Plastic article or earthenware shaping or treating: apparatus – With upstream screen or perforated plate for straining,... – Upstream of multi-orifice shaping die
Reexamination Certificate
2001-05-07
2004-04-06
Davis, Robert (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
With upstream screen or perforated plate for straining,...
Upstream of multi-orifice shaping die
C425S202000, C425S208000, C425S461000
Reexamination Certificate
active
06716019
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an extrusion molding apparatus for molding a ceramic molded product such as a honeycomb ceramic structure.
2. Description of the Related Art
For the catalyst carrier in an exhaust gas purification system of an automotive vehicle, for example, a honeycomb structure
8
is used as a ceramic molded product including a multiplicity of cells
88
having partitioning walls
81
as shown in FIG.
7
. This honeycomb structure
8
is normally produced by extrusion molding.
The conventional extrusion molding apparatus
9
comprises, for example, a mold
91
for molding the honeycomb structure
8
, and a screw extruder
98
for kneading and extruding a ceramic material
80
continuously, as shown in FIG.
8
.
As shown in
FIG. 8
, a filter unit
93
for filtering the ceramic material
80
is interposed between the screw extruder
98
and the mold
91
. This filter unit
93
is for preventing foreign matter from mixing with the honeycomb structure
8
, and intended to trap foreign matter of a predetermined size or more by a filter unit net
930
. For this purpose, the filter unit
93
includes the filter net
930
having a multiplicity of pores and a support member
935
for supporting the filter net
930
. A resistance tube
92
making up a material path is normally arranged between the filter unit
93
and the mold
91
.
In extrusion molding the honeycomb structure
8
, the ceramic material introduced into the screw extruder
98
is filtered by the filter unit
93
while being supplied to the mold
91
.
In the conventional extrusion molding apparatus
9
as described above, however, the following problem can be encountered.
Specifically, the ceramic material passing through the screw extruder is sometimes partially aggregated into a lump. The aggregated ceramic material (material lump) is trapped on the inlet surface of the filter unit
93
and reduces the fluidity of the subsequently influent ceramic material.
More specifically, as shown in
FIG. 9
, after the material lump
89
is trapped in the filter net
930
, the ceramic material
80
passes around the material lump
89
, so that the fluidity of the material is reduced while, at the same time, the flow velocity distribution of the material after the filter net is adversely affected. For this reason, various measures have been studied to supply the lumps of the ceramic material to the mold after they are restored to the original particulate form. Nevertheless, a satisfactory measure has yet to be established.
In the case where a plurality of screw extruders are provided in a plurality of stages as shown in
FIG. 8
, the filter unit
94
may be arranged also at the extrusion exit of the screw extruder
99
in the upper stage. A similar problem is posed in such a case.
This problem is shared by the extrusion molding apparatus used for extrusion molding various shapes of ceramic molded products such as sheets, round bars and pipes as well as honeycomb structures.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the problems of the prior art described above and the object thereof is to provide an extrusion molding apparatus for a ceramic molded product in which lumps of an aggregated ceramic material can be passed through the filter unit smoothly.
REFERENCES:
patent: 2488129 (1949-11-01), La Lande, Jr.
patent: 2595210 (1952-04-01), Clinefelter
patent: 2640033 (1953-05-01), Marshall
patent: 3501807 (1970-03-01), Selbach
patent: 5064586 (1991-11-01), Higashijima
patent: 5567463 (1996-10-01), Schaaf
patent: 5589203 (1996-12-01), Sato
patent: 5738884 (1998-04-01), Sato
patent: 2-251406 (1990-10-01), None
Katou Hiromi
Miura Yasunao
Tsuruta Tadashi
Yamaguchi Satoru
Davis Robert
Del Sole Joseph S.
Denso Corporation
Nixon & Vanderhye PC
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