Plastic article or earthenware shaping or treating: apparatus – With separate and distinct upstream agitating or kneading means – Plural means being diverse – or parallel and intermeshing or...
Reexamination Certificate
2001-08-30
2003-10-28
Mackey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
With separate and distinct upstream agitating or kneading means
Plural means being diverse, or parallel and intermeshing or...
C366S076300, C425S208000, C425S382400
Reexamination Certificate
active
06638051
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an extrusion molding machine for extruding a ceramic molding.
2. Description of the Related Art
For instance, a known catalyst carrier for an exhaust gas purifier for an automobile is comprised of a ceramic honey-comb structure
8
having a number of cells
88
spaced by separation walls
81
, as shown in FIG.
19
. In general, a ceramic molding such as the ceramic honey-comb structure
8
is formed by extrusion molding. Moreover, the extrusion molding can be also used to form a sheet-like ceramic product, i.e., a ceramic sheet.
A conventional extrusion molding machine
9
is comprised of, for example, a molding die
11
for forming the ceramic molding
8
, and two-stage screw extruders
2
and
3
for continuously kneading and extruding the ceramic material
80
, as shown in FIG.
17
. Note that the two-stage screw extruders can be replaced with a single-stage screw extruder or more than two-stage screw extruders.
As can be seen in the drawing, the screw extruders
2
and
3
are respectively provided with housings
21
and
31
which define material passageways
20
and
30
in which screws
22
and
32
having shaft portions
221
and
321
and helical leads
222
and
322
formed therearound extend.
A material introduction portion
93
through which the ceramic material
80
is introduced is provided above the rear end of the upper stage screw extruder
3
. The material introduction portion
93
is provided with a hopper
939
through which the material is fed and a pair of right and left feed rollers
931
. As shown in
FIG. 18
, the right and left feed rollers
931
are opposed to each other and are rotated in opposite directions (in the downward direction at the opposed surface portions), so that the ceramic material
80
dropped onto the feed rollers
931
is forced between the feed rollers
931
and fed downward.
As shown in
FIG. 17
, in case of the two-stage screw extruders
2
and
3
, a vacuum chamber
5
is provided between the screw extruders. The vacuum chamber
5
is adapted to degas the ceramic material
80
which has been kneaded by the upper stage screw extruder
3
and to feed the ceramic material
80
having a high bulk density to the lower stage screw extruder
2
. The vacuum chamber
5
is also provided therein with a pair of right and left feed rollers
921
similar to those of the material introduction portion
93
, so that the ceramic material
80
can be fed to the lower stage screw extruder
2
.
To produce the ceramic molding
8
using the extrusion molding machine
9
, the ceramic material
80
which is not kneaded is charged into the material introduction portion
93
from the hopper
939
, as shown in FIG.
17
. The ceramic material
80
is forced between the pair of right and left feed rollers
931
in accordance with the rotation thereof and is fed into the screw extruder
3
.
Thereafter, the ceramic material
80
is fed forward while being kneaded by the upper stage screw extruder
3
and is discharged from the front end thereof into the vacuum chamber
5
. Thereafter, the ceramic material
80
which has been kneaded to some extent is degassed in the vacuum chamber
5
and is fed into the lower stage screw extruder
2
by the pair of right and left feed rollers
921
. The ceramic material
80
is moved forward while being further kneaded in the screw extruder
2
, and is extruded from the extrusion molding die
11
through a resisting pipe
12
to obtain the ceramic molding
8
.
The extrusion molding machine of the prior art mentioned above has the following drawbacks.
Namely, to enhance the productivity by increasing the molding speed in the extrusion molding machine
9
, it is necessary to increase the amount of the ceramic material
80
to be charged in the material introduction portion
93
per unit time and to increase the rotation speed of the feed rollers
931
.
However, the material introduction portion
93
can respond only to a certain amount of increase in the amount of the material to be fed, so that feed of the ceramic material
80
into the screw extruder
3
may be stopped. Concretely, if a large amount of the ceramic material
80
is charged in the material introduction portion
93
, the feed rollers
931
having projections and depressions idle-rotate with the surfaces thereof having part of the ceramic material stuck thereto. Consequently, as can be seen in
FIG. 18
, the ceramic material
80
cannot be fed downward and deposit of the ceramic material
80
can be produced above the feed rollers
931
. Therefore, the increase in the molding speed is limited in the conventional extrusion molding machine
9
and, hence, it is difficult to enhance the productivity sufficiently.
One of the reasons can be considered as follows.
Namely, the ceramic material
80
which is not kneaded is charged in the material introduction portion
93
and is usually in a state of mixture of powders of a plurality of ceramic components and water mixed therewith like a clod and contains plenty of air. Thus, the ceramic material
80
in the material introduction portion
93
has a very low bulk density. Therefore, the ceramic material
80
tends not to drop due to the dead weight, thus leading to production of the deposit mentioned above.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an extrusion molding machine for producing a ceramic molding, in which the ceramic material which is not kneaded can be efficiently introduced to increase the molding speed.
To achieve the object mentioned above, according to an embodiment of the present invention, there is provided an extrusion molding machine for producing a ceramic molding, comprising a screw extruder having a housing and an extruding screw incorporated in the housing and provided with a shaft portion and a lead portion spirally wound about the shaft portion, and a material introduction portion which is adapted to introduce a ceramic material into the screw extruder, wherein the material introduction portion is provided with a casing which has an introduction passage connected to the inside of the housing of the screw extruder and an opening through which the ceramic material is charged, and a pair of right and left introduction screws provided in the introduction passage, said introduction screws being provided with lead portions wound in opposite directions and being arranged so that the lead portions are engaged substantially in a non-contact state, said introduction screws being rotated so that the ceramic material is moved in a direction opposite to the opening at the engagement portion.
In this embodiment, one of the significant features resides in that the material introduction portion is comprised of the casing and the pair of introduction screws.
The casing defines therein the introduction passage in which the pair of right and left introduction screws are provided, as mentioned above. The opening of the casing preferably opens at the rear end side of the engagement portion of the right and left introduction screws (side opposite to the feed direction of the introduction screws). With this arrangement, the charged ceramic material can be smoothly fed to the introduction screws. The position of the material introduction portion can be modified in various ways as explained later.
The effects of the embodiment of the invention will be discussed below.
The extrusion molding machine according to the embodiment of the invention is provided with the material introduction portion constructed as above. Consequently, even if a larger amount of ceramic material is charged in the material introduction portion, the ceramic material can be smoothly fed to the screw extruder. Therefore, the molding speed can be remarkably increased, in comparison with the prior art.
Namely, the material introduction portion is provided with two interengageable introduction screws which are rotated in opposite directions so as to draw and feed the ceramic material therein. Therefore, the ceramic material char
Katou Hiromi
Yamaguchi Satoru
Denso Corporation
Leyson Joseph
Mackey James P.
Nixon & Vanderhye PC
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