionally to the screw  10 , the housing  20 , and the axial support. In some cases, a method of producing a honeycomb green body includes: conveying a raw material to the extrusion die  81  based on rotation of the screw  10  of the extruder  2 ; cutting a honeycomb green body being continuously extruded from the extrusion die; and firing the honeycomb green body obtained by the cutting. Each step would be performed based on existing established condition. 
     Based on the above disclosure, an operational method of extruder that comprises at least one screw  10  extending along the axial direction AX 1  and a housing  20  that houses the at least one screw  10  is also apparently disclosed. This method includes a step of rotating the screw  10  to convey the raw material along the axial direction AX 1 . Here, the screw  10  has a downstream end  11  positioned downstream in the conveying direction of the raw material along the axial direction AX 1 , and the downstream end  11  of the screw  10  is axially supported by at least one axial support. Improved operational method of extruder  2  is provided. 
     As an additional option, the method includes rectifying, by at least one rectifier plate  30 , the raw material conveyed downstream in accordance with the rotation of the at least one screw  10 . Here, the downstream end  11  of the screw  10  is axially supported by at least one rectifier plate  30 . Accordingly, mounting a dedicated part of an axial support to the extruder  2  would be avoided, likewise the above descriptions. One or more features stated for the extruder  2  would be understood to be effective to the operational method of the extruder  2  as they are, and thus overlapping descriptions are omitted. 
     A skilled person in the art would be able to add various modifications to the respective embodiments based on the above teachings. 
     REFERENCE NUMBERS 
     
         
           2  Extruder 
           10  Screw 
           11  Downstream end 
           20  Housing 
           30  Axial support, Rectifier plate