Plastic article or earthenware shaping or treating: apparatus – Stock pressurizing means operably associated with downstream... – Including auxiliary shaping means associated with molding...
Reexamination Certificate
1998-03-02
2001-02-27
Pyon, Harold (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Stock pressurizing means operably associated with downstream...
Including auxiliary shaping means associated with molding...
C264S177120, C425S461000, C425S467000
Reexamination Certificate
active
06193497
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a honeycomb extrusion die for extruding a ceramic honeycomb body and a method of manufacturing the same. Especially, the present invention relates to a honeycomb extrusion die and a method of manufacturing the same, in which a honeycomb structural body having a small pressure loss and a predetermined strength can be extruded in an accurate shape without transforming its shape during extruding.
2. Related Art Statement
Generally, as a honeycomb extrusion die for extruding a ceramic honeycomb body, a honeycomb extrusion die is known in which a plurality of intersection slits formed by cell blocks are arranged in a front surface thereof and a plurality of raw material holes communicated with the slits are arranged in a block surface thereof. As one example of the honeycomb extrusion die, the applicant proposes a technique in Japanese Patent Publication No. 61-39167 (JP-B-61-39167) in which each of the cell blocks has a round portion formed at corners thereof. Moreover, there is a technique in Japanese Patent Laid-Open Publication No. 60-145804 (JP-A-60-145804) in which each of the cell blocks is formed by coating iron boride, chromium carbide, aluminum oxide, titanium carbide, titanium nitride or titanium nitride carbide on a cell block body by means of chemical vapor deposition (CVD).
Recently, in order to meet a severe exhaust gas regulation or to improve exhaust gas purifying properties and honeycomb article properties, there is a requirement such that a ceramic honeycomb structural body after extrusion has a thin cell wall such as 45-120 &mgr;m which is thinner than the known cell wall thickness. Also, there is a requirement such that a honeycomb extrusion die for extruding a ceramic honeycomb body having such a thin cell wall and a method of manufacturing the same are developed.
However, in the technique disclosed in JP-B-61-39167 in which a slit width is controlled by electroless plating layer, there is a drawback such that a honeycomb extrusion die which can extrude a ceramic honeycomb structural body having a thin cell wall such as 45-120 &mgr;m is not obtained, if this technique is applied as it is.
Moreover, in the technique disclosed in JP-A-60-145804 in which a slit width defining a thickness of cell wall is controlled by chemical vapor deposition (CVD) layer, there are following drawbacks. That is to say, a thick coating layer is not formed only by CVD coating, and it is at most 30 &mgr;m as shown in JP-A-60-145804. Therefore, it is necessary to preliminarily work a metal block by means of for example electrical discharge machining or grinding so as to form a slit having a relatively small width. However, even if a thickness of CVD coating layer for finally controlling a slit width takes into consideration, it is not possible to perform such a preliminarily slit working only by the known electrical discharge machining or grinding. Moreover, it is not possible to form a round portion at corners of each of the cell blocks defining the slits only by CVD coating technique.
SUMMARY OF THE INVENTION
An object of the present invention is to eliminate the drawbacks mentioned above and to provide a honeycomb extrusion die and a method of manufacturing the same, in which a ceramic honeycomb structural body having a thin cell wall of 45-120 &mgr;m can be formed.
Another object of the present invention is to provide a honeycomb extrusion die and a method of manufacturing the same, in which a round portion is formed at corners of a cell block so as to increase a strength of a ceramic honeycomb structural body after extrusion and to improve a formability thereof.
According to the invention, a honeycomb extrusion die for extruding a honeycomb structural body, comprises: a plurality of intersecting slits arranged in a front surface thereof, each of the slits being formed by cell blocks; a plurality of raw material feeding holes arranged in a back surface thereof, each of the raw material feeding holes being communicated with the slits; and a round portion formed in corners of each of the cell blocks; wherein each of the cell blocks comprises, a cell block body, a first coating layer formed by electroless plating on the cell block body, and a second coating layer formed by chemical vapor deposition on the first coating layer, and wherein a width of each of the slits is 45-120 &mgr;m.
According to the invention, a method of manufacturing a honeycomb extrusion die for extruding a honeycomb structural body, comprises the steps of: forming a plurality of intersecting slits in a front surface of the extrusion die, each of the slits being defined by cell block bodies; forming a plurality of raw material feeding holes in a back surface of the extrusion die, each of the raw material feeding holes being communicated with the slits; forming a first coating layer on each of the cell block bodies by electroless plating; and forming a second coating layer on the first coating layer by chemical vapor deposition to provide a width of each of the slits of 45-120 &mgr;m.
In the present invention, a slit width is controlled by arranging the first coating layer made of preferably nickel plating layer formed by electroless plating and a second coating layer made of preferably TiCN or W
2
C coating layer formed by chemical vapor deposition on each of the cell block bodies worked preliminarily by the known electrical discharge machining or grinding. Therefore, a slit having a predetermined slit width can be obtained by making a slit width relatively narrower by the first coating layer formed by electroless plating, which can form a relatively thick layer, and then by arranging the second coating layer formed by CVD, which can only form a relatively thin layer, on the first coating layer. In this manner, it is possible to obtain a honeycomb extrusion die having a slit width of 45-120 &mgr;m which can form a ceramic honeycomb structural body having a thin cell wall such as 45-120 &mgr;m. Moreover, in the present invention, since the first coating layer is formed by electroless plating, corners of the first coating layer formed on the cell block body is naturally rounded. Then, since the thin second coating layer having a constant thickness is arranged on the first coating layer, it is possible to obtain a honeycomb extrusion die having a round portion at corners of each of the cell blocks and also maintaining a slit width of 45-120 &mgr;m can be obtained in an easy manner.
REFERENCES:
patent: 4574459 (1986-03-01), Peters
patent: 5070588 (1991-12-01), Miwa et al.
patent: 0 017 686 A1 (1980-10-01), None
patent: 0 029 287 A1 (1981-05-01), None
patent: 0 276 083 A2 (1988-07-01), None
patent: 0 389 253 A2 (1990-09-01), None
patent: 60-145804 (1985-08-01), None
patent: 61-39167 (1986-09-01), None
Leyson Joseph
NGK Insulators Ltd.
Parkhurst & Wendel L.L.P.
Pyon Harold
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